test: add regression test for #4296

This reverts commit d37512bebd.

.github/workflows/autofix.yml

@@ -17,11 +17,10 @@ env:
 jobs:
   autofix:
     runs-on: ubuntu-latest
-    timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: actions-rust-lang/setup-rust-toolchain@v1
-        with: {toolchain: "nightly-2025-04-16", components: "rustfmt, clippy", target: "wasm32-unknown-unknown", rustflags: ""}
+        with: {toolchain: "nightly-2025-07-16", components: "rustfmt, clippy", target: "wasm32-unknown-unknown", rustflags: ""}
       - name: Install Glib
         run: |
           sudo apt-get update

.github/workflows/ci.yml

@@ -63,6 +63,6 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y libglib2.0-dev
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Semver Checks
         uses: obi1kenobi/cargo-semver-checks-action@v2

.github/workflows/get-example-changed.yml

@@ -19,7 +19,7 @@ jobs:
       matrix: ${{ steps.set-example-changed.outputs.matrix }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 0
       - name: Get example files that changed

.github/workflows/get-examples-matrix.yml

@@ -17,7 +17,7 @@ jobs:
       EXCLUDED_EXAMPLES: cargo-make
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Install jq
         run: sudo apt-get install jq
       - name: Set Matrix

.github/workflows/get-leptos-changed.yml

@@ -13,7 +13,7 @@ jobs:
       leptos_changed: ${{ steps.set-source-changed.outputs.leptos_changed }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           fetch-depth: 0
       - name: Get source files that changed

.github/workflows/get-leptos-matrix.yml

@@ -13,7 +13,7 @@ jobs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Install jq
         run: sudo apt-get install jq
       - name: Set Matrix

.github/workflows/publish-book.yml

@@ -12,7 +12,7 @@ jobs:
       contents: write # To push a branch
       pull-requests: write # To create a PR from that branch
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
         with:
           fetch-depth: 0
       - name: Install mdbook

.github/workflows/run-cargo-make-task.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        toolchain: [stable, nightly-2025-04-16]
+        toolchain: [stable, nightly-2025-07-16]
         erased_mode: [true, false]
     steps:
       - name: Free Disk Space
@@ -53,7 +53,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y libglib2.0-dev
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Setup Rust
         uses: dtolnay/rust-toolchain@master
         with:
@@ -169,7 +169,9 @@ jobs:
           cd '${{ inputs.directory }}'
           cargo make --no-workspace --profile=github-actions ci
           # check the direct-minimal-versions on release
-          if [[ "${{ github.ref_name }}" =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+          COMMIT_MSG=$(git log -1 --pretty=format:'%s')
+          # Supports: v1.2.3, v1.2.3-alpha, v1.2.3-beta1, v1.2.3-rc.1, etc.
+          if [[ "$COMMIT_MSG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(-[a-zA-Z0-9]+(\.?[0-9]+)?)?$ ]]; then
             cargo make --no-workspace --profile=github-actions check-minimal-versions
           fi
       # Check if the counter_isomorphic can be built with leptos_debuginfo cfg flag in release mode

Cargo.toml

@@ -40,47 +40,49 @@ members = [
 exclude = ["benchmarks", "examples", "projects"]
 
 [workspace.package]
-version = "0.8.2"
 edition = "2021"
-rust-version = "1.80"
+rust-version = "1.88"
 
 [workspace.dependencies]
 # members
 throw_error = { path = "./any_error/", version = "0.3.0" }
 any_spawner = { path = "./any_spawner/", version = "0.3.0" }
 const_str_slice_concat = { path = "./const_str_slice_concat", version = "0.1" }
-either_of = { path = "./either_of/", version = "0.1.5" }
+either_of = { path = "./either_of/", version = "0.1.6" }
 hydration_context = { path = "./hydration_context", version = "0.3.0" }
-leptos = { path = "./leptos", version = "0.8.2" }
-leptos_config = { path = "./leptos_config", version = "0.8.2" }
-leptos_dom = { path = "./leptos_dom", version = "0.8.2" }
-leptos_hot_reload = { path = "./leptos_hot_reload", version = "0.8.2" }
-leptos_integration_utils = { path = "./integrations/utils", version = "0.8.2" }
-leptos_macro = { path = "./leptos_macro", version = "0.8.2" }
-leptos_router = { path = "./router", version = "0.8.2" }
-leptos_router_macro = { path = "./router_macro", version = "0.8.2" }
-leptos_server = { path = "./leptos_server", version = "0.8.2" }
-leptos_meta = { path = "./meta", version = "0.8.2" }
+leptos = { path = "./leptos", version = "0.8.8" }
+leptos_config = { path = "./leptos_config", version = "0.8.7" }
+leptos_dom = { path = "./leptos_dom", version = "0.8.6" }
+leptos_hot_reload = { path = "./leptos_hot_reload", version = "0.8.5" }
+leptos_integration_utils = { path = "./integrations/utils", version = "0.8.5" }
+leptos_macro = { path = "./leptos_macro", version = "0.8.8" }
+leptos_router = { path = "./router", version = "0.8.6" }
+leptos_router_macro = { path = "./router_macro", version = "0.8.5" }
+leptos_server = { path = "./leptos_server", version = "0.8.5" }
+leptos_meta = { path = "./meta", version = "0.8.5" }
 next_tuple = { path = "./next_tuple", version = "0.1.0" }
-oco_ref = { path = "./oco", version = "0.2.0" }
+oco_ref = { path = "./oco", version = "0.2.1" }
 or_poisoned = { path = "./or_poisoned", version = "0.1.0" }
-reactive_graph = { path = "./reactive_graph", version = "0.2.0" }
-reactive_stores = { path = "./reactive_stores", version = "0.2.0" }
-reactive_stores_macro = { path = "./reactive_stores_macro", version = "0.2.0" }
-server_fn = { path = "./server_fn", version = "0.8.2" }
-server_fn_macro = { path = "./server_fn_macro", version = "0.8.2" }
-server_fn_macro_default = { path = "./server_fn/server_fn_macro_default", version = "0.8.2" }
-tachys = { path = "./tachys", version = "0.2.0" }
+reactive_graph = { path = "./reactive_graph", version = "0.2.6" }
+reactive_stores = { path = "./reactive_stores", version = "0.2.5" }
+reactive_stores_macro = { path = "./reactive_stores_macro", version = "0.2.6" }
+server_fn = { path = "./server_fn", version = "0.8.6" }
+server_fn_macro = { path = "./server_fn_macro", version = "0.8.7" }
+server_fn_macro_default = { path = "./server_fn/server_fn_macro_default", version = "0.8.5" }
+tachys = { path = "./tachys", version = "0.2.7" }
+wasm_split_helpers = { path = "./wasm_split", version = "0.1.2" }
+wasm_split_macros = { path = "./wasm_split_macros", version = "0.1.2" }
 
 # members deps
+async-once-cell = { default-features = false, version = "0.5.3" }
 itertools = { default-features = false, version = "0.14.0" }
 convert_case = { default-features = false, version = "0.8.0" }
-serde_json = { default-features = false, version = "1.0.140" }
-trybuild = { default-features = false, version = "1.0.105" }
-typed-builder = { default-features = false, version = "0.21.0" }
-thiserror = { default-features = false, version = "2.0.12" }
+serde_json = { default-features = false, version = "1.0.143" }
+trybuild = { default-features = false, version = "1.0.110" }
+typed-builder = { default-features = false, version = "0.21.2" }
+thiserror = { default-features = false, version = "2.0.16" }
 wasm-bindgen = { default-features = false, version = "0.2.100" }
-indexmap = { default-features = false, version = "2.9.0" }
+indexmap = { default-features = false, version = "2.11.0" }
 rstml = { default-features = false, version = "0.12.1" }
 rustc_version = { default-features = false, version = "0.4.1" }
 guardian = { default-features = false, version = "1.3.0" }
@@ -98,17 +100,17 @@ proc-macro-error2 = { default-features = false, version = "2.0.1" }
 const_format = { default-features = false, version = "0.2.34" }
 gloo-net = { default-features = false, version = "0.6.0" }
 url = { default-features = false, version = "2.5.4" }
-tokio = { default-features = false, version = "1.45.1" }
+tokio = { default-features = false, version = "1.47.1" }
 base64 = { default-features = false, version = "0.22.1" }
-cfg-if = { default-features = false, version = "1.0.0" }
+cfg-if = { default-features = false, version = "1.0.3" }
 wasm-bindgen-futures = { default-features = false, version = "0.4.50" }
 tower = { default-features = false, version = "0.5.2" }
-proc-macro2 = { default-features = false, version = "1.0.95" }
+proc-macro2 = { default-features = false, version = "1.0.101" }
 serde = { default-features = false, version = "1.0.219" }
 parking_lot = { default-features = false, version = "0.12.4" }
 axum = { default-features = false, version = "0.8.4" }
 serde_qs = { default-features = false, version = "0.15.0" }
-syn = { default-features = false, version = "2.0.101" }
+syn = { default-features = false, version = "2.0.106" }
 xxhash-rust = { default-features = false, version = "0.8.15" }
 paste = { default-features = false, version = "1.0.15" }
 quote = { default-features = false, version = "1.0.40" }
@@ -116,55 +118,58 @@ web-sys = { default-features = false, version = "0.3.77" }
 js-sys = { default-features = false, version = "0.3.77" }
 rand = { default-features = false, version = "0.9.1" }
 serde-lite = { default-features = false, version = "0.5.0" }
-tokio-tungstenite = { default-features = false, version = "0.26.2" }
+tokio-tungstenite = { default-features = false, version = "0.27.0" }
 serial_test = { default-features = false, version = "3.2.0" }
 erased = { default-features = false, version = "0.1.2" }
-glib = { default-features = false, version = "0.20.10" }
-async-trait = { default-features = false, version = "0.1.88" }
+glib = { default-features = false, version = "0.20.12" }
+async-trait = { default-features = false, version = "0.1.89" }
 typed-builder-macro = { default-features = false, version = "0.21.0" }
 linear-map = { default-features = false, version = "1.2.0" }
-anyhow = { default-features = false, version = "1.0.98" }
+anyhow = { default-features = false, version = "1.0.99" }
 walkdir = { default-features = false, version = "2.5.0" }
 actix-ws = { default-features = false, version = "0.3.0" }
 tower-http = { default-features = false, version = "0.6.4" }
-prettyplease = { default-features = false, version = "0.2.33" }
-inventory = { default-features = false, version = "0.3.20" }
-config = { default-features = false, version = "0.15.11" }
-camino = { default-features = false, version = "1.1.9" }
+prettyplease = { default-features = false, version = "0.2.37" }
+inventory = { default-features = false, version = "0.3.21" }
+config = { default-features = false, version = "0.15.14" }
+camino = { default-features = false, version = "1.1.11" }
 ciborium = { default-features = false, version = "0.2.2" }
 multer = { default-features = false, version = "3.1.0" }
 leptos-spin-macro = { default-features = false, version = "0.2.0" }
 sledgehammer_utils = { default-features = false, version = "0.3.1" }
 sledgehammer_bindgen = { default-features = false, version = "0.6.0" }
 wasm-streams = { default-features = false, version = "0.4.2" }
-rkyv = { default-features = false, version = "0.8.10" }
+rkyv = { default-features = false, version = "0.8.11" }
 temp-env = { default-features = false, version = "0.3.6" }
-uuid = { default-features = false, version = "1.17.0" }
+uuid = { default-features = false, version = "1.18.0" }
 bytes = { default-features = false, version = "1.10.1" }
 http = { default-features = false, version = "1.3.1" }
-regex = { default-features = false, version = "1.11.1" }
+regex = { default-features = false, version = "1.11.2" }
 drain_filter_polyfill = { default-features = false, version = "0.1.3" }
-tempfile = { default-features = false, version = "3.20.0" }
-futures-lite = { default-features = false, version = "2.6.0" }
+tempfile = { default-features = false, version = "3.21.0" }
+futures-lite = { default-features = false, version = "2.6.1" }
 log = { default-features = false, version = "0.4.27" }
-percent-encoding = { default-features = false, version = "2.3.1" }
+percent-encoding = { default-features = false, version = "2.3.2" }
 async-executor = { default-features = false, version = "1.13.2" }
-const-str = { default-features = false, version = "0.6.2" }
+const-str = { default-features = false, version = "0.6.4" }
 http-body-util = { default-features = false, version = "0.1.3" }
-hyper = { default-features = false, version = "1.6.0" }
-postcard = { default-features = false, version = "1.1.1" }
+hyper = { default-features = false, version = "1.7.0" }
+postcard = { default-features = false, version = "1.1.3" }
 rmp-serde = { default-features = false, version = "1.3.0" }
-reqwest = { default-features = false, version = "0.12.18" }
+reqwest = { default-features = false, version = "0.12.23" }
 tower-layer = { default-features = false, version = "0.3.3" }
 attribute-derive = { default-features = false, version = "0.10.3" }
 insta = { default-features = false, version = "1.43.1" }
 codee = { default-features = false, version = "0.3.0" }
-actix-http = { default-features = false, version = "3.11.0" }
+actix-http = { default-features = false, version = "3.11.1" }
 wasm-bindgen-test = { default-features = false, version = "0.3.50" }
-rustversion = { default-features = false, version = "1.0.21" }
+rustversion = { default-features = false, version = "1.0.22" }
 getrandom = { default-features = false, version = "0.3.3" }
 actix-files = { default-features = false, version = "0.6.6" }
-async-lock = { default-features = false, version = "3.4.0" }
+async-lock = { default-features = false, version = "3.4.1" }
+base16 = { default-features = false, version = "0.2.1" }
+digest = { default-features = false, version = "0.10.7" }
+sha2 = { default-features = false, version = "0.10.8" }
 
 [profile.release]
 codegen-units = 1

README.md

@@ -90,35 +90,13 @@ Here are some resources for learning more about Leptos:
 - [API Documentation](https://docs.rs/leptos/latest/leptos/)
 - [Common Bugs](https://github.com/leptos-rs/leptos/tree/main/docs/COMMON_BUGS.md) (and how to fix them!)
 
