diff --git a/app/src/main/cpp/waylandcomp/src/ahb_swapchain.c b/app/src/main/cpp/waylandcomp/src/ahb_swapchain.c
index 4a981f1ee..e567bea17 100644
--- a/app/src/main/cpp/waylandcomp/src/ahb_swapchain.c
+++ b/app/src/main/cpp/waylandcomp/src/ahb_swapchain.c
@@ -86,6 +86,9 @@ static struct ahb_buf *find_buf(uint64_t id) {
 }
 
 static void buf_free(struct ahb_buf *ab) {
+    /* A display release does not prove the compositor's Vulkan reads finished.
+     * Keep the AHB reference and its DMA-BUF record even if the client is gone. */
+    if (vkp_completion_unknown()) return;
     if (ab->resource) { wl_list_remove(&ab->resource_destroy.link); ab->resource = NULL; }
     if (ab->fence_src) { wl_event_source_remove(ab->fence_src); ab->fence_src = NULL; }
     if (ab->fence_fd >= 0) { close(ab->fence_fd); ab->fence_fd = -1; }
@@ -112,6 +115,7 @@ static void on_buffer_resource_destroyed(struct wl_listener *l, void *data) {
 /* ---- release: SurfaceFlinger is done with the buffer -> the game's next acquire waits, then wl_buffer.release */
 
 static void send_deferred_release(struct ahb_buf *ab) {
+    if (vkp_completion_unknown()) return;
     if (ab->release_pending && ab->resource)
         droiddeck_release_buffer(ab->surface, ab->resource, ab->surface != NULL, ab->deferred_ns);
     ab->release_pending = 0;
diff --git a/app/src/main/cpp/waylandcomp/src/compositor.c b/app/src/main/cpp/waylandcomp/src/compositor.c
index 805eff9fa..e8a70fec8 100644
--- a/app/src/main/cpp/waylandcomp/src/compositor.c
+++ b/app/src/main/cpp/waylandcomp/src/compositor.c
@@ -377,6 +377,18 @@ static void perf_note_release(int64_t since_ns) {
 
 /* ------------------------------------------------------------------ buffer release pacing */
 
+/* Completion-unknown is terminal for externally owned DMA-BUF contents too.
+ * Keeping a VkImage alone cannot stop the client from overwriting its backing
+ * memory after wl_buffer.release. All paths (including cursors and idle roles)
+ * use this gate; copied SHM buffers retain their normal release behaviour. */
+static struct dmabuf_buffer *get_dmabuf(struct wl_resource *buffer);
+static int buffer_release_blocked(struct wl_resource *buffer) {
+    return vkp_completion_unknown() && get_dmabuf(buffer) != NULL;
+}
+static void send_buffer_release(struct wl_resource *buffer) {
+    if (!buffer_release_blocked(buffer)) wl_buffer_send_release(buffer);
+}
+
 static void pending_release_free(struct pending_release *pr) {
     if (pr->surface && pr->surface->releases_pending > 0) pr->surface->releases_pending--;
     wl_list_remove(&pr->destroy.link);
@@ -384,7 +396,8 @@ static void pending_release_free(struct pending_release *pr) {
     free(pr);
 }
 
-/* A surface is going away: its queued releases still go out on time, they just stop counting. */
+/* A surface is going away: detach its accounting pointer, including queued
+ * DMA-BUF releases held in the completion-unknown state. */
 static void pending_releases_forget_surface(struct surface *s) {
     struct pending_release *pr;
     wl_list_for_each(pr, &g_pending_releases, link)
@@ -401,7 +414,8 @@ static void arm_release_timer(void) {
     int64_t earliest = 0;
     if (g_release_timer_fd < 0) return;
     wl_list_for_each(pr, &g_pending_releases, link)
-        if (!earliest || pr->at_ns < earliest) earliest = pr->at_ns;
+        if (!buffer_release_blocked(pr->buffer) && (!earliest || pr->at_ns < earliest))
+            earliest = pr->at_ns;
     struct itimerspec its = {0};
     if (earliest) { its.it_value.tv_sec = earliest / 1000000000LL; its.it_value.tv_nsec = earliest % 1000000000LL; }
     timerfd_settime(g_release_timer_fd, TFD_TIMER_ABSTIME, &its, NULL);
@@ -413,8 +427,8 @@ static int on_release_timer(int fd, uint32_t mask, void *data) {
     int64_t now = now_ns() + 300000; /* anything due within 0.3 ms goes now */
     if (read(fd, &expirations, sizeof(expirations)) < 0 && errno != EAGAIN) return 0;
     wl_list_for_each_safe(pr, tmp, &g_pending_releases, link) {
-        if (pr->at_ns <= now) {
-            wl_buffer_send_release(pr->buffer);
+        if (pr->at_ns <= now && !buffer_release_blocked(pr->buffer)) {
+            send_buffer_release(pr->buffer);
             perf_note_release(pr->since_ns);
             pending_release_free(pr);
         }
@@ -435,6 +449,9 @@ static int on_release_timer(int fd, uint32_t mask, void *data) {
  * delivered (a swapchain rebuild destroys buffers with queued releases) or that a coarser earlier
  * limit had spaced out, and the game's first frames after that waited on empty slots. */
 static void release_buffer(struct surface *s, struct wl_resource *buffer, int64_t since_ns) {
+    /* No allocation or immediate-release fallback is allowed for a quarantined
+     * DMA-BUF. Existing queued releases stay held; their timer is disarmed. */
+    if (buffer_release_blocked(buffer)) return;
     const int limit = g_fps_limit;
     /* Without a limit of its own a game is paced to the screen. A swapchain that does not wait for
      * frame callbacks (MAILBOX, IMMEDIATE) is held back by nothing else here, so handing a replaced
@@ -443,7 +460,7 @@ static void release_buffer(struct surface *s, struct wl_resource *buffer, int64_
      * One release per refresh is the back-pressure X11 gives, and the screen shows the same frames
      * either way. */
     const int64_t interval = limit > 0 ? 1000000000LL / limit : g_refresh_ns;
-    if (interval <= 0 || g_release_timer_fd < 0) { wl_buffer_send_release(buffer); perf_note_release(since_ns); return; }
+    if (interval <= 0 || g_release_timer_fd < 0) { send_buffer_release(buffer); perf_note_release(since_ns); return; }
     int64_t now = now_ns();
     int64_t at = s->next_release_ns + interval;
     int64_t latest = now + interval * (int64_t)(s->releases_pending + 1);
@@ -451,7 +468,7 @@ static void release_buffer(struct surface *s, struct wl_resource *buffer, int64_
     if (at > latest) at = latest;
     s->next_release_ns = at;
     struct pending_release *pr = calloc(1, sizeof(*pr));
-    if (!pr) { wl_buffer_send_release(buffer); perf_note_release(since_ns); return; }
+    if (!pr) { send_buffer_release(buffer); perf_note_release(since_ns); return; }
     pr->buffer = buffer;
     pr->surface = s;
     pr->at_ns = at;
@@ -586,7 +603,10 @@ static void constraints_focus_entered(struct wl_resource *target, struct wl_clie
 /* ------------------------------------------------------------------ dmabuf buffers */
 
 void dmabuf_buffer_unref(struct dmabuf_buffer *b) {
-    if (!b || --b->refs > 0) return;
+    /* Surface/client destruction must not close the backing FDs or free the
+     * imported-buffer record while a GPU read may still be pending. Retain the
+     * reference without allocating a quarantine node; process exit reclaims it. */
+    if (!b || vkp_completion_unknown() || --b->refs > 0) return;
     vkp_image_destroy(b->img);
     for (int i = 0; i < b->n_planes; i++)
         if (b->fd[i] >= 0) close(b->fd[i]);
@@ -677,7 +697,8 @@ static void unmap_toplevel(struct surface *s) {
 
 /* Let go of the surface's dmabuf content. paced = 1: the buffer was replaced, give it back on the
  * limiter's cadence; paced = 0: the surface is going away, give it back at once (a buffer of a
- * destroyed surface is not shown again and must not sit unreleased with the client). */
+ * destroyed surface is not shown again). Completion-unknown overrides both
+ * release modes: prior GPU reads may outlive the surface. */
 static void drop_dmabuf(struct surface *s, int paced) {
     if (s->dmabuf) {
         wl_list_remove(&s->dmabuf_destroy.link);
@@ -685,7 +706,7 @@ static void drop_dmabuf(struct surface *s, int paced) {
          * ahb_swapchain.c releases it then. */
         if (!ahb_swapchain_defer_release(s->dmabuf_buf, s->dmabuf, s, paced)) {
             if (paced) release_buffer(s, s->dmabuf, now_ns());
-            else wl_buffer_send_release(s->dmabuf);
+            else send_buffer_release(s->dmabuf);
         }
         s->dmabuf = NULL;
     }
@@ -735,7 +756,7 @@ static void take_shm(struct surface *s, struct wl_shm_buffer *shm, struct wl_res
         vkp_image_upload_shm(s->shm_img, wl_shm_buffer_get_data(shm), stride);
         wl_shm_buffer_end_access(shm);
     }
-    wl_buffer_send_release(buffer);
+    send_buffer_release(buffer);
     s->buf_w = w;
     s->buf_h = h;
     s->buf_alpha = wl_shm_buffer_get_format(shm) == WL_SHM_FORMAT_ARGB8888;
@@ -753,7 +774,7 @@ static void take_pixel(struct surface *s, const uint8_t bgra[4], struct wl_resou
     }
     if (!s->shm_img) s->shm_img = vkp_image_create_shm(1, 1);
     if (s->shm_img) vkp_image_upload_shm(s->shm_img, bgra, 4);
-    wl_buffer_send_release(buffer);
+    send_buffer_release(buffer);
     s->buf_w = 1;
     s->buf_h = 1;
     s->buf_alpha = bgra[3] != 0xff;
@@ -880,8 +901,9 @@ void **droiddeck_dmabuf_ahb_slot(struct dmabuf_buffer *b) { return &b->ahb_state
 void droiddeck_dmabuf_ref(struct dmabuf_buffer *b) { b->refs++; }
 void droiddeck_dmabuf_unref(struct dmabuf_buffer *b) { dmabuf_buffer_unref(b); }
 void droiddeck_release_buffer(struct surface *s, struct wl_resource *buffer, int paced, int64_t since_ns) {
+    if (buffer_release_blocked(buffer)) return;
     if (paced && s) release_buffer(s, buffer, since_ns);
-    else { wl_buffer_send_release(buffer); perf_note_release(since_ns); }
+    else { send_buffer_release(buffer); perf_note_release(since_ns); }
 }
 void droiddeck_surface_describe(const struct surface *s, char *out, size_t size) { describe(s, out, size); }
 const struct droiddeck_color *droiddeck_surface_color(const struct surface *s) {
@@ -1046,7 +1068,7 @@ static void surface_hold_idle(struct surface *s, struct wl_resource *buffer) {
     struct wl_shm_buffer *shm = db ? NULL : wl_shm_buffer_get(buffer);
     int64_t px = db ? (int64_t)db->width * db->height
                : shm ? (int64_t)wl_shm_buffer_get_width(shm) * wl_shm_buffer_get_height(shm) : 0;
-    if (px <= 0 || px > CURSOR_MAX_PX) { wl_buffer_send_release(buffer); return; }
+    if (px <= 0 || px > CURSOR_MAX_PX) { send_buffer_release(buffer); return; }
     s->idle_buffer = buffer;
     s->idle_buffer_destroy.notify = on_idle_buffer_destroyed;
     wl_resource_add_destroy_listener(buffer, &s->idle_buffer_destroy);
@@ -1064,7 +1086,7 @@ static struct wl_resource *surface_take_idle(struct surface *s) {
 
