diff --git a/packages/bus/src/broker.mjs b/packages/bus/src/broker.mjs
index d5e6f2bc3..b18965feb 100644
--- a/packages/bus/src/broker.mjs
+++ b/packages/bus/src/broker.mjs
@@ -1848,6 +1848,11 @@ export class Broker {
         if (a.class === 'BLOCK') this.#checkBlock(s, to, a.in_reply_to);
         if (a.decision) this.#decision(s, a.decision);
         const thread = this.#threadFor(s, to, a.in_reply_to);
+        // Row 170 (#1667): a tester's message to a role nobody holds is refused before it is
+        // stored, so a PM test never waits for the role's next run. A run launched but not yet
+        // claimed counts as no holder, as in #waiting. No lock: a holder that releases once the
+        // message is routed leaves it like any other message it held.
+        if (s.tester && !this.#recipient(s.business, to, thread)) fail('tester-target-not-running');
         const mid = randomUUID();
         this.#store.run(
           'INSERT INTO messages(id,at,business,from_role,from_run,to_role,to_name,class,in_reply_to,decision,corrects,body) VALUES(?,?,?,?,?,?,?,?,?,?,?,?)',
@@ -2489,7 +2494,8 @@ export class Broker {
   // told and whether launch.by itself has a holder. A run launched but not yet claimed counts as
   // no holder; the instance-running refusal stops a second launch. launch.by isn't told of a
   // message to it, of its own message (this result tells it) or of a tester's (a PM test
-  // authorizes nothing). Row 152 (#1646): launchable says whether the target is one of
+  // authorizes nothing); since row 170 (#1667) message.send refuses a tester's message to a role
+  // nobody holds before it gets here. Row 152 (#1646): launchable says whether the target is one of
   // launch.instances, so the sender learns at once that no launch can follow. launch.by is
   // still told: the Console shows the notice as the reply to the human's message.
   #waiting(s, mid, to, thread) {
diff --git a/packages/bus/tests/launch-notice.test.mjs b/packages/bus/tests/launch-notice.test.mjs
index a4121bdb8..fba5818cd 100644
--- a/packages/bus/tests/launch-notice.test.mjs
+++ b/packages/bus/tests/launch-notice.test.mjs
@@ -167,7 +167,7 @@ test('a run launched but not yet claimed counts as no holder', (t) => {
   assert.equal(ctx.notices().length, 1);
 });
 
-test('no notice for a message to launch.by, from it, from a tester, to the human, or in a thread to a thread instance', (t) => {
+test('no notice for a message to launch.by, from it, a refused one from a tester, to the human, or in a thread to a thread instance', (t) => {
   const ctx = setup(t);
   // To launch.by while it is stopped: the result says so, and nobody is told.
   assert.deepEqual(ctx.call('human', 'message.send', { to: 'chief', body: 'are you there?' }).waiting, {
@@ -187,9 +187,12 @@ test('no notice for a message to launch.by, from it, from a tester, to the human
     launcherRunning: true,
     launchable: true,
   });
-  // From a tester: a PM test authorizes nothing, so it wakes no launcher.
+  // From a tester to a role nobody holds: refused before it is stored (row 170, #1667), so a PM
+  // test wakes no launcher.
   ctx.caps.tester = ctx.b.bindTester({ business: 'demo' });
-  assert.equal(ctx.call('tester', 'message.send', { to: 'pm', body: '[mos test] ping' }).waiting.told, false);
+  const stored = ctx.store().get('SELECT count(*) n FROM messages').n;
+  assert.throws(() => ctx.call('tester', 'message.send', { to: 'pm', body: '[mos test] ping' }), { code: 'tester-target-not-running' });
+  assert.equal(ctx.store().get('SELECT count(*) n FROM messages').n, stored);
   // To the human or the tester, which no run holds: no waiting field at all.
   ctx.launch('coder', 'coder');
   ctx.claim('coder');
diff --git a/packages/bus/tests/tester.test.mjs b/packages/bus/tests/tester.test.mjs
index c24376be3..962649b8c 100644
--- a/packages/bus/tests/tester.test.mjs
+++ b/packages/bus/tests/tester.test.mjs
@@ -134,6 +134,61 @@ test('a tester message is from tester, starts [mos test], and writes no human.in
   assert.equal(store.get("SELECT count(*) n FROM events WHERE kind='human.input'").n, 0);
 });
 
+// Row 170 (#1667): a tester's message to a role nobody holds is refused before it is stored.
