Fix Codex Remote thread writer conflicts

README.md

@@ -181,6 +181,7 @@ limit_re  = "usage limit|limit reached"
 [backend.codex]                 # Codex TUI, exposed through Codex Remote Control
 bin             = "codex"
 preamble        = "{bin} remote-control start --json >/dev/null"
+remote_addr     = "unix://"    # connect the TUI to that daemon (one shared thread writer)
 flags           = "--dangerously-bypass-approvals-and-sandbox --dangerously-bypass-hook-trust --no-alt-screen"
 supports_resume = false         # thread-ID persistence is not implemented by this harness
 prompt_delivery = "arg"
@@ -203,11 +204,14 @@ prompt_delivery = "exec"        # {kickoff}=prompt file, {session}=session name,
 
 For an `"arg"` backend the flag *templates* are configurable (so you can point at a non-claude
 CLI): `resume_flag` (default `--resume '{id}'`), `model_flag` (default `--model '{model}'`),
-`remote_control_flag` (default `--remote-control '{session}'`). A backend that sets `process_name`
+`remote_control_flag` (default `--remote-control '{session}'`), and `remote_addr_flag` (default
+`--remote '{addr}'`). A backend that sets `process_name`
 participates in backend-mismatch healing; one that doesn't (e.g. `demo`) never does.
 An optional `preamble` runs first and must succeed before the TUI starts; it supports `{bin}`,
 `{session}`, `{model}`, and `{dir}` templates. The Codex backend uses it to idempotently start the
-shared Remote Control daemon before launching each tmux-hosted Codex TUI.
+shared Remote Control daemon, then uses `remote_addr = "unix://"` to connect each tmux-hosted Codex
+TUI to that daemon. This keeps the app-server as the sole thread-store writer while local and
+Remote clients share the session.
 For an unattended TUI with a deterministic first-run gate, `startup_prompt_re` opts into one
 screen check after `startup_prompt_delay` seconds; on a match, the harness types the explicitly
 configured `startup_prompt_response` and `submit_key`. Codex uses this to trust the agent's

agents.example.toml

@@ -53,6 +53,7 @@ fatal_re  = "redacted_thinking|blocks cannot be modified|cannot be modified"
 [backend.codex]                  # Codex TUI + the shared Remote Control app-server daemon
 bin             = "codex"
 preamble        = "{bin} remote-control start --json >/dev/null"
+remote_addr     = "unix://"     # make the TUI a client of the daemon; it must not own a second writer
 flags           = "--dangerously-bypass-approvals-and-sandbox --dangerously-bypass-hook-trust --no-alt-screen"
 supports_resume = false          # the harness does not yet persist Codex thread IDs
 prompt_delivery = "arg"

agents.py

@@ -349,6 +349,11 @@ def start_agent(cfg, agent, *, force=False):
         if backend.get("remote_control"):
             parts.append(_render_template(backend.get("remote_control_flag",
                                           "--remote-control '{session}'"), {"session": session}))
+        if backend.get("remote_addr"):
+            parts.append(_render_template(backend.get("remote_addr_flag", "--remote '{addr}'"), {
+                "addr": backend["remote_addr"], "session": session, "model": model,
+                "dir": shlex.quote(cwd),
+            }))
         if model:
             parts.append(_render_template(backend.get("model_flag", "--model '{model}'"), {"model": model}))
         if backend.get("flags"):
@@ -356,8 +361,8 @@ def start_agent(cfg, agent, *, force=False):
         parts.append(f"\"$(cat '{kf}')\"")
         cmd = " ".join(p for p in parts if p)
         # Some interactive CLIs need an idempotent service prepared before their TUI starts.
-        # Codex Remote Control is one such service: `remote-control start` ensures the shared
-        # app-server daemon is enrolled and connected, then the pane runs the ordinary Codex TUI.
+        # The Codex backend starts the shared app-server here, while remote_addr above makes the
+        # pane's TUI a client of that daemon so both local and Remote UIs share one thread writer.
         if backend.get("preamble"):
             preamble = _render_template(backend["preamble"], {
                 "bin": backend["bin"], "session": session, "model": model,

tests/smoke_codex.sh

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 # Isolated live smoke of the Codex backend, driven entirely through agents.py.
-# It starts one uniquely-named tmux session, verifies Remote Control and the Codex TUI, then
-# removes only that session. The shared Remote Control daemon intentionally remains available.
+# It starts one uniquely-named tmux session, verifies Remote Control and a daemon-connected Codex
+# TUI, then removes only that session. The shared Remote Control daemon intentionally remains
+# available.
 set -uo pipefail
 
 HERE="$(cd "$(dirname "$0")" && pwd)"
@@ -54,6 +55,7 @@ watch          = "none"
 [backend.codex]
 bin             = "$CODEX_BIN"
 preamble        = "{bin} remote-control start --json >/dev/null"
+remote_addr     = "unix://"
 flags           = "--dangerously-bypass-approvals-and-sandbox --dangerously-bypass-hook-trust --no-alt-screen"
 supports_resume = false
 prompt_delivery = "arg"

tests/test_unit.py

@@ -77,6 +77,7 @@ limit_re  = "usage limit|limit reached"
 [backend.codex]
 bin             = "codex"
 preamble        = "{bin} remote-control start --json >/dev/null"
+remote_addr     = "unix://"
 flags           = "--dangerously-bypass-approvals-and-sandbox --dangerously-bypass-hook-trust --no-alt-screen"
 supports_resume = false
 prompt_delivery = "arg"
@@ -260,7 +261,7 @@ class TestExampleConfig(unittest.TestCase):
             self.assertIn(be, cfg["backends"], f"backend {be} missing from example")
         self.assertEqual(len(agents.phases(cfg)), 2)
 
-    def test_codex_launch_prepares_remote_control_then_starts_tui(self):
+    def test_codex_launch_prepares_remote_control_then_connects_tui_to_daemon(self):
         tmp = tempfile.mkdtemp(prefix="aotest-ut-codex-")
         old_alive, old_new, old_log = agents.session_alive, agents.new_session, agents.log
         old_capture, old_run = agents.capture_pane, agents._run
@@ -277,7 +278,9 @@ class TestExampleConfig(unittest.TestCase):
             self.assertEqual(len(launched), 1)
             cmd = launched[0]
             self.assertTrue(cmd.startswith(
-                "codex remote-control start --json >/dev/null && codex "))
+                "codex remote-control start --json >/dev/null && "
+                "codex --remote 'unix://' --model 'gpt-test' "))
+            self.assertEqual(cmd.count("--remote 'unix://'"), 1)
             self.assertIn("--model 'gpt-test'", cmd)
             self.assertIn(
                 "--dangerously-bypass-approvals-and-sandbox --dangerously-bypass-hook-trust --no-alt-screen",