fix(audio): close the teardown orphan race by wiring in the ledger

Teardown used to `event_task.abort()` and then read three `Option<u32>`s.
The task's work was a synchronous `pactl` call with no await point, so the
abort could not land until the load had already returned: teardown saw
`None`, unloaded the sink, and the task then stored the new module's id into
a mutex nobody would read again. An orphan loopback, pointing at a sink that
no longer existed.

Three changes close it:

- Loads and unloads are `tokio::process::Command` with `kill_on_drop` and a
  bound, so cancellation is expressible at all. They are deliberately not
  `select!`ed against a cancel signal — dropping a completed load's index on
  the floor is the defect, not the fix. Cancellation happens by dropping the
  future, and the permit's `Drop` turns that into a question.
- `Routing::shutdown` is async and *awaits* the event task through
  `&mut JoinHandle`, falling back to abort-then-await. Dropping the handle
  would detach the task, which is how a load could still land after teardown
  believed it had finished. It then runs two reconcile-then-unload rounds:
  one round can raise exactly one new question, and a second settles it.
- `Drop` stays as the narrower synchronous backstop for the paths that never
  reach `shutdown`. It cannot await or reconcile, so when the ledger is left
  unexplained it says so and names `--repair`.

A load whose outcome cannot be observed is now distinguished from one the
server refused: a clean non-zero `pactl` exit abandons the permit (nothing
was created), while a signal death, a timeout, an unreadable index or
`PA_INVALID_INDEX` all leave it unsettled for reconciliation.

Two live gates, both A/B against the real module table: teardown leaves it
byte-identical with both modules carrying owner tokens, and a load cancelled
mid-flight is reconciled rather than orphaned. The second asserts the slot is
pending *before* reconciling, so it cannot pass by aborting before the load
ever began. Both mutate global state, so they need `--test-threads=1` —
running them in parallel makes each see the other's modules, which is how the
first run failed.

273 tests, clippy clean under `-D warnings`, `--doctor` all checks pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/host/audio.rs

@@ -35,26 +35,45 @@ use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::process::Command;
 use std::rc::Rc;
-use std::sync::{Arc, Mutex};
+use std::sync::Arc;
 use std::thread::JoinHandle;
+use std::time::Duration;
 
 use crate::cli::HostOpts;
-use crate::repair::plan::{self as repair_plan, Shape};
+use crate::host::ledger::{self, LedgerError, ModuleLedger, UnloadOutcome};
+use crate::repair::plan::{self as repair_plan, Fingerprint, Shape};
+
+/// How long a single `pactl load-module` / `unload-module` may take.
+///
+/// A bound, not a calibration: a local Pulse socket answers in milliseconds, and
+/// this exists only so a wedged server cannot hang teardown forever. It is
+/// deliberately generous because exceeding it is no longer destructive — the
+/// ledger records the attempt, and reconciliation finds whatever the server
+/// actually did.
+const PACTL_BUDGET: Duration = Duration::from_secs(5);
+
+/// How many reconcile-then-unload rounds teardown runs.
+///
+/// Two, because one round can create exactly one new question: an ambiguous load
+/// resolves to a module that then needs unloading, and an uncertain unload
+/// resolves to a module that is either gone or still there. A second round
+/// settles either. Anything still unresolved after that is left to `--repair`
+/// rather than looped over.
+const TEARDOWN_ROUNDS: usize = 2;
 
