diff --git a/crates/agentkeys-cli/src/lib.rs b/crates/agentkeys-cli/src/lib.rs
index 10b9c4f..5338543 100644
--- a/crates/agentkeys-cli/src/lib.rs
+++ b/crates/agentkeys-cli/src/lib.rs
@@ -521,6 +521,26 @@ pub enum InitMode {
 }
 
 pub async fn cmd_init(ctx: &CommandContext, mode: InitMode) -> Result<(String, Session)> {
+    cmd_init_with_force(ctx, mode, false).await
+}
+
+pub async fn cmd_init_with_force(
+    ctx: &CommandContext,
+    mode: InitMode,
+    force: bool,
+) -> Result<(String, Session)> {
+    if !force {
+        if let Ok(existing) = ctx.load_session() {
+            if is_usable_session(&existing) {
+                let msg = format!(
+                    "Already initialized as {}. Run 'agentkeys init --force' to re-initialize.",
+                    existing.wallet.0
+                );
+                return Ok((msg, existing));
+            }
+        }
+    }
+
     match mode {
         InitMode::ImportLegacyMock(token) => init_legacy_mock(ctx, token).await,
         InitMode::Email {
@@ -558,6 +578,21 @@ pub async fn cmd_init(ctx: &CommandContext, mode: InitMode) -> Result<(String, S
     }
 }
 
+fn is_usable_session(session: &Session) -> bool {
+    if session.token.is_empty() || session.wallet.0.is_empty() || session.ttl_seconds == 0 {
+        return false;
+    }
+
+    if session.created_at == 0 {
+        return true;
+    }
+
+    let Ok(now) = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH) else {
+        return true;
+    };
+    now.as_secs() <= session.created_at.saturating_add(session.ttl_seconds)
+}
+
 /// Test-only: legacy `/session/create` path. Production cannot reach this
 /// (CLI surface drops `--mock-token`).
 async fn init_legacy_mock(ctx: &CommandContext, token: String) -> Result<(String, Session)> {
diff --git a/crates/agentkeys-cli/src/main.rs b/crates/agentkeys-cli/src/main.rs
index a9d670b..5b18815 100644
--- a/crates/agentkeys-cli/src/main.rs
+++ b/crates/agentkeys-cli/src/main.rs
@@ -1,8 +1,8 @@
 use agentkeys_cli::{
-    cmd_approve, cmd_feedback, cmd_inbox_list, cmd_inbox_provision, cmd_init, cmd_provision,
-    cmd_read, cmd_revoke, cmd_run, cmd_scope, cmd_signer_derive, cmd_signer_preview_7730,
-    cmd_signer_sign, cmd_signer_sign_typed_data, cmd_store, cmd_teardown, cmd_whoami,
-    CommandContext, CredentialBackendKind, EnvelopeVersionFlag, InitMode,
+    cmd_approve, cmd_feedback, cmd_inbox_list, cmd_inbox_provision, cmd_init_with_force,
+    cmd_provision, cmd_read, cmd_revoke, cmd_run, cmd_scope, cmd_signer_derive,
+    cmd_signer_preview_7730, cmd_signer_sign, cmd_signer_sign_typed_data, cmd_store, cmd_teardown,
+    cmd_whoami, CommandContext, CredentialBackendKind, EnvelopeVersionFlag, InitMode,
 };
 
 use clap::{Parser, Subcommand};
@@ -120,6 +120,10 @@ enum Commands {
         /// click or OAuth2 callback before failing the init.
         #[arg(long, default_value_t = 300)]
         poll_timeout_seconds: u64,
+
+        /// Re-run initialization even when a usable local session already exists.
+        #[arg(long)]
+        force: bool,
     },
 
     #[command(
@@ -963,6 +967,7 @@ async fn main() {
             signer_url,
             chain_id,
             poll_timeout_seconds,
+            force,
         } => {
             let broker_opt = broker_url.clone().or_else(|| ctx.broker_url.clone());
             let signer = signer_url
@@ -1000,7 +1005,9 @@ async fn main() {
                 )),
             };
             match mode_result {
-                Ok(mode) => cmd_init(&ctx, mode).await.map(|(msg, _session)| msg),
+                Ok(mode) => cmd_init_with_force(&ctx, mode, *force)
+                    .await
+                    .map(|(msg, _session)| msg),
                 Err(e) => Err(e),
             }
         }
diff --git a/crates/agentkeys-cli/tests/cli_tests.rs b/crates/agentkeys-cli/tests/cli_tests.rs
index 6f6f942..b56db7d 100644
--- a/crates/agentkeys-cli/tests/cli_tests.rs
+++ b/crates/agentkeys-cli/tests/cli_tests.rs
@@ -1,8 +1,8 @@
 use std::sync::Arc;
 
 use agentkeys_cli::{
-    cmd_inbox_list, cmd_inbox_provision, cmd_init, cmd_provision, cmd_read, cmd_revoke, cmd_run,
-    cmd_scope, cmd_store, cmd_teardown, CommandContext, InitMode,
+    cmd_inbox_list, cmd_inbox_provision, cmd_init, cmd_init_with_force, cmd_provision, cmd_read,
+    cmd_revoke, cmd_run, cmd_scope, cmd_store, cmd_teardown, CommandContext, InitMode,
 };
 use agentkeys_core::backend::CredentialBackend;
 use agentkeys_core::session_store::SessionStore;
@@ -80,6 +80,66 @@ fn ctx_verbose_with_session(
         .with_session_store(store)
 }
 
+#[tokio::test(flavor = "multi_thread")]
+async fn init_is_idempotent_when_session_exists() {
+    let backend = create_test_backend();
+    let (store, _tmp) = test_store();
+    let ctx = CommandContext::new("unused", false, false)
+        .with_backend(backend as Arc<dyn CredentialBackend>)
+        .with_session_store(store);
+
+    let (first_output, first_session) = cmd_init(
+        &ctx,
+        InitMode::ImportLegacyMock("idempotent-token-a".to_string()),
+    )
+    .await
+    .unwrap();
+    assert!(first_output.starts_with("Initialized. Wallet: "));
+
+    let (second_output, second_session) = cmd_init(
+        &ctx,
+        InitMode::ImportLegacyMock("idempotent-token-b".to_string()),
+    )
+    .await
+    .unwrap();
+
+    assert_eq!(
+        second_output,
+        format!(
+            "Already initialized as {}. Run 'agentkeys init --force' to re-initialize.",
+            first_session.wallet.0
+        )
+    );
+    assert_eq!(second_session, first_session);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn init_force_overrides_existing_session() {
+    let backend = create_test_backend();
+    let (store, _tmp) = test_store();
+    let ctx = CommandContext::new("unused", false, false)
+        .with_backend(backend as Arc<dyn CredentialBackend>)
+        .with_session_store(store);
+
+    let (_first_output, first_session) = cmd_init(
+        &ctx,
+        InitMode::ImportLegacyMock("force-token-a".to_string()),
+    )
+    .await
+    .unwrap();
+
+    let (second_output, second_session) = cmd_init_with_force(
+        &ctx,
+        InitMode::ImportLegacyMock("force-token-b".to_string()),
+        true,
+    )
+    .await
+    .unwrap();
+
+    assert!(second_output.starts_with("Initialized. Wallet: "));
+    assert_ne!(second_session.wallet, first_session.wallet);
+}
+
 // Test 1: init creates a session and returns a wallet address
 #[tokio::test(flavor = "multi_thread")]
 async fn cli_init_creates_session() {