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REVIEW 3 major objections 4 minor 33 references

Bifrost-1: Bridging Multimodal LLMs and Diffusion Models with Patch-level CLIP Latents

T0 review · 3 major / 4 minor · reviewed 2026-08-05 · deepseek-v4-flash

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Pith's one-line read For two-dimensional SU(2) gauge theory with one massless Majorana fermion, the paper argues that a mod(2) index dictates which boundary-condition sectors survive the continuum limit, and that the fermion bilinear condensate is a topological

desk verdict A real lattice-QCD paper hiding behind a mismatched multimodal-LLM submission; the science is worth a referee's time once the postulate and the metadata are fixed. read the letter →

arxiv 2508.05954 v1 pith:T7SKSNNP submitted 2025-08-08 cs.CV cs.AIcs.CL

Han Lin , Jaemin Cho , Amir Zadeh , Chuan Li , Mohit Bansal This is my paper · ORCID
classification cs.CVcs.AIcs.CL PACS 11.15.Ha11.30.Rd
keywords mod(2)indexMajoranafermionoverlapfermionstopologicalcondensatelatticegaugetheorySU(2)boundaryconditionsspontaneoussymmetrybreaking
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

This paper asks whether the massless fermion bilinear condensate in two-dimensional SU(2) gauge theory with a single Majorana fermion is a spontaneous symmetry-breaking effect or a topological one. Using overlap fermions on the lattice, it shows that the mod(2) index — a rigidity of the fermion spectrum that forces exact zero modes to appear or not depending on boundary conditions — controls the continuum limit: only two of the four boundary-condition partition functions survive, while the other two vanish. The paper then defines a topological condensate as a ratio of mixed-boundary-condition determinants with zero modes removed, and finds it nonzero at every finite volume, tending to 0.162(3) per color degree of freedom, independent of the representation $J=1,2,3,4$. Spectral density and lowest-eigenvalue scaling indicate no spontaneous $\mathbb{Z}_2$ breaking; instead zero modes emerge only in the infinite-volume limit. This matters because it separates a genuine topological condensate from spontaneous breaking and shows that boundary conditions, normally finite-volume artifacts, can decide which partition functions exist.

What carries the argument

The central object is the gauge-field-dependent unitary operator $V=\sigma_3 R\sigma_3 R^\dagger$, where $R$ diagonalizes the Hermitian Wilson-Dirac operator $H_w$. Its spectrum is doubly degenerate and chiral-paired, with nonzero eigenvalues $e^{\pm i\phi_j}$; eigenvalues exactly $\pm1$ are zero modes and come in one pair each, producing a mod(2) index. The massive overlap Majorana Pfaffian factorizes as $m\prod_{j\neq0}(\cos^2(\phi_j/2)+m^2\sin^2(\phi_j/2))$, so the zero-mode factor $m$ can be removed and re-inserted through ratios of mixed-boundary partition functions; that ratio is what defines the topological bilinear condensate. The same spectral data feed the spectral-density criterio

What would settle it

Repeat the computation with dynamical fermions, putting the fermion determinant into the update instead of treating it as an observable, and check whether the mixed-boundary ratio still converges to $\Sigma^\infty=0.162(3)$ and whether the pure-gauge zero-mode fractions are reproduced. Alternatively, measure the spectral density at zero eigenvalue at several lattice spacings: a nonzero limiting $\rho(0)$, or lowest-eigenvalue scaling with $\gamma_m\to1$, would indicate spontaneous $\mathbb{Z}_2$ breaking and contradict the paper's conclusion.

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Extended reading notes

Core claim

In the continuum limit at fixed physical torus size $\ell$, with $L\to\infty$ and $\beta=L^2/\ell^2$, the fraction of gauge configurations carrying exact zero modes of the massless overlap Majorana operator tends to 1 or 0 according to a definite rule: untwisted gauge fields with periodic fermion boundary conditions have zero modes, anti-periodic ones do not; twisted gauge fields show the reverse. Consequently $Z_{++}$ and $Z_{--}$ are zero as continuum partition functions while $Z_{+-}$ and $Z_{-+}$ are not. Removing zero modes from the Pfaffian determinants lets ratios define topological bilinear condensates $\Sigma_{t,z,J}$; these are nonzero for all finite $\ell$ and all reach $\Sigma^\i

Load-bearing premise

The load-bearing premise is the explicitly postulated identification of the mixed-boundary-condition ratio with zero modes removed as the physical fermion bilinear condensate; if that postulate fails, the 0.162(3) value and the match to the Hamiltonian calculation collapse.

