What problem does it solve? Slow Xcode builds caused by expensive Swift type-checking, oversized modules, and mixed-language bridging are hard to localize. This Skill turns build timing summaries and Swift frontend diagnostics into a ranked, evidence-backed optimization plan so developers know exactly which files and expressions to fix first. ## Core Features & Use Cases - Hotspot Detection: Runs a diagnostic build with -warn-long-function-bodies and -warn-long-expression-type-checking thresholds, then parses warnings into a ranked JSON artifact of the slowest functions and expressions. - Build Timing Analysis: Interprets Build Timing Summary categories such as CompileSwiftSources, SwiftEmitModule, and Planning Swift module to distinguish serial bottlenecks from parallelized workload. - Recommendation Reporting: Produces recommendations in a shared structured format with observed evidence, expected wall-clock impact, confidence, actionability class, and approval requirements. - Use Case: A developer notices clean builds taking minutes and incremental builds stalling after one-line changes. The Skill runs the diagnostics script, finds a 900ms type-checking expression in a monolithic SwiftUI body, and recommends decomposing it into typed subviews with an estimated impact. ## Quick Start Ask the assistant to analyze why your Xcode project's Swift compilation is slow and produce a ranked optimization plan using the compilation diagnostics build.
