diff --git a/extensions/mattermost/src/mattermost/accounts.ts b/extensions/mattermost/src/mattermost/accounts.ts
index 9af9074087e..ca120d08c6b 100644
--- a/extensions/mattermost/src/mattermost/accounts.ts
+++ b/extensions/mattermost/src/mattermost/accounts.ts
@@ -83,7 +83,21 @@ function mergeMattermostAccountConfig(
     defaultAccount?: unknown;
   };
   const account = resolveAccountConfig(cfg, accountId) ?? {};
-  return { ...base, ...account };
+
+  // Shallow merging is fine for most keys, but `commands` should be merged
+  // so that account-specific overrides (callbackPath/callbackUrl) do not
+  // accidentally reset global settings like `native: true`.
+  const mergedCommands = {
+    ...(base.commands ?? {}),
+    ...(account.commands ?? {}),
+  };
+
+  const merged = { ...base, ...account };
+  if (Object.keys(mergedCommands).length > 0) {
+    merged.commands = mergedCommands;
+  }
+
+  return merged;
 }
 
 function resolveMattermostRequireMention(config: MattermostAccountConfig): boolean | undefined {
diff --git a/extensions/mattermost/src/mattermost/slash-http.ts b/extensions/mattermost/src/mattermost/slash-http.ts
index 3b784409378..1bc9d18773e 100644
--- a/extensions/mattermost/src/mattermost/slash-http.ts
+++ b/extensions/mattermost/src/mattermost/slash-http.ts
@@ -146,11 +146,13 @@ async function authorizeSlashInvocation(params: {
 
   const channelType = channelInfo?.type ?? undefined;
   const isDirectMessage = channelType?.toUpperCase() === "D";
-  const kind = isDirectMessage
+  const kind: SlashInvocationAuth["kind"] = isDirectMessage
     ? "direct"
-    : channelType?.toUpperCase() === "G"
-      ? "group"
-      : "channel";
+    : channelInfo
+      ? channelType?.toUpperCase() === "G"
+        ? "group"
+        : "channel"
+      : "direct";
 
   const chatType = kind === "direct" ? "direct" : kind === "group" ? "group" : "channel";