implement

name	implement
description	End-to-end workflow for taking MCP work items from backlog to merged PR. Handles git branching, schema-driven planning, implementation, independent review, and PR creation. Composes spec-quality, review-quality, and schema-workflow skills into a single pipeline. Use when a user says "implement this", "work on this item", "fix these bugs", "pick up the next task", "create a PR for this", "go through the backlog", or references specific MCP item IDs for implementation.
user-invocable	true

Implement

End-to-end workflow for taking MCP work items from queue to PR. This skill composes the schema-driven planning (spec-quality), implementation, review (review-quality), and git/PR workflow into a single pipeline.

Usage:

• /implement <item-id> — work on a specific item
• /implement — with context about what to work on
• Can process single items or multiple items in batch

---

Step 1 — Assess the Work

Load the item(s) and determine the execution tier and interaction mode.

For each item, call get_context(itemId=...) to understand:

• Current role and gate status
• Schema tag (feature-implementation, bug-fix, etc.)
• Existing notes already filled
• Dependencies and blocked status

Execution tier — classify per the output style's Tier Classification table:

Criteria	Tier
1-2 files, known fix, no migration/new API	Direct — orchestrator implements, tests, reviews inline
3-10 files, single logical unit, clear or explorable scope	Delegated — single subagent, separate review agent
11+ files, multiple independent work streams, dependency edges	Parallel — worktree agents, full pipeline

Apply force-UP signals (migration, new API, multiple work streams, collaborative language) and force-DOWN signals (user says "just fix it", schema-free item) per the output style.

If the item has no schema tag, apply quick-fix for Direct tier or leave untagged for Delegated/Parallel (the default schema catches these).

Interaction mode — orthogonal to tier:

Signal	Mode
User says "work with me on", "let's plan", or similar collaborative language	Collaborative — user participates in planning and key decisions
Scope is clear, no user participation needed	Autonomous — agent handles the pipeline
Unclear scope or ambiguous complexity	Ask the user

When processing multiple items, evaluate whether related items (e.g., bugs in the same module, fixes that touch the same files) should be grouped into a single branch and PR. Group when the changes are cohesive and independent fixes would create merge conflicts. Keep items separate when they're unrelated or when isolation makes review cleaner.

---

Step 2 — Prepare the Branch and Worktree

Sync local main before any implementation begins.

git checkout main
git pull origin main --tags

The branching/worktree strategy depends on tier:

Direct tier (orchestrator implements 1–2 files inline) — create a working branch on the main directory:

git checkout -b <branch-name>

Delegated tier (single subagent) — same as Direct: orchestrator creates the branch on the main directory, the subagent works against it. No worktree.

Parallel tier (parent feature with multiple children) — create a single feature worktree that all child agents share:

FEATURE_SLUG=<short-feature-description>          # e.g. issue-117-followup
FEATURE_BRANCH=feat/$FEATURE_SLUG
FEATURE_WORKTREE=.claude/worktrees/feat-$FEATURE_SLUG

# Resume detection — if the branch/worktree already exist (orchestrator restart
# mid-feature), reuse them rather than recreating:
if git show-ref --verify --quiet "refs/heads/$FEATURE_BRANCH"; then
  echo "Resuming existing feature branch $FEATURE_BRANCH"
else
  git branch "$FEATURE_BRANCH" main
fi
if [ ! -d "$FEATURE_WORKTREE" ]; then
  git worktree add "$FEATURE_WORKTREE" "$FEATURE_BRANCH"
fi

All child-task agents will be dispatched into this shared worktree (Step 4). The feature branch is pushed and PR'd once, when the parent feature reaches terminal (Step 6).

Why one worktree per feature, not per child: the feature is the natural PR boundary. Per-child PRs created cross-PR test contamination and PR-body staleness during the #117 follow-up (see retro a7f6024f). Shared worktree means one commit history, one CI cycle, one PR — and the parent feature's review-checklist gives a coherent point at which to finalize.