 /// Owns the pactl-loaded modules plus, when filtering is active, the
 /// libpipewire stream-router thread. Drop unloads modules as a backstop;
-/// prefer [`Routing::shutdown`] explicitly so failures get logged.
+/// prefer [`Routing::shutdown`] explicitly, which is the only path that can
+/// reconcile a load whose outcome was never observed.
 pub struct Routing {
-    sink_module: Option<u32>,
+    /// Every module this host has loaded, is loading, or must ask the server
-    /// Shared with the event task so it can `take()` and unload on the
+    /// about. Shared with the event task, which loads and unloads the two
-    /// first successful route. `Routing::shutdown` unloads whatever
+    /// loopbacks as the routed app comes and goes.
-    /// remains.
+    ///
-    loopback_module: Arc<Mutex<Option<u32>>>,
+    /// This replaced three `Option<u32>`s. The reason is in [`crate::host::ledger`]:
-    /// The `null-sink.monitor → @DEFAULT_SINK@` loopback that lets the sharer
+    /// an `Option` cannot say "a load is in flight", so a cancelled load looked
-    /// hear the routed app. Shared with the event task, which loads it on the
+    /// exactly like no load at all and its module was left behind.
-    /// first routed stream and unloads it when the app stops. `None` outside
+    ledger: Arc<ModuleLedger>,
-    /// app mode and whenever no app is currently routed.
-    local_monitor_module: Arc<Mutex<Option<u32>>>,
     sink_name: String,
     stream_router: Option<StreamRouter>,
     event_task: Option<tokio::task::JoinHandle<()>>,
@@ -66,13 +85,17 @@ impl Routing {
     pub async fn start(opts: &HostOpts) -> Result<Self> {
         let pid = std::process::id();
         let sink_name = repair_plan::sink_name_for(pid);
+        let ledger = ModuleLedger::new();
 
         // Every module this host loads carries an ownership token, minted per
         // load, so `--repair` can tell whose pid the name refers to instead of
         // assuming the number means the same thing everywhere. Without it a repair
         // run in another pid namespace can unload a live host's audio; see
-        // `repair::plan::OwnerToken`.
+        // `repair::plan::OwnerToken`. That same per-load nonce is what lets
-        let sink_module = load_module(Shape::LegacyCaptureSink, pid)
+        // reconciliation identify a module whose load was interrupted before its
+        // index was ever read.
+        load_module(&ledger, Shape::LegacyCaptureSink, pid)
+            .await
             .context("failed to load module-null-sink")?;
 
         // In strict per-app mode we never mirror the default sink: the viewer
@@ -84,29 +107,20 @@ impl Routing {
         // 20ms loopback latency keeps the mirrored audio tight; pactl's
         // default of 200ms is enough to be perceptible.
         let strict_app = opts.app.is_some() && opts.strict_audio;
-        let loopback_module = if strict_app {
+        if !strict_app {
-            None
+            load_module(&ledger, Shape::LoopbackIntoCapture, pid)
-        } else {
+                .await
-            Some(
+                .context("failed to load module-loopback (null-sink cleaned up on Drop)")?;
-                load_module(Shape::LoopbackIntoCapture, pid)
+        }
-                    .context("failed to load module-loopback (null-sink cleaned up on Drop)")?,
-            )
-        };
 
         tracing::info!(
-            sink_module,
-            ?loopback_module,
             strict_app,
             %sink_name,
             "audio routing: null-sink ready (loopback skipped in strict app mode)"
         );
 
-        let loopback_arc = Arc::new(Mutex::new(loopback_module));
-        let local_monitor_arc = Arc::new(Mutex::new(None));
         let mut routing = Self {
-            sink_module: Some(sink_module),
+            ledger: Arc::clone(&ledger),
-            loopback_module: Arc::clone(&loopback_arc),
-            local_monitor_module: Arc::clone(&local_monitor_arc),
             sink_name: sink_name.clone(),
             stream_router: None,
             event_task: None,
@@ -114,21 +128,17 @@ impl Routing {
 
