fix: preserve Mattermost mention indentation

CHANGELOG.md

@@ -58,6 +58,7 @@ Docs: https://docs.openclaw.ai
 - Sandbox/subagents: pass the real configured workspace through `sessions_spawn` inheritance when a parent agent runs in a copied-workspace sandbox, so child `/agent` mounts point at the configured workspace instead of the parent sandbox copy. (#40757) Thanks @dsantoreis.
 - Mattermost/plugin send actions: normalize direct `replyTo` fallback handling so threaded plugin sends trim blank IDs and reuse the correct reply target again. (#41176) Thanks @hnykda.
 - MS Teams/allowlist resolution: use the General channel conversation ID as the resolved team key (with Graph GUID fallback) so Bot Framework runtime `channelData.team.id` matching works for team and team/channel allowlist entries. (#41838) Thanks @BradGroux.
+- Mattermost/Markdown formatting: preserve first-line indentation when stripping bot mentions so nested list items and indented code blocks keep their structure, and render Mattermost tables natively by default instead of fenced-code fallback. (#18655) thanks @echo931.
 
 ## 2026.3.8
 

extensions/mattermost/src/mattermost/monitor-helpers.test.ts

@@ -61,10 +61,22 @@ describe("normalizeMention", () => {
     expect(result).toContain("    - deep");
   });
 
+  it("preserves first-line indentation for nested list items", () => {
+    const input = "@echobot\n  - nested\n    - deep";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("  - nested\n    - deep");
+  });
+
   it("preserves indented code blocks", () => {
     const input = "@echobot\ntext\n    code line 1\n    code line 2";
     const result = normalizeMention(input, "echobot");
     expect(result).toContain("    code line 1");
     expect(result).toContain("    code line 2");
   });
+
+  it("preserves first-line indentation for indented code blocks", () => {
+    const input = "@echobot\n    code line 1\n    code line 2";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("    code line 1\n    code line 2");
+  });
 });

extensions/mattermost/src/mattermost/monitor-helpers.ts

@@ -80,16 +80,28 @@ export function normalizeMention(text: string, mention: string | undefined): str
     return text.trim();
   }
   const escaped = mention.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
-  const re = new RegExp(`@${escaped}\\b`, "gi");
-  // Replace the mention itself, then clean up without destroying Markdown structure.
-  // 1. Remove the mention (replace with empty to avoid injecting spaces into indentation)
-  // 2. Collapse only runs of multiple spaces/tabs within a line (preserving leading indent)
-  // 3. Trim blank lines left by mention removal
-  return text
-    .replace(re, "")
-    .split("\n")
-    .map((line) => line.replace(/(\S) {2,}/g, "$1 "))
-    .join("\n")
-    .replace(/^\s*\n/, "")
-    .trim();
+  const hasMentionRe = new RegExp(`@${escaped}\\b`, "i");
+  const leadingMentionRe = new RegExp(`^([\\t ]*)@${escaped}\\b[\\t ]*`, "i");
+  const trailingMentionRe = new RegExp(`[\\t ]*@${escaped}\\b[\\t ]*$`, "i");
+  const normalizedLines = text.split("\n").map((line) => {
+    const hadMention = hasMentionRe.test(line);
+    const normalizedLine = line
+      .replace(leadingMentionRe, "$1")
+      .replace(trailingMentionRe, "")
+      .replace(new RegExp(`@${escaped}\\b`, "gi"), "")
+      .replace(/(\S)[ \t]{2,}/g, "$1 ");
+    return {
+      text: normalizedLine,
+      mentionOnlyBlank: hadMention && normalizedLine.trim() === "",
+    };
+  });
+
+  while (normalizedLines[0]?.mentionOnlyBlank) {
+    normalizedLines.shift();
+  }
+  while (normalizedLines.at(-1)?.text.trim() === "") {
+    normalizedLines.pop();
+  }
+
+  return normalizedLines.map((line) => line.text).join("\n");
 }