Branch naming:

• feat/<feature-slug> — feature-implementation parents (the integration branch)
• fix/<short-description> — bug-fix items (Direct or Delegated tier)
• fix/<grouped-description> — batch of related bug fixes (Delegated tier)
• chore/<short-description> — tech debt, refactoring (Direct tier)

---

Step 3 — Queue Phase: Planning

This step is tier-conditional:

Direct tier: Skip this step entirely. No plan mode. No queue-phase notes. Call advance_item(trigger="start") immediately to move queue→work. The quick-fix schema has no queue-phase required notes, so the gate passes.

Delegated tier: Fill queue-phase notes per schema. Use get_context(itemId=...) to see expectedNotes and guidancePointer. Pre-plan-workflow is optional — use only if scope needs exploration. Post-plan-workflow only if child items need materialization. Advance: advance_item(trigger="start").

Parallel tier: Full planning pipeline:

Collaborative mode:

1. Tell the user the item is ready for planning and ask them to enter plan mode. The pre-plan-workflow and post-plan-workflow hooks fire automatically on plan mode entry and exit, handling context gathering and materialization.
2. During planning, follow the guidancePointer for each required note — this will reference the spec-quality skill where applicable.
3. After plan approval and post-plan materialization, advance the item: advance_item(trigger="start")

Autonomous mode:

1. Read and follow the pre-plan-workflow skill — gather existing MCP state, check schema requirements, and understand the definition floor.
2. Research the codebase — explore relevant files, understand current state.
3. Fill all queue-phase notes following the guidancePointer for each. The spec-quality framework applies regardless of mode.
4. Read and follow the post-plan-workflow skill — materialize child items if the plan calls for them.
5. Advance the item: advance_item(trigger="start")

The gate will reject advancement if required notes are missing. If rejected, fill the missing notes and retry.

---

Step 4 — Work Phase: Implementation

Verification commands. Throughout this step, "run tests" means running BOTH the test suite AND the project linter:

./gradlew :current:test
./gradlew :current:ktlintCheck

CI enforces both — a green test run with failing lint will still block the PR. If ktlintCheck fails, run ./gradlew :current:ktlintFormat to auto-fix formatting violations, then verify with ktlintCheck again and re-run tests. Include both commands in every implementation-agent and review-agent prompt.

Capturing gradle's real exit code (use this pattern, not 2>&1 | tail -N). Piping gradle into tail discards gradle's exit code — tail always exits 0 on a successful read of the log, so BUILD FAILED at the end of the gradle output is reported by you as a successful run. Combined with gradle's daemon incremental cache, this can hide broken compilation through entire CI cycles (retro 568a8584: 9 silently-failing tests shipped on PR #151 before the followup audit caught it).

The reliable pattern, especially when running in run_in_background:

./gradlew :current:test 2>&1 > /tmp/gradle-out.log; EXIT=$?
echo "EXIT=$EXIT"
tail -30 /tmp/gradle-out.log

EXIT=$? captures gradle's actual exit code before any pipe consumes it. Read the captured exit code AND the tail of the log; never trust the tail alone. This applies to every orchestrator-owned gradle invocation throughout this step.

Use --rerun-tasks after dependency upgrades or large refactors. Gradle's incremental compile cache retains class files from prior good builds. After a gradle/libs.versions.toml bump or a refactor that changes public API surfaces (removed methods, renamed types, sealed-class arms, generic-parameter shifts), incremental compilation can keep the OLD class files alongside source that no longer compiles, producing apparent BUILD SUCCESSFUL on stale bytecode. Run ./gradlew :current:test --rerun-tasks once after such changes to force a clean run; ordinary incremental builds are safe afterwards.

This step is tier-conditional:

Direct tier: Implement directly. Edit the files, run the test suite. No subagent dispatch. No /simplify pass. Fill the session-tracking note (required by both quick-fix and default schemas) with a brief summary of what changed and test results. Advance to review: advance_item(trigger="start").

