Module: LittleGhost::Support::OutputTruncation

Defined in:
lib/little_ghost/support/output_truncation.rb

Overview

OutputTruncation keeps large tool results within a predictable context budget without breaking UTF-8. Its byte-to-token estimate is deliberately approximate; use a provider tokenizer when exact accounting is required.

Constant Summary collapse

APPROX_BYTES_PER_TOKEN =

Byte estimate used when no provider tokenizer is available.

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Class Method Summary collapse

Class Method Details

.approx_bytes_for_tokens(tokens) ⇒ Object

Converts a token budget to its approximate byte budget.



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# File 'lib/little_ghost/support/output_truncation.rb', line 20

def approx_bytes_for_tokens(tokens)
  Integer(tokens) * APPROX_BYTES_PER_TOKEN
end

.approx_token_count(text) ⇒ Object

Estimates tokens from the UTF-8 byte length of text.



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# File 'lib/little_ghost/support/output_truncation.rb', line 15

def approx_token_count(text)
  approx_tokens_from_byte_count(String(text).bytesize)
end

.approx_tokens_from_byte_count(bytes) ⇒ Object

Converts bytes to an approximate token count, rounded up.



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# File 'lib/little_ghost/support/output_truncation.rb', line 25

def approx_tokens_from_byte_count(bytes)
  (Integer(bytes) + APPROX_BYTES_PER_TOKEN - 1) / APPROX_BYTES_PER_TOKEN
end

.truncate_middle_with_token_budget(text, max_tokens) ⇒ Object

Keeps text within budget or produces a middle-truncated UTF-8 string and the original approximate token count.



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# File 'lib/little_ghost/support/output_truncation.rb', line 31

def truncate_middle_with_token_budget(text, max_tokens)
  content = utf8_content(text)
  max_tokens = Integer(max_tokens)
  max_bytes = approx_bytes_for_tokens(max_tokens)
  return [content, nil] if max_tokens.positive? && content.bytesize <= max_bytes

  prefix, suffix = split_string(content, max_bytes / 2, max_bytes - (max_bytes / 2))
  removed_tokens = approx_tokens_from_byte_count([content.bytesize - max_bytes, 0].max)
  truncated = "#{prefix}…#{removed_tokens} tokens truncated…#{suffix}"
  [truncated, approx_token_count(content)]
end