         if let Some(app) = &opts.app {
             let (router, mut event_rx) = StreamRouter::spawn(app.clone(), sink_name.clone())?;
-            let loopback_for_task = Arc::clone(&loopback_arc);
+            let ledger_for_task = Arc::clone(&ledger);
-            let local_monitor_for_task = Arc::clone(&local_monitor_arc);
             let strict = opts.strict_audio;
             let event_task = tokio::spawn(async move {
                 use crate::common::output::{self, AppAudioState};
                 while let Some(ev) = event_rx.recv().await {
                     match ev {
                         Event::FirstRoutedStream => {
-                            let mid = loopback_for_task.lock().unwrap().take();
-                            if let Some(id) = mid {
                             tracing::info!(
                                 "audio routing: first stream routed → unloading default-sink loopback"
                             );
-                                unload_module(id);
+                            unload_module(&ledger_for_task, Shape::LoopbackIntoCapture).await;
-                            }
                             // Mirror the routed app back to the sharer's own
                             // speakers so they hear the content they're sharing.
                             // Loaded *after* the default-sink loopback is gone so
@@ -136,20 +146,7 @@ impl Routing {
                             // sourced from the null-sink monitor — the chosen app
                             // only, never the desktop/call — so it can't echo into
                             // the capture.
-                            if local_monitor_for_task.lock().unwrap().is_none() {
+                            ensure_loaded(&ledger_for_task, Shape::LoopbackOutOfCapture, pid).await;
-                                match load_module(Shape::LoopbackOutOfCapture, pid) {
-                                    Ok(id) => {
-                                        tracing::info!(
-                                            module = id,
-                                            "audio routing: local monitor loaded (sharer hears the shared app)"
-                                        );
-                                        *local_monitor_for_task.lock().unwrap() = Some(id);
-                                    }
-                                    Err(e) => tracing::warn!(
-                                        "audio routing: failed to load local monitor loopback: {e:#}"
-                                    ),
-                                }
-                            }
                             // Tell the front-end the chosen app's audio is live.
                             output::emit(output::Event::AppAudio {
                                 state: AppAudioState::Routed,
@@ -164,13 +161,7 @@ impl Routing {
                             // The shared app is gone, so its null-sink is silent:
                             // stop mirroring it to the sharer's speakers. Re-loads
                             // on the next FirstRoutedStream if the app resumes.
-                            if let Some(id) = local_monitor_for_task.lock().unwrap().take() {
+                            unload_module(&ledger_for_task, Shape::LoopbackOutOfCapture).await;
-                                tracing::info!(
-                                    module = id,
-                                    "audio routing: last routed stream gone → unloading local monitor"
-                                );
-                                unload_module(id);
-                            }
                             if strict {
                                 // Strict mode: do NOT restore the whole-desktop
                                 // loopback. Viewers hear silence until the app
@@ -183,23 +174,12 @@ impl Routing {
                             }
                             // Best-effort mode: restore the default-sink loopback
                             // so the viewer hears system audio again instead of
-                            // silence.
+                            // silence. Already loaded is not an error — the ledger
-                            if loopback_for_task.lock().unwrap().is_some() {
+                            // refuses the load and `ensure_loaded` says so quietly.
-                                continue;
-                            }
                             tracing::info!(
                                 "audio routing: last routed stream gone → restoring default-sink loopback"
                             );
-                            match load_module(Shape::LoopbackIntoCapture, pid) {
+                            ensure_loaded(&ledger_for_task, Shape::LoopbackIntoCapture, pid).await;
-                                Ok(id) => {
-                                    *loopback_for_task.lock().unwrap() = Some(id);
-                                }
-                                Err(e) => {
-                                    tracing::warn!(
-                                        "audio routing: failed to re-load loopback: {e:#}"
-                                    );
-                                }
-                            }
                         }
                     }
                 }
@@ -225,43 +205,91 @@ impl Routing {
         &self.sink_name
     }
 
