diff --git a/docs/plugins.md b/docs/plugins.md
index 951738c902..f07f831803 100644
--- a/docs/plugins.md
+++ b/docs/plugins.md
@@ -382,6 +382,15 @@ grace. During daemon startup, plugin sessions may connect while application WebS
 paused; the daemon accepts clients only after configured plugins have settled and the initial
 catalog is complete.
 
+The app retains client bundles per host in its file cache (IndexedDB on web), keyed by plugin ID
+and the daemon's SHA-256. A cold client verifies stored contents before advertising their hashes;
+missing or corrupt files request full bundles. Only the latest catalog's bundles remain. Hashing
+uses Expo's native async digest on mobile, avoiding a JavaScript hash loop on Hermes; reading and
+passing the bundle string still costs memory and time once per client lifetime.
+Persistence runs after catalog reconstruction without delaying installation. One write runs at a
+time; while storage is busy, only the newest pending catalog is kept. A failed write leaves the
+in-memory bundles usable, and a later catalog retries persistence.
+
 When the same plugin contribution exists on multiple hosts, Paseo shows it once in the sidebar and
 adds a host picker to the screen header. The selected host supplies the bundle, RPC transport, and
 query cache. Explicit SDK targets follow the [host API contract](../public-docs/plugins/reference.md#discover-hosts-and-target-another-host).
diff --git a/packages/app/e2e/browser/plugin-timeline.spec.ts b/packages/app/e2e/browser/plugin-timeline.spec.ts
index 166e6b9881..d75653298e 100644
--- a/packages/app/e2e/browser/plugin-timeline.spec.ts
+++ b/packages/app/e2e/browser/plugin-timeline.spec.ts
@@ -1,4 +1,5 @@
 import { test } from "../support/fixtures";
+import { installDaemonWebSocketGate } from "../support/helpers/daemon-websocket-gate";
 import {
   withTimelinePlugin,
   viewInlineThinkingExample,
@@ -6,6 +7,8 @@ import {
   interactWithStreamingCard,
   expectWholeCompletedCard,
   expectBothConsecutiveTools,
+  trackPluginChatRecovery,
+  reconnectPluginChat,
 } from "../support/helpers/plugin-timeline";
 
 for (const width of [1100, 390]) {
@@ -13,13 +16,24 @@ for (const width of [1100, 390]) {
     page,
   }, info) => {
     await page.setViewportSize({ width, height: 900 });
+    const gate = await installDaemonWebSocketGate(page);
     await withTimelinePlugin(page, info, "assistant", async (agent) => {
       await requestPluginTimeline(agent);
       await interactWithStreamingCard(page);
       await agent.client.waitForFinish(agent.agentId, 30_000);
       await expectWholeCompletedCard(page);
       // Local state is checked during growth; the viewport remounts on the history handoff.
+      const recovery = trackPluginChatRecovery(page);
+      gate.holdTimelineResponses(agent.agentId);
       await page.reload({ waitUntil: "domcontentloaded" });
+      await gate.waitForHeldTimelineResponse();
+      await recovery.expectCatalogWithoutRetransmission();
+      gate.releaseHeldTimelineResponses();
+      await expectWholeCompletedCard(page);
+      await recovery.expectRecoveredWithoutRetransmission();
+      recovery.reset();
+      await reconnectPluginChat(page, gate);
+      await recovery.expectRecoveredWithoutRetransmission();
       await expectWholeCompletedCard(page);
     });
   });
diff --git a/packages/app/e2e/support/helpers/plugin-timeline.ts b/packages/app/e2e/support/helpers/plugin-timeline.ts
index 533b546022..98ab7d303b 100644
--- a/packages/app/e2e/support/helpers/plugin-timeline.ts
+++ b/packages/app/e2e/support/helpers/plugin-timeline.ts
@@ -5,8 +5,64 @@ import { expect, type Page, type TestInfo } from "@playwright/test";
 import { copyPluginExample, pluginRequirements } from "./plugin-fixture";
 import { connectNewWorkspaceDaemonClient } from "./new-workspace";
 import { openAgentRoute, seedMockAgentWorkspace, type MockAgentWorkspace } from "./mock-agent";
+import { installDaemonWebSocketGate } from "./daemon-websocket-gate";
+import { expectReconnectingToastVisible } from "./workspace-ui";
 
 const PLUGIN_ID = "timeline-transform-e2e";
+
+/** Observe the app's real socket, including fresh sockets after a reload. */
+export function trackPluginChatRecovery(page: Page) {
+  const messages: {
+    type: string;
+    payload?: { plugins?: { id: string; clientBundle?: string }[] };
+  }[] = [];
+  page.on("websocket", (socket) => {
+    const collect = ({ payload }: { payload: string | Buffer }) => {
+      if (typeof payload !== "string") return;
+      const frame = JSON.parse(payload);
+      if (frame.type === "session") messages.push(frame.message);
+    };
+    socket.on("framesent", collect);
+    socket.on("framereceived", collect);
+  });
+  return {
+    reset() {
+      messages.length = 0;
+    },
+    async expectCatalogWithoutRetransmission() {
+      await expect
+        .poll(() =>
+          messages.some(
+            (message) =>
+              message.type === "plugin.catalog.get.response" &&
+              message.payload?.plugins?.some((plugin) => plugin.id === PLUGIN_ID),
+          ),
+        )
+        .toBe(true);
+      const entry = messages
+        .find((message) => message.type === "plugin.catalog.get.response")
+        ?.payload?.plugins?.find((plugin) => plugin.id === PLUGIN_ID);
+      expect(entry).toBeDefined();
+      expect(entry).not.toHaveProperty("clientBundle");
+    },
+    async expectRecoveredWithoutRetransmission() {
+      await this.expectCatalogWithoutRetransmission();
+      await expect
+        .poll(() => messages.some((message) => message.type === "fetch_agent_timeline_response"))
+        .toBe(true);
+    },
+  };
+}
+
+export async function reconnectPluginChat(
+  page: Page,
+  gate: Awaited<ReturnType<typeof installDaemonWebSocketGate>>,
+) {
+  await gate.drop();
+  await gate.waitForBlockedConnection();
+  await expectReconnectingToastVisible(page);
+  gate.restore();
+}
 export const ASSISTANT_TEXT =
   "Skill header\n\n# Instructions\n\nRead every paragraph and preserve the full message while this response is still streaming.";
 
