feat: v0.4.0 — Agent Status Line Integration

[moose-lab]

Summary

DevLog v0.4.0 adds Claude Code status bar integration, letting DevLog display real-time cost and activity data in the terminal's status line area. The core challenge was performance: scanning 2000+ JSONL files takes >1s, but the status bar requires <300ms response.

What was done

Part A: Cache Infrastructure

• Added StatsCache interface to src/core/types.ts with today/allTime stats and cache freshness metadata (todayDate for day-change invalidation, timestamp for 5-minute TTL)
• Created src/core/cache.ts (~60 lines): atomic write via .tmp + rename, isCacheFresh() with day-change detection, updateCacheFromStats() helper to populate cache from full scans
• Created src/core/fast-discovery.ts (~70 lines): uses fs.stat() mtime to skip files not modified today, then calls existing scanSession() only on today's files — reduces scan set from 2000+ to ~10-50 files
• Hooked dashboard.ts and stats.ts to call updateCacheFromStats() as a side effect of their full scans (piggyback caching)

Part B: The statusline Command

• Created src/commands/statusline.ts (~100 lines):
  • Reads stdin via Promise.race with 50ms timeout (Claude Code pipes session JSON)
  • Cache-first: if fresh cache exists, outputs immediately
  • Falls back to fast-discovery for today stats when cache is stale
  • Outputs plain text only (no ANSI/chalk — Claude Code handles styling)
  • Format: $2.10 this session · $12.34 today (7 sessions) · $2,906 total
• Registered statusline command in cli.ts with --no-cache option

Part C: Setup Automation

• Created src/commands/setup-statusline.ts (~55 lines):
  • Auto-detects devlog binary path via which
  • Reads and merges ~/.claude/settings.json (preserving existing settings)
  • Sets statusLine: { type: "command", command: "devlog statusline" }
  • Warms the cache with a full discovery scan on first setup
• Registered setup-statusline command in cli.ts

Part D: Polish

• Exported cache.ts and fast-discovery.ts from src/index.ts
• Added "Agent Integration" section to help text
• Version bumped to 0.4.0 across cli.ts, dashboard.ts, package.json

Performance Results

Mode	Time
Cached (hot)	~200ms
Fast-discovery (today only)	~300-500ms
Full scan (2688 sessions)	>1s

Files Changed

File	Action	Lines
src/core/types.ts	Modified	+20 (StatsCache interface)
src/core/cache.ts	New	~60 lines
src/core/fast-discovery.ts	New	~70 lines
src/commands/statusline.ts	New	~100 lines
src/commands/setup-statusline.ts	New	~55 lines
src/commands/dashboard.ts	Modified	+2 lines
src/commands/stats.ts	Modified	+6 lines
src/cli.ts	Modified	+36 lines
src/index.ts	Modified	+2 lines
package.json	Modified	version bump

Test Plan

• npx tsup builds without errors
• npx tsc --noEmit type-checks clean
• devlog statusline outputs plain text status line (standalone mode)
• echo '{"costUSD": 0.5}' | devlog statusline outputs with session data from stdin
• devlog statusline --no-cache forces fresh scan
• devlog dashboard still works, cache gets updated
• devlog --version shows 0.4.0
• devlog --help shows Agent Integration section
• Performance: time devlog statusline ~200ms (cached)

🤖 Generated with Claude Code