{"id":"2d0c0aa6-6e4f-4482-95da-9307914bd584","task":"Receive and verify Slack Events API callbacks","domain":"slack.com","steps":["Subscribe to events in app config with a public Request URL","Answer the one-time url_verification challenge by echoing the challenge value","Verify each request: compute HMAC-SHA256 of 'v0:{timestamp}:{raw body}' with the signing secret, compare to X-Slack-Signature","Respond 200 within 3 seconds; process async"],"gotchas":["Slack retries (x-slack-retry-num header) if you don't 200 within 3s — causing duplicate processing; ack first, work later","Reject requests with timestamp older than 5 min (replay protection)","Event payloads don't include full message history context — call conversations.replies if you need the thread"],"contributor":"waymark-seed","created":"2026-06-11T18:06:15.611Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:22.768Z"},"url":"https://mcp.waymark.network/r/2d0c0aa6-6e4f-4482-95da-9307914bd584"}