diff --git a/changes/11787.doc.md b/changes/11787.doc.md
new file mode 100644
index 00000000000..b29644e3cac
--- /dev/null
+++ b/changes/11787.doc.md
@@ -0,0 +1 @@
+Update the advertised API version in the docs to `v9.20250722` and source it from `ai.backend.client.config.API_VERSION` via a Sphinx substitution so it stays in sync automatically.
diff --git a/docs/conf.py b/docs/conf.py
index eae7e05fc39..2b8701e23d9 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -13,6 +13,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
+import ast
 import os
 import sys
 from pathlib import Path
@@ -74,6 +75,33 @@
 # The short X.Y version.
 version = ".".join(release.split(".")[:2])
 
+# Expose the current Backend.AI client API version as the |api_version|
+# substitution so docs do not hard-code the string. Source of truth:
+# `src/ai/backend/client/config.py` (`API_VERSION`). We parse the literal
+# out of the file directly instead of importing the package, so the docs
+# build does not need aiohttp / the full client runtime installed.
+def _read_api_version() -> str:
+    config_path = root_path / "src/ai/backend/client/config.py"
+    source = config_path.read_text(encoding="utf-8")
+    for node in ast.parse(source, filename=str(config_path)).body:
+        if (
+            isinstance(node, ast.Assign)
+            and len(node.targets) == 1
+            and isinstance(node.targets[0], ast.Name)
+            and node.targets[0].id == "API_VERSION"
+            and isinstance(node.value, ast.Tuple)
+            and len(node.value.elts) == 2
+        ):
+            major, rev = (ast.literal_eval(e) for e in node.value.elts)
+            return f"v{major}.{rev}"
+    raise RuntimeError("API_VERSION not found in src/ai/backend/client/config.py")
+
+
+api_version = _read_api_version()
+rst_prolog = f"""
+.. |api_version| replace:: {api_version}
+"""
+
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
 #
diff --git a/docs/index.rst b/docs/index.rst
index 82b3ad2d4b6..0a1c7eecd3a 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -1,7 +1,7 @@
 Backend.AI Documentation
 ========================
 
-**Latest API version: v6.20220615**
+**Latest API version:** |api_version|
 
 Backend.AI is an enterprise-grade development and service backend for a wide range of AI-powered applications.
 Its core technology is tailored for operating high density computing clusters including GPUs and heterogeneous accelerators.
diff --git a/docs/install/install-from-package/install-manager.rst b/docs/install/install-from-package/install-manager.rst
index 29ae833b8c7..f2e107cf60f 100644
--- a/docs/install/install-from-package/install-manager.rst
+++ b/docs/install/install-from-package/install-manager.rst
@@ -260,7 +260,7 @@ can be configured from ``manager.toml``:
 .. code-block:: console
 
    $ curl bai-m1:8081
-   {"version": "v6.20220615", "manager": "22.09.6"}
+   {"version": "v9.20250722", "manager": "26.4.8"}
 
 Press ``Ctrl-C`` to stop the service.
 
diff --git a/docs/locales/ko/LC_MESSAGES/index.po b/docs/locales/ko/LC_MESSAGES/index.po
index c148c7f09e7..8a50be60ef2 100644
--- a/docs/locales/ko/LC_MESSAGES/index.po
+++ b/docs/locales/ko/LC_MESSAGES/index.po
@@ -24,9 +24,8 @@ msgid "Backend.AI Documentation"
 msgstr "Backend.AI 레퍼런스 문서"
 
 #: ../../index.rst:4 46ce303188ef4054a0d1690f4f5adb03
-#, fuzzy
-msgid "**Latest API version: v6.20220615**"
-msgstr "**최근 API 버전: v5.20191215**"
+msgid "**Latest API version:** |api_version|"
+msgstr "**최근 API 버전:** |api_version|"
 
 #: ../../index.rst:6 b8e94703b6e741c2bb5b33d76b5949ba
 msgid ""
diff --git a/src/ai/backend/client/config.py b/src/ai/backend/client/config.py
index 78e9485c1a4..dfb3c74cd97 100644
--- a/src/ai/backend/client/config.py
+++ b/src/ai/backend/client/config.py
@@ -28,6 +28,10 @@ class Undefined(enum.Enum):
 _config = None
 _undefined = Undefined.token
 
+# NOTE: `docs/conf.py` parses this `API_VERSION` literal with `ast` to expose
+# the `|api_version|` Sphinx substitution. Keep this as a plain `Assign` of a
+# 2-tuple `(int, str)` — changing the form (annotated assignment, different
+# arity, etc.) requires updating `docs/conf.py:_read_api_version()`.
 API_VERSION = (9, "20250722")
 MIN_API_VERSION = (7, "20230615")