diff --git a/m2d/actions/send-event.js b/m2d/actions/send-event.js
index 9b3fbec2..f26abb0a 100644
--- a/m2d/actions/send-event.js
+++ b/m2d/actions/send-event.js
@@ -73,7 +73,7 @@ async function sendEvent(event) {
 
 	// no need to sync the matrix member to the other side. but if I did need to, this is where I'd do it
 
-	let {messagesToEdit, messagesToSend, messagesToDelete} = await eventToMessage.eventToMessage(event, guild, {api})
+	let {messagesToEdit, messagesToSend, messagesToDelete} = await eventToMessage.eventToMessage(event, guild, {api, snow: discord.snow})
 
 	messagesToEdit = await Promise.all(messagesToEdit.map(async e => {
 		e.message = await resolvePendingFiles(e.message)
diff --git a/m2d/converters/event-to-message.js b/m2d/converters/event-to-message.js
index 7082fbba..e7d41df7 100644
--- a/m2d/converters/event-to-message.js
+++ b/m2d/converters/event-to-message.js
@@ -259,7 +259,7 @@ async function uploadEndOfMessageSpriteSheet(content, attachments, pendingFiles)
 /**
  * @param {Ty.Event.Outer_M_Room_Message | Ty.Event.Outer_M_Room_Message_File | Ty.Event.Outer_M_Sticker | Ty.Event.Outer_M_Room_Message_Encrypted_File} event
  * @param {import("discord-api-types/v10").APIGuild} guild
- * @param {{api: import("../../matrix/api")}} di simple-as-nails dependency injection for the matrix API
+ * @param {{api: import("../../matrix/api"), snow: import("snowtransfer").SnowTransfer}} di simple-as-nails dependency injection for the matrix API
  */
 async function eventToMessage(event, guild, di) {
 	/** @type {(DiscordTypes.RESTPostAPIWebhookWithTokenJSONBody & {files?: {name: string, file: Buffer | Readable}[]})[]} */
@@ -289,6 +289,8 @@ async function eventToMessage(event, guild, di) {
 	const attachments = []
 	/** @type {({name: string, url: string} | {name: string, url: string, key: string, iv: string} | {name: string, buffer: Buffer})[]} */
 	const pendingFiles = []
+	/** @type {DiscordTypes.APIUser[]} */
+	const ensureJoined = []
 
 	// Convert content depending on what the message is
 	if (event.type === "m.room.message" && (event.content.msgtype === "m.text" || event.content.msgtype === "m.emote")) {
@@ -502,6 +504,17 @@ async function eventToMessage(event, guild, di) {
 
 	content = displayNameRunoff + replyLine + content
 
+	// Handling written @mentions: we need to look for candidate Discord members to join to the room
+	let writtenMentionMatch = content.match(/(?:^|[^"<>/A-Za-z0-9])@([A-Za-z][A-Za-z0-9._\[\]\(\)-]+):?/d) // d flag requires Node 16+
+	if (writtenMentionMatch) {
+		const results = await di.snow.guild.searchGuildMembers(guild.id, {query: writtenMentionMatch[1]})
+		if (results[0]) {
+			assert(results[0].user)
+			content = content.slice(0, writtenMentionMatch.index) + `<@${results[0].user.id}>` + content.slice(writtenMentionMatch.index + writtenMentionMatch[0].length)
+			ensureJoined.push(results[0].user)
+		}
+	}
+
 	// Split into 2000 character chunks
 	const chunks = chunk(content, 2000)
 	messages = messages.concat(chunks.map(content => ({
@@ -543,7 +556,8 @@ async function eventToMessage(event, guild, di) {
 	return {
 		messagesToEdit,
 		messagesToSend,
-		messagesToDelete: messageIDsToEdit
+		messagesToDelete: messageIDsToEdit,
+		ensureJoined
 	}
 }
 