Editorial extensions

If this is right

  • Only two of the four boundary-condition partition functions survive the continuum limit: $Z_{++}$ and $Z_{--}$ vanish, so the theory's partition function depends on which sector is retained.
  • The topological condensate is nonzero at every finite volume and tends to $0.162(3)$ per color degree of freedom, independent of $J=1,2,3,4$; for $J=1$ it matches the Hamiltonian calculation after normalization.
  • There is no spontaneous $\mathbb{Z}_2$ symmetry breaking: the lowest Dirac eigenvalue scales as $\lambda_1\sim\ell^{-1-\gamma_m}$ with $0<\gamma_m<1$ and there is no finite spectral density at zero; zero modes emerge only in the infinite-volume limit.
  • The four mixed-boundary definitions of the condensate differ at finite $\ell$ but coincide as $\ell\to\infty$, making the condensate a boundary-condition-independent infinite-volume quantity.
  • The independent-plaquette action with $z=0$ reproduces the same infinite-volume condensate and no-spontaneous-breaking conclusion using a single partition function, without mixing boundary conditions.

Reading between the lines

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

  • If the zero-mode-removal identification survives a dynamical-fermion test, the same mixed-boundary-ratio construction could be exported to other theories with a mod(2) index, including higher-dimensional real-representation gauge theories, as a general way to separate topological from spontaneous condensates.
  • The decreasing trend in $\gamma_m$ with $J$ (from $0.814(36)$ at $J=1$ to $0.502(82)$ at $J=4$) hints that lowest-eigenvalue scaling, unlike the condensate, is sensitive to whether the infrared sector is gapped or massless; the paper reports the numbers but does not draw this connection.
  • One direct test of the paper's clustering argument: compute the fermion-bilinear two-point function at fixed boundary conditions; the paper's picture predicts it will not vanish at large separation unless the two mod(2) sectors are summed over.
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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

3 major / 4 minor

Summary. The manuscript (arXiv body: "Lattice study of two-dimensional SU(2) gauge theories with a single massless Majorana fermion") studies 2D SU(2) gauge theory with one massless Majorana fermion in the integer representation J, using overlap fermions and quenched gauge-field ensembles generated with the Wilson action. The paper claims that, in the continuum limit at fixed physical torus size, only one of the four mod(2) sectors survives for each choice of fermion and gauge boundary conditions, so that Z_{++} and Z_{--} vanish while Z_{+-} and Z_{-+} do not (Section IV). It defines a "topological bilinear condensate" as a ratio of mixed-boundary-condition partition functions with zero modes removed (Section V, Eqs. (56)-(63)) and reports a common infinite-volume value \Sigma^\infty_{t,z,J}=0.162(3) for J=1,2,3,4, matching the Hamiltonian result of [5] for J=1 after a factor-of-1/2 conversion. Spectral-density and lowest-eigenvalue analyses are used to argue against spontaneous Z2 symmetry breaking (Section VI). The paper also proposes an independent-plaquette (z=0) gauge action that reproduces the infinite-volume results with a single partition function (Section VII).

Significance. If the central identification is correct, the paper provides a concrete lattice realization of a mod(2)-index-induced fermion bilinear condensate that is non-zero in finite volume and survives the infinite-volume limit, while offering evidence against spontaneous chiral symmetry breaking. The results span J=1,2,3,4 and the claimed J-independence of the condensate per color degree of freedom is a substantive observation. The paper is technically careful in the overlap formalism, provides explicit spectral decompositions, uses jackknife errors for ratio observables, and supplies an analytic formula for the ratio of pure-gauge partition functions in Eq. (64). The main quantitative claim, however, is conditional on an explicitly postulated identification of a partition-function ratio with the physical fermion bilinear condensate; the paper labels this as a postulate, not a derived statement. The agreement with the independent Hamiltonian calculation [5] is an important cross-check, but the normalization and physical interpretation must be clarified before the numerical value can be taken as a measured condensate.

