diff --git a/.changeset/tool-call-approval-gating.md b/.changeset/tool-call-approval-gating.md
new file mode 100644
index 000000000..eb7bc47eb
--- /dev/null
+++ b/.changeset/tool-call-approval-gating.md
@@ -0,0 +1,55 @@
+---
+'@tanstack/ai': minor
+'@tanstack/ai-client': minor
+---
+
+Gate the tool-call part's `approval` field on the tool's `needsApproval` flag.
+Previously `approval?` was declared on every typed tool-call part regardless of
+whether the tool could ever request approval. Now the flag is captured as a
+literal type (`toolDefinition({ needsApproval: true })` → `true`) and threaded
+through `ClientTool` / `ToolDefinitionInstance` / `ToolDefinition`, and
+`ToolCallPartForTool` only includes `approval` for tools defined with
+`needsApproval: true`:
+
+```ts
+const { messages } = useChat({ tools: [getGuitars, addToCart] }) // addToCart: needsApproval: true
+for (const part of message.parts) {
+  if (part.type !== 'tool-call') continue
+  if (part.name === 'addToCart') part.approval?.id // ✅ typed
+  if (part.name === 'getGuitars') part.approval // ✅ compile error — no such field
+}
+```
+
+## ⚠️ Breaking change (types only)
+
+**This is the primary migration surface for this release.** When you pass a typed
+`tools` array to `useChat` / `createChat` / `injectChat`, reading `part.approval`
+on a mixed tool-call union **without first narrowing by `part.name`** no longer
+compiles. Code that previously did `part.approval?.id` in a generic handler over
+all tool-call parts must be updated:
+
+```ts
+// ❌ No longer compiles on a typed mixed union
+part.approval?.id
+
+// ✅ Narrow to an approval-required tool first
+if (part.name === 'deleteAccount') part.approval?.id
+
+// ✅ Or guard with `in`
+if ('approval' in part) part.approval?.id
+
+// ✅ Or type the handler against the base (untyped) ToolCallPart
+function handleApproval(part: ToolCallPart) {
+  return part.approval?.id
+}
+```
+
+Untyped `useChat()` (no inferred `tools` generic) and the base `ToolCallPart`
+type are unaffected: `approval` stays available on every tool-call part there.
+**Runtime behavior is unchanged** — only TypeScript narrowing is stricter.
+
+Adds a `TNeedsApproval extends boolean` type parameter (defaulting to `false`)
+to the client tool types; existing explicit type arguments keep working via the
+default. Literal capture requires `toolDefinition({ needsApproval: true })` at
+the call site — a dynamic `needsApproval: boolean` variable will not gate the
+type.
diff --git a/.changeset/tool-call-part-parsed-input.md b/.changeset/tool-call-part-parsed-input.md
new file mode 100644
index 000000000..53b9a3fcf
--- /dev/null
+++ b/.changeset/tool-call-part-parsed-input.md
@@ -0,0 +1,19 @@
+---
+'@tanstack/ai': minor
+---
+
+Populate the parsed `input` on tool-call message parts. `ToolCallPart` already
+declared a typed `input?` field, but it was never written at runtime — only the
+raw `arguments` string (and `output`) were set, so `part.input` was always
+`undefined` and consumers had to fall back to `part.input ?? JSON.parse(part.arguments)`.
+
+`input` is now set from the parsed arguments once they are complete
+(`state: 'input-complete'` and later, including `approval-requested`), in the
+streaming processor, the `TOOL_CALL_END`-with-parsed-input path, and when
+hydrating history via `modelMessagesToUIMessages`. While arguments are still
+streaming, `input` stays `undefined` and the raw `arguments` string remains the
+live source. A tool call that terminates in an error state may also keep `input`
+unset. `arguments` is unchanged, always present, and not deprecated.
+
+With typed tools (`useChat({ tools })`), `part.input` is fully typed per tool
+via the `part.name` discriminant — matching `part.output`.
diff --git a/.changeset/usechat-const-tools-inference.md b/.changeset/usechat-const-tools-inference.md
new file mode 100644
index 000000000..fb205f67a
--- /dev/null
+++ b/.changeset/usechat-const-tools-inference.md
@@ -0,0 +1,18 @@
+---
+'@tanstack/ai-angular': patch
+'@tanstack/ai-preact': patch
+'@tanstack/ai-react': patch
+'@tanstack/ai-solid': patch
+'@tanstack/ai-svelte': patch
+'@tanstack/ai-vue': patch
+---
+
+Add the `const` modifier to the `TTools` type parameter of `useChat`
+(`createChat` in Svelte, `injectChat` in Angular) so a plain inline `tools` array
+now yields full type-safe message chunks. Previously the array widened to
+`Array<Union>` and lost the literal tool `name`s that drive the
+discriminated `tool-call` part union, so callers had to wrap their tools in
+`clientTools(...)` (or add `as const`) to get narrowing. That wrapper is now
+optional — `tools: [toolA, toolB]` narrows `part.name`, `part.input`, and
+`part.output` on its own. `clientTools(...)` still works and remains useful
+for defining a shared tuple outside the hook call.
diff --git a/docs/advanced/runtime-context.md b/docs/advanced/runtime-context.md
index 18c703fb7..cb9df6b84 100644
--- a/docs/advanced/runtime-context.md
+++ b/docs/advanced/runtime-context.md
@@ -79,7 +79,6 @@ This inference also works when reusable tools or middleware are declared outside
 The same rule applies on the client:
 
 ```typescript
-import { clientTools } from "@tanstack/ai-client";
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { toolDefinition } from "@tanstack/ai";
 
@@ -99,7 +98,7 @@ const inspectClientContext = toolDefinition({
 
 useChat({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(inspectClientContext),
+  tools: [inspectClientContext],
   context: {
     currentTabId: "settings",
     mode: "debug",
@@ -184,7 +183,7 @@ When any tool or middleware in a `chat()` call declares a concrete context type,
 Client runtime context is local to `ChatClient` and framework hooks. It is passed to client tool implementations and is not serialized to the server.
 
 ```typescript
-import { createChatClientOptions, clientTools } from "@tanstack/ai-client";
+import { createChatClientOptions } from "@tanstack/ai-client";
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { toolDefinition } from "@tanstack/ai";
 
@@ -203,7 +202,7 @@ const notifyUser = toolDefinition({
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(notifyUser),
+  tools: [notifyUser],
   context: {
     currentTabId: "settings",
     toast: (message) => window.alert(message),
@@ -221,7 +220,6 @@ To send serializable client data to the server, use `forwardedProps`, validate i
 
 ```typescript
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
-import { clientTools } from "@tanstack/ai-client";
 import { toolDefinition } from "@tanstack/ai";
 
 type ClientContext = {
@@ -240,7 +238,7 @@ const notifyUser = toolDefinition({
 // Client
 useChat({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(notifyUser),
+  tools: [notifyUser],
   forwardedProps: {
     tenantId: "tenant_456",
   },
diff --git a/docs/api/ai-angular.md b/docs/api/ai-angular.md
index 438c3bf46..291ad2cc5 100644
--- a/docs/api/ai-angular.md
+++ b/docs/api/ai-angular.md
@@ -234,7 +234,6 @@ import { Component } from "@angular/core";
 import { CommonModule } from "@angular/common";
 import { injectChat, fetchServerSentEvents } from "@tanstack/ai-angular";
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -280,7 +279,7 @@ export class TypedChatComponent {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  private tools = clientTools(this.updateUI, this.saveToStorage);
+  private tools = [this.updateUI, this.saveToStorage];
 
   chat = injectChat({
     connection: fetchServerSentEvents("/api/chat"),
@@ -526,7 +525,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -534,7 +532,7 @@ import { fetchServerSentEvents } from "@tanstack/ai-angular";
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/api/ai-client.md b/docs/api/ai-client.md
index b926516dd..b08624dc4 100644
--- a/docs/api/ai-client.md
+++ b/docs/api/ai-client.md
@@ -28,7 +28,6 @@ The main client class for managing chat state.
 ```typescript
 import {
   ChatClient,
-  clientTools,
   fetchServerSentEvents,
   type UIMessage,
 } from "@tanstack/ai-client";
@@ -37,7 +36,7 @@ import { myClientTool } from "./tools";
 const client = new ChatClient({
   connection: fetchServerSentEvents("/api/chat"),
   initialMessages: [],
-  tools: clientTools(myClientTool),
+  tools: [myClientTool],
   onMessagesChange: (messages: UIMessage[]) => {
     console.log("Messages updated:", messages);
   },
@@ -281,7 +280,7 @@ const adapter = stream(async (messages, data, signal) => {
 
 ### `clientTools(...tools)`
 
-Creates a typed array of client tools with proper type inference. This eliminates the need for `as const` when defining tool arrays and enables proper discriminated union type narrowing.
+**Optional.** A plain array — `tools: [tool1, tool2]` — already narrows tool names, inputs and outputs without any wrapper or `as const`. `clientTools()` is an identity helper that performs the same capture explicitly; reach for it only when you want to build a shared, reusable tools tuple outside the hook/options call.
 
 ```typescript
 import {
@@ -320,7 +319,7 @@ const tool2Client = myTool2.client((input) => {
   return { result: input.query };
 });
 
-// Create typed tools array (no 'as const' needed!)
+// The explicit-capture form (equivalent to `[tool1Client, tool2Client]`).
 const tools = clientTools(tool1Client, tool2Client);
 
 // Now when you use these tools in chat options:
@@ -348,13 +347,12 @@ Helper function to create typed chat client options with proper type inference.
 ```typescript
 import {
   createChatClientOptions,
-  clientTools,
   fetchServerSentEvents,
   type InferChatMessages,
 } from "@tanstack/ai-client";
 import { tool1, tool2 } from "./tools";
 
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
@@ -370,7 +368,6 @@ type ChatMessages = InferChatMessages<typeof chatOptions>;
 ```typescript
 import {
   createChatClientOptions,
-  clientTools,
   fetchServerSentEvents,
 } from "@tanstack/ai-client";
 import { toolDefinition } from "@tanstack/ai";
@@ -394,7 +391,7 @@ const tool = projectTool.client<ClientContext>((input, ctx: { context: ClientCon
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(tool),
+  tools: [tool],
   context: {
     activeProjectId: "project_123",
   },
@@ -454,12 +451,12 @@ interface ToolCallPart {
   arguments: string; // JSON string (may be incomplete during streaming)
   input?: any; // Parsed tool input (typed from tool's inputSchema)
   state: ToolCallState;
-  approval?: ApprovalRequest;
+  approval?: ApprovalRequest; // only on tools declared `needsApproval: true`
   output?: any; // Tool execution output (typed from tool's outputSchema)
 }
 ```
 
-When using typed tools with `clientTools()` and `createChatClientOptions()`, the `input` and `output` fields are automatically typed based on your tool's Zod schemas, and `name` becomes a discriminated union enabling type narrowing.
+When you pass a typed `tools` array (a plain array works — `clientTools()` is optional), the `input` and `output` fields are automatically typed based on your tool's Zod schemas, and `name` becomes a discriminated union enabling type narrowing. The `approval` field is present **only** on parts for tools declared with `needsApproval: true` — narrow by `part.name` (or guard with `'approval' in part`) before accessing it.
 
