Native plugin ABI

PLLM Native Plugin ABI 1 is published by pllm-plugin-api and crates/pllm-plugin-api/include/pllm_plugin.h. It is independently versioned from the Python API, PyO3 module, component standard, and wire protocols. A plugin exports pllm_plugin_v1; the host and plugin exchange size/version-tagged C vtables.

The ABI uses explicit-width scalars, borrowed byte slices, plugin-owned output buffers with an explicit release callback, and opaque (slot, generation) handles. Status values are integer wrappers so unknown foreign values do not create invalid Rust enums. No Rust Vec, String, trait object, allocator ownership, or unwind crosses the boundary. Implementations translate panics to PLLM_STATUS_PANIC_VALUE and process whole region or batch payloads rather than scalar callbacks.

The plugin vtable exposes synchronous whole-region execution and explicit asynchronous submit, poll, and cancel operations. Host callbacks expose event delivery and cancellation checks. Vtable size checks permit compatible append-only extension inside ABI 1; an unknown ABI version or undersized table fails closed. Provider manifests lock native artifact digests, targets, and ABI version before any future runtime load.

A Rust cdylib fixture and a C11 header fixture exercise symbol lookup, version negotiation, configuration, descriptor output, opaque binary region execution, cancellation, buffer release, destruction, and stale-generation rejection. This establishes the ABI contract and conformance harness, not trust or process isolation.

No public Python API loads third-party native libraries yet. Runtime host integration, role authorization, and process-isolation policy remain unavailable. PyO3 compatibility does not establish plugin ABI compatibility. See current support.