Custom headers not propagated from AgentCore Gateway to MCP Server targets

[Amayas29]

Hi,

I'm trying to pass custom HTTP headers from the AgentCore Gateway to my MCP Server targets.

I've configured allowedRequestHeaders when creating the gateway target:

client.create_gateway_target(
    gatewayIdentifier=gateway_id,
    ...,
    metadataConfiguration={
        "allowedRequestHeaders": ["x-my-custom-header"],
    },
)

On the MCP server side (FastMCP), I try to read the header via:

ctx.request_context.request.headers.get("x-my-custom-header")

But x-my-custom-header is not present in ctx.request_context.request.headers. I also checked ctx.request_context.meta it's None.

Any solutions please?

Thanks