Update model card for v1.5 checkpoints

Add v1.5 release news and refresh checkpoint tables to match docs/checkpoints.md.
Mark previous FLUX / FLUX.2 / Qwen-Image 2kto4k checkpoints as deprecated.

README.md

@@ -31,6 +31,15 @@ base_model:
 [Sanja Fidler](https://www.cs.utoronto.ca/~fidler/),
 [Xuanchi Ren](https://xuanchiren.com/) <br>
 
+## News
+
+- [July 2026] PiD v1.5 checkpoints for **FLUX**, **FLUX.2**, and
+  **Qwen-Image** are released. See the
+  [comparison page](https://research.nvidia.com/labs/sil/projects/pid/comparison.html)
+  for the improvements:
+  - Improved decoding color fidelity
+  - Removed grid artifacts in image corners
+  - Improved anime and facial details
 
 PiD reformulates the latent-to-pixel decoder as a conditional pixel-space
 diffusion model, unifying decoding and upsampling into a single generative
@@ -38,8 +47,9 @@ module. It denoises directly in high-resolution pixel space and produces a
 super-resolved image in one pass. This repository hosts the released decoder
 checkpoints, plus the encoder/decoder ("VAE") weights they depend on.
 
-All `PiD_*` checkpoints in this repo are **4-step distilled**. The non-`PiD_*`
-entries (`ae.safetensors`, `flux2_ae.safetensors`, `sdxl_vae.safetensors`, `QwenImage_VAE_2d.pth`, `sd3_vae/`, `rae/`,
+The distilled `PiD_*` checkpoints in this repo are **4-step distilled**. The
+non-`PiD_*` entries (`ae.safetensors`, `flux2_ae.safetensors`,
+`sdxl_vae.safetensors`, `QwenImage_VAE_2d.pth`, `sd3_vae/`, `rae/`,
 `scale_rae/`) are **the corresponding encoder/decoder VAE weights** that PiD
 plugs into — they're not PiD checkpoints themselves.
 
@@ -52,38 +62,50 @@ Global
 
 ## PiD checkpoints
 
-Two variants are released for each diffusers-style backbone:
+PiD checkpoint variants:
 
