test: verify strict header prevents proxy

New test: strict header returns 503 even in record mode.
Updated recorder test for new strict-before-proxy semantics.
CHANGELOG updated with strict-before-proxy fix.

Author: jpr5

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- **Strict mode checked before proxy attempt** — in `--proxy-only` mode, the `X-AIMock-Strict` header had no effect because `proxyAndRecord()` returned before the strict check. Now all 17 handlers check strict mode first: when strict + no fixture → 503 immediately, no proxy attempt
 - **Helper utilities and error serialization** — hardened helper functions and error serialization paths for correctness and robustness
 - **Journal and fixture-loader correctness** — fixed journal entry handling and fixture-loader edge cases
 - **WebSocket handler consistency and strict-mode journal** — aligned WebSocket handler behavior and ensured strict-mode journal entries are recorded correctly

src/__tests__/recorder.test.ts

@@ -692,7 +692,7 @@ describe("recorder strict mode", () => {
     expect(body.error.message).toBe("Strict mode: no fixture matched");
   });
 
-  it("record + strict: proxy succeeds when upstream is available", async () => {
+  it("record + strict: strict blocks proxy even when upstream is available", async () => {
     await setupUpstreamAndRecorder([
       {
         match: { userMessage: "hello" },
@@ -714,14 +714,15 @@ describe("recorder strict mode", () => {
       record: { providers: { openai: upstream!.url }, fixturePath: tmpDir },
     });
 
+    // Strict mode now takes precedence over proxy — returns 503
     const resp = await post(`${recorder.url}/v1/chat/completions`, {
       model: "gpt-4",
       messages: [{ role: "user", content: "hello" }],
     });
 
-    expect(resp.status).toBe(200);
+    expect(resp.status).toBe(503);
     const body = JSON.parse(resp.body);
-    expect(body.choices[0].message.content).toBe("world");
+    expect(body.error.message).toBe("Strict mode: no fixture matched");
   });
 });
 

src/__tests__/strict-header.test.ts

@@ -219,4 +219,19 @@ describe("X-AIMock-Strict header integration", () => {
     expect(entries.length).toBe(1);
     expect(entries[0].response.strictOverride).toBe(false);
   });
+
+  it("strict header prevents proxy in record mode", async () => {
+    server = await createServer([], {
+      port: 0,
+      record: {
+        providers: { openai: "https://api.openai.com" },
+      },
+    });
+    const res = await httpPost(`${server.url}/v1/chat/completions`, chatRequest("anything"), {
+      "X-AIMock-Strict": "true",
+    });
+    expect(res.status).toBe(503);
+    const body = JSON.parse(res.body);
+    expect(body.error.message).toBe("Strict mode: no fixture matched");
+  });
 });