[elibol]

Tile operations and SIMT launches currently use separate async runtimes and cannot compose through the same operation types. This change removes cuda_async::simt and routes both programming models through the shared DeviceOp, DeviceFuture, execution context, scheduler, errors and launch API.

Closes #1461. Prerequisite #1603 is merged into main as 6a6372e4cc2e0f142471cf18f13b9072abe87757. This PR targets main and its diff now contains only the async migration. The development branch remains on the contributor's fork.

• One KernelArgument blanket implementation uses DeviceCopy. Generic Tile scalars require DType + DeviceCopy; tensor-only type parameters retain their independent DType contract. The shared argument arena preserves inline storage, padded values, over-alignment and typed destruction for the explicit unsafe boxed-argument escape hatch.
• An inert AsyncKernelLaunchBuilder requires unsafe finalization before becoming a schedulable, immutable launch. Generated typed launchers retain their checked boundaries. Tile PDL and SIMT cluster/cooperative launch paths are preserved. Raw async macros marshal slice pointers and lengths as direct scalar values; optional CPU-reference examples use the corresponding scalar bounds.
• Launches retain their function/module, allocation owners and access leases before enqueueing work. Early future drop retires owners on completion without waiting on the GPU. Partial errors and panics retain submitted resources; unknown completion deliberately leaks owners and exclusion. Forgotten futures also retain their submissions indefinitely. Outputs can contain ordinary Rust borrows and must be valid to drop during submission, as required by host combinators.
• Graphs retain captured resources and reacquire allocation access on every replay. DeviceBox transfers to/from shared typed buffers without copying and preserves ordinary read permissions. Existing DeviceOperation, and_then, apply and arc spellings delegate to the shared implementations.
• cutile_inter_kernel now uses the normal shared launch API to update the Tile-produced allocation in place, checks its pointer and allocation identity, and verifies results. Consumers, generated-project templates, documentation, UI fixtures and GPU test entry points are migrated. AGENTS.md records that future branches must originate from the user's fork.

Validation: shared async tests and doctests; Tile unit, aggregate GPU, submission-lifetime, interop and UI tests; cuda-host/cuda-macros suites; 268 cargo-oxide tests; four explicit SIMT lifetime/concurrency GPU tests. Both cargo oxide run cutile_inter_kernel and cargo oxide run async_mlp pass. Miri passes all seven argument-storage tests, and Loom passes the completion-handoff model. Host/Tile/affected SIMT clippy checks, formatting, strict async rustdoc, SPDX/API-path guards and Tile dependency checks pass.

GPU execution was validated on one RTX 5090. This does not add multi-GPU/NVLink hardware coverage. API migration and custom-operation retention obligations are documented in cuda-async/README.md.

Additional validation: the full CPU runner passes (1,381 tests; 94 intentionally ignored), all top-level SIMT example workspaces pass Clippy with warnings denied, and all 144 macro unit tests pass. The host_closure GPU example also passes all 13 scenarios, covering the corrected async slice argument marshalling.

Earlier follow-up validation after incorporating the updated #1516/#1603 stack: all 1,394 CPU tests pass (95 intentionally ignored), as do 138 selected Tile GPU/interop/graph/view/lifetime tests and all four explicit SIMT lifetime/concurrency tests. The original stress reproducer reports no false negatives in 1,000,000 raw-buffer uniqueness checks and no false positives in 100,000 aliased-tensor partition attempts. Nihal's DeviceBox::from_raw_parts shared-read fix remains included.

Restored the original cutile-rs unsafe async_on() contract: the caller independently keeps all submitted resources alive and orders their accesses. On return, including an error, async_on() releases runtime owners and access leases without synchronization or background retention. Safe futures retain their nonblocking completion-based cleanup. The existing four-tensor launch benchmark now measures 1.88 µs/launch, down from 4.95 µs before this fix (earlier main baseline: 1.68 µs). No batching or new launch API is needed for this fix.

Earlier main integration: Merged the updated #1603 prerequisite, including the CuTe host-consumer migration. The cuda-host, cuda-macros, ctm-rs and cute-rs suites pass (497 tests, 43 intentionally ignored), together with affected-package Clippy and all 16 CuTe example/model workspace Clippy checks. CI passed before this refresh; current-head CI is tracked below.

Validation for b811b7067: all 133 cuda-async tests pass (14 intentionally ignored), all 11 Tile submission-lifetime tests and all four SIMT lifetime/concurrency GPU tests pass, and Clippy/formatting/rustdoc checks pass. Both new gated-stream regressions fail on the preceding code and pass here. That revision was validated before the current refresh.

Current update (2026-10-30), head 95a51d708cc1dd203a922a28624aa087cb7a2176: Carries the #1516 source-validity and #1603 completion-retention fixes while preserving the reviewed async launch lifetime/access contracts. The combined stack passes 1,427 CPU/assembler tests, 750 GPU tests, 27 supported examples and eight benchmark smoke tests. Initial disk exhaustion was resolved and the affected suites rerun successfully. The expanded atomic example is migrated to owned conversions; all 24 atomic GPU cases also pass on the final shared-runtime head. Fresh CI is running; #1516 still needs renewed approval before this stack can merge into main.

Merge status (2026-10-30): current head 21bc9bb783429ef39da7ee9ac63bbd686a3a5895 records accepted #1603 squash ancestry. The squash commit's entire tree exactly matches the prerequisite head already included here (ba7644227). The apparent conflicts were duplicate history; this merge changes zero files relative to previously green ede42672a. GitHub reports the PR mergeable. Current-head CI has restarted; the previous identical tree passed all 70 applicable checks, including GPU tests (one expected skip). No test assertions were relaxed. The earlier intermittent drop-timing failure remains tracked as test-hardening follow-up #1680. Issue/release tracking: #1606.

[nihalpasham]

Looks good! Pushed a small commit (c68eee09e) on top:

• DeviceBox::from_raw_parts had shared_access_writes: true, which caused concurrent read-only launches across streams to fail with CUDA_ERROR_NOT_READY (same thing device_box_preserves_concurrent_read_permissions checks for from_buffer). Bounded from_raw_parts on Copy and set shared_access_writes = false.
• Updated the doc comment on pub use cuda_async; in cuda-host and a few DeviceBox::from_raw_parts snippets in the book/READMEs to pass stream.clone().

[elibol]

/ok to test 3ae634e

[elibol]

The updated combined host stack at 3ae634eeeed89ae9db537f12fe22c504e83e6712 passes the complete local CPU/assembler suite (1,427 tests, 96 ignored), GPU suite (750 tests, three ignored), 27 examples (one expected CUDA 13.3 PDL skip), and all eight benchmark smoke tests on RTX 5090 / CUDA 13.3. This includes the cast contracts, tensor ownership, cancellation/submission lifetime, buffer interop and shared graph replay tests. The initial CPU/GPU run hit disk exhaustion; the affected suites passed on rerun after clearing unused compiler artifacts. Benchmark smoke validation uses the temporary argument correction already tracked in #1634, restored afterward.

The source changes and merge resolutions have been self-reviewed. The refreshed math_special lockfile also passes the example dependency-policy guard. Fresh GitHub CI is running on each PR head.

Draft #1613 is updated to 64ee86fe8bbfd78c181048a94d0d91e98637062b, where all 36 focused debugging tests pass, including live CUDA-GDB. Rui's original SWQA pin is preserved; the new host fixes require an explicit updated handoff and retesting. CTK 13.5 validation is still outstanding.

[elibol]

/ok to test 95a51d7

The base branch was changed.