diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index 87691c28..f9cc0f11 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -55,7 +55,7 @@ jobs:
         make mototest
     - name: Upload coverage to Codecov
       if: matrix.python-version == '3.11'
-      uses: codecov/codecov-action@v3.1.5
+      uses: codecov/codecov-action@v4.1.0
       with:
         token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
         files: ./coverage.xml
diff --git a/.readthedocs.yml b/.readthedocs.yml
new file mode 100644
index 00000000..55b19858
--- /dev/null
+++ b/.readthedocs.yml
@@ -0,0 +1,17 @@
+version: 2
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.8"
+
+sphinx:
+  configuration: docs/conf.py
+
+python:
+  install:
+    - requirements: docs/requirements.txt
+
+formats:
+  - htmlzip
+  - epub
diff --git a/CHANGES.rst b/CHANGES.rst
index 04f4e65a..9e10c1ed 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,14 @@
 Changes
 -------
 
+2.12.1 (2024-03-04)
+^^^^^^^^^^^^^^^^^^^
+* fix use of proxies #1070
+
+2.12.0 (2024-02-28)
+^^^^^^^^^^^^^^^^^^^
+* bump botocore dependency specification
+
 2.11.2 (2024-02-02)
 ^^^^^^^^^^^^^^^^^^^
 * bump botocore dependency specification
diff --git a/aiobotocore/__init__.py b/aiobotocore/__init__.py
index ded7bd35..524297b5 100644
--- a/aiobotocore/__init__.py
+++ b/aiobotocore/__init__.py
@@ -1 +1 @@
-__version__ = '2.11.2'
+__version__ = '2.12.1'
diff --git a/aiobotocore/credentials.py b/aiobotocore/credentials.py
index b78d2158..885b71c8 100644
--- a/aiobotocore/credentials.py
+++ b/aiobotocore/credentials.py
@@ -914,8 +914,7 @@ async def _retrieve_or_fail(self):
             full_uri = self._fetcher.full_url(self._environ[self.ENV_VAR])
         else:
             full_uri = self._environ[self.ENV_VAR_FULL]
-        headers = self._build_headers()
-        fetcher = self._create_fetcher(full_uri, headers)
+        fetcher = self._create_fetcher(full_uri)
         creds = await fetcher()
         return AioRefreshableCredentials(
             access_key=creds['access_key'],
@@ -926,9 +925,10 @@ async def _retrieve_or_fail(self):
             refresh_using=fetcher,
         )
 
-    def _create_fetcher(self, full_uri, headers):
+    def _create_fetcher(self, full_uri, *args, **kwargs):
         async def fetch_creds():
             try:
+                headers = self._build_headers()
                 response = await self._fetcher.retrieve_full_uri(
                     full_uri, headers=headers
                 )
diff --git a/aiobotocore/httpsession.py b/aiobotocore/httpsession.py
index b98c59ed..c8c3fe41 100644
--- a/aiobotocore/httpsession.py
+++ b/aiobotocore/httpsession.py
@@ -1,4 +1,5 @@
 import asyncio
+import contextlib
 import io
 import os
 import socket
@@ -54,8 +55,11 @@ def __init__(
         proxies_config=None,
         connector_args=None,
     ):
+        self._exit_stack = contextlib.AsyncExitStack()
+
         # TODO: handle socket_options
-        self._session: Optional[aiohttp.ClientSession] = None
+        # keep track of sessions by proxy url (if any)
+        self._sessions: Dict[Optional[str], aiohttp.ClientSession] = {}
         self._verify = verify
         self._proxy_config = ProxyConfiguration(
             proxies=proxies, proxies_settings=proxies_config
@@ -93,53 +97,17 @@ def __init__(
         # it also pools by host so we don't need a manager, and can pass proxy via
         # request so don't need proxy manager
 
