diff --git a/crates/alknet-call/src/registry/context.rs b/crates/alknet-call/src/registry/context.rs
index a3ccb75..543b978 100644
--- a/crates/alknet-call/src/registry/context.rs
+++ b/crates/alknet-call/src/registry/context.rs
@@ -1,7 +1,178 @@
-//! Operation context: `OperationContext`, `AbortPolicy`,
-//! `CompositionAuthority`, and `ScopedOperationEnv`.
-//!
-//! See `docs/architecture/crates/call/operation-registry.md` for the full
-//! specification.
+use std::collections::{HashMap, HashSet};
+use std::sync::Arc;
+use std::time::Instant;
 
-// TODO: implement
+use alknet_core::auth::Identity;
+use alknet_core::types::Capabilities;
+use serde_json::Value;
+
+use super::env::OperationEnv;
+
+pub struct OperationContext {
+    pub request_id: String,
+    pub parent_request_id: Option<String>,
+    pub identity: Option<Identity>,
+    pub handler_identity: Option<CompositionAuthority>,
+    pub capabilities: Capabilities,
+    pub metadata: HashMap<String, Value>,
+    pub scoped_env: ScopedOperationEnv,
+    pub env: Arc<dyn OperationEnv + Send + Sync>,
+    pub abort_policy: AbortPolicy,
+    pub deadline: Option<Instant>,
+    pub(crate) internal: bool,
+}
+
+impl OperationContext {
+    pub fn is_internal(&self) -> bool {
+        self.internal
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum AbortPolicy {
+    #[default]
+    AbortDependents,
+    ContinueRunning,
+}
+
+#[derive(Debug, Clone)]
+pub struct CompositionAuthority {
+    pub label: String,
+    pub scopes: Vec<String>,
+    pub resources: HashMap<String, Vec<String>>,
+}
+
+impl CompositionAuthority {
+    pub fn none() -> Option<Self> {
+        None
+    }
+
+    pub fn new(label: &str, scopes: impl IntoIterator<Item = String>) -> Self {
+        Self {
+            label: label.to_string(),
+            scopes: scopes.into_iter().collect(),
+            resources: HashMap::new(),
+        }
+    }
+
+    pub fn as_identity(&self) -> Option<Identity> {
+        Some(Identity {
+            id: self.label.clone(),
+            scopes: self.scopes.clone(),
+            resources: self.resources.clone(),
+        })
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct ScopedOperationEnv {
+    allowed: HashSet<String>,
+}
+
+impl ScopedOperationEnv {
+    pub fn empty() -> Self {
+        Self {
+            allowed: HashSet::new(),
+        }
+    }
+
+    pub fn new(ops: impl IntoIterator<Item = impl Into<String>>) -> Self {
+        Self {
+            allowed: ops.into_iter().map(|s| s.into()).collect(),
+        }
+    }
+
+    pub fn allows(&self, name: &str) -> bool {
+        self.allowed.contains(name)
+    }
+}
+
+impl Default for ScopedOperationEnv {
+    fn default() -> Self {
+        Self::empty()
+    }
+}
+
+#[allow(dead_code)]
+pub(crate) fn generate_request_id() -> String {
+    uuid::Uuid::new_v4().to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn scoped_env_allows_in_set() {
+        let env = ScopedOperationEnv::new(["fs/readFile", "agent/chat"]);
+        assert!(env.allows("fs/readFile"));
+        assert!(env.allows("agent/chat"));
+    }
+
+    #[test]
+    fn scoped_env_disallows_not_in_set() {
+        let env = ScopedOperationEnv::new(["fs/readFile"]);
+        assert!(!env.allows("agent/chat"));
+        assert!(!env.allows(""));
+    }
+
+    #[test]
+    fn scoped_env_empty_allows_nothing() {
+        let env = ScopedOperationEnv::empty();
+        assert!(!env.allows("fs/readFile"));
+    }
+
+    #[test]
+    fn composition_authority_as_identity_correct() {
+        let mut resources = HashMap::new();
+        resources.insert("service".to_string(), vec!["vastai".to_string()]);
+        let authority = CompositionAuthority {
+            label: "agent-chat".to_string(),
+            scopes: vec!["llm:call".to_string(), "fs:read".to_string()],
+            resources,
+        };
+        let identity = authority.as_identity().expect("as_identity returns Some");
+        assert_eq!(identity.id, "agent-chat");
+        assert_eq!(
+            identity.scopes,
+            vec!["llm:call".to_string(), "fs:read".to_string()]
+        );
+        assert_eq!(
+            identity.resources.get("service"),
+            Some(&vec!["vastai".to_string()])
+        );
+    }
+
+    #[test]
+    fn composition_authority_new_populates_label_and_scopes() {
+        let authority = CompositionAuthority::new(
+            "agent-chat",
+            ["llm:call".to_string(), "fs:read".to_string()],
+        );
+        assert_eq!(authority.label, "agent-chat");
+        assert_eq!(
+            authority.scopes,
+            vec!["llm:call".to_string(), "fs:read".to_string()]
+        );
+        assert!(authority.resources.is_empty());
+    }
+
+    #[test]
+    fn composition_authority_none_is_none() {
+        assert!(CompositionAuthority::none().is_none());
+    }
+
+    #[test]
+    fn abort_policy_default_is_abort_dependents() {
+        let policy = AbortPolicy::default();
+        assert!(matches!(policy, AbortPolicy::AbortDependents));
+    }
+
+    #[test]
+    fn generate_request_id_is_unique_and_non_deterministic() {
+        let a = generate_request_id();
+        let b = generate_request_id();
+        assert_ne!(a, b);
+        assert!(!a.is_empty());
+    }
+}
diff --git a/crates/alknet-call/src/registry/env.rs b/crates/alknet-call/src/registry/env.rs
index 20cb725..b4cca6e 100644
--- a/crates/alknet-call/src/registry/env.rs
+++ b/crates/alknet-call/src/registry/env.rs
@@ -1,8 +1,32 @@
-//! Operation environment: the `OperationEnv` trait, `LocalOperationEnv`, and
-//! `CompositeOperationEnv`.
-//!
-//! The composition dispatch trait — handlers compose child operations through
-//! `OperationContext.env`. See
-//! `docs/architecture/crates/call/operation-registry.md` and ADR-024.
+use serde_json::Value;
 
-// TODO: implement
+use super::context::{AbortPolicy, OperationContext};
+use crate::protocol::wire::ResponseEnvelope;
+
+#[async_trait::async_trait]
+pub trait OperationEnv: Send + Sync {
+    async fn invoke(
+        &self,
+        namespace: &str,
+        operation: &str,
+        input: Value,
+        parent: &OperationContext,
+    ) -> ResponseEnvelope {
+        self.invoke_with_policy(namespace, operation, input, parent, parent.abort_policy)
+            .await
+    }
+
+    async fn invoke_with_policy(
+        &self,
+        namespace: &str,
+        operation: &str,
+        input: Value,
+        parent: &OperationContext,
+        policy: AbortPolicy,
+    ) -> ResponseEnvelope;
+
+    fn contains(&self, name: &str) -> bool {
+        let _ = name;
+        true
+    }
+}