diff --git a/ShadowsocksX-NG2/App/RulesWorkflow.swift b/ShadowsocksX-NG2/App/RulesWorkflow.swift
index 2399beeb..addfab0d 100644
--- a/ShadowsocksX-NG2/App/RulesWorkflow.swift
+++ b/ShadowsocksX-NG2/App/RulesWorkflow.swift
@@ -31,15 +31,7 @@ final class RulesWorkflow: ObservableObject {
     analysisDelay: @escaping @Sendable () async throws -> Void = {
       try await Task.sleep(for: .milliseconds(150))
     },
-    builtinSnapshots: BuiltinRuleSnapshots? = nil,
-    loadBuiltin: @escaping @Sendable (RulesSource) throws -> RuleSnapshot = { source in
-      switch source {
-      case .geolocationCN: try BuiltinRuleCatalog.loadGeolocationCN()
-      case .chinaIPv4: try BuiltinRuleCatalog.loadChinaIPv4()
-      case .gfwlist: try BuiltinRuleCatalog.loadGFWList()
-      case .custom, .fixed: throw RuleSnapshotError.missing
-      }
-    }
+    builtinSnapshots: BuiltinRuleSnapshots = BuiltinRuleSnapshots()
   ) {
     if let loadDocument {
       self.loadDocument = loadDocument
@@ -52,7 +44,7 @@ final class RulesWorkflow: ObservableObject {
     self.feedbackDelay = feedbackDelay
     self.analysisDelay = analysisDelay
     self.loadCustom = loadCustom ?? { try CustomRuleStore().load() }
-    self.builtinSnapshots = builtinSnapshots ?? BuiltinRuleSnapshots(loader: loadBuiltin)
+    self.builtinSnapshots = builtinSnapshots
   }
 
   func refresh(retryFailedSources: Bool = false) async {
diff --git a/ShadowsocksX-NG2/Domain/BuiltinRuleCatalog.swift b/ShadowsocksX-NG2/Domain/BuiltinRuleCatalog.swift
index 4421885c..264bb78e 100644
--- a/ShadowsocksX-NG2/Domain/BuiltinRuleCatalog.swift
+++ b/ShadowsocksX-NG2/Domain/BuiltinRuleCatalog.swift
@@ -19,7 +19,9 @@ struct BuiltinRuleCatalog {
     try loadSnapshot(named: "gfwlist", from: bundle)
   }
 
-  private static func loadSnapshot(named name: String, from bundle: Bundle) throws -> RuleSnapshot {
+  fileprivate static func loadSnapshot(named name: String, from bundle: Bundle) throws
+    -> RuleSnapshot
+  {
     // folder reference 保留 `rules/<source>/snapshot.json` 目录结构。
     guard
       let url = bundle.url(
@@ -62,12 +64,10 @@ actor BuiltinRuleSnapshots {
   init(bundle: Bundle = .main, loader: Loader? = nil) {
     self.loader =
       loader ?? { source in
-        switch source {
-        case .geolocationCN: try BuiltinRuleCatalog.loadGeolocationCN(from: bundle)
-        case .chinaIPv4: try BuiltinRuleCatalog.loadChinaIPv4(from: bundle)
-        case .gfwlist: try BuiltinRuleCatalog.loadGFWList(from: bundle)
-        case .fixed, .custom: throw RuleSnapshotError.missing
+        guard let kind = source.sourceKind, kind != .custom else {
+          throw RuleSnapshotError.missing
         }
+        return try BuiltinRuleCatalog.loadSnapshot(named: kind.rawValue, from: bundle)
       }
   }
 
@@ -82,12 +82,8 @@ actor BuiltinRuleSnapshots {
         id: UUID(),
         task: Task.detached(priority: .userInitiated) {
           let snapshot = try loader(source)
-          let kind: RuleSourceKind
-          switch source {
-          case .geolocationCN: kind = .geolocationCN
-          case .chinaIPv4: kind = .chinaIPv4
-          case .gfwlist: kind = .gfwlist
-          case .custom, .fixed: throw RuleSnapshotError.missing
+          guard let kind = source.sourceKind, kind != .custom else {
+            throw RuleSnapshotError.missing
           }
           guard snapshot.metadata.source.kind == kind
           else { throw RuleSnapshotError.corrupt(detail: "Unexpected rule source") }
diff --git a/ShadowsocksX-NG2/Domain/RulesBrowsing.swift b/ShadowsocksX-NG2/Domain/RulesBrowsing.swift
index a5a9604d..3dda11db 100644
--- a/ShadowsocksX-NG2/Domain/RulesBrowsing.swift
+++ b/ShadowsocksX-NG2/Domain/RulesBrowsing.swift
@@ -11,6 +11,17 @@ struct RulesQuery: Equatable, Sendable {
 enum RulesSource: String, CaseIterable, Identifiable, Sendable {
   case custom, geolocationCN, chinaIPv4, gfwlist, fixed
   var id: Self { self }
+
+  /// Fixed policy has no snapshot metadata kind.
