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fix(web): unreadable synced rows drop instead of crashing; stale tabs reload onto a new build - #2340
On 2026-11-07 a customer tab running build ef1b44e79f threw an uncaught SchemaError: Expected @maple/AlertSignalType on /services. The server had started syncing incidents with slo_burn_rate/anomaly signal types (#2296, #2318), and the old build did not know them. The Electric row mappers decoded every literal with decodeUnknownSync inside live-query callbacks, so a single unknown value threw outside Effect. On /alerts the same row brings down the whole page. Prod self-traces show the same class of failure for AlertDestinationType on 10-31 and 11-01, from builds that predate #2086's fix for that one field.
What changed
Unreadable rows are dropped instead of crashing (the whole class, not one field)
New packages/web-data/src/collections/live-row.ts: liveRowDecoder decodes a whole domain document once and returns Option. It cannot throw, and it reports each dropped row once to listeners.
alerts.ts (rules, incidents, destinations) and api-keys.ts hand raw fields to it. The mappers now return Option, and new rowsTo* helpers skip unreadable rows, so every call site was forced by the compiler to handle the drop. Decoding the whole class also covers the old new AlertRuleDocument(...) constructor, which could throw too (for example on window_minutes).
Fields that were already lenient stay lenient (ack source, labels, no-data behavior, template, draft). A rule whose stored tiers it cannot read is dropped rather than shown from its legacy columns, because saving that stand-in would overwrite the real tiers.
New lint rule maple/no-throwing-live-row-decode for packages/web-data/src/collections/** bans Schema.decode*Sync/*Promise and new *Document(. It reports 19 violations on the old alerts.ts.
investigations.ts and dashboards.ts were already safe and are unchanged.
Stale tabs recover after a deploy (apps/web/src/shell/version.ts)
Three signals trigger an immediate /version.json probe instead of waiting for the 15-minute poll: a vite:preloadError (Vite fires it for every failed dynamic import, including the "MIME type text/html" case for a removed chunk), an unhandled chunk-load rejection, or a dropped synced row.
If the deployed commit is newer, the "Maple was updated" banner shows at once (instead of after the 15-minute poll). The tab also reloads by itself only when it is hidden and its page holds no unsaved work (isBlockingUnload), and at most once per deployed commit per tab session (a sessionStorage guard, so a cached index.html cannot cause a loop). Blocked storage falls back to the banner. A transient network failure on the same build does nothing. The probe is off in dev builds (BUILT_COMMIT is empty).
Each probe runs in a StaleBuildProbe span with maple.stale_build.{trigger,detail,newer,reloading} attributes.
isChunkLoadError also matches "Failed to load module script" and "Unable to preload CSS". The unused 60s reload guard in chunk-reload.ts is removed.
Verification
Unit tests:
packages/web-data: 42 pass, including rows carrying a future signal type, severity, status, comparator, event type, hold reason, key kind, bad timestamp, bad window, bad group_by and bad stored tiers. Each drops only that row, and is reported once.
apps/web: src/shell and src/page/alerts (472 tests), plus services, overview and settings (708 tests in all), pass. That includes version.test.ts, which covers reloading once per commit, reloading again for a later deploy, the same build, an unreadable version.json, blocked storage, and a visible tab (banner, 0 reloads) versus hidden tab.
tsrs typecheck passes for web-data and apps/web. oxlint passes with both .oxlintrc.json and .oxlintrc.effect.json.
Browser, on a local stack: I inserted an open alert_incidents row with signal_type = 'a_future_signal' into local Postgres, so Electric synced it, and loaded the pages with origin/main's code and then with this branch.
renders; the readable incident is listed and the unreadable one is skipped
/services
uncaught pageerror: Expected @maple/AlertSignalType (the prod error)
no page error
On /services, the "Couldn't load services" panel in both shots is the local dev default (no warehouse running), not part of this change. The difference is the uncaught page error, which only shows in the console log.
The automatic reload cannot be exercised locally, because dev builds have no commit. It gets tested on the preview by stubbing /version.json and firing vite:preloadError.
Scope notes
Edits outside my S1 scope: the mapper signatures now return Option, so I made one- or two-line call-site swaps in apps/web/src/page/alerts/{editor,hub,rule,incident} (the S4 area; it had no changes when I started), page/services/list/subscription.ts, page/overview/subscription.ts and page/settings/update.ts. I also registered the new stream in apps/web/src/subscription.ts and imported it straight from shell/version.ts, leaving shell/index.ts (S3) untouched.
