diff --git a/docs/guide/when-clauses.md b/docs/guide/when-clauses.md
index 6bf26c0..6a0c40f 100644
--- a/docs/guide/when-clauses.md
+++ b/docs/guide/when-clauses.md
@@ -40,6 +40,23 @@ ctx.docks.register({
 
 `when: 'false'` hides an entry unconditionally.
 
+### Dynamic `when` on registered/mounted docks
+
+A dock entry's `when` also accepts a boolean or a function, resolved to the string form above once per serialization (`ctx.docks.values()`) — a server-side authoring convenience for docks whose visibility depends on live state:
+
+```ts
+ctx.docks.register({
+  id: 'my-devtool:sessions',
+  title: 'Sessions',
+  type: 'action',
+  icon: 'ph:cursor-duotone',
+  when: () => (sessions.size === 0 ? 'false' : undefined),
+  action: { importFrom: 'my-devtool/sessions' },
+})
+```
+
+The function is re-invoked on every serialization pass, so it reflects the current state each time a client reads `devframe:docks` — the same pattern the hub's built-in `~terminals` dock uses to hide itself while no terminal session is open. `false` resolves to `'false'`; `true` resolves to `undefined` (unconditionally visible); a returned string is passed through unchanged and still evaluated client-side. This is what makes a function `when` useful specifically for a dock registered via `mountDevframe`'s `dock` option — that object is spread once, so a getter would only run once, but a function value survives the spread by reference.
+
 ## Expression syntax
 
 ### Operators
diff --git a/packages/hub/src/define.ts b/packages/hub/src/define.ts
index e69b87b..6ff2ee1 100644
--- a/packages/hub/src/define.ts
+++ b/packages/hub/src/define.ts
@@ -17,7 +17,7 @@ export function defineDockEntry<
   const T extends DevframeDockUserEntry,
   const W extends string = '',
 >(
-  entry: Omit<T, 'when'> & { when?: WhenExpression<WhenContext, W> },
+  entry: Omit<T, 'when'> & { when?: WhenExpression<WhenContext, W> | boolean | (() => string | boolean | undefined) },
 ): T {
   return entry as unknown as T
 }
diff --git a/packages/hub/src/node/__tests__/host-docks.test.ts b/packages/hub/src/node/__tests__/host-docks.test.ts
index ede10a6..692b1f5 100644
--- a/packages/hub/src/node/__tests__/host-docks.test.ts
+++ b/packages/hub/src/node/__tests__/host-docks.test.ts
@@ -238,3 +238,81 @@ describe('devframeDockHost built-in gating', () => {
     expect(host.values({ includeBuiltin: false })).toEqual([])
   })
 })
+
+describe('devframeDockHost dynamic `when`', () => {
+  it('resolves a function `when` on every values() call, reflecting the current return value', () => {
+    const host = new DevframeDocksHost(createContext())
+    let hidden = false
+
+    host.register({
+      type: 'iframe',
+      id: 'app:overview',
+      title: 'Overview',
+      icon: 'ph:gauge-duotone',
+      url: '/__app/',
+      when: () => (hidden ? 'false' : undefined),
+    })
+
+    expect(host.values({ includeBuiltin: false })[0].when).toBeUndefined()
+
+    hidden = true
+    expect(host.values({ includeBuiltin: false })[0].when).toBe('false')
+
+    hidden = false
+    expect(host.values({ includeBuiltin: false })[0].when).toBeUndefined()
+  })
+
+  it('resolves boolean `when`: false -> \'false\', true -> undefined', () => {
+    const host = new DevframeDocksHost(createContext())
+    host.register({
+      type: 'iframe',
+      id: 'app:hidden',
+      title: 'Hidden',
+      icon: 'ph:gauge-duotone',
+      url: '/__hidden/',
+      when: false,
+    })
+    host.register({
+      type: 'iframe',
+      id: 'app:shown',
+      title: 'Shown',
+      icon: 'ph:gauge-duotone',
+      url: '/__shown/',
+      when: true,
+    })
+
+    const entries = host.values({ includeBuiltin: false })
+    expect(entries.find(e => e.id === 'app:hidden')!.when).toBe('false')
+    expect(entries.find(e => e.id === 'app:shown')!.when).toBeUndefined()
+  })
+
+  it('passes a string `when` through unchanged', () => {
+    const host = new DevframeDocksHost(createContext())
+    host.register({
+      type: 'iframe',
+      id: 'app:embedded-only',
+      title: 'Embedded Only',
+      icon: 'ph:gauge-duotone',
+      url: '/__embedded-only/',
+      when: 'clientType == embedded',
+    })
+
+    expect(host.values({ includeBuiltin: false })[0].when).toBe('clientType == embedded')
+  })
+
+  it('does not mutate the stored entry when resolving a function `when`', () => {
+    const host = new DevframeDocksHost(createContext())
+    const whenFn = () => 'false' as const
+    host.register({
+      type: 'iframe',
+      id: 'app:overview',
+      title: 'Overview',
+      icon: 'ph:gauge-duotone',
+      url: '/__app/',
+      when: whenFn,
+    })
+
+    host.values({ includeBuiltin: false })
+    expect(host.views.get('app:overview')!.when).toBe(whenFn)
+  })
+})
diff --git a/packages/hub/src/node/__tests__/mount-devframe.test.ts b/packages/hub/src/node/__tests__/mount-devframe.test.ts
index 9da3924..560ac5d 100644
--- a/packages/hub/src/node/__tests__/mount-devframe.test.ts
+++ b/packages/hub/src/node/__tests__/mount-devframe.test.ts
@@ -93,6 +93,20 @@ describe('mountDevframe', () => {
     expect(ctx.docks.views.size).toBe(1)
   })
 