+  var sourceKind: RuleSourceKind? {
+    switch self {
+    case .custom: .custom
+    case .geolocationCN: .geolocationCN
+    case .chinaIPv4: .chinaIPv4
+    case .gfwlist: .gfwlist
+    case .fixed: nil
+    }
+  }
 }
 
 struct RulesSourceSnapshot: Equatable, Identifiable, Sendable {
diff --git a/ShadowsocksX-NG2/Domain/RulesCollection.swift b/ShadowsocksX-NG2/Domain/RulesCollection.swift
index b3840c8e..ca2a730c 100644
--- a/ShadowsocksX-NG2/Domain/RulesCollection.swift
+++ b/ShadowsocksX-NG2/Domain/RulesCollection.swift
@@ -89,13 +89,7 @@ private struct RulesCollectionInput: Sendable {
   ) {
     do {
       let snapshot = try loadBuiltin(source)
-      let expected: RuleSourceKind
-      switch source {
-      case .geolocationCN: expected = .geolocationCN
-      case .chinaIPv4: expected = .chinaIPv4
-      case .gfwlist: expected = .gfwlist
-      case .custom, .fixed: expected = .custom
-      }
+      guard let expected = source.sourceKind else { throw RuleSnapshotError.missing }
       guard snapshot.metadata.source.kind == expected
       else { throw RuleSnapshotError.corrupt(detail: "Unexpected rule source") }
       let candidates = snapshot.rules
diff --git a/ShadowsocksX-NG2/Tests/BuiltinRuleCatalogTests.swift b/ShadowsocksX-NG2/Tests/BuiltinRuleCatalogTests.swift
index ea6eaa20..a30969a7 100644
--- a/ShadowsocksX-NG2/Tests/BuiltinRuleCatalogTests.swift
+++ b/ShadowsocksX-NG2/Tests/BuiltinRuleCatalogTests.swift
@@ -1,4 +1,5 @@
 import Foundation
+import Testing
 import XCTest
 
 @testable import ShadowsocksX_NG2
@@ -255,3 +256,25 @@ private final class SharedRuleSourceLoader: @unchecked Sendable {
     return rulesFixture(source)
   }
 }
+
+@Test func builtinSnapshotsRejectNonBuiltinSources() async {
+  let snapshots = BuiltinRuleSnapshots(loader: { _ in rulesFixture(.custom) })
+  for source in [RulesSource.custom, .fixed] {
+    do {
+      _ = try await snapshots.load(source)
+      Issue.record("Non-builtin source must not load a snapshot")
+    } catch {
+      #expect(error as? RuleSnapshotError == .missing)
+    }
+  }
+}
+
+@Test func builtinSnapshotsRejectMismatchedMetadata() async {
+  let snapshots = BuiltinRuleSnapshots(loader: { _ in rulesFixture(.chinaIPv4) })
+  do {
+    _ = try await snapshots.load(.geolocationCN)
+    Issue.record("Mismatched source metadata must be rejected")
+  } catch {
+    #expect(error as? RuleSnapshotError == .corrupt(detail: "Unexpected rule source"))
+  }
+}
diff --git a/ShadowsocksX-NG2/Tests/CustomRuleDeletionWorkflowTests.swift b/ShadowsocksX-NG2/Tests/CustomRuleDeletionWorkflowTests.swift
index f6ca4fe9..668ffc71 100644
--- a/ShadowsocksX-NG2/Tests/CustomRuleDeletionWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/CustomRuleDeletionWorkflowTests.swift
@@ -21,7 +21,9 @@ final class CustomRuleDeletionWorkflowTests: XCTestCase {
         saved = $0
         return RuleDocumentCommit(outcome: .saved, document: saved)
       },
-      loadBuiltin: { rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : []) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: {
+        rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : [])
+      }))
     await workflow.refresh()
     workflow.select(Set(workflow.snapshot.rows.map(\.id)))
     XCTAssertEqual(workflow.deletableSelection, [custom.id, other.id])
@@ -57,7 +59,7 @@ extension CustomRuleDeletionWorkflowTests {
         commits += 1
         saved = $0
         return RuleDocumentCommit(outcome: .saved, document: saved)
-      }, loadBuiltin: { rulesFixture($0) })
+      }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select(Set(workflow.snapshot.rows.map(\.id)))
     var query = workflow.snapshot.query
@@ -86,7 +88,7 @@ extension CustomRuleDeletionWorkflowTests {
       commitDocument: {
         commits += 1
         return RuleDocumentCommit(outcome: .saved, document: $0)
-      }, loadBuiltin: { rulesFixture($0) })
+      }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select(Set(workflow.snapshot.rows.map(\.id)))
     let confirmation = try XCTUnwrap(workflow.prepareCustomRuleDeletion())
@@ -114,7 +116,7 @@ extension CustomRuleDeletionWorkflowTests {
           started.fulfill()
         }
