diff --git a/AGENTS.md b/AGENTS.md
index f7631f5..82c1007 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -10,6 +10,9 @@
   及既有 Makefile 入口；公共机制归 `scripts/`，具体业务场景归示例仓库。
 - 现有 Emacs 的截图与录像默认保留用户当前应用焦点，使用已登记的窗口捕获
   入口；后台视觉证据须检查内容更新，后台耗时与前台输入到显示延迟分别报告。
+- 交互回调测量使用 `etaf-gui-verifier-measure-action`，按 scripts/README.md
+  固定场景、计时边界与前后台条件；保留全部样本，阶段记录按 observer runtime ID
+  隔离，不能用可复用的 buffer 名隔离。该入口不证明 compositor 已呈现。
 - 连续 resize 使用 `scripts/benchmark-ebox-resize.el` 的
   `ebox-resize-benchmark-start`，适用于现有 ETAF 或独立 Ebox buffer。
   按 README 选择范围、轮数和新证据文件；先验证前台与已加载版本，保留全部样本，
diff --git a/README.md b/README.md
index a32e73d..b258cde 100644
--- a/README.md
+++ b/README.md
@@ -116,6 +116,13 @@ computes operation p50/p95/max statistics on demand, while
 `etaf-performance-operation-stage-summary` groups one operation's flat stages
 by provider category.  `etaf-performance-records` returns defensive operation
 and stage snapshots; caller mutation cannot rewrite retained history.
+Pass a numeric observer runtime ID to `etaf-performance-records` to select one
+mount's history even when a buffer name is reused. Summary and report functions
+use all retained records when called without an argument; an explicit `nil`
+means an empty selection. The exported environment describes report generation,
+not each historical operation. These synchronous operation durations do not
+measure physical input-to-presentation latency; use the GUI measurement entry
+in [scripts/README.md](scripts/README.md) for per-action condition checks.
 
 Use `etaf-performance-call-operation` or
 `etaf-performance-with-operation` to trace an arbitrary operation that has no
diff --git a/README.zh-CN.md b/README.zh-CN.md
index f9339b9..1be5b07 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -108,6 +108,11 @@ p50/p95/max、每次 operation、GC 增量和有序 provider 阶段；面板 hea
 `etaf-performance-operation-stage-summary` 则按 provider category 汇总单次
 operation 的 flat 阶段。`etaf-performance-records` 返回 operation/stage 的防御性
 快照，调用方修改返回值不会改写已保留的历史。
+向 `etaf-performance-records` 传入 observer 报告中的数字 runtime ID，可以隔离
+同名 buffer 重建前后的记录。summary/report 函数省略参数时读取全部历史，
+显式传入 `nil` 时保持空结果。导出的环境是生成报告时的状态，不是每次历史操作
+的状态；同步 operation 耗时也不等于物理输入到画面呈现的延迟。逐次 GUI 条件
+检查使用 [scripts/README.md](scripts/README.md) 中的测量入口。
 
 没有内置公共边界的任意操作，可以使用
 `etaf-performance-call-operation` 或 `etaf-performance-with-operation`
diff --git a/docs/user-guide.en.md b/docs/user-guide.en.md
index 90a705c..f9169f4 100644
--- a/docs/user-guide.en.md
+++ b/docs/user-guide.en.md
@@ -765,6 +765,14 @@ requested.  `etaf-performance-operation-stage-summary` groups the flat stages
 of one recorded operation by provider category.  `etaf-performance-records`
 returns defensive operation and stage snapshots; caller mutation cannot alter
 retained history.
+Its optional numeric runtime ID selects the identity from observer reports,
+including history from a retired mount whose buffer name has since been reused.
+Summary and report functions read all retained records when their argument is
+omitted; explicit `nil` keeps an empty selection empty. The report's environment
+is observed at export time, not at every recorded operation. Runtime durations
+end at synchronous return and do not certify input-to-presentation latency;
+use [the GUI action measurement entry](../scripts/README.md#measuring-an-existing-gui-action)
+to record per-action foreground/target conditions and callback wall/CPU/GC time.
 
 Use `etaf-performance-call-operation` or `etaf-performance-with-operation` for
 application work that does not enter through a built-in public boundary.  Both
diff --git a/docs/user-guide.zh.md b/docs/user-guide.zh.md
index 4d0d121..af8061e 100644
--- a/docs/user-guide.zh.md
+++ b/docs/user-guide.zh.md
@@ -733,6 +733,11 @@ Ebox、TP、Data、Resource 与 SQLite 可以贡献按 sequence 排列的 flat p
 `etaf-performance-operation-stage-summary` 会按 provider category 汇总某条记录
 中的 flat 阶段。`etaf-performance-records` 返回 operation/stage 的防御性快照，
 调用方修改返回值不会影响保留的历史。
+该函数可选的数字 runtime ID 来自 observer 报告，可隔离 buffer 同名重建前后的
+记录。summary/report 函数省略参数时读取全部历史，显式传入 `nil` 时保持空结果。
+报告中的环境是导出时观测的状态，不是每次历史操作的状态。Runtime 耗时截至
+同步调用返回，不能证明输入到画面呈现的延迟；逐次前后台、目标与回调 wall/CPU/GC
+检查使用[GUI action 测量入口](../scripts/README.md#measuring-an-existing-gui-action)。
 
 没有经过内置公共边界的应用操作可以使用
 `etaf-performance-call-operation`/`etaf-performance-with-operation`；它们直接委托
diff --git a/etaf-performance.el b/etaf-performance.el
index c29e284..75a063b 100644
--- a/etaf-performance.el
+++ b/etaf-performance.el
@@ -112,12 +112,24 @@
    :stages (mapcar #'etaf-performance--copy-stage
                    (etaf-performance-operation-stages operation))))
 
