transcript
show notes
A vague pasted-text bug report gets turned into a reproduction, then traced with an agent that is blocked from editing anything, then fixed one narrow diff at a time. Includes how plan mode actually enforces its limits, how to check an agent's account of your code, and the case where the tests pass but the browser is still broken.
A vague report becomes a reproduction
"It keeps saying the name is too long when it isn't. Only happens when I copy the name in from somewhere else." No file, no error text, no browser. The work starts by turning that sentence into four written things: exact steps, exact data, observed result, expected result. The data is the clue — a line copied from a notes app, nine visible characters, carrying a trailing space and a newline. Reproduced twice from a clean state, so there is a before to measure against.
Trace first, edit later
The code that enforces the length rule has never been opened. Instead of asking for a fix, the request is a trace that forbids edits — done in plan mode, where file editing and writing tools are mechanically blocked rather than merely discouraged. Ways in: the permission-mode flag at launch, Shift+Tab to cycle modes, the slash-plan command, or a default mode set in settings. The caveat: plan mode gates edits, not process execution. Read-only shell commands run unprompted from a built-in allowlist you cannot edit; anything else goes to a safety classifier unless you turn off auto mode during plan. Launching with dangerously-skip-permissions overrides the gate entirely. Tool-level alternatives: allowed-tools or disallowed-tools flags, or edit and write in the deny list.
The trace may be delegated to the built-in read-only Explore subagent, which keeps file contents in its own context and returns a summary. Two consequences: intermediate work vanishes from the transcript, and the built-in Explore and Plan subagents skip the project instructions file to save tokens — so your constraints must be restated in the prompt.
Ninety seconds of checking
The account names a form component, a route handler, and a validation function comparing raw length before trimming. That is a claim until the files are opened. A confident specific you cannot find means stopping and re-asking, not waving it through — the details arrived as one story, not independently.
Green tests, broken browser
A failing test comes before the fix, read to confirm it fails for the right reason. Three lines change. The suite passes. The browser still fails, because the form component counts characters too. Why a wide diff was wrong the first time and justified the second. Then a branch, one commit, and a message naming the behavior. Three things that went wrong, each with a one-line detection method.
Recent changes worth knowing
A persistent side-by-side diff pane from slash-diff; grep and glob now returning explicit errors instead of silent "no matches" on large result sets; slash-ultrareview handling a clean tree; Control+Enter to interrupt tool work and submit at once; and AGENTS.md as a fallback when no CLAUDE.md is present.
