diff --git a/Cargo.lock b/Cargo.lock
index 40ddf5ea619..dd6f6c6ca43 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8850,6 +8850,7 @@ dependencies = [
  "regex",
  "reqwest",
  "serde_json",
+ "socket2 0.5.10",
  "spacetimedb-core",
  "spacetimedb-guard",
  "tempfile",
diff --git a/crates/smoketests/Cargo.toml b/crates/smoketests/Cargo.toml
index 473be886c55..fa2461b13c5 100644
--- a/crates/smoketests/Cargo.toml
+++ b/crates/smoketests/Cargo.toml
@@ -21,6 +21,7 @@ spacetimedb-core.workspace = true
 cargo_metadata.workspace = true
 assert_cmd = "2"
 predicates = "3"
+socket2.workspace = true
 tokio.workspace = true
 tokio-postgres.workspace = true
 xmltree.workspace = true
diff --git a/crates/smoketests/modules/Cargo.lock b/crates/smoketests/modules/Cargo.lock
index 2ce4b735807..e7adacae94a 100644
--- a/crates/smoketests/modules/Cargo.lock
+++ b/crates/smoketests/modules/Cargo.lock
@@ -609,6 +609,14 @@ dependencies = [
  "spacetimedb",
 ]
 
+[[package]]
+name = "smoketest-module-client-connection-http-cancel"
+version = "0.1.0"
+dependencies = [
+ "log",
+ "spacetimedb",
+]
+
 [[package]]
 name = "smoketest-module-client-connection-reject"
 version = "0.1.0"
diff --git a/crates/smoketests/modules/Cargo.toml b/crates/smoketests/modules/Cargo.toml
index c23de0030f6..c5a3faffebb 100644
--- a/crates/smoketests/modules/Cargo.toml
+++ b/crates/smoketests/modules/Cargo.toml
@@ -82,6 +82,7 @@ members = [
     "delete-database",
     "client-connection-reject",
     "client-connection-disconnect-panic",
+    "client-connection-http-cancel",
     "sql-connect-hook",
 
     # Log filtering tests
diff --git a/crates/smoketests/modules/client-connection-http-cancel/Cargo.toml b/crates/smoketests/modules/client-connection-http-cancel/Cargo.toml
new file mode 100644
index 00000000000..46ecd40b509
--- /dev/null
+++ b/crates/smoketests/modules/client-connection-http-cancel/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "smoketest-module-client-connection-http-cancel"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+spacetimedb.workspace = true
+log.workspace = true
diff --git a/crates/smoketests/modules/client-connection-http-cancel/src/lib.rs b/crates/smoketests/modules/client-connection-http-cancel/src/lib.rs
new file mode 100644
index 00000000000..1830b7f862d
--- /dev/null
+++ b/crates/smoketests/modules/client-connection-http-cancel/src/lib.rs
@@ -0,0 +1,25 @@
+use spacetimedb::{log, ReducerContext};
+
+#[spacetimedb::table(accessor = marker, public)]
+pub struct Marker {
+    id: u32,
+}
+
+#[spacetimedb::reducer(client_connected)]
+pub fn connected(ctx: &ReducerContext) {
+    log::info!("http_cancel_repro: connected {}", ctx.sender());
+}
+
+#[spacetimedb::reducer(client_disconnected)]
+pub fn disconnected(ctx: &ReducerContext) {
+    log::info!("http_cancel_repro: disconnected {}", ctx.sender());
+}
+
+#[spacetimedb::reducer]
+pub fn slow(_ctx: &ReducerContext) {
+    log::info!("http_cancel_repro: slow reducer started");
+    for i in 0..300_000_000u64 {
+        core::hint::black_box(i);
+    }
+    log::info!("http_cancel_repro: slow reducer finished");
+}
diff --git a/crates/smoketests/tests/smoketests/client_connection_errors.rs b/crates/smoketests/tests/smoketests/client_connection_errors.rs
index c937d750ce4..ec1fb641cb6 100644
--- a/crates/smoketests/tests/smoketests/client_connection_errors.rs
+++ b/crates/smoketests/tests/smoketests/client_connection_errors.rs
@@ -1,4 +1,9 @@
-use spacetimedb_smoketests::Smoketest;
+use socket2::SockRef;
+use spacetimedb_smoketests::{require_local_server, Smoketest};
+use std::io::Write;
+use std::net::TcpStream;
+use std::thread;
+use std::time::{Duration, Instant};
 