-- **`2k`** — trained at 2048px, used as a 4× decoder (512 LDM → 2048 px), or as
+- **`2k`** - trained at 2048px, used as a 4× decoder (512 LDM → 2048 px), or as
   an 8× decoder for the Scale-RAE backbone (256 → 2048).
-- **`2kto4k`** — trained with multi-resolution data bucketing 2048→4096 and an
-  SD3-style dynamic shift; designed for 1024 LDM → 4K (4096 px) decoding.
-
-Both checkpoint variants support multiple aspect ratios.
-
-| Path                                                            | Latent space | SR factor | Variant |
-|-----------------------------------------------------------------|--------------|-----------|---------|
-| `checkpoints/PiD_res2k_sr4x_official_flux_distill_4step`        | Flux1-dev    | 4×        | 2k      |
-| `checkpoints/PiD_res2k_sr4x_official_flux2_distill_4step`       | Flux2-dev    | 4×        | 2k      |
-| `checkpoints/PiD_res2k_sr4x_official_sd3_distill_4step`         | SD3 medium   | 4×        | 2k      |
-| `checkpoints/PiD_res2k_sr4x_official_dinov2_distill_4step`      | DINOv2-B     | 4×        | 2k      |
-| `checkpoints/PiD_res2k_sr8x_official_siglip_distill_4step`      | SigLIP-2     | 8×        | 2k      |
-| `checkpoints/PiD_res2kto4k_sr4x_official_flux_distill_4step`    | Flux1-dev    | 4×        | 2kto4k  |
-| `checkpoints/PiD_res2kto4k_sr4x_official_flux2_distill_4step_2606` | Flux2-dev  | 4×        | 2kto4k  |
-| `checkpoints/PiD_res2kto4k_sr4x_official_sd3_distill_4step`     | SD3 medium   | 4×        | 2kto4k  |
-| `checkpoints/PiD_res2kto4k_sr4x_official_sdxl_distill_4step`    | SDXL         | 4×        | 2kto4k  |
-| `checkpoints/PiD_res2kto4k_sr4x_official_qwenimage_distill_4step` | Qwen-Image  | 4×        | 2kto4k  |
-
-Each directory contains a single file, `model_ema_bf16.pth`, which is the EMA
-weights cast to bfloat16 — the format the inference scripts load by default.
-
-> **⚠️ Flux2-dev `2kto4k` — use the new `_2606` checkpoint.** The previous
-> `PiD_res2kto4k_sr4x_official_flux2_distill_4step` (without the `_2606` suffix)
-> suffered from a color-drifting issue. The new
-> `PiD_res2kto4k_sr4x_official_flux2_distill_4step_2606` fixes it — please use it
-> and do **not** use the old one. See the
-> [comparison](https://github.com/nv-tlabs/pid/blob/main/docs/FLUX2_2kto4k_new_ckpt_compare.md)
-> for details.
+- **`2kto4k_v1pt5`** - the recommended up-to-4K decoder for **FLUX**,
+  **FLUX.2**, and **Qwen-Image** latent spaces.
+- **`2kto4k`** - the legacy up-to-4K decoder still used for **SD3** and
+  **SDXL**. The previous FLUX / FLUX.2 / Qwen-Image `2kto4k` checkpoints are
+  deprecated and have been moved to `checkpoints_deprecated/`.
+
+Each checkpoint directory contains a single file, `model_ema_bf16.pth`, which
+is the EMA weights cast to bfloat16, the format the inference scripts load by
+default.
+
+### Distilled checkpoints
+
+| Backbone | decode 2k resolution only | decode 2k resolution to 4k resolution |
+|----------|---------------------------|--------------------------------------|
+| flux | `checkpoints/PiD_res2k_sr4x_official_flux_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux_distill_4step` |
+| flux2 | `checkpoints/PiD_res2k_sr4x_official_flux2_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux2_distill_4step` |
+| flux2-klein-4b | `checkpoints/PiD_res2k_sr4x_official_flux2_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux2_distill_4step` |
+| flux2-klein-9b | `checkpoints/PiD_res2k_sr4x_official_flux2_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux2_distill_4step` |
+| zimage | `checkpoints/PiD_res2k_sr4x_official_flux_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux_distill_4step` |
+| zimage-turbo | `checkpoints/PiD_res2k_sr4x_official_flux_distill_4step` | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux_distill_4step` |
+| qwenimage | - | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_qwenimage_distill_4step` |
+| qwenimage-2512 | - | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_qwenimage_distill_4step` |
+| sd3 | `checkpoints/PiD_res2k_sr4x_official_sd3_distill_4step` | `checkpoints/PiD_res2kto4k_sr4x_official_sd3_distill_4step` |
+| sdxl | - | `checkpoints/PiD_res2kto4k_sr4x_official_sdxl_distill_4step` |
+| dinov2 | `checkpoints/PiD_res2k_sr4x_official_dinov2_distill_4step` | - |
+| siglip | `checkpoints/PiD_res2k_sr8x_official_siglip_distill_4step` | - |
+
+### Undistilled checkpoints
+
+| VAE | decode 2k resolution to 4k resolution |
+|-----|--------------------------------------|
+| flux | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux_undistilled` |
+| flux2 | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_flux2_undistilled` |
+| qwenimage (wan2.1) | `checkpoints/PiD_v1pt5_res2kto4k_sr4x_official_qwenimage_undistilled` |
+
+### PixelDiT 2k-to-4k checkpoint
+
+| Model | Checkpoint path |
+|-------|-----------------|
+| PixelDiT | `checkpoints/PixelDiT_finetune_2kto4k` |
 
 ### Latent space → compatible LDMs
 
@@ -103,9 +125,9 @@ the latent space's checkpoint above.
 | SigLIP-2     | `checkpoints/scale_rae/`           | `siglip`                                  | [Scale-RAE](https://github.com/ZitengWangNYU/Scale-RAE) (text-conditional; nyu-visionx/Scale-RAE-Qwen1.5B_DiT2.4B) |
 
 For example, Z-Image and Z-Image-Turbo share Flux1-dev's VAE, so they reuse the
-`flux` checkpoints (both `2k` and `2kto4k`) — no separate `zimage` checkpoint is
-shipped. Likewise `qwenimage-2512` reuses the `qwenimage` decoder (same VAE,
-different transformer). 
+`flux` checkpoints (both `2k` and `2kto4k_v1pt5`) — no separate `zimage`
+checkpoint is shipped. Likewise `qwenimage-2512` reuses the `qwenimage`
+decoder (same VAE, different transformer). 
 
 ## Usage
 
@@ -129,7 +151,8 @@ PYTHONPATH=. python -m pid._src.inference.from_ldm --backbone flux \
     --pid_inference_steps 4
 ```
 
-Pick the `2kto4k` variant via `--pid_ckpt_type 2kto4k` when decoding at 4K.
+Pick `--pid_ckpt_type 2kto4k_v1pt5` for FLUX / FLUX.2 / Qwen-Image 4K
+decoding. Use `--pid_ckpt_type 2kto4k` for SD3 / SDXL 4K decoding.
 
 ## Citation
 ```
@@ -139,4 +162,4 @@ Pick the `2kto4k` variant via `--pid_ckpt_type 2kto4k` when decoding at 4K.
     journal={arXiv preprint arXiv:2605.23902},
     year={2026}
 }
-```
+```