+const counts = (store) => ({
+  messages: store.get('SELECT count(*) n FROM messages').n,
+  deliveries: store.get('SELECT count(*) n FROM deliveries').n,
+  notices: store.get("SELECT count(*) n FROM messages WHERE from_role='_bus'").n,
+});
+
+test('a tester message to a role no run holds refuses tester-target-not-running and stores nothing', (t) => {
+  const { b, store, call } = setup(t);
+  const tester = b.bindTester({ business: 'demo' });
+  const before = counts(store);
+  assert.throws(() => call(tester, 'message.send', { to: 'cto', body: say() }), { code: 'tester-target-not-running' });
+  assert.deepEqual(counts(store), before);
+  assert.equal(before.notices, 0);
+  // The prefix check still comes first.
+  assert.throws(() => call(tester, 'message.send', { to: 'cto', body: 'no prefix' }), { code: 'tester-prefix' });
+});
+
+test('a tester message is refused while the run is only launched, and routes once it claims', (t) => {
+  const { b, store, call } = setup(t);
+  const tester = b.bindTester({ business: 'demo' });
+  const cto = b.bindLaunch({ business: 'demo', role: 'cto', run: 'cto-run', harness: 'pi' });
+  const before = counts(store);
+  assert.throws(() => call(tester, 'message.send', { to: 'cto', body: say() }), { code: 'tester-target-not-running' });
+  assert.deepEqual(counts(store), before);
+  call(cto, 'role.claim');
+  const sent = call(tester, 'message.send', { to: 'cto', body: say() });
+  assert.equal(sent.waiting, undefined);
+  const delivered = store.all('SELECT op, holder_run FROM deliveries WHERE message=? ORDER BY seq', sent.id);
+  assert.deepEqual(delivered.map((d) => [d.op, d.holder_run]), [['routed', 'cto-run']]);
+  assert.deepEqual(call(cto, 'message.receive').map((m) => [m.id, m.from_role]), [[sent.id, 'tester']]);
+});
+
+test("a human message to a role no run holds still waits and tells launch.by", (t) => {
+  const root = mkdtempSync(join(tmpdir(), 'bus-tester-'));
+  const store = new Store(root);
+  t.after(() => {
+    store.close();
+    rmSync(root, { recursive: true, force: true });
+  });
+  const businesses = business({ 'bus.tester': true });
+  businesses.demo.launch = { by: 'pm', instances: ['pm', 'cto'], models: {}, limits: {} };
+  const b = new Broker({ store, businesses });
+  const pm = b.bindLaunch({ business: 'demo', role: 'pm', run: 'pm-run', harness: 'pi' });
+  b.request(pm, { verb: 'role.claim' });
+  const human = b.bindHuman({ business: 'demo', human: 'jason', via: 'cli', outsideAgent: true });
+  const tester = b.bindTester({ business: 'demo' });
+  assert.throws(() => b.request(tester, { verb: 'message.send', args: { to: 'cto', body: say() } }), { code: 'tester-target-not-running' });
+  const sent = b.request(human, { verb: 'message.send', args: { to: 'cto', body: 'start on it' } });
+  assert.deepEqual(sent.waiting, { role: 'cto', launcher: 'pm', told: true, launcherRunning: true, launchable: true });
+  assert.equal(store.get('SELECT to_role FROM messages WHERE id=?', sent.id).to_role, 'cto');
+  const notices = store.all("SELECT to_role, in_reply_to FROM messages WHERE from_role='_bus'");
+  assert.deepEqual(notices.map((n) => [n.to_role, n.in_reply_to]), [['pm', sent.id]]);
+});
+
 test('a role answers a tester only in reply to a tester message, and the answer never reaches the human', (t) => {
   const { b, store, pm, human, reader, call } = setup(t);
   const tester = b.bindTester({ business: 'demo' });
@@ -373,8 +428,12 @@ async function runtime(t, vars, launches = []) {
 }
 
 test('tester-cli.mjs binds through the runtime when the switch is on, and refuses off or under a run marker', async (t) => {
-  const on = await runtime(t, { 'bus.tester': true });
+  // A start time no process has, so this test process is not the shim's managed-run ancestor.
