diff --git a/issues/audio/cpal-backend-hardcodes-the-format.md b/issues/audio/cpal-backend-hardcodes-the-format.md
index 3b27aba0842..7b341a81daf 100644
--- a/issues/audio/cpal-backend-hardcodes-the-format.md
+++ b/issues/audio/cpal-backend-hardcodes-the-format.md
@@ -11,6 +11,19 @@ client and therefore effectively untested. The backend also `assert_eq!`s the
 device rate against a compile-time constant, so changing the driver's rate
 aborts every cpal app.
 
+**`Drop`'s bound on soundd is built from copies the same way.** A dropped
+`Stream` waits for soundd to close its signal pipe for at most soundd's 5 ms
+fade, in whole periods, plus the 8 periods of the stream's ring: 1280 frames at
+44100 Hz (`RELEASE_WITHIN`). Past it, `Drop` refuses by name and returns. The
+fade (`toyos_mixer::ramp_frames`) and the ring depth (soundd's `slot_count`, see
+`issues/audio/client-ring-depth-is-the-devices-pipeline-depth.md`) are copies:
+`StreamOpenResponse.slot_count` reaches `AudioStream::open` and stays private,
+and no message carries the fade. If soundd's fade grows or a device's pipeline
+deepens, the bound shrinks under what soundd needs, and a healthy soundd is
+refused. That part goes when `AudioStream` says the ring depth and the fade and
+the host derives `RELEASE_WITHIN` from them, which changes `toyos/src` and the
+audio protocol.
+
 Deferred to the quiet-tree window, not neglected: editing that fork needs
 `.cargo/config.toml` path overrides, which redirect cpal for **every** agent in
 the tree. Same scheduling constraint as the fork lint audit.
diff --git a/issues/audio/hda-client-stall-reads-one-resume-where-its-judge-wants-two.md b/issues/audio/hda-client-stall-reads-one-resume-where-its-judge-wants-two.md
index 01804c4d582..61070a4c295 100644
--- a/issues/audio/hda-client-stall-reads-one-resume-where-its-judge-wants-two.md
+++ b/issues/audio/hda-client-stall-reads-one-resume-where-its-judge-wants-two.md
@@ -13,7 +13,6 @@ FAIL hda_client_stall: soundd resumed 0 time(s) — the second stream did not fi
 ```
 
 The job itself exits 0 and prints `stalled 8 then 2 times, soundd survived`.
-Its cause is not measured; whether the judge or soundd is wrong is open.
 
 ## Measured
 
@@ -44,6 +43,40 @@ The `testcases` boot's log, from the job's spawn to its end, in order:
   the previous client's removal at `6.275` and its open at `6.333`, so
   `client_stall_on_metal`'s `resumes < 2` reds on that span too.
 
+## Measured once a job's stream is gone before the job exits
+
+The `testcases` boot of the orchestrator's T14 `--metal hda_tone` run at
+`1621eb5f0` (#641), from the tone's removal to the stall's end, in order:
+
+```
+{… 5.670 soundd} soundd: client 0 removed (closed)
+{… 5.670 soundd} soundd: wakes=645 … clients=0 …
+[… 5.670 cpu4] exit: test_rs_audio_tone pid=11 code=0 cpu=2ms
+[… 5.672 cpu7] spawn: /system/bin/test_rs_hda_client_stall pid=12 …
+{… 5.673 tid=1 soundd} soundd: opening stream: 44100Hz 2ch fmt=0
+{… 5.673 soundd} soundd: client 0 connected (id=1)
+{… 7.830 soundd} soundd: client 1 removed (closed)
+{… 7.830 soundd} soundd: wakes=79 … clients=0 …
+{… 7.854 soundd} soundd: suspended
+{… 8.130 tid=1 soundd} soundd: opening stream: 44100Hz 2ch fmt=0
+{… 8.131 soundd} soundd: client 0 connected (id=2)
+{… 8.131 soundd} soundd: resumed
+{… 9.040 soundd} soundd: client 2 removed (closed)
+{… 9.040 soundd} soundd: wakes=465 … clients=0 …
+{… 9.063 soundd} soundd: suspended
+```
+
+- The tone's stream is removed, and its session flushed, before its job
+  exits; the stall's first stream opens 3 ms after that exit.
