diff --git a/atrium-api/Cargo.toml b/atrium-api/Cargo.toml
index eff18b5b..03147540 100644
--- a/atrium-api/Cargo.toml
+++ b/atrium-api/Cargo.toml
@@ -21,3 +21,4 @@ serde_bytes = "0.11.9"
 
 [dev-dependencies]
 tokio = { version = "1.28.0", features = ["macros", "rt-multi-thread"] }
+serde_json = "1.0.96"
diff --git a/atrium-api/src/agent.rs b/atrium-api/src/agent.rs
index 76e344bf..63cdcf54 100644
--- a/atrium-api/src/agent.rs
+++ b/atrium-api/src/agent.rs
@@ -1,13 +1,12 @@
 //! An ATP "Agent".
 //! Manages session token lifecycles and provides all XRPC methods.
+use crate::client::AtpServiceClient;
 use async_trait::async_trait;
+use atrium_xrpc::error::Error;
 use atrium_xrpc::{HttpClient, XrpcClient};
 use http::{Request, Response};
-use std::error::Error;
 use std::sync::{Arc, RwLock};
 
-use crate::client::AtpServiceClient;
-
 /// Type alias for the [com::atproto::server::create_session::Output](crate::com::atproto::server::create_session::Output)
 pub type Session = crate::com::atproto::server::create_session::Output;
 
@@ -27,7 +26,7 @@ where
     async fn send(
         &self,
         req: Request<Vec<u8>>,
-    ) -> Result<Response<Vec<u8>>, Box<dyn Error + Send + Sync + 'static>> {
+    ) -> Result<Response<Vec<u8>>, Box<dyn std::error::Error + Send + Sync + 'static>> {
         HttpClient::send(&self.xrpc, req).await
     }
 }
@@ -74,9 +73,168 @@ where
         let api = AtpServiceClient::new(Arc::new(base));
         Self { api, session }
     }
-    pub fn set_session(&mut self, session: Session) {
-        if let Ok(mut lock) = self.session.write() {
-            *lock = Some(session);
+    pub fn get_session(&self) -> Option<Session> {
+        self.session.read().expect("read lock").clone()
+    }
+    pub async fn login(
+        &self,
+        identifier: &str,
+        password: &str,
+    ) -> Result<Session, Error<crate::com::atproto::server::create_session::Error>> {
+        let result = self
+            .api
+            .com
+            .atproto
+            .server
+            .create_session(crate::com::atproto::server::create_session::Input {
+                identifier: identifier.into(),
+                password: password.into(),
+            })
+            .await?;
+        self.session
+            .write()
+            .expect("write lock")
+            .replace(result.clone());
+        Ok(result)
+    }
+    pub async fn resume_session(
+        &self,
+        session: Session,
+    ) -> Result<(), Error<crate::com::atproto::server::get_session::Error>> {
+        self.session
+            .write()
+            .expect("write lock")
+            .replace(session.clone());
+        match self.api.com.atproto.server.get_session().await {
+            Ok(result) => {
+                assert_eq!(result.did, session.did);
+                self.session.write().expect("write lock").replace(Session {
+                    email: result.email,
+                    handle: result.handle,
+                    ..session
+                });
+                Ok(())
+            }
+            Err(err) => {
+                self.session.write().expect("write lock").take();
+                Err(err)
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct DummyClient {
+        session: Option<Session>,
+    }
+
+    #[async_trait]
+    impl HttpClient for DummyClient {
+        async fn send(
+            &self,
+            _req: Request<Vec<u8>>,
+        ) -> Result<Response<Vec<u8>>, Box<dyn std::error::Error + Send + Sync + 'static>> {
+            let builder =
+                Response::builder().header(http::header::CONTENT_TYPE, "application/json");
+            if let Some(session) = &self.session {
+                Ok(builder
+                    .status(http::StatusCode::OK)
+                    .body(serde_json::to_vec(&session)?)?)
+            } else {
+                Ok(builder
+                    .status(http::StatusCode::UNAUTHORIZED)
+                    .body(serde_json::to_vec(
+                        &atrium_xrpc::error::ErrorResponseBody {
+                            error: Some(String::from("AuthenticationRequired")),
+                            message: Some(String::from("Invalid identifier or password")),
+                        },
+                    )?)?)
+            }
+        }
+    }
+
+    impl XrpcClient for DummyClient {
+        fn host(&self) -> &str {
+            "http://localhost:8080"
+        }
+    }
+
+    #[test]
+    fn new_agent() {
+        let agent = AtpAgent::new(atrium_xrpc::client::reqwest::ReqwestClient::new(
+            "http://localhost:8080".into(),
+        ));
+        assert_eq!(agent.get_session(), None);
+    }
+
+    #[tokio::test]
+    async fn login() {
+        let session = Session {
+            access_jwt: "access".into(),
+            did: "did".into(),
+            email: None,
+            handle: "handle".into(),
+            refresh_jwt: "refresh".into(),
+        };
+        // success
+        {
+            let client = DummyClient {
+                session: Some(session.clone()),
+            };
+            let agent = AtpAgent::new(client);
+            agent.login("test", "pass").await.expect("failed to login");
+            assert_eq!(agent.get_session(), Some(session));
+        }
+        // failure with `createSession` error
+        {
+            let client = DummyClient { session: None };
+            let agent = AtpAgent::new(client);
+            agent
+                .login("test", "bad")
+                .await
+                .expect_err("should failed to login");
+            assert_eq!(agent.get_session(), None);
+        }
+    }
+
+    #[tokio::test]
+    async fn resume_session() {
+        let session = Session {
+            access_jwt: "access".into(),
+            did: "did".into(),
+            email: None,
+            handle: "handle".into(),
+            refresh_jwt: "refresh".into(),
+        };
+        // success
+        {
+            let client = DummyClient {
+                session: Some(session.clone()),
+            };
+            let agent = AtpAgent::new(client);
+            assert_eq!(agent.get_session(), None);
+            agent
+                .resume_session(Session {
+                    email: Some(String::from("test@example.com")),
+                    ..session.clone()
+                })
+                .await
+                .expect("failed to resume session");
+            assert_eq!(agent.get_session(), Some(session.clone()));
+        }
+        // failure with `getSession` error
+        {
+            let client = DummyClient { session: None };
+            let agent = AtpAgent::new(client);
+            assert_eq!(agent.get_session(), None);
+            agent
+                .resume_session(session)
+                .await
+                .expect_err("should failed to resume session");
+            assert_eq!(agent.get_session(), None);
         }
     }
 }