 static void surface_drop_idle(struct surface *s) {
     struct wl_resource *buffer = surface_take_idle(s);
-    if (buffer) wl_buffer_send_release(buffer);
+    if (buffer) send_buffer_release(buffer);
 }
 
 static void surface_commit(struct wl_client *c, struct wl_resource *r) {
@@ -1119,7 +1141,7 @@ static void surface_commit(struct wl_client *c, struct wl_resource *r) {
                 cursor_publish_hidden();  /* wlroots clears its cursor surface to hide the pointer */
             } else {
                 cursor_publish_buffer(s, buffer);
-                wl_buffer_send_release(buffer);
+                send_buffer_release(buffer);
             }
         } else if (s->role == ROLE_NONE) {
             /* Role-less surface: never drawn, but its buffer is kept for a set_cursor to come. */
@@ -1135,7 +1157,7 @@ static void surface_commit(struct wl_client *c, struct wl_resource *r) {
         } else {
             drop_dmabuf(s, 1);
             s->has_content = 0;
-            if (buffer) wl_buffer_send_release(buffer);
+            if (buffer) send_buffer_release(buffer);
         }
     }
 
@@ -2322,7 +2344,7 @@ static void pointer_set_cursor(struct wl_client *c, struct wl_resource *r, uint3
     struct wl_resource *buffer = surface_take_idle(s);
     if (buffer) {
         cursor_publish_buffer(s, buffer);
-        wl_buffer_send_release(buffer);
+        send_buffer_release(buffer);
     } else if (g_cursor_shown == s) {
         cursor_publish_shown();
     }
diff --git a/app/src/main/cpp/waylandcomp/src/vk_present.c b/app/src/main/cpp/waylandcomp/src/vk_present.c
index f50e44712..2b03336dc 100644
--- a/app/src/main/cpp/waylandcomp/src/vk_present.c
+++ b/app/src/main/cpp/waylandcomp/src/vk_present.c
@@ -39,7 +39,8 @@ struct vkp_image {
 
 static ANativeWindow *g_window;  /* the window frames go to; compositor thread only */
 static char *g_driver_path, *g_library_name, *g_native_lib_dir;
-static int g_dev_state;       /* 0 = not yet, 1 = ok, -1 = failed, -2 = lost (VK_ERROR_DEVICE_LOST) */
+static int g_dev_state;       /* 0 = not yet, 1 = ok, -1 = failed, -2 = lost, -3 = completion unknown */
+static void device_lost(const char *where);
 static VkInstance g_inst;
 static VkPhysicalDevice g_pd;
 static VkDevice g_dev;
@@ -112,11 +113,26 @@ static void perf_add(int64_t *sum, int64_t *max, unsigned *count, int64_t d) {
     if (d > *max) *max = d;
     (*count)++;
 }
+/* A timeout is not device loss and does not cancel a submit. Keep its images
+ * and memory alive until this compositor process exits. Resuming
+ * would reset a pending command buffer/fence or free memory still read by the GPU. */
+static void quarantine_pending_work(VkResult result, const char *where) {
+    if (g_dev_state != 1) return;
+    g_dev_state = -3;
+    g_base_black = 0;
+    LOGE("GPU completion unconfirmed (%d in %s): presenting stopped; pending resources retained; "
+         "restart DroidDeck", (int)result, where);
+}
+
 /* vkWaitForFences on the compositor's own work, timed for the perf line. */
 static VkResult timed_wait(VkFence fence, uint64_t timeout) {
+    if (g_dev_state != 1)
+        return g_dev_state == -2 ? VK_ERROR_DEVICE_LOST : VK_ERROR_UNKNOWN;
     int64_t t0 = perf_now();
     VkResult r = g_vk.WaitForFences(g_dev, 1, &fence, VK_TRUE, timeout);
     perf_add(&g_perf.wait_ns, &g_perf.wait_max_ns, &g_perf.waits, perf_now() - t0);
+    if (r != VK_SUCCESS && r != VK_ERROR_DEVICE_LOST)
+        quarantine_pending_work(r, "fence wait");
     return r;
 }
 
@@ -236,7 +252,12 @@ static void reset_sync(void) {
 static void destroy_swapchain(void) {
     g_base_black = 0; /* a new swapchain starts with nothing on it */
     if (g_dev_state != 1) return;
-    g_vk.DeviceWaitIdle(g_dev);
+    VkResult idle = g_vk.DeviceWaitIdle(g_dev);
+    if (idle != VK_SUCCESS) {
+        if (idle == VK_ERROR_DEVICE_LOST) device_lost("swapchain idle");
+        else quarantine_pending_work(idle, "swapchain idle");
+        return;
+    }
     reset_sync();
     for (uint32_t i = 0; i < g_nimg; i++) blendp_forget_image(g_images[i]);
     if (g_swapchain) g_vk.DestroySwapchainKHR(g_dev, g_swapchain, NULL);
@@ -302,6 +323,7 @@ int vkp_has_window(void) {
 }
 
 int vkp_device_lost(void) { return g_dev_state == -2; }
+int vkp_completion_unknown(void) { return g_dev_state == -3; }
 
 void vk_present_set_scale_mode(int mode, int alignment) {
     if (mode < VKP_MODE_OFF || mode > VKP_MODE_INTEGER) mode = VKP_MODE_FIT;
@@ -546,6 +568,7 @@ static int dev_init(void) {
     g_dev_state = 1;
     reset_sync();
     init_black_image();
+    if (g_dev_state != 1) return -1;
     vkp_framegen_device_ready(g_dev, g_queue, g_qfam, fg_features != NULL);
     return 0;
 }
@@ -557,7 +580,7 @@ static int swap_init_locked(void);
 static int swap_init(void) {
     struct timespec ts;
     int64_t now;
-    if (!g_window) return -1;
+    if (!g_window || g_dev_state != 1) return -1;
     clock_gettime(CLOCK_MONOTONIC, &ts);
     now = (int64_t)ts.tv_sec * 1000000000LL + ts.tv_nsec;
     if (now < g_swap_retry_at_ns) return -1;
@@ -842,10 +865,15 @@ static void init_black_image(void) {
     g_vk.EndCommandBuffer(cmd);
     VkSubmitInfo si = {.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO, .commandBufferCount = 1, .pCommandBuffers = &cmd};
     g_vk.ResetFences(g_dev, 1, &g_fence);
-    if (g_vk.QueueSubmit(g_queue, 1, &si, g_fence) == VK_SUCCESS &&
-        g_vk.WaitForFences(g_dev, 1, &g_fence, VK_TRUE, 1000000000ULL) == VK_SUCCESS)
-        g_black_state = 1;
-    else
+    VkResult qr = g_vk.QueueSubmit(g_queue, 1, &si, g_fence);
+    if (qr == VK_SUCCESS) {
+        VkResult fr = timed_wait(g_fence, 1000000000ULL);
+        if (fr == VK_SUCCESS) g_black_state = 1;
+        else if (fr == VK_ERROR_DEVICE_LOST) device_lost("black image");
+    } else if (qr == VK_ERROR_DEVICE_LOST) {
+        device_lost("black image submit");
+    }
+    if (g_black_state != 1)
         droiddeck_log("gpu", "letterbox black image unavailable: the whole output is cleared every copy-path frame");
 }
 
@@ -1084,10 +1112,10 @@ struct vkp_image *vkp_image_create_shm(int w, int h) {
     return img;
 }
 
-/* Renders are synchronous (we wait for the frame's fence), so writing between frames
- * never races the GPU. */
+/* Between successfully completed frames the GPU is idle. After an unconfirmed
+ * wait, retain the mapped bytes too: the previous submit may still read them. */
 void vkp_image_upload_shm(struct vkp_image *img, const void *data, int stride) {
-    if (!img || !img->map || !data) return;
+    if (g_dev_state != 1 || !img || !img->map || !data) return;
     size_t rowbytes = (size_t)img->w * 4;
     if ((size_t)stride < rowbytes) rowbytes = (size_t)stride;
     for (int y = 0; y < img->h; y++)
@@ -1100,6 +1128,7 @@ int vkp_image_height(const struct vkp_image *img) { return img ? img->h : 0; }
 
 void vkp_image_destroy(struct vkp_image *img) {
     if (!img) return;
+    if (g_dev_state == -3) return; /* completion unknown: retain GPU ownership */
     if (g_dev) {
         blendp_forget_image(img->image);
         if (img->map) g_vk.UnmapMemory(g_dev, img->mem);
@@ -1391,6 +1420,7 @@ static void record_screen_blit(VkCommandBuffer cmd, VkImage src, int src_w, int
  * so they never rebuild; they fail and the frame ends early. 0 on success. */
 static int acquire_image(int k, int first, uint32_t *img, VkResult *ar_out) {
     for (int attempt = 0; ; attempt++) {
+        if (g_dev_state != 1) return -1;
         if (!g_swapchain && (!first || swap_init() != 0)) return -1;
         /* A bounded wait: a surface that went away without telling us must not park the
          * compositor thread forever (clients are paced from this thread). */
@@ -1402,7 +1432,7 @@ static int acquire_image(int k, int first, uint32_t *img, VkResult *ar_out) {
         if (ar == VK_ERROR_OUT_OF_DATE_KHR || ar == VK_ERROR_SURFACE_LOST_KHR) {
             droiddeck_log("gpu", "screen surface %s on acquire: rebuilding the swapchain", vk_result_name(ar));
             destroy_swapchain();
-            if (first && attempt == 0) continue;
+            if (first && attempt == 0 && g_dev_state == 1) continue;
             return -1;
         }
         droiddeck_log("error", "present: acquire %d failed (%s %d)", k, vk_result_name(ar), (int)ar);
@@ -1530,6 +1560,7 @@ static void send_hdr_metadata(const struct droiddeck_color *c) {
 static int render_impl(int scene_w, int scene_h, const struct vkp_draw *draws, int n,
                        const struct vkp_hdr_frame *hf, int *how) {
     if (how) *how = 0;
+    if (g_dev_state < 0) return -1;
     vkp_apply_window_request();
     check_surface_changed(); /* a rotation or a fold the rebind did not cover: rebuild at the new size */
     if (g_dev_state == -2) return -1;
@@ -1552,6 +1583,7 @@ static int render_impl(int scene_w, int scene_h, const struct vkp_draw *draws, i
                                      : "no HDR frames through the screen swapchain any more: rebuilding it as SDR");
         destroy_swapchain();
     }
+    if (g_dev_state != 1) return -1;
     g_swap_hdr_want = want_hdr;
 
