diff --git a/src/Analyser/ExprHandler/BooleanOrHandler.php b/src/Analyser/ExprHandler/BooleanOrHandler.php
index d439a2c808..77f7744702 100644
--- a/src/Analyser/ExprHandler/BooleanOrHandler.php
+++ b/src/Analyser/ExprHandler/BooleanOrHandler.php
@@ -27,6 +27,7 @@
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use function array_key_first;
+use function array_key_last;
 use function array_merge;
 use function array_reverse;
 use function count;
@@ -54,6 +55,13 @@ public function supports(Expr $expr): bool
 
 	public function resolveType(MutatingScope $scope, Expr $expr): Type
 	{
+		// For deep BooleanOr chains, resolve the boolean type by iterating the flattened arms while
+		// threading the falsey scope, instead of recursing into the left operand and re-narrowing the
+		// whole chain at each level - the latter is O(n^2) (and worse) in the number of arms.
+		if (BooleanAndHandler::getBooleanExpressionDepth($expr) > self::BOOLEAN_EXPRESSION_MAX_PROCESS_DEPTH) {
+			return $this->resolveTypeForFlattenedBooleanOr($scope, $expr);
+		}
+
 		$leftBooleanType = $scope->getType($expr->left)->toBoolean();
 		if ($leftBooleanType->isTrue()->yes()) {
 			return new ConstantBooleanType(true);
@@ -80,6 +88,44 @@ public function resolveType(MutatingScope $scope, Expr $expr): Type
 		return new BooleanType();
 	}
 
+	/**
+	 * The whole chain is true if any arm is true (given the previous arms are false), false if every
+	 * arm is false, and bool otherwise. Threading the falsey scope arm by arm keeps this O(n), matching
+	 * the recursive resolveType() result without re-narrowing the whole left chain at each level.
+	 *
+	 * @param BooleanOr|LogicalOr $expr
+	 */
+	private function resolveTypeForFlattenedBooleanOr(MutatingScope $scope, Expr $expr): Type
+	{
+		$arms = [];
+		$current = $expr;
+		while ($current instanceof BooleanOr || $current instanceof LogicalOr) {
+			$arms[] = $current->right;
+			$current = $current->left;
+		}
+		$arms[] = $current;
+		$arms = array_reverse($arms);
+
+		$allArmsAreFalse = true;
+		$armScope = $scope;
+		$lastArmKey = array_key_last($arms);
+		foreach ($arms as $key => $arm) {
+			$armBooleanType = $armScope->getType($arm)->toBoolean();
+			if ($armBooleanType->isTrue()->yes()) {
+				return new ConstantBooleanType(true);
+			}
+			if (!$armBooleanType->isFalse()->yes()) {
+				$allArmsAreFalse = false;
+			}
+			if ($key === $lastArmKey) {
+				continue;
+			}
+			$armScope = $armScope->filterByFalseyValue($arm);
+		}
+
+		return $allArmsAreFalse ? new ConstantBooleanType(false) : new BooleanType();
+	}
+
 	public function specifyTypes(TypeSpecifier $typeSpecifier, Scope $scope, Expr $expr, TypeSpecifierContext $context): SpecifiedTypes
 	{
 		if (!$scope instanceof MutatingScope) {
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14477.php b/tests/PHPStan/Analyser/nsrt/bug-14477.php
new file mode 100644
index 0000000000..52bb2121b3
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14477.php
@@ -0,0 +1,42 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14477;
+
+use function PHPStan\Testing\assertType;
+
+final class C1 {}
+final class C2 {}
+final class C3 {}
+final class C4 {}
+final class C5 {}
+final class C6 {}
+final class C7 {}
+final class C8 {}
+
+// A BooleanOr chain deeper than BOOLEAN_EXPRESSION_MAX_PROCESS_DEPTH takes the flattened
+// resolveType() path; its boolean type and the truthy-branch narrowing must match the recursive one.
+function test(object $x): void
+{
+	$result = $x instanceof C1
+		|| $x instanceof C2
+		|| $x instanceof C3
+		|| $x instanceof C4
+		|| $x instanceof C5
+		|| $x instanceof C6
+		|| $x instanceof C7
+		|| $x instanceof C8;
+	assertType('bool', $result);
+
+	if (
+		$x instanceof C1
+		|| $x instanceof C2
+		|| $x instanceof C3
+		|| $x instanceof C4
+		|| $x instanceof C5
+		|| $x instanceof C6
+		|| $x instanceof C7
+		|| $x instanceof C8
+	) {
+		assertType('Bug14477\\C1|Bug14477\\C2|Bug14477\\C3|Bug14477\\C4|Bug14477\\C5|Bug14477\\C6|Bug14477\\C7|Bug14477\\C8', $x);
+	}
+}
diff --git a/tests/bench/data/or-chain-resolve-type-blowup.php b/tests/bench/data/or-chain-resolve-type-blowup.php
new file mode 100644
index 0000000000..58c11ddf8d
--- /dev/null
+++ b/tests/bench/data/or-chain-resolve-type-blowup.php
@@ -0,0 +1,117 @@
+<?php declare(strict_types = 1);
+
+namespace BenchOrChainResolveTypeBlowup;
+
+/**
+ * Regression test for O(N^2) in deep BooleanOr chains resolved via BooleanOrHandler::resolveType().
