fix(ai): mint evidence tokens with metadata:read on CopilotKit only

packages/outpost/ai/src/github-evidence-auth.test.ts

@@ -51,14 +51,15 @@ describe('GitHub evidence authentication', () => {
         });
     });
 
-    it('authorizes evidence requests with an installation token narrowed to contents:read', async () => {
+    it('authorizes evidence requests with a metadata:read token narrowed to the CopilotKit repository', async () => {
         const { create, auth } = fakeAppAuth();
         const resolver = githubEvidenceAuthFromEnv(CREDENTIALS, create);
         expect(await resolver.authorization()).toBe(`Bearer ${TOKEN}`);
         expect(auth).toHaveBeenCalledWith({
             type: 'installation',
             installationId: 7890,
-            permissions: { contents: 'read' },
+            permissions: { metadata: 'read' },
+            repositoryNames: ['CopilotKit'],
         });
     });
 
@@ -803,8 +804,8 @@ describe('GitHub evidence authentication over the real @octokit/auth-app', () =>
         body: JSON.stringify({
             token,
             expires_at: new Date(Date.now() + 3_600_000).toISOString().replace(/\.\d+Z$/, 'Z'),
-            permissions: { contents: 'read', metadata: 'read' },
-            repository_selection: 'all',
+            permissions: { metadata: 'read' },
+            repository_selection: 'selected',
         }),
     });
 
@@ -859,15 +860,18 @@ describe('GitHub evidence authentication over the real @octokit/auth-app', () =>
     });
     const elapse = (ms: number) => vi.setSystemTime(Date.now() + ms);
 
-    it('mints once, signed as the App and narrowed to contents:read, then serves the SDK cache', async () => {
+    it('mints once, signed as the App and narrowed to metadata:read on CopilotKit, then serves the SDK cache', async () => {
         const exchanges = tokenEndpoint();
         const auth = resolver();
         expect(await auth.authorization()).toBe('Bearer ghs_syntheticexchange1');
         elapse(60_000);
         expect(await auth.authorization()).toBe('Bearer ghs_syntheticexchange1');
         expect(exchanges).toHaveLength(1);
         expect(exchanges[0]?.authorization).toMatch(/^bearer [\w-]+\.[\w-]+\.[\w-]+$/);
-        expect(exchanges[0]?.body).toEqual({ permissions: { contents: 'read' } });
+        expect(exchanges[0]?.body).toEqual({
+            permissions: { metadata: 'read' },
+            repositories: ['CopilotKit'],
+        });
     });
 
     // Each of these is a 2xx the SDK returns as a success and caches on the strategy this

packages/outpost/ai/src/github-evidence-auth.ts

@@ -16,12 +16,23 @@ import { createAppAuth } from '@octokit/auth-app';
 import { Octokit } from '@octokit/rest';
 
 /**
- * Evidence reads fetch commits, file contents and release metadata. `contents:read`
- * covers all three; `metadata:read` is implicit in every installation token. Asking
- * for a narrowed token means a leaked one cannot write, and can read nothing the App
- * is installed for beyond repository contents and that implicit repository metadata.
+ * Evidence reads fetch commits, file contents and release metadata, and only from the two
+ * public repositories `support-agent.ts` allowlists. GitHub serves all three for a public
+ * repository to any token, whatever its permissions, so the token asks for nothing beyond
+ * `metadata:read`, which the App already holds. It must not ask for `contents:read`: the App
+ * is not granted it, and GitHub refuses the whole exchange with a 422 rather than narrowing.
+ * The App is deliberately not granted it either: it is installed on every org repository,
+ * private ones included, and reads untrusted issue text.
  */
-const EVIDENCE_PERMISSIONS = { contents: 'read' } as const;
+const EVIDENCE_PERMISSIONS = { metadata: 'read' } as const;
+
+/**
+ * The token is narrowed to the one allowlisted repository this installation covers, so a
+ * leaked one cannot even list metadata of the org's other repositories. `ag-ui-protocol/ag-ui`
+ * belongs to another org and cannot be named here; as a public repository it is readable with
+ * this token all the same.
+ */
+const EVIDENCE_REPOSITORIES: readonly string[] = ['CopilotKit'];
 
 /**
  * Installation ids are positive decimal integers; `Number` alone would accept `1e3` and `0x1f`.
@@ -205,6 +216,8 @@ export type InstallationTokenSource = (options: {
     type: 'installation';
     installationId: number;
     permissions: Record<string, string>;
+    /** Repository names, within the installation's owner, the token is narrowed to. */
+    repositoryNames?: string[];
     /**
      * Skip the strategy's cache and exchange again (`dist-node/index.js:182`). A call that
      * overlaps another for the same installation and permissions still shares that call's
@@ -388,6 +401,7 @@ function installationAuth(
                 type: 'installation',
                 installationId: credentials.installationId,
                 permissions: EVIDENCE_PERMISSIONS,
+                repositoryNames: [...EVIDENCE_REPOSITORIES],
                 ...(skipCache && { refresh: true }),
             });
         });