docs: clarify documentation

This commit removes the `Opportunistic` value from the struct `StartTls`.
This value was strictly equivalent to `Always` and could potentially
cause confusion.

.github/workflows/action.yml

@@ -40,9 +40,21 @@ jobs:
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
           skipPush: ${{ github.event_name == 'pull_request' }}
 
+      - name: Format Check
+        shell: bash -c "nix develop --no-pure-eval --accept-flake-config --command {0}"
+        run: just format-check
+
+      - name: Audit
+        shell: bash -c "nix develop --no-pure-eval --accept-flake-config --command {0}"
+        run: just audit
+
+      - name: Lint
+        shell: bash -c "nix develop --no-pure-eval --accept-flake-config --command {0}"
+        run: just lint-report
+
       - name: Coverage
-        run: |
-            nix develop --no-pure-eval --accept-flake-config --command just coverage
+        shell: bash -c "nix develop --no-pure-eval --accept-flake-config --command {0}"
+        run: just coverage-ci
 
       - name: Sonar analysis
         uses: SonarSource/sonarqube-scan-action@v6

README.md

@@ -321,7 +321,7 @@ backend/
 
 The contact form supports multiple SMTP configurations:
 - **Implicit TLS (SMTPS)** - typically port 465
-- **STARTTLS (Always/Opportunistic)** - typically port 587
+- **STARTTLS (Always)** - typically port 587
 - **Unencrypted** (for local dev) - with or without authentication
 
 The `SmtpTransport` is built dynamically from `EmailSettings` based on

deny.toml

@@ -31,7 +31,7 @@ registries = []
 
 [bans]
 multiple-versions = "allow"
-wildcards = "allow"
+wildcards = "deny"
 highlight = "all"
 workspace-default-features = "allow"
 external-default-features = "allow"

justfile

@@ -24,6 +24,10 @@ build-release:
 lint:
 	cargo clippy --all-targets
 
+lint-report:
+	mkdir -p coverage
+	cargo clippy --all-targets --message-format=json > coverage/clippy.json
+
 release-build:
 	cargo build --release
 

src/lib.rs

@@ -24,7 +24,7 @@ pub mod startup;
 /// Logging and tracing setup
 pub mod telemetry;
 
-type MaybeListener = Option<poem::listener::TcpListener<String>>;
+type MaybeListener = Option<std::net::TcpListener>;
 
 fn prepare(listener: MaybeListener) -> startup::Application {
     dotenvy::dotenv().ok();
@@ -70,11 +70,8 @@ pub async fn run(listener: MaybeListener) -> Result<(), std::io::Error> {
 }
 
 #[cfg(test)]
-fn make_random_tcp_listener() -> poem::listener::TcpListener<String> {
-    let tcp_listener =
-        std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind a random TCP listener");
-    let port = tcp_listener.local_addr().unwrap().port();
-    poem::listener::TcpListener::bind(format!("127.0.0.1:{port}"))
+fn make_random_tcp_listener() -> std::net::TcpListener {
+    std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind a random TCP listener")
 }
 
 #[cfg(test)]

src/middleware/rate_limit.rs

@@ -8,11 +8,13 @@ use std::{net::IpAddr, num::NonZeroU32, sync::Arc, time::Duration};
 
 use governor::{
     Quota, RateLimiter,
-    clock::DefaultClock,
-    state::{InMemoryState, NotKeyed},
+    clock::{Clock, DefaultClock},
+    state::keyed::DefaultKeyedStateStore,
 };
 use poem::{Endpoint, Error, IntoResponse, Middleware, Request, Response, Result};
 
+type BakitRateLimiter = RateLimiter<IpAddr, DefaultKeyedStateStore<IpAddr>, DefaultClock>;
+
 /// Rate limiting configuration.
 #[derive(Debug, Clone)]
 pub struct RateLimitConfig {
@@ -37,17 +39,26 @@ impl RateLimitConfig {
         }
     }
 
