diff --git a/dev-packages/e2e-tests/test-applications/hono-4/src/routes.ts b/dev-packages/e2e-tests/test-applications/hono-4/src/routes.ts
index 1a3c74630648..a712ddcdfc43 100644
--- a/dev-packages/e2e-tests/test-applications/hono-4/src/routes.ts
+++ b/dev-packages/e2e-tests/test-applications/hono-4/src/routes.ts
@@ -1,4 +1,4 @@
-import type { Hono } from 'hono';
+import { type Hono as HonoType, Hono } from 'hono';
 import { HTTPException } from 'hono/http-exception';
 import { failingMiddleware, middlewareA, middlewareB } from './middleware';
 import { errorRoutes } from './route-groups/test-errors';
@@ -6,7 +6,7 @@ import { middlewareRoutes, subAppWithInlineMiddleware, subAppWithMiddleware } fr
 import { multiFetchRoutes } from './route-groups/test-multi-fetch';
 import { routePatterns } from './route-groups/test-route-patterns';
 
-export function addRoutes(app: Hono<{ Bindings?: { E2E_TEST_DSN: string } }>): void {
+export function addRoutes(app: HonoType<{ Bindings?: { E2E_TEST_DSN: string } }>): void {
   app.get('/', c => {
     return c.text('Hello Hono!');
   });
@@ -52,4 +52,27 @@ export function addRoutes(app: Hono<{ Bindings?: { E2E_TEST_DSN: string } }>): v
 
   // Multi-fetch routes: storefront sub-app calls inventoryApp via .request()
   app.route('/test-multi-fetch', multiFetchRoutes);
+
+  // .basePath() with sub-app mounting via .route()
+  const apiSubApp = new Hono();
+  apiSubApp.use(async function apiAuth(_c, next) {
+    await next();
+  });
+  apiSubApp.get('/users', c => c.json({ users: [{ id: 1, name: 'Alice' }] }));
+  apiSubApp.get('/users/:userId', c => c.json({ userId: c.req.param('userId') }));
+
+  app.basePath('/test-basepath').route('/v1', apiSubApp);
+
+  // .use() on the cloned instance returned by .basePath() — the clone has its own
+  // .use class field, so this tests whether middleware instrumentation propagates.
+  app
+    .basePath('/test-basepath-mw')
+    .use(async function basepathMiddleware(_c, next) {
+      await new Promise(resolve => setTimeout(resolve, 50));
+      await next();
+    })
+    .get('/hello', c => c.json({ greeting: 'world' }));
+
+  // .get() registered on the root app after .basePath()/.route() chains
+  app.get('/test-late-get', c => c.json({ registered: 'after-chains' }));
 }
diff --git a/dev-packages/e2e-tests/test-applications/hono-4/tests/basepath-and-late-routes.test.ts b/dev-packages/e2e-tests/test-applications/hono-4/tests/basepath-and-late-routes.test.ts
new file mode 100644
index 000000000000..03a97816c9c5
--- /dev/null
+++ b/dev-packages/e2e-tests/test-applications/hono-4/tests/basepath-and-late-routes.test.ts
@@ -0,0 +1,80 @@
+import { expect, test } from '@playwright/test';
+import { waitForTransaction } from '@sentry-internal/test-utils';
+import { APP_NAME } from './constants';
+
+test.describe('basePath with sub-app routes', () => {
+  test('traces GET on a sub-app mounted via .basePath().route()', async ({ baseURL }) => {
+    const transactionPromise = waitForTransaction(APP_NAME, event => {
+      return event.contexts?.trace?.op === 'http.server' && event.transaction === 'GET /test-basepath/v1/users';
+    });
+
+    const response = await fetch(`${baseURL}/test-basepath/v1/users`);
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+    expect(body).toEqual({ users: [{ id: 1, name: 'Alice' }] });
+
+    const transaction = await transactionPromise;
+    expect(transaction.transaction).toBe('GET /test-basepath/v1/users');
+    expect(transaction.contexts?.trace?.op).toBe('http.server');
+  });
+
+  test('traces parameterized route under .basePath().route()', async ({ baseURL }) => {
+    const transactionPromise = waitForTransaction(APP_NAME, event => {
+      return event.contexts?.trace?.op === 'http.server' && event.transaction === 'GET /test-basepath/v1/users/:userId';
+    });
+
+    const response = await fetch(`${baseURL}/test-basepath/v1/users/42`);
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+    expect(body).toEqual({ userId: '42' });
+
+    const transaction = await transactionPromise;
+    expect(transaction.transaction).toBe('GET /test-basepath/v1/users/:userId');
+    expect(transaction.contexts?.trace?.op).toBe('http.server');
+  });
+});
+
+// TODO: this test is currently skipped because we do not yet support middleware registered on new instances (e.g. here via .basePath(..).use(...)).
+test.skip('.basePath() middleware instrumentation', () => {
+  test('creates middleware span for .use() on .basePath() clone', async ({ baseURL }) => {
+    const transactionPromise = waitForTransaction(APP_NAME, event => {
+      return event.contexts?.trace?.op === 'http.server' && event.transaction === 'GET /test-basepath-mw/hello';
+    });
+
+    const response = await fetch(`${baseURL}/test-basepath-mw/hello`);
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+    expect(body).toEqual({ greeting: 'world' });
+
+    const transaction = await transactionPromise;
+    expect(transaction.transaction).toBe('GET /test-basepath-mw/hello');
+
+    const spans = transaction.spans || [];
+    const middlewareSpan = spans.find(
+      (span: { description?: string; op?: string }) =>
+        span.op === 'middleware.hono' && span.description === 'basepathMiddleware',
+    );
+
+    expect(middlewareSpan).toBeDefined();
+    expect(middlewareSpan?.origin).toBe('auto.middleware.hono');
+  });
+});
+
+test('traces .get() route registered after .basePath()/.route() chains', async ({ baseURL }) => {
+  const transactionPromise = waitForTransaction(APP_NAME, event => {
+    return event.contexts?.trace?.op === 'http.server' && event.transaction === 'GET /test-late-get';
+  });
+
+  const response = await fetch(`${baseURL}/test-late-get`);
+  expect(response.status).toBe(200);
+
+  const body = await response.json();
+  expect(body).toEqual({ registered: 'after-chains' });
+
+  const transaction = await transactionPromise;
+  expect(transaction.transaction).toBe('GET /test-late-get');
+  expect(transaction.contexts?.trace?.op).toBe('http.server');
+});
diff --git a/packages/hono/src/bun/middleware.ts b/packages/hono/src/bun/middleware.ts
index 651cb4649378..739fb2c33ee9 100644
--- a/packages/hono/src/bun/middleware.ts
+++ b/packages/hono/src/bun/middleware.ts
@@ -1,6 +1,6 @@
 import { type BaseTransportOptions, debug, type Options } from '@sentry/core';
 import { init } from './sdk';
-import type { Hono, MiddlewareHandler } from 'hono';
+import type { Env, Hono, MiddlewareHandler } from 'hono';
 import { requestHandler, responseHandler } from '../shared/middlewareHandlers';
 import { applyPatches } from '../shared/applyPatches';
 
