Allow model choices in temporal agent

[mattbrandman]

Description

Allow a temporal agent to choose the specific model type given its provider. I would like to be able to have one agent for gpt-5 and gpt-4.1, and theoretically this should be possible as the provider is wrapped but can still be given different arguments at run time.

References

No response

[DouweM]

@mattbrandman We "temporalize" the entire Model object and attach some things that are specific to the agent, like the event_stream_handler, so it's not as simple as being able to "temporalize" a provider once and then use it with different model names. (I mean, that could technically be made to work, but is not how things work currently)

But what we could support relatively easily is something like this:

model1 = 'openai:gpt-5'
model2 = AnthropicModel('claude-sonnet-4-5')
model3 = 'google-gla:gemini-2.5-pro'
agent = Agent(model1)
temporal_agent = TemporalAgent(agent, models=[model2, model3])

# in workflow:

await temporal_agent.run(..., model=model3)

We'd only support models there that had been registered at TemporalAgent-time, so that we can eagerly create activities for them.

Would that work for your use case?

[mattbrandman]

That would be perfect

[DouweM]

@mattbrandman Great, this is a bit niche for us to prioritize, but a PR would be welcome!

[mattbrandman]

#3465 this is just an idea vs the multiple models setup. We would still want that for setting up multiple providers but within a single provider wanted your general thoughts. This PR is a draft since it only has implementation for a singular provider