chore(0pt): document the canonical-fact machine route (no behavior change)

middleware.ts

@@ -4,7 +4,7 @@
  * Customer calls use verified Zitadel bearer identity and receive immutable
  * x-0pt-verified-* headers. Explicit machine routes may instead use the
  * shared X-Internal-Token convention; mutation handlers verify it again for
- * defence in depth.
+ * defence in depth. The canonical-fact write is one such explicit machine route.
  */
 import { NextResponse, type NextRequest } from 'next/server';
 import { assertAuthConfigSafe, resolveAuthContext } from '@/src/auth/context';
@@ -26,6 +26,9 @@ const EXEMPT_PATTERNS: RegExp[] = [
 /** Routes that may be reached with a service token instead of end-user bearer auth. */
 const INTERNAL_SERVICE_ROUTES: RegExp[] = [
   /^\/api\/0pt\/quality\/bridge-run$/,
+  // Acquisition engine -> 0pt canonical observation write (machine-to-machine,
+  // same X-Internal-Token class as the quality bridge; not a blanket bypass).
+  /^\/api\/0pt\/canonical\/facts$/,
   /^\/api\/0pt\/internal\/evidence-outbox\/dispatch$/,
   /^\/api\/0pt\/internal\/er\/candidates$/,
   /^\/api\/0pt\/search\/definitions$/,

tests/auth/middleware-internal-token.test.ts

@@ -45,6 +45,13 @@ describe('middleware.ts: internal-token path for /api/0pt/quality/bridge-run', (
     expect(res.status).toBe(200);
   });
 
+  it('a valid X-Internal-Token lets the acquisition engine write canonical facts', async () => {
+    const res = await middleware(
+      req('/api/0pt/canonical/facts', { 'x-internal-token': 'engine-shared-secret' }),
+    );
+    expect(res.status).toBe(200);
+  });
+
   it('an invalid X-Internal-Token still falls through to the ordinary Bearer requirement (401, not a bypass)', async () => {
     const res = await middleware(req('/api/0pt/quality/bridge-run', { 'x-internal-token': 'wrong-secret' }));
     expect(res.status).toBe(401);