diff --git a/verilog/formatting/formatter_test.cc b/verilog/formatting/formatter_test.cc
index d43be0a63..c0c37dd19 100644
--- a/verilog/formatting/formatter_test.cc
+++ b/verilog/formatting/formatter_test.cc
@@ -582,7 +582,23 @@ static constexpr FormatterTestCase kFormatterTestCases[] = {
     },
     {
         "  parameter  int   foo=bar [ a+b ] ;",  // binary inside index expr
-        "parameter int foo = bar[a + b];\n",
+        "parameter int foo = bar[a+b];\n",       // allowed to be 0 spaces
+                                                 // (preserved)
+    },
+    {
+        "  parameter  int   foo=bar [ a+ b ] ;",  // binary inside index expr
+        "parameter int foo = bar[a+b];\n",        // allowed to be 0 spaces
+                                                  // (symmetrized)
+    },
+    {
+        "  parameter  int   foo=bar [ a +b ] ;",  // binary inside index expr
+        "parameter int foo = bar[a + b];\n",      // allowed to be 1 space
+                                                  // (symmetrized)
+    },
+    {
+        "  parameter  int   foo=bar [ a  +b ] ;",  // binary inside index expr
+        "parameter int foo = bar[a + b];\n",       // limited to 1 space (and
+                                                   // symmetrized)
     },
     {
         // with line continuations
@@ -657,7 +673,7 @@ static constexpr FormatterTestCase kFormatterTestCases[] = {
     {"  parameter int a={b^{c^{d^e}}};",
      "parameter int a = {b ^ {c ^ {d ^ e}}};\n"},
     {"  parameter int a={b^{c[d^e]}};",
-     "parameter int a = {b ^ {c[d ^ e]}};\n"},
+     "parameter int a = {b ^ {c[d^e]}};\n"},  // allow 0 spaces inside "[d^e]"
     {"  parameter int a={(b^c),(d^^e)};",
      "parameter int a = {(b ^ c), (d ^ ^e)};\n"},
 
@@ -1875,6 +1891,14 @@ static constexpr FormatterTestCase kFormatterTestCases[] = {
         "  if (foo);\n"
         "endmodule\n",
     },
+    {
+        "module conditional_generate;\n"
+        "if(foo[a*b+c])  ; \t"  // null action
+        "endmodule\n",
+        "module conditional_generate;\n"
+        "  if (foo[a*b+c]);\n"  // allow compact expressions inside []
+        "endmodule\n",
+    },
     {
         "module conditional_generate;\n"
         "if(foo)begin\n"
diff --git a/verilog/formatting/token_annotator.cc b/verilog/formatting/token_annotator.cc
index f7c37ad5c..cac9f871b 100644
--- a/verilog/formatting/token_annotator.cc
+++ b/verilog/formatting/token_annotator.cc
@@ -233,6 +233,21 @@ static WithReason<int> SpacesRequiredBetween(
   // Consider assignment operators in the same class as binary operators.
   if (left.format_token_enum == FormatTokenType::binary_operator ||
       right.format_token_enum == FormatTokenType::binary_operator) {
+    // Inside [], allows 0 or 1 spaces, and symmetrize.
+    // TODO(fangism): make this behavior configurable
+    if (right.format_token_enum == FormatTokenType::binary_operator &&
+        InRangeLikeContext(right_context)) {
+      int spaces = right.OriginalLeadingSpaces().length();
+      if (spaces > 1) {
+        spaces = 1;
+      }
+      return {spaces, "Limit <= 1 space before binary operator inside []."};
+    }
+    if (left.format_token_enum == FormatTokenType::binary_operator &&
+        InRangeLikeContext(left_context)) {
+      return {left.before.spaces_required,
+              "Symmetrize spaces before and after binary operator inside []."};
+    }
     return {1, "Space around binary and assignment operators"};
   }
 
diff --git a/verilog/formatting/token_annotator_test.cc b/verilog/formatting/token_annotator_test.cc
index b12d85f53..164493eb1 100644
--- a/verilog/formatting/token_annotator_test.cc
+++ b/verilog/formatting/token_annotator_test.cc
@@ -4665,23 +4665,29 @@ TEST(TokenAnnotatorTest, AnnotateFormattingWithContextTest) {
   }
 }  // NOLINT(readability/fn_size)
 
-struct AnnotateBreakAroundCommentsTestCase {
+struct OriginalSpacingSensitiveTestCase {
   FormatStyle style;
 