major comments (3)
  1. [Section V, Eq. (58)] Equation (58) states lim_{L->\infty} \bar Z'_{+-} = lim_{L->\infty} \bar Z'_{-+} = 0. But these are the no-zero-mode sectors (z=1 with anti-periodic fermions and z=-1 with periodic fermions), where the primed product coincides with the unprimed product and should be non-zero by the sector-survival claim of Section IV. Indeed Eq. (60) uses \bar Z_{+-} and \bar Z_{-+} as denominators, so if Eq. (58) were literal the ratios would be undefined. This is either a typo or an indication that the notation in Eqs. (56)-(57) is not what it appears to be. The definitions of \bar Z and \bar Z' must be clarified and corrected, because the central numerical value 0.162(3) is obtained from these ratios.
  2. [Section VII and Section V, Eqs. (59)-(63)] The identification of \bar Z'_{++}/\bar Z_{+-} (and the analogous ratios) with the expectation value of a fermion bilinear is explicitly postulated in Section VII ('we postulate a topological bilinear condensate'), not derived from the path-integral definition of \langle \psi\psi\rangle. Appendix A defines \Sigma_t(m) for a fixed background as a product of non-zero-mode factors, but the normalized ratio, the prefactor 1/[2m_w(2J+1)\ell L], and the factor 1/2 used in Eq. (67) to compare with [5] are not justified from a local operator insertion. If the identification or the normalization is off, the agreement 0.162(3) vs. the Hamiltonian value would be coincidental. A derivation from the Majorana generating functional, or at least a precise statement of the operational definition and its relation to a local bilinear, is needed for the central quantitative claim.
  3. [Section IV, Figure 1] The central sector-survival claim — that f tends to 0 or 1 in the continuum limit at fixed \ell — is supported only by visual extrapolation of the plotted fractions. No quantitative continuum extrapolation is reported for f, and the finite-L corrections are not modeled. Since the subsequent partition-function analysis and the topological-condensate ratios rely on this sector separation, the paper should provide a fit of f(L,\ell) to a continuum form (e.g., f = 1 - c(\ell)/L^a, with errors) or otherwise quantify the extrapolation. Without this, the statement that 'statistically speaking' only one sector survives is not fully demonstrated.
minor comments (4)
  1. [Section V, Eq. (64)] The analytic ratio of gauge partition functions is stated without derivation; defining C_n and the sign convention explicitly in the text would help. Also, the infinite sum should be justified as convergent in the L->\infty limit.
  2. [Section VI, Eq. (70)] The same notation \langle\Lambda_1\rangle(L,\ell) is used for two different boundary-condition cases; the subscript indicating the case is missing, which makes the equation ambiguous.
  3. [Section VI, text after Eq. (70)] There is a typo: 'shoes that we have reached' should be 'shows that we have reached'. Also, the statement that a value of 1 for \gamma_m is ruled out for (z,J)=(1,2) by 3.3 standard deviations should specify which fit and which lattice sizes were used.
  4. [Figures 3 and 4] The figure captions describe 'small volumes' but the panels show several \ell values and the distinction between the two figures is not stated clearly. Please state in the captions which quantity is plotted and how the free-field vertical lines are computed.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the sector survival is a direct Monte Carlo measurement, and the condensate value 0.162(3) is a defined ratio cross-checked against an external Hamiltonian result, not a fitted or self-cited input.

