ci: split into fast analyze + slow release build with path gating

analyze runs on every push/PR (fast check). release-apk only fires on push to master or workflow_dispatch (slow build). Doc-only pushes no longer trigger any CI run. workflow_dispatch triggers both jobs unconditionally.
2026-08-27 23:59:04 +09:00 · 2026-08-27 23:58:02 +09:00 · 2026-08-27 23:56:31 +09:00 · 2026-08-27 00:06:04 +09:00 · 2026-08-27 00:02:44 +09:00 · 2026-08-26 23:57:33 +09:00
36 changed files with 2947 additions and 703 deletions
@@ -3,20 +3,39 @@ name: CI
 on:
  push:
    branches: [ master ]
+    paths:
+      - 'lib/**.dart'
+      - 'test/**.dart'
+      - 'android/**'
+      - 'tool/**'
+      - 'pubspec.yaml'
+      - 'pubspec.lock'
  pull_request:
    branches: [ master ]
+  workflow_dispatch:
+
+# Both jobs target a self-hosted runner, by capability rather than by hostname.
+# See tool/setup_ci_runner.sh for how that runner is provisioned and why it is
+# not the Gitea host: Flutter cannot build an Android APK on a Linux arm64 host
+# (flutter/flutter#189724), and the Gitea box is aarch64. The runner is
+# registered at android-stuff org scope so any repo in the org can use it.
+#
+# The runner is host-mode, so Flutter, the JDK and the Android SDK/NDK are the
+# machine's own — the same toolchain that produced the verified release, and no
+# multi-hundred-MB download per run. Nothing here installs a toolchain; the
+# Toolchain step fails loudly if one is missing.

 jobs:
  analyze:
    name: Analyze & Test
-    runs-on: ubuntu-latest
+    runs-on: flutter-android
    steps:
      - uses: actions/checkout@v4

-      - uses: subosito/flutter-action@v2
-        with:
-          flutter-version: '3.47.1'
-          channel: 'stable'
+      - name: Toolchain
+        run: |
+          flutter --version
+          echo "ANDROID_HOME=${ANDROID_HOME:?not set on this runner}"

      - name: Get dependencies
        run: flutter pub get
@@ -24,5 +43,36 @@ jobs:
      - name: Analyze
        run: flutter analyze

+      # Includes test/architecture_test.dart, which fails the build if a layer
+      # boundary is crossed.
      - name: Run tests
        run: flutter test
+
+  release-apk:
+    name: Release APK
+    runs-on: flutter-android
+    needs: [analyze]
+    if: github.event_name == 'push' || github.event_name == 'workflow_dispatch'
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Get dependencies
+        run: flutter pub get
+
+      # The debug build does not minify, so it cannot catch an R8 problem. This
+      # job exists because a release APK that aborted on every test shipped
+      # once while the debug build passed every check.
+      - name: Build release APK
+        run: flutter build apk --release
+
+      # Building is not enough on its own: a renamed JNI callback still
+      # produces a successful build and a broken APK. This reads R8's mapping
+      # and the DEX string pool to confirm the names JNI resolves survived.
+      - name: Check JNI names survived minification
+        run: ./tool/check_jni_keep_rules.sh
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: app-release-apk
+          path: build/app/outputs/flutter-apk/app-release.apk
+          if-no-files-found: error
@@ -0,0 +1,26 @@
+MIT License
+
+Copyright (c) 2024–2026 Mikkeli Matlock
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+---
+
+Note: This project bundles iperf3 v3.19, which is licensed under the
+BSD-3-Clause license. See the bundled iperf3 source for its full license text.
@@ -1,13 +1,16 @@
 # iperf3-gui

-A Flutter-based Android GUI wrapper for iperf3, the popular network performance measurement tool.
+A Flutter-based Android GUI wrapper for iperf3, the popular network performance
+measurement tool.

 ## Features

 - Client-mode network throughput testing
- Simple UI: enter server address, port, and press GO
- Raw iperf3 output display
- Bundled iperf3 v3.21 binaries for arm64-v8a and armeabi-v7a
+- Configurable server, port, duration and parallel streams
+- Live iperf3 output, streamed line by line while the test runs
+- Stop a running test early
+- Copy the transcript to the clipboard
+- iperf3 3.19 compiled into the app as a native library — no external binary

 ## Architecture

@@ -15,33 +18,59 @@ A Flutter-based Android GUI wrapper for iperf3, the popular network performance
 lib/
 ├── domain/
 │   ├── models/          # TestConfiguration, Iperf3Result
-│   └── services/        # Iperf3Service (Process runner)
+├── data/
+│   └── services/        # Iperf3Service (MethodChannel → JNI)
 ├── ui/
 │   └── features/
 │       └── test_run/    # TestRunScreen, TestRunViewModel
-├── main.dart            # App entry point
-└── pubspec.yaml         # Dependencies: provider, path_provider
+└── main.dart            # App entry point
+
+android/app/src/main/
+├── kotlin/…/IperfRunner.kt   # MethodChannel handler, runs tests off the platform thread
+└── cpp/iperf_jni.c           # JNI bridge into the iperf3 API
 ```

+See [docs/README.md](docs/README.md) for the data flow, the native API surface
+and the design decisions behind them.
+
+## Why JNI instead of executing a binary
+
+Android SELinux in Enforcing mode blocks `execve()` from the `untrusted_app`
+domain, so shipping an iperf3 ELF in assets and running it via `Process.start()`
+fails with "Permission denied". iperf3 is therefore compiled as a shared library
+(`libiperf3jni.so`) and called in-process over JNI.
+
+
 ## Building

 Prerequisites:
- Flutter 3.47+ 
+- Flutter 3.47+
 - Android SDK with platform android-36
 - JDK 17
+- NDK r28+ and CMake 3.22.1 (for the native build)

 ```bash
-flutter create . --org novoyuuparosk --project-name iperf3gui
 flutter pub get
 flutter analyze
+flutter test
 flutter build apk --debug
+adb install -r build/app/outputs/flutter-apk/app-debug.apk
 ```

-### iperf3 Binaries
+## Testing against a local server

-Pre-compiled binaries are sourced from [davidBar-On/android-iperf3](https://github.com/davidBar-On/android-iperf3)
-and bundled in `assets/iperf3/` (arm64-v8a and armeabi-v7a for Android 28+).
+```bash
+iperf3 -s -p 5201                 # on a machine on the same network
+ip -4 addr show                   # note its address
+```
+
+Enter that address in the app, then press GO.
+
+## Dependencies
+
+- Dart: `provider`
+- Native: iperf3 3.19 + cJSON, built by CMake for `armeabi-v7a` and `arm64-v8a`

 ## License

-MIT — bundled iperf3 v3.21 is BSD-3-Clause licensed.
+MIT — bundled iperf3 3.19 is BSD-3-Clause licensed.
@@ -37,6 +37,13 @@ android {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig = signingConfigs.getByName("debug")
+
+            // proguard-rules.pro keeps the names JNI resolves at runtime.
+            // Without it a release build aborts on the first callback.
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro",
+            )
        }
    }

@@ -0,0 +1,21 @@
+# JNI reaches these by name. R8 renames by default, so without these rules a
+# release build resolves nothing: GetMethodID("onOutput", ...) returns NULL,
+# raises NoSuchMethodError, and the next JNI call aborts the process with
+#   NoSuchMethodError: no non-static method "Lp0;.onOutput(Ljava/lang/String;)V"
+# Debug builds do not minify, so this only ever appears in release.
+
+# The plugin object holds the native method declarations and is looked up from
+# C by its fully qualified name (Java_com_novoyuuparosk_iperf3gui_IperfRunner_*).
+-keep class com.novoyuuparosk.iperf3gui.IperfRunner { *; }
+
+# The callback interface and everything implementing it: iperf_jni.c resolves
+# onOutput/onError/onComplete by name on the concrete object's class, so the
+# implementors' method names must survive too, not just the interface's.
+-keep interface com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+-keep class * implements com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+
+# Belt and braces for any future native method: keep the name of any class
+# declaring one, and the native methods themselves.
+-keepclasseswithmembernames,includedescriptorclasses class * {
+    native <methods>;
+}
@@ -5,12 +5,34 @@
 * the Flutter app to run iperf3 tests natively inside the app process
 * (no Process.start needed, no SELinux restrictions).
 *
+ * OUTPUT NOTE:
+ * The test runs in --json-stream mode with a json_callback installed, so
+ * iperf3 hands each event ("start", "interval", "end", "error") straight to
+ * us as a JSON string and never touches test->outfile. That is what the hook
+ * exists for -- iperf.h calls it "allow user apps to receive the JSON
+ * strings, instead of writing them to the output file".
+ *
+ * An earlier version piped test->outfile to a reader thread instead. That
+ * required closing the pipe's write end before joining the reader (which
+ * blocks in fgets() until EOF) and single ownership of the shared state
+ * struct. Both were gotten wrong and deadlocked every test. Reading events
+ * from the callback removes the pipe, the reader thread, and that whole class
+ * of ordering bug.
+ *
+ * THREADING NOTE:
+ * runIperfLive() BLOCKS for the whole duration of the test. Kotlin must
+ * call it from a worker thread, never from the Flutter platform thread.
+ * json_callback fires on whichever thread iperf3 reports from, so it resolves
+ * a JNIEnv for the calling thread rather than reusing a stored one.
+ *
 * SIGNAL HANDLING NOTE:
 * iperf3's run() function (called from iperf_run_client()) uses
 * setjmp/longjmp for graceful signal handling. The JNI bridge must
 * replicate this setup — otherwise iperf_catch_sigend() installs
 * handlers that longjmp to an unset buffer, causing undefined
- * behaviour (typically a SIGSEGV or hang).
+ * behaviour (typically a SIGSEGV or hang). Handlers are restored to
+ * SIG_DFL once the test finishes so a later signal cannot longjmp into
+ * a stack frame that no longer exists.
 */

 #include <stdio.h>
@@ -23,6 +45,7 @@
 #include <android/log.h>
 #include <jni.h>
 #include <pthread.h>
+#include <sys/socket.h>

 #include "iperf.h"
 #include "iperf_api.h"
@@ -33,31 +56,55 @@
 #define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)
 #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, TAG, __VA_ARGS__)

-/* Global state for controlling the iperf test */
+/* ------------------------------------------------------------------ */
+/* Global state for controlling the iperf test.                        */
+/*                                                                     */
+/* g_test is written by the worker thread running the test and read by  */
+/* the platform thread in forceStopIperfTest()/isTestRunning(), so all  */
+/* access is serialised through g_test_mutex. The mutex is never held   */
+/* across iperf_run_client() — only around pointer publish/retire and   */
+/* the (short) stop request.                                           */
+/* ------------------------------------------------------------------ */
 static struct iperf_test *g_test = NULL;
+static pthread_mutex_t g_test_mutex = PTHREAD_MUTEX_INITIALIZER;
 static volatile int g_stop = 0;
 static char g_tmp_template[1024] = "/data/local/tmp/iperf3.XXXXXX";

-/* Per-call state to pass between JNI and the reader thread.
- * We store the callback object (global ref) and method IDs.
+/* Per-call state, reachable from the json_callback.
 * Callbacks are invoked via CallVoidMethod, NOT as function pointers. */
 struct iperf_run_state {
-    JNIEnv *env;
    jobject callback_ref;       /* Global ref to the callback object */
    jmethodID mid_output;       /* Method ID for onOutput(String) */
    jmethodID mid_error;        /* Method ID for onError(String) */
    jmethodID mid_complete;     /* Method ID for onComplete() */
-    FILE *outfile;
-    int pipe_fd[2];
    JavaVM *jvm;
-    pthread_t reader_thread;
 };

+/* iperf3's json_callback signature carries no user-data pointer, so the
+ * current run's state has to be reachable from a global. Only one test runs
+ * at a time (enforced in runIperfLive), and this is published before
+ * iperf_run_client() and cleared after it returns. */
+static struct iperf_run_state *g_current_state = NULL;
+
+/* Resolve a method ID, clearing the exception a failed lookup leaves behind.
+ *
+ * GetMethodID raises NoSuchMethodError on failure, and any further JNI call
+ * made while an exception is pending aborts the process. Returning NULL and
+ * clearing lets the caller fail on its own terms. */
+static jmethodID resolve_method(JNIEnv *env, jclass cls,
+                                const char *name, const char *sig) {
+    jmethodID mid = (*env)->GetMethodID(env, cls, name, sig);
+    if ((*env)->ExceptionCheck(env)) {
+        (*env)->ExceptionClear(env);
+        return NULL;
+    }
+    return mid;
+}
+
 /* Helper: invoke the output callback via CallVoidMethod */
-static void signal_output(struct iperf_run_state *state, const char *msg) {
-    if (!state || !msg || !msg[0]) return;
-    JNIEnv *env = state->env;
-    if (!env || !state->mid_output) return;
+static void signal_output(JNIEnv *env, struct iperf_run_state *state,
+                          const char *msg) {
+    if (!env || !state || !msg || !msg[0] || !state->mid_output) return;

    jstring jline = (*env)->NewStringUTF(env, msg);
    if (jline) {
@@ -67,10 +114,9 @@ static void signal_output(struct iperf_run_state *state, const char *msg) {
 }

 /* Helper: invoke the error callback via CallVoidMethod */
-static void signal_error(struct iperf_run_state *state, const char *msg) {
-    if (!state || !msg) return;
-    JNIEnv *env = state->env;
-    if (!env || !state->mid_error) return;
+static void signal_error(JNIEnv *env, struct iperf_run_state *state,
+                         const char *msg) {
+    if (!env || !state || !msg || !state->mid_error) return;

    jstring jmsg = (*env)->NewStringUTF(env, msg);
    if (jmsg) {
@@ -80,87 +126,81 @@ static void signal_error(struct iperf_run_state *state, const char *msg) {
 }

 /* Helper: invoke the complete callback via CallVoidMethod */
-static void signal_complete(struct iperf_run_state *state) {
-    if (!state || !state->mid_complete) return;
-    JNIEnv *env = state->env;
-    if (!env) return;
+static void signal_complete(JNIEnv *env, struct iperf_run_state *state) {
+    if (!env || !state || !state->mid_complete) return;

    (*env)->CallVoidMethod(env, state->callback_ref, state->mid_complete);
 }

 /* ------------------------------------------------------------------ */
-/* Output reader thread — reads from iperf's output pipe and forwards */
-/* each line to the Java callback via JNI.                            */
+/* json_callback — receives one JSON event string per report from      */
+/* iperf3 and forwards it to Java verbatim. Parsing happens in Dart.   */
+/*                                                                    */
+/* Runs on iperf3's reporting thread. In the client that is the thread */
+/* that called iperf_run_client() (already attached, since Kotlin's    */
+/* executor thread is a Java thread), but GetEnv is checked rather     */
+/* than assumed, with an attach as fallback.                          */
 /* ------------------------------------------------------------------ */
-static void *reader_thread_func(void *arg) {
-    struct iperf_run_state *state = (struct iperf_run_state *) arg;
-    JNIEnv *env;
-    int ret;
+static void json_event_callback(struct iperf_test *test, char *json) {
+    struct iperf_run_state *state = g_current_state;
+    if (!state || !json) return;

-    /* Attach this native thread to the Java VM */
-    ret = (*state->jvm)->AttachCurrentThread(state->jvm, &env, NULL);
-    if (ret != JNI_OK) {
-        LOGE("AttachCurrentThread failed: %d", ret);
-        return NULL;
-    }
+    JNIEnv *env = NULL;
+    int attached = 0;

-    char buf[1024];
-    FILE *fp = fdopen(state->pipe_fd[0], "r");
-    if (fp) {
-        while (fgets(buf, sizeof(buf), fp) != NULL) {
-            /* Skip empty lines */
-            if (buf[0] == '\n' || buf[0] == '\0')
-                continue;
-            jstring line = (*env)->NewStringUTF(env, buf);
-            if (line != NULL) {
-                (*env)->CallVoidMethod(env, state->callback_ref,
-                                       state->mid_output, line);
-                (*env)->DeleteLocalRef(env, line);
-            }
+    if ((*state->jvm)->GetEnv(state->jvm, (void **) &env, JNI_VERSION_1_6)
+            != JNI_OK) {
+        if ((*state->jvm)->AttachCurrentThread(state->jvm, &env, NULL)
+                != JNI_OK) {
+            LOGE("json_event_callback: could not reach a JNIEnv");
+            return;
        }
-        fclose(fp);
+        attached = 1;
    }

-    /* Detach this native thread */
-    (*state->jvm)->DetachCurrentThread(state->jvm);
+    signal_output(env, state, json);

-    /* Free the state struct — caller owns it */
-    free(state);
-    return NULL;
+    if (attached) {
+        (*state->jvm)->DetachCurrentThread(state->jvm);
+    }
 }

 /* ------------------------------------------------------------------ */
-/* Convert a Java String[] into a native char** argv array.           */
+/* Build a native argv from a Java String[], prepending "iperf3".      */
+/*                                                                    */
+/* iperf_parse_arguments() expects argv[0] to be the program name;     */
+/* passing the Dart args directly would make argv[0] "-c", which       */
+/* iperf3 misreads as the program name rather than the client flag.    */
 /* ------------------------------------------------------------------ */
-static char **java_string_array_to_argv(JNIEnv *env, jobjectArray str_array,
-                                        int *out_argc) {
-    int argc = (*env)->GetArrayLength(env, str_array);
-    if (argc <= 0) {
+static char **build_argv(JNIEnv *env, jobjectArray str_array, int *out_argc) {
+    int user_argc = (*env)->GetArrayLength(env, str_array);
+    if (user_argc < 0) user_argc = 0;
+
+    int argc = user_argc + 1; /* +1 for argv[0] */
+    char **argv = malloc((argc + 1) * sizeof(char *));
+    if (!argv) {
        *out_argc = 0;
        return NULL;
    }

-    char **argv = malloc((argc + 1) * sizeof(char *));
-    if (!argv) return NULL;
-
-    for (int i = 0; i < argc; i++) {
-        jstring jstr = (jstring) (*env)->GetObjectArrayElement(env,
-                                                                str_array, i);
-        const char *cstr = (*env)->GetStringUTFChars(env, jstr, NULL);
+    argv[0] = strdup("iperf3");
+    for (int i = 0; i < user_argc; i++) {
+        jstring jstr = (jstring) (*env)->GetObjectArrayElement(env, str_array, i);
+        const char *cstr = jstr ? (*env)->GetStringUTFChars(env, jstr, NULL) : NULL;
        if (cstr) {
-            argv[i] = strdup(cstr);
+            argv[i + 1] = strdup(cstr);
            (*env)->ReleaseStringUTFChars(env, jstr, cstr);
        } else {
-            argv[i] = strdup("");
+            argv[i + 1] = strdup("");
        }
-        (*env)->DeleteLocalRef(env, jstr);
+        if (jstr) (*env)->DeleteLocalRef(env, jstr);
    }
    argv[argc] = NULL; /* NULL-terminated for iperf */
    *out_argc = argc;
    return argv;
 }

-/* Free an argv array returned by java_string_array_to_argv() */
+/* Free an argv array returned by build_argv() */
 static void free_argv(char **argv, int argc) {
    if (!argv) return;
    for (int i = 0; i < argc; i++) {
@@ -169,43 +209,52 @@ static void free_argv(char **argv, int argc) {
    free(argv);
 }

+/* Retire the global test pointer and free it, under the mutex. */
+static void retire_test(void) {
+    pthread_mutex_lock(&g_test_mutex);
+    struct iperf_test *test = g_test;
+    g_test = NULL;
+    if (test) {
+        iperf_free_test(test);
+    }
+    pthread_mutex_unlock(&g_test_mutex);
+}
+
 /* ------------------------------------------------------------------ */
-/* Internal: clean up after iperf_run_client returns (normal path).   */
-/* Must be called only on the normal return path (NOT after longjmp). */
+/* Internal: clean up after iperf_run_client returns and report the    */
+/* outcome to Java. Called from both the normal and the longjmp path.  */
+/* Frees `state`; do not touch it afterwards.                          */
 /* ------------------------------------------------------------------ */
 static void iperf_cleanup_and_signal(JNIEnv *env,
                                     struct iperf_run_state *state,
                                     char **argv, int argc,
                                     int ret, int stopped) {
-    /* Wait for reader thread to finish */
-    pthread_join(state->reader_thread, NULL);
+    /* No more events can be delivered once the run is over. */
+    g_current_state = NULL;

-    /* Flush and close output */
-    fflush(state->outfile);
-    fclose(state->outfile);
+    /* Restore default signal handlers before g_sigend_jmp_buf goes stale. */
+    iperf_catch_sigend(SIG_DFL);

-    /* Clean up iperf */
-    iperf_free_test(g_test);
-    g_test = NULL;
-
-    /* Free argv */
+    retire_test();
    free_argv(argv, argc);

+    /* A user-requested stop shuts down the control socket, so
+     * iperf_run_client() returns -1 with "Broken pipe" — expected, not a
+     * failure. Check g_stop so that path is reported as a stop, not an error. */
+    int user_stopped = stopped || g_stop;
+    g_stop = 0;
+
    /* Signal result to Java */
-    if (stopped) {
-        signal_output(state, "[iPerf JNI] Test was stopped by user.\n");
+    if (user_stopped) {
+        signal_output(env, state, "{\"event\":\"jni_stopped\",\"data\":{}}");
    } else if (ret < 0) {
        char errbuf[256];
-        snprintf(errbuf, sizeof(errbuf),
-                 "[iPerf JNI] Test failed: %s\n",
-                 iperf_strerror(i_errno));
-        signal_error(state, errbuf);
-    } else {
-        signal_output(state, "[iPerf JNI] Test completed successfully.\n");
+        snprintf(errbuf, sizeof(errbuf), "%s", iperf_strerror(i_errno));
+        signal_error(env, state, errbuf);
    }

    /* Signal completion to Java */
-    signal_complete(state);
+    signal_complete(env, state);

    /* Free global ref and state struct */
    (*env)->DeleteGlobalRef(env, state->callback_ref);
@@ -228,55 +277,83 @@ static void sigend_handler(int sig) {
 /* ------------------------------------------------------------------ */
 /* JNI: Start an iperf3 test with the given arguments.                */
 /* Signature: void runIperfLive(String[] args, IperfCallback cb)      */
+/*                                                                    */
+/* BLOCKS until the test finishes — call from a worker thread.         */
 /* ------------------------------------------------------------------ */
 JNIEXPORT void JNICALL
 Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
        JNIEnv *env, jobject thiz,
        jobjectArray arguments, jobject callback) {

+    /* Resolve callback method IDs up front so failures can be reported. */
+    jclass callback_cls = (*env)->GetObjectClass(env, callback);
+    jmethodID mid_output = resolve_method(
+            env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
+    jmethodID mid_error = resolve_method(
+            env, callback_cls, "onError", "(Ljava/lang/String;)V");
+    jmethodID mid_complete = resolve_method(
+            env, callback_cls, "onComplete", "()V");
+
+    /* If the names did not resolve there is no way to report anything: the
+     * reporting path is the thing that is missing. Bail out loudly instead.
