Session Statistics Feature

What variant of Codex are you using?

CLI

What feature would you like to see?

feat(tui): Add /stats command to display session statistics

Description

## Problem
Users currently have no visibility into session performance metrics. There's
no way to see:

• How many commands were executed and their success/failure rate
• Which files were accessed or modified during the session
• Token usage breakdown across turns
• Time distribution between model inference and tool execution

## Proposed Solution
Add a /stats slash command that displays a scrollable popup with session
statistics organized into sections:

Commands

• Total executed, successful, failed counts
• Success rate percentage
• Total execution time

Files

• Count of files modified and accessed
• Top accessed files with frequency

Turns & Tokens

• Current turn number
• Total/input/output token counts
• Per-turn token breakdown (last 5 turns)

Timing

• Session duration
• Model wait time (with percentage)
• Tool execution time (with percentage)

## Implementation Approach

1. New SessionStats struct to track metrics throughout the session
2. New StatsView popup with keyboard navigation (↑/↓/j/k scroll, Esc close)
3. Integration points in ChatWidget to record events:

• Turn start/end
• Command execution results
• File access via MCP tools
• Patch applications (file modifications)

## Scope

• TUI only

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Additional information

_No response_