feat(agent): add agent interrupt support

alembic/versions/d8d9404cdee2_add_agent_session_status.py

@@ -0,0 +1,40 @@
+"""add_agent_session_status
+
+Revision ID: d8d9404cdee2
+Revises: c7737fa6338a
+Create Date: 2026-01-21 17:40:55.526398
+
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "d8d9404cdee2"
+down_revision: str | None = "c7737fa6338a"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column(
+        "agent_session",
+        sa.Column(
+            "status", sa.String(length=20), server_default="idle", nullable=False
+        ),
+    )
+    op.create_index(
+        op.f("ix_agent_session_status"), "agent_session", ["status"], unique=False
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index(op.f("ix_agent_session_status"), table_name="agent_session")
+    op.drop_column("agent_session", "status")
+    # ### end Alembic commands ###

frontend/src/client/schemas.gen.ts

@@ -891,6 +891,11 @@ export const $AgentOutput = {
       format: "uuid",
       title: "Session Id",
     },
+    interrupted: {
+      type: "boolean",
+      title: "Interrupted",
+      default: false,
+    },
   },
   type: "object",
   required: ["output", "duration", "session_id"],
@@ -1675,6 +1680,10 @@ export const $AgentSessionRead = {
       ],
       title: "Harness Type",
     },
+    status: {
+      $ref: "#/components/schemas/AgentSessionStatus",
+      default: "idle",
+    },
     last_stream_id: {
       anyOf: [
         {
@@ -1801,6 +1810,10 @@ export const $AgentSessionReadVercel = {
       ],
       title: "Harness Type",
     },
+    status: {
+      $ref: "#/components/schemas/AgentSessionStatus",
+      default: "idle",
+    },
     last_stream_id: {
       anyOf: [
         {
@@ -1935,6 +1948,10 @@ export const $AgentSessionReadWithMessages = {
       ],
       title: "Harness Type",
     },
+    status: {
+      $ref: "#/components/schemas/AgentSessionStatus",
+      default: "idle",
+    },
     last_stream_id: {
       anyOf: [
         {
@@ -1993,6 +2010,20 @@ export const $AgentSessionReadWithMessages = {
   description: "Response schema for agent session with message history.",
 } as const
 
+export const $AgentSessionStatus = {
+  type: "string",
+  enum: ["idle", "running", "interrupted", "completed", "failed"],
+  title: "AgentSessionStatus",
+  description: `Status of an agent session.
+
+Tracks the lifecycle state of an agent session:
+- IDLE: No active workflow running
+- RUNNING: Workflow currently executing
+- INTERRUPTED: User requested interrupt (transient state)
+- COMPLETED: Last run completed successfully
+- FAILED: Last run failed`,
+} as const
+
 export const $AgentSessionUpdate = {
   properties: {
     title: {

frontend/src/client/services.gen.ts

@@ -87,6 +87,8 @@ import type {
   AgentSessionsGetSessionResponse,
   AgentSessionsGetSessionVercelData,
   AgentSessionsGetSessionVercelResponse,
+  AgentSessionsInterruptSessionData,
+  AgentSessionsInterruptSessionResponse,
   AgentSessionsListSessionsData,
   AgentSessionsListSessionsResponse,
   AgentSessionsSendMessageData,
@@ -3543,6 +3545,41 @@ export const agentSessionsForkSession = (
   })
 }
 
+/**
+ * Interrupt Session
+ * Request interruption of a running agent session.
+ *
+ * Marks the session for interrupt. The agent executor will detect this
+ * status change and terminate execution cleanly, emitting stream.done()
+ * to prevent the frontend from hanging.
+ *
+ * Returns:
+ * {"interrupted": true} if the session was running and is now interrupted,
+ * {"interrupted": false} if the session was not in a running state.
+ * @param data The data for the request.
+ * @param data.sessionId
+ * @param data.workspaceId
+ * @returns boolean Successful Response
+ * @throws ApiError
+ */
+export const agentSessionsInterruptSession = (
+  data: AgentSessionsInterruptSessionData
+): CancelablePromise<AgentSessionsInterruptSessionResponse> => {
+  return __request(OpenAPI, {
+    method: "POST",
+    url: "/agent/sessions/{session_id}/interrupt",
+    path: {
+      session_id: data.sessionId,
+    },
+    query: {
+      workspace_id: data.workspaceId,
+    },
+    errors: {
+      422: "Validation Error",
+    },
+  })
+}
+
 /**
  * Submit Approvals
  * Submit approval decisions to a running agent workflow.

frontend/src/client/types.gen.ts

@@ -223,6 +223,7 @@ export type AgentOutput = {
   duration: number
   usage?: RunUsage | null
   session_id: string
+  interrupted?: boolean
 }
 
 export type AgentPreset = {
@@ -392,6 +393,7 @@ export type AgentSessionRead = {
   tools: Array<string> | null
   agent_preset_id: string | null
   harness_type: string | null
+  status?: AgentSessionStatus
   last_stream_id?: string | null
   parent_session_id?: string | null
   created_at: string
@@ -411,6 +413,7 @@ export type AgentSessionReadVercel = {
   tools: Array<string> | null
   agent_preset_id: string | null
   harness_type: string | null
+  status?: AgentSessionStatus
   last_stream_id?: string | null
   parent_session_id?: string | null
   created_at: string
@@ -434,6 +437,7 @@ export type AgentSessionReadWithMessages = {
   tools: Array<string> | null
   agent_preset_id: string | null
   harness_type: string | null
+  status?: AgentSessionStatus
   last_stream_id?: string | null
   parent_session_id?: string | null
   created_at: string
@@ -444,6 +448,23 @@ export type AgentSessionReadWithMessages = {
   messages?: Array<unknown>
 }
 
