diff --git a/docs/config.json b/docs/config.json
index 8860b6667..6f2c19b79 100644
--- a/docs/config.json
+++ b/docs/config.json
@@ -13,6 +13,10 @@
           "label": "Overview",
           "to": "getting-started/overview"
         },
+        {
+          "label": "Installation",
+          "to": "getting-started/installation"
+        },
         {
           "label": "Quick Start",
           "to": "getting-started/quick-start"
diff --git a/docs/getting-started/installation.md b/docs/getting-started/installation.md
new file mode 100644
index 000000000..8174132c7
--- /dev/null
+++ b/docs/getting-started/installation.md
@@ -0,0 +1,132 @@
+---
+title: Installation
+id: installation
+order: 2
+---
+
+Install TanStack AI along with a framework integration and an adapter for your preferred LLM provider.
+
+## Core
+
+Every project needs the core package:
+
+```bash
+npm install @tanstack/ai
+# or
+pnpm add @tanstack/ai
+# or
+yarn add @tanstack/ai
+```
+
+## React
+
+```bash
+npm install @tanstack/ai-react
+```
+
+The React integration provides the `useChat` hook for managing chat state. See the [@tanstack/ai-react API docs](../api/ai-react) for full details.
+
+```typescript
+import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
+
+function Chat() {
+  const { messages, sendMessage } = useChat({
+    connection: fetchServerSentEvents("/api/chat"),
+  });
+  // ...
+}
+```
+
+## Solid
+
+```bash
+npm install @tanstack/ai-solid
+```
+
+The Solid integration provides the `useChat` primitive for managing chat state. See the [@tanstack/ai-solid API docs](../api/ai-solid) for full details.
+
+```typescript
+import { useChat, fetchServerSentEvents } from "@tanstack/ai-solid";
+
+function Chat() {
+  const { messages, sendMessage } = useChat({
+    connection: fetchServerSentEvents("/api/chat"),
+  });
+  // ...
+}
+```
+
+## Preact
+
+```bash
+npm install @tanstack/ai-preact
+```
+
+The Preact integration provides the `useChat` hook for managing chat state. See the [@tanstack/ai-preact API docs](../api/ai-preact) for full details.
+
+```typescript
+import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";
+
+function Chat() {
+  const { messages, sendMessage } = useChat({
+    connection: fetchServerSentEvents("/api/chat"),
+  });
+  // ...
+}
+```
+
+## Vue
+
+```bash
+npm install @tanstack/ai-vue
+```
+
+## Svelte
+
+```bash
+npm install @tanstack/ai-svelte
+```
+
+## Headless (Framework-Agnostic)
+
+If you're using a framework without a dedicated integration, or building a custom solution, use the headless client directly:
+
+```bash
+npm install @tanstack/ai-client
+```
+
+See the [@tanstack/ai-client API docs](../api/ai-client) for full details.
+
+## Adapters
+
+You also need an adapter for your LLM provider. Install one (or more) of the following:
+
+```bash
+# OpenRouter (recommended — 300+ models with one API key)
+npm install @tanstack/ai-openrouter
+
+# OpenAI
+npm install @tanstack/ai-openai
+
+# Anthropic
+npm install @tanstack/ai-anthropic
+
+# Google Gemini
+npm install @tanstack/ai-gemini
+
+# Ollama (local models)
+npm install @tanstack/ai-ollama
+
+# Groq
+npm install @tanstack/ai-groq
+
+# Grok (xAI)
+npm install @tanstack/ai-grok
+```
+
+See the [Adapters section](../adapters/openai) for provider-specific setup guides.
+
+## Next Steps
+
+- [Quick Start Guide](./quick-start) - Build a chat app in minutes
+- [Tools Guide](../guides/tools) - Learn about the isomorphic tool system
diff --git a/docs/getting-started/quick-start.md b/docs/getting-started/quick-start.md
index b059a9c32..6f60a3736 100644
--- a/docs/getting-started/quick-start.md
+++ b/docs/getting-started/quick-start.md
@@ -1,7 +1,7 @@
 ---
 title: Quick Start
 id: quick-start
-order: 2
+order: 3
 ---
 
