fix(core): Resolve Metro from project root for source map generation by antonis · Pull Request #6625 · getsentry/sentry-react-native

antonis · 2026-08-27T11:20:49Z

📢 Type of change

Bugfix
New feature
Enhancement
Refactoring

📜 Description

The default Metro serializer resolved Metro's internal modules (baseJSBundle, bundleToString, sourceMapString) from the SDK's own location (__dirname). In a workspace/monorepo where a different Metro version is nested under @sentry/react-native than the one the app uses, that meant source maps were generated with a mismatched Metro version.

The serializer now resolves Metro internals preferring the app's options.projectRoot, falling back to the SDK-resolvable Metro. Resolution is deferred to the first serialization (when projectRoot is available) and memoized. In a normal single-Metro install both paths resolve to the same Metro, so behavior is unchanged.

💡 Motivation and Context

Surfaced while bumping the React Native sample to 0.87 (Metro 0.87) while packages/core pins Metro 0.84.4 as a devDependency: the nested SDK Metro shadowed the app's Metro 0.87 and broke production source-map generation. The fix also benefits real users who have multiple Metro versions resolvable in a monorepo.

Split out of #6617 so the sample bump carries no core changes.

💚 How did you test it?

Existing Metro serializer unit tests pass.
Local Android release build of the RN 0.87 sample produced a valid production bundle with a Debug ID via this serializer.

📝 Checklist

I added tests to verify changes.
No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
I updated the docs if needed.
I updated the wizard if needed.
All tests passing.
Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.
No breaking changes.

🔮 Next steps

Add a dedicated unit test that asserts Metro internals are resolved from options.projectRoot when a different Metro is nested under the SDK.

🤖 Generated with Claude Code

The vendored default serializer required Metro internals resolvable from the SDK's own location. In this monorepo the core package has its own Metro dev dependency (0.84.4) that shadows the app's Metro, so bundling the RN 0.87 sample generated source maps with the mismatched older Metro and threw `Unexpected module with full source map found` on the metro-runtime require.js polyfill. Resolve Metro internals from `options.projectRoot` (the app being bundled) with a fallback to the previous SDK-local resolution. In a normal install both resolve the same Metro instance, so behavior is unchanged; in the monorepo the sample now bundles with its own 0.87 Metro. Resolution is deferred to the first serialization so `options.projectRoot` is available, and memoized thereafter. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

github-actions · 2026-08-27T11:21:12Z

Semver Impact of This PR

⚪ None (no version bump detected)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

fix(core): Resolve Metro from project root for source map generation by antonis in #6625

chore(deps): update Maestro to v2.10.0 by github-actions in #6641
chore(deps): update JavaScript SDK to v10.73.0 by github-actions in #6642
test(ios): Speed up sentry-xcode-scripts tests by antonis in #6633
fix: Update recommended vscode extensions by antonis in #6640
chore(deps): bump actions/setup-java from 5.7.0 to 6.0.0 by dependabot in #6636
chore(deps): bump the codeql-action group with 3 updates by dependabot in #6635
chore(deps): update JavaScript SDK to v10.72.0 by github-actions in #6634
chore(e2e): Bump E2E tests to React Native 0.87.0 by antonis in #6616
chore(deps): update CLI to v3.7.0 by github-actions in #6632
feat(tracing): Copy app start vitals onto standalone children by buenaflor in #6631
chore(deps): update Cocoa SDK to v9.26.1 by github-actions in #6623
fix(ios): Force-load the Sentry static archive to keep ObjC category methods by antonis in #6615
feat(core): Forward feature flag evaluations to the native SDKs by antonis in #6613
chore(deps): update Android SDK to v8.54.0 by github-actions in #6624
chore(deps): update Sentry Android Gradle Plugin to v6.20.0 by github-actions in #6627

_{🤖 This preview updates automatically when you update the PR.}

sentry · 2026-08-27T12:36:42Z

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
Sentry RN	io.sentry.reactnative.sample	8.24.0 (104)	Release

⚙️ sentry-react-native Build Distribution Settings

github-actions · 2026-08-27T12:39:20Z

iOS (legacy) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	3838.64 ms	1216.90 ms	-2621.74 ms
Size	5.08 MiB	6.80 MiB	1.72 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`ecf47a2`+dirty	3835.20 ms	1222.43 ms	-2612.77 ms
`3817909`+dirty	1183.90 ms	1187.50 ms	3.60 ms
`5ee78d6`+dirty	3847.52 ms	1224.27 ms	-2623.25 ms
`890d145`+dirty	1223.59 ms	1231.37 ms	7.78 ms
`e763471`+dirty	3841.16 ms	1218.06 ms	-2623.09 ms
`3d31fcf`+dirty	3838.09 ms	1223.46 ms	-2614.63 ms
`9210ae6`+dirty	3815.93 ms	1214.14 ms	-2601.79 ms
`26843eb`+dirty	3861.60 ms	1238.77 ms	-2622.82 ms
`7a89652`+dirty	3861.46 ms	1229.61 ms	-2631.85 ms
`9ad4522`+dirty	3850.40 ms	1222.40 ms	-2628.00 ms