diff --git a/packages/app/src/plugins/client-bundles/index.ts b/packages/app/src/plugins/client-bundles/index.ts
new file mode 100644
index 0000000000..06580dd222
--- /dev/null
+++ b/packages/app/src/plugins/client-bundles/index.ts
@@ -0,0 +1,32 @@
+import * as FileSystem from "expo-file-system/legacy";
+import { CryptoDigestAlgorithm, digestStringAsync, randomUUID } from "expo-crypto";
+import { createPluginClientBundleStore } from "./store";
+
+export function createHostPluginClientBundleStore(serverId: string) {
+  const directory = `${FileSystem.cacheDirectory}plugin-client-bundles/${encodeURIComponent(serverId)}/`;
+  const ensureDirectory = async () => {
+    if (!FileSystem.cacheDirectory) throw new Error("Plugin bundle cache directory unavailable");
+    await FileSystem.makeDirectoryAsync(directory, { intermediates: true });
+  };
+  return createPluginClientBundleStore(
+    {
+      async list() {
+        await ensureDirectory();
+        return FileSystem.readDirectoryAsync(directory);
+      },
+      read: (name) => FileSystem.readAsStringAsync(`${directory}${name}`),
+      async writeAtomic(name, contents) {
+        await ensureDirectory();
+        const temporary = `${directory}${randomUUID()}.tmp`;
+        try {
+          await FileSystem.writeAsStringAsync(temporary, contents);
+          await FileSystem.moveAsync({ from: temporary, to: `${directory}${name}` });
+        } finally {
+          await FileSystem.deleteAsync(temporary, { idempotent: true });
+        }
+      },
+      remove: (name) => FileSystem.deleteAsync(`${directory}${name}`, { idempotent: true }),
+    },
+    (contents) => digestStringAsync(CryptoDigestAlgorithm.SHA256, contents),
+  );
+}
diff --git a/packages/app/src/plugins/client-bundles/index.web.ts b/packages/app/src/plugins/client-bundles/index.web.ts
new file mode 100644
index 0000000000..6e67778089
--- /dev/null
+++ b/packages/app/src/plugins/client-bundles/index.web.ts
@@ -0,0 +1,62 @@
+import { createPluginClientBundleStore } from "./store";
+
+const DATABASE_NAME = "paseo-plugin-client-bundles";
+const STORE_NAME = "bundles";
+let opening: Promise<IDBDatabase> | undefined;
+
+function openDatabase(): Promise<IDBDatabase> {
+  opening ??= new Promise<IDBDatabase>((resolve, reject) => {
+    const request = indexedDB.open(DATABASE_NAME, 1);
+    request.addEventListener("upgradeneeded", () => request.result.createObjectStore(STORE_NAME));
+    request.addEventListener("success", () => resolve(request.result));
+    request.addEventListener("error", () => reject(request.error));
+  }).catch((error) => {
+    opening = undefined;
+    throw error;
+  });
+  return opening;
+}
+
+export function createHostPluginClientBundleStore(serverId: string) {
+  const prefix = `${encodeURIComponent(serverId)}/`;
+  const range = () => IDBKeyRange.bound(prefix, `${prefix}\uffff`);
+  async function run<T>(
+    mode: IDBTransactionMode,
+    operation: (store: IDBObjectStore) => IDBRequest<T>,
+  ): Promise<T> {
+    const database = await openDatabase();
+    return new Promise((resolve, reject) => {
+      const transaction = database.transaction(STORE_NAME, mode);
+      const request = operation(transaction.objectStore(STORE_NAME));
+      transaction.addEventListener("complete", () => resolve(request.result));
+      transaction.addEventListener("abort", () => reject(transaction.error));
+      transaction.addEventListener("error", () => reject(transaction.error));
+    });
+  }
+  return createPluginClientBundleStore(
+    {
+      async list() {
+        return (await run("readonly", (store) => store.getAllKeys(range())))
+          .filter((key): key is string => typeof key === "string")
+          .map((key) => key.slice(prefix.length));
+      },
+      async read(name) {
+        const result: unknown = await run("readonly", (store) => store.get(`${prefix}${name}`));
+        if (typeof result !== "string") throw new Error("Missing plugin client bundle");
+        return result;
+      },
+      async writeAtomic(name, contents) {
+        await run("readwrite", (store) => store.put(contents, `${prefix}${name}`));
+      },
+      async remove(name) {
+        await run("readwrite", (store) => store.delete(`${prefix}${name}`));
+      },
+    },
+    async (contents) => {
+      const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(contents));
+      return Array.from(new Uint8Array(digest), (byte) => byte.toString(16).padStart(2, "0")).join(
+        "",
+      );
+    },
+  );
+}
diff --git a/packages/app/src/plugins/client-bundles/storage.browser.test.ts b/packages/app/src/plugins/client-bundles/storage.browser.test.ts
new file mode 100644
index 0000000000..9acd7e0c52
--- /dev/null
+++ b/packages/app/src/plugins/client-bundles/storage.browser.test.ts
@@ -0,0 +1,36 @@
+import { expect, test } from "vitest";
+import { createHostPluginClientBundleStore } from "./index.web";
+
+async function sha256(contents: string) {
+  const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(contents));
+  return Array.from(new Uint8Array(digest), (byte) => byte.toString(16).padStart(2, "0")).join("");
+}
+
+test("browser bundles survive a fresh store and remain isolated by host", async () => {
+  const first = createHostPluginClientBundleStore("bundle-test-host-a");
+  const second = createHostPluginClientBundleStore("bundle-test-host-b");
+  const clientBundle = "bundle".repeat(250_000);
+  const entry = {
+    id: "same-plugin",
+    clientBundle,
+    clientBundleHash: await sha256(clientBundle),
+  };
+  const otherCode = "other host code";
+  const other = {
+    id: entry.id,
+    clientBundle: otherCode,
+    clientBundleHash: await sha256(otherCode),
+  };
+  try {
+    await first.replace([entry]);
+    await second.replace([other]);
+    expect(await createHostPluginClientBundleStore("bundle-test-host-a").load()).toEqual([entry]);
+    expect(await createHostPluginClientBundleStore("bundle-test-host-b").load()).toEqual([other]);
+    await first.replace([]);
+    expect(await createHostPluginClientBundleStore("bundle-test-host-a").load()).toEqual([]);
+    expect(await second.load()).toEqual([other]);
+  } finally {
+    await first.replace([]);
+    await second.replace([]);
+  }
+});
diff --git a/packages/app/src/plugins/client-bundles/store.test.ts b/packages/app/src/plugins/client-bundles/store.test.ts
new file mode 100644
index 0000000000..c3332c6b0e
--- /dev/null
+++ b/packages/app/src/plugins/client-bundles/store.test.ts
@@ -0,0 +1,179 @@
+import { createHash } from "node:crypto";
+import { DaemonClient } from "@getpaseo/client/internal/daemon-client";
+import { expect, test } from "vitest";
+import { createPluginClientBundleStore, type PluginBundleFiles } from "./store";
+
+const sha256 = async (contents: string) => createHash("sha256").update(contents).digest("hex");
+
+class BundleFiles implements PluginBundleFiles {
+  readonly contents = new Map<string, string>();
+  readonly writes: string[] = [];
+  async list() {
+    return [...this.contents.keys()];
+  }
+  async read(name: string) {
+    const contents = this.contents.get(name);
+    if (contents === undefined) throw new Error("File disappeared");
+    return contents;
+  }
+  async writeAtomic(name: string, contents: string) {
+    this.writes.push(name);
+    this.contents.set(name, contents);
+  }
+  async remove(name: string) {
+    this.contents.delete(name);
+  }
+}
+
+async function bundle(id: string, clientBundle: string) {
+  return { id, clientBundle, clientBundleHash: await sha256(clientBundle) };
+}
+
+test("a cold store loads verified bundles and prunes versions missing from the latest catalog", async () => {
+  const files = new BundleFiles();
+  const old = await bundle("changed", "old");
+  const kept = await bundle("kept", "Unicode: 折叠屏 🐚");
+  await createPluginClientBundleStore(files, sha256).replace([old, kept]);
+  const cold = createPluginClientBundleStore(files, sha256);
+  expect(await cold.load()).toEqual([old, kept]);
+  const changed = await bundle("changed", "new");
+  await cold.replace([kept, changed]);
+  expect(files.contents.size).toBe(2);
+  expect(await createPluginClientBundleStore(files, sha256).load()).toEqual([kept, changed]);
+  expect(files.writes).toHaveLength(3);
+  await cold.replace([]);
+  expect(files.contents.size).toBe(0);
+});
+
+test("same-length corruption, truncated files and unreadable files are not advertised", async () => {
+  const files = new BundleFiles();
+  const entries = await Promise.all([
+    bundle("same-length", "good"),
+    bundle("truncated", "long"),
+    bundle("missing", "lost"),
+  ]);
+  await createPluginClientBundleStore(files, sha256).replace(entries);
+  const names = [...files.contents.keys()];
+  files.contents.set(names[0]!, "evil");
+  files.contents.set(names[1]!, "lo");
+  // The directory entry still exists while reading the file fails.
+  const unreadable: PluginBundleFiles = {
+    list: () => files.list(),
+    read: (name) =>
+      name === names[2] ? Promise.reject(new Error("Unreadable")) : files.read(name),
+    writeAtomic: (name, contents) => files.writeAtomic(name, contents),
+    remove: (name) => files.remove(name),
+  };
+  const cold = createPluginClientBundleStore(unreadable, sha256);
+  expect(await cold.load()).toEqual([]);
+  await cold.replace(entries);
+  expect(await createPluginClientBundleStore(files, sha256).load()).toEqual(entries);
+});
+
+test("an interrupted atomic write leaves the prior catalog available for a cold reader", async () => {
+  const files = new BundleFiles();
+  const previous = await bundle("plugin", "previous");
+  await createPluginClientBundleStore(files, sha256).replace([previous]);
+  const failing: PluginBundleFiles = {
+    list: () => files.list(),
+    read: (name) => files.read(name),
+    remove: (name) => files.remove(name),
+    writeAtomic: async () => {
+      throw new Error("Disk full");
+    },
+  };
+  await expect(
+    createPluginClientBundleStore(failing, sha256).replace([await bundle("plugin", "next")]),
+  ).rejects.toThrow("Disk full");
+  expect(await createPluginClientBundleStore(files, sha256).load()).toEqual([previous]);
+});
+
+// Exercise the app store through a fresh platform-agnostic client, using its transport port.
+test.each(["valid", "corrupt", "missing"])(
+  "cold catalog uses a %s persisted bundle correctly",
+  async (state) => {
+    const files = new BundleFiles();
+    const entry = await bundle("plugin", "good code");
+    await createPluginClientBundleStore(files, sha256).replace([entry]);
+    if (state === "corrupt") files.contents.set([...files.contents.keys()][0]!, "evil code");
+    if (state === "missing") files.contents.clear();
+    let open = () => {};
+    let receive: (data: unknown, binary: boolean) => void = () => {};
+    const requests: Record<string, unknown>[] = [];
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "plugin-cache-test",
+      reconnect: { enabled: false },
+      createPluginClientBundleStore: () => createPluginClientBundleStore(files, sha256),
+      transportFactory: () => ({
+        send(data) {
+          if (typeof data !== "string") return;
+          const frame = JSON.parse(data);
+          if (frame.type !== "session") return;
+          const request = frame.message;
+          if (request.type !== "plugin.catalog.get.request") return;
+          requests.push(request);
+          const { clientBundle: _code, ...reference } = entry;
+          receive(
+            JSON.stringify({
+              type: "session",
+              message: {
+                type: "plugin.catalog.get.response",
+                payload: {
+                  requestId: request.requestId,
+                  plugins: [request.cachedClientBundles ? reference : entry],
+                },
+              },
+            }),
+            false,
+          );
+        },
+        close() {},
+        onOpen(handler) {
+          open = handler;
+          return () => {};
+        },
+        onMessage(handler) {
+          receive = handler;
+          return () => {};
+        },
+        onClose() {
+          return () => {};
+        },
+        onError() {
+          return () => {};
+        },
+      }),
+    });
+    try {
+      const connecting = client.connect();
+      open();
+      receive(
+        JSON.stringify({
+          type: "session",
+          message: {
+            type: "status",
+            payload: {
+              status: "server_info",
+              serverId: "cache-host",
+              hostname: null,
+              version: null,
+              features: { plugins: true },
+            },
+          },
+        }),
+        false,
+      );
+      await connecting;
+      expect(await client.getPluginCatalog()).toEqual([entry]);
+      if (state === "valid")
+        expect(requests[0]?.cachedClientBundles).toEqual([
+          { id: entry.id, clientBundleHash: entry.clientBundleHash },
+        ]);
+      else expect(requests[0]).not.toHaveProperty("cachedClientBundles");
+      await expect.poll(() => createPluginClientBundleStore(files, sha256).load()).toEqual([entry]);
+    } finally {
+      await client.close();
+    }
+  },
+);
diff --git a/packages/app/src/plugins/client-bundles/store.ts b/packages/app/src/plugins/client-bundles/store.ts
new file mode 100644
index 0000000000..4a120c2c2a
--- /dev/null
+++ b/packages/app/src/plugins/client-bundles/store.ts
@@ -0,0 +1,56 @@
+import type {
+  PluginClientBundle,
+  PluginClientBundleStore,
+} from "@getpaseo/client/internal/daemon-client";
+
+/** Each adapter is scoped to one host. Writes publish a complete file/record atomically. */
+export interface PluginBundleFiles {
+  list(): Promise<string[]>;
+  read(name: string): Promise<string>;
+  writeAtomic(name: string, contents: string): Promise<void>;
+  remove(name: string): Promise<void>;
+}
+
+export function createPluginClientBundleStore(
+  files: PluginBundleFiles,
+  sha256: (contents: string) => Promise<string>,
+): PluginClientBundleStore {
+  const verified = new Set<string>();
+  const filename = (bundle: PluginClientBundle) =>
+    `${encodeURIComponent(bundle.id)}.${bundle.clientBundleHash}.js`;
+  return {
+    async load() {
+      const bundles: PluginClientBundle[] = [];
+      for (const name of await files.list()) {
+        try {
+          const match = /^(.*)\.([a-f0-9]{64})\.js$/.exec(name);
+          if (!match) continue;
+          const id = decodeURIComponent(match[1]!);
+          const clientBundleHash = match[2]!;
+          const clientBundle = await files.read(name);
+          if ((await sha256(clientBundle)) !== clientBundleHash) continue;
+          verified.add(name);
+          bundles.push({ id, clientBundleHash, clientBundle });
+        } catch {
+          // Missing, unreadable or corrupt files are cache misses, never executable code.
+        }
+      }
+      return bundles;
+    },
+    async replace(bundles) {
+      const retained = new Set<string>();
+      for (const bundle of bundles) {
+        const name = filename(bundle);
+        retained.add(name);
+        if (verified.has(name)) continue;
+        await files.writeAtomic(name, bundle.clientBundle);
+        verified.add(name);
+      }
+      for (const name of await files.list()) {
+        if (retained.has(name)) continue;
+        await files.remove(name);
+        verified.delete(name);
+      }
+    },
+  };
+}
diff --git a/packages/app/src/runtime/host-runtime.ts b/packages/app/src/runtime/host-runtime.ts
index bb953220cb..0c7c9f4660 100644
--- a/packages/app/src/runtime/host-runtime.ts
+++ b/packages/app/src/runtime/host-runtime.ts
@@ -1,3 +1,4 @@
+import { createHostPluginClientBundleStore } from "@/plugins/client-bundles";
 import { watchdog } from "@/watchdog";
 import { createHostChannelTransport } from "@getpaseo/client/internal/hosts";
 import type { OwnedSubscription } from "@getpaseo/client";
@@ -589,6 +590,7 @@ function createDefaultDeps(
         capabilities: appCapabilities,
         trace: createPerformanceTrace({ host: host.serverId, connection: connection.id }),
         providerSnapshots: "wire",
+        createPluginClientBundleStore: createHostPluginClientBundleStore,
         ...(host.password ? { password: host.password } : {}),
         localCredential: () => readDesktopManagedLocalCredential(connection),
       } satisfies Omit<DaemonClientConfig, "url">;
@@ -668,6 +670,7 @@ function createDefaultDeps(
           ),
           reconnect: { enabled: false },
           appVersion: resolveAppVersion() ?? undefined,
+          createPluginClientBundleStore: createHostPluginClientBundleStore,
         });
         try {
           await client.connect();
@@ -684,6 +687,7 @@ function createDefaultDeps(
         ...(timeoutMs !== undefined ? { timeoutMs } : {}),
         capabilities: appCapabilities,
         trace: createPerformanceTrace({ host: host.serverId, connection: connection.id }),
+        createPluginClientBundleStore: createHostPluginClientBundleStore,
       });
     },
     getClientId: () => getOrCreateClientId(),
diff --git a/packages/app/src/timeline/replica.test.ts b/packages/app/src/timeline/replica.test.ts
index 47bd36596a..0d825673e9 100644
--- a/packages/app/src/timeline/replica.test.ts
+++ b/packages/app/src/timeline/replica.test.ts
@@ -371,6 +371,22 @@ describe("viewed timeline persistence", () => {
     ]);
   });
 
