What is csharp-dns-server AGENTS.md?

Repository guidance for coding agents working on a C# DNS server, a service that translates domain names into network addresses. It explains the project layout, allowed changes, build steps, and development priorities.

Orienting an agent in the codebase, restoring and building the project, choosing tasks, and extending the DNS service, tests, documentation, monitoring, or zone providers.

It gives an agent the project context and boundaries needed to make changes safely and follow the repository's planned work.

How stephbu/csharp-dns-server configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to stephbu/csharp-dns-server. 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/stephbu/csharp-dns-server/master/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/stephbu/csharp-dns-server

Made for: Codex, OpenCode.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/stephbu/csharp-dns-server/agents-md/github.svg)](https://agentmods.dev/instructions/stephbu/csharp-dns-server/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/stephbu/csharp-dns-server/agents-md"><img src="https://agentmods.dev/badge/instructions/stephbu/csharp-dns-server/agents-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/stephbu/csharp-dns-server/agents-md"><img src="https://agentmods.dev/badge/instructions/stephbu/csharp-dns-server/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,305 This file is loaded in full into every session.

When invoked 1,305 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5.1	$0.01305	$0.01305
Opus 5.5	$0.00522	$0.00522
Sonnet 5.5	$0.00261	$0.00261
Haiku 4.5	$0.00130	$0.00130

Measured 2mo ago against content hash b973f0968126, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

csharp-dns-server AGENTS.md 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.md · 94 lines

How it starts

The opening of the file, as written. The whole thing — 94 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS GUIDE

Scope: assistants may edit code, tests, and documentation in this repository. Infrastructure/deployment assets remain off-limits unless explicitly approved.

1. Mission

Maintain and extend the csharp-dns-server so it becomes a production-ready DNS service with rich testing, observability, and zone-provider capabilities.
Follow the roadmap in docs/product_requirements.md, respect the priority tiers in docs/priorities.md (P0 reliability/protocol accuracy, P1 security & maintenance, P2 features), and focus on open GitHub issues aligned with those tiers.
Reference the prioritized backlog in docs/task_list.md when picking up work to stay aligned with near-term goals.

2. Repository Orientation

Project	Purpose	Notes
`Dns/`	Core library implementing DNS protocol, server loop, zone providers, HTTP status surface.	Entry point: `Dns/Program.cs`. Zone providers under `Dns/ZoneProvider`.
`dns-cli/`	Console host that runs the DNS server for local testing.	Mirrors `Dns/appsettings.json`.
`dnstest/`	xUnit suite covering protocol/utility components.	Expand here before adding new test assemblies.
`docs/`	Specs, PRD and future design docs.	`docs/product_requirements.md` drives priorities.

Key classes & files:

Dns/Program.cs: wiring for DI/config/servers via Microsoft.Extensions.DependencyInjection.
Dns/DnsServer.cs: UDP DNS loop and upstream forwarding.
Dns/SmartZoneResolver.cs: in-memory zone cache & round-robin dispenser.
Dns/HttpServer.cs: embedded status/diagnostics surface.
Dns/ZoneProvider/**: implementations (CSV, IP probes, BIND placeholder).

3. Getting Started

# restore & build
dotnet build csharp-dns-server.sln

# run tests
dotnet test csharp-dns-server.sln

# run server (localhost)
cd dns-cli
dotnet run -- ./appsettings.json

Gotchas:

UDP port 53 may be taken by Docker/ICS on Windows; change listener port in appsettings.json.
Dns/appsettings.json is copied to output; edit with care when adding samples.
Zone providers may depend on local files (CSV) or ping-able IPs—mock or isolate tests accordingly.

Read the full file on GitHub · 94 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.

2mo ago First seen · 94 lines · 1,305 tokens per session scan A b973f0968126

Subscribe to this mod's changes

csharp-dns-server AGENTS.md is an instructions file published in the GitHub repository stephbu/csharp-dns-server (121 stars, last pushed 11mo ago), licensed MIT. It adds 1,305 tokens to every session, about $0.0052 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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csharp-dns-server: Instructions file for Codex