 ### `ToolResultPart`
 
diff --git a/docs/api/ai-preact.md b/docs/api/ai-preact.md
index d22977c34..8876a6e62 100644
--- a/docs/api/ai-preact.md
+++ b/docs/api/ai-preact.md
@@ -27,7 +27,6 @@ Main hook for managing chat state in Preact with full type safety.
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -50,7 +49,7 @@ function ChatComponent() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI);
+  const tools = [updateUI];
 
   const chatOptions = createChatClientOptions({
     connection: fetchServerSentEvents("/api/chat"),
@@ -246,7 +245,6 @@ export function ChatWithApproval() {
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -282,7 +280,7 @@ export function ChatWithClientTools() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI, saveToStorage);
+  const tools = [updateUI, saveToStorage];
 
   const { messages, sendMessage } = useChat({
     connection: fetchServerSentEvents("/api/chat"),
@@ -311,7 +309,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -319,7 +316,7 @@ import { fetchServerSentEvents } from "@tanstack/ai-preact";
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/api/ai-react.md b/docs/api/ai-react.md
index 0cc599357..01eb1587b 100644
--- a/docs/api/ai-react.md
+++ b/docs/api/ai-react.md
@@ -33,7 +33,6 @@ Main hook for managing chat state in React with full type safety.
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -60,7 +59,7 @@ function ChatComponent() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI);
+  const tools = [updateUI];
 
   const chatOptions = createChatClientOptions({
     connection: fetchServerSentEvents("/api/chat"),
@@ -275,7 +274,6 @@ export function ChatWithApproval() {
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -319,7 +317,7 @@ export function ChatWithClientTools() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI, saveToStorage);
+  const tools = [updateUI, saveToStorage];
 
   const { messages, sendMessage } = useChat({
     connection: fetchServerSentEvents("/api/chat"),
@@ -348,7 +346,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import { 
-  clientTools, 
   createChatClientOptions, 
   fetchServerSentEvents,
   type InferChatMessages 
@@ -356,7 +353,7 @@ import {
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/api/ai-solid.md b/docs/api/ai-solid.md
index 855ce883e..46de176a9 100644
--- a/docs/api/ai-solid.md
+++ b/docs/api/ai-solid.md
@@ -28,7 +28,6 @@ Main primitive for managing chat state in SolidJS with full type safety.
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-solid";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -51,7 +50,7 @@ function ChatComponent() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI);
+  const tools = [updateUI];
 
   const chatOptions = createChatClientOptions({
     connection: fetchServerSentEvents("/api/chat"),
@@ -259,7 +258,6 @@ export function ChatWithApproval() {
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-solid";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -295,7 +293,7 @@ export function ChatWithClientTools() {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI, saveToStorage);
+  const tools = [updateUI, saveToStorage];
 
   const { messages, sendMessage } = useChat({
     connection: fetchServerSentEvents("/api/chat"),
@@ -328,7 +326,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -336,7 +333,7 @@ import { fetchServerSentEvents } from "@tanstack/ai-solid";
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/api/ai-svelte.md b/docs/api/ai-svelte.md
index 6f8278043..8e7768b87 100644
--- a/docs/api/ai-svelte.md
+++ b/docs/api/ai-svelte.md
@@ -28,7 +28,6 @@ Factory function for managing chat state in Svelte 5 with full type safety.
 ```typescript
 import { createChat, fetchServerSentEvents } from "@tanstack/ai-svelte";
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -52,7 +51,7 @@ const updateUI = updateUIDef.client((input) => {
   return { success: true };
 });
 
-const tools = clientTools(updateUI);
+const tools = [updateUI];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
@@ -240,7 +239,6 @@ import {
 <script lang="ts">
   import { createChat, fetchServerSentEvents } from "@tanstack/ai-svelte";
   import {
-    clientTools,
     createChatClientOptions,
     type InferChatMessages,
   } from "@tanstack/ai-client";
@@ -261,7 +259,7 @@ import {
   });
 
   // Create typed tools array (no 'as const' needed!)
-  const tools = clientTools(updateUI, saveToStorage);
+  const tools = [updateUI, saveToStorage];
 
   const chat = createChat({
     connection: fetchServerSentEvents("/api/chat"),
@@ -331,7 +329,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import {
-  clientTools,
   createChatClientOptions,
   fetchServerSentEvents,
   type InferChatMessages,
@@ -339,7 +336,7 @@ import {
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/api/ai-vue.md b/docs/api/ai-vue.md
index 5b9cf0707..06542576d 100644
--- a/docs/api/ai-vue.md
+++ b/docs/api/ai-vue.md
@@ -28,7 +28,6 @@ Main composable for managing chat state in Vue with full type safety.
 ```typescript
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-vue";
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -50,7 +49,7 @@ const updateUI = updateUIDef.client((input) => {
   return { success: true };
 });
 
-const tools = clientTools(updateUI);
+const tools = [updateUI];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
@@ -243,7 +242,6 @@ const { messages, sendMessage, addToolApprovalResponse } = useChat({
 import { ref } from "vue";
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-vue";
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -277,7 +275,7 @@ const saveToStorage = saveToStorageDef.client((input) => {
 });
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(updateUI, saveToStorage);
+const tools = [updateUI, saveToStorage];
 
 const { messages, sendMessage } = useChat({
   connection: fetchServerSentEvents("/api/chat"),
@@ -348,7 +346,6 @@ Helper to create typed chat options (re-exported from `@tanstack/ai-client`).
 
 ```typescript
 import {
-  clientTools,
   createChatClientOptions,
   type InferChatMessages,
 } from "@tanstack/ai-client";
@@ -356,7 +353,7 @@ import { fetchServerSentEvents } from "@tanstack/ai-vue";
 import { tool1, tool2 } from "./tools";
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(tool1, tool2);
+const tools = [tool1, tool2];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/docs/config.json b/docs/config.json
index ceb80c4f7..97bb9a0ed 100644
--- a/docs/config.json
+++ b/docs/config.json
@@ -73,7 +73,8 @@
         {
           "label": "Tools",
           "to": "tools/tools",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Provider Tools",
@@ -89,7 +90,8 @@
         {
           "label": "Tool Architecture",
           "to": "tools/tool-architecture",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Server Tools",
@@ -99,12 +101,14 @@
         {
           "label": "Client Tools",
           "to": "tools/client-tools",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Tool Approval Flow",
           "to": "tools/tool-approval",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Lazy Tool Discovery",
@@ -213,7 +217,8 @@
         {
           "label": "With Tools",
           "to": "structured-outputs/with-tools",
-          "addedAt": "2026-05-19"
+          "addedAt": "2026-05-19",
+          "updatedAt": "2026-07-08"
         }
       ]
     },
@@ -401,7 +406,8 @@
         {
           "label": "Runtime Context",
           "to": "advanced/runtime-context",
-          "addedAt": "2026-06-01"
+          "addedAt": "2026-06-01",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Debug Logging",
@@ -451,12 +457,14 @@
         {
           "label": "From Vercel AI SDK",
           "to": "migration/migration-from-vercel-ai",
-          "addedAt": "2026-04-20"
+          "addedAt": "2026-04-20",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "AG-UI Client Compliance",
           "to": "migration/ag-ui-compliance",
-          "addedAt": "2026-05-16"
+          "addedAt": "2026-05-16",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "Sampling → modelOptions",
@@ -476,37 +484,44 @@
         {
           "label": "@tanstack/ai-client",
           "to": "api/ai-client",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-react",
           "to": "api/ai-react",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-solid",
           "to": "api/ai-solid",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-preact",
           "to": "api/ai-preact",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-vue",
           "to": "api/ai-vue",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-svelte",
           "to": "api/ai-svelte",
-          "addedAt": "2026-04-15"
+          "addedAt": "2026-04-15",
+          "updatedAt": "2026-07-08"
         },
         {
           "label": "@tanstack/ai-angular",
           "to": "api/ai-angular",
-          "addedAt": "2026-06-15"
+          "addedAt": "2026-06-15",
+          "updatedAt": "2026-07-08"
         }
       ]
     },
diff --git a/docs/migration/ag-ui-compliance.md b/docs/migration/ag-ui-compliance.md
index 7a555f5d3..4a22e4225 100644
--- a/docs/migration/ag-ui-compliance.md
+++ b/docs/migration/ag-ui-compliance.md
@@ -116,7 +116,7 @@ export async function POST(req: Request) {
   // const provider = body.forwardedProps?.provider
 
   const stream = chat({
-    adapter: openaiText('gpt-4o'),
+    adapter: openaiText('gpt-5.5'),
     messages: body.messages, // AG-UI mixed shape — works directly
     tools: serverTools,
   })
@@ -146,7 +146,7 @@ import { serverTools } from './tools'
 export async function POST(req: Request) {
   const params = await chatParamsFromRequest(req)
   const stream = chat({
-    adapter: openaiText('gpt-4o'),
+    adapter: openaiText('gpt-5.5'),
     messages: params.messages,
     tools: serverTools,
   })
@@ -179,8 +179,9 @@ import { serverTools } from './tools'
 export async function POST(req: Request) {
   const params = await chatParamsFromRequest(req)
   const stream = chat({
-    adapter: openaiText('gpt-4o'),
+    adapter: openaiText('gpt-5.5'),
     messages: params.messages,
+    // `mergeAgentTools` returns a plain array — pass it straight to `tools`.
     tools: mergeAgentTools(serverTools, params.tools), // ← merges client-declared tools
   })
   return toServerSentEventsResponse(stream)
@@ -189,6 +190,24 @@ export async function POST(req: Request) {
 
 `mergeAgentTools` registers client-declared tools as no-execute stubs server-side. The runtime emits a `ClientToolRequest` event when the model calls one; the client executes via its registered handler and posts the result back.
 
+> **Security — merging trusts the client to define part of the tool surface.**
+> `params.tools` is attacker-controllable: a malicious or compromised client can
+> put any `name` / `description` / `parameters` it likes in `RunAgentInput.tools`.
+> Merging them means those definitions are advertised to the model. Server tools
+> still win on name collision (a client **cannot** shadow or hijack a server
+> tool's `execute`), and client-declared tools are no-execute — they only ever
+> run by round-tripping back to that same client. But a client can still **expand
+> the advertised tool surface** and **inject arbitrary text into the model's
+> context** through tool names and descriptions (a prompt-injection vector).
+>
+> **The safe default is to register your tool definitions statically** in the
+> server's `tools` array (including client-executed tools — a definition with no
+> `.server()` still works) and **not** call `mergeAgentTools`. Then any tools a
+> client declares in the payload are ignored: the model is never told about
+> them, so it never calls them and they can't run. Only reach for
+> `mergeAgentTools` when you genuinely want the client to drive tool
+> advertisement and you trust that client.
+
 ## `forwardedProps` security (Tier 2+ only)
 
 Skip this section if you're on Tier 1. `forwardedProps` is only surfaced when you opt into `chatParamsFromRequest` (or `chatParamsFromRequestBody`).
@@ -198,7 +217,7 @@ Skip this section if you're on Tier 1. `forwardedProps` is only surfaced when yo
 ```ts ignore
 // 🚫 UNSAFE — a client could override `adapter`, `model`, `tools`, system prompts, anything
 chat({
-  adapter: openaiText('gpt-4o'),
+  adapter: openaiText('gpt-5.5'),
   ...params,
   ...params.forwardedProps,
 })
@@ -222,7 +241,7 @@ export async function POST(req: Request) {
   // ✅ SAFE — explicit allowlist. Sampling params live in modelOptions under
   // each provider's native key (OpenAI: temperature / max_output_tokens).
   const stream = chat({
-    adapter: openaiText('gpt-4o'),
+    adapter: openaiText('gpt-5.5'),
     messages: params.messages,
     tools: mergeAgentTools(serverTools, params.tools),
     modelOptions: {
@@ -263,7 +282,7 @@ const tenantId =
     : defaultTenantId
 
 const stream = chat({
-  adapter: openaiText('gpt-4o'),
+  adapter: openaiText('gpt-5.5'),
   messages: params.messages,
   tools: serverTools,
   context: {
@@ -275,7 +294,7 @@ const stream = chat({
 
 ## Client-side: nothing required, one rename recommended
 
-`useChat` and the connection adapters (`fetchServerSentEvents`, `fetchHttpStream`) handle the new wire format internally. Existing `UIMessage` state is unchanged. `clientTools(...)` declarations are now automatically advertised to the server in the request payload.
+`useChat` and the connection adapters (`fetchServerSentEvents`, `fetchHttpStream`) handle the new wire format internally. Existing `UIMessage` state is unchanged. The tools you pass to `useChat({ tools })` are now automatically advertised to the server in the request payload.
 
