diff --git a/setup.py b/setup.py
index 263df0fb..da77379e 100644
--- a/setup.py
+++ b/setup.py
@@ -4,6 +4,29 @@
 this_directory = Path(__file__).parent
 long_description = (this_directory / "README.md").read_text()
 
+
+def stamp_api_version():
+    """Mirror synapse-api/VERSION into synapse/_api_version.py.
+
+    The submodule is the source of truth for the protocol version. When
+    installing from an sdist the submodule isn't present, so we leave the
+    committed _api_version.py alone.
+    """
+    version_file = this_directory / "synapse-api" / "VERSION"
+    if not version_file.exists():
+        return
+    api_version = version_file.read_text().strip()
+    output = this_directory / "synapse" / "_api_version.py"
+    contents = (
+        "# Generated from synapse-api/VERSION by setup.py. Do not edit.\n"
+        f'SYNAPSE_API_VERSION = "{api_version}"\n'
+    )
+    if not output.exists() or output.read_text() != contents:
+        output.write_text(contents)
+
+
+stamp_api_version()
+
 setup(
     name="science-synapse",
     version="2.5.0",
diff --git a/synapse-api b/synapse-api
index 6c0905e5..27b6261e 160000
--- a/synapse-api
+++ b/synapse-api
@@ -1 +1 @@
-Subproject commit 6c0905e5ce5f2680ce0fa460f0659bd7f1de715f
+Subproject commit 27b6261e253dc0163b62b01fb8b02c2710091958
diff --git a/synapse/__init__.py b/synapse/__init__.py
index b73cb136..3841437a 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -1 +1,2 @@
+from synapse._api_version import SYNAPSE_API_VERSION
 from synapse.client import *
diff --git a/synapse/_api_version.py b/synapse/_api_version.py
new file mode 100644
index 00000000..5c7f6df9
--- /dev/null
+++ b/synapse/_api_version.py
@@ -0,0 +1,2 @@
+# Generated from synapse-api/VERSION by setup.py. Do not edit.
+SYNAPSE_API_VERSION = "2.4.0"
diff --git a/synapse/cli/__main__.py b/synapse/cli/__main__.py
index af66f34e..87c3c625 100755
--- a/synapse/cli/__main__.py
+++ b/synapse/cli/__main__.py
@@ -8,6 +8,7 @@
 from rich.console import Console
 from rich.logging import RichHandler
 
+from synapse import SYNAPSE_API_VERSION
 from synapse.cli import (
     apps,
     discover,
@@ -59,7 +60,8 @@ def main():
     parser.add_argument(
         "--version",
         action="version",
-        version="synapsectl %s" % metadata.version("science-synapse"),
+        version="synapsectl %s (Synapse API %s)"
+        % (metadata.version("science-synapse"), SYNAPSE_API_VERSION),
     )
     parser.add_argument(
         "--verbose",
diff --git a/synapse/cli/device_info_display.py b/synapse/cli/device_info_display.py
index 15e8299a..72b038f4 100644
--- a/synapse/cli/device_info_display.py
+++ b/synapse/cli/device_info_display.py
@@ -2,6 +2,7 @@
 from rich.tree import Tree
 from google.protobuf.json_format import MessageToDict
 from synapse.client.device import Device
+from synapse.utils.version import decode_synapse_version
 
 
 def visualize_configuration(info_dict, status):
@@ -137,8 +138,14 @@ def summary(self, device: Device):
             f"Serial: {info_dict.get('serial', 'Unknown')}",
             highlight=False,
         )
+        synapse_version_raw = info_dict.get("synapse_version")
+        synapse_version_str = (
+            decode_synapse_version(synapse_version_raw)
+            if synapse_version_raw is not None
+            else "Unknown"
+        )
         self.console.print(
-            f"Synapse Version: {info_dict.get('synapse_version', 'Unknown')}",
+            f"Synapse Version: {synapse_version_str}",
             highlight=False,
         )
         self.console.print(
diff --git a/synapse/utils/version.py b/synapse/utils/version.py
new file mode 100644
index 00000000..d4f72bd8
--- /dev/null
+++ b/synapse/utils/version.py
@@ -0,0 +1,12 @@
+def decode_synapse_version(v: int) -> str:
+    """Decode a Synapse API version uint32 into a "major.minor.patch" string.
+
+    Encoding (see synapse-api device.proto, DeviceInfo.synapse_version):
+      bits [31:24] major (0-255)
+      bits [23:16] minor (0-255)
+      bits [15:0]  patch (0-65535)
+    """
+    major = (v >> 24) & 0xFF
+    minor = (v >> 16) & 0xFF
+    patch = v & 0xFFFF
+    return f"{major}.{minor}.{patch}"