diff --git a/CHANGELOG.md b/CHANGELOG.md
index 52207d31..4b2ea48d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 - Fixed incorrect shutdown of PostHog SDK in the worker. [#609](https://github.com/sourcebot-dev/sourcebot/pull/609)
 - Fixed race condition in job schedulers. [#607](https://github.com/sourcebot-dev/sourcebot/pull/607)
+- Fixed review agent so that it works with GHES instances [#611](https://github.com/sourcebot-dev/sourcebot/pull/611)
 
 ## [4.9.1] - 2025-11-07
 
diff --git a/packages/web/src/app/api/(server)/webhook/route.ts b/packages/web/src/app/api/(server)/webhook/route.ts
index cfd01a25..ebf3469c 100644
--- a/packages/web/src/app/api/(server)/webhook/route.ts
+++ b/packages/web/src/app/api/(server)/webhook/route.ts
@@ -6,28 +6,32 @@ import { WebhookEventDefinition} from "@octokit/webhooks/types";
 import { EndpointDefaults } from "@octokit/types";
 import { env } from "@sourcebot/shared";
 import { processGitHubPullRequest } from "@/features/agents/review-agent/app";
-import { throttling } from "@octokit/plugin-throttling";
+import { throttling, type ThrottlingOptions } from "@octokit/plugin-throttling";
 import fs from "fs";
 import { GitHubPullRequest } from "@/features/agents/review-agent/types";
 import { createLogger } from "@sourcebot/shared";
 
 const logger = createLogger('github-webhook');
 
-let githubApp: App | undefined;
+const DEFAULT_GITHUB_API_BASE_URL = "https://api.github.com";
+type GitHubAppBaseOptions = Omit<ConstructorParameters<typeof App>[0], "Octokit"> & { throttle: ThrottlingOptions };
+
+let githubAppBaseOptions: GitHubAppBaseOptions | undefined;
+const githubAppCache = new Map<string, App>();
+
 if (env.GITHUB_REVIEW_AGENT_APP_ID && env.GITHUB_REVIEW_AGENT_APP_WEBHOOK_SECRET && env.GITHUB_REVIEW_AGENT_APP_PRIVATE_KEY_PATH) {
     try {
         const privateKey = fs.readFileSync(env.GITHUB_REVIEW_AGENT_APP_PRIVATE_KEY_PATH, "utf8");
 
-        const throttledOctokit = Octokit.plugin(throttling);
-        githubApp = new App({
+        githubAppBaseOptions = {
             appId: env.GITHUB_REVIEW_AGENT_APP_ID,
-            privateKey: privateKey,
+            privateKey,
             webhooks: {
                 secret: env.GITHUB_REVIEW_AGENT_APP_WEBHOOK_SECRET,
             },
-            Octokit: throttledOctokit,
             throttle: {
-                onRateLimit: (retryAfter: number, options: Required<EndpointDefaults>, octokit: Octokit, retryCount: number) => {
+                enabled: true,
+                onRateLimit: (retryAfter, _options, _octokit, retryCount) => {
                     if (retryCount > 3) {
                         logger.warn(`Rate limit exceeded: ${retryAfter} seconds`);
                         return false;
@@ -35,13 +39,55 @@ if (env.GITHUB_REVIEW_AGENT_APP_ID && env.GITHUB_REVIEW_AGENT_APP_WEBHOOK_SECRET
 
                     return true;
                 },
-            }
-        });
+                onSecondaryRateLimit: (_retryAfter, options) => {
+                  // no retries on secondary rate limits
+                  logger.warn(`SecondaryRateLimit detected for ${options.method} ${options.url}`);
+                }
+            },
+        };
     } catch (error) {
         logger.error(`Error initializing GitHub app: ${error}`);
     }
 }
 
+const normalizeGithubApiBaseUrl = (baseUrl?: string) => {
+    if (!baseUrl) {
+        return DEFAULT_GITHUB_API_BASE_URL;
+    }
+
+    return baseUrl.replace(/\/+$/, "");
+};
+
+const resolveGithubApiBaseUrl = (headers: Record<string, string>) => {
+    const enterpriseHost = headers["x-github-enterprise-host"];
+    if (enterpriseHost) {
+        return normalizeGithubApiBaseUrl(`https://${enterpriseHost}/api/v3`);
+    }
+
+    return DEFAULT_GITHUB_API_BASE_URL;
+};
+
+const getGithubAppForBaseUrl = (baseUrl: string) => {
+    if (!githubAppBaseOptions) {
+        return undefined;
+    }
+
+    const normalizedBaseUrl = normalizeGithubApiBaseUrl(baseUrl);
+    const cachedApp = githubAppCache.get(normalizedBaseUrl);
+    if (cachedApp) {
+        return cachedApp;
+    }
+
+    const OctokitWithBaseUrl = Octokit.plugin(throttling).defaults({ baseUrl: normalizedBaseUrl });
+    const app = new App({
+        ...githubAppBaseOptions,
+        Octokit: OctokitWithBaseUrl,
+    });
+
+    githubAppCache.set(normalizedBaseUrl, app);
+    return app;
+};
+
 function isPullRequestEvent(eventHeader: string, payload: unknown): payload is WebhookEventDefinition<"pull-request-opened"> | WebhookEventDefinition<"pull-request-synchronize"> {
     return eventHeader === "pull_request" && typeof payload === "object" && payload !== null && "action" in payload && typeof payload.action === "string" && (payload.action === "opened" || payload.action === "synchronize");
 }
@@ -52,12 +98,16 @@ function isIssueCommentEvent(eventHeader: string, payload: unknown): payload is
 
 export const POST = async (request: NextRequest) => {
     const body = await request.json();
-    const headers = Object.fromEntries(request.headers.entries());
+    const headers = Object.fromEntries(Array.from(request.headers.entries(), ([key, value]) => [key.toLowerCase(), value]));
 
-    const githubEvent = headers['x-github-event'] || headers['X-GitHub-Event'];
+    const githubEvent = headers['x-github-event'];
     if (githubEvent) {
         logger.info('GitHub event received:', githubEvent);
 
+        const githubApiBaseUrl = resolveGithubApiBaseUrl(headers);
+        logger.debug('Using GitHub API base URL for event', { githubApiBaseUrl });
+        const githubApp = getGithubAppForBaseUrl(githubApiBaseUrl);
+
         if (!githubApp) {
             logger.warn('Received GitHub webhook event but GitHub app env vars are not set');
             return Response.json({ status: 'ok' });
@@ -113,4 +163,4 @@ export const POST = async (request: NextRequest) => {
     }
 
     return Response.json({ status: 'ok' });
-}
\ No newline at end of file
+}