diff --git a/crates/ember-cli/src/bench_conn.rs b/crates/ember-cli/src/bench_conn.rs
index b183116e..585882e8 100644
--- a/crates/ember-cli/src/bench_conn.rs
+++ b/crates/ember-cli/src/bench_conn.rs
@@ -11,6 +11,7 @@ use ember_protocol::parse::parse_frame;
 use ember_protocol::types::Frame;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
+use crate::connection::auth_frame;
 use crate::tls::{self, MaybeTlsStream, TlsClientConfig};
 
 /// Read buffer size for benchmark connections (256 KiB).
@@ -49,10 +50,7 @@ impl BenchConnection {
 
     /// Authenticates with the server using AUTH.
     pub async fn authenticate(&mut self, password: &str) -> Result<(), String> {
-        let frame = Frame::Array(vec![
-            Frame::Bulk(Bytes::from_static(b"AUTH")),
-            Frame::Bulk(Bytes::from(password.to_string())),
-        ]);
+        let frame = auth_frame(password);
         let mut buf = BytesMut::new();
         frame.serialize(&mut buf);
 
diff --git a/crates/ember-cli/src/connection.rs b/crates/ember-cli/src/connection.rs
index df2b820a..8bcfa210 100644
--- a/crates/ember-cli/src/connection.rs
+++ b/crates/ember-cli/src/connection.rs
@@ -100,8 +100,12 @@ impl Connection {
 
     /// Authenticates with the server using the AUTH command.
     pub async fn authenticate(&mut self, password: &str) -> Result<(), ConnectionError> {
-        let tokens = vec!["AUTH".to_string(), password.to_string()];
-        let response = self.send_command(&tokens).await?;
+        let frame = auth_frame(password);
+        self.write_buf.clear();
+        frame.serialize(&mut self.write_buf);
+        self.stream.write_all(&self.write_buf).await?;
+        self.stream.flush().await?;
+        let response = self.read_response().await?;
 
         match &response {
             Frame::Simple(s) if s == "OK" => Ok(()),
@@ -167,3 +171,14 @@ impl Connection {
         }
     }
 }
+
+/// Builds an AUTH command frame from a password string.
+///
+/// Shared by the interactive REPL connection and the benchmark connection so
+/// the AUTH wire format is defined in exactly one place.
+pub fn auth_frame(password: &str) -> Frame {
+    Frame::Array(vec![
+        Frame::Bulk(bytes::Bytes::from_static(b"AUTH")),
+        Frame::Bulk(bytes::Bytes::from(password.to_string())),
+    ])
+}
diff --git a/crates/ember-cli/src/repl.rs b/crates/ember-cli/src/repl.rs
index 01edc786..be1777b5 100644
--- a/crates/ember-cli/src/repl.rs
+++ b/crates/ember-cli/src/repl.rs
@@ -23,6 +23,14 @@ use crate::connection::{Connection, ConnectionError};
 use crate::format::format_response;
 use crate::tls::TlsClientConfig;
 
+// ANSI escape sequences for terminal coloring. Defined as constants so a
+// color change requires updating one place rather than grep-and-replace.
+const RESET: &str = "\x1b[0m";
+const GREEN: &str = "\x1b[32m";
+const RED: &str = "\x1b[31m";
+const BOLD_CYAN: &str = "\x1b[1;36m";
+const DIM: &str = "\x1b[2m";
+
 /// Runs the interactive REPL loop.
 ///
 /// Blocks the calling thread. Uses `tokio::runtime::Runtime` internally
@@ -449,9 +457,9 @@ impl Highlighter for EmberHelper {
             || LOCAL_COMMANDS.iter().any(|c| c.eq_ignore_ascii_case(first));
 
         let highlighted_cmd = if is_known {
-            format!("\x1b[1;36m{first}\x1b[0m") // bold cyan
+            format!("{BOLD_CYAN}{first}{RESET}") // bold cyan
         } else {
-            format!("\x1b[31m{first}\x1b[0m") // red
+            format!("{RED}{first}{RESET}") // red
         };
 
         // highlight quoted strings in rest
@@ -474,7 +482,7 @@ impl Highlighter for EmberHelper {
     }
 
     fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
-        Cow::Owned(format!("\x1b[2m{hint}\x1b[0m")) // dim
+        Cow::Owned(format!("{DIM}{hint}{RESET}")) // dim
     }
 
     fn highlight_char(
@@ -495,7 +503,8 @@ fn highlight_quotes(s: &str) -> String {
     while let Some(ch) = chars.next() {
         match ch {
             '"' => {
-                out.push_str("\x1b[32m\""); // green
+                out.push_str(GREEN);
+                out.push('"');
                 loop {
                     match chars.next() {
                         None => break,
@@ -512,10 +521,11 @@ fn highlight_quotes(s: &str) -> String {
                         Some(c) => out.push(c),
                     }
                 }
-                out.push_str("\x1b[0m"); // reset
+                out.push_str(RESET);
             }
             '\'' => {
-                out.push_str("\x1b[32m'"); // green
+                out.push_str(GREEN);
+                out.push('\'');
                 loop {
                     match chars.next() {
                         None => break,
@@ -526,7 +536,7 @@ fn highlight_quotes(s: &str) -> String {
                         Some(c) => out.push(c),
                     }
                 }
-                out.push_str("\x1b[0m"); // reset
+                out.push_str(RESET);
             }
             _ => out.push(ch),
         }