From 5c442cddd8dc36b6ef9ad334d21cdeebb5e5b599 Mon Sep 17 00:00:00 2001
From: Sean McArthur <sean@seanmonstar.com>
Date: Mon, 5 Oct 2026 14:49:50 -0400
Subject: [PATCH] fix(http1): always remove content-length if transfer-encoding
 is sent

---
 src/proto/h1/role.rs | 64 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/src/proto/h1/role.rs b/src/proto/h1/role.rs
index f8556db637..4c91319bc7 100644
--- a/src/proto/h1/role.rs
+++ b/src/proto/h1/role.rs
@@ -1455,7 +1455,7 @@ impl Client {
         // This is because we need a second mutable borrow to remove
         // content-length header.
         if let Some(encoder) = encoder {
-            if should_remove_con_len && existing_con_len.is_some() {
+            if should_remove_con_len {
                 headers.remove(header::CONTENT_LENGTH);
             }
             return encoder;
@@ -2572,6 +2572,7 @@ mod tests {
                     req_method: &mut None,
                     h1_parser_config: Default::default(),
                     h1_max_headers: None,
+                    h1_max_header_size: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
                     preserve_header_order: false,
@@ -2649,6 +2650,7 @@ mod tests {
                     req_method: &mut Some(Method::GET),
                     h1_parser_config: Default::default(),
                     h1_max_headers: None,
+                    h1_max_header_size: None,
                     preserve_header_case: false,
                     #[cfg(feature = "ffi")]
                     preserve_header_order: false,
@@ -2736,6 +2738,66 @@ mod tests {
         assert_eq!(unfold("obs\r\n fold\r\n\t line"), "obs fold line",);
     }
 
+    #[test]
+    fn test_client_request_encode_explicit_transfer_encoding_removes_content_length() {
+        use crate::proto::BodyLength;
+        use http::header::HeaderValue;
+
+        for values in [
+            vec!["10"],
+            vec![""],
+            vec!["abc"],
+            vec!["+10"],
+            vec!["18446744073709551616"],
+            vec!["10", "11"],
+            vec!["10, 11"],
+            vec!["10", "abc"],
+        ] {
+            for transfer_encoding in ["chunked", "gzip"] {
+                for body in [BodyLength::Known(10), BodyLength::Unknown] {
+                    let mut head = MessageHead::default();
+                    for value in &values {
+                        head.headers
+                            .append("content-length", HeaderValue::from_static(value));
+                    }
+                    head.headers.insert(
+                        "transfer-encoding",
+                        HeaderValue::from_static(transfer_encoding),
+                    );
+
+                    let mut vec = Vec::new();
+                    let encoder = Client::encode(
+                        Encode {
+                            head: &mut head,
+                            body: Some(body),
+                            #[cfg(feature = "server")]
+                            keep_alive: true,
+                            req_method: &mut None,
+                            title_case_headers: false,
+                            #[cfg(feature = "server")]
+                            date_header: true,
+                        },
+                        &mut vec,
+                    )
+                    .unwrap();
+
+                    assert!(encoder.is_chunked());
+                    let expected_te = if transfer_encoding == "chunked" {
+                        "chunked"
+                    } else {
+                        "gzip, chunked"
+                    };
+                    assert_eq!(
+                        vec,
+                        format!("GET / HTTP/1.1\r\ntransfer-encoding: {expected_te}\r\n\r\n")
+                            .as_bytes(),
+                        "content-length: {values:?}, transfer-encoding: {transfer_encoding}"
+                    );
+                }
+            }
+        }
+    }
+
     #[test]
     fn test_client_request_encode_title_case() {
         use crate::proto::BodyLength;