     uint32_t img = 0;
@@ -1762,6 +1794,10 @@ static int render_impl(int scene_w, int scene_h, const struct vkp_draw *draws, i
         if (k > 0) {
             VkResult ark;
             if (acquire_image(k, 0, &img, &ark) != 0) {
+                /* Teardown may have retained this frame's pending work, or
+                 * acquire may have reported real device loss. Neither permits
+                 * a completion-marker submit or another fence wait. */
+                if (g_dev_state != 1) return -1;
                 droiddeck_log("framegen", "present %d/%d: no swapchain image; the frame ends early", k + 1, presents);
                 pr = VK_ERROR_OUT_OF_DATE_KHR;
                 break;
@@ -1794,17 +1830,24 @@ static int render_impl(int scene_w, int scene_h, const struct vkp_draw *draws, i
         pr = g_vk.QueuePresentKHR(g_queue, &pi);
         perf_add(&g_perf.present_ns, &g_perf.present_max_ns, &g_perf.presents, perf_now() - t_pres);
         if (k < ngen) presented_gen++;
-        if (pr == VK_ERROR_OUT_OF_DATE_KHR || pr == VK_ERROR_SURFACE_LOST_KHR || pr == VK_ERROR_DEVICE_LOST) break;
+        if (pr == VK_ERROR_DEVICE_LOST) { device_lost("present"); return -1; }
+        if (pr == VK_ERROR_OUT_OF_DATE_KHR || pr == VK_ERROR_SURFACE_LOST_KHR) break;
     }
     if (!fence_submitted) {
         /* Ended early: an empty submit carrying the fence is ordered after everything queued
          * above, so the wait below still means "this frame's work is done". */
         VkSubmitInfo si = {.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO};
-        g_vk.QueueSubmit(g_queue, 1, &si, g_fence);
+        VkResult marker = g_vk.QueueSubmit(g_queue, 1, &si, g_fence);
+        if (marker != VK_SUCCESS) {
+            if (marker == VK_ERROR_DEVICE_LOST) device_lost("frame completion submit");
+            else quarantine_pending_work(marker, "frame completion submit");
+            return -1; /* no fence was submitted; never wait on its unsignalled state */
+        }
     }
     VkResult fr = timed_wait(g_fence, UINT64_MAX);
-    if (fg) vkp_framegen_presented(presented_gen);
     if (fr == VK_ERROR_DEVICE_LOST || pr == VK_ERROR_DEVICE_LOST) { device_lost("present"); return -1; }
+    if (fr != VK_SUCCESS) return -1;
+    if (fg) vkp_framegen_presented(presented_gen);
     if (pr == VK_ERROR_OUT_OF_DATE_KHR || pr == VK_ERROR_SURFACE_LOST_KHR) {
         /* The surface changed or went away under this frame: rebuild before the next one. */
         droiddeck_log("gpu", "screen surface %s on present: rebuilding the swapchain", vk_result_name(pr));
@@ -1878,6 +1921,7 @@ void vkp_signal_first_frame(void) {
 int vkp_update_map(int scene_w, int scene_h) {
     if (g_dev_state == -2 || dev_init() != 0 || !g_window || scene_w <= 0 || scene_h <= 0) return -1;
     check_surface_changed(); /* layer mode may present nothing on the base surface for a long time */
+    if (g_dev_state != 1) return -1;
     if (!g_swapchain && swap_init() != 0) return -1;
     update_map(scene_w, scene_h);
     return g_map.valid ? 0 : -1;
@@ -2116,6 +2160,7 @@ static int pass_begin_impl(int scene_w, int scene_h, const struct vkp_draw *draw
     if (g_pass.active) vkp_pass_abort();
     if (g_dev_state == -2 || dev_init() != 0 || !g_window || scene_w <= 0 || scene_h <= 0) return -1;
     check_surface_changed(); /* as in render_impl: the effects pass maps onto the output's size */
+    if (g_dev_state != 1) return -1;
     if (!g_swapchain && swap_init() != 0) return -1; /* the mapping is in output pixels */
     update_map(scene_w, scene_h);
     if (!g_map.valid) return -1;
@@ -2211,8 +2256,9 @@ static int pass_begin_impl(int scene_w, int scene_h, const struct vkp_draw *draw
 int vkp_pass_copy_to(struct vkp_image *dst, int wait_fd) {
     if (!g_pass.active) { if (wait_fd >= 0) close(wait_fd); return -1; }
     g_pass.active = 0;
+    if (g_dev_state != 1) { if (wait_fd >= 0) close(wait_fd); return -1; }
     VkCommandBuffer cmd = g_cmds[0];
-    if (!dst || !dst->blit_dst || g_dev_state == -2) {
+    if (!dst || !dst->blit_dst) {
         if (wait_fd >= 0) close(wait_fd);
         g_vk.EndCommandBuffer(cmd);
         return -1;
@@ -2267,5 +2313,6 @@ int vkp_pass_copy_to(struct vkp_image *dst, int wait_fd) {
 void vkp_pass_abort(void) {
     if (!g_pass.active) return;
     g_pass.active = 0;
-    g_vk.EndCommandBuffer(g_cmds[0]); /* never submitted; the buffer is reset before its next use */
+    if (g_dev_state == 1)
+        g_vk.EndCommandBuffer(g_cmds[0]); /* never submitted; reset before its next use */
 }
diff --git a/app/src/main/cpp/waylandcomp/src/vk_present.h b/app/src/main/cpp/waylandcomp/src/vk_present.h
index 2a752c343..9506625f1 100644
--- a/app/src/main/cpp/waylandcomp/src/vk_present.h
+++ b/app/src/main/cpp/waylandcomp/src/vk_present.h
@@ -91,6 +91,10 @@ int vkp_ready(void);
 int vkp_has_window(void);
 /* 1 once the Vulkan device was lost: nothing is presented any more (the session must restart). */
 int vkp_device_lost(void);
+/* Compositor thread only. Submitted reads may still be pending: retain imported
+ * buffer references and withhold DMA-BUF releases until the app process exits.
+ * This terminal state is distinct from genuine device loss. */
+int vkp_completion_unknown(void);
 