         return RuleDocumentCommit(outcome: .persistenceFailed, document: original)
-      }, loadBuiltin: { rulesFixture($0) })
+      }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select(Set(workflow.snapshot.rows.map(\.id)))
     let confirmation = try XCTUnwrap(workflow.prepareCustomRuleDeletion())
@@ -143,7 +145,7 @@ extension CustomRuleDeletionWorkflowTests {
       commitDocument: {
         commits += 1
         return RuleDocumentCommit(outcome: .saved, document: $0)
-      }, loadBuiltin: { rulesFixture($0) })
+      }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select(Set(workflow.snapshot.rows.map(\.id)))
     let confirmation = try XCTUnwrap(workflow.prepareCustomRuleDeletion())
diff --git a/ShadowsocksX-NG2/Tests/CustomRuleEditingWorkflowTests.swift b/ShadowsocksX-NG2/Tests/CustomRuleEditingWorkflowTests.swift
index 4354a0f9..fbc966b3 100644
--- a/ShadowsocksX-NG2/Tests/CustomRuleEditingWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/CustomRuleEditingWorkflowTests.swift
@@ -8,7 +8,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
     let workflow = RulesWorkflow(
       loadDocument: { CustomRuleDocument(rules: []) },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
@@ -40,7 +40,9 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
         saved = $0
         return RuleDocumentCommit(outcome: .saved, document: saved)
       },
-      loadBuiltin: { rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : []) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: {
+        rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : [])
+      }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft(editing: original.id))
     let unchanged = await workflow.previewCustomRule(draft)
@@ -71,7 +73,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
     let workflow = RulesWorkflow(
       loadDocument: { CustomRuleDocument(rules: []) },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
     draft.kind = .cidr
@@ -100,7 +102,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
         commits += 1
         return RuleDocumentCommit(outcome: .saved, document: $0)
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
     draft.kind = .ipAddress
@@ -134,7 +136,9 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
         CustomRuleDocument(rules: [], disabledIdentities: [builtin.identity, orphan])
       },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : []) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: {
+        rulesFixture($0, rules: $0 == .gfwlist ? [builtin] : [])
+      }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
     draft.content = ".MERGE.Example"
@@ -163,7 +167,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
     let workflow = RulesWorkflow(
       loadDocument: { CustomRuleDocument(rules: []) },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
     draft.action = .direct
@@ -200,7 +204,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
     let workflow = RulesWorkflow(
       loadDocument: { CustomRuleDocument(rules: [broad, proxy]) },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
     draft.kind = .domainExact
@@ -239,7 +243,7 @@ final class CustomRuleEditingWorkflowTests: XCTestCase {
         commits += 1
         return RuleDocumentCommit(outcome: .saved, document: $0)
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var discarded = try XCTUnwrap(workflow.makeCustomRuleDraft(editing: rule.id))
     discarded.content = "discarded.example"
@@ -274,7 +278,7 @@ extension CustomRuleEditingWorkflowTests {
         }
         return RuleDocumentCommit(outcome: .persistenceFailed, document: original)
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft())
@@ -304,7 +308,7 @@ extension CustomRuleEditingWorkflowTests {
     let workflow = RulesWorkflow(
       loadDocument: { original },
       commitDocument: { RuleDocumentCommit(outcome: outcome, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     XCTAssertNil(workflow.makeCustomRuleDraft())
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft(editing: rule.id))
@@ -319,7 +323,7 @@ extension CustomRuleEditingWorkflowTests {
     let incomplete = RulesWorkflow(