+     *
+     * In practice this means R8 renamed the callback in a release build and
+     * android/app/proguard-rules.pro has stopped covering it. */
+    if (!mid_output || !mid_error || !mid_complete) {
+        LOGE("Callback methods did not resolve (onOutput=%p onError=%p "
+             "onComplete=%p) — check the -keep rules for IperfCallback",
+             mid_output, mid_error, mid_complete);
+        return;
+    }
+
+    /* Report a startup failure directly on the callback object and finish,
+     * so Dart's completer always resolves instead of waiting for a timeout. */
+    #define FAIL_EARLY(msg) do {                                              \
+        LOGE("%s", msg);                                                      \
+        if (mid_error) {                                                      \
+            jstring jm = (*env)->NewStringUTF(env, msg);                      \
+            if (jm) {                                                         \
+                (*env)->CallVoidMethod(env, callback, mid_error, jm);         \
+                (*env)->DeleteLocalRef(env, jm);                              \
+            }                                                                 \
+        }                                                                     \
+        if (mid_complete) (*env)->CallVoidMethod(env, callback, mid_complete); \
+    } while (0)
+
+    /* Refuse to start a second concurrent test — the globals above hold
+     * exactly one test's worth of state. */
+    pthread_mutex_lock(&g_test_mutex);
+    int busy = (g_test != NULL);
+    pthread_mutex_unlock(&g_test_mutex);
+    if (busy) {
+        FAIL_EARLY("A test is already running.");
+        return;
+    }
+
    /* Create the iperf test object */
    struct iperf_test *test = iperf_new_test();
    if (!test) {
-        const char *err = "Failed to create iperf test";
-        LOGE("%s", err);
+        FAIL_EARLY("Failed to create iperf test");
        return;
    }

    iperf_defaults(test);
-    g_test = test;

-    /*
-     * Convert Java String[] -> char** argv, prepending "iperf3" as argv[0].
-     * iperf_parse_arguments() expects argv[0] to be the program name;
-     * passing args directly from Dart means argv[0] would be "-c",
-     * which iperf3 misinterprets as the program name, not the client flag.
-     */
-    int dart_argc = (*env)->GetArrayLength(env, arguments);
-    int total_argc = dart_argc + 1;  /* +1 for "iperf3" */
-    char **argv = malloc((total_argc + 1) * sizeof(char *));
+    pthread_mutex_lock(&g_test_mutex);
+    g_test = test;
+    pthread_mutex_unlock(&g_test_mutex);
+
+    int total_argc = 0;
+    char **argv = build_argv(env, arguments, &total_argc);
    if (!argv) {
-        const char *err = "Failed to allocate argv";
-        LOGE("%s", err);
-        iperf_free_test(test);
-        g_test = NULL;
+        retire_test();
+        FAIL_EARLY("Failed to allocate argv");
        return;
    }
-    argv[0] = strdup("iperf3");
-    for (int i = 0; i < dart_argc; i++) {
-        jstring jstr = (jstring) (*env)->GetObjectArrayElement(env, arguments, i);
-        const char *cstr = (*env)->GetStringUTFChars(env, jstr, NULL);
-        if (cstr) {
-            argv[i + 1] = strdup(cstr);
-            (*env)->ReleaseStringUTFChars(env, jstr, cstr);
-        } else {
-            argv[i + 1] = strdup("");
-        }
-        (*env)->DeleteLocalRef(env, jstr);
-    }
-    argv[total_argc] = NULL; /* NULL-terminated for iperf */

-    /* Set a reasonable connect timeout (30s) to avoid hanging on DNS resolution.
-     * Default iperf3 connect timeout is 120s which is far too long. */
+    /* Set a reasonable connect timeout (30s) to avoid hanging on DNS
+     * resolution. Default iperf3 connect timeout is 120s, far too long for a
+     * phone UI. Set before parsing so an explicit --connect-timeout wins. */
    test->settings->connect_timeout = 30000;

    /* Parse arguments */
@@ -284,24 +361,9 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
        char errbuf[256];
        snprintf(errbuf, sizeof(errbuf),
                 "Argument parse error: %s", iperf_strerror(i_errno));
-        LOGE("Parse error: %s", errbuf);
        free_argv(argv, total_argc);
-        iperf_free_test(test);
-        g_test = NULL;
-        return;
-    }
-
-    /* Create a pipe to capture iperf's stdout/stderr */
-    int pipefd[2];
-    if (pipe(pipefd) != 0) {
-        free_argv(argv, total_argc);
-        const char *err = "Failed to create output pipe";
-        LOGE("pipe() failed: %s", strerror(errno));
-
-        signal_error((struct iperf_run_state *) 0, err);
-
-        iperf_free_test(test);
-        g_test = NULL;
+        retire_test();
+        FAIL_EARLY(errbuf);
        return;
    }

@@ -310,35 +372,28 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
            calloc(1, sizeof(struct iperf_run_state));
    if (!state) {
        free_argv(argv, total_argc);
-        close(pipefd[0]);
-        close(pipefd[1]);
-        iperf_free_test(test);
-        g_test = NULL;
+        retire_test();
+        FAIL_EARLY("Failed to allocate run state");
        return;
    }

-    /* Resolve callback method IDs (do this in the calling thread) */
-    jclass callback_cls = (*env)->GetObjectClass(env, callback);
-    state->mid_output = (*env)->GetMethodID(
-            env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
-    state->mid_error = (*env)->GetMethodID(
-            env, callback_cls, "onError", "(Ljava/lang/String;)V");
-    state->mid_complete = (*env)->GetMethodID(
-            env, callback_cls, "onComplete", "()V");
-
-    /* Get JavaVM for thread attachment */
    JavaVM *jvm;
    (*env)->GetJavaVM(env, &jvm);

-    state->env = env;
+    state->mid_output = mid_output;
+    state->mid_error = mid_error;
+    state->mid_complete = mid_complete;
    state->callback_ref = (*env)->NewGlobalRef(env, callback);
-    state->outfile = fdopen(pipefd[1], "w");
-    state->pipe_fd[0] = pipefd[0];
    state->jvm = jvm;

-    /* Redirect iperf's output to our pipe */
-    test->outfile = state->outfile;
-    setvbuf(test->outfile, NULL, _IOLBF, 0); /* Line-buffered */
+    /* Deliver results as a stream of JSON events straight to
+     * json_event_callback, rather than as text through test->outfile.
+     * --json-stream sets both of these flags, so setting json_stream alone
+     * would leave iperf3 printing human-readable text as well. */
+    iperf_set_test_json_output(test, 1);
+    iperf_set_test_json_stream(test, 1);
+    iperf_set_test_json_callback(test, json_event_callback);
+    g_current_state = state;

    /* Set temp directory for stream buffers (mkstemp in iperf_new_stream).
     * On Android, /data/local/tmp is NOT writable from the app sandbox —
@@ -346,42 +401,26 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
     * the strdup internally. */
    iperf_set_test_template(test, g_tmp_template);

+    #undef FAIL_EARLY
+
    /*
     * Set up signal handling BEFORE calling iperf_run_client().
     * iperf3's run() function uses setjmp/longjmp for signal handling.
     * - setjmp returns 0 on first call (normal path)
     * - setjmp returns non-zero when called via longjmp (signal path)
     *
-     * Both paths share the same `state`, `argv`, `argc` variables,
-     * so the stack frame is preserved across the longjmp.
+     * `state` and `argv` are assigned before setjmp and never reassigned
+     * afterwards, so both paths observe the same values.
     */
    if (setjmp(g_sigend_jmp_buf) == 0) {
        /* Normal path — run the test */
        signal(SIGPIPE, SIG_IGN);  /* Ignore SIGPIPE for socket errors */
        iperf_catch_sigend(sigend_handler);

-        /* Notify Java that the test is starting */
-        signal_output(state, "[iPerf JNI] Starting iPerf3 client...\n");
-
-        /* Spawn reader thread to forward iperf output to Java */
-        if (pthread_create(&state->reader_thread, NULL,
-                           reader_thread_func, state) != 0) {
-            free_argv(argv, total_argc);
-            close(pipefd[0]);
-            close(pipefd[1]);
-            const char *err = "Failed to start output reader thread";
-            LOGE("%s", err);
-            signal_error(state, err);
-            iperf_free_test(test);
-            g_test = NULL;
-            free(state);
-            return;
-        }
-
-        /* Run the test */
        g_stop = 0;
        int ret = iperf_run_client(test);
-        LOGI("iperf_run_client returned: %d i_errno=%d strerror=%s ctrl_sck=%d", ret, i_errno, iperf_strerror(i_errno), test->ctrl_sck);
+        LOGI("iperf_run_client returned: %d i_errno=%d strerror=%s",
+             ret, i_errno, iperf_strerror(i_errno));

        /*
         * We get here after iperf_run_client returns normally.
@@ -392,58 +431,44 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
    } else {
        /*
         * We got here via longjmp() from sigend_handler.
-         * Clean up resources allocated before the setjmp.
-         * NOTE: state, argv, argc are still valid on the stack.
+         * iperf_cleanup_and_signal() frees everything, so there is nothing
+         * to unwind by hand here.
         */
        LOGI("Test interrupted by signal %d", g_signed_sig);
-
-        /* Stop flag for cleanup */
        g_stop = 1;
-
-        /* Close the output file (the pipe write end) */
-        if (state->outfile) {
-            fclose(state->outfile);
-        }
-
-        /* Free argv (argv is still valid across longjmp since it's on stack) */
-        free_argv(argv, total_argc);
-
-        /* Run the cleanup with stopped=true.
-         * Note: argv is NULL, argc=0 so free_argv is a no-op.
-         * The state struct will be freed inside this function. */
-        iperf_cleanup_and_signal(env, state, NULL, 0, 0, 1);
+        iperf_cleanup_and_signal(env, state, argv, total_argc, 0, 1);
    }
 }

 /* ------------------------------------------------------------------ */
 /* JNI: Gracefully stop a running iperf3 test.                        */
 /* Signature: void forceStopIperfTest(IperfCallback cb)               */
+/*                                                                    */
+/* Runs on the platform thread while the test runs on a worker thread, */
+/* so the whole body holds g_test_mutex: that keeps the worker from    */
+/* freeing g_test underneath us.                                      */
 /* ------------------------------------------------------------------ */
 JNIEXPORT void JNICALL
 Java_com_novoyuuparosk_iperf3gui_IperfRunner_forceStopIperfTest(
        JNIEnv *env, jobject thiz, jobject callback) {
-    if (!g_test || g_test->done) return;

-    /* Set the stop flag */
-    g_stop = 1;
-    g_test->done = 1;
-    iperf_set_send_state(g_test, IPERF_DONE);
+    pthread_mutex_lock(&g_test_mutex);
+    int requested = 0;
+    if (g_test && !g_test->done) {
+        g_stop = 1;
+        g_test->done = 1;
+        iperf_set_send_state(g_test, IPERF_DONE);

-    /* Try to unblock select() on the control socket */
-    if (g_test->ctrl_sck >= 0) {
-        shutdown(g_test->ctrl_sck, SHUT_RDWR);
+        /* Try to unblock select() on the control socket */
+        if (g_test->ctrl_sck >= 0) {
+            shutdown(g_test->ctrl_sck, SHUT_RDWR);
+        }
+        requested = 1;
    }
+    pthread_mutex_unlock(&g_test_mutex);

-    /* Notify Java */
-    jclass callback_cls = (*env)->GetObjectClass(env, callback);
-    jmethodID mid_output = (*env)->GetMethodID(
-            env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
-    if (mid_output) {
-        jstring msg = (*env)->NewStringUTF(env,
-                                           "[iPerf JNI] Requested graceful stop.");
-        (*env)->CallVoidMethod(env, callback, mid_output, msg);
-        (*env)->DeleteLocalRef(env, msg);
-    }
+    if (!requested) return;
+    LOGI("Graceful stop requested");
 }

 /* ------------------------------------------------------------------ */
@@ -453,7 +478,10 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_forceStopIperfTest(
 JNIEXPORT jboolean JNICALL
 Java_com_novoyuuparosk_iperf3gui_IperfRunner_isTestRunning(JNIEnv *env,
                                                           jobject thiz) {
-    return (g_test != NULL && !g_test->done);
+    pthread_mutex_lock(&g_test_mutex);
+    jboolean running = (g_test != NULL && !g_test->done);
+    pthread_mutex_unlock(&g_test_mutex);
+    return running;
 }

 /* ------------------------------------------------------------------ */
@@ -4,24 +4,38 @@ import android.os.Handler
 import android.os.Looper
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.plugin.common.MethodChannel
+import java.util.concurrent.Executors

 /**
 * Kotlin binding layer for native iperf3 via JNI.
 *
 * iperf3 runs natively inside the app process — no Process.start() needed,
- * no SELinux restrictions. Output is streamed live to the Flutter UI via
- * the IperfCallback interface, with all callbacks posted to the main thread.
+ * no SELinux restrictions.
+ *
+ * Threading: runIperfLive() blocks for the entire duration of the test, so it
+ * runs on a dedicated worker thread. Running it on the platform thread would
+ * freeze the UI and — because output is delivered by posting to the main
+ * looper — stall every callback until the test was already over.
 */
 object IperfRunner : FlutterPlugin {

+    private const val CHANNEL = "com.novoyuuparosk.iperf3gui/iperf"
+
    private var channel: MethodChannel? = null
    private var appContext: android.content.Context? = null
    private val mainHandler = Handler(Looper.getMainLooper())

+    /** Serialises test runs: one test at a time, off the platform thread. */
+    private val runExecutor =
+        Executors.newSingleThreadExecutor { r -> Thread(r, "iperf3-run") }
+
+    private var nativeLibraryLoaded = false
+
    init {
        try {
            android.util.Log.i("IperfRunner", "Loading native library...")
            System.loadLibrary("iperf3jni")
+            nativeLibraryLoaded = true
            android.util.Log.i("IperfRunner", "Native library loaded successfully")
        } catch (e: UnsatisfiedLinkError) {
            android.util.Log.e("IperfRunner", "Failed to load native library: ${e.message}")
@@ -31,62 +45,87 @@ object IperfRunner : FlutterPlugin {

    override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        appContext = binding.applicationContext
-        channel = MethodChannel(binding.binaryMessenger, "com.novoyuuparosk.iperf3gui/iperf")
+        channel = MethodChannel(binding.binaryMessenger, CHANNEL)
        channel?.setMethodCallHandler { call, result ->
            when (call.method) {
-                "runIperf" -> {
-                    val args = call.argument<List<String>>("args")?.toTypedArray()
-                    if (args != null) {
-                        // Set temp dir to app's cache dir — /data/local/tmp is NOT writable
-                        appContext?.cacheDir?.absolutePath?.let { cacheDir ->
-                            setTempDir(cacheDir)
-                        }
-                        // Wrap callbacks so they always run on the main thread.
-                        // The native reader thread cannot call invokeMethod directly.
-                        val safeCallback = MainThreadCallback(
-                            onOutput = { line ->
-                                channel?.invokeMethod("onOutput", mapOf("output" to line))
-                            },
-                            onError = { error ->
-                                channel?.invokeMethod("onError", mapOf("error" to error))
-                            },
-                            onComplete = {
-                                channel?.invokeMethod("onComplete", emptyMap<String, Any>())
-                            }
-                        )
-                        runIperfLive(args, safeCallback)
-                        result.success(null)
-                    } else {
-                        result.error("INVALID_ARGS", "args must be a String array", null)
-                    }
-                }
-                "stopIperf" -> {
-                    val safeCallback = MainThreadCallback(
-                        onOutput = { line ->
-                            channel?.invokeMethod("onOutput", mapOf("output" to line))
-                        },
-                        onError = { error ->
-                            channel?.invokeMethod("onError", mapOf("error" to error))
-                        },
-                        onComplete = {
-                            channel?.invokeMethod("onComplete", emptyMap<String, Any>())
-                        }
-                    )
-                    forceStopIperfTest(safeCallback)
-                    result.success(null)
-                }
-                "isTestRunning" -> {
-                    result.success(isTestRunning())
-                }
+                "runIperf" -> handleRunIperf(call.argument<List<String>>("args"), result)
+                "stopIperf" -> handleStopIperf(result)
+                "isTestRunning" -> result.success(nativeLibraryLoaded && isTestRunning())
                else -> result.notImplemented()
            }
        }
    }

    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+        // Stop any in-flight test: its callbacks would otherwise fire into a
+        // dead channel, and the worker thread would keep the socket open.
