Three vendor-neutral fixes to backend_cuda.cu, each with test coverage:
1. Upload check-order: a cached device tensor is now usable when the
caller's host pointers are stale or NULL. CUDA_RELEASE_HOST slots
null their host pointers after upload; the current engine reaches
those tensors through direct handles (coli_cuda_expert_mlp etc.), but
any caller going through coli_cuda_matmul/tensor_upload with a cached
tensor — as matmul_qt does for QT tensors — hits the !weights check
before the cached-tensor branch and fails spuriously. This hardens
the API contract rather than fixing a measured regression; the
contract is pinned by a 64x sustained-reuse test.
2. Sticky runtime error (real bug, test-caught): a failed allocation
left the last-error state set, so the NEXT healthy launch's
cudaGetLastError() check reported 'out of memory' and disabled a
perfectly good tensor. cuda_ok() now consumes the error on the
failure path; regression-covered.
3. COLI_GPU_FAIL_AFTER=N test hook: every GPU compute entry point (19
total: matmul, expert mlp/group, shared mlp, attention ops, pipe ops)
reports failure after N successful calls, so the engine's CPU
fallbacks and expert_host_ensure rematerialization can be exercised
end-to-end without real hardware faults. Unset = zero effect;
uploads/queries are never gated. Validated on GLM-5.2: total failure
(N=0) completes coherently with every released expert rematerialized.
Tests (run via make cuda-test on any CUDA GPU; vendor-neutral source):
64x sustained matmul reuse after host pointers are freed; upload from a
scribbled-and-freed temporary; five graceful upload-failure cases with
stats-integrity assertions; healthy-launch-after-failed-alloc (the
sticky-error regression); fault-hook on/off restore.
Verified on AMD RX 9070 XT via the companion HIP PR's compat header
(same test source); a make cuda-test run on NVIDIA hardware would
complete the matrix.
noobdev-ph
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