-(defun etaf-performance-records ()
-  "Return newest-first immutable snapshots of completed records."
-  (if etaf-performance--record-ring
-      (mapcar #'etaf-performance--copy-operation
-              (ring-elements etaf-performance--record-ring))
-    nil))
+(defun etaf-performance-records (&optional runtime-id)
+  "Return newest-first immutable snapshots of completed records.
+When RUNTIME-ID is non-nil, select only that integer observer report identity,
+as exposed by `etaf-performance-operation-runtime-id'.  This also selects
+historical records after unmount or reuse of a buffer name.  Omitted or nil
+RUNTIME-ID selects all retained records."
+  (unless (or (null runtime-id) (integerp runtime-id))
+    (signal 'wrong-type-argument (list 'integerp runtime-id)))
+  (let ((records (and etaf-performance--record-ring
+                      (ring-elements etaf-performance--record-ring))))
+    (mapcar #'etaf-performance--copy-operation
+            (if runtime-id
+                (seq-filter
+                 (lambda (operation)
+                   (equal runtime-id
+                          (etaf-performance-operation-runtime-id operation)))
+                 records)
+              records))))
 
 (defun etaf-performance--percentile (samples percentile)
   "Return nearest-rank PERCENTILE from numeric SAMPLES."
@@ -180,10 +192,12 @@ durations may overlap and are therefore never presented as exclusive time."
                    (> (plist-get left :duration-ms)
                       (plist-get right :duration-ms))))))
 
-(defun etaf-performance-summary (&optional records)
-  "Summarize completed RECORDS by operation kind and label."
+(cl-defun etaf-performance-summary
+    (&optional (records (etaf-performance-records)))
+  "Summarize completed RECORDS by operation kind and label.
+Omitted RECORDS selects all retained records; explicit nil selects none."
   (let ((groups (make-hash-table :test #'equal)) result)
-    (dolist (operation (or records (etaf-performance-records)))
+    (dolist (operation records)
       (let ((key (cons (etaf-performance-operation-kind operation)
                        (etaf-performance-operation-label operation))))
         (puthash key
@@ -469,20 +483,23 @@ BATTERY-OUTPUT identifies the active source; CUSTOM-OUTPUT contains settings."
         :power-state (etaf-performance--power-state)))
 
 ;;;###autoload
-(defun etaf-performance-report-data (&optional records)
-  "Return a portable report for completed performance RECORDS."
-  (let ((records (or records (etaf-performance-records))))
-    (list :format-version etaf-performance-report-format-version
-          :generated-at (format-time-string "%Y-%m-%dT%H:%M:%S%z")
-          :environment (etaf-performance-environment-data)
-          :summary (etaf-performance-summary records)
-          :operations
-          (mapcar #'etaf-performance--operation-report-data
-                  (reverse (copy-sequence records))))))
+(cl-defun etaf-performance-report-data
+    (&optional (records (etaf-performance-records)))
+  "Return a portable report for completed performance RECORDS.
+Omitted RECORDS selects all retained records; explicit nil selects none."
+  (list :format-version etaf-performance-report-format-version
+        :generated-at (format-time-string "%Y-%m-%dT%H:%M:%S%z")
+        :environment (etaf-performance-environment-data)
+        :summary (etaf-performance-summary records)
+        :operations
+        (mapcar #'etaf-performance--operation-report-data
+                (reverse (copy-sequence records)))))
 
 ;;;###autoload
-(defun etaf-performance-report-string (&optional records)
-  "Return completed performance RECORDS as a readable report string."
+(cl-defun etaf-performance-report-string
+    (&optional (records (etaf-performance-records)))
+  "Return completed performance RECORDS as a readable report string.
+Omitted RECORDS selects all retained records; explicit nil selects none."
   (concat ";; ETAF performance report\n"
           (pp-to-string (etaf-performance-report-data records))))
 
diff --git a/scripts/README.md b/scripts/README.md
index 65db0fd..a2d8984 100644
--- a/scripts/README.md
+++ b/scripts/README.md
@@ -13,7 +13,8 @@ scenarios live in their respective example repositories:
 
 - `emacs-gui-verifier.el` defines `Scenario`, ordered `Action`, run-local
   `Context`, checkpoint sequencing, assertions, completion, and fail-closed
-  evidence finalization.
+  evidence finalization. Its `etaf-gui-verifier-measure-action` entry records
+  callback wall/CPU/GC time and GUI conditions without taking application focus.
 - `benchmark-ebox-resize.el` drives continuous pixel-width sweeps of any
   existing mounted Ebox buffer, including ETAF apps, without taking over its
   observer. See the existing-server entry below.
@@ -68,6 +69,44 @@ Lisp callbacks and runtime timing do not require application activation; report
 them as background measurements, separately from foreground input-to-display
 latency. Use Emacs-local operations while another app is active, not global input.
 