 ### `body` → `forwardedProps` (recommended)
 
@@ -288,13 +307,13 @@ import { fetchServerSentEvents } from '@tanstack/ai-client'
 // Before — still works, but deprecated
 useChat({
   connection: fetchServerSentEvents('/api/chat'),
-  body: { provider: 'openai', model: 'gpt-4o' },
+  body: { provider: 'openai', model: 'gpt-5.5' },
 })
 
 // After — recommended
 useChat({
   connection: fetchServerSentEvents('/api/chat'),
-  forwardedProps: { provider: 'openai', model: 'gpt-4o' },
+  forwardedProps: { provider: 'openai', model: 'gpt-5.5' },
 })
 ```
 
@@ -321,7 +340,7 @@ If you don't pass `threadId`, one is generated automatically and persists for th
 ## Tool-merge semantics
 
 - **Server tools win on name collision.** A tool registered server-side via `toolDefinition().server(...)` always executes server-side.
-- **Client-only tools become no-execute stubs** in `chat()` (when registered via `mergeAgentTools`). The runtime emits a `ClientToolRequest` event back to the client; the client's registered handler (via `clientTools(...)`) executes locally and posts the result.
+- **Client-only tools become no-execute stubs** in `chat()` (when registered via `mergeAgentTools`). The runtime emits a `ClientToolRequest` event back to the client; the client's registered handler (the `.client(...)` tool in the hook's `tools` array) executes locally and posts the result.
 - **Dual-handler (both have it):** server executes, then `chat-client.ts`'s `onToolCall` fires the client's handler as a UI side-effect when the streamed tool result event arrives. The server's result is authoritative for the conversation.
 
 ## Talking to a foreign AG-UI server
diff --git a/docs/migration/migration-from-vercel-ai.md b/docs/migration/migration-from-vercel-ai.md
index 680473492..61db6636d 100644
--- a/docs/migration/migration-from-vercel-ai.md
+++ b/docs/migration/migration-from-vercel-ai.md
@@ -612,7 +612,6 @@ const { messages, addToolOutput } = useChat({
 
 ```typescript
 import { useChat, fetchServerSentEvents } from '@tanstack/ai-react'
-import { clientTools } from '@tanstack/ai-client'
 import { toolDefinition } from '@tanstack/ai'
 import { z } from 'zod'
 import { toast } from './toast'
@@ -631,12 +630,13 @@ const showNotification = showNotificationDef.client(({ message }) => {
   return { success: true }
 })
 
-// Use in component — `clientTools()` wires each client tool's `.client(...)`
-// handler to run automatically when the server-side agent calls it; you don't
-// need an onToolCall handler or an addToolOutput/addToolResult call.
+// Use in component — passing the client tools in the `tools` array wires each
+// tool's `.client(...)` handler to run automatically when the server-side
+// agent calls it; you don't need an onToolCall handler or an
+// addToolOutput/addToolResult call.
 const { messages } = useChat({
   connection: fetchServerSentEvents('/api/chat'),
-  tools: clientTools(showNotification),
+  tools: [showNotification],
 })
 ```
 
@@ -710,7 +710,7 @@ const { messages, addToolApprovalResponse } = useChat({
 })}
 ```
 
-> `part.input` is the **parsed** tool input (typed when your tools are typed via `clientTools()` + `InferChatMessages`). The raw streaming JSON is available as `part.arguments` if you need to show progress before input parsing completes.
+> `part.input` is the **parsed** tool input (typed when you pass a typed `tools` array). The raw streaming JSON is available as `part.arguments` if you need to show progress before input parsing completes.
 
 ## Structured Output
 
@@ -1336,11 +1336,11 @@ TanStack AI provides enhanced type safety that Vercel AI SDK doesn't offer:
 ### Typed Message Parts
 
 ```typescript
-import { createChatClientOptions, clientTools, type InferChatMessages } from '@tanstack/ai-client'
+import { createChatClientOptions, type InferChatMessages } from '@tanstack/ai-client'
 import { fetchServerSentEvents } from '@tanstack/ai-react'
 import { updateUI, saveData } from './tools'
 
-const tools = clientTools(updateUI, saveData)
+const tools = [updateUI, saveData]
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents('/api/chat'),
diff --git a/docs/structured-outputs/with-tools.md b/docs/structured-outputs/with-tools.md
index 8938f316f..69e43d7be 100644
--- a/docs/structured-outputs/with-tools.md
+++ b/docs/structured-outputs/with-tools.md
@@ -132,7 +132,6 @@ Client tools — defined with `.client((input) => ...)` on the tool definition 
 
 ```tsx
 import { toolDefinition } from "@tanstack/ai";
-import { clientTools } from "@tanstack/ai-client";
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { z } from "zod";
 import { runLookupOnClient } from "./client-utils";
@@ -154,7 +153,7 @@ const lookupContact = lookupContactDef.client((input) => {
 
 const { messages, sendMessage, partial, final } = useChat({
   outputSchema: RecommendationSchema,
-  tools: clientTools(lookupContact),
+  tools: [lookupContact],
   connection: fetchServerSentEvents("/api/recommend"),
 });
 ```
diff --git a/docs/tools/client-tools.md b/docs/tools/client-tools.md
index 321bcf604..a6232d6f3 100644
--- a/docs/tools/client-tools.md
+++ b/docs/tools/client-tools.md
@@ -118,6 +118,13 @@ export async function POST(request: Request) {
 }
 ```
 
+> **Security:** registering the definitions statically (as above) is the safe
+> default — the server alone decides which tools the model sees, so a client
+> can't advertise tools you didn't sanction. If you'd instead like the client
+> to declare its tools per request via AG-UI `RunAgentInput.tools`, use
+> [`mergeAgentTools`](../migration/ag-ui-compliance#tier-3--optional-let-the-client-advertise-its-tools) —
+> read its security note first, since `params.tools` is client-controlled.
+
 ### Client-Side
 
 Create client implementations with automatic execution and full type safety:
@@ -126,7 +133,6 @@ Create client implementations with automatic execution and full type safety:
 // app/chat.tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages,
   type ToolCallPart,
@@ -167,8 +173,9 @@ const saveToLocalStorage = saveToLocalStorageDef.client((input) => {
   return { saved: true };
 });
 
-// Step 2: Create typed tools array (no 'as const' needed!)
-const tools = clientTools(updateUI, saveToLocalStorage);
+// Step 2: A plain array is all you need — literal tool names, inputs and
+// outputs are inferred without any wrapper or `as const`.
+const tools = [updateUI, saveToLocalStorage];
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
@@ -235,7 +242,7 @@ Client tools are **automatically executed** when the model calls them. The flow
 Client tools can receive typed runtime context as their second argument. This context is local to the `ChatClient` or framework hook instance and is not serialized to the server.
 
 ```typescript
-import { createChatClientOptions, clientTools } from "@tanstack/ai-client";
+import { createChatClientOptions } from "@tanstack/ai-client";
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { toolDefinition } from "@tanstack/ai";
 import { toast } from "./toast";
@@ -257,7 +264,7 @@ const showToast = toolDefinition({
 
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(showToast),
+  tools: [showToast],
   context: {
     activeProjectId,
     toast: (message) => toast(message),
@@ -269,6 +276,23 @@ const chat = useChat(chatOptions);
 
 Use `context` for local browser dependencies. If the server also needs a value from the client, send it with `forwardedProps`, validate it in your route, and map it into server `chat({ context })` explicitly. See [Runtime Context](../advanced/runtime-context) for the full pattern.
 
+## The `clientTools()` helper (optional)
+
+Passing a plain array — `tools: [toolA, toolB]` — is all you need: tool names, inputs and outputs are inferred without any wrapper and without `as const`. `clientTools()` is an optional identity helper that performs the same capture explicitly. Reach for it only when you want to build a shared, reusable tools tuple **outside** the hook/options call:
+
+```ts
+import { clientTools } from "@tanstack/ai-client";
+import { toolDefinition } from "@tanstack/ai";
+
+const notify = toolDefinition({
+  name: "notify",
+  description: "Show a notification",
+}).client(() => ({ ok: true }));
+
+// Equivalent to `const tools = [notify]` — just captured explicitly.
+const tools = clientTools(notify);
+```
+
 ## Type Safety Benefits
 
 The isomorphic architecture provides complete end-to-end type safety:
diff --git a/docs/tools/tool-approval.md b/docs/tools/tool-approval.md
index 1d87a3ff8..c4520fce2 100644
--- a/docs/tools/tool-approval.md
+++ b/docs/tools/tool-approval.md
@@ -2,7 +2,7 @@
 title: Tool Approval Flow
 id: tool-approval-flow
 order: 5
-description: "Require user approval before executing sensitive tools in TanStack AI — approval states, deny flows, and batched approvals with needsApproval."
+description: 'Require user approval before executing sensitive tools in TanStack AI — approval states, deny flows, and batched approvals with needsApproval.'
 keywords:
   - tanstack ai
   - tool approval
@@ -36,14 +36,14 @@ When a tool requires approval, the typical flow is:
 Tools can be marked as requiring approval by setting `needsApproval: true` in the definition:
 
 ```typescript
-import { toolDefinition } from "@tanstack/ai";
-import { z } from "zod";
-import { emailService } from "./email-service";
+import { toolDefinition } from '@tanstack/ai'
+import { z } from 'zod'
+import { emailService } from './email-service'
 
 // Step 1: Define tool with approval requirement
 const sendEmailDef = toolDefinition({
-  name: "send_email",
-  description: "Send an email to a recipient",
+  name: 'send_email',
+  description: 'Send an email to a recipient',
   inputSchema: z.object({
     to: z.string().email(),
     subject: z.string(),
@@ -54,14 +54,14 @@ const sendEmailDef = toolDefinition({
     messageId: z.string(),
   }),
   needsApproval: true, // This tool requires approval
-});
+})
 
 // Step 2: Create server implementation
 const sendEmail = sendEmailDef.server(async ({ to, subject, body }) => {
   // Only executes if approved
-  await emailService.send({ to, subject, body });
-  return { success: true, messageId: "..." };
-});
+  await emailService.send({ to, subject, body })
+  return { success: true, messageId: '...' }
+})
 ```
 
 ## Server-Side Approval
@@ -69,20 +69,20 @@ const sendEmail = sendEmailDef.server(async ({ to, subject, body }) => {
 On the server, tools with `needsApproval: true` will pause execution and wait for approval:
 
 ```typescript
-import { chat, toServerSentEventsResponse } from "@tanstack/ai";
-import { openaiText } from "@tanstack/ai-openai";
-import { sendEmail } from "./tools";
+import { chat, toServerSentEventsResponse } from '@tanstack/ai'
+import { openaiText } from '@tanstack/ai-openai'
+import { sendEmail } from './tools'
 
 export async function POST(request: Request) {
-  const { messages } = await request.json();
+  const { messages } = await request.json()
 
   const stream = chat({
-    adapter: openaiText("gpt-5.5"),
+    adapter: openaiText('gpt-5.5'),
     messages,
     tools: [sendEmail],
-  });
+  })
 
-  return toServerSentEventsResponse(stream);
+  return toServerSentEventsResponse(stream)
 }
 ```
 
@@ -91,12 +91,12 @@ export async function POST(request: Request) {
 The client receives approval requests and can respond:
 
 ```tsx
-import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
+import { useChat, fetchServerSentEvents } from '@tanstack/ai-react'
 
 function ChatComponent() {
   const { messages, sendMessage, addToolApprovalResponse } = useChat({
-    connection: fetchServerSentEvents("/api/chat"),
-  });
+    connection: fetchServerSentEvents('/api/chat'),
+  })
 
   return (
     <div>
@@ -105,8 +105,8 @@ function ChatComponent() {
           {message.parts.map((part) => {
             // Check for approval requests
             if (
-              part.type === "tool-call" &&
-              part.state === "approval-requested" &&
+              part.type === 'tool-call' &&
+              part.state === 'approval-requested' &&
               part.approval
             ) {
               return (
@@ -134,37 +134,124 @@ function ChatComponent() {
                     Deny
                   </button>
                 </div>
-              );
+              )
             }
             // ... render other parts
-            return null;
+            return null
           })}
         </div>
       ))}
     </div>
-  );
+  )
 }
 ```
 
+> **Type safety:** When you pass typed `tools` to `useChat`, the `approval`
+> field exists **only** on tool-call parts for tools declared with
+> `needsApproval: true` — tools without approval have no `approval` field at
+> all, so reading it is a compile error that catches a real footgun (checking
+> for approval on a tool that can never request it). See
+> [Generic approval handlers](#generic-approval-handlers) for how to write a
+> tool-agnostic handler under this constraint.
+
+## Generic Approval Handlers
+
+A handler that renders an approval prompt for **any** tool (not one specific
+tool) is still fully supported — you just can't read `part.approval` off a
+typed mixed tool union without first establishing that the field exists. Pick
+whichever of these fits:
+
+**1. Narrow with `'approval' in part`.** This narrows the tool-call union to
+exactly the members that can carry approval, so one loop handles every approval
+tool with full type safety:
+
+```tsx
+import { toolDefinition } from '@tanstack/ai'
+import { z } from 'zod'
+import { useChat, fetchServerSentEvents } from '@tanstack/ai-react'
+
+const deleteData = toolDefinition({
+  name: 'delete_data',
+  description: 'Delete data (requires approval)',
+  inputSchema: z.object({ key: z.string() }),
+  needsApproval: true,
+}).client(async ({ key }) => ({ deleted: key }))
+
+const listData = toolDefinition({
+  name: 'list_data',
+  description: 'List available keys',
+  inputSchema: z.object({}),
+}).client(async () => ({ keys: [] as Array<string> }))
+
+function ApprovalHandler() {
+  const { messages, addToolApprovalResponse } = useChat({
+    connection: fetchServerSentEvents('/api/chat'),
+    tools: [deleteData, listData],
+  })
+
+  return (
+    <div>
+      {messages.flatMap((message) =>
+        message.parts.map((part, i) => {
+          // `'approval' in part` narrows the union to `needsApproval` tools,
+          // so this single handler covers every approval tool — no per-tool
+          // `part.name` branch needed.
+          if (
+            part.type === 'tool-call' &&
+            part.state === 'approval-requested' &&
+            'approval' in part &&
+            part.approval
+          ) {
+            return (
+              <button
+                key={i}
+                onClick={() =>
+                  addToolApprovalResponse({
+                    id: part.approval!.id,
+                    approved: true,
+                  })
+                }
+              >
+                Approve {part.name}
+              </button>
+            )
+          }
+          return null
+        }),
+      )}
+    </div>
+  )
+}
+```
+
+**2. Type a shared component against the base `ToolCallPart`.** The base type
+(from `@tanstack/ai-client`, untyped tools) always carries `approval?`, so a
+reusable component works across every tool regardless of the caller's tool
+union — this is the [Approval UI Example](#approval-ui-example) below.
+
+**3. Use an untyped `useChat()`.** With no `tools` generic, every tool-call
+part keeps `approval?` exactly as before — no narrowing needed.
+
 ## Approval UI Example
 
 Here's a more complete approval UI component:
 
