LongCat-Image and Seedream 4.5: Open-Weight vs Closed Image Generation Compared
A source-based comparison of LongCat-Image (6B bilingual open-weight model, 8,105-Chinese-character rendering, self-hostable) and Seedream 4.5 (ByteDance's closed image model, 4K output, 10 reference images, multi-image fusion). Covers text rendering, resolution, editing, pricing, and licensing — the predecessor of Seedream 5.0.
Independent third-party resource. Not affiliated with or endorsed by LongCat, Meituan, DeepSeek, or any other publisher discussed on this page.
Published: 2026-08-18 · Author: LongCat Community Hub editorial team
This is an independent, source-based comparison of LongCat-Image (Meituan) and Seedream 4.5 (ByteDance) — the predecessor of the Seedream 5.0 already compared on this site. It compares documented architecture, text rendering, resolution, editing, pricing, licensing, and deployment options. It does not report performance as a verdict — for publisher-reported scores, see the individual model pages and benchmark index linked below. Every claim on this page is sourced from the linked publisher documentation or attributed third-party guides.
| Dimension | LongCat-Image | Seedream 4.5 |
|---|---|---|
| Developer | Meituan (LongCat team) | ByteDance (Seed team) |
| Release date | December 8, 2025 | December 2025 (4.5) |
| Parameters | 6B (dense, documented) | Undisclosed (proprietary) |
| Architecture | MM-DiT + Single-DiT hybrid, documented | Undisclosed |
| Text rendering | Chinese: all 8,105 standard characters (ChineseWord 90.7) | Improved small-text rendering vs 4.0; still trails dedicated text models per third-party reviews |
| Max resolution | Consumer-GPU friendly (6B design) | Up to 4096×4096 (4K), no surcharge |
| Reference images | Not a documented multi-reference workflow | Up to 10 reference images, multi-image fusion |
| Editing | Text-driven editing (open-source SOTA: ImgEdit-Bench 4.50, GEdit-Bench 7.60/7.64) | Reference-guided editing; unified T2I + edit architecture |
| Pricing (per image) | Self-hosted at infrastructure cost; no per-image fee | ~$0.04 per image (BytePlus/fal.ai/Replicate) |
| License | Open source (weights + training toolchain released) | Proprietary (closed model, API only) |
| Deployment | Self-hosted on consumer GPUs; LongCat Web/App | API only (BytePlus ModelArk, fal.ai, Replicate) |
The Predecessor Comparison: Seedream 4.5 vs the 5.0 Flagship
This page compares LongCat-Image against Seedream 4.5, the version ByteDance shipped in December 2025 — before Seedream 5.0 (already compared on this site) added native 14–15 language rendering, layer separation, and precision editing. Seedream 4.5 is positioned by BytePlus as a precision-focused refinement: sharper details, consistent subjects, 4K output, multi-image fusion with up to 10 reference images, and improved small-text rendering.
LongCat-Image, also released December 2025, is a fully documented 6-billion-parameter open-weight model with a compact design explicitly aimed at consumer-GPU deployment. Teams still running Seedream 4.5 integrations — or evaluating whether the older version's cost profile suits their workflow — can use this page alongside the 5.0 comparison for version-to- version context.
Text Rendering: Character Coverage vs Refined Small Text
LongCat-Image's documented strength is character-level coverage of all 8,105 standard Chinese characters (ChineseWord 90.7). Seedream 4.5's documented strength is refined small-text clarity in English and Chinese — an improvement over 4.0 — though third-party reviews note it still trails dedicated text-rendering models. For teams whose requirement is accurate Chinese copy anywhere in an image, LongCat-Image's coverage claim is the relevant number; for teams that need clean small text in dense layouts on a hosted API, Seedream 4.5 is the documented option.
Resolution and Multi-Reference Control
Seedream 4.5 documents output up to 4096×4096 with no 4K surcharge, and multi-image fusion supporting up to 10 reference images — capabilities that require server-side rendering and are only reachable through ByteDance's API or partner platforms. LongCat-Image's 6B design is documented as consumer-GPU friendly, trading peak resolution and multi-reference fusion for local deployability and a public training pipeline.
