core: wasm groundwork — target-split deps + gate native-only transports

First real step toward the web/WASM target. The dependency graph is now
target-conditional: the legacy transports' OS-socket deps (tokio net, mdns-sd,
webrtc) + UniFFI + native reqwest live under cfg(not(wasm32)); wasm32 gets a
minimal tokio (sync/macros), the reqwest fetch backend, wasm-bindgen-futures, and
iroh with default-features off. The SSE/RTC/LAN transport modules are gated to
native (they need OS sockets). getrandom's wasm rng is wired (build-cfg for 0.4 +
the js-feature alias trick for the transitive 0.2).

Effect: `cargo build --target wasm32-unknown-unknown --features iroh-transport`
goes from "deps won't compile at all" to 15 well-understood errors, isolated to
four structural items: UniFFI (decouple the FFI layer for wasm), iroh's wasm
feature set (presets/gossip-net), the tokio runtime (→ spawn_local + ?Send), and
reqwest .timeout(). Native builds (default + iroh + examples) are byte-unaffected
— all verified clean.

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

core/Cargo.lock

@@ -4852,6 +4852,7 @@ dependencies = [
  "bytes",
  "chacha20poly1305",
  "futures-util",
+ "getrandom 0.2.17",
  "getrandom 0.4.3",
  "iroh",
  "iroh-blobs",
@@ -4863,6 +4864,7 @@ dependencies = [
  "sha2 0.11.0",
  "tokio",
  "uniffi",
+ "wasm-bindgen-futures",
  "webrtc",
 ]
 

core/Cargo.toml

@@ -15,31 +15,50 @@ name = "tethercore"
 name = "uniffi-bindgen"
 path = "src/bin/uniffi-bindgen.rs"
 
+# Common, wasm-safe dependencies (no OS sockets / threads).
 [dependencies]
-uniffi = { version = "0.28", features = ["cli"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-reqwest = { version = "0.12", default-features = false, features = ["rustls-tls", "stream", "json"] }
-tokio = { version = "1", features = ["rt-multi-thread", "time", "sync", "macros", "net", "io-util"] }
 futures-util = "0.3"
-webrtc = "0.17.1"
-mdns-sd = "0.20.0"
 sha2 = "0.11.0"
 bytes = "1.12.0"
 chacha20poly1305 = "0.10.1"
 base64 = "0.22.1"
-getrandom = "0.4.3"
-# M4: the iroh Mesh, behind the `iroh-transport` feature (off by default, so the
-# UniFFI/xcframework/agent builds are untouched). When on, IrohTransport replaces
-# the hand-rolled SSE/RTC/LAN stack.
-iroh = { version = "1", optional = true }
-iroh-gossip = { version = "0.101", optional = true }
-iroh-blobs = { version = "0.103", optional = true }
 
 [features]
 default = []
 iroh-transport = ["dep:iroh", "dep:iroh-gossip", "dep:iroh-blobs"]
 
+# ── Native (desktop/mobile): legacy transports + UniFFI + full tokio ──
+# The hand-rolled SSE/RTC/LAN stack and its OS-socket deps live here; none of it
+# compiles to wasm. iroh (behind the feature) takes full default features.
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+uniffi = { version = "0.28", features = ["cli"] }
+reqwest = { version = "0.12", default-features = false, features = ["rustls-tls", "stream", "json"] }
+tokio = { version = "1", features = ["rt-multi-thread", "time", "sync", "macros", "net", "io-util"] }
+webrtc = "0.17.1"
+mdns-sd = "0.20.0"
+getrandom = "0.4.3"
+iroh = { version = "1", optional = true }
+iroh-gossip = { version = "0.101", optional = true }
+iroh-blobs = { version = "0.103", optional = true }
+
+# ── wasm32 (browser): iroh-only, no OS sockets / UniFFI ──
+# Browser iroh is relay-only; reqwest uses fetch; the runtime is the JS event
+# loop (wasm-bindgen-futures) instead of a tokio runtime.
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+tokio = { version = "1", features = ["sync", "macros"] }
+reqwest = { version = "0.12", default-features = false, features = ["json"] }
+# wasm rng: getrandom 0.4 uses a build-cfg (--cfg getrandom_backend="wasm_js"),
+# but a transitive getrandom 0.2 needs the `js` *feature* — enable it via the
+# rename-alias trick (cargo unifies it with the transitive copy).
+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-blobs = { version = "0.103", optional = true, default-features = false }
+
 [dev-dependencies]
 # Iroh spikes (examples/iroh_*.rs) link iroh directly regardless of the feature.
 iroh = "1"

core/src/lib.rs

@@ -32,7 +32,10 @@ use tokio::sync::mpsc::{UnboundedReceiver, UnboundedSender};
 mod crypto;
 #[cfg(feature = "iroh-transport")]
 mod iroh;
+// Legacy transports use OS sockets (tokio net / mdns / webrtc) — native only.
+#[cfg(not(target_arch = "wasm32"))]
 mod lan;
+#[cfg(not(target_arch = "wasm32"))]
 mod rtc;
 
 use crypto::Crypto;
@@ -698,14 +701,17 @@ impl Dedup {
 
 // ---------------------------------------------------------------------------
 // SSE transport — the reliable floor: server relay over text/event-stream.
+// Native only (reqwest streaming / bytes_stream isn't on the wasm fetch backend).
 // ---------------------------------------------------------------------------
 
+#[cfg(not(target_arch = "wasm32"))]
 struct SseTransport {
     cfg: Config,
     http: reqwest::Client,
     events: EventTx,
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 impl Transport for SseTransport {
     fn name(&self) -> &'static str {
         "sse"
@@ -757,6 +763,7 @@ impl Transport for SseTransport {
     }
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 impl SseTransport {
     async fn stream_once(&self, running: &AtomicBool) -> Result<(), String> {
         let url = format!(
@@ -816,6 +823,7 @@ impl SseTransport {
     }
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 async fn post(http: &reqwest::Client, cfg: &Config, msg: &Message) -> Result<(), String> {
     let url = format!("{}/api/send", cfg.server.trim_end_matches('/'));
     let kind = if msg.kind.is_empty() { "clipboard" } else { msg.kind.as_str() };