Plan

/plan

Decompose a PRD into independent feature plans. Each feature is a vertical slice that can be implemented separately via /implement.

Guiding Principles

• No Plan Mode — this skill manages its own flow. EnterPlanMode/ExitPlanMode restrict Write/Edit tools and break the workflow.
• Session metadata is the source of truth — the session-start hook injects a metadata block with epic-id, epic-slug, parent artifacts, and output-target. Use these values verbatim — do NOT re-derive, re-extract, or generate alternatives.
• Thin vertical slices — each feature cuts through all relevant layers end-to-end, independently implementable
• Features map to user stories — every feature traces back to at least one PRD user story; no orphan features
• Wave number is the sole ordering primitive — no explicit dependency graph between features, just wave numbers
• Architectural, not procedural — feature plans describe WHAT to build, not step-by-step HOW; /implement discovers file paths and generates code

Phase 1: Execute

0. Check Research Trigger

Research triggers if ANY:

• Arguments contain research keywords
• Design references unfamiliar technology
• Complex integration required

If triggered, spawn an Explore agent as the researcher. It receives the research topic and returns findings with sources. Save findings, summarize to user and continue to next step.

1. Explore Codebase

Understand:

• Existing patterns, conventions, and architecture
• Module boundaries and interfaces
• Test structure and commands
• Dependencies and build tools

2. Identify Durable Architectural Decisions

Before slicing into features, identify high-level decisions that span the entire design and are unlikely to change during implementation:

• Route structures and API contracts
• Schema shapes and data models
• Authentication and authorization approach
• Service boundaries and module interfaces
• Shared infrastructure choices
• Deep modules (per Ousterhout's A Philosophy of Software Design): look for opportunities where a simple, narrow interface can hide significant implementation complexity. Prefer modules whose public surface rarely changes even as internals evolve. Flag shallow modules — those whose interface is nearly as complex as their implementation — as candidates for consolidation or redesign.

These become cross-cutting constraints that every feature must honor.

3. Decompose PRD into Features

Break the PRD into thin vertical slices. Each feature cuts through all relevant layers end-to-end.

Rules:

1. Each feature should be independently implementable
2. Features should map to user stories from the PRD
3. Avoid deep dependencies between features where possible
4. If a decision can be answered by exploring the codebase, explore instead of asking
5. If a question requires research (unfamiliar technology, external APIs), spawn an Explore agent as the researcher. It receives the research topic and returns findings with sources. Save findings to .beastmode/artifacts/research/YYYY-MM-DD-.md
6. Scope guardrail: new capabilities get deferred

"That sounds like its own design — I'll note it as a deferred idea."

1. Track deferred ideas internally

For each feature, capture:

• Name: short identifier (lowercase, hyphenated)
• User Stories: which PRD user stories this feature covers
• What to Build: architectural description of what needs to happen (no file paths or code)
• Acceptance Criteria: how to verify this feature is done
• Wave: proposed execution wave (1 = foundation, higher = depends on earlier waves)

Wave Assignment

When multiple features exist, propose wave groupings based on dependency analysis:

• Wave 1: Foundation features — no dependencies on other features
• Wave 2: Features that consume or extend wave 1 outputs
• Wave 3+: Integration features, cross-cutting concerns

Rules:

• Single-feature plans: assign wave 1 automatically
• Features with no inter-feature dependencies: same wave (parallel execution)
• Assign waves based on dependency analysis
• Wave number is the sole ordering primitive — no explicit dependency graph between features

4. Generate Integration Tests

After feature decomposition, evaluate each feature's behavioral impact and spawn the plan-integration-tester agent only for features that introduce new user-facing behavior.