 ```tsx
-import type { ToolCallPart } from "@tanstack/ai-client";
+import type { ToolCallPart } from '@tanstack/ai-client'
 
 function ApprovalPrompt({
   part,
   onApprove,
   onDeny,
 }: {
-  part: ToolCallPart;
-  onApprove: () => void;
-  onDeny: () => void;
+  part: ToolCallPart
+  onApprove: () => void
+  onDeny: () => void
 }) {
-  // When tools are passed via `clientTools(...)`, `part.input` is the
-  // parsed, fully-typed argument object. Otherwise parse `part.arguments`.
-  const args = part.input ?? JSON.parse(part.arguments);
+  // `part.input` is the parsed, fully-typed argument object — always populated
+  // by approval time (the arguments are complete). The raw `part.arguments`
+  // string is still available if you need it.
+  const args = part.input
 
   return (
     <div className="border border-yellow-500 rounded-lg p-4 bg-yellow-50">
@@ -191,26 +278,28 @@ function ApprovalPrompt({
         </button>
       </div>
     </div>
-  );
+  )
 }
 ```
 
 Wire it up from your message renderer. Note the `id` you pass is the **approval id** (`part.approval.id`), not the tool call id:
 
 ```tsx ignore
-{part.type === "tool-call" &&
-  part.state === "approval-requested" &&
-  part.approval && (
-    <ApprovalPrompt
-      part={part}
-      onApprove={() =>
-        addToolApprovalResponse({ id: part.approval!.id, approved: true })
-      }
-      onDeny={() =>
-        addToolApprovalResponse({ id: part.approval!.id, approved: false })
-      }
-    />
-  )}
+{
+  part.type === 'tool-call' &&
+    part.state === 'approval-requested' &&
+    part.approval && (
+      <ApprovalPrompt
+        part={part}
+        onApprove={() =>
+          addToolApprovalResponse({ id: part.approval!.id, approved: true })
+        }
+        onDeny={() =>
+          addToolApprovalResponse({ id: part.approval!.id, approved: false })
+        }
+      />
+    )
+}
 ```
 
 ## Client Tools with Approval
@@ -218,15 +307,14 @@ Wire it up from your message renderer. Note the `id` you pass is the **approval
 Client tools can also require approval:
 
 ```typescript
-import { toolDefinition } from "@tanstack/ai";
-import { z } from "zod";
-import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
-import { clientTools } from "@tanstack/ai-client";
+import { toolDefinition } from '@tanstack/ai'
+import { z } from 'zod'
+import { useChat, fetchServerSentEvents } from '@tanstack/ai-react'
 
 // tools/definitions.ts
 const deleteLocalDataDef = toolDefinition({
-  name: "delete_local_data",
-  description: "Delete data from local storage",
+  name: 'delete_local_data',
+  description: 'Delete data from local storage',
   inputSchema: z.object({
     key: z.string(),
   }),
@@ -234,35 +322,35 @@ const deleteLocalDataDef = toolDefinition({
     deleted: z.boolean(),
   }),
   needsApproval: true, // Requires approval even on client
-});
+})
 
 // Client: Create implementation
 const deleteLocalData = deleteLocalDataDef.client((input) => {
   // This will only execute after approval
-  localStorage.removeItem(input.key);
-  return { deleted: true };
-});
+  localStorage.removeItem(input.key)
+  return { deleted: true }
+})
 
 const { messages, addToolApprovalResponse } = useChat({
-  connection: fetchServerSentEvents("/api/chat"),
-  // Wrap client tools in `clientTools(...)` so literal tool-name inference is
-  // preserved — this is what lets `part.name === "delete_local_data"` narrow
+  connection: fetchServerSentEvents('/api/chat'),
+  // Pass client tools as a plain array — literal tool-name inference works
+  // without a wrapper, so `part.name === "delete_local_data"` still narrows
   // `part.input` / `part.output` to this tool's types.
-  tools: clientTools(deleteLocalData), // Automatic execution after approval
-});
+  tools: [deleteLocalData], // Automatic execution after approval
+})
 ```
 
 ## Example: E-commerce Purchase
 
 ```typescript
-import { toolDefinition } from "@tanstack/ai";
-import { z } from "zod";
-import { createOrder } from "./orders";
+import { toolDefinition } from '@tanstack/ai'
+import { z } from 'zod'
+import { createOrder } from './orders'
 
 // Define tool with approval requirement
 const purchaseItemDef = toolDefinition({
-  name: "purchase_item",
-  description: "Purchase an item from the store",
+  name: 'purchase_item',
+  description: 'Purchase an item from the store',
   inputSchema: z.object({
     itemId: z.string(),
     quantity: z.number(),
@@ -273,13 +361,15 @@ const purchaseItemDef = toolDefinition({
     total: z.number(),
   }),
   needsApproval: true,
-});
+})
 
 // Create server implementation
-const purchaseItem = purchaseItemDef.server(async ({ itemId, quantity, price }) => {
-  const order = await createOrder({ itemId, quantity, price });
-  return { orderId: order.id, total: price * quantity };
-});
+const purchaseItem = purchaseItemDef.server(
+  async ({ itemId, quantity, price }) => {
+    const order = await createOrder({ itemId, quantity, price })
+    return { orderId: order.id, total: price * quantity }
+  },
+)
 ```
 
 The user will see an approval prompt showing the item, quantity, and price before the purchase is made. The tool will only execute after the user approves.
diff --git a/docs/tools/tool-architecture.md b/docs/tools/tool-architecture.md
index fb7870037..9d5990f4e 100644
--- a/docs/tools/tool-architecture.md
+++ b/docs/tools/tool-architecture.md
@@ -182,7 +182,7 @@ stateDiagram-v2
 
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
-import { clientTools, createChatClientOptions } from "@tanstack/ai-client";
+import { createChatClientOptions } from "@tanstack/ai-client";
 import { getWeather, sendEmail } from "./tools";
 import { ApprovalUI } from "./approval-ui";
 
@@ -190,7 +190,7 @@ import { ApprovalUI } from "./approval-ui";
 // narrow to each tool's types below.
 const chatOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
-  tools: clientTools(getWeather, sendEmail),
+  tools: [getWeather, sendEmail],
 });
 
 function ChatComponent() {
diff --git a/docs/tools/tools.md b/docs/tools/tools.md
index debc8f2db..25d7d094e 100644
--- a/docs/tools/tools.md
+++ b/docs/tools/tools.md
@@ -234,7 +234,6 @@ export async function POST(request: Request) {
 ```tsx
 import { useChat, fetchServerSentEvents } from "@tanstack/ai-react";
 import { 
-  clientTools, 
   createChatClientOptions, 
   type InferChatMessages 
 } from "@tanstack/ai-client";
@@ -268,7 +267,7 @@ const saveToStorage = saveToStorageDef.client((input) => {
 });
 
 // Create typed tools array (no 'as const' needed!)
-const tools = clientTools(updateUI, saveToStorage);
+const tools = [updateUI, saveToStorage];
 
 const textOptions = createChatClientOptions({
   connection: fetchServerSentEvents("/api/chat"),
diff --git a/examples/ts-react-chat/src/components/Header.tsx b/examples/ts-react-chat/src/components/Header.tsx
index e7fbc6a0a..061f74d78 100644
--- a/examples/ts-react-chat/src/components/Header.tsx
+++ b/examples/ts-react-chat/src/components/Header.tsx
@@ -5,6 +5,7 @@ import {
   Activity,
   BadgeCheck,
   Braces,
+  Code2,
   FileAudio,
   FileText,
   Guitar,
@@ -218,6 +219,19 @@ export default function Header() {
             <span className="font-medium">Guitar Demo</span>
           </Link>
 
+          <Link
+            to="/typesafe-tools"
+            onClick={() => setIsOpen(false)}
+            className="flex items-center gap-3 p-3 rounded-lg hover:bg-gray-800 transition-colors mb-1"
+            activeProps={{
+              className:
+                'flex items-center gap-3 p-3 rounded-lg bg-cyan-600 hover:bg-cyan-700 transition-colors mb-1',
+            }}
+          >
+            <Code2 size={20} />
+            <span className="font-medium">Type-Safe Tools</span>
+          </Link>
+
           <Link
             to="/threads"
             onClick={() => setIsOpen(false)}
diff --git a/examples/ts-react-chat/src/routeTree.gen.ts b/examples/ts-react-chat/src/routeTree.gen.ts
index 69a7764a2..b223bce09 100644
--- a/examples/ts-react-chat/src/routeTree.gen.ts
+++ b/examples/ts-react-chat/src/routeTree.gen.ts
@@ -9,6 +9,7 @@
 // Additionally, you should also exclude this file from your linter and/or formatter to prevent it from being checked or modified.
 
 import { Route as rootRouteImport } from './routes/__root'
+import { Route as TypesafeToolsRouteImport } from './routes/typesafe-tools'
 import { Route as ThreadsRouteImport } from './routes/threads'
 import { Route as ServerFnChatRouteImport } from './routes/server-fn-chat'
 import { Route as SandboxesRouteImport } from './routes/sandboxes'
@@ -54,6 +55,11 @@ import { Route as ApiGenerateSpeechRouteImport } from './routes/api.generate.spe
 import { Route as ApiGenerateImageRouteImport } from './routes/api.generate.image'
 import { Route as ApiGenerateAudioRouteImport } from './routes/api.generate.audio'
 
+const TypesafeToolsRoute = TypesafeToolsRouteImport.update({
+  id: '/typesafe-tools',
+  path: '/typesafe-tools',
+  getParentRoute: () => rootRouteImport,
+} as any)
 const ThreadsRoute = ThreadsRouteImport.update({
   id: '/threads',
   path: '/threads',
@@ -291,6 +297,7 @@ export interface FileRoutesByFullPath {
   '/sandboxes': typeof SandboxesRoute
   '/server-fn-chat': typeof ServerFnChatRoute
   '/threads': typeof ThreadsRoute
+  '/typesafe-tools': typeof TypesafeToolsRoute
   '/api/capability-demo': typeof ApiCapabilityDemoRoute
   '/api/image-gen': typeof ApiImageGenRoute
   '/api/image-tool-repro': typeof ApiImageToolReproRoute
@@ -337,6 +344,7 @@ export interface FileRoutesByTo {
   '/sandboxes': typeof SandboxesRoute
   '/server-fn-chat': typeof ServerFnChatRoute
   '/threads': typeof ThreadsRoute
+  '/typesafe-tools': typeof TypesafeToolsRoute
   '/api/capability-demo': typeof ApiCapabilityDemoRoute
   '/api/image-gen': typeof ApiImageGenRoute
   '/api/image-tool-repro': typeof ApiImageToolReproRoute
@@ -384,6 +392,7 @@ export interface FileRoutesById {
   '/sandboxes': typeof SandboxesRoute
   '/server-fn-chat': typeof ServerFnChatRoute
   '/threads': typeof ThreadsRoute
+  '/typesafe-tools': typeof TypesafeToolsRoute
   '/api/capability-demo': typeof ApiCapabilityDemoRoute
   '/api/image-gen': typeof ApiImageGenRoute
   '/api/image-tool-repro': typeof ApiImageToolReproRoute
@@ -432,6 +441,7 @@ export interface FileRouteTypes {
     | '/sandboxes'
     | '/server-fn-chat'
     | '/threads'
+    | '/typesafe-tools'
     | '/api/capability-demo'
     | '/api/image-gen'
     | '/api/image-tool-repro'
@@ -478,6 +488,7 @@ export interface FileRouteTypes {
     | '/sandboxes'
     | '/server-fn-chat'
     | '/threads'
+    | '/typesafe-tools'
     | '/api/capability-demo'
     | '/api/image-gen'
     | '/api/image-tool-repro'
@@ -524,6 +535,7 @@ export interface FileRouteTypes {
     | '/sandboxes'
     | '/server-fn-chat'
     | '/threads'
+    | '/typesafe-tools'
     | '/api/capability-demo'
     | '/api/image-gen'
     | '/api/image-tool-repro'
@@ -571,6 +583,7 @@ export interface RootRouteChildren {
   SandboxesRoute: typeof SandboxesRoute
   ServerFnChatRoute: typeof ServerFnChatRoute
   ThreadsRoute: typeof ThreadsRoute
+  TypesafeToolsRoute: typeof TypesafeToolsRoute
   ApiCapabilityDemoRoute: typeof ApiCapabilityDemoRoute
   ApiImageGenRoute: typeof ApiImageGenRoute
   ApiImageToolReproRoute: typeof ApiImageToolReproRoute
@@ -607,6 +620,13 @@ export interface RootRouteChildren {
 
