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axum-harness: Skill for Claude Code

.agents/skills/backend-engineering/SKILL.md

backend-engineering is a skill for Claude Code, Codex from openclosed-org/axum-harness. It costs 65 tokens per session (782 once invoked), scanned A, original, Apache-2.0.

A set of rules for building and reviewing backend services in Rust and Axum, a Rust web framework. It focuses on clear boundaries, explicit behavior, and evidence for claims about correctness.

In plain words
What is it for?
Use it when changing or reviewing backend services, servers, workers, contracts, repository tools, or backend documentation.
Why use it?
It helps prevent business logic from leaking into protocol handlers and makes decisions about durable, asynchronous, retryable, or replayable work explicit.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

This is openclosed-org/axum-harness's own configuration. It tells Claude Code and Codex how to work on axum-harness itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything axum-harness configures →

not rated 51repo 5mo ago A scan 65 tokens original Apache-2.0
View source ↗ openclosed-org/axum-harness
Reuse

Borrowing it

Nothing to install: this file belongs to openclosed-org/axum-harness. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/openclosed-org/axum-harness/main/.agents/skills/backend-engineering/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/openclosed-org/axum-harness

Made for: Claude Code, Codex.

Wrote this? Show the measurements

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README.md
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for backend-engineering

Your own site · 80×15
<a href="https://agentmods.dev/skills/openclosed-org/axum-harness/backend-engineering"><img src="https://agentmods.dev/badge/skills/openclosed-org/axum-harness/backend-engineering.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 782 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00065 $0.00782
Opus 5.5 $0.00026 $0.00313
Sonnet 5.5 $0.00013 $0.00156
Haiku 4.5 $0.00006 $0.00078

Measured 2mo ago against content hash bedab4b4e34a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

backend-engineering 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 2mo 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/skills/backend-engineering/SKILL.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Backend Engineering

Use this skill as the default quality lens for backend harness work.

Workflow skills guide judgment. Ownership skills still decide writable boundaries.

Objective

Keep the template small, explicit, typed, testable, and production-minded without pretending it is production-proven.

Prefer the smallest design that preserves:

  1. backend correctness
  2. hard service, protocol, server, worker, and platform boundaries
  3. topology-late growth
  4. executable evidence
  5. template-user simplicity
  6. agent resistance to drift

Decision Kernel

Before changing backend behavior, answer:

  1. What invariant must not be violated?
  2. Which boundary owns the violated or changed behavior?
  3. What is synchronous, asynchronous, durable, idempotent, replayable, or eventually consistent?
  4. What is the cheapest correct design that restores the invariant?
  5. What evidence can honestly be claimed after this change?

Boundary Rules

  1. services/** are business capability libraries by default, not service processes.
  2. servers/** adapt protocols and compose services; handlers do not own domain logic.
  3. workers/** advance async state and must make retry, idempotency, checkpoint/replay, dedupe, and recovery explicit when touched.
  4. packages/contracts/** owns shared protocol shapes before external API or event changes land elsewhere.
  5. platform/model/** describes platform-level metadata and global defaults; service-local semantics stay in services/<name>/model.yaml.
  6. Generated artifacts are read-only; change sources and regenerate.
  7. Optional app shells and UI packages must not become backend-core prerequisites.

Quality Rules

  1. Represent important invariants in types, constructors, constraints, or final transaction boundaries.
  2. Keep expected failures typed and matchable; do not leak internal dependency details to clients.
  3. Retries for side-effecting work require durable idempotency or an explicit reason they are safe.
  4. Cross-boundary events require a clear atomic state mutation and publication story, usually outbox-driven.
  5. Async work must have bounded concurrency, cancellation/shutdown behavior, timeout or backpressure expectations, and observable failure paths when relevant.
  6. Do not add traits, managers, adapters, compatibility layers, or generic repositories unless they protect a real boundary or remove proven duplication.
  7. Prefer reference-module reuse over new structure, but do not copy business semantics blindly.
  8. Fix the smallest causal closed loop; avoid broad rewrites without an invariant-driven reason.

Read the full file on GitHub · 81 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. 2mo ago First seen · 81 lines · 65 tokens per session scan A bedab4b4e34a

Subscribe to this mod's changes

backend-engineering is a skill published in the GitHub repository openclosed-org/axum-harness (51 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 65 tokens to every session and 782 once invoked, about $0.0003 per session on Opus 5.5. 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 2026-08-30.

Backend and APIsLanguagesRustai-agentsaxum-frameworkdistributed-systemsmicroservicesplatform-engineering
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