agentscope-ai/agentscope · error · ValueError

Unsupported source type: {type(source)}

Error message

Unsupported source type: {type(source)}

What it means

The Gemini formatter's _format_media_source raises ValueError when a media block's source is neither a URLSource nor a Base64Source (the inline_data branch shown handles base64). Gemini's API accepts either inline base64 data or remote URIs, so other source types (e.g. LocalFileSource) are unsupported here.

Source

Thrown at src/agentscope/formatter/_gemini_formatter.py:108

                return {
                    "inline_data": {
                        "data": data,
                        "mime_type": source.media_type,
                    },
                }
            else:
                # Remote URL - download and convert to base64
                response = requests.get(url, timeout=30)
                response.raise_for_status()
                data = base64.b64encode(response.content).decode("utf-8")
                return {
                    "inline_data": {
                        "data": data,
                        "mime_type": source.media_type,
                    },
                }
        else:
            raise ValueError(f"Unsupported source type: {type(source)}")


class GeminiChatFormatter(_GeminiFormatterBase):
    """The Gemini formatter class for chatbot scenario, where only a user
    and an agent are involved. We use the `role` field to identify different
    entities in the conversation.
    """

    input_types: list[str] = Field(
        default_factory=lambda: [
            "text/plain",
            "image/*",
            "audio/*",
            "video/*",
            "application/pdf",
        ],
        description=(
            'The supported input types. Defaults to ``["text/plain", '

View on GitHub (pinned to e90f1c7592)

Solutions

1. Convert local files to Base64Source (read bytes, base64-encode, set the correct mime_type)
2. Use a URLSource with a publicly reachable URL (Google can fetch remote URIs)
3. Pre-validate source types before calling format() and fall back to a textual representation for unsupported ones

Example fix

# before
block = ImageBlock(source=LocalFileSource(path="pic.png"), alt="pic")

# after
import base64
block = ImageBlock(source=Base64Source(data=base64.b64encode(open("pic.png","rb").read()).decode(), media_type="image/png"), alt="pic")

from agentscope.message import URLSource, Base64Source
assert isinstance(block.source, (URLSource, Base64Source))

def is_gemini_media_source(src) -> bool:
    return isinstance(src, (URLSource, Base64Source))

try:
    formatted = formatter.format(msgs)
except ValueError as e:
    if "Unsupported source type" in str(e):
        # drop the media block or convert local file to Base64Source, retry
        ...
    raise

When it happens

Trigger: Formatting a Msg containing an ImageBlock/VideoBlock/AudioBlock whose source is a LocalFileSource or a raw path string/bytes with a GeminiChatFormatter.

Common situations: Pointing blocks at local files and expecting the Gemini formatter to upload them; reusing message pipelines built for OpenAI/Ollama formatters that handle local files; passing file-like objects as sources.

Related errors

• Unsupported audio source type: {type(source)}
• Unsupported image source type: {type(source)}
• Unsupported source type: {type(source)}
• Unsupported image source type: {type(source)}
• Unsupported audio source type: {type(source)}.

AI-assisted analysis of agentscope-ai/agentscope@e90f1c7592 (2026-08-28). Data as JSON: /api/errors/ddf6b029d9238377. Report an issue: GitHub.