-## `nightly` Note
-
-Most of the examples assume you’re using `nightly` version of Rust and the `nightly` feature of Leptos. To use `nightly` Rust, you can either set your toolchain globally or on per-project basis.
-
-To set `nightly` as a default toolchain for all projects (and add the ability to compile Rust to WebAssembly, if you haven’t already):
-
-```
-rustup toolchain install nightly
-rustup default nightly
-rustup target add wasm32-unknown-unknown
-```
-
-If you'd like to use `nightly` only in your Leptos project however, add [`rust-toolchain.toml`](https://rust-lang.github.io/rustup/overrides.html#the-toolchain-file) file with the following content:
-
-```toml
-[toolchain]
-channel = "nightly"
-targets = ["wasm32-unknown-unknown"]
-```
-
-The `nightly` feature enables the function call syntax for accessing and setting signals, as opposed to `.get()` and `.set()`. This leads to a consistent mental model in which accessing a reactive value of any kind (a signal, memo, or derived signal) is always represented as a function call. This is only possible with nightly Rust and the `nightly` feature.
-
 ## `cargo-leptos`
 
 [`cargo-leptos`](https://github.com/leptos-rs/cargo-leptos) is a build tool that's designed to make it easy to build apps that run on both the client and the server, with seamless integration. The best way to get started with a real Leptos project right now is to use `cargo-leptos` and our starter templates for [Actix](https://github.com/leptos-rs/start) or [Axum](https://github.com/leptos-rs/start-axum).
 
 ```bash
 cargo install cargo-leptos
-cargo leptos new --git https://github.com/leptos-rs/start
+cargo leptos new --git https://github.com/leptos-rs/start-axum
 cd [your project name]
 cargo leptos watch
 ```
@@ -147,7 +125,7 @@ Yes, I’m sure there are. You can see from the state of our issue tracker over
 
 This may be the big one: “production ready” implies a certain orientation to a library: that you can basically use it, without any special knowledge of its internals or ability to contribute. Everyone has this at some level in their stack: for example I (@gbj) don’t have the capacity or knowledge to contribute to something like `wasm-bindgen` at this point: I simply rely on it to work.
 
-There are several people in the community using Leptos right now for internal apps at work, who have also become significant contributors. I think this is the right level of production use for now. There may be missing features that you need, and you may end up building them! But for internal apps, if you’re willing to build and contribute missing pieces along the way, the framework is definitely usable right now.
+There are several people in the community using Leptos right now for many websites at work, who have also become significant contributors. There may be missing features that you need, and you may end up building them! But, if you're willing to contribute a few missing pieces along the way, the framework is most definitely usable for production applications, especially given the ecosystem of libraries that have sprung up around it.
 
 ### Can I use this for native GUI?
 

benchmarks/Cargo.toml

@@ -2,8 +2,6 @@
 name = "benchmarks"
 version = "0.1.0"
 edition = "2021"
-# std::sync::LazyLock is stabilized in Rust version 1.80.0
-rust-version = "1.80.0"
 
 [dependencies]
 l0410 = { package = "leptos", version = "0.4.10", features = [

examples/axum_js_ssr/Cargo.toml

@@ -19,7 +19,7 @@ leptos_meta = { path = "../../meta" }
 leptos_axum = { path = "../../integrations/axum", optional = true }
 leptos_router = { path = "../../router" }
 serde = { version = "1.0", features = ["derive"] }
-thiserror = "1.0"
+thiserror = "2.0.12"
 tokio = { version = "1.39", features = [
   "rt-multi-thread",
   "macros",

examples/cargo-make/cargo-leptos-split-webdriver-test.toml

@@ -0,0 +1,11 @@
+extend = [
+    { path = "./cargo-leptos.toml" },
+    { path = "../cargo-make/webdriver.toml" },
+]
+
+[tasks.integration-test]
+dependencies = [
+    "install-cargo-leptos",
+    "start-webdriver",
+    "cargo-leptos-e2e-split",
+]

examples/cargo-make/cargo-leptos.toml

@@ -11,6 +11,10 @@ args = ["--locked"]
 command = "cargo"
 args = ["leptos", "end-to-end"]
 
+[tasks.cargo-leptos-e2e-split]
+command = "cargo"
+args = ["leptos", "end-to-end", "--split"]
+
 [tasks.build]
 clear = true
 command = "cargo"

examples/counter_isomorphic/Cargo.toml

@@ -2,8 +2,6 @@
 name = "counter_isomorphic"
 version = "0.1.0"
 edition = "2021"
-# std::sync::LazyLock is stabilized in Rust version 1.80.0
-rust-version = "1.80.0"
 
 [lib]
 crate-type = ["cdylib", "rlib"]

examples/errors_axum/Cargo.toml

@@ -18,7 +18,7 @@ tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
 http = { version = "1.1" }
-thiserror = "1.0"
+thiserror = "2.0.12"
 wasm-bindgen = "0.2.93"
 
 [features]

examples/fetch/Cargo.toml

@@ -15,7 +15,7 @@ serde = { version = "1.0", features = ["derive"] }
 log = "0.4.22"
 console_log = "1.0"
 console_error_panic_hook = "0.1.7"
-thiserror = "1.0"
+thiserror = "2.0.12"
 tracing = "0.1.40"
 tracing-subscriber = "0.3.18"
 tracing-subscriber-wasm = "0.1.0"

examples/hackernews_axum/src/lib.rs

@@ -4,7 +4,7 @@ mod routes;
 use leptos_meta::{provide_meta_context, Link, Meta, MetaTags, Stylesheet};
 use leptos_router::{
     components::{FlatRoutes, Route, Router, RoutingProgress},
-    OptionalParamSegment, ParamSegment, StaticSegment,
+    Lazy, OptionalParamSegment, ParamSegment, StaticSegment,
 };
 use routes::{nav::*, stories::*, story::*, users::*};
 use std::time::Duration;
@@ -44,8 +44,8 @@ pub fn App() -> impl IntoView {
             <Nav />
             <main>
                 <FlatRoutes fallback=|| "Not found.">
-                    <Route path=(StaticSegment("users"), ParamSegment("id")) view=User/>
-                    <Route path=(StaticSegment("stories"), ParamSegment("id")) view=Story/>
+                    <Route path=(StaticSegment("users"), ParamSegment("id")) view={Lazy::<UserRoute>::new()}/>
+                    <Route path=(StaticSegment("stories"), ParamSegment("id")) view={Lazy::<StoryRoute>::new()}/>
                     <Route path=OptionalParamSegment("stories") view=Stories/>
                 </FlatRoutes>
             </main>

examples/hackernews_axum/src/routes/story.rs

@@ -1,24 +1,38 @@
-use crate::api;
+use crate::api::{self, Story};
 use leptos::{either::Either, prelude::*};
 use leptos_meta::Meta;
-use leptos_router::{components::A, hooks::use_params_map};
+use leptos_router::{
+    components::A, hooks::use_params_map, lazy_route, LazyRoute,
+};
 
-#[component]
-pub fn Story() -> impl IntoView {
-    let params = use_params_map();
-    let story = Resource::new_blocking(
-        move || params.read().get("id").unwrap_or_default(),
-        move |id| async move {
-            if id.is_empty() {
-                None
-            } else {
-                api::fetch_api::<api::Story>(&api::story(&format!("item/{id}")))
+#[derive(Debug)]
+pub struct StoryRoute {
+    story: Resource<Option<Story>>,
+}
+
+#[lazy_route]
+impl LazyRoute for StoryRoute {
+    fn data() -> Self {
+        let params = use_params_map();
+        let story = Resource::new_blocking(
+            move || params.read().get("id").unwrap_or_default(),
+            move |id| async move {
+                if id.is_empty() {
+                    None
+                } else {
+                    api::fetch_api::<api::Story>(&api::story(&format!(
+                        "item/{id}"
+                    )))
                     .await
-            }
-        },
-    );
+                }
+            },
+        );
+        Self { story }
+    }
 
-    Suspense(SuspenseProps::builder().fallback(|| "Loading...").children(ToChildren::to_children(move || Suspend::new(async move {
+    fn view(this: Self) -> AnyView {
+        let StoryRoute { story } = this;
+        Suspense(SuspenseProps::builder().fallback(|| "Loading...").children(ToChildren::to_children(move || Suspend::new(async move {
         match story.await.clone() {
             None => Either::Left("Story not found."),
             Some(story) => {
@@ -61,7 +75,8 @@ pub fn Story() -> impl IntoView {
                 })
             }
         }
-    }))).build())
+    }))).build()).into_any()
+    }
 }
 
 #[component]

examples/hackernews_axum/src/routes/users.rs

@@ -1,46 +1,58 @@
 use crate::api::{self, User};
 use leptos::{either::Either, prelude::*, server::Resource};
-use leptos_router::hooks::use_params_map;
+use leptos_router::{hooks::use_params_map, lazy_route, LazyRoute};
 
-#[component]
-pub fn User() -> impl IntoView {
-    let params = use_params_map();
-    let user = Resource::new(
-        move || params.read().get("id").unwrap_or_default(),
-        move |id| async move {
-            if id.is_empty() {
-                None
-            } else {
-                api::fetch_api::<User>(&api::user(&id)).await
-            }
-        },
-    );
-    view! {
-        <div class="user-view">
-            <Suspense fallback=|| view! { "Loading..." }>
-                {move || Suspend::new(async move { match user.await.clone() {
-                    None => Either::Left(view! {  <h1>"User not found."</h1> }),
-                    Some(user) => Either::Right(view! {
-                        <div>
-                            <h1>"User: " {user.id.clone()}</h1>
-                            <ul class="meta">
-                                <li>
-                                    <span class="label">"Created: "</span> {user.created}
-                                </li>
-                                <li>
-                                <span class="label">"Karma: "</span> {user.karma}
-                                </li>
-                                <li inner_html={user.about} class="about"></li>
-                            </ul>
-                            <p class="links">
-                                <a href=format!("https://news.ycombinator.com/submitted?id={}", user.id)>"submissions"</a>
-                                " | "
-                                <a href=format!("https://news.ycombinator.com/threads?id={}", user.id)>"comments"</a>
-                            </p>
-                        </div>
-                    })
-                }})}
-            </Suspense>
-        </div>
+#[derive(Debug)]
+pub struct UserRoute {
+    user: Resource<Option<User>>,
+}
+
+#[lazy_route]
+impl LazyRoute for UserRoute {
+    fn data() -> Self {
+        let params = use_params_map();
+        let user = Resource::new(
+            move || params.read().get("id").unwrap_or_default(),
+            move |id| async move {
+                if id.is_empty() {
+                    None
+                } else {
+                    api::fetch_api::<User>(&api::user(&id)).await
+                }
+            },
+        );
+        UserRoute { user }
+    }
+
+    fn view(this: Self) -> AnyView {
+        let UserRoute { user } = this;
+        view! {
+            <div class="user-view">
+                <Suspense fallback=|| view! { "Loading..." }>
+                    {move || Suspend::new(async move { match user.await.clone() {
+                        None => Either::Left(view! {  <h1>"User not found."</h1> }),
+                        Some(user) => Either::Right(view! {
+                            <div>
+                                <h1>"User: " {user.id.clone()}</h1>
+                                <ul class="meta">
+                                    <li>
+                                        <span class="label">"Created: "</span> {user.created}
+                                    </li>
+                                    <li>
+                                    <span class="label">"Karma: "</span> {user.karma}
+                                    </li>
+                                    <li inner_html={user.about} class="about"></li>
+                                </ul>
+                                <p class="links">
+                                    <a href=format!("https://news.ycombinator.com/submitted?id={}", user.id)>"submissions"</a>
+                                    " | "
+                                    <a href=format!("https://news.ycombinator.com/threads?id={}", user.id)>"comments"</a>
+                                </p>
+                            </div>
+                        })
+                    }})}
+                </Suspense>
+            </div>
+        }.into_any()
     }
 }

examples/lazy_routes/Cargo.toml

@@ -0,0 +1,95 @@
+[package]
+name = "lazy_routes"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+axum = { version = "0.8.1", optional = true }
+console_error_panic_hook = "0.1.7"
+console_log = "1.0"
+leptos = { path = "../../leptos", features = ["tracing"] }
+leptos_meta = { path = "../../meta" }
+leptos_axum = { path = "../../integrations/axum", optional = true }
+leptos_router = { path = "../../router" }
+serde = { version = "1.0", features = ["derive"] }
+thiserror = "1.0"
+tokio = { version = "1.39", features = [
+  "rt-multi-thread",
+  "macros",
+  "time",
+], optional = true }
+wasm-bindgen = "0.2.92"
+futures = "0.3.31"
+serde_json = "1.0.140"
+gloo-timers = { version = "0.3", features = ["futures"] }
+
+[features]
+hydrate = ["leptos/hydrate"]
+ssr = [
+  "dep:axum",
+  "dep:tokio",
+  "leptos/ssr",
+  "leptos_meta/ssr",
+  "dep:leptos_axum",
+  "leptos_router/ssr",
+]
+
+[profile.release]
+panic = "abort"
+
+[profile.wasm-release]
+inherits = "release"
+opt-level = 'z'
+lto = true
+codegen-units = 1
+panic = "abort"
+
+[package.metadata.cargo-all-features]
+denylist = ["axum", "tower", "tower-http", "tokio", "sqlx", "leptos_axum"]
+skip_feature_sets = [["ssr", "hydrate"]]
+
+[package.metadata.leptos]
+# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name
+output-name = "regression"
+# The site root folder is where cargo-leptos generate all output. WARNING: all content of this folder will be erased on a rebuild. Use it in your server setup.
+site-root = "target/site"
+# The site-root relative folder where all compiled output (JS, WASM and CSS) is written
+# Defaults to pkg
+site-pkg-dir = "pkg"
+# The IP and port (ex: 127.0.0.1:3000) where the server serves the content. Use it in your server setup.
+site-addr = "127.0.0.1:3000"
+# The port to use for automatic reload monitoring
+reload-port = 3001
+# [Optional] Command to use when running end2end tests. It will run in the end2end dir.
+#   [Windows] for non-WSL use "npx.cmd playwright test"
+#   This binary name can be checked in Powershell with Get-Command npx
+end2end-cmd = "cargo make test-ui"
+end2end-dir = "e2e"
+#  The browserlist query used for optimizing the CSS.
+browserquery = "defaults"
+# Set by cargo-leptos watch when building with that tool. Controls whether autoreload JS will be included in the head
+watch = false
+# The environment Leptos will run in, usually either "DEV" or "PROD"
+env = "DEV"
+# The features to use when compiling the bin target
+#
+# Optional. Can be over-ridden with the command line parameter --bin-features
+bin-features = ["ssr"]
+
+# If the --no-default-features flag should be used when compiling the bin target
+#
+# Optional. Defaults to false.
+bin-default-features = false
+
+# The features to use when compiling the lib target
+#
+# Optional. Can be over-ridden with the command line parameter --lib-features
+lib-features = ["hydrate"]
+
+# If the --no-default-features flag should be used when compiling the lib target
+#
+# Optional. Defaults to false.
+lib-default-features = false

examples/lazy_routes/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 Leptos
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

examples/lazy_routes/Makefile.toml

@@ -0,0 +1,8 @@
+extend = [
+    { path = "../cargo-make/main.toml" },
+    { path = "../cargo-make/cargo-leptos-split-webdriver-test.toml" },
+]
+
+[env]
+
+CLIENT_PROCESS_NAME = "regression"

examples/lazy_routes/README.md

@@ -0,0 +1,8 @@
+# Regression Tests
+
+This example functions as a catch-all for all current and future regression
+test cases that typically happens at integration.
+
+## Quick Start
+
+Run `cargo leptos watch` to run this example.

