fix(app): preserve socket capabilities on adopted probe clients

fix(transport): preserve native admission and pace file writes
Sockets without a drain signal retain single-frame outbound admission while accepting chunked responses. Uploads and response-bearing control sends must observe queued admission failures instead of waiting for a response that cannot arrive.
2026-10-30 21:23:04 +00:00 · 2026-10-30 17:56:57 +01:00 · 2026-10-30 17:41:57 +01:00 · 2026-10-30 17:23:27 +01:00 · 2026-10-30 17:06:29 +01:00 · 2026-10-30 16:33:13 +01:00
86 changed files with 2749 additions and 1487 deletions
@@ -52,6 +52,33 @@ On capable daemons, connecting creates no timeline or event demand. Client subsc
 release it on unsubscribe, and restore it after reconnect. Raw message observers inspect traffic
 without requesting streams. Application caches and which agents are visible remain caller-owned.

+## Binary chunking
+
+`binary_chunking_v1` in hello and optional `server_info.features.binaryChunkingV1`
+negotiate connection-scoped framing. Application serializers and routed envelopes use
+the same boundary. Small messages and handshakes keep their existing representation.
+Older peers retain existing frame limits.
+
+The reserved binary opcode `0x31` is followed by version `1`, original kind
+(`0` text, `1` binary), and START/END flag bits `0`/`1`. Remaining bytes are an
+unchanged slice. There is no total length or chunk count; a future receiver can
+consume slices incrementally. Today the receiver buffers up to the existing
+100 MiB logical limit and decodes UTF-8 only after END. Transfers cannot interleave.
+Disconnect clears partial state and negotiation.
+
+The lower transport supplies its plaintext frame budget, including encryption
+overhead. The sender waits for drain between chunks while ordinary messages keep
+the existing delivery path. Slow-client protections count messages queued behind
+an active transfer as well as bytes already in the socket.
+The framing module never selects an encryption construction.
+
+Native uploads retain the platform's existing queue limits. React Native's
+WebSocket does not report its queued bytes, so the client cannot wait for native
+drain. Android's installed OkHttp transport closes when a send would put more
+than 16 MiB in its queue. The native transport disables outbound chunking, including
+on routed channels, and retains its existing single-frame admission errors.
+Inbound chunking remains enabled; daemon-to-native responses use the daemon's paced writes.
+
 ## Owned observations

 `owned_subscriptions` and `server_info.features.ownedSubscriptions` negotiate the source-owned
@@ -21,10 +21,16 @@ The invariants are:
 > agent establishes the daemon's current tail in one complete-turn request, with older history reachable
 > through backward pagination.

-Tool output is bounded before it enters either delivery path. Canonical shell tool output is sliced
-to 64 KiB, and the same bounded item is used for runtime timeline rows and live stream events.
-Provider history hydration applies the same rule so reopening an agent cannot restore an oversized
-tool payload.
+Every item is bounded before it enters either delivery path, because a timeline page is one
+WebSocket message and the daemon closes a socket whose outbound buffer passes 64 MiB. Tool calls get
+64 KiB and other items 256 KiB. Over budget, the largest strings are cut to a shared length with a
+`…[truncated 12.3 MB]` marker, and an oversized `data:` URL is replaced by the marker. Strings up
+to 1 KiB stay whole, so ids and paths survive. Arrays drop their trailing elements without a marker
+element, so typed arrays still match the wire schema. Limiting an item twice gives the same item. The
+budget does not bound wide objects or multi-byte text. The same
+bounded item is used for runtime timeline rows and live stream events. Provider history hydration
+applies the same rule so reopening an agent cannot restore an oversized payload. Fetches apply it
+again to assistant and reasoning rows the projection merges from many chunks.

 ## Presence is not delivery

@@ -18,7 +18,7 @@ function visibleMainPane(page: Page) {
 }

 function composerChangesPill(page: Page) {
-  return page.getByTestId("composer-diff-stat-pill");
+  return page.getByRole("button", { name: "Open Changes tab", exact: true });
 }

 async function revealComposerChangesInExplorer(page: Page) {
@@ -498,6 +498,7 @@ test.describe("send review feedback", () => {
  test("only open tabs in this workspace appear in compact and wide recipient menus", async ({
    page,
  }) => {
+    test.setTimeout(120000);
    const workspace = await seedChangedAgent("review-feedback-multiple-");
    const other = await seedChangedAgent("review-feedback-other-");
    try {
@@ -1,3 +1,4 @@
+import { chooseModel, startWithoutRememberedModel } from "../support/helpers/model-memory";
 import {
  composerLocator,
  enterComposerFullscreen,
@@ -97,6 +98,7 @@ test.describe("New workspace composer draft", () => {
    const project = await seedWorkspace({ repoPrefix: "new-workspace-submitted-draft-" });

    try {
+      await startWithoutRememberedModel(page);
      await gotoAppShell(page);
      await waitForSidebarHydration(page);
      await openNewWorkspaceComposer(page, {
@@ -104,6 +106,7 @@ test.describe("New workspace composer draft", () => {
        projectDisplayName: project.projectDisplayName,
      });

+      await chooseModel(page, "mock", "Ten second stream");
      const composer = page.getByRole("textbox", { name: "Message agent..." });
      const createButton = page.getByTestId("workspace-create-submit");
      await expect(composer).toBeEditable({ timeout: 30_000 });
@@ -64,7 +64,7 @@ function resolveShouldFill(
 ): boolean {
  if (!fillAvailableHeight) return false;
  const t = detail?.type;
-  return t === "shell" || t === "edit" || t === "write" || t === "read" || t === "sub_agent";
+  return t === "shell" || t === "edit" || t === "write" || t === "read";
 }

 function useDetailStyles(
@@ -186,184 +186,6 @@ function ShellDetailSection({ command, output, ds }: ShellDetailProps) {
  );
 }

-function resolveSubAgentFallbackHeader(
-  subAgentType: string | null | undefined,
-  description: string | null | undefined,
-  fallbackText: string,
-): string {
-  if (subAgentType && description) {
-    return `${subAgentType}: ${description}`;
-  }
-  return subAgentType ?? description ?? fallbackText;
-}
-
-interface SubAgentDetailProps {
-  log: string;
-  childSessionId: string | null | undefined;
-  subAgentType: string | null | undefined;
-  description: string | null | undefined;
-  ds: DetailStyles;
-}
-
-interface SubAgentActivityRow {
-  index: number;
-  toolName: string;
-  summary?: string;
-}
-
-interface ParsedSubAgentLog {
-  actions: SubAgentActivityRow[];
-  remainingLog: string;
-}
-
-function parseBracketedSubAgentLine(line: string, index: number): SubAgentActivityRow | null {
-  const match = line.match(/^\[([^\]]+)\](?:\s+(.*))?$/);
-  if (!match) {
-    return null;
-  }
-  const toolName = match[1]?.trim();
-  if (!toolName) {
-    return null;
-  }
-  const summary = match[2]?.trim();
-  return {
-    index,
-    toolName,
-    ...(summary ? { summary } : {}),
-  };
-}
-
-function parseSubAgentLog(log: string): ParsedSubAgentLog {
-  const actions: SubAgentActivityRow[] = [];
-  const remainingLines: string[] = [];
-  for (const line of log.replace(/^\n+/, "").split("\n")) {
-    const normalizedLine = line.trim();
-    if (!normalizedLine) {
-      continue;
-    }
-    const parsedAction = parseBracketedSubAgentLine(normalizedLine, actions.length + 1);
-    if (parsedAction) {
-      actions.push(parsedAction);
-    } else {
-      remainingLines.push(line);
-    }
-  }
-  return {
-    actions,
-    remainingLog: remainingLines.join("\n").replace(/^\n+/, ""),
-  };
-}
-
-function SubAgentActionRow({ action }: { action: SubAgentActivityRow }) {
-  return (
-    <View style={styles.subAgentActionRow}>
-      <Text selectable style={styles.subAgentActionTool}>
-        {formatSubAgentToolName(action.toolName)}
-      </Text>
-      {action.summary ? (
-        <Text selectable style={styles.subAgentActionSummary}>
-          {action.summary}
-        </Text>
-      ) : null}
-    </View>
-  );
-}
-
-function formatSubAgentToolName(toolName: string): string {
-  const trimmed = toolName.trim();
-  if (!trimmed) {
-    return toolName;
-  }
-  return trimmed
-    .replace(/[._-]+/g, " ")
-    .split(" ")
-    .filter((segment) => segment.length > 0)
-    .map((segment) => `${segment[0]?.toUpperCase() ?? ""}${segment.slice(1)}`)
-    .join(" ");
-}
-
-function SubAgentLogText({
-  activityLog,
-  fallbackHeader,
-  hasActions,
-}: {
-  activityLog: string;
-  fallbackHeader: string;
-  hasActions: boolean;
-}) {
-  if (activityLog.length > 0) {
-    return (
-      <Text selectable style={styles.scrollText}>
-        {activityLog}
-      </Text>
-    );
-  }
-  if (!hasActions) {
-    return (
-      <Text selectable style={styles.scrollText}>
-        {fallbackHeader}
-      </Text>
-    );
-  }
-  return null;
-}
-
-function SubAgentDetailSection({
-  log,
-  childSessionId,
-  subAgentType,
-  description,
-  ds,
-}: SubAgentDetailProps) {
-  const { t } = useTranslation();
-  const { actions, remainingLog } = useMemo(() => parseSubAgentLog(log), [log]);
-  const fallbackHeader = resolveSubAgentFallbackHeader(
-    subAgentType,
-    description,
-    t("toolCallDetails.subAgentActivity"),
-  );
-  const hasActions = actions.length > 0;
-  return (
-    <View style={ds.sectionFillStyle}>
-      <View style={ds.codeBlockFillStyle}>
-        <ScrollView
-          style={ds.codeVerticalScrollStyle}
-          contentContainerStyle={styles.codeVerticalContent}
-          nestedScrollEnabled
-          showsVerticalScrollIndicator
-        >
-          <ScrollView
-            horizontal
-            nestedScrollEnabled
-            showsHorizontalScrollIndicator
-            contentContainerStyle={styles.codeHorizontalContent}
-          >
-            <View style={styles.codeLine} dataSet={CODE_SURFACE_DATASET}>
-              {childSessionId ? (
-                <Text selectable style={styles.subAgentSessionText}>
-                  session {childSessionId}
-                </Text>
-              ) : null}
-              {hasActions ? (
-                <View style={styles.subAgentActions}>
-                  {actions.map((action) => (
-                    <SubAgentActionRow key={action.index} action={action} />
-                  ))}
-                </View>
-              ) : null}
-              <SubAgentLogText
-                activityLog={remainingLog}
-                fallbackHeader={fallbackHeader}
-                hasActions={hasActions}
-              />
-            </View>
-          </ScrollView>
-        </ScrollView>
-      </View>
-    </View>
-  );
-}
-
 interface EditDetailProps {
  diffLines: DiffLine[] | undefined;
  ds: DetailStyles;
@@ -636,19 +458,7 @@ function buildDetailSections(
      <ShellDetailSection key="shell" command={detail.command} output={detail.output} ds={ds} />,
    ];
  }
-  if (detail.type === "worktree_setup") return [];
-  if (detail.type === "sub_agent") {
-    return [
-      <SubAgentDetailSection
-        key="sub-agent"
-        log={detail.log}
-        childSessionId={detail.childSessionId}
-        subAgentType={detail.subAgentType}
-        description={detail.description}
-        ds={ds}
-      />,
-    ];
-  }
+  if (detail.type === "worktree_setup" || detail.type === "sub_agent") return [];
  if (detail.type === "edit") {
    return [<EditDetailSection key="edit" diffLines={diffLines} ds={ds} />];
  }
@@ -900,34 +710,6 @@ const styles = StyleSheet.create((theme) => {
    shellPrompt: {
      color: theme.colors.foregroundMuted,
    },
-    subAgentSessionText: {
-      fontFamily: theme.fontFamily.mono,
-      fontSize: theme.fontSize.code,
-      color: theme.colors.foregroundMuted,
-      lineHeight: 18,
-      marginBottom: theme.spacing[2],
-    },
-    subAgentActions: {
-      gap: theme.spacing[1],
-      marginBottom: theme.spacing[2],
-    },
-    subAgentActionRow: {
-      flexDirection: "row",
-      alignItems: "center",
-      gap: theme.spacing[2],
-    },
-    subAgentActionTool: {
-      fontFamily: theme.fontFamily.mono,
-      fontSize: theme.fontSize.code,
-      color: theme.colors.foregroundMuted,
-      lineHeight: 18,
-    },
-    subAgentActionSummary: {
-      fontFamily: theme.fontFamily.mono,
-      fontSize: theme.fontSize.code,
-      color: theme.colors.foreground,
-      lineHeight: 18,
-    },
    jsonScroll: {
      borderWidth: theme.borderWidth[1],
      borderColor: theme.colors.border,
@@ -832,7 +832,6 @@ describe("translation resources", () => {
    expect(en.common.placeholders.search).toBe("Search...");
    expect(en.common.empty.noResults).toBe("No results found");
    expect(en.common.empty.noOptionsMatchSearch).toBe("No options match your search.");
-    expect(en.toolCallDetails.subAgentActivity).toBe("Sub-agent activity");
    expect(en.panels.file.failedToLoadPreview).toBe("Failed to load file preview");
  });

@@ -2013,7 +2013,6 @@ export const ar: TranslationResources = {
  toolCallDetails: {
    error: "خطأ",
    empty: "لا توجد تفاصيل إضافية متاحة",
-    subAgentActivity: "نشاط الوكيل الفرعي",
    input: "مدخل",
    output: "الإخراج",
  },
@@ -2038,7 +2038,6 @@ export const en = {
  toolCallDetails: {
    error: "Error",
    empty: "No additional details available",
-    subAgentActivity: "Sub-agent activity",
    input: "Input",
    output: "Output",
  },
@@ -2061,7 +2061,6 @@ export const es: TranslationResources = {
  toolCallDetails: {
    error: "Error",
    empty: "No hay detalles adicionales disponibles",
-    subAgentActivity: "Actividad de subagente",
    input: "Aporte",
    output: "Producción",
  },
@@ -2060,7 +2060,6 @@ export const fr: TranslationResources = {
  toolCallDetails: {
    error: "Erreur",
    empty: "Aucun détail supplémentaire disponible",
-    subAgentActivity: "Activité du sous-agent",
    input: "Entrée",
    output: "Sortie",
  },
@@ -2033,7 +2033,6 @@ export const ja: TranslationResources = {
  toolCallDetails: {
    error: "エラー",
    empty: "追加の詳細はありません",
-    subAgentActivity: "サブエージェントアクティビティ",
    input: "入力",
    output: "出力",
  },
@@ -2023,7 +2023,6 @@ export const ko: TranslationResources = {
  toolCallDetails: {
    error: "오류",
    empty: "추가 세부 정보가 없습니다",
-    subAgentActivity: "서브에이전트 활동",
    input: "입력",
    output: "출력",
  },
@@ -2046,7 +2046,6 @@ export const ptBR: TranslationResources = {
  toolCallDetails: {
    error: "Erro",
    empty: "Nenhum detalhe adicional disponível",
-    subAgentActivity: "Atividade do subagente",
    input: "Entrada",
    output: "Saída",
  },
@@ -2046,7 +2046,6 @@ export const ru: TranslationResources = {
  toolCallDetails: {
    error: "Ошибка",
    empty: "Дополнительные сведения отсутствуют",
-    subAgentActivity: "Активность субагента",
    input: "Входные данные",
    output: "Выходные данные",
  },
@@ -1991,7 +1991,6 @@ export const zhCN: TranslationResources = {
  toolCallDetails: {
    error: "错误",
    empty: "没有可用的更多详情",
-    subAgentActivity: "Sub-agent 活动",
    input: "输入",
    output: "输出",
  },
@@ -76,6 +76,25 @@ describe("test-daemon-connection connectToDaemon", () => {
    probe = new FakeDaemonProbe();
  });

+  it.each([
+    { id: "direct:lan:6767", type: "directTcp" as const, endpoint: "lan:6767" },
+    {
+      id: "relay:test",
+      type: "relay" as const,
+      relayEndpoint: "relay.paseo.sh:443",
+      daemonPublicKeyB64: "pubkey",
+    },
+  ])("adoptable $type probe clients use the app WebSocket factory", async (connection) => {
+    const { connectToDaemon } = await import("./test-daemon-connection");
+    const { createAppWebSocketFactory } = await import("@/runtime/websocket-factory");
+    const result = await connectToDaemon(connection, { serverId: "srv_probe_test" }, probe.deps);
+    try {
+      expect(result.client.config.webSocketFactory).toBe(createAppWebSocketFactory());
+    } finally {
+      await result.client.close();
+    }
+  });
+
  it("reuses the app clientId for direct connections", async () => {
    const { connectToDaemon } = await import("./test-daemon-connection");
    const first = await connectToDaemon(
@@ -6,6 +6,7 @@ import {
 } from "@getpaseo/client/internal/daemon-client";
 import type { DaemonClientConfig } from "@getpaseo/client/internal/daemon-client";
 import type { HostConnection } from "@/types/host-connection";
+import { createAppWebSocketFactory } from "@/runtime/websocket-factory";
 import { getOrCreateClientId } from "./client-id";
 import { resolveAppVersion } from "./app-version";
 import {
@@ -156,6 +157,7 @@ export async function buildClientConfig(
    clientType: "mobile" as const,
    appVersion: deps.resolveAppVersion() ?? undefined,
    suppressSendErrors: true,
+    webSocketFactory: createAppWebSocketFactory(),
    reconnect: { enabled: false },
    ...resolveConnectionCredentials(connection, options),
    ...(options.capabilities ? { capabilities: options.capabilities } : {}),
@@ -40,12 +40,6 @@ function hasMeaningfulFetchDetail(detail: Extract<ToolCallDetail, { type: "fetch
  return Boolean(detail.url || detail.result || detail.codeText);
 }

-function hasMeaningfulSubAgentDetail(
-  detail: Extract<ToolCallDetail, { type: "sub_agent" }>,
-): boolean {
-  return Boolean(detail.subAgentType || detail.description || detail.log);
-}
-
 function hasMeaningfulPlainTextDetail(
  detail: Extract<ToolCallDetail, { type: "plain_text" }>,
 ): boolean {
@@ -75,9 +69,9 @@ export function hasMeaningfulToolCallDetail(detail: ToolCallDetail | undefined):
    case "fetch":
      return hasMeaningfulFetchDetail(detail);
    case "worktree_setup":
-      return false;
+    // A sub-agent card is a launch marker; the child's activity lives in the sub-agent panel.
    case "sub_agent":
-      return hasMeaningfulSubAgentDetail(detail);
+      return false;
    case "plain_text":
      return hasMeaningfulPlainTextDetail(detail);
    case "plan":
@@ -92,7 +86,7 @@ export function isPendingToolCallDetail(params: {
  status: "executing" | "running" | "completed" | "failed" | "canceled";
  error: unknown;
 }): boolean {
-  if (params.detail?.type === "worktree_setup") return false;
+  if (params.detail?.type === "worktree_setup" || params.detail?.type === "sub_agent") return false;
  const isRunning = params.status === "running" || params.status === "executing";
  return isRunning && params.error == null && !hasMeaningfulToolCallDetail(params.detail);
 }
@@ -125,6 +125,7 @@ export class ConnectionSubscriptions extends OwnedSubscriptions {
 // Protocol support belongs to the installed client. Only browser hosting needs
 // a resource supplied by the caller. Keep this exhaustive as the protocol evolves.
 export const DEFAULT_CLIENT_CAPABILITIES = {
+  [CLIENT_CAPS.binaryChunkingV1]: true,
  [CLIENT_CAPS.helloRejection]: true,
  [CLIENT_CAPS.ownedSubscriptions]: true,
  [CLIENT_CAPS.allProviders]: true,
@@ -1,3 +1,4 @@
+import { maxSecuredPlaintextByteLength } from "@getpaseo/relay";
 import { MAX_RELAY_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import {
  openClientSecureChannel,
@@ -155,18 +156,15 @@ export function createEncryptedTransport(
  const relayTransport: RelayTransport = {
    send: (data) => {
      if (typeof data === "string") {
-        base.send(data);
-        return;
+        return base.send(data);
      }
      if (ArrayBuffer.isView(data)) {
-        base.send(normalizeTransportPayload(data));
-        return;
+        return base.send(normalizeTransportPayload(data));
      }
      if (data instanceof ArrayBuffer) {
-        base.send(data);
-        return;
+        return base.send(data);
      }
-      base.send(String(data));
+      return base.send(String(data));
    },
    // The channel decides the close code. Report it now: a socket close event
    // arrives asynchronously, and the consumer must not act on an earlier
@@ -226,6 +224,8 @@ export function createEncryptedTransport(
  });

  return {
+    supportsDrain: base.supportsDrain,
+    maxFrameBytes: maxSecuredPlaintextByteLength(MAX_RELAY_WEBSOCKET_MESSAGE_BYTES),
    send: (data) => {
      if (!channel) {
        throw new Error("Encrypted channel not ready");
@@ -239,8 +239,9 @@ export function createEncryptedTransport(
      // Encryption and its transport handoff are synchronous up to send's first await.
      // Reject capacity failures here so a routed sender loses only its own channel.
      assertOutboundCapacity(wireBytes);
-      void channel.send(payload).catch((error) => {
+      return channel.send(payload).catch((error) => {
        emitError(error);
+        throw error;
      });
    },
    close: (code?: number, reason?: string) => {
@@ -1,5 +1,8 @@
 export interface DaemonTransport {
-  send: (data: string | Uint8Array | ArrayBuffer) => void;
+  /** False when the underlying socket cannot report write drain. */
+  supportsDrain?: boolean;
+  maxFrameBytes?: number;
+  send: (data: string | Uint8Array | ArrayBuffer) => void | Promise<void>;
  close: (code?: number, reason?: string) => void;
  onMessage: (handler: (data: unknown, isBinary: boolean) => void) => () => void;
  onOpen: (handler: () => void) => () => void;
@@ -13,12 +16,16 @@ export type DaemonTransportFactory = (options: {
  protocols?: string[];
 }) => DaemonTransport;

-export type WebSocketFactory = (
-  url: string,
-  options?: { headers?: Record<string, string>; protocols?: string[] },
-) => WebSocketLike;
+export interface WebSocketFactory {
+  (
+    url: string,
+    options?: { headers?: Record<string, string>; protocols?: string[] },
+  ): WebSocketLike;
+  supportsDrain?: boolean;
+}

 export interface WebSocketLike {
+  bufferedAmount?: number;
  readyState: number;
  send: (data: string | Uint8Array | ArrayBuffer) => void;
  close: (code?: number, reason?: string) => void;
@@ -175,3 +175,18 @@ describe("daemon-client transport helpers", () => {
    expect(decodeMessageData(bytes)).toBe("hello");
  });
 });
+
+test("native drain capability survives WebSocket and encryption wrappers", async () => {
+  const { nativeWebSocketFactory } = await import("./daemon-client-websocket-transport.js");
+  expect(nativeWebSocketFactory.supportsDrain).toBe(false);
+  const factory = Object.assign(() => ({ readyState: 1, send() {}, close() {} }), {
+    supportsDrain: false,
+  });
+  const base = createWebSocketTransportFactory(factory)({ url: "ws://test" });
+  expect(base.supportsDrain).toBe(false);
+  const encrypted = createEncryptedTransport(base, {
+    daemonPublicKeyB64: "unused-key",
+    logger: { warn() {} },
+  });
+  expect(encrypted.supportsDrain).toBe(false);
+});
@@ -39,6 +39,9 @@ export function nativeWebSocketFactory(
  return new (getGlobalWebSocket())(url, options?.protocols, { headers: options?.headers });
 }

+// React Native leaves bufferedAmount at zero, including while native output is queued.
+nativeWebSocketFactory.supportsDrain = false;
+
 export function createWebSocketTransportFactory(factory: WebSocketFactory): DaemonTransportFactory {
  return ({ url, headers, protocols }) => {
    const ws = factory(url, { headers, protocols });
@@ -50,11 +53,28 @@ export function createWebSocketTransportFactory(factory: WebSocketFactory): Daem
      }
    }
    return {
+      supportsDrain: factory.supportsDrain !== false,
      send: (data) => {
        if (typeof ws.readyState === "number" && ws.readyState !== 1) {
          throw new Error(`WebSocket not open (readyState=${ws.readyState})`);
        }
        ws.send(data);
+        if ((ws.bufferedAmount ?? 0) > 1024 * 1024) {
+          return new Promise<void>((resolve, reject) => {
+            const drain = () => {
+              if (ws.readyState !== 1) {
+                reject(new Error("WebSocket closed while draining"));
+                return;
+              }
+              if ((ws.bufferedAmount ?? 0) <= 1024 * 1024) {
+                resolve();
+                return;
+              }
+              setTimeout(drain, 10);
+            };
+            drain();
+          });
+        }
      },
      close: (code?: number, reason?: string) => {
        // Node's `ws` may emit an `error` when a connecting socket is closed before the
@@ -1094,6 +1094,7 @@ test("advertises client capabilities in hello", async () => {
      provider_snapshot_references: true,
      explicit_event_subscriptions: true,
      owned_subscriptions: true,
+      binary_chunking_v1: true,
      compact_provider_snapshots: true,
      custom_mode_icons: true,
      project_updates: true,
@@ -6817,91 +6818,102 @@ test("drops legacy agent_stream tool_call payloads and logs validation warning",
  expect(logger.warn).toHaveBeenCalled();
 });

-test("parses canonical fetch_agent_timeline_response payloads without crashing", async () => {
-  const logger = createMockLogger();
-  const mock = createMockTransport();
+test.each([false, true])(
+  "parses canonical timeline responses with chunking=%s",
+  async (chunked) => {
+    const logger = createMockLogger();
+    const mock = createMockTransport();

-  const client = new DaemonClient({
-    url: "ws://test",
-    clientId: "clsk_unit_test",
-    logger,
-    reconnect: { enabled: false },
-    transportFactory: () => mock.transport,
-  });
-  clients.push(client);
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "clsk_unit_test",
+      logger,
+      reconnect: { enabled: false },
+      transportFactory: () => mock.transport,
+    });
+    clients.push(client);

-  const connectPromise = client.connect();
-  mock.triggerOpen();
-  await connectPromise;
+    const connectPromise = client.connect();
+    mock.triggerOpen({ features: { ownedSubscriptions: true, binaryChunkingV1: chunked } });
+    await connectPromise;

-  const received: unknown[] = [];
-  const unsubscribe = client.on("fetch_agent_timeline_response", (msg) => {
-    received.push(msg);
-  });
+    const received: unknown[] = [];
+    const unsubscribe = client.on("fetch_agent_timeline_response", (msg) => {
+      received.push(msg);
+    });

