incremental-build

npx skills add dotnet/skills --skill incremental-build --agent claude-code

Same command for any agent — swap --agent for codex, cursor, copilot.

## How MSBuild Incremental Build Works MSBuild's incremental build mechanism allows targets to be skipped when their outputs are already up to date, dramatically reducing build times on subsequent runs. - **Targets with `Inputs` and `Outputs` attributes**: MSBuild compares the timestamps of all files listed in `Inputs` against all files listed in `Outputs`. If every output file is newer than every input file, the target is skipped entirely. - **Without `Inputs`/`Outputs`**: The target runs every time the build is invoked. This is the default behavior and the most common cause of slow incremental builds. - **`Incremental` attribute on targets**: Targets can explicitly opt in or out of incremental behavior. Setting `Incremental="false"` forces the target to always run, even if `Inputs` and `Outputs` are specified. - **Timestamp-based comparison**: MSBuild uses file system timestamps (last write time) to determine staleness. It does not use content hashes. This means touching a file (updating its timestamp without changing content) will trigger a rebuild. ```xml <!-- This target is incremental: skipped if Output is newer than all Inputs --> <Target Name="Transform" Inputs="@(Transform

dotnet build /bl:first.binlog
dotnet build /bl:second.binlog
dotnet msbuild second.binlog -noconlog -fl -flp:v=diag;logfile=second-full.log;performancesummary
grep 'Building target\|Target.*was not skipped' second-full.log
grep "is newer than output" second-full.log
dotnet build /clp:PerformanceSummary
dotnet msbuild /pp:preprocess.xml