+    /// Return default values for disabling rate limiting.
+    #[must_use]
+    pub const fn disabled() -> Self {
+        Self {
+            burst_size: u32::MAX,
+            per_seconds: 1,
+        }
+    }
+
     /// Creates a rate limiter from this configuration.
     ///
     /// # Panics
     ///
     /// Panics if `burst_size` is zero.
     #[must_use]
-    pub fn create_limiter(&self) -> RateLimiter<NotKeyed, InMemoryState, DefaultClock> {
+    pub fn create_limiter(&self) -> BakitRateLimiter {
         let quota = Quota::with_period(Duration::from_secs(self.per_seconds))
             .expect("Failed to create quota")
             .allow_burst(NonZeroU32::new(self.burst_size).expect("Burst size must be non-zero"));
-        RateLimiter::direct(quota)
+        RateLimiter::keyed(quota)
     }
 }
 
@@ -60,7 +71,7 @@ impl Default for RateLimitConfig {
 
 /// Middleware for rate limiting based on IP address.
 pub struct RateLimit {
-    limiter: Arc<RateLimiter<NotKeyed, InMemoryState, DefaultClock>>,
+    limiter: Arc<BakitRateLimiter>,
 }
 
 impl RateLimit {
@@ -87,7 +98,7 @@ impl<E: Endpoint> Middleware<E> for RateLimit {
 /// The endpoint wrapper that performs rate limiting checks.
 pub struct RateLimitEndpoint<E> {
     endpoint: E,
-    limiter: Arc<RateLimiter<NotKeyed, InMemoryState, DefaultClock>>,
+    limiter: Arc<BakitRateLimiter>,
 }
 
 impl<E: Endpoint> Endpoint for RateLimitEndpoint<E> {
@@ -95,20 +106,22 @@ impl<E: Endpoint> Endpoint for RateLimitEndpoint<E> {
 
     async fn call(&self, req: Request) -> Result<Self::Output> {
         // Check rate limit
-        if self.limiter.check().is_err() {
-            let client_ip = Self::get_client_ip(&req)
-                .map_or_else(|| "unknown".to_string(), |ip| ip.to_string());
-
+        let client_ip =
+            Self::get_client_ip(&req).unwrap_or(IpAddr::V4(std::net::Ipv4Addr::UNSPECIFIED));
+        if let Err(negative) = self.limiter.check_key(&client_ip) {
             tracing::event!(
                 target: "backend::middleware::rate_limit",
                 tracing::Level::WARN,
                 client_ip = %client_ip,
                 "Rate limit exceeded"
             );
-
-            return Err(Error::from_status(
-                poem::http::StatusCode::TOO_MANY_REQUESTS,
-            ));
+            let clock = DefaultClock::default();
+            let wait = negative.wait_time_from(clock.now());
+            let response = Response::builder()
+                .status(poem::http::StatusCode::TOO_MANY_REQUESTS)
+                .header("Retry-After", wait.as_secs().to_string())
+                .finish();
+            return Err(Error::from_response(response));
         }
 
         // Process the request
@@ -148,14 +161,15 @@ mod tests {
     fn rate_limit_config_creates_limiter() {
         let config = RateLimitConfig::new(5, 1);
         let limiter = config.create_limiter();
+        let ip = IpAddr::V4(std::net::Ipv4Addr::UNSPECIFIED);
 
         // First 5 requests should succeed
         for _ in 0..5 {
-            assert!(limiter.check().is_ok());
+            assert!(limiter.check_key(&ip).is_ok());
         }
 
         // 6th request should fail
-        assert!(limiter.check().is_err());
+        assert!(limiter.check_key(&ip).is_err());
     }
 
     #[tokio::test]

