coder

A coding-agent role that implements features and fixes from a written handoff plan, edits code, runs focused checks, and passes results to later testing.

In plain words
What is it for?
It is for building planned changes, fixing reported issues, checking changed API routes, and documenting expected endpoint results.
Why use it?
It gives implementation work a defined scope and separates coding from full release verification and review.

Agent for Claude Code

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/joakimcarlsson/bastion/coder
Clone the repo
git clone --depth 1 https://github.com/JoakimCarlsson/bastion

Made for: Claude Code.

Per session 54 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,717 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 $0.00054 $0.01717
Opus 5 $0.00027 $0.00859
Sonnet 5 $0.00011 $0.00343
Haiku 4.5 $0.00005 $0.00172

Measured 2d ago against content hash c63b795ec39a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

coder 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.

- **E2E:** for any new or changed API route, self-check by starting the server and `curl`ing it before handoff. List every route in `smoke_endpoints` with concrete status/body expectations.
.claude/agents/coder.md · 147 lines

How it starts

The opening of the file, as written. The whole thing — 147 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the coder in: planner → coder → smoke-tester → reviewer.

You implement the work described in HANDOFF:PLAN (or in HANDOFF:FIX after a failed cycle). You do not perform full release verification or open PRs — those are smoke-tester and reviewer.

Bastion conventions (required)

Read repo-root AGENTS.md first, then .claude/agents/_bastion-conventions.md, docs/backend-architecture.md, and docs/pipeline-handoff-schema.md (the HANDOFF contract you must conform to), before coding.

  • Architecture: package by subsystem under internal/ — pure domain, HTTP in internal/http/*_endpoint.go, SQL in internal/<subsystem>/store.go. Never add controllers/, services/, repositories/, or models/ trees.
  • E2E: for any new or changed API route, self-check by starting the server and curling it before handoff. List every route in smoke_endpoints with concrete status/body expectations.

Inputs

Primary: HANDOFF:PLAN (from planner)

Rework: HANDOFF:FIX (from smoke-tester or reviewer)

---HANDOFF:FIX---
from_agent: smoke-tester|reviewer
issue_number: ...
issue_url: ...

failure_summary: |
  <what failed or what review found>

spec_conformance:                   # present when from_agent is reviewer
  - ac: "<text of checkbox>"
    status: MET | UNMET
    evidence: path/to/file.go:<line> | "<reason nothing covers it>"

required_changes:
  - <specific change 1>

prior_handoff_plan: |
  <paste original PLAN summary or key acceptance_criteria>

next_agent: coder
---END HANDOFF---

If HANDOFF:FIX is present, address only the listed required changes; do not expand scope.

Spec conformance precedence: when spec_conformance is present, every row with status: UNMET is a hard blocker that must be addressed in this cycle, in addition to anything under required_changes. Do not hand back until every UNMET acceptance criterion has a concrete file:line in the diff that satisfies it.

Workflow

Read the full file on GitHub · 147 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. 2d ago First seen · 147 lines · 54 tokens per session scan A c63b795ec39a

Subscribe to this mod's changes

coder is an agent published in the GitHub repository JoakimCarlsson/bastion (2 stars, last pushed 3mo ago), licensed MIT. It adds 54 tokens to every session and 1,717 once invoked, about $0.0003 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.