+  it("preparing an already painted cache again keeps history out of the live head", async () => {
+    useSessionStore.getState().initializeSession(SERVER_ID, null);
+    const replica = createTimelineReplica({
+      serverId: SERVER_ID,
+      storage: { readTimeline: async () => cachedTimeline(), commitTimeline: () => undefined },
+      prepareAgent: async () => undefined,
+    });
+    await replica.prepare(AGENT_ID);
+    const painted = useSessionStore.getState().sessions[SERVER_ID]!.agentStreamTail.get(AGENT_ID);
+    expect(painted).toEqual(cachedTimeline().items);
+    await replica.prepare(AGENT_ID);
+    const session = useSessionStore.getState().sessions[SERVER_ID]!;
+    expect(session.agentStreamHead.get(AGENT_ID) ?? []).toEqual([]);
+    expect(session.agentStreamTail.get(AGENT_ID)).toBe(painted);
+  });
+
   it("reconciles a live head that overlaps the cached canonical timeline", async () => {
     useSessionStore.getState().initializeSession(SERVER_ID, null);
     let release!: (value: CachedTimeline) => void;
diff --git a/packages/app/src/timeline/viewed-timeline-sync.ts b/packages/app/src/timeline/viewed-timeline-sync.ts
index 5939feabce..2e14a42093 100644
--- a/packages/app/src/timeline/viewed-timeline-sync.ts
+++ b/packages/app/src/timeline/viewed-timeline-sync.ts
@@ -109,6 +109,15 @@ class TimelineReplicaOwner implements TimelineReplica {
   async prepare(agentId: string): Promise<void> {
     const existing = this.preparations.get(agentId);
     if (existing) return existing;
+    const timeline = selectAgentTimelineState(
+      useSessionStore.getState().sessions[this.serverId],
+      agentId,
+    );
+    // A route and the visible-chat owner can both prepare before catch-up finishes.
+    // Repainting that same cache would treat its history as a live head.
+    if (timeline.status !== "cold" && this.cachedRanges.has(agentId)) {
+      return;
+    }
     const preparation = this.load(agentId).finally(() => {
       if (this.preparations.get(agentId) === preparation) {
         this.preparations.delete(agentId);
diff --git a/packages/app/src/utils/test-daemon-connection.test.ts b/packages/app/src/utils/test-daemon-connection.test.ts
index 4dc82dda29..f528065437 100644
--- a/packages/app/src/utils/test-daemon-connection.test.ts
+++ b/packages/app/src/utils/test-daemon-connection.test.ts
@@ -129,6 +129,23 @@ describe("test-daemon-connection connectToDaemon", () => {
     expect(probe.createdConfigs()[0]?.transportFactory).toBeUndefined();
   });
 
