pi-linter

Inline session linter for pi. Opt-in rules catch vague openers, pronoun soup, scope creep, unbounded loops, and other input anti-patterns before you hit Enter.

A small, deterministic linter that renders findings above the input bar in pi. No LLM calls, no latency. Pure regex/heuristic rules. Suggestions only — it never blocks your message.

▲ vague opener — add a link, file path, or error  pi-lint:vague-opener
  ↳ implement <linear/notion url>  ·  fix <file>:<line>: <error>
✖ unbounded loop — add stop criteria: when to escalate or quit  pi-lint:unbounded-loop
  ↳ "retry once on flaky tests, ping me on any other failure"

Why

System-prompt linters (PromptLint, PromptDoctor, etc.) check production prompt artifacts for things like prompt injection and token bloat. pi-lint targets a different surface: the user's chat turn in a multi-turn coding-agent session. Its rules need conversation context (last assistant turn, message count) and they fire on the soft, human anti-patterns that quietly degrade agent sessions.

Install

pi install npm:pi-linter

Or develop locally:

git clone https://github.com/tianrendong/pi-packs
cd pi-packs
npm install
pi install ./packages/pi-linter

The npm package is pi-linter (the unscoped pi-lint slot was blocked by npm's name-similarity check). Slash command is /linter; config file (~/.pi/pi-lint.json) and env vars (PI_LINT_*) still use pi-lint.

Rules

pi-linter ships with every rule off by default. Opt in per rule via /linter enable <rule> — start silent, then enable only rules you want.

Rule	Severity	Triggers when	Fix template
vague-opener	warn	First message of session, <60 chars, no URL / file path / issue ID	implement <linear/notion url> · fix <file>:<line>: <error>
reactive-noop	warn	Prompt <80 chars matching still not working, try again, same issue, didn't work, still failing/broken/wrong	"ran X, got Y instead of Z; restarted the worker first"
unbounded-loop	critical	Contains watch, monitor, keep running/trying, every <N>, until, loop, forever AND no stop criterion	"retry once on flaky tests, ping me on any other failure"
pronoun-soup	warn	Prompt <300 chars contains 2+ bare this/that/it/them/they not anchored to a noun	"the receipt processor" not "it"
imperative-only	warn	Prompt is exactly do it, yes, go, continue, ok, proceed, fix it, etc. AND last assistant turn didn't end with a question	"go ahead with option B"
scope-creep	info	Not the first message AND starts with let's also, also,, btw,, while you're at it, one more thing	capture in TODO.md, finish current PR, start a fresh pi session
reversal	info	Starts with actually, or actually	"sketch the data model first, push back if you disagree"
naked-review-paste	warn	Contains Comment N: / Hunk: AND non-paste instruction text is <40 chars	"address all"
review-drip	info	3rd+ pasted review comment in the same session	"here are 5 comments, address them all and tell me which you disagree with"

Configure

Inside pi:

/linter                    interactive menu
/linter status             show rule state
/linter disable <rule>     opt out of one rule
/linter enable <rule>      opt in to one rule
/linter off                fully disable
/linter on                 re-enable
/linter reset              clear rule opt-ins (all rules off)

Persistent config lives at ~/.pi/pi-lint.json.

Environment variables

Env vars override the persisted config so existing setups keep working:

Var	Effect
PI_LINT_OFF=1	Fully disable pi-lint for this session
PI_LINT_DISABLE=rule1,rule2	Disable specific rules for this session
PI_LINT_ENABLE=rule1,rule2	Opt in to rules for this session
PI_LINT_POLL_MS=250	How often to re-evaluate the draft (default 250ms, min 50ms)

How it works

• On session_start, pi-lint installs an interval that polls the editor text every ~250ms.
• Each tick rebuilds a small LintContext from session state (isFirstMessage, lastAssistantText, priorReviewPasteCount) and runs all enabled rules against the current draft.
• If the set of findings changes, pi-lint updates a widget above the editor via ctx.ui.setWidget("pi-lint", lines, { placement: "aboveEditor" }).
• On session_shutdown, the interval is cleared and the widget is removed.

The rules in rules.ts are pure functions over LintContext. You can read them like ESLint rules — the file is small and adding a new rule is one entry in the RULES array.

Quiet contexts

pi-linter intentionally stays silent when:

• The draft is a pi bash-mode invocation (leading ! or !!, e.g. !ls, !!grep -rn 'still failing' .). These are shell commands, not natural-language prompts — the rules don't apply.
• The draft is empty or whitespace-only.
• /linter off or PI_LINT_OFF=1.

Compatibility

Works in interactive mode (TUI). In -p print mode and JSON mode, hasUI is false and pi-lint is a no-op. In RPC mode, getEditorText() returns "", so pi-lint also stays silent there.

License

MIT — see LICENSE.