diff --git a/CHANGELOG.md b/CHANGELOG.md
index 100fa3575..bb3086bcb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -35,6 +35,7 @@
 - iOS/Android: enable stricter concurrency/lint checks; fix Swift 6 strict concurrency issues + Android lint errors (ExifInterface, obsolete SDK check). (#662) — thanks @KristijanJovanovski.
 - iOS/macOS: share `AsyncTimeout`, require explicit `bridgeStableID` on connect, and harden tool display defaults (avoids missing-resource label fallbacks).
 - Telegram: serialize media-group processing to avoid missed albums under load.
+- Signal: handle `dataMessage.reaction` events (signal-cli SSE) to avoid broken attachment errors. (#637) — thanks @neist.
 - Docs: showcase entries for ParentPay, R2 Upload, iOS TestFlight, and Oura Health. (#650) — thanks @henrino3.
 
 ## 2026.1.9
diff --git a/src/signal/monitor.tool-result.test.ts b/src/signal/monitor.tool-result.test.ts
index b9a6a24bf..07a3fa262 100644
--- a/src/signal/monitor.tool-result.test.ts
+++ b/src/signal/monitor.tool-result.test.ts
@@ -197,6 +197,45 @@ describe("monitorSignalProvider tool results", () => {
     expect(updateLastRouteMock).not.toHaveBeenCalled();
   });
 
+  it("ignores reaction-only messages when reactions live in dataMessage", async () => {
+    const abortController = new AbortController();
+
+    streamMock.mockImplementation(async ({ onEvent }) => {
+      const payload = {
+        envelope: {
+          sourceNumber: "+15550001111",
+          sourceName: "Ada",
+          timestamp: 1,
+          dataMessage: {
+            reaction: {
+              emoji: "👍",
+              targetAuthor: "+15550002222",
+              targetSentTimestamp: 2,
+            },
+            attachments: [{}],
+          },
+        },
+      };
+      await onEvent({
+        event: "receive",
+        data: JSON.stringify(payload),
+      });
+      abortController.abort();
+    });
+
+    await monitorSignalProvider({
+      autoStart: false,
+      baseUrl: "http://127.0.0.1:8080",
+      abortSignal: abortController.signal,
+    });
+
+    await flush();
+
+    expect(replyMock).not.toHaveBeenCalled();
+    expect(sendMock).not.toHaveBeenCalled();
+    expect(updateLastRouteMock).not.toHaveBeenCalled();
+  });
+
   it("enqueues system events for reaction notifications", async () => {
     config = {
       ...config,
diff --git a/src/signal/monitor.ts b/src/signal/monitor.ts
index 022219ed9..34f0c7f44 100644
--- a/src/signal/monitor.ts
+++ b/src/signal/monitor.ts
@@ -70,6 +70,7 @@ type SignalDataMessage = {
     groupName?: string | null;
   } | null;
   quote?: { text?: string | null } | null;
+  reaction?: SignalReactionMessage | null;
 };
 
 type SignalAttachment = {
@@ -143,6 +144,20 @@ function resolveSignalReactionTargets(
   return targets;
 }
 
+function isSignalReactionMessage(
+  reaction: SignalReactionMessage | null | undefined,
+): reaction is SignalReactionMessage {
+  if (!reaction) return false;
+  const emoji = reaction.emoji?.trim();
+  const timestamp = reaction.targetSentTimestamp;
+  const hasTarget = Boolean(
+    reaction.targetAuthor?.trim() || reaction.targetAuthorUuid?.trim(),
+  );
+  return Boolean(
+    emoji && typeof timestamp === "number" && timestamp > 0 && hasTarget,
+  );
+}
+
 function shouldEmitSignalReactionNotification(params: {
   mode?: SignalReactionNotificationMode;
   account?: string | null;
@@ -403,8 +418,17 @@ export async function monitorSignalProvider(
       }
       const dataMessage =
         envelope.dataMessage ?? envelope.editMessage?.dataMessage;
-      if (envelope.reactionMessage && !dataMessage) {
-        const reaction = envelope.reactionMessage;
+      const reaction = isSignalReactionMessage(envelope.reactionMessage)
+        ? envelope.reactionMessage
+        : isSignalReactionMessage(dataMessage?.reaction)
+          ? dataMessage?.reaction
+          : null;
+      const messageText = (dataMessage?.message ?? "").trim();
+      const quoteText = dataMessage?.quote?.text?.trim() ?? "";
+      const hasBodyContent =
+        Boolean(messageText || quoteText) ||
+        Boolean(!reaction && dataMessage?.attachments?.length);
+      if (reaction && !hasBodyContent) {
         if (reaction.isRemove) return; // Ignore reaction removals
         const emojiLabel = reaction.emoji?.trim() || "emoji";
         const senderDisplay = formatSignalSenderDisplay(sender);
@@ -550,7 +574,6 @@ export async function monitorSignalProvider(
           ? isSignalSenderAllowed(sender, effectiveGroupAllow)
           : true
         : dmAllowed;
-      const messageText = (dataMessage.message ?? "").trim();
 
       let mediaPath: string | undefined;
       let mediaType: string | undefined;