+  const on = await runtime(t, { 'bus.tester': true }, [{ business: 'demo', role: 'pm', run: 'pm-run', harness: 'pi', pid: process.pid, startTime: '1' }]);
   const reader = new Client({ path: on.path, cap: on.readers[0].cap });
+  // Row 170 (#1667): cto has no run, so the tester's message to it is refused.
+  assert.deepEqual(await run(on.path, { business: 'demo', verb: 'message.send', args: { to: 'cto', body: say() } }), { status: 2, out: '', err: 'tester-target-not-running' });
+  await new Client({ path: on.path, cap: on.launches[0].cap }).call('role.claim');
   const sent = await run(on.path, { business: 'demo', verb: 'message.send', args: { to: 'pm', body: say() } });
   assert.equal(sent.status, 0, sent.err);
   const id = JSON.parse(sent.out).id;
diff --git a/packages/cli/README.md b/packages/cli/README.md
index fb3ad8350..3ed8916d0 100644
--- a/packages/cli/README.md
+++ b/packages/cli/README.md
@@ -127,8 +127,8 @@ mosaic launches list [--json]
   when the bus told `launch.by`; `pm isn't running, and the business names
   no launch.by` with no launch block; `pm isn't running and isn't in the
   launch block, so chief can't launch it` when the role isn't one of
-  `launch.instances` (row 152, #1646); `pm isn't running; a tester's message
-  tells nobody to launch it` for `--tester`. When `launch.by` itself isn't
+  `launch.instances` (row 152, #1646). A `--tester` message to such a role is
+  refused instead (see `--tester` below). When `launch.by` itself isn't
   running, talk prints `<launch.by> isn't running` (or `isn't running
   either` after the told line, but not after the launch-block line) and the
   command that starts it:
@@ -168,8 +168,12 @@ mosaic launches list [--json]
   (`tester-off`), each exit 3. Like the human commands, `--tester` works
   only from the tree the bus runs from ("One pinned copy" below).
   `talk --tester` text must start with
-  `[mos test]`, else exit 2 before any call. The role's reply comes back to
-  the tester, not to the human's inbox. `decide`, `stop`, `launches` and
+  `[mos test]`, else exit 2 before any call. When no run holds the role
+  (row 170, #1667), the bus refuses the message with
+  `tester-target-not-running` and stores nothing, and talk prints `pm isn't
+  running, so the tester's message was refused and nothing was stored` and
+  exits 3. A run launched but not yet claimed counts as not running. The
+  role's reply comes back to the tester, not to the human's inbox. `decide`, `stop`, `launches` and
   `inbox --read` or `--read-all` take no `--tester` (exit 4).
 
 ## The app
diff --git a/packages/cli/src/cli.mjs b/packages/cli/src/cli.mjs
index 6a4f68be6..35a70a5d3 100644
--- a/packages/cli/src/cli.mjs
+++ b/packages/cli/src/cli.mjs
@@ -339,8 +339,6 @@ function waitingLines(w, business) {
   // Row 152 (#1646): launch.by can launch only launch.instances. An older bus sends no
   // launchable, so only an explicit false prints this line.
   if (w.launchable === false) return `${w.role} isn't running and isn't in the launch block, so ${w.launcher} can't launch it\n`;
-  // A human's message to another role always tells launch.by; a tester's never does.