Follow-up for the alerts UI workstream: the alert rule editor does not register isBlockingNavigation, so the app cannot see its unsaved draft. Today closing the tab drops it without a prompt; once it is registered, the stale-build reload respects it too.
…tale tabs reload onto a new build
Electric row mappers decoded literals with decodeUnknownSync inside live-query
callbacks, so a value a newer server added (e.g. a new alert signal type)
threw outside Effect: an uncaught SchemaError on /services and a crash page on
/alerts. Each mapper now decodes its whole document once through a shared
non-throwing liveRowDecoder that returns Option and reports the dropped row.
A lint rule keeps throwing decodes out of web-data collections.
A failed chunk load, or a dropped row, now probes /version.json; when a newer
build is deployed the tab reloads once per deployed commit (chunk failures
always, unreadable rows only while hidden) and otherwise raises the banner.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Live-row decoding now returns optional documents and reports unreadable rows. Alert and API-key consumers use the fallible converters. The shell handles selected stale-build signals by checking the deployed commit and, under specific conditions, reloading hidden tabs.
Changes: Live-row decoding and recovery
Layer / File(s)
Summary
Live-row decoders and collection converters packages/web-data/src/collections/*, scripts/oxlint-plugins/maple.mjs, .oxlintrc.json
Live-row helpers return optional decode results and report failures. Alert and API-key converters add batch conversion. Tests cover unreadable rows, and the Maple lint rule flags synchronous live-row decoding patterns.
Web consumers use fallible converters apps/web/src/page/alerts/editor/derive-rows.ts, apps/web/src/page/alerts/editor/plan.ts, apps/web/src/page/alerts/hub/*, apps/web/src/page/alerts/incident/*, apps/web/src/page/alerts/rule/derive.ts, apps/web/src/page/overview/subscription.ts, apps/web/src/page/services/list/subscription.ts, apps/web/src/page/settings/update.ts
Alert views, subscriptions, and settings use collection converters or handle optional single-row results.
Alert editor unreadable state apps/web/src/page/alerts/editor/{draft,model,steps,view}.ts, apps/web/src/page/alerts/editor/editor.scene.test.ts
The editor distinguishes a missing rule from a rule that cannot be converted. The unreadable state displays a newer-version message and a reload action.
Stale-build signal handling and recovery apps/web/src/shell/version.ts, apps/web/src/shell/version.test.ts, apps/web/src/subscription.ts, packages/web-data/src/lib/chunk-reload*
Chunk-load and undecodable-row signals trigger a debounced deployed-commit probe. Hidden tabs can reload once per newly observed commit when session storage is available. The shell subscription forwards recovery messages.
sequenceDiagram
participant LiveRowDecoder
participant StaleBuildRecovery
participant HttpClient
participant SessionStorage
participant ShellSubscription
LiveRowDecoder->>StaleBuildRecovery: report undecodable row
StaleBuildRecovery->>HttpClient: request deployed commit
HttpClient-->>StaleBuildRecovery: return commit or request failure
StaleBuildRecovery->>SessionStorage: claim reload for newer commit when tab is hidden
StaleBuildRecovery->>ShellSubscription: emit deployed-commit message
Loading
Possibly related PRs
MapleTechLabs/maple#2220: Adds memoized alert selectors that use converters updated in this pull request.
MapleTechLabs/maple#2320: Adds the anomaly overview derivation that this pull request updates to use batch converters.
MapleTechLabs/maple#2318: Adds the anomaly signal contract; this pull request makes row decoding optional for unknown signal values.
Suggested reviewers:jeremyfunk
Merge Risk: Low · previous review 8cf0e
Unreadable synced rows are now dropped instead of crashing. Two edge cases remain: a hidden tab can reload and lose an unsaved rule draft, and blocked browser storage can stop automatic stale-build recovery. Both are limited in scope and can be fixed with small changes.
Pre-merge checks: 5
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The title describes the main changes: dropping unreadable synced rows and recovering stale tabs.
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…nstead of a blank create
An unreadable rule fell through to the missing-rule path, so Save created a
duplicate. The editor now has an Unreadable terminal state that offers a reload.
