diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f3c54db1387..64ef4acda82 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -282,6 +282,12 @@ jobs:
         if: "${{ needs.classify_pr.outputs.skip_ci != 'true' && steps.ci_profile.outputs.ci_profile == 'full' }}"
         run: 'npm run check:desktop-isolation'
 
+      - name: 'Run desktop session-tools-core tests'
+        if: "${{ needs.classify_pr.outputs.skip_ci != 'true' && steps.ci_profile.outputs.ci_profile == 'full' }}"
+        run: |-
+          npm exec --yes bun@1.3.14 -- test \
+            packages/desktop/packages/session-tools-core/src/handlers/list-sessions.test.ts
+
       - name: 'Install linters'
         if: "${{ needs.classify_pr.outputs.skip_ci != 'true' && steps.ci_profile.outputs.ci_profile == 'full' }}"
         run: 'node scripts/lint.js --setup'
diff --git a/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.test.ts b/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.test.ts
new file mode 100644
index 00000000000..92250c91904
--- /dev/null
+++ b/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.test.ts
@@ -0,0 +1,89 @@
+import { describe, expect, it } from 'bun:test';
+import { handleListSessions } from './list-sessions.ts';
+import type { ListSessionsOptions, SessionToolContext } from '../context.ts';
+
+function createCtx(
+  onListSessions: (options?: ListSessionsOptions) => void,
+): SessionToolContext {
+  return {
+    listSessions: (options?: ListSessionsOptions) => {
+      onListSessions(options);
+      return {
+        total: 1,
+        returned: 1,
+        sessions: [
+          {
+            id: 'session-123',
+            name: 'Example',
+            labels: [],
+            status: 'todo',
+            createdAt: 1,
+          },
+        ],
+      };
+    },
+  } as unknown as SessionToolContext;
+}
+
+describe('handleListSessions', () => {
+  it('rejects malformed pagination values before listing sessions', async () => {
+    const cases: Array<{ args: ListSessionsOptions; message: string }> = [
+      { args: { limit: 0 }, message: 'limit must be a positive integer.' },
+      { args: { limit: -1 }, message: 'limit must be a positive integer.' },
+      { args: { limit: 1.5 }, message: 'limit must be a positive integer.' },
+      {
+        args: { offset: -1 },
+        message: 'offset must be a non-negative integer.',
+      },
+      {
+        args: { offset: 1.5 },
+        message: 'offset must be a non-negative integer.',
+      },
+    ];
+
+    for (const { args, message } of cases) {
+      const calls: Array<ListSessionsOptions | undefined> = [];
+      const ctx = createCtx((options) => calls.push(options));
+
+      const result = await handleListSessions(ctx, args);
+
+      expect(result.isError).toBe(true);
+      expect(result.content[0]?.text).toContain(message);
+      expect(calls).toEqual([]);
+    }
+  });
+
+  it('accepts minimum valid pagination boundaries', async () => {
+    const calls: Array<ListSessionsOptions | undefined> = [];
+    const ctx = createCtx((options) => calls.push(options));
+
+    const result = await handleListSessions(ctx, { limit: 1, offset: 0 });
+
+    expect(result.isError).toBe(false);
+    expect(calls).toEqual([{ limit: 1, offset: 0 }]);
+  });
+
+  it('passes valid pagination values through to the session lister', async () => {
+    const calls: Array<ListSessionsOptions | undefined> = [];
+    const ctx = createCtx((options) => calls.push(options));
+
+    const result = await handleListSessions(ctx, {
+      status: 'todo',
+      limit: 2,
+      offset: 1,
+    });
+
+    expect(result.isError).toBe(false);
+    expect(calls).toEqual([{ status: 'todo', limit: 2, offset: 1 }]);
+  });
+
+  it('preserves high integer limits for the backend clamp', async () => {
+    const calls: Array<ListSessionsOptions | undefined> = [];
+    const ctx = createCtx((options) => calls.push(options));
+
+    const result = await handleListSessions(ctx, { limit: 101 });
+
+    expect(result.isError).toBe(false);
+    expect(calls).toEqual([{ limit: 101 }]);
+  });
+});
diff --git a/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.ts b/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.ts
index 7eebd1567d5..a0e7675589c 100644
--- a/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.ts
+++ b/packages/desktop/packages/session-tools-core/src/handlers/list-sessions.ts
@@ -13,12 +13,26 @@ export interface ListSessionsArgs {
 
 export async function handleListSessions(
   ctx: SessionToolContext,
-  args: ListSessionsArgs
+  args: ListSessionsArgs,
 ): Promise<ToolResult> {
   if (!ctx.listSessions) {
     return errorResponse('list_sessions is not available in this context.');
   }
 
+  if (
+    args.limit !== undefined &&
+    (!Number.isInteger(args.limit) || args.limit < 1)
+  ) {
+    return errorResponse('limit must be a positive integer.');
+  }
+
+  if (
+    args.offset !== undefined &&
+    (!Number.isInteger(args.offset) || args.offset < 0)
+  ) {
+    return errorResponse('offset must be a non-negative integer.');
+  }
+
   try {
     const result = ctx.listSessions({
       status: args.status,
diff --git a/packages/desktop/packages/session-tools-core/src/tool-defs-filtering.test.ts b/packages/desktop/packages/session-tools-core/src/tool-defs-filtering.test.ts
index d4101d506f7..aae9cae30e8 100644
--- a/packages/desktop/packages/session-tools-core/src/tool-defs-filtering.test.ts
+++ b/packages/desktop/packages/session-tools-core/src/tool-defs-filtering.test.ts
@@ -43,6 +43,19 @@ describe('session tool filtering helpers', () => {
     expect(names.includes('send_developer_feedback')).toBe(false);
   });
 
+  it('json schema exposes list_sessions pagination controls as integers', () => {
+    const defs = getToolDefsAsJsonSchema({ includeDeveloperFeedback: false });
+    const listSessions = defs.find(d => d.name === 'list_sessions');
+    const properties = (
+      listSessions?.inputSchema as
+        | { properties?: Record<string, { type?: string }> }
+        | undefined
+    )?.properties;
+
+    expect(properties?.limit?.type).toBe('integer');
+    expect(properties?.offset?.type).toBe('integer');
+  });
+
   it('all canonical session tools declare safeMode metadata', () => {
     for (const def of SESSION_TOOL_DEFS) {
       expect(def.safeMode === 'allow' || def.safeMode === 'block').toBe(true);
diff --git a/packages/desktop/packages/session-tools-core/src/tool-defs.ts b/packages/desktop/packages/session-tools-core/src/tool-defs.ts
index 5ee64ea56de..78aa699e530 100644
--- a/packages/desktop/packages/session-tools-core/src/tool-defs.ts
+++ b/packages/desktop/packages/session-tools-core/src/tool-defs.ts
@@ -199,8 +199,8 @@ export const ListSessionsSchema = z.object({
   label: z.string().optional().describe('Filter by label'),
   search: z.string().optional().describe('Substring match on session name'),
   sortBy: z.enum(['recent', 'name', 'status']).optional().describe('Sort order (default: recent)'),
-  limit: z.number().optional().describe('Max sessions to return (default 20, max 100)'),
-  offset: z.number().optional().describe('Skip first N results (for pagination)'),
+  limit: z.number().int().min(1).optional().describe('Max sessions to return (default 20, max 100)'),
+  offset: z.number().int().min(0).optional().describe('Skip first N results (for pagination)'),
 });
 
 // Inter-session messaging