+  // TODO(fangism): group this into a TokenInfo.
   int left_token_enum;
   absl::string_view left_token_string;
 
+  // This spacing may influence token-annotation behavior.
   absl::string_view whitespace_between;
 
+  // TODO(fangism): group this into a TokenInfo.
   int right_token_enum;
   absl::string_view right_token_string;
 
+  InitializedSyntaxTreeContext left_context;
   InitializedSyntaxTreeContext right_context;
+
   ExpectedInterTokenInfo expected_annotation;
 };
 
-TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
-  const AnnotateBreakAroundCommentsTestCase kTestCases[] = {
+// These tests are allowed to be sensitive to original inter-token spacing.
+TEST(TokenAnnotatorTest, OriginalSpacingSensitiveTests) {
+  const OriginalSpacingSensitiveTestCase kTestCases[] = {
       {// No comments
        DefaultStyle,
        '=',  // left token
@@ -4690,6 +4696,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_DecNumber,  // right token
        "0",
        {/* unspecified context */},
+       {/* unspecified context */},
        {1, SpacingOptions::Undecided}},
       {// //comment1
        // //comment2
@@ -4700,6 +4707,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "//comment2",
        {},
+       {},
        {2, SpacingOptions::MustWrap}},
       {// 0 // comment
        DefaultStyle,
@@ -4709,6 +4717,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// 0// comment
        DefaultStyle,
@@ -4718,6 +4727,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// 0 \n  // comment
        DefaultStyle,
@@ -4727,6 +4737,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// // comment 1 \n  // comment 2
        DefaultStyle,
@@ -4736,6 +4747,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustWrap}},
       {// /* comment 1 */ \n  // comment 2
        DefaultStyle,
@@ -4745,6 +4757,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// /* comment 1 */  // comment 2
        DefaultStyle,
@@ -4754,6 +4767,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// ;  // comment 2
        DefaultStyle,
@@ -4763,6 +4777,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// ; \n // comment 2
        DefaultStyle,
@@ -4772,6 +4787,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// ,  // comment 2
        DefaultStyle,
@@ -4781,6 +4797,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// , \n // comment 2
        DefaultStyle,
@@ -4790,6 +4807,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// begin  // comment 2
        DefaultStyle,
@@ -4799,6 +4817,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// begin \n // comment 2
        DefaultStyle,
@@ -4808,6 +4827,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// else  // comment 2
        DefaultStyle,
@@ -4817,6 +4837,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// else \n // comment 2
        DefaultStyle,
@@ -4826,6 +4847,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// end  // comment 2
        DefaultStyle,
@@ -4835,6 +4857,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// end \n // comment 2
        DefaultStyle,
@@ -4844,6 +4867,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// generate  // comment 2
        DefaultStyle,
@@ -4853,6 +4877,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// generate \n // comment 2
        DefaultStyle,
@@ -4862,6 +4887,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {// if  // comment 2
        DefaultStyle,
@@ -4871,6 +4897,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::MustAppend}},
       {// if \n\n // comment 2
        DefaultStyle,
@@ -4880,6 +4907,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
        verilog_tokentype::TK_EOL_COMMENT,
        "// comment 2",
        {/* unspecified context */},
+       {/* unspecified context */},
        {2, SpacingOptions::Undecided}},
       {
           DefaultStyle,
@@ -4889,6 +4917,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "//comment",
           {/* any context */},
+          {/* any context */},
           {0, SpacingOptions::MustWrap},
       },
       {
@@ -4899,6 +4928,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/*comment*/",
           {/* any context */},
+          {/* any context */},
           {0, SpacingOptions::MustWrap},
       },
       {
@@ -4909,6 +4939,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/*comment*/",
           {/* unspecified context */},
+          {/* unspecified context */},
           {2, SpacingOptions::Undecided},  // could be append
       },
       {
@@ -4919,6 +4950,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/*comment*/",
           {/* unspecified context */},
+          {/* unspecified context */},
           {2, SpacingOptions::Undecided},
       },
       {