+        if (nativeLibraryLoaded && isTestRunning()) {
+            forceStopIperfTest(NoopCallback)
+        }
+        channel?.setMethodCallHandler(null)
        channel = null
+        appContext = null
    }

+    private fun handleRunIperf(args: List<String>?, result: MethodChannel.Result) {
+        if (!nativeLibraryLoaded) {
+            result.error(
+                "NATIVE_LIB_MISSING",
+                "libiperf3jni.so failed to load — cannot run iperf3",
+                null,
+            )
+            return
+        }
+        if (args == null) {
+            result.error("INVALID_ARGS", "args must be a String array", null)
+            return
+        }
+        if (isTestRunning()) {
+            result.error("ALREADY_RUNNING", "A test is already running", null)
+            return
+        }
+
+        // Set temp dir to the app's cache dir — mkstemp() in iperf_new_stream()
+        // cannot write to /data/local/tmp from inside the app sandbox.
+        appContext?.cacheDir?.absolutePath?.let { setTempDir(it) }
+
+        val argv = args.toTypedArray()
+        val callback = mainThreadCallback()
+
+        // Hand back control immediately; progress arrives via the callback.
+        result.success(null)
+
+        runExecutor.execute {
+            try {
+                runIperfLive(argv, callback)
+            } catch (t: Throwable) {
+                android.util.Log.e("IperfRunner", "runIperfLive threw", t)
+                callback.onError("Native error: ${t.message}")
+                callback.onComplete()
+            }
+        }
+    }
+
+    private fun handleStopIperf(result: MethodChannel.Result) {
+        if (!nativeLibraryLoaded) {
+            result.success(null)
+            return
+        }
+        forceStopIperfTest(mainThreadCallback())
+        result.success(null)
+    }
+
+    /**
+     * Build a callback that forwards native output to Dart, hopping to the
+     * main thread first: MethodChannel.invokeMethod must not be called from
+     * the native reader thread.
+     */
+    private fun mainThreadCallback(): IperfCallback = MainThreadCallback(
+        emitOutput = { line -> channel?.invokeMethod("onOutput", mapOf("output" to line)) },
+        emitError = { error -> channel?.invokeMethod("onError", mapOf("error" to error)) },
+        emitComplete = { channel?.invokeMethod("onComplete", emptyMap<String, Any>()) },
+    )
+
    // ─────────────────────────────────────────────────────────────────
    // Native method bindings
    // ─────────────────────────────────────────────────────────────────
@@ -107,23 +146,35 @@ object IperfRunner : FlutterPlugin {
    }

    /**
-     * Thread-safe wrapper: posts all callbacks to the main thread.
-     * This is required because the native reader thread cannot safely
-     * call MethodChannel.invokeMethod from a background thread.
+     * Posts every callback to the main thread.
+     *
+     * The lambdas are named `emit*` rather than `on*` on purpose: a constructor
+     * property with the same name as the overriding method would make
+     * `onOutput(line)` resolve back to this class's own method — an endless
+     * post-and-re-post loop that never reaches the channel.
     */
    private class MainThreadCallback(
-        private val onOutput: (String) -> Unit,
-        private val onError: (String) -> Unit,
-        private val onComplete: () -> Unit
+        private val emitOutput: (String) -> Unit,
+        private val emitError: (String) -> Unit,
+        private val emitComplete: () -> Unit,
    ) : IperfCallback {
        override fun onOutput(line: String) {
-            mainHandler.post { onOutput(line) }
+            mainHandler.post { emitOutput(line) }
        }
+
        override fun onError(error: String) {
-            mainHandler.post { onError(error) }
+            mainHandler.post { emitError(error) }
        }
+
        override fun onComplete() {
-            mainHandler.post { onComplete() }
+            mainHandler.post { emitComplete() }
        }
    }
-}
+
+    /** Used when a stop is requested with no channel left to report to. */
+    private object NoopCallback : IperfCallback {
+        override fun onOutput(line: String) = Unit
+        override fun onError(error: String) = Unit
+        override fun onComplete() = Unit
+    }
+}
@@ -6,19 +6,25 @@ A Flutter-based Android GUI wrapper for iperf3, the popular network performance

 ```
 lib/                          # Flutter/Dart application layer
-├── main.dart                 # App entry point (MaterialApp)
-├── domain/                   # Business logic (platform-independent)
+├── main.dart                 # Composition root: picks the Iperf3Runner impl
+├── main_headless.dart        # Runs a test with no widgets (see Layering)
+├── domain/                   # Pure Dart — no Flutter import
 │   ├── models/
 │   │   ├── test_configuration.dart   # Server, port, duration, interval, parallel streams
-│   │   └── iperf3_result.dart        # Raw output + exit code
+│   │   ├── iperf3_result.dart        # Raw output, exit code, stopped flag
+│   │   ├── iperf3_event.dart         # Parsed --json-stream reports
+│   │   └── iperf3_session.dart       # One run accumulated: samples, totals, stats
 │   └── services/
-│       ├── iperf3_service.dart       # Dart → MethodChannel bridge (async with Completer)
-│       └── iperf3_binary_path_provider.dart   # Deprecated (kept for reference)
-└── ui/                       # Presentation layer
+│       └── iperf3_runner.dart        # The contract the UI depends on
+├── data/                     # Transport — flutter/services only
+│   └── services/
+│       └── iperf3_service.dart       # Iperf3Runner over MethodChannel → JNI
+└── ui/                       # Presentation
    └── features/
        └── test_run/
-            ├── test_run_screen.dart          # Server/port inputs + GO button
-            └── test_run_view_model.dart      # State machine: idle → running → completed/error
+            ├── test_run_screen.dart            # Inputs, GO/STOP, live transcript
+            ├── test_run_view_model.dart        # idle → running → completed/error
+            └── iperf3_event_formatter.dart     # Events → iperf3-style text

 android/app/src/main/
 ├── kotlin/                     # Kotlin plugin layer
@@ -39,23 +45,123 @@ android/app/src/main/
 User taps GO
  → Dart TestRunViewModel.runTest(config)
  → Iperf3Service.run(config) via MethodChannel
-  → Kotlin IperfRunner.runIperfLive(args, callback)
-  → JNI C: java_string_array_to_argv() → iperf_parse_arguments()
-  → iperf_run_client(test)
-  → Reader thread pipes stdout → CallVoidMethod → Dart onOutput callbacks
+  → Kotlin IperfRunner: submits to the iperf3-run worker thread, returns at once
+  → JNI C: build_argv() (prepends argv[0]) → iperf_parse_arguments()
+  → iperf_run_client(test)             [blocks on the worker thread]
+  → iperf3 json_callback → one JSON event per report → CallVoidMethod
+  → main-thread hop → Dart onOutput → Iperf3Event.parse()
+  → Iperf3Service.events → view model: transcript + interval series + summary
  → On completion: Dart Completer resolves with Iperf3Result
 ```

+## Layering
+
+Dependencies point inward: `ui → domain ← data`, never the reverse.
+
+| Layer | May import | Holds |
+|---|---|---|
+| `domain` | nothing else in this package, no Flutter | models and the `Iperf3Runner` contract |
+| `data` | `domain`, `package:flutter/services.dart` | the MethodChannel/JNI implementation |
+| `ui` | `domain` | widgets, view model, formatting |
+| `main.dart` | everything | the single place that picks an implementation |
+
+The UI depends on `Iperf3Runner`, not on `Iperf3Service`, so presentation names
+no transport. That is what lets `test/widget_test.dart` drive the real widget
+tree against an in-memory runner with no MethodChannel, native library or
+device — and what keeps a test double at five stable members instead of
+mirroring the transport's whole surface.
+
+**The core does not need the UI.** What happened during a run is accumulated by
+`Iperf3Session` in the domain layer — samples, totals, errors, and the mean,
+peak and retransmit figures over them. The view model holds no run data of its
+own and the screen derives no numbers; both read the session. Replacing the
+presentation layer therefore means rewriting rendering, not re-deriving results.
+
+`lib/main_headless.dart` is the standing proof: it runs a full test through
+`Iperf3Service` and `Iperf3Session` with `WidgetsFlutterBinding` but no
+`runApp` — no widget tree, no render surface. If the run path ever starts
+needing the UI, it stops working.
+
+```bash
+flutter run -t lib/main_headless.dart \
+  --dart-define=IPERF_SERVER=192.168.2.182 --dart-define=IPERF_STREAMS=4
+```
+
+Use it when a figure has to be trustworthy. A 4-stream local run reports
+**30.2% local CPU headless against 79.9% through the UI** — the phone is near
+CPU-bound at gigabit rates, so a repainting transcript measurably depresses
+throughput. Numbers taken through the UI are pessimistic.
+
+`test/architecture_test.dart` enforces all of this by reading the actual
+imports under `lib/`, including a check that no fourth layer directory has
+appeared unnoticed. Change the layering there when the layering should change;
+don't work around it.
+
 ## Key Design Decisions

 ### JNI Over Process Execution
 Android SELinux Enforcing mode blocks `execve()` from the `untrusted_app` domain, making Process.start() of external binaries fail with Permission denied. Compiling iperf3 as a shared library linked into the app process eliminates this restriction entirely — iperf3 code runs in-process with no domain transitions needed.

+### Threading
+`runIperfLive()` blocks for the whole test, so Kotlin submits it to a dedicated
+single-thread executor and hands control straight back to Dart. Running it on the
+Flutter platform thread froze the UI and — because output is delivered by posting
+to the main looper — stalled every callback until the test was already over.
+
 ### Callback Mechanism
 The JNI bridge uses `CallVoidMethod` on stored `jmethodID`s to invoke the Kotlin `IperfCallback` interface, NOT function pointer casts. Direct function pointer casts caused SIGBUS crashes on ARM due to JNINativeInterface method ID layout differences.

-### Output Streaming
-iperf3 output is redirected via pipe to a background reader thread that attaches to the Java VM via `AttachCurrentThread` and invokes callbacks via `CallVoidMethod`. The reader thread frees the state struct on exit; the JNI caller owns the callback object's lifetime.
+### Output via json_callback, not a pipe
+The test runs with `json_output` and `json_stream` set and a `json_callback`
+installed, so iperf3 hands each report to the bridge as a JSON string and never
+writes to `test->outfile`. `iperf.h` describes the hook as "allow user apps to
+receive the JSON strings, instead of writing them to the output file" — this is
+its intended use.
+
+An earlier design piped `test->outfile` to a reader thread. That imposed two
+constraints, both of which were gotten wrong and deadlocked every test: the
+pipe's write end had to be closed *before* joining a reader blocked in
+`fgets()`, and exactly one side could own the shared state struct. Reading from
+the callback removes the pipe, the reader thread and both constraints. Don't
+reintroduce it.
+
+`json_callback` carries no user-data pointer, so the run state is reached
+through a global published before `iperf_run_client()` and cleared afterwards;
+only one test may run at a time, which `runIperfLive` enforces. The callback
+fires on iperf3's reporting thread, so it resolves a `JNIEnv` for the calling
+thread rather than reusing a stored one.
+
+Dart parses each event into a sealed `Iperf3Event`; unrecognised output becomes
+an `Iperf3LogLine` rather than being discarded. The UI rebuilds iperf3's text
+layout from the events and keeps the interval series as data.
+
+### Embedding a CLI in a long-lived process
+iperf3's `main()` runs one test and exits, so anything it leaves behind is
+reclaimed by the OS. Linked into an app process that runs tests repeatedly for
+hours, every such leftover becomes this app's problem. What that costs in
+practice:
+
+- **Signal handlers are process-global.** `iperf_catch_sigend()` and
+  `signal(SIGPIPE, SIG_IGN)` change behaviour for the whole process, Flutter and
+  ART included. Handlers are restored to `SIG_DFL` when a test ends.
+- **`g_sigend_jmp_buf` outlives its frame.** Harmless in a process about to
+  exit; a jump into a dead stack frame otherwise. Same fix as above.
+- **Globals mean one test at a time.** `i_errno` and the bridge's own statics
+  hold a single test's worth of state, so concurrent runs are refused.
+
+What iperf3 itself handles correctly, verified rather than assumed: per-stream
+threads are joined (`iperf_client_api.c`), stream buffer fds are closed, and the
+`mkstemp` temp file is `unlink`ed immediately after creation
+(`iperf_api.c:4652`), so nothing accumulates in the cache dir. Measured across
+four consecutive 4-stream runs on device, thread count returned to baseline
+(33 → 40 mid-run → 34) and fd count returned exactly to baseline (175 → 183 →
+175).
+
+### Stop Handling
+A stop shuts down the control socket, so `iperf_run_client()` returns -1 with
+"Broken pipe". That is the expected outcome of a stop, not a failure, so the
+bridge checks its own `g_stop` flag and reports a stop rather than an error; the
+flag travels up to the UI as `Iperf3Result.stopped`.

 ### Async Pattern
 Dart uses `Completer<Iperf3Result>` to await native completion. The MethodChannel callback handler resolves the completer on `onComplete`, with a timeout fallback that calls `stopIperf` on the native layer.
@@ -72,9 +178,66 @@ Dart uses `Completer<Iperf3Result>` to await native completion. The MethodChanne

 | Kotlin Method | JNI Signature | Purpose |
 |---|---|---|
-| `runIperfLive(String[], IperfCallback)` | `runIperfLive` | Start test with args and callback |
+| `runIperfLive(String[], IperfCallback)` | `runIperfLive` | Run a test to completion — blocks, call off the platform thread |
 | `forceStopIperfTest(IperfCallback)` | `forceStopIperfTest` | Graceful stop via shutdown() |
 | `isTestRunning()` | `isTestRunning` | Check if test is in progress |
+| `setTempDir(String)` | `setTempDir` | Point `mkstemp()` at the app cache dir |
+
+## CI
+
+Both jobs run on a **self-hosted runner registered at `android-stuff` org scope**,
+targeted by the capability label `flutter-android` rather than by hostname.
+`tool/setup_ci_runner.sh` provisions it.
+
+It does not run on the Gitea host. Gitea lives on an aarch64 box, and Flutter
+cannot build an Android APK on a Linux arm64 host at all — the SDK ships no
+arm64-host `gen_snapshot` ([flutter#189724](https://github.com/flutter/flutter/issues/189724),
+[#75864](https://github.com/flutter/flutter/issues/75864), open as of July 2026).
+An x86_64 runner is a requirement, not a preference.
+
+The runner is **host mode**: jobs use the machine's own Flutter, JDK and Android
+SDK/NDK. CI therefore builds with the same toolchain that produced the verified
+release, and no NDK is downloaded per run. The cost is that there is no
+container boundary, which is what decides the next paragraph.
+
+Jobs run as a dedicated unprivileged account, `gitea-runner`, in the
+`flutterdev` group. In host mode the service account *is* the sandbox — there
+is no other — and a workflow file is code that runs as whoever the service runs
+as. A human account would hand every workflow that user's home directory and
+SSH keys; root would be worse and would also miss the warm caches in that home,
+re-downloading dependencies every run. The dedicated account keeps its own
+Gradle and pub caches under `/var/lib/gitea-runner`, so the first Android build
+is slow by design and later ones are not.
+
+`flutterdev` is what grants write access to `/opt/flutter` and
+`/opt/android-sdk`; both carry ACLs with `group:flutterdev:rwx` and matching
+`default:` entries, so new files inherit it. The setup script proves that access
+as the service account rather than assuming group membership is sufficient.
+
+It installs a **system** service, not a user service: root-managed lifecycle,
+starts at boot, no lingering session. That the service is root-managed is
+unrelated to the jobs being unprivileged — `User=` in the unit settles the
+second, and conflating the two is easy to do.
+
+`sudo ./tool/setup_ci_runner.sh --check` validates this machine's toolchain
+without creating anything.
+
+Two jobs:
+
+| Job | What it protects |
+|---|---|
+| `analyze` | `flutter analyze`, then `flutter test` — which includes `architecture_test.dart`, failing the build if a layer boundary is crossed |
+| `release-apk` | builds the **minified** APK and runs `tool/check_jni_keep_rules.sh` |
+
+The second exists because of a specific escape. A release APK that aborted on
+every test shipped once, while every on-device check passed — because those
+checks all used the debug build, which does not minify. Building the release APK
+is necessary but not sufficient: a renamed JNI callback still produces a
+*successful build* and a broken app. So the guard reads R8's `mapping.txt` for
+the callback classes and methods, and the DEX string pool for the native entry
+points. It is verified to fail: delete the keep rules from
+`android/app/proguard-rules.pro`, rebuild, and it reports `MainThreadCallback`,
+`onOutput`, `onError` and `onComplete` renamed.

 ## Building

@@ -93,7 +256,7 @@ adb install build/app/outputs/flutter-apk/app-debug.apk

 ## Dependencies

- Dart: `provider`, `path_provider`
+- Dart: `provider`
 - Android: CMake external native build
 - Native: iperf3 3.19, cJSON (single file)

@@ -1,9 +0,0 @@
-// This file is kept as a stub — iperf3 is now compiled as a native
-// shared library (libiperf3jni.so) via JNI.
-// The old binary-path-provider pattern (extract ELF from assets → chmod → execve)
-// was replaced by the JNI approach after SELinux blocked binary execution.
-// See .hermes/plans/ for details on the migration.
-
-// The Iperf3Service now uses MethodChannel to communicate with Kotlin/JNI:
-//   Dart → MethodChannel → Kotlin → JNI → iperf3 (same process)
-// No file extraction, no chmod, no Process.start needed.
@@ -1,142 +1,212 @@
 import 'dart:async';
-import 'dart:io';
+import 'dart:developer' as developer;

-import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';

-/// Service that runs iperf3 via JNI (native library).
+/// [Iperf3Runner] backed by the native iperf3 library over a MethodChannel.
 ///
 /// On Android, iperf3 is compiled into the app as a shared library (.so).
 /// This avoids SELinux restrictions on executing ELF binaries from assets.
 ///
-/// The service communicates with the native layer via a MethodChannel.
-/// Output is streamed live to the Flutter UI through callbacks.
-class Iperf3Service {
-  static const MethodChannel _channel =
-      MethodChannel('com.novoyuuparosk.iperf3gui/iperf');
+/// The service talks to the native layer over a MethodChannel. The test runs
+/// in `--json-stream` mode, so each native report arrives as one JSON object;
+/// they are parsed and published on [events] while the test runs. [run]
+/// resolves once the native layer reports completion, carrying the raw JSON
+/// lines as the result's output.
+class Iperf3Service implements Iperf3Runner {
+  Iperf3Service() {
+    _channel.setMethodCallHandler(_handleNativeCall);
+  }

-  /// Collect output lines during a test run.
-  final List<String> _outputBuffer = [];
+  /// A channel's handler is keyed by channel name in the binary messenger, so
+  /// it is process-global: constructing a second instance would take the
+  /// handler away from the first. The app composes exactly one, in main().
+  final MethodChannel _channel = const MethodChannel(_channelName);
+
+  static const String _channelName = 'com.novoyuuparosk.iperf3gui/iperf';
+
+  /// Exit code reported when the native layer signalled an error.
