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REVIEW 4 major objections 7 minor 24 references

A Model Predictive Control Framework for Assisted Vehicle Drifting

T0 review · 4 major / 7 minor · reviewed 2026-08-02 · deepseek-v4-flash

Pith's one-line read A nonlinear model-predictive controller can stabilize drifting using a simple single-track model, letting the driver set the drift angle through the steering wheel.

desk verdict A genuinely useful NMPC architecture for RWD assisted drifting, honestly demonstrated in one high-fidelity scenario — worth refereeing, but the central claim needs more than a single favorable run. read the letter →

arxiv 2607.15117 v1 pith:7FJ2ETCF submitted 2026-07-16 eess.SY cs.SY

classification eess.SYcs.SY
keywords assisteddriftingnonlinearmodelpredictivecontrolvehicledynamicssideslipregulationsteer-by-wiredrive-by-wireactivationlogicrear-wheeldrive
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper tries to establish that assisted vehicle drifting does not require complex vehicle models, precomputed drift equilibria, or a known path. It claims that a nonlinear model predictive controller (NMPC) using only a single-track model with basic tire dynamics can stabilize a rear-wheel-drive car in a sustained drift while a human driver continuously commands the desired sideslip angle through the steering wheel. The controller takes over steering and rear throttle through steer-by-wire and drive-by-wire, freezing speed at the moment of activation. A separate activation logic engages the controller only when the yaw rate approaches its steady-state limit and the driver floors the throttle, so normal driving is unaffected. If true, this would make drift assistance practical for non-expert drivers.

What carries the argument

The key mechanism is the NMPC formulated in input-velocity form, where the control variables are the derivatives of steering and throttle commands. This lets the controller act as an online equilibrium solver: it does not need a precomputed drift point, only references for speed and sideslip. The activation logic uses the phase-plane observation that a saddle-node bifurcation occurs when counter-steering becomes necessary, formalized by the condition r > λ r_ss,max together with a full-throttle pedal signal. Once active, the driver's steering wheel is linearly mapped to a sideslip reference through β_ref = κβ δ_d, so the human chooses the drift attitude while the NMPC handles the actual actu

What would settle it

A driving-simulator study with non-expert drivers attempting to activate the system and hold a commanded sideslip: if a large fraction of drivers cannot trigger activation reliably, or cannot achieve the sideslip they intend through the linear steering mapping, the paper's central claim about an intuitive assist architecture would be contradicted.

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Extended reading notes

Core claim

The central claim is that a reduced-order NMPC, with only vehicle speed and sideslip angle as references, can converge to and stabilize a drift equilibrium without explicit equilibrium pre-computation. In high-fidelity simulation, the controller initiates the drift by counter-steering at the moment the saddle-node bifurcation is approached, sustains the drift as the driver varies the sideslip reference, and smoothly returns control to the driver on straight-line conditions. The prediction model is deliberately simple: a nonlinear single-track vehicle with a basic tire force model, driven only by steering and rear longitudinal force.

Load-bearing premise

The driver-interaction layer—activation triggered by crossing 90% of the steady-state yaw-rate limit with full throttle, and the linear mapping from steering angle to sideslip reference—is hand-tuned and has not been tested with human drivers; if drivers cannot reliably trigger or command the drift, the system fails no matter how well the NMPC stabilizes.

Editorial extensions

If this is right

  • Drift assistance can be built on a deliberately simple prediction model, easing real-time implementation and calibration.
  • No precomputed drift equilibria or prior path knowledge are needed; the controller finds and stabilizes the drift point online.
  • The driver stays in the loop and continuously adjusts the drift angle through the steering wheel, rather than just triggering a scripted maneuver.
  • The activation logic based on yaw rate threshold and full-throttle intent prevents interference during ordinary driving.
  • Control authority is handed back to the driver automatically once the vehicle returns to straight-line conditions.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The fixed gains λ = 0.9 and κβ = -1/5 are hand-tuned; a sensitivity study across drivers and vehicle types would clarify how much tuning the architecture needs in practice.
  • Because the controller only needs speed and sideslip references, the same decoupling idea could generalize to other limit-handling interventions, such as emergency obstacle avoidance.
  • A human-in-the-loop simulator test could test whether drivers intuitively trigger activation and map their steering intent to the desired sideslip; that is the next necessary validation step.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 7 minor

