tc-tracker – Coding skill for AI agents

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

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

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

# 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

# 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

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

… (full content is in the download package)