fix(onboarding): make cache.disposables safe to call after unmount

[posthog]

Problem

• The onboarding wizard's SSE reconnect crashes with a TypeError when an error event fires around unmount, killing that user's reconnect loop mid-onboarding.
• wizardSessionStreamLogic's eventSource.onerror schedules its backoff reconnect via cache.disposables.add(...), but beforeUnmount in the disposables plugin (frontend/src/kea-disposables.ts) sets cache.disposables = null.
• eventSource.close() runs as part of the same unmount pass, but a queued error event can still dispatch afterward — it hits the null manager and throws instead of scheduling a reconnect.
• The same unguarded cache.disposables pattern exists at four other call sites in that file, so any EventSource error near unmount can reproduce it.

Changes

• frontend/src/kea-disposables.ts: beforeUnmount now swaps in a no-op manager instead of null. add()/dispose() become safe by construction for every consumer of the plugin, rather than requiring each call site to remember to guard for it — this fixes the hazard at all the call sites in wizardSessionStreamLogic in one place instead of scattering optional chaining across five call sites.
• Added a regression test in kea-disposables.test.ts that reproduces the exact failure: a listener holding a raw cache reference (mirroring how EventSource.onerror closes over cache) calling disposables.add()/dispose() after unmount(). Confirmed it fails with the pre-fix null behavior and passes with the fix.

How did you test this code?

• Added frontend/src/kea-disposables.test.ts: "a callback holding a raw cache reference can call disposables.add()/dispose() after unmount without throwing" — reproduces the reported TypeError: Cannot read properties of null (reading 'add'). Verified it fails on the pre-fix code and passes after the fix.
• Ran the full kea-disposables.test.ts suite (13 tests) and wizardSessionStreamLogic.test.ts suite (7 tests) — all pass.
• Ran hogli ci:preflight --fix — clean.

Docs update

N/A — internal bug fix, no user-facing or documented behavior change.

🤖 Agent context

Autonomy: Fully autonomous

Investigated the crash trace in the report (products/wizard/frontend/wizardSessionStreamLogic.ts:280, frontend/src/kea-disposables.ts), confirmed no open PR or branch was already addressing it (gh pr list --search). Considered guarding each of the five cache.disposables call sites in wizardSessionStreamLogic.ts individually with optional chaining, but hardening the plugin's beforeUnmount to swap in a no-op manager fixes the hazard for every consumer at once and is the smaller, more root-cause change. Skills invoked: /using-kea-disposables, /writing-tests.

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[github-actions]

🤖 CI report

⚠️ Bundle size — 🔺 +290 B (+0.0%)

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

Total: 65.51 MiB · 🔺 +290 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	no change	████████░░ 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	🔺 +72 B (+0.0%)	████░░░░░░ 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
71.1 KiB	dist/toolbar/toolbar-app-6PECMLVI.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 — 🔺 +3.1 KiB (+0.0%)

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

Total: 1381.31 MiB · 🔺 +3.1 KiB (+0.0%)