OhMyCode: Skill for Claude Code

.agents/skills/customize-system-prompt/SKILL.md

customize-system-prompt is a skill for Claude Code, Codex from AlphaLab-USTC/OhMyCode. It costs 39 tokens per session (773 once invoked), scanned A, original, MIT.

A guide for changing an AI assistant’s personality, behavior, tone, or subject-matter focus through system instructions.

In plain words
What is it for?
Use it to add project-specific instructions in OHMYCODE.md or CLAUDE.md, or set global behavior such as tone, expertise, and coding preferences.
Why use it?
It lets a project apply consistent assistant behavior without changing application code.

Skill for Claude CodeCodex

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

This is AlphaLab-USTC/OhMyCode's own configuration. It tells Claude Code and Codex how to work on OhMyCode 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 OhMyCode configures →

Reuse

Borrowing it

Nothing to install: this file belongs to AlphaLab-USTC/OhMyCode. 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/AlphaLab-USTC/OhMyCode/main/.agents/skills/customize-system-prompt/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/AlphaLab-USTC/OhMyCode

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for customize-system-prompt

README.md
[![agentmods](https://agentmods.dev/badge/skills/alphalab-ustc/ohmycode/customize-system-prompt/github.svg)](https://agentmods.dev/skills/alphalab-ustc/ohmycode/customize-system-prompt)
Your own site
<a href="https://agentmods.dev/skills/alphalab-ustc/ohmycode/customize-system-prompt"><img src="https://agentmods.dev/badge/skills/alphalab-ustc/ohmycode/customize-system-prompt/github.svg" alt="Measured on agentmods" height="20"></a>

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 customize-system-prompt

Your own site · 80×15
<a href="https://agentmods.dev/skills/alphalab-ustc/ohmycode/customize-system-prompt"><img src="https://agentmods.dev/badge/skills/alphalab-ustc/ohmycode/customize-system-prompt.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 773 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 $0.00039 $0.00773
Opus 5.5 $0.00016 $0.00309
Sonnet 5.5 $0.00008 $0.00155
Haiku 4.5 $0.00004 $0.00077

Measured 1mo ago against content hash 80f5e7306c2b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

customize-system-prompt 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 1mo 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/customize-system-prompt/SKILL.md · 106 lines

How it starts

The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Customize OhMyCode's System Prompt

Change the AI assistant's personality, behavior rules, or domain expertise without writing code.

When to Use

  • User says "make it more formal", "act like a senior engineer", "focus on Python"
  • User wants to add custom instructions or constraints
  • User wants the AI to have domain-specific knowledge

Three Ways to Customize

Method 1: OHMYCODE.md (Per-Project, Recommended)

Create a OHMYCODE.md (or CLAUDE.md) file in your project root:

# Project Instructions

You are working on a Django REST API project.

## Rules
- Always use type hints
- Prefer class-based views over function-based
- Write docstrings for all public functions
- Use Black formatting style

## Tech Stack
- Python 3.12, Django 5.0, PostgreSQL
- pytest for testing, factory_boy for fixtures

OhMyCode auto-detects this file and injects it into the system prompt.

Scope: Only applies when running ohmycode in this directory.

Method 2: system_prompt_append (Global Config)

Add to ~/.ohmycode/config.json:

{
  "system_prompt_append": "Always respond in Chinese. Prefer simple solutions over clever ones. Never use global variables."
}

Scope: Applies to ALL conversations.

Method 3: Modify system_prompt.py (Advanced)

Edit ohmycode/core/system_prompt.py → build_system_prompt() to change the base role description or add new sections.

Scope: Permanent change to the codebase.

Examples

Friendly Tutor

# OHMYCODE.md
You are a patient coding tutor. Explain concepts step by step.
When the user makes a mistake, explain why it's wrong before showing the fix.
Use analogies to explain complex concepts.

Strict Code Reviewer

# OHMYCODE.md
You are a strict senior engineer doing code review.
Point out every issue: bugs, performance, readability, security.
Don't write code for the user — give them guidance to fix it themselves.
Rate code quality on a 1-10 scale.

Domain Expert

# OHMYCODE.md
You are an expert in machine learning with PyTorch.
When suggesting solutions, prefer PyTorch over TensorFlow.
Always consider GPU memory usage and training efficiency.
Reference relevant papers when explaining algorithms.

Read the full file on GitHub · 106 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. 1mo ago First seen · 106 lines · 39 tokens per session scan A 80f5e7306c2b

Subscribe to this mod's changes

customize-system-prompt is a skill published in the GitHub repository AlphaLab-USTC/OhMyCode (132 stars, last pushed 6mo ago), licensed MIT. It adds 39 tokens to every session and 773 once invoked, about $0.0002 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.

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