Summary. The paper proposes a nonlinear MPC framework for assisted drifting on a rear-wheel-drive vehicle with steer-by-wire and drive-by-wire interfaces. The driver's steering wheel is mapped to a sideslip reference through a linear gain (β_ref = κβ δ_d), and an activation logic based on a yaw-rate threshold and full-throttle input engages the controller. The NMPC uses a single-track model with a Fiala tire model, in an input-velocity formulation, to track vehicle speed and sideslip references using steering and throttle commands. Validation consists of a nominal model-in-the-loop equilibrium convergence test (Section IV-A) and one high-fidelity VI-CarRealTime simulation with scripted driver inputs (Section IV-B), showing activation, drift stabilization, and deactivation. The authors state that speed tracking is 'not fully accurate' and attribute this to 'significant model mismatch.'

Significance. The contribution is a promising architecture for driver-in-the-loop drift assistance on a rear-drive vehicle with reduced actuation authority. The idea of using the steering wheel as a sideslip reference is intuitive and potentially enabling for non-expert drivers. The paper is transparent about the limitations of its high-fidelity test and provides explicit tuning parameters, which aids reproducibility. The nominal convergence test (Fig. 3) is a useful demonstration that the velocity-form NMPC can discover drift equilibria without precomputation. If the high-fidelity result is corroborated by more extensive validation, the framework would be a valuable step beyond current 4WD/EV-specific assist systems. However, at present the central empirical claim rests on a single simulation with acknowledged model mismatch, and the driver-interaction layer is untested with human drivers.

major comments (4)
  1. [III-B, Eqs. (10)-(17)] The prediction model (1) is written in terms of rear longitudinal force F_xr, but the NMPC state includes the throttle signal τ_c (see (10)) and the control variable u_τc. No mapping from τ_c to F_xr is defined anywhere in the manuscript. Without this map, the OCP (12)-(17) is not fully specified and the results cannot be reproduced or independently checked. Please provide the throttle-to-force relationship used in the prediction model and state whether the same map is used in the high-fidelity VI-CarRealTime plant.
  2. [IV-B, Fig. 4] The high-fidelity validation is a single scripted run. The text explicitly states that 'tracking, especially for the vehicle speed, is not fully accurate' and attributes this to 'significant model mismatch.' No quantitative tracking errors, repeated runs, or sensitivity studies are reported. Consequently, the abstract's claim that 'the proposed architecture can stabilize drifting maneuvers' is supported by only one trajectory with acknowledged model error. Please add quantitative error metrics (e.g., RMSE/MAE for V and β), multiple scenarios (different activation speeds, reference profiles, tire/road friction), and at least a limited robustness analysis to support the general claim.
  3. [III-A, Eqs. (8)-(15)] The activation/deactivation logic and the sideslip reference mapping are central to the 'assisted' aspect of the framework, but they are only validated with synthetic scripted inputs. The gains λ=0.9 and κβ=-1/5 are hand-tuned; no sensitivity analysis is given, and no human-in-the-loop data support the assertion that the interface is intuitive or that the full-throttle condition reliably indicates deliberate intent. Please provide a sensitivity analysis of λ and κβ, or soften the claims about driver intent and usability to match the evidence presented.
  4. [III-B, Eq. (17); IV-A] The term 'stabilize' in the abstract is strong given that the receding-horizon controller (12)-(17) has no terminal cost/constraint or stability guarantee. The nominal test (Fig. 3) demonstrates convergence in a 5 s simulation under perfect model knowledge for a limited set of initial conditions, and the high-fidelity test is a single run. This may be acceptable for an empirical study, but the wording should be restricted to 'stabilizes the simulated vehicle in the tested conditions' unless a formal or more extensive empirical stability argument is provided.
minor comments (7)
  1. [III-B, Eq. (12d), (16)] The symbol r is used both for yaw rate in (1b)-(1c) and for the constraint vector in (12d) and (16). This is confusing; please use a different symbol (e.g., ρ) for the constraint bounds.
  2. [III-A, Eq. (8)] The condition 'τ_d = 100' should be written as 'τ_d = 100%' or 'τ_d = τ_max' to avoid ambiguity.
  3. [III-B, Eq. (13a)] In M(ξ) = 1/2 ||h_N(ξ,u)||_{W_N}, u is not an argument of h_N as defined in (13c). Correct to M(ξ) = 1/2 ||h_N(ξ)||_{W_N}.
  4. [IV, Fig. 3 and Fig. 4] Axis labels for sideslip and throttle are rendered as 'Sideslip, -' and 'Throttle, =' with missing Greek letters; please fix.
  5. [II, Eq. (7)] The symbol F_ST_z,r is not defined in the text; please define the static rear axle vertical load.
  6. [References] Reference [20] is incomplete ('2011, na'). Please provide full bibliographic details.
  7. [III-A, Eq. (8), Fig. 5a] The activation condition (8) uses signed yaw rate, while Fig. 5a plots the absolute value. Clarify how the condition is applied for drifts in the opposite direction.

