binlog-failure-analysis

name	binlog-failure-analysis
description	Analyze MSBuild binary logs to diagnose build failures. USE FOR: unclear MSBuild errors, cascading failures across the multi-project solution, tracing target execution/order, and inspecting evaluated properties/items. Requires an existing .binlog or explicit permission to generate one. DO NOT USE FOR: non-MSBuild build systems.
license	MIT

Analyzing MSBuild Failures with Binary Logs

This skill diagnoses MSBuild failures from .binlog evidence.

Dapper-FluentMap integration: prefer the narrowest failing project or Dapper.FluentMap.slnx command. Consider root Directory.Build.props, Directory.Build.targets, project-specific package versions, analyzer/generator projects, pack targets, and compatibility validation when tracing failures. A binlog-aware MCP/tool is optional, not assumed. Do not attempt to read .binlog as plain text.

Preferred path — structured binlog tooling when available

If a binlog-aware tool is available, inspect:

• errors and warnings;
• evaluated MSBuild properties;
• PackageReference and ProjectReference items;
• project evaluation data;
• target execution/order;
• the first causal failure before cascaded project failures.

Stop once the cause and affected target/property chain are sufficiently established.

Fallback — replay binary log to focused text logs

dotnet msbuild build.binlog -noconlog \
  -fl  -flp:v=diag\;logfile=full.log\;performancesummary \
  -fl1 -flp1:errorsonly\;logfile=errors.log \
  -fl2 -flp2:warningsonly\;logfile=warnings.log

PowerShell requires appropriate quoting around semicolon-delimited logger parameters.

Then search generated text logs, not the binary file:

cat errors.log
grep -n -B2 -A2 "CS0246" full.log
grep -i "CoreCompile.*FAILED\|Build FAILED\|error MSB" full.log

Generating a binlog when needed

If no binlog exists and the task requires one:

dotnet build ./Dapper.FluentMap.slnx --configuration Release /bl:build.binlog

Prefer a narrower failing .csproj command when it reproduces the issue. Treat .binlog and replay logs as temporary diagnostic artifacts unless explicitly requested otherwise.

Repository-specific checks

When the failure involves packaging/release, correlate the binlog with:

• Directory.Build.props / Directory.Build.targets;
• eng/package-catalog.json;
• package validation targets/scripts;
• analyzer/generator project settings;
• netstandard2.0 compatibility constraints;
• explicit package-version properties/PackageReference values.

Validation

• Cause is supported by properties/items/targets from the log rather than guessed from the final console error
• Cascading errors are distinguished from the first causal failure
• No binary log was parsed with plain-text tools
• Temporary diagnostic artifacts are not committed
• Fix is validated with the repository's deterministic build/test and pack checks when relevant