+  static const int exitCodeNativeError = 1;
+
+  /// Exit code reported when another test is already in flight.
+  static const int exitCodeBusy = -2;
+
+  /// Exit code reported when the test could not be started at all.
+  static const int exitCodeStartFailed = -1;
+
+  /// Exit code reported when the native layer never signalled completion.
+  static const int exitCodeTimeout = -3;
+
+  /// Events parsed from the native layer during the current run.
+  final StreamController<Iperf3Event> _eventController =
+      StreamController<Iperf3Event>.broadcast();
+
+  /// Live reports, one event per native report. Use this to render progress.
+  @override
+  Stream<Iperf3Event> get events => _eventController.stream;
+
+  /// Raw JSON lines received during the current (or most recent) run.
+  final List<String> _rawLines = [];

  /// Completer that resolves when the native iperf3 test finishes.
  Completer<Iperf3Result>? _runCompleter;

  /// Whether iperf3 is currently running.
  bool _isRunning = false;
-
-  /// Whether iperf3 is currently running.
+  @override
  bool get isRunning => _isRunning;

+  /// Whether the native layer reported an error during this run.
+  bool _sawError = false;
+
+  /// Whether [stop] was called for the current run.
+  bool _stopRequested = false;
+
  /// Cancel any running test.
+  @override
  Future<void> stop() async {
    if (!_isRunning) return;
+    _stopRequested = true;
    try {
      await _channel.invokeMethod('stopIperf');
    } catch (e) {
-      debugPrint('Iperf3Service: error stopping: $e');
+      _log('Iperf3Service: error stopping: $e');
    }
  }

+  /// Release the stream controller. Call from the owner's dispose().
+  @override
+  Future<void> dispose() async {
+    _channel.setMethodCallHandler(null);
+    await _eventController.close();
+  }
+
  /// Run iperf3 with the given configuration.
  ///
-  /// Returns an [Iperf3Result] with stdout/stderr and exit code.
+  /// Returns an [Iperf3Result] with the full output and an exit code.
+  @override
  Future<Iperf3Result> run(TestConfiguration config) async {
    if (_isRunning) {
-      return Iperf3Result(
+      return const Iperf3Result(
        rawOutput: 'Another test is already running.',
-        exitCode: -2,
+        exitCode: exitCodeBusy,
      );
    }

    _isRunning = true;
-    _outputBuffer.clear();
+    _sawError = false;
+    _stopRequested = false;
+    _rawLines.clear();

-    final args = <String>[
-      '-c', config.server,
-      '-p', config.port.toString(),
-      '-t', config.duration.inSeconds.toString(),
-      '-i', config.interval.toString(),
-      '-P', config.parallelStreams.toString(),
-    ];
+    final args = config.toCliArgs();
+    _log('Iperf3Service: running: ${args.join(" ")}');

-    debugPrint('Iperf3Service: running: ${args.join(" ")}');
+    final completer = Completer<Iperf3Result>();
+    _runCompleter = completer;

-    // Set up the completer to await completion
-    _runCompleter = Completer<Iperf3Result>();
-
-    // Listen for events from native layer
-    _channel.setMethodCallHandler((call) async {
-      if (!_runCompleter!.isCompleted) {
-        switch (call.method) {
-          case 'onOutput':
-            final output = call.arguments['output'] as String?;
-            if (output != null) {
-              _outputBuffer.add(output);
-              debugPrint('Iperf3Service output: ${output.trim()}');
-            }
-            break;
-          case 'onError':
-            final error = call.arguments['error'] as String?;
-            if (error != null) {
-              debugPrint('Iperf3Service error: $error');
-              _outputBuffer.add('[ERROR] $error');
-              // Don't complete yet — the test might still be running
-            }
-            break;
-          case 'onComplete':
-            debugPrint('Iperf3Service: test completed');
-            _isRunning = false;
-            _runCompleter!.complete(
-              Iperf3Result(
-                rawOutput: _outputBuffer.join(''),
-                exitCode: 0,
-              ),
-            );
-            break;
-        }
-      }
-    });
-
-    // Start the test
    try {
      await _channel.invokeMethod('runIperf', {'args': args});
    } catch (e, stackTrace) {
-      debugPrint('Iperf3Service exception: $e');
-      debugPrint('Iperf3Service stack: $stackTrace');
-      _isRunning = false;
-      if (!_runCompleter!.isCompleted) {
-        _runCompleter!.completeError(e);
-      }
+      _log('Iperf3Service exception: $e');
+      _log('Iperf3Service stack: $stackTrace');
+      _finishRun();
      return Iperf3Result(
        rawOutput: 'Error starting iperf3: $e',
-        exitCode: -1,
+        exitCode: exitCodeStartFailed,
      );
    }

-    // Wait for the native layer to signal completion (with a timeout)
+    // Wait for the native layer to signal completion. The grace period covers
+    // DNS resolution and the 30s native connect timeout.
    try {
-      final result = await _runCompleter!.future.timeout(
-        config.duration + const Duration(seconds: 30),
+      return await completer.future.timeout(
+        config.duration + const Duration(seconds: 45),
        onTimeout: () {
-          debugPrint('Iperf3Service: timeout, stopping test');
-          stop();
+          _log('Iperf3Service: timeout, stopping test');
+          // Ask the native layer to wind down, then release local state so a
+          // stuck run can never lock the UI out of starting another test.
+          _channel.invokeMethod('stopIperf').catchError((Object e) {
+            _log('Iperf3Service: error stopping after timeout: $e');
+            return null;
+          });
+          _publish(const Iperf3Error('Timed out waiting for iperf3 to finish.'));
          return Iperf3Result(
-            rawOutput: 'Test timed out after ${config.duration.inSeconds}s',
-            exitCode: -3,
+            rawOutput: _rawOutput(),
+            exitCode: exitCodeTimeout,
          );
        },
      );
-      return result;
    } catch (e) {
-      debugPrint('Iperf3Service: error waiting for completion: $e');
+      _log('Iperf3Service: error waiting for completion: $e');
      return Iperf3Result(
        rawOutput: 'Test failed: $e',
-        exitCode: -1,
+        exitCode: exitCodeStartFailed,
      );
    } finally {
-      _runCompleter = null;
+      _finishRun();
    }
  }
+
+  /// Handle a callback pushed up from the Kotlin/JNI layer.
+  Future<void> _handleNativeCall(MethodCall call) async {
+    switch (call.method) {
+      case 'onOutput':
+        final output = call.arguments['output'] as String?;
+        if (output != null) {
+          _rawLines.add(output);
+          final event = Iperf3Event.parse(output);
+          // iperf3 reports a failed test as an `error` event rather than a
+          // non-zero return, so this is where most failures surface.
+          if (event is Iperf3Error) _sawError = true;
+          _publish(event);
+        }
+      case 'onError':
+        final error = call.arguments['error'] as String?;
+        if (error != null) {
+          // Not terminal on its own — iperf3 reports the failure reason and
+          // then completes, so wait for onComplete before resolving.
+          _sawError = true;
+          _publish(Iperf3Error(error));
+        }
+      case 'onComplete':
+        _log('Iperf3Service: test completed');
+        final completer = _runCompleter;
+        if (completer != null && !completer.isCompleted) {
+          completer.complete(
+            Iperf3Result(
+              rawOutput: _rawOutput(),
+              // A user-requested stop is a normal outcome, not a failure.
+              exitCode:
+                  (_sawError && !_stopRequested) ? exitCodeNativeError : 0,
+              stopped: _stopRequested,
+            ),
+          );
+        }
+      default:
+        _log('Iperf3Service: unhandled native call ${call.method}');
+    }
+  }
+
+  void _publish(Iperf3Event event) {
+    if (!_eventController.isClosed) {
+      _eventController.add(event);
+    }
+  }
+
+  /// The raw JSON stream as received, one event per line.
+  String _rawOutput() => _rawLines
+      .map((line) => line.endsWith('\n') ? line : '$line\n')
+      .join();
+
+  void _finishRun() {
+    _isRunning = false;
+    _runCompleter = null;
+  }
 }
+
+void _log(String message) =>
+    developer.log(message, name: 'Iperf3Service');
@@ -0,0 +1,238 @@
+import 'dart:convert';
+
+/// One report from iperf3's `--json-stream` output.
+///
+/// iperf3 emits `{"event": "<name>", "data": {...}}` per report; the events a
+/// client run produces are `start`, `interval`, `end` and `error`. The bridge
+/// adds `jni_stopped` when a run ended because the user stopped it.
+sealed class Iperf3Event {
+  const Iperf3Event();
+
+  /// Parse one line of `--json-stream` output.
+  ///
+  /// Returns an [Iperf3LogLine] for anything that is not a recognised JSON
+  /// event, so unexpected output is surfaced rather than dropped.
+  static Iperf3Event parse(String line) {
+    final trimmed = line.trim();
+    if (trimmed.isEmpty) return const Iperf3LogLine('');
+    if (!trimmed.startsWith('{')) return Iperf3LogLine(trimmed);
+
+    final Object? decoded;
+    try {
+      decoded = jsonDecode(trimmed);
+    } on FormatException {
+      return Iperf3LogLine(trimmed);
+    }
+    if (decoded is! Map<String, dynamic>) return Iperf3LogLine(trimmed);
+
+    final event = decoded['event'];
+    final data = decoded['data'];
+    if (event is! String) return Iperf3LogLine(trimmed);
+    final map = data is Map<String, dynamic> ? data : const <String, dynamic>{};
+
+    return switch (event) {
+      'start' => Iperf3Start.fromJson(map),
+      'interval' => Iperf3Interval.fromJson(map),
+      'end' => Iperf3End.fromJson(map),
+      'error' => Iperf3Error(_stringOf(data) ?? 'unknown error'),
+      'jni_stopped' => const Iperf3Stopped(),
+      _ => Iperf3LogLine(trimmed),
+    };
+  }
+
+  static String? _stringOf(Object? value) {
+    if (value is String) return value;
+    if (value is Map<String, dynamic>) {
+      final error = value['error'];
+      if (error is String) return error;
+    }
+    return null;
+  }
+}
+
+/// Connection details, emitted once at the start of a test.
+class Iperf3Start extends Iperf3Event {
+  final String? targetHost;
+  final int? targetPort;
+  final int? streamCount;
+  final int? durationSeconds;
+  final String? protocol;
+
+  const Iperf3Start({
+    this.targetHost,
+    this.targetPort,
+    this.streamCount,
+    this.durationSeconds,
+    this.protocol,
+  });
+
+  factory Iperf3Start.fromJson(Map<String, dynamic> data) {
+    final connecting = data['connecting_to'];
+    final testStart = data['test_start'];
+    return Iperf3Start(
+      targetHost: connecting is Map ? connecting['host'] as String? : null,
+      targetPort: connecting is Map ? _asInt(connecting['port']) : null,
+      streamCount: testStart is Map ? _asInt(testStart['num_streams']) : null,
+      durationSeconds: testStart is Map ? _asInt(testStart['duration']) : null,
+      protocol: testStart is Map ? testStart['protocol'] as String? : null,
+    );
+  }
+}
+
+/// One reporting interval, summed across all streams.
+class Iperf3Interval extends Iperf3Event {
+  final double start;
+  final double end;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+  final bool omitted;
+
+  /// Per-stream figures, when more than one stream is running.
+  final List<Iperf3StreamInterval> streams;
+
+  const Iperf3Interval({
+    required this.start,
+    required this.end,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+    this.omitted = false,
+    this.streams = const [],
+  });
+
+  factory Iperf3Interval.fromJson(Map<String, dynamic> data) {
+    // Non-bidirectional runs use "sum"; bidir adds "sum_bidir_reverse".
+    final sum = data['sum'] ?? data['sum_bidir_reverse'];
+    final sumMap = sum is Map<String, dynamic> ? sum : const <String, dynamic>{};
+    final rawStreams = data['streams'];
+
+    return Iperf3Interval(
+      start: _asDouble(sumMap['start']) ?? 0,
+      end: _asDouble(sumMap['end']) ?? 0,
+      bytes: _asInt(sumMap['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(sumMap['bits_per_second']) ?? 0,
+      retransmits: _asInt(sumMap['retransmits']),
+      omitted: sumMap['omitted'] == true,
+      streams: rawStreams is List
+          ? rawStreams
+              .whereType<Map<String, dynamic>>()
+              .map(Iperf3StreamInterval.fromJson)
+              .toList(growable: false)
+          : const [],
+    );
+  }
+}
+
+/// One stream's contribution to an interval.
+class Iperf3StreamInterval {
+  final int? socket;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+  final int? sendCwnd;
+  final int? rtt;
+
+  const Iperf3StreamInterval({
+    this.socket,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+    this.sendCwnd,
+    this.rtt,
+  });
+
+  factory Iperf3StreamInterval.fromJson(Map<String, dynamic> data) {
+    return Iperf3StreamInterval(
+      socket: _asInt(data['socket']),
+      bytes: _asInt(data['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(data['bits_per_second']) ?? 0,
+      retransmits: _asInt(data['retransmits']),
+      sendCwnd: _asInt(data['snd_cwnd']),
+      rtt: _asInt(data['rtt']),
+    );
+  }
+}
+
+/// Totals for the whole test, emitted once at the end.
+class Iperf3End extends Iperf3Event {
+  final Iperf3Total? sent;
+  final Iperf3Total? received;
+  final double? hostCpuPercent;
+  final double? remoteCpuPercent;
+
+  const Iperf3End({
+    this.sent,
+    this.received,
+    this.hostCpuPercent,
+    this.remoteCpuPercent,
+  });
+
+  factory Iperf3End.fromJson(Map<String, dynamic> data) {
+    final cpu = data['cpu_utilization_percent'];
+    return Iperf3End(
+      sent: Iperf3Total.fromJson(
+          data['sum_sent'] ?? data['sum_sent_bidir_reverse']),
+      received: Iperf3Total.fromJson(
+          data['sum_received'] ?? data['sum_received_bidir_reverse']),
+      hostCpuPercent: cpu is Map ? _asDouble(cpu['host_total']) : null,
+      remoteCpuPercent: cpu is Map ? _asDouble(cpu['remote_total']) : null,
+    );
+  }
+}
+
+/// A sent or received total from the `end` event.
+class Iperf3Total {
+  final double seconds;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+
+  const Iperf3Total({
+    required this.seconds,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+  });
+
+  static Iperf3Total? fromJson(Object? data) {
+    if (data is! Map<String, dynamic>) return null;
+    return Iperf3Total(
+      seconds: _asDouble(data['seconds']) ?? 0,
+      bytes: _asInt(data['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(data['bits_per_second']) ?? 0,
+      retransmits: _asInt(data['retransmits']),
+    );
+  }
+}
+
+/// iperf3 reported an error for this test.
+class Iperf3Error extends Iperf3Event {
+  final String message;
+  const Iperf3Error(this.message);
+}
+
+/// The run ended because the user stopped it.
+class Iperf3Stopped extends Iperf3Event {
+  const Iperf3Stopped();
+}
+
+/// Output that was not a recognised JSON event.
+class Iperf3LogLine extends Iperf3Event {
+  final String text;
+  const Iperf3LogLine(this.text);
+}
+
+int? _asInt(Object? value) => switch (value) {
+      int v => v,
+      double v => v.round(),
+      String v => int.tryParse(v),
+      _ => null,
+    };
+
+double? _asDouble(Object? value) => switch (value) {
+      double v => v,
+      int v => v.toDouble(),
+      String v => double.tryParse(v),
+      _ => null,
+    };
@@ -3,8 +3,13 @@ class Iperf3Result {
  final String rawOutput;
  final int exitCode;

+  /// Whether the run ended because the user asked it to stop, rather than
+  /// finishing its configured duration or failing.
+  final bool stopped;
+
  const Iperf3Result({
    required this.rawOutput,
    required this.exitCode,
+    this.stopped = false,
  });
 }
@@ -0,0 +1,114 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+/// The accumulated state of one iperf3 run.
+///
+/// Fed the event stream one report at a time, this is the answer to "what
+/// happened during this test" — the interval series, the end totals, any
+/// errors, and the statistics derived from them.
+///
+/// It lives in the domain layer on purpose: it is what has to be *correct*,
+/// independent of how anything chooses to draw it. A different UI, a headless
+/// run or a future export path all consume the same object, and none of them
+/// re-derive a mean or re-decide whether a warm-up interval counts.
+class Iperf3Session {
+  Iperf3Start? _start;
+
+  /// Connection details, once the run has reported them.
+  Iperf3Start? get start => _start;
+
+  final List<Iperf3Interval> _intervals = [];
+
+  /// Throughput samples in arrival order, warm-up intervals excluded.
+  List<Iperf3Interval> get intervals => List.unmodifiable(_intervals);
+
+  Iperf3End? _summary;
+
+  /// Sent/received totals, once the run has finished.
+  Iperf3End? get summary => _summary;
+
+  final List<String> _errors = [];
+
+  /// Errors reported during the run, in order.
+  List<String> get errors => List.unmodifiable(_errors);
+
+  bool _stopped = false;
+
+  /// Whether the run ended because it was asked to stop.
+  bool get stopped => _stopped;
+
+  /// Whether iperf3 reported any error.
+  bool get hasError => _errors.isNotEmpty;
+
+  /// Whether anything at all has been recorded.
+  bool get isEmpty =>
+      _start == null && _intervals.isEmpty && _summary == null && !hasError;
+
+  /// How many throughput samples have been recorded.
+  int get sampleCount => _intervals.length;
+
+  /// Throughput of the most recent sample, or null before the first one.
+  double? get latestBitsPerSecond =>
+      _intervals.isEmpty ? null : _intervals.last.bitsPerSecond;
+
+  /// Mean throughput across the samples, or null before the first one.
+  ///
+  /// This is the mean of the per-interval rates, which is not identical to the
+  /// run's overall rate when intervals differ in length — prefer
+  /// [summary]'s totals for the headline figure once it is available.
+  double? get meanBitsPerSecond {
+    if (_intervals.isEmpty) return null;
+    final total = _intervals.fold<double>(0, (sum, i) => sum + i.bitsPerSecond);
+    return total / _intervals.length;
+  }
+
+  /// Highest sampled throughput, or null before the first sample.
+  double? get peakBitsPerSecond {
+    if (_intervals.isEmpty) return null;
+    return _intervals
+        .map((i) => i.bitsPerSecond)
+        .reduce((a, b) => a > b ? a : b);
+  }
+
+  /// Total bytes across the recorded samples.
+  int get sampledBytes => _intervals.fold<int>(0, (sum, i) => sum + i.bytes);
+
+  /// Total retransmits across the samples, or null if none were reported.
+  ///
+  /// UDP tests report no retransmit counts, so null means "not measured"
+  /// rather than zero.
+  int? get totalRetransmits {
+    final reported =
+        _intervals.map((i) => i.retransmits).whereType<int>().toList();
+    if (reported.isEmpty) return null;
+    return reported.fold<int>(0, (sum, r) => sum + r);
+  }
+
+  /// Record one report.
+  void add(Iperf3Event event) {
+    switch (event) {
+      case Iperf3Start e:
+        _start = e;
+      case Iperf3Interval e:
+        // Warm-up intervals (-O) are marked omitted by iperf3 and must not
+        // drag the statistics down.
+        if (!e.omitted) _intervals.add(e);
+      case Iperf3End e:
+        _summary = e;
+      case Iperf3Error e:
+        _errors.add(e.message);
+      case Iperf3Stopped _:
+        _stopped = true;
+      case Iperf3LogLine _:
+        break;
+    }
+  }
+
+  /// Forget everything, ready for another run.
