diff --git a/web/src/routes/observability.ts b/web/src/routes/observability.ts
index 25bdd99..c37f854 100644
--- a/web/src/routes/observability.ts
+++ b/web/src/routes/observability.ts
@@ -3,9 +3,16 @@
 import { Hono } from 'hono';
 import type { Env } from '../types.js';
 import { getAllProceduresWithDerivedStats, getActiveAgendaItems } from '../kernel/memory/index.js';
+import { detectEntropy } from '../kernel/scheduled/entropy.js';
+import { buildEdgeEnv } from '../edge-env.js';
 
 const observability = new Hono<{ Bindings: Env }>();
 
+function boundedDays(value: string | undefined, fallback: number, max: number): number {
+  const days = parseInt(value ?? String(fallback), 10);
+  return Number.isNaN(days) || days < 1 || days > max ? fallback : days;
+}
+
 // ─── Shadow Write Stats ─────────────────────────────────────
 
 observability.get('/api/shadow-stats', async (c) => {
@@ -46,6 +53,124 @@ observability.get('/api/shadow-read-stats', async (c) => {
   return c.json({ days, summary, by_site: bySite.results, recent: recent.results });
 });
 
+// ─── Entropy ────────────────────────────────────────────────
+
+observability.get('/api/entropy', async (c) => {
+  // detectEntropy needs the full EdgeEnv (API keys, model config) — not just c.env.DB
+  const env = buildEdgeEnv(c.env);
+  const report = await detectEntropy(env);
+  return c.json(report);
+});
+
+// ─── Shadow Read Drift ──────────────────────────────────────
+
+observability.get('/api/shadow-read-drift', async (c) => {
+  const days = boundedDays(c.req.query('days'), 7, 30);
+  const reader = c.req.query('reader');
+
+  const latestWhere = reader
+    ? "WHERE reader = ? AND sampled_at > datetime('now', '-' || ? || ' days')"
+    : "WHERE sampled_at > datetime('now', '-' || ? || ' days')";
+  // latestBindings: reader-first to match latestWhere (WHERE reader = ? AND sampled_at...)
+  // windowBindings: days-first to match the WHERE sampled_at... AND reader = ? pattern used in distribution/topDrifters
+  const latestBindings = reader ? [reader, days] : [days];
+  const windowBindings = reader ? [days, reader] : [days];
+
+  const [distribution, readiness, topDrifters] = await Promise.all([
+    c.env.DB.prepare(`
+      WITH ranked AS (
+        SELECT reader,
+          ABS((cached_count - pre_tier_count) - derived_count) AS count_abs_drift,
+          ABS(cached_avg_latency_ms - derived_avg_latency_ms) AS latency_abs_drift,
+          ABS(cached_avg_cost - derived_avg_cost) AS cost_abs_drift,
+          ROW_NUMBER() OVER (PARTITION BY reader ORDER BY ABS((cached_count - pre_tier_count) - derived_count)) AS count_rank,
+          ROW_NUMBER() OVER (PARTITION BY reader ORDER BY ABS(cached_avg_latency_ms - derived_avg_latency_ms)) AS latency_rank,
+          ROW_NUMBER() OVER (PARTITION BY reader ORDER BY ABS(cached_avg_cost - derived_avg_cost)) AS cost_rank,
+          COUNT(*) OVER (PARTITION BY reader) AS n
+        FROM shadow_read_drift
+        WHERE sampled_at > datetime('now', '-' || ? || ' days')
+        ${reader ? 'AND reader = ?' : ''}
+      )
+      SELECT reader,
+        MAX(n) AS samples,
+        ROUND(AVG(count_abs_drift), 2) AS avg_abs_count_drift,
+        ROUND(MAX(count_abs_drift), 2) AS max_abs_count_drift,
+        ROUND(MAX(CASE WHEN count_rank = MAX(1, (n + 1) / 2) THEN count_abs_drift END), 2) AS p50_count_drift,
+        ROUND(MAX(CASE WHEN count_rank = MAX(1, (n * 19 + 19) / 20) THEN count_abs_drift END), 2) AS p95_count_drift,
+        ROUND(MAX(CASE WHEN count_rank = MAX(1, (n * 99 + 99) / 100) THEN count_abs_drift END), 2) AS p99_count_drift,
+        ROUND(AVG(latency_abs_drift), 2) AS avg_latency_drift_ms,