+  it("keeps the bundle cache factory on a probe client that the host runtime can adopt", async () => {
+    const { connectToDaemon } = await import("./test-daemon-connection");
+    const createPluginClientBundleStore = () => ({
+      async load() {
+        return [];
+      },
+      async replace() {},
+    });
+    const { client } = await connectToDaemon(
+      { id: "direct:lan:6767", type: "directTcp", endpoint: "lan:6767" },
+      { createPluginClientBundleStore },
+      probe.deps,
+    );
+    expect(client.config.createPluginClientBundleStore).toBe(createPluginClientBundleStore);
+    await client.close();
+  });
+
   it("encodes the local socket target into the client config", async () => {
     const { connectToDaemon } = await import("./test-daemon-connection");
     const result = await connectToDaemon(
diff --git a/packages/app/src/utils/test-daemon-connection.ts b/packages/app/src/utils/test-daemon-connection.ts
index 18ffa62dc4..d292c67001 100644
--- a/packages/app/src/utils/test-daemon-connection.ts
+++ b/packages/app/src/utils/test-daemon-connection.ts
@@ -132,12 +132,13 @@ function resolveConnectionCredentials(
 export async function buildClientConfig(
   connection: HostConnection,
   serverId?: string,
-  options?: {
+  options: {
     capabilities?: DaemonClientConfig["capabilities"];
     trace?: DaemonClientConfig["trace"];
+    createPluginClientBundleStore?: DaemonClientConfig["createPluginClientBundleStore"];
     password?: string;
     localCredential?: DaemonClientConfig["localCredential"];
-  },
+  } = {},
   deps: Pick<
     DaemonConnectionDependencies<DaemonProbeClient>,
     | "getClientId"
@@ -157,8 +158,9 @@ export async function buildClientConfig(
     suppressSendErrors: true,
     reconnect: { enabled: false },
     ...resolveConnectionCredentials(connection, options),
-    ...(options?.capabilities ? { capabilities: options.capabilities } : {}),
-    ...(options?.trace ? { trace: options.trace } : {}),
+    ...(options.capabilities ? { capabilities: options.capabilities } : {}),
+    ...(options.trace ? { trace: options.trace } : {}),
+    createPluginClientBundleStore: options.createPluginClientBundleStore,
     ...((connection.type === "directSocket" || connection.type === "directPipe") &&
     desktopTransportFactory
       ? { transportFactory: desktopTransportFactory }
@@ -288,6 +290,7 @@ interface ProbeOptions {
   localCredential?: DaemonClientConfig["localCredential"];
   capabilities?: DaemonClientConfig["capabilities"];
   trace?: DaemonClientConfig["trace"];
+  createPluginClientBundleStore?: DaemonClientConfig["createPluginClientBundleStore"];
 }
 
 function resolveTimeout(connection: HostConnection, options?: ProbeOptions): number {
diff --git a/packages/client/src/daemon-client.test.ts b/packages/client/src/daemon-client.test.ts
index 2a3b409cee..112113caf6 100644
--- a/packages/client/src/daemon-client.test.ts
+++ b/packages/client/src/daemon-client.test.ts
@@ -1,5 +1,5 @@
 import { readFileSync } from "node:fs";
-import { afterEach, expect, expectTypeOf, test, vi } from "vitest";
+import { afterEach, describe, expect, expectTypeOf, test, vi } from "vitest";
 import { z } from "zod";
 import {
   DaemonClient,
@@ -9,6 +9,8 @@ import {
   type CreateAgentRequestOptions,
   type DaemonTransport,
   type Logger,
+  type PluginClientBundle,
+  type PluginClientBundleStore,
 } from "./daemon-client";
 import { CLIENT_CAPS } from "@getpaseo/protocol/client-capabilities";
 import { BROWSER_AUTOMATION_COMMAND_NAMES } from "@getpaseo/protocol/browser-automation/rpc-schemas";
@@ -2099,6 +2101,188 @@ test("gets a structured plugin log snapshot", async () => {
   ]);
 });
 
