experiment(confidence-engine): route UI journey provider centrally

tests/app/api/cases-overview-route.test.js

@@ -0,0 +1,29 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const mockSynthesize = vi.fn();
+
+vi.mock("@/lib/graph/investigation-overview-synthesis.js", () => ({
+  synthesizeInvestigationOverview: (...args) => mockSynthesize(...args),
+}));
+
+vi.mock("@/lib/llm/provider.js", () => ({
+  getProvider: () => ({ generateReconstruction() {} }),
+  getProviderModelName: () => "gpt-5.6-terra",
+}));
+
+describe("POST /api/cases/overview provider routing", () => {
+  beforeEach(() => mockSynthesize.mockClear());
+
+  it("passes the central provider and model resolution to overview synthesis", async () => {
+    mockSynthesize.mockResolvedValue({ understanding: "Understanding", plausibleInterpretations: "None" });
+    const { POST } = await import("@/app/api/cases/overview/route.js");
+    const response = await POST(new Request("http://localhost/api/cases/overview", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ situationGraph: { nodes: [], edges: [] }, findings: [], plausibleInterpretations: [] }),
+    }));
+
+    expect(response.status).toBe(200);
+    expect(mockSynthesize.mock.calls[0][1]).toMatchObject({ modelName: "gpt-5.6-terra" });
+  });
+});

tests/app/api/cases-start-route.test.js

@@ -39,6 +39,8 @@ describe("app/api/cases/start route", () => {
     await POST(request);
 
     expect(mockStartCase).toHaveBeenCalledWith({ scenario: "Scenario text" });
+    expect(mockStartCase.mock.calls[0][0]).not.toHaveProperty("provider");
+    expect(mockStartCase.mock.calls[0][0]).not.toHaveProperty("modelName");
   });
 
   it("returns 200 on success", async () => {

tests/app/api/cases-update-route.test.js

@@ -72,6 +72,8 @@ describe("app/api/cases/update route", () => {
     );
 
     expect(mockUpdateCase).toHaveBeenCalledWith(body, { applyProposal: true });
+    expect(mockUpdateCase.mock.calls[0][0]).not.toHaveProperty("provider");
+    expect(mockUpdateCase.mock.calls[0][0]).not.toHaveProperty("modelName");
   });
 
   it("invalid JSON returns 400", async () => {

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

@@ -10,6 +10,7 @@ vi.mock("@/lib/graph/current-understanding-synthesis.js", () => ({
 
 vi.mock("@/lib/llm/provider.js", () => ({
   getProvider: () => ({}),
+  getProviderModelName: () => "gpt-5.6-terra",
 }));
 
 // ── Helpers ─────────────────────────────────────────────────
@@ -45,6 +46,7 @@ describe("POST /api/cases/synthesis — valid request", () => {
     expect(data.success).toBe(true);
     expect(data.currentUnderstanding).toBe("Synthesized result");
     expect(mockSynthesize).toHaveBeenCalledTimes(1);
+    expect(mockSynthesize.mock.calls[0][1]).toMatchObject({ modelName: "gpt-5.6-terra" });
   });
 
   it("returns narrative result on success", async () => {