diff --git a/web/src/structured.test.ts b/web/src/structured.test.ts
index 1ea3243..3a2adf9 100644
--- a/web/src/structured.test.ts
+++ b/web/src/structured.test.ts
@@ -429,7 +429,7 @@ describe("structured connection: reconnection/error/loading", () => {
     conn.dispose();
   });
 
-  it("releases an accepted submission from an idle snapshot after reconnect", async () => {
+  it("releases an accepted submission from a post-acceptance idle snapshot", async () => {
     vi.mocked(sendStructuredPrompt).mockResolvedValueOnce(undefined);
     const first = new FakeSocket();
     const second = new FakeSocket();
@@ -452,14 +452,15 @@ describe("structured connection: reconnection/error/loading", () => {
     conn.dispose();
   });
 
-  it("releases when reconnect idle arrives before submission acceptance", async () => {
+  it("does not release from reconnect idle cached before submission acceptance", async () => {
     let accept!: () => void;
     vi.mocked(sendStructuredPrompt).mockImplementationOnce(
       () => new Promise((resolve) => { accept = resolve; }),
     );
     const first = new FakeSocket();
     const second = new FakeSocket();
-    const conn = mount({ sockets: [first, second], shouldReconnect: () => true });
+    const third = new FakeSocket();
+    const conn = mount({ sockets: [first, second, third], shouldReconnect: () => true });
     first.open();
     first.emit({ type: "transcript_snapshot", snapshot: { cursor: 0, rows: [] } });
     first.emit({ type: "reduced_state", state: idleState });
@@ -477,6 +478,12 @@ describe("structured connection: reconnection/error/loading", () => {
     accept();
     await Promise.resolve().then(() => Promise.resolve());
 
+    expect(input.disabled).toBe(true);
+    expect(second.closed).toBe(true);
+
+    third.open();
+    third.emit({ type: "transcript_snapshot", snapshot: { cursor: 0, rows: [] } });
+    third.emit({ type: "reduced_state", state: idleState });
     expect(input.disabled).toBe(false);
     conn.dispose();
   });
diff --git a/web/src/structured.ts b/web/src/structured.ts
index 0425dc6..6b8b021 100644
--- a/web/src/structured.ts
+++ b/web/src/structured.ts
@@ -297,11 +297,12 @@ export function createStructuredConnection(
     renderComposerState();
     sendStructuredPrompt(sessionId, text).then(
       () => {
-        if (generation === submissionGeneration) {
-          acceptedSubmission = { generation, socketGeneration: submissionSocketGeneration };
-          reconcileAwaitingBegin();
-          renderComposerState();
-        }
+        if (generation !== submissionGeneration || awaitingBeginGeneration !== generation) return;
+        const acceptanceSocketGeneration = socketGeneration;
+        acceptedSubmission = { generation, socketGeneration: acceptanceSocketGeneration };
+        // A replacement socket may have captured idle before the POST claimed
+        // the prompt. Reconnect again so its snapshot cannot predate the 204.
+        if (acceptanceSocketGeneration > submissionSocketGeneration) reconnectForReconciliation();
       },
       (e: unknown) => {
         if (generation !== submissionGeneration) return;
@@ -340,6 +341,21 @@ export function createStructuredConnection(
   let reconnectTimer: number | null = null;
   let disposed = false;
 
+  function reconnectForReconciliation(): void {
+    const stale = ws;
+    stale.onopen = null;
+    stale.onmessage = null;
+    stale.onerror = null;
+    stale.onclose = null;
+    try {
+      stale.close();
+    } catch {
+      // ignore
+    }
+    setConnState("reconnecting…", "connecting");
+    connect();
+  }
+
   function connect(): void {
     const connectionGeneration = ++socketGeneration;
     ws = socketFactory(sessionId);