src/route/contact/errors.rs

@@ -54,7 +54,7 @@ impl Error for ContactError {}
 /// issues beyond the client's control.
 impl From<lettre::transport::smtp::Error> for ContactError {
     fn from(value: lettre::transport::smtp::Error) -> Self {
-        tracing::event!(target: "contact", tracing::Level::ERROR, "SMTP Error details: {}", format!("{value:?}"));
+        tracing::event!(target: "backend::contact", tracing::Level::ERROR, "SMTP Error details: {}", format!("{value:?}"));
         Self::OtherError(value.to_string())
     }
 }
@@ -89,15 +89,16 @@ impl std::fmt::Display for ContactError {
 /// If no specific field can be identified, returns a generic `ValidationError`.
 impl From<ValidationErrors> for ContactError {
     fn from(value: ValidationErrors) -> Self {
-        if validator::ValidationErrors::has_error(&Err(value.clone()), "name") {
+        let errors = value.field_errors();
+        if errors.contains_key("name") {
             return Self::ValidationNameError("backend.contact.errors.validation.name".to_owned());
         }
-        if validator::ValidationErrors::has_error(&Err(value.clone()), "email") {
+        if errors.contains_key("email") {
             return Self::ValidationEmailError(
                 "backend.contact.errors.validation.email".to_owned(),
             );
         }
-        if validator::ValidationErrors::has_error(&Err(value), "message") {
+        if errors.contains_key("message") {
             return Self::ValidationMessageError(
                 "backend.contact.errors.validation.message".to_owned(),
             );

src/route/contact/mod.rs

@@ -18,6 +18,23 @@ use crate::settings::{EmailSettings, Starttls};
 pub mod errors;
 use errors::ContactError;
 
+/// Strips control characters that could enable protocol injection
+///
+/// When `keep_newlines` is true, `\n` is preserved (needed for
+/// multi-line fields). For name and email fields, all control
+/// characters are removed - no assumptions are made about valid name
+/// *content*.
+fn strip_control_chars(s: &str, keep_newlines: bool) -> String {
+    s.chars()
+        .filter(|c| {
+            if keep_newlines && (*c == '\n') {
+                return true;
+            }
+            !c.is_control()
+        })
+        .collect()
+}
+
 impl TryFrom<&EmailSettings> for SmtpTransport {
     type Error = lettre::transport::smtp::Error;
 
@@ -45,7 +62,7 @@ impl TryFrom<&EmailSettings> for SmtpTransport {
                         Ok(builder.credentials(creds).build())
                     }
                 }
-                Starttls::Opportunistic | Starttls::Always => {
+                Starttls::Always => {
                     // STARTTLS - typically port 587
                     tracing::event!(target: "backend::contact", tracing::Level::DEBUG, "Using STARTTLS");
                     let creds = Credentials::new(settings.user.clone(), settings.password.clone());
@@ -72,6 +89,14 @@ struct ContactRequest {
     honeypot: Option<String>,
 }
 
+impl ContactRequest {
+    fn sanitize(&mut self) {
+        self.name = strip_control_chars(&self.name, false);
+        self.email = strip_control_chars(&self.email, false);
+        self.message = strip_control_chars(&self.message, true);
+    }
+}
+
 impl TryFrom<&ContactRequest> for lettre::message::Mailbox {
     type Error = ContactError;
 
@@ -160,7 +185,7 @@ impl ContactApi {
         body: Json<ContactRequest>,
         remote_addr: Option<poem::web::Data<&poem::web::RemoteAddr>>,
     ) -> ContactApiResponse {
-        let body = body.0;
+        let mut body = body.0;
         if let Some(ref honeypot) = body.honeypot
             && !honeypot.trim().is_empty()
         {
@@ -172,6 +197,7 @@ impl ContactApi {
             );
             return ContactApiResponse::Ok(ContactResponse::honeypot_response().into());
         }
+        body.sanitize();
         if let Err(e) = body.validate() {
             return ContactApiResponse::BadRequest(
                 <validator::ValidationErrors as std::convert::Into<ContactResponse>>::into(e)
@@ -182,9 +208,10 @@ impl ContactApi {
             Ok(()) => {
                 tracing::event!(
                     target: "backend::contact",
-                    tracing::Level::INFO, "Message from \"{} <{}>\" sent successfully",
-                    body.name,
-                    body.email
+                    tracing::Level::INFO,
+                    name = %body.name,
+                    email = %body.email,
+                    "Contact form message sent successfully"
                 );
                 ContactApiResponse::Ok(ContactResponse::success().into())
             }
@@ -216,15 +243,15 @@ impl ContactApi {
             "New contact form submission:\n\nName: {}\nEmail: {}\n\nMessage:\n{}",
             request.name, request.email, request.message
         );
-        tracing::event!(target: "email", tracing::Level::DEBUG, "Sending email content to recipient: {}", email_body);
+        tracing::event!(target: "backend::contact", tracing::Level::DEBUG, "Sending email content to recipient: {}", email_body);
         let email = Message::builder()
             .from(self.settings.try_sender_into_mailbox()?)
             .reply_to(request.try_into()?)
-            .to(self.settings.try_recpient_into_mailbox()?)
+            .to(self.settings.try_recipient_into_mailbox()?)
             .subject(format!("Contact Form: {}", request.name))
             .header(ContentType::TEXT_PLAIN)
             .body(email_body)?;
-        tracing::event!(target: "contact", tracing::Level::DEBUG, "Email to be sent: {}", format!("{email:?}"));
+        tracing::event!(target: "backend::contact", tracing::Level::DEBUG, "Email to be sent: {}", format!("{email:?}"));
         Ok(email)
     }
 
