diff --git a/crates/orbyn-device-client/src/api.rs b/crates/orbyn-device-client/src/api.rs
index 9147a08..5b4ce9e 100644
--- a/crates/orbyn-device-client/src/api.rs
+++ b/crates/orbyn-device-client/src/api.rs
@@ -111,6 +111,10 @@ impl HttpApi {
         }
         let client = reqwest::Client::builder()
             .redirect(reqwest::redirect::Policy::none())
+            // No proxy from the environment, loopback included: reqwest reads `HTTP_PROXY`,
+            // `HTTPS_PROXY` and `ALL_PROXY` by default and does not exempt 127.0.0.1, so a request
+            // with the bearer token would go to whatever the machine names as its proxy.
+            .no_proxy()
             .timeout(TIMEOUT)
             .connect_timeout(CONNECT_TIMEOUT)
             .https_only(!loopback)
diff --git a/crates/orbyn-device-client/tests/no_proxy.rs b/crates/orbyn-device-client/tests/no_proxy.rs
new file mode 100644
index 0000000..830bba6
--- /dev/null
+++ b/crates/orbyn-device-client/tests/no_proxy.rs
@@ -0,0 +1,116 @@
+//! The real transport never goes through a proxy named in the environment. A request to the
+//! engine carries a bearer token, so a `HTTP_PROXY` or `ALL_PROXY` set on the machine (by
+//! software, a profile or an attacker) must not be able to see it, even for a loopback address.
+//!
+//! The environment is process-wide, so each case runs the same test binary again as a child with
+//! the proxy variables set. A loopback server stands for the engine and a second listener for the
+//! proxy; the proxy must get no connection.
+
+use orbyn_device_client::{DeviceApi, HttpApi, Method, Request, Zeroizing};
+use std::process::Command;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpListener;
+
+const CHILD: &str = "ORBYN_NO_PROXY_CHILD";
+
+/// A listener that counts connections and answers `status`.
+async fn listener(status: &'static str) -> (String, Arc<AtomicUsize>) {
+    let listener = TcpListener::bind("127.0.0.1:0").await.expect("bind");
+    let address = format!("http://{}", listener.local_addr().expect("addr"));
+    let count = Arc::new(AtomicUsize::new(0));
+    let seen = count.clone();
+    tokio::spawn(async move {
+        while let Ok((mut socket, _)) = listener.accept().await {
+            seen.fetch_add(1, Ordering::SeqCst);
+            tokio::spawn(async move {
+                let mut buffer = vec![0u8; 8192];
+                let _ = socket.read(&mut buffer).await;
+                let reply =
+                    format!("HTTP/1.1 {status}\r\nContent-Length: 0\r\nConnection: close\r\n\r\n");
+                let _ = socket.write_all(reply.as_bytes()).await;
+                let _ = socket.shutdown().await;
+            });
+        }
+    });
+    (address, count)
+}
+
+/// Runs in the child: one authenticated request to the address in the environment.
+#[tokio::test(flavor = "multi_thread")]
+async fn child_sends_one_request() {
+    let Ok(address) = std::env::var(CHILD) else {
+        return; // Not a child: nothing to do.
+    };
+    let response = HttpApi::new(&address)
+        .expect("loopback http is allowed")
+        .send(Request {
+            method: Method::Get,
+            path: "/v1/devices".to_owned(),
+            bearer: Some(Zeroizing::new("secret-token".to_owned())),
+            body: None,
+        })
+        .await
+        .expect("an answer");
+    assert_eq!(response.status, 204, "the answer came from the engine");
+}
+
+fn child(engine: &str, proxy: &str, variables: &[&str], no_proxy: Option<&str>) -> bool {
+    let mut command = Command::new(std::env::current_exe().expect("this test binary"));
+    command
+        .args(["--exact", "child_sends_one_request", "--nocapture"])
+        .env(CHILD, engine);
+    for name in [
+        "HTTP_PROXY",
+        "http_proxy",
+        "HTTPS_PROXY",
+        "https_proxy",
+        "ALL_PROXY",
+        "all_proxy",
+        "NO_PROXY",
+        "no_proxy",
+    ] {
+        command.env_remove(name);
+    }
+    for name in variables {
+        command.env(name, proxy);
+    }
+    if let Some(no_proxy) = no_proxy {
+        command.env("NO_PROXY", no_proxy).env("no_proxy", no_proxy);
+    }
+    command.status().expect("the child ran").success()
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn a_proxy_in_the_environment_never_sees_a_request_to_the_engine() {
+    if std::env::var(CHILD).is_ok() {
+        return; // The child runs only `child_sends_one_request`.
+    }
+    for (variables, no_proxy) in [
+        (&["HTTP_PROXY", "http_proxy"][..], None),
+        (&["ALL_PROXY", "all_proxy"][..], None),
+        (&["HTTPS_PROXY", "https_proxy"][..], None),
+        (
+            &["HTTP_PROXY", "ALL_PROXY"][..],
+            // A NO_PROXY that does not name the engine's address changes nothing.
+            Some("example.com"),
+        ),
+    ] {
+        let (engine, reached_engine) = listener("204 No Content").await;
+        let (proxy, reached_proxy) = listener("502 Bad Gateway").await;
+        let (engine_for_child, proxy_for_child) = (engine.clone(), proxy.clone());
+        let ok = tokio::task::spawn_blocking(move || {
+            child(&engine_for_child, &proxy_for_child, variables, no_proxy)
+        })
+        .await
+        .expect("joined");
+        assert_eq!(
+            reached_proxy.load(Ordering::SeqCst),
+            0,
+            "{variables:?} NO_PROXY={no_proxy:?}: the proxy was contacted"
+        );
+        assert!(ok, "{variables:?}: the request did not reach the engine");
+        assert_eq!(reached_engine.load(Ordering::SeqCst), 1, "{variables:?}");
+    }
+}
diff --git a/docs/device-client.md b/docs/device-client.md
index 799c72c..f38c1c7 100644
--- a/docs/device-client.md
+++ b/docs/device-client.md
@@ -82,10 +82,11 @@ An error never carries a password, a token, a code, a key or a URL. `Request` an
 
