# Auto-Migrating Claude Code with a Throwaway launchd Job — a Script That Deletes Itself When Its Work Is Done > Source: > Published: 2026-07-18 11:00:05+00:00 This continues my "Claude Code environment" series that started with [showing rate limits live in the status line](https://zenn.dev/bokuwalily/articles/statusline-live-limits). This time it's a one-shot model-migration job — the **"throwaway job" pattern, where the job removes its own plist with launchctl unload once it's finished**. Fable 5 shuts down on 2026-07-07. If your Claude Code `settings.json` has `model: fable-5` , it will keep pointing at that stale ID from that day onward. You could just run `jq` by hand, but **missing the shutdown moment, or being mid-task and forgetting**, is almost guaranteed to happen. So I handed it off to launchd. Writing a job that runs `jq '.model = "opus"' ~/.claude/settings.json` every day is trivial, but the day after the switch is done, a no-op process runs every single day. **Having something written down permanently for a task you only do once** just feels wrong. The ideal is a job that "runs exactly once on 07-07 and then disappears." It breaks into four steps. | Step | Purpose | |---|---| | Date guard | Neutralize catch-up firing and early launches | | jq surgery | Replace only the `model` key in settings.json | | osascript notification | Let a human know the unattended run happened | `launchctl unload` | De-register the job to make it single-use | Here is the full text of `~/.claude/scripts/model-transition-0707.sh` . ``` bash #!/bin/bash # model-transition-0707.sh — 2026-07-07にFable 5が終了するため、settings.jsonのmodelをopusへ自動切替 # 冪等: 7/7以降かつ model が fable の時だけ書き換える。成功したら自分のplistをunload。 set -uo pipefail SETTINGS="$HOME/.claude/settings.json" LOG="$HOME/.claude/logs/model-transition.log" PLIST="$HOME/Library/LaunchAgents/com.shun.model-transition-0707.plist" log() { echo "[$(date '+%F %T')] $*" >> "$LOG"; } # 7/7より前なら何もしない（catch-up発火対策） if [ "$(date +%Y%m%d)" -lt 20260707 ]; then log "skip: before 2026-07-07"; exit 0 fi current=$(jq -r '.model // empty' "$SETTINGS") if echo "$current" | grep -qi 'fable'; then cp "$SETTINGS" "$SETTINGS.bak-model-transition" jq '.model = "opus"' "$SETTINGS" > "$SETTINGS.tmp" && jq . "$SETTINGS.tmp" > /dev/null && mv "$SETTINGS.tmp" "$SETTINGS" log "switched model: $current -> opus" /usr/bin/osascript -e 'display notification "Fable 5終了に伴いデフォルトモデルをOpusへ切替えました" with title "Claude model transition"' >/dev/null 2>&1 || true else log "no-op: model is already '$current'" fi # 役目を終えたらジョブを外す（plistは残す＝再登録可能） launchctl unload "$PLIST" 2>/dev/null || true log "done (job unloaded)" if [ "$(date +%Y%m%d)" -lt 20260707 ]; then log "skip: before 2026-07-07"; exit 0 fi ``` launchd will sometimes catch-up-fire scheduled jobs when the Mac boots. There's also the case where the first firing arrives right after you `launchctl load` . By comparing `date +%Y%m%d` as an integer against `20260707` , no matter when it's launched, it always bails out at zero cost if the date is before 07-07. ``` cp "$SETTINGS" "$SETTINGS.bak-model-transition" jq '.model = "opus"' "$SETTINGS" > "$SETTINGS.tmp" && jq . "$SETTINGS.tmp" > /dev/null && mv "$SETTINGS.tmp" "$SETTINGS" ``` Going through `.tmp` is so that if `jq` fails it won't corrupt the original file. After writing out, it verifies syntax with `jq .