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fix(vertex): scope replay by client thread #1335

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Ingwannu wants to merge 1 commit into from
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fix(vertex): scope replay by client thread #1335

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4 changes: 2 additions & 2 deletions src/adapters/google.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -54,8 +54,8 @@ function resolveVertexApiKey(optKey?: string): string | undefined {
/** Prefer Codex's stable opaque thread key; retain the existing deterministic fallback for clients
* that omit it. The replay store hashes this value and never retains the raw session identifier. */
function vertexReplaySessionId(parsed: OcxParsedRequest): string {
const promptCacheKey = parsed.options.promptCacheKey?.trim();
return promptCacheKey || antigravitySessionId(parsed);
const threadId = parsed._clientThreadId?.trim();
return threadId || antigravitySessionId(parsed);
Comment on lines +57 to +58

@coderabbitai coderabbitai Bot Aug 9, 2026

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🔒 Security & Privacy | 🟠 Major | ⚡ Quick win

Hash the client thread ID before using it as the replay-session key.

Line 58 returns the raw x-codex-parent-thread-id value. vertexReplaySession receives it at Line 454 and passes it to applyAntigravityReplay at Lines 459-463, so the replay cache retains the raw client identifier.

Use the same one-way hash used by antigravitySessionId, and keep the existing fallback for an absent or blank ID.

Proposed fix 
 function vertexReplaySessionId(parsed: OcxParsedRequest): string {
   const threadId = parsed._clientThreadId?.trim();
-  return threadId || antigravitySessionId(parsed);
+  if (!threadId) return antigravitySessionId(parsed);
+  const digest = createHash("sha256").update(threadId, "utf8").digest();
+  const masked = digest.readBigUInt64BE(0) & 0x7fffffffffffffffn;
+  return `-${masked.toString()}`;
 }

Based on the PR objective to avoid persisting raw thread identifiers and the supplied replay-session contract.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
const threadId = parsed._clientThreadId?.trim();
return threadId || antigravitySessionId(parsed);
const threadId = parsed._clientThreadId?.trim();
if (!threadId) return antigravitySessionId(parsed);
const digest = createHash("sha256").update(threadId, "utf8").digest();
const masked = digest.readBigUInt64BE(0) & 0x7fffffffffffffffn;
return `-${masked.toString()}`;
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/adapters/google.ts` around lines 57 - 58, Update the thread ID selection
near antigravitySessionId so a trimmed client thread ID is transformed with the
same one-way hashing used by antigravitySessionId before being returned as the
replay-session key. Preserve the existing fallback to
antigravitySessionId(parsed) when the client ID is absent or blank, and ensure
vertexReplaySession/applyAntigravityReplay receive only the hashed value.

}

/**
Expand Down
38 changes: 38 additions & 0 deletions tests/google-vertex-thought-signature.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,16 @@ const continuation = () => request([
},
], false);

function scopedReplayRequest(
parsed: OcxParsedRequest,
threadId: string | undefined,
promptCacheKey: string | undefined,
): OcxParsedRequest {
if (threadId !== undefined) parsed._clientThreadId = threadId;
if (promptCacheKey !== undefined) parsed.options.promptCacheKey = promptCacheKey;
return parsed;
}

function vertexResponseBody(): Record<string, unknown> {
return {
candidates: [{
Expand Down Expand Up @@ -107,6 +117,34 @@ describe("Vertex thought-signature continuation (#1254)", () => {
expect(replayedFunctionCall(followup.body as string).thoughtSignature).toBe(SIGNATURE);
});

test("#1312: shared prompt cache keys cannot cross client-thread replay namespaces", async () => {
const first = scopedReplayRequest(firstTurn(false), "thread-a", "shared-cache-cohort");
const firstAdapter = createGoogleAdapter(provider);
await firstAdapter.buildRequest(first);
await firstAdapter.parseResponse!(new Response(JSON.stringify(vertexResponseBody())));

const otherThread = await createGoogleAdapter(provider).buildRequest(
scopedReplayRequest(continuation(), "thread-b", "shared-cache-cohort"),
);
expect(replayedFunctionCall(otherThread.body as string).thoughtSignature).toBeUndefined();

const originalThread = await createGoogleAdapter(provider).buildRequest(
scopedReplayRequest(continuation(), "thread-a", "different-cache-cohort"),
);
expect(replayedFunctionCall(originalThread.body as string).thoughtSignature).toBe(SIGNATURE);
});

test("#1312: threadless clients keep deterministic replay regardless of prompt cache key", async () => {
const firstAdapter = createGoogleAdapter(provider);
await firstAdapter.buildRequest(scopedReplayRequest(firstTurn(false), undefined, "cohort-a"));
await firstAdapter.parseResponse!(new Response(JSON.stringify(vertexResponseBody())));

const followup = await createGoogleAdapter(provider).buildRequest(
scopedReplayRequest(continuation(), undefined, "cohort-b"),
);
expect(replayedFunctionCall(followup.body as string).thoughtSignature).toBe(SIGNATURE);
});

test("Vertex signatures cannot enter the Antigravity replay namespace", async () => {
const first = firstTurn(false);
const adapter = createGoogleAdapter(provider);
Expand Down
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