diff --git a/packages/core/local-protocols/schemas/queuedTasks.prs b/packages/core/local-protocols/schemas/queuedTasks.prs
index 7c4877d..94744f7 100644
--- a/packages/core/local-protocols/schemas/queuedTasks.prs
+++ b/packages/core/local-protocols/schemas/queuedTasks.prs
@@ -5,10 +5,12 @@ ActionDescription =
 / @spawnActor <spawn-actor @detail OptionalAny @initialAssertions #{protocol.Handle}>
 / @stopActor <stop-actor @error OptionalAny>
 / @inertCheck <inert-check>
-/ <assert @target #!any @handle protocol.Handle @assertion any>
-/ <retract @target #!any @handle protocol.Handle>
+/ <assert @target #!any @crossSpacePins CrossSpacePins @handle protocol.Handle @assertion any>
+/ <retract @target #!any @crossSpace bool @handle protocol.Handle>
 / <message @target #!any @assertion any>
 / <sync @target #!any @callback #!any>
 .
 
+CrossSpacePins = @none #f / @some [#!any ...] .
+
 OptionalAny = <none> / <some @value any> .
diff --git a/packages/core/package.json b/packages/core/package.json
index 5a21b5b..2add573 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -29,8 +29,8 @@
   "types": "lib/index.d.ts",
   "author": "Tony Garnock-Jones <tonyg@leastfixedpoint.com>",
   "dependencies": {
-    "@preserves/core": "0.21.1",
-    "@preserves/schema": "0.22.1",
+    "@preserves/core": "0.22",
+    "@preserves/schema": "0.22.3",
     "salty-crypto": "0.3.1"
   }
 }
diff --git a/packages/core/src/runtime/actor.ts b/packages/core/src/runtime/actor.ts
index 71f5b25..a245893 100644
--- a/packages/core/src/runtime/actor.ts
+++ b/packages/core/src/runtime/actor.ts
@@ -84,7 +84,7 @@ export function assertionFrom(a: Assertable): Assertion {
     }
 }
 
-type OutboundAssertion = { handle: Handle, peer: Ref, established: boolean };
+type OutboundAssertion = { handle: Handle, peer: Ref, crossSpacePins: Ref[] | null, established: boolean };
 type OutboundMap = Map<Handle, OutboundAssertion>;
 
 let nextActorId = 0;
@@ -205,7 +205,12 @@ export class Facet {
 
     _halfLink(other: Facet): void {
         const h = nextHandle++;
-        const e = { handle: h, peer: { relay: other, target: new StopOnRetract() }, established: true };
+        const e = {
+            handle: h,
+            peer: { relay: other, target: new StopOnRetract() },
+            crossSpacePins: null,
+            established: true,
+        };
         this.outbound.set(h, e);
     }
 
@@ -449,15 +454,23 @@ export class Turn {
         const assertion = assertionFrom(assertable);
         const a = runRewrites(ref.attenuation, assertion);
         if (a !== null) {
-            const e = { handle: h, peer: ref, established: false };
+            const crossSpace = this.activeFacet.actor.space !== ref.relay.actor.space;
+            const pins = crossSpace ? this.activeFacet.actor.space.extractPins(a) : null;
+            const e = { handle: h, peer: ref, crossSpacePins: pins, established: false };
             this.activeFacet.outbound.set(h, e);
             this.enqueue(ref.relay,
                          () => {
                              e.established = true;
+                             if (crossSpace) {
+                                 ref.relay.actor.space.registerInbound(h, ref, a);
+                             }
                              ref.target.assert?.(a, h);
                          },
                          () => Q.ActionDescription.assert({
                              target: ref,
+                             crossSpacePins: (pins === null
+                                 ? Q.CrossSpacePins.none()
+                                 : Q.CrossSpacePins.some(pins)),
                              handle: h,
                              assertion,
                          }));
@@ -486,11 +499,13 @@ export class Turn {
                      () => {
                          if (e.established) {
                              e.established = false;
+                             if (e.crossSpacePins) e.peer.relay.actor.space.deregisterInbound(e.handle);
                              e.peer.target.retract?.(e.handle);
                          }
                      },
                      () => Q.ActionDescription.retract({
                          target: e.peer,
+                         crossSpace: e.crossSpacePins !== null,
                          handle: e.handle,
                      }));
     }
diff --git a/packages/core/src/runtime/space.ts b/packages/core/src/runtime/space.ts
index ac627ce..dee9a07 100644
--- a/packages/core/src/runtime/space.ts
+++ b/packages/core/src/runtime/space.ts
@@ -1,8 +1,8 @@
 /// SPDX-License-Identifier: GPL-3.0-or-later
 /// SPDX-FileCopyrightText: Copyright © 2023 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
 
-import { IdentitySet } from '@preserves/core';
-import type { Actor, ExitReason } from './actor.js';
+import { IdentityMap, IdentitySet, forEachEmbedded } from '@preserves/core';
+import type { Actor, Assertion, ExitReason, Handle, Ref } from './actor.js';
 import type { StructuredTask, TaskDescription } from './task.js';
 
 const LIMIT = 25000;
@@ -13,9 +13,12 @@ export enum ActorSpaceState {
     TERMINATED,
 }
 