full rationale

The Section IV claim that only one mod(2) sector survives is a direct Monte Carlo measurement of the fraction of gauge configurations with exact ±1 eigenvalues of V (Fig. 1), not an output of a fitted definition. The Section V topological condensate is explicitly a defined observable: Eq. (60) sets Sigma_t,1,J = (1/[2m_w(2J+1)ℓL]) Z'_++/Z_+- , and the value 0.162(3) in Eq. (63) is obtained by jackknife and L→∞ extrapolation of that ratio; it is then compared with the independent Hamiltonian computation [5] (Dempsey et al., not the present authors), with the factor-of-1/2 convention stated in the text. No parameter is fitted to [5], so the comparison is a genuine cross-check. The paper itself labels the operator identification as a 'postulate' (Section VII), which is an interpretive assumption rather than a circular derivation; whether this identification is correct is a soundness/interpretation issue, not a circularity issue. Self-citations to [7] (mod(2) index) and [26] (wavefunction renormalization) concern formalism that is re-derived in Section II and Appendices A and B; [4] is used only to convert the lightest mass in Eq. (67) for the cross-check. None of these citations supplies the central numerical result by construction.

Assumptions & free parameters 2 free parameters · 5 assumptions · 2 invented entities

The central claims rest on the mod(2) index rigidity, the fixed-volume continuum prescription, quenched sampling of zero modes, and an explicitly postulated identification of a mixed-boundary ratio with the physical condensate. The free parameters are the fitted scaling exponents gamma_m and the unstated Wilson mass m_w. No fundamentally new particles or forces are introduced.

free parameters (2)
  • gamma_m(z,J) = 0.814(36), 0.794(59), 0.786(68), 0.735(63), 0.502(82) for (z,J)=(1,1),(-1,1),(1,2),(1,3),(1,4)
    Exponent in the scaling law lambda_1+-(ell) = ell^(-1-gamma_m); fitted to the lowest eigenvalue data in Section VI (Figure 5, Eq. (72)) and used as evidence against spontaneous symmetry breaking.
  • m_w (Wilson mass in overlap operator) = not stated in text
    Appears in the overlap-Dirac operator and in the condensate normalization Eq. (60); its numerical value is not given, and finite-lattice results could depend on it.
assumptions (5)
  • domain assumption Rigidity of the mod(2) index: the number of V eigenvalues equal to ±1 mod 4 is robust under smooth gauge deformations; configurations split into disconnected sectors.
    Adopted from [7,8] and used in Section II and IV to classify configurations by presence of zero modes.
  • domain assumption The continuum limit at fixed physical volume is obtained by beta = L^2/ell^2 as L tends to infinity.
    Used throughout to define the continuum limit in a 2D asymptotically free theory (Eq. (9)).
  • domain assumption The quenched (pure gauge) ensemble with the fermion determinant treated as an observable correctly samples the zero-mode sectors.
    The simulations generate gauge fields with the Wilson action only and restart from cold starts to sample zero modes (Section III); the validity for the full path integral is assumed.
  • ad hoc to paper The mixed-boundary-condition ratio with zero modes removed equals the fermion bilinear condensate (the 'topological condensate' postulate).
    Stated explicitly in Section V and Section VII; this is the main interpretive assumption connecting an observable ratio to a physical condensate.
  • ad hoc to paper The z=0 independent-plaquette action reproduces infinite volume physics with a single partition function.
    Proposed in Section I and Section VII based on the observed ell-dependence of the zero-mode fraction; no independent derivation is given.
invented entities (2)
  • Topological condensate (Sigma_t) independent evidence
    purpose: A fermion bilinear condensate attributed to exact zero modes via the mod(2) index, defined through ratios of mixed-boundary partition functions.
    Its infinite volume value 0.162(3) matches the independent Hamiltonian calculation in [5] after a stated conversion, providing external support.
  • Independent plaquette (z=0) gauge action
    purpose: A variant of the Wilson action with one plaquette coupling set to zero, designed to reproduce infinite volume results in a single partition function.
    Proposed in this paper; its correctness is supported only by the authors' own continuum extrapolations, with no external check yet.