Circularity Check

0 steps flagged · score 2.0 of 10

No circular derivation found: the central stabilization claim is validated against an external high-fidelity simulator; self-citations are motivational, not load-bearing.

full rationale

The paper's derivation chain is not circular. The NMPC formulation (12)-(17) uses a single-track prediction model with Fiala tires and tracks velocity and sideslip references; the high-fidelity validation (Section IV-B) is performed in VI-CarRealTime, an external plant model, so the claim that the simple model 'can stabilize drifting maneuvers' is not forced by the controller's internal model. The equilibrium convergence test in Section IV-A uses the same model for plant and predictor, but the paper explicitly labels it a nominal-condition check ('under the assumption of perfect knowledge of the vehicle model'), and the main result does not rest on this self-consistency test. The hand-tuned gains λ=0.9 and κβ=-1/5, the NMPC weights, and the activation thresholds are design choices, not parameters fitted to the validation outcome, so no fitted input is renamed as a prediction. The cited works [21] and [25] are authored in part by the present authors, but they are used only to motivate the activation logic and to interpret the phase-plane plots; they do not supply the stabilization result. Even if those citations were removed, the architecture and the VI-CarRealTime demonstration would stand. The paper's own admission that speed tracking is 'not fully accurate' and 'can be attributed to significant model mismatch' is an honest statement of a robustness limitation, not evidence of circularity. The absence of human-in-the-loop data for the driver-interaction layer is a validation gap, not a circular step. Overall, the central claim has independent empirical content, with only minor, non-load-bearing self-citation, warranting a low score of 2.

Assumptions & free parameters 6 free parameters · 7 assumptions · 0 invented entities

The central claim rests on modeling and tuning assumptions rather than on fitted physical parameters: the simple prediction model, the hand-tuned activation gain λ and reference gain κβ, the NMPC weights, and the unvalidated driver-interaction heuristics. No new physical entities are introduced.

