fix(desktop): defer managed-agent pools by default

desktop/src-tauri/src/managed_agents/runtime.rs

@@ -966,6 +966,10 @@ fn child_rust_log_filter() -> String {
     }
 }
 
+fn manual_start_uses_lazy_pool() -> bool {
+    true
+}
+
 pub fn start_managed_agent_process(
     app: &AppHandle,
     record: &mut ManagedAgentRecord,
@@ -998,7 +1002,16 @@ pub fn start_managed_agent_process(
     // Scalar PIDs are migration-only and never establish pair liveness.
     record.runtime_pid = None;
 
-    let mut process = spawn_agent_child(app, record, &key.relay_url, false, owner_hex)?;
+    // Manual starts and config-driven restarts must match launch restore's
+    // lazy behavior. Eager startup reserves every configured ACP slot before
+    // an event arrives, multiplying idle child processes across a fleet.
+    let mut process = spawn_agent_child(
+        app,
+        record,
+        &key.relay_url,
+        manual_start_uses_lazy_pool(),
+        owner_hex,
+    )?;
     let now = now_iso();
     let receipt = super::ManagedAgentRuntimeReceipt {
         key: key.clone(),

desktop/src-tauri/src/managed_agents/runtime/tests.rs

@@ -1,5 +1,10 @@
 use crate::managed_agents::known_acp_runtime;
 
+#[test]
+fn manual_start_defers_agent_pool_initialization() {
+    assert!(super::manual_start_uses_lazy_pool());
+}
+
 // ── desktop binary name tests ───────────────────────────────────────────
 
 #[test]

desktop/src-tauri/src/managed_agents/types.rs

@@ -811,7 +811,7 @@ pub struct UpdateTeamRequest {
 pub const DEFAULT_ACP_COMMAND: &str = "buzz-acp";
 /// ~5 min (320s) — matches the CLI harness default (BUZZ_ACP_IDLE_TIMEOUT).
 pub const DEFAULT_AGENT_TURN_TIMEOUT_SECONDS: u64 = 320;
-pub const DEFAULT_AGENT_PARALLELISM: u32 = 10;
+pub const DEFAULT_AGENT_PARALLELISM: u32 = 1;
 
 fn default_agent_parallelism() -> u32 {
     DEFAULT_AGENT_PARALLELISM

desktop/src-tauri/src/managed_agents/types/tests.rs

@@ -694,3 +694,12 @@ fn mint_rejects_out_of_range_input_parallelism() {
         "input-branch error must not blame the definition: {err}"
     );
 }
+
+#[test]
+fn managed_agent_parallelism_defaults_to_one() {
+    assert_eq!(
+        super::DEFAULT_AGENT_PARALLELISM,
+        1,
+        "one idle managed identity must not eagerly reserve multiple ACP runtimes",
+    );
+}