ark-extract-spec

name	ark-extract-spec
description	Extract a feature SPEC from an existing codebase for brownfield Ark adoption. Produces specs/features/<slug>/SPEC.md without faking a deep-tier task. Use when the project already implements the feature and Ark needs a SPEC to reference.

ark-extract-spec <feature-name> [hint]

Author a feature SPEC for an existing implementation, then register it in the features INDEX with a provenance CHANGELOG entry. Use when the project already ships the feature (an OS kernel with copy-on-write, a webapp with auth) and Ark needs a SPEC to reference, but no deep-tier task ever produced one.

Structural mutation (write SPEC, upsert INDEX) is owned by ark agent spec import. Discovery, confirmation, and synthesis are yours.

Parse arguments: first token is <feature-name> (slugified for the SPEC dir); remainder is an optional hint to scope the search.

Preconditions

• .ark/ is initialized.
• .ark/specs/features/<slug>/SPEC.md does not already exist. If it does, stop and tell the user to amend via a deep-tier task instead — extraction is an initial SPEC operation.
• Project is a git repo (extraction stamps the current HEAD short-SHA into the SPEC's CHANGELOG as provenance).

Phase 1 — Discover

Slugify <feature-name> (lowercase, hyphen-separated, ASCII).

Sweep three sources in parallel:

1. Code — grep for symbol/file/comment matches across the source tree. Try snake / kebab / camel / Pascal variants of the feature name.
2. Docs — search docs/, top-level README*, CHANGELOG*, *.md for prose mentions.
3. Git history — git log --grep="<term>" for introducing/major commits; git log -S<symbol> for symbol introduction; pick 3–5 anchor commits.

Build a candidate set: ranked list of files, symbols, doc sections, and key commits. Do NOT synthesize a SPEC yet — discovery alone overweights "what's in the code" relative to "what the feature is."

Phase 2 — Confirm

Present the candidate set to the user. Ask them to:

1. Trim false positives (a find matching by filename but unrelated implementation).
2. Add anything missed (key files / symbols / commits the sweep didn't surface).
3. Supply a one-line intent describing what the feature is for — the why / observable contract, not the implementation. This is the hardest thing to recover from code alone, and it's what differentiates a SPEC from reference docs.

Do NOT proceed without explicit user confirmation. The confirm gate is mandatory; brownfield extraction without it reliably produces SPECs that describe the codebase rather than the feature.

Phase 3 — Synthesize

Read every confirmed source in full. Then author the SPEC body in the feature-SPEC template's shape:

• [**Goals**] — verb-led, ≤80 chars, the what (capability-oriented). Soft cap 5.
• [**Non-goals**] — only when a reader would assume it's in scope. Soft cap 3.
• [**Architecture**] — module / file layout with a one-line note per file. Tree or diagram, no prose narration.
• [**Data Structure**] — public types, fields + types + a one-line comment when meaning is non-obvious.
• [**API Surface**] — public function signatures + one-line semantics. No bodies.
• [**Constraints**] — one declarative sentence each, ≤120 chars. Cite the source of truth (constant / test / file path) when one exists.

Discipline:

• Do NOT fabricate non-goals or constraints. If evidence is thin, leave the section terse or omit it.
• Do NOT add a [**CHANGELOG**] section — spec import stamps the provenance entry.
• The SPEC describes what was built, not how the extraction happened. Process metadata belongs nowhere in the body.

Write the body to a tempfile (.ark/.extract-spec-<slug>.md or any path the skill can clean up).

Phase 4 — Import

SHA=$(git rev-parse --short HEAD)
ark agent spec import \
    --feature "<slug>" \
    --scope "<one-line intent from Phase 2>" \
    --from-file ".ark/.extract-spec-<slug>.md" \
    --from-commit "$SHA"

The CLI:

1. Validates --feature / --scope / --from-commit (no |, \n, \r; non-empty).
2. Refuses if .ark/specs/features/<slug>/SPEC.md already exists.
3. Reads the body, splices a [**CHANGELOG**] entry: - `YYYY-MM-DD` `extracted`: initial extraction from codebase at `<short-sha>`.
4. Writes .ark/specs/features/<slug>/SPEC.md.
5. Upserts a row in .ark/specs/features/INDEX.md with from-task = "extracted" (sentinel; same managed block as deep-tier promotion uses).
6. Prints a one-line summary.

Clean up the tempfile.

Phase 5 — Hand off

Tell the user:

Review .ark/specs/features/<slug>/SPEC.md. The extracted SPEC is not part of an Ark task — when satisfied, stage it (git add .ark/specs/) and commit it manually. Future deep-tier work that touches this feature will amend the SPEC through the normal flow.

Do NOT commit on the user's behalf — the SPEC is a deliberate artifact and the user owns the commit.

Failure Modes

Code	Cause	Recovery
SpecAlreadyExists	.ark/specs/features/<slug>/SPEC.md exists	Use a different slug, or amend via a deep-tier task; do not pass --force.
InvalidSpecField	--feature / --scope empty or contains |, \n, \r	Sanitize the input and retry.
Io	--from-file missing	Re-author the body file; re-run import.

See Also

• workflow.md §6 (Specs) — the feature-spec layer extraction is feeding into.
• ark-design --deep — the path for new features; produces a SPEC by promotion, not import.
• ark agent spec import --help — the CLI surface this skill drives.