diff --git a/projects/start-sdk/CHANGELOG.md b/projects/start-sdk/CHANGELOG.md
index 0bded4cb7d..0c69b74e46 100644
--- a/projects/start-sdk/CHANGELOG.md
+++ b/projects/start-sdk/CHANGELOG.md
@@ -101,7 +101,10 @@
 - **`MultiHost.retire()` and `MultiHost.retirePort()` permanently remove a host
   or a binding**, returning its external ports to the server's pool — where
   `setupInterfaces` otherwise only _disables_ what it did not declare. Call it
-  from the `up()` of the version that stops binding; re-running is safe. See
+  from the `up()` of the version that stops binding; re-running is safe.
+  `retirePort(old, { successor })` records the port the binding moved to in
+  the host's `retiredBindings`, which a URL plugin reads to move an address it
+  holds for the old port rather than park it. See
   [Retiring a Host or Binding](https://docs.start9.com/packaging/interfaces.html#retiring-a-host-or-binding)
 
 - **`sdk.getRootCa(effects)` returns this server's root CA certificate**, for a
diff --git a/projects/start-sdk/docs/src/interfaces.md b/projects/start-sdk/docs/src/interfaces.md
index c07a060c34..99fba7a30c 100644
--- a/projects/start-sdk/docs/src/interfaces.md
+++ b/projects/start-sdk/docs/src/interfaces.md
@@ -371,10 +371,13 @@ The cost is that a binding you stop declaring **for good** stays behind. It keep
 ```typescript
 await sdk.MultiHost.of(effects, 'ui-multi').retire() // the whole host
 await sdk.MultiHost.of(effects, 'api').retirePort(9090) // one port, or one range
+await sdk.MultiHost.of(effects, 'peer').retirePort(8333, { successor: 58333 }) // moved to 58333
 ```
 
 `retire()` removes the host and everything under it: its bindings and port ranges, their exported service interfaces, the user's public and private domains for that host, and their per-address enable/disable and WAN opt-in choices. `retirePort()` removes whichever of the single port and the port range is bound at that `internalPort` — and both, if both are — leaving the host and its domains in place. Both return the external ports to the server's pool. Both are irreversible: after `retire()`, binding the id again starts a fresh host with none of the user's setup.
 
+A port that moved rather than disappeared takes its `successor`: `retirePort(8333, { successor: 58333 })` records on the host, in `retiredBindings`, that 8333 is now served at 58333. StartOS itself acts on nothing there, but a URL plugin holding an address for the old port does — Tor moves a `.onion` attached to 8333 onto 58333, where without the record it parks the address until the user moves it by hand. Omit `successor` when nothing replaces the port; a `.onion` attached to it then parks. The record is dropped if the port is ever bound again.
+
 Note what that last part means: `retire()` discards configuration the **user** created, not just your package's. A domain they attached to the host goes with it, and nothing tells them. Name the host in your release notes whenever a release retires one, so they know to reattach the domain to a current interface.
 
 ### The migration pattern
@@ -412,7 +415,7 @@ This is the same shape as [retiring a replay key](tasks.md#retiring-a-replay-key
 ### Failure modes
 
 - **Retiring an id you still bind.** Migrations run before `setupInterfaces`, so the port is normally reclaimed on the same pass and nothing looks wrong. The symptom is the user's setup silently reset — a custom domain and WAN toggle back to defaults after an update.
-- **A port that moved rather than disappeared.** Retiring the old binding and adding the new one in the same release keeps the host's domains, but StartOS isolates a **public** domain from a binding added after it, so the user has to re-enable that domain on the new binding. Private domains carry over on their own. Say so in your release notes.
+- **A port that moved rather than disappeared.** Retiring the old binding and adding the new one in the same release keeps the host's domains, but StartOS isolates a **public** domain from a binding added after it, so the user has to re-enable that domain on the new binding. Private domains carry over on their own. Say so in your release notes, and pass the new port as `successor` so a Tor address follows it.
 - **Treating `false` as failure.** Both calls resolve `false` when there was nothing to remove — the normal result on a re-run, and on a server that skipped the version. Not an error.
 - **Retiring the last binding on a host.** That does not retire the host. Its domains stay, now addressing nothing. Use `retire()` when the host itself is going away.
 
diff --git a/projects/start-sdk/docs/src/service-to-service.md b/projects/start-sdk/docs/src/service-to-service.md
index a822d76995..36ec364415 100644
--- a/projects/start-sdk/docs/src/service-to-service.md
+++ b/projects/start-sdk/docs/src/service-to-service.md
@@ -63,7 +63,7 @@ Three things make this correct, and each matters:
 
 `getBridgeAddress` returns the same `Watchable` as `sdk.host.get`, so it carries every read strategy. Use `.const()` in `setupMain` and `setupOnInit`; use `.once()` only inside an action, where a live snapshot rather than a subscription is what you want.
 
