[jonathan343]

Summary

Generated HTTP clients currently install both aiohttp and urllib3, even when an application uses only one client mode. Move those dependencies into sync and async extras so customers install only the default transport dependencies they need.

Both clients, their configurations, and shared models remain in the same package with unchanged imports. Protocol dependencies and the existing CRT extra are unchanged. The mode extras also provide installation commands that can be retained if client implementations move into separate distributions later. This change does not split packages or add new transports.

Example

For a service package generated with this change, in a uv-managed project:

uv add "aws-sdk-s3[sync]"        # Default synchronous transport
uv add "aws-sdk-s3[async]"       # Default asynchronous transport
uv add "aws-sdk-s3[sync,async]"  # Both default transports

Or with pip:

pip install "aws-sdk-s3[sync]"
pip install "aws-sdk-s3[async]"
pip install "aws-sdk-s3[sync,async]"

A bare install still supports shared models and clients configured with a custom transport. Using a default transport without its dependency installed raises MissingDependencyError naming the required optional dependency, without prescribing a package manager.

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