Legacy repository adoption

Adopt A2C into an existing git repository — brownfield, not greenfield.

Most software that can benefit from A2C already exists. Use a2c migrate plus the legacy-adoption prompt for AI-guided, bounded batches (inventory → scaffold → anchoring ADRs → merge → verify).

Prompt asset: pathname:///a2c-assets/prompts/bootstrap/legacy-adoption.md. Decision record: ADR-0018.

Human in the loop

Tools never block migration. a2c migrate is deliberately cautious:

• Summarizes phase, next batch, and anchoring readiness on every call (except --status)
• Warns when readiness is Partial or Weak
• Asks “Are you sure you want to continue?” on a TTY (including --complete-batch)
• Non-interactive: warnings on stderr only

You always decide. Prefer annoying prompts over silent design drift.

When to use

Situation	Start with
Legacy repo, no A2C yet	a2c migrate --path . (inventory-first)
You already ran a2c bootstrap	a2c migrate --entry-path bootstrap-first --path .
Pure docs repo	a2c migrate --tier docs-only --path .
Software repo (default depth)	a2c migrate --tier workflow-lite --path .
Start migration over	a2c migrate --reset --path . (type reset)
Refresh readiness after new context	a2c migrate --reassess --path .

a2c migrate works before A2C root markers exist. It writes .a2c/migration.yaml and seeds the prompt at planning/migration/legacy-adoption.md when method assets are discoverable.

Migration context: inputs/

Before anchoring ADRs, place legacy context in inputs/ (design notes, wiki exports, interview notes, old READMEs). This folder is migration-only:

• AI reads it during inventory and anchoring batches
• It is not part of the long-term repo contract
• It must not be committed — batch 06 adds inputs/ to .gitignore

If some inputs/ material should live in the repo permanently, use batch 05 with inputs-intake.md after anchoring.

Anchoring ADRs and readiness

Legacy code often encodes decisions that were never written down. Batch 02 creates anchoring ADRs — Accepted, retrospective records grounded in code, in-repo docs, and inputs/.

When inventory finds explicit architecture-significant requirements (or docs/asr/ already exists), plan or record ASRs under docs/asr/ (ADR-0019). a2c migrate reports asrs= in legacy signals; a2c list asrs and a2c doctor cover ASR status including Amended.

Batch 00 produces:

• anchoring-plan.md — candidates and evidence pointers
• anchoring-readiness.md — verdict (Strong / Partial / Weak), coverage matrix, gaps, ways forward

Iterate: add inputs/ → a2c migrate --reassess → AI batch-migrate-00r → a2c migrate to review warnings → proceed when you are satisfied.

Phase reports

After each batch, the AI writes planning/migration/phase-NN-report.md (00 … 06) before you run --complete-batch. Open the folder to see where you are in the migration.

Workflow

1. Start — a2c migrate --path . (confirm on TTY).
2. Optional: add legacy context under inputs/.
3. Batch 00 in Cursor — inventory, plans, anchoring-readiness (no commits):

@planning/migration/legacy-adoption.md
Start batch-migrate-00: inventory this repository and write anchoring-readiness.md.

4. Record progress — a2c migrate --complete-batch batch-migrate-00 --path . (confirms again).
5. Batches 01–06 — one logical concern per commit; phase report each time.
6. a2c doctor — migration phase and readiness verdict (informational).

Check status without prompts: a2c migrate --status --path .

Batches (summary)

Batch	Purpose
batch-migrate-00	Inventory, plans, anchoring-readiness.md, phase-00-report.md
batch-migrate-00r	Reassess readiness only (after --reassess)
batch-migrate-01	a2c bootstrap / init
batch-migrate-02	Anchoring ADRs
batch-migrate-03	Governance merge
batch-migrate-04	Tooling merge
batch-migrate-05	Optional canonical inputs/ intake
batch-migrate-06	Hygiene and completion

Full contract: legacy-adoption prompt.

Related

• reuse.md — greenfield adoption checklist
• inputs-intake.md — canonicalizing drafts into the repo
• cli.md — a2c migrate flags