diff --git a/packages/3-extensions/sql-orm-client/src/collection-contract.ts b/packages/3-extensions/sql-orm-client/src/collection-contract.ts
index c09d7626999e..2174ee9f0426 100644
--- a/packages/3-extensions/sql-orm-client/src/collection-contract.ts
+++ b/packages/3-extensions/sql-orm-client/src/collection-contract.ts
@@ -300,8 +300,10 @@ export interface ResolvedIncludeRelation {
   readonly relatedNamespaceId: string;
   readonly relatedTableName: string;
   readonly localTableName: string;
-  readonly targetColumn: string;
-  readonly localColumn: string;
+  /** Target-side join columns, positionally paired with `localColumns`. */
+  readonly targetColumns: readonly string[];
+  /** Local-side join columns, positionally paired with `targetColumns`. */
+  readonly localColumns: readonly string[];
   readonly cardinality: RelationCardinalityTag | undefined;
   readonly through?: IncludeThroughDescriptor;
 }
@@ -336,22 +338,31 @@ export function resolveIncludeRelation(
       { meta: { model: baseModelName, relation: relationName } },
     );
   }
-  const localField = relation.on.localFields[0];
-  const targetField = relation.on.targetFields[0];
-  if (!localField || !targetField) {
+  const localFields = relation.on.localFields;
+  const targetFields = relation.on.targetFields;
+  const localColumns: string[] = [];
+  const targetColumns: string[] = [];
+  const pairCount = Math.min(localFields.length, targetFields.length);
+
+  for (let i = 0; i < pairCount; i++) {
+    const localField = localFields[i];
+    const targetField = targetFields[i];
+    if (!localField || !targetField) {
+      continue;
+    }
+    localColumns.push(resolveFieldToColumn(contract, namespaceId, declaringModelName, localField));
+    targetColumns.push(
+      resolveFieldToColumn(contract, relation.toNamespace, relation.to, targetField),
+    );
+  }
+
+  if (localColumns.length === 0) {
     throw new InternalError(
       `Relation '${relationName}' on model '${declaringModelName}' has incomplete join metadata (missing localFields or targetFields)`,
     );
   }
 
   const relatedTableName = resolveModelTableName(contract, relation.toNamespace, relation.to);
-  const localColumn = resolveFieldToColumn(contract, namespaceId, declaringModelName, localField);
-  const targetColumn = resolveFieldToColumn(
-    contract,
-    relation.toNamespace,
-    relation.to,
-    targetField,
-  );
 
   let through: IncludeThroughDescriptor | undefined;
   if (relation.through !== undefined) {
@@ -373,8 +384,8 @@ export function resolveIncludeRelation(
     relatedNamespaceId: relation.toNamespace,
     relatedTableName,
     localTableName,
-    targetColumn,
-    localColumn,
+    targetColumns,
+    localColumns,
     cardinality: relation.cardinality,
     ...ifDefined('through', through),
   };
diff --git a/packages/3-extensions/sql-orm-client/src/collection.ts b/packages/3-extensions/sql-orm-client/src/collection.ts
index 922c8ab81dbe..bc486d356a58 100644
--- a/packages/3-extensions/sql-orm-client/src/collection.ts
+++ b/packages/3-extensions/sql-orm-client/src/collection.ts
@@ -618,8 +618,8 @@ class CollectionImpl<
       relatedNamespaceId: relation.relatedNamespaceId,
       relatedTableName: relation.relatedTableName,
       localTableName: relation.localTableName,
-      targetColumn: relation.targetColumn,
-      localColumn: relation.localColumn,
+      targetColumns: relation.targetColumns,
+      localColumns: relation.localColumns,
       cardinality: relation.cardinality,
       ...ifDefined('through', relation.through),
       nested: nestedState,
diff --git a/packages/3-extensions/sql-orm-client/src/query-plan-select.ts b/packages/3-extensions/sql-orm-client/src/query-plan-select.ts
index 0153fcc6b43a..8cf5c32bf5ed 100644
--- a/packages/3-extensions/sql-orm-client/src/query-plan-select.ts
+++ b/packages/3-extensions/sql-orm-client/src/query-plan-select.ts
@@ -261,7 +261,36 @@ interface IncludeParentSource {
 }
 