examples/lazy_routes/e2e/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "lazy_routes_e2e"
+version = "0.1.0"
+edition = "2021"
+
+[dev-dependencies]
+anyhow = "1.0"
+async-trait = "0.1.81"
+cucumber = "0.21.1"
+fantoccini = "0.21.1"
+pretty_assertions = "1.4"
+serde_json = "1.0"
+tokio = { version = "1.39", features = ["macros", "rt-multi-thread", "time"] }
+url = "2.5"
+
+[[test]]
+name = "app_suite"
+harness = false    # Allow Cucumber to print output instead of libtest

examples/lazy_routes/e2e/Makefile.toml

@@ -0,0 +1,20 @@
+extend = { path = "../../cargo-make/main.toml" }
+
+[tasks.test]
+env = { RUN_AUTOMATICALLY = false }
+condition = { env_true = ["RUN_AUTOMATICALLY"] }
+
+[tasks.ci]
+
+[tasks.test-ui]
+command = "cargo"
+args = [
+  "test",
+  "--test",
+  "app_suite",
+  "--",
+  "--retry",
+  "2",
+  "--fail-fast",
+  "${@}",
+]

examples/lazy_routes/e2e/README.md

@@ -0,0 +1,30 @@
+# Lazy Routes
+
+This example demonstrates how to split the WASM bundle that is sent to the client into multiple binaries, which can be lazy-loaded, either independently or in a way that's integrated into the router.
+
+Without code splitting, the entire application is compiled to a monolithic WASM binary, the size of which grows in proportion to the complexity of the application. This means that the time to interactive (TTI) for any page is proportional to the size of the entire application, not only that page.
+
+Code splitting allows you to lazy-load some functions, by splitting off the WASM binary code for certain functions into separate files, which can be downloaded as needed. This minimizes initial TTI for any page, and then amortizes the cost of loading the binary over the lifetime of the application session.
+
+In many cases, this can be done with minimal or no cost.
+
+Lazy loading can be used in two ways, each of which is shown in the example.
+
+## `#[lazy]` macro
+
+`#[lazy]` is an attribute macro that can be used to annotate an `async fn` in order to split its code out into a separate file that will be loaded on demand, when compiled with `cargo leptos --split`.
+
+This has some limitations (for example, it must return concrete types) but can be used for most functions.
+
+## `LazyRoute`
+
+`LazyRoute` is a specialized application of `#[lazy]` that allows you to define an entire route/page of your application as being lazy-loaded.
+
+Creating a lazy route requires you to split the route into two parts:
+
+1. `data()`: A synchronous method that should be used to start loading any async data used by the page, for example by creating a `Resource`
+2. `view()`: An async (because lazy-loaded) method that renders the view.
+
+The purpose of splitting these into two parts is to avoid a “waterfall,” in which the browser first waits for a lazy-loaded WASM chunk that defines the page, _then_ makes a second request to the server to load the relevant data. Instead, a `LazyRoute` will begin loading resources created in the `data` method while lazy-loading the component body in the `view`, then render the route.
+
+This means that in many cases, the data loading “hides” the cost of the lazy-loading; i.e., the page needs to wait for the data to load, so the fact that it is waiting concurrently for the lazy-loaded view means that the lazy loading does not cost anything additional in terms of page load time.

examples/lazy_routes/e2e/features/basic.feature

@@ -0,0 +1,33 @@
+@basic
+Feature: Check that each page hydrates correctly
+
+	Scenario: Page A is rendered correctly.
+		Given I see the app
+		Then I see the page is View A
+
+	Scenario: Page A hydrates and allows navigating to page B.
+		Given I see the app
+		When I select the link B
+		Then I see the navigating indicator
+		When I wait for a second
+		Then I see the page is View B
+
+	Scenario: Page B is rendered correctly.
+		When I open the app at /b
+		Then I see the page is View B
+
+	Scenario: Page B hydrates and allows navigating to page C.
+		When I open the app at /b
+		When I select the link C
+		Then I see the navigating indicator
+		When I wait for a second
+		Then I see the page is View C
+
+	Scenario: Page C is rendered correctly.
+		When I open the app at /c
+		Then I see the page is View C
+
+	Scenario: Page C hydrates and allows navigating to page A.
+		When I open the app at /c
+		When I select the link A
+		Then I see the page is View A

examples/lazy_routes/e2e/features/duplicate_name.feature

@@ -0,0 +1,15 @@
+@duplicate_names
+Feature: Lazy functions can share the same name
+
+	Scenario: Two functions with the same name both work.
+		Given I see the app
+		Then I see the page is View A
+		When I click the button First
+		When I wait for a second
+		Then I see the result is {"a":"First Value","b":1}
+		When I click the button Second
+		When I wait for a second
+		Then I see the result is {"a":"Second Value","b":2}
+		When I click the button Third
+		When I wait for a second
+		Then I see the result is Third value.

examples/lazy_routes/e2e/features/shared_chunks.feature

@@ -0,0 +1,9 @@
+@shared_chunks
+Feature: Shared code splitting works correctly
+
+	Scenario: Two functions using same serde code both work.
+		Given I see the app
+		Then I see the page is View A
+		When I click the button First
+		When I wait for a second
+		Then I see the result is {"a":"First Value","b":1}

examples/lazy_routes/e2e/tests/app_suite.rs

@@ -0,0 +1,30 @@
+mod fixtures;
+
+use anyhow::Result;
+use cucumber::World;
+use fixtures::world::AppWorld;
+use std::{ffi::OsStr, fs::read_dir};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    // Normally the below is done, but it's now gotten to the point of
+    // having a sufficient number of tests where the resource contention
+    // of the concurrently running browsers will cause failures on CI.
+    // AppWorld::cucumber()
+    //     .fail_on_skipped()
+    //     .run_and_exit("./features")
+    //     .await;
+
+    // Mitigate the issue by manually stepping through each feature,
+    // rather than letting cucumber glob them and dispatch all at once.
+    for entry in read_dir("./features")? {
+        let path = entry?.path();
+        if path.extension() == Some(OsStr::new("feature")) {
+            AppWorld::cucumber()
+                .fail_on_skipped()
+                .run_and_exit(path)
+                .await;
+        }
+    }
+    Ok(())
+}

examples/lazy_routes/e2e/tests/fixtures/action.rs

@@ -0,0 +1,23 @@
+use super::{find, world::HOST};
+use anyhow::Result;
+use fantoccini::Client;
+use std::result::Result::Ok;
+
+pub async fn goto_path(client: &Client, path: &str) -> Result<()> {
+    let url = format!("{}{}", HOST, path);
+    client.goto(&url).await?;
+
+    Ok(())
+}
+
+pub async fn click_link(client: &Client, text: &str) -> Result<()> {
+    let link = find::link_with_text(&client, &text).await?;
+    link.click().await?;
+    Ok(())
+}
+
+pub async fn click_button(client: &Client, id: &str) -> Result<()> {
+    let btn = find::element_by_id(&client, &id).await?;
+    btn.click().await?;
+    Ok(())
+}

examples/lazy_routes/e2e/tests/fixtures/check.rs

@@ -0,0 +1,29 @@
+use crate::fixtures::find;
+use anyhow::{Ok, Result};
+use fantoccini::Client;
+use pretty_assertions::assert_eq;
+
+pub async fn page_name_is(client: &Client, expected_text: &str) -> Result<()> {
+    let actual = find::text_at_id(client, "page").await?;
+    assert_eq!(&actual, expected_text);
+    Ok(())
+}
+
+pub async fn result_is(client: &Client, expected_text: &str) -> Result<()> {
+    let actual = find::text_at_id(client, "result").await?;
+    assert_eq!(&actual, expected_text);
+    Ok(())
+}
+
+pub async fn navigating_appears(client: &Client) -> Result<()> {
+    let actual = find::text_at_id(client, "navigating").await?;
+    assert_eq!(&actual, "Navigating...");
+    Ok(())
+}
+
+pub async fn element_exists(client: &Client, id: &str) -> Result<()> {
+    find::element_by_id(client, id)
+        .await
+        .expect(&format!("could not find element with id `{id}`"));
+    Ok(())
+}

examples/lazy_routes/e2e/tests/fixtures/find.rs

@@ -0,0 +1,23 @@
+use anyhow::{Ok, Result};
+use fantoccini::{elements::Element, Client, Locator};
+
+pub async fn text_at_id(client: &Client, id: &str) -> Result<String> {
+    let element = element_by_id(client, id)
+        .await
+        .expect(format!("no such element with id `{}`", id).as_str());
+    let text = element.text().await?;
+    Ok(text)
+}
+
+pub async fn link_with_text(client: &Client, text: &str) -> Result<Element> {
+    let link = client
+        .wait()
+        .for_element(Locator::LinkText(text))
+        .await
+        .expect(format!("Link not found by `{}`", text).as_str());
+    Ok(link)
+}
+
+pub async fn element_by_id(client: &Client, id: &str) -> Result<Element> {
+    Ok(client.wait().for_element(Locator::Id(id)).await?)
+}

examples/lazy_routes/e2e/tests/fixtures/mod.rs

@@ -0,0 +1,4 @@
+pub mod action;
+pub mod check;
+pub mod find;
+pub mod world;

examples/lazy_routes/e2e/tests/fixtures/world/action_steps.rs

@@ -0,0 +1,68 @@
+use crate::fixtures::{action, world::AppWorld};
+use anyhow::{Ok, Result};
+use cucumber::{gherkin::Step, given, when};
+
+#[given("I see the app")]
+#[when("I open the app")]
+async fn i_open_the_app(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    action::goto_path(client, "").await?;
+
+    Ok(())
+}
+
+#[when(regex = "^I open the app at (.*)$")]
+async fn i_open_the_app_at(world: &mut AppWorld, url: String) -> Result<()> {
+    let client = &world.client;
+    action::goto_path(client, &url).await?;
+
+    Ok(())
+}
+
+#[when(regex = "^I select the link (.*)$")]
+async fn i_select_the_link(world: &mut AppWorld, text: String) -> Result<()> {
+    let client = &world.client;
+    action::click_link(client, &text).await?;
+
+    Ok(())
+}
+
+#[when(regex = "^I click the button (.*)$")]
+async fn i_click_the_button(world: &mut AppWorld, id: String) -> Result<()> {
+    let client = &world.client;
+    action::click_button(client, &id).await?;
+
+    Ok(())
+}
+
+#[when(expr = "I select the following links")]
+async fn i_select_the_following_links(
+    world: &mut AppWorld,
+    step: &Step,
+) -> Result<()> {
+    let client = &world.client;
+
+    if let Some(table) = step.table.as_ref() {
+        for row in table.rows.iter() {
+            action::click_link(client, &row[0]).await?;
+        }
+    }
+
+    Ok(())
+}
+
+#[when("I wait for a second")]
+async fn i_wait_for_a_second(world: &mut AppWorld) -> Result<()> {
+    tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+
+    Ok(())
+}
+
+#[given(regex = "^I (refresh|reload) the (browser|page)$")]
+#[when(regex = "^I (refresh|reload) the (browser|page)$")]
+async fn i_refresh_the_browser(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    client.refresh().await?;
+
+    Ok(())
+}

examples/lazy_routes/e2e/tests/fixtures/world/check_steps.rs

@@ -0,0 +1,31 @@
+use crate::fixtures::{check, world::AppWorld};
+use anyhow::{Ok, Result};
+use cucumber::then;
+
+#[then(regex = r"^I see the navigating indicator")]
+async fn i_see_the_nav(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    check::navigating_appears(client).await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the page is (.*)$")]
+async fn i_see_the_page_is(world: &mut AppWorld, text: String) -> Result<()> {
+    let client = &world.client;
+    check::page_name_is(client, &text).await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the result is (.*)$")]
+async fn i_see_the_result_is(world: &mut AppWorld, text: String) -> Result<()> {
+    let client = &world.client;
+    check::result_is(client, &text).await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the navbar$")]
+async fn i_see_the_navbar(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    check::element_exists(client, "nav").await?;
+    Ok(())
+}

examples/lazy_routes/e2e/tests/fixtures/world/mod.rs

@@ -0,0 +1,39 @@
+pub mod action_steps;
+pub mod check_steps;
+
+use anyhow::Result;
+use cucumber::World;
+use fantoccini::{
+    error::NewSessionError, wd::Capabilities, Client, ClientBuilder,
+};
+
+pub const HOST: &str = "http://127.0.0.1:3000";
+
+#[derive(Debug, World)]
+#[world(init = Self::new)]
+pub struct AppWorld {
+    pub client: Client,
+}
+
+impl AppWorld {
+    async fn new() -> Result<Self, anyhow::Error> {
+        let webdriver_client = build_client().await?;
+
+        Ok(Self {
+            client: webdriver_client,
+        })
+    }
+}
+
+async fn build_client() -> Result<Client, NewSessionError> {
+    let mut cap = Capabilities::new();
+    let arg = serde_json::from_str("{\"args\": [\"-headless\"]}").unwrap();
+    cap.insert("goog:chromeOptions".to_string(), arg);
+
+    let client = ClientBuilder::native()
+        .capabilities(cap)
+        .connect("http://localhost:4444")
+        .await?;
+
+    Ok(client)
+}

