From ee579a8de5ceccd397fdf27a781d519015154501 Mon Sep 17 00:00:00 2001
From: realyxl <realyuxuanli@gmail.com>
Date: Thu, 14 May 2026 01:59:52 +0800
Subject: [PATCH] Add logits processor arguments to mlx_lm.generate

---
 mlx_lm/generate.py | 74 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/mlx_lm/generate.py b/mlx_lm/generate.py
index 3573b2640..e8fccb5db 100644
--- a/mlx_lm/generate.py
+++ b/mlx_lm/generate.py
@@ -38,7 +38,7 @@
     TokenBuffer,
     load_prompt_cache,
 )
-from .sample_utils import make_sampler
+from .sample_utils import make_logits_processors, make_sampler
 from .tokenizer_utils import TokenizerWrapper
 from .utils import does_model_support_input_embeddings, load
 
@@ -51,6 +51,13 @@
 DEFAULT_XTC_PROBABILITY = 0.0
 DEFAULT_XTC_THRESHOLD = 0.0
 DEFAULT_MIN_TOKENS_TO_KEEP = 1
+DEFAULT_LOGIT_BIAS = None
+DEFAULT_REPETITION_PENALTY = 0.0
+DEFAULT_REPETITION_CONTEXT_SIZE = 20
+DEFAULT_PRESENCE_PENALTY = 0.0
+DEFAULT_PRESENCE_CONTEXT_SIZE = 20
+DEFAULT_FREQUENCY_PENALTY = 0.0
+DEFAULT_FREQUENCY_CONTEXT_SIZE = 20
 DEFAULT_SEED = None
 DEFAULT_MODEL = "mlx-community/Llama-3.2-3B-Instruct-4bit"
 DEFAULT_QUANTIZED_KV_START = 5000
@@ -60,6 +67,18 @@ def str2bool(string):
     return string.lower() not in ["false", "f"]
 
 
+def parse_logit_bias(string):
+    try:
+        bias = json.loads(string)
+        return {int(k): float(v) for k, v in bias.items()}
+    except (ValueError, TypeError, AttributeError) as e:
+        raise argparse.ArgumentTypeError(
+            "must be a JSON object mapping token ids (int) to biases (float), "
+            'e.g. \'{"100": 3.0, "200": -1.8}\'. '
+            f"({e})"
+        )
+
+
 def setup_arg_parser():
     """Set up and return the argument parser."""
     parser = argparse.ArgumentParser(description="LLM inference script")
@@ -142,6 +161,49 @@ def setup_arg_parser():
         default=DEFAULT_MIN_TOKENS_TO_KEEP,
         help="Minimum tokens to keep for min-p sampling.",
     )
+    parser.add_argument(
+        "--logit-bias",
+        type=parse_logit_bias,
+        default=DEFAULT_LOGIT_BIAS,
+        help="Additive logit bias as a JSON object mapping token ids to biases, "
+        'e.g. \'{"100": 3.0, "200": -1.8}\'.',
+    )
+    parser.add_argument(
+        "--repetition-penalty",
+        type=float,
+        default=DEFAULT_REPETITION_PENALTY,
+        help="A (sign-aware) multiplicative penalty for repeating tokens.",
+    )
+    parser.add_argument(
+        "--repetition-context-size",
+        type=int,
+        default=DEFAULT_REPETITION_CONTEXT_SIZE,
+        help="Number of previous tokens to consider for repetition penalty.",
+    )
+    parser.add_argument(
+        "--presence-penalty",
+        type=float,
+        default=DEFAULT_PRESENCE_PENALTY,
+        help="An additive penalty for each token in the recent context.",
+    )
+    parser.add_argument(
+        "--presence-context-size",
+        type=int,
+        default=DEFAULT_PRESENCE_CONTEXT_SIZE,
+        help="Number of previous tokens to consider for presence penalty.",
+    )
+    parser.add_argument(
+        "--frequency-penalty",
+        type=float,
+        default=DEFAULT_FREQUENCY_PENALTY,
+        help="An additive penalty for each occurrence in the recent context.",
+    )
+    parser.add_argument(
+        "--frequency-context-size",
+        type=int,
+        default=DEFAULT_FREQUENCY_CONTEXT_SIZE,
+        help="Number of previous tokens to consider for frequency penalty.",
+    )
     parser.add_argument(
         "--seed",
         type=int,
@@ -2069,6 +2131,15 @@ def main():
         xtc_threshold=args.xtc_threshold,
         xtc_special_tokens=tokenizer.encode("\n") + list(tokenizer.eos_token_ids),
     )
+    logits_processors = make_logits_processors(
+        logit_bias=args.logit_bias,
+        repetition_penalty=args.repetition_penalty,
+        repetition_context_size=args.repetition_context_size,
+        presence_penalty=args.presence_penalty,
+        presence_context_size=args.presence_context_size,
+        frequency_penalty=args.frequency_penalty,
+        frequency_context_size=args.frequency_context_size,
+    )
     response = generate(
         model,
         tokenizer,
@@ -2076,6 +2147,7 @@ def main():
         max_tokens=args.max_tokens,
         verbose=args.verbose,
         sampler=sampler,
+        logits_processors=logits_processors,
         max_kv_size=args.max_kv_size,
         prompt_cache=prompt_cache if using_cache else None,
         kv_bits=args.kv_bits,