 function localColumnsForRowInclude(include: IncludeExpr): readonly string[] {
-  return include.through?.parentLocalColumns ?? [include.localColumn];
+  return include.through?.parentLocalColumns ?? include.localColumns;
+}
+
+/**
+ * Correlate a child row back to its parent across every column of the
+ * relation's key. Composite foreign keys contribute one equality per
+ * column, ANDed together — mirroring the relation-filter join in
+ * `model-accessor.ts`. Correlating on a prefix of the key would match
+ * every child sharing that prefix.
+ */
+function buildIncludeJoinExpr(
+  include: IncludeExpr,
+  childTableRef: string,
+  parentLocalRefs: readonly ColumnRef[],
+): AnyExpression {
+  const joinExprs: AnyExpression[] = [];
+  const count = Math.min(parentLocalRefs.length, include.targetColumns.length);
+
+  for (let i = 0; i < count; i++) {
+    const parentLocalRef = parentLocalRefs[i];
+    const targetColumn = include.targetColumns[i];
+    if (parentLocalRef === undefined || targetColumn === undefined) {
+      continue;
+    }
+    joinExprs.push(BinaryExpr.eq(ColumnRef.of(childTableRef, targetColumn), parentLocalRef));
+  }
+
+  const firstExpr = joinExprs[0];
+  assertDefined(firstExpr, `Include '${include.relationName}' has no parent-local column ref`);
+  return joinExprs.length === 1 ? firstExpr : AndExpr.of(joinExprs);
 }
 
 function resolveParentLocalRefs(
@@ -578,15 +607,7 @@ function buildIncludeChildRowsSelect(
     whereExpr = childWhere ? AndExpr.of([artifacts.whereExpr, childWhere]) : artifacts.whereExpr;
     junctionJoins = [artifacts.junctionJoin];
   } else {
-    const parentLocalRef = parentLocalRefs[0];
-    assertDefined(
-      parentLocalRef,
-      `Include '${include.relationName}' has no parent-local column ref`,
-    );
-    const joinExpr = BinaryExpr.eq(
-      ColumnRef.of(childTableRef, include.targetColumn),
-      parentLocalRef,
-    );
+    const joinExpr = buildIncludeJoinExpr(include, childTableRef, parentLocalRefs);
     whereExpr = childWhere ? AndExpr.of([joinExpr, childWhere]) : joinExpr;
   }
 
@@ -1019,15 +1040,7 @@ function buildIncludeChildScalarSelect(
     whereExpr = childWhere ? AndExpr.of([artifacts.whereExpr, childWhere]) : artifacts.whereExpr;
     junctionJoins = [artifacts.junctionJoin];
   } else {
-    const parentLocalRef = parentLocalRefs[0];
-    assertDefined(
-      parentLocalRef,
-      `Include '${include.relationName}' has no parent-local column ref`,
-    );
-    const joinExpr = BinaryExpr.eq(
-      ColumnRef.of(childTableRef, include.targetColumn),
-      parentLocalRef,
-    );
+    const joinExpr = buildIncludeJoinExpr(include, childTableRef, parentLocalRefs);
     whereExpr = childWhere ? AndExpr.of([joinExpr, childWhere]) : joinExpr;
   }
 
