Real rival straight-line passing assist — source QA

Status: Unreal player/rival source integration, NOT a playable, verified or UE5.8-compiled game. Only the existing original single physical rival can attempt this manoeuvre.

Gameplay improvement

The original AI slowed behind a slower player but never tried to pass, leading to repeated courtesy-brake following and occasional deadlocks. A new RivalStraightPassAssist can briefly steer toward a second lane on the existing original paved four-gate circuit.

This is real steering input used by the Unreal AI actor, not a decorative indicator. The current four checkpoint planes, lap clock, career rewards and player-controlled vehicle stay unchanged.

The new limited assist:

• Requires the same actual live player and rival Chaos actor positions, velocities, race eligibility and previously qualified tire, road and collision state already used for safe driving.
• Only starts on a sufficiently long original paved straight if a slower player is 1600–2400 cm ahead, the rival is closing by at least 300 cm/s, both vehicles are largely aligned with the road and at least 2150 cm remain before the next corner.
• New passes require at least 1.8 seconds before the measured closing motion reaches the conservative contact margin, and at least 4200 cm of runway before the next corner. On the original circuit the two shorter north/south straights are excluded from passing.
• Selects the road lane opposite the player's measured offset; deterministic tie-breaking avoids oscillation. Lane aim remains 440 cm from the centreline, inside the existing 800 cm road half-width. A local, 1000 cm ahead steering target causes an actual directional change rather than an imperceptible far-gate offset.
• Caps requested passing steering at 0.65 axis; never increases throttle, directly modifies physics velocity or claims a gate.
• Keeps a per-rival lane choice until the rival has drawn more than 550 cm ahead, reaches a corner or six seconds have elapsed. Qualified pause, restart, recovery and race-finish branches reset it.
• Cancels the assist with normal braking if the player enters the selected pass lane. Invalid measurements fail closed. The original YieldRivalToPlayer collision-courtesy braking still runs AFTER the attempt and may reduce acceleration/activate ordinary braking. If it activates braking, the new ResolveRivalPassTraffic restores normal route steering and cancels the active passing lane state.

This is NOT claimed to be autonomous guaranteed collision avoidance, multiplayer, official racing placement or a multi-opponent race. Actual Chaos body orientation, wheel traction and road boundaries still require evaluation with a real installed Windows game.

Regression checks

Tests/Standalone/RivalStraightPassAssistTests.cpp checks both long directional straights and safe refusal on short straights, right/left pass selection, lateral approach and stable target, finished pass, unsafe traffic, off-pavement/corner suppression, previous brake priority, malformed physical inputs, focus interruption and 20,000 road observations.

Tests/Editor/UnrealRivalStraightPassBindingTests.py asserts that the actual rival pawn supplies observed positions/velocities, preserves all normal road/traffic/corner/grip filters and resets passing state on invalid route, recovery, pause, restart or finish.

These are source and portable C++20 verification only.

Actual UE 5.8 Win64 hardware acceptance requirements

1. Compile the actual game through UE5.8/UHT, cook the owned map and install the actual 3D Win64 package. The separate experimental 2D Windows preview is not valid evidence of this feature.
2. Follow the rival on all four straights. Put a slow player ahead at offsets of -150, 0 and +150 cm, including same-pace, near stopped and suddenly changing lanes.
3. Confirm an actual physical lane transition, plausible passing time, no wall/grass entry and return to the verified next gate.
4. Confirm no brake/steer oscillations, collisions or unqualified extra acceleration across 30/60/120 FPS.
5. Test both handling modes, worn tires, heat/damage, off-road, focus loss, pause/resume, restart, recovery, event finish and player pawn replacement. Measure race gate completion and stalls.
6. Review original pass-lane spacing relative to rendered chassis and collision geometry; tune/disable passing if two vehicles do not genuinely clear each other.

The verified playable build release gate #148 remains open.