-        ssl_context = None
-        if bool(verify):
-            if proxies:
-                proxies_settings = self._proxy_config.settings
-                ssl_context = self._setup_proxy_ssl_context(proxies_settings)
-                # TODO: add support for
-                #    proxies_settings.get('proxy_use_forwarding_for_https')
-            else:
-                ssl_context = self._get_ssl_context()
-
-                # inline self._setup_ssl_cert
-                ca_certs = get_cert_path(verify)
-                if ca_certs:
-                    ssl_context.load_verify_locations(ca_certs, None, None)
-
-        self._create_connector = lambda: aiohttp.TCPConnector(
-            limit=max_pool_connections,
-            verify_ssl=bool(verify),
-            ssl=ssl_context,
-            **self._connector_args
-        )
-        self._connector = None
-
     async def __aenter__(self):
-        assert not self._session and not self._connector
+        assert not self._sessions
 
-        self._connector = self._create_connector()
-
-        self._session = aiohttp.ClientSession(
-            connector=self._connector,
-            timeout=self._timeout,
-            skip_auto_headers={'CONTENT-TYPE'},
-            auto_decompress=False,
-        )
         return self
 
     async def __aexit__(self, exc_type, exc_val, exc_tb):
-        if self._session:
-            await self._session.__aexit__(exc_type, exc_val, exc_tb)
-            self._session = None
-            self._connector = None
+        self._sessions.clear()
+        await self._exit_stack.aclose()
 
     def _get_ssl_context(self):
-        ssl_context = create_urllib3_context()
-        if self._cert_file:
-            ssl_context.load_cert_chain(self._cert_file, self._key_file)
-        return ssl_context
+        return create_urllib3_context()
 
     def _setup_proxy_ssl_context(self, proxy_url):
         proxies_settings = self._proxy_config.settings
@@ -167,6 +135,58 @@ def _setup_proxy_ssl_context(self, proxy_url):
         except (OSError, LocationParseError) as e:
             raise InvalidProxiesConfigError(error=e)
 
+    def _chunked(self, headers):
+        transfer_encoding = headers.get('Transfer-Encoding', '')
+        if chunked := transfer_encoding.lower() == 'chunked':
+            # aiohttp wants chunking as a param, and not a header
+            del headers['Transfer-Encoding']
+        return chunked or None
+
+    def _create_connector(self, proxy_url):
+        ssl_context = None
+        if bool(self._verify):
+            if proxy_url:
+                ssl_context = self._setup_proxy_ssl_context(proxy_url)
+                # TODO: add support for
+                #    proxies_settings.get('proxy_use_forwarding_for_https')
+            else:
+                ssl_context = self._get_ssl_context()
+
+            if ssl_context:
+                if self._cert_file:
+                    ssl_context.load_cert_chain(
+                        self._cert_file,
+                        self._key_file,
+                    )
+
+                # inline self._setup_ssl_cert
+                ca_certs = get_cert_path(self._verify)
+                if ca_certs:
+                    ssl_context.load_verify_locations(ca_certs, None, None)
+
+        return aiohttp.TCPConnector(
+            limit=self._max_pool_connections,
+            verify_ssl=bool(self._verify),
+            ssl=ssl_context,
+            **self._connector_args,
+        )
+
+    async def _get_session(self, proxy_url):
+        if not (session := self._sessions.get(proxy_url)):
+            connector = self._create_connector(proxy_url)
+            self._sessions[
+                proxy_url
+            ] = session = await self._exit_stack.enter_async_context(
+                aiohttp.ClientSession(
+                    connector=connector,
+                    timeout=self._timeout,
+                    skip_auto_headers={'CONTENT-TYPE'},
+                    auto_decompress=False,
+                ),
+            )
+
+        return session
+
     async def close(self):
         await self.__aexit__(None, None, None)
 
@@ -195,20 +215,15 @@ async def send(self, request):
             # https://github.com/boto/botocore/issues/1255
             headers_['Accept-Encoding'] = 'identity'
 
