diff --git a/src/lib.rs b/src/lib.rs
index 64f371e..0c997d8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,7 +12,7 @@ use clap::Parser;
 use log::{error, info};
 use tokio::{select, sync::oneshot};
 
-use crate::utils::observability::init_observability;
+use crate::utils::{instance, observability::init_observability};
 
 /// Git hash of the aisix core at build time.
 pub const GIT_HASH: &str = env!("VERGEN_GIT_SHA");
@@ -37,6 +37,9 @@ pub struct Args {
 pub async fn run(config_file: Option<String>) -> Result<()> {
     let (ob_shutdown_signal, ob_shutdown_task) =
         init_observability().context("failed to initialize observability")?;
+
+    instance::init().context("failed to initialize instance")?;
+
     let config = match config::load(config_file).context("failed to load configuration") {
         Ok(c) => Arc::new(c),
         Err(e) => {
diff --git a/src/utils/instance.rs b/src/utils/instance.rs
new file mode 100644
index 0000000..b972ceb
--- /dev/null
+++ b/src/utils/instance.rs
@@ -0,0 +1,152 @@
+use std::{path::Path, sync::OnceLock};
+
+use anyhow::{Result, anyhow};
+use log::{debug, info, warn};
+use uuid::Uuid;
+
+const ID_FILE: &str = "/tmp/aisix_instance_id";
+
+static RUN_ID: OnceLock<String> = OnceLock::new();
+static INSTANCE_ID: OnceLock<String> = OnceLock::new();
+
+/// Initialize the instance ID and run ID.
+pub fn init() -> Result<()> {
+    RUN_ID.get_or_init(|| Uuid::new_v4().to_string());
+
+    let instance_id = resolve_instance_id_from_path(Path::new(ID_FILE))?;
+    INSTANCE_ID.get_or_init(|| instance_id);
+
+    Ok(())
+}
+
+/// Get the run ID.
+pub fn run_id() -> String {
+    RUN_ID.get().cloned().expect("run id has been initialized")
+}
+
+/// Get the instance ID.
+pub fn instance_id() -> String {
+    INSTANCE_ID
+        .get()
+        .cloned()
+        .expect("instance id has been initialized")
+}
+
+fn resolve_instance_id_from_path(path: &Path) -> Result<String> {
+    match read_id_file(path) {
+        Ok(Some(id)) => {
+            debug!("agent: loaded instance_id from {:?}", path);
+            return Ok(id);
+        }
+        Err(e) => return Err(e),
+        Ok(None) => {}
+    };
+
+    let id = Uuid::new_v4().to_string();
+
+    if let Ok(()) = write_id_file(path, &id) {
+        info!(
+            "agent: generated and persisted instance_id={id} to {:?}",
+            path
+        );
+        return Ok(id);
+    }
+
+    warn!(
+        "agent: instance_id={id} is in-memory only (could not write to {:?}) — identifier will rotate on restart",
+        path
+    );
+    Ok(id)
+}
+
+fn read_id_file(path: &Path) -> Result<Option<String>> {
+    match std::fs::read_to_string(path) {
+        Ok(content) => {
+            let trimmed = content.trim();
+            if !trimmed.is_empty() {
+                return Ok(Some(trimmed.to_string()));
+            }
+            warn!("agent: instance_id file {:?} is empty, ignoring", path);
+            Ok(None)
+        }
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(None),
+        Err(e) => Err(anyhow!("failed to read instance_id file {path:?}: {e}")),
+    }
+}
+
+fn write_id_file(path: &Path, id: &str) -> Result<()> {
+    if let Some(parent) = path.parent() {
+        if let Err(e) = std::fs::create_dir_all(parent) {
+            debug!(
+                "agent: cannot create instance_id parent dir {:?}: {e}",
+                parent
+            );
+            return Err(anyhow!(
+                "failed to create instance_id parent dir {parent:?}: {e}"
+            ));
+        }
+    }
+
+    if let Err(e) = std::fs::write(path, id) {
+        debug!("agent: cannot write instance_id to {:?}: {e}", path);
+        return Err(anyhow!("failed to write instance_id file {path:?}: {e}"));
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::PathBuf;
+
+    use super::*;
+
+    fn tmp_dir() -> PathBuf {
+        let dir = std::env::temp_dir().join(format!("aisix_instance_test_{}", Uuid::new_v4()));
+        std::fs::create_dir_all(&dir).unwrap();
+        dir
+    }
+
+    #[test]
+    fn reuses_existing_file() {
+        let dir = tmp_dir();
+        let path = dir.join("instance_id");
+        std::fs::write(&path, "existing-id\n").unwrap();
+
+        assert_eq!(resolve_instance_id_from_path(&path).unwrap(), "existing-id");
+    }
+
+    #[test]
+    fn returns_error_when_existing_path_is_not_readable_as_file() {
+        let dir = tmp_dir();
+        let path = dir.join("instance_id");
+        std::fs::create_dir_all(&path).unwrap();
+
+        assert!(resolve_instance_id_from_path(&path).is_err());
+    }
+
+    #[test]
+    fn writes_new_id_when_file_absent() {
+        let dir = tmp_dir();
+        let path = dir.join("sub/instance_id");
+
+        let id = resolve_instance_id_from_path(&path).unwrap();
+        assert!(!id.is_empty());
+        assert_eq!(std::fs::read_to_string(&path).unwrap(), id);
+    }
+
+    #[test]
+    fn falls_back_to_memory_when_unwritable() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let dir = tmp_dir();
+        let blocked = dir.join("blocked");
+        std::fs::create_dir_all(&blocked).unwrap();
+        std::fs::set_permissions(&blocked, std::fs::Permissions::from_mode(0o555)).unwrap();
+
+        let target = blocked.join("instance_id");
+        let id = resolve_instance_id_from_path(&target).unwrap();
+        assert!(!id.is_empty());
+        assert!(!target.exists());
+    }
+}
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index 7641248..754acbe 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -1,4 +1,5 @@
 pub mod future;
+pub mod instance;
 pub mod jsonschema;
 pub mod metrics;
 pub mod observability;