feature-implement

name	feature-implement
version	1.0.0
description	[Implementation] Use when you need to implement a feature [step by step].
execution-mode	subagent
context-budget	high

[BLOCKING] Execute skill steps in declared order. NEVER skip, reorder, merge steps without explicit user approval. [BLOCKING] Before each step or sub-skill call, update task tracking: in_progress on start, completed on end. [BLOCKING] Every completed/skipped step MUST include evidence or explicit skip reason. [BLOCKING] If Task tools unavailable, maintain equivalent step-by-step plan tracker with same status transitions.

Quick Summary

Goal: Ship a correct, fully-verified feature that satisfies the saved Goal Contract — implemented with deep research, comprehensive planning, and maximum quality verification (planned, reviewed, tested, documented) — with no skipped quality gate on any non-trivial change.

Workflow:

1. Research — Deep investigation, multiple researcher subagents
2. Plan — Detailed plan via /plan; user approval required
3. Implement — Execute with full code review + SRE review
4. Verify — Run all tests, review changes, update docs

Key Rules:

• Maximum thoroughness: research → plan → implement → review → test → docs
• User approval required at plan stage
• Break work into todo tasks; add final self-review task

Renamed: formerly cook — now /feature-implement. The old name no longer resolves as a slash command.

feature-implement vs plan-execute: feature-implement takes an idea/feature description and goes idea → research → plan (created here) → shipped. Use /plan-execute instead when a plan file already exists and you only need disciplined phase-by-phase execution + commit. feature-implement owns the front of the pipeline (research + planning); plan-execute owns the back (phase gates + auto-commit + --parallel/--approval/--tests flags).

Standalone Mode Pipeline (skip entirely if invoked inside a workflow)

MANDATORY — standalone /feature-implement only. When invoked OUTSIDE a workflow, wrap the core spine in this quality loop. Detect an active workflow via TaskList FIRST: if a parent [Workflow] row exists, SKIP this section — the surrounding workflow already sequences plan/review/why-review around this skill (e.g. workflow-feature wraps feature-implement with exactly these steps).

Create these as TaskCreate tasks up front, in order, then execute them:

1. /spec — spec-driven, BEFORE any plan or code. Create or update the tech-free 8-section Feature Spec under docs/specs/ so the plan and implementation satisfy an agreed contract, not chat memory. Decide the case from evidence: net-new capability with no code yet → /spec [mode=draft] (provisional, Evidence: TBD); enhancement to an already-documented feature → /spec [mode=update]; behavior/contract change to existing spec → /spec [mode=amend]; buggy/undocumented area that now warrants a spec → /spec [mode=init]. If a governing spec already exists and fully covers this change, record Spec verified current — no change with file:line evidence and proceed. Skip ONLY in fast mode (ALL Default Mode Policy trivial-task conditions met — no behavior/contract change); record the skip reason. Decide the case explicitly — skip only the authoring, never the decision.
2. /plan — author the implementation plan from the spec. feature-implement's Comprehensive Planning phase (Step 2) satisfies this; emit a reviewable plan artifact under plans/. Map each plan phase's ## Test Specifications to the spec's §8 TC-{FEATURE}-{NNN} IDs.
3. /plan-review — recursively review/validate the plan; fix validated findings before implementing.
4. Proceed — execute the core implementation spine (research already done → implement → test → review → docs).
5. /spec [mode=sync] — spec-driven closure. Reconcile the spec's §8 TC-{FEATURE}-{NNN} ↔ integration tests and refresh Evidence: TBD markers to real file:line now that code exists. Run /spec [mode=tests] first if the implementation introduced behavior not yet captured as a test case. Skip only when step 1 was skipped (fast-mode trivial, no spec touched).

First Principle — Easy to Change

The success metric of every coding decision is future change cost. DRY, SRP, abstraction, design patterns, naming, layering, tests — every technique exists to serve one goal: making the next change cheaper.

When evaluating code, refactor, test, or abstraction, ask: does this make the next change cheaper or more expensive?

• Reject "best practices" raising change cost (premature abstraction, speculative generality, leaky indirection, ceremony without payoff).
• Name real enemies in findings: coupling, hidden state, duplicated knowledge, unclear intent, irreversible decisions exposed too early.
• Simpler design easy to change beats sophisticated design that isn't.

