Problem

When switching auth backends or API keys (e.g., switching between different Claude API accounts, OpenRouter, or other providers), each session caches its auth at creation time. This means:

1. Config change applies to gateway
2. Gateway restarts with new auth
3. Existing sessions still use old cached auth
4. User must manually /reset each active session (WhatsApp, Slack, Telegram, etc.)

This creates friction for users with multiple active channels who need to switch auth globally.

Proposed Solution

Add a gateway action=reset-sessions (or similar) that:

1. Invalidates all active session auth caches
2. Sessions reinitialize with current config auth on next message
3. Preserves session memory/context across the reset (see below)
4. Can be triggered as part of auth/config changes

Session State Preservation

When resetting sessions for auth switching, the conversation context should be preserved. Options:

1. Export/restore session state: Before reset, serialize session context (recent messages, current topic, pending tasks) to a recoverable format. On reinit, restore from that state.
2. Soft reset: Only invalidate the auth cache without clearing conversation history — session continues with same context but new auth credentials.
3. Channel-specific restore:
   • Slack: Can read recent channel history via API on reinit
   • Other channels: Need explicit state export before reset

The goal: auth switch should be seamless — user doesn't lose conversation context or have to re-explain what they were working on.

Alternative Approaches

1. Auth per-request: Sessions check auth on each API call instead of caching at creation (more overhead, but no reset needed)
2. Auth invalidation signal: Gateway restart broadcasts "re-auth" event to all sessions (sessions keep context, just refresh auth)
3. /reset-all chat command: Resets all sessions globally with optional context preservation flag

Use Case

User: switch to openrouter
Agent: [patches config, restarts gateway, resets all sessions with context preserved]
Agent: ✅ Switched to OpenRouter. All sessions updated.
# Conversation continues seamlessly

One command, global effect, no manual /reset per channel, no lost context.

Additional Context

• Useful for switching between API providers (Anthropic direct, OpenRouter, AWS Bedrock, etc.)
• Useful for switching between subscription tiers or accounts
• Session context preservation is critical for good UX — users shouldn't have to re-establish context after an auth switch