diff --git a/src/Schema.php b/src/Schema.php
index c178e82..1e02a43 100644
--- a/src/Schema.php
+++ b/src/Schema.php
@@ -74,11 +74,15 @@ public static function create(string $table, callable $callback, ?string $connec
             $conn->statement($idx);
         }
 
-        // Foreign keys already inlined in CREATE TABLE for MySQL.
-        // For PostgreSQL emit separately if any.
-        foreach ($grammar->compileForeignKeys($blueprint) as $fk) {
-            $conn->statement($fk);
-        }
+        // Foreign keys are already inlined as column-level CONSTRAINTs by
+        // compileCreate() above (see SchemaGrammar::compileCreate()), so
+        // they must NOT be re-emitted here via compileForeignKeys() — doing
+        // so duplicates every constraint as a separate ALTER TABLE ADD
+        // CONSTRAINT statement, which MySQL rejects (errno 121, duplicate
+        // constraint) and SQLite rejects outright (ALTER TABLE ADD
+        // CONSTRAINT isn't valid SQLite DDL). compileForeignKeys() is still
+        // used correctly by Schema::table() below, where the table (and
+        // its inline constraints) already exist.
 
         // PostgreSQL column comments (separate COMMENT ON COLUMN statements)
         if ($grammar instanceof PostgresSchemaGrammar) {
diff --git a/tests/Integration/SchemaForeignKeyTest.php b/tests/Integration/SchemaForeignKeyTest.php
new file mode 100644
index 0000000..375659a
--- /dev/null
+++ b/tests/Integration/SchemaForeignKeyTest.php
@@ -0,0 +1,129 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Foxdb\Tests\Integration;
+
+use Foxdb\Schema;
+use Foxdb\Schema\Blueprint;
+
+/**
+ * Regression coverage for Schema::create() double-emitting foreign key
+ * constraints.
+ *
+ * Schema::create() compiles the CREATE TABLE statement (which already
+ * inlines every `$table->foreign()` as a column-level CONSTRAINT, see
+ * SchemaGrammar::compileCreate()) and then, unconditionally, ALSO runs
+ * SchemaGrammar::compileForeignKeys() — which re-emits the very same
+ * constraints as separate `ALTER TABLE ... ADD CONSTRAINT` statements.
+ * No grammar overrides compileForeignKeys() to suppress this for the
+ * "already inlined at CREATE TABLE time" case, so every driver executes
+ * a duplicate constraint statement:
+ *
+ *  - MySQL:  rejects the duplicate constraint name (errno 121,
+ *            "Duplicate key on write or update").
+ *  - SQLite: has no `ALTER TABLE ... ADD CONSTRAINT` syntax at all, so
+ *            the statement is a hard syntax error.
+ *
+ * A table defined with `$table->foreign()` therefore cannot be created
+ * via Schema::create() on any driver.
+ */
+class SchemaForeignKeyTest extends IntegrationTestCase
+{
+    public function testCreateWithForeignKeyDoesNotThrow(): void
+    {
+        $parent = 'sfk_test_parents';
+        $child  = 'sfk_test_children';
+
+        try {
+            Schema::create($parent, function (Blueprint $t) {
+                $t->id();
+                $t->string('name')->nullable();
+            });
+
+            Schema::create($child, function (Blueprint $t) use ($parent) {
+                $t->id();
+                $t->bigInteger('parent_id')->unsigned();
+                $t->foreign('parent_id')->references('id')->on($parent)->cascadeOnDelete();
+            });
+
+            $this->assertTrue(Schema::hasTable($child));
+        } finally {
+            Schema::dropIfExists($child);
+            Schema::dropIfExists($parent);
+        }
+    }
+
+    /**
+     * SQLite never enforces foreign keys unless the connection issues
+     * `PRAGMA foreign_keys = ON` — this library does not do so, which is a
+     * separate, pre-existing gap unrelated to the double-emission bug this
+     * file targets. Skipped here rather than silently asserting something
+     * false for that driver.
+     */
+    public function testCreateWithForeignKeyActuallyEnforcesTheConstraint(): void
+    {
+        if (strtolower((string) (getenv('DB_DRIVER') ?: 'sqlite')) === 'sqlite') {
+            $this->markTestSkipped('SQLite FK enforcement requires PRAGMA foreign_keys=ON, which this library does not set (separate gap).');
+        }
+
+        $parent = 'sfk_test_parents2';
+        $child  = 'sfk_test_children2';
+
+        try {
+            Schema::create($parent, function (Blueprint $t) {
+                $t->id();
+            });
+
+            Schema::create($child, function (Blueprint $t) use ($parent) {
+                $t->id();
+                $t->bigInteger('parent_id')->unsigned();
+                $t->foreign('parent_id')->references('id')->on($parent);
+            });
+
+            // A reference to a non-existent parent row must be rejected —
+            // proof the constraint is really enforced by the DB, not just
+            // that CREATE TABLE happened to succeed some other way.
+            $threw = false;
+            try {
+                \Foxdb\DB::table($child)->insert(['parent_id' => 999999]);
+            } catch (\Throwable $e) {
+                $threw = true;
+            }
+            $this->assertTrue($threw, 'Expected the foreign key constraint to reject an orphan reference.');
+        } finally {
+            Schema::dropIfExists($child);
+            Schema::dropIfExists($parent);
+        }
+    }
+
+    public function testCreateWithMultipleForeignKeysOnSameTableDoesNotThrow(): void
+    {
+        $a = 'sfk_test_a';
+        $b = 'sfk_test_b';
+        $c = 'sfk_test_c';
+
+        try {
+            Schema::create($a, function (Blueprint $t) {
+                $t->id();
+            });
+            Schema::create($b, function (Blueprint $t) {
+                $t->id();
+            });
+
+            Schema::create($c, function (Blueprint $t) use ($a, $b) {
+                $t->id();
+                $t->bigInteger('a_id')->unsigned();
+                $t->bigInteger('b_id')->unsigned();
+                $t->foreign('a_id')->references('id')->on($a);
+                $t->foreign('b_id')->references('id')->on($b);
+            });
+
+            $this->assertTrue(Schema::hasTable($c));
+        } finally {
+            Schema::dropIfExists($c);
+            Schema::dropIfExists($b);
+            Schema::dropIfExists($a);
+        }
+    }
+}