 declare module '@tanstack/react-router' {
   interface FileRoutesByPath {
+    '/typesafe-tools': {
+      id: '/typesafe-tools'
+      path: '/typesafe-tools'
+      fullPath: '/typesafe-tools'
+      preLoaderRoute: typeof TypesafeToolsRouteImport
+      parentRoute: typeof rootRouteImport
+    }
     '/threads': {
       id: '/threads'
       path: '/threads'
@@ -931,6 +951,7 @@ const rootRouteChildren: RootRouteChildren = {
   SandboxesRoute: SandboxesRoute,
   ServerFnChatRoute: ServerFnChatRoute,
   ThreadsRoute: ThreadsRoute,
+  TypesafeToolsRoute: TypesafeToolsRoute,
   ApiCapabilityDemoRoute: ApiCapabilityDemoRoute,
   ApiImageGenRoute: ApiImageGenRoute,
   ApiImageToolReproRoute: ApiImageToolReproRoute,
diff --git a/examples/ts-react-chat/src/routes/api.tanchat.ts b/examples/ts-react-chat/src/routes/api.tanchat.ts
index a815d1e13..775723aaa 100644
--- a/examples/ts-react-chat/src/routes/api.tanchat.ts
+++ b/examples/ts-react-chat/src/routes/api.tanchat.ts
@@ -358,7 +358,7 @@ export const Route = createFileRoute('/api/tanchat')({
 
           const stream = chat({
             ...options,
-            tools: Object.values(mergedTools),
+            tools: mergedTools,
             middleware: [loggingMiddleware, runtimeContextMiddleware],
             context: runtimeContext,
             systemPrompts: [SYSTEM_PROMPT],
diff --git a/examples/ts-react-chat/src/routes/index.tsx b/examples/ts-react-chat/src/routes/index.tsx
index 91c3e6cd8..b3228dd67 100644
--- a/examples/ts-react-chat/src/routes/index.tsx
+++ b/examples/ts-react-chat/src/routes/index.tsx
@@ -2,6 +2,7 @@ import { useEffect, useMemo, useRef, useState } from 'react'
 import { Link, createFileRoute } from '@tanstack/react-router'
 import {
   Braces,
+  Code2,
   FileAudio,
   FileText,
   Github,
@@ -199,6 +200,13 @@ function Messages({
               <Braces size={24} className="text-orange-400" />
               <span className="text-sm text-gray-300">Structured Chat</span>
             </Link>
+            <Link
+              to="/typesafe-tools"
+              className="flex flex-col items-center gap-2 p-4 bg-gray-800/50 border border-gray-700 rounded-lg hover:border-orange-500/40 hover:bg-gray-800 transition-colors"
+            >
+              <Code2 size={24} className="text-orange-400" />
+              <span className="text-sm text-gray-300">Type-Safe Tools</span>
+            </Link>
             <Link
               to="/sandboxes"
               className="flex flex-col items-center gap-2 p-4 bg-gray-800/50 border border-gray-700 rounded-lg hover:border-orange-500/40 hover:bg-gray-800 transition-colors"
diff --git a/examples/ts-react-chat/src/routes/typesafe-tools.tsx b/examples/ts-react-chat/src/routes/typesafe-tools.tsx
new file mode 100644
index 000000000..dbd4610d9
--- /dev/null
+++ b/examples/ts-react-chat/src/routes/typesafe-tools.tsx
@@ -0,0 +1,197 @@
+import { useState } from 'react'
+import { createFileRoute } from '@tanstack/react-router'
+import { fetchServerSentEvents, useChat } from '@tanstack/ai-react'
+import {
+  addToCartToolDef,
+  getGuitarsToolDef,
+  recommendGuitarToolDef,
+} from '@/lib/guitar-tools'
+
+/**
+ * Manual type-safety confirmation for passing a BARE inline `tools` array to
+ * `useChat` — no `clientTools(...)` wrapper and no `as const`. The `const`
+ * modifier on `useChat`'s `TTools` param now captures the tuple + literal tool
+ * names, so tool-call parts narrow on `part.name` and expose per-tool typed
+ * `input` / `output`.
+ *
+ * The assertions below are the real proof: this file only compiles if
+ * inference works. If the `const` modifier regressed, `part.name` would widen
+ * to `string`, the `===` checks would stop narrowing, and the typed field
+ * access (`.output.id` as `number`, `.input.quantity` as `number`) would error.
+ */
+function TypesafeToolsPage() {
+  const [prompt, setPrompt] = useState('Recommend me an acoustic guitar.')
+
+  const { messages, sendMessage, isLoading, error } = useChat({
+    id: 'typesafe-tools-bare-array',
+    connection: fetchServerSentEvents('/api/tanchat'),
+    body: { provider: 'openai', model: 'gpt-5.5' },
+    // 👇 Bare array literal — no clientTools(), no `as const`.
+    tools: [
+      getGuitarsToolDef,
+      recommendGuitarToolDef.client(({ id }) => ({ id: Number(id) })),
+      addToCartToolDef.client((args) => ({
+        success: true,
+        cartId: `CART_${args.guitarId}`,
+        guitarId: args.guitarId,
+        quantity: args.quantity,
+        totalItems: args.quantity,
+      })),
+    ],
+  })
+
+  const toolCalls = messages
+    .flatMap((message) => message.parts)
+    .filter((part) => part.type === 'tool-call')
+
+  // Hard regression guard: this assignment only compiles when the bare array
+  // preserved the literal tool names. If inference widened `part.name` to
+  // `string` (the pre-`const` behaviour), assigning it to the literal union
+  // below is a type error — so this file failing to compile IS the signal.
+  const _assertToolNames: Array<
+    'getGuitars' | 'recommendGuitar' | 'addToCart'
+  > = toolCalls.map((part) => part.name)
+  void _assertToolNames
+
+  // `approval` is gated on the tool's `needsApproval` flag. `addToCart` is
+  // defined with `needsApproval: true`, so its part carries `approval`;
+  // `getGuitars` isn't, so the field doesn't exist on its part at all.
+  const _assertApprovalGating = () => {
+    for (const part of toolCalls) {
+      if (part.name === 'addToCart') {
+        void part.approval // ✅ present — addToCart is needsApproval: true
+      }
+      if (part.name === 'getGuitars') {
+        // @ts-expect-error - getGuitars has no needsApproval, so no `approval`
+        void part.approval
+      }
+    }
+  }
+  void _assertApprovalGating
+
+  return (
+    <main className="min-h-screen bg-gray-950 text-gray-100">
+      <div className="mx-auto flex max-w-4xl flex-col gap-6 px-6 py-8">
+        <header>
+          <p className="text-sm font-medium uppercase tracking-wider text-orange-300">
+            Type-safety confirmation
+          </p>
+          <h1 className="mt-2 text-3xl font-semibold">
+            Bare inline <code>tools</code> array
+          </h1>
+          <p className="mt-3 max-w-2xl text-sm leading-6 text-gray-300">
+            <code>tools</code> is a plain array literal — no{' '}
+            <code>clientTools(...)</code> wrapper, no <code>as const</code>.
+            Tool-call parts below are fully narrowed on <code>part.name</code>.
+          </p>
+        </header>
+
+        <div className="flex flex-col gap-3">
+          <textarea
+            value={prompt}
+            onChange={(event) => setPrompt(event.target.value)}
+            className="min-h-24 rounded-lg border border-gray-700 bg-gray-900 p-3 text-sm outline-none focus:border-orange-400"
+          />
+          <div className="flex items-center gap-3">
+            <button
+              type="button"
+              disabled={isLoading || !prompt.trim()}
+              onClick={() => sendMessage(prompt)}
+              className="rounded-lg bg-orange-500 px-4 py-2 text-sm font-semibold text-gray-950 transition hover:bg-orange-400 disabled:cursor-not-allowed disabled:opacity-60"
+            >
+              Send
+            </button>
+            <span className="text-sm text-gray-400">
+              {error ? error.message : isLoading ? 'Running…' : 'Ready'}
+            </span>
+          </div>
+        </div>
+
+        <section className="flex flex-col gap-3">
+          {toolCalls.map((part) => {
+            // `part.name` is narrowed to the literal union of the three tool
+            // names — proven by the discriminated access below. In each branch
+            // `part.input` (parsed, populated at runtime) and `part.output` are
+            // typed to that specific tool's schema.
+            if (part.name === 'recommendGuitar') {
+              const id = part.output?.id
+
+              return (
+                <ToolRow key={part.id} part={part}>
+                  → recommended guitar id: <b>{id ?? '—'}</b> (typed{' '}
+                  <code>number</code>)
+                </ToolRow>
+              )
+            }
+            if (part.name === 'addToCart') {
+              const quantity = part.input?.quantity
+
+              return (
+                <ToolRow key={part.id} part={part}>
+                  → guitar <b>{part.input?.guitarId ?? '—'}</b> ×{' '}
+                  <b>{quantity ?? '—'}</b> (quantity typed <code>number</code>)
+                </ToolRow>
+              )
+            }
+            if (part.name === 'getGuitars') {
+              const count = part.output?.length
+
+              return (
+                <ToolRow key={part.id} part={part}>
+                  → <b>{count ?? '—'}</b> guitars returned
+                </ToolRow>
+              )
+            }
+            return null
+          })}
+          {toolCalls.length === 0 && (
+            <p className="text-sm text-gray-500">
+              No tool calls yet — send a message to trigger the tools.
+            </p>
+          )}
+        </section>
+      </div>
+    </main>
+  )
+}
+
+function ToolRow({
+  part,
+  children,
+}: {
+  part: { name: string; input?: unknown; output?: unknown }
+  children: React.ReactNode
+}) {
+  return (
+    <div className="rounded-lg border border-gray-800 bg-gray-900 p-4">
+      <div className="text-xs uppercase tracking-wider text-orange-300">
+        {part.name}
+      </div>
+      {/* The raw parsed input/output — `input` is the feature under test: it
+          used to always be undefined at runtime, now it's the parsed object. */}
+      <div className="mt-2 grid gap-1 font-mono text-xs text-gray-400">
+        <div>
+          input:{' '}
+          <code className="text-emerald-300">
+            {part.input === undefined
+              ? 'undefined'
+              : JSON.stringify(part.input)}
+          </code>
+        </div>
+        <div>
+          output:{' '}
+          <code className="text-sky-300">
+            {part.output === undefined
+              ? 'undefined'
+              : JSON.stringify(part.output)}
+          </code>
+        </div>
+      </div>
+      <div className="mt-2 text-sm text-gray-200">{children}</div>
+    </div>
+  )
+}
+
+export const Route = createFileRoute('/typesafe-tools')({
+  component: TypesafeToolsPage,
+})
diff --git a/examples/ts-solid-chat/src/routes/index.tsx b/examples/ts-solid-chat/src/routes/index.tsx
index 45f0f3657..fba21a969 100644
--- a/examples/ts-solid-chat/src/routes/index.tsx
+++ b/examples/ts-solid-chat/src/routes/index.tsx
@@ -88,10 +88,13 @@ function Messages(props: {
                       )
                     }
 