-    /// Stop the stream router (if any), then unload loopback (if still
+    /// Stop the stream router and the event task, settle anything the ledger is
-    /// loaded), then unload the null-sink. Order matters: PipeWire can
+    /// unsure about, then unload every module in shape order — the loopbacks
-    /// leave zombie links if you destroy a sink with active inputs.
+    /// before the sink they reference, because PipeWire can leave zombie links if
+    /// a sink is destroyed with active inputs.
     ///
-    /// Every step is a `take()`, so this is idempotent — `Drop` calls it again
+    /// The event task is **awaited, not merely aborted**. Aborting and walking
-    /// as a backstop and the second run is a no-op.
+    /// away is what left orphans behind: the task's load is an await point now,
-    fn cleanup(&mut self) {
+    /// so dropping its future marks the slot ambiguous rather than losing the
+    /// module — but only a path that then reconciles can actually clean it up.
+    /// `Drop` cannot await, which is why it is the narrower backstop.
+    pub async fn shutdown(mut self) {
+        if let Some(router) = self.stream_router.take() {
+            // ⚠️ Still an unbounded join: a wedged PipeWire thread parks this
+            // task indefinitely. That is the pre-existing defect S3b exists for.
+            // Nothing here makes it worse, and the ledger is what will make
+            // bounding it safe when it lands.
+            router.shutdown();
+        }
+        if let Some(mut task) = self.event_task.take() {
+            // The router's exit drops the event senders, so the task normally
+            // ends by itself. Abort is the fallback, and it is awaited through
+            // `&mut JoinHandle` so the future is genuinely dropped — and with it
+            // any in-flight permit — before reconciliation reads the ledger.
+            // Dropping the handle instead would *detach* the task, which is how a
+            // load could still land after teardown believed it was finished.
+            if tokio::time::timeout(PACTL_BUDGET, &mut task).await.is_err() {
+                tracing::warn!(
+                    "audio routing: the event task did not finish within {PACTL_BUDGET:?}; \
+                     cancelling it"
+                );
+                task.abort();
+                let _ = task.await;
+            }
+        }
+
+        for _ in 0..TEARDOWN_ROUNDS {
+            if let Err(e) = ledger::reconcile_pending(&self.ledger).await {
+                tracing::warn!("audio routing: could not reconcile the module ledger: {e:#}");
+            }
+            let loaded = self.ledger.loaded();
+            if loaded.is_empty() {
+                break;
+            }
+            for fp in loaded {
+                unload_module(&self.ledger, fp.shape).await;
+            }
+        }
+
+        if !self.ledger.is_settled() {
+            tracing::warn!(
+                "audio routing: some audio modules could not be accounted for; \
+                 `pixelpass --repair` will clean up anything left behind"
+            );
+        }
+    }
+}
+
+impl Drop for Routing {
+    /// Synchronous backstop for the paths that never reach [`Routing::shutdown`]
+    /// — an error on the way up, or a panic. It cannot await, so it can neither
+    /// wait for the event task nor reconcile; it unloads what the ledger can name
+    /// and says so plainly when something is left unexplained.
+    ///
+    /// After a completed `shutdown` the ledger holds nothing and this does nothing.
+    fn drop(&mut self) {
         if let Some(router) = self.stream_router.take() {
             router.shutdown();
         }
         if let Some(task) = self.event_task.take() {
             task.abort();
         }
-        if let Some(id) = self.loopback_module.lock().unwrap().take() {
+        for fp in self.ledger.loaded() {
-            unload_module(id);
+            if self.ledger.begin_unload(fp.shape).is_none() {
+                continue;
             }
-        // Unload the local monitor before the null-sink it reads from, so the
+            let outcome = blocking_unload(fp.id);
-        // sink has no active loopback reader when it's destroyed.
+            self.ledger.finish_unload(fp.shape, outcome);
-        if let Some(id) = self.local_monitor_module.lock().unwrap().take() {
-            unload_module(id);
         }
-        if let Some(id) = self.sink_module.take() {
+        if !self.ledger.is_settled() {
-            unload_module(id);
+            tracing::warn!(
+                "audio routing: torn down without settling the module ledger; \
+                 run `pixelpass --repair` to clean up anything left behind"
+            );
         }
     }
-
-    /// Consume the routing and tear it all down now. `Drop` is the backstop;
-    /// the real work lives in [`cleanup`](Self::cleanup).
-    pub fn shutdown(mut self) {
-        self.cleanup();
-    }
-}
-
-impl Drop for Routing {
-    fn drop(&mut self) {
-        self.cleanup();
-    }
 }
 