Pricing, Licensing, and Deployment
Seedream 4.5 is billed per image at roughly $0.04 across BytePlus, fal.ai, and Replicate. LongCat-Image has no per-image fee: it is self-hosted at infrastructure cost, or used through the LongCat Web interface and App. For sustained generation volume, a self-hosted open-weight model shifts cost from per-output billing to fixed infrastructure — but that trade requires GPU capacity, which LongCat-Image's 6B design keeps modest.
The structural contrast is distribution: a closed API with predictable per-image pricing and 4K multi-reference features, versus open weights that can be audited, fine-tuned, and run anywhere. Which ByteDance version a team should evaluate depends on whether it needs 5.0's multilingual rendering and layer separation or 4.5's simpler feature set at a lower per-image cost.
This comparison is based on publicly available documentation accessed on 2026-08-18. LongCat-Image specifications are from its technical report and HuggingFace release. Seedream 4.5 specifications are from the BytePlus announcement and attributed third-party model cards.
This is a feature-level comparison, not a performance evaluation. This site has not independently tested either model. Benchmark scores are publisher-reported or independently attributed as noted and have not been independently verified by this site.
Pricing is current as of the access date and varies by API channel; verify current terms on each vendor's official documentation before deployment.
Related pages
- LongCat-Image model profile
Full technical brief covering architecture, training, benchmarks, and deployment options.
- LongCat-Image vs Seedream 5.0 comparison
The companion comparison against the current Seedream flagship, for version-to-version context.
- LongCat-Image vs Qwen-Image 2.0 comparison
The open-weight vs open-weight comparison against Alibaba's image model.
- LongCat-2.0 model profile
The flagship language model that shares the LongCat product family.
Related comparisons in this series
- LongCat-Image and Seedream 5.0: Open-Weight vs Closed Image Generation Compared
A source-based comparison of LongCat-Image (6B bilingual open-weight model, Chinese text rendering, self-hostable) and Seedream 5.0 Pro (ByteDance's closed flagship, 14-language rendering, layer separation, API-only). Covers architecture, text rendering, editing, pricing, licensing, and deployment.
- LongCat-Image and Qwen-Image 2.0: Two Open-Weight Chinese Image Models Compared
A source-based comparison of LongCat-Image (6B bilingual open-weight model, 8,105-Chinese-character rendering, self-hostable) and Qwen-Image 2.0 (Alibaba's 7B open-weight model, native 2K, unified generation-editing). Covers architecture, text rendering, benchmarks, licensing, and deployment — an open-weight vs open-weight comparison.
- LongCat-Image and FLUX.2: Open-Weight Image Models Compared
A source-based comparison of LongCat-Image (6B bilingual open-weight model, 8,105-Chinese-character rendering, self-hostable) and FLUX.2 (Black Forest Labs' 32B open-weight image family, 4MP editing, 10 reference images). Covers architecture, text rendering, licensing nuances, pricing, and deployment.
Sources
- LongCat-Image Technical Report (arXiv:2512.07584)
Primary sourcePublished 2025-12-08Accessed 2026-08-18
Technical report describing the MM-DiT + Single-DiT hybrid architecture, data pipeline, RL fine-tuning, and benchmarks including ChineseWord 90.7 and GenEval 0.87.
- LongCat-Image on HuggingFace
Primary sourceAccessed 2026-08-18
Model weights and training toolchain under the meituan-longcat organization.
- BytePlus Seedream 4.5 announcement
Publisher documentationPublished 2025-12-04Accessed 2026-08-18
BytePlus launch announcement: sharper details, consistent subjects, 4K output, multi-image fusion with up to 10 reference images, flat-rate pricing with no 4K surcharge.
- Seedream 4.5 — Gate.AI model card
Third-partyAccessed 2026-08-18
Model card: bytedance/seedream-4.5, $0.04 per image, reference-guided editing, stronger subject recognition and denser text rendering claims.
- Seedream 4.5 — Lumenfall model page
Third-partyAccessed 2026-08-18
Specification page: 4096x4096 max resolution, unified T2I and editing, available via BytePlus/fal.ai/Replicate from $0.040/image.
Independent third-party disclosure
This page is published by an independent third-party site. It is not affiliated with, endorsed by, sponsored by, or operated by Meituan, LongCat, or any of their affiliates. The content summarizes publicly-available primary documentation and does not represent the views of any referenced organization.
Last reviewed: 2026-08-18