free parameters (6)
  • Activation sensitivity λ = 0.9
    Scales the yaw-rate threshold in Eq. (8), r > λ r_ss,max; chosen by hand to tune how easily the controller engages.
  • Sideslip reference gain κβ = -1/5
    Linear map β_ref = κβ δ_d in Eq. (15); chosen by hand to relate steering-wheel angle to sideslip reference.
  • NMPC weight matrices W, W_N = W = diag(10^3/Vmax, 10^3/βmax, 15·10^2/umaxδc, 10^3/umaxτc); W_N = diag(10^3/Vmax, 10^3/βmax)
    Stage and terminal cost weights, hand-tuned; determine the trade-off between reference tracking and actuator effort.
  • Actuator and slew-rate limits = δmax_c=3π, τmax_c=100, umaxδc=π, umaxτc=1500
    Constraints in Eq. (20); chosen for the simulated vehicle but not justified as physical datasheet limits.
  • Prediction horizon T and sampling time T_s = not reported
    N = T/T_s is used in Eq. (17), but numerical values are not given; central to real-time feasibility and closed-loop behavior.
  • Deactivation dwell time Δt = not reported
    Eq. (9) requires straight-line conditions to hold for Δt before deactivation; the duration is not specified.
assumptions (7)
  • domain assumption Single-track model (1)-(5) with Fiala tire model captures the drifting dynamics of the simulated RWD vehicle.
    Used as the NMPC prediction model; the paper asserts sufficiency but does not quantify prediction error against VI-CarRealTime.
  • domain assumption Vehicle and tire parameters in Table I match the high-fidelity vehicle in VI-CarRealTime.
    Controller performance depends on these nominal parameters; no identification or uncertainty analysis is given.
  • ad hoc to paper The activation condition r > λ r_ss,max together with full throttle reliably indicates deliberate drift intent and that counter-steering is required.
    Heuristic based on phase-plane reasoning; not validated statistically with human drivers or across driving scenarios.
  • ad hoc to paper The linear sideslip reference β_ref = κβ δ_d is an intuitive and safe driver interface.
    The mapping is assumed without user studies; non-expert drivers may not find it intuitive.
  • domain assumption VI-CarRealTime is a faithful high-fidelity representation of a real RWD vehicle.
    All validation is performed in this commercial simulator; no physical experiments are presented.
  • domain assumption Real-Time Iteration with one SQP iteration per sampling step yields acceptable suboptimality and closed-loop behavior.
    RTI is an approximation; the paper does not quantify suboptimality or provide closed-loop stability guarantees.
  • domain assumption The steady-state maximum yaw-rate formulas (6)-(7) from [22] apply to this vehicle and operating conditions.
    Used to set the activation threshold; relies on prior steady-state analysis without re-validation here.

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Cite this review

Pith. "Pith review of A Model Predictive Control Framework for Assisted Vehicle Drifting." pith.science (2026). https://pith.science/paper/7FJ2ETCF

@misc{pith2026260715117,
  author       = {Pith},
  title        = {Pith review of: A Model Predictive Control Framework for Assisted Vehicle Drifting},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/7FJ2ETCF}},
  note         = {Machine review of arXiv:2607.15117}
}
read the original abstract

Model Predictive Control (MPC) has been widely applied to autonomous vehicle drifting. Assisted drifting, that is where the driver remains in the loop, is still comparatively underexplored. Existing approaches often rely on restrictive assumptions, such as precomputed drift equilibria, full actuation authority, or prior path knowledge, which limit applicability to expert drivers. This paper proposes a nonlinear model predictive control (NMPC) framework for assisted drifting on a rear-wheel-drive vehicle. Through steer-by-wire and drive-by-wire interfaces, the controller decouples driver commands from direct actuator inputs, allowing the driver to regulate the desired sideslip through the steering wheel while the NMPC maintains vehicle stability. A dedicated activation logic ensures that the controller engages only under deliberate driver intent. High-fidelity simulations show that the proposed architecture can stabilize drifting maneuvers using a simple single-track prediction model with basic tire dynamics, even when the sideslip reference is continuously varied by the driver.

Figures

Figures reproduced from arXiv: 2607.15117 by the authors.

Figure 1
Figure 1. Schematic representation of the single track model [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Architecture of the proposed control framework vali [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Validation of the controller using the single-track [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figures from the paper (1 more)
Figure 5
Figure 5. Figure 5: Phase-plane trajectories of the uncontrolled single-track [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]

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Reference graph

Works this paper leans on

24 extracted references · 4 canonical work pages

  1. [1]

    On the dynamics of automobile drifting,

    M. Abdulrahim, “On the dynamics of automobile drifting,” inSAE Technical Paper Series, ser. ANNUAL, vol. 1. SAE International, Apr. 2006. [Online]. Available: http://dx.doi.org/10.4271/2006-01-1019

  2. [2]

    Justifying emergency drift control for automated vehicles,

    T. Zhao, E. Yurtsever, and G. Rizzoni, “Justifying emergency drift control for automated vehicles,”IFAC-PapersOnLine, vol. 55, no. 24, pp. 141–148, 2022. [Online]. Available: http://dx.doi.org/10.1016/j.ifacol.2022.10.275

