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Build Perf Diagnostics · dotnet | DecimalAI

devopsby dotnet

Build Perf Diagnostics

dotnet/build-perf-diagnostics

Source dotnet/skills ↗License MIT

Diagnose MSBuild build performance bottlenecks using binary log analysis. USE FOR: identifying why builds are slow by analyzing binlog performance summaries, detecting ResolveAssemblyReference (RAR) taking >5s, Roslyn analyzers consuming >30% of Csc time, single targets dominating >50% of build time, node utilization below 80%, excessive Copy tasks, NuGet restore running every build. Covers timeline analysis, Target/Task Performance Summary interpretation, and 7 common bottleneck categories. Use

SkillScore86Maintained

Automatic

Coding pack

Last verified 8/9/2026

What it changes

Passed 17 of 20 test cases with the skill, and 14 of 20 without it.

Without skill68%

With skill86%

Checks it passed that the model alone missed

Recommends setting SkipCopyUnchangedFiles to true.
Recommends using the '--artifacts-path' command-line parameter.
Recommends conditioning EnforceCodeStyleInBuild on ContinuousIntegrationBuild being true.

and 2 more in the full report

5 fixed14 passed either way2 still failing1 broke

Pass-rate lift: +18 pp
Tokens: +87%
Agent turns: 0%
Response time: +28%

Model gemini-3.6-flashMeasured 8/9/2026v119 of 22 cases passed with skill · 20 comparable

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/dotnet-build-perf-diagnostics/SKILL.md https://app.decimal.ai/s/dotnet-build-perf-diagnostics/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add dotnet-build-perf-diagnostics, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/dotnet-build-perf-diagnostics/ and pins it in .decimal/skills.lock

decimalai skills add dotnet-build-perf-diagnostics

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/dotnet-build-perf-diagnostics/SKILL.md https://app.decimal.ai/s/dotnet-build-perf-diagnostics/SKILL.md

Raw file: /s/dotnet-build-perf-diagnostics/SKILL.md ↗ · machine-readable summary at /s/dotnet-build-perf-diagnostics.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 5 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 5

Prompt

To reduce excessive inter-project copy tasks across 50 project files in .NET 8, what command-line option consolidates build outputs into a single centralized directory structure without manually overriding `OutputPath` in every project?

What was checked, without and with the skill
Checked	Without skill	With skill
Recommends using the '--artifacts-path' command-line parameter.	Missed	Passed

case-13 · gemini-3.6-flash · 8/9/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md144 linessingle file

Performance Analysis Methodology

Generate a binlog: dotnet build /bl:{} -m
Use the binlog MCP server (Microsoft.AITools.BinlogMcp, exposed under the binlog MCP namespace) which is bundled with this plugin

Alternate flow when MCP is unavailable: binlog replay to text logs

Generate a binlog: dotnet build /bl:{} -m

Replay to diagnostic log with performance summary:

dotnet msbuild build.binlog -noconlog -fl -flp:v=diag;logfile=full.log;performancesummary

Read the performance summary (at the end of full.log):

grep "Target Performance Summary\|Task Performance Summary" -A 50 full.log

Find expensive targets and tasks: The PerformanceSummary section lists all targets/tasks sorted by cumulative time

Check for node utilization: grep for scheduling and node messages

grep -i "node.*assigned\|building with\|scheduler" full.log | head -30

Check analyzers: grep for analyzer timing

grep -i "analyzer.*elapsed\|Total analyzer execution time\|CompilerAnalyzerDriver" full.log

Key Metrics and Thresholds

Build duration: what's "normal" — small project <10s, medium <60s, large <5min
Node utilization: ideal is >80% active time across nodes. Low utilization = serialization bottleneck
Single target domination: if one target is >50% of build time, investigate
Analyzer time vs compile time: analyzers should be <30% of Csc task time. If higher, consider removing expensive analyzers
RAR time: ResolveAssemblyReference >5s is concerning. >15s is pathological

Common Bottlenecks

1. ResolveAssemblyReference (RAR) Slowness

Symptoms: RAR taking >5s per project
Root causes: too many assembly references, network-based reference paths, large assembly search paths

Track record

Benchmark

17 / 20

test cases passed, vs 14 / 20 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/3/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

dotnet / skills

plugins/dotnet-msbuild/skills/build-perf-diagnostics/SKILL.md

View on GitHub ↗

License MITImported 8/3/2026Version v1

More skills from the same source and nearby in the registry, with their headline benchmark lift.