tc-adr

name	tc-adr
description	Use when reading, writing, promoting, or updating an Architecture Decision Record under adrs/, or when adding/editing a finding under bench/findings/. Triggers on requests like "write an ADR for X", "is there an ADR on Y", "what design decisions exist for Z", "promote this ADR to Accepted", "mark this ADR Implemented", "this session contradicts ADR 0007 — update it", "log a finding for this bench round", or whenever a multi-session design decision or post-hoc bench record needs to be captured or revised. Enforces the layered reading order (adrs/README.md -> Current state -> body), the status lifecycle (Exploring → Proposed → Accepted → Implemented, or Superseded), the template at adrs/0000-template.md, the "only write one if a single session would lose meaningful context" gate, the Current state maintenance rule (deviations flow back into the top block, not just Status notes), the trim-on-promotion rule, and the source-of-truth split (ADR = rationale, GitHub = tracked work, code = behaviour). Do NOT use for routine bug fixes or single-session work that doesn't need a written design record, and do NOT use for editing user-facing docs (that is tc-docs-write).
allowed-tools	Read, Edit, Write, Grep, Glob

Working with TcKit ADRs and findings

ADRs live under adrs/ as one Markdown file per decision; the template is at adrs/0000-template.md. Findings live under bench/findings/ as date-prefixed records of bench rounds and post-implementation reviews. Both surfaces share an always-fresh index file and a layered reading discipline.

Reading order (this is the centrepiece)

Always go top-down:

1. Index first. adrs/README.md and bench/findings/README.md. One-line summaries with status. Cheap to load; cheaper than scanning frontmatter of every file.
2. Current state block of any ADR that intersects the task. After frontmatter, before Context. Up to about six lines. This block is canonical: it captures the live decision in its post-implementation form, including any deviations.
3. Body (Context / Decision / Alternatives / Consequences) only when you need rationale or the original framing.
4. Status notes for the change journal, if you need the trail.

If Current state and the Decision section disagree on a question, Current state wins. The Decision section may be a snapshot of how the design was originally proposed; deviations flow back into Current state, not into Decision.

Status lifecycle

Frontmatter status is one of:

• Exploring: investigation is in flight; no specific proposal yet. Use this for "here are the options we've evaluated and what we know about each".
• Proposed: a recommended direction has crystallised and is awaiting review.
• Accepted: the design has been agreed; implementation may not have started.
• Implemented: the PR has landed. Fill in pr: with the GitHub PR number.
• Superseded: abandoned or replaced. Add a Status notes entry explaining why. Set superseded_by: (and where applicable, the replacement's supersedes:). Do not delete the file.

Promote forwards by editing the status field, rewriting Current state to match the new reality, and adding a dated entry to Status notes. Never skip a step silently; if you go straight from Exploring to Implemented, the trail is missing.

When to write a new ADR

Only if a single session would lose meaningful context without it. The test:

• Multi-session design decision? → ADR.
• Routine bug fix? → no ADR; the commit message is enough.
• Single-session refactor with no design crossroads? → no ADR.
• "Future me will need to understand why this is shaped like this"? → ADR.

If you're unsure, prefer not writing one. ADRs are for the decisions that span sessions; the codebase, the PR description, and the commit message cover the rest.

Writing a new ADR

1. Pick the next free number from adrs/. Use four-digit zero-padded (0011, 0012, …).
2. Copy adrs/0000-template.md to adrs/<NNNN>-<slug>.md and fill in the frontmatter (adr, title, status, created, last_reviewed, issue, pr, plus supersedes / superseded_by / related if applicable).
3. Write the Current state block as if the decision is settled now: one or two sentences for the decision, a line for "Where it lives", a list for "Open questions". For an Exploring ADR, the decision line is the live direction; for Proposed/Accepted, the recommended approach; for Implemented, the post-deviation truth.
4. Fill Context, Decision, Alternatives considered, Consequences, and a first Status notes entry dated today.
5. Add a row to adrs/README.md in the same edit. Number, status, title, one-line summary lifted from Current state. The index is the skim surface; it must move with the file.

