Python: `Agent(client=FoundryChatClient(...))` type-checks as invalid with `ty`, runtime works

[pamelafox]

Description

Agent(client=FoundryChatClient(...)) works at runtime in hosted samples, but ty reports a type mismatch.

In our deployed sample this currently requires an inline ignore on the client=... argument.

This looks similar in spirit to prior static-type mismatches (for example #560), but this case is specifically about FoundryChatClient not satisfying the expected Agent client protocol in ty diagnostics.

Minimal repro

from agent_framework import Agent
from agent_framework.foundry import FoundryChatClient
from azure.identity import DefaultAzureCredential

client = FoundryChatClient(
    project_endpoint="https://example.services.ai.azure.com/api/projects/example",
    model="gpt-5.2",
    credential=DefaultAzureCredential(),
)

agent = Agent(
    client=client,
    instructions="You are a friendly assistant",
)

Observed ty diagnostic

error[invalid-argument-type]: Argument to bound method `__init__` is incorrect
Expected `SupportsChatGetResponse[...]`, found `FoundryChatClient[...]`

Runtime behavior

The same pattern runs successfully in hosted agent code paths; this appears to be a typing/protocol mismatch rather than a runtime incompatibility.

Environment

• OS: macOS
• Python: 3.13.13
• ty: 0.0.21

Relevant package versions

From sample agents/pyproject.toml:

• agent-framework-core>=1.10.0
• agent-framework-openai>=1.10.0
• agent-framework-foundry>=1.10.0
• agent-framework-foundry-hosting>=1.0.0a260630
• agent-framework-orchestrations>=1.0.0

Request

Could you confirm whether this is an expected typing limitation with FoundryChatClient + Agent, or a bug in type annotations/protocol definitions? If it is a bug, a typing fix would help remove ignores from hosted sample code.

[github-actions]

👋 Hi @pamelafox — thanks for the report!

Your reported ty error (error[invalid-argument-type]: Expected SupportsChatGetResponse[...], found FoundryChatClient[...]) does not reproduce with ty 0.0.21 (your stated version) or ty 0.0.56 against the current v1.10.0 codebase — both pass cleanly on your exact repro snippet. To investigate further we would need: (1) your ty project configuration (any ty.toml, pyproject.toml [tool.ty] settings, or CLI flags you use), (2) the output of pip show agent-framework-core agent-framework-foundry confirming exact installed versions, and (3) whether ty is resolving types from your venv or from source. It's possible your environment is missing the .pyi stub at agent_framework/foundry/__init__.pyi or ty is picking up a different package installation.

Once you can share the details above, we'll take another look. 🙏

[eavanvalkenburg]

Hi @pamelafox
in this line, we specifically check for this:

agent-framework/python/packages/foundry/tests/foundry/test_foundry_chat_client.py

Line 159 in c67372f

assert isinstance(client, SupportsChatGetResponse)

and when I run ty (v 0.0.46) against the test file everything passes.

and when I add:

client = FoundryChatClient(project_client=mock_project, model="test-model")

agent = Agent(client=client, instructions="test agent")

as a test, it also passes ty. When I run with ty==0.0.21 I also get passing checks. I am looking further, but if you have additional info, let me know!

[pamelafox]

Hm, the full file is here:
https://github.com/Azure-Samples/foundry-hosted-agentframework-demos/blob/main/agents/stage4_foundry_hosted.py

I get the error both from the ty VS Code extension and my local ty, across all the versions (I just upgraded as well to check 0.56)

error[invalid-argument-type]: Argument to `Agent.__init__` is incorrect
  --> agents/stage4_foundry_hosted.py:99:9
   |
99 |         client=client,
   |         ^^^^^^^^^^^^^ Expected `SupportsChatGetResponse[OpenAIChatOptions[None] | (ChatOptions[None] & ChatOptions[Any]) | None | dict[str, bool]]`, found `FoundryChatClient[OpenAIChatOptions[None]]`
   |
info: type `FoundryChatClient[OpenAIChatOptions[None]]` is not assignable to protocol `SupportsChatGetResponse[OpenAIChatOptions[None] | (ChatOptions[None] & ChatOptions[Any]) | None | dict[str, bool]]`
info: └── protocol member `get_response` is incompatible
info: Method defined here
    --> agents/.venv/lib/python3.14/site-packages/agent_framework/_agents.py:1730:9
     |
1730 |     def __init__(
     |         ^^^^^^^^
1731 |         self,
1732 |         client: SupportsChatGetResponse[OptionsCoT],
     |         ------------------------------------------- Parameter declared here
     |