diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 837c8357..1ea170c7 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Fixed `validateToolArguments()` to fall back gracefully when AJV schema compilation is blocked in restricted runtimes such as Cloudflare Workers, allowing tool execution to proceed without schema validation ([#2395](https://github.com/badlogic/pi-mono/issues/2395))
 - Fixed `google-vertex` API key resolution to ignore placeholder auth markers like `<authenticated>` and fall back to ADC instead of sending them as literal API keys ([#2335](https://github.com/badlogic/pi-mono/issues/2335))
 
 ## [0.60.0] - 2026-03-18
diff --git a/packages/ai/src/utils/validation.ts b/packages/ai/src/utils/validation.ts
index b5f48faa..3a54fa13 100644
--- a/packages/ai/src/utils/validation.ts
+++ b/packages/ai/src/utils/validation.ts
@@ -11,10 +11,22 @@ import type { Tool, ToolCall } from "../types.js";
 // Chrome extensions with Manifest V3 don't allow eval/Function constructor
 const isBrowserExtension = typeof globalThis !== "undefined" && (globalThis as any).chrome?.runtime?.id !== undefined;
 
-// Create a singleton AJV instance with formats (only if not in browser extension)
-// AJV requires 'unsafe-eval' CSP which is not allowed in Manifest V3
+function canUseRuntimeCodegen(): boolean {
+	if (isBrowserExtension) {
+		return false;
+	}
+
+	try {
+		new Function("return true;");
+		return true;
+	} catch {
+		return false;
+	}
+}
+
+// Create a singleton AJV instance with formats only when runtime code generation is available.
 let ajv: any = null;
-if (!isBrowserExtension) {
+if (canUseRuntimeCodegen()) {
 	try {
 		ajv = new Ajv({
 			allErrors: true,
@@ -23,7 +35,6 @@ if (!isBrowserExtension) {
 		});
 		addFormats(ajv);
 	} catch (_e) {
-		// AJV initialization failed (likely CSP restriction)
 		console.warn("AJV validation disabled due to CSP restrictions");
 	}
 }
@@ -51,14 +62,12 @@ export function validateToolCall(tools: Tool[], toolCall: ToolCall): any {
  * @throws Error with formatted message if validation fails
  */
 export function validateToolArguments(tool: Tool, toolCall: ToolCall): any {
-	// Skip validation in browser extension environment (CSP restrictions prevent AJV from working)
-	if (!ajv || isBrowserExtension) {
-		// Trust the LLM's output without validation
-		// Browser extensions can't use AJV due to Manifest V3 CSP restrictions
+	// Skip validation in environments where runtime code generation is unavailable.
+	if (!ajv || !canUseRuntimeCodegen()) {
 		return toolCall.arguments;
 	}
 
-	// Compile the schema
+	// Compile the schema.
 	const validate = ajv.compile(tool.parameters);
 
 	// Clone arguments so AJV can safely mutate for type coercion
diff --git a/packages/ai/test/validation.test.ts b/packages/ai/test/validation.test.ts
new file mode 100644
index 00000000..60de63a6
--- /dev/null
+++ b/packages/ai/test/validation.test.ts
@@ -0,0 +1,39 @@
+import { Type } from "@sinclair/typebox";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import type { ToolCall } from "../src/types.js";
+import { validateToolArguments } from "../src/utils/validation.js";
+
+afterEach(() => {
+	vi.restoreAllMocks();
+});
+
+describe("validateToolArguments", () => {
+	it("falls back to raw arguments without writing to stderr when runtime code generation is blocked", () => {
+		const originalFunction = globalThis.Function;
+		const errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+		const tool = {
+			name: "echo",
+			description: "Echo tool",
+			parameters: Type.Object({
+				count: Type.Number(),
+			}),
+		};
+		const toolCall: ToolCall = {
+			type: "toolCall",
+			id: "tool-1",
+			name: "echo",
+			arguments: { count: "42" as unknown as number },
+		};
+
+		globalThis.Function = (() => {
+			throw new EvalError("Code generation from strings disallowed for this context");
+		}) as unknown as FunctionConstructor;
+
+		try {
+			expect(validateToolArguments(tool, toolCall)).toEqual(toolCall.arguments);
+			expect(errorSpy).not.toHaveBeenCalled();
+		} finally {
+			globalThis.Function = originalFunction;
+		}
+	});
+});