Add ephemeral/incognito mode for temporary sessions

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Description:

Problem

Sometimes users want to ask quick, one-off questions without creating a persistent
session that can be resumed later. Currently, all sessions are automatically saved and
can be recovered via /resume or claude --resume. This leads to:

• Accumulation of session logs in ~/.claude/logs/
• Unwanted sessions appearing in the resume list
• Privacy concerns for sensitive/temporary queries
• Storage bloat over time

Proposed Solution

Proposed Solution

Add an --ephemeral or --incognito flag (similar to browser private windows):

claude --ephemeral
# or
claude -e

Behavior in ephemeral mode:

• Session is NOT saved to disk
• Cannot be resumed after the session ends
• No logs written to ~/.claude/logs/
• Memory files are NOT updated during the session
• Clear visual indicator (e.g., "Ephemeral mode" in header or prompt prefix)

Alternative consideration:
A /ephemeral slash command to toggle ephemeral mode mid-session could also be useful,
but may be more complex to implement.

Use Cases

1. Quick reference questions ("How do I do X in Python?")
2. Sensitive queries the user doesn't want persisted
3. Testing/experimentation sessions
4. Temporary debugging sessions
5. Shared computer scenarios

Current Workaround

Users can manually delete session logs:
rm -rf ~/.claude/logs/*

But this is all-or-nothing and doesn't provide the UX of a proper ephemeral mode.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_