App size

Revision	Plain	With Sentry	Diff
`ecf47a2`+dirty	4.98 MiB	6.46 MiB	1.49 MiB
`3817909`+dirty	3.38 MiB	4.73 MiB	1.35 MiB
`5ee78d6`+dirty	5.15 MiB	6.69 MiB	1.53 MiB
`890d145`+dirty	3.38 MiB	4.77 MiB	1.38 MiB
`e763471`+dirty	4.98 MiB	6.51 MiB	1.53 MiB
`3d31fcf`+dirty	4.98 MiB	6.56 MiB	1.58 MiB
`9210ae6`+dirty	5.15 MiB	6.68 MiB	1.53 MiB
`26843eb`+dirty	4.98 MiB	6.53 MiB	1.55 MiB
`7a89652`+dirty	5.15 MiB	6.70 MiB	1.55 MiB
`9ad4522`+dirty	4.98 MiB	6.56 MiB	1.58 MiB

Previous results on branch: fix/metro-resolve-project-root

Startup times

Revision	Plain	With Sentry	Diff
`ade1508`+dirty	3839.98 ms	1220.75 ms	-2619.23 ms
`a1cdaff`+dirty	3856.69 ms	1221.58 ms	-2635.11 ms

App size

Revision	Plain	With Sentry	Diff
`ade1508`+dirty	5.08 MiB	6.72 MiB	1.64 MiB
`a1cdaff`+dirty	5.08 MiB	6.80 MiB	1.72 MiB

…ject-root

github-actions · 2026-08-27T12:47:51Z

Android (legacy) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	497.21 ms	507.55 ms	10.33 ms
Size	49.74 MiB	55.66 MiB	5.91 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`f9c1ed4`+dirty	431.00 ms	466.22 ms	35.22 ms
`c2e182c`+dirty	471.64 ms	553.59 ms	81.95 ms
`41d6254`+dirty	424.45 ms	474.34 ms	49.89 ms
`af33f3b`+dirty	434.90 ms	506.14 ms	71.24 ms
`882f8ae`+dirty	399.98 ms	427.06 ms	27.08 ms
`0b5120f`+dirty	503.22 ms	538.60 ms	35.38 ms
`774257e`+dirty	407.09 ms	447.46 ms	40.37 ms
`bf168a4`+dirty	418.21 ms	489.74 ms	71.53 ms
`5569641`+dirty	406.43 ms	428.51 ms	22.08 ms
`c151573`+dirty	530.34 ms	559.43 ms	29.09 ms

App size

Revision	Plain	With Sentry	Diff
`f9c1ed4`+dirty	49.74 MiB	54.86 MiB	5.12 MiB
`c2e182c`+dirty	49.74 MiB	54.85 MiB	5.11 MiB
`41d6254`+dirty	48.30 MiB	53.60 MiB	5.30 MiB
`af33f3b`+dirty	49.74 MiB	55.09 MiB	5.35 MiB
`882f8ae`+dirty	48.30 MiB	53.60 MiB	5.29 MiB
`0b5120f`+dirty	48.30 MiB	53.58 MiB	5.28 MiB
`774257e`+dirty	48.30 MiB	53.58 MiB	5.28 MiB
`bf168a4`+dirty	49.74 MiB	55.09 MiB	5.35 MiB
`5569641`+dirty	48.30 MiB	53.48 MiB	5.18 MiB
`c151573`+dirty	48.30 MiB	53.54 MiB	5.24 MiB

Previous results on branch: fix/metro-resolve-project-root

Startup times

Revision	Plain	With Sentry	Diff
`a1cdaff`+dirty	421.02 ms	430.26 ms	9.24 ms
`ade1508`+dirty	485.55 ms	545.23 ms	59.68 ms

