diff --git a/docs/ISSUES.md b/docs/ISSUES.md
index 757cb467..dd07fb1d 100644
--- a/docs/ISSUES.md
+++ b/docs/ISSUES.md
@@ -24,6 +24,30 @@ What does NOT go here:
 - Every session: scan OPEN issues at start; promote/close anything we touched during the session before ending.
 - Promoting to a Phase: mark as `DONE (promoted to Phase X)` + commit SHA where the Phase entry landed.
 
+## #383 — Installed-DAT vs committed-fixture drift: regeneration produces large diffs in existing UI fixtures
+
+**Status:** OPEN — filed 2026-08-12 at Campaign FA slice FA3. Running the
+env-gated fixture generator (`ACDREAM_REGENERATE_UI_FIXTURES=1`) on this
+machine to dump the NEW social-panel fixture also silently rewrote
+`keyboard_config_21000009.json` and `options_2100002B.json` with LARGE
+diffs — the currently-installed DATs under
+`%USERPROFILE%\Documents\Asheron's Call` no longer match the DAT state
+those fixtures were committed from (days ago, same machine). The FA3
+implementer reverted both to HEAD and committed only the new fixture.
+Possible cause observed in passing: local `mudsort` tooling artifacts in
+the Documents DAT folder (a DAT-modifying tool may have touched the
+files). **Impact/risk:** the committed fixtures drive the conformance
+suites; the live client reads the INSTALLED DATs — if they diverge, the
+fixture-green/live-broken class this project keeps meeting gets a new
+systemic cause. The env-gated live-mount probes (which read the installed
+DATs directly) are the cross-check that still holds. **Investigation
+needed before anyone regenerates fixtures on this machine again:** diff
+the two fixture regenerations structurally (what changed — geometry?
+string ids? media?), determine WHAT modified the installed DATs and when,
+and decide the canonical DAT source for fixtures (a pristine copy vs the
+live install). Do not regenerate-and-commit existing fixtures until the
+drift is understood.
+
 ## #382 — Floating chat-window tab buttons are invisible until first hovered
 
 **Status:** ROOT-CAUSED + FIXED (this commit) — pending the user's re-gate.