Draft: [PoC] Duo × Slack AI-native live progress (research/exploration)

⚠️ PoC / AI research — not for merge as-is

This is an AI-assisted research spike exploring how to make the GitLab Duo Slack integration feel "AI-native" using Slack's newer agent UI primitives. It is intended as a reference for the ideas and the verified Slack capabilities — to be split into smaller, production-hardened MRs before shipping.

Labelled type::ignore.

What it does

Replaces the "👀 → minutes of silence → ✅" Slack experience with a single, self-updating message:

1. an animated rotating status (assistant.threads.setStatus + loading_messages),
2. the agent's live todo plan as a native Slack plan block (task cards), and
3. the final answer, edited into the same message.

All on the existing channel @mention surface with only the chat:write scope — no assistant:write, no assistant-thread surface, no manifest re-consent.

Design / the spine

The value here is a generic, surface-agnostic progress spine that lets us upgrade the rendering later (e.g. token streaming) without rethinking the mechanism:

• ProgressHeartbeatWorker — generic, self-rescheduling, per-workflow progress loop. Pacing cadence is an adapter property (progress_interval); the worker owns only the mechanism. No change to the global checkpoint write path.
• Slack adapter — setStatus rotating indicator (with fallback opener), native plan block rendered lazily then edited in place, subtle session-link footer.
• Terminal delivery stays on Gitlab::EventStore (CallbackWorker), now reliable (raises → Sidekiq retry) and idempotent (final_delivered).
• Checkpoint#ui_chat_log — single reader of the checkpoint log path (also adopted by the presenter and mailer).

Full write-up, the Slack surface/method table, deferred items and the suggested MR split: slack_exploration/live-progress-design.md (in this MR).

Deferred (intentionally)

Change-detection cursor, self-healing cron reconciler, Retry-After precision, semantic lifecycle hooks, and the assistant:write streaming/assistant surface.

Tests

Specs for the heartbeat worker, Slack adapter, CallbackWorker (reliability + idempotency), Checkpoint#ui_chat_log, and the Slack::API additions.

Notes before production

• Behind the existing slack_duo_agent feature flag.
• MAX_LIFETIME heartbeat cap is a placeholder pending the CI workload timeout.
• Confirm the checkpoint payload stays whole through the incremental/diff checkpoint work, or update the single Checkpoint#ui_chat_log accessor.
• Suggested split: (a) ui_chat_log accessor refactor, (b) terminal reliability, (c) the live-progress feature.