 Get started with TanStack AI in minutes. This guide will walk you through creating a simple chat application using the React integration and OpenAI adapter.
diff --git a/packages/typescript/ai-client/src/types.ts b/packages/typescript/ai-client/src/types.ts
index 4f250edd3..922cdcf44 100644
--- a/packages/typescript/ai-client/src/types.ts
+++ b/packages/typescript/ai-client/src/types.ts
@@ -143,7 +143,8 @@ export type ToolCallPart<TTools extends ReadonlyArray<AnyClientTool> = any> =
 export interface ToolResultPart {
   type: 'tool-result'
   toolCallId: string
-  content: string
+  /** Tool result content. String for text results, or an array for multimodal results. */
+  content: string | Array<any>
   state: ToolResultState
   error?: string // Error message if state is "error"
 }
diff --git a/packages/typescript/ai-devtools/src/store/ai-context.tsx b/packages/typescript/ai-devtools/src/store/ai-context.tsx
index 979cfb123..b1bc6f196 100644
--- a/packages/typescript/ai-devtools/src/store/ai-context.tsx
+++ b/packages/typescript/ai-devtools/src/store/ai-context.tsx
@@ -805,7 +805,9 @@ export const AIProvider: ParentComponent = (props) => {
               return {
                 type: 'tool-result',
                 toolCallId: part.toolCallId,
-                content: part.content,
+                content: Array.isArray(part.content)
+                  ? JSON.stringify(part.content)
+                  : part.content,
                 state: part.state,
                 error: part.error,
               }
diff --git a/packages/typescript/ai-event-client/src/devtools-middleware.ts b/packages/typescript/ai-event-client/src/devtools-middleware.ts
index 1cc8db37c..80c2f043a 100644
--- a/packages/typescript/ai-event-client/src/devtools-middleware.ts
+++ b/packages/typescript/ai-event-client/src/devtools-middleware.ts
@@ -195,7 +195,10 @@ export function devtoolsMiddleware(): ChatMiddleware {
             ...base,
             messageId: localMessageId || undefined,
             toolCallId: chunk.toolCallId,
-            result: chunk.result || '',
+            result:
+              typeof chunk.result === 'string'
+                ? chunk.result
+                : JSON.stringify(chunk.result ?? ''),
             timestamp: Date.now(),
           })
           break
diff --git a/packages/typescript/ai-event-client/src/index.ts b/packages/typescript/ai-event-client/src/index.ts
index 98deb5285..a5da650f7 100644
--- a/packages/typescript/ai-event-client/src/index.ts
+++ b/packages/typescript/ai-event-client/src/index.ts
@@ -66,7 +66,7 @@ export interface ToolCallPart {
 export interface ToolResultPart {
   type: 'tool-result'
   toolCallId: string
-  content: string
+  content: string | Array<any>
   state: ToolResultState
   error?: string
 }
@@ -646,6 +646,20 @@ export interface AIDevtoolsEventMap {
   'client:stopped': ClientStoppedEvent
 }
 
+// Ensure a shared EventTarget exists on server environments (Node, Bun,
+// Cloudflare Workers, etc.) so that emit() and on() operate on the same
+// target.  In browsers, `window` is used automatically.
+// See https://github.com/TanStack/ai/issues/341
+if (
+  typeof globalThis !== 'undefined' &&
+  !globalThis.__TANSTACK_EVENT_TARGET__ &&
+  typeof window === 'undefined'
+) {
+  if (typeof EventTarget !== 'undefined') {
+    globalThis.__TANSTACK_EVENT_TARGET__ = new EventTarget()
+  }
+}
+
 class AiEventClient extends EventClient<AIDevtoolsEventMap> {
   constructor() {
     super({
diff --git a/packages/typescript/ai-gemini/src/adapters/image.ts b/packages/typescript/ai-gemini/src/adapters/image.ts
index 2ccf47b58..bd928c01b 100644
--- a/packages/typescript/ai-gemini/src/adapters/image.ts
+++ b/packages/typescript/ai-gemini/src/adapters/image.ts
@@ -168,7 +168,13 @@ export class GeminiImageAdapter<
       id: generateId(this.name),
       model,
       images,
-      usage: undefined,
+      usage: response.usageMetadata
+        ? {
+            inputTokens: response.usageMetadata.promptTokenCount ?? 0,
+            outputTokens: response.usageMetadata.candidatesTokenCount ?? 0,
+            totalTokens: response.usageMetadata.totalTokenCount ?? 0,
+          }
+        : undefined,
     }
   }
 
@@ -196,11 +202,26 @@ export class GeminiImageAdapter<
       }),
     )
 
