diff --git a/smartthings_local/protocol/dtls_session.py b/smartthings_local/protocol/dtls_session.py
index 4b88153..5c09dc2 100644
--- a/smartthings_local/protocol/dtls_session.py
+++ b/smartthings_local/protocol/dtls_session.py
@@ -104,9 +104,9 @@
 _BLOCK_MAX_ATTEMPTS = 3
 _BLOCK_ACK_TIMEOUT  = 4.0
 
-# How often a block wait re-checks that the reader is still alive. Short
-# enough that a mid-transfer reader death fails fast instead of burning
-# the whole per-block timeout, long enough to stay off the CPU.
+# How often a request wait re-checks that the reader is still alive. Short
+# enough that a mid-exchange reader death fails fast instead of burning
+# the whole per-attempt timeout, long enough to stay off the CPU.
 _BLOCK_LIVENESS_POLL_S = 0.25
 
 # Inter-request pacing: minimum seconds between CoAP CON sends on one session.
@@ -1095,7 +1095,7 @@ def _exchange_block(self, tok, path_segs, query, num, szx, deadline):
                         remaining if acknowledged
                         else min(_BLOCK_ACK_TIMEOUT, max(0.1, remaining))
                     )
-                    if not self._wait_for_block(ev, per_wait):
+                    if not self._wait_live(ev, per_wait):
                         if acknowledged:
                             raise SessionTimeoutError()
                         break
@@ -1115,8 +1115,16 @@ def _exchange_block(self, tok, path_segs, query, num, szx, deadline):
             self._unregister_pending_request(tok, mid, exchange)
         raise SessionTimeoutError()
 
-    def _wait_for_block(self, ev, per_wait):
-        """Wait for a block response while checking reader liveness."""
+    def _wait_live(self, ev, per_wait):
+        """Wait for one response, giving up early if the reader dies
+        underneath us.
+
+        Only the reader thread can resolve a token, so once it is gone
+        the wait can never succeed. Polling in slices turns what would
+        be a full per-attempt timeout into an immediate SessionClosedError,
+        which is the same fail-fast contract get() and post() get from
+        _check_live() at entry — it just has to hold for the whole
+        exchange, not only its first moment."""
         deadline = time.monotonic() + per_wait
         while True:
             slice_s = min(
diff --git a/tests/test_dtls_session_mid_registry.py b/tests/test_dtls_session_mid_registry.py
index b0cf6a5..3a1ed31 100644
--- a/tests/test_dtls_session_mid_registry.py
+++ b/tests/test_dtls_session_mid_registry.py
@@ -111,7 +111,7 @@ def send(datagram):
         requests.append((mid, token))
         session._dispatch_coap(build_coap(TYPE_ACK, 0, mid, b"", []))
 
-    def wait_for_block(_event, timeout):
+    def wait_live(_event, timeout):
         waits.append(timeout)
         mid, token = requests[-1]
         session._dispatch_coap(
@@ -120,7 +120,7 @@ def wait_for_block(_event, timeout):
         return True
 
     session._send_dgram = send
-    session._wait_for_block = wait_for_block
+    session._wait_live = wait_live
 
     assert session.get(["device", "0"], timeout=1.0) == (0x45, b"ok")
     assert len(requests) == 1
@@ -215,7 +215,7 @@ def fail_send(_datagram):
     else:
         session._send_dgram = lambda _datagram: None
         if operation == "get":
-            session._wait_for_block = lambda _event, _timeout: False
+            session._wait_live = lambda _event, _timeout: False
         expected = SessionTimeoutError
         timeout = 0.0
 
diff --git a/tests/test_dtls_session_reader_death.py b/tests/test_dtls_session_reader_death.py
index 1fe3bed..388cbb9 100644
--- a/tests/test_dtls_session_reader_death.py
+++ b/tests/test_dtls_session_reader_death.py
@@ -460,7 +460,7 @@ def respond(datagram):
         sess._dispatch_coap(build_empty_ack(mid))
         pending['token'] = token
 
-    def wait_for_block(_event, per_wait):
+    def wait_live(_event, per_wait):
         waits.append(per_wait)
         token = pending['token']
         if len(waits) == 1:
@@ -486,7 +486,7 @@ def wait_for_block(_event, per_wait):
         return True
 
     sess._send_dgram = respond
-    sess._wait_for_block = wait_for_block
+    sess._wait_live = wait_live
     sess.pace = lambda: None
     assert sess.get(['oic', 'res'], timeout=0.2) == (
         0x45,
diff --git a/tests/test_mid_registry_retransmission.py b/tests/test_mid_registry_retransmission.py
index b96740f..ef30c1c 100644
--- a/tests/test_mid_registry_retransmission.py
+++ b/tests/test_mid_registry_retransmission.py
@@ -61,7 +61,7 @@ def send(datagram):
 
     # Answer only once the third attempt is on the wire, so two full
     # retransmissions have to happen first.
-    def wait_for_block(_event, _timeout):
+    def wait_live(_event, _timeout):
         if len(sent) < 3:
             return False
         _mtype, _code, mid, token, _options, _payload = parse_coap(sent[-1])
@@ -70,7 +70,7 @@ def wait_for_block(_event, _timeout):
         )
         return True
 
-    session._wait_for_block = wait_for_block
+    session._wait_live = wait_live
 
     assert session.get(["device", "0"], timeout=5.0) == (0x45, b"ok")
 
@@ -85,7 +85,7 @@ def wait_for_block(_event, _timeout):
 def test_exhausted_attempts_still_release_the_single_registration():
     session = _session()
     session._send_dgram = lambda _datagram: None
-    session._wait_for_block = lambda _event, _timeout: False
+    session._wait_live = lambda _event, _timeout: False
 
     with pytest.raises(SessionTimeoutError):
         session.get(["device", "0"], timeout=0.05)