The carousel stutter is the ark history memo re-cooling on a timer: rebuilding it costs ~60ms (sort + dedupe + gift resolve + secp256k1), and its 1.5s TTL meant an unhurried flick always hit a cold rebuild, stuttering the slide's tail — 'warms up if I keep going fast, cold if I pause, refresh reproduces' is the classic TTL-expiry signature. Now keyed on a state revision (_save bumps state._rev) so it's reused until the data actually changes and never re-cools between flicks. Diagnostics still on to confirm

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01MrkLsNScXe9b6BviUSdmMr

2 files changed, 13 insertions, 9 deletions

diff --git a/src/ark/manager.js b/src/ark/manager.js
index a443370..471c4e0 100644
--- a/src/ark/manager.js
+++ b/src/ark/manager.js
@@ -161,6 +161,10 @@ export class ArkManager {
   }
 
   _save() {
+    // a monotonic revision that bumps on every state change — lets memoized
+    // derivations (history build, etc.) invalidate exactly when the data
+    // changes instead of on a timer that re-cools between interactions
+    this.state._rev = (this.state._rev || 0) + 1;
     this.storage.save(this.state);
     this.onUpdate(this);
   }
diff --git a/src/features/ark.js b/src/features/ark.js
index f846cac..1426592 100644
--- a/src/features/ark.js
+++ b/src/features/ark.js
@@ -3069,16 +3069,16 @@ export function arkFeature(ctx) {
       if (sel && sel !== 'spending') return []; // ark movements are the Spending timeline
       const s = arkStateNow();
       if (!s) return [];
-      // Memoized briefly: this rebuilds, sorts, and dedupes the whole
-      // movements list plus the accounted-inputs set — fine once, wasteful
-      // on every repaint. Movements only change through saves that trigger
-      // a render themselves, so a short reuse window costs nothing visible.
-      const key = `${(s.movements || []).length}:${(s.actions || []).length}`;
-      if (this._histMemo && this._histMemo.key === key && Date.now() - this._histMemo.t < 1500) {
-        return this._histMemo.val;
-      }
+      // Memoized on the state's REVISION, not a timer. This rebuild sorts and
+      // dedupes every movement, resolves gifts, and touches secp256k1 — ~60ms
+      // cold. A 1.5s TTL used to re-cool it between unhurried flicks, so every
+      // account switch paid the rebuild and stuttered the slide; keyed on _rev
+      // it's reused until the data actually changes (each _save bumps _rev),
+      // and stays warm no matter how slowly the user flicks back and forth.
+      const key = `${s._rev || 0}:${(s.movements || []).length}:${(s.actions || []).length}`;
+      if (this._histMemo && this._histMemo.key === key) return this._histMemo.val;
       const val = this._histBuild(s);
-      this._histMemo = { key, t: Date.now(), val };
+      this._histMemo = { key, val };
       return val;
     },
     _histBuild(s) {