Reset in Codex Codebase Explained

Reset in Codex Codebase Explained | Generated by AI

Home 2026.05

Now I have a clear picture. Here’s what “reset” means in the Codex codebase:

There are several distinct “reset” concepts in codex-rs:

1. /clear slash command (UI reset + new chat)

The /clear command does two things:

Clears the terminal UI (transcript cells, overlays, deferred history lines, backtrack state)
Starts a fresh chat session

From event_dispatch.rs:32:

AppEvent::ClearUi => {
    self.clear_terminal_ui(tui, /*redraw_header*/ false)?;
    self.reset_app_ui_state_after_clear();
    self.start_fresh_session_with_summary_hint(
        tui, app_server, Some(ThreadStartSource::Clear),
        /*initial_user_message*/ None,
    ).await;
}

The reset_app_ui_state_after_clear() method clears:

Transcript cells
Overlays
Deferred history lines
Backtrack state (primed, overlay_preview_active, pending_rollback)

But critically, it preserves the chat widget’s session state (thread_id, model, composer text, etc.) — as confirmed by the test clear_only_ui_reset_preserves_chat_session_state.

2. /new slash command (new chat, no UI clear)

Simpler — just starts a new session without clearing the terminal:

AppEvent::NewSession => {
    self.start_fresh_session_with_summary_hint(
        tui, app_server, /*session_start_source*/ None,
        /*initial_user_message*/ None,
    ).await;
}

3. WebSocket session reset (transport-level)

In core/src/client.rs:958, reset_websocket_session() drops the current WebSocket connection state:

fn reset_websocket_session(&mut self) {
    self.websocket_session.connection = None;
    self.websocket_session.last_request = None;
    self.websocket_session.last_response_rx = None;
    ...
}

This is a transport concern — it clears stale connection state when a WebSocket needs to be re-established.

4. Memory reset (memory/reset API)

An experimental API (memory/reset) that resets the memory workspace baseline. It runs reset_git_repository() on the memory root, effectively reverting uncommitted memory changes. This is part of the memories subsystem (memories/write/src/workspace.rs).

5. Turn history reset

In app-server/src/thread_state.rs, current_turn_history.reset() clears the accumulated tool call history for the current turn — a per-turn bookkeeping reset.

Summary: When most people say “reset” in Codex, they mean /clear — wipe the UI and start a fresh chat session while preserving session config (model, permissions, etc.). The other resets are internal plumbing (WebSocket connections, memory baselines, turn history buffers).

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