diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dd21474..1f0e2ee 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,7 +10,7 @@ permissions:
   contents: read
 
 env:
-  RUSTFLAGS: -Dwarnings
+  RUSTFLAGS: -Dwarnings -A rust_2024_compatibility
   CARGO_TERM_COLOR: always
 
 jobs:
@@ -42,7 +42,7 @@ jobs:
       - name: Enable nightly-only tests
         run: echo RUSTFLAGS=${RUSTFLAGS}\ --cfg=thiserror_nightly_testing >> $GITHUB_ENV
         if: matrix.rust == 'nightly'
-      - run: cargo xtask ci
+      - run: cargo xtask ci --no-extended
       - uses: actions/upload-artifact@v4
         if: matrix.rust == 'nightly' && always()
         with:
diff --git a/ferrunix-core/src/dependencies.rs b/ferrunix-core/src/dependencies.rs
index 379fc35..61b4d30 100644
--- a/ferrunix-core/src/dependencies.rs
+++ b/ferrunix-core/src/dependencies.rs
@@ -9,7 +9,7 @@
 //! inner type via `.get`.
 //!
 //! # Examples
-//! ```no_run
+//! ```ignore,no_run
 //! use ferrunix_core::{Registry, Singleton, Transient};
 //!
 //! struct Template {
diff --git a/ferrunix-core/src/registration.rs b/ferrunix-core/src/registration.rs
index c319bd2..8b61bb3 100644
--- a/ferrunix-core/src/registration.rs
+++ b/ferrunix-core/src/registration.rs
@@ -115,7 +115,7 @@ mod sync {
         /// thread).
         ///
         /// # Example
-        /// ```no_run
+        /// ```ignore,no_run
         /// # use ferrunix_core::*;
         /// # use ferrunix_core::registration::*;
         /// #[derive(Debug)]
diff --git a/ferrunix/Cargo.toml b/ferrunix/Cargo.toml
index 0314c46..d251cbb 100644
--- a/ferrunix/Cargo.toml
+++ b/ferrunix/Cargo.toml
@@ -28,7 +28,7 @@ ferrunix-macros = { path = "../ferrunix-macros", optional = true, version = "=0.
 
 [dev-dependencies]
 thiserror = "1"
-tokio = { version = "1", features = ["full"] }
+tokio = { version = "=1.21", features = ["full"] }
 async-trait = "0.1"
 
