diff --git a/p/src/cli.rs b/p/src/cli.rs
index 9462785..c439e23 100644
--- a/p/src/cli.rs
+++ b/p/src/cli.rs
@@ -75,8 +75,12 @@ pub enum Command {
         name: Option<String>,
     },
 
-    /// List registered workers and their reachability status
-    Workers,
+    /// List registered workers
+    Workers {
+        /// Check reachability of each worker over SSH
+        #[arg(short, long)]
+        check: bool,
+    },
 
     /// Set the default worker
     Default {
diff --git a/p/src/commands/register.rs b/p/src/commands/register.rs
index dc097f6..25472c6 100644
--- a/p/src/commands/register.rs
+++ b/p/src/commands/register.rs
@@ -1,6 +1,43 @@
 use anyhow::Result;
 
+use crate::{config, ssh};
+
 pub fn execute(connection: &str, name: Option<&str>) -> Result<()> {
-    let _ = (connection, name);
-    anyhow::bail!("not yet implemented")
+    let mut cfg = config::load()?;
+
+    let name = match name {
+        Some(n) => n.to_string(),
+        None => ssh::hostname_from_connection(connection),
+    };
+
+    // Reject duplicates (same name or same connection string).
+    if cfg.get_worker(&name).is_some() {
+        anyhow::bail!(
+            "a worker named '{}' is already registered\n\
+             Use 'p default {}' to make it the default, or choose a different name with -n",
+            name, name
+        );
+    }
+
+    let first = cfg.workers.is_empty();
+    cfg.workers.push(config::WorkerConfig {
+        name: name.clone(),
+        connection: connection.to_string(),
+    });
+
+    // First registered worker becomes the default automatically.
+    if first {
+        cfg.default_worker = Some(name.clone());
+    }
+
+    config::save(&cfg)?;
+
+    if first {
+        println!("Registered '{}' and set as default worker.", name);
+    } else {
+        println!("Registered '{}'.", name);
+        println!("Run 'p default {}' to make it the default.", name);
+    }
+
+    Ok(())
 }
diff --git a/p/src/commands/set_default.rs b/p/src/commands/set_default.rs
index bb49439..fb6b2d6 100644
--- a/p/src/commands/set_default.rs
+++ b/p/src/commands/set_default.rs
@@ -1,6 +1,25 @@
 use anyhow::Result;
 
+use crate::config;
+
 pub fn execute(worker: &str) -> Result<()> {
-    let _ = worker;
-    anyhow::bail!("not yet implemented")
+    let mut cfg = config::load()?;
+
+    if cfg.get_worker(worker).is_none() {
+        let known: Vec<&str> = cfg.workers.iter().map(|w| w.name.as_str()).collect();
+        if known.is_empty() {
+            anyhow::bail!("no workers registered yet — run 'p register <connection>' first");
+        }
+        anyhow::bail!(
+            "unknown worker '{}'\n\nKnown workers: {}",
+            worker,
+            known.join(", ")
+        );
+    }
+
+    cfg.default_worker = Some(worker.to_string());
+    config::save(&cfg)?;
+
+    println!("Default worker set to '{}'.", worker);
+    Ok(())
 }
diff --git a/p/src/commands/workers.rs b/p/src/commands/workers.rs
index 3a9aa7c..75866dd 100644
--- a/p/src/commands/workers.rs
+++ b/p/src/commands/workers.rs
@@ -1,5 +1,37 @@
 use anyhow::Result;
 
-pub fn execute() -> Result<()> {
-    anyhow::bail!("not yet implemented")
+use crate::{config, ssh};
+
+pub fn execute(check: bool) -> Result<()> {
+    let cfg = config::load()?;
+
+    if cfg.workers.is_empty() {
+        println!("No workers registered. Run 'p register <connection>' to add one.");
+        return Ok(());
+    }
+
+    let name_w = cfg.workers.iter().map(|w| w.name.len()).max().unwrap_or(0).max(4);
+    let conn_w = cfg.workers.iter().map(|w| w.connection.len()).max().unwrap_or(0).max(10);
+
+    if check {
+        println!("  {:<name_w$}  {:<conn_w$}  STATUS", "NAME", "CONNECTION");
+        println!("  {:<name_w$}  {:<conn_w$}  ------", "-".repeat(name_w), "-".repeat(conn_w));
+    } else {
+        println!("  {:<name_w$}  CONNECTION", "NAME");
+        println!("  {:<name_w$}  ----------", "-".repeat(name_w));
+    }
+
+    for worker in &cfg.workers {
+        let is_default = cfg.default_worker.as_deref() == Some(&worker.name);
+        let prefix = if is_default { "* " } else { "  " };
+
+        if check {
+            let status = if ssh::is_reachable(worker) { "reachable" } else { "unreachable" };
+            println!("{}{:<name_w$}  {:<conn_w$}  {}", prefix, worker.name, worker.connection, status);
+        } else {
+            println!("{}{:<name_w$}  {}", prefix, worker.name, worker.connection);
+        }
+    }
+
+    Ok(())
 }
diff --git a/p/src/main.rs b/p/src/main.rs
index 7606061..b754a14 100644
--- a/p/src/main.rs
+++ b/p/src/main.rs
@@ -61,7 +61,7 @@ fn main() -> Result<()> {
         cli::Command::Register { connection, name } => {
             commands::register::execute(&connection, name.as_deref())
         }
-        cli::Command::Workers => commands::workers::execute(),
+        cli::Command::Workers { check } => commands::workers::execute(check),
         cli::Command::Default { worker } => commands::set_default::execute(&worker),
     }
 }
diff --git a/p/src/ssh.rs b/p/src/ssh.rs
index 1bafc0a..ffced7f 100644
--- a/p/src/ssh.rs
+++ b/p/src/ssh.rs
@@ -32,6 +32,24 @@ pub fn hostname_from_connection(conn: &str) -> String {
     }
 }
 
+/// Check whether a worker is reachable over SSH (5 s timeout, no auth prompts).
+pub fn is_reachable(worker: &WorkerConfig) -> bool {
+    let mut args = vec![
+        "-o".to_string(), "ConnectTimeout=5".to_string(),
+        "-o".to_string(), "BatchMode=yes".to_string(),
+    ];
+    args.extend(ssh_args(worker));
+    args.push("true".to_string());
+
+    std::process::Command::new("ssh")
+        .args(&args)
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null())
+        .status()
+        .map(|s| s.success())
+        .unwrap_or(false)
+}
+
 /// Build the base ssh argument list for a worker (handles custom port).
 pub fn ssh_args(worker: &WorkerConfig) -> Vec<String> {
     let (user_host, port) = parse_connection(&worker.connection);