-  if (!w.told) return `${w.role} isn't running; a tester's message tells nobody to launch it\n`;
   return `${w.role} isn't running, ${w.launcher} has been told\n` + (w.launcherRunning ? "" : restart(w.launcher, " either"));
 }
 
@@ -383,6 +381,11 @@ async function talk(rest, io, deps, receiveOnly = false) {
       if (e.code === "thread-required-use-thread-send") {
         throw new CliError(`${to} runs in threads, so a message to it names one: mosaic talk --thread <thread> <text>; mosaic threads lists yours`, 2);
       }
+      // Row 170 (#1667): the bus stores no tester message to a role nobody holds. Exit 3 like the
+      // other tester refusals; transport.mjs's EXIT map stays as row 164 pinned it.
+      if (e.code === "tester-target-not-running" && parsed.flags.has("--tester")) {
+        throw new CliError(`${to} isn't running, so the tester's message was refused and nothing was stored`, 3);
+      }
       throw e;
     }
     io.stdout.write(`sent ${shortId(sent.id)} to ${to}\n`);
diff --git a/packages/cli/tests/tester.test.mjs b/packages/cli/tests/tester.test.mjs
index 5ccf7705c..0c0bb85a3 100644
--- a/packages/cli/tests/tester.test.mjs
+++ b/packages/cli/tests/tester.test.mjs
@@ -127,11 +127,43 @@ test("with no stand-in transport, --tester runs tester-cli.mjs on the data root'
   assert.deepEqual(seen, [{ argv: [TESTER_CLI, join(dataRoot, "bus", "broker.sock")], input: { business: "demo", verb: "agents", args: {} } }]);
 });
 
-// Row 146 (#1640): a tester's message to a stopped role tells launch.by nothing, and talk says so.
-test("talk --tester to a stopped role says nobody is told to launch it", async (t) => {
+// Row 170 (#1667): the bus refuses a tester's message to a stopped role and stores nothing, and
+// talk says so and exits 3.
+test("talk --tester to a stopped role exits 3, prints no sent line and stores nothing", async (t) => {
   const s = setup(t, { launch: { by: "pm", instances: ["cto", "coder"], models: {}, limits: {} } });
   const x = inAgent();
-  await main(["talk", "cto", "[mos test] hello", "--tester", "--wait", "0", "--business", "demo"], x, s.deps);
-  assert.match(x.out.text, /^sent [0-9a-f-]{8} to cto\ncto isn't running; a tester's message tells nobody to launch it\n$/);
-  assert.equal(s.store.get("SELECT count(*) n FROM messages WHERE from_role='_bus'").n, 0);
+  await assert.rejects(main(["talk", "cto", "[mos test] hello", "--tester", "--wait", "0", "--business", "demo"], x, s.deps), (e) => {
+    assert.equal(e.exitCode, 3);
+    assert.equal(e.message, "cto isn't running, so the tester's message was refused and nothing was stored");
+    return true;
+  });
+  assert.equal(x.out.text, "");
+  assert.equal(s.store.get("SELECT count(*) n FROM messages").n, 0);
+  assert.deepEqual(s.calls.tester.map((c) => c.verb), ["message.send"]);
+});
+
+test("only a --tester send refused tester-target-not-running is rewritten", async (t) => {
+  const s = setup(t);
+  const refusing = (code) => () => async (verb) => {
+    const error = new Error(code);
+    error.code = code;
+    error.exitCode = 3;
+    throw error;
+  };
+  // Another refusal of a tester send keeps the bus's error.
+  for (const code of ["tester-off", "tester-required", "tester-refused", "unknown-role"]) {
+    const x = inAgent();
+    await assert.rejects(main(["talk", "cto", "[mos test] hello", "--tester", "--wait", "0", "--business", "demo"], x, { ...s.deps, testerTransport: refusing(code) }), (e) => {
+      assert.equal(e.code, code);
+      assert.equal(e.message, code);
+      return true;
+    }, code);
+    assert.equal(x.out.text, "");
+  }
+  // The human's send never gets the tester's line, whatever its transport says.
+  await assert.rejects(main(["talk", "cto", "hello", "--wait", "0", "--business", "demo"], io(humanEnv()), { ...s.deps, transport: refusing("tester-target-not-running") }), (e) => {
+    assert.equal(e.code, "tester-target-not-running");
+    assert.equal(e.message, "tester-target-not-running");
+    return true;
+  });
 });