Describe the issue
The WebGPU Execution Provider crashes on macOS (Apple Silicon) when multiple threads create sessions and run inference concurrently. The crash is non-deterministic and manifests as different errors on each run, indicating a race condition in Dawn's Metal backend.
Observed crashes (non-deterministic, varies per run)
Run 1 — Metal assertion:
**-[AGXG15GFamilyCommandBuffer blitCommandEncoderCommon:]:832:**
failed assertion `A command encoder is already encoding to this command buffer'
Run 2 — Memory corruption:
malloc: *** error for object 0x784797e90: pointer being freed was not allocated
Run 3 — Trace trap:
[1] 56040 trace trap cargo run --release -- version-RFB-640.onnx
Notes:
- Single-threaded session creation and inference works fine - Sequential (non-concurrent) multi-session usage works fine
- The same workload works correctly with the CoreML EP
To reproduce
minimal Repo: https://github.com/altunenes/ort-webgpu-thread-crash
git clone https://github.com/altunenes/ort-webgpu-thread-crash.git
cargo run --release -- version-RFB-640.onnx
(simple face detection model)
The repro creates 2 persistent WebGPU sessions, then spawns 5 threads that each create a session and run inference concurrently while the main thread also runs inference on the persistent sessions.
Urgency
No response
Platform
Mac
OS Version
26.2
ONNX Runtime Installation
Other / Unknown
ONNX Runtime Version or Commit ID
1.24.2
ONNX Runtime API
Other / Unknown
Architecture
X64
Execution Provider
Other / Unknown
Execution Provider Library Version
No response
Describe the issue
The WebGPU Execution Provider crashes on macOS (Apple Silicon) when multiple threads create sessions and run inference concurrently. The crash is non-deterministic and manifests as different errors on each run, indicating a race condition in Dawn's Metal backend.
Observed crashes (non-deterministic, varies per run)
Run 1 — Metal assertion:
Run 2 — Memory corruption:
malloc: *** error for object 0x784797e90: pointer being freed was not allocatedRun 3 — Trace trap:
[1] 56040 trace trap cargo run --release -- version-RFB-640.onnxNotes:
To reproduce
minimal Repo: https://github.com/altunenes/ort-webgpu-thread-crash
git clone https://github.com/altunenes/ort-webgpu-thread-crash.git
cargo run --release -- version-RFB-640.onnx
(simple face detection model)
The repro creates 2 persistent WebGPU sessions, then spawns 5 threads that each create a session and run inference concurrently while the main thread also runs inference on the persistent sessions.
Urgency
No response
Platform
Mac
OS Version
26.2
ONNX Runtime Installation
Other / Unknown
ONNX Runtime Version or Commit ID
1.24.2
ONNX Runtime API
Other / Unknown
Architecture
X64
Execution Provider
Other / Unknown
Execution Provider Library Version
No response