Summary

Hardens normalized Slack interaction payloads by deduplicating selected values/labels while preserving first-seen order.

• dedupe normalized selectedValues
• dedupe normalized selectedLabels
• add regression coverage for duplicate mixed-select payload inputs

Scope

• src/slack/monitor/events/interactions.ts
• src/slack/monitor/events/interactions.test.ts

Validation

• pnpm test src/slack/monitor/events/interactions.test.ts
• pnpm check

Dependency

Depends on:

• Slack: improve Block Kit interaction handling (foundation) #18180 Slack: improve Block Kit interaction handling (foundation)
• feat(slack): capture Block Kit view_closed lifecycle events #18234 feat(slack): capture Block Kit view_closed lifecycle events
• feat(slack): use static_select for large slash arg menus #18242 feat(slack): use static_select for large slash arg menus
• feat(slack): route modal interactions with private metadata #18252 feat(slack): route modal interactions with private metadata
• feat(slack): support Block Kit blocks in sendMessage #18257 feat(slack): support Block Kit blocks in sendMessage
• feat(slack): support Block Kit blocks in editMessage #18262 feat(slack): support Block Kit blocks in editMessage
• feat(slack): support blocks in plugin send action #18268 feat(slack): support blocks in plugin send action
• feat(slack): support blocks in plugin edit action #18278 feat(slack): support blocks in plugin edit action
• feat(slack): centralize Block Kit input validation #18284 feat(slack): centralize Block Kit input validation
• fix(slack): add blocks+media send guardrails #18290 fix(slack): add blocks+media send guardrails
• test(slack): cover sendMessage Block Kit paths #18372 test(slack): cover sendMessage Block Kit paths
• refactor(slack): centralize modal private_metadata utilities #18409 refactor(slack): centralize modal private_metadata utilities
• Slack: expand interaction payload normalization coverage #18413 Slack: expand interaction payload normalization coverage
• Slack: validate runtime blocks in send and edit paths #18416 Slack: validate runtime blocks in send and edit paths

If reviewing before dependencies merge, review tip commit: 215dc56b9.

Greptile Summary

Adds deduplication to Slack Block Kit interaction payload normalization, preventing duplicate values/labels when Slack sends redundant selections across singular and plural fields (e.g., selected_user + selected_users). Uses first-seen order preservation via Set-based deduplication with trimming.

• Introduced uniqueNonEmptyStrings helper with defensive type guards
• Applied deduplication to selectedValues, selectedLabels, selectedUsers, selectedChannels, and selectedConversations
• Shared across both block actions and modal submissions via summarizeAction
• Added regression test coverage with mixed duplicate inputs

Confidence Score: 5/5

• This PR is safe to merge with no risk
• The implementation is clean, well-tested, and defensive. The deduplication logic correctly preserves first-seen order, handles edge cases (empty strings, non-strings), and applies consistently across all interaction types. Test coverage validates the exact scenario described (duplicates across singular/plural fields). No breaking changes or side effects.
• No files require special attention

_{Last reviewed commit: 7446c0a}