How to add custom_metadata when artifacts are created through savefileasartifactplugin

[subbu4github]

I am in google adk 1.30 version. I want to know how to get the custom_metadata added to the artifact when created through savefileasartifactplugin. Is there a way to get it updated afterwards in any of the callbacks? Also let me know how to retrieve them if I am able to create custom metadata.

Thanks.

[boyangsvl]

I'd recommend you subclass the plugin and add your own logic.

[subbu4github]

@boyangsvl - Thanks for your revert. I tried this. But when I try to retrieve it, its not displaying the timestamp which I stored.

class CustomMetadataArtifactsPlugin(SaveFilesAsArtifactsPlugin):
"""
An extension of SaveFilesAsArtifactsPlugin that automatically injects
the absolute creation date into the artifact's custom metadata profile.
"""

def before_agent_callback(self, *args, **kwargs):
    """
    Version-safe extraction of user message across ADK variants
    """

    callback_context = kwargs["callback_context"]

    user_message = getattr(callback_context, "user_content", None)

    if user_message is None:
        # Fail fast (your preferred pattern)
        raise RuntimeError(
            f"user_content missing in callback_context. Attributes: {dir(callback_context)}"
        )

    # ✅ Step 2: Extract parts safely
    parts = getattr(user_message, "parts", [])

    if parts:
        for part in parts:
            if hasattr(part, "inline_data") and part.inline_data:

                creation_time = datetime.utcnow().isoformat() + "Z"

                if not hasattr(part, "metadata") or part.metadata is None:
                    part.metadata = {}

                if "custom_metadata" not in part.metadata:
                    part.metadata["custom_metadata"] = {}

                part.metadata["custom_metadata"]["created_at"] = creation_time
    kwargs["callback_context"] = callback_context

    # ✅ Step 3: Always propagate kwargs
    return super().before_agent_callback(*args, **kwargs)

Can you please guide me where I am going wrong.

[subbu4github]

I tried the part_metadata field to store and retrieve the value. The save is happening in all the cases, I am able to see the artifact. But custom meta details are getting missed. Unable to retrieve them.