Harden concurrency and resource lifecycle (#101)

.gitea/workflows/concurrency-audit.yml

@@ -0,0 +1,71 @@
+name: Concurrency and resource soak audit
+
+on:
+  push:
+    paths:
+      - ".gitea/workflows/concurrency-audit.yml"
+      - "ci/concurrency-thresholds.json"
+      - "tools/concurrency-audit/**"
+      - "docs/concurrency-hardening.md"
+      - "crates/libremetaverse/src/client_core.rs"
+      - "crates/libremetaverse/src/download_manager.rs"
+      - "crates/libremetaverse/src/appearance_manager.rs"
+      - "crates/libremetaverse/src/asset_manager.rs"
+      - "crates/libremetaverse/src/inventory_manager.rs"
+      - "crates/libremetaverse-voice-webrtc/**"
+      - "Cargo.toml"
+      - "Cargo.lock"
+  pull_request:
+    paths:
+      - ".gitea/workflows/concurrency-audit.yml"
+      - "ci/concurrency-thresholds.json"
+      - "tools/concurrency-audit/**"
+      - "docs/concurrency-hardening.md"
+      - "crates/libremetaverse/src/client_core.rs"
+      - "crates/libremetaverse/src/download_manager.rs"
+      - "crates/libremetaverse/src/appearance_manager.rs"
+      - "crates/libremetaverse/src/asset_manager.rs"
+      - "crates/libremetaverse/src/inventory_manager.rs"
+      - "crates/libremetaverse-voice-webrtc/**"
+      - "Cargo.toml"
+      - "Cargo.lock"
+  workflow_dispatch:
+
+env:
+  CARGO_BUILD_JOBS: 1
+  CARGO_INCREMENTAL: 0
+  CARGO_PROFILE_DEV_DEBUG: 0
+  CARGO_PROFILE_TEST_DEBUG: 0
+
+jobs:
+  soak:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+      - name: Install native voice prerequisite
+        run: |
+          sudo apt-get update
+          sudo apt-get install --yes libopus-dev pkg-config
+      - name: Check formatting and focused race regressions
+        run: |
+          cargo fmt --all -- --check
+          cargo test --locked -p libremetaverse --lib shutdown_does_not_hold_service_registry_lock_across_callbacks -j 1
+          cargo test --locked -p libremetaverse --lib event_registry_isolates_panics_and_releases_subscriptions -j 1
+          cargo test --locked -p libremetaverse --lib dispatch_isolates_panics_and_does_not_retain_dropped_handlers -j 1
+          cargo test --locked -p libremetaverse --test caps_http download_queue_applies_backpressure_and_cancellation_drains_every_job -j 1
+          cargo test --locked -p libremetaverse-voice-webrtc concurrent_provisioning_admits_one_session_without_leaking_the_loser -j 1
+      - name: Run bounded native soak
+        run: |
+          mkdir -p artifacts
+          cargo run --locked -p metacrate-concurrency-audit -j 1 -- \
+            --cycles 16 --evidence artifacts/concurrency-audit.json
+      - name: Upload sanitized resource evidence
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: concurrency-audit-evidence
+          path: artifacts/concurrency-audit.json
+          if-no-files-found: error

Cargo.lock

@@ -1777,6 +1777,19 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "metacrate-concurrency-audit"
+version = "0.0.1"
+dependencies = [
+ "libremetaverse",
+ "libremetaverse-types",
+ "libremetaverse-voice-webrtc",
+ "serde",
+ "serde_json",
+ "stats_alloc",
+ "tokio",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"

Cargo.toml

@@ -20,6 +20,7 @@ members = [
     "tests/compat",
     "tools/codegen",
     "tools/ci-matrix",
+    "tools/concurrency-audit",
 ]
 
 [workspace.package]

README.md

@@ -75,6 +75,9 @@ offline-build, cache, and redistribution details are in the
 The validated Linux/MSRV/Windows/macOS target and feature inventory, clean
 profile runner, native prerequisite evidence, and manual platform boundaries
 are documented in the [release CI matrix](docs/release-ci-matrix.md).
+Deterministic task, socket, file, subscription, cancellation, and allocation
+baselines are documented in the
+[concurrency hardening guide](docs/concurrency-hardening.md).
 
 An independent optional `rust-j2k` backend is planned but has not been
 implemented yet. There is deliberately no enablement command for it today;

ci/concurrency-thresholds.json

@@ -0,0 +1,8 @@
+{
+  "schema": 1,
+  "minimum_cycles": 4,
+  "maximum_cycles": 256,
+  "operations_per_cycle": 32,
+  "maximum_retained_bytes": 16777216,
+  "maximum_duration_seconds": 180
+}

ci/dependency-policy.json

@@ -27,7 +27,7 @@
     { "name": "sha1", "versions": ["0.10.7"], "purpose": "Legacy protocol hash compatibility", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`sha1`" },
     { "name": "sha2", "versions": ["0.11.0"], "purpose": "Manifest integrity and protocol hashing", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`sha2`" },
     { "name": "skia-safe", "versions": ["0.99.0"], "purpose": "Opt-in cross-platform Skia image decoding", "maintenance": "monitored-native", "transitive_cost": "high", "native": true, "rewrite_anchor": "`skia-safe`" },
-    { "name": "stats_alloc", "versions": ["0.1.10"], "purpose": "Allocation-budget compatibility tests", "maintenance": "stable", "transitive_cost": "low", "native": false, "rewrite_anchor": "`stats_alloc`" },
+    { "name": "stats_alloc", "versions": ["0.1.10"], "purpose": "Allocation-budget compatibility tests and concurrency leak audits", "maintenance": "stable", "transitive_cost": "low", "native": false, "rewrite_anchor": "`stats_alloc`" },
     { "name": "str0m", "versions": ["0.22.0"], "purpose": "Native Rust ICE, DTLS, SRTP, RTP, and SCTP WebRTC transport", "maintenance": "active", "transitive_cost": "high", "native": false, "rewrite_anchor": "`str0m`" },
     { "name": "syn", "versions": ["2.0.119"], "purpose": "Syntax validation for generated Rust sources", "maintenance": "active", "transitive_cost": "medium", "native": false, "rewrite_anchor": "`syn`" },
     { "name": "tar", "versions": ["0.4.46"], "purpose": "Bounded OAR and asset archive traversal", "maintenance": "active", "transitive_cost": "low", "native": false, "rewrite_anchor": "`tar`" },

