wtf-implement-task

name	wtf:implement-task
description	This skill should be used when a developer is ready to implement a GitHub Task issue and needs to read the full spec hierarchy (Task + Feature + Epic), explore the codebase, produce a concrete Technical Approach with real file paths, and drive TDD implementation against Gherkin scenarios. Triggers on phrases like "implement task

Implement Task

Pick up an existing Task as a developer. Core value: reads the full spec (Task + Feature + Epic), maps it to the actual codebase, proposes a concrete technical approach, then drives implementation test-first against each Gherkin scenario.

The expected Task issue body structure is defined in @.github/ISSUE_TEMPLATE/TASK.md.

Process

0. GitHub CLI setup

Run steps 1–2 of ../references/gh-setup.md (install check and auth check). Stop if gh is not installed or not authenticated. Extensions are not required for this skill.

Skip this step if invoked from wtf:verify-task or another skill that already ran gh-setup this session.

1. Identify the Task

Ask: "Which Task are you implementing? (issue number)"

Fetch the Task first, extract Feature and Epic numbers from its Context section, then fetch Feature and Epic in parallel:

gh issue view <task_number>    # Gherkin, Contracts, Impacted Areas — also yields feature and epic numbers
# Extract feature and epic numbers, then in parallel:
gh issue view <feature_number> # ACs, user stories
gh issue view <epic_number>    # Goal, context, constraints

2. Lifecycle check

Check whether the task has been designed:

gh issue view <task_number> --json labels --jq '.labels[].name'

If the designed label is absent, warn the user that the task hasn't been designed yet and that the recommended flow is: write-task → design-task → implement-task → verify-task. Then call AskUserQuestion with:

• question: "This task doesn't have a designed label yet. How would you like to proceed?"

• header: "Design check"

• options: [{label: "Design it first", description: "Go back and run wtf:design-task (default)"}, {label: "Skip design", description: "Proceed to implementation anyway"}]

• Design it first → follow the wtf:design-task process, passing the Task number in as context.

• Skip design → proceed.

If the designed label is present, continue silently.

3. Load the technical steering document

Check whether docs/steering/TECH.md exists:

cat docs/steering/TECH.md 2>/dev/null

If the file exists: read it and keep it in context. Use its stack, architecture patterns, key constraints, commands, and ADRs to inform the technical approach and implementation in this session. Do not surface it to the user — just apply it silently.

If the file does not exist, call AskUserQuestion with:

• question: "docs/steering/TECH.md doesn't exist yet. This document captures your stack, architecture patterns, and technical constraints. Would you like to create it now?"

• header: "Tech steering doc missing"

• options: [{label: "Create it now", description: "Run wtf:steer-tech before continuing (recommended)"}, {label: "Skip for this session", description: "Continue without it — technical decisions won't reference project standards"}]

• Create it now → follow the wtf:steer-tech process, then return to this skill and continue from step 4.

• Skip for this session → continue without it.

4. Set up the branch

Before writing any code, set up a dedicated branch for this task (trunk-based development):

git checkout main
git pull --rebase origin main
git checkout -b task/<task-number>-<slug>

Slug generation: Spawn a subagent using the claude-haiku-4-5 model to generate the slug from the task title. Ask for a 2–4 word kebab-case summary restricted to [a-z0-9-] characters (e.g. date-range-filter).

If the branch already exists (resumed work), check it out and rebase on main:

git checkout task/<task-number>-<slug>
git rebase origin/main

Resolve any conflicts before proceeding. Print the branch name.

5. Explore the codebase

Before exploring, identify the test framework setup by reading a sample of existing test files. Record the following in a working scratchpad before proceeding — these govern every test written in step 8:

Field	Value
Test framework	(e.g. Jest, Vitest, pytest, RSpec)
Test file pattern	(e.g. **/*.test.ts, tests/test_*.py)
Import convention	(e.g. import { describe, it } from 'vitest')
Run command	(e.g. npm test, pytest)
Coverage command	(e.g. npm run coverage, pytest --cov)

Use the Agent tool to search the codebase for:

• Files and modules this task will touch
• Existing patterns at the integration point
• Current interfaces that match the contracts defined in the Task
• Existing tests covering adjacent behavior
• Dependencies that must exist first

Also fetch any relevant wiki pages or in-repo glossary docs for this task's Bounded Context. Use these to ensure the implementation and test naming aligns with the team's Ubiquitous Language.