-  mock.triggerMessage(
-    wrapSessionMessage({
-      type: "fetch_agent_timeline_response",
+    const command = chunked ? "x".repeat(50 * 1024 * 1024) : "pwd";
+    const { ChunkedTransport } = await import("@getpaseo/protocol/chunked-transport");
+    const sender = new ChunkedTransport({
+      frameBytes: 24 * 1024 * 1024,
+      send: (frame) => mock.triggerMessage(frame),
+      deliver: () => {},
+    });
+    sender.enabled = chunked;
+    await sender.send(
+      wrapSessionMessage({
+        type: "fetch_agent_timeline_response",
+        payload: {
+          requestId: "req-1",
+          agentId: "agent_cli",
+          agent: null,
+          direction: "tail",
+          projection: "projected",
+          epoch: "epoch-1",
+          reset: false,
+          staleCursor: false,
+          gap: false,
+          window: { minSeq: 1, maxSeq: 1, nextSeq: 2 },
+          startCursor: { epoch: "epoch-1", seq: 1 },
+          endCursor: { epoch: "epoch-1", seq: 1 },
+          hasOlder: false,
+          hasNewer: false,
+          entries: [
+            {
+              timestamp: "2026-02-08T20:20:00.000Z",
+              provider: "codex",
+              seqStart: 1,
+              seqEnd: 1,
+              sourceSeqRanges: [{ startSeq: 1, endSeq: 1 }],
+              collapsed: [],
+              item: {
+                type: "tool_call",
+                callId: "call_cli_snapshot",
+                name: "shell",
+                status: "running",
+                detail: {
+                  type: "shell",
+                  command,
+                },
+                error: null,
+              },
+            },
+          ],
+          error: null,
+        },
+      }),
+    );
+
+    unsubscribe();
+
+    expect(received).toHaveLength(1);
+    expect(received[0]).toMatchObject({
      payload: {
-        requestId: "req-1",
-        agentId: "agent_cli",
-        agent: null,
-        direction: "tail",
-        projection: "projected",
-        epoch: "epoch-1",
-        reset: false,
-        staleCursor: false,
-        gap: false,
-        window: { minSeq: 1, maxSeq: 1, nextSeq: 2 },
-        startCursor: { epoch: "epoch-1", seq: 1 },
-        endCursor: { epoch: "epoch-1", seq: 1 },
-        hasOlder: false,
-        hasNewer: false,
        entries: [
          {
-            timestamp: "2026-02-08T20:20:00.000Z",
-            provider: "codex",
-            seqStart: 1,
-            seqEnd: 1,
-            sourceSeqRanges: [{ startSeq: 1, endSeq: 1 }],
-            collapsed: [],
            item: {
              type: "tool_call",
-              callId: "call_cli_snapshot",
-              name: "shell",
              status: "running",
-              detail: {
-                type: "shell",
-                command: "pwd",
-              },
              error: null,
+              detail: { type: "shell", command },
            },
          },
        ],
-        error: null,
      },
-    }),
-  );
-
-  unsubscribe();
-
-  expect(received).toHaveLength(1);
-  expect(received[0]).toMatchObject({
-    payload: {
-      entries: [
-        {
-          item: {
-            type: "tool_call",
-            status: "running",
-            error: null,
-            detail: { type: "shell" },
-          },
-        },
-      ],
-    },
-  });
-  expect(logger.warn).not.toHaveBeenCalled();
-});
+    });
+    expect(logger.warn).not.toHaveBeenCalled();
+  },
+);

 test("rejects and logs a correlated response that violates the protocol schema", async () => {
  const mock = createMockTransport();
@@ -8471,3 +8483,302 @@ test("closes before admission when a protected-capable daemon is reached in lega
  expect(daemonReceived).toHaveLength(1);
  expect(JSON.parse(daemonReceived[0] as string)).toMatchObject({ type: "hello" });
 });
+
+test("uses the frame budget selected by an asynchronously opened transport", async () => {
+  const mock = createMockTransport();
+  mock.transport.maxFrameBytes = 1024;
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "dynamic-budget",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.transport.maxFrameBytes = 16;
+  mock.triggerOpen({ features: { binaryChunkingV1: true } });
+  await connecting;
+  client.sendHostFrame("route", new Uint8Array(100));
+  await vi.waitFor(() => expect(mock.sent.length).toBeGreaterThan(1));
+  expect(mock.sent.every((frame) => typeof frame !== "string" && frame.byteLength <= 16)).toBe(
+    true,
+  );
+});
+
+test.each([false, true])("routed sends wait for origin drain (binary=%s)", async (binary) => {
+  const mock = createMockTransport();
+  let drain!: () => void;
+  let blocked = false;
+  const send = mock.transport.send;
+  mock.transport.send = (frame) => {
+    send(frame);
+    if (blocked)
+      return new Promise<void>((resolve) => {
+        drain = resolve;
+      });
+  };
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "routed-drain",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.triggerOpen({ features: { binaryChunkingV1: true } });
+  await connecting;
+  blocked = true;
+  let finished = false;
+  const write = Promise.resolve(
+    client.sendHostFrame("route", binary ? new Uint8Array([1]) : "hello"),
+  ).then(() => {
+    finished = true;
+    return undefined;
+  });
+  await Promise.resolve();
+  expect(finished).toBe(false);
+  drain();
+  await write;
+  expect(finished).toBe(true);
+});
+
+test("a queued admission failure rejects its RPC without closing the client", async () => {
+  const mock = createMockTransport();
+  const send = mock.transport.send;
+  let block = false;
+  let drain!: () => void;
+  mock.transport.send = (frame) => {
+    if (!block) return send(frame);
+    if (typeof frame !== "string")
+      return new Promise<void>((resolve) => {
+        drain = resolve;
+      });
+    throw new Error("capacity");
+  };
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "queued-admission",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.triggerOpen();
+  await connecting;
+  block = true;
+  const first = client.sendHostFrame("route", new Uint8Array([1]));
+  const ping = client.ping({ timeoutMs: 1000 });
+  void ping.catch(() => {});
+  drain();
+  await first;
+  await expect(ping).rejects.toThrow("capacity");
+  expect(client.isConnected).toBe(true);
+});
+
+test("RPC deadlines remain active while a preceding frame waits for drain", async () => {
+  const mock = createMockTransport();
+  const send = mock.transport.send;
+  let blocked = false;
+  let drain!: () => void;
+  mock.transport.send = (frame) => {
+    if (!blocked) return send(frame);
+    if (typeof frame !== "string")
+      return new Promise<void>((resolve) => {
+        drain = resolve;
+      });
+  };
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "drain-deadline",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.triggerOpen();
+  await connecting;
+  blocked = true;
+  const first = client.sendHostFrame("route", new Uint8Array([1]));
+  try {
+    await expect(client.ping({ timeoutMs: 20 })).rejects.toThrow("Timeout waiting for message");
+    expect(client.isConnected).toBe(true);
+  } finally {
+    drain();
+    await first;
+  }
+});
+
+test.each([false, true])(
+  "event listener errors do not close the transport (chunked=%s)",
+  async (chunked) => {
+    const mock = createMockTransport();
+    const closed = vi.fn();
+    mock.transport.close = closed;
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "listener-error",
+      transportFactory: () => mock.transport,
+      reconnect: { enabled: false },
+    });
+    clients.push(client);
+    const connecting = client.connect();
+    mock.triggerOpen({ features: { binaryChunkingV1: chunked } });
+    await connecting;
+    const unsubscribe = client.subscribe(() => {
+      throw new Error("listener failed");
+    });
+    const text = wrapSessionMessage({
+      type: "agent_deleted",
+      payload: { agentId: "agent-test", requestId: "listener-test" },
+    });
+    const payload = new TextEncoder().encode(text);
+    const frame = chunked ? new Uint8Array([0x31, 1, 0, 3, ...payload]) : text;
+    expect(() => mock.triggerMessage(frame)).toThrow("listener failed");
+    expect(closed).not.toHaveBeenCalled();
+    unsubscribe();
+    const events: string[] = [];
+    client.subscribe((event) => {
+      events.push(event.type);
+    });
+    mock.triggerMessage(frame);
+    expect(events).toEqual(["agent_deleted"]);
+    await client.sendHostFrame("route", "still connected");
+    expect(client.isConnected).toBe(true);
+  },
+);
+
+test("malformed chunk metadata still closes the client transport", async () => {
+  const mock = createMockTransport();
+  const closed = vi.fn();
+  mock.transport.close = closed;
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "malformed-chunk",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.triggerOpen({ features: { binaryChunkingV1: true } });
+  await connecting;
+  mock.triggerMessage(new Uint8Array([0x31, 2, 0, 3, 65]));
+  expect(closed).toHaveBeenCalledWith(4003, "Invalid chunked transport");
+});
+
+test.each([FileTransferOpcode.FileBegin, FileTransferOpcode.FileChunk, FileTransferOpcode.FileEnd])(
+  "upload stops at a queued pre-write rejection (opcode=%s)",
+  async (opcode) => {
+    const mock = createMockTransport();
+    const send = mock.transport.send;
+    let drain!: () => void;
+    let blocked = false;
+    const attempts: number[] = [];
+    mock.transport.send = (frame) => {
+      if (typeof frame !== "string") {
+        const decoded = decodeFileTransferFrame(assertUint8Array(frame));
+        if (decoded) {
+          attempts.push(decoded.opcode);
+          if (decoded.opcode === opcode) throw new Error("upload capacity");
+        } else if (blocked)
+          return new Promise<void>((resolve) => {
+            drain = resolve;
+          });
+      }
+      return send(frame);
+    };
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "upload-admission",
+      transportFactory: () => mock.transport,
+      reconnect: { enabled: false },
+    });
+    clients.push(client);
+    const connecting = client.connect();
+    mock.triggerOpen();
+    await connecting;
+    blocked = true;
+    const first = client.sendHostFrame("route", new Uint8Array([1]));
+    const upload = client.uploadFile({
+      fileName: "file.bin",
+      mimeType: "application/octet-stream",
+      bytes: new Uint8Array([1, 2]),
+      chunkSize: 1,
+    });
+    let rejected: unknown;
+    void upload.catch((error) => {
+      rejected = error;
+    });
+    await new Promise<void>((resolve) => setTimeout(resolve, 0));
+    drain();
+    await first;
+    await vi.waitFor(() => expect(rejected).toMatchObject({ message: "upload capacity" }), {
+      timeout: 500,
+    });
+    expect(attempts.at(-1)).toBe(opcode);
+    expect(client.isConnected).toBe(true);
+  },
+);
+
+test.each(["latency", "dictation start", "dictation finish"])(
+  "queued control send rejection reaches its caller (%s)",
+  async (operation) => {
+    const mock = createMockTransport();
+    const send = mock.transport.send;
+    let blocked = false;
+    let drain!: () => void;
+    mock.transport.send = (frame) => {
+      if (!blocked) return send(frame);
+      if (typeof frame !== "string")
+        return new Promise<void>((resolve) => {
+          drain = resolve;
+        });
+      throw new Error("control capacity");
+    };
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "control-admission",
+      transportFactory: () => mock.transport,
+      reconnect: { enabled: false },
+    });
+    clients.push(client);
+    const connecting = client.connect();
+    mock.triggerOpen();
+    await connecting;
+    blocked = true;
+    const first = client.sendHostFrame("route", new Uint8Array([1]));
+    let result: Promise<unknown>;
+    if (operation === "latency") result = client.measureLatency({ timeoutMs: 1000 });
+    else if (operation === "dictation start")
+      result = client.startDictationStream("dictation", "pcm");
+    else result = client.finishDictationStream("dictation", 0);
+    const rejected = expect(result).rejects.toThrow("control capacity");
+    drain();
+    await first;
+    await rejected;
+    expect(client.isConnected).toBe(true);
+  },
+);
+
+test("routed channels inherit an origin without drain support", async () => {
+  const { createHostChannelTransport } = await import("./hosts/index.js");
+  const mock = createMockTransport();
+  mock.transport.supportsDrain = false;
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "unpaced-route",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connecting = client.connect();
+  mock.triggerOpen();
+  await connecting;
+  const route = createHostChannelTransport(
+    client,
+    "srv_destination",
+    "scope",
+    "route",
+  )({ url: "ws://route" });
+  expect(route.supportsDrain).toBe(false);
+  route.close();
+});
@@ -1,3 +1,7 @@
+import {
+  ChunkedTransport,
+  ChunkedTransportProtocolError,
+} from "@getpaseo/protocol/chunked-transport";
 import {
  HOST_ROUTE_OPCODE,
  encodeHostRouteFrame,
@@ -1266,7 +1270,7 @@ function toReasonCode(reason: string | null | undefined): string | null {
 }

 interface PendingSend {
-  send: () => void;
+  send: () => void | Promise<void>;
  resolve: () => void;
  reject: (error: Error) => void;
  timeoutHandle: ReturnType<typeof setTimeout>;
@@ -1366,6 +1370,7 @@ export class DaemonClient {
    failed: (error) => this.logger.error({ err: error }, "Subscription failed"),
  });
  private transport: DaemonTransport | null = null;
+  private chunkedTransport: ChunkedTransport | null = null;
  private helloAuth: HelloAuth;
  private transportCleanup: Array<() => void> = [];
  private rawMessageListeners: Set<(message: SessionOutboundMessage) => void> = new Set();
@@ -1560,6 +1565,17 @@ export class DaemonClient {
      });
      this.traceConnectionAttempt += 1;
      this.transport = transport;
+      this.chunkedTransport = new ChunkedTransport({
+        get supportsDrain() {
+          return transport.supportsDrain;
+        },
+        get frameBytes() {
+          return transport.maxFrameBytes ?? 32 * 1024 * 1024;
+        },
+        send: (frame) => transport.send(frame),
+        onFailure: () => transport.close(4003, "Transport send failed"),
+        deliver: (frame) => this.handleTransportMessage(frame),
+      });
      this.lastServerInfoMessage = null;
      this.authFailureReasonValue = null;

@@ -1666,7 +1682,16 @@ export class DaemonClient {
          });
        }),
        transport.onMessage((data) => {
-          if (this.transport === transport) this.handleTransportMessage(data);
+          if (this.transport !== transport) return;
+          const bytes = asUint8Array(data);
+          try {
+            if (typeof data === "string" || bytes)
+              this.chunkedTransport!.receive(typeof data === "string" ? data : bytes!);
+            else this.handleTransportMessage(data);
+          } catch (error) {
+            if (!(error instanceof ChunkedTransportProtocolError)) throw error;
+            transport.close(4003, "Invalid chunked transport");
+          }
        }),
      ];
    } catch (error) {
@@ -1867,9 +1892,9 @@ export class DaemonClient {
      })
    ).routeId;
  }
-  sendHostFrame(routeId: string, data: string | Uint8Array): void {
+  sendHostFrame(routeId: string, data: string | Uint8Array): Promise<void> {
    if (typeof data === "string") {
-      this.sendSessionMessageStrict({
+      return this.sendSessionMessageStrict({
        type: "hosts.route.frame.request",
        routeId,
        data,
@@ -1877,7 +1902,7 @@ export class DaemonClient {
      });
    } else {
      if (!this.isConnected || !this.transport) throw this.unavailableError();
-      this.sendTransportFrame(encodeHostRouteFrame(routeId, data));
+      return this.sendTransportFrame(encodeHostRouteFrame(routeId, data));
    }
  }
  private readonly hostFrameListeners = new Set<(frame: HostRouteFrame) => void>();
@@ -1935,6 +1960,11 @@ export class DaemonClient {
  // Message Subscription
  // ============================================================================

+  /** Drain capability inherited by transports routed through this connection. */
+  get supportsDrain(): boolean {
+    return this.transport?.supportsDrain !== false;
+  }
+
  subscribe(handler: DaemonEventHandler): () => void {
    this.eventListeners.add(handler);
    return () => {
@@ -2043,7 +2073,7 @@ export class DaemonClient {
    messageType: string,
    message: unknown,
    submitted?: () => void,
-  ): void {
+  ): Promise<void> {
    const isOpen =
      this.config.trace?.isEnabled() === true &&
      this.beginTraceSection("paseo.ws.message.outbound", {
@@ -2052,25 +2082,30 @@ export class DaemonClient {
        ...describeRequestIdentity(message),
      });
    try {
-      this.sendTransportFrame(JSON.stringify(message), submitted);
+      return this.sendTransportFrame(JSON.stringify(message), submitted);
    } finally {
      this.endTraceSection(isOpen);
    }
  }

-  private sendSessionPayload(payload: SessionInboundMessage): void {
-    this.sendJsonMessage("session", payload.type, { type: "session", message: payload }, () => {
-      if (!("requestId" in payload) || typeof payload.requestId !== "string") return;
-      for (const waiter of this.waiters) {
-        if (waiter.requestId === payload.requestId) waiter.submitted = true;
-      }
-    });
+  private sendSessionPayload(payload: SessionInboundMessage): Promise<void> {
+    return this.sendJsonMessage(
+      "session",
+      payload.type,
+      { type: "session", message: payload },
+      () => {
+        if (!("requestId" in payload) || typeof payload.requestId !== "string") return;
+        for (const waiter of this.waiters) {
+          if (waiter.requestId === payload.requestId) waiter.submitted = true;
+        }
+      },
+    );
  }

  private sendTransportFrame(
    frame: string | Uint8Array | ArrayBuffer,
    submitted?: () => void,
-  ): void {
+  ): Promise<void> {
    if (!this.transport) {
      throw this.unavailableError();
    }
@@ -2083,7 +2118,8 @@ export class DaemonClient {
    });
    try {
      submitted?.();
-      this.transport.send(frame);
+      const payload = typeof frame === "string" ? frame : asUint8Array(frame)!;
+      return this.chunkedTransport!.send(payload);
    } finally {
      this.endTraceSection(isOpen);
    }
@@ -2112,10 +2148,10 @@ export class DaemonClient {
    }
  }

-  private sendBinaryFrame(frame: Uint8Array): void {
+  private sendBinaryFrame(frame: Uint8Array): Promise<void> {
    if (!this.transport || this.connectionState.status !== "connected") {
      if (this.config.suppressSendErrors) {
-        return;
+        return Promise.resolve();
      }
      throw new Error(`Transport not connected (status: ${this.connectionState.status})`);
    }
@@ -2124,10 +2160,10 @@ export class DaemonClient {
        envelopeType: "binary",
        messageType: "binary",
      });
-      this.sendTransportFrame(frame);
+      return this.sendTransportFrame(frame);
    } catch (error) {
      if (this.config.suppressSendErrors) {
-        return;
+        return Promise.resolve();
      }
      throw error instanceof Error ? error : new Error(String(error));
    }
@@ -2142,7 +2178,7 @@ export class DaemonClient {
  private sendSessionMessageOrThrow(message: SessionInboundMessage): Promise<void> {
    return this.sendWhenConnected(() => {
      const payload = SessionInboundMessageSchema.parse(message);
-      this.sendSessionPayload(payload);
+      return this.sendSessionPayload(payload);
    });
  }

@@ -2151,13 +2187,12 @@ export class DaemonClient {
    return this.sendWhenConnected(() => undefined);
  }

-  private sendWhenConnected(send: () => void): Promise<void> {
+  private sendWhenConnected(send: () => void | Promise<void>): Promise<void> {
    const status = this.connectionState.status;

    // If connected, send immediately
    if (this.transport && status === "connected") {
-      send();
-      return Promise.resolve();
+      return Promise.resolve(send());
    }

    // If connecting, queue the message to be sent once connected
@@ -2196,8 +2231,7 @@ export class DaemonClient {
      clearTimeout(pending.timeoutHandle);
      try {
        if (this.transport && this.connectionState.status === "connected") {
-          pending.send();
-          pending.resolve();
+          void Promise.resolve(pending.send()).then(pending.resolve, pending.reject);
        } else {
          pending.reject(new DaemonConnectionError("Connection lost before message could be sent"));
        }
@@ -2253,19 +2287,17 @@ export class DaemonClient {
      { ...params.options, requestId: params.requestId },
    );

+    // The response deadline still applies while the transport waits for drain.
+    void promise.catch(() => undefined);
    try {
-      await this.sendSessionMessageOrThrow(wire.message);
+      const sent = this.sendSessionMessageOrThrow(wire.message);
+      const result = await Promise.race([promise, sent.then(() => promise)]);
+      if (result.kind === "error") throw result.error;
+      return result.value;
    } catch (error) {
      const err = error instanceof Error ? error : new Error(String(error));
      cancel(err);
-      void promise.catch(() => undefined);
      throw err;
-    }
-
-    try {
-      const result = await promise;
-      if (result.kind === "error") throw result.error;
-      return result.value;
    } finally {
      await wire.finish();
    }
@@ -2355,13 +2387,13 @@ export class DaemonClient {
    });
  }

-  private sendSessionMessageStrict(message: SessionInboundMessage): void {
+  private sendSessionMessageStrict(message: SessionInboundMessage): Promise<void> {
    if (!this.transport || this.connectionState.status !== "connected") {
      throw this.unavailableError();
    }
    const payload = SessionInboundMessageSchema.parse(message);
    try {
-      this.sendSessionPayload(payload);
+      return this.sendSessionPayload(payload);
    } catch (error) {
      throw error instanceof Error ? error : new Error(String(error));
    }
@@ -2559,15 +2591,16 @@ export class DaemonClient {
    };
    this.pingProbe = probe;

-    try {
-      this.sendJsonMessage("ping", "ping", { type: "ping" });
-    } catch (error) {
-      this.clearPingProbe();
+    const rejectSend = (error: unknown) => {
+      if (this.pingProbe !== probe) return;
      const sendError = error instanceof Error ? error : new Error(String(error));
-      if (probe.drivesLivenessFailure) {
-        this.recordLivenessFailure(sendError);
-      }
-      return Promise.reject(sendError);
+      this.rejectPingProbe(sendError);
+      if (probe.drivesLivenessFailure) this.recordLivenessFailure(sendError);
+    };
+    try {
+      void this.sendJsonMessage("ping", "ping", { type: "ping" }).catch(rejectSend);
+    } catch (error) {
+      rejectSend(error);
    }

    return promise;
@@ -4222,7 +4255,7 @@ export class DaemonClient {
  }

  async sendVoiceAudioChunk(audio: string, format: string, isLast = false): Promise<void> {
-    this.sendSessionMessage({ type: "voice_audio_chunk", audio, format, isLast });
+    return this.sendSessionMessageStrict({ type: "voice_audio_chunk", audio, format, isLast });
  }

  async startDictationStream(dictationId: string, format: string): Promise<void> {
@@ -4263,8 +4296,13 @@ export class DaemonClient {

    const cleanupError = new Error("Cancelled dictation start waiter");
    try {
-      this.sendSessionMessageStrict({ type: "dictation_stream_start", dictationId, format });
-      await Promise.race([ackPromise, errorPromise]);
+      const sent = this.sendSessionMessageStrict({
+        type: "dictation_stream_start",
+        dictationId,
+        format,
+      });
+      const response = Promise.race([ackPromise, errorPromise]);
+      await Promise.race([response, sent.then(() => response)]);
    } finally {
      ack.cancel(cleanupError);
      streamError.cancel(cleanupError);
@@ -4399,12 +4437,17 @@ export class DaemonClient {

    const cleanupError = new Error("Cancelled dictation finish waiter");
    try {
-      this.sendSessionMessageStrict({ type: "dictation_stream_finish", dictationId, finalSeq });
-      const firstOutcome = await Promise.race([
+      const sent = this.sendSessionMessageStrict({
+        type: "dictation_stream_finish",
+        dictationId,
+        finalSeq,
+      });
+      const response = Promise.race([
        finalOutcomePromise,
        errorOutcomePromise,
        finishAcceptedOutcomePromise,
      ]);
+      const firstOutcome = await Promise.race([response, sent.then(() => response)]);

      if (firstOutcome.kind === "final") {
        return firstOutcome.payload;
@@ -5320,8 +5363,10 @@ export class DaemonClient {
        return undefined;
      },
    );
+    const sendFrame = (frame: Uint8Array) =>
+      Promise.race([this.sendBinaryFrame(frame), responsePromise]);
    try {
-      this.sendBinaryFrame(
+      await sendFrame(
        encodeFileTransferFrame({
          opcode: FileTransferOpcode.FileBegin,
          requestId: resolvedRequestId,
@@ -5335,6 +5380,7 @@ export class DaemonClient {
        }),
      );

+      if (settled) return await responsePromise;
      const chunkSize = input.chunkSize ?? 128 * 1024;
      for (let offset = 0; offset < bytes.byteLength; offset += chunkSize) {
        // Native WebSocket.send encodes binary synchronously. Let rendering and
@@ -5344,7 +5390,7 @@ export class DaemonClient {
        if (this.transport !== uploadTransport || this.connectionState.status !== "connected") {
          throw new DaemonConnectionError("Connection changed during file upload");
        }
-        this.sendBinaryFrame(
+        await sendFrame(
          encodeFileTransferFrame({
            opcode: FileTransferOpcode.FileChunk,
            requestId: resolvedRequestId,
@@ -5353,7 +5399,7 @@ export class DaemonClient {
        );
      }

-      this.sendBinaryFrame(
+      await sendFrame(
        encodeFileTransferFrame({
          opcode: FileTransferOpcode.FileEnd,
          requestId: resolvedRequestId,
@@ -6763,6 +6809,8 @@ export class DaemonClient {
  }

  private disposeTransport(code = 1001, reason = "Reconnecting"): void {
+    this.chunkedTransport?.close();
+    this.chunkedTransport = null;
    this.owned.disconnected();
    this.providerSnapshotUpdates.clear();
    this.stopLivenessHeartbeat();
@@ -7232,15 +7280,6 @@ export class DaemonClient {
    probe.resolve(perfNow() - probe.startedAt);
  }

-  private clearPingProbe(): void {
-    const probe = this.pingProbe;
-    if (!probe) {
-      return;
-    }
-    this.pingProbe = null;
-    clearTimeout(probe.timeoutHandle);
-  }
-
  private rejectPingProbe(error: Error): void {
    const probe = this.pingProbe;
    if (!probe) {
@@ -7289,6 +7328,10 @@ export class DaemonClient {
    if (consumerMessage.type === "status") {
      const serverInfo = parseServerInfoStatusPayload(consumerMessage.payload);
      if (serverInfo) {
+        if (this.chunkedTransport)
+          this.chunkedTransport.enabled =
+            serverInfo.features?.binaryChunkingV1 === true &&
+            this.config.capabilities?.[CLIENT_CAPS.binaryChunkingV1] !== false;
        this.lastServerInfoMessage = serverInfo;
        this.destinationServerId = serverInfo.serverId;
        this.connectionFailure = undefined;
@@ -1,3 +1,4 @@
+import { MAX_HOST_CHANNEL_FRAME_BYTES } from "@getpaseo/protocol/binary-frames/index";
 import { safeRandomId } from "../daemon-client-transport-utils.js";
 import { DaemonClient } from "../daemon-client.js";
 import type { DaemonTransportFactory } from "../daemon-client-transport-types.js";
@@ -84,13 +85,17 @@ export function createHostChannelTransport(
      })
      .catch(close);
    return {
+      get supportsDrain() {
+        return origin.supportsDrain;
+      },
+      maxFrameBytes: MAX_HOST_CHANNEL_FRAME_BYTES,
      send(data) {
        if (closed || !routeId)
          throw Object.assign(new Error(`Host ${serverId} is offline`), {
            code: "host_offline",
            serverId,
          });
-        origin.sendHostFrame(
+        return origin.sendHostFrame(
          routeId,
          typeof data === "string" || data instanceof Uint8Array ? data : new Uint8Array(data),
        );
@@ -44,12 +44,14 @@ test("a slow consumer cannot exceed the shared byte budget and close releases re
  socket.pause();
  await ready;
  const frame = new Uint8Array(1024 * 1024);
-  for (let index = 0; index < 4; index++) transport.send(frame);
+  const writes = Array.from({ length: 4 }, () => transport.send(frame));
+  const drained = Promise.allSettled(writes);
  expect(budget.bufferedBytes).toBe(4 * 1024 * 1024);
  expect(() => transport.send(frame)).toThrow("Connected host buffer limit reached");
  expect(budget.bufferedBytes).toBeLessThanOrEqual(budget.limit);
  transport.close();
  await expect.poll(() => budget.bufferedBytes).toBe(0);
+  await drained;
 });
 test("direct connector preserves 25 MiB binary frames in both directions", async () => {
  const server = await endpoint();
@@ -65,12 +67,13 @@ test("direct connector preserves 25 MiB binary frames in both directions", async
  await ready;
  const bytes = new Uint8Array(25 * 1024 * 1024).fill(173);
  const echoed = once(socket, "message");
-  transport.send(bytes);
+  const sending = transport.send(bytes);
  const [sent, binary] = await echoed;
  expect(binary).toBe(true);
  expect(Buffer.from(sent as Uint8Array).equals(bytes)).toBe(true);
  socket.send(bytes);
  expect(Buffer.from(await received).equals(bytes)).toBe(true);
+  await sending;
 });

