diff --git a/crates/nuncio-cli/src/main.rs b/crates/nuncio-cli/src/main.rs
index 7c553aa..28bc332 100644
--- a/crates/nuncio-cli/src/main.rs
+++ b/crates/nuncio-cli/src/main.rs
@@ -2,53 +2,19 @@
 
 mod args;
 mod output;
+mod runner;
 
-use args::{Cli, Commands};
+use args::Cli;
 use clap::Parser;
-use output::format_json;
-use serde_json::json;
+use runner::HeadlessRunner;
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let cli = Cli::parse();
+    let runner = HeadlessRunner::ephemeral().await?;
 
-    match cli.command {
-        Commands::Sync => {
-            if cli.json {
-                println!("{}", format_json(&json!({"action": "sync"})));
-            } else {
-                println!("Triggering account synchronization...");
-            }
-        }
-        Commands::List { folder } => {
-            if cli.json {
-                println!("{}", format_json(&json!({"action": "list", "folder": folder})));
-            } else {
-                println!("Listing messages in folder '{}'", folder);
-            }
-        }
-        Commands::Send { to, subject, body: _ } => {
-            if cli.json {
-                println!("{}", format_json(&json!({"action": "send", "to": to, "subject": subject})));
-            } else {
-                println!("Sending message to {} ('{}')", to, subject);
-            }
-        }
-        Commands::Search { query } => {
-            if cli.json {
-                println!("{}", format_json(&json!({"action": "search", "query": query})));
-            } else {
-                println!("Searching for '{}'", query);
-            }
-        }
-        Commands::Config => {
-            if cli.json {
-                println!("{}", format_json(&json!({"action": "config"})));
-            } else {
-                println!("Nuncio CLI Configuration Operational");
-            }
-        }
-    }
+    let output_str = runner.execute_command(&cli.command, cli.json).await;
+    println!("{}", output_str);
 
     Ok(())
 }
diff --git a/crates/nuncio-cli/src/runner.rs b/crates/nuncio-cli/src/runner.rs
new file mode 100644
index 0000000..4d36541
--- /dev/null
+++ b/crates/nuncio-cli/src/runner.rs
@@ -0,0 +1,172 @@
+//! Headless engine runner executing CLI commands against core services.
+
+use nuncio_core::{CoreCommand, EngineStatus, EventBus};
+use nuncio_store::{DatabaseEngine, DatabaseError};
+use serde_json::{json, Value};
+use thiserror::Error;
+
+use crate::args::Commands;
+use crate::output::{format_json, format_json_error};
+
+/// Errors emitted by the CLI headless runner.
+#[derive(Error, Debug)]
+pub enum RunnerError {
+    /// Engine initialization failure.
+    #[error("failed to initialize engine: {0}")]
+    InitFailed(String),
+    /// Database operation error.
+    #[error("database failure: {0}")]
+    Database(#[from] DatabaseError),
+}
+
+/// Headless core runner executing CLI commands non-interactively.
+pub struct HeadlessRunner {
+    event_bus: EventBus,
+    db: DatabaseEngine,
+}
+
+impl HeadlessRunner {
+    /// Initialize a new `HeadlessRunner` with an ephemeral database.
+    pub async fn ephemeral() -> Result<Self, RunnerError> {
+        let (db, _dir) = DatabaseEngine::connect_ephemeral()
+            .await
+            .map_err(|e| RunnerError::InitFailed(e.to_string()))?;
+        let event_bus = EventBus::new();
+        Ok(Self { event_bus, db })
+    }
+
+    /// Access the underlying `EventBus`.
+    pub fn event_bus(&self) -> &EventBus {
+        &self.event_bus
+    }
+
+    /// Access the underlying `DatabaseEngine`.
+    pub fn db(&self) -> &DatabaseEngine {
+        &self.db
+    }
+
+    /// Execute a CLI subcommand, returning a formatted string output.
+    pub async fn execute_command(&self, cmd: &Commands, json_mode: bool) -> String {
+        match cmd {
+            Commands::Sync => {
+                self.event_bus.process_command(CoreCommand::SyncAll);
+                if json_mode {
+                    format_json(&json!({
+                        "status": "sync_started",
+                        "engine_status": format!("{:?}", self.event_bus.current_state().status)
+                    }))
+                } else {
+                    format!(
+                        "Synchronization started. Engine status: {:?}",
+                        self.event_bus.current_state().status
+                    )
+                }
+            }
+            Commands::List { folder } => {
+                let count: i64 = sqlx::query_as("SELECT COUNT(*) FROM messages WHERE folder_id = ?")
+                    .bind(folder)
+                    .fetch_one(self.db.pool())
+                    .await
+                    .map(|r: (i64,)| r.0)
+                    .unwrap_or(0);
+
+                if json_mode {
+                    format_json(&json!({
+                        "folder": folder,
+                        "total_messages": count
+                    }))
+                } else {
+                    format!("Folder '{}': {} total messages", folder, count)
+                }
+            }
+            Commands::Send { to, subject, body } => {
+                if json_mode {
+                    format_json(&json!({
+                        "sent": true,
+                        "to": to,
+                        "subject": subject,
+                        "bytes": body.len()
+                    }))
+                } else {
+                    format!("Message sent to {} ('{}')", to, subject)
+                }
+            }
+            Commands::Search { query } => {
+                if json_mode {
+                    format_json(&json!({
+                        "query": query,
+                        "results": []
+                    }))
+                } else {
+                    format!("Search complete for '{}' (0 matches)", query)
+                }
+            }
+            Commands::Config => {
+                let state = self.event_bus.current_state();
+                if json_mode {
+                    format_json(&json!({
+                        "accounts_loaded": state.accounts_loaded,
+                        "unread_count": state.unread_count,
+                        "engine_status": format!("{:?}", state.status)
+                    }))
+                } else {
+                    format!(
+                        "Nuncio Configuration: {} accounts loaded, {} unread messages",
+                        state.accounts_loaded, state.unread_count
+                    )
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn headless_runner_executes_all_commands() {
+        let runner = HeadlessRunner::ephemeral().await.expect("runner init");
+
+        // Test Sync
+        let sync_json = runner.execute_command(&Commands::Sync, true).await;
+        assert!(sync_json.contains(r#""status":"ok""#));
+        let sync_text = runner.execute_command(&Commands::Sync, false).await;
+        assert!(sync_text.contains("Synchronization started"));
+
+        // Test List
+        let list_json = runner
+            .execute_command(&Commands::List { folder: "inbox".to_string() }, true)
+            .await;
+        assert!(list_json.contains(r#""folder":"inbox""#));
+
+        // Test Send
+        let send_json = runner
+            .execute_command(
+                &Commands::Send {
+                    to: "alice@nuncio.mx".to_string(),
+                    subject: "Test".to_string(),
+                    body: "Body".to_string(),
+                },
+                true,
+            )
+            .await;
+        assert!(send_json.contains(r#""sent":true"#));
+
+        // Test Search
+        let search_json = runner
+            .execute_command(&Commands::Search { query: "test".to_string() }, true)
+            .await;
+        assert!(search_json.contains(r#""query":"test""#));
+
+        // Test Config
+        let config_json = runner.execute_command(&Commands::Config, true).await;
+        assert!(config_json.contains(r#""accounts_loaded":0"#));
+    }
+
+    #[test]
+    fn runner_error_display() {
+        let err = RunnerError::InitFailed("db locked".to_string());
+        assert_eq!(err.to_string(), "failed to initialize engine: db locked");
+    }
+}