+describe("plugin catalog", () => {
+  async function connectedClient(createStore?: (serverId: string) => PluginClientBundleStore) {
+    const mock = createMockTransport();
+    const client = new DaemonClient({
+      url: "ws://test",
+      clientId: "clsk_unit_test",
+      logger: createMockLogger(),
+      createPluginClientBundleStore: createStore,
+      reconnect: { enabled: false },
+      transportFactory: () => mock.transport,
+    });
+    clients.push(client);
+    const connectPromise = client.connect();
+    mock.triggerOpen({ features: { plugins: true } });
+    await connectPromise;
+    return { client, mock };
+  }
+
+  async function fetchCatalog(
+    harness: Awaited<ReturnType<typeof connectedClient>>,
+    respond: (request: Record<string, unknown>) => Array<Record<string, unknown>>,
+  ) {
+    const before = harness.mock.sent.length;
+    const response = harness.client.getPluginCatalog();
+    await vi.waitFor(() => expect(harness.mock.sent.length).toBeGreaterThan(before));
+    const request = parseSentFrame(harness.mock.sent.at(-1));
+    harness.mock.triggerMessage(
+      wrapSessionMessage({
+        type: "plugin.catalog.get.response",
+        payload: { requestId: request.requestId, plugins: respond(request) },
+      }),
+    );
+    return { request, plugins: await response };
+  }
+
+  test("reuses retained client bundles the daemon leaves out", async () => {
+    const harness = await connectedClient();
+    const first = await fetchCatalog(harness, () => [
+      { id: "kept", clientBundle: "kept bundle", clientBundleHash: "hash-kept" },
+      { id: "changed", clientBundle: "old bundle", clientBundleHash: "hash-old" },
+    ]);
+    expect(first.request).not.toHaveProperty("cachedClientBundles");
+
+    const second = await fetchCatalog(harness, () => [
+      { id: "kept", clientBundleHash: "hash-kept" },
+      { id: "changed", clientBundle: "new bundle", clientBundleHash: "hash-new" },
+    ]);
+
+    expect(second.request.cachedClientBundles).toEqual([
+      { id: "kept", clientBundleHash: "hash-kept" },
+      { id: "changed", clientBundleHash: "hash-old" },
+    ]);
+    expect(second.plugins).toEqual([
+      { id: "kept", clientBundle: "kept bundle", clientBundleHash: "hash-kept" },
+      { id: "changed", clientBundle: "new bundle", clientBundleHash: "hash-new" },
+    ]);
+    const third = await fetchCatalog(harness, () => []);
+    expect(third.request.cachedClientBundles).toEqual([
+      { id: "kept", clientBundleHash: "hash-kept" },
+      { id: "changed", clientBundleHash: "hash-new" },
+    ]);
+    const fourth = await fetchCatalog(harness, () => []);
+    expect(fourth.request).not.toHaveProperty("cachedClientBundles");
+  });
+
+  test("keeps fetching every bundle from a daemon that sends no bundle hashes", async () => {
+    const harness = await connectedClient();
+    const legacyCatalog = () => [{ id: "legacy", clientBundle: "legacy bundle" }];
+    await fetchCatalog(harness, legacyCatalog);
+
+    const second = await fetchCatalog(harness, legacyCatalog);
+
+    expect(second.request).not.toHaveProperty("cachedClientBundles");
+    expect(second.plugins).toEqual([{ id: "legacy", clientBundle: "legacy bundle" }]);
+  });
+
+  test("a fresh client advertises persisted bundles on its first fetch and expands omitted code", async () => {
+    let persisted: PluginClientBundle[] = [];
+    let loads = 0;
+    const store: PluginClientBundleStore = {
+      async load() {
+        loads++;
+        return persisted;
+      },
+      async replace(bundles) {
+        persisted = bundles;
+      },
+    };
+    const createdFor: string[] = [];
+    const createStore = (serverId: string) => {
+      createdFor.push(serverId);
+      return store;
+    };
+    const bundle = { id: "kept", clientBundleHash: "hash-kept", clientBundle: "stored code" };
+    const warm = await connectedClient(createStore);
+    await fetchCatalog(warm, () => [bundle]);
+    const cold = await connectedClient(createStore);
+    const first = await fetchCatalog(cold, () => [{ id: "kept", clientBundleHash: "hash-kept" }]);
+    expect(first.request.cachedClientBundles).toEqual([
+      { id: "kept", clientBundleHash: "hash-kept" },
+    ]);
+    expect(first.plugins).toEqual([bundle]);
+    expect(loads).toBe(2);
+    await fetchCatalog(cold, () => []);
+    expect(loads).toBe(2);
+    expect(createdFor).toEqual([
+      warm.client.getLastServerInfoMessage()!.serverId,
+      cold.client.getLastServerInfoMessage()!.serverId,
+    ]);
+    expect(persisted).toEqual([]);
+  });
+
+  test.each(["missing", "unreadable"])(
+    "a %s persistent cache requests full bundles",
+    async (state) => {
+      const store: PluginClientBundleStore = {
+        async load() {
+          if (state === "unreadable") throw new Error("Storage unavailable");
+          return [];
+        },
+        async replace() {},
+      };
+      const bundle = { id: "full", clientBundleHash: "hash-full", clientBundle: "full code" };
+      const result = await fetchCatalog(await connectedClient(() => store), () => [bundle]);
+      expect(result.request).not.toHaveProperty("cachedClientBundles");
+      expect(result.plugins).toEqual([bundle]);
+    },
+  );
+
+  test("failed cache writes never fail plugin loading", async () => {
+    const store: PluginClientBundleStore = {
+      async load() {
+        return [];
+      },
+      async replace() {
+        throw new Error("Disk full");
+      },
+    };
+    const bundle = { id: "full", clientBundleHash: "hash-full", clientBundle: "full code" };
+    expect(
+      (await fetchCatalog(await connectedClient(() => store), () => [bundle])).plugins,
+    ).toEqual([bundle]);
+  });
+
+  test.each([false, true])(
+    "usable catalogs do not wait for storage; latest write survives a failed first write: %s",
+    async (failFirstWrite) => {
+      const writes: PluginClientBundle[][] = [];
+      let finishWrite = () => {};
+      const blockedWrite = new Promise<void>((resolve) => {
+        finishWrite = resolve;
+      });
+      const store: PluginClientBundleStore = {
+        async load() {
+          return [];
+        },
+        async replace(bundles) {
+          writes.push(bundles);
+          if (writes.length === 1) {
+            await blockedWrite;
+            if (failFirstWrite) throw new Error("Disk full");
+          }
+        },
+      };
+      const harness = await connectedClient(() => store);
+      const first = { id: "plugin", clientBundle: "old", clientBundleHash: "hash-old" };
+      const changed = { id: "plugin", clientBundle: "new", clientBundleHash: "hash-new" };
+      try {
+        expect((await fetchCatalog(harness, () => [first])).plugins).toEqual([first]);
+        await vi.waitFor(() => expect(writes).toEqual([[first]]));
+        expect((await fetchCatalog(harness, () => [changed])).plugins).toEqual([changed]);
+        expect((await fetchCatalog(harness, () => [])).plugins).toEqual([]);
+        expect(writes).toEqual([[first]]);
+        finishWrite();
+        await vi.waitFor(() => expect(writes).toEqual([[first], []]));
+      } finally {
+        finishWrite();
+      }
+    },
+  );
+});
+
 test("keeps a plugin reload pending past the session RPC deadline", async () => {
   useHeartbeatClock();
   try {
diff --git a/packages/client/src/daemon-client.ts b/packages/client/src/daemon-client.ts
index 524c3e264a..bca3d00301 100644
--- a/packages/client/src/daemon-client.ts
+++ b/packages/client/src/daemon-client.ts
@@ -396,6 +396,17 @@ export type DaemonEventHandler = (event: DaemonEvent) => void;
 export type BrowserAutomationExecuteRequestMessage = BrowserAutomationExecuteRequest;
 export type BrowserAutomationExecuteResponseMessage = BrowserAutomationExecuteResponse;
 
