Metal already provides a strong precise floating-point contract. With fast math disabled (mathMode = .safe and mathFloatingPointFunctions = .precise, or -fno-fast-math), the Metal Shading Language specification requires correctly rounded FP32 add, subtract, multiply, reciprocal, divide, sqrt, rsqrt, and fma. I am looking for clarification and, if necessary, API support for the two remaining pieces needed for portable bit-exact numerical shaders: Arithmetic rounding mode MSL §8.2 says either round-to-nearest-ties-to-even or round-toward-zero may be supported for floating-point operations. I cannot find a way to select or query the arithmetic rounding mode. The newer MTLCompileOptions.floatingPointConversionRoundingMode appears to apply only to narrowing float-to-float conversions, not arithmetic operations. Do all currently supported Apple GPU families use round-to-nearest-ties-to-even for precise FP32 add/subtract/multiply/divide/sqrt? If so, could that be made a documented guarantee? Otherwise, could Metal expose an arithmetic rounding-mode compile option and a corresponding MTLDevice capability query? Denormal behavior MSL §8.1 and §8.5 permit denormalized FP32 operands and results to be flushed to zero, including with fast math disabled. I cannot find a control or capability query for preserving denormal inputs and results. Do current Apple GPU families support denormal-preserving FP32 arithmetic? Could Metal expose a preserve/flush mode and a MTLDevice query? A convenient end state would be a queryable strict FP32 configuration combining: safe math; precise FP32 functions; contraction disabled when separate rounding points are required; round-to-nearest-ties-to-even arithmetic; preserved FP32 denormal inputs and results; defined signed-zero, infinity, and NaN behavior. My use case is deterministic GPU numerical simulation. A small compute-shader probe can identify effective rounding and denormal behavior on one GPU/OS/compiler combination, but it cannot provide the portable or future-proof contract needed by applications and higher-level APIs such as WebGPU. Related cross-API work: SPIR-V/Vulkan: https://github.com/KhronosGroup/SPIRV-Registry/issues/448 HLSL/DXIL/D3D12: https://github.com/microsoft/hlsl-specs/issues/926 WebGPU/WGSL umbrella issue: https://github.com/gpuweb/gpuweb/issues/2259 Relevant Metal documentation: Metal Shading Language Specification, §§1.6.3 and 8.1–8.5: https://developer.apple.com/metal/Metal-Shading-Language-Specification.pdf MTLCompileOptions.mathMode: https://developer.apple.com/documentation/metal/mtlcompileoptions/mathmode MTLCompileOptions.floatingPointConversionRoundingMode: https://developer.apple.com/documentation/metal/mtlcompileoptions/floatingpointconversionroundingmode