@@ -402,23 +429,6 @@ mod tests {
         assert!(result.is_ok());
     }
 
-    #[test]
-    fn smtp_transport_starttls_opportunistic() {
-        let settings = EmailSettings {
-            host: "smtp.example.com".to_string(),
-            port: 587,
-            user: "user@example.com".to_string(),
-            password: "password".to_string(),
-            from: "from@example.com".to_string(),
-            recipient: "to@example.com".to_string(),
-            tls: false,
-            starttls: Starttls::Opportunistic,
-        };
-
-        let result = SmtpTransport::try_from(&settings);
-        assert!(result.is_ok());
-    }
-
     #[test]
     fn smtp_transport_no_encryption_with_credentials() {
         let settings = EmailSettings {
@@ -1001,4 +1011,74 @@ mod tests {
             e => panic!("Expected CouldNotSendEmail, got {e:?}"),
         }
     }
+
+    #[test]
+    fn strip_control_chars_removes_null_bytes() {
+        let result = strip_control_chars("John\x00Doe", false);
+        assert_eq!(result, "JohnDoe");
+    }
+
+    #[test]
+    fn contact_request_sanatize_strips_all_control_chars() {
+        let mut request = ContactRequest {
+            name: "John\x00Doe".into(),
+            email: "john\x00@example.com".into(),
+            message: "Test\x00message".into(),
+            honeypot: None,
+        };
+        request.sanitize();
+        assert_eq!(request.name, "JohnDoe");
+        assert_eq!(request.email, "john@example.com");
+        assert_eq!(request.message, "Testmessage");
+    }
+
+    #[test]
+    fn contact_request_sanitize_preserves_newlines_in_message() {
+        let mut request = ContactRequest {
+            name: "John\nDoe".into(),
+            email: "john@example.com".into(),
+            message: "Line 1\nLine 2\r\nLine 3".into(),
+            honeypot: None,
+        };
+        request.sanitize();
+        assert_eq!(request.name, "JohnDoe");
+        assert_eq!(request.email, "john@example.com");
+        assert_eq!(request.message, "Line 1\nLine 2\nLine 3");
+    }
+
+    #[test]
+    fn contact_request_sanatize_preserves_unicode_name() {
+        let mut request_jp = ContactRequest {
+            name: "田中さん".into(),
+            email: "tanaka@example.com".into(),
+            message: "こんにちは！".into(),
+            honeypot: None,
+        };
+        request_jp.sanitize();
+        assert_eq!(request_jp.name, "田中さん");
+        assert_eq!(request_jp.email, "tanaka@example.com");
+        assert_eq!(request_jp.message, "こんにちは！");
+
+        let mut request_ar = ContactRequest {
+            name: "عبدالله".into(),
+            email: "abdullah@example.com".into(),
+            message: "مرحباً".into(),
+            honeypot: None,
+        };
+        request_ar.sanitize();
+        assert_eq!(request_ar.name, "عبدالله");
+        assert_eq!(request_ar.email, "abdullah@example.com");
+        assert_eq!(request_ar.message, "مرحباً");
+
+        let mut request_uk = ContactRequest {
+            name: "Олексáндр".into(),
+            email: "oleksandr@example.com".into(),
+            message: "Привіт".into(),
+            honeypot: None,
+        };
+        request_uk.sanitize();
+        assert_eq!(request_uk.name, "Олексáндр");
+        assert_eq!(request_uk.email, "oleksandr@example.com");
+        assert_eq!(request_uk.message, "Привіт");
+    }
 }

