story-kit: merge 176_bug_stories_moved_to_current_get_supervisor_instead_of_coder

server/src/agents.rs

@@ -351,8 +351,10 @@ impl AgentPool {
                 name.to_string()
             }
             None => config
-                .default_agent()
-                .ok_or_else(|| "No agents configured".to_string())?
+                .default_coder_agent()
+                .ok_or_else(|| {
+                    "No coder agent configured. Specify an agent_name explicitly.".to_string()
+                })?
                 .name
                 .clone(),
         };

server/src/config.rs

@@ -57,6 +57,20 @@ pub struct AgentConfig {
     pub inactivity_timeout_secs: u64,
 }
 
+impl AgentConfig {
+    /// Returns true if this agent is a coder.
+    ///
+    /// Prefers the explicit `stage` field; falls back to checking whether the
+    /// agent name starts with `"coder"` for backwards compatibility.
+    pub fn is_coder(&self) -> bool {
+        match self.stage.as_deref() {
+            Some("coder") => true,
+            Some(_) => false,
+            None => self.name.starts_with("coder"),
+        }
+    }
+}
+
 fn default_path() -> String {
     ".".to_string()
 }
@@ -189,6 +203,15 @@ impl ProjectConfig {
         self.agent.first()
     }
 
+    /// Get the first coder agent config.
+    ///
+    /// Prefers the explicit `stage = "coder"` field over the legacy name-based
+    /// heuristic (names starting with "coder").  Returns `None` if no coder
+    /// agent is configured.
+    pub fn default_coder_agent(&self) -> Option<&AgentConfig> {
+        self.agent.iter().find(|a| a.is_coder())
+    }
+
     /// Render template variables in agent args and prompt for the given agent.
     /// If `agent_name` is None, uses the first (default) agent.
     pub fn render_agent_args(
@@ -480,6 +503,89 @@ name = "second"
         assert!(config.find_agent("missing").is_none());
     }
 
+    #[test]
+    fn default_coder_agent_skips_supervisor() {
+        let toml_str = r#"
+[[agent]]
+name = "supervisor"
+stage = "other"
+
+[[agent]]
+name = "coder-1"
+stage = "coder"
+"#;
+        let config = ProjectConfig::parse(toml_str).unwrap();
+        assert_eq!(config.default_coder_agent().unwrap().name, "coder-1");
+    }
+
+    #[test]
+    fn default_coder_agent_uses_name_heuristic_when_no_stage() {
+        let toml_str = r#"
+[[agent]]
+name = "supervisor"
+
+[[agent]]
+name = "coder-1"
+"#;
+        let config = ProjectConfig::parse(toml_str).unwrap();
+        assert_eq!(config.default_coder_agent().unwrap().name, "coder-1");
+    }
+
+    #[test]
+    fn default_coder_agent_returns_none_when_no_coders() {
+        let toml_str = r#"
+[[agent]]
+name = "supervisor"
+stage = "other"
+"#;
+        let config = ProjectConfig::parse(toml_str).unwrap();
+        assert!(config.default_coder_agent().is_none());
+    }
+
+    #[test]
+    fn is_coder_explicit_stage() {
+        let mut agent = AgentConfig {
+            name: "my-agent".to_string(),
+            role: String::new(),
+            command: "claude".to_string(),
+            args: vec![],
+            prompt: String::new(),
+            model: None,
+            allowed_tools: None,
+            max_turns: None,
+            max_budget_usd: None,
+            system_prompt: None,
+            stage: Some("coder".to_string()),
+            inactivity_timeout_secs: 300,
+        };
+        assert!(agent.is_coder());
+        agent.stage = Some("other".to_string());
+        assert!(!agent.is_coder());
+    }
+
+    #[test]
+    fn is_coder_name_heuristic() {
+        let make = |name: &str| AgentConfig {
+            name: name.to_string(),
+            role: String::new(),
+            command: "claude".to_string(),
+            args: vec![],
+            prompt: String::new(),
+            model: None,
+            allowed_tools: None,
+            max_turns: None,
+            max_budget_usd: None,
+            system_prompt: None,
+            stage: None,
+            inactivity_timeout_secs: 300,
+        };
+        assert!(make("coder-1").is_coder());
+        assert!(make("coder-opus").is_coder());
+        assert!(!make("supervisor").is_coder());
+        assert!(!make("qa").is_coder());
+        assert!(!make("mergemaster").is_coder());
+    }
+
     #[test]
     fn parse_project_toml_from_file() {
         let tmp = tempfile::tempdir().unwrap();

server/src/http/mcp.rs

@@ -442,7 +442,7 @@ fn handle_tools_list(id: Option<Value>) -> JsonRpcResponse {
                             },
                             "agent_name": {
                                 "type": "string",
-                                "description": "Agent name from project.toml config. If omitted, uses the first configured agent."
+                                "description": "Agent name from project.toml config. If omitted, uses the first coder agent (stage = \"coder\"). Supervisor must be requested explicitly by name."
                             }
                         },
                         "required": ["story_id"]
@@ -2890,6 +2890,71 @@ mod tests {
         assert!(result.unwrap_err().contains("story_id"));
     }
 
+    #[tokio::test]
+    async fn tool_start_agent_no_agent_name_no_coder_returns_clear_error() {
+        // Config has only a supervisor — start_agent without agent_name should
+        // refuse rather than silently assigning supervisor.
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        std::fs::create_dir_all(&sk).unwrap();
+        std::fs::write(
+            sk.join("project.toml"),
+            r#"
+[[agent]]
+name = "supervisor"
+stage = "other"
+"#,
+        )
+        .unwrap();
+        let ctx = test_ctx(tmp.path());
+        let result = tool_start_agent(&json!({"story_id": "42_my_story"}), &ctx).await;
+        assert!(result.is_err());
+        let err = result.unwrap_err();
+        assert!(
+            err.contains("coder"),
+            "error should mention 'coder', got: {err}"
+        );
+    }
+
+    #[tokio::test]
+    async fn tool_start_agent_no_agent_name_picks_coder_not_supervisor() {
+        // Config has supervisor first, then coder-1. Without agent_name the
+        // coder should be selected, not supervisor. The call will fail due to
+        // missing git repo / worktree, but the error must NOT be about
+        // "No coder agent configured".
+        let tmp = tempfile::tempdir().unwrap();
+        let sk = tmp.path().join(".story_kit");
+        std::fs::create_dir_all(&sk).unwrap();
+        std::fs::write(
+            sk.join("project.toml"),
+            r#"
+[[agent]]
+name = "supervisor"
+stage = "other"
+
+[[agent]]
+name = "coder-1"
+stage = "coder"
+"#,
+        )
+        .unwrap();
+        let ctx = test_ctx(tmp.path());
+        let result = tool_start_agent(&json!({"story_id": "42_my_story"}), &ctx).await;
+        // May succeed or fail for infrastructure reasons (no git repo), but
+        // must NOT fail with "No coder agent configured".
+        if let Err(err) = result {
+            assert!(
+                !err.contains("No coder agent configured"),
+                "should not fail on agent selection, got: {err}"
+            );
+            // Should also not complain about supervisor being absent.
+            assert!(
+                !err.contains("supervisor"),
+                "should not select supervisor, got: {err}"
+            );
+        }
+    }
+
     #[tokio::test]
     async fn tool_create_worktree_missing_story_id() {
         let tmp = tempfile::tempdir().unwrap();