Also covers the readable group_by path in the rule mapper tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The redeploy of 944a2fd was blocked by the preview cap (9 open PRs carry a preview label), so I tested the live preview at d646dc1. 944a2fd only adds the editor's Unreadable state, and a preview:web preview cannot exercise that because it has no Electric sync. An editor scene test covers it instead.
A separate agent drove the preview with Playwright, signed in as the preview reviewer, and recorded video.
Check
Result
/alerts, /services, /overview, /settings (and the Keys tab) render, no pageerror and no crash page
pass
Alert rule and incident pages
not testable here: no live sync, so /alerts has no rows
vite:preloadError with the same deployed commit
0 reloads, 1 request to version.json
vite:preloadError with a faked newer commit
exactly 1 reload, about 1.6s after the event (the 1s debounce); the guard key is set to the new commit
Same signal again after that reload (loop guard)
0 reloads; the "Maple was updated" banner is shown
StaleBuildProbe spans arrived with their attributes, each with one child GET /version.json:
trigger
newer
reloading
span
GET
chunk_load
false
(not set)
17.5 ms
16.7 ms, 200 (cold)
chunk_load
true
true
2.6 ms
1.4 ms, 200
chunk_load
true
false
1.8 ms
chunk_load
true
false
1.6 ms
Probes: one network request each, no retries, no waterfall. 4 of the 5 probes were exported; the missing one is most likely a span lost to the page unloading for its reload.
Errors: the only error span on pr-2340 is the deliberate test rejection (browser.unhandled_rejection). There are no crash or SchemaError spans.
A visible tab may hold unsaved edits (the rule editor keeps them in page state),
so any stale-build signal there raises the new-build banner at once instead of
reloading; a hidden tab still reloads once per deployed commit.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Note on the preview results above: they were run against d646dc1, where a chunk-load failure also reloaded a visible tab (B2/B4). After review F3, 8cf0e53 limits automatic reloads to hidden tabs, so on the current head those visible-tab cases show the "Maple was updated" banner straight away instead of reloading. The loop guard, the burst debounce and the same-build no-op are unchanged. The preview cap still blocks a redeploy, so this behavior is covered by version.test.ts rather than by a fresh preview run.
A newer build rewriting the rule while its form is open left a stale form
whose save wrote the old values back. Row updates now re-check the rule and
move the editor to its Unreadable state.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Actionable comments posted: 2
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at @apps/web/src/shell/version.ts:
- Line 167: Update staleBuildRecovery’s call to probeStaleBuild so it passes a
storage wrapper whose getItem and setItem methods access sessionStorage only
when called. Ensure those accesses occur inside claimReload’s Effect.try,
allowing blocked storage to follow the existing banner fallback instead of
terminating the recovery stream.
- Around line 110-113: Update the automatic reload flow around claimReload to
check whether the page has unsaved edits before claiming the reload; when edits
are unsaved, skip the claim and reload so the stale-build banner is shown
instead. Preserve the existing hidden-tab and deployed-version checks.
After applying the fix, consider running `coderabbit review --agent` for local
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…s back to the banner
The stale-build reload now also requires that the page holds no unsaved work
(the app's isBlockingUnload contract), and sessionStorage is only touched
inside the reload guard, so a SecurityError from blocked site data can no
longer end the recovery stream.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
BUILT_COMMIT is empty under Vitest, so the test returned before the comparison.
The probe now takes the built commit (defaulting to BUILT_COMMIT).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
🟢 Confidence 10/10 · safe to merge. No defect in the non-throwing row decode or the reload guard; the riskiest part, the once-per-commit reload, is pinned by the new shell tests. no findings · tests covered · risk medium · 2/2 new units observable
Synced rows this build cannot decode now drop and are reported instead of throwing out of live-query callbacks, and a stale tab probes /version.json on a chunk-load failure or dropped row, reloading a hidden tab with no unsaved work at most once per deployed commit. Safe to merge.
liveRowDecoder decodes a whole row to Option, dropping and reporting unreadable rows
rowsTo* helpers filter dropped rules, incidents and API keys at every call site
Chunk-load and undecodable-row signals probe /version.json in a StaleBuildProbe span
A hidden tab with no unsaved work reloads once per deployed commit; blocked storage falls back to the banner
d78026a · What was checked, coverage and telemetry details are on the Maple / review check. Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.
⚠️Something changed after this shipped. Details below.
