diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9fadcf22d..a36c9fe10 100644
--- a/CHANGELOG.md
+++ b/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. [#1302](https://github.com/sourcebot-dev/sourcebot/pull/1302)
+
 ## [5.0.2] - 2026-06-11
 
 ### Changed
diff --git a/packages/web/src/features/agents/review-agent/nodes/githubPrParser.test.ts b/packages/web/src/features/agents/review-agent/nodes/githubPrParser.test.ts
index d06cdd889..878974454 100644
--- a/packages/web/src/features/agents/review-agent/nodes/githubPrParser.test.ts
+++ b/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,
     };
 
@@ -54,43 +56,55 @@ 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);
@@ -98,96 +112,98 @@ describe('githubPrParser', () => {
         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",
+        );
     });
 });
diff --git a/packages/web/src/features/agents/review-agent/nodes/githubPrParser.ts b/packages/web/src/features/agents/review-agent/nodes/githubPrParser.ts
index b633450ea..f928b1962 100644
--- a/packages/web/src/features/agents/review-agent/nodes/githubPrParser.ts
+++ b/packages/web/src/features/agents/review-agent/nodes/githubPrParser.ts
@@ -1,57 +1,81 @@
-import { sourcebot_pr_payload, sourcebot_file_diff, sourcebot_diff } from "@/features/agents/review-agent/types";
+import {
+    sourcebot_pr_payload,
+    sourcebot_file_diff,
+    sourcebot_diff,
+} from "@/features/agents/review-agent/types";
 import parse from "parse-diff";
 import { Octokit } from "octokit";
 import { GitHubPullRequest } from "@/features/agents/review-agent/types";
 import { createLogger } from "@sourcebot/shared";
 
-const logger = createLogger('github-pr-parser');
+const logger = createLogger("github-pr-parser");
 
-export const githubPrParser = async (octokit: Octokit, pullRequest: GitHubPullRequest): Promise<sourcebot_pr_payload> => {
+export const githubPrParser = async (
+    octokit: Octokit,
+    pullRequest: GitHubPullRequest,
+): Promise<sourcebot_pr_payload> => {
     logger.debug("Executing github_pr_parser");
 
-    let parsedDiff: parse.File[] = [];  
+    let parsedDiff: parse.File[] = [];
     try {
-        const diff = await octokit.request(pullRequest.diff_url);
-        parsedDiff = parse(diff.data);
+        const diff = await octokit.request(
+            "GET /repos/{owner}/{repo}/pulls/{pull_number}",
+            {
+                owner: pullRequest.base.repo.owner.login,
+                repo: pullRequest.base.repo.name,
+                pull_number: pullRequest.number,
+                mediaType: {
+                    format: "diff",
+                },
+            },
+        );
+        parsedDiff = parse(diff.data as unknown as string);
     } catch (error) {
         logger.error("Error fetching diff: ", error);
         throw error;
     }
 
-    const sourcebotFileDiffs: (sourcebot_file_diff | null)[] = parsedDiff.map((file) => {
-        if (!file.from || !file.to) {
-            logger.debug(`Skipping file due to missing from (${file.from}) or to (${file.to})`)
-            return null;
-        }
+    const sourcebotFileDiffs: (sourcebot_file_diff | null)[] = parsedDiff.map(
+        (file) => {
+            if (!file.from || !file.to) {
+                logger.debug(
+                    `Skipping file due to missing from (${file.from}) or to (${file.to})`,
+                );
+                return null;
+            }
 
-        const diffs: sourcebot_diff[] = file.chunks.map((chunk) => {
-            let oldSnippet = `@@ -${chunk.oldStart},${chunk.oldLines} +${chunk.newStart},${chunk.newLines} @@\n`;
-            let newSnippet = `@@ -${chunk.oldStart},${chunk.oldLines} +${chunk.newStart},${chunk.newLines} @@\n`;
+            const diffs: sourcebot_diff[] = file.chunks.map((chunk) => {
+                let oldSnippet = `@@ -${chunk.oldStart},${chunk.oldLines} +${chunk.newStart},${chunk.newLines} @@\n`;
+                let newSnippet = `@@ -${chunk.oldStart},${chunk.oldLines} +${chunk.newStart},${chunk.newLines} @@\n`;
 
-            for (const change of chunk.changes) {
-                if (change.type === "normal") {
-                    oldSnippet += change.ln1 + ":" + change.content + "\n";
-                    newSnippet += change.ln2 + ":" + change.content + "\n";
-                } else if (change.type === "add") {
-                    newSnippet += change.ln + ":" + change.content + "\n";
-                } else if (change.type === "del") {
-                    oldSnippet += change.ln + ":" + change.content + "\n";
+                for (const change of chunk.changes) {
+                    if (change.type === "normal") {
+                        oldSnippet += change.ln1 + ":" + change.content + "\n";
+                        newSnippet += change.ln2 + ":" + change.content + "\n";
+                    } else if (change.type === "add") {
+                        newSnippet += change.ln + ":" + change.content + "\n";
+                    } else if (change.type === "del") {
+                        oldSnippet += change.ln + ":" + change.content + "\n";
+                    }
                 }
-            }
 
-            return {
-                oldSnippet: oldSnippet,
-                newSnippet: newSnippet,
-            }
-        });
+                return {
+                    oldSnippet: oldSnippet,
+                    newSnippet: newSnippet,
+                };
+            });
 
-        return {
-            from: file.from,
-            to: file.to,
-            diffs: diffs,
-        }
-    });
-    const filteredSourcebotFileDiffs: sourcebot_file_diff[] = sourcebotFileDiffs.filter((file) => file !== null) as sourcebot_file_diff[];
+            return {
+                from: file.from,
+                to: file.to,
+                diffs: diffs,
+            };
+        },
+    );
+    const filteredSourcebotFileDiffs: sourcebot_file_diff[] =
+        sourcebotFileDiffs.filter(
+            (file) => file !== null,
+        ) as sourcebot_file_diff[];
 
     logger.debug("Completed github_pr_parser");
     return {
@@ -62,6 +86,6 @@ export const githubPrParser = async (octokit: Octokit, pullRequest: GitHubPullRe
         repo: pullRequest.base.repo.name,
         file_diffs: filteredSourcebotFileDiffs,
         number: pullRequest.number,
-        head_sha: pullRequest.head.sha
-    }
-}
\ No newline at end of file
+        head_sha: pullRequest.head.sha,
+    };
+};