 /// Test that client_connected returning an error rejects the connection
 #[test]
@@ -57,3 +62,121 @@ fn test_client_disconnected_error_still_deletes_st_client() {
         "Expected at most 1 st_client row (the SQL connection itself), got {row_count}: {sql_out}",
     );
 }
+
+#[test]
+fn test_http_reducer_call_cancel_still_deletes_st_client() {
+    require_local_server!();
+
+    let test = Smoketest::builder()
+        .precompiled_module("client-connection-http-cancel")
+        .build();
+
+    let stream = send_http_reducer_call_and_hold_connection(&test, "slow");
+    wait_for_log(
+        &test,
+        "http_cancel_repro: slow reducer started",
+        Duration::from_secs(30),
+    );
+    abort_tcp_stream(stream);
+
+    wait_for_log(
+        &test,
+        "http_cancel_repro: slow reducer finished",
+        Duration::from_secs(30),
+    );
+
+    let (st_client_count, st_connection_credentials_count) = wait_for_client_rows_to_clear(&test);
+    assert!(
+        st_client_count <= 1,
+        "Expected at most 1 st_client row (the SQL connection itself) after dropping an HTTP call post-connect, got {st_client_count}",
+    );
+    assert!(
+        st_connection_credentials_count <= 1,
+        "Expected at most 1 st_connection_credentials row (the SQL connection itself) after dropping an HTTP call post-connect, got {st_connection_credentials_count}",
+    );
+}
+
+fn send_http_reducer_call_and_hold_connection(test: &Smoketest, reducer: &str) -> TcpStream {
+    let host = test.server_host();
+    let request = http_reducer_call_request(test, reducer);
+
+    let mut stream = TcpStream::connect(host).expect("Failed to connect to local server");
+    stream.set_nodelay(true).expect("Failed to set TCP_NODELAY");
+    stream
+        .write_all(request.as_bytes())
+        .expect("Failed to write HTTP request");
+    stream.flush().expect("Failed to flush HTTP request");
+    stream
+}
+
+fn abort_tcp_stream(stream: TcpStream) {
+    SockRef::from(&stream)
+        .set_linger(Some(Duration::ZERO))
+        .expect("Failed to set SO_LINGER=0");
+    drop(stream);
+}
+
+fn http_reducer_call_request(test: &Smoketest, reducer: &str) -> String {
+    let identity = test.database_identity.as_ref().expect("No database published");
+    let host = test.server_host();
+    let token = test.read_token().expect("Failed to read auth token");
+    let path = format!("/v1/database/{identity}/call/{reducer}");
+
+    // Keep the HTTP/1.1 connection alive so dropping the TCP stream is an
+    // unexpected client disconnect while the reducer call is still active.
+    format!(
+        "POST {path} HTTP/1.1\r\n\
+         Host: {host}\r\n\
+         Authorization: Bearer {token}\r\n\
+         Content-Type: application/json\r\n\
+         Content-Length: 2\r\n\
+         Connection: keep-alive\r\n\
+         \r\n\
+         []"
+    )
+}
+
+fn wait_for_log(test: &Smoketest, needle: &str, timeout: Duration) -> Vec<String> {
+    let start = Instant::now();
+    loop {
+        let logs = test.logs(200).unwrap();
+        if logs.iter().any(|l| l.contains(needle)) {
+            return logs;
+        }
+        assert!(
+            start.elapsed() < timeout,
+            "Timed out waiting for log containing {needle:?}: {:?}",
+            logs
+        );
+        thread::sleep(Duration::from_millis(1));
+    }
+}
+
+fn wait_for_client_rows_to_clear(test: &Smoketest) -> (usize, usize) {
+    let start = Instant::now();
+    let mut last = (usize::MAX, usize::MAX);
+
+    while start.elapsed() < Duration::from_secs(5) {
+        last = (
+            sql_count(test, "st_client"),
+            sql_count(test, "st_connection_credentials"),
+        );
+        if last.0 <= 1 && last.1 <= 1 {
+            return last;
+        }
+        thread::sleep(Duration::from_millis(50));
+    }
+
+    last
+}
+
+fn sql_count(test: &Smoketest, table: &str) -> usize {
+    let output = test
+        .sql(&format!("SELECT COUNT(*) AS count FROM {table}"))
+        .unwrap_or_else(|err| panic!("Failed to count rows in {table}: {err:#}"));
+
+    output
+        .lines()
+        .find_map(|line| line.trim().parse::<usize>().ok())
+        .unwrap_or_else(|| panic!("Failed to parse COUNT(*) output for {table}: {output}"))
+}