diff --git a/apps/desktop-tauri/src-tauri/src/commands/codex_accounts.rs b/apps/desktop-tauri/src-tauri/src/commands/codex_accounts.rs
new file mode 100644
index 0000000000..179c84ada1
--- /dev/null
+++ b/apps/desktop-tauri/src-tauri/src/commands/codex_accounts.rs
@@ -0,0 +1,362 @@
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::sync::{Arc, Mutex};
+
+use uuid::Uuid;
+
+use codexbar::codex_accounts::{
+    AccountStore, CodexAccount, CodexAccountApi, CodexAccountManager, CodexAccountManagerError,
+    CodexApiError, CodexSwitchResult, SnapshotStore, restart_codex_desktop,
+};
+
+use crate::state::AppState;
+
+use super::*;
+
+// ── Codex multi-account (ADR 0003, milestone 2) ──────────────────────
+
+const DEFAULT_FETCH_TIMEOUT_SECONDS: u64 = 60;
+
+/// All stored + discovered Codex accounts, with the stored list preferred.
+pub(crate) fn load_codex_accounts() -> Result<Vec<CodexAccount>, String> {
+    let store = AccountStore::new();
+    let existing = store.load_accounts().map_err(|e| e.to_string())?;
+
+    let manager = CodexAccountManager::new();
+    let managed = manager
+        .discover_managed_accounts(&existing)
+        .map_err(|e| e.to_string())?;
+    let ambient = manager.discover_ambient_account(&existing);
+
+    let mut merged: Vec<CodexAccount> = managed.clone();
+    if let Some(ambient) = ambient {
+        if let Some(entry) = merged.iter_mut().find(|account| account.matches(&ambient)) {
+            entry.merge_from(&ambient);
+        } else {
+            merged.push(ambient);
+        }
+    }
+
+    // Reconcile persisted metadata (nickname, stored timestamps) for managed homes.
+    let mut reconciled: Vec<CodexAccount> = existing
+        .iter()
+        .map(|account| {
+            let mut account = account.clone();
+            if let Some(fresh) = managed.iter().find(|fresh| fresh.matches(&account)) {
+                account.merge_from(fresh);
+            }
+            account
+        })
+        .collect();
+
+    // Add any newly discovered accounts that are not yet persisted.
+    for candidate in &merged {
+        if !reconciled.iter().any(|account| account.matches(candidate)) {
+            reconciled.push(candidate.clone());
+        }
+    }
+
+    Ok(reconciled)
+}
+
+/// Persist the given accounts to the account store.
+pub(crate) fn persist_codex_accounts(accounts: &[CodexAccount]) -> Result<(), String> {
+    let store = AccountStore::new();
+    let (_existing, removed) = store.load().map_err(|e| e.to_string())?;
+    store
+        .save(accounts, Some(&removed))
+        .map_err(|e| e.to_string())
+}
+
+/// Refresh quota snapshots for every Codex account (ADR 0003 multi-account
+/// lanes).
+///
+/// Runs on the same refresh cycle as the ambient Codex provider lane: each
+/// account (ambient + managed) is fetched concurrently, bounded by the shared
+/// provider fetch semaphore, and persisted to the account snapshot store. A
+/// `codex-accounts-updated` event lets surfaces (Settings accounts panel)
+/// re-read the store without manual fetch.
+///
+/// Failures are per-account and non-fatal: the ambient provider snapshot and
+/// the on-demand `codex_account_fetch` command remain authoritative, and the
+/// store keeps the last good snapshot per account.
