app-server: Return codex home in initialize response

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -2257,6 +2257,10 @@
     "InitializeResponse": {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "properties": {
+        "codexHome": {
+          "description": "Absolute path to the server's Codex home directory.",
+          "type": "string"
+        },
         "platformFamily": {
           "description": "Platform family for the running app-server target, for example `\"unix\"` or `\"windows\"`.",
           "type": "string"
@@ -2270,6 +2274,7 @@
         }
       },
       "required": [
+        "codexHome",
         "platformFamily",
         "platformOs",
         "userAgent"

codex-rs/app-server-protocol/schema/json/v1/InitializeResponse.json

@@ -1,6 +1,10 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "properties": {
+    "codexHome": {
+      "description": "Absolute path to the server's Codex home directory.",
+      "type": "string"
+    },
     "platformFamily": {
       "description": "Platform family for the running app-server target, for example `\"unix\"` or `\"windows\"`.",
       "type": "string"
@@ -14,6 +18,7 @@
     }
   },
   "required": [
+    "codexHome",
     "platformFamily",
     "platformOs",
     "userAgent"

codex-rs/app-server-protocol/schema/typescript/InitializeResponse.ts

@@ -3,6 +3,10 @@
 // This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
 
 export type InitializeResponse = { userAgent: string, 
+/**
+ * Absolute path to the server's Codex home directory.
+ */
+codexHome: string,
 /**
  * Platform family for the running app-server target, for example
  * `"unix"` or `"windows"`.

codex-rs/app-server-protocol/src/protocol/v1.rs

@@ -56,6 +56,8 @@ pub struct InitializeCapabilities {
 #[serde(rename_all = "camelCase")]
 pub struct InitializeResponse {
     pub user_agent: String,
+    /// Absolute path to the server's Codex home directory.
+    pub codex_home: PathBuf,
     /// Platform family for the running app-server target, for example
     /// `"unix"` or `"windows"`.
     pub platform_family: String,

codex-rs/app-server/README.md

@@ -75,7 +75,7 @@ Use the thread APIs to create, list, or archive conversations. Drive a conversat
 
 ## Initialization
 
-Clients must send a single `initialize` request per transport connection before invoking any other method on that connection, then acknowledge with an `initialized` notification. The server returns the user agent string it will present to upstream services plus `platformFamily` and `platformOs` strings describing the app-server runtime target; subsequent requests issued before initialization receive a `"Not initialized"` error, and repeated `initialize` calls on the same connection receive an `"Already initialized"` error.
+Clients must send a single `initialize` request per transport connection before invoking any other method on that connection, then acknowledge with an `initialized` notification. The server returns the user agent string it will present to upstream services, `codexHome` for the server's Codex home directory, and `platformFamily` and `platformOs` strings describing the app-server runtime target; subsequent requests issued before initialization receive a `"Not initialized"` error, and repeated `initialize` calls on the same connection receive an `"Already initialized"` error.
 
 `initialize.params.capabilities` also supports per-connection notification opt-out via `optOutNotificationMethods`, which is a list of exact method names to suppress for that connection. Matching is exact (no wildcards/prefixes). Unknown method names are accepted and ignored.
 

codex-rs/app-server/src/message_processor.rs

@@ -581,6 +581,7 @@ impl MessageProcessor {
                 let user_agent = get_codex_user_agent();
                 let response = InitializeResponse {
                     user_agent,
+                    codex_home: self.config.codex_home.clone(),
                     platform_family: std::env::consts::FAMILY.to_string(),
                     platform_os: std::env::consts::OS.to_string(),
                 };

codex-rs/app-server/tests/suite/v2/initialize.rs

@@ -30,6 +30,7 @@ async fn initialize_uses_client_info_name_as_originator() -> Result<()> {
     let responses = Vec::new();
     let server = create_mock_responses_server_sequence_unchecked(responses).await;
     let codex_home = TempDir::new()?;
+    let expected_codex_home = codex_home.path().canonicalize()?;
     create_config_toml(codex_home.path(), &server.uri(), "never")?;
     let mut mcp = McpProcess::new(codex_home.path()).await?;
 
@@ -48,11 +49,13 @@ async fn initialize_uses_client_info_name_as_originator() -> Result<()> {
     };
     let InitializeResponse {
         user_agent,
+        codex_home: response_codex_home,
         platform_family,
         platform_os,
     } = to_response::<InitializeResponse>(response)?;
 
     assert!(user_agent.starts_with("codex_vscode/"));
+    assert_eq!(response_codex_home, expected_codex_home);
     assert_eq!(platform_family, std::env::consts::FAMILY);
     assert_eq!(platform_os, std::env::consts::OS);
     Ok(())
@@ -63,6 +66,7 @@ async fn initialize_respects_originator_override_env_var() -> Result<()> {
     let responses = Vec::new();
     let server = create_mock_responses_server_sequence_unchecked(responses).await;
     let codex_home = TempDir::new()?;
+    let expected_codex_home = codex_home.path().canonicalize()?;
     create_config_toml(codex_home.path(), &server.uri(), "never")?;
     let mut mcp = McpProcess::new_with_env(
         codex_home.path(),
@@ -88,11 +92,13 @@ async fn initialize_respects_originator_override_env_var() -> Result<()> {
     };
     let InitializeResponse {
         user_agent,
+        codex_home: response_codex_home,
         platform_family,
         platform_os,
     } = to_response::<InitializeResponse>(response)?;
 
     assert!(user_agent.starts_with("codex_originator_via_env_var/"));
+    assert_eq!(response_codex_home, expected_codex_home);
     assert_eq!(platform_family, std::env::consts::FAMILY);
     assert_eq!(platform_os, std::env::consts::OS);
     Ok(())