fix(types): preserve non-streaming response metadata (#9118)

Validated in local merge-train (devbox-vm-06-dev002) @ combined-tip (FAST gates: typecheck/complexity/cognitive/changelog/vitest — only pre-existing audit.test.ts flake). Evidence: /home/diegosouzapw/dev/proxys/OmniRoute/.claude/worktrees/merge-train-20260805-222248-suite.log

changelog.d/maintenance/9118-ts7-response-meta-header-inputs.md

@@ -0,0 +1 @@
+- **fix(types):** narrowed non-streaming chat response metadata inputs to the shared header contract without changing emitted metadata headers ([#9118](https://github.com/diegosouzapw/OmniRoute/pull/9118))

open-sse/handlers/chatCore/nonStreamingResponseHeaders.ts

@@ -16,9 +16,9 @@ export function buildNonStreamingResponseHeaders(
     provider: string | null | undefined;
     model: string | null | undefined;
     startTime: number;
-    responseUsage: unknown;
+    responseUsage: Record<string, unknown> | null | undefined;
     estimatedCost: number;
-    requestId: unknown;
+    requestId: string | null | undefined;
     compressionResponseMeta?: string | null | undefined;
     comboStrategy?: string | null | undefined;
   },

tests/unit/chatcore-nonstreaming-response-headers.test.ts

@@ -6,14 +6,16 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
 
-const { buildNonStreamingResponseHeaders } = await import(
-  "../../open-sse/handlers/chatCore/nonStreamingResponseHeaders.ts"
-);
+const { buildNonStreamingResponseHeaders } =
+  await import("../../open-sse/handlers/chatCore/nonStreamingResponseHeaders.ts");
 
 function makeDeps(now = 1000) {
   const metaCalls: Array<{ headers: Record<string, string>; meta: Record<string, unknown> }> = [];
   const deps = {
-    attachOmniRouteMetaHeaders: (headers: Record<string, string>, meta: Record<string, unknown>) => {
+    attachOmniRouteMetaHeaders: (
+      headers: Record<string, string>,
+      meta: Record<string, unknown>
+    ) => {
       metaCalls.push({ headers, meta });
       headers["x-omniroute-meta"] = "attached";
     },
@@ -35,6 +37,17 @@ function baseArgs(overrides: Record<string, unknown> = {}) {
   } as Parameters<typeof buildNonStreamingResponseHeaders>[0];
 }
 
+function acceptsAttachMetaInputContract(args: {
+  responseUsage: Record<string, unknown> | null | undefined;
+  requestId: string | null | undefined;
+}) {
+  return args;
+}
+
+test("builder input types match the metadata attachment contract", () => {
+  acceptsAttachMetaInputContract(baseArgs());
+});
+
 test("static headers: Content-Type json + cache MISS", () => {
   const { deps } = makeDeps();
   const h = buildNonStreamingResponseHeaders(baseArgs(), deps);
@@ -59,7 +72,10 @@ test("meta receives provider/model/cacheHit false/latency/usage/cost/requestId",
 
 test("no compression meta → no compression header", () => {
   const { deps } = makeDeps();
-  const h = buildNonStreamingResponseHeaders(baseArgs({ compressionResponseMeta: undefined }), deps);
+  const h = buildNonStreamingResponseHeaders(
+    baseArgs({ compressionResponseMeta: undefined }),
+    deps
+  );
   assert.ok(!Object.values(h).includes("engine:x"));
 });