diff --git a/packages/base/card-api.gts b/packages/base/card-api.gts
index 3a3693f6ece..0ca5b0540ec 100644
--- a/packages/base/card-api.gts
+++ b/packages/base/card-api.gts
@@ -1370,6 +1370,35 @@ function serializeNonPresentLink(
   };
 }
 
+// Whether the `includedScope` keeps this link target's resource out of
+// `included[]`. 'all' keeps every resident target, 'local' keeps only the
+// unsaved (`lid`-bearing) ones — the write shape, where `included` is a
+// co-creation manifest — and 'none' keeps none.
+function isExcludedByIncludedScope(
+  value: CardDef,
+  includedScope: SerializeOpts['includedScope'] = 'all',
+): boolean {
+  return value.id ? includedScope !== 'all' : includedScope === 'none';
+}
+
+// The relationship entry that stands in for a link target whose own resource
+// is not inlined: a saved target by `links.self` + `id`, an unsaved one by
+// `lid`. Every reference-only path — an already-visited target, a
+// scope-excluded one, and the tail of a full serialization — emits exactly
+// this, so the spellings cannot drift apart.
+function referenceRelationship(
+  value: CardDef,
+  relationshipType: string,
+  opts?: SerializeOpts,
+): Relationship {
+  return value.id
+    ? {
+        links: { self: makeRelativeURL(value.id, opts) },
+        data: { type: relationshipType, id: value.id },
+      }
+    : { data: { type: relationshipType, lid: value[localId] } };
+}
+
 class LinksTo<CardT extends LinkableDefConstructor> implements Field<CardT> {
   readonly fieldType = 'linksTo';
   private cardThunk: () => CardT;
@@ -1522,24 +1551,22 @@ class LinksTo<CardT extends LinkableDefConstructor> implements Field<CardT> {
         `linksTo field '${this.name}' cannot serialize a FileDef without an id`,
       );
     }
-    if (visited.has(value.id)) {
-      return {
-        relationships: {
-          [this.name]: {
-            links: {
-              self: makeRelativeURL(value.id, opts),
-            },
-            data: { type: relationshipType, id: value.id },
-          },
-        },
-      };
-    }
-    if (visited.has((value as CardDef)[localId])) {
+    // A target already serialized on this walk, or one the includedScope
+    // excludes, needs only its relationship entry — so the recursive
+    // serialization of the target, and the traversal of its own linked graph,
+    // is skipped entirely.
+    if (
+      visited.has(value.id) ||
+      visited.has((value as CardDef)[localId]) ||
+      isExcludedByIncludedScope(value as CardDef, opts?.includedScope)
+    ) {
       return {
         relationships: {
-          [this.name]: {
-            data: { type: relationshipType, lid: (value as CardDef)[localId] },
-          },
+          [this.name]: referenceRelationship(
+            value as CardDef,
+            relationshipType,
+            opts,
+          ),
         },
       };
     }
@@ -1556,21 +1583,11 @@ class LinksTo<CardT extends LinkableDefConstructor> implements Field<CardT> {
     if (serialized) {
       let resource: JSONAPIResource = {
         relationships: {
-          [this.name]: {
-            ...(value.id
-              ? {
-                  links: {
-                    self: makeRelativeURL(value.id, opts),
-                  },
-                  data: { type: relationshipType, id: value.id },
-                }
-              : {
-                  data: {
-                    type: relationshipType,
-                    lid: (value as CardDef)[localId],
-                  },
-                }),
-          },
+          [this.name]: referenceRelationship(
+            value as CardDef,
+            relationshipType,
+            opts,
+          ),
         },
       };
       if (
@@ -2094,19 +2111,19 @@ class LinksToMany<FieldT extends LinkableDefConstructor> implements Field<
           `linksToMany field '${this.name}' cannot serialize a FileDef without an id`,
         );
       }
-      if (visited.has(value.id)) {
-        relationships[`${this.name}.${i}`] = {
-          links: {
-            self: makeRelativeURL(value.id, opts),
-          },
-          data: { type: relationshipType, id: value.id },
-        };
-        return;
-      }
-      if (visited.has((value as CardDef)[localId])) {
-        relationships[`${this.name}.${i}`] = {
-          data: { type: relationshipType, lid: (value as CardDef)[localId] },
-        };
+      // Same reference-only rule as linksTo: a target already serialized on
+      // this walk, or one the includedScope excludes, contributes its
+      // relationship entry and nothing else.
+      if (
+        visited.has(value.id) ||
+        visited.has((value as CardDef)[localId]) ||
+        isExcludedByIncludedScope(value as CardDef, opts?.includedScope)
+      ) {
+        relationships[`${this.name}.${i}`] = referenceRelationship(
+          value as CardDef,
+          relationshipType,
+          opts,
+        );
         return;
       }
 
