feat: add Mistral provider adapter for TanStack AI

- Implemented MistralTextAdapter and related functions for chat completions.
- Defined Mistral-specific message types and metadata structures.
- Created model metadata for various Mistral models with pricing and capabilities.
- Added text provider options and validation for Mistral text models.
- Developed utility functions for Mistral client configuration and schema conversion.
- Implemented function tool conversion for Mistral-specific formats.
- Added tests for Mistral adapters, including event emissions and error handling.
- Configured TypeScript and Vite for the new package.

Author: cstrnt

.changeset/add-ai-mistral.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-mistral': minor
+---
+
+Add new `@tanstack/ai-mistral` adapter package for Mistral models using the `@mistralai/mistralai` SDK. Supports streaming chat, tool calling, vision input (Pixtral / Mistral Medium / Small), and structured output via JSON Schema. Includes model metadata for Mistral Large, Medium, Small, Ministral 3B/8B, Codestral, Pixtral, Magistral, and Open Mistral Nemo.

packages/typescript/ai-mistral/README.md

@@ -0,0 +1,89 @@
+# @tanstack/ai-mistral
+
+Mistral adapter for TanStack AI.
+
+## Installation
+
+```bash
+npm install @tanstack/ai-mistral
+# or
+pnpm add @tanstack/ai-mistral
+# or
+yarn add @tanstack/ai-mistral
+```
+
+## Setup
+
+Get your API key from [Mistral Console](https://console.mistral.ai/) and set it as an environment variable:
+
+```bash
+export MISTRAL_API_KEY="..."
+```
+
+## Usage
+
+### Text/Chat Adapter
+
+```typescript
+import { mistralText } from '@tanstack/ai-mistral'
+import { generate } from '@tanstack/ai'
+
+const adapter = mistralText('mistral-large-latest')
+
+const result = await generate({
+  adapter,
+  model: 'mistral-large-latest',
+  messages: [
+    { role: 'user', content: 'Explain quantum computing in simple terms' },
+  ],
+})
+
+console.log(result.text)
+```
+
+### With Explicit API Key
+
+```typescript
+import { createMistralText } from '@tanstack/ai-mistral'
+
+const adapter = createMistralText('mistral-large-latest', 'api_key')
+```
+
+## Supported Models
+
+### Chat Models
+
+- `mistral-large-latest` - Frontier flagship model (128k context)
+- `mistral-medium-latest` - Balanced multimodal model (vision)
+- `mistral-small-latest` - Fast, affordable multimodal model (vision)
+- `ministral-8b-latest` - 8B edge model
+- `ministral-3b-latest` - 3B edge model
+- `codestral-latest` - Code-specialized model (256k context)
+- `pixtral-large-latest` - Large vision model
+- `pixtral-12b-2409` - 12B vision model
+- `magistral-medium-latest` - Reasoning model
+- `magistral-small-latest` - Small reasoning model
+- `open-mistral-nemo` - Open 12B model
+
+See [Mistral model comparison](https://docs.mistral.ai/getting-started/models/compare) for full details.
+
+## Features
+
+- ✅ Streaming chat completions
+- ✅ Structured output (JSON Schema)
+- ✅ Function/tool calling
+- ✅ Multimodal input (text + images for vision models)
+- ❌ Embeddings (use the Mistral SDK directly)
+- ❌ Image generation
+
+## Tree-Shakeable Adapters
+
+This package uses tree-shakeable adapters, so you only import what you need:
+
+```typescript
+import { mistralText } from '@tanstack/ai-mistral'
+```
+
+## License
+
+MIT

packages/typescript/ai-mistral/package.json

@@ -0,0 +1,52 @@
+{
+  "name": "@tanstack/ai-mistral",
+  "version": "0.1.0",
+  "type": "module",
+  "description": "Mistral adapter for TanStack AI",
+  "author": "",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/TanStack/ai.git",
+    "directory": "packages/typescript/ai-mistral"
+  },
+  "module": "./dist/esm/index.js",
+  "types": "./dist/esm/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/esm/index.d.ts",
+      "import": "./dist/esm/index.js"
+    }
+  },
+  "files": [
+    "dist",
+    "src"
+  ],
+  "scripts": {
+    "build": "vite build",
+    "clean": "premove ./build ./dist",
+    "lint:fix": "eslint ./src --fix",
+    "test:build": "publint --strict",
+    "test:eslint": "eslint ./src",
+    "test:lib": "vitest run",
+    "test:lib:dev": "pnpm test:lib --watch",
+    "test:types": "tsc"
+  },
+  "keywords": [
+    "ai",
+    "mistral",
+    "tanstack",
+    "adapter"
+  ],
+  "devDependencies": {
+    "@vitest/coverage-v8": "4.0.14",
+    "vite": "^7.2.7"
+  },
+  "peerDependencies": {
+    "@tanstack/ai": "workspace:^",
+    "zod": "^4.0.0"
+  },
+  "dependencies": {
+    "@mistralai/mistralai": "^2.2.0"
+  }
+}