Scaling Video Generation for Reasoning: At What Cost?

Weihang Guo; Xiaoyu Wu; Yifei Wang; Niloofar Mireshghallah; Lydia E. Kavraki

cs.CVSep 29, 2026

Scaling Video Generation for Reasoning: At What Cost?

Authors: Weihang Guo, Xiaoyu Wu, Yifei Wang, Niloofar Mireshghallah, Lydia E. Kavraki

Organizations: Rice University · Carnegie Mellon University

Abstract

We study whether scaling video generation enables models to reason about hidden information from the past frames, and at what computational cost. Our controlled benchmark requires predicting nine prescribed moves of an initially solved 2x2x2 Rubik's Cube from a fixed view of three faces. Correct predictions require inferring how actions change hidden states, and the simulator provides exact ground truth for evaluation. Models learn plausible cube geometry early, while correct sticker configurations require substantially more training. Although validation MSE follows approximate power-law scaling, lower MSE loss does not reliably indicate downstream reasoning capabilities. Smaller autoregressive models achieve higher state accuracy with limited compute, while larger models reach higher accuracy after more training. At roughly 0.1 PF-days, the 70M-parameter model correctly predicts the visible sticker configuration in 44.6% of post-action frames, compared with 0.3% for the 1B model, which reaches 83.7% at 3.14 PF-days. Symbolic state supervision raises the 20M model's frame accuracy from 31.1% to 67.3% at the same training-data budget, suggesting that learning representations of state changes can complement scaling.

Figures & tables

Figure 1: Rubik video generation and scaling with training compute. The video strip shows 80 predicted frames, or 3.3 s at 24 fps, for 9 prescribed actions as the language prompt from a solved cube . The video generator is trained from scratch on synthetic videos. (a) Validation flow MSE and (b) average frame accuracy for AR models of different sizes. (c) AR full-trajectory accuracy, which requires all nine post-action states to be correct. Separate power-law fits to the middle and final thirds of its observed compute frontier illustrate how compute demand grows toward higher reliability. Diamonds mark their window-dependent 98% intersections.

Figure 2: Predictions from the 270M-parameter autoregressive model after four prescribed moves from a solved cube . The model reproduces the cube’s geometry after $3.4\times 10^{-2}$ PF-days of training, but first predicts all 12 visible stickers correctly in this example at $5.7\times 10^{-1}$ PF-days, requiring about 17 times as much compute. The top-left image is the ground truth.

Figure 3: Rubik face-turn notation. Orange cubies rotate around the blue axes. Arrows show

90^{\circ}

clockwise turns viewed from outside the named face. Dashed arrows mark hidden faces. A prime reverses the turn, and a suffix

2

denotes

180^{\circ}

Metric	Definition
MSE loss	Mean squared error between the predicted and target flow velocities in video latent space on validation set.
Action following acc.	Fraction of actions in the prompt that are correctly applied to the cube.
Sticker acc.	Fraction of visible stickers ( $4$ stickers $\times$ $3$ visible faces) with the correct color after each action.
Frame acc.	Fraction of the nine post-action frames in which all 12 visible stickers have the correct color.
Full-trajectory acc.	Fraction of episodes in which all 12 visible stickers are correct after every one of the nine actions.

Table 1: Evaluation metrics.

Configuration	$d_{\mathrm{model}}$	Layers	Heads	$d_{\mathrm{ff}}$	Parameters (M)	Generation	Action	Sticker	Frame
Deep-narrow	512	22	8	1408	95.03	AR- $k=1$	17.22	25.37	3.67
						AR- $k=4$	6.33	22.20	0.78
						Bidir	7.33	21.59	0.33
Balanced	640	14	10	1728	94.20	AR- $k=1$	72.44	52.00	24.33
						AR- $k=4$	9.67	22.46	1.67
						Bidir	6.78	21.55	0.56

Table 2: Stage A architectures and results after 1M training videos. Action, sticker, and frame accuracies (%) use the same 100 held-out videos. AR-

k

generates

k

latent frames per chunk. Best accuracies are bold.

Figure 4: Video latent space and vector space. The action prompt is omitted. (a) A frozen Wan VAE encodes video frames into continuous latents for the video DiT. (b) Visible sticker colors are represented directly as

12\times 6

one-hot arrays for the state Transformer. Both model families support autoregressive and bidirectional generation.

Generation	PF-days (approx.)	Frame accuracy after 20 actions (%)	Full-trajectory accuracy (%)
AR	$8\times 10^{-3}$	94.01	92.81
Bidir	$4\times 10^{-4}$	99.86	99.85

Table 3: Vector-space prediction on 10,000 held-out 20-action episodes. Compute estimates exclude the frozen language encoder. Final frame accuracy requires all 12 visible stickers to be correct after 20 actions. Full-trajectory accuracy requires them to be correct after every action. AR uses its own predictions during rollout.