+- soundd suspends 20 to 25 ms after the last removal: `7.830`→`7.854` and
+  `9.040`→`9.063` here, `8.565`→`8.585` and `9.755`→`9.780` above.
+- So the first stream opens on a soundd that has not suspended, which is not
+  the premise `client_stall_on_metal` asks of it. The judge reads this log as:
+
+```
+FAIL hda_client_stall: soundd resumed 1 time(s) — the second stream did not find a suspended daemon, so nothing here tests a resume:
+```
+
 ## Exit condition
 
 `hda_client_stall` PASS on the orchestrator's T14 run of the head that lands
diff --git a/issues/audio/hda-tone-reads-underruns-on-the-t14-where-its-judge-wants-none.md b/issues/audio/hda-tone-reads-underruns-on-the-t14-where-its-judge-wants-none.md
deleted file mode 100644
index 662d835b131..00000000000
--- a/issues/audio/hda-tone-reads-underruns-on-the-t14-where-its-judge-wants-none.md
+++ /dev/null
@@ -1,50 +0,0 @@
----
-status: open
-kind: defect
-opened: 2026-09-29
----
-
-# `hda_tone` reads underruns on the T14 where its judge wants none
-
-The T14 run of `wt/toyos-metaljudges` at `f5c80264f` reds the row with:
-
-```
-FAIL hda_tone: soundd filled 104 period(s) the tone client had not covered, on a client that keeps its ring full:
-```
-
-The job itself exits 0 and prints `tone done`. Its cause is not measured;
-whether the judge or soundd is wrong is open.
-
-The T14 run of `main` at `7e151819` reddened the row earlier, on `the
-testcases's log carried no kernel output at all`.
-
-## Measured
-
-The `testcases` boot's log over the window the judge printed, selected lines in
-order:
-
-```
-{… 3.021 tid=1 soundd} soundd: opening stream: 44100Hz 2ch fmt=0
-{… 3.021 soundd} soundd: client 0 connected (id=0)
-{… 3.021 soundd} soundd: resumed
-{… 5.024 soundd} soundd: wakes=984 completions=689 submitted=697 underruns=0 drains=0 … clients=1 …
-[… 6.252 cpu0 tid=1] exit: test_rs_audio_tone tid=1 code=0 cpu=12ms (after 48 like it suppressed)
-{… 6.252 pid=8 test-runner} tone done
-{… 6.252 test-runner} ===TEST_END test_rs_audio_tone exit=0===
-{… 6.252 test-runner} ===TEST_START test_rs_hda_client_stall===
-[… 6.253 cpu7] spawn: /system/bin/test_rs_hda_client_stall pid=9 …
-{… 6.254 tid=1 soundd} soundd: opening stream: 44100Hz 2ch fmt=0
-{… 6.254 soundd} soundd: client 1 connected (id=1)
-{… 6.258 soundd} soundd: client 0 removed (closed)
-{… 7.024 soundd} soundd: wakes=989 completions=688 submitted=688 underruns=39 drains=0 … clients=1 …
-{… 8.412 soundd} soundd: client 1 removed (closed)
-{… 8.418 soundd} soundd: wakes=741 completions=479 submitted=479 underruns=65 drains=0 … clients=0 …
-```
-
-The printed window carries three stats lines, with `underruns=0`, `underruns=39`
-and `underruns=65`, which sum to the 104 the row names.
-
-## Exit condition
-
-`hda_tone` PASS on the orchestrator's T14 run of the head that lands the fix,
-and this file is deleted.
diff --git a/tests/checks/audio.rs b/tests/checks/audio.rs
index 2bfc573c6f7..df340713435 100644
--- a/tests/checks/audio.rs
+++ b/tests/checks/audio.rs
@@ -48,6 +48,50 @@ pub fn judges_verdict() -> Result<(), String> {
         &format!("{}{{0.600 soundd}} {NULL_SINK}\n{next}", tone(stats(0, 0, 0))),
         false,
     )?;
+    // The next job's stream connected before soundd let the tone's go, so the
+    // tone's last window is both streams' whatever it counted.