 /// The app-audio state to announce at capture start, if any. Only strict per-app
@@ -374,54 +402,143 @@ fn owner_token(pid: u32) -> Result<repair_plan::OwnerToken> {
 /// `--repair`'s exact-form matcher and this loader are one source of truth. A
 /// latency or argument change that moved only one of them would leave repair
 /// silently unable to recognise the modules this build loads.
-fn load_module(shape: Shape, pid: u32) -> Result<u32> {
+async fn load_module(ledger: &Arc<ModuleLedger>, shape: Shape, pid: u32) -> Result<Fingerprint> {
     let owner = owner_token(pid).context("could not build an audio ownership token")?;
-    let output = Command::new("pactl")
+    let permit = ledger
-        .arg("load-module")
+        .begin_load(shape, pid, owner.clone())
+        .map_err(anyhow::Error::new)
+        .with_context(|| format!("cannot load the {} module", shape.label()))?;
+
+    let mut cmd = tokio::process::Command::new("pactl");
+    cmd.arg("load-module")
         .arg(shape.module_name())
         .args(shape.render_args(pid, Some(&owner)))
-        .output()
+        .kill_on_drop(true);
-        .context("failed to run pactl load-module")?;
+
-    if !output.status.success() {
+    // Deliberately **not** `select!`ed against a cancellation signal: a completed
-        bail!(
+    // load whose index was then dropped on the floor is precisely the defect the
-            "pactl load-module failed: {}",
+    // ledger exists to prevent. Cancellation here happens by dropping this whole
-            String::from_utf8_lossy(&output.stderr).trim()
+    // future, and the permit's `Drop` turns that into a question reconciliation
-        );
+    // can answer, rather than into silence.
+    let output = match tokio::time::timeout(PACTL_BUDGET, cmd.output()).await {
+        Ok(Ok(output)) => output,
+        Ok(Err(e)) => {
+            // Spawning or reading failed. Whether the server was ever reached is
+            // not knowable from here, so leave the permit unsettled: an
+            // unnecessary reconcile costs one listing, a missed one costs an
+            // orphan.
+            drop(permit);
+            return Err(e).context("failed to run pactl load-module");
         }
-    let id_str = String::from_utf8(output.stdout)
+        Err(_) => {
-        .context("pactl returned non-UTF-8")?
+            drop(permit);
-        .trim()
+            bail!("pactl load-module did not finish within {PACTL_BUDGET:?}");
-        .to_string();
+        }
+    };
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();
+        if output.status.code().is_some() {
+            // pactl exited of its own accord, having reported the server's
+            // refusal: nothing was created, so there is nothing to reconcile.
+            permit.abandon();
+        } else {
+            // Killed by a signal, which may have arrived *after* the server
+            // created the module.
+            drop(permit);
+        }
+        bail!("pactl load-module failed: {stderr}");
+    }
+
+    let id_str = String::from_utf8_lossy(&output.stdout).trim().to_string();
     // Genuinely 32-bit, unlike `object.serial`: this is a PulseAudio module
     // index (`pa_module.index`, `uint32_t`), which `pactl unload-module` takes
     // back verbatim. Do not widen it.
-    id_str
+    let Ok(index) = id_str.parse::<u32>() else {
-        .parse::<u32>()
+        // The load may well have succeeded — we simply cannot say which module it
-        .with_context(|| format!("pactl returned unexpected module ID: {id_str:?}"))
+        // produced, which is exactly what reconciliation is for.
+        drop(permit);
+        bail!("pactl returned unexpected module ID: {id_str:?}");
+    };
+    let fp = permit.commit(index)?;
+    tracing::info!(
+        module = fp.id,
+        shape = shape.label(),
+        "audio routing: loaded pactl module"
+    );
+    Ok(fp)
 }
 