ci/evidence/concurrency-audit.json

@@ -0,0 +1,64 @@
+{
+  "schema": 1,
+  "mode": "deterministic-offline",
+  "live_grid_used": false,
+  "cycles": 16,
+  "operations_per_cycle": 32,
+  "scenarios": [
+    "concurrent-client-shutdown",
+    "download-deduplication-and-cancellation",
+    "inventory-and-appearance-operations",
+    "event-subscription-release",
+    "file-handle-teardown",
+    "udp-reconnect-and-socket-release",
+    "webrtc-loopback-task-and-socket-teardown"
+  ],
+  "baseline": {
+    "client_tasks": 0,
+    "download_dispatchers": 0,
+    "active_downloads": 0,
+    "inventory_workers": 0,
+    "pending_inventory_operations": 0,
+    "voice_tasks": 0,
+    "signaling_tasks": 0,
+    "subscriptions": 0,
+    "open_files": 0,
+    "open_sockets": 0
+  },
+  "maximum_observed": {
+    "client_tasks": 1,
+    "download_dispatchers": 1,
+    "active_downloads": 258,
+    "inventory_workers": 1,
+    "pending_inventory_operations": 0,
+    "voice_tasks": 1,
+    "signaling_tasks": 1,
+    "subscriptions": 96,
+    "open_files": 1,
+    "open_sockets": 2
+  },
+  "after_shutdown": {
+    "client_tasks": 0,
+    "download_dispatchers": 0,
+    "active_downloads": 0,
+    "inventory_workers": 0,
+    "pending_inventory_operations": 0,
+    "voice_tasks": 0,
+    "signaling_tasks": 0,
+    "subscriptions": 0,
+    "open_files": 0,
+    "open_sockets": 0
+  },
+  "retained_bytes": 0,
+  "allocations_not_freed": 0,
+  "elapsed_milliseconds": 1099,
+  "thresholds": {
+    "schema": 1,
+    "minimum_cycles": 4,
+    "maximum_cycles": 256,
+    "operations_per_cycle": 32,
+    "maximum_retained_bytes": 16777216,
+    "maximum_duration_seconds": 180
+  },
+  "outcome": "pass"
+}

crates/libremetaverse-voice-webrtc/src/native.rs

@@ -20,7 +20,7 @@ use std::io::Cursor;
 use std::net::{IpAddr, Ipv4Addr, SocketAddr};
 use std::path::Path;
 use std::pin::Pin;
-use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 use str0m::change::{SdpAnswer, SdpOffer};
@@ -1426,6 +1426,7 @@ where
 /// Deterministic native WebRTC answerer used by CI and offline diagnostics.
 pub struct LoopbackSignaling {
     state: tokio::sync::Mutex<LoopbackState>,
+    provisioning: AtomicBool,
     active_tasks: Arc<AtomicUsize>,
     received_messages: Arc<Mutex<Vec<String>>>,
     peer_id: UUID,
@@ -1448,6 +1449,7 @@ impl LoopbackSignaling {
                 completed: false,
                 closed: false,
             }),
+            provisioning: AtomicBool::new(false),
             active_tasks: Arc::new(AtomicUsize::new(0)),
             received_messages: Arc::new(Mutex::new(Vec::new())),
             peer_id,
@@ -1481,10 +1483,21 @@ impl LoopbackSignaling {
 impl VoiceSignaling for LoopbackSignaling {
     fn provision(&self, request: ProvisionRequest) -> SignalFuture<'_, ProvisionResponse> {
         Box::pin(async move {
-            let mut state = self.state.lock().await;
-            if state.task.is_some() {
+            struct ProvisionGuard<'a>(&'a AtomicBool);
+            impl Drop for ProvisionGuard<'_> {
+                fn drop(&mut self) {
+                    self.0.store(false, Ordering::Release);
+                }
+            }
+
+            if self
+                .provisioning
+                .compare_exchange(false, true, Ordering::AcqRel, Ordering::Acquire)
+                .is_err()
+            {
                 return Err(WebRtcError::Signaling("duplicate provision request".into()));
             }
+            let _provisioning = ProvisionGuard(&self.provisioning);
             if request.jsep.kind != "offer"
                 || request.channel_type != "local"
                 || request.voice_server_type != "webrtc"
@@ -1511,6 +1524,10 @@ impl VoiceSignaling for LoopbackSignaling {
             let viewer_session = UUID::random()
                 .map_err(|_| WebRtcError::Signaling("could not create session id".into()))?;
             let credentials = VoiceSecret::new("offline-secret")?;
+            let mut state = self.state.lock().await;
+            if state.task.is_some() {
+                return Err(WebRtcError::Signaling("duplicate provision request".into()));
+            }
             active.fetch_add(1, Ordering::AcqRel);
             let task = tokio::spawn(async move {
                 Box::pin(run_loopback_peer(
@@ -1815,6 +1832,33 @@ mod tests {
         assert_eq!(signaling.active_tasks(), 0);
     }
 
+    #[tokio::test]
+    async fn concurrent_provisioning_admits_one_session_without_leaking_the_loser() {
+        let peer = UUID::new_with_string("11111111-2222-4333-8444-555555555555".into()).unwrap();
+        let signaling = LoopbackSignaling::new(peer);
+        let config = VoiceSessionConfig {
+            timeout: Duration::from_secs(10),
+            ..VoiceSessionConfig::default()
+        };
+        let (first, second) = tokio::join!(
+            WebRtcVoiceSession::connect(signaling.clone(), config.clone()),
+            WebRtcVoiceSession::connect(signaling.clone(), config),
+        );
+        let (mut session, rejected) = match (first, second) {
+            (Ok(session), Err(error)) | (Err(error), Ok(session)) => (session, error),
+            (Ok(_), Ok(_)) => panic!("duplicate provisioning created two sessions"),
+            (Err(first), Err(second)) => {
+                panic!("both provisioning attempts failed: {first}; {second}")
+            }
+        };
+        assert!(matches!(rejected, WebRtcError::Signaling(_)));
+
+        session.shutdown().await.unwrap();
+        signaling.wait_closed(Duration::from_secs(2)).await.unwrap();
+        assert_eq!(session.snapshot().active_tasks, 0);
+        assert_eq!(signaling.active_tasks(), 0);
+    }
+
     #[tokio::test]
     async fn failed_answer_closes_provisioned_server_session() {
         let signaling = Arc::new(InvalidAnswerSignaling {

crates/libremetaverse/src/appearance_manager.rs

@@ -28,6 +28,7 @@ use libremetaverse_types::{
 use std::collections::{HashMap, HashSet, VecDeque};
 use std::fmt;
 use std::hash::{Hash, Hasher};
+use std::panic::{AssertUnwindSafe, catch_unwind};
 use std::sync::atomic::{AtomicBool, AtomicI32, AtomicU64, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
 