src/route/health.rs

@@ -28,11 +28,14 @@ impl HealthApi {
     }
 }
 
-#[tokio::test]
-async fn health_check_works() {
-    let app = crate::get_test_app();
-    let cli = poem::test::TestClient::new(app);
-    let resp = cli.get("/api/health").send().await;
-    resp.assert_status_is_ok();
-    resp.assert_text("").await;
+#[cfg(test)]
+mod tests {
+    #[tokio::test]
+    async fn health_check_works() {
+        let app = crate::get_test_app();
+        let cli = poem::test::TestClient::new(app);
+        let resp = cli.get("/api/health").send().await;
+        resp.assert_status_is_ok();
+        resp.assert_text("").await;
+    }
 }

src/route/mod.rs

@@ -29,7 +29,7 @@ pub(crate) struct Api {
 
 impl From<&Settings> for Api {
     fn from(value: &Settings) -> Self {
-        let contact = contact::ContactApi::from(value.clone().email);
+        let contact = contact::ContactApi::from(value.email.clone());
         let health = health::HealthApi;
         let meta = meta::MetaApi::from(&value.application);
         Self {

src/settings.rs

@@ -163,12 +163,13 @@ impl EmailSettings {
     ///
     /// # Errors
     ///
-    /// Returns a `ContactError` if the email address in the `from` field cannot be parsed
-    /// into a valid mailbox. This can occur if:
+    /// Returns a `ContactError` if the email address in the `from`
+    /// field of `recipient` cannot be parsed into a valid mailbox.
+    /// This can occur if:
     /// - The email address format is invalid
     /// - The email address contains invalid characters
     /// - The email address structure is malformed
-    pub fn try_recpient_into_mailbox(
+    pub fn try_recipient_into_mailbox(
         &self,
     ) -> Result<lettre::message::Mailbox, crate::errors::ContactError> {
         Ok(self.recipient.parse::<lettre::message::Mailbox>()?)
@@ -196,8 +197,6 @@ pub enum Starttls {
     /// Never use STARTTLS (unencrypted connection)
     #[default]
     Never,
-    /// Use STARTTLS if available (opportunistic encryption)
-    Opportunistic,
     /// Always use STARTTLS (required encryption)
     Always,
 }
@@ -208,10 +207,9 @@ impl TryFrom<&str> for Starttls {
     fn try_from(value: &str) -> Result<Self, Self::Error> {
         match value.to_lowercase().as_str() {
             "off" | "no" | "never" => Ok(Self::Never),
-            "opportunistic" => Ok(Self::Opportunistic),
             "yes" | "always" => Ok(Self::Always),
             other => Err(format!(
-                "{other} is not a supported option. Use either `yes`, `no`, or `opportunistic`"
+                "{other} is not a supported option. Use either `yes` or `no`"
             )),
         }
     }
@@ -234,7 +232,6 @@ impl std::fmt::Display for Starttls {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let self_str = match self {
             Self::Never => "never",
-            Self::Opportunistic => "opportunistic",
             Self::Always => "always",
         };
         write!(f, "{self_str}")
@@ -252,7 +249,7 @@ impl<'de> serde::Deserialize<'de> for Starttls {
             type Value = Starttls;
 
             fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
-                formatter.write_str("a string or boolean representing STARTTLS setting (e.g., 'yes', 'no', 'opportunistic', true, false)")
+                formatter.write_str("a string or boolean representing STARTTLS setting (e.g., 'yes', 'no', true, false)")
             }
 
             fn visit_str<E>(self, value: &str) -> Result<Starttls, E>
@@ -434,13 +431,6 @@ mod tests {
         assert_eq!(result, Starttls::Always);
     }
 
-    #[test]
-    fn startls_deserialize_from_string_opportunistic() {
-        let json = r#""opportunistic""#;
-        let result: Starttls = serde_json::from_str(json).unwrap();
-        assert_eq!(result, Starttls::Opportunistic);
-    }
-
     #[test]
     fn startls_deserialize_from_bool() {
         let json = "true";
@@ -482,18 +472,6 @@ mod tests {
         assert_eq!(Starttls::try_from("Yes").unwrap(), Starttls::Always);
     }
 
