fix(terminal): reconnect to running executions after page refresh

apps/sim/app/api/workflows/[id]/execute/route.ts

@@ -12,7 +12,7 @@ import {
 import { generateRequestId } from '@/lib/core/utils/request'
 import { SSE_HEADERS } from '@/lib/core/utils/sse'
 import { getBaseUrl } from '@/lib/core/utils/urls'
-import { markExecutionCancelled } from '@/lib/execution/cancellation'
+import { createExecutionEventWriter, setExecutionMeta } from '@/lib/execution/event-buffer'
 import { processInputFileFields } from '@/lib/execution/files'
 import { preprocessExecution } from '@/lib/execution/preprocessing'
 import { LoggingSession } from '@/lib/logs/execution/logging-session'
@@ -700,15 +700,27 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
     const timeoutController = createTimeoutAbortController(preprocessResult.executionTimeout?.sync)
     let isStreamClosed = false
 
+    const eventWriter = createExecutionEventWriter(executionId)
+    setExecutionMeta(executionId, {
+      status: 'active',
+      userId: actorUserId,
+      workflowId,
+    }).catch(() => {})
+
     const stream = new ReadableStream<Uint8Array>({
       async start(controller) {
-        const sendEvent = (event: ExecutionEvent) => {
-          if (isStreamClosed) return
+        let finalMetaStatus: 'complete' | 'error' | 'cancelled' | null = null
 
-          try {
-            controller.enqueue(encodeSSEEvent(event))
-          } catch {
-            isStreamClosed = true
+        const sendEvent = (event: ExecutionEvent) => {
+          if (!isStreamClosed) {
+            try {
+              controller.enqueue(encodeSSEEvent(event))
+            } catch {
+              isStreamClosed = true
+            }
+          }
+          if (event.type !== 'stream:chunk' && event.type !== 'stream:done') {
+            eventWriter.write(event).catch(() => {})
           }
         }
 
@@ -951,6 +963,7 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
                   duration: result.metadata?.duration || 0,
                 },
               })
+              finalMetaStatus = 'error'
             } else {
               logger.info(`[${requestId}] Workflow execution was cancelled`)
 
@@ -963,6 +976,7 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
                   duration: result.metadata?.duration || 0,
                 },
               })
+              finalMetaStatus = 'cancelled'
             }
             return
           }
@@ -986,6 +1000,7 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
               endTime: result.metadata?.endTime || new Date().toISOString(),
             },
           })
+          finalMetaStatus = 'complete'
         } catch (error: unknown) {
           const isTimeout = isTimeoutError(error) || timeoutController.isTimedOut()
           const errorMessage = isTimeout
@@ -1017,7 +1032,18 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
               duration: executionResult?.metadata?.duration || 0,
             },
           })
+          finalMetaStatus = 'error'
         } finally {
+          try {
+            await eventWriter.close()
+          } catch (closeError) {
+            logger.warn(`[${requestId}] Failed to close event writer`, {
+              error: closeError instanceof Error ? closeError.message : String(closeError),
+            })
+          }
+          if (finalMetaStatus) {
+            setExecutionMeta(executionId, { status: finalMetaStatus }).catch(() => {})
+          }
           timeoutController.cleanup()
           if (executionId) {
             await cleanupExecutionBase64Cache(executionId)
@@ -1032,10 +1058,7 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
       },
       cancel() {
         isStreamClosed = true
-        timeoutController.cleanup()
-        logger.info(`[${requestId}] Client aborted SSE stream, signalling cancellation`)
-        timeoutController.abort()
-        markExecutionCancelled(executionId).catch(() => {})
+        logger.info(`[${requestId}] Client disconnected from SSE stream`)
       },
     })
 

