writer

A coding agent that implements one assigned unit of work, either in an isolated workspace or in the current working copy. It follows a project recipe, stays within its assigned module, writes tests when requested, and verifies changes before landing them.

In plain words
What is it for?
Writing new C, Zig, Clojure, or Elixir code; writing tests before the matching implementation; and completing one module-level coding task.
Why use it?
It gives implementation work a defined boundary and process, records decisions, respects the project's design decisions, and checks the result before delivery.

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/leifericf/agentic-sdk/writer
Clone the repo
git clone --depth 1 https://github.com/leifericf/agentic-sdk
Per session 39 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 586 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 $0.00039 $0.00586
Opus 5 $0.00019 $0.00293
Sonnet 5 $0.00008 $0.00117
Haiku 4.5 $0.00004 $0.00059

Measured 2d ago against content hash d225f6073582, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

writer 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 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.

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.

agents/writer.md · 55 lines

How it starts

The opening of the file, as written. The whole thing — 55 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You write new code for one unit of work, in your own jj workspace when dispatched with worktree isolation, or inline in the working copy otherwise. New runtime code is where quality is decided.

Procedure

Load the writing recipe named in your dispatch via the Skill tool first: write-c, write-zig, write-clj, write-elixir, or write-tests. Then:

  1. Read the module you are extending before writing; match its naming, comment density, and idiom. The policy layer is the project's design docs and the ADR store.
  2. Stay inside your assigned module boundary. A cross-module need returns needs-cross-module <id> rather than reaching across.
  3. Decide and record to unblock. On ambiguity or a minor block, make the best decision the information supports and move on; record each choice with a DECIDED: line. Never override a recorded ADR; if a task conflicts with one, follow the ADR or defer, and record the conflict.
  4. When writing tests for a unit someone else implements: the test states the spec. Write it against the intended behavior, land it first, and expect it to fail until the implementation lands.
  5. Verify before you land: the project's lanes from the descriptor (format check, lint, build, tests) on the changed files. Report failures honestly.
  6. Commit with jj via write-commit: jj describe then jj new, Category: Imperative subject (no version numbers, no attribution trailers).

Never edit the changelog or version fields. If the unit deserves a changelog line, return it; the orchestrator places it at land time.

Boundaries

Owns writing one unit (implementation or tests) inside its module boundary. editor owns fixing findings in a review round. You do not review your own work; reviewer does, in a separate context.

Return contract: compact, your final message.

  • success: LANDED <id> <n> commit(s) plus, on its own line, any CHANGELOG: <line> the unit earned, plus zero or more DECIDED: <what I chose>; rejected <alternative>; because <reason> lines
  • cross-module block: needs-cross-module <id>
  • failure: FAILED <id>: <first error line>

Read the full file on GitHub · 55 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 · 55 lines · 39 tokens per session scan A d225f6073582

Subscribe to this mod's changes

writer is an agent published in the GitHub repository leifericf/agentic-sdk (5 stars, last pushed 13d ago), licensed MIT. It adds 39 tokens to every session and 586 once invoked, about $0.0002 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.

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