`model: inherit` is a Claude Code-specific keyword that means "use the
parent session's model." Other tools that read the same agent frontmatter
(opencode, codex, etc.) don't understand it and instead try to use
`inherit` as a literal model id, which the configured provider rejects.
Reproduction (from #167): opencode + deepseek runs `/understand`, the
project-scanner subagent dispatches with `model: inherit`, deepseek
returns `ProviderModelNotFoundError`, and the pipeline halts on every
subagent dispatch.
With the field omitted, each platform falls back to its own configured
default:
- Claude Code: user's default subagent model
- opencode / codex / etc.: globally configured model
Note for Claude Code Opus users: subagents will no longer auto-inherit
the Opus session model. If you want the previous behavior, set your
default subagent model globally — that single setting now controls all
nine agents.
Closes#167