examples/lazy_routes/src/app.rs

@@ -0,0 +1,355 @@
+use leptos::{prelude::*, task::spawn_local};
+use leptos_router::{
+    components::{Outlet, ParentRoute, Route, Router, Routes},
+    lazy_route, Lazy, LazyRoute, StaticSegment,
+};
+use serde::{Deserialize, Serialize};
+
+pub fn shell(options: LeptosOptions) -> impl IntoView {
+    view! {
+        <!DOCTYPE html>
+        <html lang="en">
+            <head>
+                <meta charset="utf-8"/>
+                <meta name="viewport" content="width=device-width, initial-scale=1"/>
+                <AutoReload options=options.clone()/>
+                <HydrationScripts options/>
+            </head>
+            <body>
+                <App/>
+            </body>
+        </html>
+    }
+}
+
+#[component]
+pub fn App() -> impl IntoView {
+    let count = RwSignal::new(0);
+    provide_context(count);
+    let (is_routing, set_is_routing) = signal(false);
+
+    view! {
+        <nav id="nav" style="width: 100%">
+            <a href="/">"A"</a> " | "
+            <a href="/b">"B"</a> " | "
+            <a href="/c">"C"</a> " | "
+            <a href="/d">"D"</a>
+            <span style="float: right" id="navigating">
+                {move || is_routing.get().then_some("Navigating...")}
+            </span>
+        </nav>
+        <Router set_is_routing>
+            <Routes fallback=|| "Not found.">
+                <Route path=StaticSegment("") view=ViewA/>
+                <Route path=StaticSegment("b") view=ViewB/>
+                <Route path=StaticSegment("c") view={Lazy::<ViewC>::new()}/>
+                // you can nest lazy routes, and there data and views will all load concurrently
+                <ParentRoute path=StaticSegment("d") view={Lazy::<ViewD>::new()}>
+                    <Route path=StaticSegment("") view={Lazy::<ViewE>::new()}/>
+                </ParentRoute>
+            </Routes>
+        </Router>
+    }
+}
+
+// View A: A plain old synchronous route, just like they all currently work. The WASM binary code
+// for this is shipped as part of the main bundle.  Any data-loading code (like resources that run
+// in the body of the component) will be shipped as part of the main bundle.
+
+#[component]
+pub fn ViewA() -> impl IntoView {
+    leptos::logging::log!("View A");
+    let result = RwSignal::new("Click a button to see the result".to_string());
+
+    view! {
+        <p id="page">"View A"</p>
+        <pre id="result">{result}</pre>
+        <button id="First" on:click=move |_| spawn_local(async move { result.set(first_value().await); })>"First"</button>
+        <button id="Second" on:click=move |_| spawn_local(async move { result.set(second_value().await); })>"Second"</button>
+        // test to make sure duplicate names in different scopes can be used
+        <button id="Third" on:click=move |_| {
+            #[lazy]
+            pub fn second_value() -> String {
+                "Third value.".to_string()
+            }
+
+            spawn_local(async move {
+                result.set(second_value().await);
+            });
+        }>"Third"</button>
+    }
+}
+
+// View B: lazy-loaded route with lazy-loaded data
+#[derive(Debug, Clone, Deserialize)]
+pub struct Comment {
+    #[serde(rename = "postId")]
+    post_id: usize,
+    id: usize,
+    name: String,
+    email: String,
+    body: String,
+}
+
+#[lazy]
+fn deserialize_comments(data: &str) -> Vec<Comment> {
+    serde_json::from_str(data).unwrap()
+}
+
+#[component]
+pub fn ViewB() -> impl IntoView {
+    let data = LocalResource::new(|| async move {
+        let preload = deserialize_comments("[]");
+        let (_, data) = futures::future::join(preload, async {
+            gloo_timers::future::TimeoutFuture::new(500).await;
+
+            r#"
+                [
+                    {
+                        "postId": 1,
+                        "id": 1,
+                        "name": "id labore ex et quam laborum",
+                        "email": "Eliseo@gardner.biz",
+                        "body": "laudantium enim quasi est quidem magnam voluptate ipsam eos\ntempora quo necessitatibus\ndolor quam autem quasi\nreiciendis et nam sapiente accusantium"
+                    },
+                    {
+                        "postId": 1,
+                        "id": 2,
+                        "name": "quo vero reiciendis velit similique earum",
+                        "email": "Jayne_Kuhic@sydney.com",
+                        "body": "est natus enim nihil est dolore omnis voluptatem numquam\net omnis occaecati quod ullam at\nvoluptatem error expedita pariatur\nnihil sint nostrum voluptatem reiciendis et"
+                    },
+                    {
+                        "postId": 1,
+                        "id": 3,
+                        "name": "odio adipisci rerum aut animi",
+                        "email": "Nikita@garfield.biz",
+                        "body": "quia molestiae reprehenderit quasi aspernatur\naut expedita occaecati aliquam eveniet laudantium\nomnis quibusdam delectus saepe quia accusamus maiores nam est\ncum et ducimus et vero voluptates excepturi deleniti ratione"
+                    }
+                ]
+            "#
+        })
+        .await;
+        deserialize_comments(data).await
+    });
+    view! {
+        <p id="page">"View B"</p>
+        <Suspense fallback=|| view! { <p id="loading">"Loading..."</p> }>
+            <ul>
+            {move || Suspend::new(async move {
+                let items = data.await;
+                items.into_iter()
+                    .map(|comment| view! {
+                        <li id=format!("{}-{}", comment.post_id, comment.id)>
+                            <strong>{comment.name}</strong>  " (by " {comment.email} ")"<br/>
+                            {comment.body}
+                        </li>
+                    })
+                    .collect_view()
+            })}
+            </ul>
+        </Suspense>
+    }
+    .into_any()
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Album {
+    #[serde(rename = "userId")]
+    user_id: usize,
+    id: usize,
+    title: String,
+}
+
+// View C: a lazy view, and some data, loaded in parallel when we navigate to /c.
+#[derive(Clone)]
+pub struct ViewC {
+    data: LocalResource<Vec<Album>>,
+}
+
+// Lazy-loaded routes need to implement the LazyRoute trait. They define a "route data" struct,
+// which is created with `::data()`, and then a separate view function which is lazily loaded.
+//
+// This is important because it allows us to concurrently 1) load the route data, and 2) lazily
+// load the component, rather than creating a "waterfall" where we can't start loading the route
+// data until we've received the view.
+//
+// The `#[lazy_route]` macro makes `view` into a lazy-loaded inner function, replacing `self` with
+// `this`.
+#[lazy_route]
+impl LazyRoute for ViewC {
+    fn data() -> Self {
+        // the data method itself is synchronous: it typically creates things like Resources,
+        // which are created synchronously but spawn an async data-loading task
+        // if you want further code-splitting, however, you can create a lazy function to load the data!
+        #[lazy]
+        async fn lazy_data() -> Vec<Album> {
+            gloo_timers::future::TimeoutFuture::new(250).await;
+            vec![
+                Album {
+                    user_id: 1,
+                    id: 1,
+                    title: "quidem molestiae enim".into(),
+                },
+                Album {
+                    user_id: 1,
+                    id: 2,
+                    title: "sunt qui excepturi placeat culpa".into(),
+                },
+                Album {
+                    user_id: 1,
+                    id: 3,
+                    title: "omnis laborum odio".into(),
+                },
+            ]
+        }
+
+        Self {
+            data: LocalResource::new(lazy_data),
+        }
+    }
+
+    fn view(this: Self) -> AnyView {
+        let albums = move || {
+            Suspend::new(async move {
+                this.data
+                    .await
+                    .into_iter()
+                    .map(|album| {
+                        view! {
+                            <li id=format!("{}-{}", album.user_id, album.id)>
+                                {album.title}
+                            </li>
+                        }
+                    })
+                    .collect::<Vec<_>>()
+            })
+        };
+        view! {
+            <p id="page">"View C"</p>
+            <hr/>
+            <Suspense fallback=|| view! { <p id="loading">"Loading..."</p> }>
+                <ul>{albums}</ul>
+            </Suspense>
+        }
+        .into_any()
+    }
+}
+
+// When two functions have shared code, that shared code will be split out automatically
+// into an additional file. For example, the shared serde code here will be split into a single file,
+// and then loaded lazily once when the first of the two functions is called
+
+#[lazy]
+pub fn first_value() -> String {
+    #[derive(Serialize)]
+    struct FirstValue {
+        a: String,
+        b: i32,
+    }
+
+    serde_json::to_string(&FirstValue {
+        a: "First Value".into(),
+        b: 1,
+    })
+    .unwrap()
+}
+
+#[lazy]
+pub fn second_value() -> String {
+    #[derive(Serialize)]
+    struct SecondValue {
+        a: String,
+        b: i32,
+    }
+
+    serde_json::to_string(&SecondValue {
+        a: "Second Value".into(),
+        b: 2,
+    })
+    .unwrap()
+}
+
+struct ViewD {
+    data: Resource<Result<Vec<i32>, ServerFnError>>,
+}
+
+#[lazy_route]
+impl LazyRoute for ViewD {
+    fn data() -> Self {
+        Self {
+            data: Resource::new(|| (), |_| d_data()),
+        }
+    }
+
+    fn view(this: Self) -> AnyView {
+        let items = move || {
+            Suspend::new(async move {
+                this.data
+                    .await
+                    .unwrap_or_default()
+                    .into_iter()
+                    .map(|item| view! { <li>{item}</li> })
+                    .collect::<Vec<_>>()
+            })
+        };
+        view! {
+            <p id="page">"View D"</p>
+            <hr/>
+            <Suspense fallback=|| view! { <p id="loading">"Loading..."</p> }>
+                <ul>{items}</ul>
+            </Suspense>
+            <Outlet/>
+        }
+        .into_any()
+    }
+}
+
+// Server functions can be made lazy by combining the two macros,
+// with `#[server]` coming first, then `#[lazy]`
+#[server]
+#[lazy]
+async fn d_data() -> Result<Vec<i32>, ServerFnError> {
+    tokio::time::sleep(std::time::Duration::from_millis(250)).await;
+    Ok(vec![1, 1, 2, 3, 5, 8, 13])
+}
+
+struct ViewE {
+    data: Resource<Result<Vec<String>, ServerFnError>>,
+}
+
+#[lazy_route]
+impl LazyRoute for ViewE {
+    fn data() -> Self {
+        Self {
+            data: Resource::new(|| (), |_| e_data()),
+        }
+    }
+
+    fn view(this: Self) -> AnyView {
+        let items = move || {
+            Suspend::new(async move {
+                this.data
+                    .await
+                    .unwrap_or_default()
+                    .into_iter()
+                    .map(|item| view! { <li>{item}</li> })
+                    .collect::<Vec<_>>()
+            })
+        };
+        view! {
+            <p id="page">"View E"</p>
+            <hr/>
+            <Suspense fallback=|| view! { <p id="loading">"Loading..."</p> }>
+                <ul>{items}</ul>
+            </Suspense>
+        }
+        .into_any()
+    }
+}
+
+#[server]
+async fn e_data() -> Result<Vec<String>, ServerFnError> {
+    tokio::time::sleep(std::time::Duration::from_millis(250)).await;
+    Ok(vec!["foo".into(), "bar".into(), "baz".into()])
+}

examples/lazy_routes/src/lib.rs

@@ -0,0 +1,9 @@
+pub mod app;
+
+#[cfg(feature = "hydrate")]
+#[wasm_bindgen::prelude::wasm_bindgen]
+pub fn hydrate() {
+    use app::*;
+    console_error_panic_hook::set_once();
+    leptos::mount::hydrate_lazy(App);
+}

examples/lazy_routes/src/main.rs

@@ -0,0 +1,37 @@
+#[cfg(feature = "ssr")]
+#[tokio::main]
+async fn main() {
+    use axum::Router;
+    use lazy_routes::app::{shell, App};
+    use leptos::prelude::*;
+    use leptos_axum::{generate_route_list, LeptosRoutes};
+
+    let conf = get_configuration(None).unwrap();
+    let addr = conf.leptos_options.site_addr;
+    let leptos_options = conf.leptos_options;
+    // Generate the list of routes in your Leptos App
+    let routes = generate_route_list(App);
+
+    let app = Router::new()
+        .leptos_routes(&leptos_options, routes, {
+            let leptos_options = leptos_options.clone();
+            move || shell(leptos_options.clone())
+        })
+        .fallback(leptos_axum::file_and_error_handler(shell))
+        .with_state(leptos_options);
+
+    // run our app with hyper
+    // `axum::Server` is a re-export of `hyper::Server`
+    println!("listening on http://{}", &addr);
+    let listener = tokio::net::TcpListener::bind(&addr).await.unwrap();
+    axum::serve(listener, app.into_make_service())
+        .await
+        .unwrap();
+}
+
+#[cfg(not(feature = "ssr"))]
+pub fn main() {
+    // no client-side main function
+    // unless we want this to work with e.g., Trunk for pure client-side testing
+    // see lib.rs for hydration function instead
+}

examples/lazy_routes/style/main.scss

@@ -0,0 +1,3 @@
+body {
+    font-family: sans-serif;
+}

examples/regression/Cargo.toml

@@ -0,0 +1,90 @@
+[package]
+name = "regression"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+axum = { version = "0.8.1", optional = true }
+console_error_panic_hook = "0.1.7"
+console_log = "1.0"
+leptos = { path = "../../leptos", features = ["tracing"] }
+leptos_meta = { path = "../../meta" }
+leptos_axum = { path = "../../integrations/axum", optional = true }
+leptos_router = { path = "../../router" }
+serde = { version = "1.0", features = ["derive"] }
+thiserror = "2.0.12"
+tokio = { version = "1.39", features = [ "rt-multi-thread", "macros", "time" ], optional = true }
+wasm-bindgen = "0.2.92"
+
+[features]
+hydrate = [
+  "leptos/hydrate",
+]
+ssr = [
+  "dep:axum",
+  "dep:tokio",
+  "leptos/ssr",
+  "leptos_meta/ssr",
+  "dep:leptos_axum",
+  "leptos_router/ssr",
+]
+
+[profile.release]
+panic = "abort"
+
+[profile.wasm-release]
+inherits = "release"
+opt-level = 'z'
+lto = true
+codegen-units = 1
+panic = "abort"
+
+[package.metadata.cargo-all-features]
+denylist = ["axum", "tower", "tower-http", "tokio", "sqlx", "leptos_axum"]
+skip_feature_sets = [["ssr", "hydrate"]]
+
+[package.metadata.leptos]
+# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name
+output-name = "regression"
+# The site root folder is where cargo-leptos generate all output. WARNING: all content of this folder will be erased on a rebuild. Use it in your server setup.
+site-root = "target/site"
+# The site-root relative folder where all compiled output (JS, WASM and CSS) is written
+# Defaults to pkg
+site-pkg-dir = "pkg"
+# The IP and port (ex: 127.0.0.1:3000) where the server serves the content. Use it in your server setup.
+site-addr = "127.0.0.1:3000"
+# The port to use for automatic reload monitoring
+reload-port = 3001
+# [Optional] Command to use when running end2end tests. It will run in the end2end dir.
+#   [Windows] for non-WSL use "npx.cmd playwright test"
+#   This binary name can be checked in Powershell with Get-Command npx
+end2end-cmd = "cargo make test-ui"
+end2end-dir = "e2e"
+#  The browserlist query used for optimizing the CSS.
+browserquery = "defaults"
+# Set by cargo-leptos watch when building with that tool. Controls whether autoreload JS will be included in the head
+watch = false
+# The environment Leptos will run in, usually either "DEV" or "PROD"
+env = "DEV"
+# The features to use when compiling the bin target
+#
+# Optional. Can be over-ridden with the command line parameter --bin-features
+bin-features = ["ssr"]
+
+# If the --no-default-features flag should be used when compiling the bin target
+#
+# Optional. Defaults to false.
+bin-default-features = false
+
+# The features to use when compiling the lib target
+#
+# Optional. Can be over-ridden with the command line parameter --lib-features
+lib-features = ["hydrate"]
+
+# If the --no-default-features flag should be used when compiling the lib target
+#
+# Optional. Defaults to false.
+lib-default-features = false

examples/regression/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 Leptos
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

examples/regression/Makefile.toml

@@ -0,0 +1,8 @@
+extend = [
+    { path = "../cargo-make/main.toml" },
+    { path = "../cargo-make/cargo-leptos-webdriver-test.toml" },
+]
+
+[env]
+
+CLIENT_PROCESS_NAME = "regression"

examples/regression/README.md

@@ -0,0 +1,8 @@
+# Regression Tests
+
+This example functions as a catch-all for all current and future regression
+test cases that typically happens at integration.
+
+## Quick Start
+
+Run `cargo leptos watch` to run this example.

