From 12b4a1d565a53794f5b55c8bd1728221c906ed41 Mon Sep 17 00:00:00 2001
From: Yaroslav <yarolegovich@gmail.com>
Date: Fri, 7 Nov 2025 11:56:53 +0100
Subject: [PATCH 01/15] feat: add metadata to send message request (#532)

Extended `client.send_message` to take `metadata` parameter which gets
attached to `MessageSendParams`.
---
 src/a2a/client/base_client.py    |  7 ++++++-
 src/a2a/client/client.py         |  1 +
 tests/client/test_base_client.py | 12 ++++++++++--
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/a2a/client/base_client.py b/src/a2a/client/base_client.py
index f4a8d03d..b8697d86 100644
--- a/src/a2a/client/base_client.py
+++ b/src/a2a/client/base_client.py
@@ -1,4 +1,5 @@
 from collections.abc import AsyncIterator
+from typing import Any
 
 from a2a.client.client import (
     Client,
@@ -47,6 +48,7 @@ async def send_message(
         request: Message,
         *,
         context: ClientCallContext | None = None,
+        request_metadata: dict[str, Any] | None = None,
     ) -> AsyncIterator[ClientEvent | Message]:
         """Sends a message to the agent.
 
@@ -57,6 +59,7 @@ async def send_message(
         Args:
             request: The message to send to the agent.
             context: The client call context.
+            request_metadata: Extensions Metadata attached to the request.
 
         Yields:
             An async iterator of `ClientEvent` or a final `Message` response.
@@ -70,7 +73,9 @@ async def send_message(
                 else None
             ),
         )
-        params = MessageSendParams(message=request, configuration=config)
+        params = MessageSendParams(
+            message=request, configuration=config, metadata=request_metadata
+        )
 
         if not self._config.streaming or not self._card.capabilities.streaming:
             response = await self._transport.send_message(
diff --git a/src/a2a/client/client.py b/src/a2a/client/client.py
index 7cc10423..0e1c4323 100644
--- a/src/a2a/client/client.py
+++ b/src/a2a/client/client.py
@@ -110,6 +110,7 @@ async def send_message(
         request: Message,
         *,
         context: ClientCallContext | None = None,
+        request_metadata: dict[str, Any] | None = None,
     ) -> AsyncIterator[ClientEvent | Message]:
         """Sends a message to the server.
 
diff --git a/tests/client/test_base_client.py b/tests/client/test_base_client.py
index d93a2203..f5ab2543 100644
--- a/tests/client/test_base_client.py
+++ b/tests/client/test_base_client.py
@@ -73,9 +73,14 @@ async def create_stream(*args, **kwargs):
 
     mock_transport.send_message_streaming.return_value = create_stream()
 
-    events = [event async for event in base_client.send_message(sample_message)]
+    meta = {'test': 1}
+    stream = base_client.send_message(sample_message, request_metadata=meta)
+    events = [event async for event in stream]
 
     mock_transport.send_message_streaming.assert_called_once()
+    assert (
+        mock_transport.send_message_streaming.call_args[0][0].metadata == meta
+    )
     assert not mock_transport.send_message.called
     assert len(events) == 1
     assert events[0][0].id == 'task-123'
@@ -92,9 +97,12 @@ async def test_send_message_non_streaming(
         status=TaskStatus(state=TaskState.completed),
     )
 
-    events = [event async for event in base_client.send_message(sample_message)]
+    meta = {'test': 1}
+    stream = base_client.send_message(sample_message, request_metadata=meta)
+    events = [event async for event in stream]
 
     mock_transport.send_message.assert_called_once()
+    assert mock_transport.send_message.call_args[0][0].metadata == meta
     assert not mock_transport.send_message_streaming.called
     assert len(events) == 1
     assert events[0][0].id == 'task-456'

From 265fd3325e1c5a3e945291b65b159282c2b84255 Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Fri, 7 Nov 2025 05:04:43 -0600
Subject: [PATCH 02/15] chore(main): release 0.3.11 (#534)

:robot: I have created a release *beep* *boop*
---


##
[0.3.11](https://github.com/a2aproject/a2a-python/compare/v0.3.10...v0.3.11)
(2025-11-07)


### Bug Fixes

* add metadata to send message request
([12b4a1d](https://github.com/a2aproject/a2a-python/commit/12b4a1d565a53794f5b55c8bd1728221c906ed41))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).
---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 449438cc..39446e61 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## [0.3.11](https://github.com/a2aproject/a2a-python/compare/v0.3.10...v0.3.11) (2025-11-07)
+
+
+### Bug Fixes
+
+* add metadata to send message request ([12b4a1d](https://github.com/a2aproject/a2a-python/commit/12b4a1d565a53794f5b55c8bd1728221c906ed41))
+
 ## [0.3.10](https://github.com/a2aproject/a2a-python/compare/v0.3.9...v0.3.10) (2025-10-21)
 
 

From c03129b99a663ae1f1ae72f20e4ead7807ede941 Mon Sep 17 00:00:00 2001
From: "agil.yolchuyev" <agilyolchuyev@outlook.com>
Date: Mon, 10 Nov 2025 16:53:23 -0500
Subject: [PATCH 03/15] fix(grpc): Add `extensions` to `Artifact` converters.
 (#523)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

# Description

Thank you for opening a Pull Request!
Before submitting your PR, there are a few things you can do to make
sure it goes smoothly:

- [ ] Follow the [`CONTRIBUTING`
Guide](https://github.com/a2aproject/a2a-python/blob/main/CONTRIBUTING.md).
- [ ] Make your Pull Request title in the
<https://www.conventionalcommits.org/> specification.
- Important Prefixes for
[release-please](https://github.com/googleapis/release-please):
- `fix:` which represents bug fixes, and correlates to a
[SemVer](https://semver.org/) patch.
- `feat:` represents a new feature, and correlates to a SemVer minor.
- `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking
change (indicated by the `!`) and will result in a SemVer major.
- [ ] Ensure the tests and linter pass (Run `bash scripts/format.sh`
from the repository root to format)
- [ ] Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

---------

Co-authored-by: yolagil <agil@peotic.com>
Co-authored-by: Lukasz Kawka <luk.kawka@gmail.com>
---
 src/a2a/utils/proto_utils.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/a2a/utils/proto_utils.py b/src/a2a/utils/proto_utils.py
index e619cd72..d077d62b 100644
--- a/src/a2a/utils/proto_utils.py
+++ b/src/a2a/utils/proto_utils.py
@@ -57,7 +57,7 @@ def make_dict_serializable(value: Any) -> Any:
     Returns:
         A serializable value.
     """
-    if isinstance(value, (str, int, float, bool)) or value is None:
+    if isinstance(value, str | int | float | bool) or value is None:
         return value
     if isinstance(value, dict):
         return {k: make_dict_serializable(v) for k, v in value.items()}
@@ -140,6 +140,7 @@ def message(cls, message: types.Message | None) -> a2a_pb2.Message | None:
             task_id=message.task_id or '',
             role=cls.role(message.role),
             metadata=cls.metadata(message.metadata),
+            extensions=message.extensions or [],
         )
 
     @classmethod
@@ -239,6 +240,7 @@ def artifact(cls, artifact: types.Artifact) -> a2a_pb2.Artifact:
             metadata=cls.metadata(artifact.metadata),
             name=artifact.name,
             parts=[cls.part(p) for p in artifact.parts],
+            extensions=artifact.extensions or [],
         )
 
     @classmethod
@@ -695,6 +697,7 @@ def artifact(cls, artifact: a2a_pb2.Artifact) -> types.Artifact:
             metadata=cls.metadata(artifact.metadata),
             name=artifact.name,
             parts=[cls.part(p) for p in artifact.parts],
+            extensions=artifact.extensions or None,
         )
 
     @classmethod

From dc59430b7f608ffb681a87f5fbf0bf01bd852206 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Tue, 11 Nov 2025 16:39:00 +0000
Subject: [PATCH 04/15] chore(deps): bump the github-actions group with 3
 updates (#528)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Bumps the github-actions group with 3 updates:
[astral-sh/setup-uv](https://github.com/astral-sh/setup-uv),
[actions/upload-artifact](https://github.com/actions/upload-artifact)
and
[actions/download-artifact](https://github.com/actions/download-artifact).

Updates `astral-sh/setup-uv` from 6 to 7
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/astral-sh/setup-uv/releases">astral-sh/setup-uv's
releases</a>.</em></p>
<blockquote>
<h2>v7.0.0 🌈 node24 and a lot of bugfixes</h2>
<h2>Changes</h2>
<p>This release comes with a load of bug fixes and a speed up. Because
of switching from node20 to node24 it is also a breaking change. If you
are running on GitHub hosted runners this will just work, if you are
using self-hosted runners make sure, that your runners are up to date.
If you followed the normal installation instructions your self-hosted
runner will keep itself updated.</p>
<p>This release also removes the deprecated input
<code>server-url</code> which was used to download uv releases from a
different server.
The <a
href="https://github.com/astral-sh/setup-uv?tab=readme-ov-file#manifest-file">manifest-file</a>
input supersedes that functionality by adding a flexible way to define
available versions and where they should be downloaded from.</p>
<h3>Fixes</h3>
<ul>
<li>The action now respects when the environment variable
<code>UV_CACHE_DIR</code> is already set and does not overwrite it. It
now also finds <a
href="https://docs.astral.sh/uv/reference/settings/#cache-dir">cache-dir</a>
settings in config files if you set them.</li>
<li>Some users encountered problems that <a
href="https://github.com/astral-sh/setup-uv?tab=readme-ov-file#disable-cache-pruning">cache
pruning</a> took forever because they had some <code>uv</code> processes
running in the background. Starting with uv version <code>0.8.24</code>
this action uses <code>uv cache prune --ci --force</code> to ignore the
running processes</li>
<li>If you just want to install uv but not have it available in path,
this action now respects <code>UV_NO_MODIFY_PATH</code></li>
<li>Some other actions also set the env var <code>UV_CACHE_DIR</code>.
This action can now deal with that but as this could lead to unwanted
behavior in some edgecases a warning is now displayed.</li>
</ul>
<h3>Improvements</h3>
<p>If you are using minimum version specifiers for the version of uv to
install for example</p>
<pre lang="toml"><code>[tool.uv]
required-version = &quot;&gt;=0.8.17&quot;
</code></pre>
<p>This action now detects that and directly uses the latest version.
Previously it would download all available releases from the uv repo
to determine the highest matching candidate for the version specifier,
which took much more time.</p>
<p>If you are using other specifiers like <code>0.8.x</code> this action
still needs to download all available releases because the specifier
defines an upper bound (not 0.9.0 or later) and &quot;latest&quot; would
possibly not satisfy that.</p>
<h2>🚨 Breaking changes</h2>
<ul>
<li>Use node24 instead of node20 <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/608">#608</a>)</li>
<li>Remove deprecated input server-url <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/607">#607</a>)</li>
</ul>
<h2>🐛 Bug fixes</h2>
<ul>
<li>Respect UV_CACHE_DIR and cache-dir <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/612">#612</a>)</li>
<li>Use --force when pruning cache <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/611">#611</a>)</li>
<li>Respect UV_NO_MODIFY_PATH <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/603">#603</a>)</li>
<li>Warn when <code>UV_CACHE_DIR</code> has changed <a
href="https://github.com/jamesbraza"><code>@​jamesbraza</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/601">#601</a>)</li>
</ul>
<h2>🚀 Enhancements</h2>
<ul>
<li>Shortcut to latest version for minimum version specifier <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/598">#598</a>)</li>
</ul>
<h2>🧰 Maintenance</h2>
<ul>
<li>Bump dependencies <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/613">#613</a>)</li>
<li>Fix test-uv-no-modify-path <a
href="https://github.com/eifinger"><code>@​eifinger</code></a> (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/604">#604</a>)</li>
</ul>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/85856786d1ce8acfbcc2f13a5f3fbd6b938f9f41"><code>8585678</code></a>
Bump dependencies (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/664">#664</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/22d500a65c34c827ebc95094040adcee254e92fa"><code>22d500a</code></a>
Bump github/codeql-action from 4.30.8 to 4.30.9 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/652">#652</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/14d557131df7147286f7ce93a5b6b0189f8e1bc3"><code>14d5571</code></a>
chore: update known checksums for 0.9.5 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/663">#663</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/29cd2350cd44d155ed44d0eba0e1b63d07fb3b69"><code>29cd235</code></a>
Use tar for extracting the uv zip file on Windows too (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/660">#660</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/2ddd2b9cb38ad8efd50337e8ab201519a34c9f24"><code>2ddd2b9</code></a>
chore: update known checksums for 0.9.4 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/651">#651</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/b7bf78939d77607a9ccb489e4ec4651ba1092d5c"><code>b7bf789</code></a>
Fix &quot;lowest&quot; resolution strategy with lower-bound only (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/649">#649</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/cb6c0a53d9c61608defba05145184489d20183b2"><code>cb6c0a5</code></a>
Change version in docs to v7 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/647">#647</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/dffc6292f2060d80116faf1baee66598a67f042c"><code>dffc629</code></a>
Use working-directory to detect empty workdir (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/645">#645</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/6e346e1653b720be5aaa194026b82bdef65869c7"><code>6e346e1</code></a>
chore: update known checksums for 0.9.3 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/644">#644</a>)</li>
<li><a
href="https://github.com/astral-sh/setup-uv/commit/3ccd0fd498ef6303a98d4125859aae05eedf6294"><code>3ccd0fd</code></a>
Bump github/codeql-action from 4.30.7 to 4.30.8 (<a
href="https://redirect.github.com/astral-sh/setup-uv/issues/639">#639</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/astral-sh/setup-uv/compare/v6...v7">compare
view</a></li>
</ul>
</details>
<br />

