wasm: gate UniFFI + reqwest timeout + enable gossip net (15 → 3 errors)

- UniFFI is the native FFI surface; cfg_attr all of it (setup_scaffolding, Record
  derives, export/callback_interface/constructor) to cfg(not(wasm32)). The wasm
  binding layer will be wasm-bindgen instead.
- rendezvous_register: reqwest Builder::timeout isn't on the wasm fetch backend —
  cfg it (browser bounds the request itself).
- iroh-gossip on wasm needs default-features=false + features=["net"] for the net
  module (Gossip/GossipSender/api).

wasm32 build now down to the two genuinely structural blockers: the tokio
multi-thread runtime (new_multi_thread → spawn_local) and the iroh wasm endpoint
(presets::N0 is native-only — pulls ring/portmapper). Native unaffected (verified).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/Cargo.toml

@@ -56,7 +56,7 @@ getrandom = "0.4.3"
 getrandom_02 = { package = "getrandom", version = "0.2", features = ["js"] }
 wasm-bindgen-futures = "0.4"
 iroh = { version = "1", optional = true, default-features = false }
-iroh-gossip = { version = "0.101", optional = true, default-features = false }
+iroh-gossip = { version = "0.101", optional = true, default-features = false, features = ["net"] }
 iroh-blobs = { version = "0.103", optional = true, default-features = false }
 
 [dev-dependencies]

core/src/iroh.rs

@@ -99,11 +99,15 @@ async fn rendezvous_register(server: &str, room: &str, my_id: &str) -> Vec<Endpo
     }
     let url = format!("{}/rendezvous/register", server.trim_end_matches('/'));
     let body = serde_json::json!({ "room": room, "id": my_id });
-    // Bounded — a stuck rendezvous must never wedge the transport.
+    // Bounded — a stuck rendezvous must never wedge the transport. On wasm the
+    // fetch backend has no Builder::timeout (the browser bounds it instead).
+    #[cfg(not(target_arch = "wasm32"))]
     let client = reqwest::Client::builder()
         .timeout(std::time::Duration::from_secs(8))
         .build()
         .unwrap_or_default();
+    #[cfg(target_arch = "wasm32")]
+    let client = reqwest::Client::new();
     let mut req = client.post(&url).json(&body);
     // Optional bearer token, matching the rendezvous's TETHER_RENDEZVOUS_TOKEN.
     if let Ok(token) = std::env::var("TETHER_RENDEZVOUS_TOKEN") {

core/src/lib.rs

@@ -40,11 +40,15 @@ mod rtc;
 
 use crypto::Crypto;
 
+// UniFFI is the native FFI surface (Swift/Kotlin). On wasm the bindings come
+// from wasm-bindgen instead, so gate all of it out for wasm32.
+#[cfg(not(target_arch = "wasm32"))]
 uniffi::setup_scaffolding!();
 
 /// 1:1 with the Go server `Message`, minus the RTC `signal` blob.
 /// `type` is renamed to `kind` (reserved word in the target languages).
-#[derive(Clone, Debug, Serialize, Deserialize, uniffi::Record)]
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[cfg_attr(not(target_arch = "wasm32"), derive(uniffi::Record))]
 pub struct Message {
     #[serde(rename = "type", default)]
     pub kind: String,
@@ -67,7 +71,7 @@ pub struct Message {
 /// Implemented on the foreign side (Swift/Kotlin) or natively (desktop agent).
 /// Callbacks fire on the engine's runtime thread — marshal to the UI thread
 /// on the consumer side.
-#[uniffi::export(callback_interface)]
+#[cfg_attr(not(target_arch = "wasm32"), uniffi::export(callback_interface))]
 pub trait MessageHandler: Send + Sync {
     fn on_message(&self, msg: Message);
     fn on_status(&self, connected: bool);
@@ -78,7 +82,8 @@ pub trait MessageHandler: Send + Sync {
 /// A tether device discovered on the local network (mDNS). Surfaced to the UI
 /// for an AirDrop-style "nearby devices" list. `room` lets the UI offer to pair
 /// (join that device's room).
-#[derive(Clone, Debug, uniffi::Record)]
+#[derive(Clone, Debug)]
+#[cfg_attr(not(target_arch = "wasm32"), derive(uniffi::Record))]
 pub struct Peer {
     pub id: String,      // stable device id (`from`)
     pub name: String,    // friendly name, e.g. "Patrick's MacBook"
@@ -94,7 +99,8 @@ type Discovered = Arc<Mutex<HashMap<String, (Peer, Instant)>>>;
 /// A delivery acknowledgement: device `from` (named `name`) received a clipboard
 /// whose text matches `text`. Lets the sender show "delivered to <name>" instead
 /// of asking. Auto-sent by the engine on every inbound clipboard.
-#[derive(Clone, Debug, uniffi::Record)]
+#[derive(Clone, Debug)]
+#[cfg_attr(not(target_arch = "wasm32"), derive(uniffi::Record))]
 pub struct Receipt {
     pub from: String,   // device that received it
     pub name: String,   // its friendly name
@@ -136,7 +142,7 @@ fn directly_covered(direct: &DirectSet, present: &PresentSet) -> bool {
 /// Defined once here and exported so every client (Swift/Kotlin/agent) derives
 /// the SAME room — that's what puts all of one account's devices together across
 /// LAN, relay, and RTC. Empty account → empty (caller falls back to a device id).
-#[uniffi::export]
+#[cfg_attr(not(target_arch = "wasm32"), uniffi::export)]
 pub fn room_for_account(account: String) -> String {
     use sha2::{Digest, Sha256};
     if account.is_empty() {
@@ -194,7 +200,8 @@ pub(crate) struct IncomingFile {
 }
 
 /// Progress of an in-flight file transfer, for the UI.
-#[derive(Clone, Debug, uniffi::Record)]
+#[derive(Clone, Debug)]
+#[cfg_attr(not(target_arch = "wasm32"), derive(uniffi::Record))]
 pub struct Transfer {
     pub name: String,
     pub received: u64,  // bytes transferred so far
@@ -320,7 +327,7 @@ trait Transport: Send + Sync {
     fn send_file(&self, _rt: &Handle, _id: String, _name: String, _mime: String, _data: Vec<u8>) {}
 }
 
-#[derive(uniffi::Object)]
+#[cfg_attr(not(target_arch = "wasm32"), derive(uniffi::Object))]
 pub struct Engine {
     cfg: Config,
     rt: Arc<tokio::runtime::Runtime>,
@@ -349,7 +356,7 @@ pub struct Engine {
     iroh_id: Arc<Mutex<Option<String>>>,
 }
 
-#[uniffi::export]
+#[cfg_attr(not(target_arch = "wasm32"), uniffi::export)]
 impl Engine {
     /// `server` is the bus base URL, e.g. "http://192.168.11.233:8765".
     /// `from` is this device's stable id (echo suppression); `source` a label.
@@ -357,7 +364,7 @@ impl Engine {
     /// `account` is a shared identity (Apple/Google `sub`); devices with the
     /// same non-empty account auto-pair on the LAN regardless of room. Pass ""
     /// when signed out.
-    #[uniffi::constructor]
+    #[cfg_attr(not(target_arch = "wasm32"), uniffi::constructor)]
     pub fn new(
         server: String,
         room: String,