Raise deterministic-core test coverage to 95%+ (Models 97.1%, Support 96.0%)

Cotabby/Services/Focus/DeepGeometryWalkThrottle.swift

@@ -40,4 +40,9 @@ final class DeepGeometryWalkThrottle {
         cachedResult = result
         return result
     }
+
+    // Mirrors FieldStyleCache: keep deallocation off the back-deployment main-actor executor
+    // shim, whose StopLookupScope double-frees on macOS 26. Only test-scoped resolvers ever
+    // deallocate this type.
+    nonisolated deinit {}
 }

Cotabby/Services/Focus/FieldStyleCache.swift

@@ -29,4 +29,10 @@ final class FieldStyleCache {
         style = resolved
         return resolved
     }
+
+    // Stored state is plain value types, safe to release anywhere. The nonisolated deinit keeps
+    // deallocation off the back-deployment main-actor executor shim, whose StopLookupScope
+    // double-frees on macOS 26 (see InputSuppressionController). Production's single long-lived
+    // instance never deallocates; test-scoped resolvers do.
+    nonisolated deinit {}
 }

Cotabby/Services/Suggestion/SuggestionDebugLogger.swift

@@ -53,6 +53,11 @@ final class SuggestionDebugLogger {
         self.colorizedOutput = colorizedOutput ?? shouldUseColor
     }
 
+    // All stored state is thread-safe to release (a Bool and an optional String). The nonisolated
+    // deinit prevents Swift from scheduling the teardown through the back-deployment main-actor
+    // executor shim, which double-frees in app-hosted tests (see InputSuppressionController).
+    nonisolated deinit {}
+
     /// Emits only the model-boundary artifacts that are useful for debugging suggestion quality.
     ///
     /// Lifecycle stages such as debounce, acceptance, and visual-context session dedup still update

Cotabby/Support/FileLogHandler.swift

@@ -29,12 +29,21 @@ final class FileLogWriter: @unchecked Sendable {
     private var handle: FileHandle?
     private var currentByteOffset: UInt64 = 0
 
-    init(sizeCapBytes: UInt64? = nil) {
+    /// `fileURL` overrides the default `~/Library/Logs/<bundle>/cotabby.jsonl` destination. Tests
+    /// inject a temp-directory URL so rotation and write behavior can be exercised against a real
+    /// file handle without touching the user's live logs.
+    init(sizeCapBytes: UInt64? = nil, fileURL: URL? = nil) {
         self.sizeCapBytesOverride = sizeCapBytes
-        self.logFileURL = Self.makeLogFileURL()
+        self.logFileURL = fileURL ?? Self.makeLogFileURL()
         openHandle()
     }
 
+    // The target's default MainActor isolation applies to this unannotated class, so without this
+    // a deallocation routes through the back-deployment main-actor executor shim, which
+    // double-frees in its StopLookupScope on macOS 26 (see InputSuppressionController). The shared
+    // singleton never deallocates in production; tests deallocate per-case writers constantly.
+    nonisolated deinit {}
+
     private let sizeCapBytesOverride: UInt64?
     private var effectiveCap: UInt64 { sizeCapBytesOverride ?? sizeCapBytes }
 

Cotabby/Support/LLMIOFileHandler.swift

@@ -25,12 +25,20 @@ final class LLMIOFileWriter: @unchecked Sendable {
     private var handle: FileHandle?
     private var currentByteOffset: UInt64 = 0
 
-    init(sizeCapBytes: UInt64? = nil) {
+    /// `fileURL` overrides the default `~/Library/Logs/<bundle>/llm-io.jsonl` destination. Tests
+    /// inject a temp-directory URL so rotation and write behavior can be exercised against a real
+    /// file handle without touching the user's live logs.
+    init(sizeCapBytes: UInt64? = nil, fileURL: URL? = nil) {
         self.sizeCapBytesOverride = sizeCapBytes
-        self.logFileURL = Self.makeLogFileURL()
+        self.logFileURL = fileURL ?? Self.makeLogFileURL()
         openHandle()
     }
 
+    // Mirrors FileLogWriter: the target's default MainActor isolation would otherwise route
+    // deallocation through the back-deployment executor shim, which double-frees in its
+    // StopLookupScope on macOS 26. Production only ever uses the never-deallocated singleton.
+    nonisolated deinit {}
+
     private let sizeCapBytesOverride: UInt64?
     private var effectiveCap: UInt64 { sizeCapBytesOverride ?? sizeCapBytes }