fix(web): filter browser extension probe errors from window.onerror handler #SUPERLOG

[superlog-app]

Summary

The @superlog/web production app is capturing browser extension and browser-native script errors as real application exceptions, creating noisy incidents for errors like ReferenceError: Can't find variable: __firefox__ and TypeError: undefined is not an object (evaluating 'window.ethereum.selectedAddress = undefined').

Root Cause

Browser extensions (MetaMask, crypto wallets) and Firefox iOS's internal bridge inject short probe scripts that run as global code at line 1 of the page URL (https://superlog.sh/). When these probes throw — because window.__firefox__ or window.ethereum don't exist on the page — window.onerror fires. The window.addEventListener("error", ...) handler in instrumentation.ts had no guard to distinguish these external probes (filename = page href, lineno = 1) from real application JS errors (filename = /assets/index-*.js, specific lineno). All three grouped issues show code.file: "https://superlog.sh/" and code.line.number: 1 with column numbers ≤ 19 — unmistakably inline/injected scripts, not application bundle code.

Remediation

Added a one-line guard in the window.error listener to skip events where event.lineno === 1 && event.filename === window.location.href. This is the canonical signature of browser-injected/extension script errors. Application bundle errors always reference a path under /assets/, so they are unaffected.

Related incident: d0faa423-c322-4197-90e2-4531c243501f

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Summary by cubic

In @superlog/web, ignore browser extension and browser-native probe errors so they don’t create noisy incidents. Adds a guard in window.onerror to skip events that come from line 1 of the page URL (injected probes), not app code.

• Bug Fixes
  • Skip window.onerror events where event.lineno === 1 and event.filename === window.location.href.
  • Prevents false positives from MetaMask/crypto wallets and Firefox iOS bridge probes; app bundle errors under /assets/ are unaffected.

^{Written for commit e100202. Summary will update on new commits.}

[superlog-app]

Observability review

• 1 warning

[superlog-app]

metrics · warning — Count filtered browser-extension probe errors

Increment a counter (e.g. browser_extension_probe_errors_filtered_total) at the filter return so operators can detect if the heuristic is over-broad or if legitimate errors are being silently dropped. Without it, a regression where real errors match lineno === 1 && filename === window.location.href would be invisible.

Suggested change

	// probes throw, window.onerror fires with filename === the page href and
	if (event.lineno === 1 && event.filename === window.location.href) {
	filteredProbeErrorsCounter.add(1, { "filter.reason": "extension_probe" });
	return;
	}

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