 import {
@@ -124,24 +127,29 @@ test("encrypted connector rejects overload synchronously and preserves the physi
  });
  await new Promise<void>((resolve) => transport.onOpen(resolve));
  await ready;
+  expect(transport.maxFrameBytes).toBeLessThan(32 * 1024 * 1024);
  peer.pause();
  const frame = new Uint8Array(1024 * 1024).fill(173);
  let rejected: unknown;
+  const writes: (void | Promise<void>)[] = [];
  for (let index = 0; index < 8; index++) {
    try {
-      transport.send(frame);
+      writes.push(transport.send(frame));
    } catch (error) {
      rejected = error;
      break;
    }
  }
+  const drained = Promise.allSettled(writes);
  expect(rejected).toMatchObject({ code: "resource_limit" });
  expect(budget.bufferedBytes).toBeLessThanOrEqual(budget.limit);
  await new Promise<void>((resolve) => setImmediate(resolve));
  expect(errors).toEqual([]);
  expect(closed).toBe(false);
-  transport.send("sibling control");
+  const sibling = transport.send("sibling control");
  peer.resume();
+  await drained;
+  await sibling;
  await expect.poll(() => received.includes("sibling control")).toBe(true);
  expect(received.filter((data) => data instanceof ArrayBuffer).length).toBeGreaterThan(0);
  expect(
@@ -172,9 +172,15 @@ export function createHostTransportFactory(
      close();
    });
    return {
+      get supportsDrain() {
+        return transport?.supportsDrain;
+      },
+      get maxFrameBytes() {
+        return transport?.maxFrameBytes;
+      },
      send(data) {
        if (closed || !transport) throw new Error("Host transport is unavailable");
-        transport.send(data);
+        return transport.send(data);
      },
      close,
      onOpen(handler) {
@@ -288,7 +288,7 @@ export type ToolCallDetail =
      subAgentType?: string;
      description?: string;
      childSessionId?: string;
-      log: string;
+      log?: string;
      actions?: Array<{
        index: number;
        toolName: string;
@@ -3,6 +3,11 @@ import { MAX_WEBSOCKET_MESSAGE_BYTES } from "../websocket-message-limit.js";
 export const HOST_ROUTE_OPCODE = 0x30;
 export const MAX_HOST_ROUTE_ID_BYTES = 256;
 export const MAX_HOST_ROUTE_HEADER_BYTES = 3 + MAX_HOST_ROUTE_ID_BYTES;
+// A logical host channel crosses the 32 MiB route admission boundary. Text can
+// expand sixfold when enclosed in JSON; binary adds the bounded route header.
+export const MAX_HOST_CHANNEL_FRAME_BYTES = Math.floor(
+  (32 * 1024 * 1024 - MAX_HOST_ROUTE_HEADER_BYTES) / 6,
+);
 export const MAX_ROUTED_PAYLOAD_BYTES = MAX_WEBSOCKET_MESSAGE_BYTES - MAX_HOST_ROUTE_HEADER_BYTES;
 export interface HostRouteFrame {
  routeId: string;
@@ -0,0 +1,392 @@
+import { describe, expect, it } from "vitest";
+import { ChunkedTransport } from "./chunked-transport.js";
+
+describe("chunked transport", () => {
+  it("delivers a large UTF-8 logical message once, preserving order", async () => {
+    const delivered: (string | Uint8Array)[] = [];
+    const receiver = new ChunkedTransport({
+      frameBytes: 17,
+      send: () => {},
+      deliver: (v) => delivered.push(v),
+    });
+    receiver.enabled = true;
+    const frames: (string | Uint8Array)[] = [];
+    const sender = new ChunkedTransport({
+      frameBytes: 17,
+      send: (v) => {
+        frames.push(v);
+        receiver.receive(v);
+      },
+      deliver: () => {},
+    });
+    sender.enabled = true;
+    const text = "🌍".repeat(100);
+    await sender.send(text);
+    expect(delivered).toEqual([text]);
+    expect(frames.length).toBeGreaterThan(1);
+    expect(frames.every((v) => v instanceof Uint8Array && v.byteLength <= 17)).toBe(true);
+  });
+});
+
+it("preserves binary kind and leaves legacy frames unchanged", async () => {
+  const delivered: (string | Uint8Array)[] = [];
+  const receiver = new ChunkedTransport({
+    frameBytes: 8,
+    send: () => {},
+    deliver: (v) => delivered.push(v),
+  });
+  const frames: (string | Uint8Array)[] = [];
+  const sender = new ChunkedTransport({
+    frameBytes: 8,
+    send: (v) => {
+      frames.push(v);
+      receiver.receive(v);
+    },
+    deliver: () => {},
+  });
+  const data = new Uint8Array(40).fill(5);
+  await sender.send(data);
+  expect(frames).toEqual([data]);
+  frames.length = 0;
+  sender.enabled = receiver.enabled = true;
+  await sender.send(data);
+  expect(frames).toHaveLength(10);
+  expect(delivered).toEqual([data, data]);
+});
+
+it("rejects malformed sequences and drops incomplete transfers on close", () => {
+  const delivered: unknown[] = [];
+  const receiver = new ChunkedTransport({
+    frameBytes: 8,
+    send: () => {},
+    deliver: (v) => delivered.push(v),
+  });
+  receiver.enabled = true;
+  receiver.receive(new Uint8Array([0x31, 1, 0, 1, 65]));
+  expect(() => receiver.receive("interrupted")).toThrow("Interrupted");
+  receiver.receive(new Uint8Array([0x31, 1, 0, 2, 66]));
+  expect(delivered).toEqual([]);
+});
+
+it("waits for drain before the next chunk and preserves logical ordering", async () => {
+  const frames: (string | Uint8Array)[] = [];
+  let drain!: () => void;
+  const sender = new ChunkedTransport({
+    frameBytes: 8,
+    send: (v) => {
+      frames.push(v);
+      if (frames.length === 1)
+        return new Promise<void>((resolve) => {
+          drain = resolve;
+        });
+    },
+    deliver: () => {},
+  });
+  sender.enabled = true;
+  const first = sender.send("abcdefghij");
+  const next = new Uint8Array([1, 2, 3, 4]);
+  const second = sender.send(next);
+  await Promise.resolve();
+  expect(frames).toHaveLength(1);
+  expect(sender.queuedByteLength).toBe(4);
+  drain();
+  await Promise.all([first, second]);
+  expect(frames).toHaveLength(4);
+  expect(frames[3]).toEqual(next);
+  expect(sender.queuedByteLength).toBe(0);
+});
+
+it.each([
+  [0x31, 2, 0, 3, 65],
+  [0x31, 1, 2, 3, 65],
+  [0x31, 1, 0, 4, 65],
+  [0x31, 1, 0, 2, 65],
+  [0x31, 1, 0, 1],
+])("rejects malformed chunk metadata %j", (...bytes) => {
+  const receiver = new ChunkedTransport({
+    frameBytes: 8,
+    send: () => {},
+    deliver: () => {
+      throw new Error("Unexpected delivery");
+    },
+  });
+  receiver.enabled = true;
+  expect(() => receiver.receive(new Uint8Array(bytes))).toThrow();
+});
+
+it("reconnect discards partial state and requires negotiation again", () => {
+  const delivered: unknown[] = [];
+  const create = () =>
+    new ChunkedTransport({ frameBytes: 8, send: () => {}, deliver: (v) => delivered.push(v) });
+  const old = create();
+  old.enabled = true;
+  old.receive(new Uint8Array([0x31, 1, 0, 1, 65]));
+  old.close();
+  old.receive(new Uint8Array([0x31, 1, 0, 2, 66]));
+  const fresh = create();
+  expect(fresh.enabled).toBe(false);
+  fresh.enabled = true;
+  fresh.receive(new Uint8Array([0x31, 1, 0, 3, 67]));
+  expect(delivered).toEqual(["C"]);
+});
+
+it("bounds logical messages waiting behind a blocked writer", async () => {
+  let drain!: () => void;
+  const transport = new ChunkedTransport({
+    frameBytes: 32 * 1024 * 1024,
+    send: () =>
+      new Promise<void>((resolve) => {
+        drain = resolve;
+      }),
+    deliver: () => {},
+  });
+  const first = transport.send(new Uint8Array(100 * 1024 * 1024));
+  const overflow = transport.send("one more byte");
+  try {
+    await expect(overflow).rejects.toThrow("queue");
+  } finally {
+    drain();
+    await first;
+  }
+});
+
+it("requests drain for chunks while ordinary frames keep the immediate write path", async () => {
+  const waits: boolean[] = [];
+  const transport = new ChunkedTransport({
+    frameBytes: 8,
+    send: (_frame, wait) => {
+      waits.push(wait);
+    },
+    deliver: () => {},
+  });
+  transport.enabled = true;
+  await transport.send("small");
+  await transport.send("abcdefghij");
+  expect(waits).toEqual([false, true, true, true]);
+});
+
+it("charges queued ASCII messages by their UTF-8 bytes", async () => {
+  let drain!: () => void;
+  let blocked = true;
+  const transport = new ChunkedTransport({
+    frameBytes: 32 * 1024 * 1024,
+    send: () => {
+      if (blocked) {
+        blocked = false;
+        return new Promise<void>((resolve) => {
+          drain = resolve;
+        });
+      }
+    },
+    deliver: () => {},
+  });
+  transport.enabled = true;
+  const first = transport.send(new Uint8Array([1]));
+  const text = "x".repeat(10 * 1024 * 1024);
+  const queued = Array.from({ length: 4 }, () => transport.send(text));
+  const settled = Promise.allSettled(queued);
+  expect(transport.queuedByteLength).toBe(40 * 1024 * 1024);
+  drain();
+  await first;
+  expect((await settled).map((result) => result.status)).toEqual([
+    "fulfilled",
+    "fulfilled",
+    "fulfilled",
+    "fulfilled",
+  ]);
+});
+
+it("notifies the socket owner when an awaited send overflows the queue", async () => {
+  let drain!: () => void;
+  const failures: unknown[] = [];
+  const transport = new ChunkedTransport({
+    frameBytes: 32 * 1024 * 1024,
+    send: () =>
+      new Promise<void>((resolve) => {
+        drain = resolve;
+      }),
+    deliver: () => {},
+    onFailure: (error) => {
+      failures.push(error);
+    },
+  });
+  const first = transport.send(new Uint8Array(100 * 1024 * 1024));
+  const overflow = transport.send("extra");
+  await expect(overflow).rejects.toThrow("queue");
+  drain();
+  await first;
+  expect(failures).toHaveLength(1);
+});
+
+it("bounds retained reassembly memory for many one-byte chunks", async () => {
+  const { spawnSync } = await import("node:child_process");
+  // Exercise the built package as a Node consumer; CI builds it before protocol tests.
+  const entry = new URL("../dist/chunked-transport.js", import.meta.url).href;
+  const result = spawnSync(
+    process.execPath,
+    [
+      "--expose-gc",
+      "--input-type=module",
+      "-e",
+      `
+    import { ChunkedTransport } from ${JSON.stringify(entry)};
+    let delivered = 0;
+    const receiver = new ChunkedTransport({ frameBytes: 8, send() {}, deliver(frame) { delivered = frame.byteLength; } });
+    receiver.enabled = true;
+    global.gc();
+    const before = process.memoryUsage().heapUsed;
+    receiver.receive(new Uint8Array([0x31, 1, 1, 1, 65]));
+    for (let index = 0; index < 300000; index++) receiver.receive(new Uint8Array([0x31, 1, 1, 0, 65]));
+    global.gc();
+    const growth = process.memoryUsage().heapUsed - before;
+    receiver.receive(new Uint8Array([0x31, 1, 1, 2, 66]));
+    console.log(JSON.stringify({ growth, delivered }));
+  `,
+    ],
+    { encoding: "utf8", timeout: 15000 },
+  );
+  expect(result.status, result.stderr).toBe(0);
+  const observed = JSON.parse(result.stdout);
+  expect(observed.delivered).toBe(300002);
+  expect(observed.growth).toBeLessThan(8 * 1024 * 1024);
+}, 20000);
+
+it.each(["ASCII", "中", "🌍", "\ud800", "\udc00", "\ud800x"])(
+  "accounts for queued UTF-8 text %j exactly",
+  async (text) => {
+    let drain!: () => void;
+    let blocked = true;
+    const transport = new ChunkedTransport({
+      frameBytes: 1024,
+      send: () => {
+        if (blocked) {
+          blocked = false;
+          return new Promise<void>((resolve) => {
+            drain = resolve;
+          });
+        }
+      },
+      deliver: () => {},
+    });
+    const first = transport.send(new Uint8Array([1]));
+    const second = transport.send(text);
+    expect(transport.queuedByteLength).toBe(new TextEncoder().encode(text).byteLength);
+    drain();
+    await Promise.all([first, second]);
+  },
+);
+
+it("notifies the owner once when an accepted writer fails", async () => {
+  const failures: unknown[] = [];
+  const error = new Error("write failed");
+  const transport = new ChunkedTransport({
+    frameBytes: 1024,
+    deliver: () => {},
+    onFailure: (failure) => {
+      failures.push(failure);
+    },
+    send: () => Promise.reject(error),
+  });
+  await expect(transport.send("hello", { waitForDrain: true })).rejects.toThrow("write failed");
+  expect(failures).toEqual([error]);
+  expect(() => transport.send("again")).toThrow("Transport closed");
+  expect(failures).toEqual([error]);
+});
+
+it.each([false, true])(
+  "a pre-write rejection preserves the sender (chunked=%s)",
+  async (chunked) => {
+    const failures: unknown[] = [];
+    let reject = true;
+    const transport = new ChunkedTransport({
+      frameBytes: 8,
+      deliver: () => {},
+      onFailure: (error) => {
+        failures.push(error);
+      },
+      send: () => {
+        if (reject) throw new Error("capacity");
+      },
+    });
+    transport.enabled = chunked;
+    expect(() => transport.send("abcdefghij")).toThrow("capacity");
+    expect(failures).toEqual([]);
+    reject = false;
+    await transport.send("sibling");
+  },
+);
+
+it("a queued pre-write rejection does not poison the next logical send", async () => {
+  let drain!: () => void;
+  const failures: unknown[] = [];
+  const delivered: string[] = [];
+  const transport = new ChunkedTransport({
+    frameBytes: 1024,
+    deliver: () => {},
+    onFailure: (error) => {
+      failures.push(error);
+    },
+    send: (frame) => {
+      if (frame === "blocked")
+        return new Promise<void>((resolve) => {
+          drain = resolve;
+        });
+      if (frame === "reject") throw new Error("capacity");
+      delivered.push(frame as string);
+    },
+  });
+  const first = transport.send("blocked");
+  const rejected = transport.send("reject");
+  const sibling = transport.send("sibling");
+  const results = Promise.allSettled([first, rejected, sibling]);
+  drain();
+  expect((await results).map((result) => result.status)).toEqual([
+    "fulfilled",
+    "rejected",
+    "fulfilled",
+  ]);
+  expect(delivered).toEqual(["sibling"]);
+  expect(failures).toEqual([]);
+});
+
+it.each([false, true])("delivery errors leave framing usable (chunked=%s)", async (chunked) => {
+  let fail = true;
+  const delivered: (string | Uint8Array)[] = [];
+  const transport = new ChunkedTransport({
+    frameBytes: 64,
+    send: () => {},
+    deliver: (frame) => {
+      if (fail) throw new Error("listener failed");
+      delivered.push(frame);
+    },
+  });
+  transport.enabled = chunked;
+  const frame = chunked ? new Uint8Array([0x31, 1, 0, 3, 65]) : "A";
+  expect(() => transport.receive(frame)).toThrow("listener failed");
+  fail = false;
+  transport.receive(frame);
+  expect(delivered).toEqual(["A"]);
+  await transport.send("still connected");
+});
+
+it("unpaced transports retain ordinary outbound admission and accept inbound chunks", async () => {
+  const frames: unknown[] = [];
+  const delivered: unknown[] = [];
+  const transport = new ChunkedTransport({
+    frameBytes: 8,
+    supportsDrain: false,
+    send: (frame) => {
+      frames.push(frame);
+      if (typeof frame === "string" && frame.length > 8) throw new Error("single frame limit");
+    },
+    deliver: (frame) => {
+      delivered.push(frame);
+    },
+  });
+  transport.enabled = true;
+  expect(() => transport.send("too large for one frame")).toThrow("single frame limit");
+  expect(frames).toEqual(["too large for one frame"]);
+  transport.receive(new Uint8Array([0x31, 1, 0, 3, 65]));
+  expect(delivered).toEqual(["A"]);
+  await transport.send("small");
+});
@@ -0,0 +1,214 @@
+import { MAX_WEBSOCKET_MESSAGE_BYTES } from "./websocket-message-limit.js";
+
+type Frame = string | Uint8Array;
+
+/** A malformed wire frame, distinct from a consumer delivery failure. */
+export class ChunkedTransportProtocolError extends Error {}
+// Reserved outside the application binary opcode space. Version, kind, flags follow.
+const OPCODE = 0x31;
+const HEADER = 4;
+
+/** Connection-scoped ordered framing, below serialization and routing, above encryption. */
+export class ChunkedTransport {
+  enabled = false;
+  private assembly: Uint8Array | undefined;
+  private size = 0;
+  private kind = 0;
+  private closed = false;
+  private pending: Promise<void> | undefined;
+  private queuedBytes = 0;
+  private activeBytes = 0;
+
+  constructor(
+    private readonly io: {
+      frameBytes: number;
+      supportsDrain?: boolean;
+      send: (frame: Frame, waitForDrain: boolean) => void | Promise<void>;
+      deliver: (frame: Frame) => void;
+      onFailure?: (error: unknown) => void;
+    },
+  ) {
+    if (io.frameBytes <= HEADER) throw new Error("Invalid transport frame budget");
+  }
+
+  /** Bytes waiting behind the active write; physical buffering owns the active frame. */
+  get queuedByteLength(): number {
+    return this.queuedBytes - this.activeBytes;
+  }
+  get isWriting(): boolean {
+    return this.pending !== undefined;
+  }
+
+  send(frame: Frame, options: { waitForDrain?: boolean; byteLength?: number } = {}): Promise<void> {
+    const byteLength = options.byteLength ?? frameByteLength(frame);
+    if (byteLength > MAX_WEBSOCKET_MESSAGE_BYTES) throw new Error("Logical message too large");
+    const chunk =
+      this.enabled && this.io.supportsDrain !== false && byteLength > this.io.frameBytes;
+    if (this.closed) throw new Error("Transport closed");
+    const write = () => {
+      if (this.closed) throw new Error("Transport closed");
+      this.activeBytes = byteLength;
+      // A synchronous rejection did not admit a frame. Only accepted writes can
+      // fail the connection; queued admission failures still belong to their sender.
+      const result = chunk
+        ? this.sendChunks(
+            typeof frame === "string" ? new TextEncoder().encode(frame) : frame,
+            typeof frame === "string",
+          )
+        : this.io.send(frame, options.waitForDrain === true);
+      if (!result) return;
+      return result.catch((error) => {
+        this.fail(error);
+        throw error;
+      });
+    };
+    if (this.queuedBytes + byteLength > MAX_WEBSOCKET_MESSAGE_BYTES) {
+      const error = new Error("Logical output queue exceeded its byte limit");
+      this.fail(error);
+      const rejected = Promise.reject<void>(error);
+      void rejected.catch(() => {});
+      return rejected;
+    }
+    this.queuedBytes += byteLength;
+    let result: void | Promise<void>;
+    try {
+      result = this.pending ? this.pending.then(write) : write();
+    } catch (error) {
+      this.queuedBytes -= byteLength;
+      this.activeBytes = 0;
+      throw error;
+    }
+    if (!result) {
+      this.queuedBytes -= byteLength;
+      this.activeBytes = 0;
+      return Promise.resolve();
+    }
+    const completion = Promise.resolve(result).finally(() => {
+      this.queuedBytes -= byteLength;
+      this.activeBytes = 0;
+    });
+    const tail = completion.then(
+      () => undefined,
+      () => undefined,
+    );
+    this.pending = tail;
+    void tail.then(() => {
+      if (this.pending === tail) this.pending = undefined;
+      return undefined;
+    });
+    return completion;
+  }
+
+  private sendChunks(bytes: Uint8Array, text: boolean): Promise<void> {
+    const capacity = this.io.frameBytes - HEADER;
+    const writeChunk = (offset: number) => {
+      if (this.closed) throw new Error("Transport closed");
+      const end = Math.min(bytes.byteLength, offset + capacity);
+      const wire = new Uint8Array(HEADER + end - offset);
+      wire.set([
+        OPCODE,
+        1,
+        text ? 0 : 1,
+        (offset === 0 ? 1 : 0) | (end === bytes.byteLength ? 2 : 0),
+      ]);
+      wire.set(bytes.subarray(offset, end), HEADER);
+      return this.io.send(wire, true);
+    };
+    const first = writeChunk(0);
+    return (async () => {
+      await first;
+      for (let offset = capacity; offset < bytes.byteLength; offset += capacity)
+        await writeChunk(offset);
+    })();
+  }
+
+  receive(frame: Frame): void {
+    if (this.closed) return;
+    let message: Frame | undefined;
+    try {
+      message = this.assemble(frame);
+    } catch (error) {
+      this.close();
+      throw new ChunkedTransportProtocolError(
+        error instanceof Error ? error.message : String(error),
+        { cause: error },
+      );
+    }
+    if (message !== undefined) this.io.deliver(message);
+  }
+
+  private assemble(frame: Frame): Frame | undefined {
+    if (typeof frame === "string" || frame[0] !== OPCODE) {
+      if (this.assembly) throw new Error("Interrupted chunked message");
+      return frame;
+    }
+    if (
+      !this.enabled ||
+      frame.length <= HEADER ||
+      frame[1] !== 1 ||
+      frame[2]! > 1 ||
+      (frame[3]! & ~3) !== 0
+    )
+      throw new Error("Invalid chunk header");
+    const start = (frame[3]! & 1) !== 0;
+    const end = (frame[3]! & 2) !== 0;
+    if (start === !!this.assembly) throw new Error("Invalid chunk sequence");
+    if (start) {
+      this.assembly = new Uint8Array(0);
+      this.kind = frame[2]!;
+      this.size = 0;
+    }
+    if (frame[2] !== this.kind) throw new Error("Chunk kind changed");
+    this.size += frame.length - HEADER;
+    if (this.size > MAX_WEBSOCKET_MESSAGE_BYTES) throw new Error("Logical message too large");
+    const payload = frame.subarray(HEADER);
+    if (this.assembly!.byteLength < this.size) {
+      const capacity = Math.min(
+        MAX_WEBSOCKET_MESSAGE_BYTES,
+        Math.max(this.size, this.assembly!.byteLength * 2, 16384),
+      );
+      const grown = new Uint8Array(capacity);
+      grown.set(this.assembly!.subarray(0, this.size - payload.byteLength));
+      this.assembly = grown;
+    }
+    this.assembly!.set(payload, this.size - payload.byteLength);
+    if (!end) return;
+    const data = this.assembly!.subarray(0, this.size);
+    this.assembly = undefined;
+    this.size = 0;
+    return this.kind === 0 ? new TextDecoder("utf-8", { fatal: true }).decode(data) : data.slice();
+  }
+
+  private fail(error: unknown): void {
+    if (this.closed) return;
+    this.close();
+    this.io.onFailure?.(error);
+  }
+
+  close(): void {
+    this.closed = true;
+    this.enabled = false;
+    this.assembly = undefined;
+    this.size = 0;
+  }
+}
+
+function frameByteLength(frame: Frame): number {
+  if (typeof frame !== "string") return frame.byteLength;
+  let bytes = 0;
+  for (let index = 0; index < frame.length; index++) {
+    const code = frame.charCodeAt(index);
+    if (code <= 0x7f) bytes++;
+    else if (code <= 0x7ff) bytes += 2;
+    else if (
+      code >= 0xd800 &&
+      code <= 0xdbff &&
+      frame.charCodeAt(index + 1) >= 0xdc00 &&
+      frame.charCodeAt(index + 1) <= 0xdfff
+    ) {
+      bytes += 4;
+      index++;
+    } else bytes += 3;
+  }
+  return bytes;
+}
@@ -1,4 +1,5 @@
 export const CLIENT_CAPS = {
+  binaryChunkingV1: "binary_chunking_v1",
  helloRejection: "hello_rejection",
  // COMPAT(ownedSubscriptions): added in v0.8.0, remove legacy ownership after 2027-03-09.
  ownedSubscriptions: "owned_subscriptions",
@@ -641,7 +641,9 @@ const ToolCallDetailPayloadSchema: z.ZodType<ToolCallDetail, unknown> = z.discri
      subAgentType: z.string().optional(),
      description: z.string().optional(),
      childSessionId: z.string().optional(),
-      log: z.string(),
+      // COMPAT(subagent-log): added in v0.14.1, remove after 2027-04-30. A sub-agent card is a
+      // launch marker; apps before v0.14.1 required `log`, so daemons still send it empty.
+      log: z.string().optional(),
      // Compat cruft for clients <= 0.1.65-beta.3 that required this field. Producers still
      // emit `[]`; nothing reads it. Drop the field (and the `[]` emissions) once those
      // clients are no longer in the field.
@@ -3832,6 +3834,7 @@ export const ServerInfoStatusPayloadSchema = z
        selectiveAgentTimeline: z.boolean().optional(),
        explicitEventSubscriptions: z.boolean().optional(),
        ownedSubscriptions: z.boolean().optional(),
+        binaryChunkingV1: z.boolean().optional(),
        workspaceSetupObservation: z.boolean().optional(),
        workspaceSortTimes: z.boolean().optional(),
        // COMPAT(canonicalSubmittedPrompts): added in v0.2.6, remove gate after 2027-01-30.
@@ -200,8 +200,8 @@ describe("wire schema compatibility", () => {
    });
  });

-  test("sub_agent tool-call payload still parses against the v0.1.65-beta.3 schema", () => {
-    const parsed = LegacySubAgentToolCallSchema.parse({
+  test("a sub-agent launch marker still parses against the v0.1.65-beta.3 schema", () => {
+    const card = {
      type: "tool_call",
      callId: "call-sub-agent-1",
      name: "Task",
@@ -212,12 +212,26 @@ describe("wire schema compatibility", () => {
        subAgentType: "Explore",
        description: "Inspect repository structure",
        childSessionId: "child-session-1",
-        log: "[Read] README.md",
+        log: "",
        actions: [],
      },
-    });
+    } as const;

-    expect(parsed.detail.actions).toEqual([]);
+    const parsed = LegacySubAgentToolCallSchema.parse(JSON.parse(JSON.stringify(card)));
+    expect(parsed.detail).toMatchObject({ log: "", actions: [] });
+    const { log: _log, ...withoutLog } = card.detail;
+    expect(LegacySubAgentToolCallSchema.safeParse({ ...card, detail: withoutLog }).success).toBe(
+      false,
+    );
+    expect(AgentTimelineItemPayloadSchema.parse({ ...card, detail: withoutLog })).toMatchObject({
+      detail: { type: "sub_agent", description: "Inspect repository structure" },
+    });
+    expect(
+      AgentTimelineItemPayloadSchema.parse({
+        ...card,
+        detail: { ...card.detail, log: "[Read] README.md" },
+      }),
+    ).toMatchObject({ detail: { log: "[Read] README.md" } });
  });

  test("old clients parse agent snapshots with rewind capabilities", () => {
@@ -247,7 +247,7 @@ second line'`,
    ]);
  });

-  it("keeps nested sub-agent logs beside the sub-agent that produced them", () => {
+  it("lists each sub-agent as its launch marker", () => {
    const timeline: AgentTimelineItem[] = [
      { type: "assistant_message", text: "Before first child." },
      toolCallItem({
@@ -257,7 +257,7 @@ second line'`,
          type: "sub_agent",
          subAgentType: "Child one",
          description: "First investigation",
-          log: "[Assistant] First child result.",
+          log: "",
        },
      }),
      { type: "assistant_message", text: "Between children." },
@@ -268,7 +268,7 @@ second line'`,
          type: "sub_agent",
          subAgentType: "Child two",
          description: "Second investigation",
-          log: "[Assistant] Second child result.",
+          log: "",
        },
      }),
      { type: "assistant_message", text: "After second child." },
@@ -279,10 +279,8 @@ second line'`,
    expect(result.split("\n")).toEqual([
      "[Assistant] Before first child.",
      "[Child one] First investigation",
-      "[Assistant] First child result.",
      "[Assistant] Between children.",
      "[Child two] Second investigation",
-      "[Assistant] Second child result.",
      "[Assistant] After second child.",
    ]);
  });
@@ -164,9 +164,6 @@ function curateProjectedActivityEntries(
          break;
        }
        entries.push(formatToolCallEntry(item, options));
-        if (item.detail.type === "sub_agent" && item.detail.log.trim()) {
-          entries.push(activityEntry(item.detail.log.trim()));
-        }
        break;
      }
      case "todo":
@@ -6,6 +6,7 @@ import { afterEach, describe, expect, test, vi } from "vitest";
 import { createTestLogger } from "../../test-utils/test-logger.js";
 import { AgentManager, type AgentManagerEvent } from "./agent-manager.js";
 import { AGENT_STREAM_COALESCE_DEFAULT_WINDOW_MS } from "./agent-stream-coalescer.js";
+import { limitAgentTimelineItemContent } from "./agent-timeline-content.js";
 import type { AgentTimelineRow } from "./agent-timeline-store-types.js";
 import { projectTimelineRows } from "./timeline-projection.js";
 import type {
@@ -31,7 +32,6 @@ import type {

 const COALESCE_WINDOW_MS = AGENT_STREAM_COALESCE_DEFAULT_WINDOW_MS;
 const BEFORE_COALESCE_WINDOW_MS = Math.max(COALESCE_WINDOW_MS - 1, 0);
-const TOOL_CALL_CONTENT_MAX_LENGTH = 64 * 1024;

 const TEST_CAPABILITIES: AgentCapabilityFlags = {
  supportsStreaming: false,
@@ -400,10 +400,7 @@ describe("target coalesced behavior", () => {
    try {
      const { agentId, session } = await createManagedSession(harness);
      const output = `${"a".repeat(512 * 1024)}${"z".repeat(512 * 1024)}`;
-      const expectedItem = toolCall({
-        status: "completed",
-        output: "a".repeat(TOOL_CALL_CONTENT_MAX_LENGTH),
-      });
+      const expectedItem = limitAgentTimelineItemContent(toolCall({ status: "completed", output }));

      session.pushEvent(timelineEvent(toolCall({ status: "completed", output })));
      await waitForSessionEventQueue();
@@ -425,10 +422,7 @@ describe("target coalesced behavior", () => {
    try {
      const { agentId } = await createManagedSession(harness);
      const output = `${"a".repeat(512 * 1024)}${"z".repeat(512 * 1024)}`;
-      const expectedItem = toolCall({
-        status: "completed",
-        output: "a".repeat(TOOL_CALL_CONTENT_MAX_LENGTH),
-      });
+      const expectedItem = limitAgentTimelineItemContent(toolCall({ status: "completed", output }));

      await harness.manager.appendTimelineItem(agentId, toolCall({ status: "completed", output }));

@@ -449,10 +443,7 @@ describe("target coalesced behavior", () => {
    try {
      const { agentId, session } = await createManagedSession(harness);
      const output = `${"a".repeat(512 * 1024)}${"z".repeat(512 * 1024)}`;
-      const expectedItem = toolCall({
-        status: "completed",
-        output: "a".repeat(TOOL_CALL_CONTENT_MAX_LENGTH),
-      });
+      const expectedItem = limitAgentTimelineItemContent(toolCall({ status: "completed", output }));
      session.setHistory([timelineEvent(toolCall({ status: "completed", output }))]);

      await harness.manager.hydrateTimelineFromProvider(agentId, { force: true });
@@ -470,10 +461,7 @@ describe("target coalesced behavior", () => {
    try {
      const { agentId } = await createManagedSession(harness);
      const output = `${"a".repeat(512 * 1024)}${"z".repeat(512 * 1024)}`;
-      const expectedItem = toolCall({
-        status: "completed",
-        output: "a".repeat(TOOL_CALL_CONTENT_MAX_LENGTH),
-      });
+      const expectedItem = limitAgentTimelineItemContent(toolCall({ status: "completed", output }));

      await harness.manager.emitLiveTimelineItem(
        agentId,
@@ -495,10 +483,9 @@ describe("target coalesced behavior", () => {
    try {
      const { agentId, session } = await createManagedSession(harness);
      const content = `${"a".repeat(512 * 1024)}${"z".repeat(512 * 1024)}`;
-      const expectedItem = toolCall({
-        status: "failed",
-        error: { content: "a".repeat(TOOL_CALL_CONTENT_MAX_LENGTH) },
-      });
+      const expectedItem = limitAgentTimelineItemContent(
+        toolCall({ status: "failed", error: { content } }),
+      );

      session.pushEvent(timelineEvent(toolCall({ status: "failed", error: { content } })));
      await waitForSessionEventQueue();
@@ -21,6 +21,7 @@ import {
 } from "./agent-manager.js";
 import { AgentStorage } from "./agent-storage.js";
 import { InMemoryAgentTimelineStore } from "./agent-timeline-store.js";
+import { limitAgentTimelineItemContent } from "./agent-timeline-content.js";
 import { toAgentPayload } from "./agent-projections.js";
 import { projectTimelineRows } from "./timeline-projection.js";
 import { getOpenAgentTabLabel, PARENT_AGENT_ID_LABEL } from "@getpaseo/protocol/agent-labels";
@@ -4592,7 +4593,7 @@ test("importProviderSession imports the selected session without listing and pub
  expect(manager.getTimeline(imported.id)).toEqual([
    { type: "user_message", text: "Trace provider imports" },
    { type: "assistant_message", text: "Done" },
-    {
+    limitAgentTimelineItemContent({
      type: "tool_call",
      callId: "large-shell-result",
      name: "shell",
@@ -4601,10 +4602,10 @@ test("importProviderSession imports the selected session without listing and pub
      detail: {
        type: "shell",
        command: "print output",
-        output: "x".repeat(64 * 1024),
+        output: "x".repeat(1024 * 1024),
        exitCode: 0,
      },
-    },
+    }),
  ]);
  expect(manager.listProviderSubagents(imported.id)).toEqual([
    expect.objectContaining({ id: "thread-child", title: "Imported child", status: "completed" }),
@@ -11957,10 +11958,7 @@ test("commits startup notices once on create and after restored history", async
      exitCode: 0,
    },
  };
-  const limitedToolOutput: AgentTimelineItem = {
-    ...toolOutput,
-    detail: { type: "shell", command: "print output", output: "x".repeat(64 * 1024), exitCode: 0 },
-  };
+  const limitedToolOutput = limitAgentTimelineItemContent(toolOutput);
  class NotifyingSession extends TestAgentSession {
    readonly initialTimeline = [{ item: notice, timestamp: "2026-09-22T00:00:00.000Z" }];
    override async *streamHistory(): AsyncGenerator<AgentStreamEvent> {
@@ -313,7 +313,10 @@ export type ToolCallDetail =
      subAgentType?: string;
      description?: string;
      childSessionId?: string;
-      log: string;
+      // COMPAT(subagent-log): added in v0.14.1, remove after 2027-04-30. Apps before v0.14.1
+      // require `log`; every producer sends it empty and carries the same tag. Optional here because
+      // protocol timeline items, where `log` is optional, flow into this type.
+      log?: string;
      actions?: Array<{
        index: number;
        toolName: string;
@@ -1,12 +1,30 @@
+import { AgentTimelineItemPayloadSchema } from "@getpaseo/protocol/messages";
 import { describe, expect, test } from "vitest";

