Crate agentstategraph_policy 

Policy primitive for AgentStateGraph.

Fourth-primitive sibling crate, parallel to agentstategraph-tasks. Implements the authorization + change-cost primitive of the Policy v1 design (§§2-7 and §22; user guide: docs/POLICY_GUIDE.md). Ships the engine surface only — MCP tools, CLI, and Lens UI live in their respective consumer crates.

What this crate is

• Policy schema (situation-matching rules + procedure + change-cost gating fields)
• PolicyStore — a handle bound to a Repository + prefix with propose / ratify / supersede / evaluate / evaluate_change
• Selector — a tagged-enum boolean expression over a Situation
• Decision — the evaluator’s result, including RequireApproval with a FallbackAction (“what to do while it waits”)

What this crate is NOT

• Not an enforcement layer (soft model — see POLICY_V1.md §11)
• Not a Rego/Cedar clone (the selector is a minimal DSL; external policy engines are a future escape hatch)
• Not an MCP tool or CLI — those belong to consumers

Example

use agentstategraph::Repository;
use agentstategraph_storage::SqliteStorage;
use agentstategraph_policy::{PolicyStore, Situation, Selector};
use std::sync::Arc;

let repo = Arc::new(Repository::new(Box::new(SqliteStorage::in_memory().expect("in-memory sqlite"))));
repo.init().unwrap();
let store = PolicyStore::new(repo, "/policies", "claude-code");
// propose, ratify, evaluate ...
let _ = store.evaluate("main", &Situation::new(), "restart_pod", "agent-1");

Re-exports

pub use error::PolicyError;

pub use external::ExternalError;

pub use external::ExternalEvaluator;

pub use external::ExternalEvaluatorRegistry;

pub use selector::Selector;

pub use selector::Situation;

pub use store::PolicyStore;

pub use types::ApprovalRule;

pub use types::AuthorizedAction;

pub use types::ChangeProposal;

pub use types::Decision;

pub use types::EvaluatorSource;

pub use types::ExternalEvaluatorRef;

pub use types::FallbackAction;

pub use types::Policy;

pub use types::PolicySignature;

pub use types::ProcedureStep;

pub use types::Severity;

pub use verifier::SignatureVerificationError;

pub use verifier::SignatureVerifier;

Modules

error

Error type for PolicyStore operations.

evaluator

Pure evaluation logic. Operates on an already-loaded slice of policies, so it can be exercised in unit tests without touching storage. The PolicyStore default impl is the production caller.

external

External-evaluator dispatcher (0.7.5 §4a).

paths

Path construction helpers for the policy store.

selector

Situation selector grammar.

store

PolicyStore — handle bound to a Repository + path prefix.

types

Public data types for policies, change proposals, and decisions.

verifier

Signature verifier trait for PolicyStore.