Feature — Lightweight Feature Specification

Generate a concise, implementation-ready feature specification that serves as the input contract for code-forge:plan.

Core Principles

1. Concise over comprehensive: 1-3 pages, not 20. Enough for a developer to plan implementation, not enough for a full architecture review.
2. Language-agnostic: Describe behavior, interfaces, and constraints — not Pydantic models or TypeBox schemas.
3. Implementation-ready: Every section should help code-forge:plan generate concrete tasks.
4. Single module focus: One feature spec per module or cohesive component. If scope spans multiple modules, suggest running /spec-forge:decompose first.
5. Two sources of truth: Can be created from scratch via Q&A, or extracted from an existing tech-design.

Output Location

docs/features/{feature-name}.md

where {feature-name} is a lowercase, kebab-case slug (e.g., core-executor, schema-system, acl-system).

CRITICAL — No Sequential Numbering: Do NOT prefix filenames with sequence numbers like F001-, F002-, 001-, etc. The filename is ONLY the kebab-case slug. Ordering and relationships between features are managed in the overview file, not encoded in filenames.

If the docs/features/ directory does not exist, create it.

Overview File

When generating feature specs for a multi-feature project (i.e., more than one feature spec exists or will exist in docs/features/), maintain an overview file:

docs/features/overview.md

Overview file rules:

• Create or update this file whenever a new feature spec is generated
• If the overview file already exists, read it and append/update the new feature entry
• If a project manifest exists (docs/project-*.md), use its execution order and dependency information
• Do NOT create the overview for a single standalone feature — only when 2+ features exist

Overview template:

# Feature Overview

> Auto-generated index of feature specs for this project.
> Updated: {date}

## Features

| Feature | Description | Dependencies | Status |
|---------|-------------|--------------|--------|
| [{feature-name}](./{feature-name}.md) | {one-line description} | {none or list} | draft |
| ... | ... | ... | ... |

## Execution Order

{Ordered list showing recommended implementation sequence, derived from dependencies.
If sourced from a project manifest, reference it.}

1. **{feature-name}** — {reason it goes first, e.g., "no dependencies"}
2. **{feature-name}** — {reason, e.g., "depends on feature-1"}
3. ...

Workflow

Step 1: Detect Mode

Parse the feature name from arguments. Then determine the mode:

Chain mode detection: If the invocation prompt contains "Chain mode" or "Auto-confirm extraction", this is being called as part of the spec-forge chain. In chain mode:

• Skip all AskUserQuestion calls — auto-select the recommended option at each step
• If existing feature spec exists → auto-select "Regenerate from scratch"
• If upstream tech-design is found → auto-select "Extract from tech-design"
• In Step 2a.2 → skip confirmation, proceed directly to generation
• CRITICAL: Filename MUST be {feature-name}.md — plain kebab-case slug, NO numeric prefixes (01-, F001-, etc.). This rule applies in ALL modes but is especially important in chain mode where multiple features are generated sequentially.
• After generating, ALWAYS create or update docs/features/overview.md (the overview tracks execution order, not filenames)

1. Check for existing feature spec: If docs/features/{feature-name}.md already exists:

   • Display: "Feature spec already exists at docs/features/{feature-name}.md"
   • Use AskUserQuestion (skip in chain mode — auto-select "Regenerate from scratch"):
     • "Update existing spec" — read current file as context, proceed to Q&A with existing content pre-loaded
     • "Regenerate from scratch" — proceed as if no file exists
     • "Cancel"

2. Check for upstream tech-design: Scan for docs/{feature-name}/tech-design.md or docs/*/tech-design.md that covers this feature.

   • Found → Extract mode (Step 2a)
   • Not found → Standalone mode (Step 2b)

3. If upstream tech-design is found, ask the user (skip in chain mode — auto-select "Extract from tech-design"):

   • "Extract from tech-design (Recommended)" — faster, ensures consistency with formal specs
   • "Create from scratch" — ignore existing tech-design, do fresh Q&A
   • "Cancel"

Step 2a: Extract Mode (from Tech Design)

Read the upstream docs/{feature-name}/tech-design.md (or the matched tech-design file).

2a.1 Scan and Extract

Extract these elements from the tech-design:

• Module purpose and scope
• Key components and their responsibilities
• Core interfaces (public API surface, not internal details)
• Data flow (input → processing → output)
• Dependencies on other modules
• Constraints and invariants
• Error handling strategy (summary, not full taxonomy)

2a.2 Confirm with User

Present a brief summary of what was extracted. Use AskUserQuestion (0-1 questions) — skip in chain mode, proceed directly to generation:

• "Anything to add or change?" with options:
  • "Looks good, generate" — proceed
  • "Add notes" — user provides additional context
  • "Cancel"

2a.3 Generate

Write the feature spec to docs/features/{feature-name}.md using the template below. Skip to Step 4.

Step 2b: Standalone Mode (Q&A)

No upstream tech-design found. Gather requirements through a brief interview.

