diff --git a/extensions/line/src/reply-payload-transform.test.ts b/extensions/line/src/reply-payload-transform.test.ts
index 3336068a64f5..2bb6113c738d 100644
--- a/extensions/line/src/reply-payload-transform.test.ts
+++ b/extensions/line/src/reply-payload-transform.test.ts
@@ -381,6 +381,54 @@ describe("parseLineDirectives", () => {
     });
   });
 
+  describe("blank comma-separated entries", () => {
+    // A trailing or doubled comma in agent output must not emit empty Flex text
+    // components (agenda) or empty action labels (device); LINE rejects those with
+    // HTTP 400 "May not be empty".
+    const collectRenderedStrings = (node: unknown, out: string[]): string[] => {
+      if (Array.isArray(node)) {
+        for (const item of node) {
+          collectRenderedStrings(item, out);
+        }
+      } else if (node && typeof node === "object") {
+        const record = node as Record<string, unknown>;
+        if (record.type === "text" && typeof record.text === "string") {
+          out.push(record.text);
+        }
+        if (typeof record.label === "string") {
+          out.push(record.label);
+        }
+        for (const value of Object.values(record)) {
+          collectRenderedStrings(value, out);
+        }
+      }
+      return out;
+    };
+
+    it("drops trailing commas in agenda events", () => {
+      const result = parseLineDirectives({ text: "[[agenda: Today | Standup:9am, Lunch:12pm,]]" });
+      const flexMessage = requireFlexMessage(
+        getLineData(result).flexMessage,
+        "agenda trailing comma",
+      );
+      expect(flexMessage.altText).toBe("📋 Today (2 events)");
+      expect(collectRenderedStrings(flexMessage.contents, [])).not.toContain("");
+    });
+
+    it("drops doubled commas and blank labels in device controls", () => {
+      const result = parseLineDirectives({
+        text: "[[device: TV | Box | Playing | Play:toggle,, :ignored, Menu:menu]]",
+      });
+      const flexMessage = requireFlexMessage(
+        getLineData(result).flexMessage,
+        "device blank controls",
+      );
+      const renderedStrings = collectRenderedStrings(flexMessage.contents, []);
+      expect(renderedStrings).toEqual(expect.arrayContaining(["Play", "Menu"]));
+      expect(renderedStrings).not.toContain("");
+    });
+  });
+
   describe("device", () => {
     it("parses device variants", () => {
       const cases = [
diff --git a/extensions/line/src/reply-payload-transform.ts b/extensions/line/src/reply-payload-transform.ts
index 5082a9ac430f..db0b55ee38e3 100644
--- a/extensions/line/src/reply-payload-transform.ts
+++ b/extensions/line/src/reply-payload-transform.ts
@@ -287,7 +287,9 @@ export function parseLineDirectives(payload: ReplyPayload): ReplyPayload {
     if (parts.length >= 2) {
       const title = expectDefined(parts[0], "agenda title field");
       const eventsStr = expectDefined(parts[1], "agenda events field");
-      const events = eventsStr.split(",").map((eventStr) => {
+      // normalizeStringEntries drops blank entries from trailing/double commas; an empty
+      // event title becomes an empty Flex text component, which LINE rejects with HTTP 400.
+      const events = normalizeStringEntries(eventsStr.split(",")).map((eventStr) => {
         const trimmed = eventStr.trim();
         const colonIdx = trimmed.lastIndexOf(":");
         if (colonIdx > 0) {
@@ -321,12 +323,16 @@ export function parseLineDirectives(payload: ReplyPayload): ReplyPayload {
       const [, deviceType, status, controlsStr] = parts;
       const deviceKey = toSlug(deviceName || "device");
       const controls = controlsStr
-        ? controlsStr.split(",").map((ctrlStr) => {
+        ? normalizeStringEntries(controlsStr.split(",")).flatMap((ctrlStr) => {
             const controlParts = ctrlStr.split(":").map((s) => s.trim());
             const label = expectDefined(controlParts[0], "device control label");
+            // A nonempty raw entry can still parse to `:data`; LINE rejects a blank action label.
+            if (!label) {
+              return [];
+            }
             const data = controlParts[1];
             const action = data || normalizeLowercaseStringOrEmpty(label).replace(/\s+/g, "_");
-            return { label, data: lineActionData(action, { "line.device": deviceKey }) };
+            return [{ label, data: lineActionData(action, { "line.device": deviceKey }) }];
           })
         : [];