@@ -4929,6 +4961,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "//comment",
           {/* unspecified context */},
+          {/* unspecified context */},
           {2, SpacingOptions::MustAppend},
       },
       {
@@ -4939,6 +4972,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "//comment",
           {/* unspecified context */},
+          {/* unspecified context */},
           {2, SpacingOptions::Undecided},
       },
       // Comments in UDP entries
@@ -4951,6 +4985,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/* comment */",
           {NodeEnum::kUdpCombEntry},
+          {NodeEnum::kUdpCombEntry},
           {2, SpacingOptions::Undecided},
       },
       {
@@ -4962,6 +4997,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           '0',
           "0",
           {NodeEnum::kUdpCombEntry},
+          {NodeEnum::kUdpCombEntry},
           {1, SpacingOptions::Undecided},
       },
       {
@@ -4973,6 +5009,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "// comment",
           {NodeEnum::kUdpCombEntry},
+          {NodeEnum::kUdpCombEntry},
           {2, SpacingOptions::MustAppend},
       },
       {
@@ -4984,6 +5021,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/* comment */",
           {NodeEnum::kUdpSequenceEntry},
+          {NodeEnum::kUdpSequenceEntry},
           {2, SpacingOptions::Undecided},
       },
       {
@@ -4995,6 +5033,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           '0',
           "0",
           {NodeEnum::kUdpSequenceEntry},
+          {NodeEnum::kUdpSequenceEntry},
           {1, SpacingOptions::Undecided},
       },
       {
@@ -5006,6 +5045,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "// comment",
           {NodeEnum::kUdpSequenceEntry},
+          {NodeEnum::kUdpSequenceEntry},
           {2, SpacingOptions::MustAppend},
       },
       {
@@ -5017,6 +5057,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/* comment */",
           {NodeEnum::kUdpPortDeclaration},
+          {NodeEnum::kUdpPortDeclaration},
           {2, SpacingOptions::Undecided},
       },
       {
@@ -5028,6 +5069,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::SymbolIdentifier,
           "i",
           {NodeEnum::kUdpPortDeclaration},
+          {NodeEnum::kUdpPortDeclaration},
           {1, SpacingOptions::Undecided},
       },
       {
@@ -5039,6 +5081,7 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_COMMENT_BLOCK,
           "/* comment */",
           {NodeEnum::kUdpPortDeclaration},
+          {NodeEnum::kUdpPortDeclaration},
           {2, SpacingOptions::Undecided},
       },
       {
@@ -5050,14 +5093,52 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
           verilog_tokentype::TK_EOL_COMMENT,
           "// comment",
           {NodeEnum::kUdpPortDeclaration},
+          {NodeEnum::kUdpPortDeclaration},
           {2, SpacingOptions::MustAppend},
       },
+
+      {
+          // [a+b]
+          DefaultStyle,
+          verilog_tokentype::SymbolIdentifier,
+          "a",
+          "",  // no spaces originally
+          '+',
+          "+",
+          {NodeEnum::kSelectVariableDimension},
+          {NodeEnum::kSelectVariableDimension},
+          {0, SpacingOptions::Undecided},
+      },
+      {
+          // [a +b]
+          DefaultStyle,
+          verilog_tokentype::SymbolIdentifier,
+          "a",
+          " ",  // 1 space originally
+          '+',
+          "+",
+          {NodeEnum::kSelectVariableDimension},
+          {NodeEnum::kSelectVariableDimension},
+          {1, SpacingOptions::Undecided},
+      },
+      {
+          // [a  +b]
+          DefaultStyle,
+          verilog_tokentype::SymbolIdentifier,
+          "a",
+          " ",  // 2 spaces originally
+          '+',
+          "+",
+          {NodeEnum::kSelectVariableDimension},
+          {NodeEnum::kSelectVariableDimension},
+          {1, SpacingOptions::Undecided},  // limit to 1
+      },
   };
   int test_index = 0;
   for (const auto& test_case : kTestCases) {
     VLOG(1) << "test_index[" << test_index << "]:";
 
-    verible::TokenInfoTestData test_data = {
+    const verible::TokenInfoTestData test_data = {
         {test_case.left_token_enum, test_case.left_token_string},
         test_case.whitespace_between,
         {test_case.right_token_enum, test_case.right_token_string}};
@@ -5067,6 +5148,8 @@ TEST(TokenAnnotatorTest, AnnotateBreakAroundComments) {
 
     PreFormatToken left(&token_vector[0]);
     PreFormatToken right(&token_vector[1]);
+    // like verible::ConnectPreFormatTokensPreservedSpaceStarts();
+    right.before.preserved_space_start = left.Text().end();
 
     left.format_token_enum =
         GetFormatTokenType(verilog_tokentype(left.TokenEnum()));