+pub(crate) async fn refresh_codex_account_lanes(
+    app: tauri::AppHandle,
+    fetch_permits: Arc<tokio::sync::Semaphore>,
+) {
+    let accounts = match load_codex_accounts() {
+        Ok(accounts) => accounts,
+        Err(e) => {
+            tracing::warn!("codex account lanes: failed to load accounts: {e}");
+            return;
+        }
+    };
+    if accounts.is_empty() {
+        return;
+    }
+
+    let mut handles = Vec::with_capacity(accounts.len());
+    for account in accounts {
+        let permits = Arc::clone(&fetch_permits);
+        handles.push(tokio::spawn(async move {
+            let Ok(_permit) = permits.acquire_owned().await else {
+                return None;
+            };
+            let api = CodexAccountApi::new();
+            let home_path = account.codex_home_path.clone();
+            let email_hint = account.email_hint.clone();
+            match tokio::time::timeout(
+                std::time::Duration::from_secs(DEFAULT_FETCH_TIMEOUT_SECONDS),
+                api.fetch_snapshot(&home_path, email_hint.as_deref(), true),
+            )
+            .await
+            {
+                Ok(Ok(snapshot)) => Some((account.id, snapshot)),
+                Ok(Err(e)) => {
+                    tracing::debug!(
+                        "codex account lane {} failed: {}",
+                        account.id,
+                        into_api_message(e)
+                    );
+                    None
+                }
+                Err(_) => {
+                    tracing::debug!("codex account lane {} timed out", account.id);
+                    None
+                }
+            }
+        }));
+    }
+
+    let mut snapshots = SnapshotStore::new().load().unwrap_or_default();
+    for handle in handles {
+        if let Ok(Some((id, snapshot))) = handle.await {
+            snapshots.insert(id, snapshot);
+        }
+    }
+    if let Err(e) = SnapshotStore::new().save(&snapshots) {
+        tracing::warn!("codex account lanes: failed to persist snapshots: {e}");
+    }
+    events::emit_codex_accounts_updated(&app);
+}
+
+#[tauri::command]
+pub fn codex_accounts_list() -> Result<Vec<CodexAccount>, String> {
+    load_codex_accounts()
+}
+
+#[tauri::command]
+pub async fn codex_account_add(app: tauri::AppHandle) -> Result<CodexAccount, String> {
+    let manager = CodexAccountManager::new();
+    let account = tauri::async_runtime::spawn_blocking(move || manager.add_managed_account(None))
+        .await
+        .map_err(|e| e.to_string())?
+        .map_err(into_user_message)?;
+
+    if let Err(e) = refresh_persisted_accounts(app) {
+        tracing::error!("failed to persist accounts after add: {e}");
+    }
+    Ok(account)
+}
+
+#[tauri::command]
+pub fn codex_account_remove(app: tauri::AppHandle, id: String) -> Result<(), String> {
+    let manager = CodexAccountManager::new();
+    let accounts = load_codex_accounts()?;
+    let target = accounts
+        .iter()
+        .find(|account| account.id.to_string() == id)
+        .ok_or_else(|| "Codex account not found.".to_string())?;
+
+    manager
+        .remove_managed_files_if_owned(target)
+        .map_err(into_user_message)?;
+
+    let remaining: Vec<CodexAccount> = accounts
+        .into_iter()
+        .filter(|account| account.id.to_string() != id)
+        .collect();
+    persist_codex_accounts(&remaining)?;
+    events::emit_settings_changed(&app);
+    Ok(())
+}
+
+#[tauri::command]
+pub async fn codex_account_switch(
+    app: tauri::AppHandle,
+    id: String,
+) -> Result<CodexSwitchResult, String> {
+    let manager = CodexAccountManager::new();
+    let accounts = load_codex_accounts()?;
+    let target = accounts
+        .iter()
+        .find(|account| account.id.to_string() == id)
+        .ok_or_else(|| "Codex account not found.".to_string())?
+        .clone();
+
+    let persisted = accounts.clone();
+    let result = tauri::async_runtime::spawn_blocking(move || {
+        manager.switch_active_account(&target, &persisted)
+    })
+    .await
+    .map_err(|e| e.to_string())?
+    .map_err(into_user_message)?;
+
+    // Materialized ambient account may need persisting.
+    if let Some(materialized) = &result.materialized_account {
+        let mut accounts = load_codex_accounts()?;
+        if let Some(entry) = accounts.iter_mut().find(|a| a.matches(materialized)) {
+            entry.merge_from(materialized);
+        } else {
+            accounts.push(materialized.clone());
+        }
+        persist_codex_accounts(&accounts)?;
+    }
+
+    events::emit_settings_changed(&app);
+    Ok(result)
+}
+
+#[tauri::command]
+pub async fn codex_account_fetch(
+    app: tauri::AppHandle,
+    id: String,
+) -> Result<codexbar::codex_accounts::AccountUsageSnapshot, String> {
+    let accounts = load_codex_accounts()?;
+    let target = accounts
+        .iter()
+        .find(|account| account.id.to_string() == id)
+        .ok_or_else(|| "Codex account not found.".to_string())?
+        .clone();
+
+    let api = CodexAccountApi::new();
+    let home_path = target.codex_home_path.clone();
+    let email_hint = target.email_hint.clone();
+    let snapshot = tokio::time::timeout(
+        std::time::Duration::from_secs(DEFAULT_FETCH_TIMEOUT_SECONDS),
+        api.fetch_snapshot(&home_path, email_hint.as_deref(), true),
+    )
+    .await
+    .map_err(|_| "Timed out waiting for the Codex usage API.".to_string())?
