What does this PR do?

Overhauls the Slack adapter with enterprise-grade capabilities. The existing inline mention logic, thread tracking sets, and thread context fetcher are replaced with testable, structured utilities extracted into slack_utils.py. New features include per-channel configuration, Block Kit message rendering, connection health monitoring, slash commands, and message edit detection.

+2,500 lines across 4 files (slack.py, slack_utils.py, slack_commands.py, test_slack_approval_buttons.py)

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

Refactors (behavior-preserving replacements of existing code)

• check_mention_gate() replaces inline mention conditional — pure function returning MentionGateResult with should_respond, was_mentioned, implicit_mention, reason (gateway/platforms/slack_utils.py)
• ThreadParticipationCache replaces _bot_message_ts / _mentioned_threads sets — LRU OrderedDict with 24h TTL, async lock, account-aware keys (gateway/platforms/slack_utils.py)
• load_thread_context() + format_thread_context_for_prompt() replaces _fetch_thread_context() — returns ThreadContext / ThreadMessage dataclasses, cursor pagination, preserves bot messages as "Assistant" (gateway/platforms/slack_utils.py)
• _has_active_session_for_thread() kept as fallback when ThreadParticipationCache misses after restart (gateway/platforms/slack.py)

New features

• Per-channel config — channels block under gateway.slack with requireMention, allowBots, users, threadHistoryLimit, replyBroadcast overrides. Resolved early via resolve_channel_config() (gateway/platforms/slack_utils.py)
• Per-channel user authorization — is_user_allowed_in_channel() whitelists user IDs per channel (gateway/platforms/slack_utils.py)
• Connection health monitoring — SlackConnectionState, probe_slack_connection(), is_non_recoverable_slack_error(), stale socket detection via _mark_event_received() (gateway/platforms/slack_utils.py)
• OAuth scope validation — fetch_slack_scopes() + validate_slack_scopes() against required/recommended sets (gateway/platforms/slack_utils.py)
• Block Kit message rendering — send() wraps every outgoing message in Block Kit section blocks via _content_to_blocks(), matching the pattern that makes send_exec_approval work. Splits on --- for native dividers, handles oversized sections at line boundaries (gateway/platforms/slack.py)
• Interactive Block Kit actions — handler for hermes:.* action IDs (buttons/selects), routes as synthetic MessageEvent (gateway/platforms/slack.py)
• Message edit detection — message_changed events extract the inner edited message and re-process it instead of being ignored (gateway/platforms/slack.py)
• Slash commands — /hermes help, /hermes skills, /hermes status, /hermes config with Block Kit formatting, dispatch via SLASH_COMMANDS registry (gateway/platforms/slack_commands.py)

Shared utilities module (gateway/platforms/slack_utils.py)

• SSRF protection (validate_slack_file_url, is_slack_hostname)
• HTML detection for failed file downloads (looks_like_html_content)
• Voice message MIME normalization (normalize_slack_voice_mimetype)
• Markdown table to Slack code block conversion (convert_markdown_tables_to_slack)
• Message update helpers (update_slack_message, SlackMessageRef)

Tests

• Updated TestSlackThreadContext to test load_thread_context() instead of removed _fetch_thread_context()
• Updated TestThreadEngagement to test ThreadParticipationCache instead of removed _bot_message_ts / _mentioned_threads sets
• 88 Slack tests passing (16 approval + 69 main + 3 assistant thread)

How to Test

1. Connect Hermes to a Slack workspace via Socket Mode
2. Send a message in a channel with @hermes — verify mention gating responds correctly
3. Reply in a thread where the bot has participated — verify implicit mention (no @ needed)
4. Edit a message the bot responded to — verify it detects the edit
5. Run /hermes status — verify Block Kit formatted response with connection state
6. Run /hermes skills — verify skills list renders
7. Run /hermes config — verify config summary renders
8. Trigger a command that requires approval — verify buttons render and clicking Approve/Deny unblocks the command
9. Test per-channel config by adding a channels block to gateway.slack in config.yaml

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A