[NinjaLikesCheez]

What was wrong

1. Double-reported deferral failures, and placeholder failures reported as command failures.
When a command takes more than 1.5 s, respond() calls deferReply(). If Discord refuses it (40060 already acknowledged, or 10062 unknown interaction), that promise had no handler until the work finished, so Node emitted unhandledRejection: process logging logged it as an error and Sentry captured it with no actor or command, and then the adapter logged it a second time as discord.duplicate_handler.
Separately, for commands with a placeholder (/status, /ha, admin roles, ...), a refused placeholder interaction.reply inside onPending was caught by the dispatcher as command.failed (error log, reporter.capture, error metric), defeating the adapter's warn-only branch.

2. Every 10062 blamed on a second instance.
10062 also happens when Pixel itself is slow to acknowledge (e.g. the form path can't defer before showModal, and beforeForm does Discord REST work), but it was always logged as a warning about a second instance and never reported.

What changed

• respond.ts: the deferral promise gets a no-op .catch when it's created. It's still awaited afterwards, so its failure surfaces once, from respond().
• dispatcher.ts (small change): if onPending throws, the dispatcher rethrows that error without logging command.failed or capturing it, and the handler still doesn't run. The adapter now decides how to log and report it. The DispatchHooks.onPending doc says so. I couldn't do this in the adapter alone: anything that keeps the handler from running has to throw out of onPending, and the dispatcher's catch captured every such throw. The change is in dispatch() only, not the form path.
• interaction-errors.ts: classifyInteractionError returns duplicate (40060), expired (10062) or other. handleInteractionFailure is the one place the adapter logs these failures, and both the command and modal paths in index.ts use it:
  • 40060: warns discord.duplicate_handler (second instance), not reported.
  • 10062: logs an error discord.slow_ack with command and actorLogFields, and reports a SlowAcknowledgementError("Discord expired /<command> before Pixel acknowledged it", { cause }) with the actor, so Sentry groups it by command. Nothing typed by the user is logged.
  • anything else: logged and reported as before.
• vitest.config.ts: interaction-errors.ts is added to the strict-coverage adapter files (a tighter floor, nothing lowered).
• Runbook: the duplicate-instance entry now names only 40060, and there's a new entry for discord.slow_ack / "The application did not respond". CHANGELOG Fixed entries added.

Tests

• discord.test.ts: a deferReply that rejects with 10062 while the work is still running causes no unhandledRejection (checked with a real setImmediate turn under fake timers), and respond() rejects once with that error. This test fails without the .catch. A refused placeholder reply makes respond() reject with that error.
• dispatcher.test.ts: when onPending rejects, dispatch rejects with the same error, the handler doesn't run, and there's no capture and no command.failed. A handler failure after a placeholder is still captured.
• interaction-errors.test.ts: classification, and log/report behaviour for 40060, 10062 and other errors, for commands and forms.
• just check passes.

Needs a human reviewer (AGENTS.md rule 14): src/core/dispatcher.ts changed. Another open PR edits the dispatcher's form path (prepareForm). This PR only touches dispatch() around onPending, so a conflict, if any, should be trivial.

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