` and then does an atomic `mv` . Since there's a backup, worst case you can restore with `cp "$SETTINGS.bak-model-transition" "$SETTINGS"` . The reason for matching case-insensitively with `grep -qi 'fable'` is to catch any of `fable-5` , `claude-fable-5` , or `FABLE` . Using `'.model // empty'` makes it return an empty string instead of null when the `model` key itself is absent (i.e. the default is in use), which prevents an unbound variable error under `set -uo pipefail` . ``` launchctl unload "$PLIST" 2>/dev/null || true log "done (job unloaded)" ``` Whether it switched the model or it was already opus (`no-op` ), whichever path it takes, it always reaches this line at the end. The `|| true` absorbs the error when it's already been unloaded. :::message `launchctl unload` does not delete the plist file. `~/Library/LaunchAgents/com.shun.model-transition-0707.plist` stays in place, so you can re-register it anytime with `launchctl load` . What's "throwaway" is only the job's registration state. ::: `~/Library/LaunchAgents/com.shun.model-transition-0707.plist` (home path shown with `~` notation): ``` Labelcom.shun.model-transition-0707 ProgramArguments /bin/bash ~/.claude/scripts/model-transition-0707.sh StartCalendarInterval Hour6Minute50 Hour12Minute50 Hour20Minute50 EnvironmentVariables PATH~/.nvm/versions/node/v24.13.0/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:~/.local/bin StandardErrorPath~/.claude/logs/model-transition.err ``` Three times a day (06:50 / 12:50 / 20:50) are specified via the `StartCalendarInterval` array. Even if you miss the morning firing on 07-07, you can catch it at noon or in the evening. Because of the date guard, everything before 07-07 is skipped, and on and after 07-07 the first run does the switch and immediately self-destructs, so no later firings arrive. Making `StartCalendarInterval` an array lets you bundle multiple times into a single plist. Be careful not to confuse it with the seconds-interval `StartInterval` . :::message The paths written in `ProgramArguments` need to be full paths, because launchd does not expand `~` . The `~` notation above is for explanation; the actual plist needs to contain the paths with `$HOME` already expanded. ::: ``` # 登録 launchctl load ~/Library/LaunchAgents/com.shun.model-transition-0707.plist # 確認 launchctl list | grep model-transition # 手動テスト（07-07より前なら "skip: before 2026-07-07" でログに記録されて終わる） ~/.claude/scripts/model-transition-0707.sh tail -5 ~/.claude/logs/model-transition.log ``` If you want to try the actual switch locally, temporarily comment out the date-guard line in the script and run it (a backup is taken in `settings.json.bak-model-transition` ). The log from a normal firing at 06:50 on 07-07: ``` php [2026-07-07 06:50:02] switched model: claude-fable-5 -> opus [2026-07-07 06:50:02] done (job unloaded) ``` It's done in two lines, and because the job is gone, the later 12:50 and 20:50 don't fire. `set -uo pipefail` , a missing `model` key kills the script with an unbound variable`'.model // empty'` return an empty string. Even if `grep -qi` gets an empty string, it's false and bails, so that's fine.`.tmp` is left behind by a kill, the next launch references the old contents`mv` is only reached after the syntax check, so it normally isn't left behind, but if you're worried you could add a guard at the top that deletes `.tmp` if it exists at launch.`launchctl unload` in an already-unloaded state exits with an error`|| true` .`/opt/homebrew/bin` in the plist's `EnvironmentVariables.PATH` .`/usr/bin/osascript` . `>/dev/null 2>&1 || true` keeps a failed notification from halting the whole script.`date +%Y%m%d` ) neutralizes catch-up firing and early launches.`.tmp` `launchctl unload "$PLIST"` A "time-limited one-shot job" isn't limited to model migration — it's a pattern usable for any work with a fixed end: deprecations, campaign periods, migration schedules, and the like. You can handle the next migration just by changing the plist's label, date, and path. Next time I plan to write about managing these launchd jobs as they accumulate — how to take stock of a `~/Library/LaunchAgents/` cluttered with scripts. *Written by **Lily** — I ship iOS apps and automate my content stack with Claude Code. Follow along: [Portfolio](https://bokuwalily.com) · [X](https://x.com/bokuwalily) · [GitHub](https://github.com/bokuwalily)*