-                    // Approval UI
+                    // Approval UI. `'approval' in part` narrows the typed
+                    // tool-call union to the tools declared `needsApproval: true`,
+                    // which is where the `approval` field exists.
                     if (
                       part.type === 'tool-call' &&
                       part.state === 'approval-requested' &&
+                      'approval' in part &&
                       part.approval
                     ) {
                       return (
diff --git a/examples/ts-vue-chat/vite.config.ts b/examples/ts-vue-chat/vite.config.ts
index f4ed32581..3d6237133 100644
--- a/examples/ts-vue-chat/vite.config.ts
+++ b/examples/ts-vue-chat/vite.config.ts
@@ -256,7 +256,7 @@ export default defineConfig({
 
             const stream = chat({
               adapter,
-              tools: Object.values(mergeAgentTools(serverTools, params.tools)),
+              tools: mergeAgentTools(serverTools, params.tools),
               systemPrompts: [SYSTEM_PROMPT],
               agentLoopStrategy: maxIterations(20),
               messages: params.messages,
diff --git a/packages/ai-angular/src/inject-chat.ts b/packages/ai-angular/src/inject-chat.ts
index 5c1453abe..570f0ce22 100644
--- a/packages/ai-angular/src/inject-chat.ts
+++ b/packages/ai-angular/src/inject-chat.ts
@@ -35,7 +35,7 @@ import type {
 let nextId = 0
 
 export function injectChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TSchema extends SchemaInput | undefined = undefined,
   TContext = InferredClientContext<TTools>,
 >(
diff --git a/packages/ai-client/src/types.ts b/packages/ai-client/src/types.ts
index 25e07c42b..8e385d45b 100644
--- a/packages/ai-client/src/types.ts
+++ b/packages/ai-client/src/types.ts
@@ -166,15 +166,27 @@ type ToolCallPartForTool<T> = T extends AnyClientTool
       /** Parsed tool input (typed from inputSchema) */
       input?: InferToolInput<T>
       state: ToolCallState
-      /** Approval metadata if tool requires user approval */
-      approval?: {
-        id: string // Unique approval ID
-        needsApproval: boolean // Always true if present
-        approved?: boolean // User's decision (undefined until responded)
-      }
       /** Tool execution output (for client tools or after approval) */
       output?: InferToolOutput<T>
-    }
+    } & (NonNullable<T['needsApproval']> extends true
+      ? {
+          /**
+           * Approval metadata — present only on tools defined with
+           * `needsApproval: true`. Populated once the call reaches
+           * `state: 'approval-requested'`. `needsApproval` is an optional
+           * property on the tool, so we index into it (rather than
+           * `T extends { needsApproval: true }`, which an optional property
+           * never satisfies) and strip `undefined` before comparing to `true`.
+           */
+          approval?: {
+            id: string // Unique approval ID
+            needsApproval: boolean // Always true if present
+            approved?: boolean // User's decision (undefined until responded)
+          }
+        }
+      : // Tools without `needsApproval: true` never carry an approval field.
+        // `& unknown` is a no-op intersection (adds nothing).
+        unknown)
   : never
 
 /**
diff --git a/packages/ai-client/tests/infer-chat-messages.test.ts b/packages/ai-client/tests/infer-chat-messages.test.ts
index 1aedcaf7d..ca2e1164c 100644
--- a/packages/ai-client/tests/infer-chat-messages.test.ts
+++ b/packages/ai-client/tests/infer-chat-messages.test.ts
@@ -16,6 +16,7 @@ import { createChatClientOptions } from '../src/types'
 import type {
   ChatClientOptions,
   InferChatMessages,
+  ToolCallPart,
   UIMessage,
 } from '../src/types'
 
@@ -231,3 +232,78 @@ describe('InferChatMessages — untyped fallback', () => {
     }
   })
 })
+
+// ===========================
+// Approval gating: `approval` present only for needsApproval tools
+// ===========================
+
+const approvalTool = toolDefinition({
+  name: 'deleteAccount',
+  description: 'Delete the account (needs approval)',
+  inputSchema: z.object({ accountId: z.string() }),
+  outputSchema: z.object({ deleted: z.boolean() }),
+  needsApproval: true,
+}).client(() => ({ deleted: true }))
+
+describe('InferChatMessages — approval gating', () => {
+  it('exposes `approval` only on tools declared with `needsApproval: true`', () => {
+    const options = createChatClientOptions({
+      connection: stubConnection,
+      tools: [guitarTool, approvalTool] as const,
+    })
+
+    type Messages = InferChatMessages<typeof options>
+    const messages = [] as Messages
+    const message = messages[0]
+
+    if (message?.role === 'assistant') {
+      for (const part of message.parts) {
+        if (part.type === 'tool-call') {
+          if (part.name === 'deleteAccount') {
+            // Approval tool → `approval` metadata is accessible + typed.
+            expectTypeOf(part.approval).toMatchTypeOf<
+              | { id: string; needsApproval: boolean; approved?: boolean }
+              | undefined
+            >()
+          }
+          if (part.name === 'getGuitar') {
+            // Non-approval tool → the `approval` field does not exist on the
+            // part. This @ts-expect-error is the bidirectional guard: if the
+            // gate regressed and `approval` reappeared, this directive would
+            // become unused and fail the type-check.
+            // @ts-expect-error - `approval` is gated behind `needsApproval: true`
+            void part.approval
+          }
+        }
+      }
+    }
+  })
+
+  // Escape hatch 1: a GENERIC approval handler over a typed, mixed tool union.
+  // Blindly reading `part.approval` off the union is a compile error, but an
+  // `'approval' in part` guard narrows to the approval-bearing members.
+  it('supports a generic handler via `in` narrowing on the typed union', () => {
+    const options = createChatClientOptions({
+      connection: stubConnection,
+      tools: [guitarTool, approvalTool] as const,
+    })
+    const messages = [] as InferChatMessages<typeof options>
+    const message = messages[0]
+
+    if (message?.role === 'assistant') {
+      for (const part of message.parts) {
+        if (part.type === 'tool-call' && 'approval' in part && part.approval) {
+          expectTypeOf(part.approval.id).toEqualTypeOf<string>()
+        }
+      }
+    }
+  })
+
+  // Escape hatch 2: type the reusable handler against the base `ToolCallPart`
+  // (default/untyped), which always carries `approval?` — so a shared approval
+  // component works across every tool regardless of the caller's tool union.
+  it('supports a generic handler typed against the base ToolCallPart', () => {
+    const handleApproval = (part: ToolCallPart) => part.approval?.id
+    expectTypeOf(handleApproval).returns.toEqualTypeOf<string | undefined>()
+  })
+})
diff --git a/packages/ai-preact/src/use-chat.ts b/packages/ai-preact/src/use-chat.ts
index e10cb171d..f1866f5e5 100644
--- a/packages/ai-preact/src/use-chat.ts
+++ b/packages/ai-preact/src/use-chat.ts
@@ -23,7 +23,7 @@ import type {
 } from './types'
 
 export function useChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TContext = InferredClientContext<TTools>,
 >(options: UseChatOptions<TTools, TContext>): UseChatReturn<TTools> {
   const hookId = useId()
diff --git a/packages/ai-react/src/use-chat.ts b/packages/ai-react/src/use-chat.ts
index 37444b569..32b3e885a 100644
--- a/packages/ai-react/src/use-chat.ts
+++ b/packages/ai-react/src/use-chat.ts
@@ -24,7 +24,7 @@ import type {
 } from './types'
 
 export function useChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TSchema extends SchemaInput | undefined = undefined,
   TContext = InferredClientContext<TTools>,
 >(
diff --git a/packages/ai-react/tests/use-chat-types.test.ts b/packages/ai-react/tests/use-chat-types.test.ts
index edeac4045..4edd539fb 100644
--- a/packages/ai-react/tests/use-chat-types.test.ts
+++ b/packages/ai-react/tests/use-chat-types.test.ts
@@ -58,6 +58,71 @@ describe('useChat() return type', () => {
     })
   })
 
+  describe('with a bare inline tools array (no clientTools / no `as const`)', () => {
+    it('narrows tool-call parts from a plain array literal', () => {
+      // Type-only assertion — the closure is never invoked, so the hook never
+      // runs at runtime (it would throw outside a React renderer). `tsc`
+      // (test:types) still checks the body, which is what proves the narrowing.
+      const check = () => {
+        const guitarTool = toolDefinition({
+          name: 'getGuitar',
+          description: 'Get guitar info',
+        }).client(() => ({ ok: true }))
+        const cartTool = toolDefinition({
+          name: 'addToCart',
+          description: 'Add to cart',
+        }).client(() => ({ ok: true }))
+
+        const { messages } = useChat({
+          connection: { connect: async function* () {} },
+          // plain array literal — the `const` modifier on useChat's TTools
+          // captures the tuple + literal tool names, so no `clientTools(...)`
+          // wrapper and no `as const` are needed for chunk narrowing.
+          tools: [guitarTool, cartTool],
+        })
+
+        const message = messages[0]
+        if (message?.role === 'assistant') {
+          for (const part of message.parts) {
+            if (part.type === 'tool-call') {
+              expectTypeOf(part.name).toEqualTypeOf<'getGuitar' | 'addToCart'>()
+            }
+          }
+        }
+      }
+      void check
+    })
+
+    it('narrows a separately-declared const array (no clientTools / no `as const`)', () => {
+      const check = () => {
+        const guitarTool = toolDefinition({
+          name: 'getGuitar',
+          description: 'Get guitar info',
+        }).client(() => ({ ok: true }))
+        const cartTool = toolDefinition({
+          name: 'addToCart',
+          description: 'Add to cart',
+        }).client(() => ({ ok: true }))
+
+        // Separate const, NO clientTools, NO `as const`:
+        const tools = [guitarTool, cartTool]
+        const { messages } = useChat({
+          connection: { connect: async function* () {} },
+          tools,
+        })
+        const message = messages[0]
+        if (message?.role === 'assistant') {
+          for (const part of message.parts) {
+            if (part.type === 'tool-call') {
+              expectTypeOf(part.name).toEqualTypeOf<'getGuitar' | 'addToCart'>()
+            }
+          }
+        }
+      }
+      void check
+    })
+  })
+
   describe('with typed client tool context', () => {
     it('requires context matching the tool tuple', () => {
       type ClientContext = { localUserId: string; a: 'literal' }
diff --git a/packages/ai-solid/src/use-chat.ts b/packages/ai-solid/src/use-chat.ts
index 9a6e404cf..23d6495e8 100644
--- a/packages/ai-solid/src/use-chat.ts
+++ b/packages/ai-solid/src/use-chat.ts
@@ -31,7 +31,7 @@ import type {
 } from './types'
 
 export function useChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TSchema extends SchemaInput | undefined = undefined,
   TContext = InferredClientContext<TTools>,
 >(
diff --git a/packages/ai-svelte/src/create-chat.svelte.ts b/packages/ai-svelte/src/create-chat.svelte.ts
index 506d9843f..4aaf99f00 100644
--- a/packages/ai-svelte/src/create-chat.svelte.ts
+++ b/packages/ai-svelte/src/create-chat.svelte.ts
@@ -52,7 +52,7 @@ import type {
  * ```
  */
 export function createChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TSchema extends SchemaInput | undefined = undefined,
   TContext = InferredClientContext<TTools>,
 >(
diff --git a/packages/ai-vue/src/use-chat.ts b/packages/ai-vue/src/use-chat.ts
index 31719591d..8c54bd9cc 100644
--- a/packages/ai-vue/src/use-chat.ts
+++ b/packages/ai-vue/src/use-chat.ts
@@ -31,7 +31,7 @@ import type {
 } from './types'
 
 export function useChat<
-  TTools extends ReadonlyArray<AnyClientTool> = any,
+  const TTools extends ReadonlyArray<AnyClientTool> = any,
   TSchema extends SchemaInput | undefined = undefined,
   TContext = InferredClientContext<TTools>,
 >(
diff --git a/packages/ai/skills/ai-core/tool-calling/SKILL.md b/packages/ai/skills/ai-core/tool-calling/SKILL.md
index 4837705ab..0196f73b9 100644
--- a/packages/ai/skills/ai-core/tool-calling/SKILL.md
+++ b/packages/ai/skills/ai-core/tool-calling/SKILL.md
@@ -289,7 +289,10 @@ function ChatPage() {
               return (
                 <div key={part.id}>
                   <p>Approve "{part.name}"?</p>
-                  <pre>{part.arguments}</pre>
+                  {/* `part.input` is the parsed, typed object (populated once
+                      the arguments are complete, as they are at approval
+                      time); `part.arguments` remains the raw JSON string. */}
+                  <pre>{JSON.stringify(part.input, null, 2)}</pre>
                   <button
                     onClick={() =>
                       addToolApprovalResponse({
@@ -322,6 +325,15 @@ function ChatPage() {
 }
 ```
 
+> **Type-safe approval:** With typed `tools`, `part.approval` exists **only**
+> on parts for tools defined with `needsApproval: true`. Tools without approval
+> have no `approval` field (reading it is a compile error). For a
+> tool-agnostic handler over a typed union, narrow with `'approval' in part`
+> (`if (part.type === 'tool-call' && 'approval' in part && part.approval)`),
+> or type a shared component against the base `ToolCallPart`. An untyped
+> `useChat()` keeps `approval` on every tool-call part, which is why the
+> snippet above (no `tools` generic) reads it directly.
+
 ### Pattern 4: Lazy Tool Discovery
 