Delegated and Parallel tiers: Use get_context(itemId=...) to see work-phase expectedNotes and guidancePointer values. Fill each required note following its guidance. Follow the delegation model from your output style (model selection, return formats, UUID inclusion). The key decisions at this step are:

• Single item (Delegated): delegate to one implementation subagent or implement directly. Subagent works in the main directory on the working branch.
• Multiple child tasks, independent (Parallel): dispatch parallel subagents into the shared feature worktree created in Step 2. Each agent receives the worktree path and branch name. Do not use isolation: "worktree" on the Agent tool — that would spawn a separate worktree per dispatch, which is the deprecated per-child PR pattern.
• Multiple child tasks, dependent: dispatch sequentially into the shared feature worktree. Wait for each agent's commit to land before dispatching the next.

Parallel dispatch into a shared feature worktree:

Agent(
  prompt="""
  Working directory: <feature-worktree-path>
  Branch (already checked out): feat/<feature-slug>
  Scope (modify ONLY these files): <explicit list>

  Compile self-check (REQUIRED before returning):
    ./gradlew -p <feature-worktree-path> :current:compileKotlin 2>&1 > /tmp/agent-compile.log; EXIT=$?
  If EXIT != 0, fix the compile error before committing and returning.
  Do NOT run :current:test or :current:ktlintCheck — orchestrator owns full build
  verification. The compile self-check is fast (~3s) and catches type-mismatch /
  signature errors that gradle's incremental cache may otherwise mask in the
  orchestrator's later test run (retro `568a8584`: H3's `dbNow()` shipped with a
  Result<T> vs Instant return type mismatch that was hidden for ~6 hours).

  After self-check passes, commit your changes with a descriptive message.
  """,
  model="sonnet",
  subagent_type="general-purpose"
  // NOTE: no isolation parameter — agents share the feature worktree
)

File-edit overlap discipline: Parallel agents in a shared worktree must operate on non-overlapping files. The orchestrator scopes each agent's prompt to a specific file list (per MEMORY.md §"Parallel File-Edit Delegation"). When inherent overlap exists, dispatch sequentially.

Contract-change sweep discipline. When a child task tightens a contract — making a parameter required, adding validate() invariants, narrowing a sealed-class arm, or otherwise rejecting inputs that earlier passed — the orchestrator must sweep the rest of the codebase before advancing to review. Two recurrences (retros a7f6024f and 568a8584) showed that:

• Pre-existing test fixtures constructed under the old contract will fail under the new one. Example: H2's WorkItem.validate() claim-field invariants broke 8+ test fixtures that constructed mixed-state items via separate Instant.now() calls (microsecond drift) or partial claim fields.
• The failure typically surfaces on a different PR's merge commit, not the PR that introduced the contract change — the original PR's tests passed because they used the new contract correctly.

For each contract-tightening change in this run:

1. Identify the affected tool / class / method.
2. Grep all test files (and other call sites) for usages: grep -rn "<tool>\|<class>\|<method>".
3. Verify every usage is consistent with the new contract. Update any that are not.
4. Re-run the full :current:test suite (orchestrator-owned, not the agent) to confirm no fixture-vs-contract conflicts surfaced elsewhere.

This sweep is part of the orchestrator's verification step between waves, not the implementing agent's responsibility — agents are file-scoped and can't see the full fixture surface.

Model selection — always set model explicitly on every Agent dispatch:

Agent purpose	Model
Implementation, code changes, test writing	model="sonnet"
Architecture, complex multi-file synthesis	model="opus"
MCP bulk ops, materialization	model="haiku"

Omitting model causes the agent to inherit the orchestrator's model (typically opus), wasting tokens on sonnet-eligible implementation work.

