♻️ Rewrite session storage with CookieAccessor and native Web Locks

[thomas-lebeau]

Motivation

The session management layer had accumulated complexity: custom cookie locking logic, duplicated session managers across packages (rum, logs), tightly coupled session store strategies, and synchronous cookie access patterns. This PR rewrites the session storage stack to be simpler, more robust, and aligned with v7 goals.

Changes

• Replace the custom cookie lock mechanism with the native Web Locks API for cross-tab coordination
• Introduce a CookieAccessor abstraction layer that decouples session logic from raw cookie I/O
• Make SessionStoreStrategy fully async with event-driven change detection instead of polling
• Move cookieObservable from rum-core to core for proper shared ownership
• Consolidate rumSessionManager and logsSessionManager into a single core SessionManager
• Merge TrackedSession into SessionContext, extract SessionReplayState and computeSessionReplayState
• Handle bridge environments in computeSessionReplayState
• Extract recording condition helpers in postStartStrategy
• Make all sampling decisions deterministic
• Consolidate session manager test mocks and specs into core and rum-core

Test instructions

• yarn test:unit — all unit tests should pass
• yarn test:e2e — session store and tracking consent scenarios updated

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

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	171.87 KiB	172.20 KiB	+332 B	+0.19%	✅
Rum Profiler	4.67 KiB	4.67 KiB	0 B	0.00%	✅
Rum Recorder	24.88 KiB	25.10 KiB	+227 B	+0.89%	✅
Logs	56.61 KiB	57.41 KiB	+825 B	+1.42%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	127.50 KiB	127.94 KiB	+460 B	+0.35%	✅
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	0.0055	0.0041	-25.45%
RUM - add action	0.0198	0.0174	-12.12%
RUM - add error	0.019	0.0161	-15.26%
RUM - add timing	0.0051	0.003	-41.18%
RUM - start view	0.0221	0.0161	-27.15%
RUM - start/stop session replay recording	0.0013	0.0008	-38.46%
Logs - log message	0.0268	0.0184	-31.34%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	27.38 KiB	26.34 KiB	-1.04 KiB
RUM - add action	115.40 KiB	303.05 KiB	+187.66 KiB
RUM - add timing	26.00 KiB	47.83 KiB	+21.83 KiB
RUM - add error	119.37 KiB	296.13 KiB	+176.76 KiB
RUM - start/stop session replay recording	26.10 KiB	32.10 KiB	+6.00 KiB
RUM - start view	503.45 KiB	644.94 KiB	+141.50 KiB
Logs - log message	46.31 KiB	230.33 KiB	+184.02 KiB

🔗 RealWorld

[datadog-datadog-prod-us1]

⚠️ Tests

✨ Fix all issues with BitsAI or with Cursor

⚠️ Warnings

🧪 3147 Tests failed

AbstractLifeCycle does nothing when notifying without subscribers from Chrome 63.0.3239.84 (Windows 10) (Datadog) (Fix with Cursor)

ReferenceError: globalThis is not defined
    at UserContext.afterEach (webpack:///packages/core/src/domain/session/storeStrategies/sessionInCookie.spec.ts:25:5 <- /tmp/_karma_webpack_358081/commons.js:45227:9)
    at <Jasmine>

AbstractLifeCycle does not notify unsubscribed subscribers from Chrome 63.0.3239.84 (Windows 10) (Datadog) (Fix with Cursor)

ReferenceError: globalThis is not defined
    at UserContext.afterEach (webpack:///packages/core/src/domain/session/storeStrategies/sessionInCookie.spec.ts:25:5 <- /tmp/_karma_webpack_358081/commons.js:45227:9)
    at <Jasmine>

AbstractLifeCycle notifies subscribers from Chrome 63.0.3239.84 (Windows 10) (Datadog) (Fix with Cursor)

ReferenceError: globalThis is not defined
    at UserContext.afterEach (webpack:///packages/core/src/domain/session/storeStrategies/sessionInCookie.spec.ts:25:5 <- /tmp/_karma_webpack_358081/commons.js:45227:9)
    at <Jasmine>

View all

ℹ️ Info

❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 66.42%
• Overall Coverage: 76.69% (-0.21%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 7fcd324 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}