incremental-build

Scope and routing

Guide for optimizing MSBuild incremental builds. USE FOR: builds slower than expected on subsequent runs, 'nothing changed but it rebuilds anyway', diagnosing why targets re-execute unnecessarily, fixing broken no-op builds. Covers 8 common causes: missing Inputs/Outputs on custom targets, volatile properties in output paths (timestamps/GUIDs), file writes outside tracked Outputs, missing FileWrites registration, glob changes, Visual Studio Fast Up-to-Date Check (FUTDC) issues. Key diagnostic: look for 'Building target completely' vs 'Skipping target' in binlog. DO NOT USE FOR: first-time build slowness (use build-perf-baseline), parallelism issues (use build-parallelism), evaluation-phase slowness (use eval-performance), non-MSBuild build systems.

Required diagnosis output

For every diagnose or explain request, the final answer must explicitly cover all of these points, even when the immediate cause is simply missing Inputs/Outputs:

• the target and exact root-cause evidence;
• the actual input/output timestamp comparison;
• missing, deleted, cleaned, or rewritten outputs;
• complete inputs, including dynamic or volatile inputs;
• evaluated input/output paths and one-to-one mapping when item lists are batched;
• two identical no-change builds and the expected second-build skip/out-of-date evidence.