# Usage tracking implementation

Implemented deterministic local telemetry.

## Added
- `bin/tool-usage-log`
  - append-only JSONL event writer
- `bin/tool-usage-report`
  - aggregates counts, success rate, avg duration, recent failures
- `extensions/_shared/tool-usage.ts`
  - TS helper for extension-side event logging

## Instrumented
- `extensions/questionnaire.ts`
- `extensions/subagent/index.ts`
- `extensions/session-memory-dispatcher.ts` (`remember-session`)
- `extensions/session-switch/index.ts` (`switch-session`, `resum`)
- `bin/pi-job-start`
- `bin/pi-job-runner`
- `bin/pi-loop`

## Event file
- default: `/home/sebas/runtime/tool-usage/events.jsonl`
- override: `PI_TOOL_USAGE_FILE`

## Status model
- `started`
- `succeeded`
- `failed`
- `cancelled`

## Validation
- shell syntax checks passed for modified bash scripts
- python compile passed for report script
- smoke test passed for log -> report flow

## Known limit
- no full TypeScript typecheck run here because `bun` is not installed on this machine path right now (`bun: command not found`)
- extension telemetry is best-effort and never blocks the main flow