tui: free-tier model rejected for custom primary agent while build works #55266

Description

Summary

Sending any prompt (even a trivial "hola") to a custom primary agent selected with Shift+Tab fails with a free-tier error, while the same prompt to the built-in build agent on the same free model works fine.

Environment

• opencode version: v2.0.28
• OS: Linux 6.18.54.1-microsoft-standard-WSL2 (linux x64)
• Terminal: TERM=xterm-256color (no TERM_PROGRAM/COLORTERM)
• Shell: /bin/bash
• Install/channel: latest (release)
• Active plugins: none (no global config, no project config, no local plugins)

Reproduction

1. Create a project custom agent at .opencode/agents/coordinator.md with mode: primary (definition below).
2. Open opencode in that project.
3. Press Shift+Tab and select the coordinator agent.
4. Type Hola and send.
5. Repeat steps 3-4 with the built-in build agent.

Expected Behavior

Both agents respond using the configured free model, since neither the agent definition nor the prompt changes the model or the channel.

Actual Behavior

• build answers normally.
• coordinator fails every time with: Error: OpenCode's free tier can only be used from within OpenCode. Download it at https://opencode.ai and keep building.

Additional Context

• Reproducible consistently, including with prompts that use no tools, reads, or subagents, so agent permissions are ruled out as the cause.
• The custom agent defines no model:, so it inherits the same session free model as build.
• Agent definition used (no secrets):

---
description: SDD - coordina el flujo SDD completo con planner, implementer y reviewer, y transmite el contexto entre fases
mode: primary
permissions:
- action: edit
  resource: "*"
  effect: deny
- action: shell
  resource: "*"
  effect: deny
- action: webfetch
  resource: "*"
  effect: deny
- action: websearch
  resource: "*"
  effect: deny
- action: subagent
  resource: "*"
  effect: deny
- action: subagent
  resource: "planner"
  effect: allow
- action: subagent
  resource: "implementer"
  effect: allow
- action: subagent
  resource: "reviewer"
  effect: allow
---
(agent system prompt omitted, unrelated to the error)

• Hypothesis: opening a session with a custom primary agent loses the "from within OpenCode" client attestation that the free-tier gateway requires, while built-in agents keep it.

Plugins

None (no global config, no project config, no local plugins)

OpenCode version

v2.0.28

Steps to reproduce

1. Create a project custom agent at .opencode/agents/coordinator.md with mode: primary (definition below).
2. Open opencode in that project.
3. Press Shift+Tab and select the coordinator agent.
4. Type Hola and send.
5. Repeat steps 3-4 with the built-in build agent.

• Reproducible consistently, including with prompts that use no tools, reads, or subagents, so agent permissions are ruled out as the cause.
• The custom agent defines no model:, so it inherits the same session free model as build.
• Agent definition used (no secrets):

---
description: SDD - coordina el flujo SDD completo con planner, implementer y reviewer, y transmite el contexto entre fases
mode: primary
permissions:
- action: edit
  resource: "*"
  effect: deny
- action: shell
  resource: "*"
  effect: deny
- action: webfetch
  resource: "*"
  effect: deny
- action: websearch
  resource: "*"
  effect: deny
- action: subagent
  resource: "*"
  effect: deny
- action: subagent
  resource: "planner"
  effect: allow
- action: subagent
  resource: "implementer"
  effect: allow
- action: subagent
  resource: "reviewer"
  effect: allow
---
(agent system prompt omitted, unrelated to the error)

Screenshot and/or share link

No response

Operating System

Linux 6.18.54.1-microsoft-standard-WSL2 (linux x64) (WSL under Windows 10 IoT Enterprise LTSC 21H2 19044.7725)

Terminal

Warp