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Apicentric includes a powerful Terminal User Interface (TUI) that provides an interactive dashboard for managing mock services, viewing real-time logs, and monitoring system status - all without leaving your terminal.

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What is the TUI?

The TUI is a keyboard-driven, full-screen terminal interface that gives you a comprehensive view of your API simulator environment. It combines service management, log monitoring, and configuration inspection into a single, unified interface.

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Key features

  • Real-time service status - See which services are running and on which ports
  • Live request logs - Monitor API requests as they happen
  • Log filtering - Filter by service, method, status code, or search terms
  • Service control - Start, stop, and manage services interactively
  • Keyboard navigation - Fast, mouse-free workflow
  • Multi-pane layout - Service list, logs, and actions all visible at once
  • Endpoint explorer - Browse available endpoints for each service

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Why use the TUI?

Visual monitoring

See request traffic in real-time without parsing log files.

Fast debugging

Quickly filter logs to find specific requests or errors.

Service management

Start, stop, and inspect services without remembering CLI commands.

Workflow efficiency

Stay in the terminal with a mouse-free, keyboard-driven interface.

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Getting started

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Launch the TUI

Simply run: 
apicentric tui
The TUI will:
  1. Load all service definitions from the current directory
  2. Start any configured services
  3. Display the interactive dashboard

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TUI layout

The interface is divided into several panes: 
┌─────────────────────────────────────────────────────────┐
│ Apicentric TUI - API Simulator Dashboard               │
├──────────────────┬──────────────────────────────────────┤
│                  │                                      │
│  Service List    │  Request Logs                        │
│                  │                                      │
│  ● user-api      │  [10:15:23] GET /users - 200 OK     │
│    :9001         │  [10:15:24] POST /users - 201       │
│                  │  [10:15:25] GET /users/123 - 200    │
│  ● payment-api   │                                      │
│    :9002         │                                      │
│                  │                                      │
│  ○ auth-api      │                                      │
│    :9003         │                                      │
│                  │                                      │
├──────────────────┴──────────────────────────────────────┤
│ Actions: [s]tart [x]stop [r]eload [f]ilter [?]help    │
└─────────────────────────────────────────────────────────┘

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Keyboard shortcuts

  • Tab - Switch between panes (service list, logs, endpoint explorer)
  • ↑/↓ - Navigate within the current pane
  • PgUp/PgDn - Scroll logs quickly
  • Home/End - Jump to top/bottom

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Service management

  • s - Start selected service
  • x - Stop selected service
  • r - Reload service configuration
  • i - Inspect service details
  • e - Open endpoint explorer

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Log management

  • f - Open filter dialog
  • c - Clear logs
  • / - Search logs
  • n - Next search result
  • N - Previous search result

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General

  • ? - Show help dialog
  • q or Ctrl+C - Quit TUI
  • Ctrl+L - Refresh screen

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Views and modes

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Dashboard view (default)

Shows service list and request logs side-by-side. This is the main view for monitoring activity.

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Endpoint explorer

Press e to open the endpoint explorer for the selected service: 
┌─────────────────────────────────────────────────────────┐
│ Endpoint Explorer - user-api                            │
├─────────────────────────────────────────────────────────┤
│                                                         │
│  GET /users                                             │
│    Description: List all users                          │
│    Response: 200 OK                                     │
│                                                         │
│  GET /users/{id}                                        │
│    Description: Get user by ID                          │
│    Parameters: id (path)                                │
│    Response: 200 OK, 404 Not Found                      │
│                                                         │
│  POST /users                                            │
│    Description: Create new user                         │
│    Request body: application/json                       │
│    Response: 201 Created, 422 Unprocessable             │
│                                                         │
├─────────────────────────────────────────────────────────┤
│ [Esc] Back  [↑↓] Navigate  [Enter] Test endpoint       │
└─────────────────────────────────────────────────────────┘

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Config inspector

Press i to view detailed service configuration: 
┌─────────────────────────────────────────────────────────┐
│ Service Configuration - user-api                        │
├─────────────────────────────────────────────────────────┤
│                                                         │
│  Name: User API                                         │
│  Version: 1.0                                           │
│  Port: 9001                                             │
│  Base Path: /api/v1                                     │
│  Endpoints: 5                                           │
│                                                         │
│  Scenarios:                                             │
│    - high_load (delay: 2000ms)                          │
│    - maintenance (503 response)                         │
│                                                         │
│  Current Scenario: default                              │
│                                                         │
│  Fixtures:                                              │
│    - users (2 items)                                    │
│    - products (10 items)                                │
│                                                         │
├─────────────────────────────────────────────────────────┤
│ [Esc] Back  [s] Change scenario                         │
└─────────────────────────────────────────────────────────┘

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Filtering logs

Press f to open the filter dialog: 
┌─────────────────────────────────────────────────────────┐
│ Filter Logs                                             │
├─────────────────────────────────────────────────────────┤
│                                                         │
│  Service: [user-api        ▼]                           │
│  Method:  [GET             ▼]                           │
│  Status:  [200-299         ▼]                           │
│  Search:  [____________________]                        │
│                                                         │
│  [ Apply ]  [ Clear ]  [ Cancel ]                       │
│                                                         │
└─────────────────────────────────────────────────────────┘

