Msbuild Server
DevOps & Securitymsbuild-serverMsbuild Server is an Agent Skill for devops & security published in the dotnet/skills repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.
Guide for using MSBuild Server to improve CLI build performance. Activate when developers report slow incremental builds from the command line, or when CLI builds are noticeably slower than IDE builds. Covers MSBUILDUSESERVER=1 environment variable for persistent server-based caching. Do not activate for IDE-based builds (Visual Studio already uses a long-lived process).
How to use this skill
Bring this guide into your coding agent with a prompt tailored to the tool you use.
- Open your project in Codex.
- Copy and paste the prompt below.
- Review files and risks before approving any action.
Inspect the Agent Skill at https://github.com/dotnet/skills/blob/HEAD/plugins/dotnet-msbuild/skills/msbuild-server/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/msbuild-server, but wait for my approval before writing files or running scripts.
Copying this prompt does not install or run the skill. Review third-party files before use.
MSBuild Server for CLI Caching
Use the MSBuild Server to cache evaluation results across CLI builds, matching the performance advantage Visual Studio gets from its long-lived MSBuild process.
When to Use
- Small incremental builds from CLI (
dotnet build) are slower than expected - Developers notice that VS builds are faster than CLI builds for the same project
- CI agents run many sequential builds of the same repo
When Not to Use
- IDE-based builds (Visual Studio already uses a long-lived MSBuild process)
- One-off builds where cold-start overhead is acceptable
- Build correctness issues are suspected (disable the server to isolate the problem)
Inputs
| Input | Required | Description |
|---|---|---|
| Shell context | No | The shell where the environment variable will be set (bash, PowerShell, or Windows persistent) |
Workflow
Step 1: Confirm CLI context
Verify the developer is building from the command line (dotnet build), not from Visual Studio or another IDE. The MSBuild Server provides no benefit inside an IDE.
Step 2: Set the environment variable
# Bash / CI
export MSBUILDUSESERVER=1
# PowerShell
$env:MSBUILDUSESERVER = "1"
# Windows (persistent)
setx MSBUILDUSESERVER 1
Step 3: Validate improvement
Run two sequential builds of the same project and compare times:
- First build (cold):
dotnet build-- server starts, no cache benefit - Second build (warm):
dotnet build-- should be noticeably faster
The most noticeable improvement is in repos with many projects or complex Directory.Build.props chains.
Validation
-
MSBUILDUSESERVER=1is set in the shell - Second sequential build is faster than the first
-
dotnet build-server shutdownfollowed by a rebuild confirms the server restarts cleanly
Common Pitfalls
| Pitfall | Solution |
|---|---|
| Expecting improvement in Visual Studio | VS already uses long-lived MSBuild nodes; the server adds no benefit |
| Build correctness issues after enabling | Run dotnet build-server shutdown to reset; if issues persist, disable the server |
| Server process using unexpected memory | The server persists in background; shut down with dotnet build-server shutdown when idle |