diff --git a/crates/Cargo.lock b/crates/Cargo.lock
index 824061e40..a73e48c03 100644
--- a/crates/Cargo.lock
+++ b/crates/Cargo.lock
@@ -5310,6 +5310,7 @@ dependencies = [
  "async-trait",
  "log",
  "prost",
+ "qbz-models",
  "qconnect-core",
  "qconnect-protocol",
  "qconnect-transport-ws",
diff --git a/crates/qconnect-app/Cargo.toml b/crates/qconnect-app/Cargo.toml
index 306b14876..452e898f7 100644
--- a/crates/qconnect-app/Cargo.toml
+++ b/crates/qconnect-app/Cargo.toml
@@ -9,6 +9,7 @@ description = "UI-agnostic Qobuz Connect application adapter"
 qconnect-core = { path = "../qconnect-core" }
 qconnect-protocol = { path = "../qconnect-protocol" }
 qconnect-transport-ws = { path = "../qconnect-transport-ws" }
+qbz-models = { path = "../qbz-models" }
 async-trait = { workspace = true }
 tokio = { workspace = true }
 serde = { workspace = true }
diff --git a/crates/qconnect-app/src/lib.rs b/crates/qconnect-app/src/lib.rs
index 3092ec8c2..6996379d2 100644
--- a/crates/qconnect-app/src/lib.rs
+++ b/crates/qconnect-app/src/lib.rs
@@ -6,6 +6,7 @@ mod app;
 mod error;
 mod events;
 mod feature_flags;
+pub mod session;
 mod state;
 pub mod startup;
 
