Paths: File paths (shared/, references/, ../ln-*) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

Implementation Task Executor

Executes a single implementation (or refactor) task from Todo to To Review using the task description and linked guides.

Purpose & Scope

• Handle one selected task only; never touch other tasks.
• Follow task Technical Approach/plan/AC; apply KISS/YAGNI and guide patterns.
• Update Linear/kanban for this task: Todo -> In Progress -> To Review.
• Run typecheck/lint; update docs/tests/config per task instructions.
• Not for test tasks (label "tests" goes to ln-404-test-executor).

Inputs

Input	Required	Source	Description
taskId	Yes	args, parent Story, kanban, user	Task to execute

Resolution: Task Resolution Chain. Status filter: Todo

Task Storage Mode

MANDATORY READ: Load shared/references/tools_config_guide.md, shared/references/storage_mode_detection.md, and shared/references/input_resolution_pattern.md

Extract: task_provider = Task Management → Provider (linear | file).

Aspect	Linear Mode	File Mode
Load task	get_issue(task_id)	Read("docs/tasks/epics/.../tasks/T{NNN}-*.md")
Update status	save_issue(id, state)	Edit the **Status:** line in file
Kanban	Updated by Linear sync	Must update kanban_board.md manually

File Mode status format:

## Status
**Status:** In Progress | **Priority:** High | **Estimate:** 4h

Mode Detection

Detect operating mode at startup:

Plan Mode Active:

• Steps 1-2: Load task context (read-only, OK in plan mode)
• Generate EXECUTION PLAN (files to create/modify, approach) → write to plan file
• Call ExitPlanMode → STOP. Do NOT implement.
• Steps 3-6: After approval → execute implementation

Normal Mode:

• Steps 1-6: Standard workflow without stopping

Progress Tracking with TodoWrite

When operating in any mode, skill MUST create detailed todo checklist tracking ALL steps.

Rules:

1. Create todos IMMEDIATELY before Step 1
2. Each workflow step = separate todo item; implementation step gets sub-items
3. Mark in_progress before starting step, completed after finishing

Todo Template (10 items):

Step 1: Resolve taskId
  - Resolve via args / Story context / kanban / AskUserQuestion (Todo filter)

Step 2: Load Context
  - Fetch full task description + linked guides/manuals/ADRs

Step 2b: Goal Articulation Gate
  - Complete 4 questions from shared/references/goal_articulation_gate.md (<=25 tokens each)

Step 2c: Implementation Blueprint
  - From task "Affected Components": extract file paths (Glob/Grep to find actual paths)
  - Read each file (or key sections) to understand current structure
  - Output:
    ## Implementation Blueprint: {taskId}
    **Files to create:** [list with brief purpose]
    **Files to modify:** [list with what changes]
    **Change order (dependencies first):**
    1. {file} — {what and why first}
    2. {file} — {depends on step 1}
    **Risks:** {shared files with parallel tasks, if any}
  - Scope: ONLY files of this task. Do not analyze other tasks.

Step 3: Start Work
  - Set task to In Progress, update kanban

Step 4: Implement
  - 4a Pattern Reuse: IF creating new file/utility, Grep src/ for existing similar patterns
    (error handlers, validators, HTTP wrappers, config loaders). Reuse if found.
  - 4b Follow task plan/AC, apply KISS/YAGNI
  - 4c Architecture Guard: IF creating service function: (1) 3+ side-effect categories in **leaf** function → split (EXCEPT orchestrator functions that delegate sequentially — these are expected to have 3+ categories);
    (2) get_*/find_*/check_* naming → verify no hidden writes; (3) 3+ service imports in **leaf** function → flatten (orchestrator imports are expected)
  - Update docs and existing tests if impacted
  - Execute verify: methods from task AC (test/command/inspect)

Step 5: Quality
  - Run typecheck and lint (or project equivalents)

Step 6: Finish
  - Set task to To Review, update kanban
  - Add summary comment (changes, tests, docs)

Workflow (concise)

