From 4ee75de984a90792f0691583968b23b6c72a1ecd Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sun, 2 Aug 2026 01:00:25 +0000
Subject: [PATCH 1/3] test(ekf): bracket the ZARU rest gate with an
 above-threshold boundary case
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zaruStopsYawDriftWhenStationaryFlat covers a gyro bias BELOW zuptGyroThreshold
(ZARU arrests the resting heading drift). This adds the complementary boundary:
a standing gyro bias ABOVE the threshold makes the raw rate itself read as
motion, so the device is classified MOVING, ZARU never engages, and yaw
free-runs — the regime that only an absolute AoA reference can recover. Maps to
the on-device self-diagnostic's "motionMode != STATIONARY" branch used to
localize orientation drift.

Verified green via :common:jvmTest.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WppuiKZt4CuQxX4N7k6SVR
---
 .../aether/mofe/engine/ImuFusionEKFTest.kt    | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/common/src/commonTest/kotlin/com/aether/mofe/engine/ImuFusionEKFTest.kt b/common/src/commonTest/kotlin/com/aether/mofe/engine/ImuFusionEKFTest.kt
index 81f01b5..cfa8249 100644
--- a/common/src/commonTest/kotlin/com/aether/mofe/engine/ImuFusionEKFTest.kt
+++ b/common/src/commonTest/kotlin/com/aether/mofe/engine/ImuFusionEKFTest.kt
@@ -724,6 +724,39 @@ class ImuFusionEKFTest {
 			"ZARU should drive the gyro-bias estimate to the resting reading (~0.05). Got: $bg")
 	}
 
+	@Test
+	fun gyroBiasAboveRestThresholdReadsMovingSoZaruCannotAnchorYaw() {
+		// Rest-gate BOUNDARY — the on-device diagnostic tree's "motionMode ≠ STATIONARY"
+		// branch. ZARU only fires while the RAW-gyro rest gate reads the device as still. A
+		// standing gyro bias that EXCEEDS zuptGyroThreshold makes the raw rate itself look
+		// like motion, so the device reads MOVING, ZARU never engages, and the bias integrates
+		// into an ever-growing heading — the regime where only an absolute AoA reference can
+		// recover yaw. Complements zaruStopsYawDriftWhenStationaryFlat (a bias BELOW the gate,
+		// which ZARU arrests); together they bracket the gate. Bias is derived from the config
+		// so the test tracks the threshold rather than hard-coding it.
+		val cfg = EkfConfig()                          // zaruEnabled = true (default)
+		val biasZ = cfg.zuptGyroThreshold + 0.08       // rad/s, safely ABOVE the rest gate
+		val e = ImuFusionEKF(TARGET_1, cfg)
+		e.update(PositionSolution(TARGET_1, Timestamp(0), Vector3D(0.0, 0.0, 0.0),
+			Matrix.diagonal(0.001, 0.001, 0.001), 2.0, true))
+		var t = 0L
+		var facingAt150: Vector3D? = null
+		var facingLast = Vector3D(0.0, 1.0, 0.0)
+		repeat(250) { i ->
+			t += 10_000                                // 100 Hz
+			e.predict(ImuSample(Timestamp(t), Vector3D(0.0, 0.0, 9.81), Vector3D(0.0, 0.0, biasZ)))
+			if (i == 149) facingAt150 = facingOf(e)
+			if (i >= 149) facingLast = facingOf(e)
+		}
+		// Raw rate exceeds the gate → never classified at rest → ZARU disarmed.
+		assertEquals(MotionMode.MOVING, e.motionMode,
+			"a gyro bias above zuptGyroThreshold must read MOVING, holding ZARU off")
+		// With ZARU disarmed the standing bias integrates → the heading keeps walking.
+		val drift = angle(facingAt150!!, facingLast)
+		assertTrue(drift > 0.03,
+			"with the rest gate holding ZARU off, a standing gyro bias must walk the heading (got $drift rad)")
+	}
+
 	// ── Motion mode + trust-gated ZUPT (mesh gear-shift) ────────────────────────
 
 	@Test
-- 
2.43.0