TabMail Thunderbird Add-on (MV3, Thunderbird 145+)

TabMail is a Thunderbird add-on that adds:

• A chat-based assistant for email + calendar workflows
• Smart compose/autocomplete in the composer
• Local full-text search (native FTS helper) for fast retrieval

This add-on targets Thunderbird MV3 and uses experiments sparingly for Thunderbird-specific integration points.

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Architecture (high level)

Thunderbird (local mail + calendars)
  ├─ chat/        (UI + tool orchestration + FSM workflows)
  ├─ agent/       (message workflows, tagging, summarization, reminders)
  ├─ compose/     (autocomplete + editing UX)
  ├─ fts/         (local search index + memory; native host required)
  ├─ theme/       (palette-based theming + UI tweaks)
  ├─ config/      (options UI)
  ├─ prompts/     (custom user prompts)
  ├─ templates/   (email templates)
  ├─ marketplace/ (community template marketplace)
  ├─ welcome/     (onboarding wizard)
  └─ popup/       (browser action popup + auth)
        │
        │ Supabase auth (OAuth popup → `tabmail.ai/auth/tb-callback`)
        ▼
Cloudflare Worker backend (`api.tabmail.ai` / `dev.tabmail.ai`)
  ├─ Bearer token auth + consent gate
  ├─ Entitlements from KV + quota/throttle via usage worker
  └─ LLM completions + server tools

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Key directories

The add-on is split into several MV3 “background modules” (see manifest.json → background.scripts):

Core modules

• agent/: Message workflows (processing, tagging, summaries, reminders), plus some privileged integrations via experiments.
• chat/: Chat window UI (chat.html/chat.js/chat.css), tool orchestration, and chat-specific modules.
  • chat/tools/ — Tool implementations for email, calendar, contacts, web, and knowledge base operations.
  • chat/fsm/ — Finite state machines for multi-step workflows (compose, delete, archive, calendar CRUD, etc.).
  • chat/modules/ — Core chat functionality (context, converse, markdown, SSE/WS tools, etc.).
• compose/: Composer integration for smart compose and inline edits.
• fts/: Local search/indexing via native FTS helper (required); see fts/README.md.

UI and configuration

• theme/: Theme system + palette; see theme/README.md and theme/palette/README.md.
• config/: Options UI and settings modules.
• gui/: UI tweaks and layout helpers (some via experiments).
• popup/: The extension popup and auth helpers.
• welcome/: Onboarding wizard with multi-page setup flow.

User customization

• prompts/: Custom user prompts UI — allows users to define custom action, composition, and knowledge base prompts.
• templates/: Email templates system — user-defined email templates with variable substitution.
• marketplace/: Community template marketplace — browse and install shared templates.

Support

• keepalive/: Keep-alive and lifecycle helpers (via experiment tmKeepAlive).
• icons/: SVG icons used by the add-on (tab icon, sort icons, view mode icons).

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Experiments

Experiments are defined in manifest.json under experiment_apis and implemented under the corresponding */experiments/ folders.

Use experiments only when the Thunderbird WebExtension API cannot provide the needed integration point.

Current experiments by module:

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Theming

All colors come from the palette system:

• Source of truth: theme/palette/palette.data.json
• Docs: theme/palette/README.md
• Theme system overview: theme/README.md
• Architecture deep dive: theme/README_ARCHITECTURE.md

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Full-text search (FTS)

FTS is implemented in fts/ and uses a native messaging host (Rust binary with bundled SQLite + FTS5) for fast local indexing.

The native FTS helper is required — it powers both email search and chat memory features.

The native FTS helper is source-available: github.com/TabMail/tabmail-native-fts

Features

• Email search — Fast full-text search across all indexed emails with stemming, synonyms, and BM25 ranking. Also provides fast access to email content and metadata.
• Memory search — Chat history is indexed locally, allowing the agent to recall past conversations
• Memory read — Retrieve full chat sessions by timestamp for context continuity

See fts/README.md for architecture and operational notes.

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Backend integration

The add-on calls the TabMail backend at:

• Production: https://api.tabmail.ai
• Development: https://dev.tabmail.ai

Authentication is via Supabase access tokens; the add-on uses the hosted TB callback page:

• https://tabmail.ai/auth/tb-callback

Backend details (routing, auth, quota/throttle, endpoints) are to be released later as API docs.

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Development

• Load temporarily: Thunderbird → Tools → Developer Tools → Debug Add-ons → “Load Temporary Add-on” → select tabmail-thunderbird/manifest.json
• Options page: config/config.html
• Chat shortcut: see manifest.json → commands.open-chat-window

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License

This project is open source under the Mozilla Public License 2.0 (MPL-2.0).

• Free to use, modify, and distribute — including commercially.
• MPL is a weak-copyleft license at file granularity: modifications to MPL-licensed files must stay open, but you may combine them with proprietary code in larger works.

Copyright © Lisem AI Ltd.

See:

• LICENSE
• THIRD_PARTY_LICENSES.md — bundled third-party libraries

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Contributing

We welcome contributions! This project uses the Developer Certificate of Origin (DCO) — sign off every commit with git commit -s.

See CONTRIBUTING.md for details.

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Trademarks

"TabMail" is a trademark of Lisem AI Ltd. This license does not grant permission to use the TabMail name or branding.

See TRADEMARKS.md.