usage-guard · Claude Code mod

Preview · a replayed session in a sandbox

claude · ~/work/app · usage-guard

› fix the failing auth test and add an audit log call ⏺ Read(src/auth.ts) ⎿ Read 6 lines ⏺ Update(src/auth.ts) ⎿ Added 2 lines, removed 1 line ⏺ Bash(bun test) ⎿ 3 pass, 1 fail ● Done. refresh now rejects expired claims and logs an audit event. ✻ Worked for 42s · done 4:20 PM › /usage-guard ⎿ usage-guard: No current 5h reading. Guard is on (warn 80%, stop 90%). ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── › ? for shortcuts

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[ -n "$BASH_VERSION" ] && [ -f "$HOME/.bashrc" ] && . "$HOME/.bashrc"

Fedora's stock ~/.bashrc already has the ~/.bashrc.d loop. On macOS, add one to ~/.bashrc, then allow Homebrew's bash before switching:

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Importing Shell History into flyline

shared.bash puts flyline on its own JSONL store, so history from a previous shell has to be imported once. Atuin's database also holds agent commands (atuin hook claude-code, dropped in 5e8d73f); filter them out on a copy first, since flyline history import takes the whole file:

sqlite3 ~/.local/share/atuin/history.db "VACUUM INTO '/tmp/atuin-user.db'"
sqlite3 /tmp/atuin-user.db "DELETE FROM history WHERE author IS NOT NULL AND author <> 'arzyk';"
flyline history import /tmp/atuin-user.db
rm /tmp/atuin-user.db

flyline is a loadable builtin, not a binary, so the import has to run from a real interactive terminal. Switching the backend also pulls in ~/.bash_history on its own, so prune that file first - agent harnesses that drove an interactive bash leave ___BEGIN___COMMAND_OUTPUT_MARKER___ wrappers and spilled heredoc bodies in it. The store is ~/.local/share/flyline/history.jsonl on Linux and ~/Library/Application Support/flyline/history.jsonl on macOS; a bad import is recoverable by deleting entries with the import's timestamp, which they all share.

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Good:

feat(lazygit): use Codex for commit messages
fix(zsh): preserve SSH agent env across shells
config(git): enable difftastic pager
chore(brew): refresh package list
docs(readme): document bootstrap steps

Avoid vague subjects:

feat: update lazygit config
chore: update files

Use a body when the commit changes behavior across multiple files or when the reason is not obvious from the subject. Keep commit titles under 50 characters and body lines under 72 characters.