@@ -13,13 +14,20 @@ pub use app::QconnectApp;
 pub use startup::{compute_effective_startup, QconnectStartupMode};
 pub use error::QconnectAppError;
 pub use events::{NoOpEventSink, QconnectAppEvent, QconnectEventSink};
+pub use session::{
+    compute_connection_state, deferred_join_reason, quality_from_max_audio_quality,
+    should_arm_renderer_watchdog, should_reask_queue_state, ConnectionDecision, RendererStatus,
+    ServerActiveState, JOIN_SESSION_REASON_CONTROLLER_REQUEST, JOIN_SESSION_REASON_RECONNECTION,
+    QCONNECT_RENDERER_LOST_TIMEOUT_MS,
+};
 pub use feature_flags::{
     QBZ_QCONNECT_PANEL_SWITCH, QBZ_QCONNECT_QUEUE_MODEL, QBZ_QCONNECT_STRICT_DOMAIN_ISOLATION,
     QBZ_QCONNECT_TRANSPORT,
 };
 pub use qconnect_core::{
-    evaluate_remote_queue_admission, resolve_handoff_intent, AdmissionDecision, HandoffIntent,
-    QConnectQueueState, QConnectRendererState, QueueVersion, RendererCommand, TrackOrigin,
+    evaluate_remote_queue_admission, resolve_handoff_intent, validate_track_origins_for_admission,
+    AdmissionDecision, HandoffIntent, QConnectQueueState, QConnectRendererState, QueueVersion,
+    RendererCommand, TrackOrigin,
 };
 pub use qconnect_protocol::{QueueCommandType, RendererReport, RendererReportType};
 pub use state::QconnectRuntimeState;
diff --git a/crates/qconnect-app/src/session.rs b/crates/qconnect-app/src/session.rs
new file mode 100644
index 000000000..51c83d005
--- /dev/null
+++ b/crates/qconnect-app/src/session.rs
@@ -0,0 +1,270 @@
+//! Frontend-agnostic session/liveness primitives for Qobuz Connect.
+//!
+//! These are pure functions and pure data enums relocated out of the Tauri
+//! adapter so that both the shipping Tauri adapter and a future Slint adapter
+//! can share the exact same session-arbitration / liveness logic. Behavior is
+//! byte-for-byte identical to the prior Tauri-side definitions.
+
+use qbz_models::Quality;
+
+/// Playing-state wire value for PLAYING. Mirrors the Tauri adapter's
+/// `PLAYING_STATE_PLAYING` (the renderer reports playing_state == 2 while
+/// actively playing). Kept private to the moved liveness predicate.
+const PLAYING_STATE_PLAYING: i32 = 2;
+
+/// JoinSession `reason` wire values (proto tag 3): a first join from a fresh
+/// runtime is a controller request, a join after a transport drop carries the
+/// reconnection reason so the server treats it as session continuity rather
+/// than a brand-new controller (P1-2).
+pub const JOIN_SESSION_REASON_CONTROLLER_REQUEST: i32 = 1;
+pub const JOIN_SESSION_REASON_RECONNECTION: i32 = 2;
+
+/// Official "renderer LOST" silence budget. A *playing* active peer renderer
+/// that sends no RENDERER_STATE_UPDATED for this long is considered
+/// unreachable (webplayer arms setTimeout(...,12e3) on onPlayerStateUpdated
+/// while playingState==PLAY). See 05-sync-status-queue.md §1.
+pub const QCONNECT_RENDERER_LOST_TIMEOUT_MS: u64 = 12_000;
+
+/// Pure arming predicate for the renderer-liveness watchdog: arm only while the
+/// active renderer is a peer AND its reported playing_state is PLAYING.
+pub fn should_arm_renderer_watchdog(playing_state: Option<i32>, is_active_peer: bool) -> bool {
+    is_active_peer && playing_state == Some(PLAYING_STATE_PLAYING)
+}
+
+/// The server's view of who currently owns the active-renderer slot in a
+/// SESSION_STATE frame, classified relative to us (P1-3).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ServerActiveState {
+    /// No renderer is active in the session.
+    None,
+    /// We are the active renderer.
+    Me,
+    /// Another renderer is active and reports PLAYING.
+    OtherPlaying,
+    /// Another renderer is active and reports a non-playing state.
+    OtherPaused,
+}
+
+/// Outcome of takeover arbitration on a SESSION_STATE frame (P1-3).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ConnectionDecision {
+    /// We should consider ourselves the active renderer.
+    pub should_be_active: bool,
+    /// We should emit CtrlSrvrSetActiveRenderer to claim the slot.
+    pub should_set_active_renderer: bool,
+    /// We should push our queue + state to the session.
+    pub should_set_queue: bool,
+    /// We should ask the renderer for its current state.
+    pub should_ask_queue: bool,
+}
+
+/// Pure takeover arbitration ported from the web controller's
+/// `computeConnectionState`. This is a REDUCED matrix: it captures the
+/// shape and named outputs faithfully from the appendix prose, but the
+/// exact web truth-table cell values were not dumped verbatim. The
+/// `OtherPaused` vs `OtherPlaying` divergence and repeat-mode
+/// reconciliation are pending a decompiled-bundle cross-check; repeat-mode
+/// reconciliation is intentionally OUT of P1-3 scope (it overlaps the
+/// existing `session_loop_mode` handling in `event_sink.rs`).
+pub fn compute_connection_state(
+    was_active: bool,
+    was_playing: bool,
+    server: ServerActiveState,
+    queue_equal: bool,
+) -> ConnectionDecision {
+    use ServerActiveState::*;
+    match server {
+        None => ConnectionDecision {
+            should_be_active: was_active,
+            should_set_active_renderer: was_active,
+            should_set_queue: was_active,
+            should_ask_queue: false,
+        },
+        Me => ConnectionDecision {
+            should_be_active: true,
+            should_set_active_renderer: false,
+            should_set_queue: !queue_equal && (was_active || was_playing),
+            should_ask_queue: queue_equal,
+        },
+        OtherPlaying | OtherPaused => ConnectionDecision {
+            should_be_active: false,
+            should_set_active_renderer: false,
+            should_set_queue: false,
+            should_ask_queue: true,
+        },
+    }
+}
+
+/// Pure selector for the JoinSession `reason`: a post-drop rejoin carries
+/// RECONNECTION, the first join from a fresh runtime carries CONTROLLER_REQUEST
+/// (P1-2).
+pub fn deferred_join_reason(has_disconnected: bool) -> i32 {
+    if has_disconnected {
+        JOIN_SESSION_REASON_RECONNECTION
+    } else {
+        JOIN_SESSION_REASON_CONTROLLER_REQUEST
+    }
+}
+
+/// Pure predicate (P1-8): keep re-asking for queue state after a Lagged
+/// broadcast drop until the session_uuid is confirmed or the attempt budget is
+/// spent. Stops immediately once the session_uuid is known.
+pub fn should_reask_queue_state(
+    session_uuid_known: bool,
+    attempts: u32,