-When a dependency [retires](interfaces.md#retiring-a-host-or-binding) the host or binding you resolve, it disappears from the database and `getBridgeAddress` resolves `null` — the same path as the dependency not being installed, so rule 3 above already covers it. With `fallbackPort` you get the fallback instead, as always.
+When a dependency [retires](interfaces.md#retiring-a-host-or-binding) the host or binding you resolve, it disappears from the database and `getBridgeAddress` resolves `null` — the same path as the dependency not being installed, so rule 3 above already covers it. With `fallbackPort` you get the fallback instead, as always. If the port moved rather than went away, the dependency's host names the new one in `retiredBindings`.
 
 ## The Tor exception: always-on flags
 
diff --git a/projects/start-sdk/lib/test/host.test.ts b/projects/start-sdk/lib/test/host.test.ts
index fc99d98076..d43b96f2f8 100644
--- a/projects/start-sdk/lib/test/host.test.ts
+++ b/projects/start-sdk/lib/test/host.test.ts
@@ -133,6 +133,22 @@ describe('host', () => {
         internalPort: 9090,
       })
     })
+
+    test('retirePort forwards the successor it was given', async () => {
+      const retireBinding = jest.fn(async () => true)
+      const host = sdk.MultiHost.of(
+        { retireBinding } as unknown as Effects,
+        'peer',
+      )
+      await expect(host.retirePort(8333, { successor: 58333 })).resolves.toBe(
+        true,
+      )
+      expect(retireBinding).toHaveBeenCalledWith({
+        id: 'peer',
+        internalPort: 8333,
+        successor: 58333,
+      })
+    })
   })
 
   describe('MultiHost.bindPortRange', () => {
diff --git a/shared-libs/crates/start-core/src/db/model/public.rs b/shared-libs/crates/start-core/src/db/model/public.rs
index 3126058870..87be920ade 100644
--- a/shared-libs/crates/start-core/src/db/model/public.rs
+++ b/shared-libs/crates/start-core/src/db/model/public.rs
@@ -98,6 +98,7 @@ impl Public {
                         public_domains: BTreeMap::new(),
                         private_domains: BTreeMap::new(),
                         port_forwards: BTreeSet::new(),
+                        retired_bindings: BTreeMap::new(),
                     },
                     wifi: WifiInfo {
                         enabled: false,
diff --git a/shared-libs/crates/start-core/src/net/host/mod.rs b/shared-libs/crates/start-core/src/net/host/mod.rs
index 75b5f8b981..60518b5924 100644
--- a/shared-libs/crates/start-core/src/net/host/mod.rs
+++ b/shared-libs/crates/start-core/src/net/host/mod.rs
@@ -44,6 +44,9 @@ pub struct Host {
     /// COMPUTED: port forwarding rules needed on gateways for public addresses to work.
     #[serde(default)]
     pub port_forwards: BTreeSet<PortForward>,
+    /// Internal ports the service retired, each with the port it named as its successor.
+    #[serde(default)]
+    pub retired_bindings: BTreeMap<u16, Option<u16>>,
 }
 
 fn default_port_forward_count() -> u16 {
@@ -666,6 +669,10 @@ impl Model<Host> {
         {
             return Err(overlap_error(&claim, &existing));
         }
+        self.as_retired_bindings_mut().mutate(|r| {
+            r.remove(&internal_port);
+            Ok(())
+        })?;
         self.as_bindings_mut().mutate(|b| {
             let info = if let Some(info) = b.remove(&internal_port) {
                 info.update(available_ports, options, privileged)?
@@ -707,6 +714,10 @@ impl Model<Host> {
         {
             return Err(overlap_error(&claim, &existing));
         }
+        self.as_retired_bindings_mut().mutate(|r| {
+            r.remove(&internal_start_port);
+            Ok(())
+        })?;
         self.as_binding_ranges_mut().mutate(|ranges| {
             let existing = ranges.get(&internal_start_port);
             // Idempotent re-bind: a package may call bindPortRange on every
@@ -1061,6 +1072,26 @@ mod tests {
         assert!(ports.try_alloc(40000, false, false).is_some());
     }
 