Source 2 files

hooks/register.ts 70 lines

1import type { EngineInterface, Register } from 'claude-code'
2
3import { LIMIT, WARN, describe, fiveHour, notes } from './guard'
4
5const CRON_TOOLS = new Set(['CronCreate', 'CronList', 'CronDelete'])
6
7async function reading($: EngineInterface) {
8  if ((await $.store.get('off')) === true) return null
9  const w = fiveHour((await $.session.usage()).rateLimits, await $.clock.now())
10  return w && w.pct >= WARN ? w : null
11}
12
13export const register: Register = on => {
14  // Last warned percentage per window and loop; a reload forgets it and warns once more.
15  const warned = new Map<string, number>()
16
17  on('session.start', async ($, e, next) => {
18    await $.command.register({
19      name: 'usage-guard',
20      description: 'Show the 5h usage guard, or turn it off/on',
21    })
22    return next(e)
23  })
24
25  on('command.run', { command: 'usage-guard' }, async ($, e) => {
26    const arg = e.args.trim()
27    if (arg === 'off' || arg === 'on') await $.store.set('off', arg === 'off')
28    const isOff = (await $.store.get('off')) === true
29    const w = fiveHour((await $.session.usage()).rateLimits, await $.clock.now())
30    const summary = w ? describe(w) : 'No current 5h reading.'
31    return { text: `${summary} Guard is ${isOff ? 'OFF' : 'on'} (warn ${WARN}%, stop ${LIMIT}%).` }
32  })
33
34  on('session.measure', async ($, e, next) => {
35    const w = e.changed.includes('rateLimits') ? fiveHour(e.rateLimits, await $.clock.now()) : null
36    const key = `toast-${w?.reset}`
37    const level = w && w.pct >= LIMIT ? LIMIT : w && w.pct >= WARN ? WARN : 0
38    if (w && level > (warned.get(key) ?? 0)) {
39      warned.set(key, level)
40      $.ui.toast(notes(w, false).status)
41    }
42    return next(e)
43  })
44
45  on('prompt.submit', async ($, e, next) => {
46    const w = await reading($)
47    if (!w) return next(e)
48    const n = notes(w, false)
49    if (w.pct >= LIMIT && e.origin.kind !== 'task-notification')
50      return { drop: `${n.status} Resume after the reset, or run /usage-guard off to override.` }
51    const note = w.pct >= LIMIT ? n.notification : `${n.status} Keep this turn short.`
52    return next({ ...e, context: [...(e.context ?? []), note] })
53  })
54
55  on('tool.call', async ($, e, next) => {
56    const w = await reading($)
57    if (!w) return next(e)
58    const n = notes(w, e.agentId !== undefined)
59    if (w.pct >= LIMIT) {
60      if (CRON_TOOLS.has(e.tool)) return next(e)
61      return { deny: e.agentId === undefined ? n.hardStop : n.wrap }
62    }
63    const key = `${w.reset}-${e.agentId ?? ''}`
64    const ran = await next(e)
65    if (ran.deny !== undefined || w.pct - (warned.get(key) ?? 0) < 3) return ran
66    warned.set(key, w.pct)
67    return { ...ran, context: [...(ran.context ?? []), n.wrap] }
68  })
69}
70

hooks/guard.ts 42 lines

1import type { SessionRateLimit } from 'claude-code'
2
3export const WARN = 80
4export const LIMIT = 90
5
6export type Window = { pct: number; reset: number }
7
8// A reading whose reset has passed is from a past window: nothing to guard.
9export const fiveHour = (limits: readonly SessionRateLimit[], now: number): Window | null => {
10  const w = limits.find(l => l.kind === 'five_hour')
11  const reset = w?.resetsAt ? Date.parse(w.resetsAt) : NaN
12  return w && reset > now ? { pct: Math.round(w.percentUsed), reset } : null
13}
14
15// One-shot cron jobs on :00/:30 may fire up to 90s early, i.e. before the reset; skip those minutes.
16export const resumeAt = (reset: number) => {
17  let d = new Date(reset + 60_000)
18  if (d.getMinutes() % 30 === 0) d = new Date(d.getTime() + 60_000)
19  const pad = (n: number) => String(n).padStart(2, '0')
20  return {
21    at: `${pad(d.getHours())}:${pad(d.getMinutes())}`,
22    cron: `${d.getMinutes()} ${d.getHours()} ${d.getDate()} ${d.getMonth() + 1} *`,
23  }
24}
25
26export const describe = ({ pct, reset }: Window) =>
27  `5h window at ${pct}% (hard stop at ${LIMIT}%, resets at ${resumeAt(reset).at}).`
28
29export const notes = (w: Window, isSubagent: boolean) => {
30  const { cron } = resumeAt(w.reset)
31  const status = `Usage guard: ${describe(w)}`
32  const schedule = `schedule the resume with CronCreate (cron "${cron}", recurring false) using a handoff prompt that says where to pick up`
33  return {
34    status,
35    wrap: isSubagent
36      ? `${status} Finish the current step and return your result to the parent now; do not start new work.`
37      : `${status} Bring the work to a clean stopping point: land or note the current edit, start no new subagents or tasks. Then ${schedule}, tell the user what is unfinished, and stop.`,
38    hardStop: `${status} Hard stop: every tool but CronCreate is denied now. ${schedule[0]!.toUpperCase()}${schedule.slice(1)}, tell the user what is unfinished, and stop.`,
39    notification: `${status} Hard stop: record this result for the user, ${schedule} if not done yet, and stop.`,
40  }
41}
42