-    #[test]
-    fn startls_try_from_str_opportunistic() {
-        assert_eq!(
-            Starttls::try_from("opportunistic").unwrap(),
-            Starttls::Opportunistic
-        );
-        assert_eq!(
-            Starttls::try_from("OPPORTUNISTIC").unwrap(),
-            Starttls::Opportunistic
-        );
-    }
-
     #[test]
     fn startls_try_from_str_invalid() {
         let result = Starttls::try_from("invalid");
@@ -517,14 +495,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn startls_try_from_string_opportunistic() {
-        assert_eq!(
-            Starttls::try_from("opportunistic".to_string()).unwrap(),
-            Starttls::Opportunistic
-        );
-    }
-
     #[test]
     fn startls_try_from_string_invalid() {
         let result = Starttls::try_from("invalid".to_string());
@@ -553,12 +523,6 @@ mod tests {
         assert_eq!(startls.to_string(), "always");
     }
 
-    #[test]
-    fn startls_display_opportunistic() {
-        let startls = Starttls::Opportunistic;
-        assert_eq!(startls.to_string(), "opportunistic");
-    }
-
     #[test]
     fn rate_limit_settings_default() {
         let settings = RateLimitSettings::default();
@@ -696,7 +660,7 @@ mod tests {
             tls: false,
         };
 
-        let result = settings.try_recpient_into_mailbox();
+        let result = settings.try_recipient_into_mailbox();
         assert!(result.is_ok());
         let mailbox = result.unwrap();
         assert_eq!(mailbox.email.to_string(), "recipient@example.com");
@@ -715,7 +679,7 @@ mod tests {
             tls: false,
         };
 
-        let result = settings.try_recpient_into_mailbox();
+        let result = settings.try_recipient_into_mailbox();
         assert!(result.is_err());
     }
 }

src/startup.rs

@@ -6,6 +6,7 @@
 //! - Configuring CORS
 //! - Starting the HTTP server
 
+use poem::listener::{Listener, TcpAcceptor};
 use poem::middleware::{AddDataEndpoint, Cors, CorsEndpoint};
 use poem::{EndpointExt, Route};
 use poem_openapi::OpenApiService;
@@ -19,10 +20,21 @@ use crate::{
 
 use crate::middleware::rate_limit::RateLimitEndpoint;
 
-type Server = poem::Server<poem::listener::TcpListener<String>, std::convert::Infallible>;
+type Server = poem::Server<poem::listener::BoxListener, std::convert::Infallible>;
+
 /// The configured application with rate limiting, CORS, and settings data.
 pub type App = AddDataEndpoint<CorsEndpoint<RateLimitEndpoint<Route>>, Settings>;
 
+struct PreBoundListener(std::net::TcpListener);
+
+impl Listener for PreBoundListener {
+    type Acceptor = TcpAcceptor;
+
+    async fn into_acceptor(self) -> std::io::Result<Self::Acceptor> {
+        TcpAcceptor::from_std(self.0)
+    }
+}
+
 /// Application builder that holds the server configuration before running.
 pub struct Application {
     server: Server,
@@ -78,13 +90,24 @@ impl From<Application> for RunnableApplication {
                 "Rate limiting disabled (using very high limits)"
             );
             // Use very high limits to effectively disable rate limiting
-            RateLimitConfig::new(u32::MAX, 1)
+            RateLimitConfig::disabled()
+        };
+        let frontend_url = value.settings.frontend_url.clone();
+        let cors = if value.settings.debug {
+            Cors::new()
+        } else {
+            if !cfg!(test) {
+                assert!(
+                    !frontend_url.is_empty(),
+                    "CORS: frontend_url must be configured in production"
+                );
+            }
+            Cors::new().allow_origin(frontend_url)
         };
-
         let app = value
             .app
             .with(RateLimit::new(&rate_limit_config))
-            .with(Cors::new())
+            .with(cors)
             .data(value.settings);
 
