build-comparison

name	build-comparison
description	Compare two MSBuild builds and report differences using binlog-insights MCP tools. Use when comparing CI vs local builds, before/after a change, different build configurations, or migrating build systems (e.g., CoreXT to stock MSBuild). Also triggers for build diff, environment differences, and package version mismatch.
metadata	{"traits":"MSBuild|DotNet|CSharp|NuGet|Build|Binlog"}

Build Comparison

Overview

Compare two .binlog files to find meaningful differences in properties, packages, and compiler inputs. Useful for build system migrations, CI vs local debugging, and verifying the effect of .props/.targets changes.

Quick Start

dotnet build /bl:before.binlog
# make changes
dotnet build /bl:after.binlog

Then ask: "Compare before.binlog and after.binlog — what changed?"

Workflow

1. Run binlog_overview on both binlogs to get build status, duration, and project counts
2. Run binlog_compare with both binlog paths to get:
   • Property differences — different MSBuild property values
   • Per-project package differences — packages with different versions in the same project
   • Solution-wide package differences — packages resolved to different versions anywhere
3. For significant property differences, use binlog_properties on each binlog to trace where the value is set
4. For package version differences, use binlog_items with type PackageReference or PackageVersion to understand why versions differ
5. If needed, use binlog_compiler on both binlogs for a specific project to compare actual compiler inputs (references, defines, flags)

Task Progress:
- [ ] Step 1: binlog_overview — both binlogs
- [ ] Step 2: binlog_compare — get all diffs
- [ ] Step 3: Investigate property differences
- [ ] Step 4: Investigate package differences
- [ ] Step 5: Compare compiler inputs if needed

Tool Reference

Tool	Purpose
binlog_overview	Build status, duration, project count
binlog_compare	Diff two binlogs: properties, packages
binlog_properties	MSBuild property values (use --filter)
binlog_items	Item groups: PackageReference, PackageVersion, etc.
binlog_compiler	Full compiler command line for diffing references
binlog_projects	Project list with status and duration

Common Patterns

Build system migration (e.g., CoreXT → stock MSBuild): Action: binlog_compare → check solution-wide package diffs → verify same packages resolve → binlog_compiler to compare reference lists

CI vs local mismatch: Action: binlog_compare → check property diffs for NuGetPackageRoot, SDK paths, Configuration → binlog_items to check if different package versions resolve

Before/after a .props change: Action: binlog_compare → check property diffs for the changed property → verify it propagated to the expected projects

Troubleshooting

• No binlog file: Rebuild with dotnet build /bl:build.binlog
• Tool not found: Ensure binlog-insights-mcp is installed: dotnet tool install -g BinlogInsights.Mcp
• Large result sets: Use --limit and --offset for pagination
• Filter to one project: Use --project <substring> on any tool to narrow results