+  it('flows a function `when` through the `options.dock` spread and re-resolves it per values() call', async () => {
+    const ctx = createContext()
+    let hidden = false
+
+    await mountDevframe(ctx, makeDevframe(), {
+      dock: { when: () => (hidden ? 'false' : undefined) },
+    })
+
+    expect(ctx.docks.values({ includeBuiltin: false })[0].when).toBeUndefined()
+
+    hidden = true
+    expect(ctx.docks.values({ includeBuiltin: false })[0].when).toBe('false')
+  })
+
   it('lets instances coexist under disambiguated ids when "duplicate"', async () => {
     const ctx = createContext()
     const setup = vi.fn()
diff --git a/packages/hub/src/node/host-docks.ts b/packages/hub/src/node/host-docks.ts
index 6a1a391..247b036 100644
--- a/packages/hub/src/node/host-docks.ts
+++ b/packages/hub/src/node/host-docks.ts
@@ -19,6 +19,7 @@ import { createEventEmitter } from 'devframe/utils/events'
 import { join } from 'pathe'
 import { DEFAULT_STATE_USER_SETTINGS } from '../constants'
 import { diagnostics } from './diagnostics'
+import { resolveWhen } from './when'
 
 interface RemoteDockRecord {
   token: string
@@ -162,13 +163,22 @@ export class DevframeDocksHost implements DevframeDocksHostType {
     ]
   }
 
+  /**
+   * Turn a registered entry into its serializable wire form: resolve
+   * `when` down to `string | undefined` (see {@link resolveWhen}) and, for
+   * remote iframes, inject the connection descriptor into the URL. Always
+   * returns a shallow copy — the stored entry (and any `when` function on
+   * it) is left untouched for the next call.
+   */
   private projectView(view: DevframeDockUserEntry): DevframeDockUserEntry {
-    if (view.type !== 'iframe' || !view.remote)
-      return view
-    const record = this.remoteDocks.get(view.id)
+    const resolved: DevframeDockUserEntry = { ...view, when: resolveWhen(view.when) }
+
+    if (resolved.type !== 'iframe' || !resolved.remote)
+      return resolved
+    const record = this.remoteDocks.get(resolved.id)
     const endpoint = getInternalContext(this.context as DevframeNodeContext).wsEndpoint
     if (!record || !endpoint)
-      return view
+      return resolved
 
     const payload: RemoteConnectionInfo = {
       v: 1,
@@ -178,8 +188,8 @@ export class DevframeDocksHost implements DevframeDocksHostType {
       origin: this.resolveDevServerOrigin(),
     }
     return {
-      ...view,
-      url: buildRemoteUrl(view.url, payload, record.options.transport),
+      ...resolved,
+      url: buildRemoteUrl(resolved.url, payload, record.options.transport),
     } satisfies DevframeViewIframe
   }
 
