diff --git a/extensions/matrix/src/matrix/monitor/replies.ts b/extensions/matrix/src/matrix/monitor/replies.ts
index e347df1c9..bb8c205ea 100644
--- a/extensions/matrix/src/matrix/monitor/replies.ts
+++ b/extensions/matrix/src/matrix/monitor/replies.ts
@@ -2,7 +2,7 @@ import type { MatrixClient } from "matrix-js-sdk";
 
 import { chunkMarkdownText } from "../../../../../src/auto-reply/chunk.js";
 import type { ReplyPayload } from "../../../../../src/auto-reply/types.js";
-import { danger } from "../../../../../src/globals.js";
+import { danger, logVerbose } from "../../../../../src/globals.js";
 import type { RuntimeEnv } from "../../../../../src/runtime.js";
 import { sendMessageMatrix } from "../send.js";
 
@@ -18,7 +18,12 @@ export async function deliverMatrixReplies(params: {
   const chunkLimit = Math.min(params.textLimit, 4000);
   let hasReplied = false;
   for (const reply of params.replies) {
-    if (!reply?.text && !reply?.mediaUrl && !(reply?.mediaUrls?.length ?? 0)) {
+    const hasMedia = Boolean(reply?.mediaUrl) || (reply?.mediaUrls?.length ?? 0) > 0;
+    if (!reply?.text && !hasMedia) {
+      if (reply?.audioAsVoice) {
+        logVerbose("matrix reply has audioAsVoice without media/text; skipping");
+        continue;
+      }
       params.runtime.error?.(danger("matrix reply missing text/media"));
       continue;
     }
@@ -57,6 +62,7 @@ export async function deliverMatrixReplies(params: {
         mediaUrl,
         replyToId: shouldIncludeReply(replyToId) ? replyToId : undefined,
         threadId: params.threadId,
+        audioAsVoice: reply.audioAsVoice,
       });
       if (shouldIncludeReply(replyToId)) {
         hasReplied = true;
diff --git a/extensions/matrix/src/matrix/send.ts b/extensions/matrix/src/matrix/send.ts
index 3ac6d9d32..7e1e2b2fe 100644
--- a/extensions/matrix/src/matrix/send.ts
+++ b/extensions/matrix/src/matrix/send.ts
@@ -1,12 +1,15 @@
 import type { AccountDataEvents, MatrixClient } from "matrix-js-sdk";
 import { EventType, MsgType, RelationType } from "matrix-js-sdk";
 import type {
-  ReactionEventContent,
   RoomMessageEventContent,
+  ReactionEventContent,
 } from "matrix-js-sdk/lib/@types/events.js";
 
 import { chunkMarkdownText, resolveTextChunkLimit } from "../../../../src/auto-reply/chunk.js";
 import { loadConfig } from "../../../../src/config/config.js";
+import { isVoiceCompatibleAudio } from "../../../../src/media/audio.js";
+import { mediaKindFromMime } from "../../../../src/media/constants.js";
+import { getImageMetadata, resizeToJpeg } from "../../../../src/media/image-ops.js";
 import type { PollInput } from "../../../../src/polls.js";
 import { loadWebMedia } from "../../../../src/web/media.js";
 import { getActiveMatrixClient } from "./active-client.js";
@@ -47,6 +50,8 @@ export type MatrixSendOpts = {
   replyToId?: string;
   threadId?: string | number | null;
   timeoutMs?: number;
+  /** Send audio as voice message (voice bubble) instead of audio file. Defaults to false. */
+  audioAsVoice?: boolean;
 };
 
 function ensureNodeRuntime() {
@@ -125,6 +130,18 @@ export async function resolveMatrixRoomId(
   return target;
 }
 
+type MatrixImageInfo = {
+  w?: number;
+  h?: number;
+  thumbnail_url?: string;
+  thumbnail_info?: {
+    w: number;
+    h: number;
+    mimetype: string;
+    size: number;
+  };
+};
+
 function buildMediaContent(params: {
   msgtype: MsgType.Image | MsgType.Audio | MsgType.Video | MsgType.File;
   body: string;
@@ -133,8 +150,24 @@ function buildMediaContent(params: {
   mimetype?: string;
   size: number;
   relation?: MatrixReplyRelation;
+  isVoice?: boolean;
+  durationMs?: number;
+  imageInfo?: MatrixImageInfo;
 }): RoomMessageEventContent {
-  const info = { mimetype: params.mimetype, size: params.size };
+  const info: Record<string, unknown> = { mimetype: params.mimetype, size: params.size };
+  if (params.durationMs !== undefined) {
+    info.duration = params.durationMs;
+  }
+  if (params.imageInfo) {
+    if (params.imageInfo.w) info.w = params.imageInfo.w;
+    if (params.imageInfo.h) info.h = params.imageInfo.h;
+    if (params.imageInfo.thumbnail_url) {
+      info.thumbnail_url = params.imageInfo.thumbnail_url;
+      if (params.imageInfo.thumbnail_info) {
+        info.thumbnail_info = params.imageInfo.thumbnail_info;
+      }
+    }
+  }
   const base: MatrixMessageContent = {
     msgtype: params.msgtype,
     body: params.body,
@@ -142,6 +175,12 @@ function buildMediaContent(params: {
     info,
     url: params.url,
   };
+  if (params.isVoice) {
+    base["org.matrix.msc3245.voice"] = {};
+    base["org.matrix.msc1767.audio"] = {
+      duration: params.durationMs,
+    };
+  }
   if (params.relation) {
     base["m.relates_to"] = params.relation;
   }
@@ -177,6 +216,75 @@ function buildReplyRelation(replyToId?: string): MatrixReplyRelation | undefined
   return { "m.in_reply_to": { event_id: trimmed } };
 }
 
