diff --git a/packages/client/src/daemon-client.ts b/packages/client/src/daemon-client.ts
index f900fe41e5..1fc580cd25 100644
--- a/packages/client/src/daemon-client.ts
+++ b/packages/client/src/daemon-client.ts
@@ -13,6 +13,7 @@ import type { z } from "zod";
 import type { SessionEventSubscription } from "@getpaseo/protocol/messages";
 import type { ClientCapability } from "@getpaseo/protocol/client-capabilities";
 import type { AgentAttentionNotificationPayload } from "@getpaseo/protocol/agent-attention-notification";
+import { MAX_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import {
   AgentCreateFailedStatusPayloadSchema,
   AgentCreatedStatusPayloadSchema,
@@ -1132,6 +1133,25 @@ function getTransportFrameSize(frame: string | Uint8Array | ArrayBuffer): number
   return frame.byteLength;
 }
 
+function assertTransportFrameFits(frame: string | Uint8Array | ArrayBuffer): void {
+  if (typeof frame !== "string") {
+    if (frame.byteLength > MAX_WEBSOCKET_MESSAGE_BYTES)
+      throw messageTooLargeError(frame.byteLength);
+    return;
+  }
+  // UTF-8 needs at most three bytes per UTF-16 unit, so only a string near the limit is measured.
+  if (frame.length * 3 <= MAX_WEBSOCKET_MESSAGE_BYTES) return;
+  const size = new TextEncoder().encode(frame).byteLength;
+  if (size > MAX_WEBSOCKET_MESSAGE_BYTES) throw messageTooLargeError(size);
+}
+
+function messageTooLargeError(size: number): Error {
+  const toMiB = (bytes: number) => (bytes / (1024 * 1024)).toFixed(1);
+  return new Error(
+    `Message is too large to send (${toMiB(size)} MiB). The limit is ${toMiB(MAX_WEBSOCKET_MESSAGE_BYTES)} MiB, so send fewer or smaller attachments.`,
+  );
+}
+
 function describeInboundTransportFrame(
   frame: unknown,
   rawBytes: Uint8Array | null,
@@ -1767,6 +1787,8 @@ export class DaemonClient {
     if (!this.transport) {
       throw new DaemonConnectionError("Transport not connected");
     }
+    // The daemon closes the connection on an oversized message, and creations resubmit on reconnect.
+    assertTransportFrameFits(frame);
     const isOpen = this.beginTraceSection("paseo.ws.frame.outbound", {
       kind: typeof frame === "string" ? "text" : "binary",
       size: String(getTransportFrameSize(frame)),
diff --git a/packages/protocol/src/websocket-message-limit.ts b/packages/protocol/src/websocket-message-limit.ts
new file mode 100644
index 0000000000..05a095003d
--- /dev/null
+++ b/packages/protocol/src/websocket-message-limit.ts
@@ -0,0 +1,2 @@
+/** Largest WebSocket message the daemon accepts. A bigger one closes the connection with 1009. */
+export const MAX_WEBSOCKET_MESSAGE_BYTES = 100 * 1024 * 1024;
diff --git a/packages/server/package.json b/packages/server/package.json
index b80941d56f..5576a2e713 100644
--- a/packages/server/package.json
+++ b/packages/server/package.json
@@ -89,7 +89,7 @@
     "speech:transcribe:local": "tsx scripts/transcribe-local-wav.ts",
     "test": "npm run test:unit && npm run test:integration",
     "test:unit": "vitest run --fileParallelism --exclude \"**/*.e2e.test.ts\"",
-    "test:integration": "vitest run --maxWorkers=1 src/server/daemon-e2e/filesystem.e2e.test.ts src/server/daemon-e2e/file-download.e2e.test.ts src/server/daemon-e2e/cli-logs-follow.e2e.test.ts src/server/creation/creation.e2e.test.ts src/server/daemon-e2e/terminal-workspace-sdk.e2e.test.ts src/server/daemon-e2e/models.e2e.test.ts src/server/daemon-e2e/live-preferences.e2e.test.ts src/server/agent/model-catalog.e2e.test.ts src/server/plugins/plugin-paseo-api.e2e.test.ts && vitest run --maxWorkers=1 src/server/daemon-e2e/git-operations.e2e.test.ts -t \"merges into\" && vitest run --maxWorkers=1 src/server/session.create-agent-worktree-autoarchive.e2e.test.ts -t \"creates a worktree and auto-archives both\" && vitest run --maxWorkers=1 src/server/agent/providers/opencode-bridge.local.e2e.test.ts -t \"versioned runtime\"",