After implementation agents return:

For Parallel-tier features, agents return having committed to feat/<feature-slug> inside the shared feature worktree. Record each agent's commit SHA range alongside the child's MCP item ID — needed for scoping the review agent later:

| Child UUID | Agent ID | Pre-SHA | Post-SHA | Changed Files |
|------------|----------|---------|----------|---------------|
| <uuid>     | <id>     | <sha>   | <sha>    | <file list>   |

Capture pre-commit SHA before dispatch (git -C <feature-worktree> rev-parse HEAD) and post-commit SHA after the agent returns. The diff between them is exactly that child's work:

git -C <feature-worktree> diff <pre-sha>..<post-sha> --name-only

Build verification (orchestrator-owned, serialized). After each parallel-batch completes (or between sequential children), run from the feature worktree:

git -C <feature-worktree> status                            # confirm clean tree
./gradlew -p <feature-worktree> :current:test
./gradlew -p <feature-worktree> :current:ktlintCheck

A failure means a recently-committed child broke something. Dispatch a fix agent (same shared worktree) before continuing. Do not advance any child to review until the build is green — the trend memory has multiple sessions of flaky-test-hides-real-bug showing why retry-until-green is wrong.

Why orchestrator owns gradle invocations: ./gradlew runs against a single Gradle daemon and a single build/ cache per project directory. Parallel gradlew test invocations against the shared feature worktree will queue at the daemon, corrupt the build cache, or hit Windows file locks. Serializing build verification at the orchestrator prevents this without slowing the agents (they're not running gradle).

For Delegated tier (single subagent), the agent commits to the working branch on the main directory. Capture the changed files via git diff main --name-only and proceed.

Post-implementation steps (run in the feature worktree for Parallel tier, or on the working branch for Direct/Delegated):

1. Run the /simplify skill on the changed code to check for reuse, quality, and efficiency — this is a cleanup pass before review, not a review itself
2. If /simplify made changes, write or update tests to cover them. The simplify pass is still part of the work phase — all code changes require test coverage before advancing to review.
3. Log findings as work items — any issues surfaced by /simplify or during implementation that are not immediately addressed (pre-existing tech debt, optimization opportunities, related bugs) must be logged via /task-orchestrator:create-item before moving on. Do not discard findings.
4. Fill all work-phase notes following their guidancePointer — focus on context that downstream agents need to know
5. After implementation completes:
   • Subagent delegation: The agent returns after filling work-phase notes. The orchestrator then calls advance_item(trigger="start") to advance the item to the next phase.
   • Direct implementation: The orchestrator calls advance_item(trigger="start") itself after filling work-phase notes. In both cases, inspect newRole in the response to determine what comes next (see Step 5).

---

Step 5 — Review Phase

Before dispatching or performing review, check the item's current role. Inspect newRole from the advance_item response in the previous step:

• If newRole is terminal: The item's schema has no review phase (lightweight lifecycle). Review dispatch is not needed — the item completed through its natural lifecycle. Proceed to Step 6.
• If newRole is review: Continue with review per tier below.

This step is tier-conditional:

Direct tier: Perform an inline review. Read the diff, verify correctness, confirm tests pass. If the review-phase note has a skillPointer (visible in the advance_item response or via get_context), invoke that skill for the evaluation framework before filling the review note. Write the review note, then advance to terminal: advance_item(trigger="start"). No separate review agent — the overhead exceeds the risk for 1-2 file changes with known fixes.

Delegated and Parallel tiers: Dispatch a separate review agent. The agent that implemented the code must not review its own work.

If the implementation used the shared feature worktree (Parallel tier), the review agent operates in that worktree, scoped to just this child's commits. The diff range is <pre-sha>..<post-sha> captured during dispatch (see Step 4).

Review agent template (copy verbatim, fill placeholders):

You are reviewing one child task within a shared feature worktree.

- Feature worktree: <FEATURE_WORKTREE_PATH>
- Feature branch: <FEATURE_BRANCH>
- This child's commit range: <PRE_SHA>..<POST_SHA>
- This child's changed files:
  <OUTPUT OF git -C <FEATURE_WORKTREE_PATH> diff <PRE_SHA>..<POST_SHA> --name-only>
- Other children may have committed before/after this one. Do NOT review their work
  — your scope is the diff range above only.

Run ALL commands from within the feature worktree.
Read ALL files from that directory. Do NOT read from the main working directory.

Tests have already been verified green by the orchestrator after the most recent
commit batch. Do NOT re-run gradle — focus on plan alignment, test quality, and
simplification per the review-quality skill.