       loadDocument: { throw CustomRuleStoreError.corrupt(detail: "fixture error") },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await incomplete.refresh()
     XCTAssertNil(incomplete.makeCustomRuleDraft())
     let refused = await incomplete.saveCustomRule(draft)
@@ -339,7 +343,7 @@ extension CustomRuleEditingWorkflowTests {
         commits += 1
         return RuleDocumentCommit(outcome: .saved, document: $0)
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     var draft = try XCTUnwrap(workflow.makeCustomRuleDraft(editing: original.id))
     draft.kind = .cidr
diff --git a/ShadowsocksX-NG2/Tests/OfflineRulesWorkflowTests.swift b/ShadowsocksX-NG2/Tests/OfflineRulesWorkflowTests.swift
index 1692548f..0e353523 100644
--- a/ShadowsocksX-NG2/Tests/OfflineRulesWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/OfflineRulesWorkflowTests.swift
@@ -6,7 +6,8 @@ import XCTest
 final class OfflineRulesWorkflowTests: XCTestCase {
   func testAddressTestUsesCompleteSavedCollectionDespiteBrowsingFilters() async throws {
     let rule = CustomRule(action: .proxy, match: try RuleMatch(domainSuffix: "example.com"))
-    let workflow = RulesWorkflow(loadCustom: { [rule] }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [rule] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(search: "hidden", action: .direct, source: .chinaIPv4))
     XCTAssertTrue(workflow.snapshot.rows.isEmpty)
@@ -19,7 +20,8 @@ final class OfflineRulesWorkflowTests: XCTestCase {
     XCTAssertTrue(result.domainWithoutDNS)
   }
   func testInvalidAndIncompleteCollectionsExposeOperationErrors() async throws {
-    let workflow = RulesWorkflow(loadCustom: { [] }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     workflow.setTestTarget("example.com")
     await workflow.testAddress()
     XCTAssertEqual(workflow.snapshot.addressTest.failure, .incompleteCollection)
@@ -29,7 +31,8 @@ final class OfflineRulesWorkflowTests: XCTestCase {
     XCTAssertEqual(workflow.snapshot.addressTest.failure, .invalidTarget)
     XCTAssertNil(workflow.snapshot.addressTest.result)
     let incomplete = RulesWorkflow(
-      loadCustom: { [] }, loadBuiltin: { _ in throw RuleSnapshotError.missing })
+      loadCustom: { [] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { _ in throw RuleSnapshotError.missing }))
     await incomplete.refresh()
     incomplete.setTestTarget("localhost")
     await incomplete.testAddress()
@@ -44,7 +47,8 @@ final class OfflineRulesWorkflowTests: XCTestCase {
     let proxy = CustomRule(action: .proxy, match: try RuleMatch(domainExact: "example.com"))
     try store.save([proxy])
     let workflow = RulesWorkflow(
-      loadCustom: { try store.load() }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { try store.load() },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.setTestTarget("example.com")
     await workflow.testAddress()
@@ -66,7 +70,8 @@ final class OfflineRulesWorkflowTests: XCTestCase {
 
   func testClearingTargetOrStartingRefreshPreventsLateTestPublication() async throws {
     let rule = CustomRule(action: .proxy, match: try RuleMatch(domainSuffix: "example.com"))
-    let workflow = RulesWorkflow(loadCustom: { [rule] }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [rule] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.setTestTarget("example.com")
     await workflow.testAddress()
@@ -102,7 +107,8 @@ final class OfflineRulesWorkflowTests: XCTestCase {
       CustomRule(action: .proxy, match: try RuleMatch(domainExact: "proxy.example")),
       CustomRule(action: .direct, match: try RuleMatch(domainExact: "direct.example")),
     ]
-    let workflow = RulesWorkflow(loadCustom: { rules }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { rules }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     for mode in [ProxyModeKind.rule, .global, .direct] {
       for defaultAction in RuleDefaultAction.allCases {
diff --git a/ShadowsocksX-NG2/Tests/RuleEnablementWorkflowTests.swift b/ShadowsocksX-NG2/Tests/RuleEnablementWorkflowTests.swift
index f4355a3c..4789f110 100644
--- a/ShadowsocksX-NG2/Tests/RuleEnablementWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/RuleEnablementWorkflowTests.swift
@@ -18,7 +18,7 @@ final class RuleEnablementWorkflowTests: XCTestCase {
