diff --git a/xls/modules/aes/aes_ctr_test.cc b/xls/modules/aes/aes_ctr_test.cc
index bac06447b1..917ea64ad5 100644
--- a/xls/modules/aes/aes_ctr_test.cc
+++ b/xls/modules/aes/aes_ctr_test.cc
@@ -77,9 +77,9 @@ static void IvToBuffer(const InitVector& iv,
 
 static void PrintTraceMessages(const InterpreterEvents& events) {
   if (absl::GetFlag(FLAGS_print_traces) && !events.trace_msgs.empty()) {
-    std::cout << "Trace messages:" << std::endl;
+    std::cout << "Trace messages:" << '\n';
     for (const auto& tm : events.trace_msgs) {
-      std::cout << " - " << tm << std::endl;
+      std::cout << " - " << tm << '\n';
     }
   }
 }
@@ -213,7 +213,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
   if (reference_ciphertext.size() != xls_ciphertext.size()) {
     std::cout << "Error: XLS and reference ciphertexts differ in num blocks: "
               << "XLS: " << xls_ciphertext.size()
-              << ", ref: " << reference_ciphertext.size() << std::endl;
+              << ", ref: " << reference_ciphertext.size() << '\n';
     return false;
   }
 
@@ -222,7 +222,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
     for (int32_t byte_idx = 0; byte_idx < kBlockBytes; byte_idx++) {
       if (reference_ciphertext[block_idx][byte_idx] !=
           xls_ciphertext[block_idx][byte_idx]) {
-        std::cout << "Error comparing block " << block_idx << ":" << std::endl;
+        std::cout << "Error comparing block " << block_idx << ":" << '\n';
         PrintFailure(reference_ciphertext[block_idx], xls_ciphertext[block_idx],
                      byte_idx, /*ciphertext=*/true);
         return false;
@@ -246,7 +246,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
   if (sample_data.input_blocks.size() != xls_plaintext.size()) {
     std::cout << "Error: XLS decrypted plaintext and input plaintext differ "
               << "in num blocks XLS: " << xls_ciphertext.size()
-              << ", ref: " << sample_data.input_blocks.size() << std::endl;
+              << ", ref: " << sample_data.input_blocks.size() << '\n';
     return false;
   }
 
@@ -255,7 +255,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
     for (int32_t byte_idx = 0; byte_idx < kBlockBytes; byte_idx++) {
       if (sample_data.input_blocks[block_idx][byte_idx] !=
           xls_plaintext[block_idx][byte_idx]) {
-        std::cout << "Error comparing block " << block_idx << ":" << std::endl;
+        std::cout << "Error comparing block " << block_idx << ":" << '\n';
         PrintFailure(sample_data.input_blocks[block_idx],
                      xls_plaintext[block_idx], byte_idx,
                      /*ciphertext=*/false);
@@ -319,21 +319,19 @@ static absl::Status RunTest(int32_t num_samples, int32_t key_bits) {
     XLS_ASSIGN_OR_RETURN(bool proceed, RunSample(&encrypt_jit_data, sample_data,
                                                  &xls_encrypt_dur));
     if (!proceed) {
-      std::cout << "Key      : " << FormatKey(sample_data.key) << std::endl;
-      std::cout << "IV       : " << FormatInitVector(sample_data.iv)
-                << std::endl;
-      std::cout << "Plaintext: " << std::endl
-                << FormatBlocks(sample_data.input_blocks, /*indent=*/4)
-                << std::endl;
+      std::cout << "Key      : " << FormatKey(sample_data.key) << '\n';
+      std::cout << "IV       : " << FormatInitVector(sample_data.iv) << '\n';
+      std::cout << "Plaintext: " << '\n'
+                << FormatBlocks(sample_data.input_blocks, /*indent=*/4) << '\n';
       return absl::InternalError(
           absl::StrCat("Testing failed at sample ", i, "."));
     }
   }
 