If using Direct or Delegated tier (single working branch on the main directory), the review agent reads from the working branch and runs tests itself per the existing template — no worktree-specific scoping needed.

The review agent:

1. Reads the review-quality skill
2. Uses get_context(itemId=...) to load the item's notes and review-phase requirements
3. Reads the changed files (from the worktree path if isolated, or the working branch)
4. Runs the test suite AND the linter (both commands from Step 4's "Verification commands") — from the worktree if isolated. A PR with failing lint will not merge.
5. Evaluates plan alignment, test quality, and simplification
6. Fills the review-phase notes per guidancePointer with a verdict

Handling the verdict:

Verdict	Action
Pass	Proceed to Step 6
Pass with observations	Proceed to Step 6; log observations for follow-up
Fail — blocking issues	Stop and report to the user with the full findings. Do not attempt to fix autonomously — bring the human into the loop.

Review failures surface issues that may indicate systemic problems worth learning from. Automatically retrying hides these signals.

---

Step 6 — Finalize and PR

The shape of Step 6 depends on tier.

Direct and Delegated tiers — finalize per item

After review passes:

1. Verify the working branch is committed (orchestrator commits if Direct tier; subagent committed if Delegated). Stage only the files related to the implementation:

   git add <specific-files>
   git commit -m "$(cat <<'EOF'
   <type>(<scope>): <description>
   
   <body — what changed and why, referencing the MCP item>
   
   Co-Authored-By: Claude <[e-mail]>
   EOF
   )"
   

   Commit types: feat for features, fix for bugs, refactor for tech debt, perf for performance, test for test-only changes, chore for maintenance.

2. Push the working branch:

   git push -u origin <branch-name>
   

3. Create the PR:

   gh pr create --base main --title "<type>(<scope>): <description>" --body "$(cat <<'EOF'
   ## Summary
   <2-4 bullets>
   
   ## Test Results
   <test count, pass/fail, new tests>
   
   ## Review
   <verdict summary>
   
   ## MCP
   <item ID>
   EOF
   )"
   

4. After PR merges:

   git checkout main
   git pull origin main
   git branch -D <branch-name>
   

5. Advance the item to terminal:

   advance_item(transitions=[{ itemId: "<uuid>", trigger: "start" }])
   

Report the PR URL and a summary.

Parallel tier — finalize ONCE at parent-feature completion

For Parallel-tier features with a shared feature worktree:

For each child task (after its review passes):

1. Confirm the child's review-checklist note is filled.
2. advance_item(itemId=<child-uuid>, trigger="start") to move work→review→terminal as the child's schema dictates.
3. Do NOT push. Do NOT create a PR. The work is committed to feat/<feature-slug> inside the shared worktree; that's the integration point.

When all children reach terminal, the parent feature is ready to finalize:

1. Fill the parent's implementation-notes and session-tracking notes (aggregating across children — distributed-tracking pattern works as today).
2. Run final verification from the feature worktree:

   ./gradlew -p <feature-worktree-path> :current:test
   ./gradlew -p <feature-worktree-path> :current:ktlintCheck
   

3. Advance the parent to review and fill review-checklist (orchestrator-authored, summarizing across all children's reviews).
4. Push the feature branch:

   git -C <feature-worktree-path> push -u origin feat/<feature-slug>
   

5. Create one PR for the whole feature:

   gh pr create --base main --title "feat(<scope>): <feature description>" --body "$(cat <<'EOF'
   ## Summary
   <feature-level summary aggregating all children>
   
   ## Children completed
   - <child-1 title> (<MCP UUID>)
   - <child-2 title> (<MCP UUID>)
   ...
   
   ## Test Results
   <total test count, new tests added across feature>
   
   ## Review
   <feature-level review verdict, references each child's review-checklist>
   
   ## MCP
   Parent: <parent UUID>
   Children: <list of child UUIDs>
   EOF
   )"
   

6. After PR merges:

   git checkout main
   git pull origin main
   git worktree remove <feature-worktree-path>
   git branch -D feat/<feature-slug>
   

