Problem

When groupPolicy: "allowlist" is configured for Slack, channel IDs in the config are often written in lowercase (e.g. c0abc12345) but Slack delivers events with uppercase IDs (C0ABC12345). Because resolveSlackChannelConfig passed only the raw channelId to buildChannelKeyCandidates, the case-sensitive property lookup in resolveChannelEntryMatch silently failed, causing all channel events to be dropped.

DMs are unaffected (they route through dmPolicy, bypassing the channel gate).

The failure is completely silent — no warning is logged — making it very difficult to diagnose.

Root Cause

resolveSlackChannelConfig builds its candidate key list as:

buildChannelKeyCandidates(
  channelId,          // C0ABC12345 — uppercase from Slack
  `#${directName}`,
  directName,
  normalizedName,
)

None of the candidates include the lowercase form. When resolveChannelEntryMatch iterates the candidates and does Object.prototype.hasOwnProperty.call(entries, key), it never finds c0abc12345.

Fix

Add both the lowercase and uppercase variants of channelId to the candidate list. buildChannelKeyCandidates already deduplicates identical keys, so there is no overhead for IDs that are already in the canonical case.

const channelIdLower = channelId.toLowerCase();
const channelIdUpper = channelId.toUpperCase();
const candidates = buildChannelKeyCandidates(
  channelId,
  channelIdLower !== channelId ? channelIdLower : undefined,
  channelIdUpper !== channelId ? channelIdUpper : undefined,
  ...
);

Tests

Two new test cases in monitor.test.ts:

• Config key lowercase, runtime ID uppercase (c0abc12345 → C0ABC12345) ✅
• Config key uppercase, runtime ID lowercase (defensive inverse) ✅

All 22 monitor tests pass. All 238 Slack tests pass.

Fixes #26874

Greptile Summary

This PR fixes a silent bug where Slack channel events were dropped when groupPolicy: "allowlist" was configured. The issue occurred because Slack delivers channel IDs in uppercase (e.g., C0ABC12345) but users commonly write them in lowercase in their config files (e.g., c0abc12345). The case-sensitive property lookup failed silently, causing all channel events to be dropped.

The fix adds both lowercase and uppercase variants of the channelId to the candidate key list in resolveSlackChannelConfig. The buildChannelKeyCandidates function already deduplicates identical keys, so there's no performance overhead for IDs already in the canonical case.

• Added conditional lowercase/uppercase channel ID variants to the candidate list
• Two comprehensive test cases cover both directions (config lowercase → runtime uppercase, and the defensive inverse)
• The fix is minimal, focused, and leverages existing deduplication logic

Confidence Score: 5/5

• This PR is safe to merge with no risk
• The fix is minimal, well-tested, and addresses a clear bug. The implementation leverages existing deduplication logic in buildChannelKeyCandidates, adds both case variants conditionally (only when they differ from the original), and includes comprehensive test coverage for both directions of the case mismatch. The change is isolated to the channel config resolution logic and follows established patterns in the codebase for case-insensitive matching.
• No files require special attention

_{Last reviewed commit: cdd9d8d}