+export type InboundAssertion = { target: Ref, pins: Ref[] };
+
 export class ActorSpace {
     actors = new IdentitySet<Actor>();
     state = ActorSpaceState.RUNNING;
+    inboundAssertions = new IdentityMap<Handle, InboundAssertion>();
 
     taskCounter = 0;
     delayedTasks: Array<StructuredTask<TaskDescription>> = [];
@@ -34,6 +37,24 @@ export class ActorSpace {
         }
     }
 
+    extractPins(assertion: Assertion): Ref[] {
+        const pins: Ref[] = [];
+        forEachEmbedded(assertion, (r: Ref) => {
+            if (r.relay.actor.space === this) {
+                pins.push(r);
+            }
+        });
+        return pins;
+    }
+
+    registerInbound(handle: Handle, target: Ref, assertion: Assertion) {
+        this.inboundAssertions.set(handle, { target, pins: this.extractPins(assertion) });
+    }
+
+    deregisterInbound(handle: Handle) {
+        this.inboundAssertions.delete(handle);
+    }
+
     shutdown(reason: Exclude<ExitReason, null>) {
         if (this.state === ActorSpaceState.TERMINATED) return;
         this.state = ActorSpaceState.TERMINATED;
diff --git a/packages/create/template/package.json b/packages/create/template/package.json
index d4bc168..b822931 100644
--- a/packages/create/template/package.json
+++ b/packages/create/template/package.json
@@ -3,8 +3,8 @@
   "version": "0.0.0",
   "license": "GPL-3.0+",
   "devDependencies": {
-    "@preserves/core": "0.21.1",
-    "@preserves/schema": "0.22.1",
+    "@preserves/core": "0.22",
+    "@preserves/schema": "0.22.3",
     "@syndicate-lang/ts-plugin": "*",
     "@syndicate-lang/tsc": "*",
     "rollup": "^2.60",
diff --git a/packages/fs/package.json b/packages/fs/package.json
index 9fc4975..6f64eb9 100644
--- a/packages/fs/package.json
+++ b/packages/fs/package.json
@@ -27,8 +27,8 @@
     "syndicate-fs": "./bin/syndicate-fs.js"
   },
   "dependencies": {
-    "@preserves/core": "0.21.1",
-    "@preserves/schema": "0.22.1",
+    "@preserves/core": "0.22",
+    "@preserves/schema": "0.22.3",
     "@syndicate-lang/core": "^0.15.1",
     "@syndicate-lang/service": "^0.15.2",
     "chokidar": "^3.5.3"
diff --git a/packages/ws-relay/package.json b/packages/ws-relay/package.json
index 7ced3ca..c3a7f2b 100644
--- a/packages/ws-relay/package.json
+++ b/packages/ws-relay/package.json
@@ -25,7 +25,7 @@
   "types": "lib/index.d.ts",
   "author": "Tony Garnock-Jones <tonyg@leastfixedpoint.com>",
   "dependencies": {
-    "@preserves/core": "0.21.1",
+    "@preserves/core": "0.22",
     "@syndicate-lang/core": "^0.15.1",
     "salty-crypto": "0.3"
   },
diff --git a/yarn.lock b/yarn.lock
index 421623f..46c937c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1415,17 +1415,17 @@
   dependencies:
     "@octokit/openapi-types" "^12.11.0"
 
-"@preserves/core@0.21.1", "@preserves/core@^0.21.1":
-  version "0.21.1"
-  resolved "https://registry.yarnpkg.com/@preserves/core/-/core-0.21.1.tgz#1e441c9f1e43b7f94543f15f85db6918780f03b5"
-  integrity sha512-oxgC9YV9PSj2xYfkQdI28RkDIEF2iKvoRZliutRG9Rxc+lvaO93Aj5QepXyPu4U/mJsm6aXPsbXtB84MFUTe4A==
+"@preserves/core@0.22", "@preserves/core@^0.22.0":
+  version "0.22.0"
+  resolved "https://registry.yarnpkg.com/@preserves/core/-/core-0.22.0.tgz#623a288dd6aa9dc88ce701d03fbfe3bf26720ced"
+  integrity sha512-7+mjuimRKK/RE8U/82nZ8QR0RLGkVv/R1F6xkWbhr0UJiWVfLByLMm8xWGffDCx9IGhMRRuawXkAuF23hx2EEw==
 
-"@preserves/schema@0.22.1":
-  version "0.22.1"
-  resolved "https://registry.yarnpkg.com/@preserves/schema/-/schema-0.22.1.tgz#5d9383d90247861ca33f35d255dd0db30f426370"
-  integrity sha512-uJHRrEdgcvMLGu6jN/W772q5lhZK6eLUR4jmovrTBUfMV6b3Es7D9yVweYoNvHrAXg4HV2kyh1p6KGkTzNsAAw==
+"@preserves/schema@0.22.3":
+  version "0.22.3"
+  resolved "https://registry.yarnpkg.com/@preserves/schema/-/schema-0.22.3.tgz#326d2123963b5015b040a2ec1c1c64d1d4838df8"
+  integrity sha512-sgcs7odGDm+ilmSmwVLMSbXwOpscNmm1CfJcYkucZy3ZzisXHc1uvpQdMAoUTLZep1QU1L0QCQDYD/22KnDQAA==
   dependencies:
-    "@preserves/core" "^0.21.1"
+    "@preserves/core" "^0.22.0"
     "@types/glob" "^7.1"
     "@types/minimatch" "^3.0"
     chalk "^4.1"