+        ROUND(MAX(latency_abs_drift), 2) AS max_latency_drift_ms,
+        ROUND(MAX(CASE WHEN latency_rank = MAX(1, (n + 1) / 2) THEN latency_abs_drift END), 2) AS p50_latency_drift_ms,
+        ROUND(MAX(CASE WHEN latency_rank = MAX(1, (n * 19 + 19) / 20) THEN latency_abs_drift END), 2) AS p95_latency_drift_ms,
+        ROUND(MAX(CASE WHEN latency_rank = MAX(1, (n * 99 + 99) / 100) THEN latency_abs_drift END), 2) AS p99_latency_drift_ms,
+        ROUND(AVG(cost_abs_drift), 6) AS avg_cost_drift,
+        ROUND(MAX(cost_abs_drift), 6) AS max_cost_drift,
+        ROUND(MAX(CASE WHEN cost_rank = MAX(1, (n + 1) / 2) THEN cost_abs_drift END), 6) AS p50_cost_drift,
+        ROUND(MAX(CASE WHEN cost_rank = MAX(1, (n * 19 + 19) / 20) THEN cost_abs_drift END), 6) AS p95_cost_drift,
+        ROUND(MAX(CASE WHEN cost_rank = MAX(1, (n * 99 + 99) / 100) THEN cost_abs_drift END), 6) AS p99_cost_drift
+      FROM ranked
+      GROUP BY reader
+    `).bind(...windowBindings).all(),
+
+    c.env.DB.prepare(`
+      WITH latest AS (
+        SELECT reader, task_pattern, cached_count, cached_success_count,
+          cached_avg_latency_ms, cached_avg_cost,
+          derived_count, derived_success_count,
+          derived_avg_latency_ms, derived_avg_cost,
+          pre_tier_count,
+          ROW_NUMBER() OVER (PARTITION BY reader, task_pattern ORDER BY sampled_at DESC) as rn
+        FROM shadow_read_drift
+        ${latestWhere}
+      )
+      SELECT
+        COUNT(*) as total_pairs,
+        COUNT(DISTINCT task_pattern) as distinct_procedures,
+        SUM(CASE WHEN pre_tier_count = 0 THEN 1 ELSE 0 END) as clean_pairs,
+        SUM(CASE
+          WHEN pre_tier_count = 0
+           AND cached_count = derived_count
+           AND cached_success_count = derived_success_count
+           AND ABS(cached_avg_latency_ms - derived_avg_latency_ms) < 10
+           AND ABS(cached_avg_cost - derived_avg_cost) < 0.0001
+          THEN 1 ELSE 0 END) as ready_pairs
+      FROM latest WHERE rn = 1
+    `).bind(...latestBindings).first(),
+
+    c.env.DB.prepare(`
+      WITH latest_per_pattern AS (
+        SELECT task_pattern, reader,
+          cached_count, derived_count, pre_tier_count,
+          cached_avg_latency_ms, derived_avg_latency_ms,
+          cached_avg_cost, derived_avg_cost,
+          sampled_at,
+          ROW_NUMBER() OVER (PARTITION BY task_pattern, reader ORDER BY sampled_at DESC) as rn
+        FROM shadow_read_drift
+        WHERE sampled_at > datetime('now', '-' || ? || ' days')
+        ${reader ? 'AND reader = ?' : ''}
+      )
+      SELECT task_pattern, reader,
+        cached_count, derived_count, pre_tier_count,
+        ABS((cached_count - pre_tier_count) - derived_count) as count_drift,
+        ROUND(ABS(cached_avg_latency_ms - derived_avg_latency_ms), 1) as latency_drift,
+        ROUND(ABS(cached_avg_cost - derived_avg_cost), 6) as cost_drift,
+        sampled_at
+      FROM latest_per_pattern
+      WHERE rn = 1
+      ORDER BY ABS((cached_count - pre_tier_count) - derived_count) DESC
+      LIMIT 15
+    `).bind(...windowBindings).all(),
+  ]);
+
+  return c.json({
+    days,
+    reader_filter: reader ?? null,
+    distribution: distribution.results,
+    readiness,
+    top_drifters: topDrifters.results,
+  });
+});
+
 // ─── Agenda ─────────────────────────────────────────────────
 
 observability.get('/agenda', async (c) => {
diff --git a/web/tests/observability.test.ts b/web/tests/observability.test.ts
index e64f07c..df87eb8 100755
--- a/web/tests/observability.test.ts
+++ b/web/tests/observability.test.ts
@@ -9,8 +9,19 @@ vi.mock('../src/kernel/memory/index.js', () => ({
   getActiveAgendaItems: vi.fn().mockResolvedValue([]),
 }));
 