4a. Collect Features

Build a feature batch from the decomposed features. For each feature, capture:

• Feature name (lowercase, hyphenated identifier)
• Associated user stories (the subset of PRD user stories this feature covers)

4b. Classify Behavioral Impact

Evaluate each feature in the batch for behavioral impact. A feature is non-behavioral if it matches any of these skip criteria:

• Documentation-only: user stories describe content changes, README updates, comment improvements, or documentation restructuring with no functional change
• Refactoring / code cleanup: user stories describe restructuring, renaming, extracting, or consolidating existing code without changing external behavior
• Configuration changes: user stories describe changes to configuration values, schema adjustments, or settings without new user-facing behavior
• Bug fix with existing coverage: user stories describe fixing a known bug where existing integration scenarios already cover the affected behavior

Classification heuristic — examine each feature's user stories for:

Behavioral indicators (feature IS behavioral):

• New user-facing behavior ("As a user, I want to...")
• Changed interaction patterns ("When the user does X, now Y happens instead of Z")
• New error modes visible to users ("...so that the user sees an error when...")
• New commands, options, or outputs

Non-behavioral indicators (feature is NOT behavioral):

• Restructuring language ("refactor", "extract", "consolidate", "rename", "move")
• Documentation language ("document", "update README", "add comments", "clarify")
• Configuration language ("change default", "add config option", "update schema")
• Internal-only changes ("improve performance", "reduce coupling", "clean up")
• Bug fix language with existing coverage ("fix bug where...", "correct behavior of...")

When ambiguous, classify as behavioral — false positives (unnecessary agent dispatch) are cheaper than false negatives (missed integration tests).

Partition the feature batch into two lists:

• behavioral_features: features that introduce new user-facing behavior
• skipped_features: features matching skip criteria

4c. Spawn Agent

If all features are non-behavioral (full skip):

Skip the agent dispatch entirely. Print a note:

Skip gate: all features non-behavioral — skipping integration test generation.
Skipped: [list of feature names]

Proceed directly to step 4d with the full-skip flag set.

If at least one feature is behavioral (partial or full dispatch):

If any features were filtered out, print a note:

Skip gate: [N] non-behavioral features filtered.
Dispatching: [list of behavioral feature names]
Skipped: [list of skipped feature names]

Spawn the plan-integration-tester agent as a subagent:

• Agent: beastmode:plan-integration-tester
• Input: Epic slug (from session metadata) and the behavioral_features batch only (each feature with its name and user stories)
• Method: Agent(subagent_type="beastmode:plan-integration-tester", prompt=)

The agent reads the existing test tree, analyzes coverage against the feature-level user stories, and produces an integration artifact at .beastmode/artifacts/plan/YYYY-MM-DD--integration.md with scenarios grouped by feature name.

Handle agent status:

• DONE or DONEWITHCONCERNS: proceed to step 4d (distribute scenarios)
• NEEDS_CONTEXT or BLOCKED: print a warning and skip integration test generation entirely. Proceed to step 5 (Finalize Features). This is warn-and-continue — not a hard gate.

4d. Distribute Scenarios into Feature Plans

If full skip (no agent was dispatched):

For every feature in the batch, inject an empty ## Integration Test Scenarios section with a comment: ``. No integration artifact is produced. Proceed to step 5.

If agent was dispatched and succeeded:

Read the integration artifact and distribute scenarios inline:

1. Read the integration artifact produced by the agent
2. Parse per-feature sections — match ### Feature: headings in the "New Scenarios" section to the behavioral features
3. For each behavioral feature:

• If matching scenarios exist: inject the Gherkin block into a ## Integration Test Scenarios section in the feature's internal record
• If no matching scenarios: inject an empty ## Integration Test Scenarios section with a comment: `` and record a warning for the missing coverage

1. For each skipped (non-behavioral) feature:

• Inject an empty ## Integration Test Scenarios section with a comment: ``

1. Preserve the integration artifact as an audit trail (do not delete it)

The plan skill does not contain BDD domain knowledge — it delegates entirely to the agent and mechanically distributes the artifact's per-feature sections into feature plans.

5. Finalize Features

• Apply YAGNI — remove unnecessary scope
• Verify all features have user stories, descriptions, and acceptance criteria
• Self-review: check feature boundaries make sense, no overlaps, no gaps

Phase 2: Validate

1. PRD Coverage Check

Extract all user stories from the PRD. For each, verify it appears in at least one feature plan.

Print a coverage table:

PRD User Story                → Feature          Status
───────────────────────────────────────────────────────
US 1: Independent implement   → plan-rewrite     ✓
US 2: Per-feature implement   → impl-decompose   ✓
US 3: All-complete validate   → validate-gate    ✓

If any story shows ✗ MISSING, go back to Execute phase and assign it to a feature or create a new one.

