Per-chat personas and isolated contexts via Telegram forum topics

[mattmezza]

Summary

Allow multiple concurrent chats, each bound to its own persona and its own conversation context,
following the existing Telegram interaction model.

Background

History is already keyed by (channel, user_id, chat_id) and the session system prompt is
snapshotted per chat, so isolated contexts already exist by construction. Two gaps remain: (1) a
chat→persona binding, and (2) a way to run several contexts within Telegram.

Proposed approach

Primary — Telegram forum topics. In a group with topics enabled, each message carries
message_thread_id / is_topic_message. Fold the thread id into the context key
(chat_id = f"{chat_id}:{thread_id}") so every topic is a separate context natively, with its own
scrollback. Bind a persona per thread via topic-name → persona, or a /persona <name> command
storing the mapping in a small chat_persona(chat_id -> persona) table. The General topic maps to
the default persona.

Fallback (no group) — modal rooms in a 1:1 DM. /room <name> switches the active room
(synthetic chat_id + persona) until switched again. Modal, so the bot should echo the active
persona on switch to avoid sending to the wrong one.

UX & product

• Onboarding is the hard part and is self-guiding: when the bot is added to a group it detects
  topics support and replies with a short, illustrated walkthrough (enable Topics, promote the bot,
  one topic per persona). A /setup_topics helper checks the group and reports what's missing.
• Admin UI: a Chats page listing active chats/threads and their bound persona, with rebind —
  responsive/touch-friendly at phone width, using consistent list/card components.
• On the go (Telegram): binding happens entirely in-app via /persona inside a topic; inline
  buttons pick the persona for a new topic. Consistent inline-keyboard conventions throughout.
• Mobile-first: the whole flow is native to the Telegram phone app — no web UI is required to
  create or use a themed chat; lean into it.

Setup & onboarding

• Works with a single default context if the user never makes a group (no setup required, works out
  of the box).
• The group/topic path is opt-in; surfaced as an optional wizard step ("set up multiple chats?")
  that links to the in-Telegram walkthrough.

Acceptance criteria

• Two topics in the same group keep fully separate histories and personas.
• /persona rebinds only the current thread.
• Adding the bot to a topics-enabled group yields a clear, mobile-only setup path with no web UI;
  the Chats page is usable at phone width.
• No regression to the default 1:1 DM flow.

Related

• Depends on: persona profiles.