Apply this lens before invoking any specific rule, pattern, or checklist below — if a downstream rule would raise change cost, this principle wins.

---

Default Mode Policy

Default mode HARD (full rigor). Every section below — deep research, mandatory /plan, full code-reviewer review, mandatory tests, mandatory /docs-update — applies by default.

Opt out to fast mode ONLY when ALL true (task genuinely trivial):

• Single-file edit, ≤30 lines changed
• No design choice (only one reasonable approach)
• No cross-service impact, no contract change, no new dependency
• No new pattern — follows existing codebase pattern
• Existing tests cover change OR change non-functional (typo, comment, log message)

Any condition fails → use full protocol below. When in doubt, default hard. Skipping review/tests on non-trivial change ships bugs.

Fast mode skips (and only skips): researcher subagent phase (direct grep instead), mandatory code-reviewer review (self-review only), separate test phase (verify inline). Does NOT skip /plan step, test execution, /docs-update triage.

Backend Context (if applicable)

When task involves backend changes, read these directly before implementing:

• CQRS commands/queries, validation, repositories, entity events: docs/project-reference/backend-patterns-reference.md
• Entity catalog, relationships, cross-service sync: docs/project-reference/domain-entities-reference.md
• Repository type (service-specific): when the project declares a per-service repository abstraction (backendServices.serviceRepositories in docs/project-config.json), use that repository type for the service — NEVER the generic root repository base.

Frontend/UI Context (if applicable)

When task involves frontend or UI changes:

• Component patterns: docs/project-reference/frontend-patterns-reference.md
• Styling/BEM guide: docs/project-reference/scss-styling-guide.md
• Design system tokens: docs/project-reference/design-system/README.md

Ultrathink plan and implement these tasks with maximum verification:

Be skeptical. Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence >80% to act.

$ARGUMENTS

Mode: Extra research, detailed planning, mandatory reviews.

Workflow

0. Goal Contract Read (BEFORE implementation)

• Resolve the active Goal Contract per SYNC:goal-contract-satisfaction-loop: active plan goal.md → plans/goals/{YYMMDD-HHmm}-{slug}/goal.md → create from the current request via .claude/templates/goal-contract-template.md.
• Read the saved success criteria BEFORE any code change — implementation serves the saved criteria, not chat memory.
• After implementation and verification, append an Iteration Log entry to the goal file: result, evidence references (file:line, command output), remaining gaps mapped to criteria.

1. Deep Research Phase

• Launch 2-3 researcher subagents in parallel covering:
  • Technical approach validation
  • Edge cases, failure modes
  • Security implications
  • Performance considerations
• Use /scout --ext for comprehensive codebase analysis
• Research reports max 150 lines each
• External Memory: Write all research to .ai/workspace/analysis/{task-name}.analysis.md. Re-read ENTIRE file before planning.
• Pre-Implementation Trace Gate: For bugfix, failed verification, stale/incorrect final output, regression, or behavior-changing fix plans, MUST ATTENTION confirm the plan/referenced analysis includes Debugger Trace: End -> Start, all feeder paths, hypothesis matrix, owning fix layer, and forward convergence proof. If missing, STOP and produce the missing-trace list before editing.

After implementing, run python .claude/scripts/code_graph connections <file> --json on modified files; verify no related files need updates.

Graph-Trace Before Implementation

When graph DB available, BEFORE writing code, trace blast radius:

• python .claude/scripts/code_graph trace <file> --direction both --json — what calls this code AND what it triggers
• python .claude/scripts/code_graph trace <file> --direction downstream --json — all downstream consumers
• Prevents breaking implicit dependencies (bus message consumers, event handlers)

2. Comprehensive Planning

• Use planner subagent with all research reports
• Create full plan directory:
  • plan.md — overview with risk assessment
  • phase-XX-*.md — detailed phase files
  • Success criteria per phase
  • Rollback strategy

3. Verified Implementation

• Implement one phase at a time
• After each phase:
  • Run type-check, compile
  • Run relevant tests
  • Self-review before proceeding

Batch Checkpoint (Large Plans)

For plans with 10+ tasks, execute in batches with human review:

1. Execute batch — Complete next 3 tasks (or user-specified size)
2. Report — Show implementation, verification output, any concerns
3. Wait — Say "Ready for feedback" and STOP. Do NOT continue automatically.
4. Apply feedback — Incorporate changes, execute next batch
5. Repeat until all tasks complete

Plans with 10+ tasks — do NOT execute all tasks continuously without checkpoint. Stop after every batch for human review. Prevents runaway execution where early mistakes compound through later tasks.