Updates `actions/upload-artifact` from 4 to 5
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/actions/upload-artifact/releases">actions/upload-artifact's
releases</a>.</em></p>
<blockquote>
<h2>v5.0.0</h2>
<h2>What's Changed</h2>
<p><strong>BREAKING CHANGE:</strong> this update supports Node
<code>v24.x</code>. This is not a breaking change per-se but we're
treating it as such.</p>
<ul>
<li>Update README.md by <a
href="https://github.com/GhadimiR"><code>@​GhadimiR</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/681">actions/upload-artifact#681</a></li>
<li>Update README.md by <a
href="https://github.com/nebuk89"><code>@​nebuk89</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/712">actions/upload-artifact#712</a></li>
<li>Readme: spell out the first use of GHES by <a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a> in
<a
href="https://redirect.github.com/actions/upload-artifact/pull/727">actions/upload-artifact#727</a></li>
<li>Update GHES guidance to include reference to Node 20 version by <a
href="https://github.com/patrikpolyak"><code>@​patrikpolyak</code></a>
in <a
href="https://redirect.github.com/actions/upload-artifact/pull/725">actions/upload-artifact#725</a></li>
<li>Bump <code>@actions/artifact</code> to <code>v4.0.0</code></li>
<li>Prepare <code>v5.0.0</code> by <a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a> in
<a
href="https://redirect.github.com/actions/upload-artifact/pull/734">actions/upload-artifact#734</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/GhadimiR"><code>@​GhadimiR</code></a>
made their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/681">actions/upload-artifact#681</a></li>
<li><a href="https://github.com/nebuk89"><code>@​nebuk89</code></a> made
their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/712">actions/upload-artifact#712</a></li>
<li><a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a>
made their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/727">actions/upload-artifact#727</a></li>
<li><a
href="https://github.com/patrikpolyak"><code>@​patrikpolyak</code></a>
made their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/725">actions/upload-artifact#725</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/upload-artifact/compare/v4...v5.0.0">https://github.com/actions/upload-artifact/compare/v4...v5.0.0</a></p>
<h2>v4.6.2</h2>
<h2>What's Changed</h2>
<ul>
<li>Update to use artifact 2.3.2 package &amp; prepare for new
upload-artifact release by <a
href="https://github.com/salmanmkc"><code>@​salmanmkc</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/685">actions/upload-artifact#685</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/salmanmkc"><code>@​salmanmkc</code></a>
made their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/685">actions/upload-artifact#685</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/upload-artifact/compare/v4...v4.6.2">https://github.com/actions/upload-artifact/compare/v4...v4.6.2</a></p>
<h2>v4.6.1</h2>
<h2>What's Changed</h2>
<ul>
<li>Update to use artifact 2.2.2 package by <a
href="https://github.com/yacaovsnc"><code>@​yacaovsnc</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/673">actions/upload-artifact#673</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/upload-artifact/compare/v4...v4.6.1">https://github.com/actions/upload-artifact/compare/v4...v4.6.1</a></p>
<h2>v4.6.0</h2>
<h2>What's Changed</h2>
<ul>
<li>Expose env vars to control concurrency and timeout by <a
href="https://github.com/yacaovsnc"><code>@​yacaovsnc</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/662">actions/upload-artifact#662</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/upload-artifact/compare/v4...v4.6.0">https://github.com/actions/upload-artifact/compare/v4...v4.6.0</a></p>
<h2>v4.5.0</h2>
<h2>What's Changed</h2>
<ul>
<li>fix: deprecated <code>Node.js</code> version in action by <a
href="https://github.com/hamirmahal"><code>@​hamirmahal</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/578">actions/upload-artifact#578</a></li>
<li>Add new <code>artifact-digest</code> output by <a
href="https://github.com/bdehamer"><code>@​bdehamer</code></a> in <a
href="https://redirect.github.com/actions/upload-artifact/pull/656">actions/upload-artifact#656</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a
href="https://github.com/hamirmahal"><code>@​hamirmahal</code></a> made
their first contribution in <a
href="https://redirect.github.com/actions/upload-artifact/pull/578">actions/upload-artifact#578</a></li>
</ul>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/actions/upload-artifact/commit/330a01c490aca151604b8cf639adc76d48f6c5d4"><code>330a01c</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/upload-artifact/issues/734">#734</a>
from actions/danwkennedy/prepare-5.0.0</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/03f282445299bbefc96171af272a984663b63a26"><code>03f2824</code></a>
Update <code>github.dep.yml</code></li>
<li><a
href="https://github.com/actions/upload-artifact/commit/905a1ecb5915b264cbc519e4eb415b5d82916018"><code>905a1ec</code></a>
Prepare <code>v5.0.0</code></li>
<li><a
href="https://github.com/actions/upload-artifact/commit/2d9f9cdfa99fedaddba68e9b5b5c281eca26cc63"><code>2d9f9cd</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/upload-artifact/issues/725">#725</a>
from patrikpolyak/patch-1</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/9687587dec67f2a8bc69104e183d311c42af6d6f"><code>9687587</code></a>
Merge branch 'main' into patch-1</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/2848b2cda0e5190984587ec6bb1f36730ca78d50"><code>2848b2c</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/upload-artifact/issues/727">#727</a>
from danwkennedy/patch-1</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/9b511775fd9ce8c5710b38eea671f856de0e70a7"><code>9b51177</code></a>
Spell out the first use of GHES</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/cd231ca1eda77976a84805c4194a1954f56b0727"><code>cd231ca</code></a>
Update GHES guidance to include reference to Node 20 version</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/de65e23aa2b7e23d713bb51fbfcb6d502f8667d8"><code>de65e23</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/upload-artifact/issues/712">#712</a>
from actions/nebuk89-patch-1</li>
<li><a
href="https://github.com/actions/upload-artifact/commit/8747d8cd7632611ad6060b528f3e0f654c98869c"><code>8747d8c</code></a>
Update README.md</li>
<li>Additional commits viewable in <a
href="https://github.com/actions/upload-artifact/compare/v4...v5">compare
view</a></li>
</ul>
</details>
<br />

Updates `actions/download-artifact` from 5 to 6
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/actions/download-artifact/releases">actions/download-artifact's
releases</a>.</em></p>
<blockquote>
<h2>v6.0.0</h2>
<h2>What's Changed</h2>
<p><strong>BREAKING CHANGE:</strong> this update supports Node
<code>v24.x</code>. This is not a breaking change per-se but we're
treating it as such.</p>
<ul>
<li>Update README for download-artifact v5 changes by <a
href="https://github.com/yacaovsnc"><code>@​yacaovsnc</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/417">actions/download-artifact#417</a></li>
<li>Update README with artifact extraction details by <a
href="https://github.com/yacaovsnc"><code>@​yacaovsnc</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/424">actions/download-artifact#424</a></li>
<li>Readme: spell out the first use of GHES by <a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a> in
<a
href="https://redirect.github.com/actions/download-artifact/pull/431">actions/download-artifact#431</a></li>
<li>Bump <code>@actions/artifact</code> to <code>v4.0.0</code></li>
<li>Prepare <code>v6.0.0</code> by <a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a> in
<a
href="https://redirect.github.com/actions/download-artifact/pull/438">actions/download-artifact#438</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a
href="https://github.com/danwkennedy"><code>@​danwkennedy</code></a>
made their first contribution in <a
href="https://redirect.github.com/actions/download-artifact/pull/431">actions/download-artifact#431</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v5...v6.0.0">https://github.com/actions/download-artifact/compare/v5...v6.0.0</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/actions/download-artifact/commit/018cc2cf5baa6db3ef3c5f8a56943fffe632ef53"><code>018cc2c</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/438">#438</a>
from actions/danwkennedy/prepare-6.0.0</li>
<li><a
href="https://github.com/actions/download-artifact/commit/815651c680ffe1c95719d0ed08aba1a2f9d5c177"><code>815651c</code></a>
Revert &quot;Remove <code>github.dep.yml</code>&quot;</li>
<li><a
href="https://github.com/actions/download-artifact/commit/bb3a066a8babc8ed7b3e4218896c548fe34e7115"><code>bb3a066</code></a>
Remove <code>github.dep.yml</code></li>
<li><a
href="https://github.com/actions/download-artifact/commit/fa1ce46bbd11b8387539af12741055a76dfdf804"><code>fa1ce46</code></a>
Prepare <code>v6.0.0</code></li>
<li><a
href="https://github.com/actions/download-artifact/commit/4a24838f3d5601fd639834081e118c2995d51e1c"><code>4a24838</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/431">#431</a>
from danwkennedy/patch-1</li>
<li><a
href="https://github.com/actions/download-artifact/commit/5e3251c4ff5a32e4cf8dd4adaee0e692365237ae"><code>5e3251c</code></a>
Readme: spell out the first use of GHES</li>
<li><a
href="https://github.com/actions/download-artifact/commit/abefc31eafcfbdf6c5336127c1346fdae79ff41c"><code>abefc31</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/424">#424</a>
from actions/yacaovsnc/update_readme</li>
<li><a
href="https://github.com/actions/download-artifact/commit/ac43a6070aa7db8a41e756e7a2846221edca7027"><code>ac43a60</code></a>
Update README with artifact extraction details</li>
<li><a
href="https://github.com/actions/download-artifact/commit/de96f4613b77ec03b5cf633e7c350c32bd3c5660"><code>de96f46</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/417">#417</a>
from actions/yacaovsnc/update_readme</li>
<li><a
href="https://github.com/actions/download-artifact/commit/7993cb44e9052f2f08f9b828ae5ef3ecca7d2ac7"><code>7993cb4</code></a>
Remove migration guide for artifact download changes</li>
<li>Additional commits viewable in <a
href="https://github.com/actions/download-artifact/compare/v5...v6">compare
view</a></li>
</ul>
</details>
<br />


Dependabot will resolve any conflicts with this PR as long as you don't
alter it yourself. You can also trigger a rebase manually by commenting
`@dependabot rebase`.

[//]: # (dependabot-automerge-start)
[//]: # (dependabot-automerge-end)

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits
that have been made to it
- `@dependabot merge` will merge this PR after your CI passes on it
- `@dependabot squash and merge` will squash and merge this PR after
your CI passes on it
- `@dependabot cancel merge` will cancel a previously requested merge
and block automerging
- `@dependabot reopen` will reopen this PR if it is closed
- `@dependabot close` will close this PR and stop Dependabot recreating
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- `@dependabot show <dependency name> ignore conditions` will show all
of the ignore conditions of the specified dependency
- `@dependabot ignore <dependency name> major version` will close this
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</details>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Holt Skinner <13262395+holtskinner@users.noreply.github.com>
---
 .github/workflows/linter.yaml          | 2 +-
 .github/workflows/python-publish.yml   | 6 +++---
 .github/workflows/unit-tests.yml       | 2 +-
 .github/workflows/update-a2a-types.yml | 2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/linter.yaml b/.github/workflows/linter.yaml
index a5e5da2b..bdd4c5b8 100644
--- a/.github/workflows/linter.yaml
+++ b/.github/workflows/linter.yaml
@@ -18,7 +18,7 @@ jobs:
         with:
           python-version-file: .python-version
       - name: Install uv
-        uses: astral-sh/setup-uv@v6
+        uses: astral-sh/setup-uv@v7
       - name: Add uv to PATH
         run: |
           echo "$HOME/.cargo/bin" >> $GITHUB_PATH
diff --git a/.github/workflows/python-publish.yml b/.github/workflows/python-publish.yml
index 96e87d9e..decb3b1d 100644
--- a/.github/workflows/python-publish.yml
+++ b/.github/workflows/python-publish.yml
@@ -15,7 +15,7 @@ jobs:
       - uses: actions/checkout@v5
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v6
+        uses: astral-sh/setup-uv@v7
 
       - name: "Set up Python"
         uses: actions/setup-python@v6
@@ -26,7 +26,7 @@ jobs:
         run: uv build
 
       - name: Upload distributions
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: release-dists
           path: dist/
@@ -40,7 +40,7 @@ jobs:
 
     steps:
       - name: Retrieve release distributions
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: release-dists
           path: dist/
diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index ce8d62ab..16052ba1 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -46,7 +46,7 @@ jobs:
           echo "MYSQL_TEST_DSN=mysql+aiomysql://a2a:a2a_password@localhost:3306/a2a_test" >> $GITHUB_ENV
 
       - name: Install uv for Python ${{ matrix.python-version }}
-        uses: astral-sh/setup-uv@v6
+        uses: astral-sh/setup-uv@v7
         with:
           python-version: ${{ matrix.python-version }}
       - name: Add uv to PATH
diff --git a/.github/workflows/update-a2a-types.yml b/.github/workflows/update-a2a-types.yml
index cb4071e7..c019afeb 100644
--- a/.github/workflows/update-a2a-types.yml
+++ b/.github/workflows/update-a2a-types.yml
@@ -18,7 +18,7 @@ jobs:
         with:
           python-version: '3.10'
       - name: Install uv
-        uses: astral-sh/setup-uv@v6
+        uses: astral-sh/setup-uv@v7
       - name: Configure uv shell
         run: echo "$HOME/.cargo/bin" >> $GITHUB_PATH
       - name: Install dependencies (datamodel-code-generator)

From 96d70e25f8d557e8fd146916d90d0af5c3589a38 Mon Sep 17 00:00:00 2001
From: Luca Muscariello <muscariello@ieee.org>
Date: Wed, 12 Nov 2025 16:43:43 +0100
Subject: [PATCH 05/15] ci(scripts): add version support to generate_types.sh
 (#539)

## Description

Adds version support to generate_types.sh to decouple the A2A
specification repository from the SDK repository.

