diff --git a/internal/tool/code_search.go b/internal/tool/code_search.go
index 4e8ee794..20029a2d 100644
--- a/internal/tool/code_search.go
+++ b/internal/tool/code_search.go
@@ -78,7 +78,14 @@ func (p *CodeSearchProvider) buildGrepArgs(searchText string, caseSensitive bool
 	cmdArgs = append(cmdArgs, "-e", searchText)
 
 	if ref := p.FileReader.Ref; ref != "" {
-		cmdArgs = append(cmdArgs, "--end-of-options")
+		if strings.HasPrefix(ref, "-") {
+			// Defense-in-depth: reject option-like refs here even though
+			// validateReviewRefs already verifies the ref upstream.
+			// NOTE: git grep < 2.45 does not support --end-of-options before
+			// the revision, so this is the one git invocation where we can't
+			// rely on that separator.
+			return nil
+		}
 		cmdArgs = append(cmdArgs, ref)
 	}
 
@@ -125,6 +132,9 @@ func (p *CodeSearchProvider) runGitGrep(parentCtx context.Context, cmdArgs []str
 
 func (p *CodeSearchProvider) gitGrep(ctx context.Context, searchText string, caseSensitive bool, usePerlRegexp bool, pathspec []string) (string, error) {
 	cmdArgs := p.buildGrepArgs(searchText, caseSensitive, usePerlRegexp, false, pathspec)
+	if cmdArgs == nil {
+		return "Error: ref must not start with '-'", nil
+	}
 
 	outStr, errStr, err := p.runGitGrep(ctx, cmdArgs)
 
diff --git a/internal/tool/code_search_test.go b/internal/tool/code_search_test.go
index 7e2e2cf1..6d65db05 100644
--- a/internal/tool/code_search_test.go
+++ b/internal/tool/code_search_test.go
@@ -33,15 +33,28 @@ func TestBuildGrepArgs_CommitMode(t *testing.T) {
 	p := NewCodeSearch(&FileReader{RepoDir: "/tmp", Ref: "abc1234"})
 	args := p.buildGrepArgs("myFunc", false, false, false, []string{"pkg/"})
 
-	assertContainsInOrder(t, args, "-e", "myFunc", "--end-of-options", "abc1234", "--", "pkg/")
+	assertContainsInOrder(t, args, "-e", "myFunc", "abc1234", "--", "pkg/")
 	assertNotContains(t, args, "--untracked")
+	assertNotContains(t, args, "--end-of-options")
 }
 
-func TestBuildGrepArgs_RefUsesEndOfOptions(t *testing.T) {
+func TestBuildGrepArgs_RejectsOptionLikeRef(t *testing.T) {
 	p := NewCodeSearch(&FileReader{RepoDir: "/tmp", Ref: "-O./pwn.sh"})
 	args := p.buildGrepArgs("myFunc", false, false, false, nil)
+	if args != nil {
+		t.Fatalf("expected buildGrepArgs to return nil for option-like ref, got %v", args)
+	}
+}
 
-	assertContainsInOrder(t, args, "-e", "myFunc", "--end-of-options", "-O./pwn.sh", "--")
+func TestGitGrep_RejectsOptionLikeRef(t *testing.T) {
+	p := NewCodeSearch(&FileReader{RepoDir: "/tmp", Ref: "-O./pwn.sh"})
+	result, err := p.gitGrep(context.Background(), "myFunc", false, false, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result != "Error: ref must not start with '-'" {
+		t.Fatalf("unexpected result: %s", result)
+	}
 }
 
 func TestBuildGrepArgs_PatternStartingWithDash(t *testing.T) {