pi-trace

Pi extension that renders a deepseek-harness-style trajectory view for every pi session — timeline gantt chart, turn-grouped ledger, rich detail panel, live SSE streaming.

Install

pi install npm:@demo-0416/pi-trace

Or try without installing:

pi -e npm:@demo-0416/pi-trace

Usage

Once installed, the extension auto-activates on every pi session:

• TUI widget — a stats line appears above the editor: ✻ 3 轮 · LLM 21.7s · 42.9 tok/s · 缓存 96.6% · $0.03
• /trace — open the current session's trajectory in the browser
• /trace pick — pick a historical session from a list

The web UI runs on http://127.0.0.1:<port> (port auto-increments from 43110; written to ~/.pi/agent/traces/.port).

Features

Timeline (Gantt)

• 3 lanes: Input / Model / Tools, with 4 projection modes (sequence, duration, time, actual)
• Scroll to zoom (cursor-anchored), right-drag to pan, drag-select to focus
• TTFT gradient ticks on model spans, turn boundary markers
• Hover crosshair + tooltip, click to focus record

Ledger (Table)

• Turn → group (Message / Step N) → cell hierarchy
• Colored kind tags (USER / ASSISTANT / TOOL / SYSTEM)
• Inline tool result previews, LLM request boundaries with cumulative usage
• Turn + assistant folding, live full-text search

Detail Panel

• User / Assistant: Summary / Preview / Raw / Source tabs — markdown rendering with syntax highlighting, token breakdown, TTFT/generation/throughput timing
• Tool: Summary / Payload / Result / Schema / Timing tabs — JSON tree, tool schema from request
• System: System Prompt / Tools tabs — full prompt snapshot, tool catalog

Data

• Rich collection: thinking blocks, tool calls, request config (temperature/thinking/stop), prompt snapshots, tool schemas, call IDs, input source, reasoning tokens
• Sidecar JSONL persistence (~/.pi/agent/traces/<session-id>.jsonl, 0600 permissions)
• Historical session reconstruction from pi's own session JSONL
• SSE live streaming (partial assistant messages + running tool calls)

Architecture

src/
├── index.ts           # extension entry (activate, widget, /trace commands)
├── collector.ts       # pi event stream → TraceRecord
├── server.ts          # node:http + SSE, serves web UI
├── store.ts           # sidecar JSONL persistence
├── model.ts           # TraceSession / TraceRecord types
├── stats.ts           # stats computation
├── session-loader.ts  # historical session reconstruction
└── web/
    ├── dist/          # pre-built React bundle (self-contained)
    ├── vendor/        # dsh ui-trajectory source (MIT, vendored)
    ├── primitives/    # dsh ui-primitives subset (MIT, vendored)
    ├── adapter.ts     # pi session JSON → dsh layout input
    ├── host.tsx       # React app: state, SSE, session picker
    ├── build.mjs      # esbuild + CSS modules plugin
    └── theme.css      # dsh design tokens (light theme)

The frontend vendors deepseek-harness's ui-trajectory package (MIT) — the same layout engine, timeline, table, and detail panel components, adapted to pi's data model via a thin adapter layer. The backend is pure TypeScript with zero runtime dependencies (pi bundles @earendil-works/pi-tui).

Development

# Backend smoke test (collector, store, server, stats)
npm test

# Frontend e2e test (Playwright, needs cached chromium)
npm run test:e2e

# Rebuild frontend after modifying vendor/ or host.tsx
npm run build:web

License

MIT. See LICENSE. Vendored dsh code retains its original MIT license — see src/web/NOTICE.md.