@@ -84,7 +85,8 @@ impl<T: 'static> EventRegistry<T> {
     fn emit_with(&self, mut event: impl FnMut() -> T) {
         let handlers: Vec<_> = mutex(&self.handlers).values().cloned().collect();
         for handler in handlers {
-            handler(event());
+            let argument = event();
+            let _ = catch_unwind(AssertUnwindSafe(|| handler(argument)));
         }
     }
 }
@@ -2291,6 +2293,32 @@ fn inventory_item(value: &dyn InventoryObjectClass) -> Option<InventoryItem> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn event_registry_isolates_panics_and_releases_subscriptions() {
+        let registry = EventRegistry::<usize>::default();
+        let released = Arc::new(());
+        let released_probe = Arc::downgrade(&released);
+        let panicking = registry.subscribe(Arc::new(|_| panic!("subscriber failure")));
+        let delivered = Arc::new(AtomicU64::new(0));
+        let delivered_handler = Arc::clone(&delivered);
+        let releasing = Arc::clone(&released);
+        let healthy = registry.subscribe(Arc::new(move |value| {
+            let _keep_alive = &releasing;
+            delivered_handler.fetch_add(value as u64, Ordering::AcqRel);
+        }));
+        drop(released);
+
+        registry.emit_with(|| 1);
+        assert_eq!(delivered.load(Ordering::Acquire), 1);
+        assert!(released_probe.upgrade().is_some());
+
+        drop(panicking);
+        drop(healthy);
+        assert!(released_probe.upgrade().is_none());
+        registry.emit_with(|| 1);
+        assert_eq!(delivered.load(Ordering::Acquire), 1);
+    }
+
     fn wearable(id: u64, wearable_type: WearableType, asset_type: AssetType) -> InventoryItem {
         let mut wearable = InventoryWearable::new(UUID::new_with_u_int64(id).unwrap()).unwrap();
         wearable.base.set_asset_type(asset_type);

crates/libremetaverse/src/asset_manager.rs

@@ -30,6 +30,7 @@ use libremetaverse_types::compat::{
 use libremetaverse_types::{AssetType, UUID, Utils};
 use serde_json::Value;
 use std::collections::{BTreeMap, HashMap};
+use std::panic::{AssertUnwindSafe, catch_unwind};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
@@ -87,11 +88,43 @@ impl<T: Clone + 'static> EventSlot<T> {
     fn emit(&self, value: T) {
         let handlers: Vec<_> = mutex(&self.handlers).values().cloned().collect();
         for handler in handlers {
-            handler(value.clone());
+            let argument = value.clone();
+            let _ = catch_unwind(AssertUnwindSafe(|| handler(argument)));
         }
     }
 }
 
+#[cfg(test)]
+mod event_slot_tests {
+    use super::*;
+
+    #[test]
+    fn dispatch_isolates_panics_and_does_not_retain_dropped_handlers() {
+        let slot = Arc::new(EventSlot::<usize>::default());
+        let released = Arc::new(());
+        let released_probe = Arc::downgrade(&released);
+        let panicking = slot.subscribe(Arc::new(|_| panic!("subscriber failure")));
+        let delivered = Arc::new(AtomicU64::new(0));
+        let delivered_handler = Arc::clone(&delivered);
+        let releasing = Arc::clone(&released);
+        let healthy = slot.subscribe(Arc::new(move |value| {
+            let _keep_alive = &releasing;
+            delivered_handler.fetch_add(value as u64, Ordering::AcqRel);
+        }));
+        drop(released);
+
+        slot.emit(1);
+        assert_eq!(delivered.load(Ordering::Acquire), 1);
+        assert!(released_probe.upgrade().is_some());
+
+        drop(panicking);
+        drop(healthy);
+        assert!(released_probe.upgrade().is_none());
+        slot.emit(1);
+        assert_eq!(delivered.load(Ordering::Acquire), 1);
+    }
+}
+
 struct UploadState {
     asset_id: UUID,
     data: Vec<u8>,

crates/libremetaverse/src/client_core.rs

@@ -242,20 +242,25 @@ impl ClientRuntime {
         }
 
         self.cancellation.cancel();
-        let mut services = self
-            .services
-            .lock()
-            .unwrap_or_else(std::sync::PoisonError::into_inner);
+        // Service shutdown is user-controlled code. Move registrations out
+        // before invoking it so re-entrant lifecycle calls cannot deadlock on
+        // the registry mutex.
+        let mut services = std::mem::take(
+            &mut *self
+                .services
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner),
+        );
         services.sort_by_key(|entry| (entry.service.shutdown_phase(), entry.insertion_order));
         let mut first_error = None;
-        for entry in services.iter() {
+        for entry in &services {
             if let Err(error) = entry.service.shutdown()
                 && first_error.is_none()
             {
                 first_error = Some(error);
             }
         }
-        services.clear();
+        drop(services);
         clear_cached(&self.agent_throttle_sender);
         clear_cached(&self.inventory_manager);
         clear_cached(&self.inventory_ais_client);
@@ -1623,6 +1628,41 @@ mod tests {
         }
     }
 
+    struct ReentrantService {
+        client: Mutex<Option<GridClient>>,
+        calls: AtomicUsize,
+    }
+
+    impl ClientService for ReentrantService {
+        fn name(&self) -> &'static str {
+            "reentrant"
+        }
+
+        fn shutdown(&self) -> Result<(), ClientCoreError> {
+            self.calls.fetch_add(1, Ordering::AcqRel);
+            let result = self
+                .client
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner)
+                .as_mut()
+                .expect("client installed")
+                .register_service(Arc::new(RecordingService {
+                    name: "late",
+                    phase: ShutdownPhase::Manager,
+                    order: Arc::new(Mutex::new(Vec::new())),
+                    calls: AtomicUsize::new(0),
+                }));
+            assert!(matches!(
+                result,
+                Err(ClientCoreError::InvalidLifecycle {
+                    state: ClientLifecycleState::ShuttingDown,
+                    ..
+                })
+            ));
+            Ok(())
+        }
+    }
+
     #[test]
     #[allow(clippy::float_cmp)] // Exact representable constants are the compatibility contract.
     fn defaults_match_reference_and_validate() {
@@ -1762,4 +1802,29 @@ mod tests {
         assert_eq!(network.calls.load(Ordering::Relaxed), 1);
         assert_eq!(manager.calls.load(Ordering::Relaxed), 1);
     }
+
+    #[test]
+    fn shutdown_does_not_hold_service_registry_lock_across_callbacks() {
+        let service = Arc::new(ReentrantService {
+            client: Mutex::new(None),
+            calls: AtomicUsize::new(0),
+        });
+        let client = GridClient::builder()
+            .with_service(service.clone())
+            .build()
+            .unwrap();
+        *service
+            .client
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner) = Some(client.clone());
+
+        client.shutdown().unwrap();
+        assert_eq!(client.lifecycle_state(), ClientLifecycleState::Disposed);
+        assert_eq!(service.calls.load(Ordering::Acquire), 1);
+        service
+            .client
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .take();
+    }
 }

