codex - side car error when attempting to talk to it

[ashleysmart]

Setup /home/kage/.config/tether/config.env

TETHER_AGENT_TOKEN=...
DISCORD_BOT_TOKEN=...
DISCORD_ACCOUNTS='[{"id": "viber_bot", "token": "..."}]'
TETHER_AGENTS='[
  { "id": "viber_agent", "adapter": "claude_auto", "model": "claude-3-5-sonnet" },
  { "id": "claude", "adapter": "claude_auto", "model": "claude-3-5-sonnet" },
  { "id": "codex", "adapter": "codex_auto", "model": "gpt-5-codex", "endpoint": "ws://127.0.0.1:8788" }
]'

TETHER_BINDINGS='[
  { "agentId": "codex", "match": { "channelId": "1481731654698668042" }, "config": { "canCreate": true } },
  { "agentId": "claude", "match": { "channelId": "1481731624491290768" }, "config": { "canCreate": true } },
  { "agentId": "viber_agent", "match": { "channelId": "1465577170436096074" }, "config": { "canCreate": true } }
]'

Start codex server

npx @openai/codex app-server --listen ws://127.0.0.1:8788 &
tether start &

In discord start codex thread

Ash
 — 
1:16 PM
!new codex /home/kage/mud/codex
ViberCoderAPP
 — 
1:16 PM
✅ New Codex session created in codex.
🧵 Open thread: ⁠Codex / Codex
in discord thread is started with "codex"
✅ New Codex session created in codex.

Thread is open and "hi" is typed

resulting in this error:

INFO:     127.0.0.1:53934 - "POST /api/sessions/sess_ad282c27c43d/start HTTP/1.1" 500 Internal Server Error
2026-03-13T04:17:01.980477Z [error    ] Failed to forward human input  [agent_tether.discord.bot] session_id=sess_ad282c27c43d
Traceback (most recent call last):
  File "/home/kage/.local/share/pipx/venvs/tether-ai/lib/python3.12/site-packages/tether/bridges/glue.py", line 164, in _send_input
    r.raise_for_status()
  File "/home/kage/.local/share/pipx/venvs/tether-ai/lib/python3.12/site-packages/httpx/_models.py", line 829, in raise_for_status
    raise HTTPStatusError(message, request=request, response=self)
httpx.HTTPStatusError: Server error '500 Internal Server Error' for url 'http://localhost:8787/api/sessions/sess_ad282c27c43d/start'
For more information check: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/500

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/kage/.local/share/pipx/venvs/tether-ai/lib/python3.12/site-packages/agent_tether/discord/bot.py", line 719, in _forward_input
    await self._send_input_or_start_via_api(session_id=session_id, text=text)
  File "/home/kage/.local/share/pipx/venvs/tether-ai/lib/python3.12/site-packages/agent_tether/base.py", line 347, in _send_input_or_start_via_api
    await self._callbacks.send_input(session_id, text)
  File "/home/kage/.local/share/pipx/venvs/tether-ai/lib/python3.12/site-packages/tether/bridges/glue.py", line 171, in _send_input
    raise RuntimeError(
RuntimeError: Failed to start runner: Sidecar request failed: 405 Request method must be `GET`

Version

pipx upgrade --force tether-ai
tether-ai is already at latest version 0.3.4 (location: /home/kage/.local/share/pipx/venvs/tether-ai)
kage@shadow:~$ codex --version
codex-cli 0.114.0