fix: harden antigravity claude support (#968)

Co-authored-by: Max <rdev@users.noreply.github.com>

src/agents/pi-embedded-helpers.sanitize-session-messages-images.keeps-tool-call-tool-result-ids-unchanged.test.ts

@@ -127,4 +127,20 @@ describe("sanitizeSessionMessagesImages", () => {
     const assistant = out[0] as { content?: Array<{ type?: string }> };
     expect(assistant.content?.map((b) => b.type)).toEqual(["text", "toolCall", "thinking", "text"]);
   });
+
+  it("does not synthesize tool call input when missing", async () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [{ type: "toolCall", id: "call_1", name: "read" }],
+      },
+    ] satisfies AgentMessage[];
+
+    const out = await sanitizeSessionMessagesImages(input, "test");
+    const assistant = out[0] as { content?: Array<Record<string, unknown>> };
+    const toolCall = assistant.content?.find((b) => b.type === "toolCall");
+    expect(toolCall).toBeTruthy();
+    expect("input" in (toolCall ?? {})).toBe(false);
+    expect("arguments" in (toolCall ?? {})).toBe(false);
+  });
 });

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

@@ -62,9 +62,9 @@ export function downgradeGeminiThinkingBlocks(messages: AgentMessage[]): AgentMe
       if (!block || typeof block !== "object") return [block as AssistantContentBlock];
       const record = block as GeminiThinkingBlock;
       if (record.type !== "thinking") return [block];
-      const signature =
+      const thinkingSig =
         typeof record.thinkingSignature === "string" ? record.thinkingSignature.trim() : "";
-      if (signature.length > 0) return [block];
+      if (thinkingSig.length > 0) return [block];
       const thinking = typeof record.thinking === "string" ? record.thinking : "";
       const trimmed = thinking.trim();
       hasDowngraded = true;

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

@@ -90,6 +90,7 @@ export async function sanitizeSessionMessagesImages(
           if (rec.type !== "text" || typeof rec.text !== "string") return true;
           return rec.text.trim().length > 0;
         });
+
         const normalizedContent = options?.enforceToolCallLast
           ? (() => {
               let lastToolIndex = -1;

src/agents/pi-embedded-runner.google-sanitize-thinking.test.ts

@@ -59,6 +59,33 @@ describe("sanitizeSessionHistory (google thinking)", () => {
     expect(assistant.content?.[0]?.thinkingSignature).toBe("sig");
   });
 
+  it("downgrades thinking blocks with Anthropic-style signatures for Google models", async () => {
+    const sessionManager = SessionManager.inMemory();
+    const input = [
+      {
+        role: "user",
+        content: "hi",
+      },
+      {
+        role: "assistant",
+        content: [{ type: "thinking", thinking: "reasoning", signature: "sig" }],
+      },
+    ] satisfies AgentMessage[];
+
+    const out = await sanitizeSessionHistory({
+      messages: input,
+      modelApi: "google-antigravity",
+      sessionManager,
+      sessionId: "session:google",
+    });
+
+    const assistant = out.find((msg) => (msg as { role?: string }).role === "assistant") as {
+      content?: Array<{ type?: string; text?: string }>;
+    };
+    expect(assistant.content?.map((block) => block.type)).toEqual(["text"]);
+    expect(assistant.content?.[0]?.text).toBe("reasoning");
+  });
+
   it("keeps unsigned thinking blocks for Antigravity Claude", async () => {
     const sessionManager = SessionManager.inMemory();
     const input = [