Type Alias NemoRelayNativeAsyncMiddlewareCb 

pub type NemoRelayNativeAsyncMiddlewareCb = unsafe extern "C" fn(user_data: *mut c_void, invocation_json: *const NemoRelayNativeString, next: *const NemoRelayNativeAsyncNext, completion: *const NemoRelayNativeAsyncCompletion) -> u32;

Completion-based native middleware callback.

invocation_json is borrowed for the call. A callback that returns NemoRelayNativeAsyncCallbackState::Pending as a u32 owns one completion reference and must settle it then call the v3 async_completion_release hook. The host validates the returned discriminant. When next is non-null, the callback owns that handle for the invocation and must call async_next_release exactly once after its final use, regardless of whether it returns Complete or Pending. The host never reclaims a next handle after handing it to the callback. next is null for non-execution middleware. Relay invokes the callback on the Tokio runtime worker polling that middleware invocation, without stable OS-thread affinity; separate invocations may run concurrently. After returning Pending, retained completion and next handles may be used from a plugin-owned thread until the completion settles. Every next operation must finish before resolving or rejecting the completion; Relay rejects or cancels unfinished and later continuation calls. The plugin must synchronize shared user_data and callback state and serialize each handle’s final release after its last operation returns.