+function resolveMatrixMsgType(
+  contentType?: string,
+  fileName?: string,
+): MsgType.Image | MsgType.Audio | MsgType.Video | MsgType.File {
+  const kind = mediaKindFromMime(contentType ?? "");
+  switch (kind) {
+    case "image":
+      return MsgType.Image;
+    case "audio":
+      return MsgType.Audio;
+    case "video":
+      return MsgType.Video;
+    default:
+      return MsgType.File;
+  }
+}
+
+function resolveMatrixVoiceDecision(opts: {
+  wantsVoice: boolean;
+  contentType?: string;
+  fileName?: string;
+}): { useVoice: boolean } {
+  if (!opts.wantsVoice) return { useVoice: false };
+  if (isVoiceCompatibleAudio({ contentType: opts.contentType, fileName: opts.fileName })) {
+    return { useVoice: true };
+  }
+  return { useVoice: false };
+}
+
+const THUMBNAIL_MAX_SIDE = 800;
+const THUMBNAIL_QUALITY = 80;
+
+async function prepareImageInfo(params: {
+  buffer: Buffer;
+  client: MatrixClient;
+}): Promise<MatrixImageInfo | undefined> {
+  const meta = await getImageMetadata(params.buffer).catch(() => null);
+  if (!meta) return undefined;
+  const imageInfo: MatrixImageInfo = { w: meta.width, h: meta.height };
+  const maxDim = Math.max(meta.width, meta.height);
+  if (maxDim > THUMBNAIL_MAX_SIDE) {
+    try {
+      const thumbBuffer = await resizeToJpeg({
+        buffer: params.buffer,
+        maxSide: THUMBNAIL_MAX_SIDE,
+        quality: THUMBNAIL_QUALITY,
+        withoutEnlargement: true,
+      });
+      const thumbMeta = await getImageMetadata(thumbBuffer).catch(() => null);
+      const thumbUri = await params.client.uploadContent(thumbBuffer as MatrixUploadContent, {
+        type: "image/jpeg",
+        name: "thumbnail.jpg",
+      });
+      imageInfo.thumbnail_url = thumbUri.content_uri;
+      if (thumbMeta) {
+        imageInfo.thumbnail_info = {
+          w: thumbMeta.width,
+          h: thumbMeta.height,
+          mimetype: "image/jpeg",
+          size: thumbBuffer.byteLength,
+        };
+      }
+    } catch {
+      // Thumbnail generation failed, continue without it
+    }
+  }
+  return imageInfo;
+}
+
 async function uploadFile(
   client: MatrixClient,
   file: MatrixUploadContent | Buffer,
@@ -257,9 +365,17 @@ export async function sendMessageMatrix(
         contentType: media.contentType,
         filename: media.fileName,
       });
-      const msgtype = MsgType.File;
+      const baseMsgType = resolveMatrixMsgType(media.contentType, media.fileName);
+      const { useVoice } = resolveMatrixVoiceDecision({
+        wantsVoice: opts.audioAsVoice === true,
+        contentType: media.contentType,
+        fileName: media.fileName,
+      });
+      const msgtype = useVoice ? MsgType.Audio : baseMsgType;
+      const isImage = msgtype === MsgType.Image;
+      const imageInfo = isImage ? await prepareImageInfo({ buffer: media.buffer, client }) : undefined;
       const [firstChunk, ...rest] = chunks;
-      const body = firstChunk ?? media.fileName ?? "(file)";
+      const body = useVoice ? "Voice message" : (firstChunk ?? media.fileName ?? "(file)");
       const content = buildMediaContent({
         msgtype,
         body,
@@ -268,10 +384,13 @@ export async function sendMessageMatrix(
         mimetype: media.contentType,
         size: media.buffer.byteLength,
         relation,
+        isVoice: useVoice,
+        imageInfo,
       });
       const response = await sendContent(content);
       lastMessageId = response.event_id ?? lastMessageId;
-      for (const chunk of rest) {
+      const textChunks = useVoice ? chunks : rest;
+      for (const chunk of textChunks) {
         const text = chunk.trim();
         if (!text) continue;
         const followup = buildTextContent(text);