diff --git a/src/cli.codex_smoke.test.ts b/src/cli.codex_smoke.test.ts
index cf5aa7c0..096de176 100644
--- a/src/cli.codex_smoke.test.ts
+++ b/src/cli.codex_smoke.test.ts
@@ -222,6 +222,7 @@ async function runDeck(input: {
   cwd?: string;
   command?: "run" | "repl";
   extraArgs?: Array<string>;
+  env?: Record<string, string>;
 }): Promise<{
   code: number;
   stdout: string;
@@ -244,6 +245,7 @@ async function runDeck(input: {
       GAMBIT_CODEX_DISABLE_MCP: "1",
       CODEX_ARGS_LOG: input.argsLogPath,
       CODEX_REQUESTS_LOG: input.requestLogPath,
+      ...(input.env ?? {}),
     },
     stdout: "piped",
     stderr: "piped",
@@ -503,6 +505,48 @@ Deno.test({
       ),
       true,
     );
+
+    await Deno.remove(mock.requestLogPath).catch((err) => {
+      if (err instanceof Deno.errors.NotFound) return;
+      throw err;
+    });
+    const nestedDeckDir = path.join(
+      dir,
+      "coworkers",
+      "agents",
+      "chief-of-staff",
+    );
+    await Deno.mkdir(nestedDeckDir, { recursive: true });
+    const nestedDeck = await writeDeck(
+      nestedDeckDir,
+      "codex-cli/default",
+      undefined,
+      "Nested Chief deck.",
+    );
+    const nestedRun = await runDeck({
+      deckPath: nestedDeck,
+      codexBinPath: mock.binPath,
+      argsLogPath: mock.argsLogPath,
+      requestLogPath: mock.requestLogPath,
+      cwd: dir,
+      env: { GAMBIT_BOT_ROOT: dir },
+    });
+    assertEquals(
+      nestedRun.code,
+      0,
+      formatCommandDiagnostics(
+        "run nested codex-cli/default under GAMBIT_BOT_ROOT",
+        nestedRun,
+      ),
+    );
+    assertEquals(
+      nestedRun.requestLog.includes(`"cwd":"${dir}"`),
+      true,
+    );
+    assertEquals(
+      nestedRun.requestLog.includes(`"writableRoots":["${dir}"]`),
+      true,
+    );
   } finally {
     await Deno.remove(dir, { recursive: true }).catch((err) => {
       if (err instanceof Deno.errors.NotFound) return;
diff --git a/src/providers/codex.ts b/src/providers/codex.ts
index e5d4c0bb..394c3690 100644
--- a/src/providers/codex.ts
+++ b/src/providers/codex.ts
@@ -170,9 +170,30 @@ function codexDeckDir(deckPath?: string): string | undefined {
   );
 }
 
+function codexBotRootCwd(deckPath?: string): string | undefined {
+  const botRootRaw = Deno.env.get(BOT_ROOT_ENV)?.trim();
+  if (!botRootRaw) return undefined;
+  const botRoot = path.resolve(botRootRaw);
+  const trimmedDeckPath = deckPath?.trim();
+  if (!trimmedDeckPath) return botRoot;
+  const deckAbsolutePath = path.isAbsolute(trimmedDeckPath)
+    ? path.resolve(trimmedDeckPath)
+    : path.resolve(botRoot, trimmedDeckPath);
+  const relative = path.relative(botRoot, deckAbsolutePath);
+  if (
+    relative === "" ||
+    (!relative.startsWith("..") && !path.isAbsolute(relative))
+  ) {
+    return botRoot;
+  }
+  return undefined;
+}
+
 function codexRunCwd(input: { cwd?: string; deckPath?: string }): string {
   const explicitCwd = input.cwd?.trim();
   if (explicitCwd) return explicitCwd;
+  const botRoot = codexBotRootCwd(input.deckPath);
+  if (botRoot) return botRoot;
   const deckDir = codexDeckDir(input.deckPath);
   if (deckDir) return deckDir;
   return runCwd();