+import type { AgentTimelineItem } from "./agent-sdk-types.js";
 import { limitAgentTimelineItemContent } from "./agent-timeline-content.js";

+function serializedBytes(item: AgentTimelineItem): number {
+  return Buffer.byteLength(JSON.stringify(item), "utf8");
+}
+
 describe("agent timeline content", () => {
+  test("returns an item within budget unchanged", () => {
+    const item: AgentTimelineItem = {
+      type: "tool_call",
+      callId: "small",
+      name: "Bash",
+      status: "completed",
+      error: null,
+      detail: { type: "shell", command: "ls", output: "x".repeat(60 * 1024) },
+    };
+    expect(limitAgentTimelineItemContent(item)).toBe(item);
+  });
+
  test.each([false, true])(
-    "preserves the exact UTF-16 prefix for oversized shell output (failed=%s)",
+    "cuts oversized shell output and keeps short fields whole (failed=%s)",
    (failed) => {
-      const text = "x".repeat(64 * 1024 - 1) + "🙂";
+      const text = "x".repeat(1024 * 1024) + "🙂";
      const item = limitAgentTimelineItemContent({
        type: "tool_call",
        callId: "large-shell",
@@ -15,45 +33,116 @@ describe("agent timeline content", () => {
        detail: { type: "shell", command: "echo large", output: text },
        error: failed ? { content: text } : null,
      });
-      expect(item).toEqual({
-        type: "tool_call",
+      expect(item).toMatchObject({
        callId: "large-shell",
        name: "Bash",
-        status: failed ? "failed" : "completed",
-        detail: { type: "shell", command: "echo large", output: text.slice(0, 64 * 1024) },
-        error: failed ? { content: text.slice(0, 64 * 1024) } : null,
+        detail: { type: "shell", command: "echo large" },
      });
+      if (item.type !== "tool_call" || item.detail.type !== "shell") throw new Error("shape");
+      expect(item.detail.output).toMatch(/^x+…\[truncated \d{3}\.\d KB\]$/);
+      expect(serializedBytes(item)).toBeLessThanOrEqual(64 * 1024);
    },
  );

-  test("marks truncated plain-text tool content within the content budget", () => {
-    const oversizedInput = "x".repeat(64 * 1024 + 1);
-
+  test("replaces an oversized data URL in an unknown tool result with a marker", () => {
+    const url = `data:image/jpeg;base64,${"A".repeat(14 * 1024 * 1024)}`;
    const item = limitAgentTimelineItemContent({
      type: "tool_call",
-      callId: "terminal-session-4242",
-      name: "terminal",
+      callId: "screenshot",
+      name: "node_repl.js",
      status: "completed",
      error: null,
      detail: {
-        type: "plain_text",
-        text: oversizedInput,
-        icon: "square_terminal",
+        type: "unknown",
+        input: { index: 1 },
+        output: { content: [{ type: "image", url }], note: "captured" },
      },
    });
-
-    expect(limitAgentTimelineItemContent(item)).toEqual(item);
    expect(item).toEqual({
      type: "tool_call",
-      callId: "terminal-session-4242",
-      name: "terminal",
+      callId: "screenshot",
+      name: "node_repl.js",
      status: "completed",
      error: null,
      detail: {
-        type: "plain_text",
-        text: "x".repeat(64 * 1024 - "\n\n[Content truncated]".length) + "\n\n[Content truncated]",
-        icon: "square_terminal",
+        type: "unknown",
+        input: { index: 1 },
+        output: { content: [{ type: "image", url: "…[truncated 14.0 MB]" }], note: "captured" },
      },
    });
  });
+
+  test("gives non-tool items a 256 KiB budget", () => {
+    const text = "a".repeat(10 * 1024 * 1024);
+    const item = limitAgentTimelineItemContent({ type: "assistant_message", text });
+    if (item.type !== "assistant_message") throw new Error("shape");
+    expect(item.text).toMatch(/^a+…\[truncated 9\.\d MB\]$/);
+    expect(item.text.length).toBeGreaterThan(200 * 1024);
+    expect(serializedBytes(item)).toBeLessThanOrEqual(256 * 1024);
+  });
+
+  test("bounds an item whose structure alone exceeds the budget", () => {
+    const item = limitAgentTimelineItemContent({
+      type: "tool_call",
+      callId: "many",
+      name: "query",
+      status: "completed",
+      error: null,
+      detail: { type: "unknown", input: null, output: Array.from({ length: 1_000_000 }, () => 1) },
+    });
+    if (item.type !== "tool_call" || item.detail.type !== "unknown") throw new Error("shape");
+    const output = item.detail.output as unknown[];
+    expect(output.length).toBeLessThan(1_000_000);
+    expect(output.every((value) => value === 1)).toBe(true);
+    expect(serializedBytes(item)).toBeLessThanOrEqual(64 * 1024);
+  });
+
+  test("keeps short strings whole and limits idempotently when an item has many strings", () => {
+    const callId = "3f2b8c1e-9a4d-4e6f-8b2a-1c3d5e7f9a0b";
+    const item = limitAgentTimelineItemContent({
+      type: "tool_call",
+      callId,
+      name: "mcp__search__files",
+      status: "completed",
+      error: null,
+      detail: {
+        type: "unknown",
+        input: { query: "useWorkspaceSomethingVeryDescriptive" },
+        output: Array.from(
+          { length: 10_000 },
+          (_, index) => `${String(index).padStart(5, "0")}${"p".repeat(28)}`,
+        ),
+      },
+    });
+    if (item.type !== "tool_call" || item.detail.type !== "unknown") throw new Error("shape");
+    expect(item.callId).toBe(callId);
+    expect(item.detail.input).toEqual({ query: "useWorkspaceSomethingVeryDescriptive" });
+    const output = item.detail.output as string[];
+    expect(output.length).toBeLessThan(10_000);
+    expect(output.every((path) => path.length === 33)).toBe(true);
+    expect(serializedBytes(item)).toBeLessThanOrEqual(64 * 1024);
+    expect(limitAgentTimelineItemContent(item)).toBe(item);
+  });
+
+  test("keeps a long typed array valid against the wire schema", () => {
+    const item = limitAgentTimelineItemContent({
+      type: "todo",
+      items: Array.from({ length: 20_000 }, (_, index) => ({
+        text: `Task ${index}`,
+        completed: false,
+      })),
+    });
+    if (item.type !== "todo") throw new Error("shape");
+    expect(item.items.length).toBeLessThan(20_000);
+    expect(AgentTimelineItemPayloadSchema.safeParse(item).success).toBe(true);
+    expect(serializedBytes(item)).toBeLessThanOrEqual(256 * 1024);
+  });
+
+  test("is stable on an already-limited item", () => {
+    const item = limitAgentTimelineItemContent({
+      type: "reasoning",
+      text: "r".repeat(1024 * 1024),
+    });
+    expect(limitAgentTimelineItemContent(item)).toBe(item);
+  });
 });
@@ -1,9 +1,19 @@
 import type { AgentTimelineItem } from "./agent-sdk-types.js";
 import type { JsonValue } from "@getpaseo/protocol/agent-types";

-const TOOL_CALL_CONTENT_MAX_LENGTH = 64 * 1024;
 export const PLUGIN_TIMELINE_DATA_MAX_BYTES = 64 * 1024;

+// One timeline fetch sends its entries in one WebSocket message, so every item must stay small.
+// Budgets count UTF-16 units plus a fixed cost per node; neither is exact JSON bytes. They bound
+// long strings and long arrays, not wide objects (every entry is kept) or multi-byte text.
+const TOOL_CALL_BUDGET = 64 * 1024;
+const ITEM_BUDGET = 256 * 1024;
+const NODE_COST = 8;
+const MARKER_COST = 32;
+// Ids, names, paths and queries stay whole, so an item keeps its identity across passes.
+const SHORT_STRING = 1024;
+const MAX_DEPTH = 64;
+
 export function assertPluginTimelineDataSize(data: JsonValue): void {
  const serializedBytes = Buffer.byteLength(JSON.stringify(data), "utf8");
  if (serializedBytes > PLUGIN_TIMELINE_DATA_MAX_BYTES) {
@@ -17,66 +27,119 @@ function retainTextPrefix(text: string, length: number): string {
  return Buffer.from(text.slice(0, length), "utf16le").toString("utf16le");
 }

-function limitFailedShellError(item: AgentTimelineItem): AgentTimelineItem {
-  if (
-    item.type !== "tool_call" ||
-    item.detail.type !== "shell" ||
-    item.status !== "failed" ||
-    typeof item.error !== "object" ||
-    item.error === null ||
-    !("content" in item.error) ||
-    typeof item.error.content !== "string" ||
-    item.error.content.length <= TOOL_CALL_CONTENT_MAX_LENGTH
-  ) {
-    return item;
-  }
-  return {
-    ...item,
-    error: {
-      ...item.error,
-      content: retainTextPrefix(item.error.content, TOOL_CALL_CONTENT_MAX_LENGTH),
-    },
-  };
+function formatSize(units: number): string {
+  if (units < 1024) return `${units} B`;
+  if (units < 1024 * 1024) return `${(units / 1024).toFixed(1)} KB`;
+  return `${(units / (1024 * 1024)).toFixed(1)} MB`;
 }

-function limitPlainText(item: AgentTimelineItem): AgentTimelineItem {
-  if (
-    item.type !== "tool_call" ||
-    item.detail.type !== "plain_text" ||
-    typeof item.detail.text !== "string" ||
-    item.detail.text.length <= TOOL_CALL_CONTENT_MAX_LENGTH
-  ) {
-    return item;
-  }
-  const notice = "\n\n[Content truncated]";
-  return {
-    ...item,
-    detail: {
-      ...item.detail,
-      text:
-        retainTextPrefix(item.detail.text, TOOL_CALL_CONTENT_MAX_LENGTH - notice.length) + notice,
-    },
-  };
+function truncatedMarker(units: number): string {
+  return `…[truncated ${formatSize(units)}]`;
 }

+interface ItemSize {
+  nodeCost: number;
+  stringLengths: number[];
+  tooDeep: boolean;
+}
+
+function measure(value: unknown, depth: number, size: ItemSize): void {
+  size.nodeCost += NODE_COST;
+  if (depth > MAX_DEPTH) {
+    size.tooDeep = true;
+  } else if (typeof value === "string") {
+    size.stringLengths.push(value.length);
+  } else if (Array.isArray(value)) {
+    for (const element of value) measure(element, depth + 1, size);
+  } else if (typeof value === "object" && value !== null) {
+    for (const [key, child] of Object.entries(value)) {
+      size.nodeCost += key.length;
+      measure(child, depth + 1, size);
+    }
+  }
+}
+
+/** The largest per-string length that keeps all strings, once cut, within `available`. */
+function findStringCap(lengths: readonly number[], available: number): number {
+  let low = 0;
+  let high = 0;
+  for (const length of lengths) high = Math.max(high, length);
+  while (low < high) {
+    const cap = Math.ceil((low + high) / 2);
+    let total = 0;
+    for (const length of lengths) total += Math.min(length, cap);
+    if (total <= available) low = cap;
+    else high = cap - 1;
+  }
+  return low;
+}
+
+interface CutState {
+  stringCap: number;
+  remaining: number;
+}
+
+function cutString(text: string, cap: number): string {
+  if (text.length <= cap) return text;
+  // A partial data URL is useless to every reader, so drop it whole.
+  if (text.startsWith("data:")) return truncatedMarker(text.length);
+  return retainTextPrefix(text, cap) + truncatedMarker(text.length - cap);
+}
+
+function cut(value: unknown, depth: number, state: CutState): unknown {
+  state.remaining -= NODE_COST;
+  if (depth > MAX_DEPTH) return "…[truncated]";
+  if (typeof value === "string") {
+    const text = cutString(value, state.stringCap);
+    state.remaining -= text.length;
+    return text;
+  }
+  if (Array.isArray(value)) {
+    let changed = false;
+    const output: unknown[] = [];
+    for (const element of value) {
+      const remainingBefore = state.remaining;
+      const next = cut(element, depth + 1, state);
+      if (state.remaining < 0) {
+        // Drop this and later elements. A marker element would break typed arrays.
+        state.remaining = remainingBefore;
+        changed = true;
+        break;
+      }
+      changed ||= next !== element;
+      output.push(next);
+    }
+    return changed ? output : value;
+  }
+  if (typeof value === "object" && value !== null) {
+    let changed = false;
+    const output: Record<string, unknown> = {};
+    for (const [key, child] of Object.entries(value)) {
+      state.remaining -= key.length;
+      const next = cut(child, depth + 1, state);
+      changed ||= next !== child;
+      output[key] = next;
+    }
+    return changed ? output : value;
+  }
+  return value;
+}
+
+/** Returns the item itself when it fits its budget; otherwise a copy with its largest strings cut. */
 export function limitAgentTimelineItemContent(item: AgentTimelineItem): AgentTimelineItem {
-  item = limitFailedShellError(item);
-  item = limitPlainText(item);
-  if (
-    item.type !== "tool_call" ||
-    item.detail.type !== "shell" ||
-    typeof item.detail.output !== "string"
-  ) {
-    return item;
-  }
-  if (item.detail.output.length <= TOOL_CALL_CONTENT_MAX_LENGTH) {
-    return item;
-  }
-  return {
-    ...item,
-    detail: {
-      ...item.detail,
-      output: retainTextPrefix(item.detail.output, TOOL_CALL_CONTENT_MAX_LENGTH),
-    },
-  };
+  const budget = item.type === "tool_call" ? TOOL_CALL_BUDGET : ITEM_BUDGET;
+  const size: ItemSize = { nodeCost: 0, stringLengths: [], tooDeep: false };
+  measure(item, 0, size);
+  let stringTotal = 0;
+  for (const length of size.stringLengths) stringTotal += length;
+  if (!size.tooDeep && size.nodeCost + stringTotal <= budget) return item;
+
+  // Strings get what structure leaves, but at least half the budget, less a margin for JSON
+  // escaping. Arrays drop the elements that do not fit, which bounds items whose short strings
+  // or structure alone are too big.
+  const markerCost =
+    MARKER_COST * size.stringLengths.filter((length) => length > SHORT_STRING).length;
+  const available = (budget * 15) / 16 - Math.min(size.nodeCost, budget / 2) - markerCost;
+  const stringCap = Math.max(SHORT_STRING, findStringCap(size.stringLengths, available));
+  return cut(item, 0, { stringCap, remaining: budget }) as AgentTimelineItem;
 }
@@ -181,6 +181,20 @@ describe("projected timeline retention", () => {
      },
    ]);
  });
+
+  it("serves a merged assistant message within the item budget", () => {
+    const store = new InMemoryAgentTimelineStore();
+    store.initialize("agent", { epoch: "e" });
+    const chunk = "a".repeat(200 * 1024);
+    for (let index = 0; index < 10; index++) {
+      store.append("agent", { type: "assistant_message", messageId: "m", text: chunk });
+    }
+    const [row] = store.fetch("agent", { limit: 1 }).rows;
+    expect(row).toMatchObject({ seqStart: 1, seqEnd: 10 });
+    expect(row.item).toMatchObject({ type: "assistant_message", messageId: "m" });
+    expect(Buffer.byteLength(JSON.stringify(row.item))).toBeLessThanOrEqual(256 * 1024);
+    expect(store.getLastAssistantMessage("agent")).toHaveLength(10 * chunk.length);
+  });
 });

 describe("projected sequence ownership", () => {
@@ -1,5 +1,6 @@
 import { randomUUID } from "node:crypto";
 import { TimelineProjection, type ProjectedTimelineRow } from "./timeline-projection.js";
+import { limitAgentTimelineItemContent } from "./agent-timeline-content.js";
 import type { AgentTimelineItem } from "./agent-sdk-types.js";
 import type {
  AgentTimelineFetchOptions,
@@ -120,7 +121,12 @@ export class InMemoryAgentTimelineStore {
      hasNewer: page.hasNewer,
      startSeq: page.startSeq,
      endSeq: page.endSeq,
-      rows: page.entries.map((entry) => Object.assign({ seq: entry.seqEnd }, entry)),
+      // Stored rows are already within budget; this bounds assistant and reasoning merges.
+      rows: page.entries.map((entry) =>
+        Object.assign({ seq: entry.seqEnd }, entry, {
+          item: limitAgentTimelineItemContent(entry.item),
+        }),
+      ),
    };
  }

@@ -80,7 +80,7 @@ describe("ProviderSubagentStore", () => {
    const [row] = subagents.fetchTimeline("parent-a", "child-1").rows;
    expect(row?.item).toMatchObject({
      type: "tool_call",
-      detail: { type: "shell", output: "x".repeat(64 * 1024) },
+      detail: { type: "shell", output: expect.stringMatching(/^x+…\[truncated \d+\.\d KB\]$/) },
    });
  });

@@ -466,13 +466,13 @@ describe("background Claude subagents", () => {
        type: "sub_agent",
        subAgentType: "general-purpose",
        description: "Count files here",
-        log: "[Bash] ls -1",
+        log: "",
      },
    });
  });

  test.each(["before", "after"])(
-    "keeps one logged Task card when child tools start %s the parent finishes",
+    "keeps one Task card when child tools start %s the parent finishes",
    async (timing) => {
      // A child can stream across the main session's turn boundary. Claude opens the next
      // main-session turn with system/init; bare child frames do not open a turn.
@@ -605,7 +605,7 @@ describe("background Claude subagents", () => {
          type: "sub_agent",
          subAgentType: "general-purpose",
          description: "Count files here",
-          log: "[Bash] ls -1",
+          log: "",
        },
      });
    },
@@ -737,7 +737,7 @@ describe("ClaudeAgentSession persisted subagent replay", () => {
    );
  }, 120_000);

-  test("limits retained child shell output to the timeline's existing content limit", async () => {
+  test("limits retained child shell output to the timeline item budget", async () => {
    const output = "x".repeat(128 * 1024);
    writeSession({
      parentLines: [taskToolUse(), taskToolResult()],
@@ -782,7 +782,10 @@ describe("ClaudeAgentSession persisted subagent replay", () => {
        type: "timeline",
        id: TOOL_USE_ID,
        item: expect.objectContaining({
-          detail: expect.objectContaining({ type: "shell", output: output.slice(0, 64 * 1024) }),
+          detail: expect.objectContaining({
+            type: "shell",
+            output: expect.stringMatching(/^x+…\[truncated \d+\.\d KB\]$/),
+          }),
        }),
      }),
    ]);
@@ -273,7 +273,7 @@ describe("ClaudeAgentSession sub-agent sidechain updates", () => {
    queryFactory.mockReset();
  });

-  test("accumulates lightweight sub_agent detail and preserves callId lifecycle collapse", async () => {
+  test("labels the Task card from its input and preserves callId lifecycle collapse", async () => {
    const session = await new ClaudeAgentClient({
      logger,
      queryFactory,
@@ -307,9 +307,7 @@ describe("ClaudeAgentSession sub-agent sidechain updates", () => {

    expect(latest.detail.subAgentType).toBe("Explore");
    expect(latest.detail.description).toBe("Inspect repository structure");
-    expect(latest.detail.log).toContain("[Read] README.md");
-    expect(latest.detail.log).toContain("[Edit] src/index.ts");
-    expect(latest.detail.log).not.toContain("VERY_LARGE_OLD_STRING");
+    expect(latest.detail.log).toBe("");

    const rows: AgentTimelineRow[] = timelineToolCalls.map((item, index) => ({
      seq: index + 1,
@@ -396,10 +394,7 @@ describe("ClaudeAgentSession sub-agent sidechain updates", () => {
      .map((event) => event.item)
      .at(-1);

-    expect(latestSubAgentUpdate?.detail).toMatchObject({
-      type: "sub_agent",
-      log: expect.stringContaining("[Read] README.md"),
-    });
+    expect(latestSubAgentUpdate?.detail).toMatchObject({ type: "sub_agent", log: "" });
  });

  test("routes a resumed SendMessage sidechain to the original child without a second Task card", async () => {
@@ -553,7 +548,7 @@ describe("ClaudeAgentSession sub-agent sidechain updates", () => {
    ).toMatchObject({ type: "upsert", id: "task-tail-1", status: "failed" });
  });

-  test("tails sub-agent actions instead of dropping latest entries at cap", async () => {
+  test("keeps the Task card the same size while the child runs", async () => {
    queryFactory.mockImplementation(() => buildQueryMock(buildTailScenarioEvents(205)));

    const session = await new ClaudeAgentClient({
@@ -568,24 +563,27 @@ describe("ClaudeAgentSession sub-agent sidechain updates", () => {
    const events = await collectUntilTerminal(streamSession(session, "delegate work"));
    await session.close();

-    const timelineToolCalls = events
-      .filter(
-        (event): event is Extract<AgentStreamEvent, { type: "timeline" }> =>
-          event.type === "timeline" && event.item.type === "tool_call",
+    const runningCards = events
+      .flatMap((event) =>
+        event.type === "timeline" &&
+        event.item.type === "tool_call" &&
+        event.item.callId === "task-tail-1" &&
+        event.item.status === "running" &&
+        event.item.detail.type === "sub_agent"
+          ? [event.item]
+          : [],
      )
-      .map((event) => event.item)
-      .filter((item) => item.callId === "task-tail-1");
-    const subAgentUpdates = timelineToolCalls.filter((item) => item.detail.type === "sub_agent");
-    const latest = subAgentUpdates[subAgentUpdates.length - 1];
-    expect(latest).toBeDefined();
-    if (!latest || latest.detail.type !== "sub_agent") {
-      throw new Error("expected sub_agent detail");
-    }
+      .map((item) => JSON.stringify(item));
+    expect(runningCards).toHaveLength(1);

-    expect(latest.detail.log).not.toContain("[Read] file-1.md");
-    expect(latest.detail.log).not.toContain("[Read] file-5.md");
-    expect(latest.detail.log).toContain("[Read] file-6.md");
-    expect(latest.detail.log).toContain("[Read] file-205.md");
+    const childToolCalls = events.filter(
+      (event) =>
+        event.type === "provider_subagent" &&
+        event.event.type === "timeline" &&
+        event.event.id === "task-tail-1" &&
+        event.event.item.type === "tool_call",
+    );
+    expect(childToolCalls).toHaveLength(205);
  });

  test("keeps a long main-thread tool call out of the subagents track", async () => {
@@ -4667,7 +4667,7 @@ class ClaudeAgentSession implements AgentSession {
  /**
   * The Task card in the parent transcript, built from the declaration.
   *
-   * The sidechain tracker also emits this card, enriched with the child's action log, and the two
+   * The sidechain tracker also emits this card when it first sees the child, and the two
   * collapse on the shared tool-call id. Emitting it at declaration matters because a
   * backgrounded subagent produces no sidechain frames at all — verified on the wire — so the
   * tracker never runs for one and its card would otherwise stay an unlabeled "Task".
@@ -6276,6 +6276,7 @@ function buildClaudeSubagentCardDetail(
    type: "sub_agent",
    ...(facts.title ? { subAgentType: facts.title } : {}),
    ...(facts.description ? { description: facts.description } : {}),
+    // COMPAT(subagent-log): remove after 2027-04-30.
    log: "",
    actions: [],
  };
@@ -4,7 +4,7 @@ import type { SDKMessage } from "@anthropic-ai/claude-agent-sdk";
 import { ClaudeSidechainTracker } from "./sidechain-tracker.js";

 describe("ClaudeSidechainTracker", () => {
-  it("retains a background child's actions across the parent finishing", () => {
+  it("keeps a background child's card across the parent finishing", () => {
    const tracker = new ClaudeSidechainTracker({
      getToolInput: () => ({ subagent_type: "general-purpose", description: "List files" }),
      isDescriptorOwnedElsewhere: () => true,
@@ -15,27 +15,67 @@ describe("ClaudeSidechainTracker", () => {
        parent_tool_use_id: "task-1",
        message: { content: [{ type: "tool_use", id, name: "Bash", input: { command } }] },
      }) as unknown as SDKMessage;
-    tracker.handleMessage(action("ls", "ls -1"), "task-1");
+    const parentCards = (events: ReturnType<typeof tracker.handleMessage>) =>
+      events.filter((event) => event.type === "timeline");
+    const childCallIds = (events: ReturnType<typeof tracker.handleMessage>) =>
+      events.flatMap((event) =>
+        event.type === "provider_subagent" &&
+        event.event.type === "timeline" &&
+        event.event.item.type === "tool_call"
+          ? [event.event.item.callId]
+          : [],
+      );
+
+    expect(parentCards(tracker.handleMessage(action("ls", "ls -1"), "task-1"))).toHaveLength(1);
    expect(tracker.finishAll("completed")).toEqual([]);
-    const events = tracker.handleMessage(action("pwd", "pwd"), "task-1");
-    expect(events).toContainEqual(
-      expect.objectContaining({
-        type: "timeline",
-        item: expect.objectContaining({
-          detail: expect.objectContaining({ log: "[Bash] ls -1\n[Bash] pwd" }),
-        }),
-      }),
-    );
+    const afterFinish = tracker.handleMessage(action("pwd", "pwd"), "task-1");
+    expect(parentCards(afterFinish)).toEqual([]);
+    expect(childCallIds(afterFinish)).toEqual(["pwd"]);
+
    tracker.delete("task-1");
    const next = tracker.handleMessage(action("next", "ls"), "task-1");
-    expect(next).toContainEqual(
-      expect.objectContaining({
-        type: "timeline",
-        item: expect.objectContaining({
-          detail: expect.objectContaining({ log: "[Bash] ls" }),
-        }),
-      }),
-    );
+    expect(parentCards(next)).toHaveLength(1);
+    expect(childCallIds(next)).toEqual(["next"]);
+  });
+
+  it("shows a streamed child tool call's input once the assistant message brings it", () => {
+    const tracker = new ClaudeSidechainTracker({ getToolInput: () => null });
+    const frames = [
+      {
+        type: "stream_event",
+        parent_tool_use_id: "task-1",
+        event: {
+          type: "content_block_start",
+          index: 0,
+          content_block: { type: "tool_use", id: "bash-1", name: "Bash", input: {} },
+        },
+      },
+      {
+        type: "assistant",
+        parent_tool_use_id: "task-1",
+        message: {
+          content: [
+            { type: "tool_use", id: "bash-1", name: "Bash", input: { command: "echo child" } },
+          ],
+        },
+      },
+    ] as unknown as SDKMessage[];
+
+    const childCards = frames
+      .flatMap((frame) => tracker.handleMessage(frame, "task-1"))
+      .flatMap((event) =>
+        event.type === "provider_subagent" &&
+        event.event.type === "timeline" &&
+        event.event.item.type === "tool_call"
+          ? [event.event.item]
+          : [],
+      );
+
+    expect(childCards.at(-1)).toMatchObject({
+      callId: "bash-1",
+      status: "running",
+      detail: { type: "shell", command: "echo child" },
+    });
  });

  it("uses Claude's native agent name for the provider subagent title", () => {
@@ -5,7 +5,6 @@ import {
  mapClaudeFailedToolCall,
  mapClaudeRunningToolCall,
 } from "./tool-call-mapper.js";
-import { buildToolCallDisplayModel } from "@getpaseo/protocol/tool-call-display";
 import {
  isClaudeSubagentHandbackToolName,
  readClaudeSubagentHandback,
@@ -20,21 +19,17 @@ interface ClaudeContentChunk {

 type ClaudeToolCallItem = Extract<AgentTimelineItem, { type: "tool_call" }>;

-interface SubAgentActionEntry {
-  index: number;
+interface SubAgentChildCall {
  toolName: string;
  input: unknown;
-  summary?: string;
 }

 interface SubAgentActivityState {
  name?: string;
  subAgentType?: string;
  description?: string;
-  actions: SubAgentActionEntry[];
-  actionKeys: string[];
-  nextActionIndex: number;
-  actionIndexByKey: Map<string, number>;
+  /** The child's tool calls awaiting results, which carry no input of their own. */
+  runningCalls: Map<string, SubAgentChildCall>;
  completedActionKeys: Set<string>;
 }

@@ -44,7 +39,6 @@ interface SubAgentActionCandidate {
  input: unknown;
 }

-const MAX_SUB_AGENT_LOG_ENTRIES = 200;
 const MAX_SUB_AGENT_SUMMARY_CHARS = 160;

 function readTrimmedString(value: unknown): string | undefined {
@@ -79,8 +73,7 @@ export class ClaudeSidechainTracker {
    needsSyntheticParentToolCard?: (toolUseId: string) => boolean;
    /**
     * The parent's tool call once Claude has answered it. A background child streams its frames
-     * after that answer, so its card keeps the settled status and output and gains the child's
-     * action log.
+     * after that answer, so its card keeps the settled status and output.
     */
    getSettledParentToolCall?: (toolUseId: string) => ClaudeToolCallItem | undefined;
  }) {
@@ -91,28 +84,27 @@ export class ClaudeSidechainTracker {
  }

  handleMessage(message: SDKMessage, parentToolUseId: string): AgentStreamEvent[] {
+    const existingState = this.activeSidechains.get(parentToolUseId);
    const state =
-      this.activeSidechains.get(parentToolUseId) ??
+      existingState ??
      ({
-        actions: [],
-        actionKeys: [],
-        nextActionIndex: 1,
-        actionIndexByKey: new Map<string, number>(),
+        runningCalls: new Map<string, SubAgentChildCall>(),
        completedActionKeys: new Set<string>(),
      } satisfies SubAgentActivityState);
    this.activeSidechains.set(parentToolUseId, state);