-fn unload_module(id: u32) {
+/// Load `shape` unless the slot already holds it.
-    let result = Command::new("pactl")
+///
+/// A busy slot is not a failure on the oscillation path: `FirstRoutedStream` and
+/// `LastRoutedStreamGone` can both ask for a module that is already in the state
+/// they want, and the ledger is what decides that rather than a separate flag.
+async fn ensure_loaded(ledger: &Arc<ModuleLedger>, shape: Shape, pid: u32) {
+    let Err(e) = load_module(ledger, shape, pid).await else {
+        return;
+    };
+    match e.downcast_ref::<LedgerError>() {
+        Some(LedgerError::Busy { state, .. }) => tracing::debug!(
+            shape = shape.label(),
+            state,
+            "audio routing: nothing to load, the slot is already occupied"
+        ),
+        _ => tracing::warn!(
+            "audio routing: failed to load the {} module: {e:#}",
+            shape.label()
+        ),
+    }
+}
+
+/// Unload whatever the ledger holds for `shape`, and record how it went.
+///
+/// A no-op for a slot holding nothing. An outcome that cannot be confirmed is
+/// recorded as uncertain rather than assumed done, so the module keeps being
+/// named until the server is asked about it.
+async fn unload_module(ledger: &Arc<ModuleLedger>, shape: Shape) {
+    let Some(fp) = ledger.begin_unload(shape) else {
+        return;
+    };
+    let mut cmd = tokio::process::Command::new("pactl");
+    cmd.arg("unload-module")
+        .arg(fp.id.to_string())
+        .kill_on_drop(true);
+    let outcome = match tokio::time::timeout(PACTL_BUDGET, cmd.output()).await {
+        Ok(Ok(output)) if output.status.success() => {
+            tracing::info!(module = fp.id, "audio routing: unloaded pactl module");
+            UnloadOutcome::Confirmed
+        }
+        Ok(Ok(output)) => UnloadOutcome::Uncertain(format!(
+            "pactl unload-module exited {}: {}",
+            output.status,
+            String::from_utf8_lossy(&output.stderr).trim()
+        )),
+        Ok(Err(e)) => UnloadOutcome::Uncertain(format!("could not run pactl unload-module: {e}")),
+        Err(_) => {
+            UnloadOutcome::Uncertain(format!("pactl unload-module exceeded {PACTL_BUDGET:?}"))
+        }
+    };
+    ledger.finish_unload(shape, outcome);
+}
+
+/// The blocking unload [`Drop`] uses, since it has no runtime to await on.
+fn blocking_unload(id: u32) -> UnloadOutcome {
+    match Command::new("pactl")
         .arg("unload-module")
         .arg(id.to_string())
-        .output();
+        .output()
-    match result {
+    {
         Ok(output) if output.status.success() => {
             tracing::info!(module = id, "audio routing: unloaded pactl module");
+            UnloadOutcome::Confirmed
         }
-        Ok(output) => {
+        Ok(output) => UnloadOutcome::Uncertain(format!(
-            tracing::warn!(
+            "pactl unload-module exited {}: {}",
-                module = id,
+            output.status,
-                stderr = %String::from_utf8_lossy(&output.stderr).trim(),
+            String::from_utf8_lossy(&output.stderr).trim()
-                "audio routing: pactl unload-module exited non-zero"
+        )),
-            );
+        Err(e) => UnloadOutcome::Uncertain(format!("could not run pactl unload-module: {e}")),
-        }
-        Err(e) => {
-            tracing::warn!(
-                module = id,
-                "audio routing: failed to run pactl unload-module: {e}"
-            );
-        }
     }
 }
 