  3. [3]

    Autonomous drifting using torque vectoring: Innovating active safety,

    B. Lenzo, T. Goel, and J. Christian Gerdes, “Autonomous drifting using torque vectoring: Innovating active safety,”IEEE Transactions on Intelligent Transportation Systems, vol. 25, no. 11, pp. 17 931–17 939, Nov. 2024. [Online]. Available: http://dx.doi.org/10.1109/TITS.2024.3437177

  4. [4]

    Equilibrium analysis of drifting vehicles for control design,

    R. Y . Hindiyeh and J. C. Gerdes, “Equilibrium analysis of drifting vehicles for control design,” inASME 2009 Dynamic Systems and Control Conference, Volume 1, ser. DSCC2009. ASMEDC, Jan. 2009, pp. 181–188. [Online]. Available: http://dx.doi.org/10.1115/DSCC2009- 2626

  5. [5]

    Steady-state drifting stabilization of rwd vehicles,

    E. Velenis, D. Katzourakis, E. Frazzoli, P. Tsiotras, and R. Happee, “Steady-state drifting stabilization of rwd vehicles,”Control Engineering Practice, vol. 19, no. 11, pp. 1363–1376, Nov. 2011. [Online]. Available: http://dx.doi.org/10.1016/j.conengprac.2011.07.010

  6. [6]

    A controller framework for autonomous drifting: Design, stability, and experimental validation,

    R. Y . Hindiyeh and J. Christian Gerdes, “A controller framework for autonomous drifting: Design, stability, and experimental validation,” Journal of Dynamic Systems, Measurement, and Control, vol. 136, no. 5, Jul. 2014. [Online]. Available: http://dx.doi.org/10.1115/1.4027471

  7. [7]

    Toward automated vehicle control beyond the stability limits: Drifting along a general path,

    J. Y . Goh, T. Goel, and J. Christian Gerdes, “Toward automated vehicle control beyond the stability limits: Drifting along a general path,” Journal of Dynamic Systems, Measurement, and Control, vol. 142, no. 2, Nov. 2019. [Online]. Available: http://dx.doi.org/10.1115/1.4045320

  8. [8]

    Exploiting linear structure for precision control of highly nonlinear vehicle dynamics,

    M. T. Peterson, T. Goel, and J. C. Gerdes, “Exploiting linear structure for precision control of highly nonlinear vehicle dynamics,”IEEE Transactions on Intelligent Vehicles, vol. 8, no. 2, pp. 1852–1862, Feb

Show all 24 references
  1. [9]

    Combined fast control of drifting state and trajectory tracking for autonomous vehicles based on mpc controller,

    C. Hu, X. Zhou, R. Duo, H. Xiong, Y . Qi, Z. Zhang, and L. Xie, “Combined fast control of drifting state and trajectory tracking for autonomous vehicles based on mpc controller,” in2022 International Conference on Robotics and Automation (ICRA). IEEE, May 2022, pp. 1373–1379. ...

  2. [10]

    Beyond the stable handling limits: nonlinear model predictive control for highly transient autonomous drifting,

    J. Y . M. Goh, M. Thompson, J. Dallas, and A. Balachandran, “Beyond the stable handling limits: nonlinear model predictive control for highly transient autonomous drifting,”Vehicle System Dynamics, vol. 62, no. 10, pp. 2590–2613, Feb. 2024. [Online]. Available: http://dx.doi.o...

  3. [11]

    A real-time nonlinear model predictive control strategy for stabilization of an electric vehicle at the limits of handling,

    E. Siampis, E. Velenis, S. Gariuolo, and S. Longo, “A real-time nonlinear model predictive control strategy for stabilization of an electric vehicle at the limits of handling,”IEEE Transactions on Control Systems Technology, vol. 26, no. 6, pp. 1982–1994, Nov. 2018. [Online]. ...

