sync-architecture

Sync Architecture (post-implementation)

Keep docs/architecture/* and the domain docs live by detecting, from a completed task's diff, what the change introduced that the docs haven't caught up with — then proposing the exact doc deltas. It runs in the same post-implementation phase as ../review-implementation/SKILL.md, but asks a different question:

review-implementation asks "is this diff good code?" — this skill asks "does this diff introduce anything the docs don't yet know about?" The first is code debt; this is documentation drift.

It is the automated detection half of the manual /update-architecture workflow. Where /update-architecture is a heavy, human-invoked pass (and also runs the improve-codebase-architecture deepening loop), this skill is a lightweight detector that runs automatically after each task so the docs stop silently drifting. It reuses /update-architecture's routing table — it does not invent its own.

Silence is the default output. A task that introduced nothing doc-worthy (a bug fix, styling, a trivial CRUD following existing patterns) produces no deltas — that is the normal case. A finding survives only if the docs are genuinely now wrong or incomplete. Never invent doc churn to look thorough.

ALWAYS check .ab-method/structure/index.yaml FIRST for where the architecture and domain docs live — paths are user-configurable. Sweep only what this task changed — the cohesive diff across its missions (git diff for the commit range) plus its progress-tracker.md mission summaries. This is not a whole-repo doc audit.

Process

1. Gather diff + context

• The changed files and their git diff for the task's commit range.
• The task's progress-tracker.md Mission Summaries — the per-mission Files / Built / Integrates with bullets already enumerate most of what's new.
• The current architecture + domain docs, so the detector proposes only what's genuinely missing (skip files that don't exist): docs/architecture/tech-stack.md, frontend-patterns.md, backend-patterns.md, UBIQUITOUS_LANGUAGE.md, CONTEXT.md, docs/adr/.

2. Spin up ONE read-only detector subagent

Spawn a single subagent — architecture-sync — with the diff, the mission summaries, and the current docs. It is read-only: it returns a routed findings list (often empty) and edits nothing. Isolating it keeps the doc analysis out of the orchestrator's context. On Codex (spawn_agent is one level deep) spawn it at the orchestrator's own level; on Claude it may nest. One detector is enough — the whole point is a single sweep of the change.

Its brief — detect only what the docs don't already capture, routed with /update-architecture's table:

For each finding return: What (the concrete thing the diff introduced, citing the file/mission), Doc (the exact target file + section), Proposed delta (the append-only line or short section to add), Class (see Step 3).

Example: "New endpoint POST /charges (src/api/charges.ts, mission 2) — not in tech-stack.md Entry Points. Proposed delta: add POST /charges — create a charge (auth: bearer) under Entry Points. Class: safe-add."

Out of scope — do not raise: code-quality issues (that's review-implementation), whole-repo deepening opportunities (that's /improve-codebase-architecture), or rewrites of existing prose. With nothing the docs are missing, return exactly: Docs in sync — no architecture updates needed.

3. Classify each finding

• safe-add — an append-only addition that follows /update-architecture's "add, don't rewrite" rule: a new Entry Points line, a new dependency, a new pattern subsection, a new glossary term. Purely additive, no existing prose touched.
• needs-judgment — anything that would change or deprecate existing prose (a pattern was swapped, a term's meaning shifted, an endpoint convention moved), a new bounded context, or an ADR candidate. These reshape the docs and belong to a human — route them to /domain-model (domain / ADR) or /update-architecture (prose deprecation), don't apply them here.

4. Act — by mode

Interactive (manual create-task tail, or standalone): present the proposed deltas grouped by target doc, each marked safe-add / needs-judgment. Apply the safe-adds the user approves; for needs-judgment findings, point at the right workflow (/domain-model, /update-architecture) rather than editing. Report what landed.

Autonomous (start-task / start-roadmap — afk): the orchestrator (not the detector) applies:

1. Apply every safe-add to its target doc — append-only, preserving format and tone, with a ### Recent Updates (YYYY-MM-DD) block for a notable shift (per /update-architecture Step 3). Docs are prose, not code, so there is no test to re-run — but never rewrite or delete existing content; if a finding can't be expressed as a pure addition, it isn't a safe-add — leave it open.
2. Commit the doc additions as one docs(<task>): sync architecture docs (repo convention). Nothing to add → no commit.
3. Leave every needs-judgment finding for the user — record them in the task's review.md (the review-implementation skill's file, if it ran) under an Architecture sync heading, or in a short note in the run report. Never write an ADR and never deprecate prose autonomously — those need /domain-model / /update-architecture.

Never prompt in autonomous mode — anything that isn't a pure safe-add stays open for the user.

Key Principles

• Documentation drift, not code quality — a distinct lens from review-implementation; the two run side by side in the post-impl phase.
• Detection half of /update-architecture — reuses its routing table (2a–2e) and its "add, don't rewrite" rule; the full manual workflow still owns prose deprecation + the deepening loop.
• Silent by default — most tasks introduce nothing doc-worthy; produce no deltas then.
• Autonomous stays conservative — append-only safe-adds only; domain reshapes and ADRs are always deferred to a human, so the docs never fill with noise.
• Scoped to the task's diff — never a whole-repo doc audit.

Remember

• Check .ab-method/structure/index.yaml for paths.
• The task's mission summaries already list Files / Built — start there, confirm against the diff.
• Always check Entry Points for API drift, even when the diff didn't obviously touch routing — the most common stale-doc victim (inherited from /update-architecture).
• Defer anything that rewrites prose, reshapes the domain, or is ADR-worthy to /domain-model / /update-architecture — this skill only adds.