Remove unused server_config from AppState, use read lock for config comparison

- AppState.server_config was stored but never read; remove it and revert
  create_app_state_with_options back to 5 parameters
- Config polling now compares under a read lock first, only acquiring
  the write lock when a change is detected

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

crates/arc-api/src/serve.rs

@@ -137,14 +137,7 @@ pub async fn serve_command(args: ServeArgs, styles: &'static Styles) -> anyhow::
         (auth_mode, client_auth, max_concurrent_runs)
     };
 
-    let state = create_app_state_with_options(
-        db,
-        factory,
-        dry_run_mode,
-        args.demo,
-        max_concurrent_runs,
-        Arc::clone(&shared_config),
-    );
+    let state = create_app_state_with_options(db, factory, dry_run_mode, args.demo, max_concurrent_runs);
     crate::server::spawn_scheduler(Arc::clone(&state));
     let router = build_router(state, auth_mode);
 
@@ -174,10 +167,14 @@ pub async fn serve_command(args: ServeArgs, styles: &'static Styles) -> anyhow::
                 interval.tick().await;
                 match crate::server_config::load_server_config() {
                     Ok(new_config) => {
-                        let mut cfg = config_for_poll.write().expect("config lock poisoned");
-                        if *cfg != new_config {
-                            info!("Server config reloaded");
+                        let changed = {
+                            let cfg = config_for_poll.read().expect("config lock poisoned");
+                            *cfg != new_config
+                        };
+                        if changed {
+                            let mut cfg = config_for_poll.write().expect("config lock poisoned");
                             *cfg = new_config;
+                            info!("Server config reloaded");
                         }
                     }
                     Err(e) => {

crates/arc-api/src/server.rs

@@ -1,8 +1,6 @@
 use std::collections::HashMap;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::{Arc, Mutex, RwLock};
-
-use crate::server_config::ServerConfig;
+use std::sync::{Arc, Mutex};
 
 use axum::extract::{Path, Query, State};
 use axum::http::StatusCode;
@@ -90,7 +88,6 @@ pub struct AppState {
     pub db: sqlx::SqlitePool,
     max_concurrent_runs: usize,
     scheduler_notify: tokio::sync::Notify,
-    pub server_config: Arc<RwLock<ServerConfig>>,
 }
 
 /// Build the axum Router with all run endpoints.
@@ -296,14 +293,7 @@ pub fn create_app_state(
     db: sqlx::SqlitePool,
     registry_factory: impl Fn(Arc<dyn Interviewer>) -> HandlerRegistry + Send + Sync + 'static,
 ) -> Arc<AppState> {
-    create_app_state_with_options(
-        db,
-        registry_factory,
-        false,
-        false,
-        5,
-        Arc::new(RwLock::new(ServerConfig::default())),
-    )
+    create_app_state_with_options(db, registry_factory, false, false, 5)
 }
 
 /// Create an `AppState` with the given database pool, registry factory, dry-run flag, and demo flag.
@@ -313,7 +303,6 @@ pub fn create_app_state_with_options(
     dry_run: bool,
     is_demo: bool,
     max_concurrent_runs: usize,
-    server_config: Arc<RwLock<ServerConfig>>,
 ) -> Arc<AppState> {
     Arc::new(AppState {
         runs: Mutex::new(HashMap::new()),
@@ -324,7 +313,6 @@ pub fn create_app_state_with_options(
         db,
         max_concurrent_runs,
         scheduler_notify: tokio::sync::Notify::new(),
-        server_config,
     })
 }
 
@@ -1596,7 +1584,7 @@ mod tests {
 
     #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
     async fn concurrency_limit_respected() {
-        let state = create_app_state_with_options(test_db().await, test_registry, false, false, 1, Arc::new(RwLock::new(ServerConfig::default())));
+        let state = create_app_state_with_options(test_db().await, test_registry, false, false, 1);
         let app = test_app_with_scheduler(state);
 
         // Submit two runs with max_concurrent_runs=1