Show initial lines before following logs

src/cortex-cli/src/logs_cmd.rs

@@ -222,6 +222,27 @@ impl LogsCli {
         println!("Following log file: {}", log_file.display());
         println!("Press Ctrl+C to stop.\n");
 
+        let content = std::fs::read_to_string(log_file)?;
+        let lines: Vec<&str> = content.lines().collect();
+        let filtered_lines: Vec<&str> = if let Some(ref level) = self.level {
+            let level_upper = level.to_uppercase();
+            lines
+                .iter()
+                .filter(|line| line.to_uppercase().contains(&level_upper))
+                .copied()
+                .collect()
+        } else {
+            lines
+        };
+        let start = if filtered_lines.len() > self.lines {
+            filtered_lines.len() - self.lines
+        } else {
+            0
+        };
+        for line in &filtered_lines[start..] {
+            println!("{}", line);
+        }
+
         let file = std::fs::File::open(log_file)?;
         let mut reader = BufReader::new(file);
 

src/cortex-cli/tests/logs_follow_lines.rs

@@ -0,0 +1,43 @@
+use std::fs;
+use std::io::Read;
+use std::process::{Command, Stdio};
+use std::thread;
+use std::time::Duration;
+
+use tempfile::tempdir;
+
+#[test]
+fn logs_follow_prints_requested_initial_lines() {
+    let home = tempdir().unwrap();
+    let cache = tempdir().unwrap();
+    let logs_dir = cache.path().join("cortex").join("logs");
+    fs::create_dir_all(&logs_dir).unwrap();
+    fs::write(logs_dir.join("cortex.log"), "one\ntwo\nthree\nfour\n").unwrap();
+
+    let mut child = Command::new(env!("CARGO_BIN_EXE_Cortex"))
+        .args(["logs", "--follow", "--lines", "2"])
+        .env("HOME", home.path())
+        .env("XDG_CACHE_HOME", cache.path())
+        .env_remove("CORTEX_HOME")
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    thread::sleep(Duration::from_millis(250));
+    let _ = child.kill();
+
+    let mut stdout = String::new();
+    child
+        .stdout
+        .take()
+        .unwrap()
+        .read_to_string(&mut stdout)
+        .unwrap();
+    let _ = child.wait();
+
+    assert!(!stdout.contains("\none\n"), "output:\n{stdout}");
+    assert!(!stdout.contains("\ntwo\n"), "output:\n{stdout}");
+    assert!(stdout.contains("\nthree\n"), "output:\n{stdout}");
+    assert!(stdout.contains("\nfour\n"), "output:\n{stdout}");
+}