diff --git a/packages/3-extensions/sql-orm-client/src/types.ts b/packages/3-extensions/sql-orm-client/src/types.ts
index f8f8efe8f583..238526d1ee0c 100644
--- a/packages/3-extensions/sql-orm-client/src/types.ts
+++ b/packages/3-extensions/sql-orm-client/src/types.ts
@@ -72,8 +72,10 @@ export interface IncludeExpr {
   readonly relatedNamespaceId: string;
   readonly relatedTableName: string;
   readonly localTableName: string;
-  readonly targetColumn: string;
-  readonly localColumn: string;
+  /** Target-side join columns, positionally paired with `localColumns`. */
+  readonly targetColumns: readonly string[];
+  /** Local-side join columns, positionally paired with `targetColumns`. */
+  readonly localColumns: readonly string[];
   readonly cardinality: RelationCardinalityTag | undefined;
   readonly through?: IncludeThroughDescriptor;
   readonly nested: CollectionState;
diff --git a/packages/3-extensions/sql-orm-client/test/collection-contract.test.ts b/packages/3-extensions/sql-orm-client/test/collection-contract.test.ts
index b78e06c5841b..df6b9ab8d51b 100644
--- a/packages/3-extensions/sql-orm-client/test/collection-contract.test.ts
+++ b/packages/3-extensions/sql-orm-client/test/collection-contract.test.ts
@@ -102,8 +102,38 @@ describe('collection-contract capability detection', () => {
       relatedNamespaceId: 'public',
       relatedTableName: 'posts',
       localTableName: 'users',
-      targetColumn: 'user_id',
-      localColumn: 'id',
+      targetColumns: ['user_id'],
+      localColumns: ['id'],
+      cardinality: '1:N',
+    });
+  });
+
+  it('resolveIncludeRelation() resolves every column of a composite foreign key', () => {
+    const composite = withPatchedDomainModels(getTestContract(), (models) => {
+      const user = models['User'] as Record<string, unknown>;
+      return {
+        ...models,
+        User: {
+          ...user,
+          relations: {
+            ...(user['relations'] as Record<string, unknown>),
+            posts: {
+              to: { model: 'Post', namespace: 'public' },
+              cardinality: '1:N',
+              on: { localFields: ['id', 'email'], targetFields: ['userId', 'title'] },
+            },
+          },
+        },
+      };
+    });
+
+    expect(resolveIncludeRelation(composite, 'public', 'User', 'posts')).toEqual({
+      relatedModelName: 'Post',
+      relatedNamespaceId: 'public',
+      relatedTableName: 'posts',
+      localTableName: 'users',
+      targetColumns: ['user_id', 'title'],
+      localColumns: ['id', 'email'],
       cardinality: '1:N',
     });
   });
diff --git a/packages/3-extensions/sql-orm-client/test/collection-dispatch.test.ts b/packages/3-extensions/sql-orm-client/test/collection-dispatch.test.ts
index 551f60101276..0cc5a7dfbd23 100644
--- a/packages/3-extensions/sql-orm-client/test/collection-dispatch.test.ts
+++ b/packages/3-extensions/sql-orm-client/test/collection-dispatch.test.ts
@@ -31,8 +31,8 @@ function includeFor(
     relatedTableName: relation.relatedTableName,
     relatedNamespaceId: relation.relatedNamespaceId,
     localTableName: relation.localTableName,
-    targetColumn: relation.targetColumn,
-    localColumn: relation.localColumn,
+    targetColumns: relation.targetColumns,
+    localColumns: relation.localColumns,
     cardinality: relation.cardinality,
     nested,
     scalar: undefined,
diff --git a/packages/3-extensions/sql-orm-client/test/collection.state.test.ts b/packages/3-extensions/sql-orm-client/test/collection.state.test.ts
index 6c064fb68c86..8f399328493a 100644
--- a/packages/3-extensions/sql-orm-client/test/collection.state.test.ts
+++ b/packages/3-extensions/sql-orm-client/test/collection.state.test.ts
@@ -188,7 +188,7 @@ describe('Collection', () => {
         relationName: 'posts',
         relatedModelName: 'Post',
         relatedTableName: 'posts',
-        targetColumn: 'user_id',
+        targetColumns: ['user_id'],
         cardinality: '1:N',
       });
       expect(withPosts.state.includes[0]?.nested.filters).toEqual([
@@ -240,8 +240,8 @@ describe('Collection', () => {
         relationName: 'author',
         relatedModelName: 'User',
         relatedTableName: 'users',
-        targetColumn: 'id',
-        localColumn: 'user_id',
+        targetColumns: ['id'],
+        localColumns: ['user_id'],
         cardinality: 'N:1',
       });
 
diff --git a/packages/3-extensions/sql-orm-client/test/query-plan-select.test.ts b/packages/3-extensions/sql-orm-client/test/query-plan-select.test.ts
index a3b96bf86d40..8bde9d2a12be 100644
--- a/packages/3-extensions/sql-orm-client/test/query-plan-select.test.ts
+++ b/packages/3-extensions/sql-orm-client/test/query-plan-select.test.ts
@@ -144,6 +144,43 @@ describe('compileSelectWithIncludes', () => {
     );
   });
 
