diff --git a/.github/workflows/.checks.yml b/.github/workflows/.checks.yml
index 41bce08..bed60e3 100644
--- a/.github/workflows/.checks.yml
+++ b/.github/workflows/.checks.yml
@@ -11,6 +11,14 @@ jobs:
         uses: soltiHQ/actions/taskfile@main
         with: { command: cargo/fmt }
 
+  check:
+    runs-on: ${{ vars.RUNS_ON }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run check
+        uses: soltiHQ/actions/taskfile@main
+        with: { command: cargo/check }
+
   test:
     runs-on: ${{ vars.RUNS_ON }}
     steps:
diff --git a/Taskfile.yml b/Taskfile.yml
index b82a474..4eeed85 100644
--- a/Taskfile.yml
+++ b/Taskfile.yml
@@ -43,7 +43,7 @@ tasks:
         \
         --volume "{{.git_root}}/{{.MOUNT_DIR}}:/workspace:rw" \
         {{if .VOLUMES}}{{range $vol := .VOLUMES}}--volume {{$vol}} {{end}}{{end}} \
-        {{if .ENVS}}{{range $env := .ENVS}}--env {{$env}} {{end}}{{end}} \
+        {{if .ENVS}}{{range $env := .ENVS}}--env "{{$env}}" {{end}}{{end}} \
         \
         --workdir /workspace \
         {{.IMAGE}} \
@@ -70,6 +70,7 @@ tasks:
             - "RUSTUP_TOOLCHAIN={{.rust_version}}"
             - "RUSTUP_NO_UPDATE_CHECK=1"
             - "CARGO_INCREMENTAL=0"
+            - "RUSTFLAGS=-D warnings"
 
   # ================================================#
   # ----------------------PUBLIC--------------------#
@@ -83,6 +84,14 @@ tasks:
         vars:
           CMD: "fmt --check --verbose"
 
+  cargo/check:
+    desc: Run 'cargo check'.
+    silent: true
+    cmds:
+      - task: _cargo/tool
+        vars:
+          CMD: "check"
+
   cargo/clippy:
     desc: Run 'cargo clippy'.
     silent: true
diff --git a/examples/controller.rs b/examples/controller.rs
index 60b5116..65662de 100644
--- a/examples/controller.rs
+++ b/examples/controller.rs
@@ -60,7 +60,7 @@ async fn main() -> anyhow::Result<()> {
     println!("Demo 1: Queue Policy");
     println!(" └► Submit 3 tasks with same name: they run sequentially");
 
-    for i in 1..=3 {
+    for _ in 1..=3 {
         let spec = make_spec("job-in-queue", 800);
         sup.submit(ControllerSpec::queue(spec)).await?;
     }
diff --git a/src/core/supervisor.rs b/src/core/supervisor.rs
index 0118bf2..75d7195 100644
--- a/src/core/supervisor.rs
+++ b/src/core/supervisor.rs
@@ -91,9 +91,12 @@
 //! ```
 
 use std::{sync::Arc, time::Duration};
-use tokio::{sync::Notify, sync::OnceCell, sync::broadcast, time::timeout};
+use tokio::{sync::Notify, sync::broadcast, time::timeout};
 use tokio_util::sync::CancellationToken;
 
+#[cfg(feature = "controller")]
+use tokio::sync::OnceCell;
+
 use crate::core::{alive::AliveTracker, builder::SupervisorBuilder, registry::Registry};
 use crate::{
     config::Config,