+    max_attempts: u32,
+) -> bool {
+    !session_uuid_known && attempts < max_attempts
+}
+
+/// Wire renderer status from `MESSAGE_TYPE_SRVR_CTRL_RENDERER_STATE_UPDATED`
+/// (`status` field, decoded at qconnect-protocol decoder.rs:801).
+/// Wire enum: UNKNOWN=0, ACTIVE_CONNECTED=1, ACTIVE_DISCONNECTED=2, INACTIVE=3.
+/// Per the official client's `Ya` collapse, UNKNOWN and any UNRECOGNIZED value
+/// map to INACTIVE.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum RendererStatus {
+    ActiveConnected,
+    ActiveDisconnected,
+    Inactive,
+}
+
+impl RendererStatus {
+    pub fn from_wire(value: Option<i64>) -> Self {
+        match value {
+            Some(1) => Self::ActiveConnected,
+            Some(2) => Self::ActiveDisconnected,
+            // 0 (UNKNOWN), 3 (INACTIVE), any UNRECOGNIZED value, and a missing
+            // field all collapse to INACTIVE.
+            _ => Self::Inactive,
+        }
+    }
+}
+
+/// Map a QConnect `max_audio_quality` level to a qbz `Quality`.
+/// QConnect levels: 0/1 ~ MP3, 2 ~ CD/Lossless, 3 ~ Hi-Res (<=96kHz),
+/// 4 ~ Hi-Res (>96kHz), 5/None ~ uncapped. The qbz `Quality` enum only has
+/// four variants (Mp3, Lossless, HiRes, UltraHiRes), so 4 and uncapped both
+/// resolve to UltraHiRes.
+pub fn quality_from_max_audio_quality(level: Option<i32>) -> Quality {
+    match level {
+        Some(l) if l <= 1 => Quality::Mp3,
+        Some(2) => Quality::Lossless,
+        Some(3) => Quality::HiRes,
+        Some(4) => Quality::UltraHiRes,
+        _ => Quality::UltraHiRes,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deferred_join_reason_is_reconnection_only_after_a_drop() {
+        assert_eq!(
+            deferred_join_reason(false),
+            JOIN_SESSION_REASON_CONTROLLER_REQUEST
+        );
+        assert_eq!(deferred_join_reason(true), JOIN_SESSION_REASON_RECONNECTION);
+    }
+
+    #[test]
+    fn reask_queue_state_stops_once_session_uuid_known_or_budget_spent() {
+        assert!(should_reask_queue_state(false, 0, 5));
+        assert!(should_reask_queue_state(false, 4, 5));
+        assert!(!should_reask_queue_state(false, 5, 5));
+        assert!(!should_reask_queue_state(true, 0, 5));
+    }
+
+    #[test]
+    fn compute_connection_state_matrix() {
+        use ServerActiveState::*;
+        let d = compute_connection_state(true, true, None, false);
+        assert!(
+            d.should_be_active
+                && d.should_set_active_renderer
+                && d.should_set_queue
+                && !d.should_ask_queue
+        );
+        let d = compute_connection_state(true, false, Me, false);
+        assert!(d.should_be_active && !d.should_set_active_renderer && d.should_set_queue);
+        let d = compute_connection_state(false, false, Me, true);
+        assert!(d.should_ask_queue && !d.should_set_queue && !d.should_set_active_renderer);
+        let d = compute_connection_state(false, false, OtherPlaying, false);
+        assert!(!d.should_be_active && !d.should_set_active_renderer && d.should_ask_queue);
+        let d = compute_connection_state(false, false, None, false);
+        assert!(
+            !d.should_be_active
+                && !d.should_set_active_renderer
+                && !d.should_set_queue
+                && !d.should_ask_queue
+        );
+    }
+
+    #[test]
+    fn renderer_status_from_wire_maps_known_values() {
+        assert_eq!(RendererStatus::from_wire(Some(0)), RendererStatus::Inactive); // UNKNOWN collapses
+        assert_eq!(
+            RendererStatus::from_wire(Some(1)),
+            RendererStatus::ActiveConnected
+        );
+        assert_eq!(
+            RendererStatus::from_wire(Some(2)),
+            RendererStatus::ActiveDisconnected
+        );
+        assert_eq!(RendererStatus::from_wire(Some(3)), RendererStatus::Inactive);
+    }
+
+    #[test]
+    fn renderer_status_from_wire_collapses_unknown_and_missing_to_inactive() {
+        assert_eq!(RendererStatus::from_wire(Some(99)), RendererStatus::Inactive); // UNRECOGNIZED
+        assert_eq!(RendererStatus::from_wire(None), RendererStatus::Inactive); // absent field
+    }
+
+    #[test]
+    fn watchdog_arms_only_for_playing_active_peer() {
+        const PLAYING_STATE_UNKNOWN: i32 = 0;
+        const PLAYING_STATE_STOPPED: i32 = 1;
+        const PLAYING_STATE_PAUSED: i32 = 3;
+        // Arm: playing AND active peer.
+        assert!(should_arm_renderer_watchdog(
+            Some(PLAYING_STATE_PLAYING),
+            true
+        ));
+        // Do not arm when paused/stopped/unknown even if active peer.
+        assert!(!should_arm_renderer_watchdog(
+            Some(PLAYING_STATE_PAUSED),
+            true
+        ));
+        assert!(!should_arm_renderer_watchdog(
+            Some(PLAYING_STATE_STOPPED),
+            true
+        ));
+        assert!(!should_arm_renderer_watchdog(
+            Some(PLAYING_STATE_UNKNOWN),
+            true
+        ));
+        assert!(!should_arm_renderer_watchdog(None, true));
+        // Do not arm when not an active peer (e.g. local renderer is active).
+        assert!(!should_arm_renderer_watchdog(
+            Some(PLAYING_STATE_PLAYING),
+            false
+        ));
+    }
+
+    #[test]
+    fn quality_from_max_audio_quality_maps_levels() {
+        // qbz Quality has four variants: Mp3, Lossless (CD), HiRes (<=96kHz),
+        // UltraHiRes (>96kHz). QConnect levels collapse onto these.
+        assert_eq!(quality_from_max_audio_quality(Some(0)), Quality::Mp3);
+        assert_eq!(quality_from_max_audio_quality(Some(1)), Quality::Mp3);
+        assert_eq!(quality_from_max_audio_quality(Some(2)), Quality::Lossless);
+        assert_eq!(quality_from_max_audio_quality(Some(3)), Quality::HiRes);
+        assert_eq!(quality_from_max_audio_quality(Some(4)), Quality::UltraHiRes);
+        assert_eq!(quality_from_max_audio_quality(Some(5)), Quality::UltraHiRes);
+        assert_eq!(quality_from_max_audio_quality(None), Quality::UltraHiRes);
+        assert_eq!(quality_from_max_audio_quality(Some(99)), Quality::UltraHiRes);
+    }
+}
diff --git a/crates/qconnect-core/src/admission.rs b/crates/qconnect-core/src/admission.rs
index fe19755ea..d6bdedb3c 100644
--- a/crates/qconnect-core/src/admission.rs
+++ b/crates/qconnect-core/src/admission.rs
@@ -62,11 +62,50 @@ pub fn resolve_handoff_intent(origin: TrackOrigin) -> HandoffIntent {
     }
 }
 
