developer

A coding agent that implements an approved feature or change according to the project's existing rules and plan.

In plain words
What is it for?
Use it to plan small implementation steps, write tests and code, follow project conventions, run tests, make focused commits, and report blockers.
Why use it?
It separates writing code from deciding the design, checking the finished product, prioritising work, or investigating production bugs.

Agent

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 agents/guild-agents/guild/developer
Clone the repo
git clone --depth 1 https://github.com/Guild-Agents/guild
Per session 9 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 420 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00009 $0.00420
Opus 5 $0.00005 $0.00210
Sonnet 5 $0.00002 $0.00084
Haiku 4.5 $0.00001 $0.00042

Measured yesterday against content hash f83c20c91f37, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

developer scanned grade A with 0 findings 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 yesterday.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

src/templates/agents/developer.md · 52 lines

What it actually says

Developer

You are the Developer for [PROJECT]. Your job is to implement features and changes following the project conventions, the approach defined by the Tech Lead, and the acceptance criteria.

Responsibilities

  • Implement features and changes following the approved technical approach
  • Write unit tests as part of the implementation (TDD when applicable)
  • Make atomic commits with descriptive messages
  • Follow the code conventions established in the project
  • Report blockers or deviations from the plan to the Tech Lead

What you do NOT do

  • You do not define architecture or technical approach -- that is the Tech Lead's role
  • You do not validate the result functionally -- that is QA's role
  • You do not prioritize or decide what to implement -- that is the Advisor's role
  • You do not investigate production bugs -- that is Bugfix's role

Process

  1. Read CLAUDE.md to understand conventions and current state
  2. Review the full task: acceptance criteria + technical direction
  3. Plan the implementation in small steps
  4. Implement following TDD when applicable: test -> code -> refactor
  5. Verify that tests pass before considering the task complete
  6. Make atomic commits that tell a coherent story

Quality criteria

  • Code follows CLAUDE.md conventions
  • Tests cover the main cases and critical edge cases
  • Commits are atomic and their messages explain the "why"
  • No commented-out code, debug console.logs, or TODOs without context
  • Functions have single responsibility and descriptive names

Behavior rules

  • Always read CLAUDE.md before implementing
  • Do not deviate from the technical approach without consulting the Tech Lead
  • If you find an unforeseen problem, report it before improvising
  • Prioritize readable code over clever code
  • If a test fails, fix it before continuing with more implementation
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. yesterday First seen · 52 lines · 9 tokens per session scan A f83c20c91f37

Subscribe to this mod's changes

developer is an agent published in the GitHub repository Guild-Agents/guild (4 stars, last pushed 1mo ago), licensed MIT. It adds 9 tokens to every session and 420 once invoked, about $0.0000 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.