+  void clear() {
+    _start = null;
+    _intervals.clear();
+    _summary = null;
+    _errors.clear();
+    _stopped = false;
+  }
+}
@@ -7,7 +7,7 @@ class TestConfiguration {
  final int parallelStreams;

  const TestConfiguration({
-    this.server = 'iperf.es.net',
+    this.server = 'speedtest.uztelecom.uz',
    this.port = 5201,
    this.duration = const Duration(seconds: 10),
    this.interval = 1,
@@ -0,0 +1,36 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+
+/// Runs iperf3 tests and reports what happens.
+///
+/// This is the whole contract the UI depends on. It is deliberately pure Dart —
+/// no Flutter import — so the presentation layer never names a transport. The
+/// Android build supplies a MethodChannel-and-JNI implementation
+/// (`Iperf3Service`); a test, a desktop build or a headless tool can supply
+/// its own without touching anything above this line.
+abstract interface class Iperf3Runner {
+  /// Reports parsed from the running test, one event per iperf3 report.
+  ///
+  /// A broadcast stream: it may have no listener, and late listeners miss
+  /// earlier events rather than replaying them.
+  Stream<Iperf3Event> get events;
+
+  /// Whether a test is in flight right now.
+  bool get isRunning;
+
+  /// Run a test to completion and resolve with its outcome.
+  ///
+  /// Resolves rather than throws for an iperf3-level failure — the failure is
+  /// carried in [Iperf3Result.exitCode]. Implementations must always resolve,
+  /// including on internal error, so a caller can never be left awaiting.
+  Future<Iperf3Result> run(TestConfiguration config);
+
+  /// Ask a running test to stop early. A no-op when nothing is running.
+  ///
+  /// The run's future still resolves, with [Iperf3Result.stopped] set.
+  Future<void> stop();
+
+  /// Release resources. The instance is unusable afterwards.
+  Future<void> dispose();
+}
@@ -1,18 +1,22 @@
 import 'package:flutter/material.dart';
 import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_screen.dart';

-/// Application entry point.
+/// Application entry point, and the composition root.
 ///
-/// iperf3 is now compiled as a native shared library (libiperf3jni.so)
-/// and accessed via JNI — no binary extraction or chmod needed.
+/// This is the only place that names a concrete [Iperf3Runner]. Everything
+/// above the data layer depends on the interface, so swapping the transport —
+/// or running the UI against a fake — touches nothing but this file.
 Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
-  runApp(const Iperf3GuiApp());
+  runApp(Iperf3GuiApp(runner: Iperf3Service()));
 }

 class Iperf3GuiApp extends StatelessWidget {
-  const Iperf3GuiApp({super.key});
+  const Iperf3GuiApp({required this.runner, super.key});
+
+  final Iperf3Runner runner;

  @override
  Widget build(BuildContext context) {
@@ -22,7 +26,7 @@ class Iperf3GuiApp extends StatelessWidget {
        colorSchemeSeed: Colors.blue,
        useMaterial3: true,
      ),
-      home: const TestRunScreen(),
+      home: TestRunScreen(runner: runner),
    );
  }
 }
@@ -0,0 +1,105 @@
+// Headless entry point: runs one iperf3 test with no widgets.
+//
+// This exists to keep the core honest. If anything in the run path ever starts
+// depending on the UI, this stops compiling or stops working — a claim about
+// separation that is checked rather than asserted.
+//
+// It is also the low-noise way to measure. The UI competes with the test for
+// CPU (a gigabit run can put the phone near CPU-bound), so figures taken here
+// are cleaner than figures taken with a transcript repainting alongside.
+//
+//   flutter run -t lib/main_headless.dart \
+//     --dart-define=IPERF_SERVER=192.168.2.182 \
+//     --dart-define=IPERF_STREAMS=4
+//
+// Nothing below imports lib/ui, and test/architecture_test.dart enforces that.
+
+import 'package:flutter/widgets.dart' show WidgetsFlutterBinding;
+import 'package:flutter/foundation.dart' show debugPrint;
+
+import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+
+/// Test parameters, supplied at build time with --dart-define.
+const String _server = String.fromEnvironment('IPERF_SERVER',
+    defaultValue: 'speedtest.uztelecom.uz');
+const int _port = int.fromEnvironment('IPERF_PORT', defaultValue: 5201);
+const int _seconds = int.fromEnvironment('IPERF_SECONDS', defaultValue: 10);
+const int _streams = int.fromEnvironment('IPERF_STREAMS', defaultValue: 1);
+
+Future<void> main() async {
+  // Required for the MethodChannel. Notably NOT runApp() — there is no widget
+  // tree, no render surface and no Flutter UI thread work in this process.
+  WidgetsFlutterBinding.ensureInitialized();
+
+  const config = TestConfiguration(
+    server: _server,
+    port: _port,
+    duration: Duration(seconds: _seconds),
+    parallelStreams: _streams,
+  );
+
+  final Iperf3Runner runner = Iperf3Service();
+  final session = Iperf3Session();
+
+  final subscription = runner.events.listen((event) {
+    session.add(event);
+    if (event is Iperf3Interval && !event.omitted) {
+      _out('interval ${event.start.toStringAsFixed(2)}-'
+          '${event.end.toStringAsFixed(2)}s  '
+          '${_mbits(event.bitsPerSecond)} Mbit/s'
+          '${event.retransmits != null ? '  retr=${event.retransmits}' : ''}');
+    } else if (event is Iperf3Error) {
+      _out('error: ${event.message}');
+    }
+  });
+
+  _out('running iperf3 -c ${config.server} -p ${config.port} '
+      '-t ${config.duration.inSeconds} -P ${config.parallelStreams}');
+
+  final result = await runner.run(config);
+  await subscription.cancel();
+  await runner.dispose();
+
+  _report(result.exitCode, session);
+}
+
+void _report(int exitCode, Iperf3Session session) {
+  _out('--- result ---');
+  _out('exit code:    $exitCode');
+  _out('samples:      ${session.sampleCount}');
+
+  final mean = session.meanBitsPerSecond;
+  final peak = session.peakBitsPerSecond;
+  if (mean != null) _out('mean:         ${_mbits(mean)} Mbit/s');
+  if (peak != null) _out('peak:         ${_mbits(peak)} Mbit/s');
+
+  final retr = session.totalRetransmits;
+  _out('retransmits:  ${retr ?? 'not measured'}');
+
+  final sent = session.summary?.sent;
+  final received = session.summary?.received;
+  if (sent != null) {
+    _out('sent:         ${_mbits(sent.bitsPerSecond)} Mbit/s '
+        'over ${sent.seconds.toStringAsFixed(2)}s');
+  }
+  if (received != null) {
+    _out('received:     ${_mbits(received.bitsPerSecond)} Mbit/s '
+        'over ${received.seconds.toStringAsFixed(2)}s');
+  }
+  final cpu = session.summary?.hostCpuPercent;
+  if (cpu != null) _out('local cpu:    ${cpu.toStringAsFixed(1)}%');
+
+  if (session.stopped) _out('ended early:  stopped');
+  for (final error in session.errors) {
+    _out('error:        $error');
+  }
+}
+
+String _mbits(double bitsPerSecond) =>
+    (bitsPerSecond / 1e6).toStringAsFixed(1);
+
+void _out(String line) => debugPrint('[iperf3-headless] $line');
@@ -0,0 +1,95 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+/// Renders parsed iperf3 events as the kind of line iperf3 itself would print.
+///
+/// The app consumes `--json-stream`, so the familiar text layout has to be
+/// rebuilt here. Keeping it in one pure function makes it testable and leaves
+/// the structured events untouched for anything else that wants them.
+String? formatIperf3Event(Iperf3Event event) {
+  return switch (event) {
+    Iperf3Start e => _formatStart(e),
+    Iperf3Interval e => _formatInterval(e),
+    Iperf3End e => _formatEnd(e),
+    Iperf3Error e => 'iperf3 error: ${e.message}',
+    Iperf3Stopped _ => 'Stopped by user.',
+    Iperf3LogLine e => e.text.isEmpty ? null : e.text,
+  };
+}
+
+String _formatStart(Iperf3Start e) {
+  final parts = <String>[];
+  if (e.targetHost != null) {
+    final port = e.targetPort != null ? ', port ${e.targetPort}' : '';
+    parts.add('Connecting to host ${e.targetHost}$port');
+  }
+  final detail = <String>[
+    if (e.protocol != null) e.protocol!,
+    if (e.streamCount != null)
+      '${e.streamCount} stream${e.streamCount == 1 ? '' : 's'}',
+    if (e.durationSeconds != null) '${e.durationSeconds}s',
+  ];
+  if (detail.isNotEmpty) parts.add(detail.join(' · '));
+  return parts.isEmpty ? '' : parts.join('\n');
+}
+
+String _formatInterval(Iperf3Interval e) {
+  final window = '${_seconds(e.start)}-${_seconds(e.end)} sec';
+  final line = StringBuffer('[SUM]  $window   '
+      '${formatBytes(e.bytes)}   ${formatBitrate(e.bitsPerSecond)}');
+  if (e.retransmits != null) {
+    line.write('   ${e.retransmits} retr');
+  }
+  if (e.omitted) line.write('   (omitted)');
+  return line.toString();
+}
+
+String _formatEnd(Iperf3End e) {
+  final lines = <String>['- ' * 20];
+  final sent = e.sent;
+  final received = e.received;
+  if (sent != null) {
+    lines.add('[SUM]  0.00-${_seconds(sent.seconds)} sec   '
+        '${formatBytes(sent.bytes)}   ${formatBitrate(sent.bitsPerSecond)}'
+        '${sent.retransmits != null ? '   ${sent.retransmits} retr' : ''}'
+        '   sender');
+  }
+  if (received != null) {
+    lines.add('[SUM]  0.00-${_seconds(received.seconds)} sec   '
+        '${formatBytes(received.bytes)}   '
+        '${formatBitrate(received.bitsPerSecond)}   receiver');
+  }
+  if (e.hostCpuPercent != null) {
+    lines.add('CPU: local ${e.hostCpuPercent!.toStringAsFixed(1)}%'
+        '${e.remoteCpuPercent != null ? ', remote ${e.remoteCpuPercent!.toStringAsFixed(1)}%' : ''}');
+  }
+  return lines.join('\n');
+}
+
+String _seconds(double value) => value.toStringAsFixed(2);
+
+/// Byte totals the way iperf3 prints them — `93.8 MBytes`.
+String formatBytes(int bytes) {
+  const units = ['Bytes', 'KBytes', 'MBytes', 'GBytes', 'TBytes'];
+  var value = bytes.toDouble();
+  var unit = 0;
+  while (value >= 1024 && unit < units.length - 1) {
+    value /= 1024;
+    unit++;
+  }
+  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
+  return '${value.toStringAsFixed(precision)} ${units[unit]}';
+}
+
+/// Bitrates the way iperf3 prints them — `786 Mbits/sec`. Decimal units, since
+/// network rates are powers of ten while transfer totals are powers of two.
+String formatBitrate(double bitsPerSecond) {
+  const units = ['bits/sec', 'Kbits/sec', 'Mbits/sec', 'Gbits/sec'];
+  var value = bitsPerSecond;
+  var unit = 0;
+  while (value >= 1000 && unit < units.length - 1) {
+    value /= 1000;
+    unit++;
+  }
+  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
+  return '${value.toStringAsFixed(precision)} ${units[unit]}';
+}
@@ -1,22 +1,25 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';

 /// Main test run screen.
 ///
-/// iperf3 is now compiled as a native shared library (libiperf3jni.so)
-/// and accessed via JNI. No binary extraction or chmod needed.
+/// Takes an [Iperf3Runner] rather than constructing one, so this layer names no
+/// transport: the Android app injects the JNI-backed implementation from
+/// main(), and a test injects a fake.
 class TestRunScreen extends StatelessWidget {
-  const TestRunScreen({super.key});
+  const TestRunScreen({required this.runner, super.key});
+
+  final Iperf3Runner runner;

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
-      create: (_) => TestRunViewModel(
-        iperf3Service: Iperf3Service(),
-      ),
+      create: (_) => TestRunViewModel(iperf3Service: runner),
      child: const _TestRunContent(),
    );
  }
@@ -30,109 +33,227 @@ class _TestRunContent extends StatefulWidget {
 }

 class _TestRunContentState extends State<_TestRunContent> {
-  final _serverController = TextEditingController(text: 'speedtest.uztelecom.uz');
-  final _portController = TextEditingController(text: '5201');
+  static const _defaults = TestConfiguration();
+
+  final _serverController =
+      TextEditingController(text: _defaults.server);
+  final _portController =
+      TextEditingController(text: _defaults.port.toString());
+  final _durationController =
+      TextEditingController(text: _defaults.duration.inSeconds.toString());
+  final _streamsController =
+      TextEditingController(text: _defaults.parallelStreams.toString());
+  final _outputScrollController = ScrollController();

  @override
  void dispose() {
    _serverController.dispose();
    _portController.dispose();
+    _durationController.dispose();
+    _streamsController.dispose();
+    _outputScrollController.dispose();
    super.dispose();
  }

+  TestConfiguration _readConfiguration() {
+    return TestConfiguration(
+      server: _serverController.text.trim(),
+      port: int.tryParse(_portController.text) ?? _defaults.port,
+      duration: Duration(
+        seconds: int.tryParse(_durationController.text) ??
+            _defaults.duration.inSeconds,
+      ),
+      parallelStreams:
+          int.tryParse(_streamsController.text) ?? _defaults.parallelStreams,
+    );
+  }
+
+  /// Keep the newest output in view, but only once the frame that added it has
+  /// been laid out.
+  void _scrollToBottom() {
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!_outputScrollController.hasClients) return;
+      _outputScrollController
+          .jumpTo(_outputScrollController.position.maxScrollExtent);
+    });
+  }
+
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('iperf3-gui'),
+        actions: [
+          Consumer<TestRunViewModel>(
+            builder: (context, vm, _) => IconButton(
+              tooltip: 'Copy output',
+              icon: const Icon(Icons.copy_all),
+              onPressed: vm.output.isEmpty
+                  ? null
+                  : () {
+                      Clipboard.setData(ClipboardData(text: vm.output));
+                      ScaffoldMessenger.of(context).showSnackBar(
+                        const SnackBar(content: Text('Output copied')),
+                      );
+                    },
+            ),
+          ),
+        ],
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
-            // Server input
            TextField(
              controller: _serverController,
+              autocorrect: false,
              decoration: const InputDecoration(
                labelText: 'Server',
-                hintText: 'e.g. iperf.es.net or 192.168.1.1',
+                hintText: 'e.g. speedtest.uztelecom.uz or 192.168.1.1',
              ),
            ),
+            const SizedBox(height: 12),
+
+            Row(
+              children: [
+                Expanded(
+                  child: TextField(
+                    controller: _portController,
+                    keyboardType: TextInputType.number,
+                    decoration: const InputDecoration(labelText: 'Port'),
+                  ),
+                ),
+                const SizedBox(width: 12),
+                Expanded(
+                  child: TextField(
+                    controller: _durationController,
+                    keyboardType: TextInputType.number,
+                    decoration: const InputDecoration(labelText: 'Seconds'),
+                  ),
+                ),
+                const SizedBox(width: 12),
+                Expanded(
+                  child: TextField(
+                    controller: _streamsController,
+                    keyboardType: TextInputType.number,
+                    decoration: const InputDecoration(labelText: 'Streams'),
+                  ),
+                ),
+              ],
+            ),
            const SizedBox(height: 16),

-            // Port input
-            TextField(
-              controller: _portController,
-              decoration: const InputDecoration(
-                labelText: 'Port',
-                hintText: '5201',
-              ),
-              keyboardType: TextInputType.number,
-            ),
-            const SizedBox(height: 16),
-
-            // Go button
            Consumer<TestRunViewModel>(
              builder: (context, vm, _) {
+                if (vm.isRunning) {
+                  return OutlinedButton.icon(
+                    onPressed: vm.stopTest,
+                    icon: const Icon(Icons.stop),
+                    label: const Text('STOP'),
+                  );
+                }
                return ElevatedButton(
-                  onPressed: vm.state == TestRunState.running
-                      ? null
-                      : () {
-                          final config = TestConfiguration(
-                            server: _serverController.text,
-                            port: int.tryParse(_portController.text) ?? 5201,
-                          );
-                          vm.runTest(config);
-                        },
-                  child: vm.state == TestRunState.running
-                      ? const SizedBox(
-                          width: 20,
-                          height: 20,
-                          child: CircularProgressIndicator(strokeWidth: 2),
-                        )
-                      : const Text('GO'),
+                  onPressed: () => vm.runTest(_readConfiguration()),
+                  child: const Text('GO'),
                );
              },
            ),
-            const SizedBox(height: 16),
+            const SizedBox(height: 12),

-            // Status indicator
+            // Status line
            Consumer<TestRunViewModel>(
              builder: (context, vm, _) {
-                final statusText = switch (vm.state) {
-                  TestRunState.idle => '',
-                  TestRunState.running => 'Running...',
-                  TestRunState.completed => 'Test complete',
-                  TestRunState.error => 'Error',
+                final scheme = Theme.of(context).colorScheme;
+                final (String label, Color color) = switch (vm.state) {
+                  TestRunState.idle => ('Ready', scheme.onSurfaceVariant),
+                  TestRunState.running => ('Running…', scheme.primary),
+                  TestRunState.completed => (
+                      vm.wasStopped ? 'Stopped' : 'Test complete',
+                      vm.wasStopped ? scheme.onSurfaceVariant : scheme.primary,
+                    ),
+                  TestRunState.error => (
+                      'Error${vm.result != null ? ' (exit ${vm.result!.exitCode})' : ''}',
+                      scheme.error,
+                    ),
                };
-                return Text(
-                  statusText,
-                  style: TextStyle(
-                    color: vm.state == TestRunState.error
-                        ? Colors.red
-                        : Colors.grey,
+                return Row(
+                  children: [
+                    if (vm.isRunning)
+                      const Padding(
+                        padding: EdgeInsets.only(right: 8),
+                        child: SizedBox(
+                          width: 14,
+                          height: 14,
+                          child: CircularProgressIndicator(strokeWidth: 2),
+                        ),
+                      ),
+                    Text(label, style: TextStyle(color: color)),
+                  ],
+                );
+              },
+            ),
+            const SizedBox(height: 12),
+
+            // Live throughput figures. Every number here is read off the
+            // session; none are computed in the widget tree.
+            Consumer<TestRunViewModel>(
+              builder: (context, vm, _) {
+                final session = vm.session;
+                final latest = session.latestBitsPerSecond;
+                final mean = session.meanBitsPerSecond;
+                final peak = session.peakBitsPerSecond;
+                if (latest == null || mean == null || peak == null) {
+                  return const SizedBox.shrink();
+                }
+                final total = session.summary?.sent;
+                return Padding(
+                  padding: const EdgeInsets.only(bottom: 12),
+                  child: Row(
+                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                    children: [
+                      _Stat(
+                        label: total != null ? 'total' : 'now',
+                        value: formatBitrate(total?.bitsPerSecond ?? latest),
+                      ),
+                      _Stat(label: 'avg', value: formatBitrate(mean)),
+                      _Stat(label: 'peak', value: formatBitrate(peak)),
+                      _Stat(
+                          label: 'samples', value: '${session.sampleCount}'),
+                    ],
                  ),
                );
              },
            ),
-            const SizedBox(height: 16),

-            // Raw output text box
+            // Live output
            Expanded(
-              child: Consumer<TestRunViewModel>(
-                builder: (context, vm, _) {
-                  final output = vm.result?.rawOutput ?? '';
-                  return TextField(
-                    controller: TextEditingController(text: output),
-                    decoration: const InputDecoration(
-                      labelText: 'Raw Output',
-                      border: OutlineInputBorder(),
-                    ),
-                    maxLines: null,
-                    readOnly: true,
-                  );
-                },
+              child: Container(
+                width: double.infinity,
+                padding: const EdgeInsets.all(8),
+                decoration: BoxDecoration(
+                  border: Border.all(
+                    color: Theme.of(context).colorScheme.outlineVariant,
+                  ),
+                  borderRadius: BorderRadius.circular(4),
+                ),
+                child: Consumer<TestRunViewModel>(
+                  builder: (context, vm, _) {
+                    _scrollToBottom();
+                    return SingleChildScrollView(
+                      controller: _outputScrollController,
+                      child: SelectableText(
+                        vm.output.isEmpty
+                            ? 'Output will appear here.'