## Changes

- Add A2A_SPEC_VERSION environment variable (default: v0.3.0)
- Support --version flag for specifying versions (tags/branches/commits)
- Add URL validation before generating types
- Improve error messages and usage documentation

## Usage

```bash
./scripts/generate_types.sh --version v0.3.0 src/a2a/types.py
A2A_SPEC_VERSION=main ./scripts/generate_types.sh src/a2a/types.py
```

## Testing

- 701 unit tests pass
- Ruff and MyPy checks pass

---------

Signed-off-by: Luca Muscariello <muscariello@ieee.org>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
 scripts/generate_types.sh | 89 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 78 insertions(+), 11 deletions(-)

diff --git a/scripts/generate_types.sh b/scripts/generate_types.sh
index b8d7dedf..6c01cff5 100755
--- a/scripts/generate_types.sh
+++ b/scripts/generate_types.sh
@@ -4,7 +4,35 @@
 # Treat unset variables as an error.
 set -euo pipefail
 
-REMOTE_URL="https://raw.githubusercontent.com/a2aproject/A2A/refs/heads/main/specification/json/a2a.json"
+# A2A specification version to use
+# Can be overridden via environment variable: A2A_SPEC_VERSION=v1.2.0 ./generate_types.sh
+# Or via command-line flag: ./generate_types.sh --version v1.2.0 output.py
+# Use a specific git tag, branch name, or commit SHA
+# Examples: "v1.0.0", "v1.2.0", "main", "abc123def"
+A2A_SPEC_VERSION="${A2A_SPEC_VERSION:-v0.3.0}"
+
+# Build URL based on version format
+# Tags use /refs/tags/, branches use /refs/heads/, commits use direct ref
+build_remote_url() {
+  local version="$1"
+  local base_url="https://raw.githubusercontent.com/a2aproject/A2A"
+  local spec_path="specification/json/a2a.json"
+  local url_part
+
+  if [[ "$version" =~ ^v[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+    # Looks like a version tag (v1.0.0, v1.2.3)
+    url_part="refs/tags/${version}"
+  elif [[ "$version" =~ ^[0-9a-f]{7,40}$ ]]; then
+    # Looks like a commit SHA (7+ hex chars)
+    url_part="${version}"
+  else
+    # Assume it's a branch name (main, develop, etc.)
+    url_part="refs/heads/${version}"
+  fi
+  echo "${base_url}/${url_part}/${spec_path}"
+}
+
+REMOTE_URL=$(build_remote_url "$A2A_SPEC_VERSION")
 
 GENERATED_FILE=""
 INPUT_FILE=""
@@ -12,20 +40,38 @@ INPUT_FILE=""
 # Parse command-line arguments
 while [[ $# -gt 0 ]]; do
   case "$1" in
-    --input-file)
-      INPUT_FILE="$2"
-      shift 2
-      ;;
-    *)
-      GENERATED_FILE="$1"
-      shift 1
-      ;;
+  --input-file)
+    INPUT_FILE="$2"
+    shift 2
+    ;;
+  --version)
+    A2A_SPEC_VERSION="$2"
+    REMOTE_URL=$(build_remote_url "$A2A_SPEC_VERSION")
+    shift 2
+    ;;
+  *)
+    GENERATED_FILE="$1"
+    shift 1
+    ;;
   esac
 done
 
 if [ -z "$GENERATED_FILE" ]; then
-  echo "Error: Output file path must be provided." >&2
-  echo "Usage: $0 [--input-file <path>] <output-file-path>"
+  cat >&2 <<EOF
+Error: Output file path must be provided.
+Usage: $0 [--input-file <path>] [--version <version>] <output-file-path>
+Options:
+  --input-file <path>   Use a local JSON schema file instead of fetching from remote
+  --version <version>   Specify A2A spec version (default: v0.3.0)
+                        Can be a git tag (v1.0.0), branch (main), or commit SHA
+Environment variables:
+  A2A_SPEC_VERSION      Override default spec version
+Examples:
+  $0 src/a2a/types.py
+  $0 --version v1.2.0 src/a2a/types.py
+  $0 --input-file local/a2a.json src/a2a/types.py
+  A2A_SPEC_VERSION=main $0 src/a2a/types.py
+EOF
   exit 1
 fi
 
@@ -33,9 +79,30 @@ echo "Running datamodel-codegen..."
 declare -a source_args
 if [ -n "$INPUT_FILE" ]; then
   echo "  - Source File: $INPUT_FILE"
+  if [ ! -f "$INPUT_FILE" ]; then
+    echo "Error: Input file does not exist: $INPUT_FILE" >&2
+    exit 1
+  fi
   source_args=("--input" "$INPUT_FILE")
 else
+  echo "  - A2A Spec Version: $A2A_SPEC_VERSION"
   echo "  - Source URL: $REMOTE_URL"
+
+  # Validate that the remote URL is accessible
+  echo "  - Validating remote URL..."
+  if ! curl --fail --silent --head "$REMOTE_URL" >/dev/null 2>&1; then
+    cat >&2 <<EOF
+
+Error: Unable to access A2A specification at version '$A2A_SPEC_VERSION'
+URL: $REMOTE_URL
+
+The version may not exist. Available versions can be found at:
+  https://github.com/a2aproject/A2A/tags
+
+EOF
+    exit 1
+  fi
+
   source_args=("--url" "$REMOTE_URL")
 fi
 echo "  - Output File: $GENERATED_FILE"

From 45ff87157a85215e904e319b315069d15e232d1c Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Wed, 12 Nov 2025 15:37:32 -0600
Subject: [PATCH 06/15] chore(main): release 0.3.12 (#538)

:robot: I have created a release *beep* *boop*
---


##
[0.3.12](https://github.com/a2aproject/a2a-python/compare/v0.3.11...v0.3.12)
(2025-11-12)


### Bug Fixes

* **grpc:** Add `extensions` to `Artifact` converters.
([#523](https://github.com/a2aproject/a2a-python/issues/523))
([c03129b](https://github.com/a2aproject/a2a-python/commit/c03129b99a663ae1f1ae72f20e4ead7807ede941))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).
---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 39446e61..d2f30a84 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## [0.3.12](https://github.com/a2aproject/a2a-python/compare/v0.3.11...v0.3.12) (2025-11-12)
+
+
+### Bug Fixes
+
+* **grpc:** Add `extensions` to `Artifact` converters. ([#523](https://github.com/a2aproject/a2a-python/issues/523)) ([c03129b](https://github.com/a2aproject/a2a-python/commit/c03129b99a663ae1f1ae72f20e4ead7807ede941))
+
 ## [0.3.11](https://github.com/a2aproject/a2a-python/compare/v0.3.10...v0.3.11) (2025-11-07)
 
 

From acdc0de4fa03d34a6b287ab252ff51b19c3016b5 Mon Sep 17 00:00:00 2001
From: Lukasz Kawka <luk.kawka@gmail.com>
Date: Thu, 13 Nov 2025 11:42:30 -0800
Subject: [PATCH 07/15] fix: return entire history when history_length=0 (#537)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

# Description

The specification states that a history length of 0 should return
unlimited results (see
[code](https://github.com/a2aproject/A2A/blob/202aa069e66f701bacf2156d42d8916fc96a5188/specification/grpc/a2a.proto#L128-L130)).
However, this was recently changed to return 0 results. This fix
restores the correct behavior.

Please note that there is an outstanding proposal to change this
behavior. See https://github.com/a2aproject/A2A/pull/1071 for more
details.

Prerequisites:
- [x] Follow the [`CONTRIBUTING`
Guide](https://github.com/a2aproject/a2a-python/blob/main/CONTRIBUTING.md).
- [x] Make your Pull Request title in the
<https://www.conventionalcommits.org/> specification.
- Important Prefixes for
[release-please](https://github.com/googleapis/release-please):
- `fix:` which represents bug fixes, and correlates to a
[SemVer](https://semver.org/) patch.
- `feat:` represents a new feature, and correlates to a SemVer minor.
- `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking
change (indicated by the `!`) and will result in a SemVer major.
- [x] Ensure the tests and linter pass (Run `bash scripts/format.sh`
from the repository root to format)
- [x] Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕
---
 src/a2a/utils/task.py                         |  6 ++----
 .../test_default_request_handler.py           | 20 ++++++++++++-------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/a2a/utils/task.py b/src/a2a/utils/task.py
index 5c5f3f07..d8215cec 100644
--- a/src/a2a/utils/task.py
+++ b/src/a2a/utils/task.py
@@ -83,11 +83,9 @@ def apply_history_length(task: Task, history_length: int | None) -> Task:
         A new task object with limited history
     """
     # Apply historyLength parameter if specified
-    if history_length is not None and task.history:
+    if history_length is not None and history_length > 0 and task.history:
         # Limit history to the most recent N messages
-        limited_history = (
-            task.history[-history_length:] if history_length > 0 else []
-        )
+        limited_history = task.history[-history_length:]
         # Create a new task instance with limited history
         return task.model_copy(update={'history': limited_history})
 
diff --git a/tests/server/request_handlers/test_default_request_handler.py b/tests/server/request_handlers/test_default_request_handler.py
index 5268af11..88dd77ab 100644
--- a/tests/server/request_handlers/test_default_request_handler.py
+++ b/tests/server/request_handlers/test_default_request_handler.py
@@ -834,6 +834,11 @@ async def test_on_message_send_non_blocking():
 
     assert task is not None
     assert task.status.state == TaskState.completed
+    assert (
+        result.history
+        and task.history
+        and len(result.history) == len(task.history)
+    )
 
 
 @pytest.mark.asyncio
@@ -855,7 +860,7 @@ async def test_on_message_send_limit_history():
         configuration=MessageSendConfiguration(
             blocking=True,
             accepted_output_modes=['text/plain'],
-            history_length=0,
+            history_length=1,
         ),
     )
 
@@ -866,17 +871,17 @@ async def test_on_message_send_limit_history():
     # verify that history_length is honored
     assert result is not None
     assert isinstance(result, Task)
-    assert result.history is not None and len(result.history) == 0
+    assert result.history is not None and len(result.history) == 1
     assert result.status.state == TaskState.completed
 
     # verify that history is still persisted to the store
     task = await task_store.get(result.id)
     assert task is not None
-    assert task.history is not None and len(task.history) > 0
+    assert task.history is not None and len(task.history) > 1
 
 
 @pytest.mark.asyncio
-async def test_on_task_get_limit_history():
+async def test_on_get_task_limit_history():
     task_store = InMemoryTaskStore()
     push_store = InMemoryPushNotificationConfigStore()
 
@@ -892,7 +897,8 @@ async def test_on_task_get_limit_history():
             parts=[Part(root=TextPart(text='Hi'))],
         ),
         configuration=MessageSendConfiguration(
-            blocking=True, accepted_output_modes=['text/plain']
+            blocking=True,
+            accepted_output_modes=['text/plain'],
         ),
     )
 
@@ -904,14 +910,14 @@ async def test_on_task_get_limit_history():
     assert isinstance(result, Task)
 
     get_task_result = await request_handler.on_get_task(
-        TaskQueryParams(id=result.id, history_length=0),
+        TaskQueryParams(id=result.id, history_length=1),
         create_server_call_context(),
     )
     assert get_task_result is not None
     assert isinstance(get_task_result, Task)
     assert (
         get_task_result.history is not None
-        and len(get_task_result.history) == 0
+        and len(get_task_result.history) == 1
     )
 
 

From ef020c5d6108e362da94deb0c4cbec14bffe16aa Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Mon, 17 Nov 2025 03:26:56 -0600
Subject: [PATCH 08/15] chore(main): release 0.3.13 (#543)

:robot: I have created a release *beep* *boop*
---


##
[0.3.13](https://github.com/a2aproject/a2a-python/compare/v0.3.12...v0.3.13)
(2025-11-13)


### Bug Fixes

* return entire history when history_length=0
([#537](https://github.com/a2aproject/a2a-python/issues/537))
([acdc0de](https://github.com/a2aproject/a2a-python/commit/acdc0de4fa03d34a6b287ab252ff51b19c3016b5))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).
---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2f30a84..c9629aea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## [0.3.13](https://github.com/a2aproject/a2a-python/compare/v0.3.12...v0.3.13) (2025-11-13)
+
+
+### Bug Fixes
+
+* return entire history when history_length=0 ([#537](https://github.com/a2aproject/a2a-python/issues/537)) ([acdc0de](https://github.com/a2aproject/a2a-python/commit/acdc0de4fa03d34a6b287ab252ff51b19c3016b5))
+
 ## [0.3.12](https://github.com/a2aproject/a2a-python/compare/v0.3.11...v0.3.12) (2025-11-12)
 
 

From ba142df821d1c06be0b96e576fd43015120fcb0b Mon Sep 17 00:00:00 2001
From: Iva Sokolaj <102302011+sokoliva@users.noreply.github.com>
Date: Mon, 17 Nov 2025 17:42:44 +0100
Subject: [PATCH 09/15] feat(jsonrpc): add option to disable oversized payload
 check in JSONRPC applications (#544)

This commit adds a constructor boolean variable
disable_content_length_check to the base class JSONRPCApplication and
it's derived classes A2AFastAPIApplication and A2AStarletteApplication.
In JSONRPCApplication's method _handle_requests it adds a if
disable_content_length_check check before checking if the payload
exceeds the MAX_CONTENT_LENGTH limit.

