Only current selected agent's model persists when resuming a session (other agent(s) revert to default)

[malventano]

Description

When resuming a session (e.g. opencode -c), the selected agent's model is restored, but the other model(s) revert to the default.

Plugins

none

OpenCode version

1.4.11

Steps to reproduce

1. Configure opencode to have a default model.
2. Set plan/build models something other than the default.
3. Close opencode.
4. opencode -c or load the session within the TUI
5. Switch agents and observe the other agent now uses the default instead of the one selected in the prior session.

Screenshot and/or share link

No response

Operating System

Ubuntu

Terminal

tmux

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [FEATURE]: Interactively selected model resets to agent default when switching between Plan and Build modes (TUI) #21351: Interactively selected model resets to agent default when switching between Plan and Build modes (TUI) — describes the same symptom of per-agent model selection not being preserved when switching between agents/modes
• Model selection is "lost" on continuation and Agent selection is "lost" on compaction #8349 (closed): Model selection is "lost" on continuation — similar loss of model selection state on session resume

If your issue is specifically about persistence across opencode -c restarts (rather than live mode-switching), it may be a distinct bug worth tracking separately.

[kagura-agent]

I'd like to work on this.

Root cause: In packages/app/src/context/local.tsx, the session model state (saved.session[id]) stores a single State object ({ agent, model, variant }) rather than per-agent model selections. When switching agents via agent.set(), the new agent's configured model (item.model) overwrites the previous selection. On session resume, session.restore() only receives the last UserMessage's agent/model pair, so only that agent's model is restored — others revert to defaults.

Proposed fix: Extend the saved session state to include a per-agent model map (agents?: Record<string, { model?: ModelKey; variant?: string | null }>). When switching agents, save the outgoing agent's model before loading the incoming one. On restore, seed the initial agent entry. Add a migration path from the old flat format.