4. Mandatory Testing

• Use tester subagent for full test coverage
• Write tests for:
  • Happy path scenarios
  • Edge cases from research
  • Error handling paths
• NO mocks or fake data
• Repeat until all tests pass

5. Mandatory Code Review

• Use code-reviewer subagent
• Address all critical and major findings
• Re-run tests after fixes
• Repeat until approved

6. Documentation Update

• Use docs-manager to update relevant docs
• Use project-manager to update project status
• Record architectural decisions

7. Final Report

• Summary of all changes
• Test coverage metrics
• Security considerations addressed
• Unresolved questions (if any)
• Ask user to review and approve

When to Use

• Critical production features
• Security-sensitive changes
• Public API modifications
• Database schema changes
• Cross-service integrations

Quality Gates

Gate	Criteria
Research	2+ researcher reports
Planning	Full plan directory
Tests	All pass, no mocks
Review	0 critical/major findings
Docs	Updated if needed

---

Next Steps (Standalone: MUST ATTENTION ask user via AskUserQuestion. Skip if inside workflow.)

MANDATORY IMPORTANT MUST ATTENTION — NO EXCEPTIONS: If this skill was called outside a workflow, MUST ATTENTION use AskUserQuestion to present these options. Do NOT skip because task seems "simple" or "obvious" — user decides:

• "Proceed with full workflow (Recommended)" — Detect best workflow to continue from here (feature implemented). Ensures review, testing, docs steps aren't skipped.
• "/code-simplifier" — Simplify and clean up implementation
• "/workflow-review-changes" — Review changes before commit
• "Skip, continue manually" — user decides

If already inside a workflow, skip — workflow handles sequencing.

[IMPORTANT] Use TaskCreate to break ALL work into small tasks BEFORE starting — including tasks for each file read. Prevents context loss from long files. For simple tasks, MUST ATTENTION ask user whether to skip.

• docs/project-reference/domain-entities-reference.md — Domain entity catalog, relationships, cross-service sync (read when task involves business entities/models)
• docs/specs/ — Test specifications by module (read existing TCs; generate/update via /spec [mode=tests] after implementation)

End-to-Start Debugger Trace — For non-trivial bugs, failed verification, regression fixes, behavior-changing code, or unclear code flow, start from the observed final state and walk backward before proposing a fix.

1. Frame 0: observed end state — Name the exact user-visible output, failing assertion, log line, persisted value, API response, rendered UI, or aggregate bucket. Record the reader/query/renderer that produced it with file:line evidence.
2. Walk backward one hop at a time — Trace final reader -> projection/cache/storage -> writer -> consumer/handler/job -> producer/caller -> original trigger. At every hop record: input, transformation, output, owner, and evidence.
3. Enumerate all feeder paths — Find every upstream producer/caller/event/job that can write into the final path, including retry, async, cache, background, and alternate UI/API paths. Mark each path verified, ruled out, or still unknown.
4. Build the hypothesis matrix — For each plausible cause, list evidence for, evidence against, how to reproduce/verify, blast radius, and status (primary, contributing, ruled out, latent). Do not fix until competing causes are explicitly resolved or bounded.
5. Choose the owning fix layer — Identify the invariant owner and the lowest shared point that protects all downstream consumers. A fix at the symptom site is rejected unless the symptom site owns the invariant.
6. Prove convergence forward — After choosing the fix, walk start -> end again and show how the corrected state reaches the observed final output. Map each root cause to a fix part and each fix part to a test/proof.

BLOCKED until: final state named · backward trace written · all feeder paths enumerated · hypothesis matrix completed · owning fix layer justified · forward convergence proof mapped to tests.

NEVER: Start at the first suspicious code path. Collapse multiple producers into one "flow". Treat duplicate symptoms as duplicate records without proving the read model. Skip ruled-out hypotheses.

