diff --git a/src/core/search/hybrid.ts b/src/core/search/hybrid.ts
index 27da6b8c1..7b451ea63 100644
--- a/src/core/search/hybrid.ts
+++ b/src/core/search/hybrid.ts
@@ -334,6 +334,32 @@ export function applyTitleBoost(
 /** Default title-phrase boost multiplier (mode-overridable via `title_boost`). */
 export const DEFAULT_TITLE_BOOST = 1.25;
 
+/**
+ * v0.42.x — Life Chronicle (#2390) E1 temporal recall arm. On temporal queries
+ * (the caller gates this on recency !== 'off'), give chronicle `event`/`diary`
+ * pages a bounded boost so the timeline surfaces for "what happened…" / "when
+ * did…" queries — ambient temporality without a separate recall arm. Bounded
+ * ([1.0, 1.25]) + floor-gated like the other metadata stages, so it can't
+ * leapfrog a strong primary hit. Mutate-in-place; caller re-sorts. Pure no-op
+ * for non-chronicle results. NOT called on non-temporal queries (recency='off'),
+ * so ordinary search is bit-for-bit unchanged.
+ */
+export function applyChronicleTypeBoost(
+  results: SearchResult[],
+  strength: 'on' | 'strong',
+  floorThreshold?: number,
+): void {
+  const factor = strength === 'strong' ? 1.25 : 1.15;
+  for (const r of results) {
+    if (!Number.isFinite(r.score)) continue;
+    if (floorThreshold !== undefined && r.score < floorThreshold) continue;
+    if (r.type === 'event' || r.type === 'diary') {
+      r.score *= factor;
+      r.chronicle_boost = factor;
+    }
+  }
+}
+
 /**
  * v0.29.1 — runPostFusionStages: wrap backlink + salience + recency in a
  * single stage that fires from EVERY hybridSearch return path (codex
@@ -472,6 +498,12 @@ export async function runPostFusionStages(
     } catch {
       // Non-fatal.
     }
+
+    // v0.42.x — Life Chronicle (#2390) E1: chronicle event/diary type boost.
+    // Gated INSIDE the recency!=off branch so it fires ONLY on temporal queries;
+    // non-temporal search never reaches here → bit-for-bit unchanged. Shares the
+    // floor threshold so it can't leapfrog a strong primary hit.
+    applyChronicleTypeBoost(results, opts.recency, floorThreshold);
   }
 
   // T2 — title-phrase boost. Runs after the metadata stages, before graph
diff --git a/src/core/types.ts b/src/core/types.ts
index 2a423e005..f94c049e4 100644
--- a/src/core/types.ts
+++ b/src/core/types.ts
@@ -761,6 +761,8 @@ export interface SearchResult {
   salience_boost?: number;
   /** Multiplier applied by applyRecencyBoost. */
   recency_boost?: number;
+  /** v0.42.x (#2390) — multiplier applied by applyChronicleTypeBoost (event/diary on temporal queries). */
+  chronicle_boost?: number;
   /** Multiplier applied by applyExactMatchBoost. */
   exact_match_boost?: number;
   /** Multiplier applied by applyGraphSignals (adjacency hit). */
diff --git a/test/chronicle-search-boost.test.ts b/test/chronicle-search-boost.test.ts
new file mode 100644
index 000000000..5b5a75af8
--- /dev/null
+++ b/test/chronicle-search-boost.test.ts
@@ -0,0 +1,43 @@
+/**
+ * v0.42.x — Life Chronicle (#2390) E1 temporal recall boost (Phase A.4).
+ * Pure-function test of applyChronicleTypeBoost: boosts event/diary on temporal
+ * queries, leaves everything else untouched (the no-regression guarantee — the
+ * function is only CALLED when recency !== 'off', and even then only moves
+ * chronicle types).
+ */
+import { describe, test, expect } from 'bun:test';
+import { applyChronicleTypeBoost } from '../src/core/search/hybrid.ts';
+import type { SearchResult } from '../src/core/types.ts';
+
+function r(slug: string, type: string, score = 1.0): SearchResult {
+  return {
+    slug, page_id: 1, title: slug, type, chunk_text: '', chunk_source: 'compiled_truth',
+    chunk_id: 1, chunk_index: 0, score, stale: false,
+  } as SearchResult;
+}
+
+describe('applyChronicleTypeBoost', () => {
+  test('boosts event + diary, leaves other types untouched', () => {
+    const rows = [r('life/events/a', 'event'), r('life/diary/b', 'diary'), r('wiki/note', 'note'), r('people/x', 'person')];
+    applyChronicleTypeBoost(rows, 'on');
+    expect(rows[0].score).toBeCloseTo(1.15);
+    expect(rows[0].chronicle_boost).toBeCloseTo(1.15);
+    expect(rows[1].score).toBeCloseTo(1.15);
+    expect(rows[2].score).toBe(1.0); // note unchanged
+    expect(rows[2].chronicle_boost).toBeUndefined();
+    expect(rows[3].score).toBe(1.0); // person unchanged
+  });
+
+  test('strong uses a larger factor', () => {
+    const rows = [r('life/events/a', 'event')];
+    applyChronicleTypeBoost(rows, 'strong');
+    expect(rows[0].score).toBeCloseTo(1.25);
+  });
+
+  test('floor gate skips low-score results', () => {
+    const rows = [r('life/events/a', 'event', 0.1)];
+    applyChronicleTypeBoost(rows, 'on', 0.5); // 0.1 < floor 0.5 → skipped
+    expect(rows[0].score).toBe(0.1);
+    expect(rows[0].chronicle_boost).toBeUndefined();
+  });
+});