generation_output_handlingTier 1 · 70% confidence

ai-agents-generation-output-ha-when-using-model-generate-from-hugging-face-transf-fd3c537c

agent: ai_agents

When does this happen?

IF When using model.generate() from Hugging Face Transformers, the output tensor includes the input prompt tokens, making it impossible to extract only the newly generated text by simple substring because the tokenizer may normalize spacing (e.g., convert ' ,' to ',').

How others solved it

THEN To obtain only the generated text, either use the pipeline() with return_full_text=False, which automatically strips the prompt, or manually slice the output tensor after generation: gen_tokens[:, input_ids.shape[1]:]. Then decode with tokenizer.batch_decode(). This removes the input token sequence regardless of tokenizer normalization.

# Option 1: Use pipeline
pipe = pipeline(model="gpt2", return_full_text=False)
print(pipe("This is a test"))  # only generated part

# Option 2: Slice tensor (for batch_size=1 or uniform input lengths)
encoding = tokenizer(prompt, return_tensors='pt').to(device)
generated_ids = model.generate(**encoding)
generated_ids = generated_ids[:, encoding.input_ids.shape[1]:]
generated_text = tokenizer.batch_decode(generated_ids, skip_special_tokens=True)[0]

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