+## Measuring an existing GUI action
+
+Reuse `etaf-gui-verifier-measure-action` with the adapter's Context and Action:
+
+```elisp
+;; Prepare the target control and fixture before entering the measured callback.
+(etaf-gui-verifier-measure-action context action t)
+(car (etaf-gui-verifier-context-measurements context))
+```
+
+The final `t` requires an already selected foreground target. It rejects a
+background, hidden, unknown or wrong target before running the action, and
+invalidates a sample if focus, target, font or geometry changes. It never raises
+Emacs. Omit that argument for background functional work; those samples are
+explicitly labeled and must not be reported as foreground latency.
+
+Timing covers exactly `Action.execute`, excluding target inspection,
+checkpoints and the verifier's intentional settle waits. Keep fixture setup,
+control lookup and focus navigation outside an activation measurement. If the
+chosen boundary includes an explicit `redisplay`, put that call in `execute`
+and describe the boundary accordingly. Returning from redisplay still does not
+prove compositor presentation. Each record says `presentation_measured=nil`.
+
+Context retains every measurement, including first use, warmups, failures and
+rejections. Failed callbacks retain their own timing and original condition;
+rejections have no duration. Checkpoints export only the most recent record.
+Report the full sample count and all-sample maximum as well as any explicitly
+labeled steady-state statistics. Compare identical payload/page size, viewport,
+loaded code, recording mode and foreground class; do not discard a slow group
+because another run is faster. The historical `.omx/component-api-implementation/
+current-workbench-sample.el` probe is superseded by this measurement boundary.
+
+For provider traces, scope `etaf-performance-records` by its numeric observer
+runtime ID, not buffer name, which can be reused after unmount. Pass the selected
+records explicitly to summary/export functions: an empty selection stays empty.
+Check operation IDs/counts as well as runtime ID when sampling the same mounted
+instance again; the recorder's bounded history is not a per-run sample store.
+
 ## Continuous resize on the existing server
 
 Use this entry for resize performance investigations instead of copying the
diff --git a/scripts/emacs-gui-verifier.el b/scripts/emacs-gui-verifier.el
index be58182..254cb46 100644
--- a/scripts/emacs-gui-verifier.el
+++ b/scripts/emacs-gui-verifier.el
@@ -34,7 +34,8 @@
 (cl-defstruct (etaf-gui-verifier-context
                (:constructor etaf-gui-verifier--context-create))
   "Mutable execution state owned only by one verifier run."
-  scenario target-buffer data (action-count 0) (last-duration-ms 0.0))
+  scenario target-buffer data (action-count 0) (last-duration-ms 0.0)
+  measurements)
 
 (defun etaf-gui-verifier-context-put (context key value)
   "Store adapter VALUE for KEY in CONTEXT and return VALUE."
@@ -45,6 +46,138 @@
   "Return CONTEXT adapter value KEY, or DEFAULT when absent."
   (alist-get key (etaf-gui-verifier-context-data context) default))
 
