dax

name	dax
version	26.2
description	DAX performance optimization for semantic models. Automatically invoke when the user asks to "optimize DAX", "fix slow DAX", "DAX performance", "tune a measure", "debug a measure", "DAX anti-patterns", or mentions slow queries, server timings, or DAX authoring.

DAX

Skills and references for writing, debugging, and optimizing DAX in semantic models.

Optimization

For systematic DAX query performance optimization, read the workflow reference first:

references/dax-performance-optimization.md — Tiered framework (4 tiers), phased workflow, decision guide, and error handling.

Detailed reference files (progressive disclosure — consult as directed by the workflow):

• references/engine-internals.md — FE/SE architecture, xmSQL, compression/segments, SE fusion, trace diagnostics
• references/dax-patterns.md — Tier 1 DAX patterns (DAX001–DAX021) + Tier 2 query structure (QRY001–QRY004)
• references/model-optimization.md — Tier 3 model patterns (MDL001–MDL010) + Tier 4 Direct Lake (DL001–DL002)

Trace capture and performance profiling:

• Local models (Power BI Desktop): Use the connect-pbid skill — specifically performance-profiling.md for FE/SE timing and evaluateandlog-debugging.md for intermediate result inspection.
• Remote models (Fabric Service / XMLA): Use the powerbi-modeling-mcp VS Code extension for trace and query operations. Install: code --install-extension analysis-services.powerbi-modeling-mcp

Related Skills

• review-semantic-model — Model auditing including DAX anti-patterns and best practices
• connect-pbid (pbi-desktop plugin) — Trace capture, performance profiling, EVALUATEANDLOG debugging
• lineage-analysis — Impact analysis before model changes