diff --git a/Cargo.lock b/Cargo.lock
index 42f4be3..67c596e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1341,7 +1341,7 @@ checksum = "b6d2cec3eae94f9f509c767b45932f1ada8350c4bdb85af2fcab4a3c14807981"
 
 [[package]]
 name = "link-assistant-router"
-version = "0.19.0"
+version = "0.20.0"
 dependencies = [
  "aes-gcm",
  "async-trait",
diff --git a/changelog.d/20260712_090000_codex_version_header.md b/changelog.d/20260712_090000_codex_version_header.md
new file mode 100644
index 0000000..6f7e30d
--- /dev/null
+++ b/changelog.d/20260712_090000_codex_version_header.md
@@ -0,0 +1,10 @@
+---
+bump: minor
+---
+
+### Added
+- Codex subscriptions now send a `version` header (default `0.144.1`, overridable via
+  `CODEX_CLIENT_VERSION`) when proxying to the ChatGPT backend. The backend gates newer
+  models (e.g. `gpt-5.6-luna`) behind a recent client version; without the header
+  `POST /responses` returns `Model not found`. This mirrors the Codex CLI so newer models
+  are usable through the router.
diff --git a/src/subscription_proxy.rs b/src/subscription_proxy.rs
index da6c8ed..0379570 100644
--- a/src/subscription_proxy.rs
+++ b/src/subscription_proxy.rs
@@ -211,7 +211,7 @@ pub async fn forward_subscription_openai(
 
 /// Collapse a Codex Responses SSE body into the final Responses JSON object.
 ///
-/// The ChatGPT Codex backend only streams (`text/event-stream`-style `event:` /
+/// The `ChatGPT` Codex backend only streams (`text/event-stream`-style `event:` /
 /// `data:` lines). For non-streaming clients we extract the `response` object
 /// carried by the terminal `response.completed` event and return it verbatim, so
 /// the client receives the single JSON object it expects. Returns `None` if no
@@ -273,6 +273,13 @@ fn subscription_headers(
         // identifies the originating client.
         out.push(("openai-beta", "responses=experimental".to_string()));
         out.push(("originator", "codex_cli_rs".to_string()));
+        // Codex gates newer models (e.g. gpt-5.6-luna) behind a recent client version
+        // advertised via the `version` header; without it the backend replies "Model not
+        // found". Mirror the Codex CLI. Overridable via CODEX_CLIENT_VERSION.
+        out.push((
+            "version",
+            std::env::var("CODEX_CLIENT_VERSION").unwrap_or_else(|_| "0.144.1".to_string()),
+        ));
     }
     out
 }
@@ -366,7 +373,7 @@ fn input_item_text(item: &serde_json::Value) -> Option<String> {
 /// - **requires** a non-empty `instructions` field (HTTP 400 "Instructions are
 ///   required").
 ///
-/// Standard Responses clients (e.g. OpenClaw's gateway) send `max_output_tokens`
+/// Standard Responses clients (e.g. `OpenClaw`'s gateway) send `max_output_tokens`
 /// and put the system prompt as a `system` message in `input`, so without this
 /// shaping the backend rejects every request. System turns are hoisted into
 /// `instructions`; a default is used only if nothing remains.
@@ -382,8 +389,8 @@ fn normalize_codex_responses_body(body: &mut serde_json::Value) {
     // Hoist system/developer turns out of `input` (Codex forbids them there).
     let mut hoisted: Vec<String> = Vec::new();
     if let Some(serde_json::Value::Array(items)) = obj.get_mut("input") {
-        items.retain(|item| {
-            match item.get("role").and_then(serde_json::Value::as_str) {
+        items.retain(
+            |item| match item.get("role").and_then(serde_json::Value::as_str) {
                 Some("system" | "developer") => {
                     if let Some(text) = input_item_text(item) {
                         hoisted.push(text);
@@ -391,8 +398,8 @@ fn normalize_codex_responses_body(body: &mut serde_json::Value) {
                     false
                 }
                 _ => true,
-            }
-        });
+            },
+        );
     }
 
     // Merge existing instructions + hoisted system turns; fall back to a default.
@@ -408,7 +415,10 @@ fn normalize_codex_responses_body(body: &mut serde_json::Value) {
     } else {
         parts.join("\n\n")
     };
-    obj.insert("instructions".to_string(), serde_json::Value::String(instructions));
+    obj.insert(
+        "instructions".to_string(),
+        serde_json::Value::String(instructions),
+    );
 }
 
 #[cfg(test)]
@@ -537,6 +547,25 @@ mod tests {
         );
     }
 
+    #[test]
+    fn codex_headers_include_version() {
+        let token = SubscriptionToken {
+            access_token: "a".into(),
+            refresh_token: None,
+            expires_at_ms: None,
+            account_id: Some("acct_9".into()),
+            resource_url: None,
+        };
+        let headers = subscription_headers(SubscriptionProvider::Codex, &token);
+        // The Codex backend gates newer models behind a recent client version
+        // advertised via the `version` header.
+        assert!(
+            headers
+                .iter()
+                .any(|(k, v)| *k == "version" && !v.is_empty())
+        );
+    }
+
     #[test]
     fn rate_limit_headers_are_selected() {
         let mut headers = HeaderMap::new();