HeartRateRecovery accepts accumulated disconnected high-intensity segments #55

Summary

HeartRateRecovery.calculate requires 120 seconds of sustained Zone-3-or-higher effort near workout end, but both Swift and Kotlin currently add eligible durations across gaps longer than the 10-second continuity cap. Several short disconnected segments can therefore satisfy the gate even though no continuous segment reaches 120 seconds.

Deterministic reproduction

Use three 40-second high-HR segments, each sampled every 10 seconds and separated by an 11-second gap:

• offsets from workout end: -300,-290,-280,-270,-260
• -249,-239,-229,-219,-209
• -198,-188,-178,-168,-158
• all at 145 bpm with maxHR = 200 (70% threshold = 140)
• cessation samples at -30,-15,0, 130 bpm
• 1-minute samples at +59,+60,+61, 110 bpm
• workout range end-300...end

No continuous high-intensity segment exceeds 40 seconds. The expected result is null.

Observed on exact fork meta base 06e3ee7868d18a0af447b10eef712dbc92f52cfd:

• Swift focused test: XCTAssertNil failed with Result(endHR: 130, after1Minute: Optional(20), after2Minutes: nil, after5Minutes: nil).
• Kotlin focused test: assertNull failed with Result(endHr=130, after1Minute=20, after2Minutes=null, after5Minutes=null).

Cause

Both sustainedSeconds helpers skip an interval when gap > maximumContinuousGapSeconds, but retain the accumulated total. Later valid intervals resume adding to that same total instead of starting a new continuous segment.

Expected behavior

Eligibility should require at least one continuous qualifying high-intensity segment of 120 seconds. A disqualifying gap or below-threshold interval should break/reset the current segment; disconnected segments must not accumulate.

This is shared cross-platform behavior, not a Swift/Kotlin parity difference. The parity rollout should characterize it explicitly until a separately authorized production fix lands.