fix(google): repair Cloud Code Assist tool-call ordering (#406)

CHANGELOG.md

@@ -136,6 +136,7 @@
 - Control UI: show a reading indicator bubble while the assistant is responding.
 - Control UI: animate reading indicator dots (honors reduced-motion).
 - Control UI: stabilize chat streaming during tool runs (no flicker/vanishing text; correct run scoping).
+- Google: recover from corrupted transcripts that start with an assistant tool call to avoid Cloud Code Assist 400 ordering errors. Thanks @jonasjancarik for PR #421. (#406)
 - Control UI: let config-form enums select empty-string values. Thanks @sreekaransrinath for PR #268.
 - Control UI: scroll chat to bottom on initial load. Thanks @kiranjd for PR #274.
 - Control UI: add Chat focus mode toggle to collapse header + sidebar.

src/agents/pi-embedded-helpers.test.ts

@@ -1,10 +1,12 @@
 import type { AssistantMessage } from "@mariozechner/pi-ai";
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import { describe, expect, it } from "vitest";
 
 import {
   buildBootstrapContextFiles,
   formatAssistantErrorText,
   isContextOverflowError,
+  sanitizeGoogleTurnOrdering,
 } from "./pi-embedded-helpers.js";
 import {
   DEFAULT_AGENTS_FILENAME,
@@ -83,3 +85,26 @@ describe("formatAssistantErrorText", () => {
     expect(formatAssistantErrorText(msg)).toContain("Context overflow");
   });
 });
+
+describe("sanitizeGoogleTurnOrdering", () => {
+  it("prepends a synthetic user turn when history starts with assistant", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          { type: "toolCall", id: "call_1", name: "bash", arguments: {} },
+        ],
+      },
+    ] satisfies AgentMessage[];
+
+    const out = sanitizeGoogleTurnOrdering(input);
+    expect(out[0]?.role).toBe("user");
+    expect(out[1]?.role).toBe("assistant");
+  });
+
+  it("is a no-op when history starts with user", () => {
+    const input = [{ role: "user", content: "hi" }] satisfies AgentMessage[];
+    const out = sanitizeGoogleTurnOrdering(input);
+    expect(out).toBe(input);
+  });
+});

src/agents/pi-embedded-helpers.ts

@@ -104,6 +104,36 @@ export async function sanitizeSessionMessagesImages(
   return out;
 }
 
+const GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT = "(session bootstrap)";
+
+export function sanitizeGoogleTurnOrdering(
+  messages: AgentMessage[],
+): AgentMessage[] {
+  const first = messages[0] as
+    | { role?: unknown; content?: unknown }
+    | undefined;
+  const role = first?.role;
+  const content = first?.content;
+  if (
+    role === "user" &&
+    typeof content === "string" &&
+    content.trim() === GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT
+  ) {
+    return messages;
+  }
+  if (role !== "assistant") return messages;
+
+  // Cloud Code Assist rejects histories that begin with a model turn (tool call or text).
+  // Prepend a tiny synthetic user turn so the rest of the transcript can be used.
+  const bootstrap: AgentMessage = {
+    role: "user",
+    content: GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT,
+    timestamp: Date.now(),
+  } as AgentMessage;
+
+  return [bootstrap, ...messages];
+}
+
 export function buildBootstrapContextFiles(
   files: WorkspaceBootstrapFile[],
 ): EmbeddedContextFile[] {

src/agents/pi-embedded-runner.ts

@@ -63,6 +63,7 @@ import {
   isRateLimitAssistantError,
   isRateLimitErrorMessage,
   pickFallbackThinkingLevel,
+  sanitizeGoogleTurnOrdering,
   sanitizeSessionMessagesImages,
 } from "./pi-embedded-helpers.js";
 import {
@@ -699,10 +700,27 @@ export async function compactEmbeddedPiSession(params: {
         }));
 
         try {
-          const prior = await sanitizeSessionMessagesImages(
+          const sanitizedImages = await sanitizeSessionMessagesImages(
             session.messages,
             "session:history",
           );
+          const needsGoogleBootstrap =
+            (model.api === "google-gemini-cli" ||
+              model.api === "google-generative-ai") &&
+            sanitizedImages[0] &&
+            typeof sanitizedImages[0] === "object" &&
+            "role" in sanitizedImages[0] &&
+            sanitizedImages[0].role === "assistant";
+          const prior =
+            model.api === "google-gemini-cli" ||
+            model.api === "google-generative-ai"
+              ? sanitizeGoogleTurnOrdering(sanitizedImages)
+              : sanitizedImages;
+          if (needsGoogleBootstrap) {
+            log.warn(
+              `google turn ordering fixup: prepended user bootstrap (sessionId=${params.sessionId})`,
+            );
+          }
           if (prior.length > 0) {
             session.agent.replaceMessages(prior);
           }
@@ -1026,8 +1044,25 @@ export async function runEmbeddedPiAgent(params: {
               session.messages,
               "session:history",
             );
-            if (prior.length > 0) {
-              session.agent.replaceMessages(prior);
+            const needsGoogleBootstrap =
+              (model.api === "google-gemini-cli" ||
+                model.api === "google-generative-ai") &&
+              prior[0] &&
+              typeof prior[0] === "object" &&
+              "role" in prior[0] &&
+              prior[0].role === "assistant";
+            const sanitizedPrior =
+              model.api === "google-gemini-cli" ||
+              model.api === "google-generative-ai"
+                ? sanitizeGoogleTurnOrdering(prior)
+                : prior;
+            if (needsGoogleBootstrap) {
+              log.warn(
+                `google turn ordering fixup: prepended user bootstrap (sessionId=${params.sessionId})`,
+              );
+            }
+            if (sanitizedPrior.length > 0) {
+              session.agent.replaceMessages(sanitizedPrior);
             }
           } catch (err) {
             session.dispose();