The markdown editor's save handlers (markDirty, save(), convertBtns
intercept) referenced a bare identifier `writable` that never existed
in their scope — the captured variable was named `writableMode`. JS
silently evaluates `!undefined` to true, so saveBtn.disabled stayed
true forever and Ctrl-S was a no-op. The download-as-* intercept
treated every dirty file as read-only and offered the "save a copy
elsewhere" toast.
YAML editor had the matching-name pattern (`writable` defined and
referenced) so the symptom was hidden, but the same stale-closure
shape: capture once at mount, never re-read when the underlying tree
node's writable bit changed.
Fix both: gating logic reads canSave(node) fresh at every click, not
from a closure. Mount-time captures stay for initial UI shape
(read-only banner, CodeMirror readOnly:'nocursor') where the decision
is correct at the moment it's applied.
Codify the pattern in AGENTS.md § "JS module pattern":
no bundler + no reactivity layer ⇒ closures don't refresh ⇒ read
fresh in handlers, never cache.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ZDDC
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