Accept story 34: Per-Project Agent Configuration and Role Definitions

Replace single [agent] config with multi-agent [[agent]] roster system.
Each agent has name, role, model, allowed_tools, max_turns, max_budget_usd,
and system_prompt fields that map to Claude CLI flags at spawn time.

- AgentConfig expanded with structured fields, validated at startup (panics
  on duplicate names, empty names, non-positive budgets/turns)
- Backwards-compatible: legacy [agent] format auto-wraps with deprecation warning
- AgentPool uses composite "story_id:agent_name" keys for concurrent agents
- agent_name added to AgentEvent variants, AgentInfo, start/stop/subscribe APIs
- GET /agents/config returns roster, POST /agents/config/reload hot-reloads
- POST /agents/start accepts optional agent_name, /agents/stop requires it
- SSE route updated to /agents/:story_id/:agent_name/stream
- Frontend: roster badges, agent selector dropdown, composite-key state
- Project root initialized to cwd at startup so config endpoints work immediately

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/http/agents.rs

@@ -1,3 +1,4 @@
+use crate::config::ProjectConfig;
 use crate::http::context::{AppContext, OpenApiResult, bad_request};
 use poem_openapi::{Object, OpenApi, Tags, payload::Json};
 use serde::Serialize;
@@ -9,18 +10,36 @@ enum AgentsTags {
 }
 
 #[derive(Object)]
-struct StoryIdPayload {
+struct StartAgentPayload {
     story_id: String,
+    agent_name: Option<String>,
+}
+
+#[derive(Object)]
+struct StopAgentPayload {
+    story_id: String,
+    agent_name: String,
 }
 
 #[derive(Object, Serialize)]
 struct AgentInfoResponse {
     story_id: String,
+    agent_name: String,
     status: String,
     session_id: Option<String>,
     worktree_path: Option<String>,
 }
 
+#[derive(Object, Serialize)]
+struct AgentConfigInfoResponse {
+    name: String,
+    role: String,
+    model: Option<String>,
+    allowed_tools: Option<Vec<String>>,
+    max_turns: Option<u32>,
+    max_budget_usd: Option<f64>,
+}
+
 pub struct AgentsApi {
     pub ctx: Arc<AppContext>,
 }
@@ -28,10 +47,11 @@ pub struct AgentsApi {
 #[OpenApi(tag = "AgentsTags::Agents")]
 impl AgentsApi {
     /// Start an agent for a given story (creates worktree, runs setup, spawns agent).
+    /// If agent_name is omitted, the first configured agent is used.
     #[oai(path = "/agents/start", method = "post")]
     async fn start_agent(
         &self,
-        payload: Json<StoryIdPayload>,
+        payload: Json<StartAgentPayload>,
     ) -> OpenApiResult<Json<AgentInfoResponse>> {
         let project_root = self
             .ctx
@@ -42,12 +62,17 @@ impl AgentsApi {
         let info = self
             .ctx
             .agents
-            .start_agent(&project_root, &payload.0.story_id)
+            .start_agent(
+                &project_root,
+                &payload.0.story_id,
+                payload.0.agent_name.as_deref(),
+            )
             .await
             .map_err(bad_request)?;
 
         Ok(Json(AgentInfoResponse {
             story_id: info.story_id,
+            agent_name: info.agent_name,
             status: info.status.to_string(),
             session_id: info.session_id,
             worktree_path: info.worktree_path,
@@ -56,7 +81,7 @@ impl AgentsApi {
 
     /// Stop a running agent and clean up its worktree.
     #[oai(path = "/agents/stop", method = "post")]
-    async fn stop_agent(&self, payload: Json<StoryIdPayload>) -> OpenApiResult<Json<bool>> {
+    async fn stop_agent(&self, payload: Json<StopAgentPayload>) -> OpenApiResult<Json<bool>> {
         let project_root = self
             .ctx
             .agents
@@ -65,7 +90,11 @@ impl AgentsApi {
 
         self.ctx
             .agents
-            .stop_agent(&project_root, &payload.0.story_id)
+            .stop_agent(
+                &project_root,
+                &payload.0.story_id,
+                &payload.0.agent_name,
+            )
             .await
             .map_err(bad_request)?;
 
