perf(web): avoid repeated terminal metadata scans

[leoisadev1]

Problem

Each sidebar and status-indicator consumer rescanned terminal metadata, rebuilt session wrappers, and resorted IDs. That repeats for every thread that only needs running-subprocess IDs.

Changes

Build one ordered metadata index per immutable snapshot. Reuse unchanged session wrappers and thread groups, with separate environment targets. Attach subscriptions stay as they were.

Adapted from pingdotgg#9747.

Scope

This PR is terminal metadata indexing only.

Covered here:

• perf(web): avoid repeated terminal metadata scans pingdotgg/t3code#9747 avoid repeated terminal metadata scans

Still assigned to this handoff, in later PRs:

• faster Ghostty snapshots (perf(web): speed up terminal snapshots pingdotgg/t3code#9663)
• terminal input (feat(mobile): paste the phone clipboard into the terminal pingdotgg/t3code#9199 fix(web): copy terminal selection with Ctrl+Insert pingdotgg/t3code#8541 fix(web): middle-click pastes in the terminal on Linux pingdotgg/t3code#11018 fix(web): honor terminal link browser overrides pingdotgg/t3code#10060)

Verification

• vp test run apps/web/src/state/terminalSessions.test.ts: 6 passed.
• vp lint on the two files: clean.

Implemented and verified by Grok 4.6 High in Grok Build via Orca.

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1 Skipped Deployment

Project	Deployment	Actions	Updated
akeru-bot-landing	Skipped		Sep 10, 2026 6:26pm UTC

[greptile-apps]

Greptile Summary

The terminal-session derivation changes optimize metadata indexing and memoized environment/thread views while preserving terminal ordering, environment isolation, stable empty results, and structural reuse.

Confidence Score: 5/5

Safe to merge.

There are no outstanding findings.

_{Reviews (2): Last reviewed commit: "Merge branch 'main' into perf/web-termin..." | Re-trigger Greptile}

[leoisadev1]

This is Leo's agent. Independent review of e2355ba: 50 focused selector, terminal-stream, drawer and status tests pass. I have not found a correctness defect in the cache. However, I cannot establish the advertised performance benefit on the current product path: AppSidebarLayout renders BotRosterSidebar; useThreadRunningTerminalIds is used by the retained Sidebar, LegacySidebar and otherwise-unused ThreadRowTrailingStatus; useAttachedTerminalSession is used by ThreadTerminalDrawer, whose component has no production caller found. SettingsFontPreviews imports only its theme helper. Please identify the supported live caller before this is accepted as a performance port. Do not revive legacy UI or expand the feature just to exercise this optimization. This is a reachability/port-fit hold, not a claim that the passing tests prove a current-app speedup.