diff --git a/src/agents/tools/embedded-gateway-stub.test.ts b/src/agents/tools/embedded-gateway-stub.test.ts
index cab2cbb22fc3..e85ab4ca1166 100644
--- a/src/agents/tools/embedded-gateway-stub.test.ts
+++ b/src/agents/tools/embedded-gateway-stub.test.ts
@@ -504,6 +504,14 @@ describe("embedded gateway stub", () => {
         params: { sessionKey: "agent:main:main", offset: 1.5 },
       }),
     ).rejects.toThrow("offset must be a non-negative integer");
+    await expect(
+      callGateway({
+        method: "chat.history",
+        params: { sessionKey: "agent:main:main", offset: "1abc" },
+      }),
+    ).rejects.toThrow("offset must be a non-negative integer");
     expect(runtime.readSessionMessagesAsync).not.toHaveBeenCalled();
+    expect(runtime.readRecentSessionMessagesWithStatsAsync).not.toHaveBeenCalled();
+    expect(runtime.readSessionMessagesPageWithStatsAsync).not.toHaveBeenCalled();
   });
 });
diff --git a/src/agents/tools/embedded-gateway-stub.ts b/src/agents/tools/embedded-gateway-stub.ts
index 23f648c4d620..69b53aa6775c 100644
--- a/src/agents/tools/embedded-gateway-stub.ts
+++ b/src/agents/tools/embedded-gateway-stub.ts
@@ -17,7 +17,7 @@ import type {
 import type { SessionsListResult } from "../../gateway/session-utils.types.js";
 import type { SessionsResolveResult } from "../../gateway/sessions-resolve.js";
 import { parseAgentSessionKey } from "../../routing/session-key.js";
-import { readNumberParam, readPositiveIntegerParam } from "./common.js";
+import { readNonNegativeIntegerParam, readPositiveIntegerParam } from "./common.js";
 
 type EmbeddedCallGateway = <T = Record<string, unknown>>(opts: CallGatewayOptions) => Promise<T>;
 
@@ -109,10 +109,7 @@ async function getRuntime(): Promise<EmbeddedGatewayRuntime> {
 }
 
 function readOffsetParam(params: Record<string, unknown>): number | undefined {
-  const offset = readNumberParam(params, "offset", {
-    integer: true,
-    nonNegativeInteger: true,
-  });
+  const offset = readNonNegativeIntegerParam(params, "offset");
   if (params.offset !== undefined && offset === undefined) {
     throw new Error("offset must be a non-negative integer");
   }
diff --git a/src/agents/tools/sessions-history-tool.test.ts b/src/agents/tools/sessions-history-tool.test.ts
index 1cb5af60bbf0..c22426d54ab9 100644
--- a/src/agents/tools/sessions-history-tool.test.ts
+++ b/src/agents/tools/sessions-history-tool.test.ts
@@ -118,12 +118,20 @@ describe("sessions_history redaction", () => {
     );
   });
 
-  it.each([-1, 1.5])("rejects invalid offset value %s", async (offset) => {
-    const tool = createHistoryToolWithMessage("hello");
+  it.each([-1, 1.5, "1abc"])("rejects invalid offset value %s", async (offset) => {
+    const requests: CallGatewayRequest[] = [];
+    const tool = createSessionsHistoryTool({
+      config: {},
+      callGateway: async <T = Record<string, unknown>>(request: CallGatewayRequest): Promise<T> => {
+        requests.push(request);
+        return { messages: [] } as T;
+      },
+    });
 
     await expect(tool.execute("call-1", { sessionKey: "main", offset })).rejects.toThrow(
       "offset must be a non-negative integer",
     );
+    expect(requests).toEqual([]);
   });
 
   it("preserves the bounded default history request", async () => {
diff --git a/src/agents/tools/sessions-history-tool.ts b/src/agents/tools/sessions-history-tool.ts
index edbb134d12e3..e9f6a66e30a0 100644
--- a/src/agents/tools/sessions-history-tool.ts
+++ b/src/agents/tools/sessions-history-tool.ts
@@ -21,7 +21,7 @@ import { stripToolMessages } from "./chat-history-text.js";
 import type { AnyAgentTool } from "./common.js";
 import {
   jsonResult,
-  readNumberParam,
+  readNonNegativeIntegerParam,
   readPositiveIntegerParam,
   readStringParam,
   ToolInputError,
@@ -53,10 +53,7 @@ type ChatHistoryPaginationMetadata = {
 };
 
 function readOffsetParam(params: Record<string, unknown>): number | undefined {
-  const offset = readNumberParam(params, "offset", {
-    integer: true,
-    nonNegativeInteger: true,
-  });
+  const offset = readNonNegativeIntegerParam(params, "offset");
   if (params.offset !== undefined && offset === undefined) {
     throw new ToolInputError("offset must be a non-negative integer");
   }