Spec Impl

/spec-impl — Implementer of approved specs

Session context

Current repository state: !git status --short

Current branch: !git branch --show-current

Specs available in this folder: !ls specs/ 2>/dev/null || echo "The specs/ folder does not exist"

Branch-creation config: !cat specs/.spec-config.yml 2>/dev/null || echo "AutoCreateBranch: true (default, no config file)"

Instructions

Follow these four phases in strict order. Do not advance to the next phase if the previous one did not complete correctly.

Phase 1 — Identify the spec

The received argument is: $ARGUMENTS

If $ARGUMENTS is empty:

• List the files available in specs/ (you already have them above).
• Ask the user to specify the exact name of the spec.
• Stop and wait for an answer. Do not continue.

If $ARGUMENTS has a value:

• Look for the file in specs/. The user may have written the full name (01-mvp-arkanoid), only the number (01), or only the slug (mvp-arkanoid). Try to find the correct file in any of those cases.
• If you do not find the file, show the available specs and ask the user to correct the name.
• If you do find it, continue to Phase 2.

Phase 2 — Validate the spec's state

Read the spec file you located in Phase 1 using the Read tool or cat.

In the file's contents, look for the line that contains the spec's state. The header label is typically **Status:** (English) or **Estado:** (Spanish), but it may use any language. Match by position (status line near the top of the spec) and by the surrounding state machine, not by the exact label.

Absolute rule: You can only continue if the state means "Approved" — regardless of the language used.

Treat any of the following (and their equivalents in other languages) as the Approved state and continue:

• English: Approved
• Spanish: Aprobado
• Portuguese: Aprovado
• French: Approuvé
• German: Genehmigt
• Italian: Approvato
• …or any other language's word that clearly means "approved"

Anything else (Draft / Borrador, In review / En revisión, Implemented / Implementado, Obsolete / Obsoleto, or any unrecognized value) means stop and show the error message below.

If you are unsure whether a value means "approved", do not assume. Stop and ask the user to clarify or to update the spec to the canonical wording.

Standard error message when the state does not mean Approved:

❌ I cannot implement this spec.

Current state: [STATE FOUND]
I only work with specs whose state means "Approved" (e.g. `Approved`, `Aprobado`,
or the equivalent in another language).

To continue you have two options:
  1. If the spec is ready to be implemented, open it and change the state
     to "Approved" (or the equivalent term your team uses) manually.
     That change is made by the human, not the agent.
  2. If the spec still needs work, use /spec [name] to resume it.

Do not offer alternatives, do not suggest "I can still start if you want". The block is intentional.

Phase 3 — Create the git branch and switch to it

Once you have confirmed the state means Approved:

1. Check the working tree first. Look at the git status --short output in the session context above. If it is not empty, stop and show the pending changes, then ask:

   ⚠️ There are uncommitted changes in the working tree.
   Switching branches would carry them over. What do you want to do?
     1. Commit or stash them yourself, then re-run this command  (recommended)
     2. Continue anyway — the changes travel to the new branch

Wait for the answer. Do not stash or commit on the user's behalf unless they explicitly ask for it. If the working tree is clean, skip straight to step 1 without mentioning it.

1. Derive the branch name from the spec file's full name, without the extension. Format: spec-NN-slug. Examples:

• 01-mvp-arkanoid.md → branch spec-01-mvp-arkanoid
• 02-powerups.md → branch spec-02-powerups

1. Read the AutoCreateBranch flag from the Branch-creation config shown in the session context above.

• If the config file does not exist, the value is missing, or the value is unrecognized → treat it as true (the default).
• Only an explicit false (in any capitalization) disables automatic branch creation.

If `AutoCreateBranch` is `true` (default): proceed without asking.

• If the branch does not exist: create it with git checkout -b spec-NN-slug.
• If it already exists: this means previous work is being resumed. Switch to it, read git log --oneline on the branch, and tell the user which steps of the plan already look done and which step you propose to resume from. Wait for confirmation on the resume point before implementing anything.
• In both cases: switch to the branch with git checkout spec-NN-slug and confirm the change was successful before continuing.

If `AutoCreateBranch` is `false`: ask before touching git. Show:

   AutoCreateBranch is set to false.
   Create and switch to the branch spec-NN-slug? [y/N]

• If the user answers yes: create/switch to the branch exactly as in the true case above.
• If the user answers no or leaves it empty: do not create any branch. Tell the user you will implement on the current branch (the one shown in the session context above) and ask for explicit confirmation to continue there. Do not improvise — wait for the answer.

1. Visually confirm to the user the spec is ready and which branch is active:

   ✅ Ready to implement.

   Spec:   specs/NN-slug.md
   Branch: spec-NN-slug  (active)   (← or the current branch, if no new branch was created)
   State:  Approved   (← echo back the actual value found in the spec)

1. Do not start implementing yet. First show the spec summary to the user so they have it fresh. Extract and show:

• The objective (the line after **Objective:** / **Objetivo:** / equivalent label).
• The scope (the ## Scope / ## Alcance / equivalent section).
• The implementation plan (the section with the numbered steps — ## Implementation plan / ## Plan de implementación / equivalent).
• The acceptance criteria (the checklist — ## Acceptance criteria / ## Criterios de aceptación / equivalent).

Match section headings by meaning, not by exact wording — the spec may be authored in any language.

Phase 4 — Implement step by step

After showing the spec summary, tell the user: