Fix OpenAI Responses transcript after model switch

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

@@ -0,0 +1,62 @@
+import { describe, expect, it } from "vitest";
+import { downgradeOpenAIReasoningBlocks } from "./pi-embedded-helpers.js";
+
+describe("downgradeOpenAIReasoningBlocks", () => {
+  it("downgrades orphaned reasoning signatures to text", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "thinking",
+            thinking: "internal reasoning",
+            thinkingSignature: JSON.stringify({ id: "rs_123", type: "reasoning" }),
+          },
+          { type: "text", text: "answer" },
+        ],
+      },
+    ];
+
+    expect(downgradeOpenAIReasoningBlocks(input as any)).toEqual([
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "internal reasoning" }, { type: "text", text: "answer" }],
+      },
+    ]);
+  });
+
+  it("drops empty thinking blocks with orphaned signatures", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "thinking",
+            thinking: "   ",
+            thinkingSignature: JSON.stringify({ id: "rs_abc", type: "reasoning" }),
+          },
+        ],
+      },
+      { role: "user", content: "next" },
+    ];
+
+    expect(downgradeOpenAIReasoningBlocks(input as any)).toEqual([{ role: "user", content: "next" }]);
+  });
+
+  it("keeps non-reasoning thinking signatures", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "thinking",
+            thinking: "t",
+            thinkingSignature: "reasoning_content",
+          },
+        ],
+      },
+    ];
+
+    expect(downgradeOpenAIReasoningBlocks(input as any)).toEqual(input);
+  });
+});