7. Advance the parent feature to terminal.

Why one PR at parent finalization, not per child

• Coherent review context. The PR diff shows the whole feature, not N disjoint pieces.
• One CI cycle per feature instead of N. Local verification (orchestrator-owned gradle runs between commits) gives equivalent regression signal during development.
• No cross-PR contamination. Contract changes can't surface on a sibling's merge commit because there are no sibling PRs.
• No PR-body staleness. The PR body is authored once, after the feature is done, describing what actually shipped.
• Aggregate retrospective material. Distributed session-tracking notes across children plus parent-level aggregation gives clean retro input (validated by retro a7f6024f).

Local main always tracks origin/main — no divergence, no reset --hard needed.

---

Autonomous Batch Processing

When processing a Parallel-tier feature with multiple child tasks autonomously:

1. Step 2 — One worktree, one branch. Orchestrator creates the feature worktree and feature branch (feat/<slug>) at planning time. All children share it.
2. Step 4 — Dispatch into shared worktree. Agents dispatched without isolation: "worktree". Independent children dispatch in parallel waves; dependent children dispatch sequentially. Orchestrator scopes each agent's file list to prevent overlap.
3. Build verification — orchestrator-owned, serialized. After each parallel wave (or between sequential children), the orchestrator runs :current:test and :current:ktlintCheck from the feature worktree. Fix failures before advancing any child to review.
4. Step 5 — Review per child, scoped to that child's commit range. Review agent reads from the shared worktree but scopes its diff to <pre-sha>..<post-sha> for the child being reviewed.
5. Step 6 — One PR at parent finalization. Children advance to terminal without pushing or PR'ing. Only when the parent feature itself reaches terminal does the orchestrator push feat/<slug> and open the single feature-level PR.
6. Track child commits — maintain a table mapping child UUID → pre-commit SHA → post-commit SHA → status (implementing / reviewing / done / failed). Worktree path is shared across all children.
7. Report at the end — summarize children completed, review failures, and the single PR URL.

If any child hits a review failure, continue processing siblings (their commits are already in the feature branch). Report all failures together at the end. The orchestrator decides whether the failed child blocks parent finalization (e.g. fix-and-re-review), can be cancelled (descope from the feature), or warrants reverting its commits.

Bug-fix batches (multiple unrelated fixes) — these are NOT a Parallel-tier feature. Use Delegated tier per item, each with its own branch and PR (the legacy per-item flow). The shared-worktree pattern applies only when items share a parent feature item.

---

Worktree Strategy

For full setup, dispatch patterns, lifecycle, parallel validation, and test baseline management, see WORKTREE.md.

Quick reference:

Tier	Worktree	Branch	PR scope
Direct / Delegated (single item)	None — work on main directory	<type>/<slug>	One PR per item
Parallel (parent feature with N children)	One shared feature worktree	feat/<feature-slug> (one branch for all children)	One PR at parent finalization

Do NOT use isolation: "worktree" on the Agent tool for Parallel-tier child dispatches. That spawns a separate worktree per dispatch — the deprecated per-child PR pattern. For Parallel tier, the orchestrator pre-creates one shared worktree in Step 2 and dispatches each child agent into it.

When NOT to create any worktree:

• Direct/Delegated tier (single item — work on the main directory)
• Pure MCP operations with no file modifications
• Orchestrator implementing directly

---

Resuming In-Progress Work

Tier classification happens at Step 1 even when resuming. Classify the tier from the item's tags, file scope, and note state, then resume using that tier's pipeline.

If an item is already past the queue phase (e.g., previously planned but not implemented), the skill picks up from the current state:

Current role	Resume from
queue (notes filled)	Step 3 — advance and proceed
queue (notes missing)	Step 3 — fill missing notes
work (in progress)	Step 4 — check implementation state
work (notes filled)	Step 4 — advance to review
review	Step 5 — run review
terminal	Already done — report status

Always call get_context(itemId=...) first to determine exact state before resuming.