✨ [RUM-16985] Capture wasm module build_ids and enrich error events by ImaneLargou · Pull Request #4920 · DataDog/browser-sdk

ImaneLargou · 2026-07-27T13:03:25Z

Motivation

Browser WebAssembly runtime errors currently lack the module metadata required for WASM symbolication.

This change identifies errors containing WebAssembly stack frames and reports the loaded WASM module URL and build ID. This allows the error-processing pipeline to distinguish ordinary browser errors from errors that should use WASM/DWARF symbolication.

Related upstream schema change: DataDog/rum-events-format#427

Changes

Track WebAssembly modules loaded through:
- WebAssembly.instantiate
- WebAssembly.instantiateStreaming
- WebAssembly.compile
- WebAssembly.compileStreaming
Extract module build IDs from the build_id custom section, with external_debug_info as a fallback.
Detect WASM errors by checking the complete error stack for WASM-specific frames.
Report the following metadata on WASM errors:
- error.source_type: "browser+wasm"
- error.wasm_modules, containing the module URL and build ID
Add support to both RUM and Browser Logs.
Keep ordinary JavaScript errors unchanged. In particular, .js frames do not qualify an error as WASM.
Update the generated RUM event types from the corresponding rum-events-format schema change.

Test instructions

Run the relevant unit tests:

packages/browser-core/src/domain/wasmModules/wasmBinaryParser.spec.ts
packages/browser-core/src/domain/wasmModules/wasmModuleTracking.spec.ts
packages/browser-rum-core/src/domain/error/errorCollection.spec.ts
packages/browser-logs/src/domain/createErrorFieldFromRawError.spec.ts

Run the E2E scenario:

yarn test:e2e -g "send WebAssembly runtime errors with module metadata"

The E2E test loads a real .wasm module using WebAssembly.instantiateStreaming, triggers a runtime error, and verifies that both RUM and Logs events contain:

  {
    "source_type": "browser+wasm",
    "wasm_modules": [
      {
        "url": "<test module URL>",
        "build_id": "abcd"
      }
    ]
  }

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

Intercepts WebAssembly.instantiate / instantiateStreaming at SDK script-load time to record (url, build_id) per loaded module, including lazily-loaded modules. On error capture, attaches error.wasm_modules[] and sets source_type='browser+wasm' so the backend can dispatch wasm symbolication. - New wasmModules/wasmModuleTracking.ts: hooks all four WebAssembly entry points; reads build_id via a minimal custom-section parser; registry stays live for lazy module loads - New wasmModules/wasmBinaryParser.ts: walks wasm binary sections, extracts build_id custom section or falls back to external_debug_info - errorCollection: populates error.wasm_modules[] and flips source_type to 'browser+wasm' when any module is registered - rawRumEvent.types: adds wasm_modules?: Array<{url, build_id}> to RawRumErrorEvent - main.ts: installs tracking synchronously at script-load time to close the race window before DD_RUM.init()'s deferred microtask Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

github-actions · 2026-07-27T13:03:37Z

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

datadog-official · 2026-07-27T13:03:41Z

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 79.55%
• Overall Coverage: 77.24% (+0.03%)

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 420fdee | Docs | Datadog PR Page | Give us feedback!}

…-experiment

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cit-pr-commenter-54b7da · 2026-08-11T09:59:53Z

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	180.44 KiB	183.27 KiB	+2.83 KiB	+1.57%	✅
Rum Profiler	8.43 KiB	8.43 KiB	0 B	0.00%	✅
Rum Recorder	21.12 KiB	21.12 KiB	0 B	0.00%	✅
Logs	57.04 KiB	59.78 KiB	+2.74 KiB	+4.81%	✅
Rum Salesforce	N/A	141.21 KiB	N/A	N/A	N/A
Rum Slim	138.47 KiB	141.24 KiB	+2.77 KiB	+2.00%	✅
Worker	22.96 KiB	22.96 KiB	0 B	0.00%	✅
Rum Shopify	N/A	202.75 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.43 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	3.72 KiB	N/A	N/A	N/A

