feat(remix): Server Timing Headers Trace Propagation PoC by onurtemizkan · Pull Request #18653 · getsentry/sentry-javascript

onurtemizkan · 2026-01-01T13:33:50Z

Adds automatic trace propagation from server to client via the Server-Timing HTTP header for Remix applications.

This provides an alternative to meta tag injection for linking server and client traces. The server automatically injects sentry-trace and baggage into the Server-Timing response header, and the client SDK reads it via the Performance API during pageload.

Server-side:

generateSentryServerTimingHeader() - generates the header value
addSentryServerTimingHeader(response) - adds header to a Response
Automatic injection in document request handler
Cloudflare apps require manual response wrapping in entry.server.tsx using addSentryServerTimingHeader

Client-side:

Reads Server-Timing from navigation timing entries
Falls back to meta tags if Server-Timing unavailable
Async retry mechanism for slow header processing

Works on both Node.js and Cloudflare Workers environments.

Closes #18696 (added automatically)

Copilot

Pull request overview

This PR implements a proof-of-concept for propagating Sentry trace context from server to client using the Server-Timing HTTP header and the browser Performance API. This provides an alternative to meta tag-based trace propagation, particularly useful for streaming SSR responses and edge runtimes.

Key changes:

Added utilities for generating and injecting Server-Timing headers with Sentry trace data
Implemented client-side parsing of Server-Timing headers via the Performance API
Updated server instrumentation to capture and propagate trace context via Server-Timing headers
Added comprehensive E2E test coverage for both Node.js and Cloudflare environments

Reviewed changes

Copilot reviewed 25 out of 27 changed files in this pull request and generated 16 comments.

Show a summary per file

File	Description
`packages/remix/src/server/serverTimingTracePropagation.ts`	New utility module for generating Server-Timing headers with trace context
`packages/remix/src/client/serverTimingTracePropagation.ts`	New client-side utilities for parsing trace data from Server-Timing headers
`packages/remix/src/server/instrumentServer.ts`	Updated server instrumentation to inject Server-Timing headers and refactored trace propagation logic
`packages/remix/src/client/performance.tsx`	Updated pageload span initialization to use Server-Timing trace propagation
`packages/remix/src/server/index.ts`	Exported new Server-Timing utilities for public API
`packages/remix/src/client/index.ts`	Exported new client-side Server-Timing utilities
`packages/remix/src/cloudflare/index.ts`	Exported Server-Timing utilities for Cloudflare runtime
`dev-packages/e2e-tests/test-applications/remix-server-timing/*`	New E2E test application validating Server-Timing trace propagation
`dev-packages/e2e-tests/test-applications/remix-hydrogen/*`	Updated Hydrogen test app to demonstrate Cloudflare support

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packages/remix/src/server/serverTimingTracePropagation.ts

packages/remix/src/server/instrumentServer.ts

packages/remix/src/client/serverTimingTracePropagation.ts

packages/remix/src/server/instrumentServer.ts

...2e-tests/test-applications/remix-server-timing/tests/server-timing-trace-propagation.test.ts

packages/remix/src/server/serverTimingTracePropagation.ts

packages/remix/src/server/instrumentServer.ts

packages/remix/src/client/performance.tsx

github-actions · 2026-01-07T16:41:56Z

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,890	-	8,520	+4%
GET With Sentry	1,700	19%	1,591	+7%
GET With Sentry (error only)	6,035	68%	5,784	+4%
POST Baseline	1,221	-	1,106	+10%
POST With Sentry	595	49%	529	+12%
POST With Sentry (error only)	977	80%	996	-2%
MYSQL Baseline	3,252	-	3,197	+2%
MYSQL With Sentry	493	15%	382	+29%
MYSQL With Sentry (error only)	2,666	82%	2,570	+4%

View base workflow run

packages/remix/src/server/instrumentServer.ts

packages/remix/src/server/serverTimingTracePropagation.ts

...2e-tests/test-applications/remix-server-timing/tests/server-timing-trace-propagation.test.ts

Lms24

@onurtemizkan sorry for the delay on this! I merged in #18673 to get support for server-timing trace continuation on the client side in the general browser SDK. Could you update the PR to use this instead of the remix-specific approach? The server side looks fine to me, though I'll give this a more proper look once the PR is updated.

