fix(web): use REST API endpoint for fetching PR diff instead of web diff_url

The Review Agent's githubPrParser was using pullRequest.diff_url to
fetch the PR diff, which points to a github.com web URL. GitHub App
installation tokens are only accepted on the REST API (api.github.com),
so requests to the web domain fail with 404 for private repositories.

Fix by using the REST API endpoint GET /repos/{owner}/{repo}/pulls/{pull_number}
with mediaType: { format: 'diff' }, which correctly authenticates with
the installation token and works for both public and private repos.

Fixes #1277

Author: AasheeshLikePanner

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Fixed Review Agent failing on private GitHub repositories when fetching the PR diff. The parser now uses the REST API endpoint with the `diff` media type instead of the web `diff_url` which is not accessible to API tokens. [#1277](https://github.com/sourcebot-dev/sourcebot/issues/1277)
+
 ## [5.0.2] - 2026-06-11
 
 ### Changed

packages/web/src/features/agents/review-agent/nodes/githubPrParser.test.ts

@@ -1,9 +1,9 @@
-import { expect, test, vi, describe } from 'vitest';
-import { Octokit } from 'octokit';
-import { githubPrParser } from './githubPrParser';
-import { GitHubPullRequest } from '../types';
+import { expect, test, vi, describe } from "vitest";
+import { Octokit } from "octokit";
+import { githubPrParser } from "./githubPrParser";
+import { GitHubPullRequest } from "../types";
 
-vi.mock('@sourcebot/shared', () => ({
+vi.mock("@sourcebot/shared", () => ({
     createLogger: () => ({
         debug: vi.fn(),
         info: vi.fn(),
@@ -13,23 +13,25 @@ vi.mock('@sourcebot/shared', () => ({
 }));
 
 // Minimal shape satisfying the fields accessed by githubPrParser
-function makePullRequest(overrides: Partial<{
-    number: number;
-    title: string;
-    body: string | null;
-    head_sha: string;
-    owner: string;
-    repo: string;
-    diff_url: string;
-}> = {}): GitHubPullRequest {
+function makePullRequest(
+    overrides: Partial<{
+        number: number;
+        title: string;
+        body: string | null;
+        head_sha: string;
+        owner: string;
+        repo: string;
+        diff_url: string;
+    }> = {},
+): GitHubPullRequest {
     const opts = {
         number: 7,
-        title: 'My PR title',
-        body: 'My PR description',
-        head_sha: 'sha_abc123',
-        owner: 'my-org',
-        repo: 'my-repo',
-        diff_url: 'https://github.com/my-org/my-repo/pull/7.diff',
+        title: "My PR title",
+        body: "My PR description",
+        head_sha: "sha_abc123",
+        owner: "my-org",
+        repo: "my-repo",
+        diff_url: "https://github.com/my-org/my-repo/pull/7.diff",
         ...overrides,
     };
 
@@ -54,140 +56,154 @@ function makeMockOctokit(diffText: string) {
     } as unknown as Octokit;
 }
 
-describe('githubPrParser', () => {
-    test('maps pull request metadata correctly', async () => {
-        const octokit = makeMockOctokit('');
+describe("githubPrParser", () => {
+    test("maps pull request metadata correctly", async () => {
+        const octokit = makeMockOctokit("");
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
 
-        expect(result.title).toBe('My PR title');
-        expect(result.description).toBe('My PR description');
+        expect(result.title).toBe("My PR title");
+        expect(result.description).toBe("My PR description");
         expect(result.number).toBe(7);
-        expect(result.head_sha).toBe('sha_abc123');
-        expect(result.owner).toBe('my-org');
-        expect(result.repo).toBe('my-repo');
-        expect(result.hostDomain).toBe('github.com');
+        expect(result.head_sha).toBe("sha_abc123");
+        expect(result.owner).toBe("my-org");
+        expect(result.repo).toBe("my-repo");
+        expect(result.hostDomain).toBe("github.com");
     });
 
-    test('uses empty string when body is null', async () => {
-        const octokit = makeMockOctokit('');
+    test("uses empty string when body is null", async () => {
+        const octokit = makeMockOctokit("");
         const pr = makePullRequest({ body: null });
 
         const result = await githubPrParser(octokit, pr);
 
-        expect(result.description).toBe('');
+        expect(result.description).toBe("");
     });
 
-    test('fetches diff using the pull request diff_url', async () => {
-        const mockRequest = vi.fn().mockResolvedValue({ data: '' });
+    test("fetches diff using the REST API endpoint instead of the web diff_url", async () => {
+        const mockRequest = vi.fn().mockResolvedValue({ data: "" });
         const octokit = { request: mockRequest } as unknown as Octokit;
-        const pr = makePullRequest({ diff_url: 'https://github.com/my-org/my-repo/pull/7.diff' });
+        const pr = makePullRequest({
+            owner: "my-org",
+            repo: "my-repo",
+            number: 7,
+        });
 
         await githubPrParser(octokit, pr);
 
-        expect(mockRequest).toHaveBeenCalledWith('https://github.com/my-org/my-repo/pull/7.diff');
+        expect(mockRequest).toHaveBeenCalledWith(
+            "GET /repos/{owner}/{repo}/pulls/{pull_number}",
+            {
+                owner: "my-org",
+                repo: "my-repo",
+                pull_number: 7,
+                mediaType: { format: "diff" },
+            },
+        );
     });
 
-    test('returns empty file_diffs for an empty diff', async () => {
-        const octokit = makeMockOctokit('');
+    test("returns empty file_diffs for an empty diff", async () => {
+        const octokit = makeMockOctokit("");
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
 
         expect(result.file_diffs).toEqual([]);
     });
 