-    const contextUpdated = this.updateSubAgentContextFromTaskInput(state, parentToolUseId);
+    // The parent card is a launch marker: it changes only when the child is first seen or the
+    // task input names it differently, never with the child's activity.
+    const cardUpdated =
+      this.updateSubAgentContextFromTaskInput(state, parentToolUseId) || !existingState;
    const actionCandidates = this.extractSubAgentActionCandidates(message);
    const childTimelineItems = [
      ...this.extractSubAgentTimelineItems(message, state),
      ...this.extractSubAgentToolResults(message, state),
    ];
-    let actionUpdated = false;
    for (const action of actionCandidates) {
      if (state.completedActionKeys.has(action.key)) continue;
-      if (this.appendSubAgentAction(state, action)) {
-        actionUpdated = true;
+      if (this.trackChildCall(state, action)) {
        const toolCall = mapClaudeRunningToolCall({
          name: action.toolName,
          callId: action.key,
@@ -125,7 +117,7 @@ export class ClaudeSidechainTracker {
      }
    }

-    if (!contextUpdated && !actionUpdated && childTimelineItems.length === 0) {
+    if (!cardUpdated && childTimelineItems.length === 0) {
      return [];
    }

@@ -145,11 +137,8 @@ export class ClaudeSidechainTracker {
      type: "sub_agent",
      ...(state.subAgentType ? { subAgentType: state.subAgentType } : {}),
      ...(state.description ? { description: state.description } : {}),
-      log: state.actions
-        .map((action) =>
-          action.summary ? `[${action.toolName}] ${action.summary}` : `[${action.toolName}]`,
-        )
-        .join("\n"),
+      // COMPAT(subagent-log): remove after 2027-04-30.
+      log: "",
      actions: [],
    };

@@ -170,18 +159,19 @@ export class ClaudeSidechainTracker {
          },
        ];

-    const parentCard: AgentStreamEvent[] = this.needsSyntheticParentToolCard(parentToolUseId)
-      ? [
-          {
-            type: "timeline",
-            item: {
-              ...toolCall,
-              detail,
+    const parentCard: AgentStreamEvent[] =
+      cardUpdated && this.needsSyntheticParentToolCard(parentToolUseId)
+        ? [
+            {
+              type: "timeline",
+              item: {
+                ...toolCall,
+                detail,
+              },
+              provider: "claude",
            },
-            provider: "claude",
-          },
-        ]
-      : [];
+          ]
+        : [];

    return [
      ...descriptorEvents,
@@ -303,8 +293,7 @@ export class ClaudeSidechainTracker {
      if (!isClaudeContentChunk(block) || !block.type.endsWith("tool_result")) continue;
      const callId = readTrimmedString(block.tool_use_id);
      if (!callId || state.completedActionKeys.has(callId)) continue;
-      const actionIndex = state.actionIndexByKey.get(callId);
-      const action = actionIndex === undefined ? undefined : state.actions[actionIndex];
+      const action = state.runningCalls.get(callId);
      const toolName = action?.toolName ?? readTrimmedString(block.tool_name);
      if (!toolName) continue;
      const params = {
@@ -317,6 +306,7 @@ export class ClaudeSidechainTracker {
        ? mapClaudeFailedToolCall({ ...params, error: block })
        : mapClaudeCompletedToolCall(params);
      if (toolCall) {
+        state.runningCalls.delete(callId);
        state.completedActionKeys.add(callId);
        items.push(toolCall);
      }
@@ -412,13 +402,12 @@ export class ClaudeSidechainTracker {
    const key =
      readTrimmedString(block.id) ??
      `stream:${block.name}:${typeof event.index === "number" ? event.index : 0}`;
-    return [
-      {
-        key,
-        toolName: block.name,
-        input: block.input ?? null,
-      },
-    ];
+    // A streamed call starts with `{}` until its input arrives, so an empty input is not final.
+    const input =
+      block.input && typeof block.input === "object" && Object.keys(block.input).length > 0
+        ? block.input
+        : null;
+    return [{ key, toolName: block.name, input }];
  }

  private extractSubAgentActionCandidates(message: SDKMessage): SubAgentActionCandidate[] {
@@ -448,84 +437,20 @@ export class ClaudeSidechainTracker {
    return [];
  }

-  private appendSubAgentAction(
+  /** Returns whether the call is new or has gained its input, so its running card changes. */
+  private trackChildCall(
    state: SubAgentActivityState,
    candidate: SubAgentActionCandidate,
  ): boolean {
-    const normalizedToolName = readTrimmedString(candidate.toolName);
-    if (!normalizedToolName) {
+    const toolName = readTrimmedString(candidate.toolName);
+    if (!toolName) {
      return false;
    }
-
-    const summary = this.deriveSubAgentActionSummary(normalizedToolName, candidate.input);
-    const existingIndex = state.actionIndexByKey.get(candidate.key);
-
-    if (existingIndex !== undefined) {
-      const existing = state.actions[existingIndex];
-      if (!existing) {
-        return false;
-      }
-      const nextSummary = existing.summary ?? summary;
-      if (existing.toolName === normalizedToolName && existing.summary === nextSummary) {
-        return false;
-      }
-      state.actions[existingIndex] = {
-        ...existing,
-        toolName: normalizedToolName,
-        input: existing.input ?? candidate.input,
-        ...(nextSummary ? { summary: nextSummary } : {}),
-      };
-      return true;
+    const existing = state.runningCalls.get(candidate.key);
+    if (existing && (existing.input !== null || candidate.input === null)) {
+      return false;
    }
-
-    state.actions.push({
-      index: state.nextActionIndex,
-      toolName: normalizedToolName,
-      input: candidate.input,
-      ...(summary ? { summary } : {}),
-    });
-    state.nextActionIndex += 1;
-    state.actionKeys.push(candidate.key);
-    this.trimSubAgentTail(state);
-    this.rebuildSubAgentActionIndex(state);
+    state.runningCalls.set(candidate.key, { toolName, input: candidate.input });
    return true;
  }
-
-  private trimSubAgentTail(state: SubAgentActivityState): void {
-    while (state.actions.length > MAX_SUB_AGENT_LOG_ENTRIES) {
-      state.actions.shift();
-      const removedKey = state.actionKeys.shift();
-      if (removedKey) state.completedActionKeys.delete(removedKey);
-    }
-  }
-
-  private rebuildSubAgentActionIndex(state: SubAgentActivityState): void {
-    state.actionIndexByKey.clear();
-    for (let index = 0; index < state.actionKeys.length; index += 1) {
-      const key = state.actionKeys[index];
-      if (key) {
-        state.actionIndexByKey.set(key, index);
-      }
-    }
-  }
-
-  private deriveSubAgentActionSummary(toolName: string, input: unknown): string | undefined {
-    const runningToolCall = mapClaudeRunningToolCall({
-      name: toolName,
-      callId: `sub-agent-summary-${toolName}`,
-      input,
-      output: null,
-    });
-    if (!runningToolCall) {
-      return undefined;
-    }
-    const display = buildToolCallDisplayModel({
-      name: runningToolCall.name,
-      status: runningToolCall.status,
-      error: runningToolCall.error,
-      detail: runningToolCall.detail,
-      metadata: runningToolCall.metadata,
-    });
-    return this.normalizeSubAgentText(display.summary);
-  }
 }
@@ -77,12 +77,19 @@ CHILD_SENTINEL in your own response.

        const completedChildIndex = events.findIndex(
          (event) =>
-            event.type === "timeline" &&
-            event.item.type === "tool_call" &&
-            event.item.status === "completed" &&
-            event.item.detail.type === "sub_agent" &&
-            event.item.detail.log.includes("CHILD_SENTINEL"),
+            event.type === "provider_subagent" &&
+            event.event.type === "upsert" &&
+            event.event.status === "completed",
        );
+        const childAssistantText = events
+          .flatMap((event) =>
+            event.type === "provider_subagent" &&
+            event.event.type === "timeline" &&
+            event.event.item.type === "assistant_message"
+              ? [event.event.item.text]
+              : [],
+          )
+          .join("");
        const rootMessageIndexes = events.flatMap((event, index) =>
          event.type === "timeline" && event.item.type === "assistant_message" ? [index] : [],
        );
@@ -105,6 +112,7 @@ CHILD_SENTINEL in your own response.
          .map((item) => item.text)
          .join("");
        expect(topLevelAssistantText).not.toContain("CHILD_SENTINEL");
+        expect(childAssistantText).toContain("CHILD_SENTINEL");
        expect(completedChildIndex).toBeGreaterThanOrEqual(0);
        expect(rootMessageIndexes[0]).toBeGreaterThan(completedChildIndex);
        expect(terminalIndexes).toHaveLength(1);
@@ -3524,7 +3524,7 @@ describe("Codex app-server provider", () => {
    ]);
  });

-  test("folds child-thread Codex activity into the parent sub-agent tool call", async () => {
+  test("keeps child-thread Codex activity out of the parent sub-agent card", async () => {
    const session = createSession();
    const events: AgentStreamEvent[] = [];
    session.subscribe((event) => events.push(event));
@@ -3562,7 +3562,6 @@ describe("Codex app-server provider", () => {
    });

    const timelineEvents = events.filter((event) => event.type === "timeline");
-    expect(timelineEvents).toHaveLength(4);
    expect(timelineEvents.every((event) => event.item.type === "tool_call")).toBe(true);
    const finalItem = timelineEvents.at(-1)?.item;
    expect(finalItem).toMatchObject({
@@ -3574,7 +3573,7 @@ describe("Codex app-server provider", () => {
        type: "sub_agent",
        subAgentType: "Sub-agent",
        description: "Report findings.",
-        log: "[Assistant] Found the path.",
+        log: "",
        actions: [],
      },
    });
@@ -3651,13 +3650,9 @@ describe("Codex app-server provider", () => {
        id: "settled-child-thread",
        status: "completed",
      });
-      expect(events.at(-1)).toMatchObject({
+      expect(events.findLast((event) => event.type === "timeline")).toMatchObject({
        type: "timeline",
-        item: {
-          callId: "call-settled-child",
-          status: "completed",
-          detail: { type: "sub_agent", log: "[Assistant] Late trailing output." },
-        },
+        item: { callId: "call-settled-child", status: "completed" },
      });

      appServer.completesSubAgentActivity({
@@ -3962,6 +3957,8 @@ describe("Codex app-server provider", () => {
      createTestLogger(),
      async () => appServer.child,
    );
+    const events: AgentStreamEvent[] = [];
+    session.subscribe((event) => events.push(event));

    try {
      const resultPromise = session.run("Delegate the investigation, then report the result.");
@@ -4005,11 +4002,18 @@ describe("Codex app-server provider", () => {
        type: "tool_call",
        callId: "spawn-child-early",
        status: "completed",
-        detail: {
-          type: "sub_agent",
-          log: "[Assistant] Early child findings.",
-        },
+        detail: { type: "sub_agent", log: "" },
      });
+      expect(events).toContainEqual(
+        expect.objectContaining({
+          type: "provider_subagent",
+          event: expect.objectContaining({
+            type: "timeline",
+            id: "child-thread-early",
+            item: expect.objectContaining({ type: "assistant_message" }),
+          }),
+        }),
+      );
      appServer.assertNoErrors();
    } finally {
      await session.close();
@@ -4080,10 +4084,7 @@ describe("Codex app-server provider", () => {
      expect(toolCalls.at(-1)).toMatchObject({
        callId: "spawn-child-stable",
        status: "canceled",
-        detail: {
-          type: "sub_agent",
-          log: "[Assistant] Still on the same card.",
-        },
+        detail: { type: "sub_agent", log: "" },
      });
      appServer.assertNoErrors();
    } finally {
@@ -4163,11 +4164,10 @@ describe("Codex app-server provider", () => {

      const result = await resultPromise;
      const toolCalls = result.timeline.filter((item) => item.type === "tool_call");
-      expect(toolCalls.map((item) => item.status)).toEqual(["running", "completed", "completed"]);
+      expect(toolCalls.map((item) => item.status)).toEqual(["running", "completed"]);
      expect(toolCalls.at(-1)).toMatchObject({
        callId: "spawn-child-late-compaction",
        status: "completed",
-        detail: { type: "sub_agent", log: "[Compacted]" },
      });
      appServer.assertNoErrors();
    } finally {
@@ -4175,7 +4175,7 @@ describe("Codex app-server provider", () => {
    }
  });

-  test("projects legacy child tools into one stable sub-agent log", async () => {
+  test("routes legacy child tools to the child timeline", async () => {
    const appServer = createFakeCodexAppServer();
    const session = new CodexAppServerAgentSession(
      createConfig({ cwd: "/workspace/project" }),
@@ -4183,6 +4183,8 @@ describe("Codex app-server provider", () => {
      createTestLogger(),
      async () => appServer.child,
    );
+    const events: AgentStreamEvent[] = [];
+    session.subscribe((event) => events.push(event));

    try {
      const resultPromise = session.run("Delegate the implementation.");
@@ -4225,19 +4227,26 @@ describe("Codex app-server provider", () => {
      expect(finalToolCall).toMatchObject({
        callId: "spawn-legacy-tool-child",
        status: "completed",
-        detail: { type: "sub_agent" },
+        detail: { type: "sub_agent", log: "" },
      });
-      if (finalToolCall?.detail.type === "sub_agent") {
-        expect(finalToolCall.detail.log.match(/\[Shell\]/g)).toHaveLength(1);
-        expect(finalToolCall.detail.log).toContain("[Edit]");
-      }
+      const childToolCalls = events.flatMap((event) =>
+        event.type === "provider_subagent" &&
+        event.event.type === "timeline" &&
+        event.event.id === "legacy-tool-child" &&
+        event.event.item.type === "tool_call"
+          ? [event.event.item]
+          : [],
+      );
+      expect(new Set(childToolCalls.map((item) => item.detail.type))).toEqual(
+        new Set(["shell", "edit"]),
+      );
      appServer.assertNoErrors();
    } finally {
      await session.close();
    }
  });

-  test("keeps nested MultiAgentV2 output inside the root sub-agent card", async () => {
+  test("keeps nested MultiAgentV2 output out of the root sub-agent card", async () => {
    const session = createSession();
    const events: AgentStreamEvent[] = [];
    session.subscribe((event) => events.push(event));
@@ -4297,8 +4306,22 @@ describe("Codex app-server provider", () => {
    expect(beforeParentCompletes.at(-1)).toMatchObject({
      callId: "spawn-child-root",
      status: "running",
-      detail: { type: "sub_agent", log: expect.stringContaining("Grandchild findings.") },
+      detail: { type: "sub_agent", log: "" },
    });
+    expect(events).toContainEqual(
+      expect.objectContaining({
+        type: "provider_subagent",
+        event: {
+          type: "timeline",
+          id: "grandchild-thread",
+          item: {
+            type: "assistant_message",
+            messageId: "grandchild-message",
+            text: "Grandchild findings.",
+          },
+        },
+      }),
+    );

    await asInternals(session).handleNotification("turn/completed", {
      threadId: "child-thread-root",
@@ -4365,13 +4388,20 @@ describe("Codex app-server provider", () => {
      "child-thread-root",
      "child-thread-root",
    ]);
-    expect(events.at(-1)).toMatchObject({
-      type: "timeline",
-      item: {
-        callId: "spawn-child-root",
-        detail: { type: "sub_agent", log: expect.stringContaining("Still nested.") },
-      },
-    });
+    expect(events).toContainEqual(
+      expect.objectContaining({
+        type: "provider_subagent",
+        event: {
+          type: "timeline",
+          id: "grandchild-thread",
+          item: {
+            type: "assistant_message",
+            messageId: "grandchild-after-wait",
+            text: "Still nested.",
+          },
+        },
+      }),
+    );
  });

  test("never treats an unmapped foreign terminal as the root terminal", async () => {
@@ -4791,7 +4821,7 @@ describe("Codex app-server provider", () => {
    expect(events).toHaveLength(eventCountAfterSpawn);
  });

-  test("keeps child context compaction inside the child card", async () => {
+  test("keeps child context compaction on the child timeline", async () => {
    const session = createSession();
    const events: AgentStreamEvent[] = [];
    session.subscribe((event) => events.push(event));
@@ -4824,10 +4854,70 @@ describe("Codex app-server provider", () => {
        (item) => item.type === "tool_call" && item.callId === "spawn-child-compaction",
      ),
    ).toBe(true);
-    expect(timelineItems.at(-1)).toMatchObject({
-      type: "tool_call",
-      detail: { type: "sub_agent", log: "[Compacted]" },
+    expect(
+      events.flatMap((event) =>
+        event.type === "provider_subagent" && event.event.type === "timeline" ? [event.event] : [],
+      ),
+    ).toEqual([
+      {
+        type: "timeline",
+        id: "child-thread-compaction",
+        item: { type: "compaction", status: "loading" },
+      },
+      {
+        type: "timeline",
+        id: "child-thread-compaction",
+        item: { type: "compaction", status: "completed" },
+      },
+    ]);
+  });
+
+  test("settles a child compaction once when the item completion is missing or duplicated", async () => {
+    const session = createSession();
+    const events: AgentStreamEvent[] = [];
+    session.subscribe((event) => events.push(event));
+
+    for (const child of ["compacted-child", "turn-ended-child"]) {
+      await asInternals(session).handleNotification("item/completed", {
+        threadId: "test-thread",
+        item: {
+          type: "subAgentActivity",
+          id: `spawn-${child}`,
+          kind: "started",
+          agentThreadId: child,
+          agentPath: `/root/${child}`,
+        },
+      });
+      await asInternals(session).handleNotification("item/started", {
+        threadId: child,
+        item: { type: "contextCompaction", id: `${child}-compaction` },
+      });
+    }
+    await asInternals(session).handleNotification("thread/compacted", {
+      threadId: "compacted-child",
    });
+    await asInternals(session).handleNotification("item/completed", {
+      threadId: "compacted-child",
+      item: { type: "contextCompaction", id: "compacted-child-compaction" },
+    });
+    await asInternals(session).handleNotification("turn/completed", {
+      threadId: "turn-ended-child",
+      turn: { status: "completed" },
+    });
+
+    const compactions = events.flatMap((event) =>
+      event.type === "provider_subagent" && event.event.type === "timeline"
+        ? [
+            `${event.event.id} ${event.event.item.type === "compaction" ? event.event.item.status : ""}`,
+          ]
+        : [],
+    );
+    expect(compactions).toEqual([
+      "compacted-child loading",
+      "turn-ended-child loading",
+      "compacted-child completed",
+      "turn-ended-child completed",
+    ]);
  });

  test("keeps the parent sub-agent running when a child command fails during the child turn", async () => {
@@ -4862,7 +4952,7 @@ describe("Codex app-server provider", () => {
      },
    });

-    expect(events.at(-1)?.item).toMatchObject({
+    expect(events.findLast((event) => event.type === "timeline")?.item).toMatchObject({
      type: "tool_call",
      callId: "call-sub-agent-child-command-failure",
      name: "Sub-agent",
@@ -5157,7 +5247,7 @@ describe("Codex app-server provider", () => {
    );
    expect(liveToolCalls.at(-1)).toMatchObject({
      status: "running",
-      detail: { type: "sub_agent", log: "[Assistant] More findings after resume." },
+      detail: { type: "sub_agent", log: "" },
    });

    liveEvents.length = 0;
@@ -5170,12 +5260,12 @@ describe("Codex app-server provider", () => {
      itemId: "legacy-child-message-after-resume",
      delta: "Legacy findings after resume.",
    });
-    expect(liveEvents.at(-1)).toMatchObject({
+    expect(liveEvents.findLast((event) => event.type === "timeline")).toMatchObject({
      type: "timeline",
      item: {
        callId: "legacy-spawn-history",
        status: "running",
-        detail: { type: "sub_agent", log: "[Assistant] Legacy findings after resume." },
+        detail: { type: "sub_agent", log: "" },
      },
    });
  });
@@ -49,10 +49,10 @@ import { Dirent } from "node:fs";
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
+import { isDeepStrictEqual } from "node:util";
 import { z } from "zod";
 import { renderPromptAttachmentAsText } from "../prompt-attachments.js";
 import { composeSystemPromptParts } from "../system-prompt.js";
-import { curateAgentActivity } from "../activity-curator.js";
 import { CodexAsyncQuestions, codexAsyncQuestionToTimeline } from "./codex/async-questions.js";
 import {
  mapCodexToolCallEnvelope,
@@ -3384,8 +3384,6 @@ interface CodexSubAgentCallState {
  activityItemIds: Set<string>;
  pendingCommandOutputDeltas: Map<string, string[]>;
  pendingFileChangeOutputDeltas: Map<string, string[]>;
-  childItemOrder: string[];
-  childItems: Map<string, AgentTimelineItem>;
  childThreadIds: Set<string>;
 }

@@ -3487,6 +3485,9 @@ export class CodexAppServerAgentSession implements AgentSession {
  private compactionTriggerByItemId = new Map<string, "auto" | "manual">();
  private pendingRootCompactionItemIds = new Set<string>();
  private pendingAnonymousRootCompactions = 0;
+  // Child threads with a compaction shown as loading. Some Codex builds settle it only through
+  // `thread/compacted` or the end of the child's turn.
+  private pendingChildCompactionThreadIds = new Set<string>();
  // Codex can report one completed compaction through both channels:
  // `thread/compacted` and a completed `contextCompaction` item.
  private unpairedCompactionNotificationCompletions = 0;
@@ -5516,6 +5517,9 @@ export class CodexAppServerAgentSession implements AgentSession {
      case "patch_apply_completed":
        this.handlePatchApplyCompletedNotification(parsed, callId);
        return;
+      case "context_compacted":
+        this.settleChildCompaction(parsed.threadId);
+        return;
      default:
        // Aggregate child telemetry is redundant and must not leak into the
        // root timeline. Concrete legacy tools are projected above for Codex
@@ -5692,20 +5696,10 @@ export class CodexAppServerAgentSession implements AgentSession {
        activityItemIds: new Set<string>(),
        pendingCommandOutputDeltas: new Map<string, string[]>(),
        pendingFileChangeOutputDeltas: new Map<string, string[]>(),
-        childItemOrder: [],
-        childItems: new Map<string, AgentTimelineItem>(),
        childThreadIds: new Set<string>(),
      } satisfies CodexSubAgentCallState);

-    state.toolCall = {
-      ...timelineItem,
-      detail: {
-        ...timelineItem.detail,
-        log:
-          timelineItem.detail.log ||
-          (state.toolCall.detail.type === "sub_agent" ? state.toolCall.detail.log : ""),
-      },
-    };
+    state.toolCall = timelineItem;
    state.parentCallId ??= parentCallId;
    state.parentSubagentId ??= parentSubagentId;
    const activity = readCodexSubAgentActivity(rawItem);
@@ -5758,25 +5752,17 @@ export class CodexAppServerAgentSession implements AgentSession {
    const activityToolCall = mapCodexToolCallFromThreadItem(rawItem, {
      cwd: this.config.cwd ?? null,
    });
-    if (
-      activityToolCall?.detail.type === "sub_agent" &&
-      state.toolCall.detail.type === "sub_agent"
-    ) {
-      state.toolCall = {
-        ...state.toolCall,
-        detail: {
-          ...state.toolCall.detail,
-          subAgentType: activityToolCall.detail.subAgentType,
-        },
-      };
-    }
+    const subAgentType =
+      activityToolCall?.detail.type === "sub_agent"
+        ? activityToolCall.detail.subAgentType
+        : undefined;
    let nextStatus: ToolCallTimelineItem["status"] | undefined = "running";
    if (activity.kind === "interrupted") {
      nextStatus = "canceled";
    } else if (isTerminalSubAgentStatus(state.toolCall.status)) {
      nextStatus = undefined;
    }
-    this.emitSubAgentActivityUpdate(callId, nextStatus);
+    this.emitSubAgentActivityUpdate(callId, nextStatus, { subAgentType });
    return true;
  }

@@ -5817,7 +5803,13 @@ export class CodexAppServerAgentSession implements AgentSession {
  ): boolean {
    if (
      childSubAgentCallId &&
-      this.handleSubAgentContextCompactionItem(childSubAgentCallId, parsed.item, "completed")
+      parsed.threadId &&
+      this.handleSubAgentContextCompactionItem(
+        childSubAgentCallId,
+        parsed.threadId,
+        parsed.item,
+        "completed",
+      )
    ) {
      return true;
    }
@@ -5827,17 +5819,6 @@ export class CodexAppServerAgentSession implements AgentSession {
    );
  }

-  private upsertSubAgentChildItem(callId: string, itemId: string, item: AgentTimelineItem): void {
-    const state = this.subAgentCallsByCallId.get(callId);
-    if (!state) {
-      return;
-    }
-    if (!state.childItems.has(itemId)) {
-      state.childItemOrder.push(itemId);
-    }
-    state.childItems.set(itemId, item);
-  }
-
  private emitCodexToolTimelineItem(
    timelineItem: ToolCallTimelineItem,
    subAgentCallId: string | null,
@@ -5847,7 +5828,6 @@ export class CodexAppServerAgentSession implements AgentSession {
      this.emitEvent({ type: "timeline", provider: CODEX_PROVIDER, item: timelineItem });
      return;
    }
-    this.upsertSubAgentChildItem(subAgentCallId, timelineItem.callId, timelineItem);
    const state = this.subAgentCallsByCallId.get(subAgentCallId);
    if (state) {
      const targetThreadIds = childThreadId ? [childThreadId] : state.childThreadIds;
@@ -5861,26 +5841,15 @@ export class CodexAppServerAgentSession implements AgentSession {
    );
  }

-  private getSubAgentChildTimeline(state: CodexSubAgentCallState): AgentTimelineItem[] {
-    return state.childItemOrder
-      .map((itemId) => state.childItems.get(itemId))
-      .filter((item): item is AgentTimelineItem => Boolean(item));
-  }
-
  private emitSubAgentActivityUpdate(
    callId: string,
    status?: ToolCallTimelineItem["status"],
-    options?: { reopen?: boolean },
+    options?: { reopen?: boolean; subAgentType?: string },
  ): void {
    const state = this.subAgentCallsByCallId.get(callId);
    if (!state || state.toolCall.detail.type !== "sub_agent") {
      return;
    }
-    const childTimeline = this.getSubAgentChildTimeline(state);
-    const log =
-      childTimeline.length > 0
-        ? curateAgentActivity(childTimeline, { labelAssistantMessages: true })
-        : "";
    let resolvedStatus = status ?? state.toolCall.status;
    if (
      status === "running" &&
@@ -5889,16 +5858,12 @@ export class CodexAppServerAgentSession implements AgentSession {
    ) {
      resolvedStatus = state.toolCall.status;
    }
-    for (const childThreadId of state.childThreadIds) {
-      this.emitProviderSubagentUpsert(childThreadId, state, resolvedStatus);
-    }
-    const baseToolCall = {
-      ...state.toolCall,
-      detail: {
-        ...state.toolCall.detail,
-        log,
-      },
-    };
+    const baseToolCall = options?.subAgentType
+      ? {
+          ...state.toolCall,
+          detail: { ...state.toolCall.detail, subAgentType: options.subAgentType },
+        }
+      : state.toolCall;
    const nextToolCall: ToolCallTimelineItem =
      resolvedStatus === "failed"
        ? {
@@ -5911,10 +5876,14 @@ export class CodexAppServerAgentSession implements AgentSession {
            status: resolvedStatus,
            error: null,
          };
+    // The card is a launch marker: the child's activity streams to its own timeline, so the card
+    // is re-sent only when its status or label changes.
+    const cardChanged = !isDeepStrictEqual(nextToolCall, state.toolCall);
    state.toolCall = nextToolCall;
-    if (state.parentCallId && state.parentCallId !== callId) {
-      this.upsertSubAgentChildItem(state.parentCallId, state.callId, nextToolCall);
-      this.emitSubAgentActivityUpdate(state.parentCallId);
+    for (const childThreadId of state.childThreadIds) {
+      this.emitProviderSubagentUpsert(childThreadId, state, resolvedStatus);
+    }
+    if (!cardChanged || (state.parentCallId && state.parentCallId !== callId)) {
      return;
    }
    this.emitEvent({ type: "timeline", provider: CODEX_PROVIDER, item: nextToolCall });
@@ -6022,7 +5991,6 @@ export class CodexAppServerAgentSession implements AgentSession {
  ): void {
    this.applyBufferedDeltaTextToTimelineItem(timelineItem, itemId);
    if (itemId) {
-      this.upsertSubAgentChildItem(callId, itemId, timelineItem);
      this.pendingAgentMessages.delete(itemId);
      this.pendingReasoning.delete(itemId);
      this.pendingCommandOutputDeltas.delete(itemId);
@@ -6033,19 +6001,29 @@ export class CodexAppServerAgentSession implements AgentSession {

  private handleSubAgentContextCompactionItem(
    callId: string,
+    childThreadId: string,
    item: { id?: string; type?: string; [key: string]: unknown },
    status: "loading" | "completed",
  ): boolean {
    if (!this.isContextCompactionItem(item)) {
      return false;
    }
-    if (item.id) {
-      this.upsertSubAgentChildItem(callId, item.id, { type: "compaction", status });
+    if (status === "loading") {
+      this.pendingChildCompactionThreadIds.add(childThreadId);
+      this.emitProviderSubagentTimeline(childThreadId, { type: "compaction", status });
+    } else {
+      this.settleChildCompaction(childThreadId);
    }
    this.emitSubAgentActivityUpdate(callId);
    return true;
  }

