Official agent skill

Build Parallelism

Guide for optimizing MSBuild build parallelism and multi-project scheduling.

OfficialMITAuto-check passed

Install Build Parallelism

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/build-parallelism .claude/skills/build-parallelism && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .claude/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/build-parallelism .agents/skills/build-parallelism && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .agents/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/build-parallelism .cursor/skills/build-parallelism && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .cursor/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/microsoft/testfx.git --path .agents/skills/build-parallelism

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/build-parallelism .gemini/skills/build-parallelism && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .gemini/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/build-parallelism .github/skills/build-parallelism && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .github/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add microsoft/testfx --skill build-parallelism -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install microsoft/testfx build-parallelism --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/microsoft/testfx.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/build-parallelism .opencode/skills/build-parallelism && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "build-parallelism" agent skill from https://github.com/microsoft/testfx/tree/main/.agents/skills/build-parallelism into .opencode/skills/build-parallelism/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "build-parallelism", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: build-parallelism
GitHub stars: 1k
Token cost: ~1.2k tokens
SKILL.md length: 493 words
Files: 1
Skills in repo: 44
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Guide for optimizing MSBuild build parallelism and multi-project scheduling.

Works in 5 steps: Use expensive_projects tool → find the… → Use expensive_targets tool → find… → Use project_target_times tool → drill… → …
: builds not utilizing all CPU cores
SKILL.md covers MSBuild Parallelism Model, Project Dependency Graph, Graph Build Mode (/graph) and Optimizing Project References, plus 4 more sections
Calls dotnet

What it does

Build Parallelism is an agent skill from microsoft/testfx, published by the product's own GitHub organization. Guide for optimizing MSBuild build parallelism and multi-project scheduling. USE FOR: builds not utilizing all CPU cores, speeding up multi-project solutions, evaluating graph build mode (/graph), build time not improving with -m flag, understanding project dependency topology. Note: /maxcpucount default is 1 (sequential) — always use -m for parallel builds. Covers /maxcpucount, graph build for better scheduling and isolation, BuildInParallel on MSBuild task, reducing unnecessary ProjectReferences, solution…

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: This repository holds the source code of Microsoft.Testing.Platform (MTP), a lightweight alternative to VSTest, as well as MSTest adapter and framework. The licence is MIT.

When your agent uses it

: builds not utilizing all CPU cores
Speeding up multi-project solutions
Evaluating graph build mode (/graph)
Build time not improving with -m flag

Example prompts

“/build-parallelism”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

Use expensive_projects tool → find the slowest projects and compare individual vs total build time
Use expensive_targets tool → find bottleneck targets
Use project_target_times tool → drill into a specific project's target-level timing
Ideal: build time should be much less than sum of project times (parallelism)
If build time ≈ sum of project times: too many serial dependencies, or one slow project blocking others

What it can do on your machine

Read from SKILL.md and the folder at commit 44b9dcc. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
- dotnet
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Build Parallelism loads about 1.2k tokens when it runs. Until then it costs about 188 tokens; SKILL.md has 493 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~188
When it runs · the whole SKILL.md, loaded when a task matches: ~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from microsoft/testfx at commit 44b9dcc, republished under its MIT licence (© microsoft). 493 words, ~1,159 tokens.

Download SKILL.mdSave it as .claude/skills/build-parallelism/SKILL.md (or your agent's skills folder).

name: build-parallelism
description: Guide for optimizing MSBuild build parallelism and multi-project scheduling. USE FOR: builds not utilizing all CPU cores, speeding up multi-project solutions, evaluating graph build mode (/graph), build time not improving with -m flag, understanding project dependency topology. Note: /maxcpucount default is 1 (sequential) — always use -m for parallel builds. Covers /maxcpucount, graph build for better scheduling and isolation, BuildInParallel on MSBuild task, reducing unnecessary ProjectReferences, solution filters (.slnf) for building subsets. DO NOT USE FOR: single-project builds, incremental build issues (use incremental-build), compilation slowness within a project (use build-perf-diagnostics), non-MSBuild build systems.
license: MIT

MSBuild Parallelism Model

/maxcpucount (or -m): number of worker nodes (processes)
Default: 1 node (sequential!). Always use -m for parallel builds
Recommended: -m without a number = use all logical processors
Each node builds one project at a time
Projects are scheduled based on dependency graph

Project Dependency Graph

MSBuild builds projects in dependency order (topological sort)
Critical path: longest chain of dependent projects determines minimum build time
Bottleneck: if project A depends on B, C, D and B takes 60s while C and D take 5s, B is the bottleneck
Diagnosis: replay binlog to diagnostic log with performancesummary and check Project Performance Summary — shows per-project time; grep for node.*assigned to check scheduling
Wide graphs (many independent projects) parallelize well; deep graphs (long chains) don't

Graph Build Mode (`/graph`)

dotnet build /graph or msbuild /graph
What it changes: MSBuild constructs the full project dependency graph BEFORE building
Benefits: better scheduling, avoids redundant evaluations, enables isolated builds
Limitations: all projects must use <ProjectReference> (no programmatic MSBuild task references)
When to use: large solutions with many projects, CI builds
When NOT to use: projects that dynamically discover references at build time

Optimizing Project References

Reduce unnecessary <ProjectReference> — each adds to the dependency chain
Use <ProjectReference ... SkipGetTargetFrameworkProperties="true"> to avoid extra evaluations
<ProjectReference ... ReferenceOutputAssembly="false"> for build-order-only dependencies
Consider if a ProjectReference should be a PackageReference instead (pre-built NuGet)
Use solution filters (.slnf) to build subsets of the solution

