fix(confidence-engine): sanitize reasoning error responses

tests/app/api/current-understanding-synthesis-route.test.js

@@ -13,6 +13,10 @@ vi.mock("@/lib/llm/provider.js", () => ({
   getProviderModelName: () => "gpt-5.6-terra",
 }));
 
+vi.mock("@/lib/supabase/api-auth.js", () => ({
+  withAuthenticatedApi: (handler) => handler,
+}));
+
 // ── Helpers ─────────────────────────────────────────────────
 
 function makeValidGraph() {
@@ -110,10 +114,13 @@ describe("POST /api/cases/synthesis — error cases", () => {
   });
 
   it("domain seam throws with statusCode → mapped status", async () => {
-    mockSynthesize.mockRejectedValue(new Error("Provider failed"));
-    // Add statusCode property to the error object after creation
-    const err = Object.assign(new Error("Provider failed"), { statusCode: 502 });
-    mockSynthesize.mockRejectedValue(err);
+    const err = Object.assign(
+      new Error("Ollama /api/generate returned 500 from private host"),
+      { statusCode: 502 },
+    );
+    mockSynthesize.mockImplementationOnce(async () => {
+      throw err;
+    });
 
     const { POST } = await import("@/app/api/cases/synthesis/route.js");
     const res = await POST(makeRequest({ situationGraph: makeValidGraph() }));
@@ -122,10 +129,17 @@ describe("POST /api/cases/synthesis — error cases", () => {
     const data = await res.json();
     expect(data.success).toBe(false);
     expect(data.stage).toBe("provider");
+    expect(data).toEqual({
+      success: false,
+      stage: "provider",
+      error: "Reasoning request could not be completed.",
+    });
   });
 
   it("domain seam throws without statusCode → 500", async () => {
-    mockSynthesize.mockRejectedValue(new Error("unknown error"));
+    mockSynthesize.mockImplementationOnce(async () => {
+      throw new Error("unknown error");
+    });
 
     const { POST } = await import("@/app/api/cases/synthesis/route.js");
     const res = await POST(makeRequest({ situationGraph: makeValidGraph() }));
@@ -138,7 +152,9 @@ describe("POST /api/cases/synthesis — error cases", () => {
 
   it("domain seam throws 400 → mapped to 400", async () => {
     const err = Object.assign(new Error("Invalid input"), { statusCode: 400 });
-    mockSynthesize.mockRejectedValue(err);
+    mockSynthesize.mockImplementationOnce(async () => {
+      throw err;
+    });
 
     const { POST } = await import("@/app/api/cases/synthesis/route.js");
     const res = await POST(makeRequest({ situationGraph: makeValidGraph() }));