diff --git a/src/session.test.ts b/src/session.test.ts
index 3e22b1b..8f11244 100644
--- a/src/session.test.ts
+++ b/src/session.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import { Session } from "./session.js";
-import type { SDKMessage, WireMessage } from "./types.js";
+import type { MessageWire, SDKMessage, WireMessage } from "./types.js";
 
 const BUFFER_LIMIT = 100;
 
@@ -96,6 +96,26 @@ function createAssistantMessage(index: number): WireMessage {
   } as WireMessage;
 }
 
+function createApprovalRequestMessage(
+  index: number,
+  toolCall: {
+    name: string;
+    arguments: string;
+    tool_call_id: string;
+  },
+): MessageWire {
+  return {
+    type: "message",
+    session_id: "session-1",
+    message_type: "approval_request_message",
+    id: `message-approval-${index}`,
+    date: "2026-01-01T00:00:00.000000+00:00",
+    uuid: `approval-${index}`,
+    tool_call: toolCall,
+    tool_calls: [toolCall],
+  };
+}
+
 function createResultMessage(): WireMessage {
   return {
     type: "result",
@@ -340,6 +360,48 @@ describe("Session", () => {
     });
   });
 
+  describe("transformMessage tool-call mapping", () => {
+    test("maps approval_request_message to SDK tool_call message", () => {
+      const session = new Session();
+      const wireMsg = createApprovalRequestMessage(1, {
+        name: "Bash",
+        arguments: JSON.stringify({ command: "pwd" }),
+        tool_call_id: "call-approval-1",
+      });
+
+      // @ts-expect-error - accessing private method for regression coverage
+      const transformed = session.transformMessage(wireMsg) as SDKMessage | null;
+
+      expect(transformed).toEqual({
+        type: "tool_call",
+        toolCallId: "call-approval-1",
+        toolName: "Bash",
+        toolInput: { command: "pwd" },
+        uuid: "approval-1",
+      });
+    });
+
+    test("falls back to raw tool arguments when approval_request_message args are not JSON", () => {
+      const session = new Session();
+      const wireMsg = createApprovalRequestMessage(2, {
+        name: "Read",
+        arguments: "path=/tmp/foo.txt",
+        tool_call_id: "call-approval-2",
+      });
+
+      // @ts-expect-error - accessing private method for regression coverage
+      const transformed = session.transformMessage(wireMsg) as SDKMessage | null;
+
+      expect(transformed).toEqual({
+        type: "tool_call",
+        toolCallId: "call-approval-2",
+        toolName: "Read",
+        toolInput: { raw: "path=/tmp/foo.txt" },
+        uuid: "approval-2",
+      });
+    });
+  });
+
   describe("background pump parity", () => {
     test("handles can_use_tool control requests before stream iteration starts", async () => {
       let callbackInvocations = 0;
diff --git a/src/session.ts b/src/session.ts
index 29939e6..11f3832 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -12,6 +12,7 @@ import type {
   SDKInitMessage,
   SDKAssistantMessage,
   SDKResultMessage,
+  MessageWire,
   WireMessage,
   ControlRequest,
   CanUseToolControlRequest,
@@ -669,7 +670,7 @@ export class Session implements AsyncDisposable {
   /**
    * Transform wire message to SDK message
    */
-  private transformMessage(wireMsg: WireMessage): SDKMessage | null {
+  private transformMessage(wireMsg: WireMessage | MessageWire): SDKMessage | null {
     // Init message
     if (wireMsg.type === "system" && "subtype" in wireMsg && wireMsg.subtype === "init") {
       const msg = wireMsg as WireMessage & {