App size

Revision	Plain	With Sentry	Diff
`a1cdaff`+dirty	49.74 MiB	55.66 MiB	5.91 MiB
`ade1508`+dirty	49.74 MiB	55.45 MiB	5.71 MiB

github-actions · 2026-08-27T12:54:03Z

iOS (new) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	3845.18 ms	1209.83 ms	-2635.34 ms
Size	5.08 MiB	6.80 MiB	1.72 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`3b6e9f9`+dirty	3822.77 ms	1208.00 ms	-2614.77 ms
`5a23c47`+dirty	3843.54 ms	1226.05 ms	-2617.50 ms
`100ce80`+dirty	3843.57 ms	1226.46 ms	-2617.12 ms
`0bd8916`+dirty	3816.17 ms	1215.05 ms	-2601.12 ms
`a0d8cf8`+dirty	3826.15 ms	1213.12 ms	-2613.03 ms
`0a9e622`+dirty	3825.35 ms	1219.04 ms	-2606.31 ms
`21a1e70`+dirty	3826.22 ms	1217.74 ms	-2608.47 ms
`9ad4522`+dirty	3862.28 ms	1226.27 ms	-2636.01 ms
`88735e9`+dirty	3837.80 ms	1216.39 ms	-2621.41 ms
`d0e3b3e`+dirty	3846.64 ms	1226.27 ms	-2620.38 ms

App size

Revision	Plain	With Sentry	Diff
`3b6e9f9`+dirty	5.15 MiB	6.68 MiB	1.53 MiB
`5a23c47`+dirty	4.98 MiB	6.46 MiB	1.49 MiB
`100ce80`+dirty	5.15 MiB	6.67 MiB	1.51 MiB
`0bd8916`+dirty	5.15 MiB	6.69 MiB	1.53 MiB
`a0d8cf8`+dirty	5.15 MiB	6.67 MiB	1.51 MiB
`0a9e622`+dirty	4.98 MiB	6.51 MiB	1.53 MiB
`21a1e70`+dirty	4.98 MiB	6.46 MiB	1.49 MiB
`9ad4522`+dirty	4.98 MiB	6.56 MiB	1.58 MiB
`88735e9`+dirty	4.98 MiB	6.46 MiB	1.49 MiB
`d0e3b3e`+dirty	4.98 MiB	6.51 MiB	1.53 MiB

Previous results on branch: fix/metro-resolve-project-root

Startup times

Revision	Plain	With Sentry	Diff
`ade1508`+dirty	3846.26 ms	1221.43 ms	-2624.83 ms
`a1cdaff`+dirty	3841.65 ms	1224.58 ms	-2617.07 ms

App size

Revision	Plain	With Sentry	Diff
`ade1508`+dirty	5.08 MiB	6.72 MiB	1.64 MiB
`a1cdaff`+dirty	5.08 MiB	6.80 MiB	1.72 MiB

… over a nested SDK copy requireMetroModule now tries each candidate path shape against the app (projectRoot) before the SDK's own location, so the app's Metro wins even when the two copies expose internals via different subpaths (app on metro/src/*, SDK on metro/private/*). Adds projectRoot-preference and ordering-regression tests using on-disk fake-Metro fixtures. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

github-actions · 2026-08-27T13:38:52Z

Android (new) Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	487.50 ms	545.33 ms	57.83 ms
Size	49.74 MiB	55.66 MiB	5.91 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`15d4514`+dirty	413.63 ms	449.62 ms	35.99 ms
`26843eb`+dirty	442.02 ms	506.29 ms	64.27 ms
`ca9d079`+dirty	460.67 ms	512.54 ms	51.87 ms
`f9c1ed4`+dirty	520.57 ms	594.84 ms	74.27 ms
`a0d8cf8`+dirty	533.71 ms	564.25 ms	30.54 ms
`20fbd51`+dirty	594.38 ms	655.35 ms	60.97 ms
`0b0f006`+dirty	446.31 ms	458.31 ms	12.00 ms
`1d3572b`+dirty	444.48 ms	478.42 ms	33.94 ms
`4953e94`+dirty	398.80 ms	431.81 ms	33.01 ms
`4e0b819`+dirty	599.31 ms	654.31 ms	55.00 ms

App size

Revision	Plain	With Sentry	Diff
`15d4514`+dirty	48.30 MiB	53.60 MiB	5.30 MiB
`26843eb`+dirty	49.74 MiB	55.26 MiB	5.52 MiB
`ca9d079`+dirty	48.30 MiB	53.58 MiB	5.28 MiB
`f9c1ed4`+dirty	49.74 MiB	54.86 MiB	5.12 MiB
`a0d8cf8`+dirty	48.30 MiB	53.49 MiB	5.19 MiB
`20fbd51`+dirty	49.74 MiB	54.81 MiB	5.07 MiB
`0b0f006`+dirty	49.74 MiB	55.66 MiB	5.91 MiB
`1d3572b`+dirty	49.74 MiB	55.38 MiB	5.63 MiB
`4953e94`+dirty	43.94 MiB	48.94 MiB	5.00 MiB
`4e0b819`+dirty	49.74 MiB	54.81 MiB	5.07 MiB