Source/test drift check. For coding, fix, debug, investigation, test, or review work: when source behavior changes, inspect affected unit/integration/E2E tests and decide from evidence whether tests should change to match intended behavior or the source change is an unintended bug to fix. Do not write tests for migration code; schema/data migrations are one-time execution paths, not core application logic.

AI Mistake Prevention — Failure modes to avoid on every task:

Re-read files after context changes. Context compaction, resume, or long-running work can make memory stale; verify current files before acting. Verify generated content against source evidence. AI hallucinates APIs, names, claims, and document facts. Check the relevant source before documenting or referencing. Check downstream references before deleting or renaming. Removing an artifact can stale docs, generated mirrors, configs, and callers; map references first. Trace the full impact chain after edits. Changing a definition can miss derived outputs and consumers. Follow the affected chain before declaring done. Verify ALL affected outputs, not just the first. One green check is not all green checks; validate every output surface the change can affect. Assume existing values are intentional — ask WHY before changing. Before changing a constant, limit, flag, wording, or pattern, read nearby context and history. Surface ambiguity before acting — don't pick silently. Multiple valid interpretations require an explicit question or stated assumption with risk. Keep shared guidance role-relevant. Universal guidance must help every receiving skill or agent; code-specific obligations belong only in code-specific protocols.

UI System Context — For ANY task touching .ts, .html, .scss, or .css files:

MUST ATTENTION READ before implementing:

1. docs/project-reference/frontend-patterns-reference.md — component base classes, stores, forms
2. docs/project-reference/scss-styling-guide.md — BEM methodology, SCSS variables, mixins, responsive
3. docs/project-reference/design-system/README.md — design tokens, component inventory, icons

Reference docs/project-config.json for project-specific paths.

Graph-Assisted Investigation — MANDATORY when .code-graph/graph.db exists.

HARD-GATE: MUST ATTENTION run at least ONE graph command on key files before concluding any investigation.

Pattern: Grep finds files → trace --direction both reveals full system flow → Grep verifies details

Task	Minimum Graph Action
Investigation/Scout	trace --direction both on 2-3 entry files
Fix/Debug	callers_of on buggy function + tests_for
Feature/Enhancement	connections on files to be modified
Code Review	tests_for on changed functions
Blast Radius	trace --direction downstream

CLI: python .claude/scripts/code_graph {command} --json. Use --node-mode file first (10-30x less noise), then --node-mode function for detail.

Nested Task Expansion Contract — For workflow-step invocation, the [Workflow] ... row is only a parent container; the child skill still creates visible phase tasks.

1. Call TaskList first. If a matching active parent workflow row exists, set nested=true and record parentTaskId; otherwise run standalone.
2. Create one task per declared phase before phase work. When nested, prefix subjects [N.M] $skill-name — phase.
3. When nested, link the parent with TaskUpdate(parentTaskId, addBlockedBy: [childIds]).
4. Orchestrators must pre-expand a child skill's phase list and link the workflow row before invoking that child skill or sub-agent.
5. Mark exactly one child in_progress before work and completed immediately after evidence is written.
6. Complete the parent only after all child tasks are completed or explicitly cancelled with reason.

Blocked until: TaskList done, child phases created, parent linked when nested, first child marked in_progress.

Project Reference Docs Gate — Run after task-tracking bootstrap and before target/source file reads, grep, edits, or analysis. Project docs override generic framework assumptions.

1. Identify scope: file types, domain area, and operation.
2. Required docs by trigger: always docs/project-reference/lessons.md; doc lookup docs-index-reference.md; review code-review-rules.md; backend/CQRS/API backend-patterns-reference.md; domain/entity domain-entities-reference.md; frontend/UI frontend-patterns-reference.md; styles/design scss-styling-guide.md + design-system/design-system-canonical.md; integration tests integration-test-reference.md; E2E e2e-test-reference.md; feature docs/specs feature-spec-reference.md + spec-system-reference.md + spec-principles.md; behavior/public-contract/spec-test-code sync workflow-spec-test-code-cycle-reference.md; derived spec index/ERD/reimplementation guides spec-system-reference.md + source Feature Specs under docs/specs/; architecture/new area project-structure-reference.md.
3. Read every required doc. If docs/project-config.json, the docs index, lessons.md, CLAUDE.md, AGENTS.md, or any task-required reference doc is missing or stale, auto-run /project-init or the narrow lower-level route (/project-config, /docs-init, /scan-all, /scan --target=<key>, /claude-md-init) before ordinary project-specific work. If Codex mirrors or AGENTS.md are missing/stale, ask the user to run /sync-codex; do not auto-run it.
4. Before target work, state: Reference docs read: ... | Not applicable: ....