examples/regression/e2e/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "regression_e2e"
+version = "0.1.0"
+edition = "2021"
+
+[dev-dependencies]
+anyhow = "1.0"
+async-trait = "0.1.81"
+cucumber = "0.21.1"
+fantoccini = "0.21.1"
+pretty_assertions = "1.4"
+serde_json = "1.0"
+tokio = { version = "1.39", features = ["macros", "rt-multi-thread", "time"] }
+url = "2.5"
+
+[[test]]
+name = "app_suite"
+harness = false    # Allow Cucumber to print output instead of libtest

examples/regression/e2e/Makefile.toml

@@ -0,0 +1,20 @@
+extend = { path = "../../cargo-make/main.toml" }
+
+[tasks.test]
+env = { RUN_AUTOMATICALLY = false }
+condition = { env_true = ["RUN_AUTOMATICALLY"] }
+
+[tasks.ci]
+
+[tasks.test-ui]
+command = "cargo"
+args = [
+  "test",
+  "--test",
+  "app_suite",
+  "--",
+  "--retry",
+  "2",
+  "--fail-fast",
+  "${@}",
+]

examples/regression/e2e/README.md

@@ -0,0 +1,34 @@
+# E2E Testing
+
+This example demonstrates e2e testing with Rust using executable requirements.
+
+## Testing Stack
+
+|    |      Role      |  Description |
+|---|---|---|
+| [Cucumber](https://github.com/cucumber-rs/cucumber/tree/main) | Test Runner | Run [Gherkin](https://cucumber.io/docs/gherkin/reference/) specifications as Rust tests |
+| [Fantoccini](https://github.com/jonhoo/fantoccini/tree/main) | Browser Client | Interact with web pages through WebDriver |
+| [Cargo Leptos](https://github.com/leptos-rs/cargo-leptos) | Build Tool |  Compile example and start the server and end-2-end tests |
+| [chromedriver](https://chromedriver.chromium.org/downloads) | WebDriver | Provide WebDriver for Chrome |
+
+## Testing Organization
+
+Testing is organized around what a user can do and see/not see. Test scenarios are grouped by the **user action** and the **object** of that action. This makes it easier to locate and reason about requirements.
+
+Here is a brief overview of how things fit together.
+
+```bash
+features
+└── {action}_{object}.feature   # Specify test scenarios
+tests
+├── fixtures
+│   ├── action.rs               # Perform a user action (click, type, etc.)
+│   ├── check.rs                # Assert what a user can see/not see
+│   ├── find.rs                 # Query page elements
+│   ├── mod.rs
+│   └── world
+│       ├── action_steps.rs     # Map Gherkin steps to user actions
+│       ├── check_steps.rs      # Map Gherkin steps to user expectations
+│       └── mod.rs
+└── app_suite.rs                # Test main
+```

examples/regression/e2e/features/issue_4005.feature

@@ -0,0 +1,7 @@
+@check_issue_4005
+Feature: Check that issue 4005 does not reappear
+
+	Scenario: The second item is selected.
+		Given I see the app
+		And I can access regression test 4005
+		Then I see the value of select is 2

examples/regression/e2e/features/issue_4088.feature

@@ -0,0 +1,20 @@
+@check_issue_4088
+Feature: Check that issue 4088 does not reappear
+
+	Scenario: I can see the navbar
+		Given I see the app
+		And I can access regression test 4088
+		Then I see the navbar
+
+	Scenario: The user info is shared via context
+		Given I see the app
+		And I can access regression test 4088
+		When I select the link Class 1
+		Then I see the result is the string Assignments for team of user with id 42
+
+	Scenario: The user info is shared via context
+		Given I see the app
+		And I can access regression test 4088
+		When I select the link Class 1
+		When I refresh the browser
+		Then I see the result is the string Assignments for team of user with id 42

examples/regression/e2e/features/issue_4217.feature

@@ -0,0 +1,9 @@
+@check_issue_4217
+Feature: Check that issue 4217 does not reappear
+
+	Scenario: All items are selected.
+		Given I see the app
+		And I can access regression test 4217
+		Then I see option1 is selected
+		And I see option2 is selected
+		And I see option3 is selected

examples/regression/e2e/features/issue_4285.feature

@@ -0,0 +1,9 @@
+@check_issue_4285
+Feature: Check that issue 4285 does not reappear
+
+	Scenario: Navigating several times to same lazy route does not cause issues.
+		Given I see the app
+		And I can access regression test 4285
+		And I can access regression test 4285
+		And I can access regression test 4285
+		Then I see the result is the string 42

examples/regression/e2e/features/issue_4296.feature

@@ -0,0 +1,18 @@
+@check_issue_4296
+Feature: Check that issue 4296 does not reappear
+
+	Scenario: Query param signals created in LazyRoute::data() are reactive in ::view().
+		Given I see the app
+		And I can access regression test 4296
+		Then I see the result is the string None
+		When I select the link abc
+		Then I see the result is the string Some("abc")
+		When I select the link def
+		Then I see the result is the string Some("def")
+
+	Scenario: Loading page with query signal works as well.
+		Given I see the app
+		And I can access regression test 4296
+		When I select the link abc
+		When I reload the page
+		Then I see the result is the string Some("abc")

examples/regression/e2e/features/pr_4015.feature

@@ -0,0 +1,8 @@
+@check_pr_4015
+Feature: Check that PR 4015 does not regress
+
+	Scenario: The correct text appears
+		Given I see the app
+		And I can access regression test 4015
+		Then I see the result is the string Some(42)
+

examples/regression/e2e/features/pr_4091.feature

@@ -0,0 +1,48 @@
+@check_pr_4091
+Feature: Regression from pull request 4091
+
+    Scenario: Signal for testing should work
+        Given I see the app
+        And I can access regression test 4091
+        When I select the link test1
+        Then I see the result is the string Test1
+
+    Scenario: The result returns to empty due to on_cleanup
+        Given I see the app
+        And I can access regression test 4091
+        When I select the following links
+            | test1     |
+            | 4091 Home |
+        Then I see the result is empty
+
+    Scenario: The result does not accumulate due to on_cleanup
+        Given I see the app
+        And I can access regression test 4091
+        When I select the following links
+            | test1     |
+            | 4091 Home |
+            | test1     |
+            | 4091 Home |
+        Then I see the result is empty
+
+    Scenario: I can see the navbar
+        Given I see the app
+        And I can access regression test 4091
+        Then I see the navbar
+
+    Scenario: If I navigate to home and back, I can still see the navbar
+        Given I see the app
+        And I can access regression test 4091
+        When I select the following links
+            | Home |
+            | 4091 |
+        Then I see the navbar
+
+    Scenario: The signal is not disposed too early
+        Given I see the app
+        And I can access regression test 4091
+        When I select the following links
+            | test1 |
+            | Home  |
+            | 4091  |
+        Then I see the navbar

examples/regression/e2e/tests/app_suite.rs

@@ -0,0 +1,30 @@
+mod fixtures;
+
+use anyhow::Result;
+use cucumber::World;
+use fixtures::world::AppWorld;
+use std::{ffi::OsStr, fs::read_dir};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    // Normally the below is done, but it's now gotten to the point of
+    // having a sufficient number of tests where the resource contention
+    // of the concurrently running browsers will cause failures on CI.
+    // AppWorld::cucumber()
+    //     .fail_on_skipped()
+    //     .run_and_exit("./features")
+    //     .await;
+
+    // Mitigate the issue by manually stepping through each feature,
+    // rather than letting cucumber glob them and dispatch all at once.
+    for entry in read_dir("./features")? {
+        let path = entry?.path();
+        if path.extension() == Some(OsStr::new("feature")) {
+            AppWorld::cucumber()
+                .fail_on_skipped()
+                .run_and_exit(path)
+                .await;
+        }
+    }
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/action.rs

@@ -0,0 +1,17 @@
+use super::{find, world::HOST};
+use anyhow::Result;
+use fantoccini::Client;
+use std::result::Result::Ok;
+
+pub async fn goto_path(client: &Client, path: &str) -> Result<()> {
+    let url = format!("{}{}", HOST, path);
+    client.goto(&url).await?;
+
+    Ok(())
+}
+
+pub async fn click_link(client: &Client, text: &str) -> Result<()> {
+    let link = find::link_with_text(&client, &text).await?;
+    link.click().await?;
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/check.rs

@@ -0,0 +1,45 @@
+use crate::fixtures::find;
+use anyhow::{Ok, Result};
+use fantoccini::Client;
+use pretty_assertions::assert_eq;
+
+pub async fn result_text_is(
+    client: &Client,
+    expected_text: &str,
+) -> Result<()> {
+    let actual = find::text_at_id(client, "result").await?;
+    assert_eq!(&actual, expected_text);
+    Ok(())
+}
+
+pub async fn element_exists(client: &Client, id: &str) -> Result<()> {
+    find::element_by_id(client, id)
+        .await
+        .expect(&format!("could not find element with id `{id}`"));
+    Ok(())
+}
+
+pub async fn select_option_is_selected(
+    client: &Client,
+    id: &str,
+) -> Result<()> {
+    let el = find::element_by_id(client, id)
+        .await
+        .expect(&format!("could not find element with id `{id}`"));
+    let selected = el.prop("selected").await?;
+    assert_eq!(selected.as_deref(), Some("true"));
+    Ok(())
+}
+
+pub async fn element_value_is(
+    client: &Client,
+    id: &str,
+    expected: &str,
+) -> Result<()> {
+    let el = find::element_by_id(client, id)
+        .await
+        .expect(&format!("could not find element with id `{id}`"));
+    let value = el.prop("value").await?;
+    assert_eq!(value.as_deref(), Some(expected));
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/find.rs

@@ -0,0 +1,23 @@
+use anyhow::{Ok, Result};
+use fantoccini::{elements::Element, Client, Locator};
+
+pub async fn text_at_id(client: &Client, id: &str) -> Result<String> {
+    let element = element_by_id(client, id)
+        .await
+        .expect(format!("no such element with id `{}`", id).as_str());
+    let text = element.text().await?;
+    Ok(text)
+}
+
+pub async fn link_with_text(client: &Client, text: &str) -> Result<Element> {
+    let link = client
+        .wait()
+        .for_element(Locator::LinkText(text))
+        .await
+        .expect(format!("Link not found by `{}`", text).as_str());
+    Ok(link)
+}
+
+pub async fn element_by_id(client: &Client, id: &str) -> Result<Element> {
+    Ok(client.wait().for_element(Locator::Id(id)).await?)
+}

examples/regression/e2e/tests/fixtures/mod.rs

@@ -0,0 +1,4 @@
+pub mod action;
+pub mod check;
+pub mod find;
+pub mod world;

examples/regression/e2e/tests/fixtures/world/action_steps.rs

@@ -0,0 +1,47 @@
+use crate::fixtures::{action, world::AppWorld};
+use anyhow::{Ok, Result};
+use cucumber::{gherkin::Step, given, when};
+
+#[given("I see the app")]
+#[when("I open the app")]
+async fn i_open_the_app(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    action::goto_path(client, "").await?;
+
+    Ok(())
+}
+
+#[given(regex = "^I can access regression test (.*)$")]
+#[when(regex = "^I select the link (.*)$")]
+async fn i_select_the_link(world: &mut AppWorld, text: String) -> Result<()> {
+    let client = &world.client;
+    action::click_link(client, &text).await?;
+
+    Ok(())
+}
+
+#[given(expr = "I select the following links")]
+#[when(expr = "I select the following links")]
+async fn i_select_the_following_links(
+    world: &mut AppWorld,
+    step: &Step,
+) -> Result<()> {
+    let client = &world.client;
+
+    if let Some(table) = step.table.as_ref() {
+        for row in table.rows.iter() {
+            action::click_link(client, &row[0]).await?;
+        }
+    }
+
+    Ok(())
+}
+
+#[given(regex = "^I (refresh|reload) the (browser|page)$")]
+#[when(regex = "^I (refresh|reload) the (browser|page)$")]
+async fn i_refresh_the_browser(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    client.refresh().await?;
+
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/world/check_steps.rs

