OpenRouter: OpenAI: GPT-5.3 Chat

This model is no longer free. See free alternatives.
openrouter/openai-gpt-5.3-chat
Released Mar 3, 2026 · 128K context ·
chat

GPT-5.3 Chat is an update to ChatGPT's most-used model that makes everyday conversations smoother, more useful, and more directly helpful. It delivers more accurate answers with better contextualization and significantly reduces unnecessary refusals, caveats, and overly cautious phrasing that can interrupt conversational flow.

Try OpenAI: GPT-5.3 Chat

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One-Click Config

Optimized configs for your favorite AI tools.

Claude Code

# Claude Code works via OpenRouter's Anthropic-compatible API.
# Note: Only paid Anthropic Claude models are supported (e.g. claude-sonnet-4.6, claude-opus-4).
# Browse available Claude models at: https://openrouter.ai/models?q=anthropic

# Add to ~/.zshrc or ~/.bashrc
export OPENROUTER_API_KEY="<your-openrouter-api-key>"  # Get at https://openrouter.ai/settings/keys
export ANTHROPIC_BASE_URL="https://openrouter.ai/api"
export ANTHROPIC_AUTH_TOKEN="$OPENROUTER_API_KEY"
export ANTHROPIC_API_KEY=""  # Must be explicitly empty to avoid conflicts

# Optional: pin specific models for each role
# export ANTHROPIC_DEFAULT_SONNET_MODEL="anthropic/claude-sonnet-4.6"
# export ANTHROPIC_DEFAULT_HAIKU_MODEL="anthropic/claude-haiku-4.5"

# Then simply run: claude

Cursor

# Cursor → Settings (⚙️) → Models → Add Model
# Enter the model name exactly as shown, then fill in:
#   Override OpenAI Base URL: https://openrouter.ai/api/v1
#   OpenAI API Key: <your-api-key>   # Get at https://openrouter.ai/workspaces/default/keys
# Click "Verify" to confirm the connection, then enable the model.
#
# Model name to add: OpenAI: GPT-5.3 Chat

Codex

# Add to ~/.zshrc or ~/.bashrc
export OPENAI_BASE_URL="https://openrouter.ai/api/v1"
export OPENAI_API_KEY="<your-api-key>"  # Get at https://openrouter.ai/workspaces/default/keys

# Then run:
codex --model "OpenAI: GPT-5.3 Chat"

Gemini CLI

# ~/.gemini/settings.json
{
  "apiKey": "<your-api-key>",
  "model": "OpenAI: GPT-5.3 Chat"
}
# Get API key at https://openrouter.ai/workspaces/default/keys

OpenCode

// ~/.config/opencode/opencode.json
{
  "$schema": "https://opencode.ai/config.json",
  "provider": {
    "free-llm": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "Free LLM",
      "options": {
        "baseURL": "https://openrouter.ai/api/v1",
        "apiKey": "<your-api-key>"
      },
      "models": {
        "OpenAI: GPT-5.3 Chat": { "name": "OpenAI: GPT-5.3 Chat" }
      }
    }
  }
}
// Get API key at https://openrouter.ai/workspaces/default/keys

Hermes

# Step 1 — Edit config.yaml
# Windows: C:\Users\<you>\AppData\Local\hermes\config.yaml
# macOS/Linux: ~/.config/hermes/config.yaml

model:
  default: OpenAI: GPT-5.3 Chat
  provider: custom
  base_url: ${CUSTOM_BASE_URL}
  api_key: ${CUSTOM_API_KEY}
  model_aliases:
    OpenAI: GPT-5.3 Chat:
      model: "OpenAI: GPT-5.3 Chat"
      provider: "custom"

# Step 2 — Edit .env (same directory as config.yaml)
# Windows: C:\Users\<you>\AppData\Local\hermes\.env
# macOS/Linux: ~/.config/hermes/.env

# ========================
# Custom API (OpenAI-compatible)
# ========================
CUSTOM_API_KEY=<your-api-key>        # Get at https://openrouter.ai/workspaces/default/keys
CUSTOM_BASE_URL=https://openrouter.ai/api/v1

OpenClaw

// ~/.openclaw/openclaw.json  (JSON5 format)
{
  "agents": {
    "defaults": {
      "model": {
        "primary": "OpenAI: GPT-5.3 Chat",
      },
    },
  },
  "models": {
    "providers": {
      // Option A — Built-in provider (OpenAI, Anthropic, Google…)
      // Just add apiKey; OpenClaw handles the baseUrl automatically
      // "openai": { "apiKey": "<your-api-key>" },

      // Option B — Custom OpenAI-compatible base URL (e.g. OpenRouter, NVIDIA)
      "free-llm": {
        "baseUrl": "https://openrouter.ai/api/v1",
        "apiKey": "<your-api-key>",  // Get at https://openrouter.ai/workspaces/default/keys
        "api": "openai-completions", // openai-completions | anthropic-messages | …
        "models": [
          { "id": "OpenAI: GPT-5.3 Chat", "name": "OpenAI: GPT-5.3 Chat" },
        ],
      },
    },
  },
}
// Apply: openclaw gateway restart
// Verify: openclaw doctor --fix

FAQ

Is it really free?

No, OpenAI: GPT-5.3 Chat was previously free but has since transitioned to a paid model. Browse our free model directory for alternatives.

How to use it with Cursor?

Go to Cursor Settings > Models, add a custom model named "OpenAI: GPT-5.3 Chat", and set the Base URL to "https://openrouter.ai/api/v1".