Previous results on branch: fix/metro-resolve-project-root

Startup times

Revision	Plain	With Sentry	Diff
`a1cdaff`+dirty	428.06 ms	458.04 ms	29.98 ms
`ade1508`+dirty	491.94 ms	520.06 ms	28.12 ms

App size

Revision	Plain	With Sentry	Diff
`a1cdaff`+dirty	49.74 MiB	55.66 MiB	5.91 MiB
`ade1508`+dirty	49.74 MiB	55.45 MiB	5.71 MiB

cursor

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 0645154. Configure here.}

lucas-zimerman · 2026-09-01T00:47:47Z

+ */
+// oxlint-disable-next-line typescript-eslint(no-explicit-any)
+function requireMetroModule(candidates: string[], projectRoot: string | undefined): any {
+  const roots = projectRoot ? [projectRoot, __dirname] : [__dirname];


could projectRoot be an empty string here? it may silently fail if thats the case

I think this should work since an empty string should fallback to [__dirname]

lucas-zimerman · 2026-09-01T00:56:26Z

+  );
+  if (typeof sourceMapString !== 'function') {
+    throw new Error(`
+[@sentry/react-native/metro] Cannot find sourceMapString function in 'metro/src/DeltaBundler/Serializers/sourceMapString'.


Isn't it also required on metro/private/DeltaBundler/Serializers/sourceMapString ?

Good point 👍 Update with 79ea609 to be path agnostic

lucas-zimerman · 2026-09-01T01:02:02Z

-      sourceMapString = (sourceMapString as { sourceMapString: typeof sourceMapStringType }).sourceMapString;
+  return (entryPoint, preModules, graph, options) => {
+    if (!internals) {
+      internals = resolveMetroInternals(options.projectRoot);


Seems like an edge-case but local AI complained about the following:

resolveMetroInternals() (and its sourceMapString shape check/throw) now runs before isHot is computed. Previously the throw only fired on non-hot builds; now it can break the dev server too. Now it fires unconditionally on the very first bundle serialized, hot or not, so a bad Metro shape that used to only break production/export builds can now break yarn start itself.

Good catch 👍 Updated with b585061

lucas-zimerman

overall looks good, there are some bits to be polished, and after that we can merge it :D

Co-authored-by: LucasZF <lucas-zimerman1@hotmail.com>

lucas-zimerman

LGTM!

antonis force-pushed the fix/metro-resolve-project-root branch from d8893b4 to addbd1d Compare August 27, 2026 11:21

antonis mentioned this pull request Aug 27, 2026

chore(sample): Bump React Native sample to 0.87.0 #6617

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antonis added the ready-to-merge Triggers the full CI test suite label Aug 27, 2026

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Comment thread packages/core/src/js/tools/vendor/metro/utils.ts

Merge remote-tracking branch 'origin/main' into fix/metro-resolve-pro…

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…ject-root

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antonis marked this pull request as ready for review August 27, 2026 13:41

antonis requested review from alwx and lucas-zimerman as code owners August 27, 2026 13:41

antonis added 2 commits August 28, 2026 11:56

Merge branch 'main' into fix/metro-resolve-project-root

467519f

Merge branch 'main' into fix/metro-resolve-project-root

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Comment thread packages/core/src/js/tools/vendor/metro/utils.ts Outdated

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antonis removed the ready-to-merge Triggers the full CI test suite label Sep 1, 2026

antonis and others added 4 commits September 1, 2026 14:22

Add inline explanation

c47fda4

Co-authored-by: LucasZF <lucas-zimerman1@hotmail.com>

Simplify function description

5dbc011

Guard all Metro internals with a descriptive error

79ea609

Resolve Metro sourceMapString lazily on the non-hot path

b585061

Merge branch 'main' into fix/metro-resolve-project-root

8c7398e

antonis added the ready-to-merge Triggers the full CI test suite label Sep 1, 2026

antonis requested a review from lucas-zimerman September 1, 2026 12:45

lucas-zimerman approved these changes Sep 2, 2026

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antonis merged commit 77b7b23 into main Sep 2, 2026
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antonis deleted the fix/metro-resolve-project-root branch September 2, 2026 06:43

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antonis commented Aug 27, 2026

📢 Type of change

📜 Description

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

🔮 Next steps

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