@@ -9,7 +9,7 @@ export interface HonoBunOptions extends Options<BaseTransportOptions> {}
 /**
  * Sentry middleware for Hono running in a Bun runtime environment.
  */
-export const sentry = (app: Hono, options: HonoBunOptions): MiddlewareHandler => {
+export const sentry = <E extends Env>(app: Hono<E>, options: HonoBunOptions): MiddlewareHandler => {
   const isDebug = options.debug;
 
   isDebug && debug.log('Initialized Sentry Hono middleware (Bun)');
diff --git a/packages/hono/src/node/middleware.ts b/packages/hono/src/node/middleware.ts
index bcfd65d573c1..bd12d7ce82f8 100644
--- a/packages/hono/src/node/middleware.ts
+++ b/packages/hono/src/node/middleware.ts
@@ -1,5 +1,5 @@
 import { type BaseTransportOptions, debug, type Options, getClient } from '@sentry/core';
-import type { Hono, MiddlewareHandler } from 'hono';
+import type { Env, Hono, MiddlewareHandler } from 'hono';
 import { requestHandler, responseHandler } from '../shared/middlewareHandlers';
 import { applyPatches } from '../shared/applyPatches';
 
@@ -13,7 +13,7 @@ export interface HonoNodeOptions extends Options<BaseTransportOptions> {}
  *
  * **Note:** You must initialize Sentry separately before using this middleware. Typically, this is done by calling `Sentry.init()` in an `instrument.ts` file and loading it via the Node `--import` flag.
  */
-export const sentry = (app: Hono): MiddlewareHandler => {
+export const sentry = <E extends Env>(app: Hono<E>): MiddlewareHandler => {
   const sentryClient = getClient();
   if (sentryClient === undefined) {
     debug.warn(
diff --git a/packages/hono/test/bun/middleware.test.ts b/packages/hono/test/bun/middleware.test.ts
index f3fc82d3696f..8e3135e52afb 100644
--- a/packages/hono/test/bun/middleware.test.ts
+++ b/packages/hono/test/bun/middleware.test.ts
@@ -29,6 +29,16 @@ describe('Hono Bun Middleware', () => {
   });
 
