firecrawl/open-lovable · error

${finalData?.error || 'Failed to apply code'}

Error message

${finalData?.error || 'Failed to apply code'}

What it means

This error is thrown after the /api/apply-ai-code-stream stream completed: the client parsed the final streamed JSON payload (finalData) and found it flagged an application failure (finalData.error set), or the stream ended without a success marker. Unlike error 40 (HTTP-level failure), this is an application-level failure reported inside an otherwise successful HTTP 200 stream — the server started applying the code but reported an error in its terminal event.

Source

Thrown at app/generation/page.tsx:1051

              // Remove old iframe
              iframeRef.current.remove();
              
              // Add new iframe
              newIframe.src = `${currentSandboxData.url}?t=${Date.now()}&recreated=true`;
              parent?.appendChild(newIframe);
              
              // Update ref
              (iframeRef as any).current = newIframe;
              
              console.log('[applyGeneratedCode] Iframe recreated with new content');
            } else {
              console.error('[applyGeneratedCode] No iframe or sandbox URL available for refresh');
            }
          }, refreshDelay); // Dynamic delay based on whether packages were installed
        }
        
        } else {
          throw new Error(finalData?.error || 'Failed to apply code');
        }
      } else {
        // If no final data was received, still close loading
        addChatMessage('Code application may have partially succeeded. Check the preview.', 'system');
      }
    } catch (error: any) {
      log(`Failed to apply code: ${error.message}`, 'error');
    } finally {
      setLoading(false);
      // Clear isEdit flag after applying code
      setGenerationProgress(prev => ({
        ...prev,
        isEdit: false
      }));
    }
  };

  const fetchSandboxFiles = async () => {

View on GitHub (pinned to 69bd93bae7)

Solutions

1. Read finalData.error (and server logs) for the specific apply failure — it is included in the thrown message
2. Retry the apply once; transient sandbox/connection failures often succeed on a second attempt
3. If the error mentions packages, verify each entry in pendingPackages is a valid installable package name/version
4. If the error mentions a specific file, inspect the generated code being applied for syntax issues
5. Recreate the sandbox (fresh sandboxId) and re-apply if the sandbox state appears corrupted

Example fix

// before
} else {
  throw new Error(finalData?.error || 'Failed to apply code');
}
// after
} else {
  const reason = finalData?.error || 'Failed to apply code';
  addChatMessage(`Apply failed: ${reason}. Retrying...`, 'system');
  throw new Error(reason);
}

// after reading the stream, before trusting finalData
const finalData = JSON.parse(lastChunk);
if (!finalData || typeof finalData !== 'object' || finalData.error) {
  throw new Error(finalData?.error || 'Stream ended without a success payload');
}

interface ApplyResult { success: boolean; error?: string; [k: string]: unknown }
function isSuccessfulApply(d: unknown): d is ApplyResult & { success: true } {
  return typeof d === 'object' && d !== null &&
    (d as ApplyResult).success === true && !(d as ApplyResult).error;
}

try {
  // stream apply...
  if (!isSuccessfulApply(finalData)) {
    throw new Error(finalData?.error || 'Failed to apply code');
  }
} catch (err: any) {
  addChatMessage(`Apply failed: ${err.message}. You can retry.`, 'system');
  // offer a one-click retry that re-POSTs the same payload
}

When it happens

Trigger: The streamed final JSON message contains { error: '...' } (e.g. file write failed, sandbox command exited non-zero, package installation failed mid-apply), or finalData is truthy but does not represent a successful application.

Common situations: Generated code contains a syntax error the sandbox builder rejects; installing pendingPackages fails partway (registry outage, peer-dependency conflict); sandbox container runs out of disk/memory during apply; WebSocket to the sandbox drops mid-write; version skew between client payload format and what the server expects.

Related errors

• Failed to apply code: ${response.statusText}
• Unsupported sandbox type
• Failed to create zip: ${error}
• Failed to read zip file: ${error}
• Failed to list files

AI-assisted analysis of firecrawl/open-lovable@69bd93bae7 (2026-08-28). Data as JSON: /api/errors/473bf9799a1d232a. Report an issue: GitHub.