Reduce background Git ref and port polling

[Quicksaver]

Summary

Reduce persistent background work from Git ref enumeration and preview port discovery while preserving freshness when users interact with either surface.

What Changed

• Revalidate only the first Git-ref page every 20 seconds instead of polling every retained page every five seconds
• Load cursor pages once per connected generation and expire inactive ref atoms after 30 seconds
• Refresh local and remote refs immediately when the composer branch or Diff comparison menu opens
• Replay the latest preview-discovery snapshot instead of running a duplicate subscription scan
• Serialize snapshot replay with concurrent broadcasts so subscribers cannot regress to stale results
• Scan immediately when managed terminal process sets change and ignore unchanged registrations or redundant removals
• Run the broad port-discovery safety net every 20 seconds while idle and every 10 seconds when a listener is known

Why

During extended use, T3 Code's resident memory climbed past 6 GB even while idle, while the renderer sustained roughly 10% CPU and the machine became noticeably warm around the CPU and GPU clusters. That pattern indicated that background work was continuing without user interaction and could compound renderer and resource pressure over long sessions.

Diagnostics identified two repeatable sources of idle churn: every retained Git-ref query, including each loaded pagination page, owned its own five-second listRefs revalidation loop, while preview discovery launched a broad lsof scan every three seconds. Preview subscription initialization could also scan twice, and unchanged terminal process registrations caused redundant probes. The new schedules reduce that steady subprocess load while immediate menu refreshes, terminal-process-triggered scans, and adaptive safety-net polling preserve freshness at interaction time.

Validation

• Port scanner focused suite passed with 6 tests, including concurrent replay ordering
• Targeted server and client-runtime type checks passed
• Isolated authenticated web verification loaded local, worktree, and remote refs when the branch selector opened
• git diff --check passed

Proof

No standalone proof artifacts were captured; the isolated browser verification is summarized above.

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Note

Medium Risk
Touches live preview discovery and Git ref caching/subscription behavior; incorrect ordering or stale snapshots could affect port lists or ref pickers, though serialization and explicit menu refresh mitigate the main regressions.

Overview
Reduces idle background work from Git ref listing and preview port discovery while keeping lists fresh when users open branch/ref UI.

Git refs (vcs.ts) — First-page ref atoms revalidate every 20s (was 5s); paginated cursor pages refresh once per connection instead of on a timer. Inactive ref atoms expire after 30s (was 5 minutes).

Preview ports (PortScanner.ts, ws.ts) — Replaces a fixed 3s lsof/probe loop with 10s when a listener is known and 20s when idle. New WebSocket subscribers replay the latest snapshot under a semaphore instead of calling scan() again; terminal PID register/unregister triggers an immediate scan only when the process set actually changes.

UI (DiffPanel.tsx) — Opening the branch comparison combobox calls refresh() on local and remote ref queries so menus do not wait on the slower background interval.

Adds BRANCH_DETAILS.md and PortScanner tests for snapshot replay, ordered delivery under concurrency, and skipped probes on duplicate registrations.

^{Reviewed by Cursor Bugbot for commit 5b816e5. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Reduce background Git ref and port polling frequency

• Increases Git ref revalidation interval from 5s to 20s and sets idle atom TTL to 30s; paginated/cursor pages are now one-shot fetches with no periodic revalidation (vcs.ts)
• Replaces the fixed 3s port scan loop with an adaptive loop sleeping 10s when active and 20s when idle or no servers are known (PortScanner.ts)
• Serializes snapshot broadcasts and subscriber replay via a Semaphore, preventing out-of-order delivery and stale replays after newer scans
• Skips polling when terminal registrations or unregistrations are unchanged, triggering immediate scans only on actual changes
• Opening the comparison-ref menu in DiffPanel now triggers an immediate refresh of local and remote branch refs

^{Macroscope summarized 5b816e5.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR significantly modifies polling intervals and subscription notification mechanics, changing how data freshness is managed throughout the application. The new semaphore-based serialization and state-dependent polling represent meaningful behavioral changes that warrant human review.

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