A Workflow resumed from DatabaseSessionService passes bytes on as base64 text #7852

Describe the Bug:

Currently, a resumed Workflow replays each finished node's output from the JSON DatabaseSessionService stored, so a node that runs after the pause and takes bytes gets the base64 text as bytes. Without the pause, or with InMemorySessionService, it gets the original bytes.

Steps to Reproduce:

pip install "google-adk[db]==2.13.0", then run:

import asyncio
from google.adk import Workflow
from google.adk.runners import Runner
from google.adk.sessions import DatabaseSessionService
from google.adk.workflow import node
from google.genai import types

def produce():
    return b"\x00\x01"

def consume(node_input: bytes):
    print(node_input)

async def main():
    svc = DatabaseSessionService("sqlite+aiosqlite:///t.db")
    wf = Workflow(name="wf", edges=[("START", produce, node(consume, require_confirmation=True))])
    runner = Runner(app_name="app", node=wf, session_service=svc)
    s = await svc.create_session(app_name="app", user_id="u")
    async def send(part):
        msg = types.UserContent(part)
        return [c async for e in runner.run_async(user_id="u", session_id=s.id, new_message=msg)
                for c in e.get_function_calls()]
    calls = await send(types.Part(text="go"))
    ok = types.FunctionResponse(id=calls[-1].id, name=calls[-1].name, response={"confirmed": True})
    await send(types.Part(function_response=ok))

asyncio.run(main())
# b'AAE=', should be b'\x00\x01'
# 'AAE=' is b'\x00\x01' in base64, the text the stored session event holds for produce's output

SqliteSessionService, which adk web uses by default, gives b'AAE=' too, and so does a pydantic model's bytes field.

Expected Behavior:

consume prints b'\x00\x01', the bytes produce returned.

Observed Behavior:

consume prints b'AAE=', and nothing raises.

Environment Details:

• ADK Library Version (pip show google-adk): 2.13.0 and main
• Desktop OS: macOS 26.7.1, arm64 (Darwin 25.6.0)
• Python Version (python -V): Python 3.12.16

Model Information:

• Are you using LiteLLM: No
• Which model is being used: N/A

Additional Context:

StorageEvent.from_event stores the event with model_dump(mode="json"), so Event's ser_json_bytes='base64' writes the bytes as text. On resume check_interception replays that text as produce's output, and _process_rehydrated_output passes anything but types.Content through unchanged.

How often has this issue occurred?:

• Always (100%)