Ready when: scope evaluated, required docs checked/read or setup route completed, lessons.md confirmed, citation emitted.

Task Tracking & External Report Persistence — Bootstrap this before execution; then run project-reference doc prefetch before target/source work.

1. Create a small task breakdown before target file reads, grep, edits, or analysis. On context loss, inspect the current task list first.
2. Mark one task in_progress before work and completed immediately after evidence; never batch transitions.
3. For plan/review work, create plans/reports/{skill}-{YYMMDD}-{HHmm}-{slug}.md before first finding.
4. Append findings after each file/section/decision and synthesize from the report file at the end.
5. Final output cites Full report: plans/reports/{filename}.

Blocked until: task breakdown exists, report path declared for plan/review work, first finding persisted before the next finding.

Critical Thinking Mindset — Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence >80% to act. Anti-hallucination: Never present guess as fact — cite sources for every claim, admit uncertainty freely, self-check output for errors, cross-reference independently, stay skeptical of own confidence — certainty without evidence root of all hallucination.

Understand Code First — HARD-GATE: Do NOT write, plan, or fix until you READ existing code.

1. Search 3+ similar patterns (grep/glob) — cite file:line evidence
2. Read existing files in target area — understand structure, base classes, conventions
3. Run python .claude/scripts/code_graph trace <file> --direction both --json when .code-graph/graph.db exists
4. Map dependencies via connections or callers_of — know what depends on your target
5. Write investigation to .ai/workspace/analysis/ for non-trivial tasks (3+ files)
6. Re-read analysis file before implementing — never work from memory alone. — why: long context drifts from the file; the file is ground truth
7. NEVER invent new patterns when existing ones work — match exactly or document deviation. — why: divergent patterns fragment the codebase and slow every future reader

BLOCKED until: - [ ] Read target files - [ ] Grep 3+ patterns - [ ] Graph trace (if graph.db exists) - [ ] Assumptions verified with evidence

Plan Quality — Every plan phase MUST ATTENTION include test specifications.

1. Add ## Test Specifications section with TC-{FEATURE}-{NNN} IDs to every phase file
2. Map every functional requirement to ≥1 TC (or explicit TBD with rationale)
3. TC IDs follow TC-{FEATURE}-{NNN} format — reference by ID, never embed full content
4. Before any new workflow step: call TaskList and re-read the phase file
5. On context compaction: call TaskList FIRST — never create duplicate tasks
6. Verify TC satisfaction per phase before marking complete (evidence must be file:line, not TBD)

Mode: TDD-first → reference existing TCs with Evidence: TBD. Implement-first → use TBD → /spec [mode=tests] fills after.

• MANDATORY IMPORTANT MUST ATTENTION search 3+ existing patterns and read code BEFORE any modification. Run graph trace when graph.db exists.

• MANDATORY IMPORTANT MUST ATTENTION cite file:line evidence for every claim. Confidence >80% to act, <60% = do NOT recommend.

• MANDATORY IMPORTANT MUST ATTENTION include ## Test Specifications with TC IDs per phase. Call TaskList before creating new tasks.

• MANDATORY IMPORTANT MUST ATTENTION read frontend-patterns-reference, scss-styling-guide, design-system/README before any UI change.

• MANDATORY IMPORTANT MUST ATTENTION run at least ONE graph command on key files when graph.db exists. Pattern: grep → graph trace → grep verify.

MUST ATTENTION apply critical + sequential thinking — every claim needs appropriate traced evidence (file:line for repo/code claims; source URL or artifact section for research, product, content, and docs claims); confidence >80% to act, <60% DO NOT recommend. Anti-hallucination: never present guess as fact, admit uncertainty freely, cross-reference independently, stay skeptical of own confidence.

MUST ATTENTION apply AI mistake prevention — verify generated content against evidence, trace downstream references before deleting or renaming, verify all affected outputs, re-read files after context loss, and surface ambiguity before acting.

