diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23d1d0779..c0e7649f6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -75,6 +75,7 @@
 - Discord: stop provider when gateway reconnects are exhausted and surface errors. (#514) — thanks @joshp123
 - Agents: strip empty assistant text blocks from session history to avoid Claude API 400s. (#210)
 - Agents: scrub unsupported JSON Schema keywords from tool schemas for Cloud Code Assist API compatibility. (#567) — thanks @erikpr1994
+- Agents: sanitize Cloud Code Assist tool call IDs and detect format/quota errors for failover. (#544) — thanks @jeffersonwarrior
 - Agents: simplify session tool schemas for Gemini compatibility. (#599) — thanks @mcinteerj
 - Agents: add `session_status` agent tool for `/status`-equivalent status (incl. usage/cost) + per-session model overrides. — thanks @steipete
 - Auto-reply: preserve block reply ordering with timeout fallback for streaming. (#503) — thanks @joshp123
diff --git a/src/agents/pi-embedded-helpers.test.ts b/src/agents/pi-embedded-helpers.test.ts
index 5b5802255..c280c1b86 100644
--- a/src/agents/pi-embedded-helpers.test.ts
+++ b/src/agents/pi-embedded-helpers.test.ts
@@ -6,12 +6,14 @@ import {
   classifyFailoverReason,
   formatAssistantErrorText,
   isBillingErrorMessage,
+  isCloudCodeAssistFormatError,
   isContextOverflowError,
   isFailoverErrorMessage,
   isMessagingToolDuplicate,
   normalizeTextForComparison,
   sanitizeGoogleTurnOrdering,
   sanitizeSessionMessagesImages,
+  sanitizeToolCallId,
   validateGeminiTurns,
 } from "./pi-embedded-helpers.js";
 import {
@@ -258,12 +260,34 @@ describe("classifyFailoverReason", () => {
   it("returns a stable reason", () => {
     expect(classifyFailoverReason("invalid api key")).toBe("auth");
     expect(classifyFailoverReason("429 too many requests")).toBe("rate_limit");
+    expect(classifyFailoverReason("resource has been exhausted")).toBe(
+      "rate_limit",
+    );
     expect(classifyFailoverReason("credit balance too low")).toBe("billing");
     expect(classifyFailoverReason("deadline exceeded")).toBe("timeout");
+    expect(classifyFailoverReason("string should match pattern")).toBeNull();
     expect(classifyFailoverReason("bad request")).toBeNull();
   });
 });
 
+describe("isCloudCodeAssistFormatError", () => {
+  it("matches format errors", () => {
+    const samples = [
+      "INVALID_REQUEST_ERROR: string should match pattern",
+      "messages.1.content.1.tool_use.id",
+      "tool_use.id should match pattern",
+      "invalid request format",
+    ];
+    for (const sample of samples) {
+      expect(isCloudCodeAssistFormatError(sample)).toBe(true);
+    }
+  });
+
+  it("ignores unrelated errors", () => {
+    expect(isCloudCodeAssistFormatError("rate limit exceeded")).toBe(false);
+  });
+});
+
 describe("formatAssistantErrorText", () => {
   const makeAssistantError = (errorMessage: string): AssistantMessage =>
     ({
@@ -277,6 +301,20 @@ describe("formatAssistantErrorText", () => {
   });
 });
 
+describe("sanitizeToolCallId", () => {
+  it("keeps valid tool call IDs", () => {
+    expect(sanitizeToolCallId("call_abc-123")).toBe("call_abc-123");
+  });
+
+  it("replaces invalid characters with underscores", () => {
+    expect(sanitizeToolCallId("call_abc|item:456")).toBe("call_abc_item_456");
+  });
+
+  it("returns default for empty IDs", () => {
+    expect(sanitizeToolCallId("")).toBe("default_tool_id");
+  });
+});
+
 describe("sanitizeGoogleTurnOrdering", () => {
   it("prepends a synthetic user turn when history starts with assistant", () => {
     const input = [
diff --git a/src/agents/pi-embedded-runner.ts b/src/agents/pi-embedded-runner.ts
index 6f2835d9b..5b21371a9 100644
--- a/src/agents/pi-embedded-runner.ts
+++ b/src/agents/pi-embedded-runner.ts
@@ -104,7 +104,6 @@ import {
 
 // Optional features can be implemented as Pi extensions that run in the same Node process.
 
-
 /**
  * Resolve provider-specific extraParams from model config.
  * Auto-enables thinking mode for GLM-4.x models unless explicitly disabled.
@@ -1530,8 +1529,7 @@ export async function runEmbeddedPiAgent(params: {
 
           // Treat timeout as potential rate limit (Antigravity hangs on rate limit)
           const shouldRotate =
-            (!aborted &&
-              (failoverFailure || cloudCodeAssistFormatError)) ||
+            (!aborted && (failoverFailure || cloudCodeAssistFormatError)) ||
             timedOut;
 
           if (shouldRotate) {