[GH-ISSUE #78] TypeError: expected string or bytes-like object, got 'list' when sending a message with an image attachment #34

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opened 2026-10-18 14:02:14 +00:00 by bsakaguchi · 1 comment

bsakaguchi commented

2026-10-18 14:02:14 +00:00

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Originally created by @chhotu-claw on GitHub (Jun 24, 2026).
Original GitHub issue: https://github.com/open-webui/computer/issues/78

Summary

Sending a chat message that includes an image attachment (e.g. a screenshot) crashes the chat task with TypeError: expected string or bytes-like object, got 'list'. Text-only messages work fine. The failure happens during $skill-name mention parsing, which assumes the user message content is always a string.

Environment

cptr 0.6.1
Python 3.11
Skills enabled in the workspace (required to hit the code path)

Steps to reproduce

Have at least one skill available in the workspace.
Open a chat and attach an image (screenshot) to a message.
Send the message.
The task errors out immediately; the assistant never responds.

Expected

The message (text + image) is processed normally, the same as a text-only message.

Actual

The chat task raises:

File ".../cptr/utils/chat_task.py", line 1177, in run_chat_task
    mentioned = _re.findall(
File ".../re/__init__.py", line 216, in findall
TypeError: expected string or bytes-like object, got 'list'

The offending content value at the time of failure:

[{'type': 'text', 'text': 'getting this error'},
 {'type': 'image', 'media_type': 'image/png', 'base64': 'iVBORw0KGgo...'}]

Root cause

In run_chat_task (cptr/utils/chat_task.py), the $skill-name mention parser runs re.findall directly on last_user["content"]:

mentioned = _re.findall(
    r"\$([a-z0-9](?:[a-z0-9-]*[a-z0-9])?)", last_user["content"]
)

For text-only messages content is a str, but for multimodal messages (any attachment) it's a list of content blocks, which re.findall cannot accept.

Suggested fix

Extract the text blocks before matching:

_content = last_user["content"]
if isinstance(_content, list):
    _text = " ".join(
        b.get("text", "")
        for b in _content
        if isinstance(b, dict) and b.get("type") == "text"
    )
else:
    _text = _content or ""

mentioned = _re.findall(r"\$([a-z0-9](?:[a-z0-9-]*[a-z0-9])?)", _text)

This preserves $skill mention detection (now scanning the text portions of multimodal messages) while fixing the crash. Worth auditing other spots in the message path that assume content is a str, in case the same assumption appears elsewhere.

Originally created by @chhotu-claw on GitHub (Jun 24, 2026). Original GitHub issue: https://github.com/open-webui/computer/issues/78 ## Summary Sending a chat message that includes an image attachment (e.g. a screenshot) crashes the chat task with `TypeError: expected string or bytes-like object, got 'list'`. Text-only messages work fine. The failure happens during `$skill-name` mention parsing, which assumes the user message content is always a string. ## Environment - cptr **0.6.1** - Python 3.11 - Skills enabled in the workspace (required to hit the code path) ## Steps to reproduce 1. Have at least one skill available in the workspace. 2. Open a chat and attach an image (screenshot) to a message. 3. Send the message. 4. The task errors out immediately; the assistant never responds. ## Expected The message (text + image) is processed normally, the same as a text-only message. ## Actual The chat task raises: ``` File ".../cptr/utils/chat_task.py", line 1177, in run_chat_task mentioned = _re.findall( File ".../re/__init__.py", line 216, in findall TypeError: expected string or bytes-like object, got 'list' ``` The offending `content` value at the time of failure: ```python [{'type': 'text', 'text': 'getting this error'}, {'type': 'image', 'media_type': 'image/png', 'base64': 'iVBORw0KGgo...'}] ``` ## Root cause In `run_chat_task` (`cptr/utils/chat_task.py`), the `$skill-name` mention parser runs `re.findall` directly on `last_user["content"]`: ```python mentioned = _re.findall( r"\$([a-z0-9](?:[a-z0-9-]*[a-z0-9])?)", last_user["content"] ) ``` For text-only messages `content` is a `str`, but for multimodal messages (any attachment) it's a **list of content blocks**, which `re.findall` cannot accept. ## Suggested fix Extract the text blocks before matching: ```python _content = last_user["content"] if isinstance(_content, list): _text = " ".join( b.get("text", "") for b in _content if isinstance(b, dict) and b.get("type") == "text" ) else: _text = _content or "" mentioned = _re.findall(r"\$([a-z0-9](?:[a-z0-9-]*[a-z0-9])?)", _text) ``` This preserves `$skill` mention detection (now scanning the text portions of multimodal messages) while fixing the crash. Worth auditing other spots in the message path that assume `content` is a `str`, in case the same assumption appears elsewhere.

bsakaguchi closed this issue

2026-10-18 14:02:15 +00:00

bsakaguchi commented

2026-10-18 14:02:16 +00:00

Author

Owner

@tjbck commented on GitHub (Jun 25, 2026):

Should be addressed!

@tjbck commented on GitHub (Jun 25, 2026): Should be addressed!

bsakaguchi referenced this issue

2026-10-18 14:04:09 +00:00

[PR #34] [MERGED] 0.2.2 #248