+    "test:integration": "vitest run --maxWorkers=1 src/server/daemon-e2e/filesystem.e2e.test.ts src/server/daemon-e2e/file-download.e2e.test.ts src/server/daemon-e2e/cli-logs-follow.e2e.test.ts src/server/creation/creation.e2e.test.ts src/server/daemon-e2e/terminal-workspace-sdk.e2e.test.ts src/server/daemon-e2e/models.e2e.test.ts src/server/daemon-e2e/live-preferences.e2e.test.ts src/server/daemon-e2e/oversized-message.e2e.test.ts src/server/agent/model-catalog.e2e.test.ts src/server/plugins/plugin-paseo-api.e2e.test.ts && vitest run --maxWorkers=1 src/server/daemon-e2e/git-operations.e2e.test.ts -t \"merges into\" && vitest run --maxWorkers=1 src/server/session.create-agent-worktree-autoarchive.e2e.test.ts -t \"creates a worktree and auto-archives both\" && vitest run --maxWorkers=1 src/server/agent/providers/opencode-bridge.local.e2e.test.ts -t \"versioned runtime\"",
     "test:hub-cli-contract": "vitest run --maxWorkers=1 src/server/hub/hub-cli-contract.test.ts",
     "test:integration:all": "npm run test:e2e",
     "test:integration:real": "vitest run real.e2e.test.ts",
diff --git a/packages/server/src/server/daemon-e2e/oversized-message.e2e.test.ts b/packages/server/src/server/daemon-e2e/oversized-message.e2e.test.ts
new file mode 100644
index 0000000000..fc68fe44f4
--- /dev/null
+++ b/packages/server/src/server/daemon-e2e/oversized-message.e2e.test.ts
@@ -0,0 +1,58 @@
+import { describe, test, expect, beforeEach, afterEach } from "vitest";
+import { mkdtempSync, rmSync } from "fs";
+import { tmpdir } from "os";
+import path from "path";
+import { createDaemonTestContext, type DaemonTestContext } from "../test-utils/index.js";
+
+let ctx: DaemonTestContext;
+let cwd: string;
+
+beforeEach(async () => {
+  ctx = await createDaemonTestContext();
+  cwd = mkdtempSync(path.join(tmpdir(), "daemon-e2e-"));
+});
+
+afterEach(async () => {
+  await ctx.cleanup();
+  rmSync(cwd, { recursive: true, force: true });
+}, 60000);
+
+describe("a message larger than the daemon accepts", () => {
+  const oversizedImage = { data: "A".repeat(101 * 1024 * 1024), mimeType: "image/png" };
+
+  test("fails the creation and keeps the connection up", async () => {
+    const statuses: string[] = [];
+    const unsubscribe = ctx.client.subscribeConnectionStatus((state) => {
+      statuses.push(state.status);
+    });
+
+    await expect(
+      ctx.client.createAgent({
+        provider: "claude",
+        cwd,
+        title: "Oversized first message",
+        initialPrompt: "Describe these screens.",
+        images: [oversizedImage],
+      }),
+    ).rejects.toThrow(/too large/);
+    unsubscribe();
+
+    expect(statuses).toEqual(["connected"]);
+    expect((await ctx.client.fetchAgents()).entries).toEqual([]);
+  }, 30000);
+
+  test("fails the send and keeps the connection up", async () => {
+    const agent = await ctx.client.createAgent({ provider: "claude", cwd, title: "Agent" });
+    const statuses: string[] = [];
+    const unsubscribe = ctx.client.subscribeConnectionStatus((state) => {
+      statuses.push(state.status);
+    });
+
+    await expect(
+      ctx.client.sendMessage(agent.id, "Describe these screens.", { images: [oversizedImage] }),
+    ).rejects.toThrow(/too large/);
+    unsubscribe();
+
+    expect(statuses).toEqual(["connected"]);
+  }, 30000);
+});
diff --git a/packages/server/src/server/websocket-server.ts b/packages/server/src/server/websocket-server.ts
index 219e04b0c2..5e93681a66 100644
--- a/packages/server/src/server/websocket-server.ts
+++ b/packages/server/src/server/websocket-server.ts
@@ -33,6 +33,7 @@ import {
 } from "./messages.js";
 import { asUint8Array, decodeBinaryFrame } from "@getpaseo/protocol/binary-frames/index";
 import type { TerminalActivity } from "@getpaseo/protocol/terminal-activity";
+import { MAX_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import type { HostnamesConfig } from "./hostnames.js";
 import { isHostnameAllowed } from "./hostnames.js";
 import {
@@ -822,6 +823,7 @@ export class VoiceAssistantWebSocketServer {
     const wss = new WebSocketServer({
       server,
       path: "/ws",
+      maxPayload: MAX_WEBSOCKET_MESSAGE_BYTES,
       handleProtocols: (protocols) => selectWebSocketProtocol(protocols, password),
       verifyClient: ({ req }, callback) => {
         this.verifyWsUpgrade(