6. Draft the Technical Approach

Produce a concrete Technical Approach with actual file paths (not generic layer names):

• Architecture decisions: which layer owns what, which patterns to follow
• Data flow: how data moves from input to output
• Trade-offs: what alternatives were considered and why this approach was chosen
• Impacted Areas: concrete file paths for Backend, Frontend, Database, APIs

7. Review approach with user

Show the Technical Approach. Then call AskUserQuestion with question: "Does this align with how you'd approach it?", header: "Approach review", and options: [{label: "Yes — looks good, proceed", description: "Continue with implementation"}, {label: "I have constraints to share", description: "I want to adjust the approach first"}, {label: "Suggest an alternative", description: "Let me describe a different approach"}].

Apply changes. Then update the Task issue with the Technical Approach and Impacted Areas.

See references/issue-body-update-pattern.md for the read-merge-write pattern. Use /tmp/updated-task-body.md as the temp file.

gh issue edit <task_number> --body-file /tmp/updated-task-body.md

8. Drive the TDD cycle

For each Gherkin scenario in the Task, work through them in order. Match the project's established test patterns discovered in step 5. Reference the Contracts & Interfaces section for exact request/response shapes.

1. Write the failing test for the scenario.

2. Implement the minimum code to make it pass.

3. Refactor if needed — keep functions under 40 lines, no deep nesting.

4. Gate — run linting and type-checking before committing. Check package.json for lint, typecheck, type-check, or check script keys and run whichever exist:

   # e.g. npm run lint && npm run typecheck
   

5. Commit — create an atomic semantic commit:

   git add <changed files>
   git commit -m "<type>(<scope>): <short description>
   
   Scenario: <scenario name>
   Task: #<task_number>"
   

   Commit type: feat for new behavior, fix for bug fixes, test for test-only changes, refactor for refactors, chore for config/build changes.

6. Do not skip ahead — each scenario is a checkpoint.

9. Verify coverage

Once all scenarios pass, confirm unit test coverage meets the minimum threshold for all new and modified code. Use the threshold specified in docs/steering/QA.md if it exists; default to 80% if the document is absent or does not define a threshold:

# Run the project's coverage command (check package.json scripts)

If coverage is below 80% on any new or modified file, add targeted tests before proceeding. Every public function must have at least one happy-path and one error-path test.

10. Update Test Mapping

Fill the Test Mapping table in the Task issue with concrete file paths:

Gherkin Scenario	Test file	Status
<scenario name>	<test file path:line>	passing

See references/issue-body-update-pattern.md for the read-merge-write pattern. Re-fetch the body (do not reuse the temp file from step 6). Use /tmp/updated-task-body-test-mapping.md as the temp file.

gh issue edit <task_number> --body-file /tmp/updated-task-body-test-mapping.md

Print the updated Task issue URL.

11. Mark implemented and offer to continue

Add the implemented lifecycle label:

gh issue edit <task_number> --add-label "implemented"

Call AskUserQuestion with:

• question: "What's next?"

• header: "Next step"

• options: [{label: "Verify this Task", description: "Run QA against the Gherkin scenarios (recommended next step, default)"}, {label: "Open a pull request", description: "Create a PR for this branch"}, {label: "Implement another Task", description: "Implement another Task for the same Feature"}]

• Verify this Task → follow the wtf:verify-task process, passing the Task number in as context so the user is not asked for it again.

• Open a pull request → follow the wtf:create-pr process, passing the Task number and branch in as context.

• Implement another Task → restart this skill from step 1.