diff --git a/contracts/v1/server-info.json b/contracts/v1/server-info.json
index 041654b..96cd52e 100644
--- a/contracts/v1/server-info.json
+++ b/contracts/v1/server-info.json
@@ -4,10 +4,12 @@
   "title": "Trixie Server Info",
   "type": "object",
   "additionalProperties": false,
-  "required": ["api_version", "server_version", "status"],
+  "required": ["api_version", "server_version", "minimum_client_version", "maximum_client_version", "status"],
   "properties": {
     "api_version": { "type": "string", "const": "v1" },
     "server_version": { "type": "string", "minLength": 1 },
+    "minimum_client_version": { "type": "string", "minLength": 1 },
+    "maximum_client_version": { "type": "string", "minLength": 1 },
     "status": { "type": "string", "enum": ["ready"] }
   }
 }
diff --git a/docs/versioning.md b/docs/versioning.md
index 1d99f56..8887373 100644
--- a/docs/versioning.md
+++ b/docs/versioning.md
@@ -5,4 +5,7 @@
 - Clients must tolerate unknown fields and events.
 - Breaking changes require a new major version, fixtures, migration notes, and coordinated releases.
 - Each release records minimum compatible client and server versions.
+- `GET /api/v1/server/info` publishes `minimum_client_version` and
+  `maximum_client_version`; clients must use these fields to detect an
+  incompatible pairing before enabling authenticated controls.
 
diff --git a/fixtures/v1/server-info.ready.json b/fixtures/v1/server-info.ready.json
index ff0a099..f97e68c 100644
--- a/fixtures/v1/server-info.ready.json
+++ b/fixtures/v1/server-info.ready.json
@@ -1,5 +1,7 @@
 {
   "api_version": "v1",
   "server_version": "0.1.0-dev",
+  "minimum_client_version": "0.1.0",
+  "maximum_client_version": "0.x",
   "status": "ready"
 }