+(defun etaf-gui-verifier--measurement-state (context)
+  "Return CONTEXT's live identities followed by JSON-safe GUI facts."
+  (let* ((frame (selected-frame))
+         (window (selected-window))
+         (target (etaf-gui-verifier-context-target-buffer context))
+         (selected-buffer (window-buffer window))
+         (focus (frame-focus-state frame)))
+    (cons
+     (list frame window target selected-buffer)
+     `((graphic . ,(and (display-graphic-p frame) t))
+       (focus . ,(cond ((eq focus t) "foreground")
+                      ((null focus) "background")
+                      (t "unknown")))
+       (frame_name . ,(frame-parameter frame 'name))
+       (frame_window_id . ,(frame-parameter frame 'window-id))
+       (frame_visible . ,(pcase (frame-visible-p frame)
+                           ('t "visible") ('icon "icon") (_ "hidden")))
+       (target_buffer . ,(and (buffer-live-p target) (buffer-name target)))
+       (selected_buffer . ,(buffer-name selected-buffer))
+       (target_selected . ,(and (buffer-live-p target)
+                               (eq target selected-buffer)))
+       (font . ,(format "%s" (frame-parameter frame 'font)))
+       (frame_width_px . ,(frame-pixel-width frame))
+       (frame_height_px . ,(frame-pixel-height frame))
+       (window_edges_px . ,(vconcat (window-pixel-edges window)))
+       (inhibit_quit . ,(and inhibit-quit t))
+       (inhibit_redisplay . ,(and inhibit-redisplay t))
+       (noninteractive . ,(and noninteractive t))))))
+
+(defun etaf-gui-verifier-measure-action (context action &optional require-foreground)
+  "Measure ACTION's execute callback once with CONTEXT; return its exact result.
+Retain a JSON-safe measurement in CONTEXT's measurements, newest first,
+including failed or quit callbacks, and update the legacy last duration.
+Wall/CPU/GC timing covers only the callback, excluding GUI-state snapshots and
+the verifier's later checkpoints, redisplay, and settling.  Calls made inside
+the callback are included.  No focus or execution bindings change.
+
+With REQUIRE-FOREGROUND, reject a non-graphical, unfocused, unknown, hidden,
+or unselected target before invoking the callback.  Rejection retains an
+untimed record and clears the legacy duration.  Changes to frame/window/buffer
+identities, graphical display, focus, visibility, native window ID, target
+selection, font, frame pixel size, or window pixel edges invalidate the record
+and, when foreground is required, signal after a successful callback.  Frame
+and buffer names and execution bindings are diagnostic observations, not
+identity guards.  Callback errors and quits propagate with their original data.
+A closing snapshot quit is recorded and propagated after a successful callback,
+but never replaces an existing callback error or quit.
+
+Background callbacks are allowed by default and labeled accordingly.  A
+valid record requires a successful callback with a live selected target in
+an unchanged environment; even a foreground record does not certify
+input-to-presentation latency."
+  (let* ((before (etaf-gui-verifier--measurement-state context))
+         (facts (cdr before))
+         (foreground (if (alist-get 'graphic facts)
+                         (alist-get 'focus facts)
+                       "unknown"))
+         (status "rejected")
+         started cpu-start gc-start gcs-start result changed snapshot-quit)
+    (unwind-protect
+        (progn
+          (when (and require-foreground
+                     (not (and (equal foreground "foreground")
+                               (equal (alist-get 'frame_visible facts) "visible")
+                               (alist-get 'target_selected facts))))
+            (error "GUI action requires a selected foreground target: %s"
+                   (etaf-gui-verifier-action-id action)))
+          (setq cpu-start (current-cpu-time)
+                gc-start gc-elapsed
+                gcs-start gcs-done
+                started (float-time))
+          (condition-case condition
+              (progn
+                (setq result
+                      (funcall (etaf-gui-verifier-action-execute action) context)
+                      status "success"))
+            ((error quit)
+             (setq status (if (eq (car condition) 'quit) "quit" "error"))
+             (signal (car condition) (cdr condition)))))
+      (let* ((finished (and started (float-time)))
+             (cpu-end (and started (current-cpu-time)))
+             (gc-end gc-elapsed)
+             (gcs-end gcs-done)
+             (wall-ms (and started (* 1000.0 (- finished started))))
+             ;; Snapshot failure must not replace an action's error or quit.
+             (after (and started
+                         (condition-case condition
+                             (etaf-gui-verifier--measurement-state context)
+                           (quit (setq snapshot-quit condition) nil)
+                           (error nil)))))
+        (setq changed
+              (and started
+                   (or (not (equal (car before) (car after)))
+                       (cl-some
+                        (lambda (key)
+                          (not (equal (alist-get key facts)
+                                      (alist-get key (cdr after)))))
+                        '(graphic focus frame_visible frame_window_id
+                          target_selected font frame_width_px frame_height_px
+                          window_edges_px)))))
+        (when (and snapshot-quit (equal status "success"))
+          (setq status "quit"))
+        (when (and changed require-foreground (equal status "success"))
+          (setq status "invalid"))
+        (setf (etaf-gui-verifier-context-last-duration-ms context) wall-ms)
+        (push
+         `((action_id . ,(etaf-gui-verifier-action-id action))
+           (boundary . "action.execute callback")
+           (presentation_measured . nil)
+           (status . ,status)
+           (valid . ,(and (equal status "success") (not changed)
+                          (alist-get 'target_selected facts)))
+           (foreground . ,(if changed "changed" foreground))
+           (foreground_required . ,(and require-foreground t))
+           (wall_ms . ,wall-ms)
+           (cpu_ms . ,(and cpu-end
+                           (* 1000.0
+                              (- (/ (float (car cpu-end)) (cdr cpu-end))
+                                 (/ (float (car cpu-start)) (cdr cpu-start))))))
+           (gc_count . ,(and started (- gcs-end gcs-start)))
+           (gc_ms . ,(and started (* 1000.0 (- gc-end gc-start))))
+           (before . ,facts)
+           (after . ,(cdr after)))
+         (etaf-gui-verifier-context-measurements context))))
+    ;; An action's nonlocal failure bypasses this point and keeps precedence.
+    (when snapshot-quit
+      (signal (car snapshot-quit) (cdr snapshot-quit)))
+    (when (equal status "invalid")
+      (error "GUI action environment changed during callback: %s"
+             (etaf-gui-verifier-action-id action)))
+    result))
+
 (defun etaf-gui-verifier-context-select-buffer (context buffer)
   "Select live BUFFER as CONTEXT's single-window target."
   (unless (buffer-live-p buffer)
@@ -86,7 +219,9 @@
       (cons 'action_count
             (etaf-gui-verifier-context-action-count context))
       (cons 'duration_ms
-            (etaf-gui-verifier-context-last-duration-ms context)))
+            (etaf-gui-verifier-context-last-duration-ms context))
+      (cons 'last_measurement
+            (car (etaf-gui-verifier-context-measurements context))))
      (and function (funcall function context)))))
 
 (defun etaf-gui-verifier--checkpoint
@@ -140,10 +275,7 @@
         (assertions (etaf-gui-verifier-action-assertions action)))
     (etaf-gui-verifier--checkpoint
      context action-id "before-action" nil)
-    (let ((started (float-time)))
-      (funcall (etaf-gui-verifier-action-execute action) context)
-      (setf (etaf-gui-verifier-context-last-duration-ms context)
-            (* 1000.0 (- (float-time) started))))
+    (etaf-gui-verifier-measure-action context action)
     (cl-incf (etaf-gui-verifier-context-action-count context))
     (etaf-gui-verifier--checkpoint
      context action-id "after-action" nil)
diff --git a/tests/etaf-gui-verifier-tests.el b/tests/etaf-gui-verifier-tests.el
index e2bb7a9..68d6060 100644
--- a/tests/etaf-gui-verifier-tests.el
+++ b/tests/etaf-gui-verifier-tests.el
@@ -4,8 +4,416 @@
 
 (require 'ert)
 (require 'cl-lib)
+(require 'json)
 (require 'emacs-gui-verifier)
 