 Set `lazy: true` on rarely-needed tools. The LLM sees their names via a synthetic
diff --git a/packages/ai/src/activities/chat/messages.ts b/packages/ai/src/activities/chat/messages.ts
index 3b7e2c0a2..8d47ba320 100644
--- a/packages/ai/src/activities/chat/messages.ts
+++ b/packages/ai/src/activities/chat/messages.ts
@@ -444,12 +444,21 @@ export function modelMessageToUIMessage(
   // Handle tool calls
   if (modelMessage.toolCalls && modelMessage.toolCalls.length > 0) {
     for (const toolCall of modelMessage.toolCalls) {
+      // Model-message arguments are complete, so surface the parsed input.
+      // A malformed arguments string just leaves `input` undefined.
+      let input: unknown
+      try {
+        input = JSON.parse(toolCall.function.arguments)
+      } catch {
+        input = undefined
+      }
       parts.push({
         type: 'tool-call',
         id: toolCall.id,
         name: toolCall.function.name,
         arguments: toolCall.function.arguments,
         state: 'input-complete', // Model messages have complete arguments
+        ...(input !== undefined && { input }),
         ...(toolCall.metadata !== undefined && { metadata: toolCall.metadata }),
       })
     }
diff --git a/packages/ai/src/activities/chat/stream/message-updaters.ts b/packages/ai/src/activities/chat/stream/message-updaters.ts
index ccb180d84..72648af11 100644
--- a/packages/ai/src/activities/chat/stream/message-updaters.ts
+++ b/packages/ai/src/activities/chat/stream/message-updaters.ts
@@ -58,6 +58,8 @@ export function updateToolCallPart(
     name: string
     arguments: string
     state: ToolCallState
+    /** Parsed input — set when the arguments are complete. */
+    input?: unknown
     metadata?: Record<string, unknown>
   },
 ): Array<UIMessage> {
@@ -76,6 +78,9 @@ export function updateToolCallPart(
     // Gemini's thoughtSignature on TOOL_CALL_START) we must not lose it on
     // subsequent updates that don't re-supply it.
     const metadata = toolCall.metadata ?? existing?.metadata
+    // Same for the parsed input: it's supplied once at completion, so
+    // subsequent arg-less updates (approval, etc.) must not drop it.
+    const input = toolCall.input ?? existing?.input
 
     const toolCallPart: ToolCallPart = {
       type: 'tool-call',
@@ -83,9 +88,10 @@ export function updateToolCallPart(
       name: toolCall.name,
       arguments: toolCall.arguments,
       state: toolCall.state,
-      // Carry forward approval and output from the existing part
+      // Carry forward approval, output and parsed input from the existing part
       ...(existing?.approval && { approval: { ...existing.approval } }),
       ...(existing?.output !== undefined && { output: existing.output }),
+      ...(input !== undefined && { input }),
       ...(metadata !== undefined && { metadata }),
     }
 
diff --git a/packages/ai/src/activities/chat/stream/processor.ts b/packages/ai/src/activities/chat/stream/processor.ts
index 610846be5..2eb6f774b 100644
--- a/packages/ai/src/activities/chat/stream/processor.ts
+++ b/packages/ai/src/activities/chat/stream/processor.ts
@@ -1298,15 +1298,35 @@ export class StreamProcessor {
       // received, back-fill the arguments string so the UIMessage ToolCallPart
       // carries the correct value (defensive against adapters that skip ARGS).
       if (chunk.input !== undefined && !existingToolCall.arguments) {
-        existingToolCall.arguments = JSON.stringify(chunk.input)
+        try {
+          existingToolCall.arguments = JSON.stringify(chunk.input)
+        } catch {
+          // circular refs, BigInt, etc. — leave arguments empty rather than
+          // aborting stream processing
+        }
       }
 
       const index = msgState.toolCallOrder.indexOf(chunk.toolCallId)
       this.completeToolCall(messageId, index, existingToolCall)
       // If TOOL_CALL_END provides parsed input, use it as the canonical parsed
       // arguments (overrides the accumulated string parse from completeToolCall)
+      // and refresh the rendered part's `input` so it reflects the canonical
+      // value rather than the possibly-divergent accumulated-args parse that
+      // completeToolCall wrote (e.g. an adapter that coerces values differently
+      // between the streamed args and the final structured input).
       if (chunk.input !== undefined) {
         existingToolCall.parsedArguments = chunk.input
+        this.messages = updateToolCallPart(this.messages, messageId, {
+          id: existingToolCall.id,
+          name: existingToolCall.name,
+          arguments: existingToolCall.arguments,
+          state: 'input-complete',
+          input: chunk.input,
+          ...(existingToolCall.metadata !== undefined && {
+            metadata: existingToolCall.metadata,
+          }),
+        })
+        this.emitMessagesChange()
       }
     }
 
@@ -1890,12 +1910,20 @@ export class StreamProcessor {
       return
     }
 
-    // Update UIMessage
+    // Update UIMessage. The arguments are complete now, so surface the parsed
+    // input on the part. For adapters that skip TOOL_CALL_ARGS the arguments
+    // string was back-filled from TOOL_CALL_END.input, so this parse matches
+    // the canonical input. If a TOOL_CALL_END.input diverges from the
+    // accumulated args, handleToolCallEndEvent re-updates the part with the
+    // canonical value after this call.
     this.messages = updateToolCallPart(this.messages, messageId, {
       id: toolCall.id,
       name: toolCall.name,
       arguments: toolCall.arguments,
       state: 'input-complete',
+      ...(toolCall.parsedArguments !== undefined && {
+        input: toolCall.parsedArguments,
+      }),
       ...(toolCall.metadata !== undefined && { metadata: toolCall.metadata }),
     })
     this.emitMessagesChange()
diff --git a/packages/ai/src/activities/chat/tools/tool-definition.ts b/packages/ai/src/activities/chat/tools/tool-definition.ts
index 10195b51b..fe62bd4ac 100644
--- a/packages/ai/src/activities/chat/tools/tool-definition.ts
+++ b/packages/ai/src/activities/chat/tools/tool-definition.ts
@@ -26,6 +26,10 @@ export interface ClientTool<
   TOutput extends SchemaInput = SchemaInput,
   TName extends string = string,
   TContext = unknown,
+  // Captured as a literal (`true` / `false`) so downstream types — notably
+  // the tool-call part's `approval` field — can be gated on it. Defaults to
+  // `false` when the tool config omits `needsApproval`.
+  TNeedsApproval extends boolean = false,
 > {
   __toolSide: 'client'
   name: TName
@@ -37,7 +41,7 @@ export interface ClientTool<
   // because `undefined` doesn't extend the schema constraint.
   inputSchema?: TInput
   outputSchema?: TOutput
-  needsApproval?: boolean
+  needsApproval?: TNeedsApproval
   lazy?: boolean
   metadata?: Record<string, unknown>
   execute?: ToolExecuteFunction<TInput, TOutput, TContext>
@@ -51,18 +55,22 @@ export interface ToolDefinitionInstance<
   TOutput extends SchemaInput = SchemaInput,
   TName extends string = string,
   TContext = unknown,
+  TNeedsApproval extends boolean = false,
 > extends Tool<TInput, TOutput, TName, TContext> {
   __toolSide: 'definition'
+  // Narrow the base `needsApproval?: boolean` to the captured literal so it
+  // survives into `ToolCallPartForTool`'s approval gate.
+  needsApproval?: TNeedsApproval
 }
 
 /**
  * Union type for any kind of client-side tool (client tool or definition)
  */
 export type AnyClientTool =
-  | (Omit<ClientTool<any, any, string, any>, 'execute'> & {
+  | (Omit<ClientTool<any, any, string, any, boolean>, 'execute'> & {
       execute?: ((args: any, context?: any) => any) | undefined
     })
-  | (Omit<ToolDefinitionInstance<any, any, string, any>, 'execute'> & {
+  | (Omit<ToolDefinitionInstance<any, any, string, any, boolean>, 'execute'> & {
       execute?: ((args: any, context?: any) => any) | undefined
     })
 
@@ -100,12 +108,13 @@ export interface ToolDefinitionConfig<
   TInput extends SchemaInput = SchemaInput,
   TOutput extends SchemaInput = SchemaInput,
   TName extends string = string,
+  TNeedsApproval extends boolean = false,
 > {
   name: TName
   description: string
   inputSchema?: TInput
   outputSchema?: TOutput
-  needsApproval?: boolean
+  needsApproval?: TNeedsApproval
   lazy?: boolean
   metadata?: Record<string, unknown>
 }
@@ -117,7 +126,14 @@ export interface ToolDefinition<
   TInput extends SchemaInput = SchemaInput,
   TOutput extends SchemaInput = SchemaInput,
   TName extends string = string,
-> extends ToolDefinitionInstance<TInput, TOutput, TName> {
+  TNeedsApproval extends boolean = false,
+> extends ToolDefinitionInstance<
+  TInput,
+  TOutput,
+  TName,
+  unknown,
+  TNeedsApproval
+> {
   /**
    * Create a server-side tool with execute function
    */
@@ -126,11 +142,13 @@ export interface ToolDefinition<
   ) => ServerTool<TInput, TOutput, TName, TContext>
 
   /**
-   * Create a client-side tool with optional execute function
+   * Create a client-side tool with optional execute function.
+   * Carries the definition's `needsApproval` literal through to the client
+   * tool so the tool-call part's `approval` field stays gated on it.
    */
   client: <TContext = unknown>(
     execute?: ToolExecuteFunction<TInput, TOutput, TContext>,
-  ) => ClientTool<TInput, TOutput, TName, TContext>
+  ) => ClientTool<TInput, TOutput, TName, TContext, TNeedsApproval>
 }
 
 /**
@@ -192,10 +210,14 @@ export function toolDefinition<
   TInput extends SchemaInput = SchemaInput,
   TOutput extends SchemaInput = SchemaInput,
   TName extends string = string,
+  // `const` forces the literal (`true` / `false`) to be captured from the
+  // config's optional `needsApproval` — without it TS widens to `boolean`,
+  // which collapses the approval gate in `ToolCallPartForTool`.
+  const TNeedsApproval extends boolean = false,
 >(
-  config: ToolDefinitionConfig<TInput, TOutput, TName>,
-): ToolDefinition<TInput, TOutput, TName> {
-  const definition: ToolDefinition<TInput, TOutput, TName> = {
+  config: ToolDefinitionConfig<TInput, TOutput, TName, TNeedsApproval>,
+): ToolDefinition<TInput, TOutput, TName, TNeedsApproval> {
+  const definition: ToolDefinition<TInput, TOutput, TName, TNeedsApproval> = {
     __toolSide: 'definition',
     ...config,
     server<TContext = unknown>(
@@ -210,7 +232,7 @@ export function toolDefinition<
 
     client<TContext = unknown>(
       execute?: ToolExecuteFunction<TInput, TOutput, TContext>,
-    ): ClientTool<TInput, TOutput, TName, TContext> {
+    ): ClientTool<TInput, TOutput, TName, TContext, TNeedsApproval> {
       return {
         __toolSide: 'client',
         ...config,
diff --git a/packages/ai/src/types.ts b/packages/ai/src/types.ts
index 6917c8140..983e220e8 100644
--- a/packages/ai/src/types.ts
+++ b/packages/ai/src/types.ts
@@ -372,6 +372,15 @@ export interface ToolCallPart<TMetadata = unknown> {
   id: string
   name: string
   arguments: string // JSON string (may be incomplete)
+  /**
+   * Parsed tool input. Set from the parsed arguments once they are complete
+   * (`state: 'input-complete'` and later). `undefined` while the raw
+   * `arguments` string is still streaming, and may stay `undefined` for a call
+   * that terminates in an error state — the raw `arguments` string is always
+   * available as a fallback. Typed per-tool on the client `ToolCallPart` (see
+   * `@tanstack/ai-client`); `unknown` on this base type.
+   */
+  input?: unknown
   state: ToolCallState
   /** Approval metadata if tool requires user approval */
   approval?: {
diff --git a/packages/ai/tests/message-converters.test.ts b/packages/ai/tests/message-converters.test.ts
index 073868fd3..f037a396d 100644
--- a/packages/ai/tests/message-converters.test.ts
+++ b/packages/ai/tests/message-converters.test.ts
@@ -580,6 +580,7 @@ describe('Message Converters', () => {
           id: 'tc-1',
           name: 'getWeather',
           arguments: '{"city": "NYC"}',
+          input: { city: 'NYC' },
           state: 'input-complete',
         },
       ])
@@ -642,6 +643,7 @@ describe('Message Converters', () => {
           id: 'tc-1',
           name: 'getWeather',
           arguments: '{"city": "NYC"}',
+          input: { city: 'NYC' },
           state: 'input-complete',
         },
       ])
@@ -919,6 +921,7 @@ describe('Message Converters', () => {
           id: 'tc-1',
           name: 'getWeather',
           arguments: '{"city":"NYC"}',
+          input: { city: 'NYC' },
           state: 'complete',
           output: { temp: 72 },
         },
@@ -997,6 +1000,7 @@ describe('Message Converters', () => {
           id: 'tc-2',
           name: 'recommend',
           arguments: '{"id":7}',
+          input: { id: 7 },
           state: 'complete',
           output: { recommended: true },
         },
@@ -1086,6 +1090,7 @@ describe('Message Converters', () => {
         id: 'tc-1',
         name: 'getWeather',
         arguments: '{"city":"NYC"}',
+        input: { city: 'NYC' },
         state: 'complete',
         output: { temp: 72 },
       })
@@ -1226,6 +1231,7 @@ describe('Message Converters', () => {
             id: 'tc-1',
             name: 'getWeather',
             arguments: '{"city":"NYC"}',
+            input: { city: 'NYC' },
             state: 'complete',
             output: { temp: 72 },
           },
@@ -1338,6 +1344,7 @@ describe('Message Converters', () => {
           id: 'tc-2',
           name: 'recommend',
           arguments: '{"id":7}',
+          input: { id: 7 },
           state: 'complete',
           output: { recommended: true },
         },
diff --git a/packages/ai/tests/message-updaters.test.ts b/packages/ai/tests/message-updaters.test.ts
index 070eefa2d..a4bad0312 100644
--- a/packages/ai/tests/message-updaters.test.ts
+++ b/packages/ai/tests/message-updaters.test.ts
@@ -244,6 +244,59 @@ describe('message-updaters', () => {
       })
     })
 