@@ -0,0 +1,45 @@
+use crate::fixtures::{check, world::AppWorld};
+use anyhow::{Ok, Result};
+use cucumber::then;
+
+#[then(regex = r"^I see the result is empty$")]
+async fn i_see_the_result_is_empty(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    check::result_text_is(client, "").await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the result is the string (.*)$")]
+async fn i_see_the_result_is_the_string(
+    world: &mut AppWorld,
+    text: String,
+) -> Result<()> {
+    let client = &world.client;
+    check::result_text_is(client, &text).await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the navbar$")]
+async fn i_see_the_navbar(world: &mut AppWorld) -> Result<()> {
+    let client = &world.client;
+    check::element_exists(client, "nav").await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see ([\d\w]+) is selected$")]
+async fn i_see_the_select(world: &mut AppWorld, id: String) -> Result<()> {
+    let client = &world.client;
+    check::select_option_is_selected(client, &id).await?;
+    Ok(())
+}
+
+#[then(regex = r"^I see the value of (\w+) is (.*)$")]
+async fn i_see_the_value(
+    world: &mut AppWorld,
+    id: String,
+    value: String,
+) -> Result<()> {
+    let client = &world.client;
+    check::element_value_is(client, &id, &value).await?;
+    Ok(())
+}

examples/regression/e2e/tests/fixtures/world/mod.rs

@@ -0,0 +1,39 @@
+pub mod action_steps;
+pub mod check_steps;
+
+use anyhow::Result;
+use cucumber::World;
+use fantoccini::{
+    error::NewSessionError, wd::Capabilities, Client, ClientBuilder,
+};
+
+pub const HOST: &str = "http://127.0.0.1:3000";
+
+#[derive(Debug, World)]
+#[world(init = Self::new)]
+pub struct AppWorld {
+    pub client: Client,
+}
+
+impl AppWorld {
+    async fn new() -> Result<Self, anyhow::Error> {
+        let webdriver_client = build_client().await?;
+
+        Ok(Self {
+            client: webdriver_client,
+        })
+    }
+}
+
+async fn build_client() -> Result<Client, NewSessionError> {
+    let mut cap = Capabilities::new();
+    let arg = serde_json::from_str("{\"args\": [\"-headless\"]}").unwrap();
+    cap.insert("goog:chromeOptions".to_string(), arg);
+
+    let client = ClientBuilder::native()
+        .capabilities(cap)
+        .connect("http://localhost:4444")
+        .await?;
+
+    Ok(client)
+}

examples/regression/src/app.rs

@@ -0,0 +1,79 @@
+use crate::{
+    issue_4005::Routes4005, issue_4088::Routes4088, issue_4217::Routes4217,
+    issue_4285::Routes4285, issue_4296::Routes4296, pr_4015::Routes4015,
+    pr_4091::Routes4091,
+};
+use leptos::prelude::*;
+use leptos_meta::{MetaTags, *};
+use leptos_router::{
+    components::{Route, Router, Routes},
+    path,
+};
+
+pub fn shell(options: LeptosOptions) -> impl IntoView {
+    view! {
+        <!DOCTYPE html>
+        <html lang="en">
+            <head>
+                <meta charset="utf-8"/>
+                <meta name="viewport" content="width=device-width, initial-scale=1"/>
+                <AutoReload options=options.clone()/>
+                <HydrationScripts options/>
+                <MetaTags/>
+            </head>
+            <body>
+                <App/>
+            </body>
+        </html>
+    }
+}
+
+#[component]
+pub fn App() -> impl IntoView {
+    provide_meta_context();
+    let fallback = || view! { "Page not found." }.into_view();
+    let (_, set_is_routing) = signal(false);
+
+    view! {
+        <Stylesheet id="leptos" href="/pkg/regression.css"/>
+        <Router set_is_routing>
+            <main>
+                <Routes fallback>
+                    <Route path=path!("") view=HomePage/>
+                    <Routes4091/>
+                    <Routes4015/>
+                    <Routes4088/>
+                    <Routes4217/>
+                    <Routes4005/>
+                    <Routes4285/>
+                    <Routes4296/>
+                </Routes>
+            </main>
+        </Router>
+    }
+}
+
+#[server]
+async fn server_call() -> Result<(), ServerFnError> {
+    tokio::time::sleep(std::time::Duration::from_millis(1)).await;
+    Ok(())
+}
+
+#[component]
+fn HomePage() -> impl IntoView {
+    view! {
+        <Title text="Regression Tests"/>
+        <h1>"Listing of regression tests"</h1>
+        <nav>
+            <ul>
+                <li><a href="/4091/">"4091"</a></li>
+                <li><a href="/4015/">"4015"</a></li>
+                <li><a href="/4088/">"4088"</a></li>
+                <li><a href="/4217/">"4217"</a></li>
+                <li><a href="/4005/">"4005"</a></li>
+                <li><a href="/4285/">"4285"</a></li>
+                <li><a href="/4296/">"4296"</a></li>
+            </ul>
+        </nav>
+    }
+}

examples/regression/src/issue_4005.rs

@@ -0,0 +1,24 @@
+use leptos::prelude::*;
+#[allow(unused_imports)]
+use leptos_router::{
+    components::Route, path, MatchNestedRoutes, NavigateOptions,
+};
+
+#[component]
+pub fn Routes4005() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <Route path=path!("4005") view=Issue4005/>
+    }
+    .into_inner()
+}
+
+#[component]
+fn Issue4005() -> impl IntoView {
+    view! {
+        <select id="select" prop:value="2">
+            <option value="1">"Option 1"</option>
+            <option value="2">"Option 2"</option>
+            <option value="3">"Option 3"</option>
+        </select>
+    }
+}

examples/regression/src/issue_4088.rs

@@ -0,0 +1,119 @@
+use leptos::{either::Either, prelude::*};
+#[allow(unused_imports)]
+use leptos_router::{
+    components::{Outlet, ParentRoute, Redirect, Route},
+    path, MatchNestedRoutes, NavigateOptions,
+};
+use serde::{Deserialize, Serialize};
+
+#[component]
+pub fn Routes4088() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <ParentRoute path=path!("4088") view=|| view!{ <LoggedIn/> }>
+			<ParentRoute path=path!("") view=||view!{<AssignmentsSelector/>}>
+				<Route path=path!("/:team_id") view=||view!{<AssignmentsForTeam/>} />
+				<Route path=path!("") view=||view!{ <p>No class selected</p> }/>
+			</ParentRoute>
+        </ParentRoute>
+    }
+    .into_inner()
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct UserInfo {
+    pub id: usize,
+}
+
+#[server]
+pub async fn get_user_info() -> Result<Option<UserInfo>, ServerFnError> {
+    Ok(Some(UserInfo { id: 42 }))
+}
+
+#[component]
+pub fn LoggedIn() -> impl IntoView {
+    let user_info_resource =
+        Resource::new(|| (), move |_| async { get_user_info().await });
+
+    view! {
+
+      <Transition fallback=move || view!{
+            "loading"
+            }
+        >
+        {move || {
+            user_info_resource.get()
+                .map(|a|
+                    match a {
+                        Ok(Some(a)) => Either::Left(view! {
+                            <LoggedInContent user_info={a} />
+                        }),
+                        _ => Either::Right(view!{
+                            <Redirect path="/not_logged_in"/>
+                        })
+                    })
+        }}
+        </Transition>
+    }
+}
+
+#[component]
+/// Component which provides UserInfo and renders it's child
+/// Can also contain some code to check for specific situations (e.g. privacy policies accepted or not? redirect if needed...)
+pub fn LoggedInContent(user_info: UserInfo) -> impl IntoView {
+    provide_context(user_info.clone());
+
+    if user_info.id == 42 {
+        Either::Left(Outlet())
+    } else {
+        Either::Right(
+            view! { <Redirect path="/somewhere" options={NavigateOptions::default()}/> },
+        )
+    }
+}
+
+#[component]
+/// This component also uses Outlet (so nested Outlet)
+fn AssignmentsSelector() -> impl IntoView {
+    let user_info = use_context::<UserInfo>().expect("user info not provided");
+
+    view! {
+        <p>"Assignments for user with ID: "{user_info.id}</p>
+        <ul id="nav">
+            <li><a href="/4088/1">"Class 1"</a></li>
+            <li><a href="/4088/2">"Class 2"</a></li>
+            <li><a href="/4088/3">"Class 3"</a></li>
+        </ul>
+
+        <Outlet />
+    }
+}
+
+#[component]
+fn AssignmentsForTeam() -> impl IntoView {
+    // THIS FAILS -> Because of the nested outlet in LoggedInContent > AssignmentsSelector?
+    // It did not fail when LoggedIn did not use a resource and transition (but a hardcoded UserInfo in the component)
+    let user_info = use_context::<UserInfo>().expect("user info not provided");
+
+    let items = vec!["Assignment 1", "Assignment 2", "Assignment 3"];
+    view! {
+        <p id="result">"Assignments for team of user with id " {user_info.id}</p>
+        <ul>
+            {
+            items.into_iter().map(|item| {
+                view! {
+                    <Assignment name=item.to_string() />
+                }
+            }).collect_view()
+            }
+        </ul>
+    }
+}
+
+#[component]
+fn Assignment(name: String) -> impl IntoView {
+    let user_info = use_context::<UserInfo>().expect("user info not provided");
+
+    view! {
+        <li>{name}" "{user_info.id}</li>
+    }
+}

examples/regression/src/issue_4217.rs

@@ -0,0 +1,24 @@
+use leptos::prelude::*;
+#[allow(unused_imports)]
+use leptos_router::{
+    components::Route, path, MatchNestedRoutes, NavigateOptions,
+};
+
+#[component]
+pub fn Routes4217() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <Route path=path!("4217") view=Issue4217/>
+    }
+    .into_inner()
+}
+
+#[component]
+fn Issue4217() -> impl IntoView {
+    view! {
+        <select multiple=true>
+            <option id="option1" value="1" selected>"Option 1"</option>
+            <option id="option2" value="2" selected>"Option 2"</option>
+            <option id="option3" value="3" selected>"Option 3"</option>
+        </select>
+    }
+}

examples/regression/src/issue_4285.rs

@@ -0,0 +1,49 @@
+use leptos::prelude::*;
+use leptos_router::LazyRoute;
+#[allow(unused_imports)]
+use leptos_router::{
+    components::Route, path, Lazy, MatchNestedRoutes, NavigateOptions,
+};
+
+#[component]
+pub fn Routes4285() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <Route path=path!("4285") view={Lazy::<Issue4285>::new()}/>
+    }
+    .into_inner()
+}
+
+struct Issue4285 {
+    data: Resource<Result<i32, ServerFnError>>,
+}
+
+impl LazyRoute for Issue4285 {
+    fn data() -> Self {
+        Self {
+            data: Resource::new(|| (), |_| slow_call()),
+        }
+    }
+
+    async fn view(this: Self) -> AnyView {
+        let Issue4285 { data } = this;
+        view! {
+            <Suspense>
+                {move || {
+                    Suspend::new(async move {
+                        let data = data.await;
+                        view! {
+                            <p id="result">{data}</p>
+                        }
+                    })
+                }}
+            </Suspense>
+        }
+        .into_any()
+    }
+}
+
+#[server]
+async fn slow_call() -> Result<i32, ServerFnError> {
+    tokio::time::sleep(std::time::Duration::from_millis(250)).await;
+    Ok(42)
+}

examples/regression/src/issue_4296.rs

@@ -0,0 +1,36 @@
+use leptos::prelude::*;
+#[allow(unused_imports)]
+use leptos_router::{
+    components::Route, path, Lazy, MatchNestedRoutes, NavigateOptions,
+};
+use leptos_router::{hooks::use_query_map, LazyRoute};
+
+#[component]
+pub fn Routes4296() -> impl MatchNestedRoutes + Clone {
+    view! {
+        <Route path=path!("4296") view={Lazy::<Issue4296>::new()}/>
+    }
+    .into_inner()
+}
+
+struct Issue4296 {
+    query: Signal<Option<String>>,
+}
+
+impl LazyRoute for Issue4296 {
+    fn data() -> Self {
+        let query = use_query_map();
+        let query = Signal::derive(move || query.read().get("q"));
+        Self { query }
+    }
+
+    async fn view(this: Self) -> AnyView {
+        let Issue4296 { query } = this;
+        view! {
+            <a href="?q=abc">"abc"</a>
+            <a href="?q=def">"def"</a>
+            <p id="result">{move || format!("{:?}", query.get())}</p>
+        }
+        .into_any()
+    }
+}

examples/regression/src/lib.rs

@@ -0,0 +1,16 @@
+pub mod app;
+mod issue_4005;
+mod issue_4088;
+mod issue_4217;
+mod issue_4285;
+mod issue_4296;
+mod pr_4015;
+mod pr_4091;
+
+#[cfg(feature = "hydrate")]
+#[wasm_bindgen::prelude::wasm_bindgen]
+pub fn hydrate() {
+    use app::*;
+    console_error_panic_hook::set_once();
+    leptos::mount::hydrate_body(App);
+}

examples/regression/src/main.rs

@@ -0,0 +1,37 @@
+#[cfg(feature = "ssr")]
+#[tokio::main]
+async fn main() {
+    use axum::Router;
+    use leptos::prelude::*;
+    use leptos_axum::{generate_route_list, LeptosRoutes};
+    use regression::app::{shell, App};
+
+    let conf = get_configuration(None).unwrap();
+    let addr = conf.leptos_options.site_addr;
+    let leptos_options = conf.leptos_options;
+    // Generate the list of routes in your Leptos App
+    let routes = generate_route_list(App);
+
+    let app = Router::new()
+        .leptos_routes(&leptos_options, routes, {
+            let leptos_options = leptos_options.clone();
+            move || shell(leptos_options.clone())
+        })
+        .fallback(leptos_axum::file_and_error_handler(shell))
+        .with_state(leptos_options);
+
+    // run our app with hyper
+    // `axum::Server` is a re-export of `hyper::Server`
+    println!("listening on http://{}", &addr);
+    let listener = tokio::net::TcpListener::bind(&addr).await.unwrap();
+    axum::serve(listener, app.into_make_service())
+        .await
+        .unwrap();
+}
+
+#[cfg(not(feature = "ssr"))]
+pub fn main() {
+    // no client-side main function
+    // unless we want this to work with e.g., Trunk for pure client-side testing
+    // see lib.rs for hydration function instead
+}

examples/regression/src/pr_4015.rs

@@ -0,0 +1,29 @@
+use leptos::{context::Provider, prelude::*};
+use leptos_router::{
+    components::{ParentRoute, Route},
+    nested_router::Outlet,
+    path,
+};
+
+#[component]
+pub fn Routes4015() -> impl leptos_router::MatchNestedRoutes + Clone {
+    view! {
+        <ParentRoute path=path!("4015") view=|| view! {
+            <Provider value=42i32>
+                <Outlet/>
+            </Provider>
+        }>
+            <Route path=path!("") view=Child/>
+        </ParentRoute>
+    }
+    .into_inner()
+}
+
+#[component]
+fn Child() -> impl IntoView {
+    let value = use_context::<i32>();
+
+    view! {
+        <p id="result">{format!("{value:?}")}</p>
+    }
+}

examples/regression/src/pr_4091.rs

@@ -0,0 +1,68 @@
+use leptos::{context::Provider, prelude::*};
+use leptos_router::{
+    components::{ParentRoute, Route, A},
+    nested_router::Outlet,
+    path,
+};
+
+// FIXME This should be a set rather than a naive vec for push and pop, as
+// it may be possible for unexpected token be popped/pushed on multi-level
+// navigation.  For basic naive tests it should be Fine(TM).
+#[derive(Clone)]
+struct Expectations(Vec<&'static str>);
+
+#[component]
+pub fn Routes4091() -> impl leptos_router::MatchNestedRoutes + Clone {
+    view! {
+        <ParentRoute path=path!("4091") view=Container>
+            <Route path=path!("") view=Root/>
+            <Route path=path!("test1") view=Test1/>
+        </ParentRoute>
+    }
+    .into_inner()
+}
+
+#[component]
+fn Container() -> impl IntoView {
+    let rw_signal = RwSignal::new(Expectations(Vec::new()));
+    provide_context(rw_signal);
+
+    view! {
+        <nav id="nav">
+            <ul>
+                <li><A href="/">"Home"</A></li>
+                <li><A href="./">"4091 Home"</A></li>
+                <li><A href="test1">"test1"</A></li>
+            </ul>
+        </nav>
+        <div id="result">{move || {
+            rw_signal.with(|ex| ex.0.iter().fold(String::new(), |a, b| a + b + " "))
+        }}</div>
+        <Provider value=rw_signal>
+            <Outlet/>
+        </Provider>
+    }
+}
+
+#[component]
+fn Root() -> impl IntoView {
+    view! {
+        <div>"This is Root"</div>
+    }
+}
+
+#[component]
+fn Test1() -> impl IntoView {
+    let signal = expect_context::<RwSignal<Expectations>>();
+
+    on_cleanup(move || {
+        signal.update(|ex| {
+            ex.0.pop();
+        });
+    });
+
+    view! {
+        {move || signal.update(|ex| ex.0.push("Test1"))}
+        <div>"This is Test1"</div>
+    }
+}

examples/regression/style/main.scss

@@ -0,0 +1,3 @@
+body {
+    font-family: sans-serif;
+}

examples/server_fns_axum/Cargo.toml

@@ -29,7 +29,7 @@ tower-http = { version = "0.6.2", features = [
   "trace",
 ], optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
-thiserror = "2.0.11"
+thiserror = "2.0.12"
 wasm-bindgen = "0.2.93"
 serde_toml = "0.0.1"
 toml = "0.8.19"

examples/ssr_modes/Cargo.toml

@@ -2,8 +2,6 @@
 name = "ssr_modes"
 version = "0.1.0"
 edition = "2021"
-# std::sync::LazyLock is stabilized in Rust version 1.80.0
-rust-version = "1.80.0"
 
