Module: Nexo::OutputTruncator

Defined in:
lib/nexo/output_truncator.rb

Overview

Bounds unbounded command output before it reaches the model, so a single npm install or git log can't blow a small context window. Pure and dependency-free — line/char based, no tokenizer (a token budget would be expensive to reimplement and is out of scope for v1).

The transform, in order: strip ANSI SGR escapes, keep the last max_lines lines (the tail is where errors and exit summaries live), append a …[truncated N lines] marker when lines were dropped, then hard-cap the result at max_chars characters. Configurable via kwargs only — there is no Nexo.config global and no per-agent macro in v1.

Constant Summary collapse

ANSI =

Matches ANSI SGR color/style escapes (e.g. \e[31m, \e[1;32m, \e[0m), the escapes real command output emits. VERIFIED against real output in Group 0.

/\e\[[0-9;]*m/

Class Method Summary collapse

Class Method Details

.call(text, max_lines: 200, max_chars: 16_000) ⇒ Object

Strips ANSI escapes from text, keeps the last max_lines lines (with a …[truncated N lines] marker when it trims), then caps the result at max_chars. Pure line/char truncation — no tokenizer.



25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
 
# File 'lib/nexo/output_truncator.rb', line 25

def call(text, max_lines: 200, max_chars: 16_000)
  return text if text.nil? || text.empty?

  stripped = text.gsub(ANSI, "")
  lines = stripped.split("\n", -1)
  dropped = lines.size - max_lines

  result = if dropped.positive?
    (lines.last(max_lines) + ["…[truncated #{dropped} lines]"]).join("\n")
  else
    stripped
  end

  (result.length > max_chars) ? result[-max_chars..] : result
end