diff --git a/frontend/src/App.test.tsx b/frontend/src/App.test.tsx
index 22a1aea8..07f94fc7 100644
--- a/frontend/src/App.test.tsx
+++ b/frontend/src/App.test.tsx
@@ -66,7 +66,12 @@ describe("App", () => {
 		mockedApi.getAnthropicApiKeyExists.mockResolvedValue(false);
 		mockedApi.getAnthropicModels.mockResolvedValue([]);
 		mockedApi.getModelPreference.mockResolvedValue(null);
-		mockedApi.getOAuthStatus.mockResolvedValue({ authenticated: false, expired: false, expires_at: 0, has_refresh_token: false });
+		mockedApi.getOAuthStatus.mockResolvedValue({
+			authenticated: false,
+			expired: false,
+			expires_at: 0,
+			has_refresh_token: false,
+		});
 	});
 
 	async function renderApp() {
diff --git a/frontend/src/components/Chat.tsx b/frontend/src/components/Chat.tsx
index 1e73e51a..bad98dc3 100644
--- a/frontend/src/components/Chat.tsx
+++ b/frontend/src/components/Chat.tsx
@@ -168,7 +168,11 @@ interface ChatProps {
 	oauthStatus?: OAuthStatus | null;
 }
 
-export function Chat({ projectPath, onCloseProject, oauthStatus = null }: ChatProps) {
+export function Chat({
+	projectPath,
+	onCloseProject,
+	oauthStatus = null,
+}: ChatProps) {
 	const { messages, setMessages, clearMessages } = useChatHistory(projectPath);
 	const [loading, setLoading] = useState(false);
 	const [model, setModel] = useState("claude-code-pty");
diff --git a/frontend/src/components/ChatHeader.tsx b/frontend/src/components/ChatHeader.tsx
index 83b5b25c..e8b925b0 100644
--- a/frontend/src/components/ChatHeader.tsx
+++ b/frontend/src/components/ChatHeader.tsx
@@ -349,7 +349,11 @@ export function ChatHeader({
 								type="button"
 								title="Authenticate with Claude via OAuth"
 								onClick={() => {
-									window.open("/oauth/authorize", "_blank", "noopener,noreferrer");
+									window.open(
+										"/oauth/authorize",
+										"_blank",
+										"noopener,noreferrer",
+									);
 								}}
 								style={{
 									padding: "6px 12px",
diff --git a/frontend/src/components/selection/SelectionScreen.tsx b/frontend/src/components/selection/SelectionScreen.tsx
index 9b3a637e..5274f760 100644
--- a/frontend/src/components/selection/SelectionScreen.tsx
+++ b/frontend/src/components/selection/SelectionScreen.tsx
@@ -66,7 +66,11 @@ export function SelectionScreen({
 						<button
 							type="button"
 							onClick={() => {
-								window.open("/oauth/authorize", "_blank", "noopener,noreferrer");
+								window.open(
+									"/oauth/authorize",
+									"_blank",
+									"noopener,noreferrer",
+								);
 							}}
 							style={{
 								padding: "8px 16px",
@@ -78,7 +82,9 @@ export function SelectionScreen({
 								fontSize: "0.9em",
 							}}
 						>
-							{oauthStatus.expired ? "Re-authenticate with Claude" : "Login with Claude"}
+							{oauthStatus.expired
+								? "Re-authenticate with Claude"
+								: "Login with Claude"}
 						</button>
 					) : (
 						<span
diff --git a/server/src/http/mod.rs b/server/src/http/mod.rs
index 11e167fa..1b4e0995 100644
--- a/server/src/http/mod.rs
+++ b/server/src/http/mod.rs
@@ -64,12 +64,13 @@ pub fn build_routes(
     ctx: AppContext,
     whatsapp_ctx: Option<Arc<WhatsAppWebhookContext>>,
     slack_ctx: Option<Arc<SlackWebhookContext>>,
+    port: u16,
 ) -> impl poem::Endpoint {
     let ctx_arc = std::sync::Arc::new(ctx);
 
     let (api_service, docs_service) = build_openapi_service(ctx_arc.clone());
 
-    let oauth_state = Arc::new(oauth::OAuthState::new(resolve_port()));
+    let oauth_state = Arc::new(oauth::OAuthState::new(port));
 
     let mut route = Route::new()
         .nest("/api", api_service)
@@ -236,6 +237,15 @@ mod tests {
     fn build_routes_constructs_without_panic() {
         let tmp = tempfile::tempdir().unwrap();
         let ctx = context::AppContext::new_test(tmp.path().to_path_buf());
-        let _endpoint = build_routes(ctx, None, None);
+        let _endpoint = build_routes(ctx, None, None, 3001);
+    }
+
+    #[test]
+    fn build_routes_accepts_custom_port() {
+        // Verify build_routes compiles and runs with a non-default port,
+        // ensuring the port parameter flows through to OAuthState.
+        let tmp = tempfile::tempdir().unwrap();
+        let ctx = context::AppContext::new_test(tmp.path().to_path_buf());
+        let _endpoint = build_routes(ctx, None, None, 9999);
     }
 }
diff --git a/server/src/http/oauth.rs b/server/src/http/oauth.rs
index 6d83d52b..8932e1ae 100644
--- a/server/src/http/oauth.rs
+++ b/server/src/http/oauth.rs
@@ -423,6 +423,13 @@ mod tests {
         assert_eq!(state.callback_url(), "http://localhost:3001/callback");
     }
 
+    #[test]
+    fn oauth_state_callback_url_uses_given_port() {
+        // Ensure OAuthState::new uses the port passed to it, not a hardcoded value.
+        let state = OAuthState::new(9876);
+        assert_eq!(state.callback_url(), "http://localhost:9876/callback");
+    }
+
     #[tokio::test]
     async fn html_response_contains_title_and_message() {
         let resp = html_response(StatusCode::OK, "Test Title", "Test message");
diff --git a/server/src/main.rs b/server/src/main.rs
index 4bd05f27..d957c081 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -495,7 +495,7 @@ async fn main() -> Result<(), std::io::Error> {
         matrix_shutdown_tx: Some(Arc::clone(&matrix_shutdown_tx)),
     };
 
-    let app = build_routes(ctx, whatsapp_ctx.clone(), slack_ctx.clone());
+    let app = build_routes(ctx, whatsapp_ctx.clone(), slack_ctx.clone(), port);
 
     // Optional Matrix bot: connect to the homeserver and start listening for
     // messages if `.storkit/bot.toml` is present and enabled.