+(ert-deftest etaf-gui-verifier-measures-success-and-original-failure ()
+  "Each callback retains its own timing, result, and error condition."
+  (let* ((scenario (etaf-gui-verifier-scenario-create :name "measurement"))
+         (context (etaf-gui-verifier--context-create :scenario scenario))
+         (result (list 'exact-result))
+         (error-data (list "original failure" result))
+         (wall-times '(1.0 1.002 10.0 10.03))
+         (cpu-times '((1000 . 1000) (1004 . 1000)
+                      (2000 . 1000) (2010 . 1000)))
+         (gcs-done 5) (gc-elapsed 0.1)
+         (calls 0))
+    (cl-letf (((symbol-function 'float-time)
+               (lambda (&optional _time) (pop wall-times)))
+              ((symbol-function 'current-cpu-time)
+               (lambda () (pop cpu-times))))
+      (should
+       (eq result
+           (etaf-gui-verifier-measure-action
+            context
+            (etaf-gui-verifier-action-create
+             :id "success"
+             :execute (lambda (current)
+                        (should (eq current context))
+                        (cl-incf calls)
+                        result)))))
+      (should
+       (equal (cons 'error error-data)
+              (should-error
+               (etaf-gui-verifier-measure-action
+                context
+                (etaf-gui-verifier-action-create
+                 :id "failure"
+                 :execute (lambda (_current)
+                            (cl-incf calls)
+                            (cl-incf gcs-done 2)
+                            (cl-incf gc-elapsed 0.003)
+                            (signal 'error error-data))))))))
+    (should (= calls 2))
+    (let* ((measurements (etaf-gui-verifier-context-measurements context))
+           (failed (car measurements))
+           (succeeded (cadr measurements))
+           (adapter (etaf-gui-verifier--adapter-data context)))
+      (should (= (length measurements) 2))
+      (should (equal (alist-get 'status succeeded) "success"))
+      (should (equal (alist-get 'status failed) "error"))
+      (should (equal (alist-get 'action_id failed) "failure"))
+      (should-not (alist-get 'valid failed))
+      (should (< (abs (- (alist-get 'wall_ms failed) 30.0)) 0.001))
+      (should (< (abs (- (alist-get 'wall_ms succeeded) 2.0)) 0.001))
+      (should (< (abs (- (alist-get 'cpu_ms failed) 10.0)) 0.001))
+      (should (= (alist-get 'gc_count failed) 2))
+      (should (< (abs (- (alist-get 'gc_ms failed) 3.0)) 0.001))
+      (should (= (alist-get 'duration_ms adapter)
+                 (alist-get 'wall_ms failed)))
+      (should (eq (alist-get 'last_measurement adapter) failed))
+      (should-not (assq 'measurements adapter)))))
+
+(ert-deftest etaf-gui-verifier-labels-callback-context-without-changing-it ()
+  "Foreground, background, and unknown callbacks keep their execution context."
+  (let* ((focus t) (calls 0)
+         (inhibit-quit t) (inhibit-redisplay t)
+         (threshold gc-cons-threshold) (percentage gc-cons-percentage)
+         (context
+          (etaf-gui-verifier--context-create
+           :target-buffer (window-buffer (selected-window)))))
+    (cl-letf (((symbol-function 'display-graphic-p)
+               (lambda (&optional _frame) t))
+              ((symbol-function 'frame-focus-state)
+               (lambda (&optional _frame) focus))
+              ((symbol-function 'redisplay)
+               (lambda (&rest _arguments) (ert-fail "Forced redisplay")))
+              ((symbol-function 'sit-for)
+               (lambda (&rest _arguments) (ert-fail "Waited for display")))
+              ((symbol-function 'garbage-collect)
+               (lambda () (ert-fail "Forced GC"))))
+      (dolist (state '((t "foreground") (nil "background") (unknown "unknown")))
+        (setq focus (car state))
+        (should
+         (eq 'exact-result
+             (etaf-gui-verifier-measure-action
+              context
+              (etaf-gui-verifier-action-create
+               :id "context"
+               :execute (lambda (_context)
+                          (cl-incf calls)
+                          (should inhibit-quit)
+                          (should inhibit-redisplay)
+                          (should (= gc-cons-threshold threshold))
+                          (should (= gc-cons-percentage percentage))
+                          'exact-result))
+              (eq focus t))))
+        (let* ((measurement
+                (car (etaf-gui-verifier-context-measurements context)))
+               (before (alist-get 'before measurement)))
+          (should (equal (alist-get 'foreground measurement) (cadr state)))
+          (should (equal (alist-get 'status measurement) "success"))
+          (should (alist-get 'valid measurement))
+          (should (alist-get 'inhibit_quit before))
+          (should (alist-get 'inhibit_redisplay before))
+          (should (eq (alist-get 'noninteractive before) noninteractive))
+          (should (stringp (json-serialize measurement))))))
+    (should (= calls 3))))
+
+(ert-deftest etaf-gui-verifier-unselected-target-runs-with-invalid-timing ()
+  "An unchanged unselected target permits the callback but invalidates timing."
+  (let* ((target (generate-new-buffer " *etaf-gui-unselected-target*"))
+         (context (etaf-gui-verifier--context-create :target-buffer target))
+         (result (list 'exact-result))
+         (calls 0))
+    (unwind-protect
+        (cl-letf (((symbol-function 'display-graphic-p)
+                   (lambda (&optional _frame) t))
+                  ((symbol-function 'frame-focus-state)
+                   (lambda (&optional _frame) nil)))
+          (should
+           (eq result
+               (etaf-gui-verifier-measure-action
+                context
+                (etaf-gui-verifier-action-create
+                 :id "unselected-target"
+                 :execute (lambda (_context)
+                            (cl-incf calls)
+                            result)))))
+          (should (= calls 1))
+          (let ((measurement
+                 (car (etaf-gui-verifier-context-measurements context))))
+            (should (equal (alist-get 'status measurement) "success"))
+            (should (equal (alist-get 'foreground measurement) "background"))
+            (should (equal (alist-get 'before measurement)
+                           (alist-get 'after measurement)))
+            (should-not (alist-get 'target_selected
+                                   (alist-get 'before measurement)))
+            (should-not (alist-get 'valid measurement))
+            (should (numberp (alist-get 'wall_ms measurement)))))
+      (kill-buffer target))))
+
+(ert-deftest etaf-gui-verifier-foreground-rejection-does-not-execute-or-focus ()
+  "Foreground requirements reject absent focus or targets before execution."