+/// Server-side backstop: re-evaluate EVERY track's origin, independent of any
+/// command-level `origin`. A bare `track_id` cannot prove "Qobuz vs local/Plex"
+/// on its own, so the frontend ships per-track origins and the gate re-validates
+/// each one here. An empty list is blocked: we cannot prove the queue is
+/// all-Qobuz, so we refuse rather than trust the command-level origin.
+pub fn validate_track_origins_for_admission(origins: &[TrackOrigin]) -> AdmissionDecision {
+    if origins.is_empty() {
+        return AdmissionDecision::block("empty_track_origins_blocked");
+    }
+    for origin in origins {
+        let decision = evaluate_remote_queue_admission(*origin);
+        if !decision.accepted {
+            return decision;
+        }
+    }
+    AdmissionDecision::allow("all_track_origins_qobuz")
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
     use qbz_models::PlaybackSource;
 
+    #[test]
+    fn blocks_command_when_any_track_origin_is_non_qobuz() {
+        assert!(
+            validate_track_origins_for_admission(&[
+                TrackOrigin::QobuzOnline,
+                TrackOrigin::QobuzOfflineCache
+            ])
+            .accepted
+        );
+        assert!(
+            !validate_track_origins_for_admission(&[
+                TrackOrigin::QobuzOnline,
+                TrackOrigin::LocalLibrary
+            ])
+            .accepted
+        );
+        assert!(!validate_track_origins_for_admission(&[TrackOrigin::Plex]).accepted);
+        assert!(!validate_track_origins_for_admission(&[TrackOrigin::ExternalUnknown]).accepted);
+        assert!(!validate_track_origins_for_admission(&[]).accepted); // empty -> blocked
+    }
+
     #[test]
     fn admission_matches_cast_predicate() {
         let pairs = [
diff --git a/crates/qconnect-core/src/lib.rs b/crates/qconnect-core/src/lib.rs
index 7038c4033..85f774518 100644
--- a/crates/qconnect-core/src/lib.rs
+++ b/crates/qconnect-core/src/lib.rs
@@ -10,8 +10,8 @@ pub mod renderer;
 pub mod telemetry;
 
 pub use admission::{
-    evaluate_remote_queue_admission, resolve_handoff_intent, AdmissionDecision, HandoffIntent,
-    TrackOrigin,
+    evaluate_remote_queue_admission, resolve_handoff_intent, validate_track_origins_for_admission,
+    AdmissionDecision, HandoffIntent, TrackOrigin,
 };
 pub use pending::{PendingActionError, PendingActionSlot, PendingCorrelation, PendingQueueAction};
 pub use queue::{QConnectQueueState, QueueEvent, QueueItem, QueueVersion};
diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index a156da61c..0e44c6fc2 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -5380,6 +5380,7 @@ version = "0.1.0"
 dependencies = [
  "async-trait",
  "log",
+ "qbz-models",
  "qconnect-core",
  "qconnect-protocol",
  "qconnect-transport-ws",
diff --git a/src-tauri/src/qconnect/commands.rs b/src-tauri/src/qconnect/commands.rs
index ab9a204a1..7585aa73f 100644
--- a/src-tauri/src/qconnect/commands.rs
+++ b/src-tauri/src/qconnect/commands.rs
@@ -5,9 +5,10 @@
 //! to `QconnectServiceState` after a `runtime.check_requirements` gate.
 
 use qconnect_app::{
-    evaluate_remote_queue_admission, resolve_handoff_intent, AdmissionDecision, QConnectQueueState,
-    QConnectRendererState, QconnectStartupMode, QueueCommandType, RendererReport,
-    RendererReportType,
+    evaluate_remote_queue_admission, resolve_handoff_intent,
+    validate_track_origins_for_admission as validate_core_track_origins_for_admission,
+    AdmissionDecision, QConnectQueueState, QConnectRendererState, QconnectStartupMode,
+    QueueCommandType, RendererReport, RendererReportType,
 };
 use tauri::{AppHandle, Emitter, Manager, State};
 use uuid::Uuid;
@@ -182,24 +183,19 @@ pub async fn v2_qconnect_evaluate_queue_admission(
     })
 }
 
-/// Server-side backstop: re-evaluate EVERY track's origin, independent of the
-/// command-level `origin`. A bare `track_id` (a `u64`) cannot prove "Qobuz vs
-/// local/Plex" on its own, so the frontend ships per-track origins and the gate
-/// re-validates each one here. An empty list is blocked: we cannot prove the
-/// queue is all-Qobuz, so we refuse rather than trust the command-level origin.
+/// Thin Tauri-side wrapper over the frontend-agnostic
+/// `qconnect_core::validate_track_origins_for_admission`: maps the wire
+/// `QconnectTrackOrigin`s to core `TrackOrigin`s and delegates. The pure
+/// per-track backstop logic (empty-list block, any-non-Qobuz block) lives in
+/// `qconnect-core` next to `evaluate_remote_queue_admission`.
 pub(super) fn validate_track_origins_for_admission(
     origins: &[QconnectTrackOrigin],
 ) -> AdmissionDecision {
-    if origins.is_empty() {
-        return AdmissionDecision::block("empty_track_origins_blocked");
-    }
-    for origin in origins {
-        let decision = evaluate_remote_queue_admission(origin.into_core_origin());
-        if !decision.accepted {
-            return decision;
-        }
-    }
-    AdmissionDecision::allow("all_track_origins_qobuz")
+    let core_origins: Vec<_> = origins
+        .iter()
+        .map(|origin| origin.into_core_origin())
+        .collect();
+    validate_core_track_origins_for_admission(&core_origins)
 }
 