This enables agent creators to disable the 10MB payload size limitation.
---
 src/a2a/server/apps/jsonrpc/fastapi_app.py    |  4 ++
 src/a2a/server/apps/jsonrpc/jsonrpc_app.py    | 42 ++++++++++++-------
 src/a2a/server/apps/jsonrpc/starlette_app.py  |  4 ++
 .../server/apps/jsonrpc/test_serialization.py | 36 ++++++++++++++++
 4 files changed, 72 insertions(+), 14 deletions(-)

diff --git a/src/a2a/server/apps/jsonrpc/fastapi_app.py b/src/a2a/server/apps/jsonrpc/fastapi_app.py
index 4ba7fdce..ace2c6ae 100644
--- a/src/a2a/server/apps/jsonrpc/fastapi_app.py
+++ b/src/a2a/server/apps/jsonrpc/fastapi_app.py
@@ -77,6 +77,7 @@ def __init__(  # noqa: PLR0913
             [AgentCard, ServerCallContext], AgentCard
         ]
         | None = None,
+        max_content_length: int | None = 10 * 1024 * 1024,  # 10MB
     ) -> None:
         """Initializes the A2AFastAPIApplication.
 
@@ -94,6 +95,8 @@ def __init__(  # noqa: PLR0913
             extended_card_modifier: An optional callback to dynamically modify
               the extended agent card before it is served. It receives the
               call context.
+            max_content_length: The maximum allowed content length for incoming
+              requests. Defaults to 10MB. Set to None for unbounded maximum.
         """
         if not _package_fastapi_installed:
             raise ImportError(
@@ -108,6 +111,7 @@ def __init__(  # noqa: PLR0913
             context_builder=context_builder,
             card_modifier=card_modifier,
             extended_card_modifier=extended_card_modifier,
+            max_content_length=max_content_length,
         )
 
     def add_routes_to_app(
diff --git a/src/a2a/server/apps/jsonrpc/jsonrpc_app.py b/src/a2a/server/apps/jsonrpc/jsonrpc_app.py
index d258916c..3e7c2854 100644
--- a/src/a2a/server/apps/jsonrpc/jsonrpc_app.py
+++ b/src/a2a/server/apps/jsonrpc/jsonrpc_app.py
@@ -91,8 +91,6 @@
         Response = Any
         HTTP_413_REQUEST_ENTITY_TOO_LARGE = Any
 
-MAX_CONTENT_LENGTH = 10_000_000
-
 
 class StarletteUserProxy(A2AUser):
     """Adapts the Starlette User class to the A2A user representation."""
@@ -185,6 +183,7 @@ def __init__(  # noqa: PLR0913
             [AgentCard, ServerCallContext], AgentCard
         ]
         | None = None,
+        max_content_length: int | None = 10 * 1024 * 1024,  # 10MB
     ) -> None:
         """Initializes the JSONRPCApplication.
 
@@ -202,6 +201,8 @@ def __init__(  # noqa: PLR0913
             extended_card_modifier: An optional callback to dynamically modify
               the extended agent card before it is served. It receives the
               call context.
+            max_content_length: The maximum allowed content length for incoming
+              requests. Defaults to 10MB. Set to None for unbounded maximum.
         """
         if not _package_starlette_installed:
             raise ImportError(
@@ -220,6 +221,7 @@ def __init__(  # noqa: PLR0913
             extended_card_modifier=extended_card_modifier,
         )
         self._context_builder = context_builder or DefaultCallContextBuilder()
+        self._max_content_length = max_content_length
 
     def _generate_error_response(
         self, request_id: str | int | None, error: JSONRPCError | A2AError
@@ -261,6 +263,22 @@ def _generate_error_response(
             status_code=200,
         )
 
+    def _allowed_content_length(self, request: Request) -> bool:
+        """Checks if the request content length is within the allowed maximum.
+
+        Args:
+            request: The incoming Starlette Request object.
+
+        Returns:
+            False if the content length is larger than the allowed maximum, True otherwise.
+        """
+        if self._max_content_length is not None:
+            with contextlib.suppress(ValueError):
+                content_length = int(request.headers.get('content-length', '0'))
+                if content_length and content_length > self._max_content_length:
+                    return False
+        return True
+
     async def _handle_requests(self, request: Request) -> Response:  # noqa: PLR0911
         """Handles incoming POST requests to the main A2A endpoint.
 
@@ -291,18 +309,14 @@ async def _handle_requests(self, request: Request) -> Response:  # noqa: PLR0911
                     request_id, str | int
                 ):
                     request_id = None
-            # Treat very large payloads as invalid request (-32600) before routing
-            with contextlib.suppress(Exception):
-                content_length = int(request.headers.get('content-length', '0'))
-                if content_length and content_length > MAX_CONTENT_LENGTH:
-                    return self._generate_error_response(
-                        request_id,
-                        A2AError(
-                            root=InvalidRequestError(
-                                message='Payload too large'
-                            )
-                        ),
-                    )
+            # Treat payloads lager than allowed as invalid request (-32600) before routing
+            if not self._allowed_content_length(request):
+                return self._generate_error_response(
+                    request_id,
+                    A2AError(
+                        root=InvalidRequestError(message='Payload too large')
+                    ),
+                )
             logger.debug('Request body: %s', body)
             # 1) Validate base JSON-RPC structure only (-32600 on failure)
             try:
diff --git a/src/a2a/server/apps/jsonrpc/starlette_app.py b/src/a2a/server/apps/jsonrpc/starlette_app.py
index b268d043..1effa9d5 100644
--- a/src/a2a/server/apps/jsonrpc/starlette_app.py
+++ b/src/a2a/server/apps/jsonrpc/starlette_app.py
@@ -59,6 +59,7 @@ def __init__(  # noqa: PLR0913
             [AgentCard, ServerCallContext], AgentCard
         ]
         | None = None,
+        max_content_length: int | None = 10 * 1024 * 1024,  # 10MB
     ) -> None:
         """Initializes the A2AStarletteApplication.
 
@@ -76,6 +77,8 @@ def __init__(  # noqa: PLR0913
             extended_card_modifier: An optional callback to dynamically modify
               the extended agent card before it is served. It receives the
               call context.
+            max_content_length: The maximum allowed content length for incoming
+              requests. Defaults to 10MB. Set to None for unbounded maximum.
         """
         if not _package_starlette_installed:
             raise ImportError(
@@ -90,6 +93,7 @@ def __init__(  # noqa: PLR0913
             context_builder=context_builder,
             card_modifier=card_modifier,
             extended_card_modifier=extended_card_modifier,
+            max_content_length=max_content_length,
         )
 
     def routes(
diff --git a/tests/server/apps/jsonrpc/test_serialization.py b/tests/server/apps/jsonrpc/test_serialization.py
index 9365017b..f6778046 100644
--- a/tests/server/apps/jsonrpc/test_serialization.py
+++ b/tests/server/apps/jsonrpc/test_serialization.py
@@ -136,6 +136,42 @@ def test_handle_oversized_payload(agent_card_with_api_key: AgentCard):
     assert data['error']['code'] == InvalidRequestError().code
 
 
+@pytest.mark.parametrize(
+    'max_content_length',
+    [
+        None,
+        11 * 1024 * 1024,
+        30 * 1024 * 1024,
+    ],
+)
+def test_handle_oversized_payload_with_max_content_length(
+    agent_card_with_api_key: AgentCard,
+    max_content_length: int | None,
+):
+    """Test handling of JSON payloads with sizes within custom max_content_length."""
+    handler = mock.AsyncMock()
+    app_instance = A2AStarletteApplication(
+        agent_card_with_api_key, handler, max_content_length=max_content_length
+    )
+    client = TestClient(app_instance.build())
+
+    large_string = 'a' * 11 * 1_000_000  # 11MB string
+    payload = {
+        'jsonrpc': '2.0',
+        'method': 'test',
+        'id': 1,
+        'params': {'data': large_string},
+    }
+
+    response = client.post('/', json=payload)
+    assert response.status_code == 200
+    data = response.json()
+    # When max_content_length is set, requests up to that size should not be
+    # rejected due to payload size. The request might fail for other reasons,
+    # but it shouldn't be an InvalidRequestError related to the content length.
+    assert data['error']['code'] != InvalidRequestError().code
+
+
 def test_handle_unicode_characters(agent_card_with_api_key: AgentCard):
     """Test handling of unicode characters in JSON payload."""
     handler = mock.AsyncMock()

From 9e35eb8500a5fbc8f7dd59c18282e3ffa9c976f5 Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Tue, 18 Nov 2025 02:58:14 -0600
Subject: [PATCH 10/15] chore(main): release 0.3.14 (#547)

:robot: I have created a release *beep* *boop*
---


##
[0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14)
(2025-11-17)


### Features

* **jsonrpc:** add option to disable oversized payload check in JSONRPC
applications
([ba142df](https://github.com/a2aproject/a2a-python/commit/ba142df821d1c06be0b96e576fd43015120fcb0b))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).
---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c9629aea..a684ac02 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## [0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14) (2025-11-17)
+
+
+### Features
+
+* **jsonrpc:** add option to disable oversized payload check in JSONRPC applications ([ba142df](https://github.com/a2aproject/a2a-python/commit/ba142df821d1c06be0b96e576fd43015120fcb0b))
+
 ## [0.3.13](https://github.com/a2aproject/a2a-python/compare/v0.3.12...v0.3.13) (2025-11-13)
 
 

From 89e9b7cb0ab24c3c22b7da04e04d77ec5f15dc1c Mon Sep 17 00:00:00 2001
From: Martim Santos <martimfasantos@gmail.com>
Date: Tue, 18 Nov 2025 09:30:30 +0000
Subject: [PATCH 11/15] chore(client): Expose BaseClient from a2a.client
 package (#529)

# Description

This pull request introduces a minor update to the
`src/a2a/client/__init__.py` file, focusing on the module's imports. The
change makes the `BaseClient` class available for import from this
package.

* Added `BaseClient` to the list of imported symbols and to the module's
`__all__`, making it accessible when importing from `a2a.client`.
[[1]](diffhunk://#diff-e472e7970567ab144a39be570324db52d9da69a3f678438f6ee5f3aecd79b474R10)
[[2]](diffhunk://#diff-e472e7970567ab144a39be570324db52d9da69a3f678438f6ee5f3aecd79b474R55)

---

- [x] Follow the [`CONTRIBUTING`
Guide](https://github.com/a2aproject/a2a-python/blob/main/CONTRIBUTING.md).
- [x] Make your Pull Request title in the
<https://www.conventionalcommits.org/> specification.
- Important Prefixes for
[release-please](https://github.com/googleapis/release-please):
- `fix:` which represents bug fixes, and correlates to a
[SemVer](https://semver.org/) patch.
- `feat:` represents a new feature, and correlates to a SemVer minor.
- `feat!:`, or `fix!:`, `refactor!:`, etc., which represent a breaking
change (indicated by the `!`) and will result in a SemVer major.
- [x] Ensure the tests and linter pass (Run `bash scripts/format.sh`
from the repository root to format)
- [x] Appropriate docs were updated (if necessary)

Co-authored-by: Lukasz Kawka <luk.kawka@gmail.com>
---
 src/a2a/client/__init__.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/a2a/client/__init__.py b/src/a2a/client/__init__.py
index 726a089d..4fccd081 100644
--- a/src/a2a/client/__init__.py
+++ b/src/a2a/client/__init__.py
@@ -7,6 +7,7 @@
     CredentialService,
     InMemoryContextCredentialStore,
 )
+from a2a.client.base_client import BaseClient
 from a2a.client.card_resolver import A2ACardResolver
 from a2a.client.client import Client, ClientConfig, ClientEvent, Consumer
 from a2a.client.client_factory import ClientFactory, minimal_agent_card
@@ -51,6 +52,7 @@ def __init__(self, *args, **kwargs):
     'A2AClientTimeoutError',
     'A2AGrpcClient',
     'AuthInterceptor',
+    'BaseClient',
     'Client',
     'ClientCallContext',
     'ClientCallInterceptor',

From 9a92bd238e7560b195165ac5f78742981760525e Mon Sep 17 00:00:00 2001
From: Iva Sokolaj <102302011+sokoliva@users.noreply.github.com>
Date: Wed, 19 Nov 2025 12:13:10 +0100
Subject: [PATCH 12/15] feat: Add client-side extension support (#525)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

feat(rest, jsonrpc): Add client-side extension support
This commit introduces support for clients to declare the extensions
they support.