+vi.mock('../src/kernel/scheduled/entropy.js', () => ({
+  detectEntropy: vi.fn().mockResolvedValue({
+    score: 0,
+    ghostAgendaItems: [],
+    ghostTasks: [],
+    dormantGoals: [],
+    summary: 'Entropy 0% - all clear.',
+  }),
+}));
+
 import { observability } from '../src/routes/observability.js';
 import { getAllProceduresWithDerivedStats, getActiveAgendaItems } from '../src/kernel/memory/index.js';
+import { detectEntropy } from '../src/kernel/scheduled/entropy.js';
 import type { Env } from '../src/types.js';
 
 // ─── D1 Mock ──────────────────────────────────────────────────
@@ -134,6 +145,102 @@ describe('observability routes', () => {
     });
   });
 
+  describe('GET /api/entropy', () => {
+    it('returns entropy report from detector', async () => {
+      const report = {
+        score: 25,
+        ghostAgendaItems: [{ id: 1, item: 'Stale item', daysSinceCreated: 9 }],
+        ghostTasks: [],
+        dormantGoals: [],
+        summary: 'Entropy 25% - 1 agenda item stale >7d.',
+      };
+      vi.mocked(detectEntropy).mockResolvedValueOnce(report as any);
+
+      const db = createMockDb();
+      const app = createApp(db);
+
+      const res = await app.request('/api/entropy');
+      expect(res.status).toBe(200);
+      expect(await res.json()).toEqual(report);
+      expect(detectEntropy).toHaveBeenCalledWith(expect.objectContaining({ db }));
+    });
+  });
+
+  describe('GET /api/shadow-read-drift', () => {
+    it('returns drift distribution, readiness, and top drifters', async () => {
+      const distribution = [{
+        reader: 'observability',
+        samples: 4,
+        p95_count_drift: 1,
+        p95_latency_drift_ms: 5,
+        p95_cost_drift: 0.00001,
+      }];
+      const readiness = {
+        total_pairs: 2,
+        distinct_procedures: 2,
+        clean_pairs: 2,
+        ready_pairs: 1,
+      };
+      const topDrifters = [{
+        task_pattern: 'dispatch:mid',
+        reader: 'observability',
+        count_drift: 1,
+        latency_drift: 5,
+        cost_drift: 0.00001,
+        sampled_at: '2026-04-24 00:00:00',
+      }];
+      const db = createMockDb({
+        firstResults: [readiness],
+        allResults: [distribution, topDrifters],
+      });
+      const app = createApp(db);
+
+      const res = await app.request('/api/shadow-read-drift?days=14&reader=observability');
+      expect(res.status).toBe(200);
+      const json = await res.json() as any;
+      expect(json).toEqual({
+        days: 14,
+        reader_filter: 'observability',
+        distribution,
+        readiness,
+        top_drifters: topDrifters,
+      });
+      expect(db._queries[0].bindings).toEqual([14, 'observability']);
+      expect(db._queries[1].bindings).toEqual(['observability', 14]);
+      expect(db._queries[2].bindings).toEqual([14, 'observability']);
+    });
+
+    it('defaults invalid days and omits reader filter', async () => {
+      const db = createMockDb({
+        firstResults: [{ total_pairs: 0, distinct_procedures: 0, clean_pairs: 0, ready_pairs: 0 }],
+        allResults: [[], []],
+      });
+      const app = createApp(db);
+
+      const res = await app.request('/api/shadow-read-drift?days=999');
+      expect(res.status).toBe(200);
+      const json = await res.json() as any;
+      expect(json.days).toBe(7);
+      expect(json.reader_filter).toBeNull();
+      expect(db._queries[0].bindings).toEqual([7]);
+      expect(db._queries[1].bindings).toEqual([7]);
+      expect(db._queries[2].bindings).toEqual([7]);
+    });
+
+    it('defaults days=0 to fallback', async () => {
+      const db = createMockDb({
+        firstResults: [{ total_pairs: 0, distinct_procedures: 0, clean_pairs: 0, ready_pairs: 0 }],
+        allResults: [[], []],
+      });
+      const app = createApp(db);
+
+      const res = await app.request('/api/shadow-read-drift?days=0');
+      expect(res.status).toBe(200);
+      const json = await res.json() as any;
+      expect(json.days).toBe(7);
+    });
+  });
+
   describe('GET /agenda', () => {
     it('returns active agenda items', async () => {
       const items = [