   describe('sentry middleware', () => {
+    it('accepts Hono with custom env types without requiring a cast', () => {
+      type CustomEnv = { Bindings: { DATABASE_URL: string }; Variables: { userId: string } };
+      const app = new Hono<CustomEnv>();
+
+      const middleware = sentry(app, { dsn: 'https://public@dsn.ingest.sentry.io/1337' });
+
+      expect(typeof middleware).toBe('function');
+      expect(middleware).toHaveLength(2);
+    });
+
     it('calls applySdkMetadata with "hono" and "bun"', () => {
       const app = new Hono();
       const options = {
diff --git a/packages/hono/test/node/middleware.test.ts b/packages/hono/test/node/middleware.test.ts
index 745e924e7804..443d1b48ea3b 100644
--- a/packages/hono/test/node/middleware.test.ts
+++ b/packages/hono/test/node/middleware.test.ts
@@ -36,6 +36,16 @@ describe('Hono Node Middleware', () => {
       expect(initNodeMock).not.toHaveBeenCalled();
     });
 
+    it('accepts Hono with custom env types without requiring a cast', () => {
+      type CustomEnv = { Bindings: { DATABASE_URL: string }; Variables: { userId: string } };
+      const app = new Hono<CustomEnv>();
+
+      const middleware = sentry(app);
+
+      expect(typeof middleware).toBe('function');
+      expect(middleware).toHaveLength(2);
+    });
+
     it('returns a middleware handler function', () => {
       const app = new Hono();
       const middleware = sentry(app);
diff --git a/packages/hono/test/shared/applyPatches.test.ts b/packages/hono/test/shared/applyPatches.test.ts
index 7a029367250f..51a68859e614 100644
--- a/packages/hono/test/shared/applyPatches.test.ts
+++ b/packages/hono/test/shared/applyPatches.test.ts
@@ -494,6 +494,79 @@ describe('applyPatches', () => {
     });
   });
 
+  describe('main-app .get() routes after applyPatches', () => {
+    it('responds correctly from .get() routes registered after applyPatches', async () => {
+      const app = new Hono();
+      applyPatches(app);
+
+      app.get('/docs', c => c.text('API Documentation'));
+      app.get('/openapi.json', c => c.json({ openapi: '3.0.0', paths: {} }));
+
+      const docsRes = await app.fetch(new Request('http://localhost/docs'));
+      expect(docsRes.status).toBe(200);
+      expect(await docsRes.text()).toBe('API Documentation');
+
+      const specRes = await app.fetch(new Request('http://localhost/openapi.json'));
+      expect(specRes.status).toBe(200);
+      expect(await specRes.json()).toEqual({ openapi: '3.0.0', paths: {} });
+    });
+
+    it('preserves .get() routes registered after .basePath() and .route() chains', async () => {
+      const app = new Hono();
+      applyPatches(app);
+
+      const subApp = new Hono();
+      subApp.use(async function authMiddleware(_c: unknown, next: () => Promise<void>) {
+        await next();
+      });
+      subApp.get('/resource', () => new Response('resource'));
+
+      app.basePath('/api').route('/v1', subApp);
+
+      app.get('/docs', c => c.text('Docs page'));
+      app.get('/openapi.json', c => c.json({ openapi: '3.0.0' }));
+
+      const resourceRes = await app.fetch(new Request('http://localhost/api/v1/resource'));
+      expect(resourceRes.status).toBe(200);
+      expect(await resourceRes.text()).toBe('resource');
+
+      const docsRes = await app.fetch(new Request('http://localhost/docs'));
+      expect(docsRes.status).toBe(200);
+      expect(await docsRes.text()).toBe('Docs page');
+
+      const specRes = await app.fetch(new Request('http://localhost/openapi.json'));
+      expect(specRes.status).toBe(200);
+      expect(await specRes.json()).toEqual({ openapi: '3.0.0' });
+    });
+
+    it('does not corrupt app.routes for third-party route introspection', () => {
+      const app = new Hono();
+      applyPatches(app);
+
+      app.use(async function globalMw(_c: unknown, next: () => Promise<void>) {
+        await next();
+      });
+      app.get('/users', () => new Response('users'));
+      app.post('/users', () => new Response('created'));
+
+      const subApp = new Hono();
+      subApp.get('/items', () => new Response('items'));
+      app.route('/api', subApp);
+
+      const routes = app.routes as Array<{ method: string; path: string; handler: Function }>;
+      const getPaths = routes.filter(r => r.method === 'GET').map(r => r.path);
+      const postPaths = routes.filter(r => r.method === 'POST').map(r => r.path);
+
+      expect(getPaths).toContain('/users');
+      expect(getPaths).toContain('/api/items');
+      expect(postPaths).toContain('/users');
+
+      for (const route of routes) {
+        expect(typeof route.handler).toBe('function');
+      }
+    });
+  });
+
   describe('patchAppRequest integration', () => {
     it('patches .request() on sub-apps when they are mounted via route()', async () => {
       const app = new Hono();