+    // GenerateImagesResponse may include usageMetadata in newer SDK versions
+    const usageMeta = (response as any).usageMetadata as
+      | {
+          promptTokenCount?: number
+          candidatesTokenCount?: number
+          totalTokenCount?: number
+        }
+      | undefined
+
     return {
       id: generateId(this.name),
       model,
       images,
-      usage: undefined,
+      usage: usageMeta
+        ? {
+            inputTokens: usageMeta.promptTokenCount ?? 0,
+            outputTokens: usageMeta.candidatesTokenCount ?? 0,
+            totalTokens: usageMeta.totalTokenCount ?? 0,
+          }
+        : undefined,
     }
   }
 }
diff --git a/packages/typescript/ai-openai/src/adapters/text.ts b/packages/typescript/ai-openai/src/adapters/text.ts
index 1747ce4ec..2644bcbbd 100644
--- a/packages/typescript/ai-openai/src/adapters/text.ts
+++ b/packages/typescript/ai-openai/src/adapters/text.ts
@@ -706,11 +706,14 @@ export class OpenAITextAdapter<
         result.push({
           type: 'function_call_output',
           call_id: message.toolCallId || '',
+          // Support multimodal tool outputs (OpenAI Responses API accepts
+          // string or array of content parts for function_call_output).
           output:
-            typeof message.content === 'string'
+            typeof message.content === 'string' ||
+            Array.isArray(message.content)
               ? message.content
               : JSON.stringify(message.content),
-        })
+        } as any)
         continue
       }
 
diff --git a/packages/typescript/ai-openrouter/src/adapters/text.ts b/packages/typescript/ai-openrouter/src/adapters/text.ts
index 387110b8b..07100111b 100644
--- a/packages/typescript/ai-openrouter/src/adapters/text.ts
+++ b/packages/typescript/ai-openrouter/src/adapters/text.ts
@@ -39,6 +39,25 @@ import type {
   Message,
 } from '@openrouter/sdk/models'
 
+/**
+ * Convert snake_case keys to camelCase.
+ * The OpenRouter SDK's Zod transformer expects camelCase input and silently
+ * discards any snake_case fields.  This helper normalises user-supplied
+ * modelOptions so that common snake_case variants (e.g. `tool_choice`)
+ * are accepted as well.
+ * See https://github.com/TanStack/ai/issues/314
+ */
+function snakeToCamelKeys<T extends Record<string, unknown>>(
+  obj: T,
+): Record<string, unknown> {
+  const result: Record<string, unknown> = {}
+  for (const key of Object.keys(obj)) {
+    const camelKey = key.replace(/_([a-z])/g, (_, c: string) => c.toUpperCase())
+    result[camelKey] = obj[key]
+  }
+  return result
+}
+
 export interface OpenRouterConfig extends SDKOptions {}
 export type OpenRouterTextModels = (typeof OPENROUTER_CHAT_MODELS)[number]
 
@@ -521,15 +540,23 @@ export class OpenRouterTextAdapter<
       })
     }
 
+    // Normalise snake_case keys to camelCase so the SDK's Zod transformer
+    // does not silently discard them (see #314).
+    const normalizedModelOptions = modelOptions
+      ? snakeToCamelKeys(modelOptions as Record<string, unknown>)
+      : undefined
+
     const request: ChatGenerationParams = {
       model:
         options.model +
-        (modelOptions?.variant ? `:${modelOptions.variant}` : ''),
+        (normalizedModelOptions?.variant
+          ? `:${normalizedModelOptions.variant}`
+          : ''),
       messages,
       temperature: options.temperature,
       maxTokens: options.maxTokens,
       topP: options.topP,
-      ...modelOptions,
+      ...normalizedModelOptions,
       tools: options.tools
         ? convertToolsToProviderFormat(options.tools)
         : undefined,
diff --git a/packages/typescript/ai/src/activities/chat/index.ts b/packages/typescript/ai/src/activities/chat/index.ts
index 74c5d5ce5..2e329e215 100644
--- a/packages/typescript/ai/src/activities/chat/index.ts
+++ b/packages/typescript/ai/src/activities/chat/index.ts
@@ -1001,7 +1001,12 @@ class TextEngine<
     const chunks: Array<StreamChunk> = []
 
     for (const result of results) {
-      const content = JSON.stringify(result.result)
+      // Preserve arrays (e.g. multimodal content parts) and strings;
+      // stringify other values.
+      const content =
+        typeof result.result === 'string' || Array.isArray(result.result)
+          ? result.result
+          : JSON.stringify(result.result)
 
