fix(livestream): stop capturing AbortErrors from cancelled SSE streams

[posthog]

Problem

• Users can't click-to-copy things they obviously want to copy: the suggested proxy subdomain, values inside CodeSnippet blocks, event names in the Activity table, and Max's answer text are all plain, non-interactive text. Two independent sessions showed people rage-clicking or dead-clicking these exact spots, often while mid-setup (configuring an SDK, bouncing between proxy settings and the Activity page to verify events landed) — the worst time to hit friction.
• The same 30-minute proxy-setup session also threw 49 DOMException: AbortError: signal is aborted without reason into error tracking (28 on /settings/organization-proxy, 21 on /activity/explore).
• Pulling the actual error tracking issue behind that message (478 occurrences / 122 sessions / 69 users over 30 days, not just the one session) traced it to api.stream() in lib/api.ts — the helper behind the sidebar's live-notifications SSE connection (and other streaming endpoints). It mounts app-wide, which is why the error shows up on effectively every page, not just the two the report called out. Whenever that connection is torn down early (tab hidden, explicit stop, unmount), the underlying fetch/stream reader can reject with a native AbortError, and stream() had no catch around fetchEventSource() to treat that as the clean cancellation it is — so it reached exception capture as an unhandled rejection instead.

Changes

• lib/api.ts: wrap api.stream()'s fetchEventSource() call in a try/catch that swallows AbortError (matching the isAbortError convention already used elsewhere in this file) and rethrows anything else.
• ManagedReverseProxy.tsx: wrap the suggested subdomain example (t.mydomain.com) in the existing CopyToClipboardInline component so it's click-to-copy, since it sits right next to a form asking the user to type that exact value.

I scoped this PR to the two clearest, most defensible fixes rather than the full list of copy affordances the report raised (CodeSnippet per-value copy, Activity table event-name click, a hover copy control on Max message bubbles) — those are real UX friction with existing workarounds (drag-select, whole-block copy) and each is its own small design decision better done as a follow-up than bundled here.

How did you test this code?

• Added two Jest cases to lib/api.test.ts covering api.stream(): resolves cleanly when the underlying stream rejects with AbortError, and still propagates non-abort errors. Neither existing test exercised this path.
• pnpm --filter=@posthog/frontend typescript:check and fix (lint + format) — clean on the changed files (pre-existing unrelated failures elsewhere in the repo, from a missing @posthog/quill-primitives package, are untouched by this change).
• Did not spin up the app to click the new copy affordance manually; relied on CopyToClipboardInline being an existing, already-used component for exactly this pattern (wrapping literal text children for click-to-copy).

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

Docs update

N/A — no user-facing workflow or API changed.

🤖 Agent context

Autonomy: Fully autonomous

Investigated via the PostHog MCP error-tracking tools to find the actual issue behind the reported AbortError message (not just the two sessions cited in the report), which is what pointed at api.stream() in lib/api.ts rather than the dataNodeLogic.ts/proxy-logic code paths the report's own analysis suggested. Ruled out the dataNodeLogic.ts lazyLoaders count-query catches as a red herring — those don't currently pass an AbortSignal so can't produce this specific native abort message. Descoped the CodeSnippet/Activity-table/Max-bubble copy affordances mentioned in the report to a follow-up, since verifying those needed either a live app session or a larger design call I didn't want to make unreviewed.

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Created with PostHog Desktop from this inbox report.

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[github-actions]

🤖 CI report

⚠️ Bundle size — 🔺 +57 B (+0.0%)

Uncompressed size of every built .js bundle, compared against the base branch.

Total: 65.51 MiB · 🔺 +57 B (+0.0%)

No file changed by more than 1000 B.

_{Posted automatically by build-bundle-size-report · uncompressed bytes from dist-report}

✅ Eager graph — within budget

How much code each root ships on the eager path — downloaded and parsed before the surface is interactive. Measured from the esbuild output chunks (post-tree-shake, static imports only); lazy import() / React.lazy chunks are not counted.

Root	Eager (shipped)	Δ vs base	Budget
entry (logged-out pages, app bootstrap) src/index.tsx	1.25 MiB · 22 files	no change	███░░░░░░░ 27.7% of 4.51 MiB
authenticated shell (every logged-in page) src/scenes/AuthenticatedShell.tsx	8.13 MiB · 3,035 files	🔺 +56 B (+0.0%)	████████░░ 83.8% of 9.71 MiB

🟢 node_modules/monaco-editor/ stays out of src/index.tsx
🟢 src/lib/components/ActivityLog/describers stays out of src/index.tsx
🟢 [object Object] stays out of src/index.tsx
🟢 [object Object] stays out of src/index.tsx
🟢 node_modules/monaco-editor/ stays out of src/scenes/AuthenticatedShell.tsx
🟢 src/lib/components/ActivityLog/describers stays out of src/scenes/AuthenticatedShell.tsx
🟢 [object Object] stays out of src/scenes/AuthenticatedShell.tsx
🟢 [object Object] stays out of src/scenes/AuthenticatedShell.tsx

