[Feature Request] Cross-Session File Persistence: Reliability guarantees, versioning, and export

[cc3wangdehai-hue]

Problem

The current file system has persistence and isolation risks:

1. Weak session isolation: Other session directories are enumerable and potentially readable
2. No persistence SLA: Files may be lost without clear retention guarantees
3. No version control: Accidental overwrites are irreversible
4. No cross-session consistency: Files referenced in one session may not exist in another
5. No export mechanism: Users cannot reliably download all their files

Proposed Solution

1. Strong Session Isolation

• Each session gets an isolated storage volume
• No cross-session access by default
• Explicit opt-in sharing with access control

2. Persistence Tiers with SLA

Tier	Retention	Use Case
Ephemeral	Session lifetime	Temp files, cache
Standard	30 days	Working documents
Persistent	1 year	Knowledge bases, configs
Permanent	Indefinite	Critical records

Users can explicitly tag files/directories with persistence tier.

3. File Versioning

• Automatic versioning for modified files (like git history)
• file_history API to browse previous versions
• One-click rollback to any previous version
• Configurable version retention policy

4. Backup & Recovery

• Automatic daily backups for persistent+ files
• Point-in-time recovery for critical data
• User-initiated backup before risky operations

5. Export & Migration

• Bulk export: download all session files as zip
• Selective export: mark files for long-term archival
• Migration: move files between sessions or platforms

Impact

• Data reliability increases user trust
• Enterprise customers require persistence guarantees
• Version control prevents accidental data loss
• Export enables offline workflows and vendor independence

Priority

P2 (Medium) - Essential for enterprise adoption and data safety