fix(kernel): carry agent transport in specs

kernel/relayflowd-core/src/spec.rs

@@ -313,6 +313,7 @@ const STEP_AGENT_FIELDS: &[&str] = &[
     "instruction",
     "cli",
     "model",
+    "transport",
     "recovery_mode",
     "surfaces",
     "permissions",
@@ -423,6 +424,11 @@ pub enum StepKind {
         /// then handed to the worker, which surfaces it to the CLI.
         #[serde(default, skip_serializing_if = "Option::is_none")]
         model: Option<String>,
+        /// How the attached worker invokes the declared CLI. The kernel does
+        /// not implement either transport; it journals and dispatches the
+        /// choice so the worker can honor it deterministically.
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        transport: Option<AgentTransport>,
         #[serde(default)]
         recovery_mode: RecoveryMode,
         /// Declared mutable surfaces (RFC Appendix A rule 1) — names only.
@@ -450,6 +456,13 @@ pub enum StepType {
     Agent,
 }
 
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum AgentTransport {
+    Direct,
+    Relay,
+}
+
 #[derive(Debug, Clone, Copy, Default, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(rename_all = "snake_case")]
 pub enum RecoveryMode {

kernel/relayflowd-core/tests/spec_parity.rs

@@ -67,6 +67,41 @@ fn the_kernel_parses_the_rung_c_agent_spec_and_stamps_the_same_hash() {
     );
 }
 
+#[test]
+fn the_kernel_round_trips_declared_agent_transports_and_rejects_unknown_values() {
+    for transport in ["direct", "relay"] {
+        let value = serde_json::json!({
+            "steps": [{
+                "id": "agent",
+                "type": "agent",
+                "instruction": "work",
+                "transport": transport,
+            }],
+        });
+        let parsed = RunSpec::parse(&value).expect("declared agent transport must parse");
+        parsed
+            .validate()
+            .expect("declared agent transport must validate");
+        assert_eq!(
+            serde_json::to_value(parsed).unwrap()["steps"][0]["transport"],
+            transport
+        );
+    }
+
+    let unknown = serde_json::json!({
+        "steps": [{
+            "id": "agent",
+            "type": "agent",
+            "instruction": "work",
+            "transport": "telepathy",
+        }],
+    });
+    assert!(
+        RunSpec::parse(&unknown).is_err(),
+        "unknown transport must fail closed"
+    );
+}
+
 #[test]
 fn the_kernel_parses_the_event_triggered_spec_and_stamps_the_same_hash() {
     assert_parity(