# Coderadd Feature > Add a feature to an existing codebase (brownfield workflow) Use when this capability is needed. - Skill: `tomevault-io/coderadd-feature` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/coderadd-feature` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/coderadd-feature/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Productivity - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/coderadd-feature --- # Coder Add-Feature Add a new feature to an EXISTING codebase using eri-coder workflow. Designed for brownfield development - modifying projects that already have code. ## Dynamic Context **CLI analysis:** !`python3 -m erirpg.commands.add_feature $ARGUMENTS --json 2>/dev/null || echo '{"error": "CLI failed"}'` **Codebase mapping status:** !`ls .planning/codebase/*.md 2>/dev/null | head -5 || echo "NOT_MAPPED"` **Existing features:** !`ls -d .planning/features/*/ 2>/dev/null | head -5 || echo "none"` --- ## Two Modes ### Standard Mode Add new features to a codebase: ```bash python3 -m erirpg.commands.add_feature "" --json ``` ### Reference Mode (Feature Porting) Port a feature from another program using behavior specs: ```bash python3 -m erirpg.commands.add_feature "" --reference /
--json ``` Example: ```bash python3 -m erirpg.commands.add_feature eritrainer sana "Sana model" --reference onetrainer/models/sana --json ``` --- ## Prerequisites 1. Must be in a project root (package.json, Cargo.toml, pyproject.toml, go.mod) 2. Codebase should be mapped (auto-runs `/coder:map-codebase` if not) ## Output Structure ``` .planning/features/{feature-name}/ ├── SPEC.md # Feature specification ├── CONTEXT.md # Discussion decisions (optional) ├── RESEARCH.md # Technical research (if needed) ├── PLAN-*.md # Implementation plans └── SUMMARY.md # Completion summary ``` --- ## Workflow Steps ### Step 1: Validate Environment Check project root and codebase mapping status. See [reference.md](reference.md#step-1-validate-environment). ### Step 2: Load Codebase Context Read STACK.md, ARCHITECTURE.md, CONVENTIONS.md from `.planning/codebase/`. See [reference.md](reference.md#step-2-load-codebase-context). ### Step 3: Feature Discussion Ask clarifying questions with AskUserQuestion. See [reference.md](reference.md#step-3-feature-discussion). ### Step 4: Write Feature Spec Create SPEC.md with problem, user stories, acceptance criteria. See [reference.md](reference.md#step-4-write-feature-spec). ### Step 5: Context Discussion (Optional) Discuss UI, API, or complex decisions if needed. See [reference.md](reference.md#step-5-context-discussion). ### Step 6: Research Phase (If Needed) Spawn `eri-phase-researcher` for non-trivial features. See [reference.md](reference.md#step-6-research-phase). ### Step 7: Create Implementation Plan Spawn `eri-planner` with full context. See [reference.md](reference.md#step-7-create-implementation-plan). ### Step 8: Plan Verification Spawn `eri-plan-checker` to verify coverage. See [reference.md](reference.md#step-8-plan-verification). ### Step 9: Execute Show summary, confirm with user, spawn `eri-executor` agents. See [reference.md](reference.md#step-9-execute). ### Step 10: Verification Verify criteria met, create SUMMARY.md, commit. See [reference.md](reference.md#step-10-verification). --- ## Reference Mode Details For porting features from another program, see [reference.md](reference.md#reference-porting-workflow). Key insight: **Behavior specs are portable**, implementation details are not. --- ## Agent Strategy | Task | Agent | Model | |------|-------|-------| | Codebase mapping | eri-codebase-mapper | sonnet | | Research | eri-phase-researcher | sonnet | | Planning | eri-planner | sonnet/opus | | Execution | eri-executor | sonnet | | Verification | eri-verifier | sonnet/haiku | --- ## Key Principles 1. ALWAYS respect existing codebase patterns 2. NEVER create new patterns when existing ones work 3. Read CONVENTIONS.md before writing ANY code 4. Integrate at the RIGHT place (check ARCHITECTURE.md) 5. Update existing tests if modifying tested code --- ## Completion Use [templates/completion-box.md](templates/completion-box.md) format. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/codealexx) — claim your Tome and manage your conversions.