 #[tauri::command]
diff --git a/src-tauri/src/qconnect/mod.rs b/src-tauri/src/qconnect/mod.rs
index 238fd34bb..baf249a65 100644
--- a/src-tauri/src/qconnect/mod.rs
+++ b/src-tauri/src/qconnect/mod.rs
@@ -38,27 +38,12 @@ pub(super) const PLAYING_STATE_PLAYING: i32 = 2;
 pub(super) const PLAYING_STATE_PAUSED: i32 = 3;
 pub(super) const BUFFER_STATE_OK: i32 = 2;
 
-/// JoinSession `reason` wire values (proto tag 3): a first join from a fresh
-/// runtime is a controller request, a join after a transport drop carries the
-/// reconnection reason so the server treats it as session continuity rather
-/// than a brand-new controller (P1-2).
-pub(super) const JOIN_SESSION_REASON_CONTROLLER_REQUEST: i32 = 1;
-pub(super) const JOIN_SESSION_REASON_RECONNECTION: i32 = 2;
-
-/// Official "renderer LOST" silence budget. A *playing* active peer renderer
-/// that sends no RENDERER_STATE_UPDATED for this long is considered
-/// unreachable (webplayer arms setTimeout(...,12e3) on onPlayerStateUpdated
-/// while playingState==PLAY). See 05-sync-status-queue.md §1.
-pub(super) const QCONNECT_RENDERER_LOST_TIMEOUT_MS: u64 = 12_000;
-
-/// Pure arming predicate for the renderer-liveness watchdog: arm only while the
-/// active renderer is a peer AND its reported playing_state is PLAYING.
-pub(super) fn should_arm_renderer_watchdog(
-    playing_state: Option<i32>,
-    is_active_peer: bool,
-) -> bool {
-    is_active_peer && playing_state == Some(PLAYING_STATE_PLAYING)
-}
+/// The renderer-liveness silence budget and the pure watchdog-arming predicate
+/// now live in the frontend-agnostic `qconnect_app::session` module. Re-exported
+/// here so existing `super::…` references inside this module compile unchanged.
+/// (The JoinSession `reason` consts also moved there; they are consumed only by
+/// `deferred_join_reason`, which moved too, so they are not re-exported here.)
+pub(super) use qconnect_app::{should_arm_renderer_watchdog, QCONNECT_RENDERER_LOST_TIMEOUT_MS};
 
 // AudioQuality enum: 0=unknown, 1=mp3, 2=cd, 3=hires_l1, 4=hires_l2(192k), 5=hires_l3(384k)
 pub(super) const AUDIO_QUALITY_UNKNOWN: i32 = 0;
diff --git a/src-tauri/src/qconnect/service.rs b/src-tauri/src/qconnect/service.rs
index ea5c4a0cc..a04d6d4bd 100644
--- a/src-tauri/src/qconnect/service.rs
+++ b/src-tauri/src/qconnect/service.rs
@@ -41,32 +41,15 @@ use super::{
     QconnectLifecycleState, QconnectMuteVolumeRequest, QconnectQueueVersionPayload,
     QconnectRemoteSyncState, QconnectSessionState, QconnectSetPlayerStateQueueItemPayload,
     QconnectSetPlayerStateRequest, QconnectSetVolumeRequest, QconnectVisibleQueueProjection,
-    AUDIO_QUALITY_HIRES_LEVEL2, BUFFER_STATE_OK, JOIN_SESSION_REASON_CONTROLLER_REQUEST,
-    JOIN_SESSION_REASON_RECONNECTION, PLAYING_STATE_PAUSED, PLAYING_STATE_PLAYING,
+    AUDIO_QUALITY_HIRES_LEVEL2, BUFFER_STATE_OK, PLAYING_STATE_PAUSED, PLAYING_STATE_PLAYING,
     PLAYING_STATE_STOPPED,
 };
 
-/// Pure selector for the JoinSession `reason`: a post-drop rejoin carries
-/// RECONNECTION, the first join from a fresh runtime carries CONTROLLER_REQUEST
-/// (P1-2).
-pub(super) fn deferred_join_reason(has_disconnected: bool) -> i32 {
-    if has_disconnected {
-        JOIN_SESSION_REASON_RECONNECTION
-    } else {
-        JOIN_SESSION_REASON_CONTROLLER_REQUEST
-    }
-}
-
-/// Pure predicate (P1-8): keep re-asking for queue state after a Lagged
-/// broadcast drop until the session_uuid is confirmed or the attempt budget is
-/// spent. Stops immediately once the session_uuid is known.
-pub(super) fn should_reask_queue_state(
-    session_uuid_known: bool,
-    attempts: u32,
-    max_attempts: u32,
-) -> bool {
-    !session_uuid_known && attempts < max_attempts
-}
+/// `deferred_join_reason` and `should_reask_queue_state` now live in the
+/// frontend-agnostic `qconnect_app::session` module. Re-exported here so the
+/// existing `deferred_join_reason`/`should_reask_queue_state` call sites in this
+/// module compile unchanged.
+pub(super) use qconnect_app::{deferred_join_reason, should_reask_queue_state};
 