Deployed to maple-web (pr-2344) at 2026-11-07 14:24 UTC as 116918d, the first version after the merge (the merge commit itself never reported). Compared the 60 minutes before and after.
Maple looks once, an hour after the first deploy that carries the merge.
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Why
On 2026-11-07 a customer tab running build
ef1b44e79fthrew an uncaughtSchemaError: Expected @maple/AlertSignalTypeon /services. The server had started syncing incidents withslo_burn_rate/anomalysignal types (#2296, #2318), and the old build did not know them. The Electric row mappers decoded every literal withdecodeUnknownSyncinside live-query callbacks, so a single unknown value threw outside Effect. On /alerts the same row brings down the whole page. Prod self-traces show the same class of failure forAlertDestinationTypeon 10-31 and 11-01, from builds that predate #2086's fix for that one field.What changed
Unreadable rows are dropped instead of crashing (the whole class, not one field)
packages/web-data/src/collections/live-row.ts:liveRowDecoderdecodes a whole domain document once and returnsOption. It cannot throw, and it reports each dropped row once to listeners.alerts.ts(rules, incidents, destinations) andapi-keys.tshand raw fields to it. The mappers now returnOption, and newrowsTo*helpers skip unreadable rows, so every call site was forced by the compiler to handle the drop. Decoding the whole class also covers the oldnew AlertRuleDocument(...)constructor, which could throw too (for example onwindow_minutes).maple/no-throwing-live-row-decodeforpackages/web-data/src/collections/**bansSchema.decode*Sync/*Promiseandnew *Document(. It reports 19 violations on the oldalerts.ts.investigations.tsanddashboards.tswere already safe and are unchanged.Stale tabs recover after a deploy (
apps/web/src/shell/version.ts)/version.jsonprobe instead of waiting for the 15-minute poll: avite:preloadError(Vite fires it for every failed dynamic import, including the "MIME type text/html" case for a removed chunk), an unhandled chunk-load rejection, or a dropped synced row.isBlockingUnload), and at most once per deployed commit per tab session (a sessionStorage guard, so a cached index.html cannot cause a loop). Blocked storage falls back to the banner. A transient network failure on the same build does nothing. The probe is off in dev builds (BUILT_COMMITis empty).StaleBuildProbespan withmaple.stale_build.{trigger,detail,newer,reloading}attributes.isChunkLoadErroralso matches "Failed to load module script" and "Unable to preload CSS". The unused 60s reload guard inchunk-reload.tsis removed.Verification
packages/web-data: 42 pass, including rows carrying a future signal type, severity, status, comparator, event type, hold reason, key kind, bad timestamp, bad window, bad group_by and bad stored tiers. Each drops only that row, and is reported once.apps/web:src/shellandsrc/page/alerts(472 tests), plus services, overview and settings (708 tests in all), pass. That includesversion.test.ts, which covers reloading once per commit, reloading again for a later deploy, the same build, an unreadableversion.json, blocked storage, and a visible tab (banner, 0 reloads) versus hidden tab.tsrstypecheck passes forweb-dataandapps/web.oxlintpasses with both.oxlintrc.jsonand.oxlintrc.effect.json.alert_incidentsrow withsignal_type = 'a_future_signal'into local Postgres, so Electric synced it, and loaded the pages with origin/main's code and then with this branch.Application crash: SchemaError: Expected @maple/AlertSignalTypepageerror: Expected @maple/AlertSignalType(the prod error)On /services, the "Couldn't load services" panel in both shots is the local dev default (no warehouse running), not part of this change. The difference is the uncaught page error, which only shows in the console log.
The automatic reload cannot be exercised locally, because dev builds have no commit. It gets tested on the preview by stubbing
/version.jsonand firingvite:preloadError.Scope notes
Option, so I made one- or two-line call-site swaps inapps/web/src/page/alerts/{editor,hub,rule,incident}(the S4 area; it had no changes when I started),page/services/list/subscription.ts,page/overview/subscription.tsandpage/settings/update.ts. I also registered the new stream inapps/web/src/subscription.tsand imported it straight fromshell/version.ts, leavingshell/index.ts(S3) untouched.isBlockingNavigation, so the app cannot see its unsaved draft. Today closing the tab drops it without a prompt; once it is registered, the stale-build reload respects it too.🤖 Generated with Claude Code
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