Running into TypeError: can only concatenate str (not "list") to str

[hv15]

Hi,

Recently, I've run into an issue when using AIChat where the returned request response is malformed (is a list instead of a string):

>>> user

Test


<<< error getting response: can only concatenate str (not "list") to str

```python
Traceback (most recent call last):
  File "/home/hans/.vim/plugged/vim-ai/py/chat.py", line 180, in run
    self.buffer += chunk["content"]
TypeError: can only concatenate str (not "list") to str

```

<<< assistant

>>> user

I'm using the latest commit 8887f9f and am running vim 9.1 on ArchLinux. I suspect something has changed with the Python requests package which is causing the above issue, I have version 2.32.5 installed.

Additionally, I also get an error when running just AIEdit, and suspect it is due to the same issue:

Error detected while processing function vim_ai#AIEditRun[31]..function vim_ai#AIEditRun:                                                                                              
line   28:
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/hans/.vim/plugged/vim-ai/py/complete.py", line 41, in run_ai_completition
    handle_completion_error(config['provider'], error)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hans/.vim/plugged/vim-ai/py/utils.py", line 308, in handle_completion_error
    raise error
  File "/home/hans/.vim/plugged/vim-ai/py/complete.py", line 37, in run_ai_completition
    render_text_chunks(text_chunks, append_to_eol=command_type == 'complete')
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hans/.vim/plugged/vim-ai/py/utils.py", line 114, in render_text_chunks
    text = text.lstrip() # trim newlines from the beginning
           ^^^^^^^^^^^
AttributeError: 'list' object has no attribute 'lstrip'

Please let me know if there's anymore information I can provide. Thanks!

[madox2]

Hi, thanks for reporting the issue!

Are you using the default openai configuration or some custom config?

Does this issue happen every time you run vim ai on your system or just occasionaly?

Could you provide me with more details of your environment, exact version of vim (vim --version) and system?

I am not aware of any breaking changes of python's requests lib like this. If you are using vim (not nvim) the python you have installed on the system shouldn't matter , vim comes with it's own python, you can find out python version and requests lib version this way:

:python3 from importlib.metadata import version; print(version('requests'))
:python3 import sys; print(sys.version)

[hv15]

Hi @madox2, thanks for looking into this, sorry I didn't reply sooner.

I'm using the default vim-ai config but have defined Mistral as the default OpenAI-API to connect to:

let g:vim_ai_chat = {
\  "options": {
\    "token_file_path": "~/.config/mistral.token",
\    "endpoint_url": "https://api.mistral.ai/v1/chat/completions",
\    "model": "magistral-small-2506",
\  },
\}
let g:vim_ai_complete = {
\  "options": {
\    "token_file_path": "~/.config/mistral.token",
\    "endpoint_url": "https://api.mistral.ai/v1/chat/completions",
\    "model": "magistral-small-2506",
\  },
\}
let g:vim_ai_edit = {
\  "options": {
\    "token_file_path": "~/.config/mistral.token",
\    "endpoint_url": "https://api.mistral.ai/v1/chat/completions",
\    "model": "magistral-small-2506",
\  },
\}

As to python and request lib versions:

:python3 from importlib.metadata import version; print(version('requests'))
2.32.5
:python3 import sys; print(sys.version)
3.13.11 (main, Dec  7 2025, 13:01:45) [GCC 15.2.1 20251112]

note that on ArchLinux vim systems to use the system python.

The issue is persistent, regardless of what prompt I write, I get the same error message.

Please let me know if there's anymore info I can provide, or other troubleshooting actions. Thanks!