 [lib]
 crate-type = ["cdylib", "rlib"]
@@ -19,7 +17,7 @@ leptos_actix = { path = "../../integrations/actix", optional = true }
 leptos_router = { path = "../../router" }
 log = "0.4.22"
 serde = { version = "1.0", features = ["derive"] }
-thiserror = "1.0"
+thiserror = "2.0.12"
 tokio = { version = "1.39", features = ["time"] }
 wasm-bindgen = "0.2.93"
 

examples/ssr_modes_axum/Cargo.toml

@@ -2,8 +2,6 @@
 name = "ssr_modes_axum"
 version = "0.1.0"
 edition = "2021"
-# std::sync::LazyLock is stabilized in Rust version 1.80.0
-rust-version = "1.80.0"
 
 [lib]
 crate-type = ["cdylib", "rlib"]
@@ -19,7 +17,7 @@ leptos_axum = { path = "../../integrations/axum", optional = true }
 leptos_router = { path = "../../router" }
 log = "0.4.22"
 serde = { version = "1.0", features = ["derive"] }
-thiserror = "1.0"
+thiserror = "2.0.12"
 axum = { version = "0.8.1", optional = true }
 tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }

examples/static_routing/Cargo.toml

@@ -17,7 +17,7 @@ leptos_axum = { path = "../../integrations/axum", optional = true }
 leptos_router = { path = "../../router" }
 log = "0.4.22"
 serde = { version = "1.0", features = ["derive"] }
-thiserror = "1.0"
+thiserror = "2.0.12"
 axum = { version = "0.8.1", optional = true }
 tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }

examples/stores/src/lib.rs

@@ -159,7 +159,7 @@ fn TodoRow(
 
     view! {
         <li style:text-decoration=move || {
-            status.done().then_some("line-through").unwrap_or_default()
+          if status.done() { "line-through" } else { Default::default() }
         }>
 
             <p

examples/tailwind_axum/Cargo.toml

@@ -20,7 +20,7 @@ tokio = { version = "1.39", features = [
 tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }
 wasm-bindgen = "0.2.93"
-thiserror = "1.0"
+thiserror = "2.0.12"
 tracing = { version = "0.1.40", optional = true }
 http = "1.1"
 

examples/todo_app_sqlite/Cargo.toml

@@ -20,7 +20,7 @@ leptos_actix = { path = "../../integrations/actix", optional = true }
 log = "0.4.22"
 simple_logger = "5.0"
 gloo = { git = "https://github.com/rustwasm/gloo" }
-sqlx = { version = "0.8.0", features = [
+sqlx = { version = "0.8.6", features = [
   "runtime-tokio-rustls",
   "sqlite",
 ], optional = true }
@@ -44,12 +44,12 @@ denylist = ["actix-files", "actix-web", "leptos_actix", "sqlx"]
 skip_feature_sets = [["csr", "ssr"], ["csr", "hydrate"], ["ssr", "hydrate"], []]
 
 [package.metadata.leptos]
-# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name   
+# The name used by wasm-bindgen/cargo-leptos for the JS/WASM bundle. Defaults to the crate name
 output-name = "todo_app_sqlite"
 # The site root folder is where cargo-leptos generate all output. WARNING: all content of this folder will be erased on a rebuild. Use it in your server setup.
 site-root = "target/site"
 # The site-root relative folder where all compiled output (JS, WASM and CSS) is written
-# Defaults to pkg	
+# Defaults to pkg
 site-pkg-dir = "pkg"
 # [Optional] The source CSS file. If it ends with .sass or .scss then it will be compiled by dart-sass into CSS. The CSS is optimized by Lightning CSS before being written to <site-root>/<site-pkg>/app.css
 style-file = "./style.css"

examples/todo_app_sqlite_axum/Cargo.toml

@@ -20,11 +20,11 @@ axum = { version = "0.8.1", optional = true }
 tower = { version = "0.4.13", optional = true }
 tower-http = { version = "0.5.2", features = ["fs"], optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
-sqlx = { version = "0.8.0", features = [
+sqlx = { version = "0.8.6", features = [
   "runtime-tokio-rustls",
   "sqlite",
 ], optional = true }
-thiserror = "1.0"
+thiserror = "2.0.12"
 wasm-bindgen = "0.2.93"
 
 [features]

examples/todo_app_sqlite_csr/Cargo.toml

@@ -20,11 +20,11 @@ tower = { version = "0.5.1", features = ["util"], optional = true }
 tower-http = { version = "0.6.1", features = ["fs"], optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
 http = { version = "1.1" }
-sqlx = { version = "0.8.0", features = [
+sqlx = { version = "0.8.6", features = [
   "runtime-tokio-rustls",
   "sqlite",
 ], optional = true }
-thiserror = "2.0"
+thiserror = "2.0.12"
 wasm-bindgen = "0.2.93"
 
 [features]

examples/websocket/Cargo.toml

@@ -17,7 +17,7 @@ simple_logger = "5.0"
 serde = { version = "1.0", features = ["derive"] }
 axum = { version = "0.8.1", optional = true }
 tokio = { version = "1.39", features = ["full"], optional = true }
-thiserror = "2.0"
+thiserror = "2.0.12"
 wasm-bindgen = "0.2.100"
 
 [features]

integrations/actix/Cargo.toml

@@ -4,14 +4,14 @@ authors = ["Greg Johnston"]
 license = "MIT"
 repository = "https://github.com/leptos-rs/leptos"
 description = "Actix integrations for the Leptos web framework."
-version = { workspace = true }
+version = "0.8.5"
 rust-version.workspace = true
 edition.workspace = true
 
 [dependencies]
 actix-http = { workspace = true, default-features = true }
 actix-files = { workspace = true, default-features = true }
-actix-web = { workspace = true, default-features = true }
+actix-web = { workspace = true, default-features = false }
 futures = { workspace = true, default-features = true }
 any_spawner = { workspace = true, features = ["tokio"] }
 hydration_context = { workspace = true }
@@ -20,12 +20,12 @@ leptos_integration_utils = { workspace = true }
 leptos_macro = { workspace = true, features = ["actix"] }
 leptos_meta = { workspace = true, features = ["nonce"] }
 leptos_router = { workspace = true, features = ["ssr"] }
-server_fn = { workspace = true, features = ["actix"] }
+server_fn = { workspace = true, features = ["actix-no-default"] }
 tachys = { workspace = true }
-serde_json = { workspace = true , default-features = true }
+serde_json = { workspace = true, default-features = true }
 parking_lot = { workspace = true, default-features = true }
-tracing = { optional = true , workspace = true, default-features = true }
-tokio = { features = ["rt", "fs"] , workspace = true, default-features = true }
+tracing = { optional = true, workspace = true, default-features = true }
+tokio = { features = ["rt", "fs"], workspace = true, default-features = true }
 send_wrapper = { workspace = true, default-features = true }
 dashmap = { workspace = true, default-features = true }
 
@@ -33,6 +33,8 @@ dashmap = { workspace = true, default-features = true }
 rustdoc-args = ["--generate-link-to-definition"]
 
 [features]
+default = ["actix-default"]
+actix-default = ["actix-web/default"]
 islands-router = ["tachys/islands"]
 tracing = ["dep:tracing"]
 

integrations/actix/src/lib.rs

@@ -282,6 +282,7 @@ pub fn redirect(path: &str) {
 ///   // call ServerFn::register() for each of the server functions you've defined
 /// }
 ///
+/// # #[cfg(feature = "default")]
 /// #[actix_web::main]
 /// async fn main() -> std::io::Result<()> {
 ///     // make sure you actually register your server functions
@@ -297,6 +298,8 @@ pub fn redirect(path: &str) {
 ///     .run()
 ///     .await
 /// }
+/// # #[cfg(not(feature = "default"))]
+/// # fn main() {}
 /// ```
 ///
 /// ## Provided Context Types
@@ -442,6 +445,7 @@ pub fn handle_server_fns_with_context(
 ///     view! { <main>"Hello, world!"</main> }
 /// }
 ///
+/// # #[cfg(feature = "default")]
 /// #[actix_web::main]
 /// async fn main() -> std::io::Result<()> {
 ///     let conf = get_configuration(Some("Cargo.toml")).unwrap();
@@ -461,6 +465,8 @@ pub fn handle_server_fns_with_context(
 ///     .run()
 ///     .await
 /// }
+/// # #[cfg(not(feature = "default"))]
+/// # fn main() {}
 /// ```
 ///
 /// ## Provided Context Types
@@ -499,6 +505,7 @@ where
 ///     view! { <main>"Hello, world!"</main> }
 /// }
 ///
+/// # #[cfg(feature = "default")]
 /// #[actix_web::main]
 /// async fn main() -> std::io::Result<()> {
 ///     let conf = get_configuration(Some("Cargo.toml")).unwrap();
@@ -521,6 +528,9 @@ where
 ///     .run()
 ///     .await
 /// }
+///
+/// # #[cfg(not(feature = "default"))]
+/// # fn main() {}
 /// ```
 ///
 /// ## Provided Context Types
@@ -557,6 +567,7 @@ where
 ///     view! { <main>"Hello, world!"</main> }
 /// }
 ///
+/// # #[cfg(feature = "default")]
 /// #[actix_web::main]
 /// async fn main() -> std::io::Result<()> {
 ///     let conf = get_configuration(Some("Cargo.toml")).unwrap();
@@ -576,6 +587,8 @@ where
 ///     .run()
 ///     .await
 /// }
+/// # #[cfg(not(feature = "default"))]
+/// # fn main() {}
 /// ```
 ///
 /// ## Provided Context Types

integrations/axum/Cargo.toml

@@ -4,7 +4,7 @@ authors = ["Greg Johnston"]
 license = "MIT"
 repository = "https://github.com/leptos-rs/leptos"
 description = "Axum integrations for the Leptos web framework."
-version = "0.8.2"
+version = "0.8.6"
 rust-version.workspace = true
 edition.workspace = true
 
@@ -13,7 +13,7 @@ any_spawner = { workspace = true, features = ["tokio"] }
 hydration_context = { workspace = true }
 axum = { default-features = false, features = [
   "matched-path",
-] , workspace = true }
+], workspace = true }
 dashmap = { workspace = true, default-features = true }
 futures = { workspace = true, default-features = true }
 leptos = { workspace = true, features = ["nonce", "ssr"] }
@@ -24,14 +24,17 @@ leptos_router = { workspace = true, features = ["ssr"] }
 leptos_integration_utils = { workspace = true }
 tachys = { workspace = true }
 parking_lot = { workspace = true, default-features = true }
-tokio = { default-features = false , workspace = true }
-tower = { features = ["util"] , workspace = true, default-features = true }
+tokio = { default-features = false, workspace = true }
+tower = { features = ["util"], workspace = true, default-features = true }
 tower-http = { workspace = true, default-features = true }
-tracing = { optional = true , workspace = true, default-features = true }
+tracing = { optional = true, workspace = true, default-features = true }
 
 [dev-dependencies]
 axum = { workspace = true, default-features = true }
-tokio = { features = ["net", "rt-multi-thread"] , workspace = true, default-features = true }
+tokio = { features = [
+  "net",
+  "rt-multi-thread",
+], workspace = true, default-features = true }
 
 [features]
 wasm = []

integrations/axum/src/lib.rs

@@ -1177,7 +1177,7 @@ where
     generate_route_list_with_exclusions_and_ssg(app_fn, None).0
 }
 
-/// Generates a list of all routes defined in Leptos's Router in your app. We can then use t.clone()his to automatically
+/// Generates a list of all routes defined in Leptos's Router in your app. We can then use this to automatically
 /// create routes in Axum's Router without having to use wildcard matching or fallbacks. Takes in your root app Element
 /// as an argument so it can walk you app tree. This version is tailored to generate Axum compatible paths.
 #[cfg_attr(
@@ -2061,10 +2061,12 @@ where
                         req,
                         |app, chunks, _supports_ooo| {
                             Box::pin(async move {
-                                let app = app
-                                    .to_html_stream_in_order()
-                                    .collect::<String>()
-                                    .await;
+                                let app = if cfg!(feature = "islands-router") {
+                                    app.to_html_stream_in_order_branching()
+                                } else {
+                                    app.to_html_stream_in_order()
+                                };
+                                let app = app.collect::<String>().await;
                                 let chunks = chunks();
                                 Box::pin(once(async move { app }).chain(chunks))
                                     as PinnedStream<String>

integrations/utils/Cargo.toml

@@ -4,7 +4,7 @@ authors = ["Greg Johnston"]
 license = "MIT"
 repository = "https://github.com/leptos-rs/leptos"
 description = "Utilities to help build server integrations for the Leptos web framework."
-version = { workspace = true }
+version = "0.8.5"
 rust-version.workspace = true
 edition.workspace = true
 

integrations/utils/src/lib.rs

@@ -3,12 +3,14 @@
 use futures::{stream::once, Stream, StreamExt};
 use hydration_context::{SharedContext, SsrSharedContext};
 use leptos::{
+    context::provide_context,
     nonce::use_nonce,
+    prelude::ReadValue,
     reactive::owner::{Owner, Sandboxed},
-    IntoView,
+    IntoView, PrefetchLazyFn, WasmSplitManifest,
 };
 use leptos_config::LeptosOptions;
-use leptos_meta::ServerMetaContextOutput;
+use leptos_meta::{Link, ServerMetaContextOutput};
 use std::{future::Future, pin::Pin, sync::Arc};
 
 pub type PinnedStream<T> = Pin<Box<dyn Stream<Item = T> + Send>>;
@@ -41,6 +43,8 @@ pub trait ExtendResponse: Sized {
         IV: IntoView + 'static,
     {
         async move {
+            let prefetches = PrefetchLazyFn::default();
+
             let (owner, stream) = build_response(
                 app_fn,
                 additional_context,
@@ -48,6 +52,8 @@ pub trait ExtendResponse: Sized {
                 supports_ooo,
             );
 