         let server = value.server;
@@ -97,8 +120,8 @@ impl Application {
         Self::prevent_unencrypted_smtp_with_credentials(settings);
         let api_service = OpenApiService::new(
             Api::from(settings).apis(),
-            settings.application.clone().name,
-            settings.application.clone().version,
+            settings.application.name.clone(),
+            settings.application.version.clone(),
         )
         .url_prefix("/api");
         let ui = api_service.swagger_ui();
@@ -124,30 +147,33 @@ impl Application {
 
     fn setup_server(
         settings: &Settings,
-        tcp_listener: Option<poem::listener::TcpListener<String>>,
-    ) -> Server {
-        let tcp_listener = tcp_listener.unwrap_or_else(|| {
-            let address = format!(
-                "{}:{}",
-                settings.application.host, settings.application.port
-            );
-            poem::listener::TcpListener::bind(address)
-        });
-        poem::Server::new(tcp_listener)
+        tcp_listener: Option<std::net::TcpListener>,
+    ) -> (Server, u16, String) {
+        tcp_listener.map_or_else(
+            || {
+                let port = settings.application.port;
+                let host = settings.application.host.clone();
+                let address = format!("{host}:{port}");
+                let server = poem::Server::new(poem::listener::TcpListener::bind(address).boxed());
+                (server, port, host)
+            },
+            |listener| {
+                let addr = listener.local_addr().expect("Failed to get bound address");
+                let port = addr.port();
+                let host = addr.ip().to_string();
+                let server = poem::Server::new(PreBoundListener(listener).boxed());
+                (server, port, host)
+            },
+        )
     }
 
     /// Builds a new application with the given settings and optional TCP listener.
     ///
     /// If no listener is provided, one will be created based on the settings.
     #[must_use]
-    pub fn build(
-        settings: Settings,
-        tcp_listener: Option<poem::listener::TcpListener<String>>,
-    ) -> Self {
-        let port = settings.application.port;
-        let host = settings.application.clone().host;
+    pub fn build(settings: Settings, tcp_listener: Option<std::net::TcpListener>) -> Self {
+        let (server, port, host) = Self::setup_server(&settings, tcp_listener);
         let app = Self::setup_app(&settings);
-        let server = Self::setup_server(&settings, tcp_listener);
         Self {
             server,
             app,
@@ -165,8 +191,8 @@ impl Application {
 
     /// Returns the host address the application is configured to bind to.
     #[must_use]
-    pub fn host(&self) -> String {
-        self.host.clone()
+    pub fn host(&self) -> &str {
+        &self.host
     }
 
     /// Returns the port the application is configured to bind to.
@@ -232,13 +258,11 @@ mod tests {
     #[test]
     fn application_with_custom_listener() {
         let settings = create_test_settings();
-        let tcp_listener =
+        let listener =
             std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind random port");
-        let port = tcp_listener.local_addr().unwrap().port();
-        let listener = poem::listener::TcpListener::bind(format!("127.0.0.1:{port}"));
-
+        let expected_port = listener.local_addr().unwrap().port();
         let app = Application::build(settings, Some(listener));
         assert_eq!(app.host(), "127.0.0.1");
-        assert_eq!(app.port(), 8080);
+        assert_eq!(app.port(), expected_port);
     }
 }

src/telemetry.rs

@@ -14,16 +14,13 @@ pub fn get_subscriber(debug: bool) -> impl tracing::Subscriber + Send + Sync {
     let env_filter = if debug { "debug" } else { "info" }.to_string();
     let env_filter = tracing_subscriber::EnvFilter::try_from_default_env()
         .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new(env_filter));
-    let stdout_log = tracing_subscriber::fmt::layer().pretty();
-    let subscriber = tracing_subscriber::Registry::default()
-        .with(env_filter)
-        .with(stdout_log);
-    let json_log = if debug {
-        None
+    let subscriber = tracing_subscriber::Registry::default().with(env_filter);
+    let (stdout_log, json_log) = if debug {
+        (Some(tracing_subscriber::fmt::layer().pretty()), None)
     } else {
-        Some(tracing_subscriber::fmt::layer().json())
+        (None, Some(tracing_subscriber::fmt::layer().json()))
     };
-    subscriber.with(json_log)
+    subscriber.with(stdout_log).with(json_log)
 }
 
 /// Initializes the global tracing subscriber.