[juliusmarminge]

Problem

Render audit, lane 4, thread view on a 5.5k-item thread, idle across one providerStatuses push where only providers[].checkedAt, usageLimits.checkedAt and versionAdvisory.checkedAt change: 818 renders in 2 commits. The audit found two causes:

1. ChatView passed the environment's serverConfig.providers to MessagesTimeline as providerStatuses, and MessagesTimeline put it in the TimelineRowCtx shared state. Each push builds a new providers array, so sharedState was rebuilt and every row that reads the context re-rendered: about 14 AssistantTimelineRow/AssistantMessageMeta/AssistantForkButton, 12 TurnFoldTimelineRow, and about 300 tooltips under them. Only subagent rows, subagent notification links and handoff rows use providers.
2. Every ChatMarkdown subscribed to the whole server-config map through usePullRequestLinking. perf(web): markdown replies no longer re-render on reconnects and config pushes #20852 already fixes this with a per-environment linkModeAtom, so this PR does not touch it.

Fix

• providerStatuses is gone from TimelineRowCtx, the MessagesTimeline props, and ChatView, which also drops timelineProviders.
• The leaves that need providers read serverEnvironment.providersValueAtom(environmentId) themselves:
  • EnvironmentSubagentAvatar (subagent group header and SubagentTimelineLink) uses two useAtomValue selectors that return only displayName and iconUrl. Those are strings, so a checkedAt-only push gives Object.is-equal results and the avatar does not re-render.
  • SubagentTimelineTooltip reads the full list. It mounts only while its hover popup is open.
  • Handoff rows go through EnvironmentHandoffRow, which reads the list and renders the existing HandoffRow. ChatView's pending-handoff HandoffRow is unchanged.

No useMemo, useCallback, memo or "use memo" was added.

Why consumers now bail out (compiled output, oxc-transform-react)

These files were compiled with reactCompiler: { reportDiagnostics: true }, the same call reactCompilerCoverage.test.ts makes: MessagesTimeline.tsx, V2LifecycleRow.tsx and ChatView.tsx. All three report 0 diagnostics.

ConversationTimeline builds sharedState (t88) under one guard. That guard used to include $[…] !== providerStatuses. It now reads:

if ($[178] !== activeThreadEnvironmentId || $[179] !== citationThreadRef || … || $[202] !== runs || $[203] !== skills || … || $[211] !== workspaceRoot) {
  t88 = { citationRequest: readyCitationRequest, … };

Nothing in that guard changes on a provider push, so TimelineRowCtx keeps its value and the use(TimelineRowCtx) readers do not re-render.

EnvironmentSubagentAvatar compiles to:

t2 = (providers) => providers?.find((provider) => provider.instanceId === providerInstanceId)?.displayName; // cached on providerInstanceId
const displayName = useAtomValue(providersAtom, t2);

The selector is stable and returns a string. useSyncExternalStore compares that string, so the avatar only re-renders when the name or icon actually changes.

What still renders on a provider push

• ChatView itself, which reads providers for the composer, the model picker and the pending-handoff row.
• Visible handoff rows and open subagent tooltips, which use model names and display names from the full list.
• ChatMarkdown blocks, until perf(web): markdown replies no longer re-render on reconnects and config pushes #20852 lands.

After:

Checks run: MessagesTimeline.test.tsx (88 passed; the handoff test now supplies providers through the atom with RegistryProvider initialValues), the apps/web typecheck, and scoped lint on the changed files.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at d5c5684

Macroscope's review found this PR approvable — This is a contained web performance refactor that removes provider-status updates from the shared timeline context while preserving provider data access where the UI needs it. It introduces no new capability, schema or default change, deployment change, or static-analysis suppression.

^{You can add or adjust custom eligibility rules. Learn more.}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Path: .coderabbit.config.ts
• Review profile: CHILL
• Plan: Team
• Run ID: 2d7a501f-1ca3-4335-9c1a-223edf88295b

📥 Commits

Reviewing files that changed from the base of the PR and between 2fbd431 and d5c5684.

