diff --git a/tests/persona-matrix-mouth.test.mjs b/tests/persona-matrix-mouth.test.mjs
index 463429e..610dd3b 100644
--- a/tests/persona-matrix-mouth.test.mjs
+++ b/tests/persona-matrix-mouth.test.mjs
@@ -3,7 +3,7 @@ import assert from "node:assert/strict";
 import { createServer } from "node:http";
 import { readFileSync, readdirSync, statSync } from "node:fs";
 import { resolve, join } from "node:path";
-import { createMouth, createBrakeReader, guarded, redact } from "../tools/persona-matrix-mouth.mjs";
+import { createMouth, createBrakeReader, guarded, redact, roomsFor, projectRoomsVariable } from "../tools/persona-matrix-mouth.mjs";
 
 const TOKEN = "syt_SECRET_TOKEN_9f3";
 const HS_NAME = "gamecult.test";
@@ -577,3 +577,24 @@ test("a same-server invitation to a room that is not a DM is neither joined nor
     assert.deepEqual([joinsOf(hs), leavesOf(hs)], [[], []]);
   } finally { await hs.close(); }
 });
+
+test("project rooms: slug mapping, per-Persona lists, absent variable, malformed alias", () => {
+  assert.equal(projectRoomsVariable("eureka"), "MATRIX_ROOMS_EUREKA");
+  assert.equal(projectRoomsVariable("nova-2.x"), "MATRIX_ROOMS_NOVA_2_X");
+  const env = { MATRIX_ROOMS: "#swarm:t, #ops:t", MATRIX_ROOMS_EUREKA: "#eureka-proj:t,#ops:t", MATRIX_ROOMS_NOVA_2: "#nova-proj:t" };
+  assert.deepEqual(roomsFor(env, "eureka"), ["#swarm:t", "#ops:t", "#eureka-proj:t"], "shared plus own, deduplicated");
+  assert.deepEqual(roomsFor(env, "nova-2"), ["#swarm:t", "#ops:t", "#nova-proj:t"], "dash maps to underscore");
+  assert.ok(!roomsFor(env, "nova-2").includes("#eureka-proj:t") && !roomsFor(env, "eureka").includes("#nova-proj:t"));
+  assert.deepEqual(roomsFor(env, "other"), ["#swarm:t", "#ops:t"], "absent variable: shared rooms only");
+  assert.throws(() => roomsFor({ ...env, MATRIX_ROOMS_EUREKA: "#ok:t,nope" }, "eureka"), /MATRIX_ROOMS_EUREKA.*malformed/);
+});
+
+test("send to another Persona's project room is refused as UnknownRoom", async () => {
+  const hs = await fakeHomeserver({ sync: script });
+  try {
+    const env = { MATRIX_ROOMS: `#swarm:${HS_NAME}`, MATRIX_ROOMS_EUREKA: `#eureka-proj:${HS_NAME}`, MATRIX_ROOMS_NOVA: `#nova-proj:${HS_NAME}` };
+    const mouth = mouthFor(hs, { rooms: roomsFor(env, "eureka") });
+    assert.equal((await mouth.send({ requestId: "p", persona: "eureka", roomAlias: `#nova-proj:${HS_NAME}`, text: "x" })).refusal, "UnknownRoom");
+    assert.equal(hs.puts().length, 0);
+  } finally { await hs.close(); }
+});
diff --git a/tools/persona-matrix-mouth.mjs b/tools/persona-matrix-mouth.mjs
index c991288..6ea8246 100644
--- a/tools/persona-matrix-mouth.mjs
+++ b/tools/persona-matrix-mouth.mjs
@@ -396,12 +396,32 @@ function credential(env, name) {
   return readFileSync(join(required(env, "CREDENTIALS_DIRECTORY"), name), "utf8").trim();
 }
 
+const ROOM_ALIAS = /^#[^\s:,]+:[^\s,]+$/;
+
+// The env variable holding one Persona's project rooms: MATRIX_ROOMS_<SLUG>, the slug
+// upper-cased with "." and "-" turned into "_".
+export function projectRoomsVariable(persona) {
+  return `MATRIX_ROOMS_${persona.toUpperCase().replace(/[.-]/g, "_")}`;
+}
+
+// One Persona's rooms: the shared MATRIX_ROOMS plus her own project rooms, deduplicated.
+// Another Persona's project variable is never read. A malformed project alias is refused.
+export function roomsFor(env, persona) {
+  const list = text => text.split(",").map(s => s.trim()).filter(Boolean);
+  const name = projectRoomsVariable(persona);
+  const project = list(env[name] ?? "");
+  const bad = project.find(alias => !ROOM_ALIAS.test(alias));
+  if (bad) throw new Error(`${name} has a malformed room alias: ${JSON.stringify(bad)} (expected #name:server)`);
+  return [...new Set([...list(required(env, "MATRIX_ROOMS")), ...project])];
+}
+
 // PERSONAS is the comma-separated list of Persona slugs this process speaks for.
 // Each slug names its credential (matrix-token-<slug>), its cursor directory under
 // STATE_DIRECTORY and its brake at CONTROL_ROOT/<slug>/control.cc.
 export async function main(env = process.env) {
   const personas = required(env, "PERSONAS").split(",").map(s => s.trim()).filter(Boolean);
   if (personas.length === 0 || new Set(personas).size !== personas.length || !personas.every(p => SLUG.test(p))) throw new Error("PERSONAS must be distinct slugs");
+  if (new Set(personas.map(projectRoomsVariable)).size !== personas.length) throw new Error("PERSONAS must map to distinct MATRIX_ROOMS_<SLUG> variables");
   const tokens = new Map(personas.map(p => [p, credential(env, `matrix-token-${p}`)]));
   const chatKey = credential(env, "chat-key");
   const secrets = [...tokens.values(), chatKey];
@@ -410,13 +430,13 @@ export async function main(env = process.env) {
     const log = line => console.error(redact(line, secrets));
     const homeserver = required(env, "MATRIX_HOMESERVER").replace(/\/$/, "");
     const serverName = required(env, "MATRIX_SERVER_NAME");
-    const rooms = required(env, "MATRIX_ROOMS").split(",").map(s => s.trim()).filter(Boolean);
+    const roomsByPersona = new Map(personas.map(persona => [persona, roomsFor(env, persona)]));
     const stateRoot = required(env, "STATE_DIRECTORY");
     const controlRoot = env.CONTROL_ROOT ?? "/etc/gamecult/minds";
     const mouths = new Map(personas.map(persona => {
       mkdirSync(join(stateRoot, persona), { recursive: true });
       return [persona, createMouth({
-        persona, homeserver, serverName, rooms, token: tokens.get(persona), log: line => log(`${persona}: ${line}`),
+        persona, homeserver, serverName, rooms: roomsByPersona.get(persona), token: tokens.get(persona), log: line => log(`${persona}: ${line}`),
         state: cultcacheState({ runtime, path: join(stateRoot, persona, "cursor.cc") }),
         brake: createBrakeReader({ controlPath: join(controlRoot, persona, "control.cc"), readStore: runtime.readSingleFileStore, decode: runtime.msgpack.decode }),
       })];