feat: Added initial support for native Loki agent nodes in the graph-based agent system

src/graph/agent.rs

@@ -0,0 +1,188 @@
+//! Execution of `agent`-type graph nodes.
+//!
+//! Spawns a child agent via `function::supervisor::run_agent_for_graph`,
+//! interpolating the prompt against current graph state. After the agent
+//! finishes, applies the node's `state_updates` (templates can reference
+//! `{{output}}` for the agent's stdout).
+
+use super::state::StateManager;
+use super::types::AgentNode;
+use crate::config::RequestContext;
+use crate::function::supervisor::run_agent_for_graph;
+use anyhow::{Context, Result};
+use serde_json::Value;
+use std::time::Duration;
+use tokio::time::timeout;
+
+const OUTPUT_KEY: &str = "output";
+const DEFAULT_TIMEOUT_SECS: u64 = 300;
+
+pub struct AgentNodeExecutor;
+
+impl AgentNodeExecutor {
+    /// Interpolate the node's prompt, spawn the agent, wait for it to
+    /// finish, then apply `state_updates`. Returns the agent's full output.
+    pub async fn execute(
+        node: &AgentNode,
+        state_manager: &mut StateManager,
+        parent_ctx: &mut RequestContext,
+    ) -> Result<String> {
+        let prompt = state_manager
+            .interpolate(&node.prompt)
+            .with_context(|| format!("Failed to interpolate prompt for agent '{}'", node.agent))?;
+
+        let timeout_dur = Duration::from_secs(node.timeout.unwrap_or(DEFAULT_TIMEOUT_SECS));
+
+        let output = timeout(
+            timeout_dur,
+            run_agent_for_graph(parent_ctx, &node.agent, &prompt),
+        )
+        .await
+        .with_context(|| {
+            format!(
+                "Agent '{}' timed out after {}s",
+                node.agent,
+                timeout_dur.as_secs()
+            )
+        })?
+        .with_context(|| format!("Agent '{}' failed", node.agent))?;
+
+        apply_state_updates(node, state_manager, &output);
+
+        Ok(output)
+    }
+}
+
+/// Exposes the agent's output as `{{output}}` for template evaluation, then
+/// applies every key/template in `state_updates`. The temporary `output`
+/// state key is removed at the end so it doesn't leak into subsequent
+/// nodes' templates.
+fn apply_state_updates(node: &AgentNode, state_manager: &mut StateManager, output: &str) {
+    let Some(updates) = &node.state_updates else {
+        return;
+    };
+    let prev_output = state_manager.state().get(OUTPUT_KEY).cloned();
+    state_manager
+        .state_mut()
+        .set(OUTPUT_KEY.into(), Value::String(output.to_string()));
+
+    for (key, template) in updates {
+        let value = state_manager.interpolate_lenient(template);
+        state_manager
+            .state_mut()
+            .set(key.clone(), Value::String(value));
+    }
+
+    match prev_output {
+        Some(v) => state_manager.state_mut().set(OUTPUT_KEY.into(), v),
+        None => {
+            state_manager
+                .state_mut()
+                .set(OUTPUT_KEY.into(), Value::Null);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::types::AgentNode;
+    use super::*;
+    use serde_json::json;
+    use std::collections::HashMap;
+
+    fn manager_with(pairs: &[(&str, Value)]) -> StateManager {
+        let mut map = HashMap::new();
+        for (k, v) in pairs {
+            map.insert((*k).into(), v.clone());
+        }
+        StateManager::new(map)
+    }
+
+    fn node_with(prompt: &str, updates: Option<HashMap<String, String>>) -> AgentNode {
+        AgentNode {
+            agent: "test_agent".into(),
+            prompt: prompt.into(),
+            state_updates: updates,
+            timeout: None,
+        }
+    }
+
+    #[test]
+    fn state_updates_use_output_placeholder() {
+        let node = {
+            let mut u = HashMap::new();
+            u.insert("findings".into(), "{{output}}".into());
+            node_with("hi", Some(u))
+        };
+        let mut state = manager_with(&[]);
+        apply_state_updates(&node, &mut state, "agent finished its work");
+        assert_eq!(
+            state.state().get("findings"),
+            Some(&json!("agent finished its work"))
+        );
+    }
+
+    #[test]
+    fn state_updates_can_reference_existing_keys_and_output() {
+        let node = {
+            let mut u = HashMap::new();
+            u.insert("summary".into(), "{{topic}}: {{output}}".into());
+            node_with("hi", Some(u))
+        };
+        let mut state = manager_with(&[("topic", json!("auth"))]);
+        apply_state_updates(&node, &mut state, "JWT vs sessions");
+        assert_eq!(
+            state.state().get("summary"),
+            Some(&json!("auth: JWT vs sessions"))
+        );
+    }
+
+    #[test]
+    fn output_key_is_cleaned_up_after_state_updates() {
+        let node = {
+            let mut u = HashMap::new();
+            u.insert("findings".into(), "{{output}}".into());
+            node_with("hi", Some(u))
+        };
+        let mut state = manager_with(&[]);
+        apply_state_updates(&node, &mut state, "anything");
+        assert_eq!(state.state().get("output"), Some(&Value::Null));
+    }
+
+    #[test]
+    fn pre_existing_output_value_is_preserved() {
+        let node = {
+            let mut u = HashMap::new();
+            u.insert("greeting".into(), "{{output}}".into());
+            node_with("hi", Some(u))
+        };
+        let mut state = manager_with(&[("output", json!("preserved"))]);
+        apply_state_updates(&node, &mut state, "new agent output");
+        assert_eq!(
+            state.state().get("greeting"),
+            Some(&json!("new agent output"))
+        );
+        assert_eq!(state.state().get("output"), Some(&json!("preserved")));
+    }
+
+    #[test]
+    fn no_state_updates_is_a_noop() {
+        let node = node_with("hi", None);
+        let mut state = manager_with(&[("k", json!("v"))]);
+        apply_state_updates(&node, &mut state, "ignored");
+        assert_eq!(state.state().get("k"), Some(&json!("v")));
+        assert!(state.state().get("output").is_none());
+    }
+
+    #[test]
+    fn interpolate_lenient_on_state_updates_handles_missing_keys() {
+        let node = {
+            let mut u = HashMap::new();
+            u.insert("decorated".into(), "[{{missing}}] {{output}}".into());
+            node_with("hi", Some(u))
+        };
+        let mut state = manager_with(&[]);
+        apply_state_updates(&node, &mut state, "DATA");
+        assert_eq!(state.state().get("decorated"), Some(&json!("[] DATA")));
+    }
+}

src/graph/mod.rs

@@ -1,12 +1,14 @@
 //! Graph-based agent orchestration. Declarative YAML workflows over a shared
 //! JSON state, composed of agent/script/approval/input/end nodes.
 
+pub mod agent;
 pub mod parser;
 pub mod script;
 pub mod state;
 pub mod types;
 pub mod validator;
 
+pub use agent::AgentNodeExecutor;
 pub use parser::{GraphParser, agent_has_graph, load_agent_graph};
 pub use script::ScriptExecutor;
 pub use state::{StateManager, StateRepresentation};