Updating an existing ADR

The rule that keeps ADRs honest: when a session lands on something that contradicts or extends an ADR, update its Current state block before moving on, in the same edit as the code or follow-on ADR.

• Add a dated entry to Status notes describing what changed.
• Rewrite Current state so the live answer is correct. If the original Decision section no longer matches reality, do not edit the Decision section; that's history. Update Current state instead, and let the Decision/Current state divergence stand as a record.
• Update the adrs/README.md row if the summary changed.
• Update last_reviewed: to today's date.
• If the change reverses the original decision, mark the ADR Superseded, set superseded_by:, and link to the replacement (or the PR that walked it back) in Status notes.

When a PR lands that implements the ADR's decision:

• Set status: Implemented and fill pr:.
• Rewrite Current state to capture the post-deviation truth.
• Trim on promotion. Collapse Alternatives to one short line per option (rejected paths don't earn paragraphs once the decision is locked). Compact Status notes to a single "Implementation outcome" entry plus any later course-corrections; the dated walk-through of intermediate decisions is checkpoint history that git already owns.
• Add a final Status notes entry: YYYY-MM-DD: Implementation outcome. followed by the deviations and lessons that matter going forward.

Writing or updating a finding

Findings are post-hoc records of bench rounds, post-implementation reviews, or any other "what we learned" writeup that an ADR Status notes entry references. They live under bench/findings/ named YYYY-MM-DD-<slug>.md.

Minimal frontmatter:

---
date: YYYY-MM-DD
status: Current   # Current | Superseded | Stale
related_adrs: [N, ...]
superseded_by:    # optional path, e.g. bench/findings/YYYY-MM-DD-...md
---

• A finding starts Current. Mark it Superseded when a later finding or ADR explicitly walks the result back (re-bench round with different numbers, a fix that invalidates the measurement, etc.). Set superseded_by: to the replacement.
• Mark Stale if the finding predates a major change with no explicit successor; the measurements are historical only. Rare.
• Add a row to bench/findings/README.md in the same edit. Newest first. If superseding an earlier finding, also update the "Why Superseded" section with a one-line explanation.

When a finding feeds into an ADR's Current state, the ADR's "Where it lives" line names the finding by relative path. The findings index already exposes the reverse direction via related_adrs.

Source-of-truth split

• adrs/*.md: design rationale (how something should work, why this approach won). Current state is the live answer; Decision is history.
• adrs/README.md: always-fresh skim list.
• bench/findings/*.md: post-hoc records of bench rounds and reviews.
• bench/findings/README.md: always-fresh skim list, status-aware.
• GitHub issues / PRs: tracked work (what is open, what shipped).
• Code: implemented behaviour (the truth on what currently exists).
• CLAUDE.md: cross-session rules and conventions.

If two artefacts try to own the same thing, one is wrong. In particular: don't restate code behaviour in an ADR (link to the file), and don't restate the ADR's rationale in the code (link to the ADR from the PR description, not from the code).

Anti-patterns

• Writing an ADR for a single-session bug fix or refactor. The commit message is the right home.
• Updating Status notes but not Current state when a session reveals a deviation. The next session will then act on a stale top-block.
• Editing the Decision section to "fix" history. Decision is the original framing; deviations live in Current state.
• Setting status: Implemented before the PR has actually merged. Accepted is the right status while the PR is open.
• Promoting to Implemented without trimming Alternatives and compacting Status notes. The bloat compounds across ADRs and makes the index less useful.
• Deleting a Superseded ADR. The history matters; mark it Superseded and leave the file.
• Linking to ADRs from user-facing docs (docs/content/, README, MCP tool descriptions, CLI help). ADRs are internal. See the tc-docs-write skill for the user-facing voice rule.
• Adding a new ADR or finding without updating the corresponding README.md index in the same edit.

Next

After an ADR write or update, return to the calling task (typically the implementation work the ADR describes). No further handoff.