diff --git a/CLAUDE.md b/CLAUDE.md
index c96c8954ee..7e843cd303 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -417,3 +417,7 @@ When methods are called on union types (`Foo|Bar`), the resolved method reflecti
 - `react/child-process`, `react/async` - Parallel analysis
 - `symfony/console` - CLI interface
 - `hoa/compiler` - Used for regex type parsing
+
+### Ternary expression type narrowing in TypeSpecifier
+
+`TypeSpecifier::specifyTypesInCondition()` handles ternary expressions (`$cond ? $a : $b`) for type narrowing. In a truthy context (e.g., inside `assert()`), the ternary is semantically equivalent to `($cond && $a) || (!$cond && $b)` — meaning if the condition is true, the "if" branch must be truthy, and if false, the "else" branch must be truthy. The fix converts ternary expressions to this `BooleanOr(BooleanAnd(...), BooleanAnd(...))` form so the existing OR/AND narrowing logic handles both branches correctly. This enables `assert($cond ? $x instanceof A : $x instanceof B)` to narrow `$x` to `A|B`. The `AssertFunctionTypeSpecifyingExtension` calls `specifyTypesInCondition` with `TypeSpecifierContext::createTruthy()` context for the assert argument.
diff --git a/src/Analyser/TypeSpecifier.php b/src/Analyser/TypeSpecifier.php
index 64f9841cf0..64e835780b 100644
--- a/src/Analyser/TypeSpecifier.php
+++ b/src/Analyser/TypeSpecifier.php
@@ -1062,12 +1062,12 @@ public function specifyTypesInCondition(
 		} elseif (
 			$expr instanceof Expr\Ternary
 			&& !$context->null()
-			&& $scope->getType($expr->else)->isFalse()->yes()
 		) {
-			$conditionExpr = $expr->cond;
-			if ($expr->if !== null) {
-				$conditionExpr = new BooleanAnd($conditionExpr, $expr->if);
-			}
+			$ifExpr = $expr->if ?? $expr->cond;
+			$conditionExpr = new BooleanOr(
+				new BooleanAnd($expr->cond, $ifExpr),
+				new BooleanAnd(new Expr\BooleanNot($expr->cond), $expr->else),
+			);
 
 			return $this->specifyTypesInCondition($scope, $conditionExpr, $context)->setRootExpr($expr);
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14100.php b/tests/PHPStan/Analyser/nsrt/bug-14100.php
new file mode 100644
index 0000000000..013668ddad
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14100.php
@@ -0,0 +1,55 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14100;
+
+use function PHPStan\Testing\assertType;
+
+interface Foo {}
+interface Bar {}
+interface Baz {}
+
+class HelloWorld
+{
+	/** @param resource|object $conn */
+	public function ternaryAssertInstanceof($conn): void
+	{
+		assert(rand(0, 1) ? $conn instanceof Foo : $conn instanceof Bar);
+		assertType('Bug14100\Bar|Bug14100\Foo', $conn);
+	}
+
+	/** @param resource|object $conn */
+	public function ifElseAssertInstanceof($conn): void
+	{
+		if (rand(0, 1)) {
+			assert($conn instanceof Foo);
+		} else {
+			assert($conn instanceof Bar);
+		}
+		assertType('Bug14100\Bar|Bug14100\Foo', $conn);
+	}
+
+	/** @param resource|object $conn */
+	public function ternaryAssertThreeBranches($conn): void
+	{
+		assert(rand(0, 2) === 0 ? $conn instanceof Foo : (rand(0, 2) === 1 ? $conn instanceof Bar : $conn instanceof Baz));
+		assertType('Bug14100\Bar|Bug14100\Baz|Bug14100\Foo', $conn);
+	}
+
+	/** @param mixed $val */
+	public function ternaryAssertScalar($val): void
+	{
+		assert(rand(0, 1) ? is_string($val) : is_int($val));
+		assertType('int|string', $val);
+	}
+
+	/**
+	 * Short ternary syntax (Elvis operator): $a ?: $b
+	 *
+	 * @param resource|object $conn
+	 */
+	public function shortTernaryAssert($conn): void
+	{
+		assert($conn instanceof Foo ?: $conn instanceof Bar);
+		assertType('Bug14100\Bar|Bug14100\Foo', $conn);
+	}
+}
diff --git a/tests/PHPStan/Rules/Classes/InstantiationRuleTest.php b/tests/PHPStan/Rules/Classes/InstantiationRuleTest.php
index 3232e63282..511bf6136d 100644
--- a/tests/PHPStan/Rules/Classes/InstantiationRuleTest.php
+++ b/tests/PHPStan/Rules/Classes/InstantiationRuleTest.php
@@ -484,7 +484,7 @@ public function testBug10248(): void
 		$this->analyse([__DIR__ . '/data/bug-10248.php'], []);
 	}
 
-	#[RequiresPhp('>= 8.0')]
+	#[RequiresPhp('>= 8.2')]
 	public function testBug11815(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-11815.php'], []);