diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4609f19..136d506 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Python SDK floor bumped to `youdotcom>=3.1.2,<4` (was `>=3.0.0,<4`). The 3.1.2 release ships the `X-Client-Info` attribution header and the `app_name` / `app_version` / `app_title` / `app_url` constructor kwargs on `You`
+- The plugin now passes `app_name="youdotcom-temporal"` and `app_version=<package version>` to the `You(...)` constructor instead of mutating `client.sdk_configuration.user_agent` post-construction. Each outbound request carries `X-Client-Info: sdk; client=youdotcom-temporal/<version>; ua=python/<v> httpx/<v>`; the SDK's own `user-agent` stays as `youdotcom-python-sdk/<v>`. The `_USER_AGENT` constant is removed
+
 ## [1.0.1] — 2026-08-18
 
 ### Fixed
diff --git a/pyproject.toml b/pyproject.toml
index 926773b..61895c6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ dependencies = [
     # Floor, not a pin: SimplePlugin needs 1.19.0+; use a recent stable floor and
     # let CI test the latest. Upper bound only guards the next major.
     "temporalio>=1.27.0,<2",
-    "youdotcom>=3.0.0,<4",
+    "youdotcom>=3.1.2,<4",
 ]
 
 [project.urls]
diff --git a/src/youdotcom_temporal/_client.py b/src/youdotcom_temporal/_client.py
index 21a687a..2339e2a 100644
--- a/src/youdotcom_temporal/_client.py
+++ b/src/youdotcom_temporal/_client.py
@@ -8,7 +8,12 @@
 from . import __version__
 from .config import YouConfig
 
-_USER_AGENT = f"youdotcom-temporal/{__version__}"
+# Caller-identity segments emitted in the SDK's ``X-Client-Info`` header on
+# every outbound request (shipped in youdotcom 3.1.2). The SDK keeps its own
+# ``user-agent`` as ``youdotcom-python-sdk/<v>``; the plugin identity rides
+# the attribution header instead.
+_APP_NAME = "youdotcom-temporal"
+_APP_VERSION = __version__
 
 
 @asynccontextmanager
@@ -17,10 +22,11 @@ async def you_client(cfg: YouConfig) -> AsyncIterator[You]:
         "api_key_auth": cfg.api_key,
         "retry_config": None,
         "timeout_ms": int(cfg.timeout_seconds * 1000),
+        "app_name": _APP_NAME,
+        "app_version": _APP_VERSION,
     }
     if cfg.server_url:
         kwargs["server_url"] = cfg.server_url
     client = You(**kwargs)  # type: ignore[arg-type]
-    client.sdk_configuration.user_agent = _USER_AGENT
     async with client as entered:
         yield entered
diff --git a/tests/test_client.py b/tests/test_client.py
index ac63f7b..ec90868 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -3,7 +3,7 @@
 from unittest.mock import AsyncMock, patch
 
 from youdotcom_temporal import __version__
-from youdotcom_temporal._client import _USER_AGENT, you_client
+from youdotcom_temporal._client import you_client
 from youdotcom_temporal.config import YouConfig
 
 
@@ -23,6 +23,8 @@ async def test_client_kwargs_without_server_url():
         "api_key_auth": "k",
         "retry_config": None,
         "timeout_ms": 30000,
+        "app_name": "youdotcom-temporal",
+        "app_version": __version__,
     }
 
 async def test_client_default_timeout_is_300s():
@@ -43,18 +45,11 @@ async def test_client_includes_server_url_when_set():
         "api_key_auth": "k",
         "retry_config": None,
         "timeout_ms": 5000,
+        "app_name": "youdotcom-temporal",
+        "app_version": __version__,
         "server_url": "https://custom",
     }
 
 
-async def test_client_sets_custom_user_agent():
-    cfg = YouConfig(api_key="k", timeout_seconds=30.0)
-    fake = _fake_you()
-    with patch("youdotcom_temporal._client.You", return_value=fake):
-        async with you_client(cfg):
-            pass
-    assert fake.sdk_configuration.user_agent == _USER_AGENT
-
-
-def test_user_agent_includes_package_version():
-    assert _USER_AGENT == f"youdotcom-temporal/{__version__}"
+def test_attribution_header_includes_package_version():
+    assert __version__ != "0.0.0-dev"
diff --git a/uv.lock b/uv.lock
index 58e1913..8f557ca 100644
--- a/uv.lock
+++ b/uv.lock
@@ -757,16 +757,16 @@ wheels = [
 
 [[package]]
 name = "youdotcom"
-version = "3.0.0"
+version = "3.1.2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "httpcore" },
     { name = "httpx" },
     { name = "pydantic" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/27/78/841c142d36037411e6c8d461e4b2e9ffcf106d46c3d3271e2208e2fc47c0/youdotcom-3.0.0.tar.gz", hash = "sha256:e425805ab11b9e7221ecd766f2fe55fe950cb8ed6e4da17d50b8a96ea93d42ab", size = 106479, upload-time = "2026-08-06T18:05:46.89Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/2d/99/77c5b7246ca4ffbb0ae0fc98757836b2a6cd114e2454e2bc73cd52c2bef0/youdotcom-3.1.2.tar.gz", hash = "sha256:73b4801203b6fca15f0531c5c34ae1dc680d2d41edf83748f572023c6137916d", size = 141929, upload-time = "2026-08-21T06:46:55.788Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/2a/81/da737799f0e1ac01eaaa41a2ef14ef43ecd68d7d494eb76108e329499046/youdotcom-3.0.0-py3-none-any.whl", hash = "sha256:141c601ef8a9e448348b96dc585e00792d3ef597bc26e6429bbb8570b0037e99", size = 99999, upload-time = "2026-08-06T18:05:45.689Z" },
+    { url = "https://files.pythonhosted.org/packages/e8/bb/258571903378fc865b87b3749c460dad7a8534bbccf8c4a3873203359536/youdotcom-3.1.2-py3-none-any.whl", hash = "sha256:1ef5c66871e0fe3320d5fa0869ba59420511560648e9fb793f9c7f1e0e7d641c", size = 114867, upload-time = "2026-08-21T06:46:54.5Z" },
 ]
 
 [[package]]
@@ -789,7 +789,7 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "temporalio", specifier = ">=1.27.0,<2" },
-    { name = "youdotcom", specifier = ">=3.0.0,<4" },
+    { name = "youdotcom", specifier = ">=3.1.2,<4" },
 ]
 
 [package.metadata.requires-dev]