 // Clear to black, blit the draws in order (first = bottom) and present.
 // Returns 0 on success, -1 if nothing could be presented (no window yet, etc.).
diff --git a/docs/development/gpu-pending-completion.md b/docs/development/gpu-pending-completion.md
new file mode 100644
index 000000000..db036ba21
--- /dev/null
+++ b/docs/development/gpu-pending-completion.md
@@ -0,0 +1,88 @@
+# Compositor work whose completion is unknown
+
+A timed-out fence wait does not cancel submitted GPU work. Continuing after
+that result can reset a command buffer or fence still in use, or destroy an
+image and its memory while the GPU may still read them. Previously the finite
+wait paths returned without putting the compositor into a terminal state, and
+swapchain teardown ignored the result of `vkDeviceWaitIdle`.
+
+An unsuccessful completion check other than real `VK_ERROR_DEVICE_LOST` now
+puts the compositor in a distinct completion-unknown state. It stops subsequent
+presentation and retains potentially pending image/memory and swapchain
+resources until the DroidDeck app process exits. Device loss continues through
+the existing device-loss path. This is deliberate retention rather than an
+automatic recovery; restarting a guest session cannot reset the in-process GPU
+state, so the diagnostic asks for an app restart.
+
+Initialization checks the black-image submit and fence result. An unsuccessful
+empty completion-marker submit no longer causes a wait on an unsignalled fence.
+Surface-rebuild and effect-map paths stop when teardown cannot establish idle.
+Acquire retries also stop: retaining the old swapchain is not permission to
+acquire from it again. A later frame-generation acquire that ends in a terminal
+state returns before the completion marker, fence wait or any further recording.
+Real device loss on present is handled before attempting that marker, too.
+Mapped SHM bytes are retained unchanged, including same-size `wl_shm` and
+single-pixel commits; keeping only the allocation would still race a GPU read.
+Off-screen pass copy/abort and the internal fence wait reject terminal states
+without further Vulkan calls. Release fds are still consumed on rejected copies.
+The normal frame fence still has its existing infinite timeout; this change is
+not a general GPU hang watchdog.
+
+Externally owned DMA-BUF contents need the same protection. `vkp_completion_unknown()`
+exposes the terminal state to compositor-thread lifecycle paths. Replacement,
+surface/client destruction, cursor/idle-role releases, previously queued paced
+releases and SurfaceFlinger callbacks no longer return a DMA-BUF to its client
+after quarantine. The compositor retains DMA-BUF references/backing FDs and AHB
+references until app process exit. A display fence alone does not establish that
+the compositor's Vulkan reads completed. Queued releases detach destroyed surfaces
+and remain held without repeatedly arming an expired timer. New terminal releases
+require no allocation, so allocation failure cannot fall back to an unsafe release.
+Copied SHM releases and healthy/genuine-device-loss cleanup keep their existing
+behaviour. This intentionally prevents further client buffer reuse; restarting
+the Android app process, not just the guest session, is required.
+
+## Regression coverage
+
+`python3 -m unittest discover -s tools/tests -p test_vk_pending_completion.py -v`
+compiles the production wait/destructor and swapchain teardown functions with a
+fake Vulkan dispatch table. The two cases cover success, timeout, host-memory
+errors, genuine device loss, resource retention and suppressed repeated teardown.
+No real GPU fault is injected. The harness matches main's Vulkan-image resources;
+it does not assume the experimental PowerVR branch's additional AHB fields.
+
+`python3 -m unittest discover -s tools/tests -p test_vk_terminal_callers.py -v`
+additionally compiles the **entire production `vk_present.c`**, with fake Vulkan
+dispatch callbacks and stub external modules. The compositor's `take_shm` and
+`take_pixel` callers are inserted verbatim, not rewritten. It needs the Android
+NDK's Vulkan-Headers (`ANDROID_HOME`/`ANDROID_SDK_ROOT`/`NDK`), a host Vulkan
+development package, or `DROIDDECK_VULKAN_INCLUDE`; absent headers are explicitly
+reported as a skip. No Android runtime or GPU is required.
+
+The 12 scenarios include first/later OUT_OF_DATE and SURFACE_LOST followed by an
+idle failure, a finite blit timeout followed by same-size SHM/single-pixel
+uploads, normal presentation/frame generation, a healthy later acquire timeout
+whose earlier work still needs draining, real acquire/present device loss, and
+terminal off-screen pass entry. Every work-issuing fake callback asserts the
+device is live. After quarantine, the tests verify retained handles and unchanged
+mapped bytes, and probe the public render/blit/readback/import/pass entry points
+for suppressed acquire/submit/wait/reset and destruction. Consumed fds are checked.
+Against PR #560's `68dc1c45` the same harness compiles, but nine scenarios fail
+(the three healthy controls pass); the corrected production unit passes all 12.
+
+The baseline production fence/destructor compiles but fails the timeout-state
+oracle; the corrected functions pass both cases with `-Wall -Wextra -Werror`.
+The change was also exercised in an independently integrated Pixel PowerVR Lab,
+but its short game observations do not establish the cause of the earlier GNOC
+reboot or sustained device stability. Main's native CI and APK build remain
+separate validation.
+
+`python3 -m unittest discover -s tools/tests -p test_vk_dmabuf_quarantine.py -v`
+compiles the production compositor/AHB release, reference and listener functions
+verbatim, using the real Wayland list layouts/macros with fake IPC/timer/AHB
+endpoints. It covers paced replacement, immediate surface cleanup, already queued
+releases, a mixed DMA-BUF/SHM queue, client destruction, a display-fence callback,
+healthy cleanup and genuine device loss. It checks withheld releases, retained
+FDs/references/AHB ownership, removal of surface listeners and disarmed timers.
+The same harness can test an old source directory via
+`DROIDDECK_DMABUF_TEST_SOURCE`; it does not inject a real driver fault or prove
+long-term device stability.
diff --git a/tools/tests/test_vk_dmabuf_quarantine.py b/tools/tests/test_vk_dmabuf_quarantine.py
new file mode 100644
index 000000000..b6e035b6a
--- /dev/null
+++ b/tools/tests/test_vk_dmabuf_quarantine.py
@@ -0,0 +1,106 @@
+"""Exercise production DMA-BUF release/ownership paths without a GPU.
+
+Wayland resources and OS timer/Android AHB endpoints are fake; list macros and
+the compositor/AHB lifecycle functions come directly from the repository.
+"""
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+from test_vk_pending_completion import function
+
+ROOT = Path(__file__).resolve().parents[2]
+SRC = ROOT / 'app/src/main/cpp/waylandcomp/src'
+
+
+class VkDmabufQuarantineTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cc = shutil.which(os.environ.get('CC', 'cc'))
+        if not cc:
+            raise AssertionError('C compiler required')
+        # Optional old-head input allows a genuine negative control using the
+        # identical harness, rather than a model of the previous behaviour.
+        source_dir = Path(os.environ.get('DROIDDECK_DMABUF_TEST_SOURCE', SRC))
+        comp = (source_dir / 'compositor.c').read_text()
+        ahb = (source_dir / 'ahb_swapchain.c').read_text()
+        vk = (source_dir / 'vk_present.c').read_text()
+        names = ['get_dmabuf', 'pending_release_free',
+                 'pending_releases_forget_surface', 'on_pending_release_buffer_destroyed',
+                 'arm_release_timer', 'on_release_timer', 'release_buffer',
+                 'dmabuf_buffer_unref', 'drop_dmabuf', 'on_dmabuf_destroyed',
+                 'droiddeck_dmabuf_ahb_slot', 'droiddeck_dmabuf_unref',
+                 'droiddeck_release_buffer']
+        helpers = []
+        if re.search(r'\bstatic int buffer_release_blocked\(', comp):
+            helpers = [function(comp, n) for n in ('buffer_release_blocked', 'send_buffer_release')]
+        else:
+            helpers = ['static int __attribute__((unused)) buffer_release_blocked(struct wl_resource *b) { (void)b; return 0; }']
+        query = function(vk, 'vkp_completion_unknown') if 'int vkp_completion_unknown(' in vk else \
+            'int vkp_completion_unknown(void) { return g_dev_state == -3; }'
+        comp_functions = [function(comp, names[0])] + helpers + [function(comp, n) for n in names[1:]]
+        ahb_functions = [function(ahb, n) for n in ('buf_free', 'maybe_free',
+                         'on_buffer_resource_destroyed', 'send_deferred_release',
+                         'on_fence_readable', 'ahb_swapchain_defer_release',
+                         'ahb_swapchain_surface_gone')]
+        structs = re.search(r'struct pending_release \{.*?\n\};', comp, re.S).group() + '\n' + \
+            re.search(r'struct ahb_buf \{.*?\n\};', ahb, re.S).group()
+        harness = Path(__file__).with_name('vk_dmabuf_quarantine_test.c').read_text()
+        harness = harness.replace('/* PRODUCTION_STRUCTS */', structs)
+        harness = harness.replace('/* PRODUCTION_FUNCTIONS */', '\n'.join([query] + comp_functions + ahb_functions))
+        cls.tmp = tempfile.TemporaryDirectory(prefix='droiddeck-dmabuf-')
+        cls.addClassCleanup(cls.tmp.cleanup)
+        probe = Path(cls.tmp.name) / 'probe.c'
+        probe.write_text(harness)
+        cls.binary = probe.with_suffix('')
+        built = subprocess.run([cc, '-std=c11', '-Wall', '-Wextra', '-Werror',
+                                '-Wno-unused-parameter', '-UNDEBUG',
+                                '-I', str(SRC.parent / 'prebuilt/include'),