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Cite this review

Pith. "Pith review of Bifrost-1: Bridging Multimodal LLMs and Diffusion Models with Patch-level CLIP Latents." pith.science (2026). https://pith.science/paper/T7SKSNNP

@misc{pith2026250805954,
  author       = {Pith},
  title        = {Pith review of: Bifrost-1: Bridging Multimodal LLMs and Diffusion Models with Patch-level CLIP Latents},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/T7SKSNNP}},
  note         = {Machine review of arXiv:2508.05954}
}
read the original abstract

There is growing interest in integrating high-fidelity visual synthesis capabilities into large language models (LLMs) without compromising their strong reasoning capabilities. Existing methods that directly train LLMs or bridge LLMs and diffusion models usually suffer from costly training since the backbone LLMs have not seen image representations during pretraining. We present Bifrost-1, a unified framework that bridges pretrained multimodal LLMs (MLLMs) and diffusion models using patch-level CLIP image embeddings as latent variables, which are natively aligned with the MLLM's CLIP visual encoder. These patch-level image embeddings are integrated into the diffusion model with a lightweight adaptation of its ControlNet. To retain the original multimodal reasoning capabilities of MLLMs, we equip the MLLM with a visual generation branch initialized from the original MLLM parameters when predicting the patch-level image embeddings. By seamlessly integrating pretrained MLLMs and diffusion models with patch-level CLIP latents, our framework enables high-fidelity controllable image generation with significant training efficiency. Our experiments demonstrate that Bifrost-1 achieves comparable or better performance than previous methods in terms of visual fidelity and multimodal understanding, with substantially lower compute during training. We also provide comprehensive ablation studies showing the effectiveness of our design choices.

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Reference graph

Works this paper leans on

33 extracted references · 13 canonical work pages

  1. [5]

    Delmastro, J

    D. Delmastro, J. Gomis, and M. Yu, JHEP 02, 157 (2023), arXiv:2108.02202 [hep-th]

    arXiv 2023

  2. [1]

    Therefore, in the context of Eq

    Statistically speaking, all configurations with periodic boundary for gauge fields and fermions and all configura- tions with twisted boundary conditions for gauge fields and anti-periodic boundary conditions for fermions have zero modes. Therefore, in the context of Eq. (3), Z++ and Z−− are zero in the continuum limit. Numerical evidence is shown in Section IV

    work page

  3. [2]

    Therefore, in the context of Eq

    Statistically speaking, no configuration with periodic boundary for gauge fields and anti-periodic boundary conditions for fermions and all configurations with twisted boundary conditions for gauge fields and periodic boundary conditions for fermions have zero modes. Therefore, in the context of Eq. (3), Z+− and Z−+ are non-zero. Numerical evidence is sho...

    work page

  4. [3]

    (7) are finite and non-zero for all ℓ >0

    Results for the topological bilinear condensate at finite ℓ are presented in Section V and we numerically show that ⟨Mi⟩; i = 1, 2, 3, 4, defined in Eq. (7) are finite and non-zero for all ℓ >0. In addition all of them approach the same value in the limit of ℓ → ∞and the density per color degree of freedom seems to be independent of J, the representation ...

    work page

  5. [4]

    Such an approach requires one to first establish the small mass range and then study the behavior in that range

    One could study spontaneous symmetry breaking by introducing a mass term and studying the massless limit. Such an approach requires one to first establish the small mass range and then study the behavior in that range. A better option from the numerical perspective is to study the spectral density which carries the same information. The spectral density o...

    work page

  6. [6]

    Karthik, R

    N. Karthik, R. Narayanan, and S. A. Narayanan, Phys. Rev. D 109, 054502 (2024), arXiv:2312.13929 [hep-lat]

    arXiv 2024

  7. [7]

    Dempsey, I

    R. Dempsey, I. R. Klebanov, L. L. Lin, and S. S. Pufu, JHEP 04, 107 (2023), arXiv:2210.10895 [hep-th]

    arXiv 2023

  8. [8]

    Narayanan and S

    R. Narayanan and S. A. Narayanan, Phys. Rev. D 108, 094005 (2023), arXiv:2308.12887 [hep-th]

    arXiv 2023

Show all 33 references
  1. [9]

    Dempsey, I

    R. Dempsey, I. R. Klebanov, S. S. Pufu, and B. T. Søgaard, JHEP 08, 009 (2024), arXiv:2311.09334 [hep-th]

    2024 arXiv

  2. [10]

    Bergner, S

    G. Bergner, S. Piemonte, and M. ¨Unsal, JHEP 07, 048 (2024), arXiv:2404.03801 [hep-lat]

    2024 arXiv

  3. [11]