+    .map_err(into_api_message)?;
+
+    // Persist snapshot to the snapshot store, keyed by account id.
+    if let Ok(mut snapshots) = SnapshotStore::new().load() {
+        snapshots.insert(target.id, snapshot.clone());
+        let _ = SnapshotStore::new().save(&snapshots);
+    }
+
+    if refresh_persisted_accounts(app).is_err() {
+        // Non-fatal: the snapshot was still fetched.
+    }
+    Ok(snapshot)
+}
+
+#[tauri::command]
+pub fn codex_account_snapshots()
+-> Result<HashMap<Uuid, codexbar::codex_accounts::AccountUsageSnapshot>, String> {
+    SnapshotStore::new().load().map_err(|e| e.to_string())
+}
+
+#[tauri::command]
+pub async fn codex_account_restart_desktop(
+    _app: tauri::AppHandle,
+    session_root: Option<String>,
+    backup_destination: Option<String>,
+    restore_source: Option<String>,
+) -> Result<(), String> {
+    tauri::async_runtime::spawn_blocking(move || {
+        let session_root = session_root.map(PathBuf::from);
+        let backup_destination = backup_destination.map(PathBuf::from);
+        let restore_source = restore_source.map(PathBuf::from);
+        restart_codex_desktop(
+            0.8,
+            session_root.as_deref(),
+            backup_destination.as_deref(),
+            restore_source.as_deref(),
+        )
+    })
+    .await
+    .map_err(|e| e.to_string())?
+    .map_err(|e| e.to_string())?;
+    Ok(())
+}
+
+/// Merge discovered accounts back into the persisted list after identity
+/// changes (login/switch) so the store reflects reality.
+fn refresh_persisted_accounts(app: tauri::AppHandle) -> Result<(), String> {
+    let accounts = load_codex_accounts()?;
+    persist_codex_accounts(&accounts)?;
+    events::emit_settings_changed(&app);
+    Ok(())
+}
+
+fn into_user_message(error: CodexAccountManagerError) -> String {
+    match error {
+        CodexAccountManagerError::Message(msg) => msg,
+        CodexAccountManagerError::Io(e) => e.to_string(),
+    }
+}
+
+fn into_api_message(error: CodexApiError) -> String {
+    match error {
+        CodexApiError::Message(msg) => msg,
+        CodexApiError::Network(e) => format!("network error: {e}"),
+        CodexApiError::Parse(e) => format!("failed to parse Codex payload: {e}"),
+    }
+}
+
+#[derive(Debug, serde::Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CodexAccountsStateBridge {
+    pub accounts: Vec<CodexAccount>,
+    pub snapshots: HashMap<Uuid, codexbar::codex_accounts::AccountUsageSnapshot>,
+}
+
+#[tauri::command]
+pub fn get_codex_accounts_state(
+    state: tauri::State<'_, Mutex<AppState>>,
+) -> Result<CodexAccountsStateBridge, String> {
+    let _guard = state.lock().map_err(|e| e.to_string())?;
+    Ok(CodexAccountsStateBridge {
+        accounts: load_codex_accounts()?,
+        snapshots: codex_account_snapshots()?,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn sample_account() -> CodexAccount {
+        CodexAccount::new(
+            Uuid::new_v4(),
+            None,
+            Some("user@example.com".to_string()),
+            Some("auth0|acct".to_string()),
+            Some("acct".to_string()),
+            std::path::PathBuf::from("/tmp/fake-home"),
+            codexbar::codex_accounts::CodexAccountSource::ManagedByApp,
+            codexbar::codex_accounts::utc_now(),
+            codexbar::codex_accounts::utc_now(),
+            Some(codexbar::codex_accounts::utc_now()),
+        )
+    }
+
+    #[test]
+    fn into_user_message_preserves_friendly_text() {
+        assert_eq!(
+            into_user_message(CodexAccountManagerError::Message(
+                "The `codex` command could not be found.".to_string()
+            )),
+            "The `codex` command could not be found."
