# SGLang v0.5.12.post1

- Product: SGLang (https://whatsnew.fyi/product/sglang)
- Vendor: LMSYS
- Date: 2026-05-26
- Version: v0.5.12.post1
- Original notes: https://github.com/sgl-project/sglang/releases/tag/v0.5.12.post1
- Permalink: https://whatsnew.fyi/product/sglang/releases/v0.5.12.post1

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — DSV4-Pro emits garbled text during single-token decode on B200/B300 by fixing deep_gemm UE8M0 scale-packing path to ceiling activation scales before packing
- **fixed** — DSV4 + EAGLE/MTP in disaggregation decode crashes around 2000 requests with SWA allocator assertion by preventing recycled KV pages from keeping stale sliding-window mappings
- **fixed** — DSV4 NSA prefill context-parallel in disaggregation prefill mode no longer crashes at scheduler startup
- **fixed** — DSV4 HiSparse with SGLANG_OPT_USE_COMPRESSOR_V2=1 restores GSM8K accuracy from 0.825 to 0.960
- **fixed** — DSV4 PD disaggregation now works with pipeline parallelism > 1 by removing stale pp_size=1 assertion
- **fixed** — DSV4-Flash with --load-format dummy and FlashInfer mxfp4 no longer hits CUDA illegal memory access during CUDA-graph capture by initializing the integer HashTopK.tid2eid lookup table in dummy load
- **fixed** — DSV4 HiCache with SGLANG_OPT_CACHE_SWA_TRANSLATION=1 no longer returns stale translation indices after cache rebuild, preventing OOB writes and wrong outputs
- **fixed** — PD NIXL disaggregation always sends aux on is_last and only expects state when truthy
- **fixed** — Fix missing group arg in get_dp_buffer
- **changed** — DSV4 warm MHC token-count buckets at startup when SGLANG_OPT_DEEPGEMM_HC_PRENORM=1 and SGLANG_OPT_USE_TILELANG_MHC_PRE=1 and hybrid SWA are enabled to eliminate 20-40s cold-bucket forward stalls
- **changed** — DSV4-Pro precompile a DeepGEMM branch for _dispatch_bf16_fp32_backend to cut runtime JIT compile cost
- **changed** — Use nvidia-cutlass-dsl with cu13 extra for CUDA 13 support required for sm_103 / B300

v0.5.12.post1 is a stability patch on top of v0.5.12. It cherry-picks 12 fixes — primarily for DeepSeek V4 — onto the release branch.

#### Bug Fixes

##### DeepSeek V4
* DSV4-Pro emits garbled text during single-token decode on B200/B300 (fix `deep_gemm` UE8M0 scale-packing path by ceiling activation scales before packing): #25733
* DSV4 + EAGLE/MTP in disaggregation decode crashes around 2000 requests with a SWA allocator assertion (recycled KV pages kept stale sliding-window mappings): #25805
* DSV4 NSA prefill context-parallel (`--enable-nsa-prefill-context-parallel --nsa-prefill-cp-mode round-robin-split`) in `--disaggregation-mode prefill`: scheduler crash at startup: #25396
* DSV4 HiSparse + `SGLANG_OPT_USE_COMPRESSOR_V2=1`: GSM8K accuracy restored from 0.825 → 0.960: #25646
* DSV4 PD disaggregation now works with pipeline parallelism > 1 (removed stale `pp_size=1` assertion): #25771
* DSV4-Flash with `--load-format dummy` + FlashInfer mxfp4 hits CUDA illegal memory access during CUDA-graph capture (the integer `HashTopK.tid2eid` lookup table was left uninitialized by dummy load): #25892
* DSV4 HiCache + `SGLANG_OPT_CACHE_SWA_TRANSLATION=1` returns stale translation indices after a cache rebuild, causing OOB writes / wrong outputs: #25889

##### Disaggregation
* [PD][NIXL] Always send aux on `is_last`; only expect state when truthy: #25699

##### Other
* Fix missing `group` arg in `get_dp_buffer`: #25585

#### Performance

* DSV4: warm MHC token-count buckets at startup (gated to `SGLANG_OPT_DEEPGEMM_HC_PRENORM=1` + `SGLANG_OPT_USE_TILELANG_MHC_PRE=1` + hybrid SWA) to eliminate 20–40s cold-bucket forward stalls: #25810
* DSV4-Pro: precompile a DeepGEMM branch for `_dispatch_bf16_fp32_backend` to cut runtime JIT compile cost: #25860

#### Dependencies

* Use `[cu13]` extra for `nvidia-cutlass-dsl` (default to CUDA 13; required for sm_103 / B300): #25576

**All PRs included in this release**: https://github.com/sgl-project/sglang/compare/v0.5.12...v0.5.12.post1

**Full Changelog**: https://github.com/sgl-project/sglang/compare/v0.5.12...v0.5.12.post1