+    judged(
+        "a tone another job's stream joined",
+        tone_on_metal,
+        &format!(
+            "{configured}{}{{1.000 soundd}} soundd: client 0 connected (id=1)\n{}{next}\
+             {{3.000 soundd}} soundd: client 1 connected (id=2)\n\
+             {{3.000 soundd}} soundd: client 1 removed (closed)\n{}\
+             {{4.000 soundd}} soundd: client 2 removed (closed)\n{}",
+            spawn("test_rs_audio_tone"),
+            stats(0, 1, 0),
+            stats(0, 1, 0),
+            stats(0, 0, 0),
+        ),
+        false,
+    )?;
+    judged(
+        "a tone whose window ended before its stream connected",
+        tone_on_metal,
+        &format!(
+            "{configured}{}{{0.900 soundd}} soundd: client 0 removed (closed)\n{}{}{next}",
+            spawn("test_rs_audio_tone"),
+            stats(0, 0, 0),
+            session(stats(0, 1, 0), "closed", stats(0, 0, 0))
+        ),
+        false,
+    )?;
+    // Another job's stream, held since before the spawn, is still held when the
+    // tone's connects: one connect in the window, and two removals.
+    judged(
+        "a tone beside a stream soundd held at its spawn",
+        tone_on_metal,
+        &format!(
+            "{configured}{{0.900 soundd}} soundd: client 0 connected (id=0)\n{}\
+             {{1.000 soundd}} soundd: client 1 connected (id=1)\n{}\
+             {{2.500 soundd}} soundd: client 0 removed (closed)\n\
+             {{3.000 soundd}} soundd: client 1 removed (closed)\n{}{next}",
+            spawn("test_rs_audio_tone"),
+            stats(0, 2, 0),
+            stats(0, 0, 0),
+        ),
+        false,
+    )?;
 
     let stall = |second: String, rest: &str| {
         format!(
diff --git a/tests/common/audio.rs b/tests/common/audio.rs
index 5c3f9601bf8..ec089233663 100644
--- a/tests/common/audio.rs
+++ b/tests/common/audio.rs
@@ -10,6 +10,10 @@ use super::serial::Serial;
 /// that carries `clients=0`, which soundd writes after the removal — and not at
 /// the next job's spawn, which can land before it. A job that plays nothing
 /// (`sessions` of 0) ends at the next test binary's spawn.
+///
+/// Sessions are refused unless each is one stream: soundd counts one window
+/// across every client it holds, so a session another job's stream shared has
+/// no count that is the job's alone.
 fn job_window<'a>(log: &'a str, job: &str, sessions: usize) -> Result<&'a str, String> {
     let head = format!("spawn: /system/bin/{job} ");
     let at = log.find(&head).ok_or_else(|| format!("no `{head}` record: {job} never ran"))?;
@@ -32,7 +36,21 @@ fn job_window<'a>(log: &'a str, job: &str, sessions: usize) -> Result<&'a str, S
             })?;
         end = rest[flushed..].find('\n').map_or(rest.len(), |nl| flushed + nl + 1);
     }
-    Ok(&rest[..end])
+    let window = &rest[..end];
+    let said = |what: &str| {
+        window.lines().filter(|l| l.contains("soundd: client ") && l.contains(what)).count()
+    };
+    // A removal counts too: a stream soundd held before the spawn connected
+    // outside the window and leaves inside it.
+    let (streams, removed) = (said(" connected (id="), said(" removed ("));
+    if streams != sessions || removed != sessions {
+        return Err(format!(
+            "soundd connected {streams} and removed {removed} stream(s) in {job}'s {sessions} \
+             session(s): another job's stream shared soundd with {job}'s, and no count in the \
+             window is {job}'s alone:\n{window}"
+        ));
+    }
+    Ok(window)
 }
 
 /// What soundd's flush on its last client leaving carries, and no other stats
diff --git a/tests/toyos-rust-tests/Cargo.lock b/tests/toyos-rust-tests/Cargo.lock
index 5879429cd2b..a7acd1875f0 100644
--- a/tests/toyos-rust-tests/Cargo.lock
+++ b/tests/toyos-rust-tests/Cargo.lock
@@ -337,7 +337,7 @@ dependencies = [
 [[package]]
 name = "cpal"
 version = "0.18.0"
-source = "git+https://github.com/ToyOSOrg/cpal?branch=toyos-0.18.0#7e9775d5dc50b0da933fb947c806bd420ff6e85d"
+source = "git+https://github.com/ToyOSOrg/cpal?branch=toyos-0.18.0#29180f7b5a524e6709d30c010e7e0280cd82ccda"
 dependencies = [
  "alsa",
  "block2 0.6.2",
diff --git a/tests/toyos-rust-tests/src/bin/cpal_drop_unreleased.rs b/tests/toyos-rust-tests/src/bin/cpal_drop_unreleased.rs
new file mode 100644
index 00000000000..092814e2d0c
--- /dev/null
+++ b/tests/toyos-rust-tests/src/bin/cpal_drop_unreleased.rs
@@ -0,0 +1,146 @@
+//! cpal's ToyOS host, dropped while its stream's server never lets go of it.
