fix: cap tool call IDs for OpenAI/OpenRouter (#875) (thanks @j1philli)

src/agents/tool-call-id.test.ts

@@ -65,4 +65,48 @@ describe("sanitizeToolCallIdsForCloudCodeAssist", () => {
     expect(r1.toolCallId).toBe(a.id);
     expect(r2.toolCallId).toBe(b.id);
   });
+
+  it("caps tool call IDs at 40 chars while preserving uniqueness", () => {
+    const longA = `call_${"a".repeat(60)}`;
+    const longB = `call_${"a".repeat(59)}b`;
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          { type: "toolCall", id: longA, name: "read", arguments: {} },
+          { type: "toolCall", id: longB, name: "read", arguments: {} },
+        ],
+      },
+      {
+        role: "toolResult",
+        toolCallId: longA,
+        toolName: "read",
+        content: [{ type: "text", text: "one" }],
+      },
+      {
+        role: "toolResult",
+        toolCallId: longB,
+        toolName: "read",
+        content: [{ type: "text", text: "two" }],
+      },
+    ] satisfies AgentMessage[];
+
+    const out = sanitizeToolCallIdsForCloudCodeAssist(input);
+    const assistant = out[0] as Extract<AgentMessage, { role: "assistant" }>;
+    const a = assistant.content?.[0] as { id?: string };
+    const b = assistant.content?.[1] as { id?: string };
+
+    expect(typeof a.id).toBe("string");
+    expect(typeof b.id).toBe("string");
+    expect(a.id).not.toBe(b.id);
+    expect(a.id?.length).toBeLessThanOrEqual(40);
+    expect(b.id?.length).toBeLessThanOrEqual(40);
+    expect(isValidCloudCodeAssistToolId(a.id as string)).toBe(true);
+    expect(isValidCloudCodeAssistToolId(b.id as string)).toBe(true);
+
+    const r1 = out[1] as Extract<AgentMessage, { role: "toolResult" }>;
+    const r2 = out[2] as Extract<AgentMessage, { role: "toolResult" }>;
+    expect(r1.toolCallId).toBe(a.id);
+    expect(r2.toolCallId).toBe(b.id);
+  });
 });