ImaneLargou · 2026-08-11T15:57:51Z

I have read the CLA Document and I hereby sign the CLA

…-experiment

mormubis · 2026-08-21T13:44:18Z

+// wrapper only resolves once both are done. This guarantees that an error
+// thrown immediately by an exported function can reference the loaded module.
+function captureFromResponse(response: Response): Promise<void> {
+  const url = response.url || '<wasm-instantiate-streaming-no-url>'


❓ question: ‏How could the URL be empty? Is this just because of the types?

mormubis · 2026-08-21T13:45:07Z

+  trackingClients += 1
+  if (!stopTracking) {
+    stopTracking = installWasmModuleTracking()
+  }
+
+  let stopped = false
+  return () => {
+    if (stopped) {
+      return
+    }
+    stopped = true
+    trackingClients -= 1
+    if (trackingClients === 0) {
+      stopTracking?.()
+      stopTracking = undefined
+      registry.clear()
+    }
+  }


❓ question: ‏How many clients could we expect tracking WebAssembly?

mormubis · 2026-08-21T13:53:13Z

 import { makeLogsPublicApi } from '../boot/logsPublicApi'

+// Install WebAssembly hooks before deferred Logs initialization so eagerly loaded modules are captured.
+startWasmModuleTracking()


🔨 warning: ‏The philosophy of the SDK is not to override any APIs unless we are allowed to track the user.

This should be deferred until SDK initialization.

mormubis · 2026-08-21T13:54:31Z

+  // reads it to set source_type='browser+wasm' and error.wasm_modules.
+  // Must start before any wasm load — RUM is initialised before the page's
+  // wasm fetch in typical setups.
+  const stopWasmModuleTracking = startWasmModuleTracking()


❓ question: ‏Are we not initializing this in different places?

mormubis · 2026-08-21T13:56:33Z

+// wasm modules — by the time the deferred wrap installs, instantiateStreaming
+// may have already been called. Installing here (before any deferral) closes
+// that race.
+startWasmModuleTracking()


🔨 warning: ‏Mentioned before.

mormubis · 2026-08-21T13:56:51Z

 import { makeProfilerApiStub } from '../boot/stubProfilerApi'

+// Install WebAssembly hooks before deferred RUM initialization so eagerly loaded modules are captured.
+startWasmModuleTracking()


🔨 warning: ‏Keeping track of all the places where this is automatically tracked.

ImaneLargou changed the title ~~✨ [RUM-WASM] Capture wasm module build_ids and enrich error events~~ [WASM] Capture wasm module build_ids and enrich error events Jul 27, 2026

Merge remote-tracking branch 'origin/main' into imane.largou/wasm-sdk…

4d8b227

…-experiment

ImaneLargou marked this pull request as ready for review August 11, 2026 09:47

ImaneLargou requested a review from a team as a code owner August 11, 2026 09:47

🔧 [RUM-WASM] Remove stale fallback comment from wasmBinaryParser

193a2da

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ImaneLargou marked this pull request as draft August 11, 2026 10:10

✨ [RUM-WASM] Report WASM errors from Browser Logs

0070e34

ImaneLargou changed the title ~~[WASM] Capture wasm module build_ids and enrich error events~~ ✨ [RUM-16985] Capture wasm module build_ids and enrich error events Aug 11, 2026

✅ [RUM-16985] Test WASM error reporting

aded8c6

ImaneLargou mentioned this pull request Aug 12, 2026

[RUM-16985] Add browser WASM error metadata DataDog/rum-events-format#427

Open

ImaneLargou added 4 commits August 12, 2026 13:54

🐛 [RUM-16985] Stabilize WASM error metadata

8f16b67

✅ [RUM-16985] Support browsers without streaming WASM

5f43474

✅ [RUM-16985] Scope WASM runtime E2E by browser

511f810

Merge remote-tracking branch 'origin/main' into imane.largou/wasm-sdk…

420fdee

…-experiment

mormubis reviewed Aug 21, 2026

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✨ [RUM-16985] Capture wasm module build_ids and enrich error events - #4920

✨ [RUM-16985] Capture wasm module build_ids and enrich error events#4920
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