• MANDATORY Bootstrap task tracking before target work; transition one task at a time.
• MANDATORY Persist plan/review findings to plans/reports/ incrementally and synthesize from disk.

• MANDATORY After task-tracking bootstrap and before target/source work, read required project-reference docs and cite Reference docs read: ....
• MANDATORY Always include lessons.md; project conventions override generic defaults.
• MANDATORY If project config, root instruction files, or any required reference doc is missing or stale, auto-run /project-init or the narrow lower-level route before ordinary project-specific work.

IMPORTANT MUST ATTENTION debugger trace gate: for non-trivial bug/fix/investigation/review work, start at the observed final output and trace backward through reader -> storage/projection -> writer -> consumer/job -> producer/trigger. Enumerate all feeder paths and hypotheses before fixing. BLOCKED until trace, hypothesis matrix, owning fix layer, and forward convergence proof exist.

• MANDATORY Parent workflow rows do not replace child phase tracking; expand phases and link the parent when nested.
• MANDATORY Orchestrators pre-expand child skill phases before invocation; use [N.M] $skill-name — phase prefixes and one-in_progress discipline.

• MANDATORY Resolve the active Goal Contract BEFORE work (active plan goal.md → plans/goals/{YYMMDD-HHmm}-{slug}/goal.md → create from current request) and read saved success criteria before editing.
• MANDATORY Append iteration evidence after execution; emit a Goal Satisfaction matrix (PASS/FAIL/BLOCKED) before reporting PASS; loop on validated FAIL; escalate repeated no-progress or blockers. NEVER store secrets in goal files.

Closing Reminders

IMPORTANT MUST ATTENTION Goal: Ship a correct, fully-verified feature that satisfies the saved Goal Contract — research-backed, planned, reviewed, tested, documented — with no skipped quality gate on any non-trivial change.

IMPORTANT MUST ATTENTION — Protocols in force (concise digest of the SYNC/shared blocks this skill carries; each line is a signpost to its canonical body above):

• End-To-Start Debugger Trace: Trace observed output backward through every feeder path before fixing.

• Source/Test Drift Check: When source behavior changes, reconcile affected tests from evidence.

• AI Mistake Prevention: verify generated content against evidence, trace downstream references, verify all affected outputs, re-read after context loss, surface ambiguity.

• UI System Context: Read frontend, SCSS, and design-system docs before any UI change.

• Graph-Assisted Investigation: Run a graph command on key files when graph.db exists.

• Nested Task Creation: Expand child phase tasks and link the parent when nested.

• Project Reference Docs Guide: Read required project-reference docs (always lessons.md) before target work.

• Task Tracking External Report: Bootstrap task tracking; persist plan/review findings incrementally to disk.

• Critical Thinking Mindset: Critical + sequential thinking; every claim needs traced proof, confidence >80%.

• Understand Code First: Search 3+ patterns and read code before any modification.

• Plan Quality: Add ## Test Specifications with TC IDs to every plan phase.

• MANDATORY IMPORTANT MUST ATTENTION default mode HARD — opt out to fast mode ONLY when ALL trivial-task conditions met

• MANDATORY IMPORTANT MUST ATTENTION break work into small todo tasks via TaskCreate BEFORE starting

• MANDATORY IMPORTANT MUST ATTENTION search codebase for 3+ similar patterns before creating new code

• MANDATORY IMPORTANT MUST ATTENTION cite file:line evidence for every claim (confidence >80% to act)

• MANDATORY IMPORTANT MUST ATTENTION add final review todo task to verify work quality

• MANDATORY IMPORTANT MUST ATTENTION validate decisions with user via AskUserQuestion — never auto-decide

• MANDATORY IMPORTANT MUST ATTENTION NEVER skip review or test execution on non-trivial change

[TASK-PLANNING] Before acting, analyze task scope and systematically break into small todo tasks and sub-tasks via TaskCreate.

---

Closing reminder — Easy to Change is the success metric. Every finding, test, refactor, and abstraction must answer one question: does this make the next change cheaper or more expensive? If it doesn't reduce future change cost, reject it. Coupling, hidden state, duplicated knowledge, and unclear intent are the real enemies — call them out by name.