@@ -2134,21 +2151,11 @@ class LinksToMany<FieldT extends LinkableDefConstructor> implements Field<
         doc.included.push(serialized);
       }
 
-      relationships[`${this.name}.${i}`] = {
-        ...(value.id
-          ? {
-              links: {
-                self: makeRelativeURL(value.id, opts),
-              },
-              data: { type: relationshipType, id: value.id },
-            }
-          : {
-              data: {
-                type: relationshipType,
-                lid: (value as CardDef)[localId],
-              },
-            }),
-      };
+      relationships[`${this.name}.${i}`] = referenceRelationship(
+        value as CardDef,
+        relationshipType,
+        opts,
+      );
     });
 
     return { relationships };
diff --git a/packages/base/card-serialization.ts b/packages/base/card-serialization.ts
index 6dd656ab75d..60e1e2f40e9 100644
--- a/packages/base/card-serialization.ts
+++ b/packages/base/card-serialization.ts
@@ -75,6 +75,22 @@ export interface SerializeOpts {
   useAbsoluteURL?: boolean;
   omitFields?: [typeof BaseDef];
   omitQueryFields?: boolean;
+  // How much of the linked graph rides along in `included[]`. 'all' — the
+  // default, and what a direct `serializeCard` call gets — serializes every
+  // resident link target. 'local' serializes only the local (unsaved,
+  // `lid`-bearing) targets reachable without crossing an excluded one: the
+  // write shape, where `included` is a co-creation manifest and saved targets
+  // are reference-only. 'none' serializes no link targets at all.
+  //
+  // An excluded target contributes its relationship entry only, and its own
+  // linked graph is not traversed — which is the point: a new card linking
+  // into a large saved graph serializes none of that graph on save. Under
+  // 'local' that also bounds what a write co-creates to the local targets it
+  // reaches directly. An unsaved card hanging off a saved link is not
+  // co-created, because nothing the write persists could reference it: the
+  // saved link's own file is not rewritten, and the write's response names
+  // only the primary card, so its id would never reach the client.
+  includedScope?: 'all' | 'local' | 'none';
   maybeRelativeReference?: (possibleReference: string) => string;
   overrides?: Map<string, typeof BaseDef>;
 }
diff --git a/packages/host/app/services/card-service.ts b/packages/host/app/services/card-service.ts
index 66c69152a7b..b1c9df874b3 100644
--- a/packages/host/app/services/card-service.ts
+++ b/packages/host/app/services/card-service.ts
@@ -233,18 +233,32 @@ export default class CardService extends Service {
     return;
   }
 
+  // `includedScope` is this method's to decide — a caller states its intent
+  // with `withLocalResourcesIncluded` and the scope follows — so the parameter
+  // does not accept one rather than silently discarding it in the spread below.
   async serializeCard(
     card: CardDef,
-    opts?: SerializeOpts & { withIncluded?: true },
+    opts?: Omit<SerializeOpts, 'includedScope'> & {
+      withLocalResourcesIncluded?: true;
+    },
   ): Promise<LooseSingleCardDocument> {
     let api = await this.getAPI();
     if (opts?.includeComputeds) {
       await this.settleQueryBackedFields(api, card);
     }
+    // The scope pushes the realm's write-retention rule into the serializer
+    // itself: the realm keeps only the primary card plus the local (unsaved,
+    // `lid`-bearing) links it co-creates, and discards every already-saved
+    // link in `included` — so saved link targets are never serialized here at
+    // all, and a card linking into a large resident graph pays nothing for
+    // it on save.
     let serialized = api.serializeCard(card, {
       ...opts,
+      includedScope: opts?.withLocalResourcesIncluded ? 'local' : 'none',
     });
-    if (!opts?.withIncluded) {
+    if (!opts?.withLocalResourcesIncluded) {
+      // includedScope 'none' builds no included; the delete guards the
+      // contract against any custom serialize hook that pushes one anyway.
       delete serialized.included;
     }
     return serialized;
diff --git a/packages/host/app/services/store.ts b/packages/host/app/services/store.ts
index 7ab7320cbf5..28e77e957db 100644
--- a/packages/host/app/services/store.ts
+++ b/packages/host/app/services/store.ts
@@ -3582,7 +3582,7 @@ export default class StoreService extends Service implements StoreInterface {
               // relativeTo because its up to the realm server to assign us an ID, so
               // URL's should be absolute
               useAbsoluteURL: true,
-              withIncluded: true,
+              withLocalResourcesIncluded: true,
               omitQueryFields: true,
             });
 
