Analyzing MSBuild Failures with Binary Logs
This skill diagnoses MSBuild build failures from a .binlog file. The preferred
path uses the binlog MCP server (Microsoft.AITools.BinlogMcp, exposed under the
binlog MCP namespace) which is bundled with this plugin. If the MCP server is
not available, fall back to the binlog replay workflow at the bottom.
Primary workflow — binlog MCP
The MCP server exposes structured tools for inspecting a .binlog without
parsing text logs. Call them directly instead of replaying the binlog to a text
file. Call tools/list for the MCP first if you are unsure which tools are available.
Important constraints:
- The
.binlogfile is a binary format — do NOT try tocat,head,strings, or read it directly. Use only the MCP tools to query it. - The original source/project files might or might NOT be available on disk. Project files (.csproj, .props, .targets, App.config, etc.) - if you cannot locate them on disk, they can only be read from within the binlog via MCP tools (e.g., embedded/source file retrieval).
- Synthesize findings as you go. Do not spend all available time investigating — once you have enough evidence, present your conclusions. A partial answer with clear reasoning is better than timing out mid-investigation.
Use the available MCP server tools to query the binary log for:
- Build errors and warnings
- MSBuild properties and their values
- MSBuild items (PackageReference, ProjectReference, etc.)
- Project evaluation data
- Target execution details
- File contents embedded in the binlog
Fallback workflow — text-log replay (when MCP is unavailable)
Use this only when the MCP server cannot be started (for example, on an older SDK or in an offline environment).
Replay the binlog to text logs
PowerShell note: Use
-flp:"v=diag;logfile=full.log;performancesummary"(quoted semicolons).