2. Feature Completeness Check

Verify every feature has:

• [ ] Name (lowercase, hyphenated)
• [ ] At least one user story
• [ ] What to Build section (non-empty)
• [ ] At least one acceptance criterion
• [ ] Link to parent PRD

If incomplete, go back to Execute phase.

3. Overlap Analysis

Check for user stories that appear in multiple features. If found:

• If intentional (shared concern): note in both features
• If accidental: remove from one and re-verify coverage

Print summary:

Overlap Analysis
────────────────
US 1: plan-rewrite only
US 2: impl-decompose only
US 3: validate-gate, impl-decompose (shared — intentional)

4. Wave Stamping

Stamp wave: N into each feature's internal record based on execute phase's proposed wave assignments.

Rules:

• Single-feature plans: stamp wave: 1 automatically
• Multi-feature plans: use the wave assignments from execute phase
• Verify no circular dependencies exist (wave N features should not depend on wave N+1)

Print wave assignment:

Wave Assignment
───────────────
Wave 1: feature-a, feature-b (foundation — no dependencies)
Wave 2: feature-c (depends on wave 1 outputs)
Wave 3: feature-d (integration — cross-cutting)

5. Executive Summary

Present a consolidated view for debugging:

### Feature Plan Summary

**Design:** [PRD path]

**Architectural Decisions:**
| Decision | Choice |
|----------|--------|
| [decision 1] | [choice] |

**Features:** [count] features covering [count] user stories in [count] waves

| Wave | Feature | Stories | Scope | Rationale |
|------|---------|---------|-------|-----------|
| 1    | [slug]  | US 1, 3 | [one-line] | Foundation — no dependencies |
| 1    | [slug]  | US 4    | [one-line] | Foundation — no dependencies |
| 2    | [slug]  | US 2    | [one-line] | Depends on [wave 1 feature] |

This is read-only — do NOT ask new questions here.

Phase 3: Checkpoint

1. Write Feature Plan Files

For each feature, save to .beastmode/artifacts/plan/YYYY-MM-DD---..md using the feature plan format below.

Where ` is from session metadata, is the feature's name slugified (lowercase, hyphenated), and is assigned sequentially (.1, .2, .3`) based on feature creation order.

Each feature plan file must begin with YAML frontmatter:

---
phase: plan
epic-id: 
epic-slug: 
feature-name: 
wave: 
---

The feature-name field is the human-readable feature name in title case (e.g. Remove Topic Arg, not remove-topic-arg). Slugification is handled downstream.

2. Commit and Handoff

Commit all work to the feature branch:

git add -A
git commit -m "plan(): checkpoint"

Print features and their implement commands:

Features ready for implementation:

Wave 1:
  1.  → beastmode implement  
  2.  → beastmode implement  

Wave 2:
  3.  → beastmode implement  

STOP. No additional output.

Reference

Feature Plan Format

Template

Each feature plan file follows this structure:

---
phase: plan
epic-id: 
epic-slug: 
feature-name: 
wave: 
---

# [Feature Name]

**Design:** [path to parent PRD]

## User Stories

[Numbered list of user stories this feature covers, copied from the PRD]

## What to Build

[Architectural description of what needs to happen. Describe modules, interfaces, and interactions. Do NOT include specific file paths or code — /implement will discover those via codebase exploration.]

## Integration Test Scenarios

[Optional. Gherkin scenarios distributed from the plan-integration-tester agent. If present, contains one or more tagged Gherkin feature blocks. If no scenarios were produced, contains a comment noting the absence.]

## Acceptance Criteria

- [ ] [Criterion 1]
- [ ] [Criterion 2]
- [ ] [Criterion N]

Guidelines

• No file paths — /implement explores the codebase and determines exact files
• No code snippets — /implement generates task-level code during decomposition
• Architectural, not procedural — describe WHAT, not step-by-step HOW
• Self-contained — each feature should be implementable without reading other feature plans
• Linked — always reference the parent PRD and shared architectural decisions
• Wave field — stamped by validate phase, indicates execution order (1 = foundation, higher = later)

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: BugRoger
• Source: BugRoger/beastmode
• License: MIT

Install and usage instructions live in the source repository linked above.