Relax dependency bounds and make comet optional

README.md

@@ -51,6 +51,15 @@ The latest tagged version is also available via PyPI:
 pip install lm-polygraph
 ```
 
+### Optional dependencies
+
+Some features require additional packages that are not installed by default:
+
+- **COMET metric** (translation evaluation): `unbabel-comet` pins `numpy<2.0` which may conflict with other packages (e.g., vLLM). Install via extras:
+  ```shell
+  pip install lm-polygraph[comet]
+  ```
+
 ## <a name="basic_usage"></a>Basic usage
 1. Initialize the base model (encoder-decoder or decoder-only) and tokenizer from HuggingFace or a local file, and use them to initialize the WhiteboxModel for evaluation:
 ```python

pyproject.toml

@@ -37,6 +37,9 @@ classifiers = [
 "Repository" = "https://github.com/IINemo/lm-polygraph"
 "Documentation" = "https://lm-polygraph.readthedocs.io"
 
+[project.optional-dependencies]
+comet = ["unbabel-comet<3"]
+
 [tool.setuptools]
 script-files = [
   "scripts/polygraph_eval",

requirements.txt

@@ -7,7 +7,7 @@ matplotlib>=3.6
 pandas>=1.3.5
 torch>=2.6.0
 bs4
-transformers>=4.50.0
+transformers>=4.50.0,<5
 nltk>=3.6.5
 sacrebleu>=1.5.0
 sentencepiece>=0.2.1
@@ -29,10 +29,9 @@ openai>=1.52.0
 wget
 sentence-transformers
 bert-score>=0.3.13
-unbabel-comet<3
 nltk>=3.7,<4
 evaluate>=0.4.2
-spacy>=3.4.0,<3.8.0
+spacy>=3.4.0
 fastchat
 diskcache>=5.6.3
 boostedprob

src/lm_polygraph/generation_metrics/__init__.py

@@ -3,7 +3,12 @@
 from .model_score import ModelScoreSeqMetric, ModelScoreTokenwiseMetric
 from .bart_score import BartScoreSeqMetric
 from .accuracy import AccuracyMetric
-from .comet import Comet
+
+try:
+    from .comet import Comet
+except ImportError:
+    Comet = None
+
 from .alignscore import AlignScore
 from .openai_fact_check import OpenAIFactCheck
 from .bert_score import BertScoreMetric

src/lm_polygraph/generation_metrics/comet.py

@@ -1,6 +1,5 @@
 import re
 import numpy as np
-from evaluate import load
 
 from typing import List, Dict
 from .generation_metric import GenerationMetric
@@ -14,6 +13,8 @@ class Comet(GenerationMetric):
 
     def __init__(self, source_ignore_regex=None, lang="en"):
         super().__init__(["greedy_texts", "input_texts"], "sequence")
+        from evaluate import load
+
         self.scorer = load("comet")
         self.source_ignore_regex = (
             re.compile(source_ignore_regex) if source_ignore_regex else None