+                                str(probe), '-o', str(cls.binary)], capture_output=True, text=True)
+        if built.returncode:
+            raise AssertionError(built.stdout + built.stderr)
+
+    def run_scenario(self, name):
+        result = subprocess.run([str(self.binary), name], capture_output=True, text=True, timeout=10)
+        self.assertEqual(result.returncode, 0, result.stdout + result.stderr)
+
+    def test_replacement_retains_reference_and_release(self):
+        self.run_scenario('replacement')
+
+    def test_surface_destroy_retains_reference_and_release(self):
+        self.run_scenario('surface-gone')
+
+    def test_queued_release_is_held_and_timer_disarmed(self):
+        self.run_scenario('queued')
+
+    def test_mixed_queue_releases_only_copied_shm(self):
+        self.run_scenario('mixed')
+
+    def test_client_destroy_retains_backing_fd(self):
+        self.run_scenario('client-gone')
+
+    def test_ahb_callback_retains_ownership_and_release(self):
+        self.run_scenario('ahb')
+
+    def test_active_client_destroy_retains_reference(self):
+        self.run_scenario('active-client-gone')
+
+    def test_healthy_ahb_callback_and_cleanup(self):
+        self.run_scenario('ahb-healthy')
+
+    def test_device_lost_ahb_callback_and_cleanup(self):
+        self.run_scenario('ahb-device-lost')
+
+    def test_healthy_release_and_reference_cleanup(self):
+        self.run_scenario('healthy')
+
+    def test_genuine_device_loss_keeps_existing_cleanup(self):
+        self.run_scenario('device-lost')
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tools/tests/test_vk_pending_completion.py b/tools/tests/test_vk_pending_completion.py
new file mode 100644
index 000000000..5f69c820d
--- /dev/null
+++ b/tools/tests/test_vk_pending_completion.py
@@ -0,0 +1,184 @@
+"""Fault-inject the production fence wait and imported-image destructor.
+
+No GPU is wedged: a fake dispatch table returns the same result a timed-out
+submit would return. The compiled functions come from vk_present.c itself.
+"""
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+SOURCE = Path(__file__).resolve().parents[2] / 'app/src/main/cpp/waylandcomp/src/vk_present.c'
+
+
+def function(text, name):
+    match = re.search(r'^(?:static )?[^\n;]+\b' + name + r'\([^;]*?\)\s*\{', text, re.M)
+    if not match:
+        raise AssertionError('Production function not found: ' + name)
+    start = match.start()
+    pos = text.index('{', match.start())
+    depth = 1
+    end = pos + 1
+    while depth:
+        depth += (text[end] == '{') - (text[end] == '}')
+        end += 1
+    return text[start:end]
+
+
+HARNESS = r'''
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdarg.h>
+typedef int VkResult;
+typedef uintptr_t VkFence;
+#define VK_TRUE 1
+#define VK_SUCCESS 0
+#define VK_TIMEOUT 2
+#define VK_ERROR_DEVICE_LOST -4
+#define VK_ERROR_OUT_OF_HOST_MEMORY -1
+#define VK_ERROR_UNKNOWN -13
+static int g_dev_state, g_base_black;
+static uintptr_t g_dev = 1;
+static struct { int64_t wait_ns, wait_max_ns; unsigned waits; } g_perf;
+static VkResult answer;
+static unsigned destroyed, unmapped, freed_memory, forgotten, errors;
+static int64_t perf_now(void) { return 10; }
+static void perf_add(int64_t *s, int64_t *m, unsigned *c, int64_t d) { *s+=d; *m=d; ++*c; }
+static void __attribute__((unused)) droiddeck_log(const char *tag, const char *fmt, ...) { (void)tag; (void)fmt; ++errors; }
+#define LOGE(...) droiddeck_log("error", __VA_ARGS__)
+static VkResult wait_fn(uintptr_t dev, unsigned n, const VkFence *f, int all, uint64_t timeout) {
+    (void)dev; (void)n; (void)f; (void)all; (void)timeout; return answer;
+}
+static void unmap_fn(uintptr_t dev, uintptr_t mem) { (void)dev; (void)mem; ++unmapped; }
+static void destroy_fn(uintptr_t dev, uintptr_t img, void *allocator) { (void)dev; (void)img; (void)allocator; ++destroyed; }
+static void free_fn(uintptr_t dev, uintptr_t mem, void *allocator) { (void)dev; (void)mem; (void)allocator; ++freed_memory; }
+static struct {
+    VkResult (*WaitForFences)(uintptr_t, unsigned, const VkFence *, int, uint64_t);
+    void (*UnmapMemory)(uintptr_t, uintptr_t);
+    void (*DestroyImage)(uintptr_t, uintptr_t, void *);
+    void (*FreeMemory)(uintptr_t, uintptr_t, void *);
+} g_vk = {wait_fn, unmap_fn, destroy_fn, free_fn};
+struct vkp_image { uintptr_t image, mem; void *map; };
+static void blendp_forget_image(uintptr_t image) { (void)image; ++forgotten; }
+/* PRODUCTION_FUNCTIONS */
+static struct vkp_image *image(void) {
+    struct vkp_image *p = calloc(1, sizeof(*p)); assert(p);
+    p->image=1; p->mem=2; p->map=p; return p;
+}
+int main(void) {
+    g_dev_state=1; answer=VK_SUCCESS;
+    assert(timed_wait(1, 1000)==VK_SUCCESS);
+    assert(g_dev_state==1);
+    vkp_image_destroy(image());
+    assert(destroyed==1 && unmapped==1 && freed_memory==1 && forgotten==1);
+
+    g_dev_state=1; g_base_black=1; answer=VK_TIMEOUT;
+    assert(timed_wait(1, 1000)==VK_TIMEOUT);
+    assert(g_dev_state!=1 && g_dev_state!=-2); /* pending work is not DEVICE_LOST */
+    struct vkp_image *pending=image();
+    vkp_image_destroy(pending);
+    assert(destroyed==1 && unmapped==1 && freed_memory==1 && forgotten==1);
+    unsigned first_errors=errors;
+    assert(first_errors>0);
+    assert(timed_wait(1, 1000)==VK_ERROR_UNKNOWN);
+    assert(errors==first_errors); /* one terminal diagnostic, no repeated recovery */
+    free(pending); /* fake GPU exists only in this test */
+
+    g_dev_state=1; answer=VK_ERROR_OUT_OF_HOST_MEMORY;
+    assert(timed_wait(1, 1000)==VK_ERROR_OUT_OF_HOST_MEMORY);
+    assert(g_dev_state!=1 && g_dev_state!=-2);
+    pending=image(); vkp_image_destroy(pending);
+    assert(destroyed==1 && unmapped==1 && freed_memory==1 && forgotten==1);
+    free(pending);
+
+    g_dev_state=1; answer=VK_ERROR_DEVICE_LOST;
+    assert(timed_wait(1, 1000)==VK_ERROR_DEVICE_LOST);
+    assert(g_dev_state==1); /* existing caller performs genuine device-loss cleanup */
+    return 0;
+}
+'''
+
+SWAPCHAIN_HARNESS = r'''
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+typedef int VkResult;
+#define VK_SUCCESS 0
+#define VK_ERROR_DEVICE_LOST -4
+#define VK_ERROR_OUT_OF_HOST_MEMORY -1
+#define VK_NULL_HANDLE 0
+static int g_dev_state, g_base_black, g_swap_md_identity;
+static uintptr_t g_dev=1, g_inst=1, g_swapchain, g_surface, *g_images;
+static uint32_t g_nimg;
+static unsigned resets, forgotten, destroyed, errors, lost;
+static VkResult answer;
+#define LOGE(...) (++errors)
+static VkResult idle_fn(uintptr_t dev) { (void)dev; return answer; }
+static void destroy_fn(uintptr_t dev, uintptr_t obj, void *alloc) {
+    (void)dev; (void)obj; (void)alloc; ++destroyed;
+}
+static struct {
+    VkResult (*DeviceWaitIdle)(uintptr_t);
+    void (*DestroySwapchainKHR)(uintptr_t, uintptr_t, void *);
+    void (*DestroySurfaceKHR)(uintptr_t, uintptr_t, void *);
+} g_vk={idle_fn, destroy_fn, destroy_fn};
+static void reset_sync(void) { ++resets; }
+static void blendp_forget_image(uintptr_t img) { (void)img; ++forgotten; }
+static void device_lost(const char *where) { (void)where; ++lost; g_dev_state=-2; }
+/* PRODUCTION_FUNCTIONS */
+static void setup(void) {
+    g_dev_state=1; g_base_black=1; g_swap_md_identity=1;
+    g_swapchain=2; g_surface=3; g_nimg=1;
+    g_images=calloc(1,sizeof(*g_images)); assert(g_images); *g_images=4;
+}
+int main(void) {
+    setup(); answer=VK_SUCCESS; destroy_swapchain();
+    assert(resets==1 && destroyed==2 && forgotten==1);
+    assert(!g_swapchain && !g_surface && !g_images && !g_nimg && !g_swap_md_identity);
+    setup(); answer=VK_ERROR_OUT_OF_HOST_MEMORY; destroy_swapchain();
+    assert(g_dev_state==-3 && errors==1);
+    assert(resets==1 && destroyed==2 && forgotten==1);
+    assert(g_swapchain && g_surface && g_images && g_nimg);
+    destroy_swapchain();
+    assert(errors==1 && resets==1 && destroyed==2);
+    free(g_images); /* fake GPU resources only */
+    setup(); answer=VK_ERROR_DEVICE_LOST; destroy_swapchain();
+    assert(lost==1 && g_dev_state==-2);
+    assert(resets==1 && destroyed==2 && forgotten==1);
+    free(g_images);
+    return 0;
+}
+'''
+
+
+class VkPendingCompletionTest(unittest.TestCase):
+    def compile_and_run(self, harness, names):
+        cc = shutil.which(os.environ.get('CC', 'cc'))
+        self.assertIsNotNone(cc, 'A C compiler is required')
+        text = SOURCE.read_text()
+        production = '\n'.join(function(text, n) for n in names)
+        with tempfile.TemporaryDirectory(prefix='droiddeck-pending-') as tmp:
+            source=Path(tmp)/'probe.c'; binary=Path(tmp)/'probe'
+            source.write_text(harness.replace('/* PRODUCTION_FUNCTIONS */', production))
+            built=subprocess.run([cc,'-std=c11','-Wall','-Wextra','-Werror','-UNDEBUG',str(source),'-o',str(binary)],capture_output=True,text=True)
+            self.assertEqual(built.returncode,0,built.stdout+built.stderr)
+            ran=subprocess.run([str(binary)],capture_output=True,text=True,timeout=10)
+            self.assertEqual(ran.returncode,0,ran.stdout+ran.stderr)
+
+    def test_unknown_completion_retains_gpu_resources(self):
+        self.compile_and_run(HARNESS, ['quarantine_pending_work', 'timed_wait', 'vkp_image_destroy'])
+
+    def test_failed_device_idle_does_not_destroy_swapchain(self):
+        # LOGE's arguments must be evaluated as real production logging does.
+        harness = SWAPCHAIN_HARNESS.replace('#define LOGE(...) (++errors)',
+            'static void log_error(const char *fmt, int result, const char *where) { '
+            '(void)fmt; (void)result; (void)where; ++errors; }\n#define LOGE(...) log_error(__VA_ARGS__)')
+        self.compile_and_run(harness, ['quarantine_pending_work', 'destroy_swapchain'])
+
+
+if __name__=='__main__':
+    unittest.main()
