{
 "schema_version": "1.7.0",
 "id": "x_NXMC-2025-0055",
 "modified": "2026-10-19T02:33:38.839Z",
 "published": "2026-10-18T09:00:52.565Z",
 "summary": "NVIDIA-Nemotron-Nano-9B-v2: tokenizer change at b27e387 (2025-08-15)",
 "details": "NVIDIA-Nemotron-Nano-9B-v2: the chat template changed and renders differently (multi-turn, tool-call); prompts rendered with the old one no longer match what the model now expects, so cached prompts and eval sets need re-rendering; add_bos_token true to false; encoding the same text yields different ids (2025-08-15).\n\nRepository: https://huggingface.co/nvidia/NVIDIA-Nemotron-Nano-9B-v2. Revisions from b27e3876f3db535003a7635f4fc20c4ed77e02fa onward carry this change; a pin at 85507799cec2b7978deff4329546aff29456f916 or earlier does not.\n\nChanged keys:\n- tokenizer add_bos_token: true -> false (tokenizer)\n- tokenizer chat_template_sha256: b64f57c601cc2f85 -> b7a3a520a4bc1bea (template)\n\nThis record says what the change does mechanically. It is not a report that anything broke for anyone.",
 "affected": [
  {
   "ranges": [
    {
     "type": "GIT",
     "repo": "https://huggingface.co/nvidia/NVIDIA-Nemotron-Nano-9B-v2",
     "events": [
      {
       "introduced": "b27e3876f3db535003a7635f4fc20c4ed77e02fa"
      }
     ]
    }
   ],
   "database_specific": {
    "model": "nvidia/NVIDIA-Nemotron-Nano-9B-v2",
    "previous_revision": "85507799cec2b7978deff4329546aff29456f916"
   }
  }
 ],
 "references": [
  {
   "type": "INTRODUCED",
   "url": "https://huggingface.co/nvidia/NVIDIA-Nemotron-Nano-9B-v2/commit/b27e3876f3db535003a7635f4fc20c4ed77e02fa"
  },
  {
   "type": "PACKAGE",
   "url": "https://huggingface.co/nvidia/NVIDIA-Nemotron-Nano-9B-v2"
  },
  {
   "type": "WEB",
   "url": "https://www.neurarch.com/changes-feeds/models/nvidia/NVIDIA-Nemotron-Nano-9B-v2.html"
  }
 ],
 "database_specific": {
  "source": "neurarch model change tracker",
  "model": "nvidia/NVIDIA-Nemotron-Nano-9B-v2",
  "kind": "tokenizer",
  "classes": [
   "tokenizer",
   "template"
  ],
  "changed_keys": [
   {
    "file": "tokenizer",
    "key": "add_bos_token",
    "before": true,
    "after": false,
    "class": "tokenizer"
   },
   {
    "file": "tokenizer",
    "key": "chat_template_sha256",
    "before": "b64f57c601cc2f85",
    "after": "b7a3a520a4bc1bea",
    "class": "template"
   }
  ],
  "impact": {
   "memory": false,
   "serving": true,
   "tokenizer": true,
   "licence": null
  },
  "breaking": true,
  "breaking_rule": "https://www.neurarch.com/changes-feeds/advisories/index.json#breaking_rule",
  "consequence": {
   "params": null,
   "weightsGbBf16": null,
   "trainPeakGb": null,
   "fingerprint": null,
   "context": null,
   "eos": null,
   "bos": null
  },
  "commit_date": "2025-08-15T04:03:41.000Z",
  "detected_at": "2026-10-18T09:00:52.565Z",
  "detected_by": "backfill",
  "days_since_first_commit": 2,
  "license": "CC-BY-4.0"
 }
}