diff --git a/kernel/src/sync.c b/kernel/src/sync.c
index 14dd98c2..4d1868ca 100644
--- a/kernel/src/sync.c
+++ b/kernel/src/sync.c
@@ -171,7 +171,8 @@ int eos_mutex_lock(eos_mutex_handle_t h, uint32_t timeout_ms)
     }
 
     /* Refuse rather than block: a task that is not enqueued is never granted
-     * the mutex, so with EOS_WAIT_FOREVER it would sleep forever. */
+     * the mutex, so with EOS_WAIT_FOREVER it would sleep forever. Refusing
+     * also avoids boosting the owner on behalf of a caller that never waits. */
     if (g_mtx[h].waiter_count >= MTX_MAX_WAITERS) {
         eos_port_exit_critical(crit);
         return EOS_KERN_NO_MEMORY;
@@ -197,7 +198,8 @@ int eos_mutex_lock(eos_mutex_handle_t h, uint32_t timeout_ms)
         return EOS_KERN_OK;
     }
 
-    /* Timeout — leave the queue and drop the boost we were causing. */
+    /* Timeout — leave the queue and drop the boost we were causing, so a
+     * waiter that gave up no longer keeps the owner running elevated. */
     uint8_t owner = g_mtx[h].owner;
     mtx_remove_waiter(&g_mtx[h], caller);
     pi_propagate(owner);
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index e82ff348..0207944c 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -56,39 +56,21 @@ add_executable(test_crypto test_crypto.c)
 target_link_libraries(test_crypto PRIVATE eos_crypto)
 add_test(NAME test_crypto COMMAND test_crypto)
 
-# --- test_crc: CRC-32 / CRC-64 known answers and file error paths ---
-add_executable(test_crc test_crc.c)
-target_link_libraries(test_crc PRIVATE eos_crypto)
-add_test(NAME test_crc COMMAND test_crc)
-
-# --- test_crypto_aes / _ecc / _rsa / _sha512: were sitting in tests/ unused ---
+# --- test_crypto_aes: AES-128/192/256 ECB + CBC, NIST FIPS-197 / SP 800-38A ---
 add_executable(test_crypto_aes test_crypto_aes.c)
 target_link_libraries(test_crypto_aes PRIVATE eos_crypto)
 add_test(NAME test_crypto_aes COMMAND test_crypto_aes)
 
+# --- test_crypto_ecc: ECC point arithmetic and ECDSA ---
 add_executable(test_crypto_ecc test_crypto_ecc.c)
 target_link_libraries(test_crypto_ecc PRIVATE eos_crypto)
 add_test(NAME test_crypto_ecc COMMAND test_crypto_ecc)
 
+# --- test_crypto_rsa: RSA modular exponentiation and verify ---
 add_executable(test_crypto_rsa test_crypto_rsa.c)
 target_link_libraries(test_crypto_rsa PRIVATE eos_crypto)
 add_test(NAME test_crypto_rsa COMMAND test_crypto_rsa)
 
-add_executable(test_crypto_sha512 test_crypto_sha512.c)
-target_link_libraries(test_crypto_sha512 PRIVATE eos_crypto)
-add_test(NAME test_crypto_sha512 COMMAND test_crypto_sha512)
-
-# --- test_crypto_failclosed: unimplemented RSA/ECC stubs refuse to run ---
-# Must NOT define EOS_ALLOW_STUB_CRYPTO; this is the production fail-closed path.
-add_executable(test_crypto_failclosed test_crypto_failclosed.c)
-target_link_libraries(test_crypto_failclosed PRIVATE eos_crypto)
-add_test(NAME test_crypto_failclosed COMMAND test_crypto_failclosed)
-
-# --- test_crypto_aes: AES-128/192/256 ECB + CBC, NIST FIPS-197 / SP 800-38A ---
-add_executable(test_crypto_aes test_crypto_aes.c)
-target_link_libraries(test_crypto_aes PRIVATE eos_crypto)
-add_test(NAME test_crypto_aes COMMAND test_crypto_aes)
-
 # --- test_crypto_sha512: SHA-512 against NIST vectors ---
 add_executable(test_crypto_sha512 test_crypto_sha512.c)
 target_link_libraries(test_crypto_sha512 PRIVATE eos_crypto)