diff --git a/packages/hub/src/node/index.ts b/packages/hub/src/node/index.ts
index c5160de..faf3dc6 100644
--- a/packages/hub/src/node/index.ts
+++ b/packages/hub/src/node/index.ts
@@ -6,3 +6,4 @@ export * from './host-terminals'
 export * from './mount-devframe'
 export * from './rpc-builtins'
 export * from './utils'
+export * from './when'
diff --git a/packages/hub/src/node/mount-devframe.ts b/packages/hub/src/node/mount-devframe.ts
index 935ebd2..0e83ab3 100644
--- a/packages/hub/src/node/mount-devframe.ts
+++ b/packages/hub/src/node/mount-devframe.ts
@@ -15,6 +15,11 @@ export interface MountDevframeOptions {
    * customize the entry's `category`, override the icon, hide it via
    * `when`, etc. Cannot change `id`, `type`, or `url` — those are
    * derived from the devframe definition.
+   *
+   * `when` may be a function (`() => string | boolean | undefined`),
+   * re-invoked every time the dock is serialized — the mounted-dock
+   * equivalent of the built-in docks' `when` getters, since a getter here
+   * would only ever run once through this spread.
    */
   dock?: Partial<Omit<DevframeViewIframe, 'id' | 'type' | 'url'>>
 }
diff --git a/packages/hub/src/node/when.ts b/packages/hub/src/node/when.ts
new file mode 100644
index 0000000..4cde10a
--- /dev/null
+++ b/packages/hub/src/node/when.ts
@@ -0,0 +1,20 @@
+import type { DevframeWhen } from '../types/docks'
+
+/**
+ * Resolve a dock entry's authored {@link DevframeWhen} down to the wire
+ * contract (`string | undefined`) that clients evaluate with `whenexpr`.
+ *
+ * Called once per serialization (`DevframeDocksHost.values()` /
+ * `projectView`) so a function `when` is re-invoked on every pass — the
+ * server-side equivalent of the built-ins' `get when()` getters, but one
+ * that survives being copied by value (e.g. `mountDevframe`'s
+ * `...options.dock` spread).
+ */
+export function resolveWhen(when: DevframeWhen | undefined): string | undefined {
+  const value = typeof when === 'function' ? when() : when
+  if (value === false)
+    return 'false'
+  if (value === true || value == null)
+    return undefined
+  return value
+}
diff --git a/packages/hub/src/types/docks.ts b/packages/hub/src/types/docks.ts
index 92d8714..83e5401 100644
--- a/packages/hub/src/types/docks.ts
+++ b/packages/hub/src/types/docks.ts
@@ -54,6 +54,26 @@ export type DevframeDockEntryCategory
 