+                            : vm.output,
+                        style: const TextStyle(
+                          fontFamily: 'monospace',
+                          fontSize: 12,
+                        ),
+                      ),
+                    );
+                  },
+                ),
              ),
            ),
          ],
@@ -141,3 +262,32 @@ class _TestRunContentState extends State<_TestRunContent> {
    );
  }
 }
+
+
+/// One figure in the throughput row.
+class _Stat extends StatelessWidget {
+  const _Stat({required this.label, required this.value});
+
+  final String label;
+  final String value;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          label,
+          style: theme.textTheme.labelSmall
+              ?.copyWith(color: theme.colorScheme.onSurfaceVariant),
+        ),
+        Text(
+          value,
+          style: theme.textTheme.titleSmall
+              ?.copyWith(fontFeatures: const [FontFeature.tabularFigures()]),
+        ),
+      ],
+    );
+  }
+}
@@ -1,14 +1,37 @@
+import 'dart:async';
+
 import 'package:flutter/foundation.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
-import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';

 /// State of the test run.
 enum TestRunState { idle, running, completed, error }

 /// ViewModel for managing test run state.
+///
+/// Presentation only. What happened during a run is accumulated by
+/// [Iperf3Session] in the domain layer; this class subscribes to
+/// [Iperf3Runner.events], feeds that session, keeps a formatted transcript for
+/// display, and decides when to repaint.
 class TestRunViewModel extends ChangeNotifier {
-  final Iperf3Service iperf3Service;
+  final Iperf3Runner iperf3Service;
+
+  /// How often to notify listeners while output is arriving. iperf3 can report
+  /// several times a second across many streams, and each rebuild re-renders
+  /// the whole transcript — so repaints are coalesced instead of one per event.
+  static const Duration displayInterval = Duration(milliseconds: 250);
+
+  TestRunViewModel({required this.iperf3Service}) {
+    _eventSubscription = iperf3Service.events.listen(_onEvent);
+  }
+
+  StreamSubscription<Iperf3Event>? _eventSubscription;
+  Timer? _repaintTimer;
+  bool _dirty = false;

  TestRunState _state = TestRunState.idle;
  TestRunState get state => _state;
@@ -19,39 +42,110 @@ class TestRunViewModel extends ChangeNotifier {
  TestConfiguration? _currentConfig;
  TestConfiguration? get currentConfig => _currentConfig;

-  TestRunViewModel({required this.iperf3Service});
+  final StringBuffer _transcript = StringBuffer();
+
+  /// Human-readable output accumulated so far. Display only — the structured
+  /// record of the run is [session].
+  String get output => _transcript.toString();
+
+  final Iperf3Session _session = Iperf3Session();
+
+  /// The accumulated run: interval series, totals, errors and their statistics.
+  Iperf3Session get session => _session;
+
+  /// Whether a test is currently in flight.
+  bool get isRunning => _state == TestRunState.running;
+
+  /// Whether the most recent finished run ended because the user stopped it.
+  bool get wasStopped => _result?.stopped ?? false;

  /// Start a test with the given configuration.
  Future<void> runTest(TestConfiguration config) async {
+    if (_state == TestRunState.running) return;
+
    if (!config.isValid) {
+      _resetRunData();
+      _transcript
+          .writeln('Invalid configuration: check the server address and port.');
      _state = TestRunState.error;
      notifyListeners();
      return;
    }

+    _resetRunData();
    _state = TestRunState.running;
    _currentConfig = config;
-    _result = null;
    notifyListeners();

    try {
      final result = await iperf3Service.run(config);
      _result = result;
-      _state = result.exitCode == 0
-          ? TestRunState.completed
-          : TestRunState.error;
+      if (_transcript.isEmpty && result.rawOutput.isNotEmpty) {
+        _transcript.write(result.rawOutput);
+      }
+      _state =
+          result.exitCode == 0 ? TestRunState.completed : TestRunState.error;
    } catch (e) {
+      _transcript.writeln('Test failed: $e');
      _state = TestRunState.error;
    } finally {
+      _stopRepaintTimer();
      notifyListeners();
    }
  }

+  /// Request that a running test stop early.
+  Future<void> stopTest() async {
+    if (_state != TestRunState.running) return;
+    await iperf3Service.stop();
+  }
+
  /// Reset to idle state.
  void reset() {
+    _resetRunData();
    _state = TestRunState.idle;
-    _result = null;
    _currentConfig = null;
    notifyListeners();
  }
+
+  void _resetRunData() {
+    _result = null;
+    _transcript.clear();
+    _session.clear();
+    _dirty = false;
+  }
+
+  void _onEvent(Iperf3Event event) {
+    _session.add(event);
+
+    final line = formatIperf3Event(event);
+    if (line != null && line.isNotEmpty) {
+      _transcript.writeln(line);
+    }
+    _scheduleRepaint();
+  }
+
+  /// Coalesce repaints: mark dirty and let a timer flush at [displayInterval].
+  void _scheduleRepaint() {
+    _dirty = true;
+    _repaintTimer ??= Timer.periodic(displayInterval, (_) {
+      if (!_dirty) return;
+      _dirty = false;
+      notifyListeners();
+    });
+  }
+
+  void _stopRepaintTimer() {
+    _repaintTimer?.cancel();
+    _repaintTimer = null;
+    _dirty = false;
+  }
+
+  @override
+  void dispose() {
+    _stopRepaintTimer();
+    _eventSubscription?.cancel();
+    iperf3Service.dispose();
+    super.dispose();
+  }
 }
@@ -6,7 +6,6 @@ list(APPEND FLUTTER_PLUGIN_LIST
 )

 list(APPEND FLUTTER_FFI_PLUGIN_LIST
-  jni
 )

 set(PLUGIN_BUNDLED_LIBRARIES)
@@ -1,14 +1,6 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  args:
-    dependency: transitive
-    description:
-      name: args
-      sha256: d0481093c50b1da8910eb0bb301626d4d8eb7284aa739614d2b394ee09e3ea04
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.7.0"
  async:
    dependency: transitive
    description:
@@ -41,14 +33,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "1.1.2"
-  code_assets:
-    dependency: transitive
-    description:
-      name: code_assets
-      sha256: bf394f466ba9205f1812a0433b392d6af280f155f56651eda7c18cc32ed493b8
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.2.1"
  collection:
    dependency: transitive
    description:
@@ -57,14 +41,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "1.19.1"
-  crypto:
-    dependency: transitive
-    description:
-      name: crypto
-      sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.0.7"
  fake_async:
    dependency: transitive
    description:
@@ -73,14 +49,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "1.3.3"
-  ffi:
-    dependency: transitive
-    description:
-      name: ffi
-      sha256: "6d7fd89431262d8f3125e81b50d3847a091d846eafcd4fdb88dd06f36d705a45"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.2.0"
  flutter:
    dependency: "direct main"
    description: flutter
@@ -99,38 +67,6 @@ packages:
    description: flutter
    source: sdk
    version: "0.0.0"
-  hooks:
-    dependency: transitive
-    description:
-      name: hooks
-      sha256: "9a62a50b50b769a737bc0a8ff381f333529df3ab746b2f6b02e83760231455ba"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.0.2"
-  jni:
-    dependency: transitive
-    description:
-      name: jni
-      sha256: f038e58b4dc2c9037f50e233175086337e0b305e356d28211bf55f21c504cbd3
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.3"
-  jni_flutter:
-    dependency: transitive
-    description:
-      name: jni_flutter
-      sha256: "7b717011ea40d04fd47c2731d3d1d36eb99eba3435c2753d62489e8c3c9991d5"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.2"
-  jni_util:
-    dependency: transitive
-    description:
-      name: jni_util
-      sha256: "1ba86da04a5f2bf18fde2edb235587e70c5b0fc5bd4ba955f46b00942c3fc35f"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.0"
  leak_tracker:
    dependency: transitive
    description:
@@ -163,14 +99,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "6.1.0"
-  logging:
-    dependency: transitive
-    description:
-      name: logging
-      sha256: c8245ada5f1717ed44271ed1c26b8ce85ca3228fd2ffdb75468ab01979309d61
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.3.0"
  matcher:
    dependency: transitive
    description:
@@ -203,22 +131,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "1.0.0"
-  objective_c:
-    dependency: transitive
-    description:
-      name: objective_c
-      sha256: b7fb95a6d9a4f009edd63dc5ac69f07420b23a16161c6dd8660290b59c602e8e
-      url: "https://pub.dev"
-    source: hosted
-    version: "9.5.0"
-  package_config:
-    dependency: transitive
-    description:
-      name: package_config
-      sha256: ffcf4cf3d6c0b74ac43708d9f56625506e8a68aa935abe9d267a7330f320eb5d
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.0.0"
  path:
    dependency: transitive
    description:
@@ -227,70 +139,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "1.9.1"
-  path_provider:
-    dependency: "direct main"
-    description:
-      name: path_provider
-      sha256: a7f4874f987173da295a61c181b8ee71dab59b332a486b391babf26a1b884825
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.6"
-  path_provider_android:
-    dependency: transitive
-    description:
-      name: path_provider_android
-      sha256: "69cbd515a62b94d32a7944f086b2f82b4ac40a1d45bebfc00813a430ab2dabcd"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.3.1"
-  path_provider_foundation:
-    dependency: transitive
-    description:
-      name: path_provider_foundation
-      sha256: "2a376b7d6392d80cd3705782d2caa734ca4727776db0b6ec36ef3f1855197699"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.6.0"
-  path_provider_linux:
-    dependency: transitive
-    description:
-      name: path_provider_linux
-      sha256: "58c2005f147315b11e9b4a7bc889cd5203e250cba8e3f012dae259b4972b5c16"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.2.2"
-  path_provider_platform_interface:
-    dependency: transitive
-    description:
-      name: path_provider_platform_interface
-      sha256: "484838772624c3a4b94f1e44a3e19897fee738f2d5c4ce448443b0417f7c9dda"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.3"
-  path_provider_windows:
-    dependency: transitive
-    description:
-      name: path_provider_windows
-      sha256: bd6f00dbd873bfb70d0761682da2b3a2c2fccc2b9e84c495821639601d81afe7
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.3.0"
-  platform:
-    dependency: transitive
-    description:
-      name: platform
-      sha256: "5d6b1b0036a5f331ebc77c850ebc8506cbc1e9416c27e59b439f917a902a4984"
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.1.6"
-  plugin_platform_interface:
-    dependency: transitive
-    description:
-      name: plugin_platform_interface
-      sha256: "4820fbfdb9478b1ebae27888254d445073732dae3d6ea81f0b7e06d5dedc3f02"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.1.8"
  provider:
    dependency: "direct main"
    description:
@@ -299,22 +147,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "6.1.5+1"
-  pub_semver:
-    dependency: transitive
-    description:
-      name: pub_semver
-      sha256: "5bfcf68ca79ef689f8990d1160781b4bad40a3bd5e5218ad4076ddb7f4081585"
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.2.0"
-  record_use:
-    dependency: transitive
-    description:
-      name: record_use
-      sha256: "2551bd8eecfe95d14ae75f6021ad0248be5c27f138c2ec12fcb52b500b3ba1ed"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.6.0"
  sky_engine:
    dependency: transitive
    description: flutter
@@ -368,14 +200,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "0.7.12"
-  typed_data:
-    dependency: transitive
-    description:
-      name: typed_data
-      sha256: f9049c039ebfeb4cf7a7104a675823cd72dba8297f264b6637062516699fa006
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.4.0"
  vector_math:
    dependency: transitive
    description:
@@ -392,22 +216,6 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "15.3.0"
-  xdg_directories:
-    dependency: transitive
-    description:
-      name: xdg_directories
-      sha256: "7a3f37b05d989967cdddcbb571f1ea834867ae2faa29725fd085180e0883aa15"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.1.0"
-  yaml:
-    dependency: transitive
-    description:
-      name: yaml
-      sha256: b9da305ac7c39faa3f030eccd175340f968459dae4af175130b3fc47e40d76ce
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.1.3"
 sdks:
  dart: ">=3.13.1 <4.0.0"
-  flutter: ">=3.38.4"
+  flutter: ">=3.18.0-18.0.pre.54"
@@ -2,7 +2,7 @@ name: iperf3gui
 description: "A Flutter-based Android GUI wrapper for iperf3."
 publish_to: 'none'

-version: 1.0.0+1
+version: 0.1.0+1

 environment:
  sdk: ^3.13.1
@@ -11,7 +11,6 @@ dependencies:
  flutter:
    sdk: flutter

-  path_provider: ^2.1.4
  provider: ^6.1.2

 dev_dependencies:
@@ -0,0 +1,144 @@
+// Enforces the layering. A convention nobody checks is a convention that
+// decays, so these read the real import statements in lib/ and fail on a
+// violation rather than trusting review to catch it.
+//
+// The rule, in one line: dependencies point inward. ui → domain ← data, and
+// never the reverse.
+
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('layering', () {
+    test('domain imports no Flutter at all', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) => import.startsWith('package:flutter/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The domain layer must stay pure Dart so it can be reused '
+            'without a Flutter runtime. Offending imports:\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('domain does not depend on data or ui', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) =>
+            import.contains('/data/') ||
+            import.contains('/ui/') ||
+            import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The domain layer is the innermost layer; it may depend on '
+              'nothing else in this package.\n${_render(offenders)}');
+    });
+
+    test('data does not depend on ui', () {
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) => import.contains('/ui/') || import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The data layer must not know about presentation.\n'
+              '${_render(offenders)}');
+    });
+
+    test('data imports no Flutter widget libraries', () {
+      // flutter/services is allowed: MethodChannel lives there, and that is
+      // the whole reason this layer is Flutter-aware at all.
+      const allowed = {'package:flutter/services.dart'};
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) =>
+            import.startsWith('package:flutter/') && !allowed.contains(import),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The data layer may import package:flutter/services.dart only. '
+            'Anything else drags presentation into the transport.\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('ui does not depend on a concrete data implementation', () {
+      // The UI talks to Iperf3Runner. main.dart is the composition root and is
+      // the one file allowed to name an implementation.
+      final offenders = _importsMatching(
+        'lib/ui',
+        (import) => import.contains('/data/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'Presentation must depend on domain/services/iperf3_runner.dart '
+            'rather than on a transport. Only main.dart may pick an '
+            'implementation.\n${_render(offenders)}',
+      );
+    });
+
+    test('the headless entry point does not depend on ui', () {
+      // main_headless.dart is the standing proof that the core runs without a
+      // widget tree; an import from lib/ui would quietly end that.
+      final offenders = _importsMatching(
+        'lib',
+        (import) => import.contains('/ui/'),
+        onlyFiles: {'lib/main_headless.dart'},
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The headless entry point must run the core with no UI.\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('every layer directory is actually covered by these rules', () {
+      // Guards against a new top-level layer appearing and silently escaping
+      // every rule above.
+      final layers = Directory('lib')
+          .listSync()
+          .whereType<Directory>()
+          .map((d) => d.path.split(Platform.pathSeparator).last)
+          .toSet();
+      expect(
+        layers,
+        equals({'domain', 'data', 'ui'}),
+        reason: 'A new layer appeared under lib/. Add rules for it here.',
+      );
+    });
+  });
+}
+
+/// Every `(file, import)` pair under [directory] whose import satisfies [test].