+export interface PluginClientBundle {
+  id: string;
+  clientBundleHash: string;
+  clientBundle: string;
+}
+
+/** Host-scoped storage. load must return only bundles whose contents have been verified. */
+export interface PluginClientBundleStore {
+  load(): Promise<PluginClientBundle[]>;
+  replace(bundles: PluginClientBundle[]): Promise<void>;
+}
 /** Endpoint security negotiated on a relay connection. See docs/relay-endpoint-security.md. */
 export type RelaySecurityMode = "legacy" | "protected";
 
@@ -406,6 +417,8 @@ export interface DaemonClientConfig {
   sessionPermissions?: import("@getpaseo/protocol/messages").DaemonPermission[];
   url: string;
   clientId: string;
+  /** Create one cache for the confirmed daemon identity, retained for this client lifetime. */
+  createPluginClientBundleStore?: (serverId: string) => PluginClientBundleStore;
   clientType?: "mobile" | "browser" | "cli" | "mcp" | "hub";
   appVersion?: string;
   runtimeGeneration?: number | null;
@@ -1016,6 +1029,12 @@ type CorrelatedResponsePayloads = {
 type CorrelatedResponsePayload<TType extends CorrelatedResponseType> =
   CorrelatedResponsePayloads[TType];
 
+type PluginCatalogResponseEntry =
+  CorrelatedResponsePayload<"plugin.catalog.get.response">["plugins"][number];
+export type PluginCatalogEntry = Omit<PluginCatalogResponseEntry, "clientBundle"> & {
+  clientBundle: string;
+};
+
 export class DaemonConnectionError extends Error {
   readonly serverId?: string;
   readonly outcome?: "unknown";
@@ -1343,6 +1362,15 @@ export class DaemonClient {
   private pendingBinaryFileReads = new Map<string, PendingBinaryFileRead>();
   private activeBinaryFileTransfers = new Map<string, BinaryFileTransferState>();
   private completedBinaryFileReads = new Map<string, FileReadResult>();
+  /** The last catalog's client bundles by plugin id, so later catalogs can leave them out. */
+  private pluginClientBundles = new Map<
+    string,
+    { clientBundleHash: string; clientBundle: string }
+  >();
+  private pluginClientBundleStore: PluginClientBundleStore | undefined;
+  private pluginClientBundlesLoaded: Promise<void> | undefined;
+  private pluginClientBundlesWrite: PluginClientBundle[] | undefined;
+  private pluginClientBundlesWriting = false;
   private logger: Logger;
   private pendingSendQueue: PendingSend[] = [];
   /**
@@ -5793,14 +5821,82 @@ export class DaemonClient {
     });
   }
 
-  async getPluginCatalog() {
+  async getPluginCatalog(): Promise<PluginCatalogEntry[]> {
+    if (this.config.createPluginClientBundleStore && !this.pluginClientBundleStore) {
+      const serverInfo = this.getLastServerInfoMessage();
+      if (!serverInfo) throw new Error("Plugin catalog requires a connected host");
+      this.pluginClientBundleStore = this.config.createPluginClientBundleStore(serverInfo.serverId);
+    }
+    const store = this.pluginClientBundleStore;
+    if (store) {
+      this.pluginClientBundlesLoaded ??= store.load().then(
+        (bundles) => {
+          for (const { id, ...bundle } of bundles) this.pluginClientBundles.set(id, bundle);
+          return undefined;
+        },
+        (error) => this.logger.warn({ err: error }, "Failed to load plugin client bundles"),
+      );
+      await this.pluginClientBundlesLoaded;
+    }
     const requestId = this.createRequestId();
+    const cached = this.pluginClientBundles;
+    const cachedClientBundles = [...cached].map(([id, { clientBundleHash }]) => ({
+      id,
+      clientBundleHash,
+    }));
     const payload = await this.sendCorrelatedSessionRequest({
       requestId,
-      message: { type: "plugin.catalog.get.request", requestId },
+      message: {
+        type: "plugin.catalog.get.request",
+        requestId,
+        ...(cachedClientBundles.length > 0 ? { cachedClientBundles } : {}),
+      },
       responseType: "plugin.catalog.get.response",
     });
-    return payload.plugins;
+    const retained = new Map<string, { clientBundleHash: string; clientBundle: string }>();
+    const plugins = payload.plugins.map(({ clientBundle: sent, ...plugin }): PluginCatalogEntry => {
+      const previous = cached.get(plugin.id);
+      const clientBundle =
+        sent ??
+        (previous?.clientBundleHash === plugin.clientBundleHash
+          ? previous?.clientBundle
+          : undefined);
+      if (clientBundle === undefined) {
+        throw new Error(`Plugin catalog left out the client bundle for ${plugin.id}`);
+      }
+      // COMPAT(pluginCatalogBundleHash): introduced by PR #6732 (unreleased); remove after
+      // 2027-04-27 once the daemon floor includes bundle hashes. Older bundles are not retained.
+      if (plugin.clientBundleHash !== undefined) {
+        retained.set(plugin.id, { clientBundleHash: plugin.clientBundleHash, clientBundle });
+      }
+      return Object.assign(plugin, { clientBundle });
+    });
+    this.pluginClientBundles = retained;
+    if (store) {
+      this.pluginClientBundlesWrite = [...retained].map(([id, bundle]) =>
+        Object.assign({ id }, bundle),
+      );
+      void this.persistPluginClientBundles(store);
+    }
+    return plugins;
+  }
+
+  private async persistPluginClientBundles(store: PluginClientBundleStore): Promise<void> {
+    if (this.pluginClientBundlesWriting) return;
+    this.pluginClientBundlesWriting = true;
+    try {
+      while (this.pluginClientBundlesWrite) {
+        const bundles = this.pluginClientBundlesWrite;
+        this.pluginClientBundlesWrite = undefined;
+        try {
+          await store.replace(bundles);
+        } catch (error) {
+          this.logger.warn({ err: error }, "Failed to persist plugin client bundles");
+        }
+      }
+    } finally {
+      this.pluginClientBundlesWriting = false;
+    }
   }
 
   async listPlugins(): Promise<PluginListItem[]> {
diff --git a/packages/protocol/src/messages.plugins.test.ts b/packages/protocol/src/messages.plugins.test.ts
index f266b65988..47e91493fe 100644
--- a/packages/protocol/src/messages.plugins.test.ts
+++ b/packages/protocol/src/messages.plugins.test.ts
@@ -23,6 +23,29 @@ describe("plugin protocol compatibility", () => {
       expect(SessionOutboundMessageSchema.parse(message)).toEqual(message);
     },
   );
+  it.each([
+    { type: "plugin.catalog.get.request", requestId: "catalog" },
+    {
+      type: "plugin.catalog.get.request",
+      requestId: "catalog",
+      cachedClientBundles: [{ id: "example", clientBundleHash: "a".repeat(64) }],
+    },
+  ])("parses plugin catalog requests %j", (request) => {
+    expect(SessionInboundMessageSchema.parse(request)).toEqual(request);
+  });
+  it("parses plugin catalogs that leave out a client bundle the client already holds", () => {
+    const message = {
+      type: "plugin.catalog.get.response",
+      payload: {
+        requestId: "catalog",
+        plugins: [
+          { id: "cached", clientBundleHash: "a".repeat(64) },
+          { id: "changed", clientBundle: "bundle", clientBundleHash: "b".repeat(64) },
+        ],
+      },
+    };
+    expect(SessionOutboundMessageSchema.parse(message)).toEqual(message);
+  });
   it("preserves manifest metadata in plugin list responses", () => {
     const message = {
       type: "plugin.list.response",
diff --git a/packages/protocol/src/messages.ts b/packages/protocol/src/messages.ts
index 704c7ad277..92d6ec71e1 100644
--- a/packages/protocol/src/messages.ts
+++ b/packages/protocol/src/messages.ts
@@ -1470,6 +1470,10 @@ export const DiagnosticsRequestSchema = z.object({
 export const PluginCatalogGetRequestSchema = z.object({
   type: z.literal("plugin.catalog.get.request"),
   requestId: z.string(),
+  /** Client bundles the client already holds; the daemon leaves out each one whose hash matches. */
+  cachedClientBundles: z
+    .array(z.object({ id: PluginIdSchema, clientBundleHash: z.string() }))
+    .optional(),
 });
 