2b.1 Read Context

1. Glob the project tree (top 3 levels) for structure awareness
2. Read README.md if it exists
3. Scan docs/ for related documents (PRD, SRS, other feature specs)
4. Scan existing code if the module partially exists

Summarize context internally — do not present to user.

2b.2 Interview (2-3 rounds)

Use AskUserQuestion to understand the feature. Adapt based on answers.

Round 1 — Purpose and Scope:

• What does this module/component do? (one paragraph)
• What are its core responsibilities? (3-5 bullet points)
• What is explicitly out of scope?

Round 2 — Interfaces and Data:

• What does it receive as input? From whom?
• What does it produce as output? For whom?
• What external systems or modules does it depend on?
• Are there key data structures or models involved?

Round 3 — Constraints (if needed):

• Performance requirements? (throughput, latency)
• Security or access control requirements?
• Concurrency or ordering guarantees?
• Any hard constraints from the protocol or spec layer?

Stop when you have enough to write a clear feature spec. Do NOT over-interview — 2 rounds is often sufficient.

Step 3: Generate Feature Spec

Write the document to docs/features/{feature-name}.md using the template below.

Reminder: The filename MUST be {feature-name}.md — a plain kebab-case slug with NO numeric prefixes (no F001-, 001-, etc.).

Step 3b: Update Overview (if applicable)

After writing the feature spec, check if 2+ feature specs now exist in docs/features/ (excluding overview.md):

• If yes: Create or update docs/features/overview.md using the overview template from the Output Location section
• If no (this is the only feature spec): Skip overview generation

Step 4: Quality Check

Verify the generated feature spec against these criteria:

• Purpose is clear: A developer can understand what this module does in 30 seconds
• Scope is bounded: What's included AND what's excluded is explicit
• Interfaces are defined: Inputs, outputs, and dependencies are listed
• Language-agnostic: No language-specific types, libraries, or patterns
• Actionable: code-forge:plan could generate implementation tasks from this
• Concise: Under 3 pages / ~150 lines
• No numbered prefix: Filename is a plain kebab-case slug, NOT prefixed with F00X or similar

Fix any issues before presenting.

Step 5: Summary

Display:

Feature spec generated: {feature-name}
  Location: docs/features/{feature-name}.md
  Source: {extracted from tech-design | standalone Q&A}
  Length: {line count} lines
  Overview: {updated | not needed (single feature)}

Next steps:
  /code-forge:plan @docs/features/{feature-name}.md   → Generate implementation plan
  /spec-forge:tech-design {feature-name}               → Generate full technical design (if needed)

Feature Spec Template

# {Feature Name}

> Feature spec for code-forge implementation planning.
> Source: {standalone | extracted from docs/{name}/tech-design.md}
> Created: {date}

## Purpose

{One paragraph describing what this module does and why it exists.}

## Scope

**Included:**
- {responsibility 1}
- {responsibility 2}
- ...

**Excluded:**
- {explicitly out of scope item 1}
- ...

## Core Responsibilities

1. **{Responsibility name}** — {brief description of what it does}
2. **{Responsibility name}** — {brief description}
3. ...

## Interfaces

### Inputs
- **{input name}** ({source}) — {description}
- ...

### Outputs
- **{output name}** ({destination}) — {description}
- ...

### Dependencies
- **{module/system name}** — {what it provides and why it's needed}
- ...

## Data Flow

{Describe the main processing pipeline or data flow. Use a mermaid diagram if the flow has 3+ steps:}

```mermaid
graph LR
    A[Input] --> B[Process Step 1]
    B --> C[Process Step 2]
    C --> D[Output]

Key Behaviors

{Describe the important behavioral rules, algorithms, or processing logic. Focus on WHAT happens, not HOW to implement it.}

{Behavior 1}

{Description}

{Behavior 2}

{Description}

Constraints

• {constraint type}: {description}
• ...

Error Handling

{Summary of error categories and expected behavior. Not a full error taxonomy — just enough to guide implementation.}

Notes

{Any additional context, open questions, or references to related documents.}

## Relationship to Other spec-forge Documents

| Document | Relationship |
|----------|-------------|
| **PRD** | Feature spec may reference PRD requirements but does not duplicate them |
| **SRS** | Feature spec is less formal — no requirement IDs, no CRUD matrix |
| **Tech Design** | Feature spec is a condensed derivative; tech-design is the authoritative source |
| **Test Plan** | Feature spec does not cover testing strategy |
| **Decompose** | If a project is decomposed, each sub-feature can have its own feature spec |

## When to Use This vs Tech Design

| Scenario | Use |
|----------|-----|
| Quick module planning, daily development | `/spec-forge:feature` |
| Formal architecture review, team alignment | `/spec-forge:tech-design` |
| Full project specification chain | `/spec-forge <name>` (includes tech-design) |
| Already have tech-design, need implementation input | `/spec-forge:feature` (extract mode) |