diff --git a/packages/host/tests/integration/store-test.gts b/packages/host/tests/integration/store-test.gts
index 116ffd9a1ef..40747ba3582 100644
--- a/packages/host/tests/integration/store-test.gts
+++ b/packages/host/tests/integration/store-test.gts
@@ -2240,6 +2240,89 @@ module('Integration | Store', function (hooks) {
     }
   });
 
+  test('includedScope controls which link targets the serializer builds', async function (assert) {
+    // The write path's saving lives in the serializer itself: an excluded
+    // target contributes only its relationship entry, and neither it nor its
+    // own linked graph is serialized.
+    let cardService = getService('card-service') as any;
+    let api = await cardService.getAPI();
+
+    let saved = new PersonDef({ name: 'Saved' });
+    await (storeService as any).persistAndUpdate(saved);
+    let unsaved = new PersonDef({ name: 'Unsaved' });
+    let instance = new PersonDef({ name: 'Consumer' });
+    (instance as any).bestFriend = saved;
+    (instance as any).friends = [unsaved];
+
+    let all = api.serializeCard(instance, {
+      useAbsoluteURL: true,
+      includedScope: 'all',
+    });
+    assert.ok(
+      (all.included ?? []).find((r: any) => r.id === (saved as any).id),
+      "'all' serializes saved targets into included",
+    );
+    assert.ok(
+      (all.included ?? []).find(
+        (r: any) => r.lid === (unsaved as any)[localId],
+      ),
+      "'all' serializes local targets into included",
+    );
+
+    let local = api.serializeCard(instance, {
+      useAbsoluteURL: true,
+      includedScope: 'local',
+    });
+    assert.notOk(
+      (local.included ?? []).find((r: any) => r.id === (saved as any).id),
+      "'local' does not serialize saved targets",
+    );
+    assert.ok(
+      (local.included ?? []).find(
+        (r: any) => r.lid === (unsaved as any)[localId],
+      ),
+      "'local' serializes local targets — the write's co-creation manifest",
+    );
+
+    let none = api.serializeCard(instance, {
+      useAbsoluteURL: true,
+      includedScope: 'none',
+    });
+    assert.strictEqual(
+      none.included,
+      undefined,
+      "'none' builds no included at all",
+    );
+
+    // What makes the narrower scopes safe wherever they replace 'all': the
+    // primary resource is identical under every scope, because an excluded
+    // target emits the same reference relationship the full walk's tail does
+    // — `links.self` + `id` for a saved target, `lid` for a local one. Only
+    // `included` differs.
+    assert.deepEqual(
+      local.data,
+      all.data,
+      "'local' leaves the primary resource identical to 'all'",
+    );
+    assert.deepEqual(
+      none.data,
+      all.data,
+      "'none' leaves the primary resource identical to 'all'",
+    );
+
+    // The one write-path caller asks for the write shape by intent, and
+    // CardService maps that intent onto the 'local' scope.
+    let viaCardService = await cardService.serializeCard(instance, {
+      useAbsoluteURL: true,
+      withLocalResourcesIncluded: true,
+    });
+    assert.deepEqual(
+      viaCardService,
+      local,
+      "withLocalResourcesIncluded serializes at the 'local' scope",
+    );
+  });
+
   test('an oversized unsaved link created alongside a card still fails the size check', async function (assert) {
     // The counterpart that makes the per-resource filter load-bearing: a
     // `lid`-bearing side-load becomes its own file on the realm, so it must