Agents: sanitize OpenRouter Gemini thoughtSignature

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

@@ -145,6 +145,44 @@ describe("sanitizeSessionHistory (google thinking)", () => {
     expect(assistant.content?.[1]?.text).toBe("internal note");
   });
 
+  it("strips non-base64 thought signatures for OpenRouter Gemini", async () => {
+    const sessionManager = SessionManager.inMemory();
+    const input = [
+      {
+        role: "user",
+        content: "hi",
+      },
+      {
+        role: "assistant",
+        content: [
+          { type: "text", text: "hello", thought_signature: "msg_abc123" },
+          { type: "thinking", thinking: "ok", thought_signature: "c2ln" },
+          { type: "toolCall", id: "call_1", thoughtSignature: "{\"id\":1}" },
+          { type: "toolCall", id: "call_2", thoughtSignature: "c2ln" },
+        ],
+      },
+    ] satisfies AgentMessage[];
+
+    const out = await sanitizeSessionHistory({
+      messages: input,
+      modelApi: "openrouter",
+      provider: "openrouter",
+      modelId: "google/gemini-1.5-pro",
+      sessionManager,
+      sessionId: "session:openrouter-gemini",
+    });
+
+    const assistant = out.find((msg) => (msg as { role?: string }).role === "assistant") as {
+      content?: Array<{ type?: string; thought_signature?: string; thoughtSignature?: string }>;
+    };
+    expect(assistant.content).toEqual([
+      { type: "text", text: "hello" },
+      { type: "thinking", thinking: "ok", thought_signature: "c2ln" },
+      { type: "toolCall", id: "call_1" },
+      { type: "toolCall", id: "call_2", thoughtSignature: "c2ln" },
+    ]);
+  });
+
   it("downgrades only unsigned thinking blocks when mixed with signed ones", async () => {
     const sessionManager = SessionManager.inMemory();
     const input = [