♻️ [Core] Allow passing a session store factory to startSessionManager

[BeltranBulbarellaDD]

Motivation

Following the question about whether the custom / Shopify store could call register: yes, the idea is for the Shopify SDK to own the registration and pass its store to browser-core.

This PR contains the browser-core changes needed for that. The Shopify side lives in #5108.

Changes

Browser-core receives a third parameter in startSessionManager:

mockable(startSessionManager)(configuration, trackingConsentState, createSessionStore)

The Shopify SDK would call register(startRegisteredWebPixel) and create the factory inside that callback:

mockable(startWebPixelRum)(configuration, api, createShopifySessionStoreFactory(api.browser))

The important part is that createShopifySessionStoreFactory(api.browser) lives in the Shopify SDK. Browser-core only receives the factory, so we don't need to put browser.cookie in the public initialization configuration.

Existing callers keep the default store selection, and sessionPersistence stays as it is. If the supplied factory cannot provide a store, the session manager doesn't start.

This also exposes the cookie string builder and shared cookie session store so the Shopify adapter can reuse them. Legacy document.cookie lookup can be disabled for environments without a DOM, and the cookie availability check handles a factory that throws.

Test instructions

Passed locally: yarn lint, yarn typecheck, yarn format, yarn build, and 145 targeted unit tests covering cookie access, session storage, and the session manager.

The added tests cover the injected store, unavailable storage without fallback, a throwing cookie-access factory, and disabling legacy cookie reads.

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

[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-13T11:31:09.206940Z	9b3faa3	PR opened

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[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum Salesforce	N/A	185.58 KiB	N/A	N/A	N/A
Rum	185.41 KiB	185.55 KiB	+144 B	+0.08%	✅
Rum-salesforce Profiler	N/A	8.38 KiB	N/A	N/A	N/A
Rum Profiler	8.38 KiB	8.38 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	59.48 KiB	+144 B	+0.24%	✅
Rum Slim	143.42 KiB	143.56 KiB	+144 B	+0.10%	✅
Worker	22.96 KiB	22.96 KiB	0 B	0.00%	✅
Rum Shopify	N/A	215.97 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.38 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	4.77 KiB	N/A	N/A	N/A

[datadog-datadog-prod-us1]

More details

Existing callers retain default storage selection, while an unavailable injected store stops session startup without falling back to browser storage. The shared cookie store can disable legacy document.cookie reads for DOM-free adapters.

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🧪 All tests passed
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🎯 Code Coverage (details)
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• Overall Coverage: 77.20% (-0.01%)

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