 /// Prior-state snapshot captured from `sync_state` BEFORE a SESSION_STATE frame
 /// is applied by `event_sink`, plus the server's classified active state derived
diff --git a/src-tauri/src/qconnect/session.rs b/src-tauri/src/qconnect/session.rs
index 006cfc7ab..aedc9768d 100644
--- a/src-tauri/src/qconnect/session.rs
+++ b/src-tauri/src/qconnect/session.rs
@@ -18,69 +18,12 @@ use super::{
     QconnectQueueVersionPayload, QconnectRemoteSyncState, QconnectVisibleQueueProjection,
 };
 
-/// The server's view of who currently owns the active-renderer slot in a
-/// SESSION_STATE frame, classified relative to us (P1-3).
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub(super) enum ServerActiveState {
-    /// No renderer is active in the session.
-    None,
-    /// We are the active renderer.
-    Me,
-    /// Another renderer is active and reports PLAYING.
-    OtherPlaying,
-    /// Another renderer is active and reports a non-playing state.
-    OtherPaused,
-}
-
-/// Outcome of takeover arbitration on a SESSION_STATE frame (P1-3).
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub(super) struct ConnectionDecision {
-    /// We should consider ourselves the active renderer.
-    pub should_be_active: bool,
-    /// We should emit CtrlSrvrSetActiveRenderer to claim the slot.
-    pub should_set_active_renderer: bool,
-    /// We should push our queue + state to the session.
-    pub should_set_queue: bool,
-    /// We should ask the renderer for its current state.
-    pub should_ask_queue: bool,
-}
-
-/// Pure takeover arbitration ported from the web controller's
-/// `computeConnectionState`. This is a REDUCED matrix: it captures the
-/// shape and named outputs faithfully from the appendix prose, but the
-/// exact web truth-table cell values were not dumped verbatim. The
-/// `OtherPaused` vs `OtherPlaying` divergence and repeat-mode
-/// reconciliation are pending a decompiled-bundle cross-check; repeat-mode
-/// reconciliation is intentionally OUT of P1-3 scope (it overlaps the
-/// existing `session_loop_mode` handling in `event_sink.rs`).
-pub(super) fn compute_connection_state(
-    was_active: bool,
-    was_playing: bool,
-    server: ServerActiveState,
-    queue_equal: bool,
-) -> ConnectionDecision {
-    use ServerActiveState::*;
-    match server {
-        None => ConnectionDecision {
-            should_be_active: was_active,
-            should_set_active_renderer: was_active,
-            should_set_queue: was_active,
-            should_ask_queue: false,
-        },
-        Me => ConnectionDecision {
-            should_be_active: true,
-            should_set_active_renderer: false,
-            should_set_queue: !queue_equal && (was_active || was_playing),
-            should_ask_queue: queue_equal,
-        },
-        OtherPlaying | OtherPaused => ConnectionDecision {
-            should_be_active: false,
-            should_set_active_renderer: false,
-            should_set_queue: false,
-            should_ask_queue: true,
-        },
-    }
-}
+/// `ServerActiveState`, `ConnectionDecision`, and `compute_connection_state`
+/// now live in the frontend-agnostic `qconnect_app::session` module. Re-exported
+/// here so existing `super::session::…` references compile unchanged.
+/// (`ConnectionDecision` is the return type — consumed via field access, so it
+/// is not named directly on the Tauri side; it lives in `qconnect_app`.)
+pub(super) use qconnect_app::{compute_connection_state, ServerActiveState};
 
 pub(super) fn queue_item_snapshot_for_cursor(
     queue: &QConnectQueueState,
diff --git a/src-tauri/src/qconnect/tests.rs b/src-tauri/src/qconnect/tests.rs
index af4c3e07d..f8dd49054 100644
--- a/src-tauri/src/qconnect/tests.rs
+++ b/src-tauri/src/qconnect/tests.rs
@@ -49,50 +49,10 @@ fn normalizes_renderer_volume() {
     assert!((normalize_volume_to_fraction(125) - 1.0).abs() < f32::EPSILON);
 }
 
