diff --git a/change/@fluentui-react-breadcrumb-78372ea0-823d-4939-b9f5-600d215feb68.json b/change/@fluentui-react-breadcrumb-78372ea0-823d-4939-b9f5-600d215feb68.json
new file mode 100644
index 00000000000000..07a3955938b1b2
--- /dev/null
+++ b/change/@fluentui-react-breadcrumb-78372ea0-823d-4939-b9f5-600d215feb68.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: make BreadcrumbButtonBaseProps distribute over the ARIA button union so the anchor arm's href stays assignable",
+  "packageName": "@fluentui/react-breadcrumb",
+  "email": "array.knight@gmail.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react-components/react-breadcrumb/library/etc/react-breadcrumb.api.md b/packages/react-components/react-breadcrumb/library/etc/react-breadcrumb.api.md
index 21b597d5eb78d6..e16f1f764e21fa 100644
--- a/packages/react-components/react-breadcrumb/library/etc/react-breadcrumb.api.md
+++ b/packages/react-components/react-breadcrumb/library/etc/react-breadcrumb.api.md
@@ -9,6 +9,7 @@ import type { ButtonSlots } from '@fluentui/react-button';
 import type { ButtonState } from '@fluentui/react-button';
 import type { ComponentProps } from '@fluentui/react-utilities';
 import type { ComponentState } from '@fluentui/react-utilities';
+import type { DistributiveOmit } from '@fluentui/react-utilities';
 import type { ForwardRefComponent } from '@fluentui/react-utilities';
 import type { JSXElement } from '@fluentui/react-utilities';
 import * as React_2 from 'react';
@@ -29,7 +30,7 @@ export type BreadcrumbBaseState = Omit<BreadcrumbState, 'size'>;
 export const BreadcrumbButton: ForwardRefComponent<BreadcrumbButtonProps>;
 
 // @public (undocumented)
-export type BreadcrumbButtonBaseProps = Omit<BreadcrumbButtonProps, 'size'>;
+export type BreadcrumbButtonBaseProps = DistributiveOmit<BreadcrumbButtonProps, 'size'>;
 
 // @public (undocumented)
 export type BreadcrumbButtonBaseState = Omit<BreadcrumbButtonState, 'appearance' | 'size' | 'shape'>;
diff --git a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.test.tsx b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.test.tsx
index 6e39e8274ceac9..1fdfad49551d75 100644
--- a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.test.tsx
+++ b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.test.tsx
@@ -1,6 +1,7 @@
 import * as React from 'react';
-import { render } from '@testing-library/react';
+import { render, renderHook } from '@testing-library/react';
 import { BreadcrumbButton } from './BreadcrumbButton';
+import { useBreadcrumbButtonBase_unstable } from './useBreadcrumbButton';
 import type { BreadcrumbButtonProps } from './BreadcrumbButton.types';
 import { isConformant } from '../../testing/isConformant';
 import { breadcrumbButtonClassNames } from './useBreadcrumbButtonStyles.styles';
@@ -67,4 +68,32 @@ describe('BreadcrumbButton', () => {
       </div>
     `);
   });
+
+  // Regression test for https://github.com/microsoft/fluentui/issues/36645: a plain `Omit`
+  // collapsed the distributive ARIA button union, so the anchor arm's `href` was not assignable.
+  // Type-check runs against tests, so this covers the base hook and the types together.
+  it('accepts the anchor arm of the ARIA button union in the base hook', () => {
+    const { result } = renderHook(() =>
+      useBreadcrumbButtonBase_unstable({ as: 'a', href: '/somewhere' }, React.createRef<HTMLAnchorElement>()),
+    );
+
+    // `components.root` stays 'button' (the slot's declared default); the anchor arm resolves
+    // through the slot props, where useARIAButtonProps carries `as: 'a'` to the render layer.
+    expect(result.current).toMatchObject({
+      root: { as: 'a', href: '/somewhere' },
+    });
+  });
+
+  // Regression test for the controlType operator-precedence bug: `as ?? href ? 'a' : 'button'`
+  // parses as `(as ?? href) ? 'a' : 'button'`, so an explicit `as: 'button'` (truthy) computed
+  // controlType 'a' and the ARIA button pipeline emitted the anchor arm (`as: 'a'`, role="button")
+  // for a caller who asked for a real <button>.
+  it('keeps an explicit as="button" on the button arm of the base hook', () => {
+    const { result } = renderHook(() =>
+      useBreadcrumbButtonBase_unstable({ as: 'button' }, React.createRef<HTMLButtonElement>()),
+    );
+
+    expect(result.current.root.as).toBe('button');
+    expect(result.current.root.role).toBeUndefined();
+  });
 });
diff --git a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.types.ts b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.types.ts
index a9220b965983e5..95bf28bd914499 100644
--- a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.types.ts
+++ b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/BreadcrumbButton.types.ts
@@ -1,4 +1,4 @@
-import type { ComponentProps, ComponentState } from '@fluentui/react-utilities';
+import type { ComponentProps, ComponentState, DistributiveOmit } from '@fluentui/react-utilities';
 import type { ButtonProps, ButtonSlots, ButtonState } from '@fluentui/react-button';
 import type { BreadcrumbProps } from '../Breadcrumb/Breadcrumb.types';
 
@@ -25,6 +25,6 @@ export type BreadcrumbButtonState = ComponentState<BreadcrumbButtonSlots> &
   Omit<ButtonState, keyof ButtonSlots | 'components'> &
   Required<Pick<BreadcrumbButtonProps, 'current' | 'size'>>;
 
-export type BreadcrumbButtonBaseProps = Omit<BreadcrumbButtonProps, 'size'>;
+export type BreadcrumbButtonBaseProps = DistributiveOmit<BreadcrumbButtonProps, 'size'>;
 
 export type BreadcrumbButtonBaseState = Omit<BreadcrumbButtonState, 'appearance' | 'size' | 'shape'>;
diff --git a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/useBreadcrumbButton.ts b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/useBreadcrumbButton.ts
index 5935f389ded72d..d2837d424d52ab 100644
--- a/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/useBreadcrumbButton.ts
+++ b/packages/react-components/react-breadcrumb/library/src/components/BreadcrumbButton/useBreadcrumbButton.ts
@@ -49,7 +49,7 @@ export const useBreadcrumbButtonBase_unstable = (
 ): BreadcrumbButtonBaseState => {
   const { current = false, as, ...rest } = props;
 
-  const controlType = as ?? (props as ARIAButtonProps<'a'>).href ? 'a' : 'button';
+  const controlType = as ?? ((props as ARIAButtonProps<'a'>).href ? 'a' : 'button');
 
   const buttonState = useButtonBase_unstable(
     {