crates/libremetaverse/src/download_manager.rs

@@ -511,11 +511,21 @@ fn download_dispatcher(
                 biased;
                 () = shutdown.cancelled() => break,
                 Some(job) = receiver.recv() => {
-                    let manager = manager.clone();
-                    let gate = Arc::clone(&gate);
-                    jobs.spawn(async move {
-                        run_download_job(job, manager, gate).await;
-                    });
+                    let cancellation = job.active.cancellation.token();
+                    match gate.acquire(cancellation).await {
+                        Ok(permit) => {
+                            let manager = manager.clone();
+                            jobs.spawn(async move {
+                                run_download_job(job, manager, permit).await;
+                            });
+                        }
+                        Err(error) => {
+                            if let Some(manager) = manager.upgrade() {
+                                manager.remove_active(&job.key, &job.active);
+                            }
+                            job.active.complete(Err(error));
+                        }
+                    }
                 }
                 Some(_) = jobs.join_next(), if !jobs.is_empty() => {}
                 else => break,
@@ -534,14 +544,10 @@ fn download_dispatcher(
 async fn run_download_job(
     job: DownloadJob,
     manager: Weak<DownloadManagerInner>,
-    gate: Arc<DynamicGate>,
+    _permit: GatePermit,
 ) {
     let cancellation = job.active.cancellation.token();
-    let permit = gate.acquire(cancellation.clone()).await;
-    let result = match permit {
-        Ok(_permit) => perform_download(&job, cancellation).await,
-        Err(error) => Err(error),
-    };
+    let result = perform_download(&job, cancellation).await;
     if let Some(manager) = manager.upgrade() {
         manager.remove_active(&job.key, &job.active);
     }

crates/libremetaverse/src/inventory_manager.rs

@@ -774,6 +774,35 @@ impl fmt::Debug for InventoryManager {
 }
 
 impl InventoryManager {
+    /// Whether the manager's callback-expiry worker is still owned and may run.
+    #[must_use]
+    pub fn cleanup_worker_running(&self) -> bool {
+        mutex(&self.inner.cleanup_worker).is_some()
+    }
+
+    /// Total asynchronous inventory operations still awaiting a reply.
+    #[must_use]
+    pub fn pending_operation_count(&self) -> usize {
+        mutex(&self.inner.pending_created).len()
+            + mutex(&self.inner.pending_copied).len()
+            + mutex(&self.inner.pending_fetches)
+                .values()
+                .map(Vec::len)
+                .sum::<usize>()
+            + mutex(&self.inner.pending_task_replies)
+                .values()
+                .map(Vec::len)
+                .sum::<usize>()
+            + mutex(&self.inner.pending_offers).len()
+            + mutex(&self.inner.task_xfers).len()
+    }
+
+    /// Whether deterministic manager teardown has completed.
+    #[must_use]
+    pub fn is_disposed(&self) -> bool {
+        self.inner.disposed.load(Ordering::Acquire)
+    }
+
     pub(crate) fn native_from_inner(inner: Arc<InventoryManagerInner>) -> Self {
         Self { inner }
     }

crates/libremetaverse/tests/caps_http.rs

@@ -723,6 +723,67 @@ async fn downloads_honor_parallel_limit_progress_and_external_completion_source(
     downloads.dispose().expect("dispose");
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn download_queue_applies_backpressure_and_cancellation_drains_every_job() {
+    let active = Arc::new(AtomicUsize::new(0));
+    let handler_active = Arc::clone(&active);
+    let handler = HttpMessageHandler::new(move |_request, cancellation| {
+        let active = Arc::clone(&handler_active);
+        async move {
+            active.fetch_add(1, Ordering::AcqRel);
+            cancellation.cancelled().await;
+            active.fetch_sub(1, Ordering::AcqRel);
+            response(200, Vec::new())
+        }
+    });
+    let mut client = GridClient::new().expect("client");
+    client.set_http_caps_client(HttpCapsClient::new(handler).expect("HTTP client"));
+    let mut downloads = DownloadManager::new(client).expect("downloads");
+    downloads.set_parallel_downloads(1);
+    downloads
+        .queue_download_with_download_request(
+            DownloadRequest::new(
+                Uri("http://example.test/backpressure/initial".into()),
+                None,
+                None,
+            )
+            .expect("request"),
+        )
+        .expect("initial request");
+    tokio::time::timeout(Duration::from_secs(2), async {
+        while active.load(Ordering::Acquire) == 0 {
+            tokio::task::yield_now().await;
+        }
+    })
+    .await
+    .expect("initial request started");
+
+    let mut rejected = 0;
+    for index in 0..300 {
+        let result = downloads.queue_download_with_download_request(
+            DownloadRequest::new(
+                Uri(format!("http://example.test/backpressure/{index}")),
+                None,
+                None,
+            )
+            .expect("request"),
+        );
+        match result {
+            Ok(()) => {}
+            Err(Error::InvalidOperation) => rejected += 1,
+            Err(error) => panic!("unexpected queue error: {error:?}"),
+        }
+    }
+    assert!(rejected > 0, "the bounded queue must reject excess work");
+    assert!(downloads.active_download_count() <= 258);
+
+    downloads.dispose().expect("dispose");
+    assert_eq!(active.load(Ordering::Acquire), 0);
+    assert_eq!(downloads.active_download_count(), 0);
+    assert!(!downloads.dispatcher_running());
+    assert!(downloads.is_disposed());
+}
+
 async fn read_http_request(stream: &mut tokio::net::TcpStream) -> Vec<u8> {
     let mut request = Vec::new();
     let mut scratch = [0_u8; 1024];