diff --git a/tools/tests/test_vk_terminal_callers.py b/tools/tests/test_vk_terminal_callers.py
new file mode 100644
index 000000000..7048f5e1b
--- /dev/null
+++ b/tools/tests/test_vk_terminal_callers.py
@@ -0,0 +1,115 @@
+"""Fault-inject complete production render/blit/upload callers, without a GPU.
+
+Uses Vulkan-Headers from the Android NDK (as installed by APK CI), or the host
+Vulkan development package. Only Android platform declarations and the external
+effect/frame-generation modules are mocked; vk_present.c is compiled unmodified.
+"""
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+from test_vk_pending_completion import function
+
+ROOT = Path(__file__).resolve().parents[2]
+SOURCE = ROOT / 'app/src/main/cpp/waylandcomp/src/vk_present.c'
+
+
+def vulkan_include():
+    candidates = [Path(p) for p in [os.environ.get('DROIDDECK_VULKAN_INCLUDE', ''),
+                                  '/usr/include', '/usr/local/include'] if p]
+    for name in ('ANDROID_HOME', 'ANDROID_SDK_ROOT', 'ANDROID_NDK_HOME', 'NDK'):
+        if os.environ.get(name):
+            root = Path(os.environ[name])
+            candidates += sorted(root.glob('ndk/*/toolchains/llvm/prebuilt/*/sysroot/usr/include'), reverse=True)
+            candidates += list(root.glob('toolchains/llvm/prebuilt/*/sysroot/usr/include'))
+    return next((p for p in candidates if (p / 'vulkan/vulkan.h').is_file()), None)
+
+
+class VkTerminalCallersTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        headers = vulkan_include()
+        if headers is None:
+            raise unittest.SkipTest('NDK or host Vulkan-Headers required for full production-C caller tests')
+        cc = shutil.which(os.environ.get('CC', 'cc'))
+        if not cc:
+            raise AssertionError('C compiler required')
+        cls.tmp = tempfile.TemporaryDirectory(prefix='droiddeck-callers-')
+        cls.addClassCleanup(cls.tmp.cleanup)
+        tmp = Path(cls.tmp.name)
+        (tmp / 'android').mkdir()
+        (tmp / 'android/native_window.h').write_text('''
+#pragma once
+#include <stdint.h>
+typedef struct ANativeWindow ANativeWindow;
+int32_t ANativeWindow_getWidth(ANativeWindow *);
+int32_t ANativeWindow_getHeight(ANativeWindow *);
+void ANativeWindow_release(ANativeWindow *);
+''')
+        (tmp / 'android/hardware_buffer.h').write_text('#pragma once\ntypedef struct AHardwareBuffer AHardwareBuffer;\n')
+        (tmp / 'android/log.h').write_text('''
+#pragma once
+#define ANDROID_LOG_INFO 4
+int __android_log_print(int, const char *, const char *, ...);
+''')
+        (tmp / 'wayland-server.h').write_text('#pragma once\nstruct wl_display; struct wl_resource; struct wl_client;\n')
+        compositor = (SOURCE.parent / 'compositor.c').read_text()
+        callers = '\n'.join(function(compositor, n) for n in ('buffer_release_blocked', 'send_buffer_release', 'take_shm', 'take_pixel'))
+        harness = (Path(__file__).with_name('vk_terminal_callers_test.c')).read_text()
+        probe = tmp / 'probe.c'
+        probe.write_text(harness.replace('/* COMPOSITOR_CALLERS */', callers))
+        cls.binary = tmp / 'probe'
+        built = subprocess.run([cc, '-std=c11', '-Wall', '-Wextra', '-Werror',
+                                '-Wno-unused-parameter', '-Wno-missing-field-initializers', '-UNDEBUG',
+                                '-I', str(tmp), '-idirafter', str(headers), '-I', str(SOURCE.parent),
+                                str(probe), '-pthread', '-o', str(cls.binary)],
+                               capture_output=True, text=True)
+        if built.returncode:
+            raise AssertionError(built.stdout + built.stderr)
+
+    def run_scenario(self, name):
+        ran = subprocess.run([str(self.binary), name], capture_output=True, text=True, timeout=10)
+        self.assertEqual(ran.returncode, 0, ran.stdout + ran.stderr)
+
+    def test_first_acquire_idle_failure(self):
+        self.run_scenario('first-out-of-date')
+
+    def test_first_surface_lost_idle_failure(self):
+        self.run_scenario('first-surface-lost')
+
+    def test_later_framegen_acquire_idle_failure(self):
+        self.run_scenario('later-out-of-date')
+
+    def test_later_framegen_surface_lost_idle_failure(self):
+        self.run_scenario('later-surface-lost')
+
+    def test_finite_blit_timeout_same_size_shm_upload(self):
+        self.run_scenario('shm-timeout')
+
+    def test_finite_blit_timeout_same_size_pixel_upload(self):
+        self.run_scenario('pixel-timeout')
+
+    def test_normal_present(self):
+        self.run_scenario('normal')
+
+    def test_normal_framegen_present(self):
+        self.run_scenario('framegen')
+
+    def test_healthy_later_acquire_timeout_drains_work(self):
+        self.run_scenario('later-timeout')
+
+    def test_real_device_lost_on_acquire(self):
+        self.run_scenario('acquire-device-lost')
+
+    def test_real_device_lost_on_present(self):
+        self.run_scenario('present-device-lost')
+
+    def test_pass_copy_and_abort_terminal_entry(self):
+        self.run_scenario('pass-terminal')
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tools/tests/vk_dmabuf_quarantine_test.c b/tools/tests/vk_dmabuf_quarantine_test.c
new file mode 100644
index 000000000..cbcf724b1
--- /dev/null
+++ b/tools/tests/vk_dmabuf_quarantine_test.c
@@ -0,0 +1,199 @@
+/* Production lifecycle functions are inserted verbatim by Python. No GPU,
+ * Android app, external client or real timer is involved in this probe. */
+#define _POSIX_C_SOURCE 200809L
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <wayland-util.h>
+#ifndef __linux__
+struct itimerspec { struct timespec it_interval, it_value; };
+#endif
+
+struct wl_listener { struct wl_list link; void (*notify)(struct wl_listener *, void *); };
+struct wl_resource { int dma; void *user_data; struct wl_list listeners; unsigned releases; };
+struct wl_client;
+struct wl_event_source { int unused; };
+typedef struct AHardwareBuffer { int unused; } AHardwareBuffer;
+struct vkp_image { int unused; };
+struct dmabuf_buffer {
+    int refs, n_planes, fd[4];
+    struct vkp_image *img;
+    void *ahb_state;
+};
+struct surface {
+    struct wl_resource *dmabuf;
+    struct dmabuf_buffer *dmabuf_buf;
+    struct wl_listener dmabuf_destroy;
+    int releases_pending;
+    int64_t next_release_ns;
+};
+/* PRODUCTION_STRUCTS */
+static int g_dev_state, g_fps_limit, g_release_timer_fd;
+static int64_t g_refresh_ns;
+static struct wl_list g_pending_releases, g_bufs;
+static void *g_display;
+static unsigned image_destroys, ahb_releases, source_removes;
+static struct itimerspec last_timer;
+static const int wl_buffer_interface = 1, dbuf_buffer_impl = 2;
+#define TFD_TIMER_ABSTIME 1
+
+/* List operations use the real Wayland layouts/macros. OS/IPC endpoints alone
+ * are fakes, so no event is sent and no process or hardware is touched. */
+void wl_list_init(struct wl_list *l) { l->prev = l; l->next = l; }
+void wl_list_insert(struct wl_list *l, struct wl_list *e) {
+    e->next = l->next; e->prev = l; l->next->prev = e; l->next = e;
+}
+void wl_list_remove(struct wl_list *e) { e->next->prev = e->prev; e->prev->next = e->next; }
+static int wl_resource_instance_of(struct wl_resource *r, const void *i, const void *impl) { return r->dma; }
+static void *wl_resource_get_user_data(struct wl_resource *r) { return r->user_data; }
+static void wl_resource_add_destroy_listener(struct wl_resource *r, struct wl_listener *l) {
+    wl_list_insert(r->listeners.prev, &l->link);
+}
+static void wl_buffer_send_release(struct wl_resource *r) { ++r->releases; }
+static void wl_display_flush_clients(void *d) {}
+static int timerfd_settime(int fd, int flags, const struct itimerspec *v, void *old) { last_timer = *v; return 0; }
+static void perf_note_release(int64_t since) {}
+static int64_t now_ns(void) { return 1000000000LL; }
+static void vkp_image_destroy(struct vkp_image *img) { ++image_destroys; }
+static void AHardwareBuffer_release(AHardwareBuffer *ahb) { ++ahb_releases; }
+static int wl_event_source_remove(struct wl_event_source *src) { ++source_removes; return 0; }
+static struct dmabuf_buffer *get_dmabuf(struct wl_resource *r);
+int ahb_swapchain_defer_release(struct dmabuf_buffer *, struct wl_resource *, struct surface *, int);
+/* PRODUCTION_FUNCTIONS */
+
+static void init_resource(struct wl_resource *r, struct dmabuf_buffer *b) {
+    *r = (struct wl_resource){.dma = b != NULL, .user_data = b};
+    wl_list_init(&r->listeners);
+}
+static struct dmabuf_buffer *init_buffer(struct surface *s, struct wl_resource *r) {
+    struct dmabuf_buffer *b = calloc(1, sizeof(*b)); assert(b);
+    b->refs = 2; b->n_planes = 1;
+    int fds[2]; assert(pipe(fds) == 0); b->fd[0] = fds[0]; close(fds[1]);
+    init_resource(r, b);
+    assert(get_dmabuf(r) == b);
+    *s = (struct surface){.dmabuf = r, .dmabuf_buf = b};
+    s->dmabuf_destroy.notify = on_dmabuf_destroyed;
+    wl_resource_add_destroy_listener(r, &s->dmabuf_destroy);
+    return b;
+}
+static void destroy_resource(struct wl_resource *r) {
+    while (r->listeners.next != &r->listeners) {
+        struct wl_listener *l = wl_container_of(r->listeners.next, l, link);
+        l->notify(l, r);
+    }
+    if (r->dma) dmabuf_buffer_unref(r->user_data);
+    r->user_data = NULL;
+}
+static void fire_timer(void) {
+    int fd[2]; uint64_t expirations = 1;
+    assert(pipe(fd) == 0 && write(fd[1], &expirations, sizeof(expirations)) == sizeof(expirations));
+    on_release_timer(fd[0], 0, NULL); close(fd[0]); close(fd[1]);
+}
+static void assert_retained(struct dmabuf_buffer *b, int refs) {
+    assert(b->refs == refs && fcntl(b->fd[0], F_GETFD) >= 0 && !image_destroys);
+}
+static void test_drop(int paced) {
+    struct surface s; struct wl_resource r;
+    struct dmabuf_buffer *b = init_buffer(&s, &r);
+    g_dev_state = -3; drop_dmabuf(&s, paced);