…eader

github-actions · 2026-02-02T14:07:38Z

Codecov Results 📊

Generated by Codecov Action

packages/remix/src/server/instrumentServer.ts

… browser SDK

packages/remix/src/server/instrumentServer.ts

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dev-packages/e2e-tests/test-applications/remix-hydrogen/app/entry.server.tsx

onurtemizkan requested a review from Copilot January 1, 2026 13:33

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onurtemizkan force-pushed the onur/remix-server-timing-headers branch 4 times, most recently from 1f07bc8 to 67ec468 Compare January 2, 2026 15:42

onurtemizkan marked this pull request as ready for review January 5, 2026 12:55

onurtemizkan force-pushed the onur/remix-server-timing-headers branch from 3e06c9b to 48e03dd Compare January 5, 2026 12:55

github-actions bot mentioned this pull request Jan 5, 2026

feat(remix): Server Timing Headers Trace Propagation PoC #18696

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onurtemizkan force-pushed the onur/remix-server-timing-headers branch from d882ca3 to 982c420 Compare January 5, 2026 15:31

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onurtemizkan force-pushed the onur/remix-server-timing-headers branch from 1b1481d to 8a43e90 Compare January 8, 2026 09:25

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onurtemizkan force-pushed the onur/remix-server-timing-headers branch from fa61b3c to 7518ec6 Compare January 23, 2026 14:35

Lms24 reviewed Feb 2, 2026

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onurtemizkan added 11 commits February 2, 2026 13:59

feat(remix): Server Timing Headers Trace Propagation PoC

0403684

Reduce duplication

cb0d98f

Enhance trace context handling with status management

04e1662

Fix memory leak and race condition

ccbb500

Improve dynamic sampling context and baggage consistency

17322a6

Enhance e2e tests

e17f237

Add dynamic sampling context handling to server timing tests

6ed2bb0

Prioritize Server-Timing headers over meta tags

2d76278

Update integration tests

aa22331

Use quoted-string escaping instead of URL-encoding

b455ccf

Fix race condition and improve navigation state management

5deb1cf

onurtemizkan added 6 commits February 2, 2026 13:59

Update E2E tests for Server-Timing header trace propagation

2324526

Fix race condition with shared variables

8f8a88e

Simplify Server-Timing header baggage generation using spanToBaggageH…

3dd1901

…eader

Make Server-Timing E2E tests fail when headers are missing

7832807

Update Remix dependencies to 2.17.4 to fix security vulnerabilities

54bbbcf

Inject Server-Timing header on redirect responses

1f7c85c

onurtemizkan force-pushed the onur/remix-server-timing-headers branch from 7518ec6 to 1f7c85c Compare February 2, 2026 13:59

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packages/remix/src/server/instrumentServer.ts Show resolved Hide resolved

sentry bot reviewed Feb 2, 2026

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packages/remix/src/server/instrumentServer.ts Show resolved Hide resolved

Remove custom client-side Server-Timing trace propagation in favor of…

3f48804

… browser SDK

sentry bot reviewed Feb 3, 2026

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packages/remix/src/server/instrumentServer.ts Outdated Show resolved Hide resolved

onurtemizkan added 2 commits February 3, 2026 21:17

Always call continueTrace

ebf2eca

Merge branch 'develop' into onur/remix-server-timing-headers

488415f

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dev-packages/e2e-tests/test-applications/remix-hydrogen/app/entry.server.tsx Show resolved Hide resolved

Skip Server-Timing header injection when sentry-trace already exists

25fa718

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onurtemizkan commented Jan 1, 2026 •

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