Generate implementation specs from design specs. Takes a design spec file and produces a detailed, phased task breakdown ready for autonomous execution. Use after brainstorming is complete and design spec is written. Invoke with the design spec file path as argument.
/plugin marketplace add elertan/planspec/plugin install planspec@planspecThis skill inherits all available tools. When active, it can use any tool Claude has access to.
Transform validated design specs into actionable, phased implementation plans.
planspec:impl-spec planspec/designs/[topic].md
The design spec must contain (as produced by planspec:brainstorm):
Creates planspec/implementations/[topic].md with:
Read the design spec file
Verify all required sections exist:
If sections missing, abort with specific feedback:
"Cannot generate implementation spec. Design spec missing:
- [missing section 1]
- [missing section 2]
Run planspec:brainstorm to complete the design spec first."
Read existing codebase structure:
Map design components to concrete file paths:
Identify project conventions:
From the design spec, extract:
Security review needed if design spec mentions:
Mark phases for security review based on which tasks touch these areas
Each task should be:
### Task [Phase].[Number]: [Action verb] [what]
**Context:** [Why this task exists - link to design decision]
**Files:**
- Create: `path/to/new/file.ts`
- Modify: `path/to/existing/file.ts` - [what changes]
**Requirements:**
- [Specific requirement from design spec]
- [Another requirement]
**Acceptance Criteria:**
- [ ] [Verifiable condition - can be checked]
- [ ] [Another verifiable condition]
**Dependencies:** None | Task X.Y, Task X.Z
Group tasks into logical phases:
## Phase 1: [Foundation/Core/Setup]
[Tasks that must come first - shared infrastructure, types, utilities]
### Task 1.1: ...
### Task 1.2: ...
---
## Phase 2: [Core Implementation]
[Main feature implementation]
### Task 2.1: ...
### Task 2.2: ...
### Task 2.3: Write tests for Phase 2
**Tests should cover:**
- [Critical path from design spec]
- [Edge cases from design spec's Behavior section]
- [Error cases from design spec]
### CHECKPOINT
Gate: Tests pass, issues resolved before Phase 3.
---
## Phase 3: [Integration/Security-Sensitive]
### Task 3.1: ...
### Task 3.2: Write tests for Phase 3
### CHECKPOINT
Security: Auth flow, user input handling, database queries
Gate: Tests pass, issues resolved before completion.
| Design Section | Maps To |
|---|---|
| Architecture Overview | Phase 1 tasks (setup, structure) |
| Data Model | Early tasks (types, schemas, migrations) |
| Interfaces | API/contract tasks |
| Behavior - Happy Path | Core implementation tasks |
| Behavior - Edge Cases | Test requirements |
| Behavior - Error Handling | Implementation + test tasks |
| Testing Requirements | Test tasks per phase |
| Risks - Security | Security review checkpoints |
| Dependencies - Blocking | Task dependencies, Phase 1 setup |
Create file at planspec/implementations/[topic].md:
---
date: YYYY-MM-DD
design-spec: ../designs/[topic].md
status: ready
executor: planspec:impl-spec-executor
---
# Implementation: [Title]
> **Execute with:** `planspec:impl-spec-executor planspec/implementations/[topic].md`
## Overview
[1-2 sentence summary of what we're implementing]
**Design spec:** [link to design spec]
**Security reviews:** Phases X, Y (or "None")
## Prerequisites
- [ ] [Dependency from design spec]
- [ ] [Another dependency]
## Phase 1: [Name]
### Task 1.1: [Title]
...
---
## Phase 2: [Name]
### Task 2.1: [Title]
...
### Task 2.N: Tests for Phase 2
**Test file:** `path/to/tests/feature.test.ts`
**Cover:**
- [ ] [Happy path scenario]
- [ ] [Edge case 1]
- [ ] [Edge case 2]
- [ ] [Error case 1]
### CHECKPOINT
Gate: Tests pass, issues resolved before Phase 3.
---
## Completion Checklist
- [ ] All tasks completed
- [ ] All tests passing
- [ ] All review checkpoints passed
- [ ] Design spec success criteria met:
- [ ] [Criterion 1]
- [ ] [Criterion 2]
After writing the file:
Implementation spec created: planspec/implementations/[topic].md
Summary:
- Phases: [N]
- Tasks: [M]
- Checkpoints: [X]
- Security reviews: Phases [list] (or "None")
Prerequisites to verify:
- [Any blocking dependencies]
Ready to execute with: planspec:impl-spec-executor planspec/implementations/[topic].md
| Input | Design spec file path |
|---|---|
| Output | planspec/implementations/[topic].md |
| Phases | Logical groupings with review gates |
| Tasks | Mid-level granularity, verifiable |
| Tests | Per-phase, meaningful edge cases |
| Reviews | Code review at every checkpoint, security review where Security: specified |
This skill should be used when the user asks to "create an agent", "add an agent", "write a subagent", "agent frontmatter", "when to use description", "agent examples", "agent tools", "agent colors", "autonomous agent", or needs guidance on agent structure, system prompts, triggering conditions, or agent development best practices for Claude Code plugins.
This skill should be used when the user asks to "create a slash command", "add a command", "write a custom command", "define command arguments", "use command frontmatter", "organize commands", "create command with file references", "interactive command", "use AskUserQuestion in command", or needs guidance on slash command structure, YAML frontmatter fields, dynamic arguments, bash execution in commands, user interaction patterns, or command development best practices for Claude Code.
This skill should be used when the user asks to "create a hook", "add a PreToolUse/PostToolUse/Stop hook", "validate tool use", "implement prompt-based hooks", "use ${CLAUDE_PLUGIN_ROOT}", "set up event-driven automation", "block dangerous commands", or mentions hook events (PreToolUse, PostToolUse, Stop, SubagentStop, SessionStart, SessionEnd, UserPromptSubmit, PreCompact, Notification). Provides comprehensive guidance for creating and implementing Claude Code plugin hooks with focus on advanced prompt-based hooks API.