diff --git a/Sources/FluidAudio/Diarizer/Offline/Core/OfflineDiarizerManager.swift b/Sources/FluidAudio/Diarizer/Offline/Core/OfflineDiarizerManager.swift
index 17f04669b..e618f980f 100644
--- a/Sources/FluidAudio/Diarizer/Offline/Core/OfflineDiarizerManager.swift
+++ b/Sources/FluidAudio/Diarizer/Offline/Core/OfflineDiarizerManager.swift
@@ -3,6 +3,12 @@ import Accelerate
 import Foundation
 import OSLog
 
+@available(macOS 14.0, iOS 17.0, *)
+private enum OfflinePreparationWorkerResult: Sendable {
+    case segmentation(SegmentationOutput, TimeInterval)
+    case embeddings([TimedEmbedding], TimeInterval)
+}
+
 @available(macOS 14.0, iOS 17.0, *)
 public final class OfflineDiarizerManager {
     private let logger = AppLogger(category: "OfflineDiarizer")
@@ -187,64 +193,93 @@ public final class OfflineDiarizerManager {
         let capturedModels = models
         let capturedConfig = config
 
-        let segmentationTask = Task.detached(priority: .userInitiated) {
-            [capturedModels, capturedConfig] () throws -> (SegmentationOutput, TimeInterval) in
-            let processor = OfflineSegmentationProcessor()
-            let start = Date()
-            do {
-                let segmentation = try await processor.process(
-                    audioSource: audioSource,
-                    segmentationModel: capturedModels.segmentationModel,
-                    config: capturedConfig,
-                    chunkHandler: { chunk in
-                        progressCallback?(chunk.chunkIndex + 1, totalChunks)
-                        switch chunkContinuation.yield(chunk) {
-                        case .enqueued, .dropped:
-                            return .continue
-                        case .terminated:
-                            return .stop
-                        @unknown default:
-                            return .stop
+        let results = try await withThrowingTaskGroup(
+            of: OfflinePreparationWorkerResult.self,
+            returning: (
+                segmentation: (SegmentationOutput, TimeInterval),
+                embeddings: ([TimedEmbedding], TimeInterval)
+            ).self
+        ) { group in
+            group.addTask(priority: .userInitiated) { [capturedModels, capturedConfig] in
+                let processor = OfflineSegmentationProcessor()
+                let start = Date()
+                do {
+                    let segmentation = try await processor.process(
+                        audioSource: audioSource,
+                        segmentationModel: capturedModels.segmentationModel,
+                        config: capturedConfig,
+                        chunkHandler: { chunk in
+                            progressCallback?(chunk.chunkIndex + 1, totalChunks)
+                            switch chunkContinuation.yield(chunk) {
+                            case .enqueued, .dropped:
+                                return .continue
+                            case .terminated:
+                                return .stop
+                            @unknown default:
+                                return .stop
+                            }
                         }
-                    }
+                    )
+                    chunkContinuation.finish()
+                    return .segmentation(
+                        segmentation,
+                        Date().timeIntervalSince(start)
+                    )
+                } catch {
+                    chunkContinuation.finish(throwing: error)
+                    throw error
+                }
+            }
+
+            group.addTask(priority: .userInitiated) { [capturedModels, capturedConfig] in
+                let extractor = OfflineEmbeddingExtractor(
+                    fbankModel: capturedModels.fbankModel,
+                    embeddingModel: capturedModels.embeddingModel,
+                    pldaTransform: PLDATransform(
+                        pldaRhoModel: capturedModels.pldaRhoModel,
+                        psi: capturedModels.pldaPsi
+                    ),
+                    config: capturedConfig
+                )
+                let start = Date()
+                let embeddings = try await extractor.extractEmbeddings(
+                    audioSource: audioSource,
+                    segmentationStream: chunkStream
+                )
+                return .embeddings(
+                    embeddings,
+                    Date().timeIntervalSince(start)
                 )
-                chunkContinuation.finish()
-                return (segmentation, Date().timeIntervalSince(start))
+            }
+
+            var segmentationResult: (SegmentationOutput, TimeInterval)?
+            var embeddingResult: ([TimedEmbedding], TimeInterval)?
+
+            do {
+                while let result = try await group.next() {
+                    switch result {
+                    case .segmentation(let segmentation, let duration):
+                        segmentationResult = (segmentation, duration)
+                    case .embeddings(let embeddings, let duration):
+                        embeddingResult = (embeddings, duration)
+                    }
+                }
             } catch {
+                group.cancelAll()
                 chunkContinuation.finish(throwing: error)
                 throw error
             }
-        }
 