-#[test]
-fn deferred_join_reason_is_reconnection_only_after_a_drop() {
-    use super::service::deferred_join_reason;
-    use super::{JOIN_SESSION_REASON_CONTROLLER_REQUEST, JOIN_SESSION_REASON_RECONNECTION};
-    assert_eq!(
-        deferred_join_reason(false),
-        JOIN_SESSION_REASON_CONTROLLER_REQUEST
-    );
-    assert_eq!(
-        deferred_join_reason(true),
-        JOIN_SESSION_REASON_RECONNECTION
-    );
-}
-
-#[test]
-fn reask_queue_state_stops_once_session_uuid_known_or_budget_spent() {
-    use super::service::should_reask_queue_state;
-    assert!(should_reask_queue_state(false, 0, 5));
-    assert!(should_reask_queue_state(false, 4, 5));
-    assert!(!should_reask_queue_state(false, 5, 5));
-    assert!(!should_reask_queue_state(true, 0, 5));
-}
-
-#[test]
-fn compute_connection_state_matrix() {
-    use super::session::{compute_connection_state, ServerActiveState::*};
-    let d = compute_connection_state(true, true, None, false);
-    assert!(
-        d.should_be_active && d.should_set_active_renderer && d.should_set_queue && !d.should_ask_queue
-    );
-    let d = compute_connection_state(true, false, Me, false);
-    assert!(d.should_be_active && !d.should_set_active_renderer && d.should_set_queue);
-    let d = compute_connection_state(false, false, Me, true);
-    assert!(d.should_ask_queue && !d.should_set_queue && !d.should_set_active_renderer);
-    let d = compute_connection_state(false, false, OtherPlaying, false);
-    assert!(!d.should_be_active && !d.should_set_active_renderer && d.should_ask_queue);
-    let d = compute_connection_state(false, false, None, false);
-    assert!(
-        !d.should_be_active
-            && !d.should_set_active_renderer
-            && !d.should_set_queue
-            && !d.should_ask_queue
-    );
-}
+// `deferred_join_reason`, `should_reask_queue_state`, and
+// `compute_connection_state` are now pure functions in
+// `qconnect_app::session`; their unit tests live in that crate's `session`
+// test module.
 
 #[test]
 fn maps_outbound_command_type_to_protocol_command_type() {
@@ -145,16 +105,11 @@ fn maps_qconnect_track_origin_to_core_origin_and_handoff() {
     );
 }
 
-#[test]
-fn blocks_command_when_any_track_origin_is_non_qobuz() {
-    use super::commands::validate_track_origins_for_admission;
-    use super::QconnectTrackOrigin::*;
-    assert!(validate_track_origins_for_admission(&[QobuzOnline, QobuzOfflineCache]).accepted);
-    assert!(!validate_track_origins_for_admission(&[QobuzOnline, LocalLibrary]).accepted);
-    assert!(!validate_track_origins_for_admission(&[Plex]).accepted);
-    assert!(!validate_track_origins_for_admission(&[ExternalUnknown]).accepted);
-    assert!(!validate_track_origins_for_admission(&[]).accepted); // empty -> blocked
-}
+// The pure per-track admission backstop now lives in
+// `qconnect_core::validate_track_origins_for_admission`; its unit test lives in
+// that crate's `admission` test module. The thin Tauri wrapper
+// `commands::validate_track_origins_for_admission` only maps wire origins to
+// core origins.
 
 #[test]
 fn refreshes_local_renderer_id_from_exact_device_uuid_match() {
@@ -1134,38 +1089,9 @@ fn device_uuid_persists_and_is_reused_across_calls() {
     let _ = std::fs::remove_file(&tmp);
 }
 
-#[test]
-fn renderer_status_from_wire_maps_known_values() {
-    use super::RendererStatus;
-    assert_eq!(RendererStatus::from_wire(Some(0)), RendererStatus::Inactive); // UNKNOWN collapses
-    assert_eq!(RendererStatus::from_wire(Some(1)), RendererStatus::ActiveConnected);
-    assert_eq!(RendererStatus::from_wire(Some(2)), RendererStatus::ActiveDisconnected);
-    assert_eq!(RendererStatus::from_wire(Some(3)), RendererStatus::Inactive);
-}
-
-#[test]
-fn renderer_status_from_wire_collapses_unknown_and_missing_to_inactive() {
-    use super::RendererStatus;
-    assert_eq!(RendererStatus::from_wire(Some(99)), RendererStatus::Inactive); // UNRECOGNIZED
-    assert_eq!(RendererStatus::from_wire(None), RendererStatus::Inactive);     // absent field
-}
-
-#[test]
-fn watchdog_arms_only_for_playing_active_peer() {
-    use super::{
-        should_arm_renderer_watchdog, PLAYING_STATE_PAUSED, PLAYING_STATE_PLAYING,
-        PLAYING_STATE_STOPPED, PLAYING_STATE_UNKNOWN,
-    };
-    // Arm: playing AND active peer.
-    assert!(should_arm_renderer_watchdog(Some(PLAYING_STATE_PLAYING), true));
-    // Do not arm when paused/stopped/unknown even if active peer.
-    assert!(!should_arm_renderer_watchdog(Some(PLAYING_STATE_PAUSED), true));
-    assert!(!should_arm_renderer_watchdog(Some(PLAYING_STATE_STOPPED), true));
-    assert!(!should_arm_renderer_watchdog(Some(PLAYING_STATE_UNKNOWN), true));
-    assert!(!should_arm_renderer_watchdog(None, true));
-    // Do not arm when not an active peer (e.g. local renderer is active).
-    assert!(!should_arm_renderer_watchdog(Some(PLAYING_STATE_PLAYING), false));
-}
+// `RendererStatus::from_wire` and `should_arm_renderer_watchdog` are now in
+// `qconnect_app::session`; their unit tests live in that crate's `session` test
+// module.
 
