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Guide for diagnosing and improving MSBuild project evaluation performance. USE FOR: builds slow before any compilation starts, high evaluation time in binlog analysis, expensive glob patterns walking
The skill file stays in the publisher's repository.
Paste the copied command in a terminal. It installs this SKILL.md into that agent.
npx skills add dotnet/skills --skill eval-performance -a cursor -y
Guide for diagnosing and improving MSBuild project evaluation performance. USE FOR: builds slow before any compilation starts, high evaluation time in binlog analysis, expensive glob patterns walking large directories (node_modules, .git, bin/obj), deep import chains (>20 levels), preprocessed output >10K lines indicating heavy evaluation, property functions with file I/O ($([System.IO.File]::ReadAllText(...))), multiple evaluations per project. Covers the 5 MSBuild evaluation phases, glob optimization via DefaultItemExcludes, import chain analysis with /pp preprocessing. DO NOT USE FOR: compilation-time slowness (use build-perf-diagnostics), incremental build issues (use incremental-build), non-MSBuild build systems.
Guide for diagnosing and improving MSBuild project evaluation performance. USE FOR: builds slow before any compilation starts, high evaluation time in binlog analysis, expensive glob patterns walking large directories (node_modules, .git, bin/obj), deep import chains (>20 levels), preprocessed output >10K lines indicating heavy evaluation, property functions with file I/O ($([System.IO.File]::ReadAllText(...))), multiple evaluations per project. Covers the 5 MSBuild evaluation phases, glob optimization via DefaultItemExcludes, import chain analysis with /pp preprocessing. DO NOT USE FOR: compilation-time slowness (use build-perf-diagnostics), incremental build issues (use incremental-build), non-MSBuild build systems.
Evaluation is the work MSBuild does before any target runs — reading project files, processing imports, expanding globs. This skill helps you find and confirm evaluation bottlenecks. Measure first; recommend a change only when a measurement proves it is warranted.
Engage only when evaluation is measurably the bottleneck. Do NOT act when:
build-perf-diagnostics instead.incremental-build instead.EnableDefaultItems are only worth flagging when the numbers show
they cost real time. A project that evaluates quickly needs no change.When a pattern is present but unmeasured, report it as an observation and let the user decide — do not rewrite working configuration to match a "best practice" without evidence it costs measurable evaluation time. Prefer the smallest, most targeted change; never disable SDK defaults as a first move.
For a comprehensive overview of MSBuild's evaluation and execution model, see Build process overview.
<Import>, evaluate <PropertyGroup> top-to-bottom<ItemDefinitionGroup> metadata defaults<ItemGroup> with Include, Remove, Update, glob expansionKey insight: evaluation happens BEFORE any targets run. Slow evaluation = slow build start even when nothing needs compiling.
Use the binlog MCP server (Microsoft.AITools.BinlogMcp, exposed under the binlog MCP namespace) to analyze evaluation performance:
dotnet msbuild build.binlog -noconlog -fl "-flp:v=diag;logfile=full.log"grep -i 'Evaluation started\|Evaluation finished' full.logdotnet msbuild -pp:full.xml MyProject.csprojOnly pursue these remedies once a measurement shows item evaluation is slow and the globs are the cause; a custom glob that isn't walking large trees is fine.
**/*.cs walk the entire directory treenode_modules/, .git/, bin/, obj/ — millions of files<DefaultItemExcludes> to exclude large directoriessrc/**/*.cs instead of **/*.cs<EnableDefaultItems>false</EnableDefaultItems> only as a last resort (loses SDK defaults) — prefer the two options above first/pp output → search for <!-- Importing comments to see import treegrep 'Evaluation started.*ProjectName' full.log → if count > 1, check for differing global properties/graph)$([System.IO.File]::ReadAllText(...)) during evaluation — reads file on every evaluationdotnet msbuild -pp:full.xml