fix(processing): enforce waitForCompletion inside markAsFailed to prevent completion races

Move waitForCompletion() into markAsFailed() so every call site is
automatically safe against in-flight fire-and-forget completions.
Remove the now-redundant external waitForCompletion() calls in route.ts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: waleedlatif1

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

@@ -641,7 +641,6 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
           logger.info(`[${requestId}] Non-SSE execution timed out`, {
             timeoutMs: timeoutController.timeoutMs,
           })
-          await loggingSession.waitForCompletion()
           await loggingSession.markAsFailed(timeoutErrorMessage)
 
           return NextResponse.json(
@@ -1027,7 +1026,6 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
               logger.error(`[${requestId}] Missing snapshot seed for paused execution`, {
                 executionId,
               })
-              await loggingSession.waitForCompletion()
               await loggingSession.markAsFailed('Missing snapshot seed for paused execution')
             } else {
               try {
@@ -1043,7 +1041,6 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
                   executionId,
                   error: pauseError instanceof Error ? pauseError.message : String(pauseError),
                 })
-                await loggingSession.waitForCompletion()
                 await loggingSession.markAsFailed(
                   `Failed to persist pause state: ${pauseError instanceof Error ? pauseError.message : String(pauseError)}`
                 )
@@ -1060,7 +1057,6 @@ export async function POST(req: NextRequest, { params }: { params: Promise<{ id:
                 timeoutMs: timeoutController.timeoutMs,
               })
 
-              await loggingSession.waitForCompletion()
               await loggingSession.markAsFailed(timeoutErrorMessage)
 
               sendEvent({

apps/sim/lib/logs/execution/logging-session.ts

@@ -675,8 +675,8 @@ export class LoggingSession {
 
   /**
    * Wait for any in-flight fire-and-forget completion to finish.
-   * Used by callers (e.g. markAsFailed) that need to ensure completion
-   * has settled before overwriting execution status.
+   * Called internally by markAsFailed to ensure completion has settled
+   * before overwriting execution status.
    */
   async waitForCompletion(): Promise<void> {
     if (this.completionPromise) {
@@ -793,6 +793,7 @@ export class LoggingSession {
   }
 
   async markAsFailed(errorMessage?: string): Promise<void> {
+    await this.waitForCompletion()
     await LoggingSession.markExecutionAsFailed(this.executionId, errorMessage, this.requestId)
   }