BuildInParallel

<MSBuild Projects="@(ProjectsToBuild)" BuildInParallel="true" /> in custom targets
Without BuildInParallel="true", MSBuild task batches projects sequentially
Ensure /maxcpucount > 1 for this to have effect

Multi-threaded MSBuild Tasks

Individual tasks can run multi-threaded within a single project build
Tasks implementing IMultiThreadableTask can run on multiple threads
Tasks must declare thread-safety via [MSBuildMultiThreadableTask]

Analyzing Parallelism with Binlog

Show full SKILL.md (207 more words)Show less

Primary: binlog MCP (preferred)

Use the binlog MCP server (Microsoft.AITools.BinlogMcp, exposed under the binlog MCP namespace):

Use expensive_projects tool → find the slowest projects and compare individual vs total build time
Use expensive_targets tool → find bottleneck targets
Use project_target_times tool → drill into a specific project's target-level timing
Ideal: build time should be much less than sum of project times (parallelism)
If build time ≈ sum of project times: too many serial dependencies, or one slow project blocking others

Fallback: text-log replay (when MCP is unavailable)

Step-by-step:

Replay the binlog: dotnet msbuild build.binlog -noconlog -fl -flp:v=diag;logfile=full.log;performancesummary
Check Project Performance Summary at the end of full.log
Ideal: build time should be much less than sum of project times (parallelism)
If build time ≈ sum of project times: too many serial dependencies, or one slow project blocking others
grep 'Target Performance Summary' -A 30 full.log → find the bottleneck targets
Consider splitting large projects or optimizing the critical path

CI/CD Parallelism Tips

Use -m in CI (many CI runners have multiple cores)
Consider splitting solution into build stages for extreme parallelism
Use build caching (NuGet lock files, deterministic builds) to avoid rebuilding unchanged projects
dotnet build /graph works well with structured CI pipelines

Files

Just SKILL.md in .agents/skills/build-parallelism of microsoft/testfx.

Open the folder on GitHubat commit 44b9dcc

Compare with similar skills

Build Parallelism next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Build Parallelism compared with similar skills
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Parallel Execution Optimizeraffaan-m/ECC	274k	—	~363	Automated safety check: Pass	MIT	2 days ago
Scheduleasgeirtj/system_prompts_leaks	69k	—	~2.7k	Automated safety check: Pass	CC0-1.0	yesterday
Scheduleasgeirtj/system_prompts_leaks	69k	—	~597	Automated safety check: Pass	CC0-1.0	yesterday
SQL Optimizationgithub/awesome-copilot	40k	2 repos	~2.3k	Automated safety check: Pass	MIT	today

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Questions about Build Parallelism

What does Build Parallelism do?

Guide for optimizing MSBuild build parallelism and multi-project scheduling. Build Parallelism is an agent skill from microsoft/testfx, published by the product's own GitHub organization. Guide for optimizing MSBuild build parallelism and multi-project scheduling.

When should I use Build Parallelism?

Build Parallelism fits situations like: : builds not utilizing all CPU cores; speeding up multi-project solutions; evaluating graph build mode (/graph); build time not improving with -m flag.

How do I install Build Parallelism in Claude Code?

Run `npx skills add microsoft/testfx --skill build-parallelism -a claude-code`. Or copy the skill folder (.agents/skills/build-parallelism in microsoft/testfx) into .claude/skills/build-parallelism in your project. Claude Code loads it when a task matches its description.

How do I install Build Parallelism in Codex?

Run `npx skills add microsoft/testfx --skill build-parallelism -a codex`. Or copy the skill folder (.agents/skills/build-parallelism in microsoft/testfx) into .agents/skills/build-parallelism in your project. Codex loads it when a task matches its description.

Can I use Build Parallelism in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add microsoft/testfx --skill build-parallelism -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/build-parallelism, .gemini/skills/build-parallelism, .github/skills/build-parallelism and .opencode/skills/build-parallelism in your project.

What does Build Parallelism need to run?

Going by SKILL.md and its folder, Build Parallelism needs the command-line tools its instructions call (dotnet).

Does Build Parallelism access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Build Parallelism safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Build Parallelism use?

Build Parallelism is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Build Parallelism use?

About 1.2k tokens (SKILL.md is roughly 4.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Build Parallelism?

Skills that share tags, products or a category with Build Parallelism: Parallel Execution Optimizer (affaan-m/ECC, 274k stars), Parallel Execution Optimizer (affaan-m/ECC, 274k stars), Schedule (asgeirtj/system_prompts_leaks, 69k stars) and Schedule (asgeirtj/system_prompts_leaks, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Build Parallelism?

microsoft (a GitHub organization, an official publisher) maintains it in microsoft/testfx, which has 1,047 GitHub stars. The repository holds 44 skills in this directory. The repository was last updated on October 7, 2026.

Source: microsoft/testfx on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Build Parallelism

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

MSBuild Parallelism Model

Project Dependency Graph

Graph Build Mode (/graph)

Optimizing Project References

BuildInParallel

Multi-threaded MSBuild Tasks

Analyzing Parallelism with Binlog

Primary: binlog MCP (preferred)

Fallback: text-log replay (when MCP is unavailable)

CI/CD Parallelism Tips

Files

Compare with similar skills

Similar skills

More from microsoft/testfx

Questions about Build Parallelism

Graph Build Mode (`/graph`)