diff --git a/shell/plugins/steve/__tests__/projectAndNamespaceFiltering.utils.test.ts b/shell/plugins/steve/__tests__/projectAndNamespaceFiltering.utils.test.ts
new file mode 100644
index 00000000000..4b6bea12e9b
--- /dev/null
+++ b/shell/plugins/steve/__tests__/projectAndNamespaceFiltering.utils.test.ts
@@ -0,0 +1,187 @@
+import pAndNFiltering from '@shell/plugins/steve/projectAndNamespaceFiltering.utils';
+import { NAMESPACE_FILTER_NS_FULL_PREFIX, NAMESPACE_FILTER_P_FULL_PREFIX } from '@shell/utils/namespace-filter';
+import { MANAGEMENT } from '@shell/config/types';
+import { SETTING } from '@shell/config/settings';
+
+const makeRootGetters = (overrides: { currentProduct?: any; perfSettingValue?: string } = {}) => {
+  const { currentProduct = { inStore: 'cluster', showWorkspaceSwitcher: false }, perfSettingValue } = overrides;
+
+  return {
+    currentProduct,
+    'management/byId': (type: string, id: string) => {
+      if (type === MANAGEMENT.SETTING && id === SETTING.UI_PERFORMANCE && perfSettingValue !== undefined) {
+        return { value: perfSettingValue };
+      }
+
+      return undefined;
+    },
+  } as any;
+};
+
+describe('projectAndNamespaceFiltering.utils', () => {
+  describe('isApplicable', () => {
+    it.each([
+      {
+        desc:     'returns true when namespaced is an empty array',
+        opt:      { namespaced: [] },
+        expected: true,
+      },
+      {
+        desc:     'returns true when namespaced is a non-empty array',
+        opt:      { namespaced: ['ns://my-ns'] },
+        expected: true,
+      },
+      {
+        desc:     'returns false when namespaced is undefined',
+        opt:      { namespaced: undefined },
+        expected: false,
+      },
+      {
+        desc:     'returns false when namespaced is a string',
+        opt:      { namespaced: 'ns://my-ns' } as any,
+        expected: false,
+      },
+      {
+        desc:     'returns false when namespaced property is absent',
+        opt:      {} as any,
+        expected: false,
+      },
+    ])('$desc', ({ opt, expected }) => {
+      expect(pAndNFiltering.isApplicable(opt)).toStrictEqual(expected);
+    });
+  });
+
+  describe('isEnabled', () => {
+    it('returns true when all conditions are met', () => {
+      const rootGetters = makeRootGetters({ perfSettingValue: JSON.stringify({ forceNsFilterV2: { enabled: true } }) });
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(true);
+    });
+
+    it('returns false when inStore is not cluster', () => {
+      const rootGetters = makeRootGetters({
+        currentProduct:   { inStore: 'management', showWorkspaceSwitcher: false },
+        perfSettingValue: JSON.stringify({ forceNsFilterV2: { enabled: true } }),
+      });
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(false);
+    });
+
+    it('returns false when showWorkspaceSwitcher is true', () => {
+      const rootGetters = makeRootGetters({
+        currentProduct:   { inStore: 'cluster', showWorkspaceSwitcher: true },
+        perfSettingValue: JSON.stringify({ forceNsFilterV2: { enabled: true } }),
+      });
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(false);
+    });
+
+    it('returns false when forceNsFilterV2 is disabled', () => {
+      const rootGetters = makeRootGetters({ perfSettingValue: JSON.stringify({ forceNsFilterV2: { enabled: false } }) });
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(false);
+    });
+
+    it('returns false when forceNsFilterV2 is absent (default perf setting)', () => {
+      const rootGetters = makeRootGetters();
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(false);
+    });
+
+    it('returns false when currentProduct is null', () => {
+      const rootGetters = makeRootGetters({
+        currentProduct:   null,
+        perfSettingValue: JSON.stringify({ forceNsFilterV2: { enabled: true } }),
+      });
+
+      expect(pAndNFiltering.isEnabled(rootGetters)).toBe(false);
+    });
+  });
+
+  describe('createParam', () => {
+    it('returns empty string for undefined filter', () => {
+      expect(pAndNFiltering.createParam(undefined)).toStrictEqual('');
+    });
+
+    it('returns empty string for empty array', () => {
+      expect(pAndNFiltering.createParam([])).toStrictEqual('');
+    });
+
+    it.each([
+      {
+        desc:     'plain namespace without prefix',
+        filter:   ['my-namespace'],
+        expected: 'projectsornamespaces=my-namespace',
+      },
+      {
+        desc:     'namespace with ns:// prefix stripped',
+        filter:   [`${ NAMESPACE_FILTER_NS_FULL_PREFIX }my-namespace`],
+        expected: 'projectsornamespaces=my-namespace',
+      },
+      {
+        desc:     'project with project:// prefix stripped',
+        filter:   [`${ NAMESPACE_FILTER_P_FULL_PREFIX }my-project`],
+        expected: 'projectsornamespaces=my-project',
+      },
+      {
+        desc:     'multiple includes joined with comma',
+        filter:   ['ns-a', 'ns-b', 'ns-c'],
+        expected: 'projectsornamespaces=ns-a,ns-b,ns-c',
+      },
+      {
+        desc:     'multiple includes with mixed prefixes joined',
+        filter:   [`${ NAMESPACE_FILTER_NS_FULL_PREFIX }ns-a`, `${ NAMESPACE_FILTER_P_FULL_PREFIX }proj-b`],
+        expected: 'projectsornamespaces=ns-a,proj-b',
+      },
+    ])('include: $desc', ({ filter, expected }) => {
+      expect(pAndNFiltering.createParam(filter)).toStrictEqual(expected);
+    });
+
+    it.each([
+      {
+        desc:     'single exclude with leading dash',
+        filter:   ['-my-namespace'],
+        expected: 'projectsornamespaces!=my-namespace',
+      },
+      {
+        desc:     'multiple excludes joined with comma',
+        filter:   ['-ns-a', '-ns-b'],
+        expected: 'projectsornamespaces!=ns-a,ns-b',
+      },
+    ])('exclude: $desc', ({ filter, expected }) => {
+      expect(pAndNFiltering.createParam(filter)).toStrictEqual(expected);
+    });
+
+    it('exclude overrides include when both are present', () => {
+      const filter = ['ns-include', '-ns-exclude'];
+
+      expect(pAndNFiltering.createParam(filter)).toStrictEqual('projectsornamespaces!=ns-exclude');
+    });
+  });
+
+  describe('checkAndCreateParam', () => {
+    it('returns empty string when opt.namespaced is not an array', () => {
+      const result = pAndNFiltering.checkAndCreateParam({ namespaced: undefined } as any);
+
+      expect(result).toStrictEqual('');
+    });
+
+    it('returns empty string when opt.namespaced is an empty array', () => {
+      const result = pAndNFiltering.checkAndCreateParam({ namespaced: [] });
+
+      expect(result).toStrictEqual('');
+    });
+
+    it('returns query param when opt.namespaced is a populated array', () => {
+      const result = pAndNFiltering.checkAndCreateParam({ namespaced: ['my-namespace'] });
+
+      expect(result).toStrictEqual('projectsornamespaces=my-namespace');
+    });
+
+    it('returns query param with prefix stripping for ns:// values', () => {
+      const result = pAndNFiltering.checkAndCreateParam({ namespaced: [`${ NAMESPACE_FILTER_NS_FULL_PREFIX }my-namespace`] });
+
+      expect(result).toStrictEqual('projectsornamespaces=my-namespace');
+    });
+  });
+});