Lumitrace instruments Ruby source code at load time, records expression results, and renders an HTML view that overlays recorded values on your code. It is designed for quick, local “what happened here?” inspection during test runs or scripts.

• runv/: Lumitrace demonstration Ruby playground with inlined tracing
• Tutorial
• Tutorial in Japanese
• Spec
• AI Help
• AI Schema
• Supported Syntax
• GitHub repository

Lumitrace hooks RubyVM::InstructionSequence.translate (when available) to rewrite files at require-time. It records expression results and renders an HTML view that shows them inline. Only the last N values per expression are kept to avoid huge output.

Run a script and emit text output (default):

lumitrace path/to/entry.rb

Run another command via exec:

lumitrace exec rake test

Emit HTML output:

lumitrace -h path/to/entry.rb

Limit the number of recorded values per expression (defaults to 3):

LUMITRACE_MAX_SAMPLES=5 lumitrace path/to/entry.rb

Write JSON output explicitly:

lumitrace -j path/to/entry.rb
lumitrace --json=out/lumitrace_recorded.json path/to/entry.rb

Restrict to specific line ranges:

lumitrace --range path/to/entry.rb:10-20,30-35 path/to/entry.rb

Show AI/human help:

lumitrace help
lumitrace help --format json
lumitrace schema --format json

AI-oriented usage guide:

• docs/tutorial.md section "Using with AI agents"
• docs/tutorial.ja.md section "AI と使う"

Enable instrumentation and HTML output at exit:

require "lumitrace"
Lumitrace.enable!

Enable only for diff ranges (current file):

require "lumitrace/enable_git_diff"

If you want to enable via a single require:

require "lumitrace/enable"

• Text: printed by default; use --text=PATH to write to a file.
• HTML: lumitrace_recorded.html by default, or --html=PATH.
• JSON: written only when --json (CLI) or LUMITRACE_JSON (library/CLI) is provided. Default filename is lumitrace_recorded.json.
• JSON collection mode: --collect-mode=last|types|history (default last).
• Fork/exec: merged by default. Child processes write fragments under LUMITRACE_RESULTS_DIR.

JSON event entries always include types (type-name => count).

{
  "file": "/abs/path/app.rb",
  "start_line": 10,
  "start_col": 2,
  "end_line": 10,
  "end_col": 9,
  "kind": "expr",
  "types": { "Integer": 3, "NilClass": 1 },
  "total": 4
}

• LUMITRACE_MAX_SAMPLES: default max samples per expression (default 3 if unset).
• LUMITRACE_COLLECT_MODE: value collection mode (last, types, history; default last).
• LUMITRACE_ROOT: root directory used to decide which files are instrumented.
• LUMITRACE_TEXT: control text output. 1 forces text on, 0/false disables. Any other value is treated as the text output path.
• LUMITRACE_HTML: enable HTML output; 1 uses the default path, otherwise treats the value as the HTML output path. 0/false disables.
• LUMITRACE_JSON: enable JSON output; 1 uses the default path, otherwise treats the value as the JSON output path. 0/false disables.
• LUMITRACE_ENABLE: when 1/true, require "lumitrace" will call Lumitrace.enable!. When set to a non-boolean string, it is parsed as CLI-style arguments and passed to enable!.
• LUMITRACE_VERBOSE: verbosity level (1-3). 1/true enables basic logs, 2 adds instrumented file names, 3 adds instrumented source output.
• LUMITRACE_RANGE: semicolon-separated range specs (e.g. a.rb:1-3,5-6;b.rb).
• LUMITRACE_RESULTS_DIR: internal use. Shared results directory for fork/exec merge (default: Dir.tmpdir/lumitrace_results/<user>_<parent_pid>).
• LUMITRACE_RESULTS_PARENT_PID: internal use. Parent PID for fork/exec merge (auto-set).
• LUMITRACE_GIT_DIFF=working|staged|base:REV|range:SPEC: diff source for enable_git_diff.
• LUMITRACE_GIT_DIFF_CONTEXT=N: expand diff hunks by +/-N lines (default 3).
• LUMITRACE_GIT_CMD: git executable override (default git).
• LUMITRACE_GIT_DIFF_UNTRACKED: include untracked files in git diff ranges (1 default). Set to 0 to exclude.

• Requires RubyVM::InstructionSequence.translate support.
• Very large projects or hot loops can still generate large HTML; use LUMITRACE_MAX_SAMPLES.
• Instrumentation changes evaluation order for debugging, not for production.

Install dependencies:

bundle install

Run the CLI locally:

lumitrace path/to/entry.rb