         return RuleDocumentCommit(outcome: .saved, document: $0)
       },
       analysisDelay: { await gate.wait() },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(source: .custom))
     let originalOrder = workflow.snapshot.rows.map(\.id)
@@ -69,7 +69,7 @@ final class RuleEnablementWorkflowTests: XCTestCase {
         }
       },
       analysisDelay: { await gate.wait() },
-      loadBuiltin: { source in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { source in
         if source == .geolocationCN {
           return rulesFixture(
             source,
@@ -79,7 +79,7 @@ final class RuleEnablementWorkflowTests: XCTestCase {
             ])
         }
         return rulesFixture(source)
-      })
+      }))
     await workflow.refresh()
     XCTAssertTrue(workflow.snapshot.isComplete)
     XCTAssertTrue(workflow.snapshot.sources.contains { $0.id == .geolocationCN })
@@ -109,10 +109,10 @@ final class RuleEnablementWorkflowTests: XCTestCase {
         return CustomRuleDocument(rules: [rule])
       },
       commitDocument: { RuleDocumentCommit(outcome: .saved, document: $0) },
-      loadBuiltin: { source in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { source in
         reads.recordSource()
         return rulesFixture(source)
-      })
+      }))
     await workflow.refresh()
     await workflow.setEnabled(false, identities: [rule.identity])
     XCTAssertEqual(reads.documentCount, 1)
@@ -147,7 +147,7 @@ final class RuleEnablementWorkflowTests: XCTestCase {
             outcome: .persistenceFailed, document: try? store.loadDocument())
         }
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let pending = Task { await workflow.setEnabled(false, identities: [rule.identity]) }
     await fulfillment(of: [started], timeout: 3)
@@ -181,7 +181,7 @@ final class RuleEnablementWorkflowTests: XCTestCase {
         commits += 1
         return RuleDocumentCommit(outcome: .persistenceFailed, document: try? store.loadDocument())
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     await workflow.setEnabled(false, identities: [rule.identity])
diff --git a/ShadowsocksX-NG2/Tests/RuleStatusWorkflowTests.swift b/ShadowsocksX-NG2/Tests/RuleStatusWorkflowTests.swift
index 93c08b55..1d291b5c 100644
--- a/ShadowsocksX-NG2/Tests/RuleStatusWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/RuleStatusWorkflowTests.swift
@@ -18,7 +18,7 @@ final class RuleStatusWorkflowTests: XCTestCase {
         return RuleDocumentCommit(outcome: .saved, document: nil)
       },
       feedbackDelay: { XCTFail("An incomplete collection must not start the success timer") },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let rows = workflow.snapshot.rows
     await workflow.setEnabled(false, identities: [rule.identity])
@@ -46,7 +46,7 @@ final class RuleStatusWorkflowTests: XCTestCase {
         saveFixture(document, to: store, outcome: .saved)
       },
       feedbackDelay: { await clock.wait() },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let fixed = try XCTUnwrap(workflow.snapshot.rows.first { $0.isFixed }?.identity)
     await workflow.setEnabled(true, identities: [disabled.identity, enabled.identity, fixed])
@@ -80,7 +80,7 @@ final class RuleStatusWorkflowTests: XCTestCase {
         await gate.wait()
         return saveFixture(document, to: store, outcome: .saved)
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let pending = Task { await workflow.setEnabled(false, identities: [rule.identity]) }
     await fulfillment(of: [reloadStarted], timeout: 3)
@@ -121,7 +121,7 @@ final class RuleStatusWorkflowTests: XCTestCase {
         await clock.wait()
         timerReturned.fulfill()
       },
-      loadBuiltin: { rulesFixture($0) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     await workflow.setEnabled(false, identities: [rule.identity])
     await fulfillment(of: [timerStarted], timeout: 3)
diff --git a/ShadowsocksX-NG2/Tests/RulesPresentationTests.swift b/ShadowsocksX-NG2/Tests/RulesPresentationTests.swift
index 9bc18d14..ff7d88bc 100644
--- a/ShadowsocksX-NG2/Tests/RulesPresentationTests.swift
+++ b/ShadowsocksX-NG2/Tests/RulesPresentationTests.swift
@@ -6,7 +6,8 @@ import XCTest
 final class RulesPresentationTests: XCTestCase {