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Filter options

  • Service - Show logs from specific service only
  • Method - Filter by HTTP method (GET, POST, etc.)
  • Status - Filter by status code range:
    • 200-299 - Success responses
    • 400-499 - Client errors
    • 500-599 - Server errors
    • All - No filtering
  • Search - Text search in request path or response

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Active filters indicator

When filters are active, the status bar shows: 
📋 Logs (filtered: service=user-api, method=GET)

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Log entry details

Select a log entry and press Enter to see details: 
┌─────────────────────────────────────────────────────────┐
│ Request Details                                         │
├─────────────────────────────────────────────────────────┤
│                                                         │
│  Timestamp: 2026-03-01 10:15:23                         │
│  Service: user-api                                      │
│  Method: POST                                           │
│  Path: /api/v1/users                                    │
│  Status: 201 Created                                    │
│  Duration: 45ms                                         │
│                                                         │
│  Request Headers:                                       │
│    Content-Type: application/json                       │
│    Authorization: Bearer xyz...                         │
│                                                         │
│  Request Body:                                          │
│    {                                                    │
│      "name": "Alice Johnson",                           │
│      "email": "[email protected]"                       │
│    }                                                    │
│                                                         │
│  Response Body:                                         │
│    {                                                    │
│      "id": 123,                                         │
│      "name": "Alice Johnson",                           │
│      "email": "[email protected]",                      │
│      "created_at": "2026-03-01T10:15:23Z"               │
│    }                                                    │
│                                                         │
├─────────────────────────────────────────────────────────┤
│ [Esc] Back  [c] Copy response  [r] Replay request       │
└─────────────────────────────────────────────────────────┘

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Service status indicators

  • 🟢 Green dot - Service is running
  • 🔴 Red dot - Service is stopped
  • 🟡 Yellow dot - Service is starting/stopping
  • ⚠️ Warning - Service has errors

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Practical workflows

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Debugging a failing endpoint

1

Open TUI

apicentric tui
2

Filter logs

Press f and filter by status code 400-499 or 500-599 to see only errors.
3

Inspect request

Select the failing request and press Enter to see full details including request body and headers.
4

Check service config

Press i on the service to verify endpoint configuration.
5

Reload and test

After fixing the YAML, press r to reload the service and test again.

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Monitoring multiple services

1

Start all services

The TUI automatically starts all configured services on launch.
2

Watch the logs

Logs from all services appear in the log pane, color-coded by service.
3

Filter by service

Press f to focus on one service at a time when debugging.
4

Check status

Service list shows which services are active and their ports at a glance.

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Testing scenario changes

1

Open endpoint explorer

Press e to see available scenarios.
2

Inspect config

Press i to see defined scenarios and their parameters.
3

Activate scenario

In the config inspector, press s to change scenarios.
4

Monitor behavior

Watch logs to verify scenario effects (delays, error rates, etc.).

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Configuration

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TUI settings

Configure TUI behavior in apicentric.json: 
{
  "tui": {
    "log_buffer_size": 1000,  // Max log entries to keep
    "auto_scroll": true,       // Auto-scroll to new logs
    "color_scheme": "default", // Color theme
    "refresh_rate_ms": 100     // UI refresh rate
  }
}

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Custom themes

Supported color schemes:
  • default - Standard terminal colors
  • dark - Dark background optimized
  • light - Light background optimized
  • solarized - Solarized color palette

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Performance tips

If log scrolling becomes slow, reduce log_buffer_size or clear logs periodically with c.
Use filters to reduce log volume when monitoring high-traffic services.
The TUI automatically throttles log updates to prevent terminal overload during traffic spikes.

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Troubleshooting

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TUI not rendering correctly

Issue: Garbled display or incorrect colors. Solutions:
  • Ensure your terminal supports 256 colors: echo $TERM should show xterm-256color or similar
  • Try resizing the terminal window (minimum 80x24)
  • Use a modern terminal emulator (iTerm2, Alacritty, Windows Terminal)

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Service won’t start

Issue: Service shows red dot and won’t start. Solutions:
  1. Press i to inspect service configuration
  2. Check for YAML syntax errors
  3. Verify port is not already in use
  4. Press r to reload after fixing issues

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Logs not appearing

Issue: Request logs aren’t showing up. Solutions:
  • Check if filters are active (status bar shows filter indicator)
  • Press f and click “Clear” to remove all filters
  • Verify the service is actually receiving requests
  • Press Ctrl+L to refresh the display

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Tips and best practices

Keep the TUI open in a dedicated terminal window or tmux pane for continuous monitoring.
Use the search feature (/) to quickly find requests containing specific IDs or paths.
The TUI suppresses console logging to prevent interference. Use the log pane for all debugging information.
The TUI requires the tui feature, which is included in most installation methods. If unavailable, reinstall with: cargo install apicentric --features tui

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Next steps

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