921a3cfc44
Tried to turn the gamma-ramp inference into a direct observation. canary's trace_gpu_stream records gamma ramps as their own command type (kGammaRamp, index 11 in TraceCommandType), so a boot trace should show the write. Two bounded runs produced NO trace file at all -- nothing under the prefix, no .xtr anywhere, no scratch/gpu/. Bounded deliberately: the disk is at 95% (50 GiB free) and a trace of all GPU packets during boot includes video decode, so the runner carried its own watchdog that killed the emulator the moment output passed a 2 GiB cap. It never fired -- there was nothing to cap -- and disk stayed at 95% throughout. Bounding from inside cost nothing and removed any need to gamble on how coarsely I could poll. What the attempt did establish. BeginTracing() runs at GPU init when the cvar is set (graphics_system.cc:237), but EndTracing() runs only from GraphicsSystem::Shutdown() -- so the kill -9 this session has used routinely can never finalise a trace. The second run was stopped with SIGTERM and exited cleanly; still no file, so that is not the whole story. Two candidates remain unseparated: the CLI flag not reaching the cvar, or BeginTracing failing silently. The next run removes the ambiguity by setting trace_gpu_stream in the config FILE instead. And a trap I nearly fell into. The startup config dump showed trace_gpu_stream = false after I passed --trace_gpu_stream=true, which reads as "flag ignored". It is not evidence either way: the gamma run passed --log_mask=12 --log_level=3, its dump printed log_mask = 0 and log_level = 2, and Kernel Debug logging was demonstrably ON -- that run is where VdGetCurrentDisplayGamma was captured. The dump reflects the config file and can neither confirm nor refute a command-line override. (It does not undo the earlier user_language conclusion: absence of a NAME from the dump still shows a cvar is unregistered.) The gamma-ramp write therefore remains an inference, unchanged.