remix: Trailing-underscore route segments leak into transaction names

[suhailopensource]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/remix

SDK Version

10.73.0

Framework Version

Remix 2.17.4

Link to Sentry event

No response

Reproduction Example/SDK Setup

Any Remix v2 app using the trailing-underscore convention reproduces this. Given app/routes/concerts_.mine.tsx, requesting /concerts/mine produces a server transaction named /concerts_/mine.

A unit test in this repo reproduces it without a server. Save as packages/remix/test/utils/trailing-underscore.test.ts and run cd packages/remix && yarn test:unit --run test/utils/trailing-underscore.test.ts:

import type { AgnosticRouteObject } from '@remix-run/router';
import { describe, expect, it } from 'vitest';
import { convertRemixRouteIdToPath, getTransactionName } from '../../src/utils/utils';

describe('trailing-underscore routes', () => {
  // `path` is what Remix itself computes for these route files.
  const routes: AgnosticRouteObject[] = [
    { id: 'routes/concerts_.mine', path: '/concerts/mine' },
    { id: 'routes/app_.projects.$id.roadmap', path: '/app/projects/:id/roadmap' },
    { id: 'routes/concerts.$city', path: '/concerts/:city' },
  ];

  it('convertRemixRouteIdToPath strips a trailing underscore', () => {
    expect(convertRemixRouteIdToPath('routes/concerts_.mine')).toBe('/concerts/mine');
    expect(convertRemixRouteIdToPath('routes/app_.projects.$id.roadmap')).toBe('/app/projects/:id/roadmap');
    // controls, already correct today
    expect(convertRemixRouteIdToPath('routes/concerts.$city')).toBe('/concerts/:city');
    expect(convertRemixRouteIdToPath('routes/_layout.dashboard')).toBe('/dashboard');
  });

  it('getTransactionName names the server transaction correctly', () => {
    expect(getTransactionName(routes, new URL('http://localhost/concerts/mine'))).toEqual(['/concerts/mine', 'route']);
    expect(getTransactionName(routes, new URL('http://localhost/app/projects/42/roadmap'))).toEqual([
      '/app/projects/:id/roadmap',
      'route',
    ]);
  });
});

Steps to Reproduce

Any Remix v2 app using the trailing-underscore convention reproduces this. Given app/routes/concerts_.mine.tsx, requesting /concerts/mine produces a server transaction named /concerts_/mine.

A unit test in this repo reproduces it without a server. Save as packages/remix/test/utils/trailing-underscore.test.ts and run cd packages/remix && yarn test:unit --run test/utils/trailing-underscore.test.ts:

import type { AgnosticRouteObject } from '@remix-run/router';
import { describe, expect, it } from 'vitest';
import { convertRemixRouteIdToPath, getTransactionName } from '../../src/utils/utils';

describe('trailing-underscore routes', () => {
  // `path` is what Remix itself computes for these route files.
  const routes: AgnosticRouteObject[] = [
    { id: 'routes/concerts_.mine', path: '/concerts/mine' },
    { id: 'routes/app_.projects.$id.roadmap', path: '/app/projects/:id/roadmap' },
    { id: 'routes/concerts.$city', path: '/concerts/:city' },
  ];

  it('convertRemixRouteIdToPath strips a trailing underscore', () => {
    expect(convertRemixRouteIdToPath('routes/concerts_.mine')).toBe('/concerts/mine');
    expect(convertRemixRouteIdToPath('routes/app_.projects.$id.roadmap')).toBe('/app/projects/:id/roadmap');
    // controls, already correct today
    expect(convertRemixRouteIdToPath('routes/concerts.$city')).toBe('/concerts/:city');
    expect(convertRemixRouteIdToPath('routes/_layout.dashboard')).toBe('/dashboard');
  });

  it('getTransactionName names the server transaction correctly', () => {
    expect(getTransactionName(routes, new URL('http://localhost/concerts/mine'))).toEqual(['/concerts/mine', 'route']);
    expect(getTransactionName(routes, new URL('http://localhost/app/projects/42/roadmap'))).toEqual([
      '/app/projects/:id/roadmap',
      'route',
    ]);
  });
});

Expected Result

Per the file route conventions, a trailing underscore opts a route out of layout nesting without appearing in the URL:

URL	Matched Route
/concerts/mine	app/routes/concerts_.mine.tsx

The trailing_ underscore creates a path segment, but it does not create layout nesting.

So routes/concerts_.mine should yield /concerts/mine, and the transaction should be named /concerts/mine.

Actual Result

The underscore is kept as part of the path segment:

route id	expected	actual
routes/concerts_.mine	/concerts/mine	/concerts_/mine
routes/app_.projects.$id.roadmap	/app/projects/:id/roadmap	/app_/projects/:id/roadmap
routes/concerts.$city	/concerts/:city	/concerts/:city (control, correct)
routes/_layout.dashboard	/dashboard	/dashboard (control, correct)

Through the real consumer, getTransactionName returns:

/concerts/mine          -> ["/concerts_/mine", "route"]
/app/projects/42/roadmap -> ["/app_/projects/:id/roadmap", "route"]

Both tests above fail. Note the source is route, not url — the name is reported as a high-confidence parameterized route while being wrong.

Additional Context

Where it bites

getTransactionName (packages/remix/src/utils/utils.ts) derives the name from match.route.id and runs it through convertRemixRouteIdToPath, ignoring match.route.path — which Remix has already resolved correctly. It is used for server transaction naming at packages/remix/src/server/instrumentServer.ts:182 and :362.

Because the returned source is route, affected transactions are grouped under a route name that does not correspond to any real URL, so they never group with the same route reported from elsewhere.

The same segment loop is duplicated in packages/remix/src/config/createRemixRouteManifest.ts, so the build-time route manifest carries the same wrong path.

Suggested fix

Strip a trailing _ from each non-dynamic segment, mirroring the adjacent leading-underscore branch — roughly 2 lines in each of the two loops. Existing coverage in packages/remix/test/config/routeConversion.test.ts and packages/remix/test/utils/utils.test.ts covers leading _ and _index but has no trailing-underscore case. Happy to open a PR with the test above.

Affected versions

Present in 10.73.0 (both packages/remix/src/utils/utils.ts and packages/remix/src/config/createRemixRouteManifest.ts) and on current develop.

Priority

No response

[linear-code]

JS-3598

[suhailopensource]

I would be interested in raising a PR for this after Triage.