-        let embeddingTask = Task.detached(priority: .userInitiated) {
-            [capturedModels, capturedConfig] () throws -> ([TimedEmbedding], TimeInterval) in
-            let extractor = OfflineEmbeddingExtractor(
-                fbankModel: capturedModels.fbankModel,
-                embeddingModel: capturedModels.embeddingModel,
-                pldaTransform: PLDATransform(pldaRhoModel: capturedModels.pldaRhoModel, psi: capturedModels.pldaPsi),
-                config: capturedConfig
-            )
-            let start = Date()
-            let embeddings = try await extractor.extractEmbeddings(
-                audioSource: audioSource,
-                segmentationStream: chunkStream
-            )
-            return (embeddings, Date().timeIntervalSince(start))
+            guard let segmentationResult, let embeddingResult else {
+                throw OfflineDiarizationError.processingFailed(
+                    "Offline preparation workers ended without complete results"
+                )
+            }
+            return (segmentationResult, embeddingResult)
         }
 
-        let segmentationResult: (SegmentationOutput, TimeInterval)
-        let embeddingResult: ([TimedEmbedding], TimeInterval)
-        do {
-            async let awaitedSegmentation = segmentationTask.value
-            async let awaitedEmbeddings = embeddingTask.value
-            segmentationResult = try await awaitedSegmentation
-            embeddingResult = try await awaitedEmbeddings
-        } catch {
-            segmentationTask.cancel()
-            embeddingTask.cancel()
-            chunkContinuation.finish(throwing: error)
-            throw error
-        }
+        let segmentationResult = results.segmentation
+        let embeddingResult = results.embeddings
 
         let (segmentation, segmentationTime) = segmentationResult
         logger.debug("Segmentation completed in \(segmentationTime)s (async)")
diff --git a/Tests/FluidAudioTests/Diarizer/Offline/OfflineDiarizerCancellationTests.swift b/Tests/FluidAudioTests/Diarizer/Offline/OfflineDiarizerCancellationTests.swift
new file mode 100644
index 000000000..8491ce7bf
--- /dev/null
+++ b/Tests/FluidAudioTests/Diarizer/Offline/OfflineDiarizerCancellationTests.swift
@@ -0,0 +1,80 @@
+import os
+import XCTest
+
+@testable import FluidAudio
+
+@available(macOS 14.0, iOS 17.0, *)
+final class OfflineDiarizerCancellationTests: XCTestCase {
+    func testCancellingFileProcessingStopsAllInferenceWorkers() async throws {
+        try requireOfflineDiarizerModels()
+
+        guard
+            let audioPath = ProcessInfo.processInfo.environment[
+                "FLUIDAUDIO_CANCELLATION_TEST_AUDIO"
+            ],
+            FileManager.default.fileExists(atPath: audioPath)
+        else {
+            throw XCTSkip(
+                "Set FLUIDAUDIO_CANCELLATION_TEST_AUDIO to a real meeting recording"
+            )
+        }
+        let audioURL = URL(fileURLWithPath: audioPath)
+
+        let manager = OfflineDiarizerManager()
+        let progress = AsyncStream<Void>.makeStream(bufferingPolicy: .bufferingNewest(1))
+        let progressCount = OSAllocatedUnfairLock<Int>(initialState: 0)
+        var progressIterator = progress.stream.makeAsyncIterator()
+
+        let processingTask = Task {
+            try await manager.process(audioURL) { _, _ in
+                progressCount.withLock { $0 += 1 }
+                progress.continuation.yield(())
+            }
+        }
+
+        guard await progressIterator.next() != nil else {
+            processingTask.cancel()
+            XCTFail("Diarization ended before inference began")
+            return
+        }
+
+        let cancellationStart = ContinuousClock.now
+        processingTask.cancel()
+
+        do {
+            _ = try await processingTask.value
+            XCTFail("Cancelled diarization unexpectedly completed")
+        } catch is CancellationError {
+            // Expected. Returning from the structured task group also proves both
+            // inference workers have stopped rather than continuing in the background.
+        } catch {
+            XCTFail("Expected CancellationError, received \(error)")
+        }
+
+        let cancellationDuration = cancellationStart.duration(to: .now)
+        XCTAssertLessThan(
+            cancellationDuration,
+            .seconds(2),
+            "Cancellation should stop segmentation and embedding between model calls"
+        )
+
+        let countWhenCancelledCallReturned = progressCount.withLock { $0 }
+        try await Task.sleep(for: .milliseconds(250))
+        XCTAssertEqual(
+            progressCount.withLock { $0 },
+            countWhenCancelledCallReturned,
+            "No inference progress may continue after process(URL) returns"
+        )
+    }
+
+    private func requireOfflineDiarizerModels() throws {
+        let repoDirectory = OfflineDiarizerModels.defaultModelsDirectory()
+            .appendingPathComponent(Repo.diarizer.folderName, isDirectory: true)
+        let allPresent = ModelNames.OfflineDiarizer.requiredModels.allSatisfy {
+            FileManager.default.fileExists(atPath: repoDirectory.appendingPathComponent($0).path)
+        }
+        guard allPresent else {
+            throw XCTSkip("Offline diarizer models not available")
+        }
+    }
+}