Steering specs (vllm.steer_vectors)

The user-facing v2 steering API is defined in vllm-steer/vllm/steer_vectors/api.py and imported as:

from vllm.steer_vectors import ApplySpec, SelectSpec, SteeringSpec, VectorSpec

The Steering guide is the canonical reference for these classes — every field of SteeringSpec, VectorSpec, ApplySpec, and SelectSpec is documented there, with defaults, semantics, and examples.

This page is intentionally a hand-written summary rather than a generated one: rendering these classes with mkdocstrings would require importing the vllm-steer fork (and its CUDA/torch stack) in the docs build environment, and the docs build is kept dependency-light so it can run in CI with only requirements-docs.txt.

The four classes in one breath

Class	Role
SelectSpec	The shared where-clause language: phases, tokens, positions, exclude_tokens, exclude_positions, generation_window. Also used by hidden-state capture.
ApplySpec	A SelectSpec subclass: where/when one vector applies.
VectorSpec	One vector: source, algorithm, scale, layers, normalize, apply, params, name.
SteeringSpec	Ordered vectors list plus a conflict policy ("priority" / "sequential" / "error") and debug.

For the design rationale, see the engineering record STEERING_API_V2.md.