feat: Automatically Detect MFE AJAX

[metal-messiah]

Add support for automatic Micro Frontend (MFE) attribution of AjaxRequest events. Previously, AjaxRequest events were only ever captured globally by the container browser application. With this change, the agent cross-compares the call stack signature of the AJAX call to the call stack signature of the MFE module that registered with the register API. If the file that is responsible for registering with the browser agent is found in the call stack signature of the AJAX request being triggered, that event will be attributed to the MFE instead of the container.

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Overview

Split from #1706

Line by line in the trace, If any file path in the call stack of the AJAX executor contains a match to the file path captured during use of the .register API, the event is captured as belonging to that MFE.

Logic is included to support reporting to both the MFE and the container application if the duplication configuration is enabled.

Testing

The vite-react-mfe test build is a great example app that implements the register API and supplies the correct set ups to replicate the behaviors across the auto-MFE PRs. See the new e2e and jest tests around this new behavior and play around with that vite build to see this in action.

[github-actions]

Supportability Metric Usage Changes:

No matching changes found

Supportability Metrics .md File Changes:

supportability_metrics.md was changed? false

New supportability metrics require changes to supportability_metrics.md, as well as a new PR to Angler. Please ensure an Angler PR is created and linked to this PR.

[github-actions]

Asset Size Report

Merging this pull request will result in the following asset size changes:

Agent	Asset	Previous Size	New Size	Diff
lite	loader	26.55 kB / 10.06 kB (gzip)	26.55 kB / 10.06 kB (gzip)	0% / -0.02% (gzip)
lite	async-chunk	55.07 kB / 18.52 kB (gzip)	55.07 kB / 18.52 kB (gzip)	0% / 0% (gzip)
pro	loader	62.4 kB / 21.93 kB (gzip)	63.17 kB / 22.24 kB (gzip)	1.23% / 1.43% (gzip)
pro	async-chunk	91.24 kB / 28.92 kB (gzip)	91.51 kB / 28.98 kB (gzip)	0.29% / 0.22% (gzip)
spa	loader	64.8 kB / 22.73 kB (gzip)	65.57 kB / 23.09 kB (gzip)	1.18% / 1.56% (gzip)
spa	async-chunk	102.46 kB / 31.77 kB (gzip)	102.77 kB / 31.85 kB (gzip)	0.31% / 0.24% (gzip)

[codecov]

Codecov Report

❌ Patch coverage is 81.08108% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.74%. Comparing base (847b6a7) to head (d145b55).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/features/ajax/instrument/index.js	40.00%	6 Missing ⚠️
src/loaders/api/register.js	42.85%	4 Missing ⚠️
src/common/util/v2.js	86.95%	2 Missing and 1 partial ⚠️
src/common/wrap/wrap-fetch.js	87.50%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1722   +/-   ##
=======================================
  Coverage   88.74%   88.74%           
=======================================
  Files         210      209    -1     
  Lines        7567     7598   +31     
  Branches     1559     1599   +40     
=======================================
+ Hits         6715     6743   +28     
- Misses        759      761    +2     
- Partials       93       94    +1     

Flag	Coverage Δ
unit-tests	82.47% <81.08%> (-0.02%)	⬇️

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[github-actions]

Last ran on March 17, 2026 10:11:24 CDT
Checking merge of (dccdc6a) into main (76024d0)

[ptang-nr]

Reviewed to the best of my abilities. Might be good to get another set of eyes.

[cwli24]

lgtm 👍