+            owner.with(|| provide_context(prefetches.clone()));
+
             let sc = owner.shared_context().unwrap();
 
             let stream = stream.await.ready_chunks(32).map(|n| n.join(""));
@@ -56,6 +62,40 @@ pub trait ExtendResponse: Sized {
                 pending.await;
             }
 
+            if !prefetches.0.read_value().is_empty() {
+                use leptos::prelude::*;
+
+                let nonce =
+                    use_nonce().map(|n| n.to_string()).unwrap_or_default();
+                if let Some(manifest) = use_context::<WasmSplitManifest>() {
+                    let (pkg_path, manifest) = &*manifest.0.read_value();
+                    let prefetches = prefetches.0.read_value();
+
+                    let all_prefetches = prefetches.iter().flat_map(|key| {
+                        manifest.get(*key).into_iter().flatten()
+                    });
+
+                    for module in all_prefetches {
+                        // to_html() on leptos_meta components registers them with the meta context,
+                        // rather than returning HTML directly
+                        _ = view! {
+                            <Link
+                                rel="preload"
+                                href=format!("{pkg_path}/{module}.wasm")
+                                as_="fetch"
+                                type_="application/wasm"
+                                crossorigin=nonce.clone()
+                            />
+                        }
+                        .to_html();
+                    }
+                    _ = view! {
+                        <Link rel="modulepreload" href=format!("{pkg_path}/__wasm_split.js") crossorigin=nonce/>
+                    }
+                    .to_html();
+                }
+            }
+
             let mut stream = Box::pin(
                 meta_context.inject_meta_context(stream).await.then({
                     let sc = Arc::clone(&sc);

leptos/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "leptos"
-version = { workspace = true }
+version = "0.8.8"
 authors = ["Greg Johnston"]
 license = "MIT"
 repository = "https://github.com/leptos-rs/leptos"
@@ -24,14 +24,14 @@ leptos_hot_reload = { workspace = true }
 leptos_macro = { workspace = true }
 leptos_server = { workspace = true, features = ["tachys"] }
 leptos_config = { workspace = true }
-leptos-spin-macro = { optional = true , workspace = true, default-features = true }
+leptos-spin-macro = { optional = true, workspace = true, default-features = true }
 oco_ref = { workspace = true }
 or_poisoned = { workspace = true }
 paste = { workspace = true, default-features = true }
-rand = { optional = true , workspace = true, default-features = true }
+rand = { optional = true, workspace = true, default-features = true }
 # NOTE: While not used directly, `getrandom`'s `wasm_js` feature is needed when `rand` is used on WASM to
 #       avoid a compilation error
-getrandom = { optional = true , workspace = true, default-features = true }
+getrandom = { optional = true, workspace = true, default-features = true }
 reactive_graph = { workspace = true, features = ["serde"] }
 rustc-hash = { workspace = true, default-features = true }
 tachys = { workspace = true, features = [
@@ -44,7 +44,7 @@ tracing = { optional = true, workspace = true, default-features = true }
 typed-builder = { workspace = true, default-features = true }
 typed-builder-macro = { workspace = true, default-features = true }
 serde = { workspace = true, default-features = true }
-serde_json = { optional = true, workspace = true, default-features = true }
+serde_json = { workspace = true, default-features = true }
 server_fn = { workspace = true, features = ["form-redirects", "browser"] }
 web-sys = { features = [
   "ShadowRoot",
@@ -52,10 +52,12 @@ web-sys = { features = [
   "ShadowRootMode",
 ], workspace = true, default-features = true }
 wasm-bindgen = { workspace = true, default-features = true }
+wasm-bindgen-futures = { workspace = true, default-features = true }
 serde_qs = { workspace = true, default-features = true }
 slotmap = { workspace = true, default-features = true }
 futures = { workspace = true, default-features = true }
 send_wrapper = { workspace = true, default-features = true }
+wasm_split_helpers.workspace = true
 
 [features]
 hydration = [
@@ -93,7 +95,7 @@ tracing = [
 ]
 nonce = ["base64", "rand", "dep:getrandom"]
 spin = ["leptos-spin-macro"]
-islands = ["leptos_macro/islands", "dep:serde_json"]
+islands = ["leptos_macro/islands"]
 trace-component-props = [
   "leptos_macro/trace-component-props",
   "leptos_dom/trace-component-props",
@@ -102,7 +104,10 @@ delegation = ["tachys/delegation"]
 islands-router = ["tachys/mark_branches"]
 
 [dev-dependencies]
-tokio = { features = ["rt-multi-thread", "macros"] , workspace = true, default-features = true }
+tokio = { features = [
+  "rt-multi-thread",
+  "macros",
+], workspace = true, default-features = true }
 tokio-test = { workspace = true, default-features = true }
 any_spawner = { workspace = true, features = ["futures-executor", "tokio"] }
 

leptos/src/attribute_interceptor.rs

@@ -157,6 +157,14 @@ impl<T: IntoView + 'static, A: Attribute> RenderHtml
         self.children.hydrate::<FROM_SERVER>(cursor, position)
     }
 
+    async fn hydrate_async(
+        self,
+        cursor: &leptos::tachys::hydration::Cursor,
+        position: &leptos::tachys::view::PositionState,
+    ) -> Self::State {
+        self.children.hydrate_async(cursor, position).await
+    }
+
     fn into_owned(self) -> Self::Owned {
         AttributeInterceptorInner {
             children_builder: self.children_builder,

leptos/src/children.rs

@@ -262,6 +262,16 @@ where
     }
 }
 
+impl<C> From<View<C>> for ViewFn
+where
+    C: Clone + Send + Sync + 'static,
+    View<C>: IntoAny,
+{
+    fn from(value: View<C>) -> Self {
+        Self(Arc::new(move || value.clone().into_any()))
+    }
+}
+
 impl ViewFn {
     /// Execute the wrapped function
     pub fn run(&self) -> AnyView {
@@ -289,6 +299,16 @@ where
     }
 }
 
+impl<C> From<View<C>> for ViewFnOnce
+where
+    C: Send + Sync + 'static,
+    View<C>: IntoAny,
+{
+    fn from(value: View<C>) -> Self {
+        Self(Box::new(move || value.into_any()))
+    }
+}
+
 impl ViewFnOnce {
     /// Execute the wrapped function
     pub fn run(self) -> AnyView {

leptos/src/error_boundary.rs

@@ -2,6 +2,7 @@ use crate::{children::TypedChildren, IntoView};
 use futures::{channel::oneshot, future::join_all};
 use hydration_context::{SerializedDataId, SharedContext};
 use leptos_macro::component;
+use or_poisoned::OrPoisoned;
 use reactive_graph::{
     computed::ArcMemo,
     effect::RenderEffect,
@@ -10,7 +11,12 @@ use reactive_graph::{
     traits::{Get, Update, With, WithUntracked, WriteValue},
 };
 use rustc_hash::FxHashMap;
-use std::{collections::VecDeque, fmt::Debug, mem, sync::Arc};
+use std::{
+    collections::VecDeque,
+    fmt::Debug,
+    mem,
+    sync::{Arc, Mutex},
+};
 use tachys::{
     html::attribute::{any_attribute::AnyAttribute, Attribute},
     hydration::Cursor,
@@ -508,6 +514,79 @@ where
         )
     }
 
+    async fn hydrate_async(
+        self,
+        cursor: &Cursor,
+        position: &PositionState,
+    ) -> Self::State {
+        let mut children = Some(self.children);
+        let hook = Arc::clone(&self.hook);
+        let cursor = cursor.to_owned();
+        let position = position.to_owned();
+
+        let fallback_fn = Arc::new(Mutex::new(self.fallback));
+        let initial = {
+            let errors_empty = self.errors_empty.clone();
+            let errors = self.errors.clone();
+            let fallback_fn = Arc::clone(&fallback_fn);
+            async move {
+                let children = children.take().unwrap();
+                let (children, fallback) = if errors_empty.get() {
+                    (children.hydrate_async(&cursor, &position).await, None)
+                } else {
+                    let children = children.build();
+                    let fallback =
+                        (fallback_fn.lock().or_poisoned())(errors.clone());
+                    let fallback =
+                        fallback.hydrate_async(&cursor, &position).await;
+                    (children, Some(fallback))
+                };
+
+                ErrorBoundaryViewState { children, fallback }
+            }
+        };
+
+        RenderEffect::new_with_async_value(
+            move |prev: Option<
+                ErrorBoundaryViewState<Chil::State, Fal::State>,
+            >| {
+                let _hook = throw_error::set_error_hook(Arc::clone(&hook));
+                if let Some(mut state) = prev {
+                    match (self.errors_empty.get(), &mut state.fallback) {
+                        // no errors, and was showing fallback
+                        (true, Some(fallback)) => {
+                            fallback.insert_before_this(&mut state.children);
+                            state.fallback.unmount();
+                            state.fallback = None;
+                        }
+                        // yes errors, and was showing children
+                        (false, None) => {
+                            state.fallback = Some(
+                                (fallback_fn.lock().or_poisoned())(
+                                    self.errors.clone(),
+                                )
+                                .build(),
+                            );
+                            state
+                                .children
+                                .insert_before_this(&mut state.fallback);
+                            state.children.unmount();
+                        }
+                        // either there were no errors, and we were already showing the children
+                        // or there are errors, but we were already showing the fallback
+                        // in either case, rebuilding doesn't require us to do anything
+                        _ => {}
+                    }
+                    state
+                } else {
+                    unreachable!()
+                }
+            },
+            initial,
+        )
+        .await
+    }
+
     fn into_owned(self) -> Self::Owned {
         self
     }

leptos/src/hydration/island_script.js

@@ -8,46 +8,49 @@
 			c();
 		}
 	}
-	function hydrateIslands(rootNode, mod) {
-		function traverse(node) {
+	async function hydrateIslands(rootNode, mod) {
+		async function traverse(node) {
 			if (node.nodeType === Node.ELEMENT_NODE) {
 				const tag = node.tagName.toLowerCase();
 				if(tag === 'leptos-island') {
 					const children = [];
 					const id = node.dataset.component || null;
 
-					hydrateIsland(node, id, mod);
+					await hydrateIsland(node, id, mod);
 					
 					for(const child of node.children) {
-						traverse(child, children);
+						await traverse(child, children);
 					}
 				} else {
 					if (tag === 'leptos-children') {
 						MOST_RECENT_CHILDREN_CB.push(node.$$on_hydrate);
 						for(const child of node.children) {
-							traverse(child);
+							await traverse(child);
 						};
 						// un-set the "most recent children"
 						MOST_RECENT_CHILDREN_CB.pop();
 					} else {
 						for(const child of node.children) {
-							traverse(child);
+							await traverse(child);
 						};
 					}
 				}
 			}
 		}
 
-		traverse(rootNode);
+		await traverse(rootNode);
 	}
-	function hydrateIsland(el, id, mod) {
+	async function hydrateIsland(el, id, mod) {
 		const islandFn = mod[id];
 		if (islandFn) {
 			const children_cb = MOST_RECENT_CHILDREN_CB[MOST_RECENT_CHILDREN_CB.length-1];
 			if (children_cb) {
 				children_cb();
 			}
-			islandFn(el);
+			const res = islandFn(el);
+			if (res && res.then) {
+				await res;
+			}
 		} else {
 			console.warn(`Could not find WASM function for the island ${id}.`);
 		}

leptos/src/hydration/mod.rs

@@ -1,8 +1,9 @@
 #![allow(clippy::needless_lifetimes)]
 
-use crate::prelude::*;
+use crate::{prelude::*, WasmSplitManifest};
 use leptos_config::LeptosOptions;
 use leptos_macro::{component, view};
+use std::{path::PathBuf, sync::OnceLock};
 
 /// Inserts auto-reloading code used in `cargo-leptos`.
 ///
@@ -58,6 +59,29 @@ pub fn HydrationScripts(
     #[prop(optional, into)]
     root: Option<String>,
 ) -> impl IntoView {
+    static SPLIT_MANIFEST: OnceLock<Option<WasmSplitManifest>> =
+        OnceLock::new();
+
+    if let Some(splits) = SPLIT_MANIFEST.get_or_init(|| {
+        let root = root.clone().unwrap_or_default();
+
+        let site_dir = &options.site_root;
+        let pkg_dir = &options.site_pkg_dir;
+        let path = PathBuf::from(site_dir.to_string());
+        let path = path
+            .join(pkg_dir.to_string())
+            .join("__wasm_split_manifest.json");
+        let file = std::fs::read_to_string(path).ok()?;
+        let manifest = WasmSplitManifest(ArcStoredValue::new((
+            format!("{root}/{pkg_dir}"),
+            serde_json::from_str(&file).expect("could not read manifest file"),
+        )));
+
+        Some(manifest)
+    }) {
+        provide_context(splits.clone());
+    }
+
     let mut js_file_name = options.output_name.to_string();
     let mut wasm_file_name = options.output_name.to_string();
     if options.hash_files {
@@ -112,7 +136,7 @@ pub fn HydrationScripts(
 
     let root = root.unwrap_or_default();
     view! {
-        <link rel="modulepreload" href=format!("{root}/{pkg_path}/{js_file_name}.js") nonce=nonce.clone()/>
+        <link rel="modulepreload" href=format!("{root}/{pkg_path}/{js_file_name}.js") crossorigin=nonce.clone()/>
         <link
             rel="preload"
             href=format!("{root}/{pkg_path}/{wasm_file_name}.wasm")