  4. [14]

    Toward intuitive drift assist control: driver drift intention recognition using a data-based approach,

    ——, “Toward intuitive drift assist control: driver drift intention recognition using a data-based approach,”Vehicle System Dynamics, pp. 1–26, Jun. 2025. [Online]. Available: http://dx.doi.org/10.1080/00423114.2025.2520492

  5. [15]

    Vehicle drifting dynamics: discovery of new equilibria,

    S. Milani, H. Marzbani, and R. N. Jazar, “Vehicle drifting dynamics: discovery of new equilibria,”Vehicle System Dynamics, vol. 60, no. 6, pp. 1933–1958, Feb. 2021. [Online]. Available: http://dx.doi.org/10.1080/00423114.2021.1887499

  6. [16]

    Dynamics and control of drifting in automobiles,

    R. Y . Hindiyeh, “Dynamics and control of drifting in automobiles,” Ph.D. dissertation, Stanford University, 2013. [Online]. Available: https://purl.stanford.edu/vz162hz7668

  7. [17]

    Opening new dimensions: Vehicle motion planning and control using brakes while drifting,

    T. Goel, J. Y . Goh, and J. C. Gerdes, “Opening new dimensions: Vehicle motion planning and control using brakes while drifting,” in2020 IEEE Intelligent Vehicles Symposium (IV). IEEE, Oct. 2020, pp. 560–565. [Online]. Available: http://dx.doi.org/10.1109/IV47402.2020.9304728

  8. [18]

    T. D. Gillespie,Fundamentals of Vehicle Dynamics. Warrendale, PA: SAE International, 1992

  9. [19]

    Steady-state cornering equilibria and stabilisation for a vehicle during extreme operating conditions,

    E. Velenis, E. Frazzoli, and P. Tsiotras, “Steady-state cornering equilibria and stabilisation for a vehicle during extreme operating conditions,”International Journal of Vehicle Autonomous Systems, vol. 8, no. 2/3/4, p. 217, 2010. [Online]. Available: http://dx.doi.org/10.150...

  10. [20]

    Analysis of steady-state vehicle handling and driver behaviour at extreme driving conditions,

    J. Edelmann, M. Pl ¨ochl, and P. Pfeffer, “Analysis of steady-state vehicle handling and driver behaviour at extreme driving conditions,” 2011, na

  11. [21]

    Drifting maneuver investigation via phase plane analysis of experimental data,

    G. Righetti, G. N. dell’Annunziata, F. Farroni, M. Massaro, and B. Lenzo, “Drifting maneuver investigation via phase plane analysis of experimental data,” inAdvanced Vehicle Control Symposium. Springer, 2024, pp. 22–28

  12. [22]

    Vehicle control synthesis using phase portraits of planar dynamics,

    C. G. Bobier-Tiu, C. E. Beal, J. C. Kegelman, R. Y . Hindiyehet al., “Vehicle control synthesis using phase portraits of planar dynamics,” Vehicle System Dynamics, vol. 57, no. 9, pp. 1318–1337, 2019

  13. [23]

    Diehl, H

    M. Diehl, H. J. Ferreau, and N. Haverbeke,Efficient Numerical Methods for Nonlinear MPC and Moving Horizon Estimation. Berlin, Heidel- berg: Springer Berlin Heidelberg, 2009, pp. 391–417

  14. [24]

    Matmpc - a matlab based toolbox for real-time nonlinear model predictive control,

    Y . Chen, M. Bruschetta, E. Picotti, and A. Beghi, “Matmpc - a matlab based toolbox for real-time nonlinear model predictive control,” 06 2019, pp. 3365–3370

  15. [25]

    On the investigation of car steady-state cornering equilibria and drifting,

    G. Righetti, E. Binetti, R. Pinto de Castro, R. Lotet al., “On the investigation of car steady-state cornering equilibria and drifting,” SAE International, Technical Paper 2024-01-2764, 2024. [Online]. Available: https://doi.org/10.4271/2024-01-2764

  16. [2023]

    Available: http://dx.doi.org/10.1109/TIV .2022.3171734

    [Online]. Available: http://dx.doi.org/10.1109/TIV .2022.3171734

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Reviewed August 2, 2026 · model on record in the stance chip above.