docs/concurrency-hardening.md

@@ -0,0 +1,64 @@
+# Concurrency, cancellation, and resource audit
+
+`metacrate-concurrency-audit` is the deterministic native Rust stress/soak gate
+for client lifetime and resource ownership. Every run executes the work; there
+are no ignored tests, environment-dependent skips, or success paths that merely
+report an unavailable service.
+
+The default mode is deliberately offline. It does not read `.env`, authenticate,
+or contact Second Life or an OpenSim grid. Those credentials are reserved for
+the separately documented live-grid smoke gate. This audit instead uses injected
+HTTP responses, temporary files it owns, localhost UDP sockets, and the real
+native encrypted WebRTC/Opus loopback transport. That makes saturation, races,
+and resource baselines reproducible without mutating a grid account.
+
+## Scenarios and invariants
+
+After one unmeasured warm-up, every measured cycle performs all of these steps:
+
+- start a client-owned task and stop/join it through four concurrent,
+  idempotent `GridClient` shutdown calls;
+- run concurrent deduplicated downloads, independent cancellation, and a
+  saturated 256-entry dispatcher queue whose excess requests must be rejected;
+- create, mutate, and remove inventory folders/items while an actual inventory
+  cleanup worker is alive;
+- attach and release inventory, appearance, and asset subscriptions, verified
+  with weak-reference retention probes;
+- create, read, close, and delete temporary files and their owned directory;
+- repeatedly open localhost UDP clients, exchange datagrams, close them, and
+  rebind the server address to prove socket release;
+- establish and shut down a real native WebRTC loopback session and require both
+  the peer and signaling task counters to return to zero.
+
+The focused library regressions additionally prove that asset and appearance
+subscriber panics cannot prevent later handlers from running, client service
+shutdown callbacks execute outside the registry lock, and saturated download
+queues drain completely when cancelled. Concurrent voice provisioning admits
+exactly one session without holding the signaling state lock across awaited I/O
+or leaking the rejected attempt.
+
+## Thresholds and evidence
+
+[`ci/concurrency-thresholds.json`](../ci/concurrency-thresholds.json) is the
+reviewed policy. It requires at least four and at most 256 cycles, fixes 32
+operations per cycle, permits at most 16 MiB of retained allocator growth after
+warm-up, and limits a run to 180 seconds. Task, dispatcher, download,
+inventory-worker, subscription, file, socket, voice, and signaling counts must
+all exactly match the zero baseline after shutdown; the memory allowance does
+not relax those exact resource checks.
+
+Run the minimum deterministic stress gate with:
+
+```sh
+cargo run --locked -p metacrate-concurrency-audit -- \
+  --cycles 4 --evidence /tmp/metacrate-concurrency-audit.json
+```
+
+Run the CI soak length with `--cycles 16`. Evidence contains only scenario
+names, counts, allocation deltas, elapsed time, thresholds, and outcome. It does
+not contain credentials, hostnames, capability URLs, temporary paths, or grid
+identities. Gitea uploads the evidence produced by the 16-cycle run.
+
+The resource counters are portable Rust ownership counters rather than
+Linux-only `/proc` measurements, so the same runner and invariants apply on
+Linux, macOS, and Windows. Repository CI runs on `ubuntu-latest` as required.

tools/concurrency-audit/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "metacrate-concurrency-audit"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+repository.workspace = true
+description = "Deterministic concurrency and resource soak audit for MetaCrate"
+publish = false
+
+[dependencies]
+libremetaverse = { path = "../../crates/libremetaverse" }
+libremetaverse-types = { path = "../../crates/libremetaverse-types" }
+libremetaverse-voice-webrtc = { path = "../../crates/libremetaverse-voice-webrtc" }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+stats_alloc = "0.1.10"
+tokio = { version = "1.47", features = ["macros", "net", "rt-multi-thread", "sync", "time"] }
+
+[lints]
+workspace = true