   func testReportIsAnExplicitSnapshotUnaffectedByQueryOrRefresh() async throws {
     let loader = ReportFixtureLoader()
-    let workflow = RulesWorkflow(loadCustom: { [] }, loadBuiltin: { loader.load($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { loader.load($0) }))
     await workflow.refresh()
     XCTAssertTrue(workflow.openSourceReport(.gfwlist))
     let opened = try XCTUnwrap(workflow.reportSource)
@@ -26,7 +27,8 @@ final class RulesPresentationTests: XCTestCase {
     let narrow = CustomRule(action: .direct, match: try RuleMatch(domainExact: "a.example.com"))
     let independent = CustomRule(action: .direct, match: try RuleMatch(domainExact: "other.net"))
     let workflow = RulesWorkflow(
-      loadCustom: { [broad, narrow, independent] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [broad, narrow, independent] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     XCTAssertNil(workflow.selectedRelationshipRow)
     workflow.select([.rule(narrow.identity)])
@@ -45,7 +47,8 @@ final class RulesPresentationTests: XCTestCase {
     let narrow = CustomRule(action: .direct, match: try RuleMatch(domainExact: "a.example.net"))
     let local = CustomRule(action: .direct, match: try RuleMatch(domainExact: "device.local"))
     let workflow = RulesWorkflow(
-      loadCustom: { [broad, narrow, local] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [broad, narrow, local] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select([.rule(narrow.identity)])
     let absorbed = try XCTUnwrap(workflow.selectedRelationshipRow)
diff --git a/ShadowsocksX-NG2/Tests/RulesWorkflowCoverageTests.swift b/ShadowsocksX-NG2/Tests/RulesWorkflowCoverageTests.swift
index b2862b34..c6b3aae7 100644
--- a/ShadowsocksX-NG2/Tests/RulesWorkflowCoverageTests.swift
+++ b/ShadowsocksX-NG2/Tests/RulesWorkflowCoverageTests.swift
@@ -10,7 +10,8 @@ final class RulesWorkflowCoverageTests: XCTestCase {
     let duplicate = CustomRule(
       action: .direct, match: try RuleMatch(domainExact: "www.example.com"))
     let workflow = RulesWorkflow(
-      loadCustom: { [broad, narrow, duplicate] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [broad, narrow, duplicate] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(action: .direct, source: .custom))
     let broadRow = try XCTUnwrap(workflow.snapshot.rows.first { $0.identity == broad.identity })
@@ -30,7 +31,8 @@ final class RulesWorkflowCoverageTests: XCTestCase {
     let lower = CustomRule(action: .direct, match: try RuleMatch(ipv4CIDR: "8.8.8.0/25"))
     let upper = CustomRule(action: .direct, match: try RuleMatch(ipv4CIDR: "8.8.8.128/25"))
     let workflow = RulesWorkflow(
-      loadCustom: { [proxy, lower, upper] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [proxy, lower, upper] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(action: .proxy, source: .custom))
     let row = try XCTUnwrap(workflow.snapshot.rows.first)
@@ -51,10 +53,10 @@ final class RulesWorkflowCoverageTests: XCTestCase {
     let nationalDirect = CustomRule(action: .direct, match: .domainSuffix("cn"))
     let workflow = RulesWorkflow(
       loadCustom: { [localDirect, nationalDirect] },
-      loadBuiltin: { requested in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { requested in
         rulesFixture(
           requested, rules: requested == .gfwlist ? [simple, simpleSuffix, localProxy] : [])
-      })
+      }))
     await workflow.refresh()
     workflow.query(RulesQuery(source: .gfwlist))
     let simpleRow = try XCTUnwrap(workflow.snapshot.rows.first { $0.identity == simple.identity })
@@ -79,9 +81,9 @@ final class RulesWorkflowCoverageTests: XCTestCase {
     let proxy = ProxyRule(action: .proxy, match: try RuleMatch(domainExact: "cn"))
     let workflow = RulesWorkflow(
       loadCustom: { [direct] },
-      loadBuiltin: { requested in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { requested in
         rulesFixture(requested, rules: requested == .gfwlist ? [proxy] : [])
-      })
+      }))
     await workflow.refresh()
     workflow.query(RulesQuery(source: .custom))
     let row = try XCTUnwrap(workflow.snapshot.rows.first)