+/**
+ * Status of an agent session.
+ *
+ * Tracks the lifecycle state of an agent session:
+ * - IDLE: No active workflow running
+ * - RUNNING: Workflow currently executing
+ * - INTERRUPTED: User requested interrupt (transient state)
+ * - COMPLETED: Last run completed successfully
+ * - FAILED: Last run failed
+ */
+export type AgentSessionStatus =
+  | "idle"
+  | "running"
+  | "interrupted"
+  | "completed"
+  | "failed"
+
 /**
  * Request schema for updating an agent session.
  */
@@ -6802,6 +6823,15 @@ export type AgentSessionsForkSessionData = {
 
 export type AgentSessionsForkSessionResponse = AgentSessionRead
 
+export type AgentSessionsInterruptSessionData = {
+  sessionId: string
+  workspaceId: string
+}
+
+export type AgentSessionsInterruptSessionResponse = {
+  [key: string]: boolean
+}
+
 export type ApprovalsSubmitApprovalsData = {
   requestBody: ApprovalSubmission
   sessionId: string
@@ -9598,6 +9628,23 @@ export type $OpenApiTs = {
       }
     }
   }
+  "/agent/sessions/{session_id}/interrupt": {
+    post: {
+      req: AgentSessionsInterruptSessionData
+      res: {
+        /**
+         * Successful Response
+         */
+        200: {
+          [key: string]: boolean
+        }
+        /**
+         * Validation Error
+         */
+        422: HTTPValidationError
+      }
+    }
+  }
   "/approvals/{session_id}": {
     post: {
       req: ApprovalsSubmitApprovalsData

frontend/src/components/ai-elements/prompt-input.tsx

@@ -678,6 +678,7 @@ export const PromptInputActionMenuItem = ({
 
 export type PromptInputSubmitProps = ComponentProps<typeof Button> & {
   status?: ChatStatus
+  onInterrupt?: () => void
 }
 
 export const PromptInputSubmit = ({
@@ -686,6 +687,7 @@ export const PromptInputSubmit = ({
   size = "icon",
   status,
   children,
+  onInterrupt,
   ...props
 }: PromptInputSubmitProps) => {
   let Icon = <ArrowUpIcon className="size-3.5" />
@@ -698,17 +700,22 @@ export const PromptInputSubmit = ({
     Icon = <XIcon className="size-3.5" />
   }
 
+  // When streaming, the button becomes an interrupt/stop button
+  const isStreaming = status === "streaming"
+  const handleClick = isStreaming && onInterrupt ? onInterrupt : undefined
+
   return (
     <Button
-      aria-label="Send message"
+      aria-label={isStreaming ? "Stop generation" : "Send message"}
       className={cn("size-6 rounded-md hover:text-muted-foreground", className)}
       size={size}
-      type="submit"
+      type={isStreaming ? "button" : "submit"}
       variant={variant}
+      onClick={handleClick}
       {...props}
     >
       {children ?? Icon}
-      <span className="sr-only">Send message</span>
+      <span className="sr-only">{isStreaming ? "Stop" : "Send message"}</span>
     </Button>
   )
 }

frontend/src/components/chat/chat-session-pane.tsx

@@ -153,13 +153,21 @@ export function ChatSessionPane({
     () => (chat?.messages || []).map(toUIMessage),
     [chat?.messages]
   )
-  const { sendMessage, messages, status, regenerate, lastError, clearError } =
-    useVercelChat({
-      chatId: chat.id,
-      workspaceId,
-      messages: uiMessages,
-      modelInfo,
-    })
+
+  const {
+    sendMessage,
+    messages,
+    status,
+    regenerate,
+    lastError,
+    clearError,
+    interrupt,
+  } = useVercelChat({
+    chatId: chat.id,
+    workspaceId,
+    messages: uiMessages,
+    modelInfo,
+  })
 
   // Track whether we've sent the pending message to avoid double-sends
   const pendingMessageSentRef = useRef(false)
@@ -451,8 +459,9 @@ export function ChatSessionPane({
               </PromptInputTools>
             )}
             <PromptInputSubmit
-              disabled={isReadonly || !input || !!status}
+              disabled={isReadonly || (!input && !status)}
               status={status}
+              onInterrupt={interrupt}
               className="ml-auto text-muted-foreground/80"
             />
           </PromptInputToolbar>

frontend/src/components/copilot/copilot-chat-pane.tsx

@@ -89,13 +89,21 @@ export function CopilotChatPane({
     () => (chat?.messages || []).map(toUIMessage),
     [chat?.messages]
   )
-  const { sendMessage, messages, status, regenerate, lastError, clearError } =
-    useVercelChat({
-      chatId: chat.id,
-      workspaceId,
-      messages: uiMessages,
-      modelInfo,
-    })
+
+  const {
+    sendMessage,
+    messages,
+    status,
+    regenerate,
+    lastError,
+    clearError,
+    interrupt,
+  } = useVercelChat({
+    chatId: chat.id,
+    workspaceId,
+    messages: uiMessages,
+    modelInfo,
+  })
 
   const isWaitingForResponse = useMemo(() => {
     if (status === "submitted") return true
@@ -248,6 +256,7 @@ export function CopilotChatPane({
         <PromptInputSubmit
           disabled={isReadonly || (!input && !status)}
           status={status}
+          onInterrupt={interrupt}
           className="ml-auto text-muted-foreground/80"
         />
       </PromptInputToolbar>