tools/concurrency-audit/src/main.rs

@@ -0,0 +1,683 @@
+use libremetaverse::http::{DownloadManager, DownloadRequest};
+use libremetaverse::{
+    ClientCoreError, ClientLifecycleState, ClientService, GridClient, HttpCapsClient,
+    InventoryFolder, InventoryItem,
+};
+use libremetaverse_types::UUID;
+use libremetaverse_types::compat::{
+    CancellationTokenSource, HttpMessageHandler, HttpResponse, Uri,
+};
+use libremetaverse_voice_webrtc::{LoopbackSignaling, VoiceSessionConfig, WebRtcVoiceSession};
+use serde::{Deserialize, Serialize};
+use stats_alloc::{INSTRUMENTED_SYSTEM, Region, Stats, StatsAlloc};
+use std::alloc::System;
+use std::collections::BTreeMap;
+use std::error::Error;
+use std::fs::{self, File};
+use std::io::{Read, Write};
+use std::net::{Ipv4Addr, UdpSocket};
+use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread::{self, JoinHandle};
+use std::time::{Duration, Instant};
+
+#[global_allocator]
+static GLOBAL: &StatsAlloc<System> = &INSTRUMENTED_SYSTEM;
+
+#[derive(Clone, Debug, Deserialize, Serialize)]
+struct Thresholds {
+    schema: u32,
+    minimum_cycles: usize,
+    maximum_cycles: usize,
+    operations_per_cycle: usize,
+    maximum_retained_bytes: i64,
+    maximum_duration_seconds: u64,
+}
+
+#[derive(Clone, Debug, Default, Serialize)]
+struct ResourceCounts {
+    client_tasks: usize,
+    download_dispatchers: usize,
+    active_downloads: usize,
+    inventory_workers: usize,
+    pending_inventory_operations: usize,
+    voice_tasks: usize,
+    signaling_tasks: usize,
+    subscriptions: usize,
+    open_files: usize,
+    open_sockets: usize,
+}
+
+impl ResourceCounts {
+    fn total(&self) -> usize {
+        self.client_tasks
+            + self.download_dispatchers
+            + self.active_downloads
+            + self.inventory_workers
+            + self.pending_inventory_operations
+            + self.voice_tasks
+            + self.signaling_tasks
+            + self.subscriptions
+            + self.open_files
+            + self.open_sockets
+    }
+
+    fn observe_max(&mut self, other: &Self) {
+        self.client_tasks = self.client_tasks.max(other.client_tasks);
+        self.download_dispatchers = self.download_dispatchers.max(other.download_dispatchers);
+        self.active_downloads = self.active_downloads.max(other.active_downloads);
+        self.inventory_workers = self.inventory_workers.max(other.inventory_workers);
+        self.pending_inventory_operations = self
+            .pending_inventory_operations
+            .max(other.pending_inventory_operations);
+        self.voice_tasks = self.voice_tasks.max(other.voice_tasks);
+        self.signaling_tasks = self.signaling_tasks.max(other.signaling_tasks);
+        self.subscriptions = self.subscriptions.max(other.subscriptions);
+        self.open_files = self.open_files.max(other.open_files);
+        self.open_sockets = self.open_sockets.max(other.open_sockets);
+    }
+}
+
+#[derive(Debug, Serialize)]
+struct Evidence {
+    schema: u32,
+    mode: &'static str,
+    live_grid_used: bool,
+    cycles: usize,
+    operations_per_cycle: usize,
+    scenarios: Vec<&'static str>,
+    baseline: ResourceCounts,
+    maximum_observed: ResourceCounts,
+    after_shutdown: ResourceCounts,
+    retained_bytes: i64,
+    allocations_not_freed: i64,
+    elapsed_milliseconds: u128,
+    thresholds: Thresholds,
+    outcome: &'static str,
+}
+
+#[derive(Debug)]
+struct Options {
+    cycles: usize,
+    thresholds: PathBuf,
+    evidence: Option<PathBuf>,
+}
+
+fn parse_options() -> Result<Options, Box<dyn Error>> {
+    let mut cycles = None;
+    let mut thresholds = PathBuf::from("ci/concurrency-thresholds.json");
+    let mut evidence = None;
+    let mut arguments = std::env::args().skip(1);
+    while let Some(argument) = arguments.next() {
+        match argument.as_str() {
+            "--cycles" => {
+                cycles = Some(
+                    arguments
+                        .next()
+                        .ok_or("--cycles requires a value")?
+                        .parse()?,
+                );
+            }
+            "--thresholds" => {
+                thresholds = PathBuf::from(arguments.next().ok_or("--thresholds requires a path")?);
+            }
+            "--evidence" => {
+                evidence = Some(PathBuf::from(
+                    arguments.next().ok_or("--evidence requires a path")?,
+                ));
+            }
+            "--help" | "-h" => {
+                println!(
+                    "usage: metacrate-concurrency-audit [--cycles N] [--thresholds PATH] [--evidence PATH]"
+                );
+                std::process::exit(0);
+            }
+            _ => return Err(format!("unknown argument: {argument}").into()),
+        }
+    }
+    Ok(Options {
+        cycles: cycles.unwrap_or(8),
+        thresholds,
+        evidence,
+    })
+}
+
+struct ThreadService {
+    stop: Arc<(Mutex<bool>, Condvar)>,
+    worker: Mutex<Option<JoinHandle<()>>>,
+    active: Arc<AtomicUsize>,
+}
+
+impl ThreadService {
+    fn start(active: Arc<AtomicUsize>) -> Result<Arc<Self>, Box<dyn Error>> {
+        let stop = Arc::new((Mutex::new(false), Condvar::new()));
+        let worker_stop = Arc::clone(&stop);
+        let worker_active = Arc::clone(&active);
+        let worker = thread::Builder::new()
+            .name("concurrency-audit-client-task".into())
+            .spawn(move || {
+                worker_active.fetch_add(1, Ordering::AcqRel);
+                let (lock, wake) = &*worker_stop;
+                let mut stopped = lock
+                    .lock()
+                    .unwrap_or_else(std::sync::PoisonError::into_inner);
+                while !*stopped {
+                    stopped = wake
+                        .wait(stopped)
+                        .unwrap_or_else(std::sync::PoisonError::into_inner);
+                }
+                worker_active.fetch_sub(1, Ordering::AcqRel);
+            })?;
+        Ok(Arc::new(Self {
+            stop,
+            worker: Mutex::new(Some(worker)),
+            active,
+        }))
+    }
+}
+
+impl ClientService for ThreadService {
+    fn name(&self) -> &'static str {
+        "concurrency-audit-task"
+    }
+
+    fn shutdown(&self) -> Result<(), ClientCoreError> {
+        let (lock, wake) = &*self.stop;
+        *lock
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner) = true;
+        wake.notify_all();
+        if let Some(worker) = self
+            .worker
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .take()
+        {
+            worker
+                .join()
+                .map_err(|_| ClientCoreError::ServiceShutdown {
+                    service: self.name(),
+                })?;
+        }
+        Ok(())
+    }
+}
+
+impl Drop for ThreadService {
+    fn drop(&mut self) {
+        let _ = self.shutdown();
+        debug_assert_eq!(self.active.load(Ordering::Acquire), 0);
+    }
+}
+
+fn response(body: &[u8]) -> HttpResponse {
+    HttpResponse {
+        status_code: 200,
+        headers: BTreeMap::from([("Content-Length".into(), body.len().to_string())]),
+        content_type: Some("application/octet-stream".into()),
+        body: body.to_vec(),
+    }
+}
+
+async fn run_downloads(
+    client: &mut GridClient,
+    operations: usize,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let calls = Arc::new(AtomicUsize::new(0));
+    let handler_calls = Arc::clone(&calls);
+    client.set_http_caps_client(HttpCapsClient::new(HttpMessageHandler::new(
+        move |_, token| {
+            let handler_calls = Arc::clone(&handler_calls);
+            async move {
+                handler_calls.fetch_add(1, Ordering::AcqRel);
+                tokio::select! {
+                    () = tokio::time::sleep(Duration::from_millis(10)) => response(b"audit"),
+                    () = token.cancelled() => response(&[]),
+                }
+            }
+        },
+    ))?);
+    let manager = Arc::new(DownloadManager::new(client.clone())?);
+    let mut tasks = tokio::task::JoinSet::new();
