wasi:http/service p3 component generated by wit-bindgen is rejected by wasmtime serve (wasi:http/types resource mismatch)

[mizchi]

Summary

Using wit-bindgen (crate 0.51.0) to generate a wasi:http/service@0.3.0-rc-2026-01-06 component produces a valid component (wasm-tools validate passes), but the generated import shape appears incompatible with wasmtime serve.

Related wasmtime issue: bytecodealliance/wasmtime#12714

Versions

• wit-bindgen crate: 0.51.0
• rustc: 1.92.0
• wasm-tools: 1.245.1
• wasmtime: 41.0.3

Repro

src/lib.rs:

wit_bindgen::generate!({
    inline: r#"
      package vibe:http-adapter;

      world serviceonly {
        include wasi:http/service@0.3.0-rc-2026-01-06;
      }
    "#,
    path: "<wasmtime repo>/crates/wasi-http/src/p3/wit",
    world: "vibe:http-adapter/serviceonly",
    pub_export_macro: true,
    generate_all,
});

use exports::wasi::http::handler::Guest;
use wasi::http::types::{ErrorCode, Request, Response};

struct Component;

impl Guest for Component {
    async fn handle(request: Request) -> Result<Response, ErrorCode> {
        let _ = request;
        Err(ErrorCode::InternalError(None))
    }
}

export!(Component);

cargo build --target wasm32-unknown-unknown --release
wasm-tools component new target/wasm32-unknown-unknown/release/<crate>.wasm -o service_only.component.wasm
wasm-tools component wit service_only.component.wasm > service_only.wit

Generated service_only.wit starts as:

package root:component;

world root {
  import wasi:http/types@0.3.0-rc-2026-01-06;

  export wasi:http/handler@0.3.0-rc-2026-01-06;
}
package wasi:http@0.3.0-rc-2026-01-06 {
  interface types {
    resource request;
    resource response;
    ...

Then wasmtime serve fails:

instance export `request` has the wrong type
resource implementation is missing

Question

Is this import/type shape expected from wit-bindgen for P3 wasi:http/service, or should wit-bindgen preserve a fuller types resource shape so hosts can link canonical wasi:http/types implementations?

If this is expected behavior, is there a recommended generation mode/flag to avoid this incompatibility?

[alexcrichton]

To clarify, is this a different issue from bytecodealliance/wasmtime#12714, or is that an evolution of this issue? (should this be closed in favor of that?)