+  (let ((focus t) (graphic t) (calls 0)
+        (context (etaf-gui-verifier--context-create)))
+    (cl-letf (((symbol-function 'display-graphic-p)
+               (lambda (&optional _frame) graphic))
+              ((symbol-function 'frame-focus-state)
+               (lambda (&optional _frame) focus))
+              ((symbol-function 'raise-frame)
+               (lambda (&rest _arguments) (ert-fail "Raised frame")))
+              ((symbol-function 'select-frame-set-input-focus)
+               (lambda (&rest _arguments) (ert-fail "Changed focus")))
+              ((symbol-function 'x-focus-frame)
+               (lambda (&rest _arguments) (ert-fail "Focused frame"))))
+      (dolist (state '((nil t t) (unknown t t) (t nil t) (t t nil)))
+        (setq focus (nth 0 state) graphic (nth 1 state))
+        (setf (etaf-gui-verifier-context-target-buffer context)
+              (and (nth 2 state) (window-buffer (selected-window))))
+        (should-error
+         (etaf-gui-verifier-measure-action
+          context
+          (etaf-gui-verifier-action-create
+           :id "foreground-only" :execute (lambda (_context) (cl-incf calls)))
+          t))
+        (let ((measurement
+               (car (etaf-gui-verifier-context-measurements context))))
+          (should (equal (alist-get 'status measurement) "rejected"))
+          (should-not (alist-get 'valid measurement))
+          (should-not (alist-get 'wall_ms measurement)))))
+    (should (zerop calls))))
+
+(ert-deftest etaf-gui-verifier-retains-valid-timing-when-frame-title-changes ()
+  "A GC count in the frame title must not invalidate a stable target."
+  (let* ((gcs-done 713)
+         (calls 0)
+         (result (list 'exact-result))
+         (frame-parameter-function (symbol-function 'frame-parameter))
+         (context
+          (etaf-gui-verifier--context-create
+           :target-buffer (window-buffer (selected-window)))))
+    (cl-letf (((symbol-function 'display-graphic-p)
+               (lambda (&optional _frame) t))
+              ((symbol-function 'frame-focus-state)
+               (lambda (&optional _frame) t))
+              ((symbol-function 'frame-parameter)
+               (lambda (frame parameter)
+                 (if (eq parameter 'name) (format "GC%d" gcs-done)
+                   (funcall frame-parameter-function frame parameter)))))
+      (should
+       (eq result
+           (etaf-gui-verifier-measure-action
+            context
+            (etaf-gui-verifier-action-create
+             :id "title-update"
+             :execute (lambda (_context)
+                        (cl-incf calls)
+                        (cl-incf gcs-done)
+                        result))
+            t))))
+    (should (= calls 1))
+    (let ((measurement
+           (car (etaf-gui-verifier-context-measurements context))))
+      (should (equal (alist-get 'status measurement) "success"))
+      (should (equal (alist-get 'foreground measurement) "foreground"))
+      (should (alist-get 'valid measurement))
+      (should (= (alist-get 'gc_count measurement) 1))
+      (should (equal (alist-get 'frame_name (alist-get 'before measurement))
+                     "GC713"))
+      (should (equal (alist-get 'frame_name (alist-get 'after measurement))
+                     "GC714")))))
+
+(ert-deftest etaf-gui-verifier-invalidates-replaced-selected-target ()
+  "A different live selected buffer remains an identity change."
+  (let ((target (generate-new-buffer " *etaf-gui-original-target*"))
+        (replacement (generate-new-buffer " *etaf-gui-replacement-target*"))
+        (calls 0))
+    (unwind-protect
+        (save-window-excursion
+          (switch-to-buffer target)
+          (let ((context (etaf-gui-verifier--context-create :target-buffer target)))
+            (cl-letf (((symbol-function 'display-graphic-p)
+                       (lambda (&optional _frame) t))
+                      ((symbol-function 'frame-focus-state)
+                       (lambda (&optional _frame) t)))
+              (should-error
+               (etaf-gui-verifier-measure-action
+                context
+                (etaf-gui-verifier-action-create
+                 :id "replace-selected-target"
+                 :execute (lambda (_context)
+                            (cl-incf calls)
+                            (setf (etaf-gui-verifier-context-target-buffer context)
+                                  replacement)
+                            (set-window-buffer (selected-window) replacement)))
+                t)))
+            (should (= calls 1))
+            (let ((measurement
+                   (car (etaf-gui-verifier-context-measurements context))))
+              (should (alist-get 'target_selected
+                                 (alist-get 'before measurement)))
+              (should (alist-get 'target_selected
+                                 (alist-get 'after measurement)))
+              (should (equal (alist-get 'status measurement) "invalid"))
+              (should-not (alist-get 'valid measurement)))))
+      (kill-buffer target)
+      (kill-buffer replacement))))
+
+(ert-deftest etaf-gui-verifier-invalidates-changed-foreground-environment ()
+  "Changed focus, target, font, or dimensions invalidate strict timing."
+  (let ((focus t) (width 800) (font "original-font") (calls 0)
+        (frame-parameter-function (symbol-function 'frame-parameter))
+        (context (etaf-gui-verifier--context-create)))
+    (cl-letf (((symbol-function 'display-graphic-p)
+               (lambda (&optional _frame) t))
+              ((symbol-function 'frame-focus-state)
+               (lambda (&optional _frame) focus))
+              ((symbol-function 'frame-pixel-width)
+               (lambda (&optional _frame) width))
+              ((symbol-function 'frame-parameter)
+               (lambda (frame parameter)
+                 (if (eq parameter 'font) font
+                   (funcall frame-parameter-function frame parameter)))))
+      (dolist (change '(focus target font dimensions))
+        (setq focus t width 800 font "original-font")
+        (setf (etaf-gui-verifier-context-target-buffer context)
+              (window-buffer (selected-window)))
+        (should-error
+         (etaf-gui-verifier-measure-action
+          context
+          (etaf-gui-verifier-action-create
+           :id (symbol-name change)
+           :execute
+           (lambda (_context)
+             (cl-incf calls)
+             (pcase change
+               ('focus (setq focus nil))
+               ('target
+                (setf (etaf-gui-verifier-context-target-buffer context) nil))
+               ('font (setq font "changed-font"))
+               ('dimensions (setq width 900)))))
+          t))
+        (let ((measurement
