---
name: tc-tracker
description: Track code changes with structured JSON records, an enforced state machine, and a session handoff format for AI continuity.
---

# TC Tracker

Track every code change with structured JSON records, an enforced state machine, and a session handoff format that lets a new AI session resume work cleanly when a previous one expires.

## Overview

A Technical Change (TC) is a structured record that captures **what** changed, **why** it changed, **who** changed it, **when** it changed, **how it was tested**, and **where work stands** for the next session. Records live as JSON in `docs/TC/` inside the target project, validated against a strict schema and a state machine.

**Use this skill when the user:**
- Asks to "track this change" or wants an audit trail for code modifications
- Wants to hand off in-progress work to a future AI session
- Needs structured release notes that go beyond commit messages
- Onboards an existing project and wants retroactive change documentation
- Asks for `/tc init`, `/tc create`, `/tc update`, `/tc status`, `/tc resume`, or `/tc close`

**Do NOT use this skill when:**
- The user only wants a changelog from git history (use `engineering/changelog-generator`)
- The user only wants to track tech debt items (use `engineering/tech-debt-tracker`)
- The change is trivial (typo, formatting) and won't affect behavior

## Storage Layout

Each project stores TCs at `{project_root}/docs/TC/`:

```
docs/TC/
├── tc_config.json          # Project settings
├── tc_registry.json        # Master index + statistics
├── records/
│   └── TC-001-04-05-26-user-auth/
│       └── tc_record.json  # Source of truth
└── evidence/
    └── TC-001/             # Log snippets, command output, screenshots
```

## TC ID Convention

- **Parent TC:** `TC-NNN-MM-DD-YY-functionality-slug` (e.g., `TC-001-04-05-26-user-authentication`)
- **Sub-TC:** `TC-NNN.A` or `TC-NNN.A.1` (letter = revision, digit = sub-revision)
- `NNN` is sequential, `MM-DD-YY` is the creation date, slug is kebab-case.

## State Machine

```
planned -> in_progress -> implemented -> tested -> deployed
   |            |              |           |          |
   +-> blocked -+              +- in_progress <-------+
        |                          (rework / hotfix)
        +-> planned
```

> See [references/lifecycle.md](references/lifecycle.md) for the full transition table and recovery flows.

## Workflow Commands

The skill ships five Python scripts that perform deterministic, stdlib-only operations on TC records. Each one supports `--help` and `--json`.

### 1. Initialize tracking in a project

```bash
python3 scripts/tc_init.py --project "My Project" --root .
```

Creates `docs/TC/`, `docs/TC/records/`, `docs/TC/evidence/`, `tc_config.json`, and `tc_registry.json`. Idempotent — re-running reports "already initialized" with current stats.

### 2. Create a new TC record

```bash
python3 scripts/tc_create.py \
  --root . \
  --name "user-authentication" \
  --title "Add JWT-based user authentication" \
  --scope feature \
  --priority high \
  --summary "Adds JWT login + middleware" \
  --motivation "Required for protected endpoints"
```

Generates the next sequential TC ID, creates the record directory, writes a fully populated `tc_record.json` (status `planned`, R1 creation revision), and updates the registry.

### 3. Update a TC record

```bash
# Status transition (validated against the state machine)
python3 scripts/tc_update.py --root . --tc-id TC-001-04-05-26-user-auth \
  --set-status in_progress --reason "Starting implementation"

# Add a file
python3 scripts/tc_update.py --root . --tc-id TC-001-04-05-26-user-auth \
  --add-file src/auth.py:created

# Append handoff data
python3 scripts/tc_update.py --root . --tc-id TC-001-04-05-26-user-auth \
  --handoff-progress "JWT middleware wired up" \
  --handoff-next "Write integration tests" \
  --handoff-next "Update README"
```

Every change appends a sequential `R<n>` revision entry, refreshes `updated`, and re-validates against the schema before writing atomically (`.tmp` then rename).

### 4. View status

```bash
# Single TC
python3 scripts/tc_status.py --root . --tc-id TC-001-04-05-26-user-auth

# All TCs (registry summary)
python3 scripts/tc_status.py --root . --all --json
```

### 5. Validate a record or registry

```bash
python3 scripts/tc_validator.py --record docs/TC/records/TC-001-.../tc_record.json
python3 scripts/tc_validator.py --registry docs/TC/tc_registry.json
```

Validator enforces the schema, checks state-machine legality, verifies sequential `R<n>` and `T<n>` IDs, and asserts approval consistency (`approved=true` requires `approved_by` and `approved_date`).

> See [references/tc-schema.md](references/tc-schema.md) for the full schema.