+    it('should preserve existing input when updating a tool call without input in payload', () => {
+      const parsedInput = { path: '/tmp/file' }
+      const messages = [
+        createMessage('msg-1', 'assistant', [
+          {
+            type: 'tool-call',
+            id: 'call-1',
+            name: 'deleteFile',
+            arguments: '{"path":"/tmp/file"}',
+            state: 'input-complete',
+            input: parsedInput,
+          },
+        ]),
+      ]
+
+      const result = updateToolCallPart(messages, 'msg-1', {
+        id: 'call-1',
+        name: 'deleteFile',
+        arguments: '{"path":"/tmp/file"}',
+        state: 'approval-requested',
+      })
+
+      const part = result[0]?.parts[0] as ToolCallPart | undefined
+      expect(part?.input).toEqual(parsedInput)
+    })
+
+    it('should preserve existing input through approval request updates', () => {
+      const parsedInput = { path: '/tmp/file' }
+      const messages = [
+        createMessage('msg-1', 'assistant', [
+          {
+            type: 'tool-call',
+            id: 'call-1',
+            name: 'deleteFile',
+            arguments: '{"path":"/tmp/file"}',
+            state: 'input-complete',
+            input: parsedInput,
+          },
+        ]),
+      ]
+
+      const result = updateToolCallApproval(
+        messages,
+        'msg-1',
+        'call-1',
+        'approval-123',
+      )
+
+      const part = result[0]?.parts[0] as ToolCallPart | undefined
+      expect(part?.input).toEqual(parsedInput)
+      expect(part?.state).toBe('approval-requested')
+    })
+
     it('should preserve existing output when updating a tool call', () => {
       const toolOutput = { temperature: 20, conditions: 'sunny' }
       const messages = [
diff --git a/packages/ai/tests/stream-processor.test.ts b/packages/ai/tests/stream-processor.test.ts
index d3b5fd194..4921f7e2f 100644
--- a/packages/ai/tests/stream-processor.test.ts
+++ b/packages/ai/tests/stream-processor.test.ts
@@ -460,6 +460,8 @@ describe('StreamProcessor', () => {
       expect(toolCallPart.name).toBe('getWeather')
       expect(toolCallPart.arguments).toBe('{"city":"NYC"}')
       expect(toolCallPart.state).toBe('input-complete')
+      // Parsed input is surfaced on the part once the arguments are complete.
+      expect(toolCallPart.input).toEqual({ city: 'NYC' })
 
       const state = processor.getState()
       expect(state.content).toBe('')
@@ -541,6 +543,47 @@ describe('StreamProcessor', () => {
       })
     })
 
+    it('populates part.input from TOOL_CALL_END.input when no args were streamed', () => {
+      const processor = new StreamProcessor()
+      processor.prepareAssistantMessage()
+
+      // Adapter skips TOOL_CALL_ARGS and only sends parsed input on END.
+      processor.processChunk(ev.toolStart('tc-1', 'getWeather'))
+      processor.processChunk(
+        ev.toolEnd('tc-1', 'getWeather', {
+          input: { city: 'NYC', unit: 'celsius' },
+        }),
+      )
+      processor.finalizeStream()
+
+      const toolCallPart = processor
+        .getMessages()[0]!
+        .parts.find((p) => p.type === 'tool-call') as ToolCallPart
+      expect(toolCallPart.state).toBe('input-complete')
+      expect(toolCallPart.input).toEqual({ city: 'NYC', unit: 'celsius' })
+    })
+
+    it('part.input reflects TOOL_CALL_END.input when it diverges from streamed args', () => {
+      const processor = new StreamProcessor()
+      processor.prepareAssistantMessage()
+
+      // Args stream one value, then END provides a canonical (coerced) input
+      // that differs. The rendered part must reflect the END override, not the
+      // stale accumulated-args parse.
+      processor.processChunk(ev.toolStart('tc-1', 'getWeather'))
+      processor.processChunk(ev.toolArgs('tc-1', '{"city":"nyc"}'))
+      processor.processChunk(
+        ev.toolEnd('tc-1', 'getWeather', { input: { city: 'NYC' } }),
+      )
+      processor.finalizeStream()
+
+      const toolCallPart = processor
+        .getMessages()[0]!
+        .parts.find((p) => p.type === 'tool-call') as ToolCallPart
+      expect(toolCallPart.state).toBe('input-complete')
+      expect(toolCallPart.input).toEqual({ city: 'NYC' })
+    })
+
     it('should default tool call index to toolCalls.size when index is not provided', () => {
       const processor = new StreamProcessor()
       processor.prepareAssistantMessage()
@@ -2670,6 +2713,7 @@ describe('StreamProcessor', () => {
           id: 'tc-1',
           name: 'getWeather',
           arguments: '{"loc":"Berlin"}',
+          input: { loc: 'Berlin' },
           state: 'input-complete',
         },
         {
@@ -3073,6 +3117,7 @@ describe('StreamProcessor', () => {
           id: 'tc-1',
           name: 'lookupWeather',
           arguments: '{"location":"Berlin"}',
+          input: { location: 'Berlin' },
           state: 'input-complete',
         },
         {
diff --git a/testing/e2e/src/components/ToolCallDisplay.tsx b/testing/e2e/src/components/ToolCallDisplay.tsx
index 706cd4449..10a523b70 100644
--- a/testing/e2e/src/components/ToolCallDisplay.tsx
+++ b/testing/e2e/src/components/ToolCallDisplay.tsx
@@ -8,6 +8,16 @@ export function ToolCallDisplay({ part }: { part: any }) {
       <div className="text-gray-400 mt-1">
         Args: <code>{part.arguments}</code>
       </div>
+      {/* Parsed, typed input — populated once the arguments are complete. */}
+      <div
+        data-testid={`tool-call-input-${part.name}`}
+        className="text-gray-400 mt-1"
+      >
+        Input:{' '}
+        <code>
+          {part.input === undefined ? '' : JSON.stringify(part.input)}
+        </code>
+      </div>
     </div>
   )
 }
diff --git a/testing/e2e/src/lib/media-providers.ts b/testing/e2e/src/lib/media-providers.ts
index b61829ca0..0a9b1e81a 100644
--- a/testing/e2e/src/lib/media-providers.ts
+++ b/testing/e2e/src/lib/media-providers.ts
@@ -177,9 +177,14 @@ export function createVideoAdapter(
         defaultHeaders: headers,
       }),
     gemini: () =>
+      // `httpOptions` is a valid inherited `GoogleGenAIOptions` key (image/audio
+      // pass it the same way), but `GeminiVideoConfig`'s own `allowUrlFetch`
+      // member makes tsc drop the inherited keys from `Omit<…, 'apiKey'>`, so
+      // the literal is rejected here only. Cast to the param type — the mock
+      // base URL is required at runtime.
       createGeminiVideo('veo-3.1-generate-preview', DUMMY_KEY, {
         httpOptions: { baseUrl: llmockBase(aimockPort), headers },
-      }),
+      } as unknown as Parameters<typeof createGeminiVideo>[2]),
   }
   const factory = factories[provider]
   if (!factory) throw new Error(`No video adapter for provider: ${provider}`)
diff --git a/testing/e2e/src/routes/tools-test.tsx b/testing/e2e/src/routes/tools-test.tsx
index ddc8fbcf9..7022e6585 100644
--- a/testing/e2e/src/routes/tools-test.tsx
+++ b/testing/e2e/src/routes/tools-test.tsx
@@ -6,6 +6,7 @@ import {
   modelMessagesToUIMessages,
   toolDefinition,
   type ModelMessage,
+  type ToolCallPart,
 } from '@tanstack/ai'
 import { z } from 'zod'
 import { SCENARIO_LIST } from '@/lib/tools-test-tools'
@@ -218,7 +219,11 @@ function ToolsTestPage() {
     // Include scenario in ID so client is recreated when scenario changes
     id: `tools-test-${scenario}-${historyFixture || 'empty'}`,
     connection: fetchServerSentEvents('/api/tools-test'),
-    initialMessages,
+    // History fixtures are untyped model-message replays; cast to the typed
+    // message shape so they don't fight the concrete `tools` tuple inference.
+    initialMessages: initialMessages as unknown as Array<
+      UIMessage<typeof clientTools>
+    >,
     forwardedProps: {
       scenario,
       testId,
@@ -278,15 +283,22 @@ function ToolsTestPage() {
     sendMessage(`[${scenario}] run test`)
   }, [sendMessage])
 
-  // Extract tool call parts from messages for display
-  const toolCalls = messages.flatMap((msg) =>
-    msg.parts
-      .filter((p) => p.type === 'tool-call')
-      .map((p) => ({
-        messageId: msg.id,
-        ...p,
-      })),
-  )
+  // Extract tool call parts from messages for display. This harness inspects
+  // `approval` across a mixed tool set, so it uses the generic (untyped)
+  // `ToolCallPart` view — the typed per-tool parts gate `approval` behind
+  // `needsApproval`, which is exactly what we don't want to narrow on here.
+  const toolCalls: Array<ToolCallPart & { messageId: string }> =
+    messages.flatMap((msg) =>
+      msg.parts
+        .filter(
+          (p): p is Extract<typeof p, { type: 'tool-call' }> =>
+            p.type === 'tool-call',
+        )
+        .map((p) => ({
+          messageId: msg.id,
+          ...p,
+        })),
+    )
 
   // Extract tool result parts (for server tools)
   const toolResultIds = new Set(
diff --git a/testing/e2e/tests/tool-calling.spec.ts b/testing/e2e/tests/tool-calling.spec.ts
index 241f68b59..ff11ed8bd 100644
--- a/testing/e2e/tests/tool-calling.spec.ts
+++ b/testing/e2e/tests/tool-calling.spec.ts
@@ -24,6 +24,28 @@ for (const provider of providersFor('tool-calling')) {
       expect(toolCalls.length).toBeGreaterThanOrEqual(1)
       expect(toolCalls[0].name).toBe('getGuitars')
 
+      // The parsed `input` is populated on the tool-call part (previously it
+      // was always `undefined` at runtime — only `arguments` was set). It is
+      // the raw `arguments` string parsed as JSON. `getGuitars` takes no
+      // arguments, so it serializes as `{}` — assert the round-trip whenever
+      // the args carry a JSON value (an empty/absent args string correctly
+      // parses to no input, so we don't force a non-empty input there).
+      const inputText = await page
+        .getByTestId('tool-call-input-getGuitars')
+        .locator('code')
+        .first()
+        .innerText()
+      const argsText = (
+        await page
+          .getByTestId('tool-call-getGuitars')
+          .locator('code')
+          .first()
+          .innerText()
+      ).trim()
+      if (argsText.length > 0) {
+        expect(JSON.parse(inputText)).toEqual(JSON.parse(argsText))
+      }
+
       // Wait for the text response after tool execution (agentic loop's second LLM call)
       await waitForAssistantText(page, 'Fender Stratocaster')
     })