CSharpCoder

A coding assistant for writing C# parts of the Foundry Local SDK and connecting them to its native C library. It works with native calls, asynchronous wrappers, data conversion, streaming, and project files.

In plain words
What is it for?
Use it to port SDK features to C#, write native interop, wrap synchronous calls with async APIs, stream data through Channels, marshal native types, fix AOT or trimming issues, and update project files.
Why use it?
C# code that calls native libraries must carefully handle memory, types, asynchronous behavior, and compatibility with ahead-of-time compilation and trimming. This helps implement and maintain those boundaries.

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/microsoft/foundry-local/csharpcoder
Clone the repo
git clone --depth 1 https://github.com/microsoft/foundry-local
Per session 69 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,074 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00069 $0.02074
Opus 5 $0.00034 $0.01037
Sonnet 5 $0.00014 $0.00415
Haiku 4.5 $0.00007 $0.00207

Measured 2d ago against content hash 1ef167debc62, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

CSharpCoder 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.

.github/agents/CSharpCoder.agent.md · 148 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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 · 148 lines · 69 tokens per session scan A 1ef167debc62

Subscribe to this mod's changes

CSharpCoder is an agent published in the GitHub repository microsoft/foundry-local (2,532 stars, last pushed 2d ago), with no licence file. It adds 69 tokens to every session and 2,074 once invoked, about $0.0003 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 2026-08-30.