-            chunked = None
-            if headers_.get('Transfer-Encoding', '').lower() == 'chunked':
-                # aiohttp wants chunking as a param, and not a header
-                headers_.pop('Transfer-Encoding', '')
-                chunked = True
-
             if isinstance(data, io.IOBase):
                 data = _IOBaseWrapper(data)
 
             url = URL(url, encoded=True)
-            response = await self._session.request(
+            session = await self._get_session(proxy_url)
+            response = await session.request(
                 request.method,
                 url=url,
-                chunked=chunked,
+                chunked=self._chunked(headers_),
                 headers=headers_,
                 data=data,
                 proxy=proxy_url,
diff --git a/docs/conf.py b/docs/conf.py
index f6ca032a..f70c81f2 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -89,7 +89,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
@@ -123,10 +123,6 @@
     'github_type': 'star',
     'github_banner': True,
 }
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
 
 
 # -- Options for HTMLHelp output ------------------------------------------
diff --git a/docs/examples/s3/basic_usage.rst b/docs/examples/s3/basic_usage.rst
index 3b8d4732..a9aeb496 100644
--- a/docs/examples/s3/basic_usage.rst
+++ b/docs/examples/s3/basic_usage.rst
@@ -1,5 +1,6 @@
 Put, Get and Delete
------------
+-------------------
+
 Simple put, get, delete example for S3 service:
 
 .. literalinclude:: ../../../examples/simple.py
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 4f81946d..5388c883 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1 +1 @@
-sphinx==2.4.1
+sphinx==5.3.0
diff --git a/readthedocs.yml b/readthedocs.yml
deleted file mode 100644
index 7a70b110..00000000
--- a/readthedocs.yml
+++ /dev/null
@@ -1,11 +0,0 @@
-name: aiobotocore
-type: sphinx
-requirements_file: docs/requirements.txt
-build:
-  image: latest
-python:
-  version: 3.6
-  setup_py_install: true
-formats:
-  - htmlzip
-  - epub
diff --git a/setup.py b/setup.py
index 4d7fe28f..adf7feba 100644
--- a/setup.py
+++ b/setup.py
@@ -7,15 +7,15 @@
 # NOTE: When updating botocore make sure to update awscli/boto3 versions below
 install_requires = [
     # pegged to also match items in `extras_require`
-    'botocore>=1.33.2,<1.34.35',
+    'botocore>=1.34.41,<1.34.52',
     'aiohttp>=3.7.4.post0,<4.0.0',
     'wrapt>=1.10.10, <2.0.0',
     'aioitertools>=0.5.1,<1.0.0',
 ]
 
 extras_require = {
-    'awscli': ['awscli>=1.31.2,<1.32.35'],
-    'boto3': ['boto3>=1.33.2,<1.34.35'],
+    'awscli': ['awscli>=1.32.41,<1.32.52'],
+    'boto3': ['boto3>=1.34.41,<1.34.52'],
 }
 
 
diff --git a/tests/test_patches.py b/tests/test_patches.py
index 05d2569a..570fa495 100644
--- a/tests/test_patches.py
+++ b/tests/test_patches.py
@@ -185,11 +185,9 @@
         'f09731451ff6ba0645dc82e5c7948dfbf781e025',
     },
     BaseClient.get_paginator: {
-        '3531d5988aaaf0fbb3885044ccee1a693ec2608b',
         '1c38079de68ccd43a5a06e36b1a47ec62233a7c2',
     },
     BaseClient.get_waiter: {
-        '44f0473d993d49ac7502984a7ccee3240b088404',
         '4a4aeabe53af25d3737204187a31f930230864b4',
     },
     BaseClient.__getattr__: {'3ec17f468f50789fa633d6041f40b66a2f593e77'},
@@ -266,10 +264,10 @@
     ContainerProvider.__init__: {'ea6aafb2e12730066af930fb5a27f7659c1736a1'},
     ContainerProvider.load: {'57c35569050b45c1e9e33fcdb3b49da9e342fdcf'},
     ContainerProvider._retrieve_or_fail: {
-        '7c14f1cdee07217f847a71068866bdd10c3fa0fa'
+        'c99153a4c68927810a3edde09ee98c5ba33d3697'
     },
     ContainerProvider._create_fetcher: {
-        '935ae28fdb1c76f419523d4030265f8c4d9d0b00'
+        'a921ee40b9b4779f238adcf369a3757b19857fc7'
     },
     InstanceMetadataProvider.load: {
         '15becfc0373ccfbc1bb200bd6a34731e61561d06'