- Adds an `extensions` list to `ClientConfig`.
- Updates `ClientFactory` to pass `client_extensions` to
`JsonRpcTransport` and `RestTransport`.
- Adds `_update_extension_header` method to both transports to update
the `X-A2A-Extensions` header.
- Modifies `send_message` and `send_message_streaming` in
`JsonRpcTransport` to include the extension headers.
- Modifies `_prepare_send_message` in `RestTransport` to include the
extension headers.
- Adds tests for the extension header logic in both JSON-RPC and REST
transports, including a new test file `test_rest_client.py`.
-
Fixes #504 🦕
---
 src/a2a/client/base_client.py                 |  46 +++++--
 src/a2a/client/client.py                      |  14 +-
 src/a2a/client/client_factory.py              |  19 ++-
 src/a2a/client/transports/base.py             |   8 ++
 src/a2a/client/transports/grpc.py             |  55 ++++++--
 src/a2a/client/transports/jsonrpc.py          |  62 +++++++--
 src/a2a/client/transports/rest.py             |  65 +++++++--
 src/a2a/extensions/common.py                  |  14 ++
 tests/client/test_client_factory.py           |   4 +
 .../{ => transports}/test_grpc_client.py      | 124 ++++++++++++++++--
 .../{ => transports}/test_jsonrpc_client.py   |  90 +++++++++++++
 tests/client/transports/test_rest_client.py   | 121 +++++++++++++++++
 tests/extensions/test_common.py               |  88 +++++++++++++
 .../test_client_server_integration.py         |  62 ++++++++-
 14 files changed, 715 insertions(+), 57 deletions(-)
 rename tests/client/{ => transports}/test_grpc_client.py (80%)
 rename tests/client/{ => transports}/test_jsonrpc_client.py (89%)
 create mode 100644 tests/client/transports/test_rest_client.py

diff --git a/src/a2a/client/base_client.py b/src/a2a/client/base_client.py
index b8697d86..5719bc1b 100644
--- a/src/a2a/client/base_client.py
+++ b/src/a2a/client/base_client.py
@@ -49,6 +49,7 @@ async def send_message(
         *,
         context: ClientCallContext | None = None,
         request_metadata: dict[str, Any] | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncIterator[ClientEvent | Message]:
         """Sends a message to the agent.
 
@@ -60,6 +61,7 @@ async def send_message(
             request: The message to send to the agent.
             context: The client call context.
             request_metadata: Extensions Metadata attached to the request.
+            extensions: List of extensions to be activated.
 
         Yields:
             An async iterator of `ClientEvent` or a final `Message` response.
@@ -79,7 +81,7 @@ async def send_message(
 
         if not self._config.streaming or not self._card.capabilities.streaming:
             response = await self._transport.send_message(
-                params, context=context
+                params, context=context, extensions=extensions
             )
             result = (
                 (response, None) if isinstance(response, Task) else response
@@ -89,7 +91,9 @@ async def send_message(
             return
 
         tracker = ClientTaskManager()
-        stream = self._transport.send_message_streaming(params, context=context)
+        stream = self._transport.send_message_streaming(
+            params, context=context, extensions=extensions
+        )
 
         first_event = await anext(stream)
         # The response from a server may be either exactly one Message or a
@@ -126,74 +130,91 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task.
 
         Args:
             request: The `TaskQueryParams` object specifying the task ID.
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Returns:
             A `Task` object representing the current state of the task.
         """
-        return await self._transport.get_task(request, context=context)
+        return await self._transport.get_task(
+            request, context=context, extensions=extensions
+        )
 
     async def cancel_task(
         self,
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task.
 
         Args:
             request: The `TaskIdParams` object specifying the task ID.
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Returns:
             A `Task` object containing the updated task status.
         """
-        return await self._transport.cancel_task(request, context=context)
+        return await self._transport.cancel_task(
+            request, context=context, extensions=extensions
+        )
 
     async def set_task_callback(
         self,
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task.
 
         Args:
             request: The `TaskPushNotificationConfig` object with the new configuration.
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Returns:
             The created or updated `TaskPushNotificationConfig` object.
         """
-        return await self._transport.set_task_callback(request, context=context)
+        return await self._transport.set_task_callback(
+            request, context=context, extensions=extensions
+        )
 
     async def get_task_callback(
         self,
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task.
 
         Args:
             request: The `GetTaskPushNotificationConfigParams` object specifying the task.
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Returns:
             A `TaskPushNotificationConfig` object containing the configuration.
         """
-        return await self._transport.get_task_callback(request, context=context)
+        return await self._transport.get_task_callback(
+            request, context=context, extensions=extensions
+        )
 
     async def resubscribe(
         self,
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncIterator[ClientEvent]:
         """Resubscribes to a task's event stream.
 
@@ -202,6 +223,7 @@ async def resubscribe(
         Args:
             request: Parameters to identify the task to resubscribe to.
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Yields:
             An async iterator of `ClientEvent` objects.
@@ -219,12 +241,15 @@ async def resubscribe(
         # we should never see Message updates, despite the typing of the service
         # definition indicating it may be possible.
         async for event in self._transport.resubscribe(
-            request, context=context
+            request, context=context, extensions=extensions
         ):
             yield await self._process_response(tracker, event)
 
     async def get_card(
-        self, *, context: ClientCallContext | None = None
+        self,
+        *,
+        context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the agent's card.
 
@@ -233,11 +258,14 @@ async def get_card(
 
         Args:
             context: The client call context.
+            extensions: List of extensions to be activated.
 
         Returns:
             The `AgentCard` for the agent.
         """
-        card = await self._transport.get_card(context=context)
+        card = await self._transport.get_card(
+            context=context, extensions=extensions
+        )
         self._card = card
         return card
 
diff --git a/src/a2a/client/client.py b/src/a2a/client/client.py
index 0e1c4323..fd97b4d1 100644
--- a/src/a2a/client/client.py
+++ b/src/a2a/client/client.py
@@ -67,6 +67,9 @@ class ClientConfig:
     )
     """Push notification callbacks to use for every request."""
 
+    extensions: list[str] = dataclasses.field(default_factory=list)
+    """A list of extension URIs the client supports."""
+
 
 UpdateEvent = TaskStatusUpdateEvent | TaskArtifactUpdateEvent | None
 # Alias for emitted events from client
@@ -111,6 +114,7 @@ async def send_message(
         *,
         context: ClientCallContext | None = None,
         request_metadata: dict[str, Any] | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncIterator[ClientEvent | Message]:
         """Sends a message to the server.
 
@@ -129,6 +133,7 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task."""
 
@@ -138,6 +143,7 @@ async def cancel_task(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task."""
 
@@ -147,6 +153,7 @@ async def set_task_callback(
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task."""
 
@@ -156,6 +163,7 @@ async def get_task_callback(
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task."""
 
@@ -165,6 +173,7 @@ async def resubscribe(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncIterator[ClientEvent]:
         """Resubscribes to a task's event stream."""
         return
@@ -172,7 +181,10 @@ async def resubscribe(
 
     @abstractmethod
     async def get_card(
-        self, *, context: ClientCallContext | None = None
+        self,
+        *,
+        context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the agent's card."""
 
diff --git a/src/a2a/client/client_factory.py b/src/a2a/client/client_factory.py
index 65b3fb5f..fabd7270 100644
--- a/src/a2a/client/client_factory.py
+++ b/src/a2a/client/client_factory.py
@@ -80,6 +80,7 @@ def _register_defaults(
                     card,
                     url,
                     interceptors,
+                    config.extensions or None,
                 ),
             )
         if TransportProtocol.http_json in supported:
@@ -90,6 +91,7 @@ def _register_defaults(
                     card,
                     url,
                     interceptors,
+                    config.extensions or None,
                 ),
             )
         if TransportProtocol.grpc in supported:
@@ -113,6 +115,7 @@ async def connect(  # noqa: PLR0913
         relative_card_path: str | None = None,
         resolver_http_kwargs: dict[str, Any] | None = None,
         extra_transports: dict[str, TransportProducer] | None = None,
+        extensions: list[str] | None = None,
     ) -> Client:
         """Convenience method for constructing a client.
 
@@ -142,6 +145,7 @@ async def connect(  # noqa: PLR0913
             A2AAgentCardResolver.get_agent_card as the http_kwargs parameter.
           extra_transports: Additional transport protocols to enable when
             constructing the client.
+          extensions: List of extensions to be activated.
 
         Returns:
           A `Client` object.
@@ -166,7 +170,7 @@ async def connect(  # noqa: PLR0913
         factory = cls(client_config)
         for label, generator in (extra_transports or {}).items():
             factory.register(label, generator)
-        return factory.create(card, consumers, interceptors)
+        return factory.create(card, consumers, interceptors, extensions)
 
     def register(self, label: str, generator: TransportProducer) -> None:
         """Register a new transport producer for a given transport label."""
@@ -177,6 +181,7 @@ def create(
         card: AgentCard,
         consumers: list[Consumer] | None = None,
         interceptors: list[ClientCallInterceptor] | None = None,
+        extensions: list[str] | None = None,
     ) -> Client:
         """Create a new `Client` for the provided `AgentCard`.
 
@@ -186,6 +191,7 @@ def create(
           interceptors: A list of interceptors to use for each request. These
             are used for things like attaching credentials or http headers
             to all outbound requests.
+          extensions: List of extensions to be activated.
 
         Returns:
           A `Client` object.
@@ -226,12 +232,21 @@ def create(
         if consumers:
             all_consumers.extend(consumers)
 
+        all_extensions = self._config.extensions.copy()
+        if extensions:
+            all_extensions.extend(extensions)
+            self._config.extensions = all_extensions
+
         transport = self._registry[transport_protocol](
             card, transport_url, self._config, interceptors or []
         )
 
         return BaseClient(
-            card, self._config, transport, all_consumers, interceptors or []
+            card,
+            self._config,
+            transport,
+            all_consumers,
+            interceptors or [],
         )
 
 
diff --git a/src/a2a/client/transports/base.py b/src/a2a/client/transports/base.py
index 3573cb7c..8f114d95 100644
--- a/src/a2a/client/transports/base.py
+++ b/src/a2a/client/transports/base.py
@@ -25,6 +25,7 @@ async def send_message(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task | Message:
         """Sends a non-streaming message request to the agent."""
 
@@ -34,6 +35,7 @@ async def send_message_streaming(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
@@ -47,6 +49,7 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task."""
 
@@ -56,6 +59,7 @@ async def cancel_task(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task."""
 
@@ -65,6 +69,7 @@ async def set_task_callback(
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task."""
 
@@ -74,6 +79,7 @@ async def get_task_callback(
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task."""
 
@@ -83,6 +89,7 @@ async def resubscribe(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Task | Message | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
@@ -95,6 +102,7 @@ async def get_card(
         self,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the AgentCard."""
 
diff --git a/src/a2a/client/transports/grpc.py b/src/a2a/client/transports/grpc.py
index e50b0ea8..4e27953a 100644
--- a/src/a2a/client/transports/grpc.py
+++ b/src/a2a/client/transports/grpc.py
@@ -12,10 +12,12 @@
         "'pip install a2a-sdk[grpc]'"
     ) from e
 
+
 from a2a.client.client import ClientConfig
 from a2a.client.middleware import ClientCallContext, ClientCallInterceptor
 from a2a.client.optionals import Channel
 from a2a.client.transports.base import ClientTransport
+from a2a.extensions.common import HTTP_EXTENSION_HEADER
 from a2a.grpc import a2a_pb2, a2a_pb2_grpc
 from a2a.types import (
     AgentCard,
@@ -44,6 +46,7 @@ def __init__(
         self,
         channel: Channel,
         agent_card: AgentCard | None,
+        extensions: list[str] | None = None,
     ):
         """Initializes the GrpcTransport."""
         self.agent_card = agent_card
@@ -54,6 +57,18 @@ def __init__(
             if agent_card
             else True
         )
+        self.extensions = extensions
+
+    def _get_grpc_metadata(
+        self,
+        extensions: list[str] | None = None,
+    ) -> list[tuple[str, str]] | None:
+        """Creates gRPC metadata for extensions."""
+        if extensions is not None:
+            return [(HTTP_EXTENSION_HEADER, ','.join(extensions))]
+        if self.extensions is not None:
+            return [(HTTP_EXTENSION_HEADER, ','.join(self.extensions))]
+        return None
 