   std::cout << "AES-CTR: Successfully ran " << num_samples << " samples."
-            << std::endl;
+            << '\n';
   std::cout << "AES-CTR: Avg. XLS encryption time: "
-            << xls_encrypt_dur / num_samples << std::endl;
+            << xls_encrypt_dur / num_samples << '\n';
 
   return absl::OkStatus();
 }
diff --git a/xls/modules/aes/aes_gcm_test.cc b/xls/modules/aes/aes_gcm_test.cc
index 7167cafce9..7ab6fb3f40 100644
--- a/xls/modules/aes/aes_gcm_test.cc
+++ b/xls/modules/aes/aes_gcm_test.cc
@@ -206,7 +206,7 @@ static bool CompareBlock(const Block& expected, const Block& actual,
                          std::string_view failure_msg, bool is_ciphertext) {
   for (int byte_idx = 0; byte_idx < kBlockBytes; byte_idx++) {
     if (expected[byte_idx] != actual[byte_idx]) {
-      std::cout << failure_msg << std::endl;
+      std::cout << failure_msg << '\n';
       PrintFailure(expected, actual, byte_idx, is_ciphertext);
       return false;
     }
@@ -245,7 +245,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
       xls_encrypted.output_data.size()) {
     std::cout << "Reference & XLS ciphertext differed in sizes: "
               << "reference: " << reference_encrypted.output_data.size()
-              << ", XLS: " << xls_encrypted.output_data.size() << std::endl;
+              << ", XLS: " << xls_encrypted.output_data.size() << '\n';
     return false;
   }
 
@@ -275,8 +275,7 @@ static absl::StatusOr<bool> RunSample(JitData* jit_data,
   if (xls_decrypted.output_data.size() != xls_encrypted.output_data.size()) {
     std::cout << "Input plaintext and XLS deciphered text differed in sizes: "
               << "input: " << sample_data.input_data.size()
-              << ", decrypted: " << xls_decrypted.output_data.size()
-              << std::endl;
+              << ", decrypted: " << xls_decrypted.output_data.size() << '\n';
     return false;
   }
 
@@ -365,21 +364,20 @@ static absl::Status RunTest(int num_samples, int key_bits) {
 
     XLS_ASSIGN_OR_RETURN(bool proceed, RunSample(&jit_data, sample_data));
     if (!proceed) {
-      std::cout << "Key      : " << FormatKey(sample_data.key) << std::endl;
+      std::cout << "Key      : " << FormatKey(sample_data.key) << '\n';
       std::cout << "IV       : " << FormatInitVector(sample_data.init_vector)
-                << std::endl;
-      std::cout << "Plaintext: " << std::endl
-                << FormatBlocks(sample_data.input_data, /*indent=*/4)
-                << std::endl;
-      std::cout << "AAD: " << std::endl
-                << FormatBlocks(sample_data.aad, /*indent=*/4) << std::endl;
+                << '\n';
+      std::cout << "Plaintext: " << '\n'
+                << FormatBlocks(sample_data.input_data, /*indent=*/4) << '\n';
+      std::cout << "AAD: " << '\n'
+                << FormatBlocks(sample_data.aad, /*indent=*/4) << '\n';
       return absl::InternalError(
           absl::StrCat("Testing failed at sample ", sample_idx, "."));
     }
   }
 
   std::cout << "AES-GCM: Successfully ran " << num_samples << " " << key_bits
-            << "-bit samples." << std::endl;
+            << "-bit samples." << '\n';
 
   return absl::OkStatus();
 }
diff --git a/xls/modules/aes/aes_test.cc b/xls/modules/aes/aes_test.cc
index d40506c296..a5be16eba9 100644
--- a/xls/modules/aes/aes_test.cc
+++ b/xls/modules/aes/aes_test.cc
@@ -88,8 +88,8 @@ static absl::StatusOr<bool> RunSample(const Block& input, const Key& key,
   *xls_encrypt_dur += absl::Now() - start_time;
 