+        );
+    }
+
+    #[test]
+    fn sample_account_serializes_camel_case() {
+        let json = serde_json::to_value(sample_account()).unwrap();
+        assert!(json.get("codexHomePath").is_some());
+        assert!(json.get("providerAccountId").is_some());
+    }
+}
diff --git a/apps/desktop-tauri/src-tauri/src/commands/mod.rs b/apps/desktop-tauri/src-tauri/src/commands/mod.rs
index 2e32d549ad..5e8e5b2d2b 100644
--- a/apps/desktop-tauri/src-tauri/src/commands/mod.rs
+++ b/apps/desktop-tauri/src-tauri/src/commands/mod.rs
@@ -30,6 +30,7 @@ mod usage_spend;
 mod agent_sessions;
 mod bridge;
 mod browser_import;
+mod codex_accounts;
 mod codex_workspaces;
 mod credential_detection;
 mod credentials;
@@ -45,6 +46,7 @@ mod system;
 pub use agent_sessions::*;
 pub(crate) use bridge::*;
 pub use browser_import::*;
+pub use codex_accounts::*;
 pub use codex_workspaces::*;
 pub use credential_detection::*;
 pub use credentials::*;
diff --git a/apps/desktop-tauri/src-tauri/src/commands/providers.rs b/apps/desktop-tauri/src-tauri/src/commands/providers.rs
index b38f8d6180..9f2137597a 100644
--- a/apps/desktop-tauri/src-tauri/src/commands/providers.rs
+++ b/apps/desktop-tauri/src-tauri/src/commands/providers.rs
@@ -352,6 +352,19 @@ fn spawn_provider_refreshes(
         }));
     }
 
+    // ADR 0003 multi-account lanes: when Codex is enabled, refresh every
+    // account snapshot (ambient + managed) on the same cycle, bounded by the
+    // shared fetch semaphore. The ambient account still publishes the single
+    // "codex" provider snapshot used by tray/menu; the lanes fill the account
+    // snapshot store consumed by the Settings accounts panel.
+    if inputs.enabled_ids.contains(&ProviderId::Codex) {
+        let app_handle = app.clone();
+        let fetch_permits = Arc::clone(&fetch_permits);
+        handles.push(tokio::spawn(async move {
+            super::codex_accounts::refresh_codex_account_lanes(app_handle, fetch_permits).await;
+        }));
+    }
+
     handles
 }
 
diff --git a/apps/desktop-tauri/src-tauri/src/events.rs b/apps/desktop-tauri/src-tauri/src/events.rs
index 2de636c1f0..8d9dd774d8 100644
--- a/apps/desktop-tauri/src-tauri/src/events.rs
+++ b/apps/desktop-tauri/src-tauri/src/events.rs
@@ -15,6 +15,7 @@ pub const REFRESH_COMPLETE: &str = "refresh-complete";
 pub const UPDATE_STATE_CHANGED: &str = "update-state-changed";
 pub const LOCALE_CHANGED: &str = "locale-changed";
 pub const SETTINGS_CHANGED: &str = "settings-changed";
+pub const CODEX_ACCOUNTS_UPDATED: &str = "codex-accounts-updated";
 
 // ── Payloads ─────────────────────────────────────────────────────────
 
@@ -80,6 +81,13 @@ pub fn emit_refresh_complete(app: &AppHandle, provider_count: usize, error_count
     );
 }
 
+/// Broadcast that the Codex account snapshot store was refreshed (ADR 0003
+/// multi-account lanes). Payload-less; listeners re-fetch via
+/// `get_codex_accounts_state`.
+pub fn emit_codex_accounts_updated(app: &AppHandle) {
+    let _ = app.emit(CODEX_ACCOUNTS_UPDATED, ());
+}
+
 pub fn emit_update_state_changed(app: &AppHandle, payload: &UpdateStatePayload) {
     let _ = app.emit(UPDATE_STATE_CHANGED, payload);
 }
diff --git a/apps/desktop-tauri/src-tauri/src/main.rs b/apps/desktop-tauri/src-tauri/src/main.rs
index 3ec981376e..0602135c1d 100644
--- a/apps/desktop-tauri/src-tauri/src/main.rs
+++ b/apps/desktop-tauri/src-tauri/src/main.rs
@@ -156,6 +156,14 @@ fn main() {
             commands::refresh_providers,
             commands::refresh_providers_if_stale,
             commands::get_cached_providers,
+            commands::codex_accounts_list,
+            commands::codex_account_add,
+            commands::codex_account_remove,
+            commands::codex_account_switch,
+            commands::codex_account_fetch,
+            commands::codex_account_snapshots,
+            commands::codex_account_restart_desktop,
+            commands::get_codex_accounts_state,
             commands::get_credential_storage_status,
             commands::get_update_state,
             commands::check_for_updates,