diff --git a/packages/core/src/agents/local-session-invocation.ts b/packages/core/src/agents/local-session-invocation.ts
index 08e8f34593..0e49bf6240 100644
--- a/packages/core/src/agents/local-session-invocation.ts
+++ b/packages/core/src/agents/local-session-invocation.ts
@@ -22,6 +22,7 @@ import {
   SUBAGENT_REJECTED_ERROR_PREFIX,
   SUBAGENT_CANCELLED_ERROR_MESSAGE,
   isToolActivityError,
+  SubagentState,
 } from './types.js';
 import { randomUUID } from 'node:crypto';
 import type { MessageBus } from '../confirmation-bus/message-bus.js';
@@ -141,7 +142,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
               id: randomUUID(),
               type: 'thought',
               content: sanitizeThoughtContent(text),
-              status: 'running',
+              status: SubagentState.RUNNING,
             });
           }
           updated = true;
@@ -169,7 +170,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
             displayName,
             description,
             args,
-            status: 'running',
+            status: SubagentState.RUNNING,
           });
           updated = true;
 
@@ -189,9 +190,11 @@ export class LocalSessionInvocation extends BaseToolInvocation<
             if (
               recentActivity[i].type === 'tool_call' &&
               recentActivity[i].content === name &&
-              recentActivity[i].status === 'running'
+              recentActivity[i].status === SubagentState.RUNNING
             ) {
-              recentActivity[i].status = isError ? 'error' : 'completed';
+              recentActivity[i].status = isError
+                ? SubagentState.ERROR
+                : SubagentState.COMPLETED;
               updated = true;
 
               this.publishActivity(recentActivity[i]);
@@ -221,9 +224,9 @@ export class LocalSessionInvocation extends BaseToolInvocation<
               if (
                 recentActivity[i].type === 'tool_call' &&
                 recentActivity[i].content === toolName &&
-                recentActivity[i].status === 'running'
+                recentActivity[i].status === SubagentState.RUNNING
               ) {
-                recentActivity[i].status = 'cancelled';
+                recentActivity[i].status = SubagentState.CANCELLED;
                 updated = true;
                 break;
               }
@@ -234,9 +237,9 @@ export class LocalSessionInvocation extends BaseToolInvocation<
               if (
                 recentActivity[i].type === 'tool_call' &&
                 recentActivity[i].content === toolName &&
-                recentActivity[i].status === 'running'
+                recentActivity[i].status === SubagentState.RUNNING
               ) {
-                recentActivity[i].status = 'error';
+                recentActivity[i].status = SubagentState.ERROR;
                 updated = true;
                 break;
               }
@@ -250,7 +253,10 @@ export class LocalSessionInvocation extends BaseToolInvocation<
               isCancellation || isRejection
                 ? sanitizedError
                 : `Error: ${sanitizedError}`,
-            status: isCancellation || isRejection ? 'cancelled' : 'error',
+            status:
+              isCancellation || isRejection
+                ? SubagentState.CANCELLED
+                : SubagentState.ERROR,
           });
           updated = true;
           break;
@@ -269,7 +275,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
           isSubagentProgress: true,
           agentName: this.definition.name,
           recentActivity: [...recentActivity], // Copy to avoid mutation issues
-          state: 'running',
+          state: SubagentState.RUNNING,
         };
 
         updateOutput(progress);
@@ -300,7 +306,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
           isSubagentProgress: true,
           agentName: this.definition.name,
           recentActivity: [],
-          state: 'running',
+          state: SubagentState.RUNNING,
         };
         updateOutput(initialProgress);
       }
@@ -323,7 +329,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
           isSubagentProgress: true,
           agentName: this.definition.name,
           recentActivity: [...recentActivity],
-          state: 'cancelled',
+          state: SubagentState.CANCELLED,
         };
 
         if (updateOutput) {
@@ -339,7 +345,7 @@ export class LocalSessionInvocation extends BaseToolInvocation<
         isSubagentProgress: true,
         agentName: this.definition.name,
         recentActivity: [...recentActivity],
-        state: 'completed',
+        state: SubagentState.COMPLETED,
         result: output.result,
         terminateReason: output.terminate_reason,
       };
@@ -367,20 +373,20 @@ ${output.result}`;
 
       // Mark any running items as error/cancelled
       for (const item of recentActivity) {
-        if (item.status === 'running') {
-          item.status = isAbort ? 'cancelled' : 'error';
+        if (item.status === SubagentState.RUNNING) {
+          item.status = isAbort ? SubagentState.CANCELLED : SubagentState.ERROR;
         }
       }
 
       // Ensure the error is reflected in the recent activity for display
       if (!isAbort) {
         const lastActivity = recentActivity[recentActivity.length - 1];
-        if (!lastActivity || lastActivity.status !== 'error') {
+        if (!lastActivity || lastActivity.status !== SubagentState.ERROR) {
           recentActivity.push({
             id: randomUUID(),
             type: 'thought',
             content: `Error: ${errorMessage}`,
-            status: 'error',
+            status: SubagentState.ERROR,
           });
           if (recentActivity.length > MAX_RECENT_ACTIVITY) {
             recentActivity = recentActivity.slice(-MAX_RECENT_ACTIVITY);
@@ -392,7 +398,7 @@ ${output.result}`;
         isSubagentProgress: true,
         agentName: this.definition.name,
         recentActivity: [...recentActivity],
-        state: isAbort ? 'cancelled' : 'error',
+        state: isAbort ? SubagentState.CANCELLED : SubagentState.ERROR,
       };
 
       if (updateOutput) {