diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index a0ec90a..eeb1281 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -30,7 +30,7 @@ jobs:
       RUN_WINDOWS_JOBS: 0
 
       PRIMARY_PHP_VERSION: '8.3'
-      PHP_VERSION_MATRIX: '["8.3", "8.4", "8.5"]'
+      PHP_VERSION_MATRIX: '["8.1", "8.3", "8.4", "8.5"]'
 
   # phpBB 4.0 (master): the same tests with the framework's master branch
   call-tests-master:
diff --git a/composer.json b/composer.json
index 4e2f230..75a9534 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,7 @@
 		}
 	],
 	"require": {
-		"php": ">=8.3.36",
+		"php": ">=8.1.0",
 		"composer/installers": "^1.0 || ^2.0"
 	},
 	"extra": {
diff --git a/docs/phpbb-4.0-compatibility.md b/docs/phpbb-4.0-compatibility.md
index 46fd862..1e39e59 100644
--- a/docs/phpbb-4.0-compatibility.md
+++ b/docs/phpbb-4.0-compatibility.md
@@ -11,8 +11,8 @@ From `composer.json`:
 - `require.phpbb/phpbb`: `>=3.3.19 <4.1.0`
 - `extra.soft-require.phpbb/phpbb`: `>=3.3.19,<4.1.0@dev` — phpBB 3.3.x and 4.0.x,
   including 4.0 development builds. (Until 10/12/2026 both said `<4.0.0`.)
-- `require.php`: `>=8.3.36` (also enforced when the extension is enabled, by `ext.php`,
-  due to security fixes; CI uses the latest PHP 8.3 patch release)
+- `require.php`: `>=8.1.0` (also enforced when the extension is enabled, by `ext.php`;
+  phpBB 4.0 itself needs PHP 8.2 or later)
 
 phpBB 4.0.x is still in development, so specifics below are marked
 verified vs. pending as they're confirmed against real code/changelog
@@ -162,8 +162,8 @@ rendered, and an article submitted through the posting form was saved without er
    3.3.x test board give the same result as before.
 
 **Declared support.** The PHP floor was raised from 8.0 to 8.2 on 10/12/2026, then to 8.3.36
-on 10/22/2026 due to security fixes. The CI matrix lists PHP 8.3 through 8.5 and uses PHP 8.3
-as its primary version. Boards running PHP below 8.3.36 cannot enable this extension.
+on 10/22/2026 due to security fixes, and lowered to 8.1 on 11/10/2026. The CI matrix lists PHP 8.3 through 8.5 and uses PHP 8.3
+as its primary version. The phpBB 3.3 jobs also run PHP 8.1. Boards running PHP below 8.1 cannot enable this extension.
 The phpBB constraints were widened to `<4.1.0`, so
 the extension can be enabled on 4.0.x; it was enabled on a 4.0.0-a3-dev board with the constraints
 as shipped. 4.0 is still a development release, so "supported" here means "checked as below", not a
diff --git a/ext.php b/ext.php
index 9655c9a..e13b514 100644
--- a/ext.php
+++ b/ext.php
@@ -19,8 +19,8 @@ class ext extends \phpbb\extension\base
 	/** Minimum phpBB version - 3.3.19 carries the security fixes from 3.3.17-3.3.19 */
 	public const MIN_PHPBB_VERSION = '3.3.19';
 
-	/** Minimum PHP version - 8.3.36 includes security fixes. */
-	public const MIN_PHP_VERSION = '8.3.36';
+	/** Minimum PHP version. */
+	public const MIN_PHP_VERSION = '8.1.0';
 
 	/** The original package this extension can take over from; it must be disabled first. */
 	public const ORIGINAL_EXTENSION = 'sheer/knowledgebase';
@@ -67,13 +67,13 @@ public function check_phpbb_version()
 	}
 
 	/**
-	 * Requires PHP 8.3.36 due to security fixes.
+	 * Requires PHP 8.1.0 or later.
 	 *
 	 * @return bool
 	 */
 	public function check_php_version()
 	{
-		return PHP_VERSION_ID >= 80336;
+		return PHP_VERSION_ID >= 80100;
 	}
 
 	/**
diff --git a/tests/kb_declared_support_test.php b/tests/kb_declared_support_test.php
index e2ad419..6e5f540 100644
--- a/tests/kb_declared_support_test.php
+++ b/tests/kb_declared_support_test.php
@@ -30,14 +30,14 @@ private function composer(): array
 		return json_decode(file_get_contents(self::ROOT . '/composer.json'), true, 512, JSON_THROW_ON_ERROR);
 	}
 
-	public function test_composer_requires_php_8_3_36_or_newer()
+	public function test_composer_requires_php_8_1_or_newer()
 	{
-		$this->assertSame('>=8.3.36', $this->composer()['require']['php']);
+		$this->assertSame('>=8.1.0', $this->composer()['require']['php']);
 	}
 
 	public function test_the_extension_refuses_to_enable_below_the_same_minimum()
 	{
-		$this->assertSame('8.3.36', ext::MIN_PHP_VERSION);
+		$this->assertSame('8.1.0', ext::MIN_PHP_VERSION);
 		$this->assertSame('>=' . ext::MIN_PHP_VERSION, $this->composer()['require']['php']);
 	}
 
@@ -51,14 +51,11 @@ public function php_versions(): array
 	{
 		return [
 			'8.0 is too old'            => ['8.0.30', false],
-			'8.1 is too old'            => ['8.1.31', false],
-			'8.2 development build'     => ['8.2.0-dev', false],
-			'first 8.2 release'         => ['8.2.0', false],
-			'8.2 patch release'         => ['8.2.27', false],
-			'first 8.3 release'         => ['8.3.0', false],
-			'below security minimum'    => ['8.3.35', false],
-			'security minimum'          => ['8.3.36', true],
-			'later 8.3 patch release'   => ['8.3.37', true],
+			'8.1 development build'     => ['8.1.0-dev', false],
+			'minimum'                   => ['8.1.0', true],
+			'later 8.1 patch release'   => ['8.1.31', true],
+			'8.2'                       => ['8.2.27', true],
+			'8.3'                       => ['8.3.36', true],
 			'8.4'                       => ['8.4.26', true],
 			'a future major version'    => ['9.0.0', true],
 		];
@@ -103,7 +100,7 @@ public function test_the_compatibility_notes_state_the_same_php_floor()
 	{
 		$notes = file_get_contents(self::ROOT . '/docs/phpbb-4.0-compatibility.md');
 
-		$this->assertStringContainsString('`require.php`: `>=8.3.36`', $notes);
+		$this->assertStringContainsString('`require.php`: `>=8.1.0`', $notes);
 		$this->assertStringNotContainsString('`>=8.0`', $notes);
 	}
 }
diff --git a/tests/kb_ext_enableable_test.php b/tests/kb_ext_enableable_test.php
index 3c40a69..07516ad 100644
--- a/tests/kb_ext_enableable_test.php
+++ b/tests/kb_ext_enableable_test.php
@@ -35,10 +35,10 @@ private function ext(bool $original_enabled): ext
 		return $ext;
 	}
 
-	public function test_php_security_minimum()
+	public function test_php_minimum()
 	{
-		$this->assertFalse(ext::php_version_meets_minimum('8.3.35'));
-		$this->assertTrue(ext::php_version_meets_minimum('8.3.36'));
+		$this->assertFalse(ext::php_version_meets_minimum('8.0.30'));
+		$this->assertTrue(ext::php_version_meets_minimum('8.1.0'));
 		$this->assertTrue(ext::php_version_meets_minimum('8.4.0'));
 	}