Prerequisites

• I have checked the existing issues to ensure this is not a duplicate.
• I am running the latest version of Tailcall.

Describe the bug

I tried to follow docs example referencing " {{.headers.x-user-id}} "" and found it never get evaluated successfully.
When hyphen is involved in the header key, it just doesn't evaluate.
When is a a-z header key, it evaluates to empty.

Note: I already added allowedHeaders in @upstream directive.

Steps to reproduce

1. tailcall init hello && cd hello
2. Replace the main.graphql content as below

schema @server @upstream(allowedHeaders: ["aaa", "x-user-id"]) {
  query: Query
}

type Query {
  greet: String! @expr(body: "Hello, World!")
  debugHeader(name: String!): String @expr(body: "{{.headers.{{.args.name}}}}")
  aaa: String @expr(body: "{{.headers.aaa}}")
  xUserId: String @expr(body: "{{.headers.x-user-id}}")
}

Then tailall start ./main.json

4. Now try to make a graphQL request as below

HTTP headers:
{
"aaa": "my-aaa-value",
"x-user-id": "my-user-id"
}

Query

{
    greet
    debugHeader(name: "aaa")
    aaa
    xUserId
}

Expected behavior

{
    "data": {
        "greet": "Hello, World!",
        "debugHeader": "my-aaa-value",
        "aaa": "my-aaa-value",
        "xUserId": "my-user-id"
    }
}

Actual behavior

Received response:

{
    "data": {
        "greet": "Hello, World!",
        "debugHeader": "{{.headers.{{.args.name}}}}",
        "aaa": "",
        "xUserId": "{{.headers.x-user-id}}"
    }
}

Screenshots

N/A

Environment information:

• Operating System: (MacOS 15.4.1 (24E263))
• Tailcall Version: (v1.6.8)
• GraphQL Client/version : I tried both the playgound and Postman, same result.