diff --git a/ShadowsocksX-NG2/Tests/RulesWorkflowPublicationTests.swift b/ShadowsocksX-NG2/Tests/RulesWorkflowPublicationTests.swift
index 89fd6f01..7e7c78e1 100644
--- a/ShadowsocksX-NG2/Tests/RulesWorkflowPublicationTests.swift
+++ b/ShadowsocksX-NG2/Tests/RulesWorkflowPublicationTests.swift
@@ -5,7 +5,8 @@ import XCTest
 @MainActor
 final class RulesWorkflowPublicationTests: XCTestCase {
   func testNativeControlsWritingTheSameQueryDoNotRepublishThePage() async {
-    let workflow = RulesWorkflow(loadCustom: { [] }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(source: .gfwlist))
     var changes = 0
@@ -16,7 +17,8 @@ final class RulesWorkflowPublicationTests: XCTestCase {
   }
 
   func testNativeControlsWritingTheSameVisibleSelectionDoNotRepublishThePage() async {
-    let workflow = RulesWorkflow(loadCustom: { [] }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { [] }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select([.noDotHostname])
     var changes = 0
diff --git a/ShadowsocksX-NG2/Tests/RulesWorkflowTests.swift b/ShadowsocksX-NG2/Tests/RulesWorkflowTests.swift
index ded17efc..c35f895f 100644
--- a/ShadowsocksX-NG2/Tests/RulesWorkflowTests.swift
+++ b/ShadowsocksX-NG2/Tests/RulesWorkflowTests.swift
@@ -27,14 +27,14 @@ final class RulesWorkflowTests: XCTestCase {
             outcome: .persistenceFailed, document: try? store.loadDocument())
         }
       },
-      loadBuiltin: { source in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { source in
         guard source == .gfwlist else { return rulesFixture(source) }
         return rulesFixture(
           source,
           rules: [
             ProxyRule(action: .proxy, match: broad.match)
           ])
-      })
+      }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     let covered = try XCTUnwrap(workflow.snapshot.rows.first { $0.identity == narrow.identity })
@@ -72,7 +72,9 @@ final class RulesWorkflowTests: XCTestCase {
       rules: [ProxyRule(action: .direct, match: match)])
     let workflow = RulesWorkflow(
       loadCustom: { [custom] },
-      loadBuiltin: { source in source == .geolocationCN ? snapshot : rulesFixture(source) })
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { source in
+        source == .geolocationCN ? snapshot : rulesFixture(source)
+      }))
     await workflow.refresh()
     workflow.query(RulesQuery(search: "EXAMPLE", action: .direct, source: .geolocationCN))
     let row = try XCTUnwrap(workflow.snapshot.rows.first)
@@ -85,9 +87,9 @@ final class RulesWorkflowTests: XCTestCase {
   func testWrongBuiltinSourceIsAnIncompleteCollectionRatherThanMislabeledRules() async {
     let workflow = RulesWorkflow(
       loadCustom: { [] },
-      loadBuiltin: { _ in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { _ in
         rulesFixture(.geolocationCN)
-      })
+      }))
     await workflow.refresh()
     XCTAssertFalse(workflow.snapshot.isComplete)
     XCTAssertEqual(workflow.snapshot.issues.count, 2)
@@ -97,7 +99,8 @@ final class RulesWorkflowTests: XCTestCase {
     let direct = CustomRule(action: .direct, match: try RuleMatch(domainSuffix: "example.com"))
     let proxy = CustomRule(action: .proxy, match: try RuleMatch(domainExact: "outside.net"))
     let workflow = RulesWorkflow(
-      loadCustom: { [direct, proxy] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [direct, proxy] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.select([.rule(direct.identity), .rule(proxy.identity), .noDotHostname])
     workflow.query(RulesQuery(search: "EXAMPLE", action: .direct, source: .custom))
@@ -114,7 +117,8 @@ final class RulesWorkflowTests: XCTestCase {
       CustomRule(action: .proxy, match: try RuleMatch(domainExact: "z.net")),
       CustomRule(action: .direct, match: try RuleMatch(domainExact: "a.net")),
     ]
-    let workflow = RulesWorkflow(loadCustom: { entries }, loadBuiltin: { rulesFixture($0) })
+    let workflow = RulesWorkflow(
+      loadCustom: { entries }, builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     workflow.query(RulesQuery(source: .custom))
@@ -134,10 +138,10 @@ final class RulesWorkflowTests: XCTestCase {
   func testCorruptUserDocumentAndMissingBuiltinStayDistinctFromEmptySearch() async {
     let workflow = RulesWorkflow(
