Refactor: Extract bot-turn throttling from message() into resolve/record/evaluate/execute pipeline

[chaodu-agent]

Motivation

Bot turn counting, channel gating, warning emission, and business logic are all mixed in message(). This caused #529 (warning sent to non-allowed channels) and makes #530 (dedup) hard to fix cleanly.

Both Discord and Slack adapters have this problem. The warning-before-gating pattern exists in both discord.rs and slack.rs.

Proposed Architecture

message() arrives
  → resolve_context()           // build ResolvedMessageContext (shared, cross-adapter)
  → record_turns()              // pure counting, no side effects (#483 invariant)
  → evaluate_gating()           // channel/user/bot permission check
  → evaluate_throttle_effects() // decide: Continue | Stop | StopWithEffect(Warning)
  → execute_effects()           // single place for side effects (say, react, etc.)
  → dispatch_business_logic()   // handle_message, streaming, etc.

Design Requirements

1. Shared ResolvedMessageContext — channel_id, parent_id, is_bot, allowed_here, etc. computed once, shared across all stages. No duplicate resolution.

2. Decisions, not side effects — each stage returns a decision enum (Continue, Stop, StopWithEffect(Effect::Warning(...))). Side effects executed by a single coordinator, not inside the stage.

3. Throttle state abstracted behind store/policy — don't let stages directly operate on HashMap. Enables Bug: Multiple allowed bots each post their own turn limit warning in the same thread #530 dedup and future shared state without re-splitting.

4. Counting before gating, emission after gating — the key insight: counting and emission must be decoupled. Counting runs early (all bot messages), emission runs after gating (only allowed channels).

5. Cross-adapter design — the pipeline must apply to both Discord (discord.rs) and Slack (slack.rs). Both have the same warning-before-gating bug pattern today.

Affected Code

• discord.rs line ~258-290: bot turn counting + warning say() before channel gating
• slack.rs line ~678-697: same pattern — classify_bot_message + send_message before allow_bot_messages gating

Incremental Rollout

1. ✅ PR fix: gate bot turn warning behind allowed_channels check #528 — hotfix for Discord gating correctness (merge first)
2. Extract resolve_message_context() and evaluate_turn_policy() as minimal first step (both adapters)
3. Full pipeline refactor
4. Bug: Multiple allowed bots each post their own turn limit warning in the same thread #530 dedup solved naturally in the throttle evaluation layer

Related

• Bug: Bot turn warning posted to threads where bot is not allowed #529 — gating bug (root cause: mixed concerns)
• Bug: Multiple allowed bots each post their own turn limit warning in the same thread #530 — dedup (blocked by mixed concerns)
• fix(discord): bot turn limit never triggers in multi-bot ping-pong #483 — counting invariant (must be preserved)

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