Detect and fix performance issues in Rust projects using a modern 2026 toolchain. Use when the user asks to "profile rust", "optimize rust binary", "make it faster", "flamegraph", "pgo", "bolt", "find hotspots", "why is this slow", or mentions latency/throughput regressions in Rust code. Adapts to what's already in the repo (hotpath, criterion, custom allocator) before suggesting new tools. Covers CPU sampling, in-process pprof, deterministic benchmarks, heap profiling, causal profiling, and the PGO+BOLT pipeline.
