Mintplex-Labs/anything-llm · error
Failed to download file
Error message
Failed to download file
What it means
Catch-all HTTP 500 from the generated-files download handler. Anything that throws after the early guards — setting headers (e.g. invalid characters in the sanitized display filename), an unexpected shape from getGeneratedFile (missing buffer), response.send failures, or client-abort edge cases — is logged as '[agentFileServer] Download error: <message>' server-side and returned to the client as this generic message. The console.error line is the only place the real cause appears.
Solutions
- Correlate with the server console at the request timestamp — the '[agentFileServer] Download error:' line holds the actual error message
- Retry once; transient stream aborts and races often clear
- Manually verify the file exists in the storage directory and getGeneratedFile returns a buffer for that name
- If persistent, temporarily log the full error object (not just error.message) in the catch to get a stack, then fix the specific fault
Example fix
// before: only the message is logged, stacks are lost
console.error('[agentFileServer] Download error:', error.message);
// after: capture the stack while investigating
console.error('[agentFileServer] Download error:', error); Defensive patterns
Strategy: try-catch
Try / catch
try {
const res = await fetch(url, {credentials: 'include'});
if (res.status === 500) {
// generic by design — the '[agentFileServer] Download error:' server log
// at this timestamp holds the actual cause; retry once for transient aborts
return await fetch(url, {credentials: 'include'});
}
} catch (e) {
// client/network-level failure
} Prevention
- Always correlate these 500s with server logs before changing client code
- Retry once — mid-stream aborts are frequently transient
- Sanitize display filenames (strip quotes/newlines) before they reach Content-Disposition
When it happens
Trigger: fileData.buffer undefined because storage returned a record without content; Content-Disposition header containing newline/quote characters from a malformed displayFilename; socket closed by the client between the guards and response.send; ENOSPC or permission errors while streaming from the storage driver.
Common situations: Diagnosing production download failures where the HTTP message alone is useless; downloads that fail only for specific files (bad display names); transient failures under load that disappear on retry.
Related errors
AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18).
Data as JSON: /api/errors/a0fb074b4630e74f.
Report an issue: GitHub.
Appendix: source
Thrown at server/endpoints/agentFileServer.js:85
// Get mime type and set headers for download
const mimeType = createFilesLib.getMimeType(`.${parsed.extension}`);
const safeFilename = createFilesLib.sanitizeFilenameForHeader(
fileSource.displayFilename || filename
);
response.setHeader("Content-Type", mimeType);
response.setHeader(
"Content-Disposition",
`attachment; filename="${safeFilename}"`
);
response.setHeader("Content-Length", fileData.buffer.length);
response.send(fileData.buffer);
Telemetry.sendTelemetry("agent_generated_file_downloaded", {
type: mimeType,
}).catch(() => {});
return;
} catch (error) {
console.error("[agentFileServer] Download error:", error.message);
return response.status(500).json({ error: "Failed to download file" });
}
}
);
/**
* Serve a generated image inline (so it can be used as an <img> src).
* Validates that the requesting user has access to a chat that references
* the image before serving it from storage/generated-images.
*/
app.get(
"/image-generation/generated-images/:filename",
[validatedRequest, flexUserRoleValid([ROLES.all])],
async (request, response) => {
try {
const fs = require("fs");
const path = require("path");
const {
generatedImagesPath,View on GitHub (pinned to 3aec848f28)