+//!
+//! This binary is the stream's server: it answers the open as soundd does, and
+//! then holds the signal pipe open without writing it until the client's
+//! `Drop` has come back — a soundd whose mix loop has stopped. Its child, the
+//! same binary with `client`, reaches it as `soundd`, builds a stream through
+//! cpal and drops it unplayed. The stream thread sends the close and waits on
+//! the pipe; `Drop` has to come back with the refusal by name through the error
+//! callback rather than wait for good. One signal then has to end the stream
+//! thread while its process lives, so the stream's connection closes as it
+//! would for soundd.
+//!
+//! No sound is played and soundd is not involved.
+
+use std::io::{BufRead, BufReader, Read};
+use std::os::toyos::process::CommandExt;
+use std::process::{Command, Stdio};
+use std::sync::mpsc;
+
+use cpal::traits::{DeviceTrait, HostTrait};
+use toyos::audio::{
+    StreamOpenRequest, StreamOpenResponse, MSG_STREAM_CLOSE, MSG_STREAM_OPEN, MSG_STREAM_OPENED,
+};
+use toyos::ipc::IpcError;
+use toyos::shm::SharedMemory;
+use toyos::{namespace, port};
+use toyos_abi::audio::AudioSlotHeader;
+use toyos_abi::syscall::SVC_LABEL;
+
+const SELF: &str = "/system/bin/test_rs_cpal_drop_unreleased";
+
+/// cpal's ToyOS host's words for a soundd that did not let go.
+const REFUSAL: &str = "soundd did not let go of the closed stream within ";
+
+/// What soundd answers a 44100 Hz stereo open with, which is the one stream
+/// cpal's ToyOS host opens.
+const OPENED: StreamOpenResponse = StreamOpenResponse {
+    client_period_frames: 128,
+    client_period_bytes: 512,
+    device_sample_rate: 44_100,
+    device_channels: 2,
+    slot_count: 8,
+};
+
+fn main() {
+    match std::env::args().nth(1).as_deref() {
+        None => serve(),
+        Some("client") => client(),
+        Some(other) => panic!("no role {other:?}"),
+    }
+}
+
+fn serve() {
+    let (acceptor, connector) = port::create().expect("a port");
+    let names = namespace::build()
+        .add("soundd", &connector)
+        .finish()
+        .expect("a namespace naming this binary soundd");
+    let mut child = Command::new(SELF)
+        .arg("client")
+        .endow(SVC_LABEL, names.into_raw().0)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()
+        .expect("spawn the client");
+
+    let conn = acceptor.accept().expect("the client's connection");
+    let (kind, _): (u32, StreamOpenRequest) = conn.recv().expect("the client's open");
+    assert_eq!(kind, MSG_STREAM_OPEN, "the client's first frame is not an open");
+    let ring = SharedMemory::create(
+        AudioSlotHeader::SIZE + OPENED.slot_count as usize * OPENED.client_period_bytes as usize,
+    )
+    .expect("a ring");
+    let (signal_read, signal_write) = toyos::pipe_pair().expect("a signal pipe");
+    conn.send_with_handles(
+        &[ring.share().expect("the ring to share"), signal_read.into_raw()],
+        MSG_STREAM_OPENED,
+        &OPENED,
+    )
+    .expect("the open answered");
+
+    let close = conn.recv_header().expect("the client's close");
+    assert_eq!(close.msg_type, MSG_STREAM_CLOSE, "the dropped stream did not close");
+
+    // The write end is held until the client has gone, so nothing but its
+    // own deadline can end its wait. The client says the refusal once `Drop`
+    // has returned with it.