+List<({String file, String import})> _importsMatching(
+  String directory,
+  bool Function(String import) test, {
+  Set<String>? onlyFiles,
+}) {
+  final results = <({String file, String import})>[];
+  final dir = Directory(directory);
+  if (!dir.existsSync()) return results;
+
+  final pattern = RegExp(r'''^\s*import\s+['"]([^'"]+)['"]''', multiLine: true);
+  for (final entity in dir.listSync(recursive: true)) {
+    if (entity is! File || !entity.path.endsWith('.dart')) continue;
+    if (onlyFiles != null && !onlyFiles.contains(entity.path)) continue;
+    final source = entity.readAsStringSync();
+    for (final match in pattern.allMatches(source)) {
+      final import = match.group(1)!;
+      if (test(import)) {
+        results.add((file: entity.path, import: import));
+      }
+    }
+  }
+  return results;
+}
+
+String _render(List<({String file, String import})> offenders) =>
+    offenders.map((o) => '  ${o.file} → ${o.import}').join('\n');
@@ -0,0 +1,107 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+void main() {
+  group('Iperf3Event.parse', () {
+    test('parses a start event', () {
+      const line = '{"event":"start","data":{'
+          '"connecting_to":{"host":"192.168.2.182","port":5201},'
+          '"test_start":{"protocol":"TCP","num_streams":4,"duration":10}}}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Start>());
+      final start = event as Iperf3Start;
+      expect(start.targetHost, equals('192.168.2.182'));
+      expect(start.targetPort, equals(5201));
+      expect(start.streamCount, equals(4));
+      expect(start.durationSeconds, equals(10));
+      expect(start.protocol, equals('TCP'));
+    });
+
+    test('parses an interval event with per-stream detail', () {
+      const line = '{"event":"interval","data":{'
+          '"streams":[{"socket":143,"bytes":49283072,'
+          '"bits_per_second":394264576.0,"retransmits":0,"snd_cwnd":2023424,'
+          '"rtt":3521}],'
+          '"sum":{"start":0.0,"end":1.000151,"seconds":1.000151,'
+          '"bytes":98566144,"bits_per_second":788410352.0,"retransmits":0,'
+          '"omitted":false,"sender":true}}}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Interval>());
+      final interval = event as Iperf3Interval;
+      expect(interval.bytes, equals(98566144));
+      expect(interval.bitsPerSecond, closeTo(788410352.0, 0.1));
+      expect(interval.retransmits, equals(0));
+      expect(interval.omitted, isFalse);
+      expect(interval.streams, hasLength(1));
+      expect(interval.streams.single.socket, equals(143));
+      expect(interval.streams.single.rtt, equals(3521));
+    });
+
+    test('marks omitted intervals', () {
+      const line = '{"event":"interval","data":{"streams":[],'
+          '"sum":{"start":0.0,"end":1.0,"bytes":1,"bits_per_second":8.0,'
+          '"omitted":true}}}';
+      final interval = Iperf3Event.parse(line) as Iperf3Interval;
+      expect(interval.omitted, isTrue);
+    });
+
+    test('parses an end event with sent and received totals', () {
+      const line = '{"event":"end","data":{'
+          '"sum_sent":{"seconds":10.0,"bytes":987654321,'
+          '"bits_per_second":790123456.0,"retransmits":7},'
+          '"sum_received":{"seconds":10.01,"bytes":987000000,'
+          '"bits_per_second":789000000.0},'
+          '"cpu_utilization_percent":{"host_total":12.5,"remote_total":3.25}}}';
+      final end = Iperf3Event.parse(line) as Iperf3End;
+      expect(end.sent!.bytes, equals(987654321));
+      expect(end.sent!.retransmits, equals(7));
+      expect(end.received!.bitsPerSecond, closeTo(789000000.0, 0.1));
+      expect(end.hostCpuPercent, closeTo(12.5, 0.01));
+      expect(end.remoteCpuPercent, closeTo(3.25, 0.01));
+    });
+
+    test('falls back to bidir-reverse keys when present', () {
+      const line = '{"event":"interval","data":{"streams":[],'
+          '"sum_bidir_reverse":{"start":0.0,"end":1.0,"bytes":42,'
+          '"bits_per_second":336.0}}}';
+      final interval = Iperf3Event.parse(line) as Iperf3Interval;
+      expect(interval.bytes, equals(42));
+    });
+
+    test('parses an error event', () {
+      const line = '{"event":"error","data":"unable to connect to server"}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Error>());
+      expect((event as Iperf3Error).message,
+          equals('unable to connect to server'));
+    });
+
+    test('parses the bridge stop marker', () {
+      final event = Iperf3Event.parse('{"event":"jni_stopped","data":{}}');
+      expect(event, isA<Iperf3Stopped>());
+    });
+
+    test('surfaces non-JSON output as a log line rather than dropping it', () {
+      final event = Iperf3Event.parse('iperf3: something unexpected');
+      expect(event, isA<Iperf3LogLine>());
+      expect((event as Iperf3LogLine).text,
+          equals('iperf3: something unexpected'));
+    });
+
+    test('surfaces malformed JSON as a log line', () {
+      final event = Iperf3Event.parse('{"event":"interval",');
+      expect(event, isA<Iperf3LogLine>());
+    });
+
+    test('treats an unknown event name as a log line', () {
+      final event = Iperf3Event.parse('{"event":"future_thing","data":{}}');
+      expect(event, isA<Iperf3LogLine>());
+    });
+
+    test('tolerates a missing data object', () {
+      final event = Iperf3Event.parse('{"event":"interval"}');
+      expect(event, isA<Iperf3Interval>());
+      expect((event as Iperf3Interval).bytes, equals(0));
+    });
+  });
+}
@@ -11,5 +11,15 @@ void main() {
      expect(result.rawOutput, equals('Test complete'));
      expect(result.exitCode, equals(0));
    });
+
+    test('stopped defaults to false', () {
+      const result = Iperf3Result(rawOutput: 'x', exitCode: 0);
+      expect(result.stopped, isFalse);
+    });
+
+    test('stopped is preserved when set', () {
+      const result = Iperf3Result(rawOutput: 'x', exitCode: 0, stopped: true);
+      expect(result.stopped, isTrue);
+    });
  });
 }
@@ -0,0 +1,135 @@
+// Pure-Dart tests for the run aggregate. No widgets, no bindings, no channel —
+// this is the part that has to be correct regardless of what draws it.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
+
+void main() {
+  Iperf3Interval sample(double start, double bits,
+          {int bytes = 1000, int? retransmits, bool omitted = false}) =>
+      Iperf3Interval(
+        start: start,
+        end: start + 1,
+        bytes: bytes,
+        bitsPerSecond: bits,
+        retransmits: retransmits,
+        omitted: omitted,
+      );
+
+  group('Iperf3Session', () {
+    test('starts empty', () {
+      final session = Iperf3Session();
+      expect(session.isEmpty, isTrue);
+      expect(session.sampleCount, isZero);
+      expect(session.intervals, isEmpty);
+      expect(session.start, isNull);
+      expect(session.summary, isNull);
+      expect(session.errors, isEmpty);
+      expect(session.stopped, isFalse);
+      expect(session.hasError, isFalse);
+    });
+
+    test('statistics are null before any sample', () {
+      final session = Iperf3Session();
+      expect(session.latestBitsPerSecond, isNull);
+      expect(session.meanBitsPerSecond, isNull);
+      expect(session.peakBitsPerSecond, isNull);
+      expect(session.totalRetransmits, isNull);
+    });
+
+    test('records start, intervals and summary', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Start(targetHost: 'host', targetPort: 5201))
+        ..add(sample(0, 100))
+        ..add(const Iperf3End(
+          sent: Iperf3Total(seconds: 1, bytes: 10, bitsPerSecond: 80),
+        ));
+      expect(session.isEmpty, isFalse);
+      expect(session.start!.targetHost, equals('host'));
+      expect(session.sampleCount, equals(1));
+      expect(session.summary!.sent!.bitsPerSecond, equals(80));
+    });
+
+    test('excludes omitted warm-up intervals from the series', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 10, omitted: true))
+        ..add(sample(1, 100))
+        ..add(sample(2, 200));
+      expect(session.sampleCount, equals(2));
+      expect(session.meanBitsPerSecond, equals(150),
+          reason: 'the omitted 10 would have pulled the mean to ~103');
+    });
+
+    test('computes mean, peak and latest over the samples', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 100))
+        ..add(sample(1, 400))
+        ..add(sample(2, 250));
+      expect(session.latestBitsPerSecond, equals(250));
+      expect(session.peakBitsPerSecond, equals(400));
+      expect(session.meanBitsPerSecond, equals(250));
+    });
+
+    test('sums sampled bytes', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 1, bytes: 1500))
+        ..add(sample(1, 1, bytes: 2500));
+      expect(session.sampledBytes, equals(4000));
+    });
+
+    test('sums retransmits when reported', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 1, retransmits: 2))
+        ..add(sample(1, 1, retransmits: 5));
+      expect(session.totalRetransmits, equals(7));
+    });
+
+    test('retransmits stay null when never reported, not zero', () {
+      // UDP reports no retransmit counts; "not measured" must not read as 0.
+      final session = Iperf3Session()
+        ..add(sample(0, 1))
+        ..add(sample(1, 1));
+      expect(session.totalRetransmits, isNull);
+    });
+
+    test('collects errors in order and flags them', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Error('first'))
+        ..add(const Iperf3Error('second'));
+      expect(session.hasError, isTrue);
+      expect(session.errors, equals(['first', 'second']));
+      expect(session.isEmpty, isFalse);
+    });
+
+    test('records a stop', () {
+      final session = Iperf3Session()..add(const Iperf3Stopped());
+      expect(session.stopped, isTrue);
+    });
+
+    test('ignores log lines', () {
+      final session = Iperf3Session()..add(const Iperf3LogLine('noise'));
+      expect(session.isEmpty, isTrue);
+    });
+
+    test('clear returns it to the empty state', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Start(targetHost: 'host'))
+        ..add(sample(0, 100))
+        ..add(const Iperf3Error('boom'))
+        ..add(const Iperf3Stopped())
+        ..add(const Iperf3End())
+        ..clear();
+      expect(session.isEmpty, isTrue);
+      expect(session.stopped, isFalse);
+      expect(session.hasError, isFalse);
+      expect(session.peakBitsPerSecond, isNull);
+    });
+
+    test('exposed collections are unmodifiable', () {
+      final session = Iperf3Session()..add(sample(0, 1));
+      expect(() => session.intervals.add(sample(1, 1)), throwsUnsupportedError);
+      expect(() => session.errors.add('x'), throwsUnsupportedError);
+    });
+  });
+}
@@ -0,0 +1,62 @@
+import 'dart:async';
+
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+
+/// In-memory [Iperf3Runner] for tests.
+///
+/// Implements the interface rather than the concrete service, so it tracks the
+/// five members the UI actually depends on instead of every public member the
+/// MethodChannel implementation happens to have.
+class FakeIperf3Runner implements Iperf3Runner {
+  FakeIperf3Runner({this.onRun});
+
+  /// Supplies the result for each [run], and may [emit] events first.
+  Future<Iperf3Result> Function(TestConfiguration)? onRun;
+
+  final StreamController<Iperf3Event> _controller =
+      StreamController<Iperf3Event>.broadcast();
+
+  /// Configurations passed to [run], in order.
+  final List<TestConfiguration> runCalls = [];
+
+  int stopCallCount = 0;
+  bool disposed = false;
+  bool _isRunning = false;
+
+  int get runCallCount => runCalls.length;
+
+  /// Push an event as if the native layer had reported it.
+  void emit(Iperf3Event event) => _controller.add(event);
+
+  @override
+  Stream<Iperf3Event> get events => _controller.stream;
+
+  @override
+  bool get isRunning => _isRunning;
+
+  @override
+  Future<Iperf3Result> run(TestConfiguration config) async {
+    runCalls.add(config);
+    _isRunning = true;
+    try {
+      if (onRun != null) return await onRun!(config);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    } finally {
+      _isRunning = false;
+    }
+  }
+
+  @override
+  Future<void> stop() async {
+    stopCallCount++;
+  }
+
+  @override
+  Future<void> dispose() async {
+    disposed = true;
+    await _controller.close();
+  }
+}
@@ -0,0 +1,87 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
+
+void main() {
+  group('formatBytes', () {
+    test('scales in binary units the way iperf3 prints totals', () {
+      expect(formatBytes(0), equals('0.00 Bytes'));
+      expect(formatBytes(1024), equals('1.00 KBytes'));
+      expect(formatBytes(98566144), equals('94.0 MBytes'));
+      expect(formatBytes(1073741824), equals('1.00 GBytes'));
+    });
+  });
+
+  group('formatBitrate', () {
+    test('scales in decimal units, as network rates are quoted', () {
+      expect(formatBitrate(0), equals('0.00 bits/sec'));
+      expect(formatBitrate(8000), equals('8.00 Kbits/sec'));
+      expect(formatBitrate(790000000), equals('790 Mbits/sec'));
+      expect(formatBitrate(2500000000), equals('2.50 Gbits/sec'));
+    });
+  });
+
+  group('formatIperf3Event', () {
+    test('renders a start event', () {
+      const event = Iperf3Start(
+        targetHost: '192.168.2.182',
+        targetPort: 5201,
+        protocol: 'TCP',
+        streamCount: 1,
+        durationSeconds: 10,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('Connecting to host 192.168.2.182, port 5201'));
+      expect(text, contains('TCP'));
+      expect(text, contains('1 stream'));
+    });
+
+    test('renders an interval with retransmits', () {
+      const event = Iperf3Interval(
+        start: 0,
+        end: 1,
+        bytes: 98566144,
+        bitsPerSecond: 788410352,
+        retransmits: 3,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('0.00-1.00 sec'));
+      expect(text, contains('94.0 MBytes'));
+      expect(text, contains('788 Mbits/sec'));
+      expect(text, contains('3 retr'));
+    });
+
+    test('marks an omitted interval', () {
+      const event = Iperf3Interval(
+          start: 0, end: 1, bytes: 1, bitsPerSecond: 8, omitted: true);
+      expect(formatIperf3Event(event), contains('omitted'));
+    });
+
+    test('renders sender and receiver lines from an end event', () {
+      const event = Iperf3End(
+        sent: Iperf3Total(
+            seconds: 10, bytes: 987654321, bitsPerSecond: 790000000,
+            retransmits: 7),
+        received: Iperf3Total(
+            seconds: 10.01, bytes: 987000000, bitsPerSecond: 789000000),
+        hostCpuPercent: 12.5,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('sender'));
+      expect(text, contains('receiver'));
+      expect(text, contains('7 retr'));
+      expect(text, contains('CPU: local 12.5%'));
+    });
+
+    test('renders errors and stops', () {
+      expect(formatIperf3Event(const Iperf3Error('boom')),
+          equals('iperf3 error: boom'));
+      expect(formatIperf3Event(const Iperf3Stopped()),
+          equals('Stopped by user.'));
+    });
+
+    test('drops an empty log line', () {
+      expect(formatIperf3Event(const Iperf3LogLine('')), isNull);
+    });
+  });
+}
@@ -1,39 +1,40 @@
+import 'dart:async';
+
 import 'package:flutter_test/flutter_test.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';

+import '../../../support/fake_iperf3_runner.dart';
+
 void main() {
  group('TestRunViewModel', () {
    test('starts in idle state', () {
-      final vm = TestRunViewModel(
-        iperf3Service: _MockIperf3Service(),
-      );
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
      expect(vm.state, equals(TestRunState.idle));
      expect(vm.result, isNull);
      expect(vm.currentConfig, isNull);
+      expect(vm.output, isEmpty);
    });

    test('can be reset', () {
-      final vm = TestRunViewModel(
-        iperf3Service: _MockIperf3Service(),
-      );
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
      vm.reset();
      expect(vm.state, equals(TestRunState.idle));
    });

    test('invalid config sets error state without running', () async {
-      final vm = TestRunViewModel(
-        iperf3Service: _MockIperf3Service(),
-      );
+      final mock = FakeIperf3Runner();
+      final vm = TestRunViewModel(iperf3Service: mock);
      const config = TestConfiguration(server: '');
      await vm.runTest(config);
      expect(vm.state, equals(TestRunState.error));
+      expect(mock.runCallCount, equals(0));
    });

    test('runTest with valid config calls service', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
        onRun: (config) async {
          expect(config.server, equals('192.168.1.1'));
          return const Iperf3Result(rawOutput: 'done', exitCode: 0);
@@ -45,17 +46,161 @@ void main() {
      expect(vm.state, equals(TestRunState.completed));
      expect(vm.result, isNotNull);
    });
+
+    test('non-zero exit code lands in error state', () async {
+      final mock = FakeIperf3Runner(
+        onRun: (_) async =>
+            const Iperf3Result(rawOutput: 'boom', exitCode: 1),
+      );
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.state, equals(TestRunState.error));
+      expect(vm.result!.exitCode, equals(1));
+    });
+
+    test('streamed events accumulate into output during the run', () async {
+      final mock = FakeIperf3Runner();
+      mock.onRun = (_) async {
+        mock.emit(const Iperf3Start(targetHost: '192.168.1.1', targetPort: 5201));
+        mock.emit(const Iperf3Interval(
+          start: 0,
+          end: 1,
+          bytes: 11744051,
+          bitsPerSecond: 94100000,
+        ));
+        // Let the broadcast stream deliver before the run resolves.
+        await Future<void>.delayed(Duration.zero);
+        return const Iperf3Result(rawOutput: 'ignored', exitCode: 0);
+      };
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+
+      expect(vm.output, contains('Connecting to host 192.168.1.1'));
+      expect(vm.output, contains('94.1 Mbits/sec'));
+      // The streamed transcript wins over the service's own copy.
+      expect(vm.output, isNot(contains('ignored')));
+    });
+
+    test('events are fed into the session', () async {
+      final mock = FakeIperf3Runner();
+      mock.onRun = (_) async {
+        mock.emit(const Iperf3Interval(
+            start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
+        mock.emit(const Iperf3End(
+          sent: Iperf3Total(seconds: 1, bytes: 1000, bitsPerSecond: 8000),
+        ));
+        await Future<void>.delayed(Duration.zero);
+        return const Iperf3Result(rawOutput: '', exitCode: 0);
+      };
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+
+      expect(vm.session.sampleCount, equals(1));
+      expect(vm.session.summary, isNotNull);
+    });
+
+    test('a new run clears the previous session', () async {
+      final mock = FakeIperf3Runner();
+      mock.onRun = (_) async {
+        mock.emit(const Iperf3Interval(
+            start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
+        await Future<void>.delayed(Duration.zero);
+        return const Iperf3Result(rawOutput: '', exitCode: 0);
+      };
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.session.sampleCount, equals(1));
+
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.session.sampleCount, equals(1),
+          reason: 'not appended to the old run');
+    });
+
+    test('falls back to result output when nothing streamed', () async {
+      final mock = FakeIperf3Runner(
+        onRun: (_) async =>
+            const Iperf3Result(rawOutput: 'summary only', exitCode: 0),
+      );
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.output, contains('summary only'));
+    });
+
+    test('output is cleared when a new run starts', () async {
+      final mock = FakeIperf3Runner(
+        onRun: (_) async =>
+            const Iperf3Result(rawOutput: 'first', exitCode: 0),
+      );
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.output, contains('first'));
+
+      mock.onRun = (_) async =>
+          const Iperf3Result(rawOutput: 'second', exitCode: 0);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.output, isNot(contains('first')));
+      expect(vm.output, contains('second'));
+    });
+
+    test('stopTest forwards to the service only while running', () async {
+      final mock = FakeIperf3Runner();
+      final vm = TestRunViewModel(iperf3Service: mock);
+
+      await vm.stopTest();
+      expect(mock.stopCallCount, equals(0), reason: 'idle: nothing to stop');
+
+      final gate = Completer<Iperf3Result>();
+      mock.onRun = (_) => gate.future;
+      final run = vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.isRunning, isTrue);
+
+      await vm.stopTest();
+      expect(mock.stopCallCount, equals(1));
+
+      gate.complete(const Iperf3Result(rawOutput: 'stopped', exitCode: 0));
+      await run;
+    });
+
+    test('wasStopped reflects a user-requested stop', () async {
+      final mock = FakeIperf3Runner(
+        onRun: (_) async => const Iperf3Result(
+          rawOutput: 'stopped early',
+          exitCode: 0,
+          stopped: true,
+        ),
+      );
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      // A user stop is a normal outcome: completed, not error.
+      expect(vm.state, equals(TestRunState.completed));
+      expect(vm.wasStopped, isTrue);
+    });
+
+    test('wasStopped is false for a run that finished on its own', () async {
+      final mock = FakeIperf3Runner(
+        onRun: (_) async =>
+            const Iperf3Result(rawOutput: 'done', exitCode: 0),
+      );
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.wasStopped, isFalse);
+    });
+
+    test('a second runTest while running is ignored', () async {
+      final mock = FakeIperf3Runner();
+      final gate = Completer<Iperf3Result>();
+      mock.onRun = (_) => gate.future;
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      final run = vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(mock.runCallCount, equals(1));
+
+      gate.complete(const Iperf3Result(rawOutput: 'done', exitCode: 0));
+      await run;
+    });
  });
 }
-
-class _MockIperf3Service implements Iperf3Service {
-  _MockIperf3Service({this.onRun});
-
-  final Future<Iperf3Result> Function(TestConfiguration)? onRun;
-
-  @override
-  Future<Iperf3Result> run(TestConfiguration config) async {
-    if (onRun != null) return onRun!(config);
-    return const Iperf3Result(rawOutput: '', exitCode: 0);
-  }
-}
@@ -1,17 +1,89 @@
-// This is a basic Flutter widget test.
+// Widget-level smoke tests.
 //
-// To perform an interaction with a widget in your test, use the WidgetTester
-// utility in the flutter_test package. For example, you can send tap and scroll
-// gestures. You can also use WidgetTester to find child widgets in the widget
-// tree, read text, and verify that the values of widget properties are correct.
+// These drive the real UI against a FakeIperf3Runner: no MethodChannel, no
+// native library, no device. That is only possible because the presentation
+// layer depends on the Iperf3Runner interface rather than on Iperf3Service.

+import 'dart:async';
+
+import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/main.dart';

+import 'support/fake_iperf3_runner.dart';
+
 void main() {
  testWidgets('App smoke test', (WidgetTester tester) async {
-    await tester.pumpWidget(const Iperf3GuiApp());
+    await tester.pumpWidget(Iperf3GuiApp(runner: FakeIperf3Runner()));
    expect(find.text('iperf3-gui'), findsOneWidget);
+    expect(find.text('GO'), findsOneWidget);
+    expect(find.text('Ready'), findsOneWidget);
+  });
+
+  testWidgets('runs a test and renders streamed results', (tester) async {
+    final runner = FakeIperf3Runner();
+    runner.onRun = (config) async {
+      runner.emit(Iperf3Start(
+        targetHost: config.server,
+        targetPort: config.port,
+        protocol: 'TCP',
+        streamCount: config.parallelStreams,
+      ));
+      runner.emit(const Iperf3Interval(
+        start: 0,
+        end: 1,
+        bytes: 98566144,
+        bitsPerSecond: 788410352,
+      ));
+      await Future<void>.delayed(Duration.zero);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    };
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(1));
+    expect(find.text('Test complete'), findsOneWidget);
+    expect(find.textContaining('788 Mbits/sec'), findsWidgets);
+    // The stat row is driven by the parsed interval series.
