Fix tape nav rerender loop

apps/web/app/terminal.test.ts

@@ -28,6 +28,7 @@ import {
   mergeNewestWithOverflow,
   normalizeAlertSeverity,
   nextFlowFilterPopoverState,
+  prunePinnedEntries,
   projectPausableTapeState,
   reducePausableTapeData,
   shouldRetainLiveSnapshotHistory,
@@ -77,6 +78,20 @@ const makeAlert = (overrides: Record<string, unknown> = {}) =>
     ...overrides
   }) as any;
 
+describe("pinned evidence pruning", () => {
+  it("returns the existing map when no entries need pruning", () => {
+    const now = 50_000;
+    const current = new Map([
+      ["flowpacket:1", { value: { id: "flowpacket:1" }, updatedAt: now - 500 }],
+      ["trace:2", { value: { id: "trace:2" }, updatedAt: now - 1_000 }]
+    ]);
+
+    const next = prunePinnedEntries(current, new Set(), now);
+
+    expect(next).toBe(current);
+  });
+});
+
 describe("live manifest", () => {
   it("includes only tape channels on /tape", () => {
     const filters = buildDefaultFlowFilters();

apps/web/app/terminal.tsx

@@ -1894,7 +1894,7 @@ const upsertPinnedEntries = <T,>(
   return next;
 };
 
-const prunePinnedEntries = <T,>(
+export const prunePinnedEntries = <T,>(
   current: Map<string, PinnedEntry<T>>,
   activeKeys: Set<string>,
   now: number
@@ -1909,6 +1909,24 @@ const prunePinnedEntries = <T,>(
 
   surviving.sort((a, b) => b[1].updatedAt - a[1].updatedAt);
   const trimmed = surviving.slice(0, PINNED_EVIDENCE_MAX_ITEMS);
+
+  if (trimmed.length === current.size) {
+    let unchanged = true;
+    let index = 0;
+    for (const entry of current) {
+      const next = trimmed[index];
+      if (!next || next[0] !== entry[0] || next[1] !== entry[1]) {
+        unchanged = false;
+        break;
+      }
+      index += 1;
+    }
+
+    if (unchanged) {
+      return current;
+    }
+  }
+
   return new Map(trimmed);
 };