Show resolved subagent model in backgrounded-agent manage pane

Summary

When sub-agents are spawned via the Agent tool (especially in background mode), the manage pane / backgrounded-agent UI shows:

<subagent_type>(<description>)

For example:

t1k-git-manager(Process lesson queue (5 entries))

It would be very useful to also surface the resolved model that the agent is running on. Agents declare their model via frontmatter (model: claude-opus-4-7, model: inherit, etc.), and PreToolUse hooks may override the actual model at spawn time. Today there is no way to see which model an agent is using from the UI without expanding into the transcript.

Use case

In multi-agent workflows different subagents intentionally use different models (cheap models for mechanical work, expensive for design judgment). When 3–8 background agents are running in parallel I want to verify at a glance:

• Is t1k-fullstack-developer running on Opus 4.7 or downgraded?
• Did transparent routing correctly downgrade a cheap-coder agent to a small model?
• Did I accidentally spawn general-purpose on the wrong tier?

Without native display I either trust the frontmatter (stale if any hook overrides it) or read the JSONL transcript.

Suggested UI

Inline:

t1k-git-manager(Process lesson queue (5 entries) · claude-opus-4-7)

Or as a separate dim line:

t1k-git-manager(Process lesson queue (5 entries))
  ↳ claude-opus-4-7

The displayed value should be the resolved model — whichever the runtime actually dispatched to (frontmatter model: after any PreToolUse override / model-routing hook). If the agent uses model: inherit, show the parent's effective model.

Workaround in our kit

We built a PreToolUse:Task hook in TheOneKit that rewrites the description parameter to embed [<model>], e.g. description: "Process queue [glm-5.1]". It works but pollutes the description string. Native display would be cleaner because (a) it doesn't pollute the description, (b) it works for any user not running our kit, (c) it survives kit updates that change the hook.

Environment

• Claude Code CLI (current as of 2026-05-27)
• Linux + macOS, same behavior