+    #[test]
+    fn binding_a_retired_port_again_drops_its_tombstone() {
+        let mut ports = AvailablePorts::new();
+        let mut host = host();
+        host.as_retired_bindings_mut()
+            .mutate(|r| {
+                r.insert(8333, Some(58333));
+                r.insert(28332, None);
+                Ok(())
+            })
+            .unwrap();
+
+        host.add_binding(&mut ports, 8333, plain(8333), false)
+            .unwrap();
+        host.add_binding_range(&mut ports, 28332, 40000, 2, false)
+            .unwrap();
+
+        assert!(host.as_retired_bindings().de().unwrap().is_empty());
+    }
+
     #[test]
     fn a_dormant_binding_does_not_block_the_range_that_supersedes_it() {
         let mut ports = AvailablePorts::new();
diff --git a/shared-libs/crates/start-core/src/net/net_controller.rs b/shared-libs/crates/start-core/src/net/net_controller.rs
index 4e2a0814f9..730e6d534e 100644
--- a/shared-libs/crates/start-core/src/net/net_controller.rs
+++ b/shared-libs/crates/start-core/src/net/net_controller.rs
@@ -1466,10 +1466,17 @@ impl NetService {
     /// Permanently remove one binding — or the port range at the same key,
     /// which `bindings` and `binding_ranges` share — and its exported service
     /// interfaces, returning its external ports to the pool. `false` if nothing
-    /// was bound at `internal_port`.
+    /// was bound at `internal_port`. What was retired is recorded on the host
+    /// with `successor`, the port the service moved it to, so a plugin holding
+    /// an address for the old port can follow it.
     ///
     /// The host survives, so the ordinary reconcile tears the datapath down.
-    pub async fn retire_binding(&self, id: HostId, internal_port: u16) -> Result<bool, Error> {
+    pub async fn retire_binding(
+        &self,
+        id: HostId,
+        internal_port: u16,
+        successor: Option<u16>,
+    ) -> Result<bool, Error> {
         let (ctrl, pkg_id) = {
             let data = self.data.lock().await;
             (data.net_controller()?, data.id.clone())
@@ -1506,6 +1513,10 @@ impl NetService {
                 if !retired {
                     return Ok(false);
                 }
+                host.as_retired_bindings_mut().mutate(|r| {
+                    r.insert(internal_port, successor);
+                    Ok(())
+                })?;
                 // `port_forwards` is computed from the bindings, so it still
                 // advertises the retired one until this re-derives it.
                 host.update_addresses(&hostname, &gateways, &ports)?;
diff --git a/shared-libs/crates/start-core/src/service/effects/net/bind.rs b/shared-libs/crates/start-core/src/service/effects/net/bind.rs
index 0dcceaa994..43eedaf08f 100644
--- a/shared-libs/crates/start-core/src/service/effects/net/bind.rs
+++ b/shared-libs/crates/start-core/src/service/effects/net/bind.rs
@@ -128,18 +128,24 @@ pub async fn retire_host(
 pub struct RetireBindingParams {
     pub id: HostId,
     pub internal_port: u16,
+    #[ts(optional)]
+    pub successor: Option<u16>,
 }
 
 pub async fn retire_binding(
     context: EffectContext,
-    RetireBindingParams { id, internal_port }: RetireBindingParams,
+    RetireBindingParams {
+        id,
+        internal_port,
+        successor,
+    }: RetireBindingParams,
 ) -> Result<bool, Error> {
     let context = context.deref()?;
     context
         .seed
         .persistent_container
         .net_service
-        .retire_binding(id, internal_port)
+        .retire_binding(id, internal_port, successor)
         .await
 }
 
diff --git a/shared-libs/ts-modules/start-core/lib/Effects.ts b/shared-libs/ts-modules/start-core/lib/Effects.ts
index c05c66bd08..c554c40c8d 100644
--- a/shared-libs/ts-modules/start-core/lib/Effects.ts
+++ b/shared-libs/ts-modules/start-core/lib/Effects.ts
@@ -205,7 +205,8 @@ export type Effects = {
    * Permanently removes whichever of the single-port binding and the port range
    * is bound at `internalPort` — and both, if both are — along with their
    * exported service interfaces. The external ports return to the server's
-   * pool. The host survives, keeping its domains.
+   * pool. The host survives, keeping its domains, and records the retired
+   * port with its `successor` in `retiredBindings`.
    *
    * Resolves `false` if nothing was bound at `internalPort`.
    */
diff --git a/shared-libs/ts-modules/start-core/lib/interfaces/Host.ts b/shared-libs/ts-modules/start-core/lib/interfaces/Host.ts
index b409039f44..494e3c4f6f 100644
--- a/shared-libs/ts-modules/start-core/lib/interfaces/Host.ts
+++ b/shared-libs/ts-modules/start-core/lib/interfaces/Host.ts
@@ -279,6 +279,10 @@ export class MultiHost {
    * @param internalPort - the container-side port passed to
    * {@link MultiHost.bindPort}, or the `internalStartPort` passed to
    * {@link MultiHost.bindPortRange}
+   * @param options.successor - the port on this host the service now serves
+   * in its place. Recorded on the host, so a URL plugin such as Tor moves an
+   * address it holds for the old port instead of parking it. Omit it when
+   * nothing replaces the port.
    * @returns `true` if something was removed, `false` if nothing was bound
    * there — the normal result on a re-run, not an error.
    *
@@ -286,12 +290,18 @@ export class MultiHost {
    * ```
    * // upstream dropped the bundled metrics listener in 3.0
    * await sdk.MultiHost.of(effects, 'api').retirePort(9090)
+   * // the P2P listener moved from 8333 to 58333
+   * await sdk.MultiHost.of(effects, 'peer').retirePort(8333, { successor: 58333 })
    * ```
    */
-  async retirePort(internalPort: number): Promise<boolean> {
+  async retirePort(
+    internalPort: number,
+    options?: { successor?: number },
+  ): Promise<boolean> {
     return this.options.effects.retireBinding({
       id: this.options.id,
       internalPort,
+      successor: options?.successor,
     })
   }