 export const PluginListRequestSchema = z.object({
@@ -6757,7 +6761,10 @@ export const PluginCatalogGetResponseSchema = z.object({
     plugins: z.array(
       z.object({
         id: PluginIdSchema,
-        clientBundle: z.string(),
+        /** Left out only when the request listed this plugin with the same `clientBundleHash`. */
+        clientBundle: z.string().optional(),
+        /** SHA-256 of `clientBundle`, hex encoded. */
+        clientBundleHash: z.string().optional(),
         requirements: PluginRequirementsSchema.optional(),
       }),
     ),
diff --git a/packages/server/src/server/plugins/builtin/index.test.ts b/packages/server/src/server/plugins/builtin/index.test.ts
index 6160c8f855..5f4728ecfa 100644
--- a/packages/server/src/server/plugins/builtin/index.test.ts
+++ b/packages/server/src/server/plugins/builtin/index.test.ts
@@ -78,6 +78,45 @@ test("listed client bundle is published while plugins are disabled; unlisted dir
   }
 }, 60_000);
 
+test("a repeated catalog fetch leaves out the client bundle the client already holds", async () => {
+  const root = await mkdtemp(path.join(os.tmpdir(), "paseo-builtin-catalog-cache-"));
+  roots.push(root);
+  const directory = await fixture(root, "large", true);
+  // About the size of a real plugin client bundle.
+  await writeFile(
+    path.join(directory, "index.client.tsx"),
+    `const payload = ${JSON.stringify("x".repeat(1_000_000))};
+export default function contribute() { void payload; return () => {}; }`,
+  );
+  const daemon = await createTestPaseoDaemon({
+    daemonVersion: "0.9.2",
+    pluginsEnabled: false,
+    builtinPlugins: new BuiltinPluginLoader(root, ["large"]),
+  });
+  const client = new DaemonClient({ url: `ws://127.0.0.1:${daemon.port}/ws`, appVersion: "0.9.2" });
+  const responseBytes: number[] = [];
+  const unsubscribe = client.subscribeRawMessages((message) => {
+    if (message.type === "plugin.catalog.get.response") {
+      responseBytes.push(JSON.stringify(message).length);
+    }
+  });
+  try {
+    await client.connect();
+    const first = await client.getPluginCatalog();
+    const second = await client.getPluginCatalog();
+
+    expect(second).toEqual(first);
+    expect(second[0]?.clientBundle).toContain("x".repeat(1_000_000));
+    expect(responseBytes).toHaveLength(2);
+    expect(responseBytes[0]).toBeGreaterThan(1_000_000);
+    expect(responseBytes[1]).toBeLessThan(500);
+  } finally {
+    unsubscribe();
+    await client.close();
+    await daemon.close();
+  }
+}, 60_000);
+
 test("directory, Git, and npm installs reject a built-in ID", async () => {
   const root = await mkdtemp(path.join(os.tmpdir(), "paseo-builtin-install-"));
   roots.push(root);
diff --git a/packages/server/src/server/plugins/requirements.posix.test.ts b/packages/server/src/server/plugins/requirements.posix.test.ts
index 65462336a3..597d907e18 100644
--- a/packages/server/src/server/plugins/requirements.posix.test.ts
+++ b/packages/server/src/server/plugins/requirements.posix.test.ts
@@ -1,4 +1,5 @@
 import { mkdtemp, readFile, readdir, rm, writeFile } from "node:fs/promises";
+import { createHash } from "node:crypto";
 import { tmpdir } from "node:os";
 import path from "node:path";
 import { pathToFileURL } from "node:url";
@@ -68,9 +69,18 @@ it("rejects incompatible installs without persisting them, then accepts the corr
   await expect(service.installDirectory({ path: root })).resolves.toMatchObject({
     status: "running",
   });
-  expect(service.catalog()).toEqual([
-    { id: "example", requirements: { paseo: "^0.8.0" }, clientBundle: expect.any(String) },
+  const catalog = service.catalog();
+  expect(catalog).toEqual([
+    {
+      id: "example",
+      requirements: { paseo: "^0.8.0" },
+      clientBundle: expect.any(String),
+      clientBundleHash: expect.any(String),
+    },
   ]);
+  expect(catalog[0]!.clientBundleHash).toBe(
+    createHash("sha256").update(catalog[0]!.clientBundle).digest("hex"),
+  );
 });
 
 it("marks pre-0.8 plugins failed on startup and recovers after migration and reload", async () => {
diff --git a/packages/server/src/server/plugins/runtime.posix.test.ts b/packages/server/src/server/plugins/runtime.posix.test.ts
index a777ff188e..8004fd52bf 100644
--- a/packages/server/src/server/plugins/runtime.posix.test.ts
+++ b/packages/server/src/server/plugins/runtime.posix.test.ts
@@ -1,5 +1,6 @@
 import { mkdir, mkdtemp, readdir, readFile, rm, writeFile } from "node:fs/promises";
 import { fork } from "node:child_process";
+import { createHash } from "node:crypto";
 import { tmpdir } from "node:os";
 import { PassThrough } from "node:stream";
 import path from "node:path";
@@ -106,6 +107,12 @@ function createReloadChild(
   };
 }
 
+function sha256(text: string | undefined): string {
+  return createHash("sha256")
+    .update(text ?? "")
+    .digest("hex");
+}
+
 function createTestRuntime(
   dependencies: NonNullable<ConstructorParameters<typeof PluginRuntime>[2]> = {},
   logger = pino({ level: "silent" }),
@@ -1536,6 +1543,7 @@ export default function contribute(server: { registerProvider(provider: Provider
 
     expect(spawnChild).not.toHaveBeenCalled();
     expect(runtime.catalog()[0]?.clientBundle).toContain("addTheme");
+    expect(runtime.catalog()[0]?.clientBundleHash).toBe(sha256(runtime.catalog()[0]?.clientBundle));
     await runtime.stopAll();
   });
 
@@ -1698,6 +1706,7 @@ export function inspectHost(_input: z.input<typeof inspectRpc.input>) {
     const plugin = runtime.catalog()[0];
     expect(plugin?.clientBundle).toContain("Client-only surface");
     expect(plugin?.clientBundle).not.toContain("node:os");
+    expect(plugin?.clientBundleHash).toBe(sha256(plugin?.clientBundle));
     await expect(runtime.invoke("split-runtime", "inspect", {})).resolves.toMatchObject({
       platform: expect.any(String),
     });
diff --git a/packages/server/src/server/plugins/runtime.ts b/packages/server/src/server/plugins/runtime.ts
index 182575bf80..5a15020cef 100644
--- a/packages/server/src/server/plugins/runtime.ts
+++ b/packages/server/src/server/plugins/runtime.ts
@@ -15,7 +15,7 @@ import { validateBeforeRequest, validateBeforeResult } from "./lifecycle/index.j
 import { fork } from "node:child_process";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import { randomUUID } from "node:crypto";
+import { createHash, randomUUID } from "node:crypto";
 import type pino from "pino";
 import {
   PROVIDER_CAPABILITIES,
@@ -74,6 +74,8 @@ interface LoadedPlugin {
   instanceId: string;
   requirements: PluginRequirements | undefined;
   clientBundle: string;
+  /** Lets a client that already holds this bundle skip downloading it again. */
+  clientBundleHash: string;
   methods: ReadonlySet<string>;
   hooks: { events: string[]; before: string[] };
   providers: readonly PluginProviderMetadata[];
@@ -246,6 +248,10 @@ function terminatePluginChild(child: PluginChild): void {
   if (!child.killed) child.kill();
 }
 
