fix(confidence-engine): supply synthesis output schema

docs/current-handoff.md

@@ -41,7 +41,8 @@ If YES, the next live experiment is one timed/costed OpenAI UI investigation mea
 - Current deterministic final-fetch schema remains internally valid, yet the live rejection contradicts it. `CONFIDENCE_ENGINE_EXPERIMENT_TRACE_OPENAI_SCHEMA=1` now emits one safe, server-side structural summary immediately before the OpenAI fetch—no prompt, answer, request body, secret, or model output.
 - The focused-deconstruction route now emits complementary safe server diagnostics for start, provider success/failure, focused validation, and end status; the OpenAI schema trace remains provider-owned. No user content or secrets are logged.
 - Canonical focused relationship items are now strict `{ from, to, type }`: all required non-empty strings, free-text `type`, and no `rationale`; `relationships` remains required and may be `[]`. Schema, prompt field names, and validator align; the stale rationale-bearing test fixture was corrected.
-- Focused and provider deterministic suites pass; the OpenAI projector is unchanged. Zero live calls occurred. Next evidence boundary: live provider compatibility of this same canonical focused contract.
+- Live Terra focused deconstruction now passes through the real UI, but the following Current Understanding synthesis exposed a separate caller/schema mismatch: its prompt and validator require `{ currentUnderstanding }` while the provider received the default initial-reconstruction schema.
+- Synthesis now supplies its own output schema as provider argument three; provider implementation is unchanged. Synthesis and provider deterministic suites pass with zero live calls. Next boundary: one isolated live synthesis request using the already captured situationGraph and findings payload.
 
 ## Repository checkpoint
 

lib/graph/current-understanding-synthesis.js

@@ -186,6 +186,15 @@ export const synthesisResponseSchema = z.object({
     .min(1, "currentUnderstanding must be a non-empty string"),
 });
 
+export const synthesisOutputSchema = {
+  type: "object",
+  properties: {
+    currentUnderstanding: { type: "string" },
+  },
+  required: ["currentUnderstanding"],
+  additionalProperties: false,
+};
+
 /** Validate raw provider output against synthesis response schema */
 export function validateSynthesisResponse(raw) {
   if (raw == null) {
@@ -274,7 +283,8 @@ export async function synthesizeCurrentUnderstanding(
   try {
     rawResponse = await provider.generateReconstruction(
       prompt,
-      modelName
+      modelName,
+      synthesisOutputSchema,
     );
   } catch (error) {
     const err = new Error(error.message ?? "Synthesis provider call failed");

tests/graph/current-understanding-synthesis.test.js

@@ -375,6 +375,12 @@ describe("synthesizeCurrentUnderstanding — full seam", () => {
     const prompt = fake.generateReconstruction.mock.calls[0][0];
     expect(prompt).toContain("Complaint count increased by 35%");
     expect(prompt).toContain("[known]");
+    expect(fake.generateReconstruction.mock.calls[0][2]).toEqual({
+      type: "object",
+      properties: { currentUnderstanding: { type: "string" } },
+      required: ["currentUnderstanding"],
+      additionalProperties: false,
+    });
   });
 
   it("supported node content flows to provider via synthesis prompt", async () => {