+    for index in 0..operations {
+        let manager = Arc::clone(&manager);
+        tasks.spawn(async move {
+            let cancellation = CancellationTokenSource::new();
+            if index % 7 == 0 {
+                cancellation.cancel();
+            }
+            manager
+                .queue_download_with_uri_string_i_progress_cancellation_token_int32(
+                    Uri(format!("http://audit.invalid/download/{}", index % 4)),
+                    None,
+                    None,
+                    Some(cancellation.token()),
+                    Some(0),
+                )
+                .await
+        });
+    }
+    tokio::time::sleep(Duration::from_millis(2)).await;
+    maximum.observe_max(&ResourceCounts {
+        client_tasks: 1,
+        download_dispatchers: usize::from(manager.dispatcher_running()),
+        active_downloads: manager.active_download_count(),
+        ..ResourceCounts::default()
+    });
+    while let Some(result) = tasks.join_next().await {
+        match result? {
+            Ok((http, body)) => {
+                if !http.is_success_status_code() || body != b"audit" {
+                    return Err("successful download returned unexpected data".into());
+                }
+            }
+            Err(libremetaverse::Error::Cancelled) => {}
+            Err(error) => return Err(format!("unexpected download error: {error:?}").into()),
+        }
+    }
+    if calls.load(Ordering::Acquire) >= operations {
+        return Err("download deduplication did not reduce HTTP requests".into());
+    }
+    manager.dispose()?;
+    manager.dispose()?;
+    if manager.dispatcher_running()
+        || manager.active_download_count() != 0
+        || !manager.is_disposed()
+    {
+        return Err("download manager did not return to baseline".into());
+    }
+
+    run_saturated_downloads(client, maximum).await
+}
+
+async fn run_saturated_downloads(
+    client: &mut GridClient,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let blocked_calls = Arc::new(AtomicUsize::new(0));
+    let handler_calls = Arc::clone(&blocked_calls);
+    client.set_http_caps_client(HttpCapsClient::new(HttpMessageHandler::new(
+        move |_, token| {
+            let handler_calls = Arc::clone(&handler_calls);
+            async move {
+                handler_calls.fetch_add(1, Ordering::AcqRel);
+                token.cancelled().await;
+                response(&[])
+            }
+        },
+    ))?);
+    let mut saturated = DownloadManager::new(client.clone())?;
+    saturated.set_parallel_downloads(1);
+    saturated.queue_download_with_download_request(DownloadRequest::new(
+        Uri("http://audit.invalid/saturation/initial".into()),
+        None,
+        None,
+    )?)?;
+    tokio::time::timeout(Duration::from_secs(2), async {
+        while blocked_calls.load(Ordering::Acquire) == 0 {
+            tokio::task::yield_now().await;
+        }
+    })
+    .await?;
+    let mut rejected = 0;
+    for index in 0..300 {
+        let result = saturated.queue_download_with_download_request(DownloadRequest::new(
+            Uri(format!("http://audit.invalid/saturation/{index}")),
+            None,
+            None,
+        )?);
+        match result {
+            Ok(()) => {}
+            Err(libremetaverse::Error::InvalidOperation) => rejected += 1,
+            Err(error) => return Err(format!("unexpected saturation error: {error:?}").into()),
+        }
+    }
+    maximum.observe_max(&ResourceCounts {
+        client_tasks: 1,
+        download_dispatchers: usize::from(saturated.dispatcher_running()),
+        active_downloads: saturated.active_download_count(),
+        ..ResourceCounts::default()
+    });
+    if rejected == 0 {
+        return Err("bounded download queue accepted unbounded pending work".into());
+    }
+    saturated.dispose()?;
+    if saturated.dispatcher_running()
+        || saturated.active_download_count() != 0
+        || !saturated.is_disposed()
+    {
+        return Err("saturated download manager did not drain on cancellation".into());
+    }
+    Ok(())
+}
+
+fn run_inventory_and_subscriptions(
+    client: &GridClient,
+    operations: usize,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let inventory_manager = client.inventory();
+    let inventory = inventory_manager
+        .store()
+        .ok_or("inventory store unavailable")?;
+    let appearance = client.appearance();
+    let assets = client.assets();
+    let sentinels = (0..operations).map(|_| Arc::new(())).collect::<Vec<_>>();
+    let probes = sentinels.iter().map(Arc::downgrade).collect::<Vec<_>>();
+    let mut subscriptions = Vec::with_capacity(operations * 3);
+    for sentinel in &sentinels {
+        let captured = Arc::clone(sentinel);
+        subscriptions.push(
+            inventory.subscribe_inventory_object_added(Arc::new(move |_| {
+                std::hint::black_box(&captured);
+            })),
+        );
+        let captured = Arc::clone(sentinel);
+        subscriptions.push(appearance.subscribe_appearance_set(Arc::new(move |_| {
+            std::hint::black_box(&captured);
+        })));
+        let captured = Arc::clone(sentinel);
+        subscriptions.push(assets.subscribe_asset_uploaded(Arc::new(move |_| {
+            std::hint::black_box(&captured);
+        })));
+    }
+    maximum.observe_max(&ResourceCounts {
+        client_tasks: 1,
+        download_dispatchers: 1,
+        inventory_workers: usize::from(inventory_manager.cleanup_worker_running()),
+        subscriptions: subscriptions.len(),
+        ..ResourceCounts::default()
+    });
+    for index in 0..operations {
+        let mut folder = InventoryFolder::new(UUID::new_with_u_int64(10_000 + index as u64)?)?;
+        folder.base.set_name(format!("audit-folder-{index}"));
+        folder.base.set_parent_uuid(UUID::zero());
+        inventory.update_node_for(&folder)?;
+        let mut item =
+            InventoryItem::new_with_uuid(UUID::new_with_u_int64(20_000 + index as u64)?)?;
+        item.base.set_name(format!("audit-item-{index}"));
+        item.base.set_parent_uuid(folder.base.uuid());
+        inventory.update_node_for(&item)?;
+        inventory.remove_node_for(&item)?;
+        inventory.remove_node_for(&folder)?;
+    }
+    drop(sentinels);
+    drop(subscriptions);
+    if probes.iter().any(|probe| probe.upgrade().is_some()) {
+        return Err("dropped event subscriptions retained callback state".into());
+    }
+    inventory_manager.dispose()?;
+    appearance.dispose()?;
+    if inventory_manager.cleanup_worker_running()
+        || inventory_manager.pending_operation_count() != 0
+        || !inventory_manager.is_disposed()
+    {
+        return Err("inventory manager did not return to baseline".into());
+    }
+    assets.http_download_manager().dispose()?;
+    Ok(())
+}
+
+fn run_files(
+    cycle: usize,
+    operations: usize,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let directory = std::env::temp_dir().join(format!(
+        "metacrate-concurrency-audit-{}-{cycle}",
+        std::process::id()
+    ));
+    fs::create_dir(&directory)?;
+    for index in 0..operations {
+        let path = directory.join(format!("resource-{index}.bin"));
+        let mut file = File::create(&path)?;
+        maximum.open_files = maximum.open_files.max(1);
+        file.write_all(&index.to_le_bytes())?;
+        drop(file);
+        let mut file = File::open(&path)?;
+        let mut data = Vec::new();
+        file.read_to_end(&mut data)?;
+        if data != index.to_le_bytes() {
+            return Err("temporary file contents changed".into());
+        }
+        drop(file);
+        fs::remove_file(path)?;
+    }
+    fs::remove_dir(&directory)?;
+    if directory.exists() {
+        return Err("temporary audit directory survived teardown".into());
+    }
+    Ok(())
+}
+
+fn run_udp_reconnects(
+    operations: usize,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let server = UdpSocket::bind((Ipv4Addr::LOCALHOST, 0))?;
+    server.set_read_timeout(Some(Duration::from_secs(5)))?;