+ * Without the flattening, resolving the boolean type of the chain recursed into the left operand
+ * and re-narrowed the whole left chain with filterByFalseyValue() at each level, creating O(N^2)
+ * scope operations. Uses instanceof arms so the per-level narrowing is expensive enough to show
+ * at the BOOLEAN_EXPRESSION_MAX_PROCESS_DEPTH = 4 default (no raised cap needed).
+ */
+final class C1 {}
+final class C2 {}
+final class C3 {}
+final class C4 {}
+final class C5 {}
+final class C6 {}
+final class C7 {}
+final class C8 {}
+final class C9 {}
+final class C10 {}
+final class C11 {}
+final class C12 {}
+final class C13 {}
+final class C14 {}
+final class C15 {}
+final class C16 {}
+final class C17 {}
+final class C18 {}
+final class C19 {}
+final class C20 {}
+final class C21 {}
+final class C22 {}
+final class C23 {}
+final class C24 {}
+final class C25 {}
+final class C26 {}
+final class C27 {}
+final class C28 {}
+final class C29 {}
+final class C30 {}
+final class C31 {}
+final class C32 {}
+final class C33 {}
+final class C34 {}
+final class C35 {}
+final class C36 {}
+final class C37 {}
+final class C38 {}
+final class C39 {}
+final class C40 {}
+final class C41 {}
+final class C42 {}
+final class C43 {}
+final class C44 {}
+final class C45 {}
+final class C46 {}
+final class C47 {}
+final class C48 {}
+final class C49 {}
+final class C50 {}
+final class C51 {}
+final class C52 {}
+final class C53 {}
+final class C54 {}
+final class C55 {}
+final class C56 {}
+final class C57 {}
+final class C58 {}
+final class C59 {}
+final class C60 {}
+final class C61 {}
+final class C62 {}
+final class C63 {}
+final class C64 {}
+final class C65 {}
+final class C66 {}
+final class C67 {}
+final class C68 {}
+final class C69 {}
+final class C70 {}
+final class C71 {}
+final class C72 {}
+final class C73 {}
+final class C74 {}
+final class C75 {}
+final class C76 {}
+final class C77 {}
+final class C78 {}
+final class C79 {}
+final class C80 {}
+final class C81 {}
+final class C82 {}
+final class C83 {}
+final class C84 {}
+final class C85 {}
+final class C86 {}
+final class C87 {}
+final class C88 {}
+final class C89 {}
+final class C90 {}
+final class C91 {}
+final class C92 {}
+final class C93 {}
+final class C94 {}
+final class C95 {}
+final class C96 {}
+final class C97 {}
+final class C98 {}
+final class C99 {}
+final class C100 {}
+
+function test(object $x): void {
+	if ($x instanceof C1 || $x instanceof C2 || $x instanceof C3 || $x instanceof C4 || $x instanceof C5 || $x instanceof C6 || $x instanceof C7 || $x instanceof C8 || $x instanceof C9 || $x instanceof C10 || $x instanceof C11 || $x instanceof C12 || $x instanceof C13 || $x instanceof C14 || $x instanceof C15 || $x instanceof C16 || $x instanceof C17 || $x instanceof C18 || $x instanceof C19 || $x instanceof C20 || $x instanceof C21 || $x instanceof C22 || $x instanceof C23 || $x instanceof C24 || $x instanceof C25 || $x instanceof C26 || $x instanceof C27 || $x instanceof C28 || $x instanceof C29 || $x instanceof C30 || $x instanceof C31 || $x instanceof C32 || $x instanceof C33 || $x instanceof C34 || $x instanceof C35 || $x instanceof C36 || $x instanceof C37 || $x instanceof C38 || $x instanceof C39 || $x instanceof C40 || $x instanceof C41 || $x instanceof C42 || $x instanceof C43 || $x instanceof C44 || $x instanceof C45 || $x instanceof C46 || $x instanceof C47 || $x instanceof C48 || $x instanceof C49 || $x instanceof C50 || $x instanceof C51 || $x instanceof C52 || $x instanceof C53 || $x instanceof C54 || $x instanceof C55 || $x instanceof C56 || $x instanceof C57 || $x instanceof C58 || $x instanceof C59 || $x instanceof C60 || $x instanceof C61 || $x instanceof C62 || $x instanceof C63 || $x instanceof C64 || $x instanceof C65 || $x instanceof C66 || $x instanceof C67 || $x instanceof C68 || $x instanceof C69 || $x instanceof C70 || $x instanceof C71 || $x instanceof C72 || $x instanceof C73 || $x instanceof C74 || $x instanceof C75 || $x instanceof C76 || $x instanceof C77 || $x instanceof C78 || $x instanceof C79 || $x instanceof C80 || $x instanceof C81 || $x instanceof C82 || $x instanceof C83 || $x instanceof C84 || $x instanceof C85 || $x instanceof C86 || $x instanceof C87 || $x instanceof C88 || $x instanceof C89 || $x instanceof C90 || $x instanceof C91 || $x instanceof C92 || $x instanceof C93 || $x instanceof C94 || $x instanceof C95 || $x instanceof C96 || $x instanceof C97 || $x instanceof C98 || $x instanceof C99 || $x instanceof C100) {
+		echo "yes";
+	}
+}