Subagent return re-renders startup banner, indistinguishable from session restart

Description

When a subagent (Explore/Plan) spawned via the Agent tool completes and returns to the main agent, the terminal re-renders the full startup banner (robot icon, version info, working directory). This is followed by "Philosophising..." or "Galloping..." with the --continue/--resume tip, making it visually identical to a real session restart or crash recovery.

Steps to Reproduce

1. Start a conversation that uses the Agent tool to spawn subagents (e.g., subagent_type: "Explore" or "Plan")
2. Observe the terminal when the subagent completes and control returns to the main agent
3. The full startup banner re-renders as if Claude Code restarted

Expected Behavior

When returning from a subagent to the main agent, the UI should clearly indicate it is a subagent completion, not a session restart. For example:

• Display a message like "Subagent completed, returning to main conversation"
• Skip the startup banner on subagent return
• Or visually differentiate it from a fresh start (e.g., different color/icon)

Actual Behavior

The startup banner (robot icon + version + path) is re-rendered identically to a fresh session start. The only way to confirm the session is the same is to check whether the JSONL file changed:

ls -lt ~/.claude/projects/<project>/*.jsonl | head -3

Environment

• Claude Code v2.1.90
• Model: Opus 4.6 (1M context) / Claude Max
• macOS (Darwin 25.3.0)
• Terminal: default macOS Terminal with caffeinate