Custom primary agent mode name not shown in system-reminder notification

Description

Description

When switching to a custom primary agent (defined via .opencode/agents/*.md or opencode.json's agent field), the system reminder notification always shows either "build" or "plan" instead of the actual custom agent name.

Steps to reproduce

1. Create a custom primary agent, e.g. .opencode/agents/manual.md
2. Press Tab to cycle through agents: build → plan → manual
3. Observe the <system-reminder> notification

Expected behavior

The notification should say something like:

Your operational mode has changed from plan to manual.

Actual behavior

It says:

Your operational mode has changed from plan to build.

This means the notification falls back to "build" for any unrecognized custom primary agent name, which is misleading for both the user and the LLM.

Impact

Custom primary agents work correctly (permissions, prompt) but the misleading notification text may confuse the LLM into thinking it's in build mode, potentially affecting its conservative/aggressive behavior.

Plugins

None, just the original version.

OpenCode version

1.18.4

Steps to reproduce

1. Create .opencode/agents/manual.md (or any custom primary agent)
2. Press Tab to cycle: build → plan → manual
3. The always says "build" or "plan", never "manual", and "manual" will be recognized as "plan" by OpenCode

Screenshot and/or share link

No response

Operating System

Windows 10

Terminal

Windows Terminal