💥 use ESM dynamic imports for CDN async chunks

[BenoitZugmeyer]

Motivation

CDN async chunks (recorder, profiler) were previously loaded via JSONP (script tag injection). Switching to native ESM dynamic imports aligns chunk loading with modern browser capabilities and removes the need for a global chunk registry.

ESM dynamic imports require the main script tag to have a crossorigin attribute, and the developer extension's inline script injection needed to be updated to rewrite relative chunk import paths to absolute URLs.

Changes

• webpack.base.ts: set chunkFormat: 'module' and chunkLoading: 'import' to emit async chunks as ES modules loaded via import(). The main entry bundle format is unchanged.
• All <script> tags and createElement('script') calls loading the SDK bundle now include a crossorigin attribute (test apps, E2E framework, performance tests, sandbox).
• developer-extension: the dev bundle injection rewrites relative import('./...') paths to absolute URLs, since the script is injected inline rather than loaded via <script src\>.

Test instructions

Build the SDK (yarn build) and verify the generated files in bundle/chunks/ are valid ES modules.

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-datadog-prod-us1-2]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 76.94% (+0.03%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 26f952a | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	172.00 KiB	170.35 KiB	-1.64 KiB	-0.96%	✅
Rum Profiler	4.67 KiB	4.69 KiB	+23 B	+0.48%	✅
Rum Recorder	24.88 KiB	24.91 KiB	+23 B	+0.09%	✅
Logs	56.38 KiB	56.38 KiB	0 B	0.00%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	127.63 KiB	127.63 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	0.0056	+43.59%
RUM - add action	0.0126	0.0192	+52.38%
RUM - add error	0.0125	0.0178	+42.40%
RUM - add timing	0.0025	0.0037	+48.00%
RUM - start view	0.0122	0.0178	+45.90%
RUM - start/stop session replay recording	0.0006	0.0011	+83.33%
Logs - log message	0.0139	0.0227	+63.31%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	27.21 KiB	27.53 KiB	+326 B
RUM - add action	112.50 KiB	113.67 KiB	+1.18 KiB
RUM - add timing	26.47 KiB	26.06 KiB	-419 B
RUM - add error	117.98 KiB	119.57 KiB	+1.59 KiB
RUM - start/stop session replay recording	25.43 KiB	26.27 KiB	+860 B
RUM - start view	505.98 KiB	499.36 KiB	-6.62 KiB
Logs - log message	44.79 KiB	46.05 KiB	+1.26 KiB

🔗 RealWorld

[BenoitZugmeyer]

/to-staging

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-02-20 11:15:50 UTC ℹ️ Start processing command /to-staging

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2026-02-20 11:15:56 UTC ℹ️ Branch Integration: starting soon, merge expected in approximately 24m (p90)

Commit 26f952a1f2 will soon be integrated into staging-08.

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2026-02-20 11:32:14 UTC ℹ️ Branch Integration: this commit was successfully integrated

Commit 26f952a1f2 has been merged into staging-08 in merge commit 4e179f9a3b.

Check out the triggered DDCI request.

If you need to revert this integration, you can use the following command: /code revert-integration -b staging-08