+    assert(!s.dmabuf && !s.dmabuf_buf && !r.releases && !s.releases_pending);
+    assert(r.listeners.next == &r.listeners); /* no listener into a dead surface */
+    assert_retained(b, 2);
+    destroy_resource(&r); assert_retained(b, 2);
+    close(b->fd[0]); free(b); /* fake GPU only */
+}
+static void test_queue(int mixed, int client_gone) {
+    struct surface s; struct wl_resource r, shm;
+    struct dmabuf_buffer *b = init_buffer(&s, &r);
+    g_release_timer_fd = 123; g_refresh_ns = 100000;
+    drop_dmabuf(&s, 1); assert(s.releases_pending == 1 && !r.releases);
+    assert(last_timer.it_value.tv_sec || last_timer.it_value.tv_nsec);
+    if (mixed) { init_resource(&shm, NULL); release_buffer(&s, &shm, now_ns()); }
+    pending_releases_forget_surface(&s);
+    g_dev_state = -3;
+    fire_timer();
+    assert(!r.releases && g_pending_releases.next != &g_pending_releases);
+    if (mixed) assert(shm.releases == 1);
+    assert(!last_timer.it_value.tv_sec && !last_timer.it_value.tv_nsec);
+    assert_retained(b, 1);
+    if (client_gone) {
+        destroy_resource(&r);
+        assert(g_pending_releases.next == &g_pending_releases);
+        assert_retained(b, 1);
+    }
+    close(b->fd[0]); free(b); /* fake GPU only */
+}
+static void test_active_client_destroy(void) {
+    struct surface s; struct wl_resource r;
+    struct dmabuf_buffer *b = init_buffer(&s, &r);
+    g_dev_state = -3;
+    destroy_resource(&r);
+    assert(!s.dmabuf && s.dmabuf_buf == b && !r.releases);
+    drop_dmabuf(&s, 0); assert(!s.dmabuf_buf);
+    assert_retained(b, 2);
+    close(b->fd[0]); free(b); /* fake GPU only */
+}
+static void test_ahb(int terminal, int lost) {
+    struct surface s; struct wl_resource r;
+    struct dmabuf_buffer *b = init_buffer(&s, &r);
+    struct ahb_buf *ab = calloc(1, sizeof(*ab)); assert(ab);
+    AHardwareBuffer ahb;
+    *ab = (struct ahb_buf){.b = b, .ahb = &ahb, .resource = &r, .on_layer = 1, .fence_fd = -1};
+    b->ahb_state = ab; ++b->refs;
+    ab->resource_destroy.notify = on_buffer_resource_destroyed;
+    wl_resource_add_destroy_listener(&r, &ab->resource_destroy);
+    wl_list_insert(&g_bufs, &ab->link);
+    drop_dmabuf(&s, 1); assert(ab->release_pending && ab->surface == &s);
+    int backing_fd = b->fd[0];
+    g_dev_state = terminal ? -3 : lost ? -2 : 1;
+    ahb_swapchain_surface_gone(&s); assert(!ab->surface);
+    /* Actual event-loop callback after the display's fence becomes readable. */
+    struct wl_event_source source; int fds[2]; assert(pipe(fds) == 0);
+    ab->on_layer = 0; ab->fence_src = &source; ab->fence_fd = fds[0];
+    on_fence_readable(fds[0], 0, ab); close(fds[1]);
+    assert(source_removes == 1 && ab->fence_fd == -1 && !ab->fence_src);
+    assert(r.releases == (terminal ? 0u : 1u));
+    assert(ab->release_pending == terminal && !ahb_releases);
+    destroy_resource(&r);
+    if (terminal) {
+        assert(!ab->resource && b->ahb_state == ab && !ahb_releases);
+        assert_retained(b, 2);
+        close(b->fd[0]); free(ab); free(b); /* fake GPU only */
+    } else {
+        assert(ahb_releases == 1 && image_destroys == 1);
+        errno = 0; assert(fcntl(backing_fd, F_GETFD) == -1 && errno == EBADF);
+    }
+}
+static void test_cleanup(int lost) {
+    struct surface s; struct wl_resource r;
+    struct dmabuf_buffer *b = init_buffer(&s, &r);
+    int fd = b->fd[0]; g_dev_state = lost ? -2 : 1;
+    assert(!vkp_completion_unknown());
+    drop_dmabuf(&s, 0);
+    assert(r.releases == 1 && b->refs == 1 && !image_destroys);
+    destroy_resource(&r); assert(image_destroys == 1);
+    errno = 0; assert(fcntl(fd, F_GETFD) == -1 && errno == EBADF);
+}
+int main(int argc, char **argv) {
+    assert(argc == 2);
+    wl_list_init(&g_pending_releases); wl_list_init(&g_bufs);
+    g_dev_state = 1; g_release_timer_fd = -1;
+    if (!strcmp(argv[1], "replacement")) test_drop(1);
+    else if (!strcmp(argv[1], "surface-gone")) test_drop(0);
+    else if (!strcmp(argv[1], "queued")) test_queue(0, 0);
+    else if (!strcmp(argv[1], "mixed")) test_queue(1, 0);
+    else if (!strcmp(argv[1], "client-gone")) test_queue(0, 1);
+    else if (!strcmp(argv[1], "ahb")) test_ahb(1, 0);
+    else if (!strcmp(argv[1], "ahb-healthy")) test_ahb(0, 0);
+    else if (!strcmp(argv[1], "ahb-device-lost")) test_ahb(0, 1);
+    else if (!strcmp(argv[1], "active-client-gone")) test_active_client_destroy();
+    else if (!strcmp(argv[1], "healthy")) test_cleanup(0);
+    else if (!strcmp(argv[1], "device-lost")) test_cleanup(1);
+    else assert(0 && "unknown scenario");
+    return 0;
+}
diff --git a/tools/tests/vk_terminal_callers_test.c b/tools/tests/vk_terminal_callers_test.c
new file mode 100644
index 000000000..d9364e318
--- /dev/null
+++ b/tools/tests/vk_terminal_callers_test.c
@@ -0,0 +1,247 @@
+/* Compiled with the complete, unmodified production translation unit. The
+ * compositor's take_shm/take_pixel functions are inserted verbatim by Python. */
+#include "vk_present.c"
+#include <assert.h>
+
+struct vk_api g_vk;
+static unsigned operations, acquires, submits, markers, waits, idle_calls, resets;
+static unsigned destroys, releases, lost_notifications, presented_notifications;
+static VkResult idle_answer, fence_answer, acquire_answer, present_answer;
+static unsigned fail_acquire_at;
+static int generated;
+
+/* Every work-issuing callback is an oracle: no GPU operation after a terminal
+ * result. Object destruction is counted separately for genuine device loss. */
+static void live(void) { assert(g_dev_state == 1); ++operations; }
+static VkResult acquire(VkDevice d, VkSwapchainKHR s, uint64_t t, VkSemaphore a, VkFence f, uint32_t *i) {
+    live(); ++acquires; *i = 0;
+    return acquires == fail_acquire_at ? acquire_answer : VK_SUCCESS;
+}
+static VkResult idle(VkDevice d) { live(); ++idle_calls; return idle_answer; }
+static VkResult wait_fences(VkDevice d, uint32_t n, const VkFence *f, VkBool32 all, uint64_t t) {
+    live(); ++waits; return fence_answer;
+}
+static VkResult submit(VkQueue q, uint32_t n, const VkSubmitInfo *s, VkFence f) {
+    live(); ++submits; if (!s->commandBufferCount) ++markers; return VK_SUCCESS;
+}
+static VkResult present(VkQueue q, const VkPresentInfoKHR *p) { live(); return present_answer; }
+static VkResult reset_cmd(VkCommandBuffer c, VkCommandBufferResetFlags f) { live(); ++resets; return VK_SUCCESS; }
+static VkResult reset_fence(VkDevice d, uint32_t n, const VkFence *f) { live(); ++resets; return VK_SUCCESS; }
+static VkResult begin_cmd(VkCommandBuffer c, const VkCommandBufferBeginInfo *b) { live(); return VK_SUCCESS; }
+static VkResult end_cmd(VkCommandBuffer c) { live(); return VK_SUCCESS; }
+static void barrier(VkCommandBuffer c, VkPipelineStageFlags s, VkPipelineStageFlags d, VkDependencyFlags f,
+                    uint32_t nm, const VkMemoryBarrier *m, uint32_t nb, const VkBufferMemoryBarrier *b,
+                    uint32_t ni, const VkImageMemoryBarrier *i) { live(); }
+static void clear(VkCommandBuffer c, VkImage i, VkImageLayout l, const VkClearColorValue *v,
+                  uint32_t n, const VkImageSubresourceRange *r) { live(); }
+static void blit(VkCommandBuffer c, VkImage s, VkImageLayout sl, VkImage d, VkImageLayout dl,
+                 uint32_t n, const VkImageBlit *b, VkFilter f) { live(); }
+static void destroy_swap(VkDevice d, VkSwapchainKHR s, const VkAllocationCallbacks *a) { ++destroys; }
+static void destroy_surface(VkInstance i, VkSurfaceKHR s, const VkAllocationCallbacks *a) { ++destroys; }
+static void destroy_sem(VkDevice d, VkSemaphore s, const VkAllocationCallbacks *a) { live(); ++destroys; }
+static VkResult create_sem(VkDevice d, const VkSemaphoreCreateInfo *c, const VkAllocationCallbacks *a, VkSemaphore *s) {
+    live(); *s = (VkSemaphore)(uintptr_t)1; return VK_SUCCESS;
+}
+static void destroy_image(VkDevice d, VkImage i, const VkAllocationCallbacks *a) { ++destroys; }
+static void free_memory(VkDevice d, VkDeviceMemory m, const VkAllocationCallbacks *a) { ++destroys; }
+static void unmap(VkDevice d, VkDeviceMemory m) { ++destroys; }
+
+/* External modules are not the subject of this fault injection. Their declared
+ * signatures remain checked by the production headers. */
+int __android_log_print(int p, const char *t, const char *f, ...) { return 0; }
+void droiddeck_log(const char *t, const char *f, ...) {}
+void droiddeck_on_first_frame(void) {}
+int32_t ANativeWindow_getWidth(ANativeWindow *w) { return 64; }
+int32_t ANativeWindow_getHeight(ANativeWindow *w) { return 64; }
+void ANativeWindow_release(ANativeWindow *w) {}
+void sc_layer_window_gone(void) {}
+int vk_loader_open(const char *a, const char *b, const char *c) { assert(0); return -1; }
+void vk_loader_load_instance(VkInstance i) { assert(0); }
+void vk_loader_load_device(VkDevice d) { assert(0); }
+PFN_vkGetInstanceProcAddr vk_loader_gipa(void) { return NULL; }
+void vkp_effects_bind_device(VkDevice d, VkPhysicalDevice p, const VkPhysicalDeviceMemoryProperties *m) {}
+int vkp_effects_active(void) { return 0; }
+VkFilter vkp_effects_blit_filter(void) { return VK_FILTER_NEAREST; }
+void vkp_effects_set_formats(VkFormat a, VkFormat b) {}
+VkImage vkp_effects_run(VkCommandBuffer c, VkImage i, int w, int h, int ow, int oh, int *rw, int *rh) {
+    *rw = w; *rh = h; return i;
+}
+const void *vkp_framegen_device_features(VkInstance i, PFN_vkGetInstanceProcAddr p, VkPhysicalDevice d) { return NULL; }
+void vkp_framegen_device_ready(VkDevice d, VkQueue q, uint32_t f, int e) {}
+void vkp_framegen_device_lost(void) { ++lost_notifications; }
+int vkp_framegen_active(void) { return generated != 0; }
+int vkp_framegen_extra_images(void) { return generated; }
+int vkp_framegen_format_ok(VkFormat f) { return 0; }
+int vkp_framegen_run(VkCommandBuffer c, VkImage s, VkImageView v, int w, int h,