       chunks.push({
         type: 'TOOL_CALL_END',
diff --git a/packages/typescript/ai/src/activities/chat/messages.ts b/packages/typescript/ai/src/activities/chat/messages.ts
index b7f97b880..b8244271d 100644
--- a/packages/typescript/ai/src/activities/chat/messages.ts
+++ b/packages/typescript/ai/src/activities/chat/messages.ts
@@ -248,7 +248,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
     if (part.output !== undefined && !emittedToolResultIds.has(part.id)) {
       messageList.push({
         role: 'tool',
-        content: JSON.stringify(part.output),
+        content: Array.isArray(part.output)
+          ? part.output
+          : JSON.stringify(part.output),
         toolCallId: part.id,
       })
       emittedToolResultIds.add(part.id)
diff --git a/packages/typescript/ai/src/activities/chat/stream/message-updaters.ts b/packages/typescript/ai/src/activities/chat/stream/message-updaters.ts
index 80b94d59a..be7b2833d 100644
--- a/packages/typescript/ai/src/activities/chat/stream/message-updaters.ts
+++ b/packages/typescript/ai/src/activities/chat/stream/message-updaters.ts
@@ -97,7 +97,7 @@ export function updateToolResultPart(
   messages: Array<UIMessage>,
   messageId: string,
   toolCallId: string,
-  content: string,
+  content: string | Array<any>,
   state: ToolResultState,
   error?: string,
 ): Array<UIMessage> {
diff --git a/packages/typescript/ai/src/activities/chat/stream/processor.ts b/packages/typescript/ai/src/activities/chat/stream/processor.ts
index dc215366b..2ac59582e 100644
--- a/packages/typescript/ai/src/activities/chat/stream/processor.ts
+++ b/packages/typescript/ai/src/activities/chat/stream/processor.ts
@@ -288,7 +288,11 @@ export class StreamProcessor {
     )
 
     // Step 2: Create a tool-result part (for LLM conversation history)
-    const content = typeof output === 'string' ? output : JSON.stringify(output)
+    // Preserve arrays (e.g. multimodal content parts) as-is.
+    const content =
+      typeof output === 'string' || Array.isArray(output)
+        ? output
+        : JSON.stringify(output)
     const toolResultState: ToolResultState = error ? 'error' : 'complete'
 
     updatedMessages = updateToolResultPart(
@@ -944,10 +948,14 @@ export class StreamProcessor {
       // Step 1: Update the tool-call part's output field (for UI consistency
       // with client tools — see GitHub issue #176)
       let output: unknown
-      try {
-        output = JSON.parse(chunk.result)
-      } catch {
+      if (Array.isArray(chunk.result)) {
         output = chunk.result
+      } else {
+        try {
+          output = JSON.parse(chunk.result)
+        } catch {
+          output = chunk.result
+        }
       }
       this.messages = updateToolCallWithOutput(
         this.messages,
diff --git a/packages/typescript/ai/src/activities/chat/tools/tool-calls.ts b/packages/typescript/ai/src/activities/chat/tools/tool-calls.ts
index f6fe2060e..e14fd1d0f 100644
--- a/packages/typescript/ai/src/activities/chat/tools/tool-calls.ts
+++ b/packages/typescript/ai/src/activities/chat/tools/tool-calls.ts
@@ -161,7 +161,7 @@ export class ToolCallManager {
     for (const toolCall of toolCallsArray) {
       const tool = this.tools.find((t) => t.name === toolCall.function.name)
 
-      let toolResultContent: string
+      let toolResultContent: string | Array<any>
       if (tool?.execute) {
         try {
           // Parse arguments (normalize "null" to "{}" for empty tool_use blocks)
@@ -213,8 +213,12 @@ export class ToolCallManager {
             }
           }
 
+          // Preserve arrays (e.g. multimodal content parts) as-is;
+          // stringify other non-string values for the conversation history.
           toolResultContent =
-            typeof result === 'string' ? result : JSON.stringify(result)
+            typeof result === 'string' || Array.isArray(result)
+              ? result
+              : JSON.stringify(result)
         } catch (error: unknown) {
           // If tool execution fails, add error message
           const message =
diff --git a/packages/typescript/ai/src/types.ts b/packages/typescript/ai/src/types.ts
index ca195bc4a..1b7ace0e1 100644
--- a/packages/typescript/ai/src/types.ts
+++ b/packages/typescript/ai/src/types.ts
@@ -298,7 +298,8 @@ export interface ToolCallPart {
 export interface ToolResultPart {
   type: 'tool-result'
   toolCallId: string
-  content: string
+  /** Tool result content. String for text results, or an array for multimodal results (e.g. images). */
+  content: string | Array<ContentPart>
   state: ToolResultState
   error?: string // Error message if state is "error"
 }
@@ -872,8 +873,8 @@ export interface ToolCallEndEvent extends BaseAGUIEvent {
   toolName: string
   /** Final parsed input arguments */
   input?: unknown
-  /** Tool execution result (if executed) */
-  result?: string
+  /** Tool execution result (if executed). String for text, array for multimodal content. */
+  result?: string | Array<ContentPart>
 }
 
 /**