diff --git a/emacs/flan-dev.el b/emacs/flan-dev.el
index 75b3723..e1005e7 100644
--- a/emacs/flan-dev.el
+++ b/emacs/flan-dev.el
@@ -345,6 +345,11 @@ socket at all and this buffer is the only account of why."
 It builds the program first, which for a cold project is most of this."
   :type 'number)
 
+(defvar flan-dev--file nil
+  "The program the daemon this Emacs started was started on, or nil.
+Kept so that it can be started again on the same program and the same
+socket, which is what `flan-dev-restart-program' is.")
+
 (defvar flan-dev--daemon nil
   "The `flan dev' process this Emacs started, or nil.
 A daemon started in a terminal is not here, and `flan-connect' still works
@@ -432,6 +437,7 @@ which is the one thing a dev loop exists to avoid doing by accident."
                                        (file-name-directory file)))))
     (unless (file-exists-p file)
       (user-error "flan dev: no such file: %s" file))
+    (setq flan-dev--file file)
     (setq flan-dev--daemon (flan-dev--start-daemon file socket))
     (flan-dev--connect-when-ready socket flan-dev--daemon)
     ;; Connected by now, so the rest is what `flan-connect' does after opening:
@@ -474,11 +480,44 @@ socket; the process is killed only if it does not take it."
         (while (and (process-live-p proc) (< (float-time) deadline))
           (accept-process-output proc 0.05)))
       (when (process-live-p proc)
-        (delete-process proc)))
+        ;; Killed rather than asked, so its own cleanup never runs — and that
+        ;; cleanup is what signals the program.  The program is therefore
+        ;; probably still running, reparented, holding its agent socket, and
+        ;; saying "stopped" here would be the one place in this client where
+        ;; a success message meant "probably".
+        (delete-process proc)
+        (setq flan-dev--daemon nil)
+        (force-mode-line-update t)
+        (user-error
+         "flan dev: the daemon would not close and was killed; its program may still be running")))
     (setq flan-dev--daemon nil)
     (force-mode-line-update t)
     (message "flan dev: stopped")))
 
+;;;###autoload
+(defun flan-dev-restart-program ()
+  "Stop the program this Emacs started and start it again from source.
+
+For a change the running program cannot take: a struct whose layout moved, a
+function whose signature changed, anything the daemon refuses by telling you
+to restart.  There is no smaller version of this.  A session's struct layouts
+and global types describe the memory of a process only if that session
+compiled it, so a new layout means a new build, which means a new process and
+the session that made it — and the program's state goes with it, which is the
+whole cost and the reason this is a separate command rather than something
+`C-c C-c' falls back to.
+
+The old daemon is waited for before the new one starts, because it unlinks
+the socket on its way out and would otherwise unlink the one its successor
+had just bound."
+  (interactive)
+  (unless (process-live-p flan-dev--daemon)
+    (user-error "flan dev: no daemon started from Emacs to restart"))
+  (let ((file flan-dev--file)
+        (socket flan-dev--socket))
+    (flan-dev-quit)                     ; returns only once it is really gone
+    (flan-dev file socket)))
+
 ;;; The modeline
 
 ;; Whether there is a program on the other end is the one thing worth a
diff --git a/emacs/flan-mode.el b/emacs/flan-mode.el
index 4b04f60..2daab24 100644
--- a/emacs/flan-mode.el
+++ b/emacs/flan-mode.el
@@ -121,8 +121,10 @@ line is off screen."
     (define-key map (kbd "C-c C-b") #'flan-break)
     ;; Help on the name at point.  C-c C-d is taken by `flan-describe', which
     ;; is about the session rather than about a name, and renaming a key that
-    ;; is already documented costs more than it is worth.
-    (define-key map (kbd "C-c C-h") #'flan-doc)
+    ;; is already documented costs more than it is worth.  Not C-c C-h either:
+    ;; C-h after a prefix is how anyone finds out what is under C-c, and a
+    ;; binding there takes that away.
+    (define-key map (kbd "C-c C-v") #'flan-doc)
     map)
   "Keymap for `flan-mode'.")
 
diff --git a/emacs/test-flan-dev.el b/emacs/test-flan-dev.el
index 6639d7f..cd5cfa9 100644
--- a/emacs/test-flan-dev.el
+++ b/emacs/test-flan-dev.el
@@ -537,6 +537,25 @@ is written instead — the real `message' call the real command makes."
                         (and raised (string-match-p "already running" raised))))
     ;; The daemon owns the program's lifetime, so quitting has to actually end
     ;; the process — not just drop the socket and leave it running.
+    ;; Restarting the program: for a change the running one cannot take — a
+    ;; struct whose layout moved — where the answer is a new build, a new
+    ;; process and the session that compiled it.  Proved by what it throws
+    ;; away: a name installed into the old program is not in the new one.
+    (flan-dev--eval "(defn only-in-the-old-program [] i64 1)" "form")
+    (test-flan--check "a name installed into the running program is there"
+                      (assoc "only-in-the-old-program" flan-dev--defs))
+    (let ((old flan-dev--daemon))
+      (flan-dev-restart-program)
+      (test-flan--check "restarting gives a different daemon, connected"
+                        (and (not (process-live-p old))
+                             (process-live-p flan-dev--daemon)
+                             (not (eq old flan-dev--daemon))
+                             (eq (flan-dev-state) 'live))))
+    (test-flan--check "and a program built from source, without the addition"
+                      (and (assoc "step" flan-dev--defs)
+                           (null (assoc "only-in-the-old-program"
+                                        flan-dev--defs))))
+
     (let ((proc flan-dev--daemon))
       (flan-dev-quit)
       ;; The process, not the variable: forgetting a daemon is not stopping