Make channel history visible to new members upon joining (with optional server-side caching)

Description:

Hello Delta Chat team,

I’m using Delta Chat channels successfully for a small neighborhood community (e.g., announcing local events like running meetups or mulled wine evenings). The broadcast-like nature works great: share a QR-code invite link on our bulletin board, no account hassle, and auto-deletion after 1 year keeps things tidy – perfect!

However, there’s one key limitation: when someone joins an existing channel late (e.g., via QR scan), they cannot see previous announcements. This misses the core use case for announcements – newcomers need access to past events to catch up (e.g., “What was the last run date?”).

Proposed Feature:

  • Option for channel admins: Toggle “Share history with new members” (on by default for new channels).
  • Implementation idea: Upon join, auto-resend the last N messages (e.g., 50, or last 6 months, respecting 1-year deletion) from admin devices/server, or use lightweight server-side caching (e.g., on Chatmail providers) for recent history. New members get them chronologically placed.
  • UI: In channel settings: “History for new members: Visible / From join date only”. Show a note on join: “You’ve joined! Loading recent history…”.
  • Privacy/Security: Only admins control this; E2EE preserved; limit to recent messages to avoid bloat.

Why this matters:

  • Matches real-world broadcast needs (like Telegram channels or mailing lists with archives).
  • No full server dependency – hybrid: P2P where possible, minimal sync for late joiners.
  • Enhances adoption for communities/groups without forcing Matrix/Discord alternatives.

Existing discussions (e.g., resend history on add, announcement channels ) align with this. Happy to discuss/test!

Thanks for the great app – this would make channels perfect!

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this is at least partly a duplicate of Channels: Make old posts visible to new members when needed

something in that direction is planned, see channels: resend the last 10 messages on joining · Issue #7678 · chatmail/core · GitHub

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