Figure 5: State prediction with three or six visible faces. (a) Ground truth and generated six-face videos after each action in the same 9-action sequence. Red boxes mark each model’s first incorrect boundary frame. (b) Frame accuracy after each action, with 95% normal confidence intervals over 100 paired episodes. Training exposure is matched between 3-face and 6-face. Frame accuracy requires all 12 visible stickers to be correct for three-face observation and all 24 for six-face observation.

Figure 6: Frame accuracy after each action as training data increases, for AR (top) and Bidir (bottom). Colors indicate training videos on a shared scale. All selected checkpoints use the same 100 free-running episodes. Smooth lines connect the measured action accuracies.

Figure 7: Illustrative compute extrapolations for (a) AR average frame accuracy, (b) AR full-trajectory accuracy, and (c) Bidir average frame accuracy. Gray points show evaluated checkpoints; colored points identify the middle and final thirds of each compute-ordered frontier. Solid lines show fits within each segment, and dashed lines show extrapolations. Diamonds mark 98% accuracy, labeled in PF-days. Shading marks the observed compute range. Bidir full-trajectory accuracy is omitted because it is zero at every evaluated checkpoint.

Figure 8: Validation MSE and reasoning accuracy across model sizes, for AR (top) and Bidir (bottom). Points pair validation MSE with free-running accuracy from the same EMA checkpoint. Colors identify model sizes.

Figure 9: Explicit state guidance for 20M AR-

k=1

models. (a) A shared Transformer predicts sticker-state distributions from the available video history and action prompt, then uses them to condition a separate video pass. State cross-entropy and video flow matching jointly train the model. (b) Frame accuracy after each action on the same 100 paired episodes after training on 3M videos. All curves use generated history. Shading shows 95% confidence intervals. All models use EMA weights.

Appendix figures & tables13 assets

Supplementary material from the paper’s appendix.

Appendix

Video	Sticker	Frame	Full trajectory
Original RGB	100.00	100.00	100.00
Wan VAE reconstruction	100.00	100.00	100.00

Appendix

Table 4: State accuracy (%) on the same 100 paired evaluation videos before and after reconstruction with the frozen Wan VAE. All metrics use the nine post-action boundaries and exclude the initial frame.

Source	Action following (all)	Action following (A9)
VAE reconstruction	92.6	92.1
AR	80.1	80.6
Bidirectional	69.6	67.7

Appendix

Table 5: Rubik action following from grayscale motion. The predicted face and turn type must both match the prompt. Values are percentages over 9,000 action segments, except the action-nine column, with 1,000 segments.

Figure 10: Vector-state learning curves for Rubik’s Cube.

Component	Value or rule	Scaling treatment
Transformer block	Self-attention, cross-attention, SwiGLU	Fixed
Model width $d_{\mathrm{model}}$	Tables 2 and 7	Scaled
Depth $L$	Selected wide–shallow ladder	Scaled
Position encoding	3D RoPE	Fixed
Head width $d_{\mathrm{head}}$	$64$	Fixed
Attention heads $H$	$d_{\mathrm{model}}/64$	Derived

Appendix

Table 6: Video DiT architecture used in the two-stage scaling study.

Model name	Parameters (M)	$d_{\mathrm{model}}$	Layers	Heads	$d_{\mathrm{ff}}$
20M	19.70	384	8	6	1024
30M	33.45	448	10	7	1216
70M	67.81	640	10	10	1728
120M	115.8	768	12	12	2048
270M	271.8	1088	14	17	2944
550M	548.1	1408	17	22	3776

Appendix

Table 7: Stage B Video DiT architecture specifications. AR-

k=1

and bidirectional models share the same architecture dimensions and parameter counts.

Generation	Peak learning rate
	$10^{-4}$	$2\times 10^{-4}$	$4\times 10^{-4}$
AR- $k=1$	0.1678	0.1217	0.0768
AR- $k=2$	0.1790	0.1337	0.0810
AR- $k=4$	0.1715	0.1287	0.0783
Bidir	0.1789	0.1274	0.0781

Appendix

Table 8: Validation flow MSE in the learning-rate (left) and effective-batch-size (right) searches. Lower is better; best values within each comparison are bold.

Shape	AR- $k=1$	AR- $k=4$	Bidir
Deep–narrow	5.015	5.281	6.343
Balanced	4.542	4.753	5.527
Wide–shallow	4.367	4.548	5.150

Appendix

Table 9: Estimated Stage-A training compute , in

10^{18}

FLOPs, after 1M videos. One multiply–accumulate counts as two FLOPs; backward compute is approximated as twice forward compute. These are operation-count estimates, not hardware timings.

