diff --git a/apps/api/tests/broker/expand.test.ts b/apps/api/tests/broker/expand.test.ts
index b76e0a3..a80d333 100644
--- a/apps/api/tests/broker/expand.test.ts
+++ b/apps/api/tests/broker/expand.test.ts
@@ -1,23 +1,21 @@
 /**
- * RED test stubs for expandOccurrences() — Wave 0 state.
+ * Tests for expandOccurrences() — GREEN state.
  *
- * These tests encode the concrete behavioral contracts that Plan 02 (GREEN phase) must satisfy.
- * All tests reference the not-yet-built module apps/api/src/broker/expand.ts and are expected
- * to fail until that module is implemented.
- *
- * Contracts locked here:
+ * Contracts verified here:
  *  1. DST wall-clock correctness: occurrences in America/New_York must show 10:00 local time
  *     on BOTH sides of the March 2026 EST→EDT boundary (not shifted ±1h by UTC fallback).
  *  2. All-day events return allDay:true and start as 'YYYY-MM-DD' with no time component.
  *  3. EXDATE exclusions reduce the returned array by exactly one occurrence.
+ *  4. Timed event start/end strings are IANA-annotated ('...±HH:MM[IANA/Zone]') so
+ *     Temporal.ZonedDateTime.from() can parse them without throwing (cross-contract test).
  */
 
+import 'temporal-polyfill/global'
 import { describe, it, expect } from 'vitest'
 import { readFileSync } from 'fs'
 import { join, dirname } from 'path'
 import { fileURLToPath } from 'url'
 
-// Not yet built — import will fail (RED state) until Plan 02 implements expand.ts
 import { expandOccurrences } from '../../src/broker/expand.js'
 
 const __dirname = dirname(fileURLToPath(import.meta.url))
@@ -27,7 +25,7 @@ function loadFixture(name: string): string {
   return readFileSync(join(FIXTURES, name), 'utf8')
 }
 
-describe('expandOccurrences — RED stubs (Wave 0)', () => {
+describe('expandOccurrences', () => {
 
   describe('DST correctness — weekly-dst.ics', () => {
     it('returns 10:00 America/New_York wall-clock time on BOTH sides of March 2026 DST boundary', () => {
@@ -56,13 +54,14 @@ describe('expandOccurrences — RED stubs (Wave 0)', () => {
       expect(occurrences.length).toBeGreaterThan(0)
 
       // The key contract: every occurrence must have local hour === 10 in America/New_York.
-      // We verify this by checking the ISO string offset — before DST: offset is -05:00
-      // (so 10:00-05:00 = 15:00 UTC); after DST: offset is -04:00 (10:00-04:00 = 14:00 UTC).
-      // Both are valid as long as the LOCAL wall-clock hour is 10.
+      // We verify this by checking the ISO string — before DST: '...T10:00:00-05:00[America/New_York]'
+      // after DST: '...T10:00:00-04:00[America/New_York]'. Both include the IANA bracket.
       for (const occ of occurrences) {
         expect(occ.allDay).toBe(false)
-        // start must be an offset-aware ISO string: '2026-03-01T10:00:00-05:00' or similar
+        // start must be IANA-annotated: '2026-03-01T10:00:00-05:00[America/New_York]'
         expect(occ.start).toMatch(/T10:00:00/)
+        // Must include IANA bracket — offset-only strings fail Temporal.ZonedDateTime.from()
+        expect(occ.start).toContain('[America/New_York]')
       }
 
       // Explicitly check one pre-transition occurrence (EST) and one post-transition (EDT)
@@ -72,10 +71,12 @@ describe('expandOccurrences — RED stubs (Wave 0)', () => {
       expect(preTransition).toBeDefined()
       expect(postTransition).toBeDefined()
 
-      // Pre-transition occurrence: EST offset -05:00
+      // Pre-transition occurrence: EST — '2026-03-01T10:00:00-05:00[America/New_York]'
       expect(preTransition!.start).toContain('T10:00:00')
-      // Post-transition occurrence: EDT offset -04:00
+      expect(preTransition!.start).toContain('-05:00[America/New_York]')
+      // Post-transition occurrence: EDT — '2026-03-15T10:00:00-04:00[America/New_York]'
       expect(postTransition!.start).toContain('T10:00:00')
+      expect(postTransition!.start).toContain('-04:00[America/New_York]')
     })
   })
 
@@ -138,4 +139,43 @@ describe('expandOccurrences — RED stubs (Wave 0)', () => {
       expect(june15).toBeUndefined()
     })
   })
+
+  describe('Cross-contract: expand output → Temporal.ZonedDateTime.from (regression guard)', () => {
+    it('timed event start/end strings from weekly-dst.ics parse via Temporal.ZonedDateTime.from without throwing', () => {
+      // This is the integration test that was missing. It takes the actual serializeTime output
+      // (from expandOccurrences) and feeds each start/end through Temporal.ZonedDateTime.from()
+      // to prove the expand→hydrate contract holds end-to-end.
+      //
+      // Previously, serializeTime emitted offset-only strings like '2026-03-01T10:00:00-05:00'
+      // which caused Temporal.ZonedDateTime.from() to throw RangeError: Cannot parse.
+      // Now it emits IANA-annotated strings like '2026-03-01T10:00:00-05:00[America/New_York]'.
+      const rawVevent = loadFixture('weekly-dst.ics')
+      const windowStart = new Date('2026-03-01T00:00:00Z')
+      const windowEnd = new Date('2026-04-01T00:00:00Z')
+
+      const occurrences = expandOccurrences(
+        rawVevent,
+        windowStart,
+        windowEnd,
+        1,
+        'My Calendar',
+        1,
+        '#4A90D9',
+        false,
+      )
+
+      expect(occurrences.length).toBeGreaterThan(0)
+
+      for (const occ of occurrences) {
+        // These must not throw — this is the cross-service contract
+        expect(() => Temporal.ZonedDateTime.from(occ.start)).not.toThrow()
+        expect(() => Temporal.ZonedDateTime.from(occ.end)).not.toThrow()
+
+        // Parsed ZonedDateTime must round-trip the wall-clock hour
+        const startZdt = Temporal.ZonedDateTime.from(occ.start)
+        expect(startZdt.hour).toBe(10)
+        expect(startZdt.timeZoneId).toBe('America/New_York')
+      }
+    })
+  })
 })