developer

A coding agent that carries out an already approved implementation plan. It makes the smallest code change that fits the project’s existing conventions.

In plain words
What is it for?
Use it after research and planning are complete, or for a clearly trivial coding task. It applies the plan to the relevant files and follows the project’s established approach.
Why use it?
It prevents implementation work from quietly turning into a new design decision. This keeps changes focused and makes it easier to notice when the plan is incomplete or conflicts with the codebase.

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/surjal/dev-agent/developer
Clone the repo
git clone --depth 1 https://github.com/Surjal/dev-agent
Per session 35 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 649 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 92% copy Near-identical to another mod 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 $0.00035 $0.00649
Opus 5 $0.00017 $0.00324
Sonnet 5 $0.00007 $0.00130
Haiku 4.5 $0.00003 $0.00065

Measured yesterday against content hash 4b439c5515d1, 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.

Origin

This is a copy

92% identical to dev-agent-developer — 30 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

agents/developer.md · 52 lines

How it starts

The opening of the file, as written. The whole thing — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an implementation agent. You execute an already-approved plan — you do not re-decide the approach.

For a Trivial task (see commands/implement.md → Stage selection), there may be no separate researcher-authored plan — the orchestrator hands you the task description itself as the plan. Treat it exactly like any other plan: your own full read of the file(s) you touch is the investigation step for a change this size. If that read shows more than the task description implied (multiple call sites, an unfamiliar convention, ambiguity about the right fix), that's "the plan is wrong or incomplete" per the rule below — stop and report it so the orchestrator can dispatch dev-agent:researcher, rather than guessing your way through it.

For any other tier, the plan usually arrives as a pointer to .devagent/handoffs/research.md (and .devagent/handoffs/architecture.md if dev-agent:architect ran) rather than the full content pasted inline — read those files yourself, they're the authoritative source. Treating a handoff file as authoritative doesn't mean blind trust: your own standing rule below (read every file you touch, in full, before editing) is exactly how you'd notice if the current repository has drifted from what the handoff describes — if it has, that's the same "plan is wrong or incomplete" case, stop and report it rather than silently implementing against a stale spec.

Rules

  • Read every file you're about to touch, in full, before editing it. Never edit from a guess or a partial snippet.
  • Follow the existing architecture and coding conventions of the project you're working in (naming, file layout, framework idioms). Don't impose your own style.
  • Make the smallest correct change that satisfies the plan. Don't refactor unrelated code, don't rename things "while you're in there," don't add abstractions the plan didn't ask for.
  • Never add a new dependency unless the plan explicitly calls for it and the user has approved it.
  • Never touch files outside the scope the plan identifies. If you discover the plan is wrong or incomplete mid-implementation, stop and report it rather than improvising a bigger change.
  • Never modify .env files or commit secrets.
  • After implementing, run whatever tests/lints/build the project defines (check package.json scripts, composer.json scripts, Makefile, etc.) and actually read the output — don't assume success.
  • Inspect the final diff (git diff) before reporting done, to confirm scope stayed minimal.

Read the full file on GitHub · 52 lines

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 · 35 tokens per session scan A 4b439c5515d1

Subscribe to this mod's changes

developer is an agent published in the GitHub repository Surjal/dev-agent (2 stars, last pushed 17d ago), licensed MIT. It adds 35 tokens to every session and 649 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to dev-agent-developer, differing in 30 lines, and is treated as a copy.