Largest files eagerly shipped from src/index.tsx

Size	File
126.8 KiB	../node_modules/.pnpm/react-dom@18.3.1_react@18.3.1/node_modules/react-dom/cjs/react-dom.production.min.js
24.6 KiB	../node_modules/.pnpm/buffer@6.0.3/node_modules/buffer/index.js
6.3 KiB	../node_modules/.pnpm/react@18.3.1/node_modules/react/cjs/react.production.min.js
4.5 KiB	../node_modules/.pnpm/@jspm+core@2.1.0/node_modules/@jspm/core/nodelibs/browser/process.js
3.9 KiB	../node_modules/.pnpm/scheduler@0.23.2/node_modules/scheduler/cjs/scheduler.production.min.js
1.4 KiB	../node_modules/.pnpm/base64-js@1.5.1/node_modules/base64-js/index.js
1.3 KiB	src/RootErrorBoundary.tsx
912 B	../node_modules/.pnpm/ieee754@1.2.1/node_modules/ieee754/index.js
789 B	src/scenes/ChunkLoadErrorBoundary.tsx
762 B	src/index.tsx

Largest files eagerly shipped from src/scenes/AuthenticatedShell.tsx

Size	File
285.6 KiB	../node_modules/.pnpm/posthog-js@1.409.5/node_modules/posthog-js/dist/rrweb.js
267.7 KiB	../node_modules/.pnpm/@posthog+icons@0.38.0_react-dom@18.3.1_react@18.3.1__react@18.3.1/node_modules/@posthog/icons/dist/posthog-icons.es.js
235.5 KiB	src/taxonomy/core-filter-definitions-by-group.json
231.5 KiB	../node_modules/.pnpm/posthog-js@1.409.5/node_modules/posthog-js/dist/module.js
154.3 KiB	../node_modules/.pnpm/re2js@0.4.1/node_modules/re2js/build/index.esm.js
126.8 KiB	../node_modules/.pnpm/react-dom@18.3.1_react@18.3.1/node_modules/react-dom/cjs/react-dom.production.min.js
105.3 KiB	src/lib/api.ts
94.7 KiB	../packages/quill/packages/quill/dist/index.js
93.3 KiB	../node_modules/.pnpm/prosemirror-view@1.40.1/node_modules/prosemirror-view/dist/index.js
90.6 KiB	../node_modules/.pnpm/@tiptap+core@3.20.6_@tiptap+pm@3.20.6/node_modules/@tiptap/core/dist/index.js

_{Posted automatically by check-eager-graph · sizes are eager output bytes (shipped, post-tree-shake) from the esbuild metafile · part of #32479}

✅ Toolbar bundle — eager 2.19 MiB within budget

What the toolbar ships to customer pages, measured from the esbuild output (minified, post-tree-shake). The eager set is the entry plus everything statically imported from it — fetched before any feature runs; deferred chunks load lazily. The eager guardrail is 5.72 MiB. Each output file must also stay below 10 MB, where CloudFront stops compressing it. The module boundary is enforced separately by check-toolbar-graph.

Metric	Size	Δ vs base	Budget
Eager (shipped) entry + static imports	2.19 MiB · 17 files	no change	████░░░░░░ 38.3% of 5.72 MiB
Deferred (lazy)	2.08 MiB · 33 files	no change	n/a — loads on demand
Loader dist/toolbar.js	1.1 KiB	no change	█░░░░░░░░░ 5.8% of 19.5 KiB

Largest eagerly-shipped chunks

Size	File
718.3 KiB	dist/toolbar/toolbar-app-FT4UJ3IP.css
551.4 KiB	dist/toolbar/chunk-chunk-AGSGCCBT.js
484.6 KiB	dist/toolbar/chunk-chunk-T44C2V5C.js
133.6 KiB	dist/toolbar/chunk-chunk-KBLX73CM.js
131.8 KiB	dist/toolbar/chunk-chunk-T5KY5WYR.js
71.0 KiB	dist/toolbar/toolbar-app-FKUW2FOM.js
69.0 KiB	dist/toolbar/chunk-chunk-27JL52RE.js
35.6 KiB	dist/toolbar/chunk-chunk-3JVI3ZTF.js
20.9 KiB	dist/toolbar/chunk-chunk-HJ3ZJMTU.js
12.2 KiB	dist/toolbar/chunk-chunk-PIK3PADE.js

_{Posted automatically by check-toolbar-size · sizes are toolbar output bytes (shipped, post-tree-shake) from the esbuild metafile}

✅ Dist folder size — 🔺 +3.9 KiB (+0.0%)

Total size of the built frontend/dist folder (all assets), compared against the base branch.

Total: 1381.31 MiB · 🔺 +3.9 KiB (+0.0%)