+  private settleChildCompaction(childThreadId: string): void {
+    if (this.pendingChildCompactionThreadIds.delete(childThreadId)) {
+      this.emitProviderSubagentTimeline(childThreadId, { type: "compaction", status: "completed" });
+    }
+  }
+
  private shouldSkipCompletedThreadItem(
    timelineItem: AgentTimelineItem,
    normalizedItemType: string | undefined,
@@ -6076,11 +6054,6 @@ export class CodexAppServerAgentSession implements AgentSession {
            text: parsed.delta,
          });
        }
-        this.upsertSubAgentChildItem(subAgentCallId, parsed.itemId, {
-          type: "assistant_message",
-          messageId: parsed.itemId,
-          text,
-        });
        this.emitSubAgentActivityUpdate(subAgentCallId, "running");
        return;
      }
@@ -6114,10 +6087,6 @@ export class CodexAppServerAgentSession implements AgentSession {
            text: parsed.delta,
          });
        }
-        this.upsertSubAgentChildItem(subAgentCallId, parsed.itemId, {
-          type: "reasoning",
-          text: prev.join(""),
-        });
        this.emitSubAgentActivityUpdate(subAgentCallId, "running");
        return;
      }
@@ -6185,6 +6154,7 @@ export class CodexAppServerAgentSession implements AgentSession {
  ): void {
    const subAgentCallId = this.getSubAgentCallIdForThread(parsed.threadId);
    if (subAgentCallId) {
+      if (parsed.threadId) this.settleChildCompaction(parsed.threadId);
      let status: ToolCallTimelineItem["status"] = "completed";
      if (parsed.status === "failed") {
        status = "failed";
@@ -6771,7 +6741,13 @@ export class CodexAppServerAgentSession implements AgentSession {
    const childSubAgentCallId = this.getSubAgentCallIdForThread(parsed.threadId);
    if (
      childSubAgentCallId &&
-      this.handleSubAgentContextCompactionItem(childSubAgentCallId, parsed.item, "loading")
+      parsed.threadId &&
+      this.handleSubAgentContextCompactionItem(
+        childSubAgentCallId,
+        parsed.threadId,
+        parsed.item,
+        "loading",
+      )
    ) {
      return;
    }
@@ -6802,9 +6778,6 @@ export class CodexAppServerAgentSession implements AgentSession {
    });
    if (childSubAgentCallId) {
      this.emitStartedProviderSubagentItem(parsed.threadId, timelineItem);
-      if (parsed.item.id) {
-        this.upsertSubAgentChildItem(childSubAgentCallId, parsed.item.id, timelineItem);
-      }
      this.emitSubAgentActivityUpdate(childSubAgentCallId, "running");
      await this.replayPendingSubAgentNotifications(registeredChildThreadIds);
      return;
@@ -6858,9 +6831,6 @@ export class CodexAppServerAgentSession implements AgentSession {
      if (parsed.threadId) {
        this.emitProviderSubagentTimeline(parsed.threadId, timelineItem);
      }
-      if (itemId) {
-        this.upsertSubAgentChildItem(childSubAgentCallId, itemId, timelineItem);
-      }
      this.emitSubAgentActivityUpdate(childSubAgentCallId, "running");
      return;
    }
@@ -950,6 +950,7 @@ function mapCollabAgentToolCallItem(
    type: "sub_agent",
    subAgentType: "Sub-agent",
    ...(item.prompt ? { description: item.prompt } : {}),
+    // COMPAT(subagent-log): remove after 2027-04-30.
    log: "",
    actions: [],
  };
@@ -1006,6 +1007,7 @@ function mapSubAgentActivityItem(
      type: "sub_agent",
      subAgentType: nativeName,
      description,
+      // COMPAT(subagent-log): remove after 2027-04-30.
      log: "",
      actions: [],
    },
@@ -69,7 +69,7 @@ import {
  type OmpRuntimeOptions,
 } from "./provider-config.js";
 export { formatOmpVersionSupport, resolveOmpDiagnosticPaths } from "./provider-config.js";
-import { OmpSubagentCardTracker, type OmpSubagentCardScheduler } from "./subagent-card-tracker.js";
+import { OmpSubagentCardTracker } from "./subagent-card-tracker.js";
 import { ompSkillPromptUserText, shouldDisplayOmpCustomMessage } from "./custom-message.js";
 import { getUserMessageText } from "./message-history.js";
 import { mapOmpSystemNoticeToNotification } from "./system-notice.js";
@@ -130,7 +130,6 @@ export interface OmpAgentClientOptions {
  logger: Logger;
  runtimeSettings?: ProviderRuntimeSettings;
  runtime?: OmpRuntime;
-  subagentCardScheduler?: OmpSubagentCardScheduler;
  providerIdleScheduler?: OmpProviderIdleScheduler;
  noTurnScheduler?: OmpNoTurnScheduler;
  usagePollScheduler?: OmpUsagePollScheduler;
@@ -205,7 +204,6 @@ interface OmpAgentSessionOptions {
  initialState: OmpSessionState;
  currentModeId?: string | null;
  logger: Logger;
-  subagentCardScheduler?: OmpSubagentCardScheduler;
  providerIdleScheduler?: OmpProviderIdleScheduler;
  noTurnScheduler?: OmpNoTurnScheduler;
  usagePollScheduler?: OmpUsagePollScheduler;
@@ -773,9 +771,7 @@ export class OmpAgentSession implements AgentSession {
        this.logger.debug({ err: error }, "OMP context usage poll failed");
      },
    });
-    this.subagentCardTracker = new OmpSubagentCardTracker({
-      scheduler: options.subagentCardScheduler,
-    });
+    this.subagentCardTracker = new OmpSubagentCardTracker();
    this.lastKnownThinkingOptionId =
      normalizeOmpThinkingOption(options.config.thinkingOptionId) ??
      this.state.thinkingLevel ??
@@ -2155,8 +2151,7 @@ export class OmpAgentSession implements AgentSession {
    return mapOmpToolDetail(toolCall, result, {
      toolCallId,
      bridgedTool: this.hostTools?.bridge?.tool(toolCall.toolName),
-      mapSubagentDetail: (detail) =>
-        this.subagentCardTracker.detailFor(toolCallId, detail) ?? detail,
+      mapSubagentDetail: (detail) => this.subagentCardTracker.detailFor(toolCallId, detail),
    });
  }

@@ -2246,7 +2241,6 @@ export class OmpAgentClient implements AgentClient {

  private readonly logger: Logger;
  private readonly runtimeSettings?: ProviderRuntimeSettings;
-  private readonly subagentCardScheduler?: OmpSubagentCardScheduler;
  private readonly providerIdleScheduler?: OmpProviderIdleScheduler;
  private readonly noTurnScheduler?: OmpNoTurnScheduler;
  private readonly usagePollScheduler?: OmpUsagePollScheduler;
@@ -2265,7 +2259,6 @@ export class OmpAgentClient implements AgentClient {
    );
    this.logger = options.logger;
    this.runtimeSettings = runtimeSettings;
-    this.subagentCardScheduler = options.subagentCardScheduler;
    this.providerIdleScheduler = options.providerIdleScheduler;
    this.noTurnScheduler = options.noTurnScheduler;
    this.usagePollScheduler = options.usagePollScheduler;
@@ -2349,7 +2342,6 @@ export class OmpAgentClient implements AgentClient {
        initialState,
        currentModeId: launchMode.modeId,
        logger: this.logger,
-        subagentCardScheduler: this.subagentCardScheduler,
        providerIdleScheduler: this.providerIdleScheduler,
        noTurnScheduler: this.noTurnScheduler,
        usagePollScheduler: this.usagePollScheduler,
@@ -2421,7 +2413,6 @@ export class OmpAgentClient implements AgentClient {
        initialState,
        currentModeId: launchMode.modeId,
        logger: this.logger,
-        subagentCardScheduler: this.subagentCardScheduler,
        providerIdleScheduler: this.providerIdleScheduler,
        noTurnScheduler: this.noTurnScheduler,
        usagePollScheduler: this.usagePollScheduler,
@@ -637,7 +637,7 @@ describe("OMP history mapper", () => {
            subAgentType: "explore",
            description: "Inspect files",
            childSessionId: "/tmp/omp-task/Explore.jsonl",
-            log: "done\ntranscript: /tmp/omp-task/Explore.jsonl",
+            log: "",
          },
          error: null,
        },
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "vitest";

-import { OmpSubagentCardTracker, type OmpSubagentCardScheduler } from "./subagent-card-tracker.js";
+import { OmpSubagentCardTracker } from "./subagent-card-tracker.js";
 import type { OmpSubagentLifecyclePayload, OmpSubagentProgressPayload } from "./rpc-types.js";

 const PARENT_TOOL_CALL_ID = "task-1";
@@ -59,184 +59,84 @@ const PROGRESS: OmpSubagentProgressPayload[] = [
  },
 ];

-class ManualScheduler implements OmpSubagentCardScheduler {
-  private currentMs = 0;
-  private nextId = 1;
-  private readonly timers = new Map<number, { dueMs: number; callback: () => void }>();
-
-  now(): number {
-    return this.currentMs;
-  }
-
-  setTimeout(callback: () => void, delayMs: number) {
-    const id = this.nextId;
-    this.nextId += 1;
-    this.timers.set(id, { dueMs: this.currentMs + delayMs, callback });
-    return { token: id };
-  }
-
-  clearTimeout(timer: { token: unknown }): void {
-    if (typeof timer.token === "number") {
-      this.timers.delete(timer.token);
-    }
-  }
-
-  advance(ms: number): void {
-    this.currentMs += ms;
-    const dueTimers = [...this.timers.entries()]
-      .filter(([, timer]) => timer.dueMs <= this.currentMs)
-      .sort((left, right) => left[1].dueMs - right[1].dueMs);
-    for (const [id, timer] of dueTimers) {
-      if (this.timers.delete(id)) {
-        timer.callback();
-      }
-    }
-  }
-}
-
 describe("OmpSubagentCardTracker", () => {
-  test("folds lifecycle and progress into one throttled sub-agent detail", () => {
-    const scheduler = new ManualScheduler();
+  test("keeps the card a launch marker while the child runs", () => {
    const emitted: string[] = [];
-    const tracker = new OmpSubagentCardTracker({
-      scheduler,
-      emitToolCall: (toolCallId) => {
-        emitted.push(toolCallId);
-        return true;
-      },
-    });
-    tracker.handleLifecycle(LIFECYCLE);
+    const emit = (toolCallId: string) => {
+      emitted.push(toolCallId);
+      return true;
+    };
+    const tracker = new OmpSubagentCardTracker();
+    tracker.handleLifecycle(LIFECYCLE, emit);
    for (const payload of PROGRESS) {
-      tracker.handleProgress(payload);
+      tracker.handleProgress(payload, emit);
    }

    expect(emitted).toEqual([PARENT_TOOL_CALL_ID]);
-    const detailBeforeTrailing = tracker.detailFor(PARENT_TOOL_CALL_ID, {
-      type: "sub_agent",
-      subAgentType: "task",
-      description: "Task arg description wins",
-      log: "",
-    });
-    expect(detailBeforeTrailing).toEqual({
-      type: "sub_agent",
-      subAgentType: "task",
-      description: "Task arg description wins",
-      childSessionId: SESSION_FILE,
-      log: [
-        "EchoSubagent started",
-        "[bash] echo subagent-hi",
-        "[yield]",
-        "EchoSubagent completed",
-      ].join("\n"),
-    });
-
-    scheduler.advance(500);
-
-    expect(emitted).toEqual([PARENT_TOOL_CALL_ID, PARENT_TOOL_CALL_ID]);
-  });
-
-  test("aggregates batch progress streams into one index-prefixed log", () => {
-    const scheduler = new ManualScheduler();
-    const emitted: string[] = [];
-    const tracker = new OmpSubagentCardTracker({
-      scheduler,
-      emitToolCall: (toolCallId) => {
-        emitted.push(toolCallId);
-        return true;
-      },
-    });
-
-    tracker.handleLifecycle({
-      id: "Explore",
-      agent: "task",
-      description: "Inspect files",
-      status: "started",
-      sessionFile: "/tmp/one.jsonl",
-      parentToolCallId: "task.batch-1",
-      index: 0,
-    });
-    scheduler.advance(600);
-    tracker.handleProgress({
-      index: 5,
-      agent: "task",
-      task: "Run tests",
-      parentToolCallId: "task.batch-1",
-      progress: {
-        id: "Test",
-        status: "running",
-        description: "Run tests",
-        recentTools: [{ tool: "bash", args: "npm test", endMs: 10 }],
-      },
-      sessionFile: "/tmp/two.jsonl",
-    });
-
-    expect(emitted).toEqual(["task.batch-1", "task.batch-1"]);
    expect(
-      tracker.detailFor("task.batch-1", {
+      tracker.detailFor(PARENT_TOOL_CALL_ID, {
        type: "sub_agent",
-        subAgentType: "batch",
-        actions: [],
+        subAgentType: "task",
+        description: "Task arg description wins",
        log: "",
      }),
    ).toEqual({
      type: "sub_agent",
-      subAgentType: "batch",
-      description: "Inspect files",
-      childSessionId: "/tmp/one.jsonl",
-      log: "[1/6] Explore started\n[6/6] [bash] npm test",
-      actions: [],
+      subAgentType: "task",
+      description: "Task arg description wins",
+      childSessionId: SESSION_FILE,
+      log: "",
    });
  });

-  test("keeps dirty trailing state available for final detail and cancels it on cleanup", () => {
-    const scheduler = new ManualScheduler();
+  test("re-emits the card when a later event names the child", () => {
    const emitted: string[] = [];
-    const tracker = new OmpSubagentCardTracker({
-      scheduler,
-      emitToolCall: (toolCallId) => {
-        emitted.push(toolCallId);
-        return true;
+    const emit = (toolCallId: string) => {
+      emitted.push(toolCallId);
+      return true;
+    };
+    const tracker = new OmpSubagentCardTracker();
+    tracker.handleLifecycle({ ...LIFECYCLE, description: undefined, sessionFile: undefined }, emit);
+    tracker.handleProgress(PROGRESS[0], emit);
+
+    expect(emitted).toEqual([PARENT_TOOL_CALL_ID, PARENT_TOOL_CALL_ID]);
+    expect(tracker.detailFor(PARENT_TOOL_CALL_ID, { type: "sub_agent", log: "" })).toEqual({
+      type: "sub_agent",
+      childSessionId: SESSION_FILE,
+      log: "",
+    });
+
+    tracker.delete(PARENT_TOOL_CALL_ID);
+    expect(tracker.detailFor(PARENT_TOOL_CALL_ID, { type: "sub_agent", log: "" })).toEqual({
+      type: "sub_agent",
+      log: "",
+    });
+  });
+  test("leaves the card alone when a later child of the same task starts", () => {
+    const emitted: string[] = [];
+    const emit = (toolCallId: string) => {
+      emitted.push(toolCallId);
+      return true;
+    };
+    const tracker = new OmpSubagentCardTracker();
+    tracker.handleLifecycle(LIFECYCLE, emit);
+    tracker.handleLifecycle(
+      {
+        ...LIFECYCLE,
+        id: "Second",
+        index: 1,
+        description: "Second child",
+        sessionFile: "/s.jsonl",
      },
+      emit,
+    );
+
+    expect(emitted).toEqual([PARENT_TOOL_CALL_ID]);
+    expect(tracker.detailFor(PARENT_TOOL_CALL_ID, { type: "sub_agent", log: "" })).toEqual({
+      type: "sub_agent",
+      description: "Run echo in subagent",
+      childSessionId: SESSION_FILE,
+      log: "",
    });
-
-    tracker.handleLifecycle({
-      id: "Explore",
-      agent: "task",
-      description: "Inspect files",
-      status: "started",
-      parentToolCallId: "task-1",
-      index: 0,
-    });
-    scheduler.advance(100);
-    tracker.handleProgress({
-      index: 0,
-      agent: "task",
-      task: "Inspect files",
-      parentToolCallId: "task-1",
-      progress: {
-        id: "Explore",
-        status: "running",
-        recentOutput: ["found target file"],
-      },
-    });
-
-    expect(emitted).toEqual(["task-1"]);
-    expect(
-      tracker.detailFor("task-1", {
-        type: "sub_agent",
-        log: "",
-      }).log,
-    ).toBe("Explore started\nfound target file");
-
-    tracker.delete("task-1");
-    scheduler.advance(500);
-
-    expect(emitted).toEqual(["task-1"]);
-    expect(
-      tracker.detailFor("task-1", {
-        type: "sub_agent",
-        log: "static",
-      }).log,
-    ).toBe("static");
  });
 });
@@ -1,361 +1,106 @@
 import type { ToolCallDetail } from "../../agent-sdk-types.js";
 import type { OmpSubagentLifecyclePayload, OmpSubagentProgressPayload } from "./rpc-types.js";

-export interface OmpSubagentCardTimer {
-  readonly token: unknown;
-}
-
-export interface OmpSubagentCardScheduler {
-  now(): number;
-  setTimeout(callback: () => void, delayMs: number): OmpSubagentCardTimer;
-  clearTimeout(timer: OmpSubagentCardTimer): void;
-}
-
-export interface OmpSubagentCardTrackerOptions {
-  scheduler?: OmpSubagentCardScheduler;
-  emitToolCall?: (toolCallId: string) => boolean;
-}
-
-interface OmpSubagentLogLine {
-  key: string;
-  text: string;
-}
-
-interface OmpSubagentCardItem {
+interface OmpSubagentCardChild {
  index: number;
  description?: string;
-  agent?: string;
-  status?: "pending" | "running" | "completed" | "failed" | "aborted";
  childSessionId?: string;
-  lines: OmpSubagentLogLine[];
-  lineKeys: Set<string>;
-}
-
-interface OmpSubagentCardState {
-  items: Map<number, OmpSubagentCardItem>;
-  emitToolCall: (toolCallId: string) => boolean;
-  lastEmitMs: number | null;
-  trailingTimer: OmpSubagentCardTimer | null;
-  dirty: boolean;
-}
-
-const MAX_LOG_LINES_PER_ITEM = 200;
-const MAX_LOG_LINE_CHARS = 240;
-const THROTTLE_INTERVAL_MS = 500;
-
-export function createOmpSubagentCardScheduler(): OmpSubagentCardScheduler {
-  return {
-    now: () => Date.now(),
-    setTimeout: (callback, delayMs) => ({ token: setTimeout(callback, delayMs) }),
-    clearTimeout: (timer) => {
-      clearTimeout(timer.token as ReturnType<typeof setTimeout>);
-    },
-  };
 }

+/**
+ * Fills a task card's description and child session from OMP's sub-agent events. The card is a
+ * launch marker that names the task's first child; the children's activity belongs to their own
+ * timelines.
+ */
 export class OmpSubagentCardTracker {
-  private readonly scheduler: OmpSubagentCardScheduler;
-  private readonly emitToolCall: (toolCallId: string) => boolean;
-  private readonly states = new Map<string, OmpSubagentCardState>();
-
-  constructor(options: OmpSubagentCardTrackerOptions) {
-    this.scheduler = options.scheduler ?? createOmpSubagentCardScheduler();
-    this.emitToolCall = options.emitToolCall ?? (() => false);
-  }
+  private readonly firstChildren = new Map<string, OmpSubagentCardChild>();

  handleLifecycle(
    payload: OmpSubagentLifecyclePayload,
-    emitToolCall: (toolCallId: string) => boolean = this.emitToolCall,
+    emitToolCall: (toolCallId: string) => boolean,
  ): void {
-    const parentToolCallId = readTrimmedString(payload.parentToolCallId);
-    if (!parentToolCallId) {
-      return;
-    }
-    this.stateFor(parentToolCallId).emitToolCall = emitToolCall;
-    const item = this.upsertItem(parentToolCallId, {
-      index: payload.index,
-      agent: payload.agent,
-      description: payload.description,
-      status: payload.status === "started" ? "running" : payload.status,
-      childSessionId: payload.sessionFile,
-    });
-    this.appendLine(
-      item,
-      `lifecycle:${payload.status}:${payload.id}`,
-      `${payload.id} ${payload.status}`,
+    this.update(
+      payload.parentToolCallId,
+      {
+        index: payload.index,
+        description: payload.description,
+        childSessionId: payload.sessionFile,
+      },
+      emitToolCall,
    );
-    this.requestEmit(parentToolCallId);
  }

  handleProgress(
    payload: OmpSubagentProgressPayload,
-    emitToolCall: (toolCallId: string) => boolean = this.emitToolCall,
+    emitToolCall: (toolCallId: string) => boolean,
  ): void {
-    const parentToolCallId = readTrimmedString(payload.parentToolCallId);
-    if (!parentToolCallId) {
-      return;
-    }
-    this.stateFor(parentToolCallId).emitToolCall = emitToolCall;
-    const item = this.upsertItem(parentToolCallId, {
-      index: payload.index,
-      agent: payload.agent,
-      description: payload.progress.description,
-      status: payload.progress.status,
-      childSessionId: payload.sessionFile,
-    });
-
-    const currentToolLine = summarizeTool(readRecord(payload.progress.currentTool));
-    if (currentToolLine) {
-      this.appendLine(item, `current:${currentToolLine.key}`, currentToolLine.text);
-    }
-
-    for (const tool of readRecordArray(payload.progress.recentTools)) {
-      const line = summarizeTool(tool);
-      if (line) {
-        this.appendLine(item, `tool:${line.key}`, line.text);
-      }
-    }
-
-    for (const output of readOutputLines(payload.progress.recentOutput)) {
-      this.appendLine(item, `output:${output}`, output);
-    }
-
-    if (payload.progress.status !== "running") {
-      this.appendLine(
-        item,
-        `status:${payload.progress.status}:${payload.progress.id}`,
-        `${payload.progress.id} ${payload.progress.status}`,
-      );
-    }
-
-    this.requestEmit(parentToolCallId);
+    this.update(
+      payload.parentToolCallId,
+      {
+        index: payload.index,
+        description: payload.progress.description,
+        childSessionId: payload.sessionFile,
+      },
+      emitToolCall,
+    );
  }

  detailFor(toolCallId: string, baseDetail: ToolCallDetail): ToolCallDetail {
    if (baseDetail.type !== "sub_agent") {
      return baseDetail;
    }
-    const state = this.states.get(toolCallId);
-    if (!state) {
+    const first = this.firstChildren.get(toolCallId);
+    if (!first) {
      return baseDetail;
    }
-    const items = [...state.items.values()].sort((left, right) => left.index - right.index);
-    const firstItem = items[0];
-    if (!firstItem) {
-      return baseDetail;
-    }
-
-    const detail: ToolCallDetail = {
-      type: "sub_agent",
-      ...(baseDetail.subAgentType ? { subAgentType: baseDetail.subAgentType } : {}),
-      ...((baseDetail.description ?? firstItem.description)
-        ? { description: baseDetail.description ?? firstItem.description }
-        : {}),
-      ...((firstItem.childSessionId ?? baseDetail.childSessionId)
-        ? { childSessionId: firstItem.childSessionId ?? baseDetail.childSessionId }
-        : {}),
-      log: buildLog(items, baseDetail.log),
+    const description = baseDetail.description ?? first.description;
+    const childSessionId = first.childSessionId ?? baseDetail.childSessionId;
+    return {
+      ...baseDetail,
+      ...(description ? { description } : {}),
+      ...(childSessionId ? { childSessionId } : {}),
    };
-    return baseDetail.actions ? { ...detail, actions: baseDetail.actions } : detail;
-  }
-
-  flush(toolCallId: string): void {
-    const state = this.states.get(toolCallId);
-    if (!state || !state.dirty) {
-      return;
-    }
-    this.emitNow(toolCallId, state);
  }

  delete(toolCallId: string): void {
-    const state = this.states.get(toolCallId);
-    if (state?.trailingTimer) {
-      this.scheduler.clearTimeout(state.trailingTimer);
-    }
-    this.states.delete(toolCallId);
+    this.firstChildren.delete(toolCallId);
  }

  clear(): void {
-    for (const toolCallId of this.states.keys()) {
-      this.delete(toolCallId);
-    }
+    this.firstChildren.clear();
  }

-  private upsertItem(
-    parentToolCallId: string,
-    input: {
-      index: number;
-      agent?: string;
-      status?: "pending" | "running" | "completed" | "failed" | "aborted";
-      description?: string;
-      childSessionId?: string;
-    },
-  ): OmpSubagentCardItem {
-    const state = this.stateFor(parentToolCallId);
-    const existing = state.items.get(input.index);
-    if (existing) {
-      existing.agent = readTrimmedString(input.agent) ?? existing.agent;
-      existing.status = input.status ?? existing.status;
-      existing.description = readTrimmedString(input.description) ?? existing.description;
-      existing.childSessionId = readTrimmedString(input.childSessionId) ?? existing.childSessionId;
-      return existing;
+  private update(
+    parentToolCallId: string | undefined,
+    input: { index: number; description?: string; childSessionId?: string },
+    emitToolCall: (toolCallId: string) => boolean,
+  ): void {
+    const toolCallId = readTrimmedString(parentToolCallId);
+    if (!toolCallId) {
+      return;
    }
-
-    const item: OmpSubagentCardItem = {
+    const first = this.firstChildren.get(toolCallId);
+    if (first && input.index > first.index) {
+      return;
+    }
+    const existing = first?.index === input.index ? first : undefined;
+    const next: OmpSubagentCardChild = {
      index: input.index,
-      lines: [],
-      lineKeys: new Set<string>(),
-      ...(readTrimmedString(input.agent) ? { agent: readTrimmedString(input.agent) } : {}),
-      ...(input.status ? { status: input.status } : {}),
-      ...(readTrimmedString(input.description)
-        ? { description: readTrimmedString(input.description) }
-        : {}),
-      ...(readTrimmedString(input.childSessionId)
-        ? { childSessionId: readTrimmedString(input.childSessionId) }
-        : {}),
+      description: readTrimmedString(input.description) ?? existing?.description,
+      childSessionId: readTrimmedString(input.childSessionId) ?? existing?.childSessionId,
    };
-    state.items.set(input.index, item);
-    return item;
-  }
-
-  private stateFor(parentToolCallId: string): OmpSubagentCardState {
-    const existing = this.states.get(parentToolCallId);
-    if (existing) {
-      return existing;
-    }
-    const state: OmpSubagentCardState = {
-      items: new Map(),
-      emitToolCall: this.emitToolCall,
-      lastEmitMs: null,
-      trailingTimer: null,
-      dirty: false,
-    };
-    this.states.set(parentToolCallId, state);
-    return state;
-  }
-
-  private appendLine(item: OmpSubagentCardItem, key: string, text: string): void {
-    const normalizedText = normalizeLine(text);
-    if (!normalizedText || item.lineKeys.has(key)) {
+    if (
+      existing &&
+      existing.description === next.description &&
+      existing.childSessionId === next.childSessionId
+    ) {
      return;
    }
-    item.lines.push({ key, text: normalizedText });
-    item.lineKeys.add(key);
-    while (item.lines.length > MAX_LOG_LINES_PER_ITEM) {
-      const removed = item.lines.shift();
-      if (removed) {
-        item.lineKeys.delete(removed.key);
-      }
-    }
+    this.firstChildren.set(toolCallId, next);
+    emitToolCall(toolCallId);
  }
-
-  private requestEmit(toolCallId: string): void {
-    const state = this.stateFor(toolCallId);
-    const now = this.scheduler.now();
-    const elapsedMs = state.lastEmitMs === null ? THROTTLE_INTERVAL_MS : now - state.lastEmitMs;
-    if (elapsedMs >= THROTTLE_INTERVAL_MS) {
-      this.emitNow(toolCallId, state);
-      return;
-    }
-
-    state.dirty = true;
-    if (state.trailingTimer) {
-      return;
-    }
-    state.trailingTimer = this.scheduler.setTimeout(() => {
-      state.trailingTimer = null;
-      if (state.dirty) {
-        this.emitNow(toolCallId, state);
-      }
-    }, THROTTLE_INTERVAL_MS - elapsedMs);
-  }
-
-  private emitNow(toolCallId: string, state: OmpSubagentCardState): void {
-    if (state.trailingTimer) {
-      this.scheduler.clearTimeout(state.trailingTimer);
-      state.trailingTimer = null;
-    }
-    state.dirty = false;
-    state.lastEmitMs = this.scheduler.now();
-    state.emitToolCall(toolCallId);
-  }
-}
-
-function buildLog(items: OmpSubagentCardItem[], fallback: string): string {
-  const itemCount = Math.max(...items.map((item) => item.index)) + 1;
-  const lines = items.flatMap((item) => {
-    const prefix = itemCount > 1 ? `[${item.index + 1}/${itemCount}] ` : "";
-    return item.lines.map((line) => `${prefix}${line.text}`);
-  });
-  return lines.length > 0 ? lines.join("\n") : fallback;
-}
-
-function summarizeTool(tool: Record<string, unknown> | null): OmpSubagentLogLine | null {
-  if (!tool) {
-    return null;
-  }
-  const toolName = readTrimmedString(tool.tool) ?? readTrimmedString(tool.name);
-  if (!toolName) {
-    return null;
-  }
-  const args = readTrimmedString(tool.args) ?? summarizeUnknown(tool.input);
-  const endMs = typeof tool.endMs === "number" ? `:${tool.endMs}` : "";
-  return {
-    key: `${toolName}:${args ?? ""}${endMs}`,
-    text: args ? `[${toolName}] ${args}` : `[${toolName}]`,
-  };
-}
-
-function readOutputLines(value: unknown): string[] {
-  if (!Array.isArray(value)) {
-    return [];
-  }
-  return value.flatMap((item) => {
-    const text =
-      readTrimmedString(item) ??
-      (isRecord(item)
-        ? (readTrimmedString(item.text) ??
-          readTrimmedString(item.output) ??
-          readTrimmedString(item.content))
-        : undefined);
-    return text ? [text] : [];
-  });
-}
-
-function readRecord(value: unknown): Record<string, unknown> | null {
-  return isRecord(value) ? value : null;
-}
-
-function readRecordArray(value: unknown): Record<string, unknown>[] {
-  return Array.isArray(value) ? value.filter(isRecord) : [];
-}
-
-function summarizeUnknown(value: unknown): string | undefined {
-  if (value === undefined || value === null) {
-    return undefined;
-  }
-  if (typeof value === "string") {
-    return readTrimmedString(value);
-  }
-  const json = JSON.stringify(value);
-  return typeof json === "string" ? normalizeLine(json) : undefined;
-}
-
-function normalizeLine(value: string): string | undefined {
-  const normalized = value.trim().replace(/\s+/g, " ");
-  if (!normalized) {
-    return undefined;
-  }
-  if (normalized.length <= MAX_LOG_LINE_CHARS) {
-    return normalized;
-  }
-  return `${normalized.slice(0, MAX_LOG_LINE_CHARS)}...`;
 }

 function readTrimmedString(value: unknown): string | undefined {
  return typeof value === "string" && value.trim().length > 0 ? value.trim() : undefined;
 }
-
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value);
-}
@@ -85,7 +85,7 @@ describe("OMP tool call mapper", () => {
    expect(mapOmpToolDetail(parseToolArgs("todo", { op: "view" }), null)).toBeNull();
  });

