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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"bug: `on_connect` arg is `AgentSideConnection` at runtime while methods and params are different than `Client`","articleBody":"### Summary\n\nType `Client` and `AgentSideConnection` are not the same, while `on_connect` params is a `Client`, it is a `AgentSideConnection` at runtime (https://github.com/agentclientprotocol/python-sdk/blob/4cc2dfdbeebc224db92de92ce308a1820f7f42f1/src/acp/core.py#L59)\n\nThere is a cast forced here\n\nhttps://github.com/agentclientprotocol/python-sdk/blob/main/src/acp/agent/connection.py#L64\n\nWhen using `Client`, there are method such as `create_terminal` that does not return the same values nor property\n\nI really like the move to snake case, but I think it added a lot of breaking changes, especially to load the Agent. Shouldn't this release have been a major ?\n\n### Reproduction steps\n\n```python\nclass ExampleAgent(Agent)\n  #...\n\n  @override\n    def on_connect(self, conn: Client) -\u003e None:\n        self.client = conn\n        # ^ this is AgentSideConnection at runtime\n```\n\n```python\n    terminal_handle = await client.create_terminal(...)\n    print(terminal_handle.terminal_id)\n    # ^ this break because terminal_handle is not `CreateTerminalResponse` with `terminal_id` but `TerminalHandle` with `id`\n```\n\nAlso, having `Client` and `AgentSideConnection` being different type with no inheritence + `AgenceSideConnection` being now final make the test harder to write, especially when you need to stub `AgentSideConnection`\n\n### Expected result\n\n`Client` and `AgentSideConnection` should have similar property so that the types expected at runtime are the same. I'd expect `on_connect` to receive an `AgentSideConnection` instead of `Client` which is a protocol\n\n### Actual result\n\n```python\nclass ExampleAgent(Agent)\n  #...\n\n  @override\n    def on_connect(self, conn: Client) -\u003e None:\n        self.client = conn\n        # ^ this is AgentSideConnection at runtime\n```\n\n```python\n    terminal_handle = await client.create_terminal(...)\n    print(terminal_handle.terminal_id)\n    # ^ this break because terminal_handle is not `CreateTerminalResponse` with `terminal_id` but `TerminalHandle` with `id`\n\n```\n\n\n### Versions / environment\n\nsdk 0.7.0, Python 3.12, macOS 15.7.3\n\n\nQuick fix for now is to force cast `Client` into `AgentSideConnection`","author":{"url":"https://github.com/Nemtecl","@type":"Person","name":"Nemtecl"},"datePublished":"2025-12-18T19:25:04.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":13},"url":"https://github.com/49/python-sdk/issues/49"}