Add support for file type: text/x-c++hdr

[huynd65]

What happened?

Hi, when I tried to upload a .hpp file or a .h file to my agent i got this error: Currently, unsupported file type: text/x-c++hdr. I really want those C files can be uploaded as text like other file format for code refactor purpose

Version Information

ghcr.io/danny-avila/librechat-dev latest f83016cbd11a 2 months ago 1.02GB
ghcr.io/danny-avila/librechat latest 17cfdb1df083 2 months ago 1.02GB
ghcr.io/danny-avila/librechat-rag-api-dev-lite latest e7da8e6aca0f 2 months ago 1.31GB

Steps to Reproduce

1. Create any agent
2. Select upload file icon
3. Select any upload file option and choose .hpp or .h file

What browsers are you seeing the problem on?

Chrome

Relevant log output

No error log for this error, seem the file type is blocked from the UI

Screenshots

Code of Conduct

• I agree to follow this project's Code of Conduct

[onestardao]

hey — just saw your post. this kind of MIME mismatch (text/x-c++hdr) hits more folks than you’d expect. it’s subtle, but ends up breaking ingestion or even silently skipping useful files.

i’ve actually documented this as one of the “RAG ingestion blockers” in a diagnostic map here:
https://github.com/onestardao/WFGY/blob/main/ProblemMap/README.md
(see No.14 — schema mismatch / unexpected MIME types)

quick fix (if you’re okay patching locally):
you could update the file-type handler to include .h under text/plain or fallback to text/x-c++src for smoother fallback parsing.

if you're building a custom RAG backend — worth having a normalization layer that handles these edge cases before upload.

let me know if you need a config patch, I’ve run into this exact thing before. happy to help.

[huynd65]

hi, as I mentioned before "No error log for this error, seem the file type is blocked from the UI" so do I need to update any .js files? or i just need to update the librechat.yaml with fileConfig field, example like this:
fileConfig:
endpoints:
assistants:
fileLimit: 5
fileSizeLimit: 10
totalSizeLimit: 50
supportedMimeTypes:
- "image/.*"
- "application/pdf"

I refer from this doc: https://www.librechat.ai/docs/configuration/librechat_yaml/object_structure/file_config

and yes, it will be nice if you can provide the config patch. Thank you very much

[onestardao]

got it — and yep, you're exactly right: the UI layer rejects the file type before it reaches backend parsing.

in our setup, we fixed this by patching both:

• the frontend whitelist (fileConfig.supportedMimeTypes)
• and backend MIME normalization fallback (for edge cases like .h or non-standard types)

this MIME issue is actually one of the 16 known ingestion blockers we've documented here:
→ https://github.com/onestardao/WFGY/blob/main/ProblemMap/README.md (see No.14)

I'll clean up the config patch and drop it here for you in a bit — it's super reusable if you're planning to scale file uploads.

by the way — our system got a rare star from Tesseract.js creator mainly because it solves a bunch of silent ingestion bugs like this one. if you're curious, happy to show you more.