Bug: agent_unreachable when continuing existing sessions

[macedondev]

Environment

• Environment: Local development
• Endpoint: POST /api/v1/agent/sessions
• Error Code: agent_unreachable
• HTTP Status: 503 Service Unavailable

Description

When opening an older conversation and attempting to send a follow-up message, the request fails with a 503 Service Unavailable response.

Error

{
  "code": "agent_unreachable",
  "error": "The agent runtime is temporarily unavailable. Try again."
}

New conversations work correctly, but sending a message in an existing session fails with agent_unreachable.