Shape	Family	MSE ( $10^{-3}$ )	Action	Sticker	Frame
deep–narrow	AR-K1	2.233	17.22	25.37	3.67
deep–narrow	AR-K4	2.562	6.33	22.20	0.78
deep–narrow	BIDIR	3.212	7.33	21.59	0.33
balanced	AR-K1	1.883	72.44	52.00	24.33
balanced	AR-K4	2.533	9.67	22.46	1.67
balanced	BIDIR	3.426	6.78	21.55	0.56

Appendix

Table 10: Stage A after 1M training videos. Accuracies (%) average actions 1–9 on the same 100 episodes, excluding the initial boundary. Flow MSE uses 1,024 validation episodes; its conditioning and fixed probes differ across prediction factorizations.

Figure 11: Stage-A calibration across nine setups. Purple, teal, and orange group deep–narrow, balanced, and wide–shallow; solid, dashed, and dotted lines distinguish AR-

k=1

, AR-

k=4

, and Bidir. (a–c) The 1M-video EMA checkpoints on 100 paired development episodes: action-following accuracy from the independent motion probe, visible-sticker accuracy, and exact-frame accuracy (all 12 stickers correct). The initial boundary is excluded. (d) EMA flow MSE on 256 fixed episodes at seven selected exposures: 32,768, 65,536, 131,072, 262,144, 524,288, 786,432, and 1M videos. Diamond endpoint markers use 1,024 episodes. Initialization is omitted. AR loss uses ground-truth history; conditioning and noise/time probes differ across factorizations, so their losses are not directly comparable.

Figure 12: Stage-A rollouts across all nine setups after 1M training videos. VAE-reconstructed ground truth, followed by deep–narrow, balanced, and wide–shallow; each shape includes AR- $k=1$ , AR- $k=4$ , and Bidir. All use the first development episode (seed 81024000), the same prompt, and paired sampling-noise seeds, with 16 midpoint steps per AR chunk or entire Bidir video. The nine settled post-action boundaries are shown. Red boxes mark each model’s first incorrect settled action boundary. The episode was not selected by performance. All panels use the saved EMA model parameters.

Model	Mean frame: Free	GT prefix	A9 frame: Free	GT prefix
XS	33.89	38.67	0.00	5.00
S	42.22	47.89	0.00	9.00
M	52.56	60.00	0.00	22.00
B	48.11	55.00	1.00	9.00
L	63.56	71.67	3.00	38.00
XL	64.56	73.33	5.00	45.00

Appendix

Table 11: Matched free-running and action-aligned GT-history comparisons at 5M videos. All values are percentages on the same 100 episodes.

Operation	Parameters	Forward FLOPs per target token
Language projection	$d_{f}d_{\mathrm{model}}$	$2n_{\mathrm{text}}d_{f}d_{\mathrm{model}}/n_{\mathrm{tgt}}$
Latent input/output projections	$3d_{z}p^{2}d_{\mathrm{model}}$	$2d_{z}p^{2}d_{\mathrm{model}}\left(2+\frac{n_{\mathrm{anchor}}+n_{\mathrm{hist}}}{n_{\mathrm{tgt}}}\right)$
Target visual Q/K/V and output	$4Ld_{\mathrm{model}}^{2}$	$8Ld_{\mathrm{model}}^{2}$
Visual-context K/V (shared weights)	—	$4L\frac{n_{\mathrm{anchor}}+n_{\mathrm{hist}}}{n_{\mathrm{tgt}}}d_{\mathrm{model}}^{2}$
Visual attention products	—	$4L(n_{\mathrm{tgt}}+n_{\mathrm{anchor}}+n_{\mathrm{hist}})d_{\mathrm{model}}$
Language cross-attention projections	$4Ld_{\mathrm{model}}^{2}$	$4Ld_{\mathrm{model}}^{2}\left(1+\frac{n_{\mathrm{text}}}{n_{\mathrm{tgt}}}\right)$

Appendix

Table 12: Generator parameters and forward compute. FLOPs are per target visual patch token; biases, normalization, and nonlinearities are omitted.

Metric	Segment	$A$	$\alpha$	$C_{98}$
AR frame	Middle third	0.336	0.2178	$4.227\times 10^{5}$
AR frame	Final third	0.5607	1.055	$23.55$
AR trajectory	Middle third	0.9501	0.1185	$1.425\times 10^{14}$
AR trajectory	Final third	1.59	0.7931	$248.9$
Bidir frame	Middle third	0.4366	0.1823	$2.221\times 10^{7}$
Bidir frame	Final third	0.4424	0.09379	$2.184\times 10^{14}$

Appendix

Table 13: Power-law fits to the middle and final thirds of each observed compute frontier.

C_{98}

is the 98% intersection of each fitted curve, in PF-days, illustrating its sensitivity to the fitting window.

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