     @classmethod
     def create(
@@ -66,16 +81,14 @@ def create(
         """Creates a gRPC transport for the A2A client."""
         if config.grpc_channel_factory is None:
             raise ValueError('grpc_channel_factory is required when using gRPC')
-        return cls(
-            config.grpc_channel_factory(url),
-            card,
-        )
+        return cls(config.grpc_channel_factory(url), card, config.extensions)
 
     async def send_message(
         self,
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task | Message:
         """Sends a non-streaming message request to the agent."""
         response = await self.stub.SendMessage(
@@ -85,7 +98,8 @@ async def send_message(
                     request.configuration
                 ),
                 metadata=proto_utils.ToProto.metadata(request.metadata),
-            )
+            ),
+            metadata=self._get_grpc_metadata(extensions),
         )
         if response.HasField('task'):
             return proto_utils.FromProto.task(response.task)
@@ -96,6 +110,7 @@ async def send_message_streaming(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
@@ -107,7 +122,8 @@ async def send_message_streaming(
                     request.configuration
                 ),
                 metadata=proto_utils.ToProto.metadata(request.metadata),
-            )
+            ),
+            metadata=self._get_grpc_metadata(extensions),
         )
         while True:
             response = await stream.read()
@@ -116,13 +132,18 @@ async def send_message_streaming(
             yield proto_utils.FromProto.stream_response(response)
 
     async def resubscribe(
-        self, request: TaskIdParams, *, context: ClientCallContext | None = None
+        self,
+        request: TaskIdParams,
+        *,
+        context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Task | Message | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
         """Reconnects to get task updates."""
         stream = self.stub.TaskSubscription(
-            a2a_pb2.TaskSubscriptionRequest(name=f'tasks/{request.id}')
+            a2a_pb2.TaskSubscriptionRequest(name=f'tasks/{request.id}'),
+            metadata=self._get_grpc_metadata(extensions),
         )
         while True:
             response = await stream.read()
@@ -135,13 +156,15 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task."""
         task = await self.stub.GetTask(
             a2a_pb2.GetTaskRequest(
                 name=f'tasks/{request.id}',
                 history_length=request.history_length,
-            )
+            ),
+            metadata=self._get_grpc_metadata(extensions),
         )
         return proto_utils.FromProto.task(task)
 
@@ -150,10 +173,12 @@ async def cancel_task(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task."""
         task = await self.stub.CancelTask(
-            a2a_pb2.CancelTaskRequest(name=f'tasks/{request.id}')
+            a2a_pb2.CancelTaskRequest(name=f'tasks/{request.id}'),
+            metadata=self._get_grpc_metadata(extensions),
         )
         return proto_utils.FromProto.task(task)
 
@@ -162,6 +187,7 @@ async def set_task_callback(
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task."""
         config = await self.stub.CreateTaskPushNotificationConfig(
@@ -171,7 +197,8 @@ async def set_task_callback(
                 config=proto_utils.ToProto.task_push_notification_config(
                     request
                 ),
-            )
+            ),
+            metadata=self._get_grpc_metadata(extensions),
         )
         return proto_utils.FromProto.task_push_notification_config(config)
 
@@ -180,12 +207,14 @@ async def get_task_callback(
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task."""
         config = await self.stub.GetTaskPushNotificationConfig(
             a2a_pb2.GetTaskPushNotificationConfigRequest(
                 name=f'tasks/{request.id}/pushNotificationConfigs/{request.push_notification_config_id}',
-            )
+            ),
+            metadata=self._get_grpc_metadata(extensions),
         )
         return proto_utils.FromProto.task_push_notification_config(config)
 
@@ -193,6 +222,7 @@ async def get_card(
         self,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the agent's card."""
         card = self.agent_card
@@ -203,6 +233,7 @@ async def get_card(
 
         card_pb = await self.stub.GetAgentCard(
             a2a_pb2.GetAgentCardRequest(),
+            metadata=self._get_grpc_metadata(extensions),
         )
         card = proto_utils.FromProto.agent_card(card_pb)
         self.agent_card = card
diff --git a/src/a2a/client/transports/jsonrpc.py b/src/a2a/client/transports/jsonrpc.py
index bfba09d7..d8011cf4 100644
--- a/src/a2a/client/transports/jsonrpc.py
+++ b/src/a2a/client/transports/jsonrpc.py
@@ -18,6 +18,7 @@
 )
 from a2a.client.middleware import ClientCallContext, ClientCallInterceptor
 from a2a.client.transports.base import ClientTransport
+from a2a.extensions.common import update_extension_header
 from a2a.types import (
     AgentCard,
     CancelTaskRequest,
@@ -62,6 +63,7 @@ def __init__(
         agent_card: AgentCard | None = None,
         url: str | None = None,
         interceptors: list[ClientCallInterceptor] | None = None,
+        extensions: list[str] | None = None,
     ):
         """Initializes the JsonRpcTransport."""
         if url:
@@ -79,6 +81,7 @@ def __init__(
             if agent_card
             else True
         )
+        self.extensions = extensions
 
     async def _apply_interceptors(
         self,
@@ -113,13 +116,18 @@ async def send_message(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task | Message:
         """Sends a non-streaming message request to the agent."""
         rpc_request = SendMessageRequest(params=request, id=str(uuid4()))
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'message/send',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_request(payload, modified_kwargs)
@@ -133,6 +141,7 @@ async def send_message_streaming(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Message | Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
@@ -140,13 +149,16 @@ async def send_message_streaming(
         rpc_request = SendStreamingMessageRequest(
             params=request, id=str(uuid4())
         )
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'message/stream',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
-
         modified_kwargs.setdefault(
             'timeout', self.httpx_client.timeout.as_dict().get('read', None)
         )
@@ -207,13 +219,18 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task."""
         rpc_request = GetTaskRequest(params=request, id=str(uuid4()))
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'tasks/get',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_request(payload, modified_kwargs)
@@ -227,13 +244,18 @@ async def cancel_task(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task."""
         rpc_request = CancelTaskRequest(params=request, id=str(uuid4()))
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'tasks/cancel',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_request(payload, modified_kwargs)
@@ -247,15 +269,20 @@ async def set_task_callback(
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task."""
         rpc_request = SetTaskPushNotificationConfigRequest(
             params=request, id=str(uuid4())
         )
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'tasks/pushNotificationConfig/set',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_request(payload, modified_kwargs)
@@ -271,15 +298,20 @@ async def get_task_callback(
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task."""
         rpc_request = GetTaskPushNotificationConfigRequest(
             params=request, id=str(uuid4())
         )
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'tasks/pushNotificationConfig/get',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_request(payload, modified_kwargs)
@@ -295,18 +327,22 @@ async def resubscribe(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Task | Message | TaskStatusUpdateEvent | TaskArtifactUpdateEvent
     ]:
         """Reconnects to get task updates."""
         rpc_request = TaskResubscriptionRequest(params=request, id=str(uuid4()))
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             'tasks/resubscribe',
             rpc_request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
-
         modified_kwargs.setdefault('timeout', None)
 
         async with aconnect_sse(
@@ -339,6 +375,7 @@ async def get_card(
         self,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the agent's card."""
         card = self.agent_card
@@ -356,13 +393,16 @@ async def get_card(
             return card
 
         request = GetAuthenticatedExtendedCardRequest(id=str(uuid4()))
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             request.method,
             request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
-
         response_data = await self._send_request(
             payload,
             modified_kwargs,
diff --git a/src/a2a/client/transports/rest.py b/src/a2a/client/transports/rest.py
index eef7b0f2..83c26787 100644
--- a/src/a2a/client/transports/rest.py
+++ b/src/a2a/client/transports/rest.py
@@ -13,6 +13,7 @@
 from a2a.client.errors import A2AClientHTTPError, A2AClientJSONError
 from a2a.client.middleware import ClientCallContext, ClientCallInterceptor
 from a2a.client.transports.base import ClientTransport
+from a2a.extensions.common import update_extension_header
 from a2a.grpc import a2a_pb2
 from a2a.types import (
     AgentCard,
@@ -43,6 +44,7 @@ def __init__(
         agent_card: AgentCard | None = None,
         url: str | None = None,
         interceptors: list[ClientCallInterceptor] | None = None,
+        extensions: list[str] | None = None,
     ):
         """Initializes the RestTransport."""
         if url:
@@ -61,6 +63,7 @@ def __init__(
             if agent_card
             else True
         )
+        self.extensions = extensions
 
     async def _apply_interceptors(
         self,
@@ -79,7 +82,10 @@ def _get_http_args(
         return context.state.get('http_kwargs') if context else None
 
     async def _prepare_send_message(
-        self, request: MessageSendParams, context: ClientCallContext | None
+        self,
+        request: MessageSendParams,
+        context: ClientCallContext | None,
+        extensions: list[str] | None = None,
     ) -> tuple[dict[str, Any], dict[str, Any]]:
         pb = a2a_pb2.SendMessageRequest(
             request=proto_utils.ToProto.message(request.message),
@@ -93,9 +99,13 @@ async def _prepare_send_message(
             ),
         )
         payload = MessageToDict(pb)
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             payload,
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         return payload, modified_kwargs
@@ -105,10 +115,11 @@ async def send_message(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task | Message:
         """Sends a non-streaming message request to the agent."""
         payload, modified_kwargs = await self._prepare_send_message(
-            request, context
+            request, context, extensions
         )
         response_data = await self._send_post_request(
             '/v1/message:send', payload, modified_kwargs
@@ -122,12 +133,13 @@ async def send_message_streaming(
         request: MessageSendParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent | Message
     ]:
         """Sends a streaming message request to the agent and yields responses as they arrive."""
         payload, modified_kwargs = await self._prepare_send_message(
-            request, context
+            request, context, extensions
         )
 
         modified_kwargs.setdefault('timeout', None)
@@ -204,11 +216,16 @@ async def get_task(
         request: TaskQueryParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Retrieves the current state and history of a specific task."""
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         _payload, modified_kwargs = await self._apply_interceptors(
             request.model_dump(mode='json', exclude_none=True),
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_get_request(
@@ -227,13 +244,18 @@ async def cancel_task(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> Task:
         """Requests the agent to cancel a specific task."""
         pb = a2a_pb2.CancelTaskRequest(name=f'tasks/{request.id}')
         payload = MessageToDict(pb)
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             payload,
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_post_request(
@@ -248,6 +270,7 @@ async def set_task_callback(
         request: TaskPushNotificationConfig,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Sets or updates the push notification configuration for a specific task."""
         pb = a2a_pb2.CreateTaskPushNotificationConfigRequest(
@@ -256,8 +279,12 @@ async def set_task_callback(
             config=proto_utils.ToProto.task_push_notification_config(request),
         )
         payload = MessageToDict(pb)
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
-            payload, self._get_http_args(context), context
+            payload, modified_kwargs, context
         )
         response_data = await self._send_post_request(
             f'/v1/tasks/{request.task_id}/pushNotificationConfigs',
@@ -273,15 +300,20 @@ async def get_task_callback(
         request: GetTaskPushNotificationConfigParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> TaskPushNotificationConfig:
         """Retrieves the push notification configuration for a specific task."""
         pb = a2a_pb2.GetTaskPushNotificationConfigRequest(
             name=f'tasks/{request.id}/pushNotificationConfigs/{request.push_notification_config_id}',
         )
         payload = MessageToDict(pb)
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         payload, modified_kwargs = await self._apply_interceptors(
             payload,
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_get_request(
@@ -298,18 +330,22 @@ async def resubscribe(
         request: TaskIdParams,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AsyncGenerator[
         Task | TaskStatusUpdateEvent | TaskArtifactUpdateEvent | Message
     ]:
         """Reconnects to get task updates."""
-        http_kwargs = self._get_http_args(context) or {}
-        http_kwargs.setdefault('timeout', None)
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
+        modified_kwargs.setdefault('timeout', None)
 
         async with aconnect_sse(
             self.httpx_client,
             'GET',
             f'{self.url}/v1/tasks/{request.id}:subscribe',
-            **http_kwargs,
+            **modified_kwargs,
         ) as event_source:
             try:
                 async for sse in event_source.aiter_sse():
@@ -331,6 +367,7 @@ async def get_card(
         self,
         *,
         context: ClientCallContext | None = None,
+        extensions: list[str] | None = None,
     ) -> AgentCard:
         """Retrieves the agent's card."""
         card = self.agent_card
@@ -347,9 +384,13 @@ async def get_card(
         if not self._needs_extended_card:
             return card
 
+        modified_kwargs = update_extension_header(
+            self._get_http_args(context),
+            extensions if extensions is not None else self.extensions,
+        )
         _, modified_kwargs = await self._apply_interceptors(
             {},
-            self._get_http_args(context),
+            modified_kwargs,
             context,
         )
         response_data = await self._send_get_request(
diff --git a/src/a2a/extensions/common.py b/src/a2a/extensions/common.py
index 2f752caa..cba3517e 100644
--- a/src/a2a/extensions/common.py
+++ b/src/a2a/extensions/common.py
@@ -1,3 +1,5 @@
+from typing import Any
+
 from a2a.types import AgentCard, AgentExtension
 
