♻️ Make session manager injectable and isolate for v7 rewrite

[thomas-lebeau]

Motivation

Prepare the session manager layer for a from-scratch rewrite in v7. The existing session manager internals (cookies, storage, core session store) are tightly coupled to boot-level tests, making it hard to replace the implementation without breaking unrelated tests.

This PR decouples all non-session-manager code from session internals, so the session manager can be rewritten in isolation.

Changes

1. Injectable session manager factory

Move the stub-vs-real session manager branching from createPreStartStrategy to the caller (rumPublicApi / logsPublicApi) via a factory parameter:

graph LR
    A[rumPublicApi / logsPublicApi] -->|ternary: bridge ? stub : real| B[factory]
    B -->|passed as param| C[createPreStartStrategy]
    C -->|calls factory| D[session manager instance]

Loading

• BREAKING CHANGE: When no storage strategy is available (cookies/localStorage unavailable), neither SDK will send data. Previously Logs would still start without storage — now it requires explicit sessionPersistence: 'memory' to work without storage. In worker environments, Logs uses the real session manager with memory persistence (we can revisit that when we star using CookieStore as this seems supported in service workers). RUM is explicitly blocked with a warning.
• createPreStartStrategy receives one factory, just calls it — no branching logic
• Callers use: canUseEventBridge() ? stub : real

2. Prove isolation via gut-then-restore

To verify that all non-session-manager tests use mocks (not real implementations), the session manager bodies were temporarily gutted and their unit tests skipped (xdescribe). All 3071 remaining tests passed with zero failures, proving the isolation is complete. The implementations and tests were then fully restored.

3. Mock infrastructure

• Boot tests (preStartRum.spec, preStartLogs.spec) inject mock factories — no more stopSessionManager() cleanup or cookie manipulation
• Public API tests (rumPublicApi.spec, logsPublicApi.spec) inject mock session managers via optional parameter on makeRumPublicApi / makeLogsPublicApi
• mockRumSessionManager / mockLogsSessionManager updated with factory wrappers

4. Worker environment support

Use a defense-in-depth strategy for worker environments, handling workers at multiple layers:

• Storage layer: selectSessionStoreStrategyType forces SessionPersistence.MEMORY in workers — cookies and localStorage are unavailable in worker contexts
• Session manager: Skip DOM event tracking (trackActivity, trackVisibility, trackResume) in workers — no DOM events to listen to
• RUM: Block entirely in preStartRum with an explicit warning — RUM features (DOM observation, user interactions) are not applicable in workers
• Logs: Uses the real session manager (not a stub) — the storage and session manager layers handle the worker context, so Logs works normally with memory-backed sessions

New exports from @datadog/browser-core: selectSessionStoreStrategyType, SessionStoreStrategyType
startSessionManager now takes sessionStoreStrategyType as a direct parameter.

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	169.73 KiB	169.84 KiB	+110 B	+0.06%	✅
Rum Profiler	4.29 KiB	4.29 KiB	0 B	0.00%	✅
Rum Recorder	24.61 KiB	24.61 KiB	0 B	0.00%	✅
Logs	56.95 KiB	56.90 KiB	-57 B	-0.10%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	126.56 KiB	126.66 KiB	+105 B	+0.08%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Pending...

🧠 Memory Performance

Pending...

🔗 RealWorld

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 76.92%
• Overall Coverage: 77.26%

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: e356ec1 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Honor sessionSampleRate in bridge session stub

The bridge stub now always reports a tracked session via findTrackedSession: () => ({}), so Logs events are never discarded by startSessionContext even when sessionSampleRate is 0. Before this change, the stub used sampling logic and could return undefined for non-tracked sessions. In event-bridge/WebView integrations, this regresses sampling behavior and will forward logs that should be dropped.

Useful? React with 👍 / 👎.

[thomas-lebeau]

Good catch. Sampling decision should be handled by the other side of bridge (i.e. the mobile SDK), similarly than RUM

[chatgpt-codex-connector]

Guard session manager start when no storage strategy exists

This path now always starts the logs session manager after consent, but configuration.sessionStoreStrategyType can still be undefined when cookies/localStorage are unavailable. In that case startSessionManager later dereferences configuration.sessionStoreStrategyType! and throws before tryStartLogs() can run, so initialization fails through a monitored exception instead of a controlled no-session behavior.

Useful? React with 👍 / 👎.