Audience: repository-aware assistants and reviewers
Authority: non-normative vocabulary
Canonical sources: AGENTS.md and the named repository snapshot

This glossary defines only durable review language. It does not describe the current class hierarchy, API surface, backend inventory, or roadmap.

Evidence Terms

Named snapshot

The branch, commit, tag, PR, or diff whose behavior is under discussion. Current main is the default only when the user does not name another snapshot.

Canonical subsystem documentation

Repository documentation that defines intended subsystem behavior. It must be read from the named snapshot; an uploaded copy may be stale.

Current implementation detail

Behavior established by source, tests, and build configuration in the named snapshot. Its presence in an AI guidance file is not evidence that it still exists.

Design direction

A maintainer decision or canonical design statement not yet fully represented by implementation. Do not infer it merely from an unfinished helper or draft.

Correctness Terms

Epoch causality

The dependency order that makes an async operation legal. Scheduler timing or a particular task order is not a correctness argument.

Semantic view

A view whose layout or accessor changes the values observed through it. A pointer-shaped data handle alone does not permit bypassing those semantics.

Clean decline

A backend's refusal before execution effects. Inputs and fixed/update outputs remain unchanged. An operation may authorize provisional preparation of a replaceable output for reuse or replacement by later backends. Once a backend writes result elements, submits work, or commits a completed result, failure is an operation error and must not trigger fallback.

Symmetry metadata

Quantum-number, block-space, local-space, and leg-orientation information that is part of the mathematical object. It must not be silently erased or replaced by an implicit dense path.

Explicit cost

Allocation, materialization, synchronization, host/device transfer, and dense projection that is visible in the API or documented operation contract rather than hidden in lowering.