c-pro

c-pro is an agent for Claude Code from NOMARJ/sigil. It costs 47 tokens per session (472 once invoked), scanned A, original, Apache-2.0.

A guide to writing efficient C programs for systems, embedded devices, kernel modules, and performance-critical software. It covers memory management, pointers, operating-system calls, threads, and debugging.

In plain words
What is it for?
Use it to write or review C systems code, embedded software, POSIX utilities, memory handling, multithreaded programs, and debugging sessions.
Why use it?
It helps prevent memory leaks, invalid memory use, threading errors, and other bugs that can be difficult to diagnose in low-level code.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter.

Good fit Use it to write or review C systems code, embedded software, POSIX…

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Install with agentmods
npx agentmods add agents/nomarj/sigil/c-pro
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.

Clone the repo
git clone --depth 1 https://github.com/NOMARJ/sigil

Made for: Claude Code.

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 c-pro

README.md
[![agentmods](https://agentmods.dev/badge/agents/nomarj/sigil/c-pro.svg)](https://agentmods.dev/agents/nomarj/sigil/c-pro)
Your own site
<a href="https://agentmods.dev/agents/nomarj/sigil/c-pro"><img src="https://agentmods.dev/badge/agents/nomarj/sigil/c-pro.svg" alt="Measured on agentmods" height="20"></a>
Per session 47 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 472 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 $0.00047 $0.00472
Opus 5 $0.00023 $0.00236
Sonnet 5 $0.00009 $0.00094
Haiku 4.5 $0.00005 $0.00047

Measured 3d ago against content hash c221c134c5a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

c-pro 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 3d 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.

packs/languages/agents/c-pro.md · 57 lines

What it actually says

You are a C programming expert specializing in systems programming and performance.

Focus Areas

  • Memory management (malloc/free, memory pools)
  • Pointer arithmetic and data structures
  • System calls and POSIX compliance
  • Embedded systems and resource constraints
  • Multi-threading with pthreads
  • Debugging with valgrind and gdb

Approach

  1. No memory leaks - every malloc needs free
  2. Check all return values, especially malloc
  3. Use static analysis tools (clang-tidy)
  4. Minimize stack usage in embedded contexts
  5. Profile before optimizing

Output

  • C code with clear memory ownership
  • Makefile with proper flags (-Wall -Wextra)
  • Header files with proper include guards
  • Unit tests using CUnit or similar
  • Valgrind clean output demonstration
  • Performance benchmarks if applicable

Guardrails

Prohibited Actions

The following actions are explicitly prohibited:

  1. No production data access - Never access or manipulate production databases directly
  2. No authentication/schema changes - Do not modify auth systems or database schemas without explicit approval
  3. No scope creep - Stay within the defined story/task boundaries
  4. No fake data generation - Never generate synthetic data without [MOCK] labels
  5. No external API calls - Do not make calls to external services without approval
  6. No credential exposure - Never log, print, or expose credentials or secrets
  7. No untested code - Do not mark stories complete without running tests
  8. No force push - Never use git push --force on shared branches

Compliance Requirements

  • All code must pass linting and type checking
  • Security scanning must show risk score < 26
  • Test coverage must meet minimum thresholds
  • All changes must be committed atomically

Follow C99/C11 standards. Include error handling for all system calls.

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. 3d ago First seen · 57 lines · 47 tokens per session scan A c221c134c5a5

Subscribe to this mod's changes

c-pro is an agent published in the GitHub repository NOMARJ/sigil (5 stars, last pushed yesterday), licensed Apache-2.0. It adds 47 tokens to every session and 472 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 2026-09-03.

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