diff --git a/experiments/shell/run.py b/experiments/shell/run.py
index a4878c4d..dc054577 100644
--- a/experiments/shell/run.py
+++ b/experiments/shell/run.py
@@ -40,6 +40,21 @@
 }
 
 
+def require_fixed_vim(mode):
+    """candidate-tui types a Vim command into the real shell, so Vim must be on PATH.
+
+    Without this check a missing Vim surfaces as a 33-second scenario timeout whose
+    only trace is the shell echoing "not recognized as an internal or external
+    command"; the requirement itself is documented in
+    docs/research/joint-conpty-baseline.md and is a failure, not a skippable
+    optional dependency (docs/research/more-capture-ech.md).
+    """
+    if mode == "candidate-tui" and shutil.which("vim") is None:
+        raise RuntimeError(
+            "candidate-tui drives Vim inside the shell but no fixed Vim is on PATH; "
+            "see docs/research/joint-conpty-baseline.md")
+
+
 def validate(row, mode):
     if mode in WORKSPACE_DATA_MODES:
         closed = 3 if mode in ("ui-workspace-save", "ui-workspace-restore") else 0 if mode == "ui-workspace-empty" else 1
@@ -430,6 +445,7 @@ def close(self, record=None):
 def execute(exe, mode, out, timeout=40, settings_source=None, *, resources=False):
     if mode in ("ui-paste-system", "ui-clipboard-system", "ui-copy-system", "ui-copy-bytes-system", "ui-copy-context-system", "ui-actions-system"):
         require_hosted_clipboard(os.environ)
+    require_fixed_vim(mode)
     if resources and mode != "ui-workflow-sessions":
         raise ValueError("resource observation is limited to the bounded sessions workflow")
     out.mkdir(parents=True, exist_ok=False)
diff --git a/experiments/shell/shell.cpp b/experiments/shell/shell.cpp
index 94d14d7d..29aa6e1f 100644
--- a/experiments/shell/shell.cpp
+++ b/experiments/shell/shell.cpp
@@ -821,8 +821,13 @@ class ShellWindow {
             case 2: terminal_title_ = utf16(event.bytes); break;
             case 3: terminal_title_.clear(); break;
             case 4: MessageBeep(MB_OK); break;
-            case 5: case 7: case 12: break;
+            case 5: case 7: case 10: case 11: case 12: break;
             case 6: begin_close(); break;
+            // The candidate adapter also reports clipboard traffic (8, 9) and the
+            // child's exit status (13). This harness compares text, modes and
+            // lifecycle; it owns no clipboard and reads the exit code from the
+            // session, so these are drained instead of failing the scenario.
+            case 8: case 9: case 13: break;
             default: throw std::runtime_error("unsupported terminal event kind");
             }
         }