    P. Y. Huet, R. Narayanan, and H. Neuberger, Phys. Lett. B 380, 291 (1996), arXiv:hep-th/9602176

    1996 arXiv

  4. [12]

    Cherman, T

    A. Cherman, T. Jacobson, Y. Tanizaki, and M. ¨Unsal, SciPost Phys. 8, 072 (2020), arXiv:1908.09858 [hep-th]

    2020 arXiv

  5. [13]

    ’t Hooft, Nucl

    G. ’t Hooft, Nucl. Phys. B 153, 141 (1979)

    1979

  6. [14]

    ’t Hooft, Acta Phys

    G. ’t Hooft, Acta Phys. Austriaca Suppl. 22, 531 (1980)

    1980

  7. [15]

    Komargodski, K

    Z. Komargodski, K. Ohmori, K. Roumpedakis, and S. Seifnashri, Journal of High Energy Physics 2021 (2021), 10.1007/jhep03(2021)103

    2021 doi

  8. [16]

    M. M. Anber and E. Poppitz, JHEP 01, 118 (2023), arXiv:2210.13568 [hep-th]

    2023 arXiv

  9. [17]

    M. M. Anber and E. Poppitz, JHEP 02, 114 (2025), arXiv:2408.16058 [hep-th]

    2025 arXiv

  10. [18]

    M. M. Anber and E. Poppitz, (2025), arXiv:2509.00157 [hep-th]

    2025

  11. [19]

    Banks and A

    T. Banks and A. Casher, Nucl. Phys. B169, 103 (1980)

    1980

  12. [20]

    Narayanan and H

    R. Narayanan and H. Neuberger, Nucl.Phys. B443, 305 (1995), arXiv:hep-th/9411108 [hep-th]

    1995 arXiv

  13. [21]

    Neuberger, Phys.Lett

    H. Neuberger, Phys.Lett. B417, 141 (1998), arXiv:hep-lat/9707022 [hep-lat]

    1998 arXiv

  14. [22]

    Garcia Perez, A

    M. Garcia Perez, A. Gonzalez-Arroyo, and B. Soderberg, Phys. Lett. B 235, 117 (1990)

    1990

  15. [23]

    Kaushal, N

    A. Kaushal, N. S. Prabhakar, and S. R. Wadia, JHEP 11, 162 (2023), arXiv:2307.15015 [hep-th]

    2023 arXiv

  16. [24]

    Narayanan, H

    R. Narayanan, H. Neuberger, and P. M. Vranas, Phys. Lett. B 353, 507 (1995), arXiv:hep-lat/9503013

    1995 arXiv

  17. [25]

    A. D. Kennedy and B. J. Pendleton, Phys. Lett. B 156, 393 (1985)

    1985

  18. [26]

    Creutz, Phys

    M. Creutz, Phys. Rev. D 36, 515 (1987)

    1987

  19. [27]

    S. L. Adler, Phys. Rev. D 23, 2901 (1981)

    1981

  20. [28]

    S. L. Adler, Phys. Rev. D 37, 458 (1988)

    1988

  21. [29]

    Neuberger, Phys

    H. Neuberger, Phys. Rev. Lett. 59, 1877 (1987)

    1987

  22. [30]

    R. G. Edwards, U. M. Heller, and R. Narayanan, Phys.Rev. D59, 094510 (1999), arXiv:hep-lat/9811030 [hep-lat]

    1999 arXiv

  23. [31]

    Karthik and R

    N. Karthik and R. Narayanan, Phys. Rev. D94, 065026 (2016), arXiv:1606.04109 [hep-th]

    2016 arXiv

  24. [32]

    J. J. M. Verbaarschot and T. Wettig, Ann. Rev. Nucl. Part. Sci. 50, 343 (2000), arXiv:hep-ph/0003017 [hep-ph]

    2000 arXiv

  25. [33]

    Narayanan and H

    R. Narayanan and H. Neuberger, Phys.Rev.Lett. 71, 3251 (1993), arXiv:hep-lat/9308011 [hep-lat]

    1993 arXiv

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Reviewed August 5, 2026 · model on record in the stance chip above.