-    test('parses a unified diff with added and context lines', async () => {
+    test("parses a unified diff with added and context lines", async () => {
         const unifiedDiff = [
-            'diff --git a/src/foo.ts b/src/foo.ts',
-            '--- a/src/foo.ts',
-            '+++ b/src/foo.ts',
-            '@@ -1,2 +1,3 @@',
-            ' context line',
-            '+added line',
-            ' another context',
-        ].join('\n');
+            "diff --git a/src/foo.ts b/src/foo.ts",
+            "--- a/src/foo.ts",
+            "+++ b/src/foo.ts",
+            "@@ -1,2 +1,3 @@",
+            " context line",
+            "+added line",
+            " another context",
+        ].join("\n");
         const octokit = makeMockOctokit(unifiedDiff);
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
 
         expect(result.file_diffs).toHaveLength(1);
-        expect(result.file_diffs[0].from).toBe('src/foo.ts');
-        expect(result.file_diffs[0].to).toBe('src/foo.ts');
+        expect(result.file_diffs[0].from).toBe("src/foo.ts");
+        expect(result.file_diffs[0].to).toBe("src/foo.ts");
         expect(result.file_diffs[0].diffs).toHaveLength(1);
     });
 
-    test('newSnippet contains added lines and context', async () => {
+    test("newSnippet contains added lines and context", async () => {
         const unifiedDiff = [
-            'diff --git a/src/foo.ts b/src/foo.ts',
-            '--- a/src/foo.ts',
-            '+++ b/src/foo.ts',
-            '@@ -1,1 +1,2 @@',
-            ' context',
-            '+new line here',
-        ].join('\n');
+            "diff --git a/src/foo.ts b/src/foo.ts",
+            "--- a/src/foo.ts",
+            "+++ b/src/foo.ts",
+            "@@ -1,1 +1,2 @@",
+            " context",
+            "+new line here",
+        ].join("\n");
         const octokit = makeMockOctokit(unifiedDiff);
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
         const diff = result.file_diffs[0].diffs[0];
 
-        expect(diff.newSnippet).toContain('+new line here');
-        expect(diff.oldSnippet).not.toContain('+new line here');
+        expect(diff.newSnippet).toContain("+new line here");
+        expect(diff.oldSnippet).not.toContain("+new line here");
     });
 
-    test('oldSnippet contains deleted lines', async () => {
+    test("oldSnippet contains deleted lines", async () => {
         const unifiedDiff = [
-            'diff --git a/src/foo.ts b/src/foo.ts',
-            '--- a/src/foo.ts',
-            '+++ b/src/foo.ts',
-            '@@ -1,2 +1,1 @@',
-            ' context',
-            '-removed line',
-        ].join('\n');
+            "diff --git a/src/foo.ts b/src/foo.ts",
+            "--- a/src/foo.ts",
+            "+++ b/src/foo.ts",
+            "@@ -1,2 +1,1 @@",
+            " context",
+            "-removed line",
+        ].join("\n");
         const octokit = makeMockOctokit(unifiedDiff);
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
         const diff = result.file_diffs[0].diffs[0];
 
-        expect(diff.oldSnippet).toContain('-removed line');
-        expect(diff.newSnippet).not.toContain('-removed line');
+        expect(diff.oldSnippet).toContain("-removed line");
+        expect(diff.newSnippet).not.toContain("-removed line");
     });
 
-    test('parses multiple files from a diff', async () => {
+    test("parses multiple files from a diff", async () => {
         const unifiedDiff = [
-            'diff --git a/src/a.ts b/src/a.ts',
-            '--- a/src/a.ts',
-            '+++ b/src/a.ts',
-            '@@ -1,1 +1,2 @@',
-            ' ctx',
-            '+add',
-            'diff --git a/src/b.ts b/src/b.ts',
-            '--- a/src/b.ts',
-            '+++ b/src/b.ts',
-            '@@ -1,2 +1,1 @@',
-            ' ctx',
-            '-remove',
-        ].join('\n');
+            "diff --git a/src/a.ts b/src/a.ts",
+            "--- a/src/a.ts",
+            "+++ b/src/a.ts",
+            "@@ -1,1 +1,2 @@",
+            " ctx",
+            "+add",
+            "diff --git a/src/b.ts b/src/b.ts",
+            "--- a/src/b.ts",
+            "+++ b/src/b.ts",
+            "@@ -1,2 +1,1 @@",
+            " ctx",
+            "-remove",
+        ].join("\n");
         const octokit = makeMockOctokit(unifiedDiff);
         const pr = makePullRequest();
 
         const result = await githubPrParser(octokit, pr);
 
         expect(result.file_diffs).toHaveLength(2);
-        expect(result.file_diffs[0].to).toBe('src/a.ts');
-        expect(result.file_diffs[1].to).toBe('src/b.ts');
+        expect(result.file_diffs[0].to).toBe("src/a.ts");
+        expect(result.file_diffs[1].to).toBe("src/b.ts");
     });
 
-    test('throws when the diff request fails', async () => {
+    test("throws when the diff request fails", async () => {
         const octokit = {
-            request: vi.fn().mockRejectedValue(new Error('Network error')),
+            request: vi.fn().mockRejectedValue(new Error("Network error")),
         } as unknown as Octokit;
         const pr = makePullRequest();
 
-        await expect(githubPrParser(octokit, pr)).rejects.toThrow('Network error');
+        await expect(githubPrParser(octokit, pr)).rejects.toThrow(
+            "Network error",
+        );
     });
 });