From e026439a3652e579baddf4027213db89b23884fa Mon Sep 17 00:00:00 2001
From: Justin King <jcking@google.com>
Date: Wed, 14 Oct 2026 16:12:57 -0700
Subject: [PATCH] Fix bug in optimized regex matching step

PiperOrigin-RevId: 999692402
---
 eval/eval/regex_match_step.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/eval/eval/regex_match_step.cc b/eval/eval/regex_match_step.cc
index 3c949ee9f..4df758e76 100644
--- a/eval/eval/regex_match_step.cc
+++ b/eval/eval/regex_match_step.cc
@@ -66,6 +66,10 @@ class RegexMatchStep final : public ExpressionStepBase {
     }
     auto input_args = frame->value_stack().GetSpan(kNumRegexMatchArguments);
     const auto& subject = input_args[kRegexMatchStepSubject];
+    if (subject.IsUnknown() || subject.IsError()) {
+      // Propagate unknowns and errors.
+      return;
+    }
     if (!subject->Is<cel::StringValue>()) {
       frame->Abort(absl::InternalError(
           "First argument for regular expression match must be a string"));