Skills binlog-failure-analysis
Analyze MSBuild binary logs to diagnose build failures by replaying binlogs to searchable text logs. Only activate in MSBuild/.NET build context. USE FOR: build errors that are unclear from console output, diagnosing cascading failures across multi-project builds, tracing MSBuild target execution order, investigating common errors like CS0246 (type not found), MSB4019 (imported project not found), NU1605 (package downgrade), MSB3277 (version conflicts), and ResolveProjectReferences failures. Requires an existing .binlog file. DO NOT USE FOR: generating binlogs (use binlog-generation), build performance analysis (use build-perf-diagnostics), non-MSBuild build systems. INVOKES: dotnet msbuild binlog replay, grep, cat, head, tail for log analysis.
git clone https://github.com/dotnet/skills
T=$(mktemp -d) && git clone --depth=1 https://github.com/dotnet/skills "$T" && mkdir -p ~/.claude/skills && cp -r "$T/plugins/dotnet-msbuild/skills/binlog-failure-analysis" ~/.claude/skills/dotnet-skills-binlog-failure-analysis && rm -rf "$T"
plugins/dotnet-msbuild/skills/binlog-failure-analysis/SKILL.mdAnalyzing MSBuild Failures with Binary Logs
Use MSBuild's built-in binlog replay to convert binary logs into searchable text logs, then analyze with standard tools (
grepcatheadtailfindBuild Error Investigation (Primary Workflow)
Step 1: Replay the binlog to text logs
Replay produces multiple focused log files in one pass:
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 note: Use
(quoted semicolons).-flp:"v=diag;logfile=full.log;performancesummary"
Step 2: Read the errors
cat errors.log
This gives all errors with file paths, line numbers, error codes, and project context.
Step 3: Search for context around specific errors
# Find all occurrences of a specific error code with surrounding context grep -n -B2 -A2 "CS0246" full.log # Find which projects failed to compile grep -i "CoreCompile.*FAILED\|Build FAILED\|error MSB" full.log # Find project build order and results grep "done building project\|Building with" full.log | head -50
Step 4: Detect cascading failures
Projects that never reached
CoreCompile# List all projects that ran CoreCompile grep 'Target "CoreCompile"' full.log | grep -oP 'project "[^"]*"' # Compare against projects that had errors to identify cascading failures grep "project.*FAILED" full.log
Step 5: Examine project files for root causes
# Read the .csproj of the failing project cat path/to/Services/Services.csproj # Check PackageReference and ProjectReference entries grep -n "PackageReference\|ProjectReference" path/to/Services/Services.csproj
Write your diagnosis as soon as you have enough information. Do not over-investigate.
Additional Workflows
Performance Investigation
# The PerformanceSummary is at the end of full.log tail -100 full.log # shows target/task timing summary grep "Target Performance Summary\|Task Performance Summary" -A 50 full.log
Dependency/Evaluation Issues
# Check evaluation properties grep -i "OutputPath\|IntermediateOutputPath\|TargetFramework" full.log | head -30 # Check item groups grep "PackageReference\|ProjectReference" full.log | head -30
Replay reference
| Command | Purpose |
|---|---|
| Full diagnostic log with perf summary |
| Errors only |
| Warnings only |
| Search for patterns in the replayed log |
| Preprocess — inline all imports into one file |
Generating a binlog (only if none exists)
dotnet build /bl:build.binlog
Common error patterns
- CS0246 / "type not found" → Missing PackageReference — check the .csproj
- MSB4019 / "imported project not found" → SDK install or global.json issue
- NU1605 / "package downgrade" → Version conflict in package graph
- MSB3277 / "version conflicts" → Binding redirect or version alignment issue
- Project failed at ResolveProjectReferences → Cascading failure from a dependency