+                     VkFormat f, VkImage images[VKP_FG_MAX_GENERATIONS]) {
+    for (int i = 0; i < generated; ++i) images[i] = s;
+    return generated;
+}
+void vkp_framegen_presented(int n) { ++presented_notifications; }
+void hdrc_bind_device(VkDevice d, const VkPhysicalDeviceMemoryProperties *m) {}
+void hdrc_forget_image(VkImage i) {}
+int hdrc_encode(VkCommandBuffer c, VkImage a, VkImage b, VkFormat f, int w, int h, const struct hdrc_params *p) { return -1; }
+void blendp_bind_device(VkDevice d) {}
+void blendp_forget_image(VkImage i) {}
+void blendp_begin_frame(void) {}
+int blendp_draw(VkCommandBuffer c, VkImage s, VkFormat sf, int sw, int sh, int sg,
+                VkImage d, VkFormat df, int dw, int dh, const VkImageBlit *b) { return -1; }
+int droiddeck_color_requested(void) { return 0; }
+float droiddeck_color_sdr_white(void) { return 203.0f; }
+
+struct surface {
+    struct vkp_image *shm_img;
+    struct wl_resource *resource;
+    int buf_w, buf_h, buf_alpha, has_content;
+};
+struct client_info { int asked_feedback, shm_frames; };
+struct wl_shm_buffer { int w, h, stride; const void *data; };
+#define WL_SHM_FORMAT_ARGB8888 0
+static unsigned g_stat_shm;
+static int wl_shm_buffer_get_width(struct wl_shm_buffer *b) { return b->w; }
+static int wl_shm_buffer_get_height(struct wl_shm_buffer *b) { return b->h; }
+static int wl_shm_buffer_get_stride(struct wl_shm_buffer *b) { return b->stride; }
+static int wl_shm_buffer_get_format(struct wl_shm_buffer *b) { return WL_SHM_FORMAT_ARGB8888; }
+static const void *wl_shm_buffer_get_data(struct wl_shm_buffer *b) { return b->data; }
+static void wl_shm_buffer_begin_access(struct wl_shm_buffer *b) {}
+static void wl_shm_buffer_end_access(struct wl_shm_buffer *b) {}
+static void wl_buffer_send_release(struct wl_resource *b) { ++releases; }
+static struct wl_client *wl_resource_get_client(struct wl_resource *r) { return NULL; }
+static struct client_info *client_info_of(struct wl_client *c) { return NULL; }
+/* This harness exercises copied SHM/pixel callers; DMA-BUF lifecycle paths are
+ * compiled separately by test_vk_dmabuf_quarantine.py. */
+struct dmabuf_buffer;
+static struct dmabuf_buffer *get_dmabuf(struct wl_resource *buffer) { return NULL; }
+/* COMPOSITOR_CALLERS */
+
+static void setup(int extra) {
+    g_vk = (struct vk_api){.AcquireNextImageKHR = acquire, .DeviceWaitIdle = idle,
+        .WaitForFences = wait_fences, .QueueSubmit = submit, .QueuePresentKHR = present,
+        .ResetCommandBuffer = reset_cmd, .ResetFences = reset_fence, .BeginCommandBuffer = begin_cmd,
+        .EndCommandBuffer = end_cmd, .CmdPipelineBarrier = barrier, .CmdClearColorImage = clear,
+        .CmdBlitImage = blit, .DestroySwapchainKHR = destroy_swap, .DestroySurfaceKHR = destroy_surface,
+        .DestroySemaphore = destroy_sem, .CreateSemaphore = create_sem,
+        .DestroyImage = destroy_image, .FreeMemory = free_memory, .UnmapMemory = unmap};
+    idle_answer = fence_answer = acquire_answer = present_answer = VK_SUCCESS;
+    generated = g_swap_extra = extra;
+    g_dev_state = 1;
+    g_dev = (VkDevice)(uintptr_t)1; g_inst = (VkInstance)(uintptr_t)1;
+    g_window = (ANativeWindow *)(uintptr_t)1; g_queue = (VkQueue)(uintptr_t)1;
+    g_swapchain = (VkSwapchainKHR)(uintptr_t)2; g_surface = (VkSurfaceKHR)(uintptr_t)3;
+    g_images = calloc(1, sizeof(*g_images)); assert(g_images);
+    *g_images = (VkImage)(uintptr_t)4; g_nimg = 1;
+    g_extent = g_caps_extent = (VkExtent2D){64, 64};
+    g_surface_checked_ns = INT64_MAX; /* no simulated geometry change */
+    g_scene.img = (VkImage)(uintptr_t)5; g_scene.mem = (VkDeviceMemory)(uintptr_t)6;
+    g_scene.w = g_scene.h = 64;
+    for (int k = 0; k < MAX_PRESENTS; ++k) {
+        g_cmds[k] = (VkCommandBuffer)(uintptr_t)(10 + k);
+        g_acqs[k] = (VkSemaphore)(uintptr_t)(20 + k);
+        g_rnds[k] = (VkSemaphore)(uintptr_t)(30 + k);
+    }
+    g_fence = (VkFence)(uintptr_t)40;
+}
+
+/* Probe the public GPU entry points after a terminal result. This includes an
+ * active off-screen pass and consumed release fds, not just the render guard. */
+static void assert_stopped(void) {
+    unsigned before = operations, before_destroys = destroys;
+    struct vkp_image src = {.image = (VkImage)(uintptr_t)7, .w = 1, .h = 1};
+    struct vkp_image dst = {.image = (VkImage)(uintptr_t)8, .w = 1, .h = 1, .blit_dst = 1};
+    uint32_t pixel = 0; uint64_t mod = 0;
+    assert(vkp_render(64, 64, NULL, 0) == -1);
+    assert(vkp_render_plain(64, 64) == -1);
+    assert(vkp_render_hdr(64, 64, NULL, 0, NULL, NULL) == -1);
+    assert(vkp_base_black(64, 64) == -1);
+    assert(vkp_update_map(64, 64) == -1);
+    assert(vkp_ready() == -1);
+    assert(vkp_image_create_shm(1, 1) == NULL);
+    assert(vkp_image_import_dmabuf(-1, 0, VKP_MOD_LINEAR, 1, 1, 4, 0, 0) == NULL);
+    assert(vkp_dmabuf_modifiers(0, &mod, 1) == 0);
+    assert(vkp_image_readback(&src, &pixel, 1) == -1);
+    assert(vkp_pass_begin(64, 64, NULL, 0, NULL, NULL) == -1);
+    int fd[2]; assert(pipe(fd) == 0);
+    assert(vkp_blit_image(&src, &dst, fd[0]) == -1);
+    errno = 0; assert(close(fd[0]) == -1 && errno == EBADF); close(fd[1]);
+    g_pass.active = 1;
+    assert(pipe(fd) == 0);
+    assert(vkp_pass_copy_to(&dst, fd[0]) == -1 && !g_pass.active);
+    errno = 0; assert(close(fd[0]) == -1 && errno == EBADF); close(fd[1]);
+    g_pass.active = 1; vkp_pass_abort(); assert(!g_pass.active);
+    assert(timed_wait(g_fence, UINT64_MAX) != VK_SUCCESS);
+    assert(operations == before && destroys == before_destroys);
+}
+
+static void acquire_failure(int later, VkResult result) {
+    setup(later ? 1 : 0);
+    fail_acquire_at = later ? 2 : 1; acquire_answer = result;
+    idle_answer = VK_ERROR_OUT_OF_HOST_MEMORY;
+    VkImage *retained = g_images;
+    assert(vkp_render(64, 64, NULL, 0) == -1);
+    assert(g_dev_state == -3 && vkp_completion_unknown() && !vkp_device_lost());
+    assert(acquires == fail_acquire_at && idle_calls == 1);
+    assert(submits == (unsigned)later && markers == 0 && waits == 0);
+    assert(destroys == 0 && g_images == retained && g_nimg == 1);
+    assert(g_swapchain && g_surface && g_fence && g_scene.img && g_scene.mem);
+    assert_stopped();
+    free(g_images); /* test-owned fake resources only */
+}
+
+static void upload_timeout(int single_pixel) {
+    setup(0);
+    uint8_t bytes[48], saved[48], data[16];
+    memset(bytes, 0xa5, sizeof(bytes)); memset(data, 0x3c, sizeof(data));
+    struct vkp_image *img = calloc(1, sizeof(*img)); assert(img);
+    *img = (struct vkp_image){.image = (VkImage)(uintptr_t)7, .mem = (VkDeviceMemory)(uintptr_t)8,
+        .map = bytes, .offset = 3, .row_pitch = 16,
+        .w = single_pixel ? 1 : 2, .h = single_pixel ? 1 : 2};
+    struct surface s = {.shm_img = img};
+    struct wl_shm_buffer b = {.w = img->w, .h = img->h, .stride = img->w * 4, .data = data};
+    if (single_pixel) take_pixel(&s, data, NULL); else take_shm(&s, &b, NULL);
+    assert(bytes[3] == 0x3c && bytes[0] == 0xa5 && releases == 1);
+    memcpy(saved, bytes, sizeof(saved));
+    struct vkp_image dst = {.image = (VkImage)(uintptr_t)9, .blit_dst = 1, .w = img->w, .h = img->h};
+    fence_answer = VK_TIMEOUT;
+    assert(vkp_blit_image(img, &dst, -1) == -1);
+    assert(g_dev_state == -3 && submits == 1 && waits == 1);
+    memset(data, 0x7e, sizeof(data));
+    if (single_pixel) take_pixel(&s, data, NULL); else take_shm(&s, &b, NULL);
+    assert(s.shm_img == img && memcmp(saved, bytes, sizeof(saved)) == 0 && releases == 2);
+    vkp_image_destroy(img);
+    assert(destroys == 0 && img->map == bytes && img->image && img->mem);
+    assert_stopped();
+    free(img); free(g_images); /* fake resources only, not production cleanup */
+}
+
+int main(int argc, char **argv) {
+    assert(argc == 2);
+    const char *name = argv[1];
+    if (!strcmp(name, "first-out-of-date")) acquire_failure(0, VK_ERROR_OUT_OF_DATE_KHR);
+    else if (!strcmp(name, "first-surface-lost")) acquire_failure(0, VK_ERROR_SURFACE_LOST_KHR);
+    else if (!strcmp(name, "later-out-of-date")) acquire_failure(1, VK_ERROR_OUT_OF_DATE_KHR);
+    else if (!strcmp(name, "later-surface-lost")) acquire_failure(1, VK_ERROR_SURFACE_LOST_KHR);
+    else if (!strcmp(name, "shm-timeout")) upload_timeout(0);
+    else if (!strcmp(name, "pixel-timeout")) upload_timeout(1);
+    else if (!strcmp(name, "pass-terminal")) { setup(0); g_dev_state = -3; assert_stopped(); free(g_images); }
+    else if (!strcmp(name, "normal") || !strcmp(name, "framegen")) {
+        int extra = !strcmp(name, "framegen"); setup(extra);
+        assert(vkp_render(64, 64, NULL, 0) == 0 && g_dev_state == 1);
+        assert(acquires == (unsigned)(1 + extra) && submits == (unsigned)(1 + extra));
+        assert(waits == 1 && markers == 0 && idle_calls == 0 && destroys == 0);
+        assert(presented_notifications == (unsigned)extra); free(g_images);
+    } else if (!strcmp(name, "later-timeout")) {
+        setup(1); fail_acquire_at = 2; acquire_answer = VK_TIMEOUT;
+        assert(vkp_render(64, 64, NULL, 0) == -1 && g_dev_state == 1);
+        assert(acquires == 2 && submits == 2 && markers == 1 && waits == 1); free(g_images);
+    } else if (!strcmp(name, "acquire-device-lost") || !strcmp(name, "present-device-lost")) {
+        setup(1);
+        if (!strcmp(name, "acquire-device-lost")) { fail_acquire_at = 2; acquire_answer = VK_ERROR_DEVICE_LOST; }
+        else present_answer = VK_ERROR_DEVICE_LOST;
+        assert(vkp_render(64, 64, NULL, 0) == -1 && vkp_device_lost());
+        assert(!vkp_completion_unknown());
+        assert(g_dev_state == -2 && lost_notifications == 1 && markers == 0 && waits == 0);
+        assert(!g_images && !g_swapchain && !g_surface && destroys == 2);
+        assert_stopped();
+    } else assert(0 && "unknown scenario");
+    return 0;
+}