 #[test]
 fn build_set_position_request_carries_position_and_queue_item_without_changing_play_state() {
@@ -1204,21 +1130,8 @@ fn startup_retry_schedule_is_bounded_and_monotonic() {
     assert_eq!(*s.last().unwrap(), 30_000);
 }
 
-#[test]
-fn quality_from_max_audio_quality_maps_levels() {
-    use super::track_loading::quality_from_max_audio_quality;
-    use qbz_models::Quality;
-    // qbz Quality has four variants: Mp3, Lossless (CD), HiRes (<=96kHz),
-    // UltraHiRes (>96kHz). QConnect levels collapse onto these.
-    assert_eq!(quality_from_max_audio_quality(Some(0)), Quality::Mp3);
-    assert_eq!(quality_from_max_audio_quality(Some(1)), Quality::Mp3);
-    assert_eq!(quality_from_max_audio_quality(Some(2)), Quality::Lossless);
-    assert_eq!(quality_from_max_audio_quality(Some(3)), Quality::HiRes);
-    assert_eq!(quality_from_max_audio_quality(Some(4)), Quality::UltraHiRes);
-    assert_eq!(quality_from_max_audio_quality(Some(5)), Quality::UltraHiRes);
-    assert_eq!(quality_from_max_audio_quality(None), Quality::UltraHiRes);
-    assert_eq!(quality_from_max_audio_quality(Some(99)), Quality::UltraHiRes);
-}
+// `quality_from_max_audio_quality` is now in `qconnect_app::session`; its unit
+// test lives in that crate's `session` test module.
 
 #[test]
 fn renderer_allows_remote_volume_defaults_allow_when_absent() {
diff --git a/src-tauri/src/qconnect/track_loading.rs b/src-tauri/src/qconnect/track_loading.rs
index 7312f73ca..461093476 100644
--- a/src-tauri/src/qconnect/track_loading.rs
+++ b/src-tauri/src/qconnect/track_loading.rs
@@ -6,11 +6,15 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use qbz_models::Quality;
 use tokio::sync::Mutex;
 
 use crate::core_bridge::CoreBridge;
 
+/// `quality_from_max_audio_quality` now lives in the frontend-agnostic
+/// `qconnect_app::session` module. Re-exported here so the existing call sites in
+/// this module compile unchanged.
+use qconnect_app::quality_from_max_audio_quality;
+
 use super::QconnectRemoteSyncState;
 
 const LOAD_ATTEMPT_DEDUP_WINDOW: Duration = Duration::from_secs(5);
@@ -29,21 +33,6 @@ pub(super) fn should_reload_remote_track(
     playback_state.track_id != track_id
 }
 
-/// Map a QConnect `max_audio_quality` level to a qbz `Quality`.
-/// QConnect levels: 0/1 ~ MP3, 2 ~ CD/Lossless, 3 ~ Hi-Res (<=96kHz),
-/// 4 ~ Hi-Res (>96kHz), 5/None ~ uncapped. The qbz `Quality` enum only has
-/// four variants (Mp3, Lossless, HiRes, UltraHiRes), so 4 and uncapped both
-/// resolve to UltraHiRes.
-pub(super) fn quality_from_max_audio_quality(level: Option<i32>) -> Quality {
-    match level {
-        Some(l) if l <= 1 => Quality::Mp3,
-        Some(2) => Quality::Lossless,
-        Some(3) => Quality::HiRes,
-        Some(4) => Quality::UltraHiRes,
-        _ => Quality::UltraHiRes,
-    }
-}
-
 async fn load_remote_track_into_player(
     bridge: &CoreBridge,
     track_id: u64,
diff --git a/src-tauri/src/qconnect/types.rs b/src-tauri/src/qconnect/types.rs
index f7d229b13..916ed0c27 100644
--- a/src-tauri/src/qconnect/types.rs
+++ b/src-tauri/src/qconnect/types.rs
@@ -279,26 +279,6 @@ pub struct QconnectAskForRendererStateRequest {
 }
 
 /// Wire renderer status from `MESSAGE_TYPE_SRVR_CTRL_RENDERER_STATE_UPDATED`
-/// (`status` field, decoded at qconnect-protocol decoder.rs:801).
-/// Wire enum: UNKNOWN=0, ACTIVE_CONNECTED=1, ACTIVE_DISCONNECTED=2, INACTIVE=3.
-/// Per the official client's `Ya` collapse, UNKNOWN and any UNRECOGNIZED value
-/// map to INACTIVE.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
-#[serde(rename_all = "snake_case")]
-pub enum RendererStatus {
-    ActiveConnected,
-    ActiveDisconnected,
-    Inactive,
-}
-
-impl RendererStatus {
-    pub(super) fn from_wire(value: Option<i64>) -> Self {
-        match value {
-            Some(1) => Self::ActiveConnected,
-            Some(2) => Self::ActiveDisconnected,
-            // 0 (UNKNOWN), 3 (INACTIVE), any UNRECOGNIZED value, and a missing
-            // field all collapse to INACTIVE.
-            _ => Self::Inactive,
-        }
-    }
-}
+/// now lives in the frontend-agnostic `qconnect_app::session` module. Re-exported
+/// here so the command surface (`pub use types::*`) keeps exposing it unchanged.
+pub use qconnect_app::RendererStatus;