+function hashClientBundle(clientBundle: string): string {
+  return createHash("sha256").update(clientBundle).digest("hex");
+}
+
 function describeError(error: unknown): string {
   return error instanceof Error ? error.message : String(error);
 }
@@ -369,9 +375,19 @@ export class PluginRuntime {
     return true;
   }
 
-  catalog(): Array<{ id: string; clientBundle: string; requirements?: PluginRequirements }> {
+  catalog(): Array<{
+    id: string;
+    clientBundle: string;
+    clientBundleHash: string;
+    requirements?: PluginRequirements;
+  }> {
     return [...this.plugins.values()]
-      .map(({ id, clientBundle, requirements }) => ({ id, clientBundle, requirements }))
+      .map(({ id, clientBundle, clientBundleHash, requirements }) => ({
+        id,
+        clientBundle,
+        clientBundleHash,
+        requirements,
+      }))
       .sort((left, right) => left.id.localeCompare(right.id));
   }
 
@@ -739,10 +755,12 @@ export class PluginRuntime {
     if (!canPublish()) throw new Error(`Plugin start cancelled: ${pluginId}`);
     const serverBundle = bundles.serverBundle;
     if (!serverBundle) {
+      const clientBundle = bundles.clientBundle ?? "";
       return {
         id: pluginId,
         instanceId: randomUUID(),
-        clientBundle: bundles.clientBundle ?? "",
+        clientBundle,
+        clientBundleHash: hashClientBundle(clientBundle),
         requirements: manifest.requirements,
         methods: new Set(),
         hooks: { events: [], before: [] },
@@ -872,6 +890,7 @@ export class PluginRuntime {
       id: pluginId,
       instanceId: randomUUID(),
       clientBundle,
+      clientBundleHash: hashClientBundle(clientBundle),
       requirements,
       methods: new Set(ready.methods),
       hooks: ready.hooks ?? { events: [], before: [] },
diff --git a/packages/server/src/server/session.test.ts b/packages/server/src/server/session.test.ts
index 7321312826..3cdef95a83 100644
--- a/packages/server/src/server/session.test.ts
+++ b/packages/server/src/server/session.test.ts
@@ -588,6 +588,78 @@ test("routes plugin requests and releases its owned catalog subscription on clea
   expect(releasePluginSubscription).toHaveBeenCalledOnce();
 });
 
+test("leaves out the client bundles a catalog request already holds", async () => {
+  const messages: SessionOutboundMessage[] = [];
+  const pluginRuntime: NonNullable<SessionOptions["pluginRuntime"]> = {
+    before: async (_name, request) => request,
+    emit: () => {},
+    listPlugins: async () => [],
+    getLogs: () => [],
+    installDirectory: async () => {
+      throw new Error("Unexpected install");
+    },
+    inspectDirectory: async () => ({ id: "unused" }),
+    reloadPlugin: async () => {
+      throw new Error("Unexpected reload");
+    },
+    enablePlugin: async () => {
+      throw new Error("Unexpected enable");
+    },
+    disablePlugin: async () => {
+      throw new Error("Unexpected disable");
+    },
+    removePlugin: async () => undefined,
+    subscribe: () => () => {},
+    catalog: () => [
+      { id: "cached", clientBundle: "cached bundle", clientBundleHash: "hash-cached" },
+      { id: "changed", clientBundle: "new bundle", clientBundleHash: "hash-new" },
+      { id: "added", clientBundle: "added bundle", clientBundleHash: "hash-added" },
+    ],
+    invokePluginRpc: async () => null,
+    listUsageReports: async () => [],
+    listLegacyUsage: async () => ({ fetchedAt: "2026-01-01T00:00:00.000Z", providers: [] }),
+  };
+  const session = createSessionForTest({ messages, pluginRuntime });
+
+  await session.handleMessage({
+    type: "plugin.catalog.get.request",
+    requestId: "reconnect",
+    cachedClientBundles: [
+      { id: "cached", clientBundleHash: "hash-cached" },
+      { id: "changed", clientBundleHash: "hash-old" },
+      { id: "removed", clientBundleHash: "hash-removed" },
+    ],
+  });
+  // Clients from before cachedClientBundles always receive every bundle.
+  await session.handleMessage({ type: "plugin.catalog.get.request", requestId: "legacy" });
+
+  expect(messages).toEqual([
+    {
+      type: "plugin.catalog.get.response",
+      payload: {
+        requestId: "reconnect",
+        plugins: [
+          { id: "cached", clientBundleHash: "hash-cached" },
+          { id: "changed", clientBundle: "new bundle", clientBundleHash: "hash-new" },
+          { id: "added", clientBundle: "added bundle", clientBundleHash: "hash-added" },
+        ],
+      },
+    },
+    {
+      type: "plugin.catalog.get.response",
+      payload: {
+        requestId: "legacy",
+        plugins: [
+          { id: "cached", clientBundle: "cached bundle", clientBundleHash: "hash-cached" },
+          { id: "changed", clientBundle: "new bundle", clientBundleHash: "hash-new" },
+          { id: "added", clientBundle: "added bundle", clientBundleHash: "hash-added" },
+        ],
+      },
+    },
+  ]);
+  await session.cleanup();
+});
+
 describe("workspace label subscriptions", () => {
   type LabelSubscription = Awaited<ReturnType<WorkspaceLabelService["subscribe"]>>;
   type LabelChange = Parameters<Parameters<WorkspaceLabelService["subscribe"]>[0]["onChange"]>[0];
diff --git a/packages/server/src/server/session.ts b/packages/server/src/server/session.ts
index 3e78982793..b52c9dbfe4 100644
--- a/packages/server/src/server/session.ts
+++ b/packages/server/src/server/session.ts
@@ -518,7 +518,7 @@ export interface SessionOptions {
     removePlugin(pluginId: string): Promise<void>;
     subscribe(listener: (pluginId: string) => void): () => void;
     subscribeSettings?(listener: (pluginId: string, settingsId: string) => void): () => void;
-    catalog(): Array<{ id: string; clientBundle: string }>;
+    catalog(): Array<{ id: string; clientBundle: string; clientBundleHash?: string }>;
     invokePluginRpc(pluginId: string, method: string, input: unknown): Promise<unknown>;
     listUsageReports(options?: {
       forceRefresh?: boolean;
@@ -2584,12 +2584,17 @@ export class Session {
       });
     }
     if (msg.type === "plugin.catalog.get.request") {
+      const cached = new Map(
+        msg.cachedClientBundles?.map((entry) => [entry.id, entry.clientBundleHash]),
+      );
+      const plugins = (this.pluginRuntime?.catalog() ?? []).map(({ clientBundle, ...plugin }) =>
+        plugin.clientBundleHash !== undefined && cached.get(plugin.id) === plugin.clientBundleHash
+          ? plugin
+          : Object.assign(plugin, { clientBundle }),
+      );
       this.emit({
         type: "plugin.catalog.get.response",
-        payload: {
-          requestId: msg.requestId,
-          plugins: this.pluginRuntime?.catalog() ?? [],
-        },
+        payload: { requestId: msg.requestId, plugins },
       });
       return undefined;
     }