🐛 [RUM Profiler] Fix profiler stuck when session expires

[thomasbertet]

Motivation

The profiler can get stuck in "stopped" status after periods of inactivity, preventing it from collecting profiling data. Two race conditions were identified:

1. Session expires while profiler is paused: When the tab is hidden, the profiler pauses. If the session expires during this time, stopProfilerInstance returned early without updating the instance state from 'paused' to 'stopped', causing the session renewal check to fail.

2. Session renews while stop is in progress: When SESSION_RENEWED fires while the async stopProfiling was still executing, the check instance.state === 'stopped' failed because the state hadn't been updated yet.

Changes

Fix 1: Handle paused state in stopProfilerInstance

When stopProfilerInstance is called while the profiler is paused, properly transition the state to 'stopped' with the appropriate stateReason.

Fix 2: Sync state changes with fire-and-forget data collection

Instead of using await to wait for profiler to stop (with data being sent), we use a sync stopProfiling :

• stopProfilerInstance and pauseProfilerInstance now update state synchronously
• Data collection (collectProfilerInstance) continues in the background as fire-and-forget
• This eliminates the race condition by design: when SESSION_RENEWED fires, the state is already 'stopped'
• Changed stop() return type from Promise<void> to void

This approach is simpler and more robust than the flag-based solution (commit 2 in this PR) because:

• No flags to track or reset
• State transitions are immediate and predictable
• No risk of forgetting to handle edge cases in flag logic

Unit tests

Since we changed the stop and stopProfilerInstance functions to be sync instead of async, and we don't wait for the profiles to be sent, we needed to update the unit tests to account for:

• stop is updating synchronously the status of the profiler.
• Checking isStopped no longer tells you the latest "Profile" was sent.
  So overall we needed to await the requests to make sure it was properly sent.

Test instructions

1. Start the profiler
2. Switch to another tab (profiler pauses)
3. Wait for session to expire (15 min inactivity) or manually trigger SESSION_EXPIRED
4. Trigger session renewal (or return to tab and interact)
5. Verify profiler restarts

For the race condition test:

1. Fire SESSION_EXPIRED immediately followed by SESSION_RENEWED
2. Verify profiler restarts immediately (state is already 'stopped' when renewal fires)

Both of theses have unit test to cover it.

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	168.31 KiB	168.30 KiB	-12 B	-0.01%	✅
Rum Profiler	4.31 KiB	4.29 KiB	-21 B	-0.48%	✅
Rum Recorder	24.54 KiB	24.54 KiB	0 B	0.00%	✅
Logs	56.25 KiB	56.25 KiB	0 B	0.00%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	125.19 KiB	125.19 KiB	0 B	0.00%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base CPU Time (ms)	Local CPU Time (ms)	𝚫%
RUM - add global context	0.0039	0.0046	+17.95%
RUM - add action	0.0125	0.0161	+28.80%
RUM - add error	0.0122	0.0198	+62.30%
RUM - add timing	0.0025	0.0034	+36.00%
RUM - start view	0.0119	0.0146	+22.69%
RUM - start/stop session replay recording	0.0006	0.001	+66.67%
Logs - log message	0.0137	0.0175	+27.74%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	26.41 KiB	27.75 KiB	+1.34 KiB
RUM - add action	48.86 KiB	49.78 KiB	+945 B
RUM - add timing	28.07 KiB	27.53 KiB	-549 B
RUM - add error	54.07 KiB	54.48 KiB	+423 B
RUM - start/stop session replay recording	26.78 KiB	26.34 KiB	-457 B
RUM - start view	452.59 KiB	455.20 KiB	+2.61 KiB
Logs - log message	45.03 KiB	45.56 KiB	+535 B

🔗 RealWorld

[thomasbertet]

/to-staging

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-02-09 12:53:45 UTC ℹ️ Start processing command /to-staging

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2026-02-09 12:53:51 UTC ℹ️ Branch Integration: starting soon, merge expected in approximately 0s (p90)

Commit 7e19e6260a will soon be integrated into staging-07.

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2026-02-09 13:07:42 UTC ℹ️ Branch Integration: this commit was successfully integrated

Commit 7e19e6260a has been merged into staging-07 in merge commit b6bcfd462c.

Check out the triggered pipeline on Gitlab 🦊

If you need to revert this integration, you can use the following command: /code revert-integration -b staging-07