 ## The transport
 
-`HttpApi` is reqwest with **rustls and ring only** (no OpenSSL, no aws-lc). **Redirects are off**: a redirect could carry the bearer token elsewhere, and a redirect is returned as an answer. The address must be `https`, or `http` to a **loopback IP literal** (`127.0.0.1`, `[::1]`) for a local stack, with no user info, query or path. A name such as `localhost` is not a loopback literal, because a name can be made to point anywhere. `is_loopback_literal(address)` is public so the app's "local only" gate can use the same test. Calls time out at 30 seconds, connects at 10, and a response body is capped at 32 MiB (`with_body_limit` lowers it), counted **while reading**, so a server that sends no `Content-Length`, or lies about it, is stopped too.
+`HttpApi` is reqwest with **rustls and ring only** (no OpenSSL, no aws-lc). **No proxy is used, whatever `HTTP_PROXY`, `HTTPS_PROXY`, `ALL_PROXY` or `NO_PROXY` say** (reqwest reads them by default and does not exempt loopback, so the bearer token would reach the proxy); **Redirects are off**: a redirect could carry the bearer token elsewhere, and a redirect is returned as an answer. The address must be `https`, or `http` to a **loopback IP literal** (`127.0.0.1`, `[::1]`) for a local stack, with no user info, query or path. A name such as `localhost` is not a loopback literal, because a name can be made to point anywhere. `is_loopback_literal(address)` is public so the app's "local only" gate can use the same test. Calls time out at 30 seconds, connects at 10, and a response body is capped at 32 MiB (`with_body_limit` lowers it), counted **while reading**, so a server that sends no `Content-Length`, or lies about it, is stopped too.
 
 ## Tests
 
+- `tests/no_proxy.rs` runs the test binary again as a child with `HTTP_PROXY`, `ALL_PROXY` and `HTTPS_PROXY` set (and a `NO_PROXY` that does not name the engine) to a second listener, sends one authenticated request to a loopback engine and checks that the proxy gets no connection and the engine gets the request.
 - `tests/redirects.rs` serves 301, 302, 303, 307 and 308 from a loopback server with a `Location` to a second listener, sends every method with a bearer token through `HttpApi`, and checks that each redirect comes back as the answer and the second listener never gets a connection; it also checks that plain `http` is refused for any host that is not a loopback IP literal.
 - `tests/client.rs` runs the client against an in-memory engine (`tests/support`) that speaks the **real OPAQUE server side** and checks the real signatures: proof of work, invite, code, trusted start, second factor, re-login after eleven minutes, account gone, rate limit, and that no request body holds the password. The same file serves a raw HTTP reply to check that redirects are not followed and `Retry-After` is read.
 - `tests/local_stack.rs` (ignored by default, and skipped with a printed note unless `ORBYN_LOCAL_STACK=1`, so `cargo test -- --include-ignored` in CI passes without a stack) runs sign-up, a second pending device, a wrong password, the re-login and sign-out against the real engine on `scripts/local.sh up`, using `scripts/local.sh invite-code` and `scripts/local.sh latest-code <email>`.