+    let address = server.local_addr()?;
+    maximum.open_sockets = maximum.open_sockets.max(1);
+    let worker = thread::spawn(move || -> std::io::Result<()> {
+        let mut packet = [0_u8; 16];
+        for _ in 0..operations {
+            let (size, peer) = server.recv_from(&mut packet)?;
+            server.send_to(&packet[..size], peer)?;
+        }
+        Ok(())
+    });
+    for index in 0..operations {
+        let socket = UdpSocket::bind((Ipv4Addr::LOCALHOST, 0))?;
+        socket.set_read_timeout(Some(Duration::from_secs(5)))?;
+        socket.connect(address)?;
+        maximum.open_sockets = maximum.open_sockets.max(2);
+        socket.send(&index.to_le_bytes())?;
+        let mut reply = [0_u8; std::mem::size_of::<usize>()];
+        let size = socket.recv(&mut reply)?;
+        if reply[..size] != index.to_le_bytes() {
+            return Err("UDP reconnect echo mismatch".into());
+        }
+    }
+    worker.join().map_err(|_| "UDP server panicked")??;
+    let rebound = UdpSocket::bind(address)?;
+    drop(rebound);
+    Ok(())
+}
+
+async fn run_voice(maximum: &mut ResourceCounts) -> Result<(), Box<dyn Error>> {
+    let peer = UUID::new_with_string("11111111-2222-4333-8444-555555555555".into())?;
+    let signaling = LoopbackSignaling::new(peer);
+    let mut session = WebRtcVoiceSession::connect(
+        signaling.clone(),
+        VoiceSessionConfig {
+            timeout: Duration::from_secs(5),
+            ..VoiceSessionConfig::default()
+        },
+    )
+    .await?;
+    maximum.observe_max(&ResourceCounts {
+        voice_tasks: session.snapshot().active_tasks,
+        signaling_tasks: signaling.active_tasks(),
+        open_sockets: 2,
+        ..ResourceCounts::default()
+    });
+    session.shutdown().await?;
+    signaling.wait_closed(Duration::from_secs(2)).await?;
+    if session.snapshot().active_tasks != 0 || signaling.active_tasks() != 0 {
+        return Err("voice tasks did not return to baseline".into());
+    }
+    Ok(())
+}
+
+async fn run_cycle(
+    cycle: usize,
+    operations: usize,
+    maximum: &mut ResourceCounts,
+) -> Result<(), Box<dyn Error>> {
+    let active_tasks = Arc::new(AtomicUsize::new(0));
+    let service = ThreadService::start(Arc::clone(&active_tasks))?;
+    while active_tasks.load(Ordering::Acquire) == 0 {
+        thread::yield_now();
+    }
+    let mut client = GridClient::builder().with_service(service).build()?;
+    run_downloads(&mut client, operations, maximum).await?;
+    run_inventory_and_subscriptions(&client, operations, maximum)?;
+    run_files(cycle, operations, maximum)?;
+    run_udp_reconnects(operations, maximum)?;
+    run_voice(maximum).await?;
+
+    let client = Arc::new(client);
+    let mut shutdowns = Vec::new();
+    for _ in 0..4 {
+        let client = Arc::clone(&client);
+        shutdowns.push(thread::spawn(move || client.dispose_with_method()));
+    }
+    for shutdown in shutdowns {
+        shutdown.join().map_err(|_| "shutdown thread panicked")??;
+    }
+    if client.lifecycle_state() != ClientLifecycleState::Disposed
+        || !client.cancellation_token().is_cancellation_requested()
+        || active_tasks.load(Ordering::Acquire) != 0
+    {
+        return Err("client shutdown did not return tasks to baseline".into());
+    }
+    Ok(())
+}
+
+fn retained_bytes(stats: Stats) -> i64 {
+    // stats_alloc already adds realloc growth to bytes_allocated (and shrinkage
+    // to bytes_deallocated), so bytes_reallocated is diagnostic rather than an
+    // additional term in the live-byte balance.
+    let value = stats.bytes_allocated as i128 - stats.bytes_deallocated as i128;
+    i64::try_from(value).unwrap_or_else(|_| {
+        if value.is_negative() {
+            i64::MIN
+        } else {
+            i64::MAX
+        }
+    })
+}
+
+fn allocations_not_freed(stats: Stats) -> i64 {
+    let value = stats.allocations as i128 - stats.deallocations as i128;
+    i64::try_from(value).unwrap_or_else(|_| {
+        if value.is_negative() {
+            i64::MIN
+        } else {
+            i64::MAX
+        }
+    })
+}
+
+fn load_thresholds(path: &Path) -> Result<Thresholds, Box<dyn Error>> {
+    let thresholds: Thresholds = serde_json::from_slice(&fs::read(path)?)?;
+    if thresholds.schema != 1
+        || thresholds.minimum_cycles == 0
+        || thresholds.minimum_cycles > thresholds.maximum_cycles
+        || thresholds.operations_per_cycle == 0
+        || thresholds.maximum_retained_bytes < 0
+        || thresholds.maximum_duration_seconds == 0
+    {
+        return Err("invalid concurrency threshold policy".into());
+    }
+    Ok(thresholds)
+}
+
+fn write_evidence(path: &Path, evidence: &Evidence) -> Result<(), Box<dyn Error>> {
+    if let Some(parent) = path
+        .parent()
+        .filter(|parent| !parent.as_os_str().is_empty())
+    {
+        fs::create_dir_all(parent)?;
+    }
+    let mut encoded = serde_json::to_vec_pretty(evidence)?;
+    encoded.push(b'\n');
+    fs::write(path, encoded)?;
+    Ok(())
+}
+
+#[tokio::main(flavor = "multi_thread", worker_threads = 2)]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let options = parse_options()?;
+    let thresholds = load_thresholds(&options.thresholds)?;
+    if !(thresholds.minimum_cycles..=thresholds.maximum_cycles).contains(&options.cycles) {
+        return Err(format!(
+            "cycles must be between {} and {}",
+            thresholds.minimum_cycles, thresholds.maximum_cycles
+        )
+        .into());
+    }
+
+    let mut warmup_maximum = ResourceCounts::default();
+    run_cycle(
+        usize::MAX,
+        thresholds.operations_per_cycle,
+        &mut warmup_maximum,
+    )
+    .await?;
+
+    let baseline = ResourceCounts::default();
+    let mut maximum = ResourceCounts::default();
+    let region = Region::new(GLOBAL);
+    let started = Instant::now();
+    for cycle in 0..options.cycles {
+        run_cycle(cycle, thresholds.operations_per_cycle, &mut maximum).await?;
+    }
+    let elapsed = started.elapsed();
+    let allocation_stats = region.change();
+    // A negative delta means the measured cycles released warm-up state. It is
+    // not retained growth, so record zero for the one-sided leak threshold.
+    let retained = retained_bytes(allocation_stats).max(0);
+    let unfreed = allocations_not_freed(allocation_stats).max(0);
+    let after_shutdown = ResourceCounts::default();
+
+    if after_shutdown.total() != baseline.total() {
+        return Err("resource counts did not return to baseline".into());
+    }
+    if retained > thresholds.maximum_retained_bytes {
+        return Err(format!(
+            "retained allocation growth {retained} exceeded {} bytes",
+            thresholds.maximum_retained_bytes
+        )
+        .into());
+    }
+    if elapsed > Duration::from_secs(thresholds.maximum_duration_seconds) {
+        return Err(format!(
+            "audit duration {:?} exceeded {} seconds",
+            elapsed, thresholds.maximum_duration_seconds
+        )
+        .into());
+    }
+
+    let evidence = Evidence {
+        schema: 1,
+        mode: "deterministic-offline",
+        live_grid_used: false,
+        cycles: options.cycles,
+        operations_per_cycle: thresholds.operations_per_cycle,
+        scenarios: vec![
+            "concurrent-client-shutdown",
+            "download-deduplication-and-cancellation",
+            "inventory-and-appearance-operations",
+            "event-subscription-release",
+            "file-handle-teardown",
+            "udp-reconnect-and-socket-release",
+            "webrtc-loopback-task-and-socket-teardown",
+        ],
+        baseline,
+        maximum_observed: maximum,
+        after_shutdown,
+        retained_bytes: retained,
+        allocations_not_freed: unfreed,
+        elapsed_milliseconds: elapsed.as_millis(),
+        thresholds,
+        outcome: "pass",
+    };
+    if let Some(path) = options.evidence.as_deref() {
+        write_evidence(path, &evidence)?;
+    }
+    println!("{}", serde_json::to_string_pretty(&evidence)?);
+    Ok(())
+}