@@ -82,6 +111,7 @@ impl AgentsApi {
                 .into_iter()
                 .map(|info| AgentInfoResponse {
                     story_id: info.story_id,
+                    agent_name: info.agent_name,
                     status: info.status.to_string(),
                     session_id: info.session_id,
                     worktree_path: info.worktree_path,
@@ -89,4 +119,62 @@ impl AgentsApi {
                 .collect(),
         ))
     }
+
+    /// Get the configured agent roster from project.toml.
+    #[oai(path = "/agents/config", method = "get")]
+    async fn get_agent_config(
+        &self,
+    ) -> OpenApiResult<Json<Vec<AgentConfigInfoResponse>>> {
+        let project_root = self
+            .ctx
+            .agents
+            .get_project_root(&self.ctx.state)
+            .map_err(bad_request)?;
+
+        let config = ProjectConfig::load(&project_root).map_err(bad_request)?;
+
+        Ok(Json(
+            config
+                .agent
+                .iter()
+                .map(|a| AgentConfigInfoResponse {
+                    name: a.name.clone(),
+                    role: a.role.clone(),
+                    model: a.model.clone(),
+                    allowed_tools: a.allowed_tools.clone(),
+                    max_turns: a.max_turns,
+                    max_budget_usd: a.max_budget_usd,
+                })
+                .collect(),
+        ))
+    }
+
+    /// Reload project config and return the updated agent roster.
+    #[oai(path = "/agents/config/reload", method = "post")]
+    async fn reload_config(
+        &self,
+    ) -> OpenApiResult<Json<Vec<AgentConfigInfoResponse>>> {
+        let project_root = self
+            .ctx
+            .agents
+            .get_project_root(&self.ctx.state)
+            .map_err(bad_request)?;
+
+        let config = ProjectConfig::load(&project_root).map_err(bad_request)?;
+
+        Ok(Json(
+            config
+                .agent
+                .iter()
+                .map(|a| AgentConfigInfoResponse {
+                    name: a.name.clone(),
+                    role: a.role.clone(),
+                    model: a.model.clone(),
+                    allowed_tools: a.allowed_tools.clone(),
+                    max_turns: a.max_turns,
+                    max_budget_usd: a.max_budget_usd,
+                })
+                .collect(),
+        ))
+    }
 }

server/src/http/agents_sse.rs

@@ -5,16 +5,16 @@ use poem::web::{Data, Path};
 use poem::{Body, IntoResponse, Response};
 use std::sync::Arc;
 
-/// SSE endpoint: `GET /agents/:story_id/stream`
+/// SSE endpoint: `GET /agents/:story_id/:agent_name/stream`
 ///
 /// Streams `AgentEvent`s as Server-Sent Events. Each event is JSON-encoded
 /// with `data:` prefix and double newline terminator per the SSE spec.
 #[handler]
 pub async fn agent_stream(
-    Path(story_id): Path<String>,
+    Path((story_id, agent_name)): Path<(String, String)>,
     ctx: Data<&Arc<AppContext>>,
 ) -> impl IntoResponse {
-    let mut rx = match ctx.agents.subscribe(&story_id) {
+    let mut rx = match ctx.agents.subscribe(&story_id, &agent_name) {
         Ok(rx) => rx,
         Err(e) => {
             return Response::builder()

server/src/http/mod.rs

@@ -35,7 +35,7 @@ pub fn build_routes(ctx: AppContext) -> impl poem::Endpoint {
         .nest("/docs", docs_service.swagger_ui())
         .at("/ws", get(ws::ws_handler))
         .at(
-            "/agents/:story_id/stream",
+            "/agents/:story_id/:agent_name/stream",
             get(agents_sse::agent_stream),
         )
         .at("/health", get(health::health))