 
@@ -25,3 +27,15 @@ def find_extension_by_uri(card: AgentCard, uri: str) -> AgentExtension | None:
             return ext
 
     return None
+
+
+def update_extension_header(
+    http_kwargs: dict[str, Any] | None,
+    extensions: list[str] | None,
+) -> dict[str, Any]:
+    """Update the X-A2A-Extensions header with active extensions."""
+    http_kwargs = http_kwargs or {}
+    if extensions is not None:
+        headers = http_kwargs.setdefault('headers', {})
+        headers[HTTP_EXTENSION_HEADER] = ','.join(extensions)
+    return http_kwargs
diff --git a/tests/client/test_client_factory.py b/tests/client/test_client_factory.py
index 847b256f..16a1433f 100644
--- a/tests/client/test_client_factory.py
+++ b/tests/client/test_client_factory.py
@@ -39,12 +39,14 @@ def test_client_factory_selects_preferred_transport(base_agent_card: AgentCard):
             TransportProtocol.jsonrpc,
             TransportProtocol.http_json,
         ],
+        extensions=['https://example.com/test-ext/v0'],
     )
     factory = ClientFactory(config)
     client = factory.create(base_agent_card)
 
     assert isinstance(client._transport, JsonRpcTransport)
     assert client._transport.url == 'http://primary-url.com'
+    assert ['https://example.com/test-ext/v0'] == client._transport.extensions
 
 
 def test_client_factory_selects_secondary_transport_url(
@@ -65,12 +67,14 @@ def test_client_factory_selects_secondary_transport_url(
             TransportProtocol.jsonrpc,
         ],
         use_client_preference=True,
+        extensions=['https://example.com/test-ext/v0'],
     )
     factory = ClientFactory(config)
     client = factory.create(base_agent_card)
 
     assert isinstance(client._transport, RestTransport)
     assert client._transport.url == 'http://secondary-url.com'
+    assert ['https://example.com/test-ext/v0'] == client._transport.extensions
 
 
 def test_client_factory_server_preference(base_agent_card: AgentCard):
diff --git a/tests/client/test_grpc_client.py b/tests/client/transports/test_grpc_client.py
similarity index 80%
rename from tests/client/test_grpc_client.py
rename to tests/client/transports/test_grpc_client.py
index 6dab75e9..111e44ba 100644
--- a/tests/client/test_grpc_client.py
+++ b/tests/client/transports/test_grpc_client.py
@@ -4,6 +4,7 @@
 import pytest
 
 from a2a.client.transports.grpc import GrpcTransport
+from a2a.extensions.common import HTTP_EXTENSION_HEADER
 from a2a.grpc import a2a_pb2, a2a_pb2_grpc
 from a2a.types import (
     AgentCapabilities,
@@ -64,7 +65,14 @@ def grpc_transport(
 ) -> GrpcTransport:
     """Provides a GrpcTransport instance."""
     channel = AsyncMock()
-    transport = GrpcTransport(channel=channel, agent_card=sample_agent_card)
+    transport = GrpcTransport(
+        channel=channel,
+        agent_card=sample_agent_card,
+        extensions=[
+            'https://example.com/test-ext/v1',
+            'https://example.com/test-ext/v2',
+        ],
+    )
     transport.stub = mock_grpc_stub
     return transport
 
@@ -185,9 +193,19 @@ async def test_send_message_task_response(
         task=proto_utils.ToProto.task(sample_task)
     )
 
-    response = await grpc_transport.send_message(sample_message_send_params)
+    response = await grpc_transport.send_message(
+        sample_message_send_params,
+        extensions=['https://example.com/test-ext/v3'],
+    )
 
     mock_grpc_stub.SendMessage.assert_awaited_once()
+    _, kwargs = mock_grpc_stub.SendMessage.call_args
+    assert kwargs['metadata'] == [
+        (
+            HTTP_EXTENSION_HEADER,
+            'https://example.com/test-ext/v3',
+        )
+    ]
     assert isinstance(response, Task)
     assert response.id == sample_task.id
 
@@ -207,6 +225,13 @@ async def test_send_message_message_response(
     response = await grpc_transport.send_message(sample_message_send_params)
 
     mock_grpc_stub.SendMessage.assert_awaited_once()
+    _, kwargs = mock_grpc_stub.SendMessage.call_args
+    assert kwargs['metadata'] == [
+        (
+            HTTP_EXTENSION_HEADER,
+            'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+        )
+    ]
     assert isinstance(response, Message)
     assert response.message_id == sample_message.message_id
     assert get_text_parts(response.parts) == get_text_parts(
@@ -255,6 +280,13 @@ async def test_send_message_streaming(  # noqa: PLR0913
     ]
 
     mock_grpc_stub.SendStreamingMessage.assert_called_once()
+    _, kwargs = mock_grpc_stub.SendStreamingMessage.call_args
+    assert kwargs['metadata'] == [
+        (
+            HTTP_EXTENSION_HEADER,
+            'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+        )
+    ]
     assert isinstance(responses[0], Message)
     assert responses[0].message_id == sample_message.message_id
     assert isinstance(responses[1], Task)
@@ -278,7 +310,13 @@ async def test_get_task(
     mock_grpc_stub.GetTask.assert_awaited_once_with(
         a2a_pb2.GetTaskRequest(
             name=f'tasks/{sample_task.id}', history_length=None
-        )
+        ),
+        metadata=[
+            (
+                HTTP_EXTENSION_HEADER,
+                'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+            )
+        ],
     )
     assert response.id == sample_task.id
 
@@ -297,7 +335,13 @@ async def test_get_task_with_history(
     mock_grpc_stub.GetTask.assert_awaited_once_with(
         a2a_pb2.GetTaskRequest(
             name=f'tasks/{sample_task.id}', history_length=history_len
-        )
+        ),
+        metadata=[
+            (
+                HTTP_EXTENSION_HEADER,
+                'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+            )
+        ],
     )
 
 
@@ -312,11 +356,14 @@ async def test_cancel_task(
         cancelled_task
     )
     params = TaskIdParams(id=sample_task.id)
-
-    response = await grpc_transport.cancel_task(params)
+    extensions = [
+        'https://example.com/test-ext/v3',
+    ]
+    response = await grpc_transport.cancel_task(params, extensions=extensions)
 
     mock_grpc_stub.CancelTask.assert_awaited_once_with(
-        a2a_pb2.CancelTaskRequest(name=f'tasks/{sample_task.id}')
+        a2a_pb2.CancelTaskRequest(name=f'tasks/{sample_task.id}'),
+        metadata=[(HTTP_EXTENSION_HEADER, 'https://example.com/test-ext/v3')],
     )
     assert response.status.state == TaskState.canceled
 
@@ -345,7 +392,13 @@ async def test_set_task_callback_with_valid_task(
             config=proto_utils.ToProto.task_push_notification_config(
                 sample_task_push_notification_config
             ),
-        )
+        ),
+        metadata=[
+            (
+                HTTP_EXTENSION_HEADER,
+                'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+            )
+        ],
     )
     assert response.task_id == sample_task_push_notification_config.task_id
 
@@ -402,7 +455,13 @@ async def test_get_task_callback_with_valid_task(
                 f'tasks/{params.id}/'
                 f'pushNotificationConfigs/{params.push_notification_config_id}'
             ),
-        )
+        ),
+        metadata=[
+            (
+                HTTP_EXTENSION_HEADER,
+                'https://example.com/test-ext/v1,https://example.com/test-ext/v2',
+            )
+        ],
     )
     assert response.task_id == sample_task_push_notification_config.task_id
 
@@ -434,3 +493,50 @@ async def test_get_task_callback_with_invalid_task(
         'Bad TaskPushNotificationConfig resource name'
         in exc_info.value.error.message
     )
+
+
+@pytest.mark.parametrize(
+    'initial_extensions, input_extensions, expected_metadata',
+    [
+        (
+            None,
+            None,
+            None,
+        ),  # Case 1: No initial, No input
+        (
+            ['ext1'],
+            None,
+            [(HTTP_EXTENSION_HEADER, 'ext1')],
+        ),  # Case 2: Initial, No input
+        (
+            None,
+            ['ext2'],
+            [(HTTP_EXTENSION_HEADER, 'ext2')],
+        ),  # Case 3: No initial, Input
+        (
+            ['ext1'],
+            ['ext2'],
+            [(HTTP_EXTENSION_HEADER, 'ext2')],
+        ),  # Case 4: Initial, Input (override)
+        (
+            ['ext1'],
+            ['ext2', 'ext3'],
+            [(HTTP_EXTENSION_HEADER, 'ext2,ext3')],
+        ),  # Case 5: Initial, Multiple inputs (override)
+        (
+            ['ext1', 'ext2'],
+            ['ext3'],
+            [(HTTP_EXTENSION_HEADER, 'ext3')],
+        ),  # Case 6: Multiple initial, Single input (override)
+    ],
+)
+def test_get_grpc_metadata(
+    grpc_transport: GrpcTransport,
+    initial_extensions: list[str] | None,
+    input_extensions: list[str] | None,
+    expected_metadata: list[tuple[str, str]] | None,
+) -> None:
+    """Tests _get_grpc_metadata for correct metadata generation and self.extensions update."""
+    grpc_transport.extensions = initial_extensions
+    metadata = grpc_transport._get_grpc_metadata(input_extensions)
+    assert metadata == expected_metadata
diff --git a/tests/client/test_jsonrpc_client.py b/tests/client/transports/test_jsonrpc_client.py
similarity index 89%
rename from tests/client/test_jsonrpc_client.py
rename to tests/client/transports/test_jsonrpc_client.py
index 58feec25..bd705d93 100644
--- a/tests/client/test_jsonrpc_client.py
+++ b/tests/client/transports/test_jsonrpc_client.py
@@ -17,6 +17,7 @@
     create_text_message_object,
 )
 from a2a.client.transports.jsonrpc import JsonRpcTransport
+from a2a.extensions.common import HTTP_EXTENSION_HEADER
 from a2a.types import (
     AgentCapabilities,
     AgentCard,
@@ -785,3 +786,92 @@ async def test_close(self, mock_httpx_client: AsyncMock):
         )
         await client.close()
         mock_httpx_client.aclose.assert_called_once()
+
+
+class TestJsonRpcTransportExtensions:
+    @pytest.mark.asyncio
+    async def test_send_message_with_default_extensions(
+        self, mock_httpx_client: AsyncMock, mock_agent_card: MagicMock
+    ):
+        """Test that send_message adds extension headers when extensions are provided."""
+        extensions = [
+            'https://example.com/test-ext/v1',
+            'https://example.com/test-ext/v2',
+        ]
+        client = JsonRpcTransport(
+            httpx_client=mock_httpx_client,
+            agent_card=mock_agent_card,
+            extensions=extensions,
+        )
+        params = MessageSendParams(
+            message=create_text_message_object(content='Hello')
+        )
+        success_response = create_text_message_object(
+            role=Role.agent, content='Hi there!'
+        )
+        rpc_response = SendMessageSuccessResponse(
+            id='123', jsonrpc='2.0', result=success_response
+        )
+        # Mock the response from httpx_client.post
+        mock_response = AsyncMock(spec=httpx.Response)
+        mock_response.status_code = 200
+        mock_response.json.return_value = rpc_response.model_dump(mode='json')
+        mock_httpx_client.post.return_value = mock_response
+
+        await client.send_message(request=params)
+
+        mock_httpx_client.post.assert_called_once()
+        _, mock_kwargs = mock_httpx_client.post.call_args
+
+        headers = mock_kwargs.get('headers', {})
+        assert HTTP_EXTENSION_HEADER in headers
+        header_value = headers[HTTP_EXTENSION_HEADER]
+        actual_extensions_list = [e.strip() for e in header_value.split(',')]
+        actual_extensions = set(actual_extensions_list)
+
+        expected_extensions = {
+            'https://example.com/test-ext/v1',
+            'https://example.com/test-ext/v2',
+        }
+        assert len(actual_extensions_list) == 2
+        assert actual_extensions == expected_extensions
+
+    @pytest.mark.asyncio
+    @patch('a2a.client.transports.jsonrpc.aconnect_sse')
+    async def test_send_message_streaming_with_new_extensions(
+        self,
+        mock_aconnect_sse: AsyncMock,
+        mock_httpx_client: AsyncMock,
+        mock_agent_card: MagicMock,
+    ):
+        """Test X-A2A-Extensions header in send_message_streaming."""
+        new_extensions = ['https://example.com/test-ext/v2']
+        extensions = ['https://example.com/test-ext/v1']
+        client = JsonRpcTransport(
+            httpx_client=mock_httpx_client,
+            agent_card=mock_agent_card,
+            extensions=extensions,
+        )
+        params = MessageSendParams(
+            message=create_text_message_object(content='Hello stream')
+        )
+
+        mock_event_source = AsyncMock(spec=EventSource)
+        mock_event_source.aiter_sse.return_value = async_iterable_from_list([])
+        mock_aconnect_sse.return_value.__aenter__.return_value = (
+            mock_event_source
+        )
+
+        async for _ in client.send_message_streaming(
+            request=params, extensions=new_extensions
+        ):
+            pass
+
+        mock_aconnect_sse.assert_called_once()
+        _, kwargs = mock_aconnect_sse.call_args
+
+        headers = kwargs.get('headers', {})
+        assert HTTP_EXTENSION_HEADER in headers
+        assert (
+            headers[HTTP_EXTENSION_HEADER] == 'https://example.com/test-ext/v2'
+        )
diff --git a/tests/client/transports/test_rest_client.py b/tests/client/transports/test_rest_client.py
new file mode 100644
index 00000000..04bd1036
--- /dev/null
+++ b/tests/client/transports/test_rest_client.py
@@ -0,0 +1,121 @@
+from collections.abc import AsyncGenerator
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import httpx
+import pytest
+
+from httpx_sse import EventSource, ServerSentEvent
+
+from a2a.client import create_text_message_object
+from a2a.client.transports.rest import RestTransport
+from a2a.extensions.common import HTTP_EXTENSION_HEADER
+from a2a.types import AgentCard, MessageSendParams, Role
+
+
+@pytest.fixture
+def mock_httpx_client() -> AsyncMock:
+    return AsyncMock(spec=httpx.AsyncClient)
+
+
+@pytest.fixture
+def mock_agent_card() -> MagicMock:
+    mock = MagicMock(spec=AgentCard, url='http://agent.example.com/api')
+    mock.supports_authenticated_extended_card = False
+    return mock
+
+
+async def async_iterable_from_list(
+    items: list[ServerSentEvent],
+) -> AsyncGenerator[ServerSentEvent, None]:
+    """Helper to create an async iterable from a list."""
+    for item in items:
+        yield item
+
+
+class TestRestTransportExtensions:
+    @pytest.mark.asyncio
+    async def test_send_message_with_default_extensions(
+        self, mock_httpx_client: AsyncMock, mock_agent_card: MagicMock
+    ):
+        """Test that send_message adds extensions to headers."""
+        extensions = [
+            'https://example.com/test-ext/v1',
+            'https://example.com/test-ext/v2',
+        ]
+        client = RestTransport(
+            httpx_client=mock_httpx_client,
+            extensions=extensions,
+            agent_card=mock_agent_card,
+        )
+        params = MessageSendParams(
+            message=create_text_message_object(content='Hello')
+        )
+
+        # Mock the build_request method to capture its inputs
+        mock_build_request = MagicMock(
+            return_value=AsyncMock(spec=httpx.Request)
+        )
+        mock_httpx_client.build_request = mock_build_request
+
+        # Mock the send method
+        mock_response = AsyncMock(spec=httpx.Response)
+        mock_response.status_code = 200
+        mock_httpx_client.send.return_value = mock_response
+
+        await client.send_message(request=params)
+
+        mock_build_request.assert_called_once()
+        _, kwargs = mock_build_request.call_args
+
+        headers = kwargs.get('headers', {})
+        assert HTTP_EXTENSION_HEADER in headers
+        header_value = kwargs['headers'][HTTP_EXTENSION_HEADER]
+        actual_extensions_list = [e.strip() for e in header_value.split(',')]
+        actual_extensions = set(actual_extensions_list)
+
+        expected_extensions = {
+            'https://example.com/test-ext/v1',
+            'https://example.com/test-ext/v2',
+        }
+        assert len(actual_extensions_list) == 2
+        assert actual_extensions == expected_extensions
+
+    @pytest.mark.asyncio
+    @patch('a2a.client.transports.rest.aconnect_sse')
+    async def test_send_message_streaming_with_new_extensions(
+        self,
+        mock_aconnect_sse: AsyncMock,
+        mock_httpx_client: AsyncMock,
+        mock_agent_card: MagicMock,
+    ):
+        """Test X-A2A-Extensions header in send_message_streaming."""
+        new_extensions = ['https://example.com/test-ext/v2']
+        extensions = ['https://example.com/test-ext/v1']
+        client = RestTransport(
+            httpx_client=mock_httpx_client,
+            agent_card=mock_agent_card,
+            extensions=extensions,
+        )
+        params = MessageSendParams(
+            message=create_text_message_object(content='Hello stream')
+        )
+
+        mock_event_source = AsyncMock(spec=EventSource)
+        mock_event_source.aiter_sse.return_value = async_iterable_from_list([])
+        mock_aconnect_sse.return_value.__aenter__.return_value = (
+            mock_event_source
+        )
+
+        async for _ in client.send_message_streaming(
+            request=params, extensions=new_extensions
+        ):
+            pass
+
+        mock_aconnect_sse.assert_called_once()
+        _, kwargs = mock_aconnect_sse.call_args
+
+        headers = kwargs.get('headers', {})
+        assert HTTP_EXTENSION_HEADER in headers
+        assert (
+            headers[HTTP_EXTENSION_HEADER] == 'https://example.com/test-ext/v2'
+        )
diff --git a/tests/extensions/test_common.py b/tests/extensions/test_common.py
index 137e64c9..b3123028 100644
--- a/tests/extensions/test_common.py
+++ b/tests/extensions/test_common.py
@@ -1,6 +1,9 @@
+import pytest
 from a2a.extensions.common import (
+    HTTP_EXTENSION_HEADER,
     find_extension_by_uri,
     get_requested_extensions,
+    update_extension_header,
 )
 from a2a.types import AgentCapabilities, AgentCard, AgentExtension
 
