Feature request: per-session input history (arrow-up isolation)

Feature request

When running multiple Claude Code sessions in parallel (e.g., in separate terminal tabs), pressing arrow-up cycles through input history from all sessions, not just the current one. This is because ~/.claude/history.jsonl is shared globally.

Desired behavior

Each Claude Code session should have its own isolated arrow-up history, so pressing arrow-up only recalls prompts typed in the current session. Cross-session history search (e.g., via Ctrl+R) could optionally still work across all sessions.

Why this matters

When working on different tasks in parallel sessions, the shared history makes it hard to quickly re-run the last prompt in each session — you end up scrolling past prompts from unrelated sessions.

Suggested implementation

• Store per-session history keyed by session ID
• Fall back to the global history.jsonl for Ctrl+R / search
• Optionally add a setting like "historyMode": "per-session" | "shared" in settings.json