@@ -718,6 +835,130 @@ fn try_flush(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::repair::plan::{ModuleObservation, classify};
+
+    /// Whole-desktop routing: no app filter, so no PipeWire thread and no event
+    /// task — just the null-sink and its default-sink loopback.
+    fn whole_desktop_opts() -> HostOpts {
+        HostOpts {
+            window: false,
+            app: None,
+            strict_audio: false,
+            display_server: None,
+            quality: crate::cli::Quality::Auto,
+            bitrate: None,
+            framerate: None,
+            max_height: None,
+            no_hwencode: false,
+            max_viewers: None,
+            interactive: false,
+            relay: None,
+        }
+    }
+
+    /// The module table exactly as `--repair` observes it.
+    fn module_snapshot() -> Vec<(u32, String, String)> {
+        let mut session =
+            crate::repair::introspect::PulseSession::connect().expect("a local Pulse server");
+        session
+            .list_modules()
+            .expect("the server lists its modules")
+            .into_iter()
+            .map(|m| (m.id, m.name, m.args))
+            .collect()
+    }
+
+    /// A/B against the live graph: routing must leave the module table exactly
+    /// as it found it. The same shape as `--repair`'s field gate, because the
+    /// property is the same one — nothing of ours outlives the session.
+    #[tokio::test]
+    #[ignore = "loads real Pulse modules; run with --ignored --test-threads=1"]
+    async fn live_teardown_leaves_the_module_table_as_it_found_it() {
+        let before = module_snapshot();
+        let routing = Routing::start(&whole_desktop_opts())
+            .await
+            .expect("routing starts");
+
+        let during = module_snapshot();
+        let ours: Vec<_> = during
+            .iter()
+            .filter(|m| !before.iter().any(|b| b.0 == m.0))
+            .collect();
+        assert_eq!(
+            ours.len(),
+            2,
+            "the null-sink and its default-sink loopback must both be loaded"
+        );
+        for (id, name, args) in ours {
+            let fp = classify(&ModuleObservation::new(*id, name, args))
+                .expect("a module we loaded must match one of our canonical forms");
+            assert!(
+                fp.owner.is_some(),
+                "every module we load carries an owner token, or --repair cannot \
+                 attribute it to this host's pid namespace"
+            );
+        }
+
+        routing.shutdown().await;
+        assert_eq!(
+            module_snapshot(),
+            before,
+            "teardown must leave the module table byte-identical"
+        );
+    }
+
+    /// The orphan race, staged against a real server: a load cancelled while
+    /// `pactl` is in flight must still be findable and removable.
+    ///
+    /// Whether the server got as far as creating the module is genuinely racy,
+    /// and that is the point — the gate does not care which way it went, only
+    /// that the ledger can account for both. With the permit's `Drop` disarmed
+    /// and the module created, the final comparison fails.
+    #[tokio::test]
+    #[ignore = "loads real Pulse modules; run with --ignored --test-threads=1"]
+    async fn live_a_cancelled_load_is_reconciled_not_orphaned() {
+        let before = module_snapshot();
+        let ledger = ModuleLedger::new();
+        let pid = std::process::id();
+
+        let ledger_for_task = Arc::clone(&ledger);
+        let task = tokio::spawn(async move {
+            let _ = load_module(&ledger_for_task, Shape::LegacyCaptureSink, pid).await;
+        });
+        // Let the task run up to its first await — the spawned `pactl` — so the
+        // abort lands mid-flight rather than before the load ever started, which
+        // would make this gate vacuous.
+        tokio::task::yield_now().await;
+        task.abort();
+        let _ = task.await;
+
+        // Non-vacuity: the permit is taken *before* `pactl` is spawned, so a
+        // cancelled load must leave a question behind whichever side of the spawn
+        // the abort landed on. Without this the gate could pass while the abort
+        // fired before the load ever began, proving nothing.
+        assert_eq!(
+            ledger.pending().len(),
+            1,
+            "the cancelled load must have left exactly one question behind"
+        );
+
+        ledger::reconcile_pending(&ledger)
+            .await
+            .expect("the ledger reconciles against the server");
+        for fp in ledger.loaded() {
+            unload_module(&ledger, fp.shape).await;
+        }
+
+        assert!(
+            ledger.is_settled(),
+            "every slot must end in a state we can explain"
+        );
+        assert_eq!(
+            module_snapshot(),
+            before,
+            "a cancelled load must leave nothing behind"
+        );
+    }
 
     #[test]
     fn object_serial_parses_past_u32() {

src/host/ledger.rs

@@ -191,6 +191,13 @@ impl ModuleLedger {
     }
 
     /// The current state of one slot. Absent keys read as [`SlotState::Vacant`].
+    ///
+    /// Test-only: production code never needs to look a slot up, because every
+    /// decision that depends on one is made *by* the ledger — `begin_load`
+    /// refuses a busy slot and says which state refused, `begin_unload` returns
+    /// nothing for a slot holding nothing. An accessor callers could branch on
+    /// would invite exactly the check-then-act races the permit removes.
+    #[cfg(test)]
     pub fn state(&self, shape: Shape) -> SlotState {
         self.slots
             .lock()
@@ -200,10 +207,6 @@ impl ModuleLedger {
             .unwrap_or(SlotState::Vacant)
     }
 
-    fn set(&self, shape: Shape, state: SlotState) {
-        self.slots.lock().unwrap().insert(shape, state);
-    }
-
     /// Take permission to load `shape`, moving the slot to
     /// [`SlotState::Loading`].
     ///
@@ -372,14 +375,6 @@ pub struct LoadPermit {
 }
 
 impl LoadPermit {
-    pub fn shape(&self) -> Shape {
-        self.shape
-    }
-
-    pub fn token(&self) -> &OwnerToken {
-        &self.token
-    }
-
     /// Record that the server created the module at `index`.
     ///
     /// Fails on [`PA_INVALID_INDEX`], leaving the permit unsettled so that

src/host/pipeline.rs

@@ -47,7 +47,7 @@ impl CaptureHandle {
             let _ = child.start_kill();
         }
         if let Some(audio) = self.audio.take() {
-            audio.shutdown();
+            audio.shutdown().await;
         }
         if let Some(serve) = self.serve.take() {
             serve.shutdown().await;