+               (car (etaf-gui-verifier-context-measurements context))))
+          (should (equal (alist-get 'status measurement) "invalid"))
+          (should (equal (alist-get 'foreground measurement) "changed"))
+          (should-not (alist-get 'valid measurement))
+          (should (numberp (alist-get 'wall_ms measurement))))))
+    (should (= calls 4))))
+
+(ert-deftest etaf-gui-verifier-preserves-quit-despite-focus-change ()
+  "A quit keeps its exact data even if strict environment checks also fail."
+  (let* ((focus t)
+         (quit-data (list 'original-quit))
+         (context
+          (etaf-gui-verifier--context-create
+           :target-buffer (window-buffer (selected-window)))))
+    (cl-letf (((symbol-function 'display-graphic-p)
+               (lambda (&optional _frame) t))
+              ((symbol-function 'frame-focus-state)
+               (lambda (&optional _frame) focus)))
+      (should
+       (equal (cons 'quit quit-data)
+              (condition-case condition
+                  (etaf-gui-verifier-measure-action
+                   context
+                   (etaf-gui-verifier-action-create
+                    :id "quit"
+                    :execute (lambda (_context)
+                               (setq focus nil)
+                               (signal 'quit quit-data)))
+                   t)
+                (quit condition)))))
+    (let ((measurement
+           (car (etaf-gui-verifier-context-measurements context))))
+      (should (equal (alist-get 'status measurement) "quit"))
+      (should (equal (alist-get 'foreground measurement) "changed"))
+      (should-not (alist-get 'valid measurement))
+      (should (numberp (alist-get 'wall_ms measurement))))))
+
+(ert-deftest etaf-gui-verifier-retains-timing-despite-closing-snapshot-failure ()
+  "Snapshot errors and quits preserve action failures and retain fresh timing."
+  (dolist (action-outcome '(error quit success))
+    (dolist (snapshot-outcome '(error quit))
+      (let* ((context
+              (etaf-gui-verifier--context-create
+               :target-buffer (window-buffer (selected-window))
+               :last-duration-ms 999.0))
+             (before (etaf-gui-verifier--measurement-state context))
+             (result (list 'exact-result))
+             (action-data (list "original-action-failure" result))
+             (snapshot-data (list "snapshot-interrupted" result))
+             (wall-times '(1.0 1.025))
+             (calls 0) (snapshots 0) observed-condition returned)
+        (cl-letf (((symbol-function 'float-time)
+                   (lambda (&optional _time) (pop wall-times)))
+                  ((symbol-function 'etaf-gui-verifier--measurement-state)
+                   (lambda (_context)
+                     (if (= (cl-incf snapshots) 1) before
+                       (signal snapshot-outcome snapshot-data)))))
+          (setq returned
+                (condition-case condition
+                    (etaf-gui-verifier-measure-action
+                     context
+                     (etaf-gui-verifier-action-create
+                      :id "snapshot-failure"
+                      :execute (lambda (_context)
+                                 (cl-incf calls)
+                                 (if (eq action-outcome 'success) result
+                                   (signal action-outcome action-data)))))
+                  ((error quit)
+                   (setq observed-condition condition)
+                   nil))))
+        (should (= calls 1))
+        (should (= snapshots 2))
+        (cond
+         ((not (eq action-outcome 'success))
+          (should (eq (car observed-condition) action-outcome))
+          (should (eq (cdr observed-condition) action-data)))
+         ((eq snapshot-outcome 'quit)
+          (should (eq (car observed-condition) 'quit))
+          (should (eq (cdr observed-condition) snapshot-data)))
+         (t
+          (should-not observed-condition)
+          (should (eq returned result))))
+        (let* ((measurements (etaf-gui-verifier-context-measurements context))
+               (measurement (car measurements)))
+          (should (= (length measurements) 1))
+          (should-not (alist-get 'valid measurement))
+          (should-not (alist-get 'after measurement))
+          (should
+           (equal (alist-get 'status measurement)
+                  (symbol-name
+                   (if (and (eq action-outcome 'success)
+                            (eq snapshot-outcome 'quit))
+                       'quit action-outcome))))
+          (should (< (abs (- (alist-get 'wall_ms measurement) 25.0)) 0.001))
+          (should (= (etaf-gui-verifier-context-last-duration-ms context)
+                     (alist-get 'wall_ms measurement))))))))
+
+(ert-deftest etaf-gui-verifier-measures-callback-without-settle-or-checkpoints ()
+  "The action callback is timed separately from checkpoints and settling."
+  (let ((context (etaf-gui-verifier--context-create))
+        (clock 0.0) events)
+    (cl-letf (((symbol-function 'float-time)
+               (lambda (&optional _time) clock))
+              ((symbol-function 'etaf-gui-verifier--checkpoint)
+               (lambda (_context _id phase _screenshot &optional _extra)
+                 (cl-incf clock 1.0)
+                 (push phase events)))
+              ((symbol-function 'etaf-gui-verifier--settle-action)
+               (lambda (_context _action)
+                 (cl-incf clock 2.0)
+                 (push 'settle events))))
+      (etaf-gui-verifier--run-action
+       context
+       (etaf-gui-verifier-action-create
+        :id "callback-only"
+        :execute (lambda (_context)
+                   (cl-incf clock 0.025)
+                   (push 'execute events)))))
+    (should (< (abs (- (etaf-gui-verifier-context-last-duration-ms context)
+                      25.0))
+               0.001))
+    (should (equal (nreverse events)
+                   '("before-action" execute "after-action"
+                     settle "after-redisplay")))
+    (let ((measurement
+           (car (etaf-gui-verifier-context-measurements context))))
+      (should (equal (alist-get 'boundary measurement) "action.execute callback"))
+      (should-not (alist-get 'presentation_measured measurement)))))
+
 (ert-deftest etaf-gui-verifier-runs-and-settles-without-raising-frame ()
   "Actions and settled checkpoints must complete without raising Emacs."
   (let ((context (etaf-gui-verifier--context-create))
diff --git a/tests/etaf-performance-tests.el b/tests/etaf-performance-tests.el
index 29bcd03..bfd6731 100644
--- a/tests/etaf-performance-tests.el
+++ b/tests/etaf-performance-tests.el
@@ -236,6 +236,89 @@
                        (plist-get (etaf-performance-stage-metadata stage)
                                   :detail)))))))
 
