From 558723421f320d00a1d9c7704cae567a00e17310 Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Mon, 22 Jun 2026 12:51:15 -0400
Subject: chore(todo): mark jumper register-hygiene bug done

---
 todo.org | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/todo.org b/todo.org
index 688d19352..eb8d6a776 100644
--- a/todo.org
+++ b/todo.org
@@ -4014,10 +4014,12 @@ Tie this into the existing coverage work:
 - Tests cover adapter detection, command building, scope resolution, result
   storage, and key interactive paths.
 
-** TODO [#B] jumper: register collisions and dead-marker errors :bug:solo:
+** DONE [#B] jumper: register collisions and dead-marker errors :bug:solo:
+CLOSED: [2026-06-22 Mon]
 :PROPERTIES:
 :LAST_REVIEWED: 2026-06-13
 :END:
+Fixed 2026-06-22: (1) store now allocates the first unused register char in the live slice (=jumper--first-free-register=) instead of by next-index, and removal clears the freed register, so a store after a removal no longer overwrites a surviving slot's marker; (2) =jumper--with-marker-at= guards =(buffer-live-p (marker-buffer marker))= so killed-buffer entries are skipped instead of signaling wrong-type errors; (3) the single-location toggle jumps back to the last-location register when set (returns =jumped-back=). New =test-jumper--register-hygiene.el= (8 tests); all 42 jumper tests green. Pre-existing unused-lexical =i= warning in =jumper--location-exists-p= left alone (separate nit).
 Two related defects from the 2026-06 config audit:
 - =modules/jumper.el:155= — removal shifts the vector without renumbering registers, so a later store allocates a register still held by a surviving location and silently overwrites it. Allocate the first free register char in the live slice; =set-register nil= on removal so freed markers don't pin buffers.
 - =modules/jumper.el:117,132= — guards check =(markerp marker)= but not =(buffer-live-p (marker-buffer marker))=; after killing a buffer holding a location, M-SPC SPC and M-SPC j signal wrong-type errors. Treat dead entries as skippable/removable.
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