apps/sim/app/api/workflows/[id]/executions/[executionId]/stream/route.ts

@@ -0,0 +1,176 @@
+import { createLogger } from '@sim/logger'
+import { type NextRequest, NextResponse } from 'next/server'
+import { checkHybridAuth } from '@/lib/auth/hybrid'
+import { SSE_HEADERS } from '@/lib/core/utils/sse'
+import {
+  type ExecutionStreamStatus,
+  getExecutionMeta,
+  readExecutionEvents,
+} from '@/lib/execution/event-buffer'
+import { formatSSEEvent } from '@/lib/workflows/executor/execution-events'
+import { authorizeWorkflowByWorkspacePermission } from '@/lib/workflows/utils'
+
+const logger = createLogger('ExecutionStreamReconnectAPI')
+
+const POLL_INTERVAL_MS = 500
+const MAX_POLL_DURATION_MS = 10 * 60 * 1000 // 10 minutes
+
+function isTerminalStatus(status: ExecutionStreamStatus): boolean {
+  return status === 'complete' || status === 'error' || status === 'cancelled'
+}
+
+export const runtime = 'nodejs'
+export const dynamic = 'force-dynamic'
+
+export async function GET(
+  req: NextRequest,
+  { params }: { params: Promise<{ id: string; executionId: string }> }
+) {
+  const { id: workflowId, executionId } = await params
+
+  try {
+    const auth = await checkHybridAuth(req, { requireWorkflowId: false })
+    if (!auth.success || !auth.userId) {
+      return NextResponse.json({ error: auth.error || 'Unauthorized' }, { status: 401 })
+    }
+
+    const workflowAuthorization = await authorizeWorkflowByWorkspacePermission({
+      workflowId,
+      userId: auth.userId,
+      action: 'read',
+    })
+    if (!workflowAuthorization.allowed) {
+      return NextResponse.json(
+        { error: workflowAuthorization.message || 'Access denied' },
+        { status: workflowAuthorization.status }
+      )
+    }
+
+    const meta = await getExecutionMeta(executionId)
+    if (!meta) {
+      return NextResponse.json({ error: 'Execution buffer not found or expired' }, { status: 404 })
+    }
+
+    if (meta.workflowId && meta.workflowId !== workflowId) {
+      return NextResponse.json(
+        { error: 'Execution does not belong to this workflow' },
+        { status: 403 }
+      )
+    }
+
+    const fromParam = req.nextUrl.searchParams.get('from')
+    const parsed = fromParam ? Number.parseInt(fromParam, 10) : 0
+    const fromEventId = Number.isFinite(parsed) && parsed >= 0 ? parsed : 0
+
+    logger.info('Reconnection stream requested', {
+      workflowId,
+      executionId,
+      fromEventId,
+      metaStatus: meta.status,
+    })
+
+    const encoder = new TextEncoder()
+
+    // Hoisted so cancel() can signal the polling loop to stop
+    let closed = false
+
+    const stream = new ReadableStream<Uint8Array>({
+      async start(controller) {
+        let lastEventId = fromEventId
+        const pollDeadline = Date.now() + MAX_POLL_DURATION_MS
+
+        const enqueue = (text: string) => {
+          if (closed) return
+          try {
+            controller.enqueue(encoder.encode(text))
+          } catch {
+            closed = true
+          }
+        }
+
+        try {
+          // Replay buffered events
+          const events = await readExecutionEvents(executionId, lastEventId)
+          for (const entry of events) {
+            if (closed) return
+            enqueue(formatSSEEvent(entry.event))
+            lastEventId = entry.eventId
+          }
+
+          // Check if execution is already done
+          const currentMeta = await getExecutionMeta(executionId)
+          if (!currentMeta || isTerminalStatus(currentMeta.status)) {
+            enqueue('data: [DONE]\n\n')
+            if (!closed) controller.close()
+            return
+          }
+
+          // Poll for new events until execution completes or deadline is reached
+          while (!closed && Date.now() < pollDeadline) {
+            await new Promise((resolve) => setTimeout(resolve, POLL_INTERVAL_MS))
+            if (closed) return
+
+            const newEvents = await readExecutionEvents(executionId, lastEventId)
+            for (const entry of newEvents) {
+              if (closed) return
+              enqueue(formatSSEEvent(entry.event))
+              lastEventId = entry.eventId
+            }
+
+            const polledMeta = await getExecutionMeta(executionId)
+            if (!polledMeta || isTerminalStatus(polledMeta.status)) {
+              // One final read to catch any events flushed alongside the meta update
+              const finalEvents = await readExecutionEvents(executionId, lastEventId)
+              for (const entry of finalEvents) {
+                if (closed) return
+                enqueue(formatSSEEvent(entry.event))
+                lastEventId = entry.eventId
+              }
+              enqueue('data: [DONE]\n\n')
+              if (!closed) controller.close()
+              return
+            }
+          }
+
+          // Deadline reached — close gracefully
+          if (!closed) {
+            logger.warn('Reconnection stream poll deadline reached', { executionId })
+            enqueue('data: [DONE]\n\n')
+            controller.close()
+          }
+        } catch (error) {
+          logger.error('Error in reconnection stream', {
+            executionId,
+            error: error instanceof Error ? error.message : String(error),
+          })
+          if (!closed) {
+            try {
+              controller.close()
+            } catch {}
+          }
+        }
+      },
+      cancel() {
+        closed = true
+        logger.info('Client disconnected from reconnection stream', { executionId })
+      },
+    })
+
+    return new NextResponse(stream, {
+      headers: {
+        ...SSE_HEADERS,
+        'X-Execution-Id': executionId,
+      },
+    })
+  } catch (error: any) {
+    logger.error('Failed to start reconnection stream', {
+      workflowId,
+      executionId,
+      error: error.message,
+    })
+    return NextResponse.json(
+      { error: error.message || 'Failed to start reconnection stream' },
+      { status: 500 }
+    )
+  }
+}