+(ert-deftest etaf-performance-records-filter-by-runtime-report-identity ()
+  "Select isolated history by report identity when buffer names are reused."
+  (etaf-performance-test--isolated
+    (dolist (entry '((1 101 "first mount")
+                     (1 202 "second mount")
+                     (2 101 "first unmount")))
+      (etaf-performance--retain
+       (etaf-performance--operation-create
+        :id (nth 0 entry) :runtime-id (nth 1 entry) :label (nth 2 entry)
+        :buffer-name " *reused performance buffer*"
+        :metadata '(:detail ("stable")))))
+    (should (= 3 (length (etaf-performance-records))))
+    (should (equal (etaf-performance-records)
+                   (etaf-performance-records nil)))
+    (let ((first (etaf-performance-records 101))
+          (second (etaf-performance-records 202)))
+      (should (equal '("first unmount" "first mount")
+                     (mapcar #'etaf-performance-operation-label first)))
+      (should (equal '("second mount")
+                     (mapcar #'etaf-performance-operation-label second)))
+      (setf (etaf-performance-operation-label (car first)) "changed")
+      (setcar (plist-get (etaf-performance-operation-metadata (car first))
+                         :detail)
+              "changed")
+      (let ((retained (car (etaf-performance-records 101))))
+        (should (equal "first unmount"
+                       (etaf-performance-operation-label retained)))
+        (should (equal '("stable")
+                       (plist-get (etaf-performance-operation-metadata retained)
+                                  :detail)))))
+    (should-not (etaf-performance-records 303))
+    (should-error (etaf-performance-records "101")
+                  :type 'wrong-type-argument)))
+
+(ert-deftest etaf-performance-summary-keeps-explicit-empty-selection ()
+  "An omitted selection summarizes all records; an explicit nil stays empty."
+  (etaf-performance-test--isolated
+    (etaf-performance--retain
+     (etaf-performance--operation-create
+      :kind 'report :label "retained fixture" :elapsed 1.0))
+    (should (= 1 (length (etaf-performance-summary))))
+    (should-not (etaf-performance-summary nil))))
+
+(ert-deftest etaf-performance-report-data-keeps-explicit-empty-selection ()
+  "An empty data export cannot fall back to previously retained records."
+  (etaf-performance-test--isolated
+    (etaf-performance--retain
+     (etaf-performance--operation-create
+      :kind 'report :label "retained fixture" :elapsed 1.0))
+    (let ((all (etaf-performance-report-data))
+          (empty (etaf-performance-report-data nil)))
+      (should (= 1 (length (plist-get all :summary))))
+      (should (= 1 (length (plist-get all :operations))))
+      (should-not (plist-get empty :summary))
+      (should-not (plist-get empty :operations)))))
+
+(ert-deftest etaf-performance-report-string-keeps-explicit-empty-selection ()
+  "Report strings preserve both omitted and explicitly empty selections."
+  (etaf-performance-test--isolated
+    (etaf-performance--retain
+     (etaf-performance--operation-create
+      :kind 'report :label "retained fixture" :elapsed 1.0))
+    (let ((all (read (etaf-performance-report-string)))
+          (empty (read (etaf-performance-report-string nil))))
+      (should (= 1 (length (plist-get all :summary))))
+      (should (= 1 (length (plist-get all :operations))))
+      (should-not (plist-get empty :summary))
+      (should-not (plist-get empty :operations)))))
+
+(ert-deftest etaf-performance-reports-keep-empty-runtime-selection ()
+  "An unmatched runtime report identity produces empty summary and exports."
+  (etaf-performance-test--isolated
+    (etaf-performance--retain
+     (etaf-performance--operation-create
+      :runtime-id 101 :kind 'report :label "retained fixture" :elapsed 1.0))
+    (let ((records (etaf-performance-records 202)))
+      (should-not records)
+      (should-not (etaf-performance-summary records))
+      (dolist (report (list (etaf-performance-report-data records)
+                            (read (etaf-performance-report-string records))))
+        (should-not (plist-get report :summary))
+        (should-not (plist-get report :operations))))))
+
 (ert-deftest etaf-performance-summary-uses-flat-duration ()
   "Summaries expose percentiles and overlapping provider durations honestly."
   (etaf-performance-test--isolated