fix: patch bug in approve plan mode (handle empty toolArgs for tools with no parameters) (#387)

Co-authored-by: Letta <noreply@letta.com>

src/agent/approval-execution.ts

@@ -56,6 +56,9 @@ const PARALLEL_SAFE_TOOLS = new Set([
   "BashOutput",
   // Task spawns independent subagents
   "Task",
+  // Plan mode tools (no parameters, no file operations)
+  "EnterPlanMode",
+  "ExitPlanMode",
 ]);
 
 function isParallelSafe(toolName: string): boolean {
@@ -194,10 +197,18 @@ async function executeSingleDecision(
 
     // Execute the approved tool
     try {
-      const parsedArgs =
-        typeof decision.approval.toolArgs === "string"
-          ? JSON.parse(decision.approval.toolArgs)
-          : decision.approval.toolArgs || {};
+      // Safe parse - toolArgs should be "{}" but handle edge cases
+      let parsedArgs: Record<string, unknown> = {};
+      if (typeof decision.approval.toolArgs === "string") {
+        try {
+          parsedArgs = JSON.parse(decision.approval.toolArgs);
+        } catch {
+          // Empty or malformed args - use empty object
+          parsedArgs = {};
+        }
+      } else {
+        parsedArgs = decision.approval.toolArgs || {};
+      }
 
       const toolResult = await executeTool(
         decision.approval.toolName,
@@ -328,10 +339,18 @@ export async function executeApprovalBatch(
       parallelIndices.push(i);
     } else {
       // Get resource key for write tools
-      const args =
-        typeof decision.approval.toolArgs === "string"
-          ? JSON.parse(decision.approval.toolArgs)
-          : decision.approval.toolArgs || {};
+      // Safe parse - handle empty or malformed toolArgs
+      let args: Record<string, unknown> = {};
+      if (typeof decision.approval.toolArgs === "string") {
+        try {
+          args = JSON.parse(decision.approval.toolArgs);
+        } catch {
+          // Empty or malformed args - use empty object (will use global lock)
+          args = {};
+        }
+      } else {
+        args = decision.approval.toolArgs || {};
+      }
       const resourceKey = getResourceKey(toolName, args);
 
       const indices = writeToolsByResource.get(resourceKey) || [];

src/cli/helpers/stream.ts

@@ -215,10 +215,12 @@ export async function drainStream(
 
     // Include ALL tool_call_ids - don't filter out incomplete entries
     // Missing name/args will be handled by denial logic in App.tsx
+    // Default empty toolArgs to "{}" - empty string causes JSON.parse("") to fail
+    // This happens for tools with no parameters (e.g., EnterPlanMode, ExitPlanMode)
     approvals = allPending.map((a) => ({
       toolCallId: a.toolCallId,
       toolName: a.toolName || "",
-      toolArgs: a.toolArgs || "",
+      toolArgs: a.toolArgs || "{}",
     }));
 
     if (approvals.length === 0) {