Runtime State Ownership

This document is the canonical ownership and authority reference for the current runtime. It is conservative, documentation-only, and describes current contracts only.

How to read this document

Use this file for authority boundaries: which component owns which decision.

• Canonical here: parse authority, diagnostics authority, parse-tree authority, scheduling ownership, registry ownership, and lifecycle ownership boundaries.
• Canonical in companion file: metadata-only limitations, unsupported semantics, duplicated-work/execution-sharing constraints, and future activation preconditions.
• Companion: ParserMetadataAndRuntimeLimitations.md.
• Contribution/process rules remain in Utils.Parser/AGENTS.md; roadmap direction remains in Utils.Parser/ROADMAP.md.

Topic ownership map (canonical + companion)

Topic	Canonical document	Companion summary
Runtime authority and component ownership	RuntimeStateOwnership.md	ParserMetadataAndRuntimeLimitations.md
Metadata-only limitations	ParserMetadataAndRuntimeLimitations.md	RuntimeStateOwnership.md
Diagnostics authority	RuntimeStateOwnership.md	ParserMetadataAndRuntimeLimitations.md
Lookahead fallback semantics	ParserMetadataAndRuntimeLimitations.md	RuntimeStateOwnership.md
Registry lifecycle ownership	RuntimeStateOwnership.md	ParserMetadataAndRuntimeLimitations.md
Duplicated-work/execution-sharing constraints	ParserMetadataAndRuntimeLimitations.md	RuntimeStateOwnership.md
Compatibility boundaries	ParserMetadataAndRuntimeLimitations.md	RuntimeStateOwnership.md

Runtime authority model (current contract)

• ParserEngine owns final parse acceptance.
• ParserEngine owns final diagnostics.
• ParserEngine owns final parse-tree outcome.
• AlternativeScheduler is orchestration-only and does not own global parse success/failure.
• ScheduledAlternativeExecutor is local and non-authoritative.
• ParserStateRegistry is parse-lifecycle-scoped storage and does not own final parse acceptance.
• ActiveParseState is descriptive state and is not a runtime invocation frame.

Supported runtime ownership semantics

Current supported ownership contracts are:

• deterministic syntax-oriented parsing with ParserEngine as final authority;
• non-authoritative orchestration and metadata transport;
• advisory lookahead plus parser-authoritative fallback;
• invocation-local registry lifecycle and deterministic reuse boundaries;
• metadata-only continuation/shared-prefix/lookahead observability.

For unsupported semantics and compatibility interpretation (including parseable/observable boundaries), see ParserMetadataAndRuntimeLimitations.md.

Parsing, scheduling, and local execution boundaries

Parsing authority

ParserEngine remains authoritative for:

• recursive rule parsing decisions,
• branch acceptance/rejection,
• trailing-token validation,
• final parse materialization.

Scheduling authority

AlternativeScheduler:

• coordinates deterministic ordering and local candidate comparison,
• can aggregate observability metadata,
• does not own global parse success/failure,
• does not own diagnostics authority.

ScheduledAlternativeExecutor:

• performs local attempt execution,
• can use lookahead for deterministic local reject evidence only,
• cannot accept a branch from lookahead-only outcomes,
• cannot finalize parse acceptance.

Lookahead authority boundaries (ownership view)

Lookahead is advisory and non-authoritative.

• lookahead cannot independently finalize parse acceptance;
• lookahead cannot independently finalize diagnostics authority;
• lookahead cannot accept a branch;
• non-reject lookahead outcomes require real parsing;
• no adaptive parsing exists in the current runtime.

ImmediateReject may be used only as deterministic local reject evidence in allowed contexts. RequiresParse, Unknown, and EpsilonPossible require parser-authoritative execution.

For conceptual fallback lists and limitations detail, see ParserMetadataAndRuntimeLimitations.md.

ParserStateRegistry lifecycle ownership

ParserStateRegistry owns parse-lifecycle-scoped runtime storage for:

• visited parser-state tracking,
• invocation-local continuation transport metadata,
• invocation-local completed results,
• deterministic reusable completion selection inputs.

Boundaries:

• Clear() resets registry-owned state for a new parse lifecycle;
• reusable results are invocation-local completion artifacts;
• reusable result selection is not final parse acceptance;
• invocation reuse != execution reuse;
• current memoization is syntax-oriented and non-semantic;
• semantic evaluator external state is not modeled by memoization keys;
• parser action side effects are not modeled by memoization keys.

Continuation and shared-prefix ownership boundaries

Ownership view only (limitations remain canonical in companion file):

• continuation metadata is metadata-only;
• shared-prefix metadata is metadata-only;
• lookahead metadata is metadata-only;
• metadata transport is non-authoritative and discardable.

Mandatory boundaries:

• metadata does not authorize replay;
• metadata does not authorize continuation execution;
• metadata does not authorize branch merging;
• metadata does not establish semantic equivalence;
• metadata does not imply rollback safety;
• metadata does not override diagnostics ownership.

For lifecycle details, anti-feature boundaries, and future activation preconditions, see:

• ParserMetadataAndRuntimeLimitations.md#continuation-metadata-model-current-metadata-only
• ParserMetadataAndRuntimeLimitations.md#shared-prefix-metadata-authority-limitations-and-lifecycle
• ParserMetadataAndRuntimeLimitations.md#execution-sharing-safety-boundaries-limitations-view

Diagnostics authority boundaries (canonical)

• ParserEngine is final diagnostics authority.
• Orchestration diagnostics are non-authoritative.
• pruning != syntax failure.
• backtracking observation != syntax failure.
• metadata transport != diagnostics authority.
• branch equivalence != parse rejection.
• trailing-token validation is parser-authoritative.

Observability can exist without authority transfer.

Deterministic observability boundary

Observable runtime artifacts may include scheduler metadata, lookahead observations, continuation/shared-prefix metadata, and branch-state collections. These are testable for auditability but remain non-authoritative.

Incidental internal ordering/layout remains non-contractual unless explicitly documented.

Explicit non-goals (current runtime)

No support for:

• replay,
• rollback,
• execution sharing,
• branch-merge execution,
• resumable continuation execution,
• semantic-aware memoization.

These boundaries are current-contract statements only.

Runtime observation

The optional IParserRuntimeObserver infrastructure is passive and descriptive only. Observer callbacks do not return control decisions and cannot influence scheduling, pruning, parse acceptance, parse-tree shape, or diagnostics authority.

Additional observation contract clarifications:

• runtime observation ordering is deterministic for a given deterministic parser run;
• event payloads are immutable descriptive snapshots with explicit event kind and status, not execution handles;
• observer callback exceptions are isolated by the scheduler and do not alter parser runtime outcomes.