diff --git a/m2d/converters/event-to-message.test.js b/m2d/converters/event-to-message.test.js
index f5649064..7581e6b7 100644
--- a/m2d/converters/event-to-message.test.js
+++ b/m2d/converters/event-to-message.test.js
@@ -63,6 +63,7 @@ test("event2message: body is used when there is no formatted_body", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -89,8 +90,15 @@ test("event2message: any markdown in body is escaped, except strikethrough", asy
 			unsigned: {
 				age: 405299
 			}
+		}, {}, {
+			snow: {
+				guild: {
+					searchGuildMembers: () => []
+				}
+			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -122,6 +130,7 @@ test("event2message: links in formatted body are not broken", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -151,6 +160,7 @@ test("event2message: links in plaintext body are not broken", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -181,6 +191,7 @@ test("event2message: basic html is converted to markdown", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -211,6 +222,7 @@ test("event2message: spoilers work", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -241,6 +253,7 @@ test("event2message: markdown syntax is escaped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -271,6 +284,7 @@ test("event2message: html lines are bridged correctly", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -301,6 +315,7 @@ test("event2message: html lines are bridged correctly", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -332,6 +347,7 @@ test("event2message: whitespace is collapsed", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -364,6 +380,7 @@ test("event2message: lists are bridged correctly", async t => {
 			"room_id": "!BpMdOUkWWhFxmTrENV:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -392,6 +409,7 @@ test("event2message: long messages are split", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -426,6 +444,7 @@ test("event2message: code blocks work", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -457,6 +476,7 @@ test("event2message: code block contents are formatted correctly and not escaped
 			"room_id": "!BpMdOUkWWhFxmTrENV:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -487,6 +507,7 @@ test("event2message: quotes have an appropriate amount of whitespace", async t =
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -528,6 +549,7 @@ test("event2message: lists have appropriate line breaks", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -556,6 +578,7 @@ test("event2message: m.emote plaintext works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -586,6 +609,7 @@ test("event2message: m.emote markdown syntax is escaped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -633,6 +657,7 @@ test("event2message: rich reply to a sim user", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -709,6 +734,7 @@ test("event2message: rich reply to an already-edited message will quote the new
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -756,6 +782,7 @@ test("event2message: should avoid using blockquote contents as reply preview in
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -841,6 +868,7 @@ test("event2message: should include a reply preview when message ends with a blo
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -921,6 +949,7 @@ test("event2message: should include a reply preview when replying to a descripti
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -970,6 +999,7 @@ test("event2message: entities are not escaped in main message or reply preview",
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1048,6 +1078,7 @@ test("event2message: editing a rich reply to a sim user", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1144874214311067708",
@@ -1102,6 +1133,7 @@ test("event2message: editing a plaintext body message", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1153,6 +1185,7 @@ test("event2message: editing a plaintext message to be longer", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1208,6 +1241,7 @@ test("event2message: editing a plaintext message to be shorter", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: ["1145688633186193481"],
 			messagesToEdit: [{
 				id: "1145688633186193480",
@@ -1265,6 +1299,7 @@ test("event2message: editing a formatted body message", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [{
 				id: "1145688633186193479",
@@ -1317,6 +1352,7 @@ test("event2message: rich reply to a matrix user's long message with formatting"
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1376,6 +1412,7 @@ test("event2message: rich reply to an image", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1427,6 +1464,7 @@ test("event2message: rich reply to a spoiler should ensure the spoiler is hidden
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1478,6 +1516,7 @@ test("event2message: with layered rich replies, the preview should only be the r
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1508,6 +1547,7 @@ test("event2message: raw mentioning discord users in plaintext body works", asyn
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1538,6 +1578,7 @@ test("event2message: raw mentioning discord users in formatted body works", asyn
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1568,6 +1609,7 @@ test("event2message: mentioning discord users works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1598,6 +1640,7 @@ test("event2message: mentioning matrix users works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1628,6 +1671,7 @@ test("event2message: mentioning bridged rooms works", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1658,6 +1702,7 @@ test("event2message: colon after mentions is stripped", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1699,6 +1744,7 @@ test("event2message: caches the member if the member is not known", async t => {
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1743,6 +1789,7 @@ test("event2message: skips caching the member if the member does not exist, some
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1786,6 +1833,7 @@ test("event2message: overly long usernames are shifted into the message content"
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1818,6 +1866,7 @@ test("event2message: overly long usernames are not treated specially when the ms
 			}
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1847,6 +1896,7 @@ test("event2message: text attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1881,6 +1931,7 @@ test("event2message: image attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1930,6 +1981,7 @@ test("event2message: encrypted image attachments work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -1974,6 +2026,7 @@ test("event2message: stickers work", async t => {
 			room_id: "!BnKuBPCvyfOkhcUjEu:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2002,6 +2055,7 @@ test("event2message: static emojis work", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2028,6 +2082,7 @@ test("event2message: animated emojis work", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2054,6 +2109,7 @@ test("event2message: unknown emojis in the middle are linked", async t => {
 			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
 		}),
 		{
+			ensureJoined: [],
 			messagesToDelete: [],
 			messagesToEdit: [],
 			messagesToSend: [{
@@ -2065,6 +2121,53 @@ test("event2message: unknown emojis in the middle are linked", async t => {
 	)
 })
 
+test("event2message: guessed @mentions may join members to mention", async t => {
+	let called = 0
+	const subtext = {
+		user: {
+			id: "321876634777218072",
+			username: "subtext",
+			discriminator: "0"
+		}
+	}
+	t.deepEqual(
+		await eventToMessage({
+			type: "m.room.message",
+			sender: "@cadence:cadence.moe",
+			content: {
+				msgtype: "m.text",
+				body: "@subtext: what food would you like to order?"
+			},
+			event_id: "$u5gSwSzv_ZQS3eM00mnTBCor8nx_A_AwuQz7e59PZk8",
+			room_id: "!kLRqKKUQXcibIMtOpl:cadence.moe"
+		}, {
+			id: "112760669178241024"
+		}, {
+			snow: {
+				guild: {
+					async searchGuildMembers(guildID, options) {
+						called++
+						t.equal(guildID, "112760669178241024")
+						t.deepEqual(options, {query: "subtext"})
+						return [subtext]
+					}
+				}
+			}
+		}),
+		{
+			messagesToDelete: [],
+			messagesToEdit: [],
+			messagesToSend: [{
+				username: "cadence [they]",
+				content: "<@321876634777218072> what food would you like to order?",
+				avatar_url: undefined
+			}],
+			ensureJoined: [subtext.user]
+		}
+	)
+	t.equal(called, 1, "searchGuildMembers should be called once")
+})
+
 slow()("event2message: unknown emoji in the end is reuploaded as a sprite sheet", async t => {
 	const messages = await eventToMessage({
 		type: "m.room.message",