   XLS_VLOG(2) << "Reference ciphertext: " << FormatBlock(reference_ciphertext)
-              << std::endl;
-  XLS_VLOG(2) << "XLS ciphertext: " << FormatBlock(xls_ciphertext) << std::endl;
+              << '\n';
+  XLS_VLOG(2) << "XLS ciphertext: " << FormatBlock(xls_ciphertext) << '\n';
 
   // Verify the ciphertexts match, to ensure we're actually doing the encryption
   // properly.
@@ -105,8 +105,7 @@ static absl::StatusOr<bool> RunSample(const Block& input, const Key& key,
   XLS_ASSIGN_OR_RETURN(Block xls_decrypted, XlsDecrypt(key, key_bytes, input));
   *xls_decrypt_dur += absl::Now() - start_time;
 
-  XLS_VLOG(2) << "Decrypted plaintext: " << FormatBlock(xls_decrypted)
-              << std::endl;
+  XLS_VLOG(2) << "Decrypted plaintext: " << FormatBlock(xls_decrypted) << '\n';
 
   // We can just compare the XLS result to the input to verify we're decrypting
   // right.
@@ -140,19 +139,19 @@ static absl::Status RunTest(int32_t key_bits, int32_t num_samples) {
         bool proceed,
         RunSample(input, key, key_bytes, &xls_encrypt_dur, &xls_decrypt_dur));
     if (!proceed) {
-      std::cout << "Plaintext: " << FormatBlock(input) << std::endl;
-      std::cout << "Key: " << FormatKey(key) << std::endl;
+      std::cout << "Plaintext: " << FormatBlock(input) << '\n';
+      std::cout << "Key: " << FormatKey(key) << '\n';
       return absl::InternalError(
           absl::StrCat(key_bits, "-bit validation failed."));
     }
   }
 
   std::cout << "Successfully ran " << num_samples << " " << key_bits
-            << "-bit samples." << std::endl;
+            << "-bit samples." << '\n';
   std::cout << "Avg. XLS encryption time: " << xls_encrypt_dur / num_samples
-            << std::endl;
+            << '\n';
   std::cout << "Avg. XLS decryption time: " << xls_decrypt_dur / num_samples
-            << std::endl;
+            << '\n';
 
   return absl::OkStatus();
 }
diff --git a/xls/modules/aes/aes_test_common.cc b/xls/modules/aes/aes_test_common.cc
index e18b67f2c0..9a4fb489fb 100644
--- a/xls/modules/aes/aes_test_common.cc
+++ b/xls/modules/aes/aes_test_common.cc
@@ -63,10 +63,9 @@ void PrintFailure(const Block& expected_block, const Block& actual_block,
   std::cout << "Mismatch in " << type_str << " at byte " << index << ": "
             << std::hex << "expected: 0x"
             << static_cast<uint32_t>(expected_block[index]) << "; actual: 0x"
-            << static_cast<uint32_t>(actual_block[index]) << std::endl;
-  std::cout << " - Expected block: " << FormatBlock(expected_block)
-            << std::endl;
-  std::cout << " - Actual block  : " << FormatBlock(actual_block) << std::endl;
+            << static_cast<uint32_t>(actual_block[index]) << '\n';
+  std::cout << " - Expected block: " << FormatBlock(expected_block) << '\n';
+  std::cout << " - Actual block  : " << FormatBlock(actual_block) << '\n';
 }
 
 Value InitVectorToValue(const InitVector& iv) {
diff --git a/xls/modules/aes/sample_generator.cc b/xls/modules/aes/sample_generator.cc
index d8d7272152..af3193597f 100644
--- a/xls/modules/aes/sample_generator.cc
+++ b/xls/modules/aes/sample_generator.cc
@@ -231,7 +231,7 @@ static absl::Status RealMain(EncryptionMode mode, int key_bits,
 
   XLS_ASSIGN_OR_RETURN(Result result, RunGcm(sample));
 
-  std::cout << DslxFormatOutput(sample, result) << std::endl;
+  std::cout << DslxFormatOutput(sample, result) << '\n';
 
   return absl::OkStatus();
 }