diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01023da69a3..df98ab8f376 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -49,6 +49,7 @@ Docs: https://docs.openclaw.ai
 - Discord/Typing indicator: prevent stuck typing indicators by sealing channel typing keepalive callbacks after idle/cleanup and ensuring Discord dispatch always marks typing idle even if preview-stream cleanup fails. (#26295) Thanks @ngutman.
 - Channels/Typing indicator: guard typing keepalive start callbacks after idle/cleanup close so post-close ticks cannot re-trigger stale typing indicators. (#26325) Thanks @win4r.
 - Followups/Typing indicator: ensure followup turns mark dispatch idle on every exit path (including `NO_REPLY`, empty payloads, and agent errors) so typing keepalive cleanup always runs and channel typing indicators do not get stuck after queued/silent followups. (#26881) Thanks @codexGW.
+- Slack/Allowlist channels: match channel IDs case-insensitively during channel allowlist resolution so lowercase config keys (for example `c0abc12345`) correctly match Slack runtime IDs (`C0ABC12345`) under `groupPolicy: "allowlist"`, preventing silent channel-event drops. (#26878) Thanks @lbo728.
 - Tests/Low-memory stability: disable Vitest `vmForks` by default on low-memory local hosts (`<64 GiB`), keep low-profile extension lane parallelism at 4 workers, and align cron isolated-agent tests with `setSessionRuntimeModel` usage to avoid deterministic suite failures. (#26324) Thanks @ngutman.
 - Slack/Inbound media fallback: deliver file-only messages even when Slack media downloads fail by adding a filename placeholder fallback, capping fallback names to the shared media-file limit, and normalizing empty filenames to `file` so attachment-only messages are not silently dropped. (#25181) Thanks @justinhuangcode.
 
diff --git a/src/slack/monitor/channel-config.ts b/src/slack/monitor/channel-config.ts
index 15ba7c3b146..b594a34d43b 100644
--- a/src/slack/monitor/channel-config.ts
+++ b/src/slack/monitor/channel-config.ts
@@ -96,8 +96,16 @@ export function resolveSlackChannelConfig(params: {
   const keys = Object.keys(entries);
   const normalizedName = channelName ? normalizeSlackSlug(channelName) : "";
   const directName = channelName ? channelName.trim() : "";
+  // Slack always delivers channel IDs in uppercase (e.g. C0ABC12345) but
+  // operators commonly write them in lowercase in their config. Add both
+  // case variants so the lookup is case-insensitive without requiring a full
+  // entry-scan. buildChannelKeyCandidates deduplicates identical keys.
+  const channelIdLower = channelId.toLowerCase();
+  const channelIdUpper = channelId.toUpperCase();
   const candidates = buildChannelKeyCandidates(
     channelId,
+    channelIdLower !== channelId ? channelIdLower : undefined,
+    channelIdUpper !== channelId ? channelIdUpper : undefined,
     channelName ? `#${directName}` : undefined,
     directName,
     normalizedName,
diff --git a/src/slack/monitor/monitor.test.ts b/src/slack/monitor/monitor.test.ts
index 3262873718d..3da7f08164e 100644
--- a/src/slack/monitor/monitor.test.ts
+++ b/src/slack/monitor/monitor.test.ts
@@ -60,6 +60,27 @@ describe("resolveSlackChannelConfig", () => {
       matchSource: "direct",
     });
   });
+
+  it("matches channel config key stored in lowercase when Slack delivers uppercase channel ID", () => {
+    // Slack always delivers channel IDs in uppercase (e.g. C0ABC12345).
+    // Users commonly copy them in lowercase from docs or older CLI output.
+    const res = resolveSlackChannelConfig({
+      channelId: "C0ABC12345",
+      channels: { c0abc12345: { allow: true, requireMention: false } },
+      defaultRequireMention: true,
+    });
+    expect(res).toMatchObject({ allowed: true, requireMention: false });
+  });
+
+  it("matches channel config key stored in uppercase when user types lowercase channel ID", () => {
+    // Defensive: also handle the inverse direction.
+    const res = resolveSlackChannelConfig({
+      channelId: "c0abc12345",
+      channels: { C0ABC12345: { allow: true, requireMention: false } },
+      defaultRequireMention: true,
+    });
+    expect(res).toMatchObject({ allowed: true, requireMention: false });
+  });
 });
 
 const baseParams = () => ({