browser_session() and BrowserClient.start() do not support proxyConfiguration

[kevin-orellana]

Description

The Browser Proxy feature launched GA on February 10, 2026, and the underlying StartBrowserSession Boto3 API fully supports the proxyConfiguration parameter. However, the bedrock-agentcore SDK (v1.3.1) does not expose this parameter in browser_session() or BrowserClient.start().

Customers who want to use proxy configuration through the high-level SDK are forced to drop down to raw Boto3 calls, bypassing the SDK's session lifecycle management, WebSocket header generation, and live view URL generation.

Expected behavior

from bedrock_agentcore.tools.browser_client import browser_session

proxy_config = {
    "proxies": [
        {
            "externalProxy": {
                "server": "proxy.example.com",
                "port": 8080,
                "domainPatterns": [".example.com", ".internal.corp"],
                "credentials": {
                    "basicAuth": {
                        "secretArn": "arn:aws:secretsmanager:us-east-1:123456789012:secret:proxy-creds"
                    }
                }
            }
        }
    ],
    "bypass": {
        "domainPatterns": [".amazonaws.com", "169.254.169.254"]
    }
}

with browser_session("us-east-1", proxy_configuration=proxy_config) as client:
    ws_url, headers = client.generate_ws_headers()
    # ... use proxied session

Current behavior

browser_session() accepts only region, viewport, and identifier. There is no way to pass proxy configuration through the SDK.

Proposed changes

1. Add proxy_configuration: Optional[Dict] = None parameter to BrowserClient.start(), passing it as proxyConfiguration to the Boto3 start_browser_session call
2. Add proxy_configuration: Optional[Dict] = None parameter to browser_session(), forwarding it to BrowserClient.start()
3. Add TypedDict definitions for the proxy configuration structure (improves developer experience with IDE autocomplete)
4. Bump minimum boto3/botocore to >=1.42.54 (the version that added proxyConfiguration to the bedrock-agentcore service model)

SDK version

bedrock-agentcore v1.3.1