diff --git a/.devcontainer/README.md b/.devcontainer/README.md
index 2326fc8..fc6cf78 100644
--- a/.devcontainer/README.md
+++ b/.devcontainer/README.md
@@ -24,7 +24,7 @@ This directory contains the configuration for developing the Navien NWP500 Home
 
 ### Python Packages
 All packages from `requirements.txt` are pre-installed:
-- `nwp500-python==8.1.2` - Core library for Navien device communication
+- `nwp500-python==8.1.3` - Core library for Navien device communication
 - `awsiotsdk>=1.29.0` - AWS IoT SDK for MQTT
 - `homeassistant>=2024.1.0` - Home Assistant core
 - `mypy`, `pyright` - Type checkers
diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index 103f269..90c8266 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -29,7 +29,7 @@ This is a Home Assistant custom component that provides integration for Navien N
   - **GitHub Repository**: https://github.com/eman/nwp500-python
   - **Documentation**: https://nwp500-python.readthedocs.io/en/stable/
   - **PyPI Package**: https://pypi.org/project/nwp500-python/
-  - **Current Version**: 8.1.1 (see `custom_components/nwp500/manifest.json`)
+  - **Current Version**: 8.1.3 (see `custom_components/nwp500/manifest.json`)
   - **Note**: When instructions refer to "adopting a new library version" or "updating the library," they mean updating nwp500-python
 
 ### Home Assistant Integration
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4265867..ff75fab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,16 @@
 
 ## [Unreleased]
 
+### Changed
+- **Library Dependency: nwp500-python**: Upgraded to 8.1.3. Fixes a
+  thread-safety bug in `on_connection_resumed` where `Task.cancel()` was called
+  directly from an AWS IoT SDK background thread. When the event loop was busy,
+  the cancellation could be silently dropped, leaving a stale
+  `_reconnect_with_backoff` task that would complete its sleep and tear down an
+  otherwise healthy connection — restarting the
+  disconnect → reconnect → `AWS_ERROR_MQTT_UNEXPECTED_HANGUP` cycle. See
+  [nwp500-python PR #89](https://github.com/eman/nwp500-python/pull/89).
+
 ## [0.15.4] - 2026-06-05
 
 ## [0.15.4] - 2026-06-05
diff --git a/README.md b/README.md
index 60ceb14..519f27a 100644
--- a/README.md
+++ b/README.md
@@ -178,7 +178,7 @@ action:
 
 ## Library Version
 
-Uses **[nwp500-python v8.1.2](https://github.com/eman/nwp500-python/releases/tag/v8.1.2)**. See [CHANGELOG.md](CHANGELOG.md#library-dependency-nwp500-python) for version history.
+Uses **[nwp500-python v8.1.3](https://github.com/eman/nwp500-python/releases/tag/v8.1.3)**. See [CHANGELOG.md](CHANGELOG.md#library-dependency-nwp500-python) for version history.
 
 ## License
 
diff --git a/custom_components/nwp500/config_flow.py b/custom_components/nwp500/config_flow.py
index 915ad5b..59c57a0 100644
--- a/custom_components/nwp500/config_flow.py
+++ b/custom_components/nwp500/config_flow.py
@@ -214,7 +214,7 @@ async def validate_input(
     if not nwp500_available:
         _LOGGER.error(
             "nwp500-python library not installed. Please install with: "
-            'uv pip install "nwp500-python==8.1.2" awsiotsdk>=1.29.0'
+            'uv pip install "nwp500-python==8.1.3" awsiotsdk>=1.29.0'
         )
         raise CannotConnect("nwp500-python library not available")
 
diff --git a/custom_components/nwp500/coordinator.py b/custom_components/nwp500/coordinator.py
index 79c6b6b..19cfcea 100644
--- a/custom_components/nwp500/coordinator.py
+++ b/custom_components/nwp500/coordinator.py
@@ -587,7 +587,7 @@ async def _setup_clients(self) -> None:
         except ImportError as err:
             _LOGGER.error(
                 "nwp500-python library not installed. Please install: "
-                'uv pip install "nwp500-python==8.1.2" awsiotsdk>=1.29.0'
+                'uv pip install "nwp500-python==8.1.3" awsiotsdk>=1.29.0'
             )
             raise UpdateFailed(
                 f"nwp500-python library not available: {err}"
diff --git a/custom_components/nwp500/manifest.json b/custom_components/nwp500/manifest.json
index 2fc7418..901b422 100644
--- a/custom_components/nwp500/manifest.json
+++ b/custom_components/nwp500/manifest.json
@@ -18,7 +18,7 @@
     "custom_components.nwp500"
   ],
   "requirements": [
-    "nwp500-python==8.1.2",
+    "nwp500-python==8.1.3",
     "awsiotsdk>=1.29.0"
   ],
   "single_config_entry": true,
diff --git a/requirements.txt b/requirements.txt
index 32ac002..6506467 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@
 
 # Usage: uv pip install -r requirements.txt
 # Core integration library
-nwp500-python==8.1.2
+nwp500-python==8.1.3
 
 # AWS IoT SDK for MQTT communication
 awsiotsdk>=1.29.0
diff --git a/tox.ini b/tox.ini
index e415956..ca99d07 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ deps =
     pytest-timeout>=2.1.0
 commands_pre =
     python -m pip install awsiotsdk>=1.29.0
-    python -m pip install "nwp500-python==8.1.2" --no-deps
+    python -m pip install "nwp500-python==8.1.3" --no-deps
 
 [testenv:py314]
 description = Run tests on Python 3.14
@@ -24,7 +24,7 @@ description = Run mypy type checking
 deps =
     mypy>=1.0.0
     homeassistant>=2026.4.0
-    nwp500-python==8.1.2
+    nwp500-python==8.1.3
 commands_pre =
 
 [testenv:basedpyright]
@@ -32,7 +32,7 @@ description = Run basedpyright type checking
 deps =
     basedpyright>=1.0.0
     homeassistant>=2026.4.0
-    nwp500-python==8.1.2
+    nwp500-python==8.1.3
 commands_pre =
 
 [testenv:ruff]
@@ -64,7 +64,7 @@ deps =
     {[testenv]deps}
 commands_pre =
     python -m pip install awsiotsdk>=1.29.0
-    python -m pip install "nwp500-python==8.1.2" --no-deps
+    python -m pip install "nwp500-python==8.1.3" --no-deps
 commands =
     pytest --cov=custom_components.nwp500 \
            --cov-report=html \