## Slash-Command Dispatcher

The repo ships a `/tc` slash command at `commands/tc.md` that dispatches to these scripts based on subcommand:

| Command | Action |
|---------|--------|
| `/tc init` | Run `tc_init.py` for the current project |
| `/tc create <name>` | Prompt for fields, run `tc_create.py` |
| `/tc update <tc-id>` | Apply user-described changes via `tc_update.py` |
| `/tc status [tc-id]` | Run `tc_status.py` |
| `/tc resume <tc-id>` | Display handoff, archive prior session, start a new one |
| `/tc close <tc-id>` | Transition to `deployed`, set approval |
| `/tc export` | Re-render all derived artifacts |
| `/tc dashboard` | Re-render the registry summary |

The slash command is the user interface; the Python scripts are the engine.

## Session Handoff Format

The handoff block lives at `session_context.handoff` inside each TC and is the single most important field for AI continuity. It contains:

- `progress_summary` — what has been done
- `next_steps` — ordered list of remaining actions
- `blockers` — anything preventing progress
- `key_context` — critical decisions, gotchas, patterns the next bot must know
- `files_in_progress` — files being edited and their state (`editing`, `needs_review`, `partially_done`, `ready`)
- `decisions_made` — architectural decisions with rationale and timestamp

> See [references/handoff-format.md](references/handoff-format.md) for the full structure and fill-out rules.

## Validation Rules (Always Enforced)

1. **State machine** — only valid transitions are allowed.
2. **Sequential IDs** — `revision_history` uses `R1, R2, R3...`; `test_cases` uses `T1, T2, T3...`.
3. **Append-only history** — revision entries are never modified or deleted.
4. **Approval consistency** — `approved=true` requires `approved_by` and `approved_date`.
5. **TC ID format** — must match `TC-NNN-MM-DD-YY-slug`.
6. **Sub-TC ID format** — must match `TC-NNN.A` or `TC-NNN.A.N`.
7. **Atomic writes** — JSON is written to `.tmp` then renamed.
8. **Registry stats** — recomputed on every registry write.

## Non-Blocking Bookkeeping Pattern

TC tracking must NOT interrupt the main workflow.

- **Never stop to update TC records inline.** Keep coding.
- At natural milestones, spawn a background subagent to update the record.
- Surface questions only when genuinely needed ("This work doesn't match any active TC — create one?"), and ask once per session, not per file.
- At session end, write a final handoff block before closing.

## Retroactive Bulk Creation

For onboarding an existing project with undocumented history, build a `retro_changelog.json` (one entry per logical change) and feed it to `tc_create.py` in a loop, or extend the script for batch mode. Group commits by feature, not by file.

## Anti-Patterns

| Anti-pattern | Why it's bad | Do this instead |
|--------------|--------------|-----------------|
| Editing `revision_history` to "fix" a typo | History is append-only — tampering destroys the audit trail | Add a new revision that corrects the field |
| Skipping the state machine ("just set status to deployed") | Bypasses validation and hides skipped phases | Walk through `in_progress -> implemented -> tested -> deployed` |
| Creating one TC per file changed | Fragments related work and explodes the registry | One TC per logical unit (feature, fix, refactor) |
| Updating TC inline between every code edit | Slows the main agent, wastes context | Spawn a background subagent at milestones |
| Marking `approved=true` without `approved_by` | Validator will reject; misleading audit trail | Always set `approved_by` and `approved_date` together |
| Overwriting `tc_record.json` directly with a text editor | Risks corruption mid-write and skips validation | Use `tc_update.py` (atomic write + schema check) |
| Putting secrets in `notes` or evidence | Records are committed to the repo | Reference an env var or external secret store |
| Reusing TC IDs after deletion | Breaks the sequential guarantee and confuses history | Increment forward only — never recycle |
| Letting `next_steps` go stale | Defeats the purpose of handoff | Update on every milestone, even if it's "nothing changed" |

## Cross-References

- `engineering/changelog-generator` — Generates Keep-a-Changelog release notes from Conventional Commits. Pair it with TC tracker: TC for the granular per-change audit trail, changelog for user-facing release notes.
- `engineering/tech-debt-tracker` — For tracking long-lived debt items rather than discrete code changes.
- `engineering/focused-fix` — When a bug fix needs systematic feature-wide repair, run `/focused-fix` first then capture the result as a TC.
- `project-management/decision-log` — Architectural decisions made inside a TC's `decisions_made` block can also be promoted to a project-wide decision log.
- `engineering-team/code-reviewer` — Pre-merge review fits naturally into the `tested -> deployed` transition; capture the reviewer in `approval.approved_by`.

## References in This Skill

- [references/tc-schema.md](references/tc-schema.md) — Full JSON schema for TC records and the registry.
- [references/lifecycle.md](references/lifecycle.md) — State machine, valid transitions, and recovery flows.
- [references/handoff-format.md](references/handoff-format.md) — Session handoff structure and best practices.