✨ Report the websocket_closing vital

[bdibon]

Motivation

The browser fires no event when the closing handshake starts, so without instrumenting close() the backend cannot tell a connection the application closed from one the server or the network ended.

Part of the WebSocket vitals stack. Every PR targets the previous one; the first one targets the boris.dibon/websocket-vitals integration branch, which is merged into main in one go once the whole stack is approved. #5055 stays open as the reference implementation: the tip of this stack is content-identical to it, rebased on the current main.

1. 🔧 Pin rum-events-format and add WebSocket test utilities #5092 🔧 Pin rum-events-format and add WebSocket test utilities
2. ✨ Collect connecting, open and closed WebSocket vitals #5093 ✨ Collect connecting, open and closed WebSocket vitals
3. ✨ Report the websocket_closing vital #5094 ✨ Report the websocket_closing vital 👈 this PR
4. ✨ Pulse open WebSocket vitals on a shared heartbeat #5095 ✨ Pulse open WebSocket vitals on a shared heartbeat
5. ✨ Report WebSocket silences and send queue depth, and protect WebSocket vitals in beforeSend #5096 ✨ Report WebSocket silences and send queue depth, and protect WebSocket vitals in beforeSend
6. ✨ End WebSocket tracking when the page is discarded #5097 ✨ End WebSocket tracking when the page is discarded

Changes

Commit by commit:

• ✨ Notify a closing context when the application calls close(): close() is instrumented; a call on a socket already closing or closed is a no-op and notifies nothing.
• 🐛 Do not count a WebSocket payload the socket discarded: send() outside OPEN never reaches the wire (it throws before the handshake, and is silently dropped once closing or closed), so it is no longer counted as an outbound message.
• ✨ Report the websocket_closing vital: carries closing_date and close_initiator: "client", takes no snapshot version, and the closed vital that follows keeps the closing date. A close() during the handshake reports the closing phase without an open date.
• ✅ Cover the closing phase end to end: closing before open, and close() called twice.

Test instructions

• Unit: yarn test:unit --spec "packages/browser-rum-core/src/domain/webSocket/*.spec.ts" --spec packages/browser-rum-core/src/browser/webSocketObservable.spec.ts
• E2E: yarn test:e2e -g "rum websockets"

Note

check-staging-merge is expected to fail: staging-40 already contains the earlier merge of #5055, which touches the same files. It clears at the next staging bump; the other checks should be green.

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

[datadog-prod-us1-5]

✅ All CI checks and tests passed.

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 85.71%
• Overall Coverage: 77.35% (+0.02%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 5ef2033 | Docs | View more details | Give us feedback!}

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum Salesforce	N/A	186.13 KiB	N/A	N/A	N/A
Rum	185.57 KiB	186.10 KiB	+546 B	+0.29%	✅
Rum-salesforce Profiler	N/A	8.35 KiB	N/A	N/A	N/A
Rum Profiler	8.35 KiB	8.35 KiB	0 B	0.00%	✅
Rum-salesforce Recorder	N/A	31.94 KiB	N/A	N/A	N/A
Rum Recorder	31.94 KiB	31.94 KiB	0 B	0.00%	✅
Logs	59.34 KiB	59.34 KiB	0 B	0.00%	✅
Rum Slim	143.59 KiB	144.11 KiB	+531 B	+0.36%	✅
Worker	22.96 KiB	22.96 KiB	0 B	0.00%	✅
Rum Shopify	N/A	216.52 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.35 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	4.77 KiB	N/A	N/A	N/A

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-13T12:54:17.428629Z	5ef2033	New commits

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[bcaudan]

LGTM but could be impacted by #5093 (comment)

[chatgpt-codex-connector]

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Reviewed commit: 5ef20335e3

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[chatgpt-codex-connector]

Capture the closing clock before invoking close

issue: When WebSocket.prototype.close was already wrapped by customer code or another SDK that performs synchronous work, this samples the clock only after that wrapper returns. The resulting closing_date and view attribution can therefore be delayed—or assigned to a view started inside the wrapper—instead of representing when the application called close(). Capture the clock in the pre-call callback and use it from onPostCall, which still avoids reporting calls that throw.

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