FastContext-1.0-4B-SFT

<div style="border:2px solid currentColor; font-family:ui-monospace,'SF Mono','Cascadia Mono',Consolas,'Liberation Mono',monospace;"> <div style="border-bottom:1px solid currentColor; padding:6px 12px; font-size:11px; letter-spacing:3px; text-transform:uppercase; opacity:0.7; text-align:center;">PRESERVED ORIGINAL // REMOVED BY MICROSOFT FROM HF + GITHUB // MIT</div> <div style="padding:14px; display:flex; flex-wrap:wrap; align-items:center; justify-content:center; gap:18px;"> <pre style="margin:0; flex:0 0 auto; font-family:ui-monospace,'SF Mono','Cascadia Mono',Consolas,monospace; font-size:9px; line-height:1.15; letter-spacing:0;"> microsoft/FastContext ──▶ 404 github.com/microsoft/FastContext ──▶ 404 │ ▼ ┌──────────────────────────┐ │ weights preserved here │ │ bf16 · 8.0 GB · intact │ └──────────────────────────┘ you can't un-open-source </pre> <div style="flex:0 1 auto; max-width:100%; text-align:center;"> <div style="font-size:23px; font-weight:800; letter-spacing:1px;">FASTCONTEXT-1.0-4B-SFT</div> <div style="font-size:12.5px; letter-spacing:1px; opacity:0.8; margin-top:5px;"><span style="white-space:nowrap;">PRESERVED ORIGINAL WEIGHTS</span> · <span style="white-space:nowrap;">QWEN3 DENSE 4B</span> · <span style="white-space:nowrap;">256K CONTEXT</span> · <span style="white-space:nowrap;">BF16 · 8.0 GB</span></div> </div> </div> <table style="display:table; table-layout:fixed; width:100%; margin:0; border-collapse:collapse; font-family:ui-monospace,'SF Mono',Consolas,monospace; font-size:12px;"> <tr> <td style="border-top:1px solid currentColor; border-right:1px solid currentColor; padding:8px 12px;"><div style="font-size:10px; letter-spacing:1px; opacity:0.6;">WEIGHTS</div><div style="font-weight:700;">BF16 · UNMODIFIED</div></td> <td style="border-top:1px solid currentColor; border-right:1px solid currentColor; padding:8px 12px;"><div style="font-size:10px; letter-spacing:1px; opacity:0.6;">ARCH</div><div style="font-weight:700;">QWEN3 DENSE · 36L</div></td> <td style="border-top:1px solid currentColor; border-right:1px solid currentColor; padding:8px 12px;"><div style="font-size:10px; letter-spacing:1px; opacity:0.6;">CONTEXT</div><div style="font-weight:700;">256K NATIVE</div></td> <td style="border-top:1px solid currentColor; padding:8px 12px;"><div style="font-size:10px; letter-spacing:1px; opacity:0.6;">LICENSE</div><div style="font-weight:700;">MIT</div></td> </tr> </table> </div>

Microsoft open-sourced FastContext under MIT, then deleted it from both HuggingFace and GitHub about two weeks later (verified: 404 on both, 2026-07-02). MIT means preservation is legal — so here it is, unmodified. Own your AI: a model on your disk can't be sunset by a quarterly review.

🔍 What it is

A repository-exploration subagent for coding agents. Invoked on demand by your main agent, it fires parallel read-only tool calls (READ / GLOB / GREP) across a repo and returns only the file paths + line ranges that matter, as compact context. Your frontier coding agent stops wasting its context window (and your bill) crawling the file tree.

Microsoft's (now-deleted) announcement reported ~60% fewer tokens from the main coding agent and +5.5% on SWE-bench — their figures; the source no longer exists to cite.

Architecture: plain Qwen3ForCausalLM dense 4B — 36 layers, 256K native context. No exotic modules; loads with standard transformers.

🚀 Quick start

from transformers import AutoModelForCausalLM, AutoTokenizer
m = AutoModelForCausalLM.from_pretrained("KikoCis/FastContext-1.0-4B-SFT", torch_dtype="bfloat16", device_map="auto")
tok = AutoTokenizer.from_pretrained("KikoCis/FastContext-1.0-4B-SFT")

Don't want 8 GB? Grab the GGUF quants (1.96–2.5 GB, long-context imatrix, retrieval-validated 30/30 vs this bf16): 👉 KikoCis/FastContext-1.0-4B-longctx-imatrix-GGUF

⚠️ Good to know

• It's a scout, not a solver — it finds and returns evidence; pair it with a main coding agent that writes the actual fix.
• Upstream docs, harness code and issues were deleted along with the repos; usage conventions here come from the announcement and community mirrors.
• Weights are byte-identical to the (re-uploaded) original — no fine-tuning, no edits.

📚 Credit & license

Model, weights, training: © Microsoft (MIT). This is a preservation mirror sourced via the ShaunGves/FastContext-1.0-4B-SFT re-upload after microsoft/FastContext-1.0-4B-SFT was removed. Nothing modified. Quantized companion + validation: KikoCis.