diff --git a/Sources/KeyPathAppKit/Services/Packs/PackDependencyChecker.swift b/Sources/KeyPathAppKit/Services/Packs/PackDependencyChecker.swift
index 45850c388..f9d4d6cf4 100644
--- a/Sources/KeyPathAppKit/Services/Packs/PackDependencyChecker.swift
+++ b/Sources/KeyPathAppKit/Services/Packs/PackDependencyChecker.swift
@@ -5,7 +5,7 @@ import KeyPathRulesCore
 ///
 /// Simple flat validation — iterates each pack's requirements and checks
 /// if they're met. No graph traversal needed for ~15 packs with 1-2 depth chains.
-@MainActor
+/// Pure: it reads only the immutable registry, so any actor may ask.
 enum PackDependencyChecker {
     /// Returns unmet hard requirements for a specific pack.
     static func unmetRequirements(
diff --git a/Sources/KeyPathAppKit/Services/RuleCollections/AdmissionEngine.swift b/Sources/KeyPathAppKit/Services/RuleCollections/AdmissionEngine.swift
index fe99c294f..539efecbd 100644
--- a/Sources/KeyPathAppKit/Services/RuleCollections/AdmissionEngine.swift
+++ b/Sources/KeyPathAppKit/Services/RuleCollections/AdmissionEngine.swift
@@ -9,8 +9,8 @@ import KeyPathRulesCore
 /// Phase 3 of docs/architecture/rules-admission-review.md; every caller (toggle,
 /// editor, pack install, save gate, startup, doctor) asks it. Conflicts are
 /// computed here from claims — what each rule puts on which slot — attributed
-/// by rule id, never by display name (§4.4g).
-@MainActor
+/// by rule id, never by display name (§4.4g). Pure: value types in, verdicts
+/// out, no actor; the save gate, the CLI and the UI all call it directly.
 enum AdmissionEngine {
     struct State {
         var collections: [RuleCollection]
@@ -97,9 +97,9 @@ enum AdmissionEngine {
 
     /// Every conflict in `collections` (enabled ones; custom rules already folded
     /// in as collections) plus the leader key. Pure, so the save gate and the CLI
-    /// call it off the main actor. Order is the slot order of the claims; callers
+    /// call it directly. Order is the slot order of the claims; callers
     /// that need a total order sort (see `mappingConflicts`).
-    nonisolated static func conflicts(in collections: [RuleCollection], leaderKey: LeaderKeyPreference? = nil)
+    static func conflicts(in collections: [RuleCollection], leaderKey: LeaderKeyPreference? = nil)
         -> [AdmissionVerdict]
     {
         let owners: [(subject: AdmissionSubject, collection: RuleCollection)] =
@@ -108,7 +108,7 @@ enum AdmissionEngine {
     }
 
     /// The same, for the save gate and the CLI, in the error type they report.
-    nonisolated static func mappingConflicts(in collections: [RuleCollection], leaderKey: LeaderKeyPreference? = nil)
+    static func mappingConflicts(in collections: [RuleCollection], leaderKey: LeaderKeyPreference? = nil)
         -> [KeyPathError.MappingConflictInfo]
     {
         let names = Dictionary(collections.map { ($0.id, $0.name) }, uniquingKeysWith: { first, _ in first })
@@ -142,8 +142,8 @@ enum AdmissionEngine {
         conflicts(owners: owners, leaderKey: state.leaderKey)
     }
 
-    private nonisolated static func conflicts(owners: [(subject: AdmissionSubject, collection: RuleCollection)],
-                                              leaderKey: LeaderKeyPreference?) -> [AdmissionVerdict]
+    private static func conflicts(owners: [(subject: AdmissionSubject, collection: RuleCollection)],
+                                  leaderKey: LeaderKeyPreference?) -> [AdmissionVerdict]
     {
         var verdicts: [AdmissionVerdict] = []
         func conflict(_ key: String, _ layer: String, _ stakes: [Stake], subject: AdmissionSubject? = nil) {
diff --git a/Sources/KeyPathAppKit/Services/RuleCollections/RuleCollectionCatalog.swift b/Sources/KeyPathAppKit/Services/RuleCollections/RuleCollectionCatalog.swift
index 9f8bdcdef..5eec740f8 100644
--- a/Sources/KeyPathAppKit/Services/RuleCollections/RuleCollectionCatalog.swift
+++ b/Sources/KeyPathAppKit/Services/RuleCollections/RuleCollectionCatalog.swift
@@ -17,7 +17,7 @@ struct RuleCollectionCatalog {
     /// rules list and the toggle all say the same thing. Only the backend's
     /// own limits count here: whether a companion app is installed is a
     /// question for install or toggle time, with the user's real files.
-    @MainActor static func driverlessUnavailableReason(for id: UUID, profile: BackendCapabilityProfile = .shared) -> String? {
+    static func driverlessUnavailableReason(for id: UUID, profile: BackendCapabilityProfile = .shared) -> String? {
         guard let collection = installedDefinitions.first(where: { $0.id == id }) else { return nil }
         var enabled = collection
         enabled.isEnabled = true
diff --git a/Tests/KeyPathTests/SessionRuntime/BackendCapabilityProfileTests.swift b/Tests/KeyPathTests/SessionRuntime/BackendCapabilityProfileTests.swift
index fe66ef4c3..af65a7a7f 100644
--- a/Tests/KeyPathTests/SessionRuntime/BackendCapabilityProfileTests.swift
+++ b/Tests/KeyPathTests/SessionRuntime/BackendCapabilityProfileTests.swift
@@ -33,7 +33,6 @@ final class BackendCapabilityProfileTests: XCTestCase {
         XCTAssertFalse(profile.supportsDeviceTargeting)
     }
 
-    @MainActor
     func testFormerHardCodedListsGiveTheSameAnswersThroughTheBridge() throws {
         BackendCapabilityProfile.testOverride = try bridgeProfile()
 
diff --git a/Tests/KeyPathTests/SessionRuntime/SessionCapsGeneratedConfigTests.swift b/Tests/KeyPathTests/SessionRuntime/SessionCapsGeneratedConfigTests.swift
index 7a81297e0..b73faa44f 100644
--- a/Tests/KeyPathTests/SessionRuntime/SessionCapsGeneratedConfigTests.swift
+++ b/Tests/KeyPathTests/SessionRuntime/SessionCapsGeneratedConfigTests.swift
@@ -23,7 +23,6 @@ final class SessionCapsGeneratedConfigTests: XCTestCase {
         if case .valid = admission.result { XCTFail("Unsupported media output must remain rejected") }
     }
 
-    @MainActor
     func testEveryBuiltInDefaultWithLeaderIsAdmitted() throws {
         try SessionBridgeTestFixture.requireAvailable()
         let catalog = RuleCollectionCatalog().defaultCollections()
diff --git a/docs/architecture/rules-admission-review.md b/docs/architecture/rules-admission-review.md
index f8f6ff56d..793f9d036 100644
--- a/docs/architecture/rules-admission-review.md
+++ b/docs/architecture/rules-admission-review.md
@@ -502,6 +502,10 @@ carries names and details rather than ids, and lives in KeyPathCore where the ve
 types cannot be seen. It is produced from verdicts in exactly one place
 (`AdmissionEngine.mappingConflicts`).
 
+The engine and `PackDependencyChecker` are plain enums with no actor: both only read
+value types and the immutable registry. `driverlessUnavailableReason` lost the
+main-actor annotation that had followed from the engine's.
+
 ### 4.5 Lowering: intent in rules, backend output in the generator
 
 Rules keep expressing intent (`volu`, `caps` → Hyper, "this keyboard only").