+  it('correlates a composite foreign key on every column pair', () => {
+    const include: IncludeExpr = {
+      relationName: 'posts',
+      relatedModelName: 'Post',
+      relatedNamespaceId: 'public',
+      relatedTableName: 'posts',
+      localTableName: 'users',
+      targetColumns: ['user_id', 'title'],
+      localColumns: ['id', 'email'],
+      cardinality: '1:N',
+      nested: emptyState(),
+      scalar: undefined,
+      combine: undefined,
+    };
+
+    const plan = compileSelectWithIncludes(baseContract, getTestAggregates(), 'public', 'users', {
+      ...emptyState(),
+      includes: [include],
+    });
+
+    expectSelectAst(plan.ast);
+    const postsProjection = plan.ast.projection.find((item) => item.alias === 'posts');
+    expectSubqueryExpr(postsProjection?.expr);
+
+    const childRowsSource = postsProjection.expr.query.from;
+    expectDerivedTableSource(childRowsSource);
+
+    // Correlating on `user_id` alone would match every post sharing it,
+    // so both pairs of the key have to appear.
+    expect(childRowsSource.query.where).toEqual(
+      AndExpr.of([
+        BinaryExpr.eq(ColumnRef.of('posts', 'user_id'), ColumnRef.of('users', 'id')),
+        BinaryExpr.eq(ColumnRef.of('posts', 'title'), ColumnRef.of('users', 'email')),
+      ]),
+    );
+  });
+
   it('builds lexicographic cursor filters with distinctOn, limit, and offset', () => {
     const { collection } = createCollection();
     const state = collection
@@ -1400,8 +1437,8 @@ describe('compileSelectWithIncludes polymorphic targets', () => {
       relatedTableName: relation.relatedTableName,
       relatedNamespaceId: relation.relatedNamespaceId,
       localTableName: relation.localTableName,
-      targetColumn: relation.targetColumn,
-      localColumn: relation.localColumn,
+      targetColumns: relation.targetColumns,
+      localColumns: relation.localColumns,
       cardinality: relation.cardinality,
       nested,
       scalar: undefined,
diff --git a/packages/3-extensions/sql-orm-client/test/variant-include.collection-contract.test.ts b/packages/3-extensions/sql-orm-client/test/variant-include.collection-contract.test.ts
index 6651e02409ac..18b17c165ad4 100644
--- a/packages/3-extensions/sql-orm-client/test/variant-include.collection-contract.test.ts
+++ b/packages/3-extensions/sql-orm-client/test/variant-include.collection-contract.test.ts
@@ -17,8 +17,8 @@ describe('resolveIncludeRelation() with a selected parent variant', () => {
       relatedNamespaceId: 'public',
       relatedTableName: 'assignees',
       localTableName: 'features',
-      localColumn: 'assignee_id',
-      targetColumn: 'id',
+      localColumns: ['assignee_id'],
+      targetColumns: ['id'],
       cardinality: 'N:1',
     });
   });
@@ -37,8 +37,8 @@ describe('resolveIncludeRelation() with a selected parent variant', () => {
       relatedNamespaceId: 'public',
       relatedTableName: 'assignees',
       localTableName: 'tasks',
-      localColumn: 'assignee_id',
-      targetColumn: 'id',
+      localColumns: ['assignee_id'],
+      targetColumns: ['id'],
       cardinality: 'N:1',
     });
   });
@@ -57,8 +57,8 @@ describe('resolveIncludeRelation() with a selected parent variant', () => {
       relatedNamespaceId: 'public',
       relatedTableName: 'tasks',
       localTableName: 'tasks',
-      localColumn: 'id',
-      targetColumn: 'parent_id',
+      localColumns: ['id'],
+      targetColumns: ['parent_id'],
       cardinality: '1:N',
     });
   });
diff --git a/packages/3-extensions/sql-orm-client/test/variant-include.query-plan-fixtures.ts b/packages/3-extensions/sql-orm-client/test/variant-include.query-plan-fixtures.ts
index 44df4657ba4b..82494b992bde 100644
--- a/packages/3-extensions/sql-orm-client/test/variant-include.query-plan-fixtures.ts
+++ b/packages/3-extensions/sql-orm-client/test/variant-include.query-plan-fixtures.ts
@@ -45,8 +45,8 @@ export function includeExpr(options: {
     relatedNamespaceId: 'public',
     relatedTableName: options.relatedTableName,
     localTableName: options.localTableName,
-    targetColumn: options.targetColumn,
-    localColumn: options.localColumn,
+    targetColumns: [options.targetColumn],
+    localColumns: [options.localColumn],
     cardinality: options.cardinality,
     ...ifDefined('through', options.through),
     nested: options.nested ?? emptyState(),