       loadCustom: { throw CustomRuleStoreError.corrupt(detail: "fixture") },
-      loadBuiltin: { source in
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { source in
         if source == .chinaIPv4 { throw RuleSnapshotError.missing }
         return rulesFixture(source)
-      })
+      }))
     await workflow.refresh()
     XCTAssertFalse(workflow.snapshot.isComplete)
     XCTAssertEqual(
@@ -154,14 +158,7 @@ final class RulesWorkflowTests: XCTestCase {
     let bundle = AppArtifact.bundle
     let workflow = RulesWorkflow(
       loadCustom: { [] },
-      loadBuiltin: { source in
-        switch source {
-        case .geolocationCN: try BuiltinRuleCatalog.loadGeolocationCN(from: bundle)
-        case .chinaIPv4: try BuiltinRuleCatalog.loadChinaIPv4(from: bundle)
-        case .gfwlist: try BuiltinRuleCatalog.loadGFWList(from: bundle)
-        case .custom, .fixed: throw RuleSnapshotError.missing
-        }
-      })
+      builtinSnapshots: BuiltinRuleSnapshots(bundle: bundle))
     await workflow.refresh()
     XCTAssertTrue(workflow.snapshot.isComplete, "\(workflow.snapshot.issues)")
     XCTAssertEqual(workflow.snapshot.sources.count, 5)
@@ -185,7 +182,8 @@ final class RulesWorkflowTests: XCTestCase {
     let new = CustomRule(action: .proxy, match: try RuleMatch(domainExact: "new.net"))
     try store.save([old])
     let workflow = RulesWorkflow(
-      loadCustom: { try store.load() }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { try store.load() },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     workflow.query(RulesQuery(source: .custom))
     workflow.select([.rule(old.identity)])
@@ -215,7 +213,8 @@ final class RulesWorkflowTests: XCTestCase {
     let firstRead = XCTestExpectation(description: "first read")
     let barrier = RulesReadBarrier(firstRead: firstRead)
     let workflow = RulesWorkflow(
-      loadCustom: { try barrier.read() }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { try barrier.read() },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     let older = Task { await workflow.refresh() }
     await fulfillment(of: [firstRead], timeout: 3)
     defer { barrier.release.signal() }
@@ -237,8 +236,12 @@ extension RulesWorkflowTests {
   func testCandidatePermutationKeepsVersionAndCoverageWhilePreservingInputOrder() async throws {
     let broad = CustomRule(action: .direct, match: try RuleMatch(domainSuffix: "example.com"))
     let narrow = CustomRule(action: .proxy, match: try RuleMatch(domainExact: "www.example.com"))
-    let forward = RulesWorkflow(loadCustom: { [broad, narrow] }, loadBuiltin: { rulesFixture($0) })
-    let reverse = RulesWorkflow(loadCustom: { [narrow, broad] }, loadBuiltin: { rulesFixture($0) })
+    let forward = RulesWorkflow(
+      loadCustom: { [broad, narrow] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
+    let reverse = RulesWorkflow(
+      loadCustom: { [narrow, broad] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await forward.refresh()
     await reverse.refresh()
     XCTAssertEqual(forward.snapshot.version, reverse.snapshot.version)
@@ -255,7 +258,8 @@ extension RulesWorkflowTests {
     let exact = CustomRule(action: .direct, match: try RuleMatch(domainExact: "example.com"))
     let suffix = CustomRule(action: .direct, match: try RuleMatch(domainSuffix: "example.com"))
     let workflow = RulesWorkflow(
-      loadCustom: { [suffix, exact] }, loadBuiltin: { rulesFixture($0) })
+      loadCustom: { [suffix, exact] },
+      builtinSnapshots: BuiltinRuleSnapshots(loader: { rulesFixture($0) }))
     await workflow.refresh()
     let version = workflow.snapshot.version
     let identities = workflow.snapshot.rows.map(\.identity)
@@ -292,12 +296,8 @@ extension RulesWorkflowTests {
 func rulesFixture(
   _ source: RulesSource, rules: [ProxyRule] = []
 ) -> RuleSnapshot {
-  let kind: RuleSourceKind
-  switch source {
-  case .geolocationCN: kind = .geolocationCN
-  case .chinaIPv4: kind = .chinaIPv4
-  case .gfwlist: kind = .gfwlist
-  case .custom, .fixed: kind = .custom
+  guard let kind = source.sourceKind else {
+    preconditionFailure("Fixed policy has no rule snapshot")
   }
   return RuleSnapshot(
     metadata: RuleSnapshotMetadata(