📒 Files selected for processing: 4

• apps/web/src/components/ChatView.tsx
• apps/web/src/components/chat/MessagesTimeline.test.tsx
• apps/web/src/components/chat/MessagesTimeline.tsx
• apps/web/src/components/chat/V2LifecycleRow.tsx

💤 Files with no reviewable changes: 1

• apps/web/src/components/ChatView.tsx

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📝 Walkthrough

Chat timelines no longer receive provider status lists through props. Handoff rows, subagent avatars, and tooltips read provider data from the relevant environment. The timeline props also support optional skills data.

Changes: Chat timeline provider data

Layer / File(s)	Summary
Timeline provider contract and wiring apps/web/src/components/ChatView.tsx, apps/web/src/components/chat/MessagesTimeline.tsx, apps/web/src/components/chat/V2LifecycleRow.tsx	Timeline props and row state no longer carry provider statuses. ChatView and timeline call sites stop passing those statuses.
Environment-scoped handoff and subagent rendering apps/web/src/components/chat/V2LifecycleRow.tsx, apps/web/src/components/chat/MessagesTimeline.tsx, apps/web/src/components/chat/MessagesTimeline.test.tsx	Handoff rows, subagent avatars, and tooltips read provider data from the relevant environment. Handoff tests provide provider data through the environment atom.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Refactor

Suggested reviewers: maria-rcks

Merge Risk: ⚪ Minimal · up to d5c56

This change stops provider-status pushes from re-rendering every timeline row. Provider data is now read at the components that use it. No concrete merge-blocking risk was identified.

Pre-merge checks: 3 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Description check		The description clearly explains the problem, root causes, implementation, remaining renders, and checks performed. However, it omits the required Scope and approval section, does not provide issue or…	Add the required Scope and approval section with the triaged issue or explicit maintainer approval, or explain why this focused fix qualifies for an exemption. Add a Verification section with the observed post-change render result and state…

Passed checks: 3 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the primary performance change: provider-status pushes no longer re-render timeline rows.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description clearly explains the problem, root causes, implementation, remaining renders, and checks performed. However, it omits the required Scope and approval section, does not provide issue or maintainer-approval information, and does not report the post-change render measurement. It also uses ## Fix and Checks run instead of the template headings.

Resolution

Add the required Scope and approval section with the triaged issue or explicit maintainer approval, or explain why this focused fix qualifies for an exemption. Add a Verification section with the observed post-change render result and state any checks that remain incomplete. Use the template headings, and include UI evidence if the changed behavior requires it.

• Fix all pre-merge checks with AI

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• Commit to this branch
• Create a new PR

🧪 Generate unit tests (beta)

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• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[juliusmarminge]

Re-measured in the app (seeded data, same scenario, median of 3):

Measured against main at 489d08a, with this PR's commit cherry-picked onto that same commit (it applies cleanly). The server ran without --watch, and no window had a reconnect.

Scenario: the large thread (Evaluate Markdown Renderer Replacement, 713 messages) sits idle. A second browser session clicks Settings > Providers > Refresh provider status, and I measure a 15 s window. Each refresh delivers 3 to 4 providerStatuses pushes, and both sides got the same number.

scenario	main	this PR
large thread idle across a provider refresh: commits / renders	4 / 1626	4 / 1254
↳ timeline renders	580	41
↳ AssistantTimelineRow / TurnFoldTimelineRow	28 / 24	0 / 0
↳ TooltipTrigger	230	134

The timeline fan-out from props:providerStatuses → TimelineRowCtx is gone. On main every push re-rendered every visible assistant row, its meta, its fork button and every turn fold. With this PR, the only timeline renders left are ChatMarkdown state#8 (one per message) and MessagesTimeline itself.

What still renders:

• In one of the three PR windows, 20 SkillInlineText props:skills renders and a handful of row context renders showed up. That's the first refresh after a server restart, when skills actually change. perf(client): a reconnect snapshot keeps unchanged skills and providers identical #20855 handles skill identity separately.
• Outside the timeline (~1050 per window, same on both sides): sidebar rows (~570), the thread details panel (~220) and the composer (~115) all re-render on each provider push. Those read the provider list or the presentation for other reasons, so they're out of scope here.

Behaviour check: in the "Take Over PR 6315" thread, subagent rows in the timeline still show the provider avatar ("Build layer 1: issue tracker core · Finished"). Hovering it still opens the subagent tooltip with the model and status ("Claude Fable 5.1 · medium · completed 24m 34s"). The lineage panel still lists all six previous agents with their icons.