From de476d5b8fc629163654b2c7f0517f0fe7030b1c Mon Sep 17 00:00:00 2001
From: anessbelbati <102622182+anessbelbati@users.noreply.github.com>
Date: Wed, 7 Oct 2026 04:54:28 +0100
Subject: [PATCH] Name the display variables for the tool server Codex starts
 on Linux

Codex starts an MCP server with a fixed short list of environment variables
(HOME, PATH, LANG and a few more), not with its own environment. On Linux
the launcher in .codex/config.toml is the desktop app itself, and without
DISPLAY it exits at startup:

    Missing X server or $DISPLAY
    The platform failed to initialize.  Exiting.

Codex then logs "MCP server startup failed" for video-fs and offers the
model none of its tools. Measured with Codex 0.160.1 on ubuntu-latest
against a stand-in model server: none of the app's tools in the model
request with the entry as it was written before, the video-fs tools in the
request with this change. Started by hand with only the variables Codex
passes, the launcher ended after 1.2 s without answering; with the display
variables added it answered the MCP initialize request.

The entry now lists the display variables under env_vars, the key Codex
reads for variables to pass through from its own environment. Only an X11
display could be tried on the runner. The Wayland names are there so that
a Wayland session can reach its compositor the same way. Claude Code needed
no change: on the same runner it offered the video-fs tools already. What
is written on macOS and Windows does not change.
---
 desktop/agent-setup.mjs      | 14 ++++++++++++++
 desktop/agent-setup.test.mjs |  9 +++++++++
 2 files changed, 23 insertions(+)

diff --git a/desktop/agent-setup.mjs b/desktop/agent-setup.mjs
index ed572f5..3384af2 100644
--- a/desktop/agent-setup.mjs
+++ b/desktop/agent-setup.mjs
@@ -21,6 +21,17 @@ import { validateProjectId } from "./project-binding.mjs";
 
 const GUIDE_NAME = "VIDEO_FS_AGENT_GUIDE.md";
 
+/** Codex starts an MCP server with a short fixed list of environment variables.
+ * On Linux the launcher is the desktop app, which exits at startup when it
+ * cannot reach the session's display, so Codex has to pass these on as well. */
+const CODEX_DISPLAY_ENV_VARS = [
+  "DISPLAY",
+  "WAYLAND_DISPLAY",
+  "XAUTHORITY",
+  "XDG_RUNTIME_DIR",
+  "XDG_SESSION_TYPE",
+];
+
 export function projectIdFromAppUrl(candidate, appUrl) {
   let url;
   try {
@@ -70,6 +81,9 @@ export async function setupAgentProject({ projectId: rawProjectId, state }) {
     "[mcp_servers.video-fs]",
     `command = ${tomlString(launcher.command)}`,
     `args = ${tomlStringArray(launcher.args)}`,
+    ...(process.platform === "linux"
+      ? [`env_vars = ${tomlStringArray(CODEX_DISPLAY_ENV_VARS)}`]
+      : []),
     "",
   ].join("\n");
   const claudeHookConfig = hookConfig(claudeHookLauncher);
diff --git a/desktop/agent-setup.test.mjs b/desktop/agent-setup.test.mjs
index 95bf0b8..f26c0b3 100644
--- a/desktop/agent-setup.test.mjs
+++ b/desktop/agent-setup.test.mjs
@@ -337,6 +337,15 @@ test("both generated launchers bind exactly the opened project", async () => {
   );
   assert.match(codex, /args = \["--mcp", "--project-id", "bound-project"\]/);
   assert.doesNotMatch(codex, /project-a|project-b/);
+  // Codex hands an MCP server none of the display variables unless they are
+  // named, and on Linux the launcher cannot start without them.
+  assert.equal(
+    codex.includes(
+      'env_vars = ["DISPLAY", "WAYLAND_DISPLAY", "XAUTHORITY", "XDG_RUNTIME_DIR", "XDG_SESSION_TYPE"]\n',
+    ),
+    process.platform === "linux",
+  );
+  assert.equal(codex.includes("env_vars"), process.platform === "linux");
 
   const claudeHooks = JSON.parse(
     await readFile(