fix(cron): keep scheduled jobs single-owner across desktop instances

scripts/core-boundaries/explicit-test-topology.mjs

@@ -41,6 +41,7 @@ export const servicesCoreIntegrationTestTargets = [
   { name: 'permission_store_contracts', path: 'tests/permission_store_contracts.rs' },
   { name: 'workspace_instruction_contracts', path: 'tests/workspace_instruction_contracts.rs' },
   { name: 'session_write_lock_contracts', path: 'tests/session_write_lock_contracts.rs' },
+  { name: 'exclusive_file_lease_contracts', path: 'tests/exclusive_file_lease_contracts.rs' },
   { name: 'process_runtime_contracts', path: 'tests/process_runtime_contracts.rs' },
   { name: 'service_contracts', path: 'tests/service_contracts.rs' },
   { name: 'storage_owner_contracts', path: 'tests/storage_owner_contracts.rs' },

src/crates/assembly/core/src/agentic/coordination/scheduler.rs

@@ -71,6 +71,15 @@ pub use openbitfun_runtime_ports::{
     DialogSubmitOutcome,
 };
 
+/// Rejection prefix for a submission that reuses a dialog turn ID the session
+/// already owns.
+///
+/// The scheduled-job service classifies enqueue failures from the port message
+/// text, so producers and classifiers share this constant instead of repeating
+/// the wording.
+pub(crate) const DIALOG_TURN_ID_ALREADY_SETTLED_MESSAGE: &str =
+    "Dialog turn ID is already active or completed";
+
 /// A message waiting to be dispatched to the coordinator
 #[derive(Debug, Clone)]
 pub struct QueuedTurn {
@@ -2772,7 +2781,7 @@ impl DialogScheduler {
                 PortError::new(
                     PortErrorKind::InvalidRequest,
                     format!(
-                        "Dialog turn ID is already active or completed: session_id={}, turn_id={resolved_turn_id}",
+                        "{DIALOG_TURN_ID_ALREADY_SETTLED_MESSAGE}: session_id={}, turn_id={resolved_turn_id}",
                         request.session_id
                     ),
                 )

src/crates/assembly/core/src/agentic/tools/implementations/cron_tool.rs

@@ -1127,6 +1127,14 @@ Patch schema for "update":
                         session_id
                     ));
                 }
+                if !cron_service.is_scheduling_owner() {
+                    // Two instances can share one user data directory. Saying so
+                    // here stops the agent from presenting a standby list as the
+                    // state that will actually run.
+                    result_for_assistant.push_str(
+                        "\n\nScheduling note: another running OpenBitFun instance owns scheduled job execution right now, so these jobs run there and edits or manual runs are refused in this instance.",
+                    );
+                }
 
                 Ok(vec![ToolResult::Result {
                     data: json!({

src/crates/assembly/core/src/infrastructure/app_paths/path_manager.rs

@@ -320,6 +320,15 @@ impl PathManager {
         self.user_cron_dir().join("jobs.json")
     }
 
+    /// Lease file identifying the process that owns scheduled job scheduling.
+    ///
+    /// It sits beside `jobs.json` because it guards exactly that store: the
+    /// holder is the only process allowed to schedule jobs and write the file.
+    /// The file itself is inert — ownership is the OS lock on it.
+    pub fn cron_scheduler_lease_file(&self) -> PathBuf {
+        self.user_cron_dir().join("scheduler.lock")
+    }
+
     /// Get miniapps root directory: ~/.config/openbitfun/data/miniapps/
     pub fn miniapps_dir(&self) -> PathBuf {
         self.user_data_dir().join("miniapps")