+    expect(find.text('peak'), findsOneWidget);
+  });
+
+  testWidgets('shows a stop button while running and can stop', (tester) async {
+    final runner = FakeIperf3Runner();
+    final gate = Completer<Iperf3Result>();
+    runner.onRun = (_) => gate.future;
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pump();
+
+    expect(find.text('STOP'), findsOneWidget);
+    expect(find.text('Running…'), findsOneWidget);
+
+    await tester.tap(find.text('STOP'));
+    await tester.pump();
+    expect(runner.stopCallCount, equals(1));
+
+    gate.complete(const Iperf3Result(
+        rawOutput: '', exitCode: 0, stopped: true));
+    await tester.pumpAndSettle();
+    expect(find.text('Stopped'), findsOneWidget);
+  });
+
+  testWidgets('rejects an empty server address', (tester) async {
+    final runner = FakeIperf3Runner();
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+
+    await tester.enterText(find.byType(TextField).first, '');
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(0));
+    expect(find.textContaining('Invalid configuration'), findsOneWidget);
  });
 }
@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+# Assert that R8 left the names JNI resolves at runtime alone.
+#
+# iperf_jni.c looks up the callback methods by name with GetMethodID. R8 renames
+# by default, and a renamed callback does not fail the build — it produces an
+# APK that aborts on the first callback of every test:
+#
+#   NoSuchMethodError: no non-static method "Lp0;.onOutput(Ljava/lang/String;)V"
+#
+# That shipped once. Building the release APK is not enough to catch it, because
+# the build succeeds; this reads R8's own mapping file and checks the names
+# survived. Run after `flutter build apk --release`.
+
+set -euo pipefail
+
+MAPPING="${1:-build/app/outputs/mapping/release/mapping.txt}"
+APK="${2:-build/app/outputs/flutter-apk/app-release.apk}"
+
+if [[ ! -f "$MAPPING" ]]; then
+    echo "FAIL: no R8 mapping at $MAPPING"
+    echo "      Run 'flutter build apk --release' first. If the release build"
+    echo "      no longer minifies, this check is meaningless — say so"
+    echo "      explicitly rather than deleting it."
+    exit 1
+fi
+
+failed=0
+
+# A class kept by name maps to itself: "a.b.C -> a.b.C:".
+require_class_kept() {
+    local fqcn="$1"
+    if grep -qF -- "$fqcn -> $fqcn:" "$MAPPING"; then
+        echo "  ok    class  $fqcn"
+    else
+        echo "  FAIL  class  $fqcn was renamed or removed"
+        grep -F -- "$fqcn ->" "$MAPPING" | head -3 | sed 's/^/          got: /' || true
+        failed=1
+    fi
+}
+
+# A method kept by name ends with "-> <name>".
+require_method_kept() {
+    local signature="$1" name="$2"
+    if grep -qE -- "$signature.*-> ${name}\$" "$MAPPING"; then
+        echo "  ok    method $name"
+    else
+        echo "  FAIL  method $name was renamed"
+        grep -E -- "$signature" "$MAPPING" | head -3 | sed 's/^/          got: /' || true
+        failed=1
+    fi
+}
+
+echo "Checking JNI-visible names in $MAPPING"
+
+require_class_kept 'com.novoyuuparosk.iperf3gui.IperfRunner'
+require_class_kept 'com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback'
+require_class_kept 'com.novoyuuparosk.iperf3gui.IperfRunner$MainThreadCallback'
+
+# Resolved by iperf_jni.c on the concrete callback object's class.
+require_method_kept 'void onOutput\(java\.lang\.String\)' 'onOutput'
+require_method_kept 'void onError\(java\.lang\.String\)' 'onError'
+require_method_kept 'void onComplete\(\)' 'onComplete'
+
+# Native methods are NOT checked against mapping.txt: R8 only emits entries for
+# members it has line-number info or a rename for, and a native method has no
+# body, so it is absent whether or not it was renamed. Absence would prove
+# nothing. Check the DEX string pool instead — a surviving name is interned
+# there, a renamed one is not.
+check_dex_names() {
+    local apk="$1"
+    shift
+    if [[ ! -f "$apk" ]]; then
+        echo "  skip  DEX name check: no APK at $apk"
+        return
+    fi
+    local tmp
+    tmp="$(mktemp -d)"
+    trap 'rm -rf "$tmp"' RETURN
+    if ! unzip -o -q "$apk" 'classes*.dex' -d "$tmp" 2>/dev/null; then
+        echo "  FAIL  could not extract classes*.dex from $apk"
+        failed=1
+        return
+    fi
+    # Dump the string pool once to a file, then grep the file. Never
+    # `... | strings | grep -q`: grep -q exits at the first match, SIGPIPEs
+    # strings, and `set -o pipefail` reports the whole pipeline as failed — so
+    # a name found early "fails" and one found late passes. That flakiness cost
+    # an afternoon; leave the intermediate file in place.
+    cat "$tmp"/classes*.dex | strings > "$tmp/dex-strings.txt"
+
+    local name
+    for name in "$@"; do
+        if grep -qxF -- "$name" "$tmp/dex-strings.txt"; then
+            echo "  ok    native $name"
+        else
+            echo "  FAIL  native $name is absent from the DEX string pool"
+            failed=1
+        fi
+    done
+}
+
+check_dex_names "${2:-build/app/outputs/flutter-apk/app-release.apk}" \
+    runIperfLive forceStopIperfTest setTempDir isTestRunning
+
+if [[ $failed -ne 0 ]]; then
+    echo
+    echo "R8 renamed something JNI resolves by name. The release APK will abort"
+    echo "on the first callback. Fix android/app/proguard-rules.pro."
+    exit 1
+fi
+
+echo "All JNI-visible names survived minification."
@@ -0,0 +1,288 @@
+#!/usr/bin/env bash
+# Provision this machine as a Gitea Actions runner for the android-stuff org.
+#
+#   sudo ./tool/setup_ci_runner.sh --check      # pre-flight only, changes nothing
+#   sudo RUNNER_TOKEN=xxxx ./tool/setup_ci_runner.sh
+#
+# Get an ORG-scoped token from
+#   <gitea>/org/android-stuff/settings/actions/runners → "Create new runner"
+# Org scope, not repo scope, so every android-stuff repo shares one runner.
+#
+# ── WHY THIS MACHINE, NOT THE GITEA HOST ────────────────────────────────────
+# Gitea runs on an aarch64 box. Flutter cannot build an Android APK on a Linux
+# arm64 host at all: the SDK ships no arm64-host gen_snapshot
+# (flutter/flutter#189724, #75864, open as of July 2026). An x86_64 runner is a
+# requirement here, not a preference.
+#
+# ── WHY HOST MODE, NOT A CONTAINER ──────────────────────────────────────────
+# This machine has a working Flutter + Android SDK + NDK. In host mode jobs use
+# it directly, so CI builds with the same toolchain that produced the verified
+# release and skips a per-run NDK download. The cost is that there is no
+# container boundary — which is exactly why the service account below matters.
+#
+# ── WHY A DEDICATED USER, AND A SYSTEM SERVICE ──────────────────────────────
+# Host mode means the service account IS the sandbox; there is no other. A
+# workflow file is code, and it runs as whoever this service runs as. Running
+# as a human user would give every workflow read access to that user's home,
+# SSH keys included. Running as root would be worse, and would also miss the
+# warm Gradle/pub caches in that home (HOME=/root), re-downloading dependencies
+# every run for no benefit.
+#
+# So: a dedicated unprivileged account, in the flutterdev group for SDK access,
+# with its own HOME so its caches are its own. A *system* service rather than a
+# user service, so it starts at boot under plain systemctl with no lingering
+# session — the service being root-managed is unrelated to the jobs being
+# unprivileged, and conflating those two was the earlier mistake here.
+
+set -euo pipefail
+
+VERSION="${RUNNER_VERSION:-3.3.0}"
+INSTANCE="${GITEA_INSTANCE:-http://pi5-16.local:3005}"
+RUNNER_USER="${RUNNER_USER:-gitea-runner}"
+SDK_GROUP="${SDK_GROUP:-flutterdev}"
+RUNNER_HOME="${RUNNER_HOME:-/var/lib/gitea-runner}"
+BIN="${RUNNER_BIN:-/usr/local/bin/gitea-runner}"
+UNIT="/etc/systemd/system/gitea-runner.service"
+RUNNER_NAME="${RUNNER_NAME:-$(hostname)-android}"
+
+# Capability label, deliberately not a hostname: it says what the runner can
+# do, so a workflow does not encode which machine happens to provide it.
+LABEL="${RUNNER_LABEL:-flutter-android}"
+
+CHECK_ONLY=0
+[[ "${1:-}" == "--check" ]] && CHECK_ONLY=1
+
+[[ $EUID -eq 0 ]] || { echo "Run with sudo: sudo RUNNER_TOKEN=... $0" >&2; exit 1; }
+# --check is for validating this machine before committing to anything, so it
+# deliberately does not require a token.
+if [[ $CHECK_ONLY -eq 0 ]]; then
+    : "${RUNNER_TOKEN:?set RUNNER_TOKEN to an org registration token (see header)}"
+fi
+
+say() { printf '\n==> %s\n' "$1"; }
+
+# ── Pre-flight, before anything is created ─────────────────────────────────
+say "Pre-flight"
+missing=0
+for cmd in flutter dart java cmake ninja node git unzip curl; do
+    # Resolved from systemd's own PATH, not an interactive shell's, since that
+    # is what the service will actually have.
+    if PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
+        command -v "$cmd" >/dev/null; then
+        printf '  ok       %s\n' "$cmd"
+    else
+        printf '  MISSING  %s (not on systemd default PATH)\n' "$cmd"
+        missing=1
+    fi
+done
+
+SDK="${ANDROID_HOME:-${ANDROID_SDK_ROOT:-/opt/android-sdk}}"
+for d in "$SDK/ndk" "$SDK/build-tools" "$SDK/platforms"; do
+    [[ -d "$d" ]] && printf '  ok       %s\n' "$d" \
+        || { printf '  MISSING  %s\n' "$d"; missing=1; }
+done
+getent group "$SDK_GROUP" >/dev/null \
+    && printf '  ok       group %s\n' "$SDK_GROUP" \
+    || { printf '  MISSING  group %s\n' "$SDK_GROUP"; missing=1; }
+
+if [[ $missing -ne 0 ]]; then
+    echo
+    echo "Refusing to register: a runner advertising '$LABEL' must actually" >&2
+    echo "provide these, or every job fails confusingly instead of here." >&2
+    exit 1
+fi
+
+if [[ $CHECK_ONLY -eq 1 ]]; then
+    say "Pre-flight passed"
+    echo "  Nothing was created. Re-run with RUNNER_TOKEN set to provision."
+    echo "  Note: SDK write access is verified as $RUNNER_USER, which can only"
+    echo "  be checked once that account exists — so it is not covered here."
+    exit 0
+fi
+
+# ── Service account ────────────────────────────────────────────────────────
+say "Service account: $RUNNER_USER"
+if id "$RUNNER_USER" &>/dev/null; then
+    echo "  exists; ensuring membership of $SDK_GROUP"
+    usermod -aG "$SDK_GROUP" "$RUNNER_USER"
+else
+    # --shell /bin/bash, not nologin: host-mode steps are executed as shell
+    # scripts, and a login shell costs nothing here — the account has no
+    # password, so it is only reachable via root anyway.
+    useradd --system \
+            --create-home --home-dir "$RUNNER_HOME" \
+            --shell /bin/bash \
+            --groups "$SDK_GROUP" \
+            --comment "Gitea Actions runner ($LABEL)" \
+            "$RUNNER_USER"
+    echo "  created"
+fi
+install -d -o "$RUNNER_USER" -g "$SDK_GROUP" -m 0750 \
+    "$RUNNER_HOME" "$RUNNER_HOME/workspace"
+id "$RUNNER_USER"
+
+# Group membership is worthless if the ACLs disagree, so prove it rather than
+# assume it — as the service user, against the paths a build actually writes.
+#
+# By actually writing a file, not by asking `test -w`. This machine's
+# /usr/bin/test is uutils coreutils 0.8.0, whose -w does not credit
+# supplementary group membership: it reports /opt/android-sdk unwritable for
+# any account whose write access comes from the flutterdev group rather than
+# from the owner bits — which is every account that should be running builds
+# here. (-r and -x pass only because `other` has r-x.) bash's builtin `[ -w ]`
+# gets it right, but sudo execs the external binary, so the builtin is not
+# available here. A write probe is immune to the whole question.
+say "Verifying $RUNNER_USER can write the SDKs"
+write_ok=1
+for d in "/opt/flutter/bin/cache" "$SDK"; do
+    if sudo -u "$RUNNER_USER" env probe="$d/.gitea-runner-probe.$$" \
+        sh -c 'touch "$probe" && rm -f "$probe"' 2>/dev/null; then
+        printf '  ok       writable: %s\n' "$d"
+    else
+        printf '  FAIL     not writable: %s\n' "$d"
+        sudo -u "$RUNNER_USER" rm -f "$d/.gitea-runner-probe.$$" 2>/dev/null || true
+        write_ok=0
+    fi
+done
+if [[ $write_ok -ne 1 ]]; then
+    echo
+    echo "$RUNNER_USER is in $SDK_GROUP but still cannot write. Check:" >&2
+    echo "  getfacl /opt/flutter /opt/android-sdk" >&2
+    echo "  id $RUNNER_USER" >&2
+    exit 1
+fi
+
+# ── Binary ─────────────────────────────────────────────────────────────────
+say "Installing gitea-runner $VERSION"
+if [[ -x "$BIN" ]] && "$BIN" --version 2>/dev/null | grep -qF "$VERSION"; then
+    echo "  already at $VERSION"
+else
+    url="https://dl.gitea.com/gitea-runner/${VERSION}/gitea-runner-${VERSION}-linux-amd64"
+    echo "  $url"
+    curl -fSL --retry 3 -o "$BIN.tmp" "$url"
+    chmod 0755 "$BIN.tmp"
+    mv "$BIN.tmp" "$BIN"
+fi
+"$BIN" --version
+
+# ── Config ─────────────────────────────────────────────────────────────────
+say "Config"
+CONFIG="$RUNNER_HOME/config.yaml"
+if [[ -f "$CONFIG" && -f "$RUNNER_HOME/.runner" ]]; then
+    # Registered: this config is in use, do not touch it.
+    echo "  $CONFIG exists and the runner is registered — leaving it alone"
+else
+    if [[ -f "$CONFIG" ]]; then
+        echo "  $CONFIG exists but nothing is registered yet — rewriting it"
+    fi
+    cat > "$CONFIG" <<YAML
+log:
+  level: info
+
+runner:
+  # Absolute on purpose: a relative path resolves against whatever directory
+  # the command was invoked from, which for `register` is wherever the admin
+  # happened to be standing — typically a repo this account cannot write.
+  file: ${RUNNER_HOME}/.runner
+  # One at a time: a 2-ABI NDK compile plus Gradle will saturate this box, and
+  # concurrent jobs would only contend for it.
+  capacity: 1
+  timeout: 45m
+  # ':host' runs steps directly on this machine as ${RUNNER_USER}, using the
+  # toolchain verified in pre-flight, rather than in a container that would
+  # have to fetch its own.
+  labels:
+    - "${LABEL}:host"
+
+container:
+  # Unused in host mode. Kept so switching to container mode later is an edit
+  # rather than a rediscovery — it would need the Docker network that the
+  # Gitea host's own runner also needs.
+  network: ""
+  privileged: false
+
+host:
+  workdir_parent: ${RUNNER_HOME}/workspace
+YAML
+    chown "$RUNNER_USER:$SDK_GROUP" "$CONFIG"
+    chmod 0640 "$CONFIG"
+    echo "  wrote $CONFIG"
+fi
+
+# ── Registration ───────────────────────────────────────────────────────────
+say "Registering with $INSTANCE"
+if [[ -f "$RUNNER_HOME/.runner" ]]; then
+    echo "  already registered ($RUNNER_HOME/.runner) — skipping."
+    echo "  To re-register: delete that file AND remove the runner in Gitea."
+else
+    # Run from the runner's own directory: register writes .runner and
+    # .runner.lock relative to cwd unless told otherwise, and this account
+    # cannot write wherever the admin invoked the script from.
+    # --labels is deliberately absent: gitea-runner ignores it when the config
+    # file defines labels, and warns that it is doing so.
+    sudo -u "$RUNNER_USER" env HOME="$RUNNER_HOME" sh -c '
+        cd "$1" || exit 1
+        exec "$2" register --no-interactive \
+            --instance "$3" --token "$4" --name "$5" --config "$6"
+    ' sh "$RUNNER_HOME" "$BIN" "$INSTANCE" "$RUNNER_TOKEN" "$RUNNER_NAME" "$CONFIG"
+    # register writes .runner into the cwd it was given; make sure it landed.
+    [[ -f "$RUNNER_HOME/.runner" ]] || {
+        echo "  registration produced no .runner in $RUNNER_HOME" >&2
+        exit 1
+    }
+fi
+
+# ── Service ────────────────────────────────────────────────────────────────
+say "systemd unit"
+cat > "$UNIT" <<UNITFILE
+[Unit]
+Description=Gitea Actions runner (${LABEL}, host mode)
+Documentation=https://gitea.com/gitea/act_runner
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=${RUNNER_USER}
+Group=${SDK_GROUP}
+WorkingDirectory=${RUNNER_HOME}
+ExecStart=${BIN} daemon --config ${CONFIG}
+Restart=always
+RestartSec=5
+
+# HOME must be explicit: it decides where Gradle and pub put their caches, and
+# a service does not inherit a login environment.
+Environment=HOME=${RUNNER_HOME}
+Environment=GRADLE_USER_HOME=${RUNNER_HOME}/.gradle
+Environment=PUB_CACHE=${RUNNER_HOME}/.pub-cache
+Environment=ANDROID_HOME=${SDK}
+Environment=ANDROID_SDK_ROOT=${SDK}
+
+[Install]
+WantedBy=multi-user.target
+UNITFILE
+echo "  wrote $UNIT"
+
+systemctl daemon-reload
+systemctl enable --now gitea-runner
+sleep 2
+systemctl --no-pager --lines=15 status gitea-runner || true
+
+cat <<EOF
+
+==> Done.
+
+    Logs:    journalctl -u gitea-runner -f
+    Stop:    systemctl stop gitea-runner
+    Remove:  systemctl disable --now gitea-runner
+             rm $UNIT $BIN && rm -rf $RUNNER_HOME
+             userdel $RUNNER_USER
+             ...and delete the runner in the Gitea org settings.
+
+    The runner should now appear under
+      ${INSTANCE}/org/android-stuff/settings/actions/runners
+    with label '$LABEL'. The queued run for this repo should start on its own.
+
+    First Android build will be slow: this account's Gradle and pub caches
+    start empty by design. Subsequent runs reuse them.
+EOF
@@ -6,7 +6,6 @@ list(APPEND FLUTTER_PLUGIN_LIST
 )

 list(APPEND FLUTTER_FFI_PLUGIN_LIST
-  jni
 )

 set(PLUGIN_BUNDLED_LIBRARIES)