implement

A workflow step that builds the next unfinished feature milestone from a product requirements document (PRD), a file describing what the product should do. It organizes the work and sends individual tasks through an agent pipeline.

In plain words
What is it for?
Use it to implement the next pending milestone in a Belmont feature. It reads the feature’s PRD and planning files, creates the active milestone file, and runs the required tasks.
Why use it?
It removes the need to manually choose the next feature task and coordinate each implementation step. It also keeps plans, progress, and milestone files together for the selected feature.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/blake-simpson/belmont/implement
Any agent
npx skills add blake-simpson/belmont --skill implement
Clone the repo
git clone --depth 1 https://github.com/blake-simpson/belmont

Made for: Claude Code, Codex.

Per session 15 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 11,463 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00015 $0.11463
Opus 5 $0.00008 $0.05731
Sonnet 5 $0.00003 $0.02293
Haiku 4.5 $0.00002 $0.01146

Measured 2d ago against content hash 6ddc389c46a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implement scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

1. **Never curl, probe, or assume `localhost:3000`** (or any other well-known default) is "yours". A port that's already bound from outside your worktree belongs to someone else — another worktree, the user's own dev ses
plugin/skills/implement/SKILL.md · 597 lines

How it starts

The opening of the file, as written. The whole thing — 597 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Belmont: Implement

You are the implementation orchestrator. Your job is to implement the next pending milestone from the PRD by creating a focused MILESTONE file and executing tasks through a structured agent pipeline.

Feature Selection

Belmont organizes work into features — each feature gets its own directory under .belmont/features/<slug>/ with its own PRD, PROGRESS, TECH_PLAN, and MILESTONE files.

Select the Active Feature

  1. List all feature directories under .belmont/features/
  2. If features exist: read each feature's PRD.md for its name and status, then Ask which feature to implement, or auto-select the one with pending tasks
  3. If no features exist: tell the user to run /belmont:product-plan to create their first feature, then stop
  4. Set the base path to .belmont/features/<selected-slug>/

Base Path Convention

Once the base path is resolved, use {base} as shorthand:

  • {base}/PRD.md — the feature PRD
  • {base}/PROGRESS.md — the feature progress tracker
  • {base}/TECH_PLAN.md — the feature tech plan
  • {base}/MILESTONE.md — the active milestone file
  • {base}/MILESTONE-*.done.md — archived milestones
  • {base}/NOTES.md — learnings and discoveries from previous sessions

Master files (always at .belmont/ root):

  • .belmont/PR_FAQ.md — strategic PR/FAQ document
  • .belmont/PRD.md — master PRD (feature catalog)
  • .belmont/PROGRESS.md — master progress tracking (feature summary table)
  • .belmont/TECH_PLAN.md — master tech plan (cross-cutting architecture)

Worktree Environment

If the environment variable BELMONT_WORKTREE is set to 1, you are running in an isolated git worktree for parallel execution. Several sibling worktrees may be running the same project concurrently on different ports. Ignoring the port rules below will cause silent merge conflicts, verification flakes, and processes killing each other — treat this section as load-bearing.

Port variables set for you

Belmont populates these before your process starts. Use them directly; do not guess at port numbers, and do not copy ports out of package.json or config files.

Read the full file on GitHub · 597 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 597 lines · 15 tokens per session scan A 6ddc389c46a5

Subscribe to this mod's changes

implement is a skill published in the GitHub repository blake-simpson/belmont (4 stars, last pushed 14d ago), licensed Apache-2.0. It adds 15 tokens to every session and 11,463 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.