-  test("uses task result text and transcript path as the best static replay detail", () => {
+  test("takes the child session from the task transcript path", () => {
    expect(
      mapOmpToolDetail(
        parseToolArgs("task", {
@@ -106,7 +106,7 @@ describe("OMP tool call mapper", () => {
      subAgentType: "explore",
      description: "Inspect the target files",
      childSessionId: "/tmp/omp-task-static/Explore.jsonl",
-      log: "done\ntranscript: /tmp/omp-task-static/Explore.jsonl",
+      log: "",
    });
  });

@@ -179,7 +179,6 @@ const OPAQUE_TEXT_TOOLS = new Set([
 function mapOmpTaskDetail(args: unknown, result: OmpToolResult): ToolCallDetail {
  const argRecord = isRecord(args) ? args : {};
  const firstTask = Array.isArray(argRecord.tasks) ? argRecord.tasks.find(isRecord) : undefined;
-  const resultText = extractTextFromToolResult(result);
  const childSessionId = readChildSessionId(result);
  return {
    type: "sub_agent",
@@ -200,7 +199,8 @@ function mapOmpTaskDetail(args: unknown, result: OmpToolResult): ToolCallDetail
      argRecord.assignment,
    ),
    ...(childSessionId ? { childSessionId } : {}),
-    log: resultText?.trim() ?? "",
+    // COMPAT(subagent-log): remove after 2027-04-30.
+    log: "",
  };
 }

@@ -4846,15 +4846,6 @@ class OpenCodeAgentSession implements AgentSession {
            ...item,
            status: "failed",
            error,
-            detail:
-              item.detail.type === "sub_agent"
-                ? {
-                    ...item.detail,
-                    log: [item.detail.log, error.message]
-                      .filter((entry) => entry.trim().length > 0)
-                      .join("\n"),
-                  }
-                : item.detail,
          },
        },
        turnId,
@@ -153,21 +153,6 @@ const OpencodeGrepOutputSchema = z
  ])
  .nullable();

-function formatLogEntry(value: unknown): string | undefined {
-  const outputText = readOutputText(value);
-  if (outputText) {
-    return outputText;
-  }
-  if (value === null || value === undefined) {
-    return undefined;
-  }
-  try {
-    return JSON.stringify(value, null, 2);
-  } catch {
-    return String(value);
-  }
-}
-
 function extractOpenCodeTaskSessionId(value: unknown): string | undefined {
  const text = readOutputText(value);
  if (text) {
@@ -195,7 +180,6 @@ function extractOpenCodeTaskSessionId(value: unknown): string | undefined {
 function deriveOpencodeTaskDetail(
  input: unknown,
  output: unknown,
-  error: unknown,
  metadata: Record<string, unknown> | undefined,
 ): ToolCallDetail | null {
  if (!isRecord(input)) {
@@ -208,7 +192,6 @@ function deriveOpencodeTaskDetail(
    return null;
  }

-  const log = [formatLogEntry(output), formatLogEntry(error)].filter((entry) => entry).join("\n");
  const childSessionId =
    normalizeSubAgentText(metadata?.sessionId) ?? extractOpenCodeTaskSessionId(output);
  return {
@@ -216,7 +199,8 @@ function deriveOpencodeTaskDetail(
    ...(subAgentType ? { subAgentType } : {}),
    ...(description ? { description } : {}),
    ...(childSessionId ? { childSessionId } : {}),
-    log,
+    // COMPAT(subagent-log): remove after 2027-04-30.
+    log: "",
    actions: [],
  };
 }
@@ -373,11 +357,10 @@ export function deriveOpencodeToolDetail(
  toolName: string,
  input: unknown,
  output: unknown,
-  error: unknown = null,
  metadata?: Record<string, unknown>,
 ): ToolCallDetail {
  if (toolName.trim().toLowerCase() === "task") {
-    const taskDetail = deriveOpencodeTaskDetail(input, output, error, metadata);
+    const taskDetail = deriveOpencodeTaskDetail(input, output, metadata);
    if (taskDetail) {
      return taskDetail;
    }
@@ -460,7 +460,7 @@ describe("opencode tool-call mapper", () => {
    });
  });

-  it("maps completed task calls with final output log to sub_agent detail", () => {
+  it("maps completed task calls to sub_agent detail", () => {
    const item = expectMapped(
      mapOpencodeToolCall({
        toolName: "task",
@@ -480,7 +480,7 @@ describe("opencode tool-call mapper", () => {
      type: "sub_agent",
      subAgentType: "explore",
      description: "Explore agent-tools codebase",
-      log: "Found the CLI entrypoint and provider registry.",
+      log: "",
      actions: [],
    });
  });
@@ -505,12 +505,12 @@ describe("opencode tool-call mapper", () => {
      subAgentType: "explore",
      description: "Explore current directory",
      childSessionId: "ses_2268db431ffe299vL1bbot8R7Z",
-      log: '<task id="ses_2268db431ffe299vL1bbot8R7Z">done</task>',
+      log: "",
      actions: [],
    });
  });

-  it("maps aborted task calls with preserved error log to sub_agent detail", () => {
+  it("maps aborted task calls to sub_agent detail", () => {
    const item = expectMapped(
      mapOpencodeToolCall({
        toolName: "task",
@@ -531,7 +531,7 @@ describe("opencode tool-call mapper", () => {
      type: "sub_agent",
      subAgentType: "explore",
      description: "Explore agent-tools codebase",
-      log: "Tool execution aborted",
+      log: "",
      actions: [],
    });
  });
@@ -43,7 +43,7 @@ export function mapOpencodeToolCall(params: OpencodeToolCallParams): ToolCallTim
  const error = raw.error ?? null;
  const rawStatus = typeof raw.status === "string" ? raw.status : undefined;
  const status = normalizeToolCallStatus(rawStatus, error, output);
-  const detail = deriveOpencodeToolDetail(name, input, output, error, raw.metadata);
+  const detail = deriveOpencodeToolDetail(name, input, output, raw.metadata);

  if (status === "failed") {
    return {
@@ -1,5 +1,4 @@
 import { z } from "zod";
-import { extractTextFromToolResult } from "../../tool-call-mapper.js";
 import type { PiChildSessionFile, PiExtension } from "../contract.js";
 import type { ProviderSubagentInputEvent } from "../../../../provider-subagents/store.js";

@@ -99,7 +98,8 @@ export const edxethPiSubagents: PiExtension = {
          detail: {
            type: "sub_agent",
            description,
-            log: extractTextFromToolResult(call.result)?.trim() ?? "",
+            // COMPAT(subagent-log): remove after 2027-04-30.
+            log: "",
          },
          subagents,
          childSessions,
@@ -130,6 +130,18 @@ describe("@gotgenes/pi-subagents adapter", () => {
        .filter((event) => event.event.type === "upsert")
        .map((event) => (event.event.type === "upsert" ? event.event.status : null)),
    ).toEqual(["running", "completed"]);
+    expect(
+      events.flatMap((event) => (event.event.type === "timeline" ? [event.event] : [])),
+    ).toEqual([
+      {
+        type: "timeline",
+        id: "call_502323",
+        item: {
+          type: "assistant_message",
+          text: "Agent completed in 4.7s (1 tool uses, 9.0k token).\nAgent ID: 848583f5-6749-4a1\n\nThe workspace is empty.",
+        },
+      },
+    ]);
  });
  test("correlates a background notification and result collection", async () => {
    const source = readSubagentFixture(new URL("./fixtures/background.json", import.meta.url));
@@ -64,7 +64,8 @@ export const gotgenesPiSubagents: PiExtension = {
        type: "sub_agent" as const,
        subAgentType: title,
        description,
-        log: extractTextFromToolResult(call.result)?.trim() ?? "",
+        // COMPAT(subagent-log): remove after 2027-04-30.
+        log: "",
      };
      if (call.status === "running")
        return {
@@ -92,6 +93,10 @@ export const gotgenesPiSubagents: PiExtension = {
        outputFileFromToolResult(call.result) ?? pendingFilesByAgent.get(details.data.agentId);
      pendingFilesByAgent.delete(details.data.agentId);
      const childSessions = childSession(call.callId, file);
+      const childStatus = status(details.data.status);
+      // Without a session file, as on replay, the child's answer is the tool result.
+      const answer =
+        !file && childStatus !== "running" ? extractTextFromToolResult(call.result)?.trim() : "";
      return {
        detail,
        subagents: [
@@ -101,8 +106,17 @@ export const gotgenesPiSubagents: PiExtension = {
            title,
            description,
            toolCallId: call.callId,
-            status: status(details.data.status),
+            status: childStatus,
          },
+          ...(answer
+            ? [
+                {
+                  type: "timeline" as const,
+                  id: call.callId,
+                  item: { type: "assistant_message" as const, text: answer },
+                },
+              ]
+            : []),
        ],
        childSessions,
      };
@@ -118,7 +132,8 @@ export const gotgenesPiSubagents: PiExtension = {
      const detail = {
        type: "sub_agent" as const,
        description: details.success ? details.data.description : undefined,
-        log: extractTextFromToolResult(call.result)?.trim() ?? "",
+        // COMPAT(subagent-log): remove after 2027-04-30.
+        log: "",
      };
      if (call.status === "running" || !details.success) return { detail };
      const file = details.data.transcriptPath;
@@ -210,7 +210,7 @@ describe("Pi extension host", () => {
          type: "sub_agent",
          subAgentType: "scout",
          description: "Inspect files",
-          log: "Found two files",
+          log: "",
        },
      }),
    );
@@ -137,7 +137,7 @@ describe("pi-subagents adapter", () => {
      type: "sub_agent",
      subAgentType: "reviewer",
      description: "Review the Pi mapper change",
-      log: "The mapper change preserves provider status.",
+      log: "",
    });
  });

@@ -131,7 +131,8 @@ export const piSubagents: PiExtension = {
        type: "sub_agent" as const,
        subAgentType: args.data.agent,
        description: args.data.task,
-        log: extractTextFromToolResult(call.result)?.trim() ?? "",
+        // COMPAT(subagent-log): remove after 2027-04-30.
+        log: "",
      };
      const base = {
        type: "upsert" as const,
@@ -54,8 +54,6 @@ export async function verifySubagentFixture(
  try {
    await session.startTurn("Delegate work");
    for (const event of fixture.events) pi.latestSession().emit(event);
-    const immediate = live.filter((event) => event.type === "provider_subagent");
-    expect(immediate.some((event) => event.event.type === "timeline")).toBe(false);
    pi.latestSession().finishTurn();
    const replay: AgentStreamEvent[] = [];
    for await (const event of streamPiHistory("pi", fixture.messages)) replay.push(event);
@@ -36,12 +36,17 @@ describe("@tintinweb/pi-subagents adapter", () => {
    });
    expect(mapping?.subagents).toEqual([
      expect.objectContaining({ id: "call-1", status: "completed" }),
+      {
+        type: "timeline",
+        id: "call-1",
+        item: { type: "assistant_message", text: "Wrapped up (turn limit)" },
+      },
    ]);
    expect(mapping?.detail).toEqual({
      type: "sub_agent",
      subAgentType: "Explore",
      description: "Inspect",
-      log: "Wrapped up (turn limit)",
+      log: "",
    });
  });
  test("maps captured foreground lifecycle live and on replay", async () => {
@@ -53,6 +58,18 @@ describe("@tintinweb/pi-subagents adapter", () => {
        .filter((event) => event.event.type === "upsert")
        .map((event) => (event.event.type === "upsert" ? event.event.status : null)),
    ).toEqual(["running", "completed"]);
+    expect(
+      events.flatMap((event) => (event.event.type === "timeline" ? [event.event] : [])),
+    ).toEqual([
+      {
+        type: "timeline",
+        id: "call_458926",
+        item: {
+          type: "assistant_message",
+          text: "Agent completed in 6.6s (1 tool uses, 18.8k token).\n\nThe workspace directory `/tmp/paseo-pi-extension-phase3/workspace` is empty (no files or hidden dotfiles).",
+        },
+      },
+    ]);
  });
  test("uses a structured notification to complete a background child", async () => {
    const source = readSubagentFixture(new URL("./fixtures/background.json", import.meta.url));
@@ -147,7 +164,7 @@ describe("@tintinweb/pi-subagents adapter", () => {
      expect(mapping?.detail).toEqual({
        type: "sub_agent",
        description: undefined,
-        log: "Wrapped up (turn limit)",
+        log: "",
      });
    },
  );
@@ -57,7 +57,8 @@ export const tintinwebPiSubagents: PiExtension = {
        type: "sub_agent" as const,
        subAgentType: title,
        description,
-        log: extractTextFromToolResult(call.result)?.trim() ?? "",
+        // COMPAT(subagent-log): remove after 2027-04-30.
+        log: "",
      };
      if (call.status === "running")
        return {
@@ -84,6 +85,10 @@ export const tintinwebPiSubagents: PiExtension = {
      const file = outputFileFromToolResult(call.result);
      const childSessions = file && !readSessions.has(file) ? [{ id: call.callId, file }] : [];
      if (file) readSessions.add(file);
+      const childStatus = status(details.data.status);
+      // A foreground child has no session file; its answer is the tool result.
+      const answer =
+        !file && childStatus !== "running" ? extractTextFromToolResult(call.result)?.trim() : "";
      return {
        detail,
        subagents: [
@@ -93,8 +98,17 @@ export const tintinwebPiSubagents: PiExtension = {
            title,
            description,
            toolCallId: call.callId,
-            status: status(details.data.status),
+            status: childStatus,
          },
+          ...(answer
+            ? [
+                {
+                  type: "timeline" as const,
+                  id: call.callId,
+                  item: { type: "assistant_message" as const, text: answer },
+                },
+              ]
+            : []),
        ],
        childSessions,
      };
@@ -110,7 +124,8 @@ export const tintinwebPiSubagents: PiExtension = {
      const detail = {
        type: "sub_agent" as const,
        description: details.success ? details.data.description : undefined,
-        log: extractTextFromToolResult(call.result)?.trim() ?? "",
+        // COMPAT(subagent-log): remove after 2027-04-30.
+        log: "",
      };
      if (call.status === "running" || !details.success) return { detail };
      return {
@@ -2091,3 +2091,80 @@ test.each(["removed", "disabled"] as const)(
    ).toEqual([]);
  },
 );
+
+test(
+  "a 50 MiB timeline crosses a routed host without dropping content or the route",
+  { timeout: 30000 },
+  async () => {
+    const b = await daemon();
+    const a = await daemon();
+    const destination = await api(b);
+    const origin = await api(a);
+    const workspace = await destination.paseo.workspaces.create({
+      source: { kind: "directory", path: b.staticDir },
+    });
+    const agent = await workspace.agents.create({
+      config: { provider: "claude/claude-test", modeId: "full-access" },
+      title: "Large history",
+    });
+    // Keep each row below the established item budget; exercise transport size across rows.
+    const text = "x".repeat(240 * 1024);
+    const rowCount = 220;
+    for (let index = 0; index < rowCount; index++) {
+      await b.daemon.agentManager.appendTimelineItem(agent.id, { type: "user_message", text });
+    }
+    await origin.paseo.hosts.add({ connection: `127.0.0.1:${b.port}` });
+    const serverId = (await online(origin.paseo)).hosts[0]!.serverId!;
+    const remote = await origin.paseo.hosts.client(serverId);
+    const response = await remote.agents.ref(agent.id).timeline.refetch({ limit: 0 });
+    const messages = response.entries.flatMap((row) =>
+      row.item.type === "user_message" ? [row.item.text] : [],
+    );
+    expect(messages).toHaveLength(rowCount);
+    expect(messages.every((message) => message === text)).toBe(true);
+    expect(
+      messages.reduce((bytes, message) => bytes + Buffer.byteLength(message), 0),
+    ).toBeGreaterThan(50 * 1024 * 1024);
+    expect((await remote.workspaces.list()).entries).toHaveLength(1);
+    await remote.dispose();
+  },
+);
+
+test("a pre-write host budget rejection leaves sibling routes connected", async () => {
+  const { HostTransportBudget } = await import("@getpaseo/client/node");
+  const b = await daemon();
+  const origin = createHostClient(
+    `127.0.0.1:${b.port}`,
+    { clientId: "budget-origin", reconnect: { enabled: false } },
+    new HostTransportBudget(1024 * 1024),
+  );
+  cleanup.push(() => origin.close());
+  await origin.connect();
+  const serverId = origin.getLastServerInfoMessage()!.serverId;
+  const routeIds = [
+    await origin.openHostLink("budget-first"),
+    await origin.openHostLink("budget-sibling"),
+  ];
+  const peers = routeIds.map(
+    (id, index) =>
+      new DaemonClient({
+        url: "ws://host-link/ws",
+        clientId: `budget-child-${index}`,
+        reconnect: { enabled: false },
+        transportFactory: createHostChannelTransport(origin, serverId, `budget-${index}`, id),
+      }),
+  );
+  for (const peer of peers) {
+    cleanup.push(() => peer.close());
+    await peer.connect();
+  }
+  await expect(async () =>
+    origin.sendHostFrame(routeIds[0]!, new Uint8Array(2 * 1024 * 1024)),
+  ).rejects.toMatchObject({ code: "resource_limit" });
+  await peers[1]!.ping({ timeoutMs: 2000 });
+  expect([origin.isConnected, ...peers.map((peer) => peer.isConnected)]).toEqual([
+    true,
+    true,
+    true,
+  ]);
+}, 30000);
@@ -510,10 +510,13 @@ export class ConnectedHosts {
          return;
        }
        if (!verified) throw new HostError("host_offline", "Host identity has not been verified");
-        try {
-          transport.send(data);
-        } catch {
+        const rejectWrite = () =>
          route.close("resource_limit", "Host buffer limit reached or transport unavailable");
+        try {
+          const write = transport.send(data);
+          if (write) void write.catch(rejectWrite);
+        } catch {
+          rejectWrite();
        }
      },
    };
@@ -1,7 +1,11 @@
 import type { SessionDelivery } from "../session/owned-subscriptions/index.js";
 import { EventEmitter } from "node:events";
 import { createHash } from "node:crypto";
-import { encodeHostRouteFrame, type HostRouteFrame } from "@getpaseo/protocol/binary-frames/index";
+import {
+  MAX_HOST_CHANNEL_FRAME_BYTES,
+  encodeHostRouteFrame,
+  type HostRouteFrame,
+} from "@getpaseo/protocol/binary-frames/index";
 import type {
  DaemonPermission,
  SessionInboundMessage,
@@ -10,6 +14,7 @@ import type {

 /** A logical socket has no network resources or authority of its own. */
 export class VirtualHostSocket extends EventEmitter {
+  readonly maxFrameBytes = MAX_HOST_CHANNEL_FRAME_BYTES;
  readyState = 1;
  constructor(
    private readonly output: (data: string | Uint8Array) => Promise<void>,
@@ -1,6 +1,3 @@
-import { execFile } from "node:child_process";
-import { promisify } from "node:util";
-import { fileURLToPath } from "node:url";
 import { mkdtempSync, rmSync } from "node:fs";
 import { tmpdir } from "node:os";
 import path from "node:path";
@@ -10,7 +7,7 @@ import { ClaudeAgentClient } from "../agent/providers/claude/agent.js";
 import { createTestPaseoDaemon } from "../test-utils/paseo-daemon.js";
 import { DaemonClient } from "../test-utils/daemon-client.js";

-test("background cards retain child actions after the parent finishes (#6253)", async () => {
+test("background children keep their actions after the parent finishes (#6253)", async () => {
  const cwd = mkdtempSync(path.join(tmpdir(), "paseo-background-card-"));
  const logger = pino({ level: "silent" });
  const daemon = await createTestPaseoDaemon({
@@ -62,22 +59,6 @@ test("background cards retain child actions after the parent finishes (#6253)",
      limit: 0,
      projection: "projected",
    });
-    const { stdout } = await promisify(execFile)(
-      process.execPath,
-      [
-        "--conditions=source",
-        "--import",
-        "tsx",
-        fileURLToPath(new URL("../../../../cli/src/index.ts", import.meta.url)),
-        "--host",
-        `127.0.0.1:${daemon.port}`,
-        "logs",
-        agent.id,
-      ],
-      { env: { ...process.env, PASEO_HOME: daemon.paseoHome }, timeout: 30_000 },
-    );
-    expect(stdout).toContain("[Bash] ls -1");
-    expect(stdout).toContain("[Bash] pwd");
    expect(
      atFinish.entries.filter(
        (row) => row.item.type === "tool_call" && row.item.detail?.type === "sub_agent",
@@ -94,9 +75,6 @@ test("background cards retain child actions after the parent finishes (#6253)",
        ),
      ).toBe(true);
    }
-    for (const card of cards) {
-      expect(card.detail?.type === "sub_agent" ? card.detail.log : "").toContain("[Bash]");
-    }
  } finally {
    await client.close();
    await daemon.close();
@@ -0,0 +1,46 @@
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import { expect, test } from "vitest";
+import { createDaemonTestContext } from "../test-utils/index.js";
+
+// #2220: a timeline page is one WebSocket message, so a few huge entries used to close the socket.
+test.each([40, 0])(
+  "fetching image-heavy history with limit %i keeps the direct connection usable",
+  async (limit) => {
+    const ctx = await createDaemonTestContext();
+    const cwd = mkdtempSync(path.join(tmpdir(), "oversized-timeline-"));
+    try {
+      const agent = await ctx.client.createAgent({ provider: "codex", cwd });
+      const imageUrl = `data:image/jpeg;base64,${"A".repeat(14 * 1024 * 1024)}`;
+      for (let index = 0; index < 5; index += 1) {
+        await ctx.daemon.daemon.agentManager.appendTimelineItem(agent.id, {
+          type: "tool_call",
+          callId: `screenshot-${index}`,
+          name: "node_repl.js",
+          status: "completed",
+          error: null,
+          detail: {
+            type: "unknown",
+            input: { index },
+            output: { _meta: { "codex/toolSurface": { screenshot: { url: imageUrl } } } },
+          },
+        });
+      }
+
+      const page = await ctx.client.fetchAgentTimeline(agent.id, { direction: "tail", limit });
+      const screenshots = page.entries.filter((entry) => entry.item.type === "tool_call");
+      expect(screenshots).toHaveLength(5);
+      for (const entry of screenshots) {
+        expect(Buffer.byteLength(JSON.stringify(entry.item))).toBeLessThanOrEqual(64 * 1024);
+      }
+
+      const next = await ctx.client.fetchAgentTimeline(agent.id, { direction: "tail", limit: 1 });
+      expect(next.entries).toHaveLength(1);
+    } finally {
+      await ctx.cleanup();
+      rmSync(cwd, { recursive: true, force: true });
+    }
+  },
+  60_000,
+);
@@ -9,7 +9,7 @@ import {
 } from "@getpaseo/protocol/binary-frames/index";
 import {
  getDaemonAuthFailureReason,
-  type DaemonClient as HostClient,
+  DaemonClient as HostClient,
 } from "@getpaseo/client/internal/daemon-client";
 import type { SessionOutboundMessage } from "@getpaseo/protocol/messages";
 import { describe, expect, test } from "vitest";
@@ -593,72 +593,112 @@ async function waitForCapturedLog(
    }
  }, 90000);

-  test("oversized attachments fail without disconnecting or resubmitting over the relay", async () => {
-    await startRelay({ useLocalRelay: true });
-    const daemon = await createTestPaseoDaemon({
-      relayEnabled: true,
-      relayEndpoint: `127.0.0.1:${relayPort}`,
-      relayUseTls: false,
-      relayPublicUseTls: false,
-    });
-    let client: DaemonClient | null = null;
-    try {
-      const offerUrl = await getPairingOfferUrl({
-        paseoHome: daemon.paseoHome,
+  test.each([true, false])(
+    "large messages cross the relay with unpaced upload admission preserved (supportsDrain=%s)",
+    async (supportsDrain) => {
+      await startRelay({ useLocalRelay: true });
+      const daemon = await createTestPaseoDaemon({
        relayEnabled: true,
-        relayEndpoint: daemon.config.relayEndpoint,
+        relayEndpoint: `127.0.0.1:${relayPort}`,
+        relayUseTls: false,
+        relayPublicUseTls: false,
      });
-      const { serverId, daemonPublicKeyB64 } = decodeOfferFromFragmentUrl(offerUrl);
-      client = new DaemonClient({
-        url: buildRelayWebSocketUrl({
-          endpoint: `127.0.0.1:${relayPort}`,
-          useTls: false,
-          serverId,
-          role: "client",
-        }),
-        e2ee: { enabled: true, daemonPublicKeyB64 },
-        reconnect: { baseDelayMs: 100, maxDelayMs: 100 },
-      });
-      await client.connect();
-      const statuses: string[] = [];
-      client.subscribeConnectionStatus((state) => statuses.push(state.status));
-      for (const imageMiB of [30, 61]) {
-        // Attachments are base64 in the JSON, then E2EE base64 expands the frame again.
-        const images = [
-          { data: "A".repeat(4 * Math.ceil((imageMiB * 1024 * 1024) / 3)), mimeType: "image/png" },
-        ];
+      let client: HostClient | null = null;
+      try {
+        const offerUrl = await getPairingOfferUrl({
+          paseoHome: daemon.paseoHome,
+          relayEnabled: true,
+          relayEndpoint: daemon.config.relayEndpoint,
+        });
+        const { serverId, daemonPublicKeyB64 } = decodeOfferFromFragmentUrl(offerUrl);
+        client = new HostClient({
+          clientId: "paced-relay-regression",
+          webSocketFactory: Object.assign((url: string) => new WebSocket(url), { supportsDrain }),
+          url: buildRelayWebSocketUrl({
+            endpoint: `127.0.0.1:${relayPort}`,
+            useTls: false,
+            serverId,
+            role: "client",
+          }),
+          e2ee: { enabled: true, daemonPublicKeyB64 },
+          reconnect: { baseDelayMs: 100, maxDelayMs: 100 },
+        });
+        await client.connect();
+        const statuses: string[] = [];
+        client.subscribeConnectionStatus((state) => statuses.push(state.status));
+        for (const imageMiB of [30, 61]) {
+          const images = [
+            {
+              data: "A".repeat(4 * Math.ceil((imageMiB * 1024 * 1024) / 3)),
+              mimeType: "image/png",
+            },
+          ];
+          const creation = client.createWorkspace({
+            source: { kind: "directory", path: daemon.staticDir },
+            agent: {
+              provider: "claude",
+              cwd: daemon.staticDir,
+              initialPrompt: "Describe these screens.",
+              images,
+            },
+          });
+          if (supportsDrain)
+            await withTimeout(creation, 30000, "Chunked workspace creation did not settle");
+          else await expect(creation).rejects.toThrow(/too large.*32\.0 MiB/);
+        }
+        expect((await client.fetchAgents()).entries).toHaveLength(supportsDrain ? 2 : 0);
        await expect(
-          withTimeout(
-            client.createWorkspace({
-              source: { kind: "directory", path: daemon.staticDir },
-              agent: {
-                provider: "claude",
-                cwd: daemon.staticDir,
-                initialPrompt: "Describe these screens.",
-                images,
-              },
-            }),
-            10000,
-            "Workspace creation did not settle",
-          ),
-        ).rejects.toThrow(/too large.*32\.0 MiB/);
-        expect((await client.fetchAgents()).entries).toEqual([]);
-      }
-      const agent = await client.createAgent({ provider: "claude", cwd: daemon.staticDir });
-      await expect(
-        client.sendMessage(agent.id, "Describe these screens.", {
+          client.createWorkspace({
+            source: { kind: "directory", path: daemon.staticDir },
+            agent: {
+              provider: "claude",
+              cwd: daemon.staticDir,
+              initialPrompt: "Describe these screens.",
+              images: [{ data: "A".repeat(101 * 1024 * 1024), mimeType: "image/png" }],
+            },
+          }),
+        ).rejects.toThrow(/too large.*100\.0 MiB/);
+        expect((await client.fetchAgents()).entries).toHaveLength(supportsDrain ? 2 : 0);
+        const agent = await client.createAgent({ provider: "claude", cwd: daemon.staticDir });
+        const attachment = client.sendMessage(agent.id, "Describe these screens.", {
          images: [{ data: "A".repeat(40 * 1024 * 1024), mimeType: "image/png" }],
-        }),
-      ).rejects.toThrow(/too large.*32\.0 MiB/);
-      await client.sendMessage(agent.id, "A small follow-up still works.");
-      expect((await client.fetchAgents()).entries).toHaveLength(1);
-      expect(statuses).toEqual(["connected"]);
-    } finally {
-      await client?.close();
-      await daemon.close();
-      await stopRelay();
-    }
-  }, 60000);
+        });
+        if (supportsDrain) await attachment;
+        else await expect(attachment).rejects.toThrow(/too large.*32\.0 MiB/);
+        await expect(
+          client.sendMessage(agent.id, "Describe these screens.", {
+            images: [{ data: "A".repeat(101 * 1024 * 1024), mimeType: "image/png" }],
+          }),
+        ).rejects.toThrow(/too large.*100\.0 MiB/);
+        await client.sendMessage(agent.id, "A small follow-up still works.");
+        expect((await client.fetchAgents()).entries).toHaveLength(supportsDrain ? 3 : 1);
+        // Respect the per-item content budget while exceeding the relay frame limit.
+        const text = "x".repeat(240 * 1024);
+        for (let row = 0; row < 220; row++)
+          await daemon.daemon.agentManager.appendTimelineItem(agent.id, {
+            type: "user_message",
+            text,
+          });
+        const timeline = await client.fetchAgentTimeline(agent.id, {
+          projection: "canonical",
+          limit: 0,
+          timeout: 30000,
+        });
+        const delivered = timeline.entries.filter(
+          (row) => row.item.type === "user_message" && row.item.text === text,
+        );
+        expect(delivered).toHaveLength(220);
+        expect(delivered.length * Buffer.byteLength(text)).toBeGreaterThan(50 * 1024 * 1024);
+        await client.ping();
+        expect(statuses).toEqual(["connected"]);
+      } finally {
+        await client?.close();
+        await daemon.close();
+        await stopRelay();
+      }
+    },
+    120000,
+  );

  test("daemon connects to relay and client ping/pong works through relay", async () => {
    process.env.PASEO_PRIMARY_LAN_IP = "192.168.1.12";
@@ -1836,3 +1836,58 @@ describe("list terminals across directories", () => {
    ]);
  });
 });
+
+test("a paused terminal consumer catches up through a snapshot instead of retaining every output frame", async () => {
+  const { existsSync } = await import("node:fs");
+  const cwd = tmpCwd();
+  tempDirs.push(cwd);
+  const marker = path.join(cwd, "output-complete");
+  const created = await createTerminalInWorkspace(ctx.client, {
+    cwd,
+    options: {
+      command: process.execPath,
+      args: [
+        "-e",
+        `
+      const fs = require('node:fs');
+      process.stdin.setRawMode?.(true);
+      process.stdin.resume();
+      process.stdin.once('data', () => {
+        const chunk = Buffer.alloc(256 * 1024, 120);
+        let remaining = 128;
+        const write = () => {
+          if (remaining-- === 0) { fs.writeFileSync(${JSON.stringify(marker)}, 'done'); return; }
+          process.stdout.write(chunk, write);
+        };
+        write();
+      });
+    `,
+      ],
+    },
+  });
+  const ws = await connectRawWebSocket(ctx.daemon.port);
+  try {
+    const slot = await subscribeRawTerminal(ws, created.terminal!.id, "slow-terminal");
+    await waitForRawBinaryFrame(
+      ws,
+      (frame) => frame.slot === slot && frame.opcode === TerminalStreamOpcode.Snapshot,
+    );
+    const capture = startTerminalOutputCapture(ws, slot);
+    try {
+      ws.pause();
+      sendRawTerminalInput(ws, slot, "go\n");
+      await waitForCondition(() => existsSync(marker), 20000);
+      ws.resume();
+      await waitForCondition(() => capture.snapshotCount > 0, 10000);
+      expect(ws.readyState).toBe(WebSocket.OPEN);
+      expect(capture.frames.reduce((total, frame) => total + frame.payloadBytes, 0)).toBeLessThan(
+        32 * 1024 * 1024,
+      );
+    } finally {
+      ws.resume();
+      capture.stop();
+    }
+  } finally {
+    await closeWebSocket(ws);
+  }
+}, 40000);
@@ -90,7 +90,11 @@ test(
  TEST_TIMEOUT_MS,
 );