+    let mut said = String::new();
+    BufReader::new(child.stdout.take().expect("the client's stdout"))
+        .read_line(&mut said)
+        .expect("the client's line");
+    assert!(said.starts_with("client: "), "the client said {said:?} before its drop came back");
+    print!("{said}");
+
+    signal_write.write(&[1]).expect("a signal to the stream thread");
+    match conn.recv_header() {
+        Err(IpcError::Disconnected) => {}
+        other => panic!(
+            "the stream's connection gave {:?} after its close, not its end",
+            other.map(|h| h.msg_type)
+        ),
+    }
+    // The client exits once its stdin closes, so the connection's end above
+    // was the stream thread's.
+    drop(child.stdin.take());
+    let status = child.wait().expect("wait for the client");
+    drop(signal_write);
+    assert!(status.success(), "the client exited {status:?}");
+    println!(
+        "cpal's drop came back while its server held the signal pipe, and the next signal \
+         ended its stream thread"
+    );
+}
+
+fn client() {
+    let device = cpal::default_host()
+        .default_output_device()
+        .expect("the ToyOS host's output");
+    let config = device.default_output_config().expect("its config");
+    let (said, heard) = mpsc::channel();
+    let stream = device
+        .build_output_stream(
+            config.into(),
+            |_: &mut [i16], _: &cpal::OutputCallbackInfo| {
+                unreachable!("a stream never played is never asked for audio")
+            },
+            move |error: cpal::Error| said.send(error).expect("main hears every error"),
+            None,
+        )
+        .expect("the open answered");
+    drop(stream);
+
+    let errors: Vec<cpal::Error> = heard.try_iter().collect();
+    assert!(
+        matches!(
+            errors.as_slice(),
+            [refused] if refused.kind() == cpal::ErrorKind::HostUnavailable
+                && refused.to_string().starts_with(REFUSAL)
+        ),
+        "the drop came back with {errors:?}, not the refusal"
+    );
+    println!("client: {}", errors[0]);
+
+    let mut rest = Vec::new();
+    std::io::stdin().read_to_end(&mut rest).expect("the server's end of stdin");
+}
diff --git a/tests/toyos-rust-tests/src/tone.rs b/tests/toyos-rust-tests/src/tone.rs
index 72e0e5f7e38..12088219b80 100644
--- a/tests/toyos-rust-tests/src/tone.rs
+++ b/tests/toyos-rust-tests/src/tone.rs
@@ -27,6 +27,8 @@ pub fn play_tone() {
     let done = Arc::new(AtomicBool::new(false));
     let done2 = done.clone();
     let position = Arc::new(AtomicU64::new(0));
+    let failed = Arc::new(AtomicBool::new(false));
+    let failed2 = failed.clone();
 
     let stream = device
         .build_output_stream(
@@ -48,7 +50,10 @@ pub fn play_tone() {
                     done2.store(true, Ordering::Relaxed);
                 }
             },
-            |err| eprintln!("audio error: {err}"),
+            move |err| {
+                eprintln!("audio error: {err}");
+                failed2.store(true, Ordering::Relaxed);
+            },
             None,
         )
         .expect("failed to build audio stream");
@@ -61,4 +66,7 @@ pub fn play_tone() {
 
     // Let the tail of the tone drain through soundd and the device.
     std::thread::sleep(std::time::Duration::from_millis(200));
+
+    drop(stream);
+    assert!(!failed.load(Ordering::Relaxed), "the tone's stream reported an error, printed above");
 }
diff --git a/userland/Cargo.lock b/userland/Cargo.lock
index 600a2d3b028..5489d455e17 100644
--- a/userland/Cargo.lock
+++ b/userland/Cargo.lock
@@ -605,7 +605,7 @@ dependencies = [
 [[package]]
 name = "cpal"
 version = "0.18.0"
-source = "git+https://github.com/ToyOSOrg/cpal?branch=toyos-0.18.0#7e9775d5dc50b0da933fb947c806bd420ff6e85d"
+source = "git+https://github.com/ToyOSOrg/cpal?branch=toyos-0.18.0#29180f7b5a524e6709d30c010e7e0280cd82ccda"
 dependencies = [
  "alsa",
  "block2 0.6.2",