OpenRouter: Mistral: Mistral Small 4

This model is no longer free. See free alternatives.
openrouter/mistralai-mistral-small-2603
Released Mar 16, 2026 · 262K context ·
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Mistral Small 4 is the next major release in the Mistral Small family, unifying the capabilities of several flagship Mistral models into a single system. It combines strong reasoning from Magistral, multimodal understanding from Pixtral, and agentic coding capabilities from Devstral, enabling one model to handle complex analysis, software development, and visual tasks within the same workflow.

Try Mistral: Mistral Small 4

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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: Mistral: Mistral Small 4

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 "Mistral: Mistral Small 4"

Gemini CLI

# ~/.gemini/settings.json
{
  "apiKey": "<your-api-key>",
  "model": "Mistral: Mistral Small 4"
}
# 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": {
        "Mistral: Mistral Small 4": { "name": "Mistral: Mistral Small 4" }
      }
    }
  }
}
// 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: Mistral: Mistral Small 4
  provider: custom
  base_url: ${CUSTOM_BASE_URL}
  api_key: ${CUSTOM_API_KEY}
  model_aliases:
    Mistral: Mistral Small 4:
      model: "Mistral: Mistral Small 4"
      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": "Mistral: Mistral Small 4",
      },
    },
  },
  "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": "Mistral: Mistral Small 4", "name": "Mistral: Mistral Small 4" },
        ],
      },
    },
  },
}
// Apply: openclaw gateway restart
// Verify: openclaw doctor --fix

FAQ

Is it really free?

No, Mistral: Mistral Small 4 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 "Mistral: Mistral Small 4", and set the Base URL to "https://openrouter.ai/api/v1".