1. Resolve taskId: Run Task Resolution Chain per guide (status filter: [Todo]).
2. Load context: Fetch full task description (Linear: get_issue; File: Read task file); read linked guides/manuals/ADRs/research; auto-discover team/config if needed. 2b) Goal gate: MANDATORY READ: shared/references/goal_articulation_gate.md — Complete the 4-question gate (<=25 tokens each). State REAL GOAL (deliverable as subject), DONE LOOKS LIKE, NOT THE GOAL, INVARIANTS & HIDDEN CONSTRAINTS. 2c) Implementation Blueprint: From task "Affected Components", find actual file paths via Glob/Grep. Read key sections of each file. Output structured plan: files to create/modify, change order (dependencies first), risks (shared files with parallel tasks). Scope: this task only.
3. Start work: Update this task to In Progress (Linear: update_issue; File: Edit status line); move it in kanban (keep Epic/Story indent).
4. Implement (with verification loop): Before writing new utilities/handlers, Grep src/ for existing patterns (error handling, validation, config access). Reuse if found; if not reusable, document rationale in code comment. Follow checkboxes/plan; keep it simple; avoid hardcoded values; reuse existing components; update docs noted in Affected Components; update existing tests if impacted (no new tests here). Before creating service functions, apply Architecture Guard (cascade depth, interface honesty, flat orchestration). After implementation, execute verify: methods from task AC: test → run specified test; command → execute and check output; inspect → verify file/content exists. If any verify fails → fix before proceeding.
5. Quality: Run typecheck and lint (or project equivalents); ensure instructions in Existing Code Impact are addressed.
6. Finish: Mark task To Review (Linear: update_issue; File: Edit status line); update kanban to To Review; add summary comment (what changed, tests run, docs touched).

Pre-Submission Checklist

Context: Self-assessment before To Review reduces review round-trips and catches obvious issues early.

MANDATORY READ: Load shared/references/code_efficiency_criterion.md — self-check before submission.

Before setting To Review, verify all items:

#	Check	Verify
0	AC verified	Each AC verify: method executed with pass evidence
1	Approach alignment	Implementation matches Story Technical Approach
2	Clean code	No dead code, no backward-compat shims, unused imports removed
3	Config hygiene	No hardcoded creds/URLs/magic numbers
4	Docs updated	Affected Components docs reflect changes
5	Tests pass	Existing tests still pass after changes
6	Pattern reuse	New utilities checked against existing codebase; no duplicate patterns introduced
7	Architecture guard	Cascade depth <= 2 (leaf functions); no hidden writes in read-named functions; no service chains >= 3 in leaf functions (orchestrator imports exempt)
8	Destructive op safety	If task has "Destructive Operation Safety" section: (1) backup step executed/planned before destructive code, (2) rollback mechanism exists in code, (3) environment guard present, (4) preview/dry-run evidence attached or referenced
9	Code efficiency	No unnecessary intermediates, verbose patterns replaced by language idioms, no boilerplate framework handles (per shared/references/code_efficiency_criterion.md)

MANDATORY READ: Load shared/references/destructive_operation_safety.md for severity classification and safety requirements.

HITL Gate: IF task severity = CRITICAL (per destructive_operation_safety.md loaded above): Use AskUserQuestion to confirm before marking To Review: "Task contains CRITICAL destructive operation: {operation}. Backup plan: {plan}. Proceed?" Do NOT mark To Review until user confirms.

If any check fails: Fix before setting To Review. Do not rely on reviewer to catch preventable issues.

Critical Rules

• Single-task updates only; no bulk status changes.
• Keep language of the task (EN/RU) in edits/comments.
• No code snippets in the description; code lives in repo, not in Linear.
• No new test creation; only update existing tests if required.
• Preserve Foundation-First ordering from orchestrator; do not reorder tasks.
• Do NOT commit. Leave all changes uncommitted — the reviewer reviews and commits.

Definition of Done

• Task selected and set to In Progress; kanban updated accordingly.
• Guides/manuals/ADRs/research read; approach aligned with task Technical Approach.
• Implementation completed per plan/AC; each AC verify: method executed with pass evidence.
• Docs and impacted tests updated.
• Typecheck and lint passed (or project quality commands) with evidence in comment.
• Task set to To Review; kanban moved to To Review; summary comment added.

Reference Files

• Tools config: shared/references/tools_config_guide.md
• Storage mode operations: shared/references/storage_mode_detection.md
• Guides/manuals/ADRs/research: docs/guides/, docs/manuals/, docs/adrs/, docs/research/
• Kanban format: docs/tasks/kanban_board.md

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Version: 3.0.0 Last Updated: 2025-12-23