 export type DevframeDockEntryIcon = string | { light: string, dark: string }
 
+/**
+ * A dock entry's `when` value, as authored.
+ *
+ * - `string` — a `whenexpr` expression, evaluated client-side against a
+ *   `WhenContext` (unchanged from before).
+ * - `boolean` — a static shortcut: `false` unconditionally hides the entry,
+ *   `true` unconditionally shows it.
+ * - `() => string | boolean | undefined` — a live clause, invoked server-side
+ *   every time the dock's shared state is serialized. Lets a host give a
+ *   registered/mounted dock the same dynamic visibility the built-in
+ *   `~terminals`/`~messages` entries have, without relying on a getter that
+ *   would be evaluated only once by `mountDevframe`'s `...options.dock` spread.
+ *
+ * Whichever form is authored, it is resolved down to the wire contract
+ * (`string | undefined`) during serialization — see
+ * {@link import('../node/when').resolveWhen}. Clients only ever see a
+ * `string | undefined`, evaluated the same way as always.
+ */
+export type DevframeWhen = string | boolean | (() => string | boolean | undefined)
+
 export interface DevframeDockEntryBase {
   id: string
   title: string
@@ -70,16 +90,21 @@ export interface DevframeDockEntryBase {
    */
   category?: DevframeDockEntryCategory
   /**
-   * Conditional visibility expression.
-   * When set, the dock entry is only visible when the expression evaluates to true.
-   * Uses the same syntax as command `when` clauses.
+   * Conditional visibility.
+   * When set, the dock entry is only visible when it resolves to true.
+   * A string uses the same `whenexpr` syntax as command `when` clauses and
+   * is still evaluated client-side. A boolean or a function is a
+   * server-side authoring convenience, resolved to a `string | undefined`
+   * once per serialization — see {@link DevframeWhen}.
    *
-   * Set to `'false'` to unconditionally hide the entry.
+   * Set to `'false'` (or a function returning `false`) to unconditionally
+   * hide the entry.
    *
    * @example 'clientType == embedded'
+   * @example () => sessions.size === 0 ? 'false' : undefined
    * @see {@link import('devframe/utils/when').evaluateWhen}
    */
-  when?: string
+  when?: DevframeWhen
   /**
    * Badge text to display on the dock icon (e.g., unread count)
    */
diff --git a/tests/__snapshots__/tsnapi/@devframes/hub/index.snapshot.d.ts b/tests/__snapshots__/tsnapi/@devframes/hub/index.snapshot.d.ts
index 6230f5d..68d57c4 100644
--- a/tests/__snapshots__/tsnapi/@devframes/hub/index.snapshot.d.ts
+++ b/tests/__snapshots__/tsnapi/@devframes/hub/index.snapshot.d.ts
@@ -6,7 +6,7 @@ export declare function defineCommand<const W extends string = ''>(_: Omit<Devfr
   when?: WhenExpression<WhenContext, W>;
 }): DevframeServerCommandInput;
 export declare function defineDockEntry<const T extends DevframeDockUserEntry, const W extends string = ''>(_: Omit<T, 'when'> & {
-  when?: WhenExpression<WhenContext, W>;
+  when?: WhenExpression<WhenContext, W> | boolean | (() => string | boolean | undefined);
 }): T;
 export declare function defineJsonRenderSpec(_: JsonRenderSpec): JsonRenderSpec;
 // #endregion
@@ -77,6 +77,7 @@ export { DevframeViewIframe }
 export { DevframeViewJsonRender }
 export { DevframeViewLauncher }
 export { DevframeViewLauncherStatus }
+export { DevframeWhen }
 export { EntriesToObject }
 export { EventEmitter }
 export { EventsMap }
diff --git a/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.d.ts b/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.d.ts
index 9af324f..d82c65d 100644
--- a/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.d.ts
+++ b/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.d.ts
@@ -92,6 +92,7 @@ export declare class DevframeTerminalsHost implements DevframeTerminalsHost$1 {
 // #region Functions
 export declare function createSimpleClientScript(_: string | ((_: any) => void)): ClientScriptEntry;
 export declare function mountDevframe(_: DevframeHubContext, _: DevframeDefinition, _?: MountDevframeOptions): Promise<void>;
+export declare function resolveWhen(_: DevframeWhen | undefined): string | undefined;
 // #endregion
 
 // #region Variables
diff --git a/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.js b/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.js
index 5740f8f..b46e9a3 100644
--- a/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.js
+++ b/tests/__snapshots__/tsnapi/@devframes/hub/node.snapshot.js
@@ -76,6 +76,7 @@ export class DevframeTerminalsHost {
 export async function createHubContext(_) {}
 export function createSimpleClientScript(_) {}
 export async function mountDevframe(_, _, _) {}
+export function resolveWhen(_) {}
 // #endregion
 
 // #region Variables
diff --git a/tests/__snapshots__/tsnapi/@devframes/hub/types.snapshot.d.ts b/tests/__snapshots__/tsnapi/@devframes/hub/types.snapshot.d.ts
index 752de5c..84066d5 100644
--- a/tests/__snapshots__/tsnapi/@devframes/hub/types.snapshot.d.ts
+++ b/tests/__snapshots__/tsnapi/@devframes/hub/types.snapshot.d.ts
@@ -63,6 +63,7 @@ export { DevframeViewIframe }
 export { DevframeViewJsonRender }
 export { DevframeViewLauncher }
 export { DevframeViewLauncherStatus }
+export { DevframeWhen }
 export { EntriesToObject }
 export { EventEmitter }
 export { EventsMap }