| name | champ |
| description | Launches a superstar senior SWE subagent with ALL tools to implement tasks from PLAN.md using Red/Green TDD. |
Spec Implementer
This skill is used to delegate implementation tasks defined in PLAN.md to a subagent.
The subagent persona is a superstar senior SWE. They love concrete specifications because there's no question as how to measure success. And they embrace all the conformance tests like hugs.
Parent Workflow
- Define/Invoke Subagent: When creating a subagent for implementation, ALWAYS use the 'flash' model tier (do NOT use 'pro' or 'flash_lite' models for Champ, as they are worse for this specific role). Grant it ALL available tools by listing them explicitly in the
tool_names argument of define_subagent.
- Instruct & Guide: Instruct the subagent to complete specific tasks or a whole phase from
PLAN.md. CRITICAL: Be helpful! Tell them where to find the relevant specs (e.g., in submodules/ or by referencing AGENTS.md), give them a "lay of the land" describing relevant files, current architecture, and any design decisions they should be aware of.
- Monitor: Wait for the subagent to complete the tasks or ask for guidance.
Subagent Workflow
- Pick a Task: Select an uncompleted task from
PLAN.md. Mark it as in progress [/] using the plan-manager skill if available.
- Diagnostic Cluster Triage (for WPT tasks): When tackling WPT conformance tasks, run
node scripts/wpt/node/cluster.ts --spec=<target> to inspect top failure clusters and prioritize high-frequency patterns.
- Red Phase: Write a failing test in the appropriate test file (or create a new one in
tests/) that demonstrates the missing feature or bug.
- Green Phase: Implement the code in
src/ to make the test pass, adding explicit spec anchor citations in comments.
- Verify: Run the targeted test to ensure it passes.
- Preflight: Run
pnpm run preflight to ensure all tests pass and types/linters are 100% clean.
- Commit: Commit the targeted changes with a human-readable, lowercase message describing the action. Do NOT use
git add . or git commit -a.
Constraints & Mandatory Standards
- Mandatory Spec Anchor Citations: You MUST cite the exact Bikeshed specification section and anchor in code comments for every implemented algorithm, branch, or validation rule (e.g.
// cssom-1 § 6.5.3 #insert-a-css-rule or // selectors-4 § 4.1 #forgiving-selector). This maps our implementation directly to the normative standard and allows reviewers to verify correctness.
- Consult Normative Specs First: Actively inspect the normative
.bs source files in submodules/csswg-drafts/ and submodules/css-houdini-drafts/ to understand spec algorithms and edge cases before implementing.
- File Editing: Do NOT use bash redirection or scratch scripts for editing files. Use the specialized tools:
replace_file_content for single contiguous edits, multi_replace_file_content for multiple non-contiguous edits, or write_to_file for new files.
- Subagent Reuse: If a subagent with the appropriate role and context already exists from a previous task, prefer reusing it via
send_message instead of invoking a new one.
