debug-bug

Debug Bug

Systematically find and fix bugs while reading as little code as possible.

Workflow

Reproduce → Localize → Trace → Fix → Verify

1. Reproduce

tl run "<repro command>"   # Capture the actual error output

No fix without reproduction. If no repro command is given, ask for one. If the bug is in tests, run the failing test. This step is non-negotiable.

2. Localize

Narrow down where the bug lives:

tl parallel \
  "errors=tl errors" \
  "blame=tl blame <file>" \
  "history=tl history <file>"

If the error includes a stack trace, start with the top frame. If it's vague, use tl search "<error message>" to find where the error originates.

3. Trace

Understand the code path without reading entire files:

tl parallel \
  "flow=tl flow <function> <file>" \
  "deps=tl deps <file>" \
  "snippet=tl snippet <function> <file>"

4. Fix

Apply the minimal fix. Then check for side effects:

tl parallel "guard=tl guard" "impact=tl impact <file>"

5. Verify

tl parallel "repro=tl run '<repro command>'" "tests=tl run '<test command>'"

Decision tree

Bug report → Can you reproduce it?
  ├─ Yes → What layer does the error come from?
  │   ├─ Stack trace points to a file → tl blame + tl snippet on that file
  │   ├─ Error is vague / no stack → tl errors + tl search for the error message
  │   └─ Happening in dependency → tl deps to confirm, check dep version
  ├─ No → Ask for reproduction steps before proceeding
  └─ Intermittent → tl history on suspect files, look for recent changes

Tips

• Use tl parallel to run context-gathering commands simultaneously
• Use tl search "<error message>" to find where errors are thrown
• Check tl diff for recent regressions — the bug may be in the last few commits
• If a file is under 150 lines, just read it directly — tokenlean overhead isn't worth it
• After fixing, run tl impact to ensure dependents aren't affected by the change