@@ -56,3 +59,88 @@ def test_find_extension_by_uri_no_extensions():
     )
 
     assert find_extension_by_uri(card, 'foo') is None
+
+
+@pytest.mark.parametrize(
+    'extensions, header, expected_extensions',
+    [
+        (
+            ['ext1', 'ext2'],  # extensions
+            '',  # header
+            {
+                'ext1',
+                'ext2',
+            },  # expected_extensions
+        ),  # Case 1: New extensions provided,  empty header.
+        (
+            None,  # extensions
+            'ext1, ext2',  # header
+            {
+                'ext1',
+                'ext2',
+            },  # expected_extensions
+        ),  # Case 2: Extensions is None, existing header extensions.
+        (
+            [],  # extensions
+            'ext1',  # header
+            {},  # expected_extensions
+        ),  # Case 3: New extensions is empty list, existing header extensions.
+        (
+            ['ext1', 'ext2'],  # extensions
+            'ext3',  # header
+            {
+                'ext1',
+                'ext2',
+            },  # expected_extensions
+        ),  # Case 4: New extensions provided, and an existing header. New extensions should override active extensions.
+    ],
+)
+def test_update_extension_header_merge_with_existing_extensions(
+    extensions: list[str],
+    header: str,
+    expected_extensions: set[str],
+):
+    http_kwargs = {'headers': {HTTP_EXTENSION_HEADER: header}}
+    result_kwargs = update_extension_header(http_kwargs, extensions)
+    header_value = result_kwargs['headers'][HTTP_EXTENSION_HEADER]
+    if not header_value:
+        actual_extensions = {}
+    else:
+        actual_extensions_list = [e.strip() for e in header_value.split(',')]
+        actual_extensions = set(actual_extensions_list)
+    assert actual_extensions == expected_extensions
+
+
+def test_update_extension_header_with_other_headers():
+    extensions = ['ext']
+    http_kwargs = {'headers': {'X_Other': 'Test'}}
+    result_kwargs = update_extension_header(http_kwargs, extensions)
+    headers = result_kwargs.get('headers', {})
+    assert HTTP_EXTENSION_HEADER in headers
+    assert headers[HTTP_EXTENSION_HEADER] == 'ext'
+    assert headers['X_Other'] == 'Test'
+
+
+@pytest.mark.parametrize(
+    'http_kwargs',
+    [
+        None,
+        {},
+    ],
+)
+def test_update_extension_header_headers_not_in_kwargs(
+    http_kwargs: dict[str, str] | None,
+):
+    extensions = ['ext']
+    http_kwargs = {}
+    result_kwargs = update_extension_header(http_kwargs, extensions)
+    headers = result_kwargs.get('headers', {})
+    assert HTTP_EXTENSION_HEADER in headers
+    assert headers[HTTP_EXTENSION_HEADER] == 'ext'
+
+
+def test_update_extension_header_with_other_headers_extensions_none():
+    http_kwargs = {'headers': {'X_Other': 'Test'}}
+    result_kwargs = update_extension_header(http_kwargs, None)
+    assert HTTP_EXTENSION_HEADER not in result_kwargs['headers']
+    assert result_kwargs['headers']['X_Other'] == 'Test'
diff --git a/tests/integration/test_client_server_integration.py b/tests/integration/test_client_server_integration.py
index 88d4d3d1..e0a564ee 100644
--- a/tests/integration/test_client_server_integration.py
+++ b/tests/integration/test_client_server_integration.py
@@ -1,7 +1,7 @@
 import asyncio
 from collections.abc import AsyncGenerator
 from typing import NamedTuple
-from unittest.mock import ANY, AsyncMock
+from unittest.mock import ANY, AsyncMock, patch
 
 import grpc
 import httpx
@@ -9,6 +9,8 @@
 import pytest_asyncio
 from grpc.aio import Channel
 
+from a2a.client import ClientConfig
+from a2a.client.base_client import BaseClient
 from a2a.client.transports import JsonRpcTransport, RestTransport
 from a2a.client.transports.base import ClientTransport
 from a2a.client.transports.grpc import GrpcTransport
@@ -767,3 +769,61 @@ def channel_factory(address: str) -> Channel:
     assert transport._needs_extended_card is False
 
     await transport.close()
+
+
+@pytest.mark.asyncio
+async def test_base_client_sends_message_with_extensions(
+    jsonrpc_setup: TransportSetup, agent_card: AgentCard
+) -> None:
+    """
+    Integration test for BaseClient with JSON-RPC transport to ensure extensions are included in headers.
+    """
+    transport = jsonrpc_setup.transport
+    agent_card.capabilities.streaming = False
+
+    # Create a BaseClient instance
+    client = BaseClient(
+        card=agent_card,
+        config=ClientConfig(streaming=False),
+        transport=transport,
+        consumers=[],
+        middleware=[],
+    )
+
+    message_to_send = Message(
+        role=Role.user,
+        message_id='msg-integration-test-extensions',
+        parts=[Part(root=TextPart(text='Hello, extensions test!'))],
+    )
+    extensions = [
+        'https://example.com/test-ext/v1',
+        'https://example.com/test-ext/v2',
+    ]
+
+    with patch.object(
+        transport, '_send_request', new_callable=AsyncMock
+    ) as mock_send_request:
+        mock_send_request.return_value = {
+            'id': '123',
+            'jsonrpc': '2.0',
+            'result': TASK_FROM_BLOCKING.model_dump(mode='json'),
+        }
+
+        # Call send_message on the BaseClient
+        async for _ in client.send_message(
+            request=message_to_send, extensions=extensions
+        ):
+            pass
+
+        mock_send_request.assert_called_once()
+        call_args, _ = mock_send_request.call_args
+        kwargs = call_args[1]
+        headers = kwargs.get('headers', {})
+        assert 'X-A2A-Extensions' in headers
+        assert (
+            headers['X-A2A-Extensions']
+            == 'https://example.com/test-ext/v1,https://example.com/test-ext/v2'
+        )
+
+    if hasattr(transport, 'close'):
+        await transport.close()

From 2c544f4e8a8cee6bcb5fa2b7c628afb9c31ba336 Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Wed, 19 Nov 2025 05:20:06 -0600
Subject: [PATCH 13/15] chore(main): release 0.4.0 (#553)

:robot: I have created a release *beep* *boop*
---


##
[0.4.0](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.4.0)
(2025-11-19)


### Features

* Add client-side extension support
([#525](https://github.com/a2aproject/a2a-python/issues/525))
([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
* **rest, jsonrpc:** Add client-side extension support
([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).
---
 CHANGELOG.md | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a684ac02..ddab2267 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## [0.4.0](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.4.0) (2025-11-19)
+
+
+### Features
+
+* Add client-side extension support ([#525](https://github.com/a2aproject/a2a-python/issues/525)) ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
+* **rest, jsonrpc:** Add client-side extension support ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
+
 ## [0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14) (2025-11-17)
 
 

From 5c59c1a38ceebd1fea354799f35f79bcc2c5a0ac Mon Sep 17 00:00:00 2001
From: Lukasz Kawka <luk.kawka@gmail.com>
Date: Wed, 19 Nov 2025 15:41:00 +0100
Subject: [PATCH 14/15] chore: Revert "chore(main): release 0.4.0" (#554)

Reverts a2aproject/a2a-python#553

Release had an incorrect version.

Release-As: 0.3.15
---
 CHANGELOG.md | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ddab2267..a684ac02 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,13 +1,5 @@
 # Changelog
 
-## [0.4.0](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.4.0) (2025-11-19)
-
-
-### Features
-
-* Add client-side extension support ([#525](https://github.com/a2aproject/a2a-python/issues/525)) ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
-* **rest, jsonrpc:** Add client-side extension support ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
-
 ## [0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14) (2025-11-17)
 
 

From fdb47310d75e746b35b798f93402418447ac0e22 Mon Sep 17 00:00:00 2001
From: "Agent2Agent (A2A) Bot" <a2a-bot@google.com>
Date: Wed, 19 Nov 2025 09:42:03 -0600
Subject: [PATCH 15/15] chore(main): release 0.3.15 (#555)

:robot: I have created a release *beep* *boop*
---


##
[0.3.15](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.3.15)
(2025-11-19)


### Features

* Add client-side extension support

([https://github.com/a2aproject/a2a-python/pull/525](https://github.com/a2aproject/a2a-python/pull/525))

([https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
* **rest, jsonrpc:** Add client-side extension support

([https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

---------

Co-authored-by: Lukasz Kawka <luk.kawka@gmail.com>
---
 CHANGELOG.md | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a684ac02..f5e6048d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,12 @@
-# Changelog
+ # Changelog
+
+## [0.3.15](https://github.com/a2aproject/a2a-python/compare/v0.3.14...v0.3.15) (2025-11-19)
+
+
+### Features
+
+* Add client-side extension support ([#525](https://github.com/a2aproject/a2a-python/issues/525)) ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
+* **rest, jsonrpc:** Add client-side extension support ([9a92bd2](https://github.com/a2aproject/a2a-python/commit/9a92bd238e7560b195165ac5f78742981760525e))
 
 ## [0.3.14](https://github.com/a2aproject/a2a-python/compare/v0.3.13...v0.3.14) (2025-11-17)