-async function connectSocket(port: number, clientId: string): Promise<WebSocket> {
+async function connectSocket(
+  port: number,
+  clientId: string,
+  capabilities?: Record<string, unknown>,
+): Promise<WebSocket> {
  const socket = new WebSocket(`ws://127.0.0.1:${port}/ws`);
  await new Promise<void>((resolve, reject) => {
    socket.once("open", resolve);
@@ -98,7 +102,7 @@ async function connectSocket(port: number, clientId: string): Promise<WebSocket>
  });
  await sendAndWait(
    socket,
-    { type: "hello", clientId, clientType: "browser", protocolVersion: 1 },
+    { type: "hello", clientId, clientType: "browser", protocolVersion: 1, capabilities },
    (message) =>
      message.type === "session" &&
      message.message.type === "status" &&
@@ -166,3 +170,97 @@ function sendAndWait(
  socket.send(JSON.stringify(message));
  return response;
 }
+
+test("an awaited timeline framing overflow closes the actual daemon socket", async () => {
+  const { createHostClient } = await import("@getpaseo/client/node");
+  const { createPaseoApi } = await import("@getpaseo/client");
+  const { default: pino } = await import("pino");
+  const { Writable } = await import("node:stream");
+  const messages: string[] = [];
+  const logger = pino(
+    { level: "warn" },
+    new Writable({
+      write(chunk, _encoding, done) {
+        messages.push(JSON.parse(chunk.toString()).msg);
+        done();
+      },
+    }),
+  );
+  daemon = await createTestPaseoDaemon({ logger });
+  const client = createHostClient(`127.0.0.1:${daemon.port}`, {
+    clientId: "framing-seed",
+    reconnect: { enabled: false },
+  });
+  await client.connect();
+  const api = createPaseoApi(client);
+  try {
+    const workspace = await api.workspaces.create({
+      source: { kind: "directory", path: daemon.staticDir },
+    });
+    const agents = [];
+    const text = "x".repeat(240 * 1024);
+    for (const [index, rows] of [350, 90].entries()) {
+      const agent = await workspace.agents.create({
+        config: { provider: "claude/claude-test", modeId: "full-access" },
+        title: `Framing overflow ${index}`,
+      });
+      agents.push(agent.id);
+      for (let row = 0; row < rows; row++)
+        await daemon.daemon.agentManager.appendTimelineItem(agent.id, {
+          type: "user_message",
+          text,
+        });
+    }
+    const source = await connectSocket(daemon.port, "framing-overflow", {
+      binary_chunking_v1: true,
+    });
+    sockets.push(source);
+    const closed = new Promise<void>((resolve) => source.once("close", () => resolve()));
+    const firstChunk = new Promise<void>((resolve) => {
+      const listener = (data: RawData, binary: boolean) => {
+        if (!binary || (data as Buffer)[0] !== 0x31) return;
+        source.off("message", listener);
+        source.pause();
+        resolve();
+      };
+      source.on("message", listener);
+    });
+    const fetch = (agentId: string, requestId: string) =>
+      source.send(
+        JSON.stringify({
+          type: "session",
+          message: {
+            type: "fetch_agent_timeline_request",
+            requestId,
+            agentId,
+            direction: "tail",
+            projection: "canonical",
+            limit: 0,
+          },
+        }),
+      );
+    fetch(agents[0]!, "first");
+    await firstChunk;
+    fetch(agents[1]!, "overflow");
+    await expect
+      .poll(() => messages.includes("Closing physical WebSocket after outbound framing failure"), {
+        timeout: 15000,
+      })
+      .toBe(true);
+    expect(messages).not.toContain("Closing physical WebSocket at outbound high-water mark");
+    source.resume();
+    await closed;
+  } finally {
+    await api.dispose();
+    await client.close();
+  }
+}, 60000);
+
+test("malformed chunk metadata closes the daemon socket with a protocol error", async () => {
+  daemon = await createTestPaseoDaemon();
+  const source = await connectSocket(daemon.port, "invalid-framing", { binary_chunking_v1: true });
+  sockets.push(source);
+  const closed = new Promise<number>((resolve) => source.once("close", (code) => resolve(code)));
+  source.send(new Uint8Array([0x31, 2, 0, 3, 65]));
+  expect(await closed).toBe(1002);
+});
@@ -1,3 +1,7 @@
+import {
+  ChunkedTransport,
+  ChunkedTransportProtocolError,
+} from "@getpaseo/protocol/chunked-transport";
 import { type WorkspaceRuntimeStore } from "./workspace-runtime-store/index.js";
 import {
  createAgentMessageDelivery,
@@ -124,8 +128,8 @@ import {
  MAX_PHYSICAL_SOCKET_BUFFERED_BYTES,
  outboundFrameByteLength,
  physicalSocketHasCapacity,
-  sendBoundedPhysicalFrame,
  sendBoundedPhysicalFrameAndWait,
+  sendBoundedPhysicalFrame,
 } from "./websocket/physical-socket.js";

 const WS_CLOSE_DAEMON_AUTH_FAILED = 4401;
@@ -440,6 +444,7 @@ function bufferFromWsData(data: Buffer | ArrayBuffer | Buffer[] | string): Buffe
 }

 export interface WebSocketLike {
+  maxFrameBytes?: number;
  readyState: number;
  bufferedAmount?: number;
  send: (
@@ -1273,6 +1278,67 @@ export class VoiceAssistantWebSocketServer {
    return { sockets: writableSockets, payload, bytes: outboundFrameByteLength(payload) };
  }

+  private sendHelloResponse(ws: WebSocketLike, session: Session, hello: WSHelloMessage): void {
+    // The peer learns our support from this ordinary response before receiving chunks.
+    this.sendToClient(ws, this.createServerInfoMessage(session));
+    this.chunkedSocket(ws).enabled = hello.capabilities?.[CLIENT_CAPS.binaryChunkingV1] === true;
+  }
+
+  private readonly chunkedSockets = new WeakMap<WebSocketLike, ChunkedTransport>();
+
+  private chunkedSocket(ws: WebSocketLike): ChunkedTransport {
+    let transport = this.chunkedSockets.get(ws);
+    if (!transport) {
+      transport = new ChunkedTransport({
+        frameBytes: ws.maxFrameBytes ?? 32 * 1024 * 1024,
+        onFailure: (err) =>
+          this.closePhysicalSocket({
+            ws,
+            logMessage: "Closing physical WebSocket after outbound framing failure",
+            logFields: { err },
+          }),
+        send: (frame, waitForDrain) => {
+          const params = {
+            socket: ws,
+            frame,
+            onHighWater: () => this.closeAtOutboundHighWater(ws),
+          };
+          if (waitForDrain)
+            return sendBoundedPhysicalFrameAndWait(params).then((sent) => {
+              if (!sent) throw new Error("Source is closed");
+              return undefined;
+            });
+          if (!sendBoundedPhysicalFrame(params)) throw new Error("Source is closed");
+        },
+        deliver: (frame) =>
+          this.handleRawMessage(ws, typeof frame === "string" ? frame : Buffer.from(frame)),
+      });
+      this.chunkedSockets.set(ws, transport);
+    }
+    return transport;
+  }
+
+  private socketBufferedAmount(ws: WebSocketLike): number | null {
+    const queued = this.chunkedSockets.get(ws)?.queuedByteLength ?? 0;
+    if (typeof ws.bufferedAmount === "number") return ws.bufferedAmount + queued;
+    return queued > 0 ? queued : null;
+  }
+
+  private sendSocketFrame(
+    ws: WebSocketLike,
+    frame: string | Uint8Array,
+    bytes: number,
+    waitForDrain = false,
+  ): Promise<void> {
+    const transport = this.chunkedSocket(ws);
+    const admittedBytes = transport.isWriting
+      ? bytes
+      : Math.min(bytes, ws.maxFrameBytes ?? 32 * 1024 * 1024);
+    if (!this.ensureOutboundCapacity(ws, admittedBytes))
+      return Promise.reject(new Error("Source is closed"));
+    return transport.send(frame, { waitForDrain, byteLength: bytes });
+  }
+
  private async sendMessageToClientAndWait(
    ws: WebSocketLike,
    message: WSOutboundMessage,
@@ -1280,13 +1346,7 @@ export class VoiceAssistantWebSocketServer {
    const prepared = this.prepareJsonDelivery([ws], message, true);
    if (!prepared) throw new Error("Source message delivery unavailable");
    try {
-      const sent = await sendBoundedPhysicalFrameAndWait({
-        socket: ws,
-        frame: prepared.payload,
-        frameBytes: prepared.bytes,
-        onHighWater: () => this.closeAtOutboundHighWater(ws),
-      });
-      if (!sent) throw new Error("Source is closed");
+      await this.sendSocketFrame(ws, prepared.payload, prepared.bytes, true);
      this.runtimeMetrics.recordOutboundMessage(message, ws.bufferedAmount);
    } catch (err) {
      this.logger.warn({ err }, "ws_send_failed");
@@ -1313,14 +1373,7 @@ export class VoiceAssistantWebSocketServer {
      return;
    }
    try {
-      const sent = await sendBoundedPhysicalFrameAndWait({
-        socket: ws,
-        frame,
-        onHighWater: () => this.closeAtOutboundHighWater(ws),
-      });
-      if (!sent) {
-        throw new Error("Physical WebSocket is not open");
-      }
+      await this.sendSocketFrame(ws, frame, frame.byteLength, true);
      this.runtimeMetrics.recordOutboundBinaryFrame(ws.bufferedAmount);
    } catch (err) {
      this.logger.warn({ err }, "ws_send_failed");
@@ -1335,13 +1388,9 @@ export class VoiceAssistantWebSocketServer {
    recordSent: () => void,
  ): void {
    try {
-      const sent = sendBoundedPhysicalFrame({
-        socket: ws,
-        frame,
-        frameBytes,
-        onHighWater: () => this.closeAtOutboundHighWater(ws),
+      void this.sendSocketFrame(ws, frame, frameBytes).then(recordSent, (err) => {
+        this.logger.warn({ err }, "ws_send_failed");
      });
-      if (sent) recordSent();
    } catch (err) {
      this.logger.warn({ err }, "ws_send_failed");
    }
@@ -1349,7 +1398,13 @@ export class VoiceAssistantWebSocketServer {

  private ensureOutboundCapacity(ws: WebSocketLike, frameBytes: number): boolean {
    if (ws.readyState !== 1) return false;
-    if (physicalSocketHasCapacity(ws, frameBytes)) return true;
+    if (
+      physicalSocketHasCapacity(
+        { bufferedAmount: this.socketBufferedAmount(ws) ?? undefined },
+        frameBytes,
+      )
+    )
+      return true;

    this.closeAtOutboundHighWater(ws);
    return false;
@@ -1522,16 +1577,15 @@ export class VoiceAssistantWebSocketServer {
        if (!connection) {
          return null;
        }
-        if (source) return (source as WebSocketLike).bufferedAmount ?? null;
+        if (source) return this.socketBufferedAmount(source as WebSocketLike);
        // Relay-attached sockets are a WebSocketLike that doesn't expose
        // bufferedAmount. Return null when no socket gives a signal so the
        // terminal fallback can't mistake "no signal" for "client keeping up";
        // a direct ws reports its real buffered bytes (0 when drained).
        let maxBuffered: number | null = null;
        for (const socket of connection.sockets) {
-          if (typeof socket.bufferedAmount === "number") {
-            maxBuffered = Math.max(maxBuffered ?? 0, socket.bufferedAmount);
-          }
+          const buffered = this.socketBufferedAmount(socket);
+          if (buffered !== null) maxBuffered = Math.max(maxBuffered ?? 0, buffered);
        }
        return maxBuffered;
      },
@@ -1568,8 +1622,9 @@ export class VoiceAssistantWebSocketServer {
        let total = 0;
        for (const socket of this.sessions.keys()) {
          if (socket instanceof VirtualHostSocket) continue;
-          if (typeof socket.bufferedAmount !== "number") return null;
-          total += socket.bufferedAmount;
+          const buffered = this.socketBufferedAmount(socket);
+          if (buffered === null) return null;
+          total += buffered;
        }
        return total;
      },
@@ -1770,7 +1825,7 @@ export class VoiceAssistantWebSocketServer {
      this.externalSessionsByKey.set(sessionKey, connection);
    }
    pending.identity.sessionId = connection.session.getSessionId();
-    this.sendToClient(ws, this.createServerInfoMessage(connection.session));
+    this.sendHelloResponse(ws, connection.session, message);
    connection.connectionLogger.info(
      {
        ...toConnectionLogFields(pending.identity),
@@ -1906,7 +1961,7 @@ export class VoiceAssistantWebSocketServer {
    existing.sockets.add(ws);
    this.sessions.set(ws, existing);
    pending.identity.sessionId = existing.session.getSessionId();
-    this.sendToClient(ws, this.createServerInfoMessage(existing.session));
+    this.sendHelloResponse(ws, existing.session, message);
    pending.connectionLogger.info(
      {
        ...toConnectionLogFields(pending.identity),
@@ -1952,6 +2007,7 @@ export class VoiceAssistantWebSocketServer {
        usageSetting: true,
        usageSources: true,
        ownedSubscriptions: true,
+        binaryChunkingV1: true,
        agentRequestReceipts: true,
        workspaceRequestReceipts: true,
        creationLifecycle: true,
@@ -2165,10 +2221,16 @@ export class VoiceAssistantWebSocketServer {
  private bindSocketHandlers(ws: WebSocketLike): void {
    ws.on("message", (...args: unknown[]) => {
      const data = args[0] as Buffer | ArrayBuffer | Buffer[] | string;
-      this.handleRawMessage(ws, data);
+      try {
+        this.chunkedSocket(ws).receive(typeof data === "string" ? data : bufferFromWsData(data));
+      } catch (error) {
+        if (!(error instanceof ChunkedTransportProtocolError)) throw error;
+        ws.close(1002, "Invalid chunked transport");
+      }
    });

    ws.on("close", async (...args: unknown[]) => {
+      this.chunkedSockets.get(ws)?.close();
      const code = args[0];
      const reason = args[1];
      await this.detachSocket(ws, {
@@ -2568,7 +2630,7 @@ export class VoiceAssistantWebSocketServer {
        identity: JSON.stringify([connection.principalId, connection.clientId]),
        permissions: () => connection.session.getPermissions(),
        routed: () => connection.session.isRouted(),
-        bufferedAmount: () => ws.bufferedAmount ?? null,
+        bufferedAmount: () => this.socketBufferedAmount(ws),
        delivery: connection.session.delivery,
        admit: (socket, permissions) =>
          this.attachSocket(socket, undefined, undefined, false, {
@@ -140,3 +140,74 @@ test("encrypted sockets do not double-count bytes already buffered by the transp

  expect(socket.bufferedAmount).toBe(payload.byteLength + 40);
 });
+
+test("50 MiB logical text and routed binary cross encrypted relay frames in both directions", async () => {
+  const { ChunkedTransport } = await import("@getpaseo/protocol/chunked-transport");
+  const { openClientSecureChannel, openDaemonSecureChannel } = await import("@getpaseo/relay/e2ee");
+  const { generateKeyPair, exportPublicKey, maxSecuredPlaintextByteLength } =
+    await import("@getpaseo/relay");
+  const { encodeHostRouteFrame, decodeHostRouteFrame } =
+    await import("@getpaseo/protocol/binary-frames/index");
+  type Transport = import("@getpaseo/relay/e2ee").Transport;
+  const limit = 32 * 1024 * 1024;
+  const wireSizes: number[] = [];
+  const endpoint = (): Transport => ({
+    send: () => {},
+    close: () => {},
+    onmessage: null,
+    onclose: null,
+    onerror: null,
+  });
+  const left = endpoint();
+  const right = endpoint();
+  const wire = (destination: Transport) => (data: string | ArrayBuffer) => {
+    const size = typeof data === "string" ? Buffer.byteLength(data) : data.byteLength;
+    expect(size).toBeLessThanOrEqual(limit);
+    wireSizes.push(size);
+    queueMicrotask(() => destination.onmessage?.({ data, isBinary: typeof data !== "string" }));
+  };
+  left.send = wire(right);
+  right.send = wire(left);
+  const key = generateKeyPair();
+  const delivered: (string | Uint8Array)[][] = [[], []];
+  let receivers: InstanceType<typeof ChunkedTransport>[] = [];
+  const incoming = (index: number) => (data: string | ArrayBuffer) =>
+    receivers[index]!.receive(typeof data === "string" ? data : new Uint8Array(data));
+  const daemonPromise = openDaemonSecureChannel(right, {
+    daemonKeyPair: key,
+    events: { onmessage: incoming(1) },
+  });
+  const client = await openClientSecureChannel(left, {
+    daemonPublicKeyB64: exportPublicKey(key.publicKey),
+    events: { onmessage: incoming(0) },
+  });
+  const daemon = await daemonPromise;
+  receivers = [client, daemon].map(
+    (channel, index) =>
+      new ChunkedTransport({
+        frameBytes: maxSecuredPlaintextByteLength(limit),
+        send: (frame) => channel.send(typeof frame === "string" ? frame : frame.slice().buffer),
+        deliver: (frame) => {
+          delivered[index]!.push(frame);
+        },
+      }),
+  );
+  for (const receiver of receivers) receiver.enabled = true;
+  const text = "x".repeat(50 * 1024 * 1024);
+  wireSizes.length = 0;
+  await receivers[1]!.send(text);
+  await new Promise<void>((resolve) => setImmediate(resolve));
+  expect(delivered[0]).toEqual([text]);
+  expect(wireSizes.length).toBeGreaterThan(1);
+  const routed = encodeHostRouteFrame("route", new Uint8Array(50 * 1024 * 1024).fill(7));
+  await receivers[0]!.send(routed);
+  await new Promise<void>((resolve) => setImmediate(resolve));
+  expect(delivered[1]).toHaveLength(1);
+  const received = decodeHostRouteFrame(delivered[1]![0] as Uint8Array)!;
+  expect(received.routeId).toBe("route");
+  expect(
+    Buffer.from(received.payload).equals(Buffer.from(new Uint8Array(50 * 1024 * 1024).fill(7))),
+  ).toBe(true);
+  client.close();
+  daemon.close();
+}, 30_000);
@@ -1,3 +1,5 @@
+import { maxSecuredPlaintextByteLength } from "@getpaseo/relay";
+import { MAX_RELAY_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import { EventEmitter } from "node:events";
 import { MAX_PHYSICAL_SOCKET_BUFFERED_BYTES } from "./physical-socket.js";

@@ -8,6 +10,7 @@ export interface EncryptedRelayChannel {
 }

 export interface EncryptedRelaySocket {
+  readonly maxFrameBytes: number;
  readonly readyState: number;
  readonly bufferedAmount: number;
  send: (data: string | Uint8Array | ArrayBuffer) => void | Promise<void>;
@@ -43,6 +46,7 @@ export function createEncryptedRelaySocket(params: {
  });

  return {
+    maxFrameBytes: maxSecuredPlaintextByteLength(MAX_RELAY_WEBSOCKET_MESSAGE_BYTES),
    get readyState() {
      return readyState;
    },
@@ -120,3 +120,96 @@ test("the awaitable physical send rejects callback errors", async () => {
    }),
  ).rejects.toThrow("send failed");
 });
+
+test("ordinary frames expose a paused real socket's backlog and terminate at the physical backstop", async () => {
+  const { once } = await import("node:events");
+  const { WebSocket, WebSocketServer } = await import("ws");
+  const { ChunkedTransport } = await import("@getpaseo/protocol/chunked-transport");
+  const server = new WebSocketServer({ host: "127.0.0.1", port: 0 });
+  await once(server, "listening");
+  const connected = once(server, "connection");
+  const address = server.address();
+  if (typeof address === "string" || !address) throw new Error("Missing server address");
+  const client = new WebSocket(`ws://127.0.0.1:${address.port}`);
+  await once(client, "open");
+  const [socket] = (await connected) as [InstanceType<typeof WebSocket>];
+  const tcp = (socket as unknown as { _socket: import("node:net").Socket })._socket;
+  let terminated = false;
+  const transport = new ChunkedTransport({
+    frameBytes: 32 * 1024 * 1024,
+    deliver: () => {},
+    send: (frame, wait) => {
+      const options = {
+        socket,
+        frame,
+        onHighWater: () => {
+          terminated = true;
+          socket.terminate();
+        },
+      };
+      if (wait) return sendBoundedPhysicalFrameAndWait(options).then(() => undefined);
+      sendBoundedPhysicalFrame(options);
+    },
+  });
+  try {
+    client.pause();
+    tcp.cork();
+    const frame = new Uint8Array(256 * 1024);
+    for (let count = 0; count < 200; count++) await transport.send(frame);
+    expect(socket.bufferedAmount).toBeGreaterThan(4 * 1024 * 1024);
+    expect(transport.queuedByteLength).toBe(0);
+    for (let count = 0; count < 100; count++) {
+      if (terminated) break;
+      await transport.send(frame);
+    }
+    expect(terminated).toBe(true);
+  } finally {
+    transport.close();
+    client.terminate();
+    socket.terminate();
+    await new Promise<void>((resolve) => server.close(() => resolve()));
+  }
+});
+
+test("an awaited framing failure terminates its real socket immediately", async () => {
+  const { once } = await import("node:events");
+  const { WebSocket, WebSocketServer } = await import("ws");
+  const { ChunkedTransport } = await import("@getpaseo/protocol/chunked-transport");
+  const server = new WebSocketServer({ host: "127.0.0.1", port: 0 });
+  await once(server, "listening");
+  const connected = once(server, "connection");
+  const address = server.address();
+  if (typeof address === "string" || !address) throw new Error("Missing server address");
+  const client = new WebSocket(`ws://127.0.0.1:${address.port}`);
+  await once(client, "open");
+  const [socket] = (await connected) as [InstanceType<typeof WebSocket>];
+  const tcp = (socket as unknown as { _socket: import("node:net").Socket })._socket;
+  const transport = new ChunkedTransport({
+    frameBytes: 32 * 1024 * 1024,
+    deliver: () => {},
+    onFailure: () => socket.terminate(),
+    send: (frame) =>
+      sendBoundedPhysicalFrameAndWait({
+        socket,
+        frame,
+        onHighWater: () => socket.terminate(),
+      }).then(() => undefined),
+  });
+  transport.enabled = true;
+  try {
+    client.pause();
+    tcp.cork();
+    const closed = once(socket, "close");
+    const first = transport.send(new Uint8Array(100 * 1024 * 1024), { waitForDrain: true });
+    const overflow = transport.send(new Uint8Array([1]), { waitForDrain: true });
+    const settled = Promise.allSettled([first, overflow]);
+    await closed;
+    expect(socket.readyState).toBe(WebSocket.CLOSED);
+    expect((await settled).map((result) => result.status)).toEqual(["rejected", "rejected"]);
+  } finally {
+    transport.close();
+    client.terminate();
+    socket.terminate();
+    await new Promise<void>((resolve) => server.close(() => resolve()));
+  }
+});
Author	SHA1	Message	Date
Mohamed Boudra	41d9bb4294	fix(app): preserve socket capabilities on adopted probe clients	2026-10-30 17:56:57 +01:00
Mohamed Boudra	b044201f62	fix(transport): preserve native admission and pace file writes Sockets without a drain signal retain single-frame outbound admission while accepting chunked responses. Uploads and response-bearing control sends must observe queued admission failures instead of waiting for a response that cannot arrive.	2026-10-30 17:41:57 +01:00
Mohamed Boudra	cacf186a94	fix(transport): keep listener errors outside framing validation Only malformed wire data should close a connection as a protocol violation. Delivery exceptions must leave framing state usable for subsequent messages.	2026-10-30 17:23:27 +01:00
Mohamed Boudra	47b18ffb50	fix(transport): isolate rejected sends from sibling routes Capacity rejection before the first frame is admitted must leave the shared link usable. Observe queued RPC admission failures while keeping response deadlines active during drain.	2026-10-30 17:06:29 +01:00
Mohamed Boudra	ab55377458	test(transport): preserve large coverage with bounded timeline rows Build a response above 50 MiB from rows below the existing content budget. Make the deferred draft-publication journey select a model before submitting so it does not test unresolved provider selection.	2026-10-30 16:33:13 +01:00
Mohamed Boudra	f3d8718c6a	Merge main into transparent transport chunking	2026-10-30 16:25:23 +01:00
Mohamed Boudra	26db1a4672	fix(transport): account for exact bytes and terminate failed framing Bound reassembly by a growing byte buffer instead of retaining an object for every chunk. Notify socket owners of fatal sends even when source delivery discards the promise. Repair the ambiguous composer selector and give its multi-workspace journey enough time to complete.	2026-10-30 16:25:21 +01:00
Mohamed Boudra	f28f0fee3d	fix(transport): preserve backpressure across framing and routes Ordinary daemon writes must remain visible to terminal catch-up and socket admission. Pace chunked writes and explicit completion requests, include waiting logical messages in pressure readings, and propagate origin completion through routed client transports.	2026-10-30 15:51:50 +01:00
Mohamed Boudra	98f667f93e	fix(transport): bound logical messages queued behind slow writers	2026-10-30 15:32:33 +01:00
Mohamed Boudra	8c2a2a9a88	feat(transport): deliver large messages across bounded connections Frame logical messages below serialization and routing so large history responses preserve their contents while fitting encrypted relay and host-channel limits. Negotiate support per connection and retain the existing logical size bound.	2026-10-30 15:28:41 +01:00
Mohamed Boudra	a4f696620b	Keep big agents loadable by bounding every timeline item (#8274 ) * fix(server): bound every timeline item so one fetch cannot close the socket A timeline page is one WebSocket message. Only three tool-call fields were capped, so MCP results, file contents, errors and merged assistant rows could make a 20-entry or even a 1-entry fetch pass the outbound high-water mark. limitAgentTimelineItemContent is now one budgeted walk over any item: 64 KiB for tool calls, 256 KiB for other items. Over budget, the largest strings are cut to a shared length with a visible marker and oversized data URLs become a marker. Fetches also apply it to merged assistant and reasoning rows. * fix(server): keep short strings whole and typed arrays valid when limiting items Strings up to 1 KiB are never cut, so a tool call keeps its callId and an item limits to the same result twice. Arrays drop trailing elements without inserting a marker element, which typed arrays such as todo items would reject.	2026-10-30 15:27:27 +01:00
Mohamed Boudra	184ab66cde	Show sub-agents as launch markers in the parent timeline (#8276 ) * fix: make sub-agent cards launch markers Sub-agent tool calls no longer accumulate the child's activity into `log`. Claude, Codex, OpenCode, OMP and Pi emit the card when the child starts and when its label or status changes; the child's messages and tool calls stay in the sub-agent's own timeline. The app no longer renders a sub-agent log. The wire schema makes `log` optional. Daemons still send `log: ""` so apps that require the field keep parsing the card. * fix(server): put a tintinweb foreground answer in the child timeline A foreground @tintinweb/pi-subagents child has no session file, so its answer only exists in the Agent tool result. Emit that text as the child's assistant message when the child finishes. Tag every sub_agent producer's `log: ""` with COMPAT(subagent-log) so the shim removal finds them. * fix(server): settle child compactions and keep sub-agent cards stable - Codex: a child compaction shown as loading now completes on the child's thread/compacted or turn end, once. - Claude: a streamed child tool call's empty start input is a placeholder, so the assistant message's input reaches its card. - OMP: the task card follows only its first child, so later children no longer re-send an unchanged card. * fix(server): keep a gotgenes foreground answer on replay A foreground @gotgenes/pi-subagents child finds its session file only through the live runtime marker, which history does not keep. Without a file, emit the spawn result text as the child's assistant message.	2026-10-30 21:26:38 +07:00