Missing artifacts when state returned

[davidjsanders]

🔴 Required Information

Describe the Bug:
Artifacts (specifically PDF and PNG files) saved via tool_context.save_artifact are not visible in the ADK Web UI sidebar when GCS artifact storage is enabled, especially when the artifact generation is preceded by an authentication flow. While logs confirm the files are successfully uploaded to the GCS bucket, the UI fails to reflect the update. This suggests a disconnect in the SSE event propagation or state management specifically when GCS storage is combined with tool-interruption flows (like authentication).

Steps to Reproduce:

1. Configure a GCS bucket for artifact storage.
2. Start the ADK Web Server forcing the GCS URI:
   adk web --artifact_service_uri=gs://your-bucket-name .
3. Trigger an agent action that requires authentication followed by an artifact save:
   a. Authentication (e.g., using a direct access token from tool_context.state).
   b. Save artifact (e.g., await tool_context.save_artifact("test.pdf", part)).
4. Observe logs confirming successful upload to GCS.
5. Check the ADK Web UI sidebar; the artifact is missing despite the successful upload.

Expected Behavior:
The saved artifact should appear in the sidebar immediately after the tool execution completes, and its content should be viewable when selected.

Observed Behavior:
The sidebar remains empty or does not show the new artifact. No artifactDelta events seem to trigger a UI refresh for GCS-backed artifacts.

Environment Details:

• ADK Library Version (pip show google-adk): 1.24.1
• Desktop OS: Linux (Debian 12 / Rodete)
• Python Version (python -V): 3.13.11

Model Information:

• Are you using LiteLLM: No
• Which model is being used: gemini-2.5-pro

---

🟡 Optional Information

Regression:
N/A (Observed in current version).

Logs:

DEBUG:google_adk.artifacts.gcs_artifact_service:Uploading artifact test.pdf to gs://telranopt-artifacts/sessions/sess-123/artifacts/test.pdf
INFO:google_adk.runners:Artifact saved: test.pdf (version 1)
[Sidebar remains empty in UI]

contact: djsanders@