Responses API stopped supporting .xlsx files

API Bugs
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1

Today, the Responses API stopped accepting .xlsx files in input_file. It says:

Invalid input: Expected context stuffing file type to be a supported format: .bat, .c, .css, .csv, .doc, .dot, .eml, .h, .htm, .html, .hwp, .hwpx, .js, .json, .ksh, .markdown, .md, .mht, .mhtml, .mjs, .nws, .pdf, .pl, .pot, .ppa, .pps, .ppt, .pwz, .py, .rst, .srt, .svg, .txt, .vcf, .vtt, .wiz, .xlb, .xls, .xml but got .xlsx.

However, yesterday, I got similar error (for different reason), and the supported file types was larger:

Invalid input: Expected context stuffing file type to be a supported format: .art, .bat, .brf, .c, .cls, .css, .csv, .diff, .doc, .docx, .dot, .eml, .es, .h, .hs, .htm, .html, .hwp, .hwpx, .ics, .ifb, .java, .js, .json, .keynote, .ksh, .ltx, .mail, .markdown, .md, .mht, .mhtml, .mjs, .nws, .odt, .pages, .patch, .pdf, .pl, .pm, .pot, .ppa, .pps, .ppt, .pptx, .pwz, .py, .rst, .rtf, .scala, .sh, .shtml, .srt, .sty, .svg, .svgz, .tex, .text, .txt, .vcf, .vtt, .wiz, .xla, .xlb, .xlc, .xlm, .xls, .xlsx, .xlt, .xlw, .xml, .yaml, .yml but got .PDF

It seems like .xlsx support was dropped overnight.

2

Hi and welcome to the Community!

Thanks for raising this.

I was able to reproduce it. When I passed my test file as uploaded input_file.file_id, I got the same context stuffing error you quoted. But the exact same workbook worked when sent inline as input_file.file_data, on both gpt-4.1-mini and gpt-5.2.

So this appears to be a real docs/runtime inconsistency, not a blanket .xlsx ban across all input_file modes.

At least this should help unblock you for now. I’ll ping the team about it.

3

vb, thank you for the workaround!!

It might be useful, but it would require changing a lot of moving parts. Will do only as last resort. I hope the issue with the API is resolved soon.

If any new information surfaces around this issue, please keep us informed!

4

Minimal repro:

upload a docx file to the files api, then try to generate a response by passing in the file id as per the example in the File Inputs documentation

Result: “Invalid input: Expected context stuffing file type to be a supported format: .bat, .c, .css, .csv, .doc, .dot, .eml, .h, .htm, .html, .hwp, .hwpx, .js, .json, .ksh, .markdown, .md, .mht, .mhtml, .mjs, .nws, .pdf, .pl, .pot, .ppa, .pps, .ppt, .pwz, .py, .rst, .srt, .svg, .txt, .vcf, .vtt, .wiz, .xlb, .xls, .xml but got .docx.”

5

I am having the same issue.

Screenshot 2026-03-19 235331
Screenshot 2026-03-19 2353311047×220 12.9 KB

6

any ETA to get this fixed? it is a major blocker. thanks

7

I have also had the exact same problem with .xlsx and .docx files with responses api. Was working perfectly for a month and suddenly stopped working as of yesterday morning. Has caused havoc as my organisations workflows and development have come to a halt as we all use .docx and .xlsx.

Any ETA on when this will be fixed would be greatly appreciated

8

Also doing a +1 to how this has been working for months and randomly stopped working affecting our organizations’ document processing needs!

9

We’ve identified the issue and are actively working on a fix.

Thanks for your patience while we resolve this.

10

Hi - this should have been fixed. Let us know if you are still running into issues!