Impl Tracking

# Implementation Tracking

## Core Principle: Track Everything, Especially Failures

Implementation tracking documents are **living records** that agents read and update every session. They serve as persistent memory across iterations, preventing duplicate work and preserving hard-won knowledge about what works and what does not.

The most valuable information in an implementation tracking document is not what succeeded — it is **what failed and why**. Dead ends documented today prevent agents from wasting hours retrying the same failed approaches tomorrow.

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## Why Implementation Tracking Matters

| Purpose | What It Prevents |
|---------|-----------------|
| **Cross-iteration continuity** | Agents starting from scratch every session |
| **Dead end prevention** | Agents retrying approaches that already failed |
| **Progress visibility** | Humans not knowing what was done or what is left |
| **Test health awareness** | Agents not knowing current test state |
| **Issue tracking** | Known issues being forgotten between sessions |
| **File change tracking** | Uncertainty about what files were created or modified |

Without implementation tracking, every agent session begins with expensive rediscovery. With it, agents resume exactly where the last session left off.

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## Full Implementation Tracking Document Template

Use this template for every implementation tracking document:

```markdown
# Implementation Tracking: {Domain or Scope}

## Status: {IN_PROGRESS | COMPLETE | BLOCKED}

**Last Updated:** {Date}
**Current Phase:** {Spec | Plan | Implement | Iterate | Monitor}
**Blocking Issues:** {None | Brief description of blockers}

---

## Task Status

| Task ID | Task | Status | Notes |
|---------|------|--------|-------|
| T-1 | {Task description} | DONE | {Completion notes} |
| T-2 | {Task description} | DONE | {Completion notes} |
| T-3 | {Task description} | IN_PROGRESS | {Current state, what remains} |
| T-4 | {Task description} | BLOCKED | {What is blocking, dependency} |
| T-5 | {Task description} | NOT_STARTED | {Prerequisites} |

### Task Dependencies
- T-4 blockedBy T-3 (needs auth module before API integration)
- T-5 blockedBy T-3, T-4

---

## Files Created

| File | Purpose | Spec Reference |
|------|---------|---------------|
| `src/auth/login.{ext}` | Login handler | spec-auth.md R1 |
| `src/auth/session.{ext}` | Session management | spec-auth.md R2 |
| `tests/auth/login.test.{ext}` | Login unit tests | spec-auth.md R1 AC1-3 |

## Files Modified

| File | Change | Reason |
|------|--------|--------|
| `src/app.{ext}` | Added auth middleware | spec-auth.md R3 |
| `src/config.{ext}` | Added session config | spec-auth.md R2 |

---

## Issues & TODOs

- [ ] **Issue:** Session expiry not tested under concurrent access — need load test
- [ ] **TODO:** Add rate limiting to login endpoint (spec-api.md R7)
- [ ] **TODO:** Implement password reset flow (spec-auth.md R4, NOT_STARTED)
- [x] **Resolved:** TypeScript compilation error in session.ts — fixed incorrect import path

---

## Dead Ends & Failed Approaches

### DE-1: JWT with asymmetric keys for session tokens
**What was attempted:** Implemented RS256 JWT tokens with public/private key pair.
**Root cause of failure:** Key rotation complexity exceeded the session management requirements. Added 200+ lines of key management code for no user-visible benefit. Symmetric HS256 with server-side session store is simpler and meets all spec criteria.
**Verdict:** Do not reattempt. Use symmetri