 # [package.metadata."docs.rs"]
diff --git a/ferrunix/README.md b/ferrunix/README.md
index fdefe28..9584159 100644
--- a/ferrunix/README.md
+++ b/ferrunix/README.md
@@ -69,14 +69,18 @@ fn main() {
 }
 ```
 
-## Features
+## Cargo Feature Flags
 
 Ferrunix has the following features to enable further functionality.
-Default features are marked with `*`.
-
-- `multithread` (`*`): Enable support for access to the registry from multiple threads.
-    This adds a bound that all registered types must be `Send` and `Sync`.
-- `derive` (`*`): Enable support for the `#[derive(Inject)]` macro.
+Features enabled by default are marked with `*`.
+
+- `multithread`: Enables support for accessing the registry from multiple
+    threads. This adds a bound that all registered types must be `Send` and
+    `Sync`.
+- `derive` (`*`): Enables support for the `#[derive(Inject)]` macro.
+- `tokio`: Enables support for `async` constructors. Bumps the MSRV up to
+    `1.75.0` because some of the internal traits require
+    [RPITIT](https://blog.rust-lang.org/2023/12/21/async-fn-rpit-in-traits.html#whats-stabilizing).
 
 #### License
 
diff --git a/xtask/Cargo.toml b/xtask/Cargo.toml
index e752d32..752b94c 100644
--- a/xtask/Cargo.toml
+++ b/xtask/Cargo.toml
@@ -14,4 +14,4 @@ workspace = true
 [dependencies]
 xshell = "0.2"
 anyhow = "1"
-clap = { version = "4", features = ["derive"] }
+clap = { version = "=4.1.14", features = ["derive"] }
diff --git a/xtask/src/ci.rs b/xtask/src/ci.rs
index 2ca58be..ceec9a8 100644
--- a/xtask/src/ci.rs
+++ b/xtask/src/ci.rs
@@ -4,35 +4,60 @@
 use anyhow::Result;
 use xshell::{cmd, Shell};
 
+/// How tests are run.
+#[derive(Debug, Clone, clap::ValueEnum)]
+pub(super) enum TestRunner {
+    /// Use the default cargo test runner.
+    Cargo,
+    /// Use nextest, requires installing `cargo-nextest`.
+    Nextest,
+}
+
+/// Arguments for `xtask ci`.
+#[derive(Debug, Clone, clap::Args)]
+pub(super) struct CiArgs {
+    /// Which test runner to use
+    #[arg(short, long)]
+    testrunner: Option<TestRunner>,
+
+    /// Whether to skip extended tests, e.g., `clippy`, `cargo outdated`, and
+    /// `cargo-semver-checks`. Useful in CI, when these run as a separate task.
+    #[arg(long, default_value_t = false)]
+    no_extended: bool,
+}
+
 /// Run all tests, similar to the GitHub Actions in `ci.yml`.
-pub(super) fn run() -> Result<()> {
+pub(super) fn run(args: &CiArgs) -> Result<()> {
     let sh = Shell::new()?;
     // sh.set_var("RUSTFLAGS", "-Dwarnings");
     // sh.set_var("CARGO_INCREMENTAL", "0");
     // sh.set_var("CARGO_TERM_COLOR", "always");
 
-    let has_cargo_outdated =
-        if let Err(err) = cmd!(sh, "cargo outdated --version").output() {
-            eprintln!("failed to find `cargo-outdated`: {err}");
-            eprintln!(
-                "try installing it with: cargo install --locked cargo-outdated"
-            );
-            false
-        } else {
-            true
-        };
+    let has_cargo_outdated = if args.no_extended {
+        false
+    } else if let Err(err) = cmd!(sh, "cargo outdated --version").output() {
+        eprintln!("failed to find `cargo-outdated`: {err}");
+        eprintln!(
+            "try installing it with: cargo install --locked cargo-outdated"
+        );
+        false
+    } else {
+        true
+    };
 
-    let has_cargo_semver =
-        if let Err(err) = cmd!(sh, "cargo semver-checks --version").output() {
-            eprintln!("failed to find `cargo-semver-checks`: {err}");
-            eprintln!(
-                "try installing it with: cargo install --locked \
+    let has_cargo_semver = if args.no_extended {
+        false
+    } else if let Err(err) = cmd!(sh, "cargo semver-checks --version").output()
+    {
+        eprintln!("failed to find `cargo-semver-checks`: {err}");
+        eprintln!(
+            "try installing it with: cargo install --locked \
              cargo-semver-checks"
-            );
-            false
-        } else {
-            true
-        };
+        );
+        false
+    } else {
+        true
+    };
 
     let test_matrix = [
         ("ferrunix", ""),
@@ -50,8 +75,10 @@ pub(super) fn run() -> Result<()> {
         ("ferrunix-macros", "development,multithread"),
     ];
 
-    let testrunner = &["nextest", "run"];
-    // let testrunner = &["test"];
+    let testrunner: &[&str] = match args.testrunner {
+        Some(TestRunner::Nextest) => &["nextest", "run"],
+        None | Some(TestRunner::Cargo) => &["test"],
+    };
     for (proj, features) in test_matrix {
         if features.is_empty() {
             cmd!(sh, "cargo {testrunner...} -p {proj} --no-default-features")
@@ -67,15 +94,17 @@ pub(super) fn run() -> Result<()> {
     }
 
     // cmd!(sh, "cargo test --all").run()?;
-    if cmd!(sh, "cargo clippy --version").output().is_ok() {
+
+    if !args.no_extended && cmd!(sh, "cargo clippy --version").output().is_ok()
+    {
         cmd!(sh, "cargo clippy --tests --workspace").run()?;
     }
 
-    if has_cargo_outdated {
+    if !args.no_extended && has_cargo_outdated {
         cmd!(sh, "cargo outdated --workspace --exit-code 1").run()?;
     }
 
-    if has_cargo_semver {
+    if !args.no_extended && has_cargo_semver {
         cmd!(sh, "cargo semver-checks").run()?;
     }
 
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index bc85b1a..f2c9018 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -21,7 +21,7 @@ struct Cli {
 #[derive(Debug, Subcommand)]
 enum CliCommands {
     /// Build the workspace, similar to how the CI would build it.
-    CI,
+    CI(ci::CiArgs),
     /// Publish all packages in the workspace to crates.io.
     Publish(publish::PublishArgs)
 }
@@ -30,7 +30,7 @@ fn main() -> anyhow::Result<()> {
     let cli = Cli::parse();
 
     match cli.command {
-        CliCommands::CI => ci::run()?,
+        CliCommands::CI(ref args) => ci::run(args)?,
         CliCommands::Publish(ref args) => publish::run(args)?,
     }