| name | fable-low-power |
| description | Fable Low Power mode — token-saving profile when Anthropic usage limits run low: the frontier model acts as decision maker, judge, and orchestrator ONLY; every execution step routes to cheaper models. Auto-armed by the limit-sense hook when the 5h/7d windows cross thresholds; also on demand. Use for: "low power", "save Fable", "limits are low", "running out of quota", "/fable-low-power", "conserve tokens", "battery mode". |
Fable Low Power Mode
A power profile, not a new orchestrator. This skill defines what CHANGES when
your Anthropic usage limits run low, and how the mode switches.
State machine
State file: ~/.claude/fable-low-power.json ·
Sensor: ~/.claude/skills/fable-low-power/limit-sense.sh
- Signal:
rate_limits.five_hour/.seven_day.used_percentage from the
statusline payload Claude Code pipes per render tick, teed to
~/.claude/cache/statusline-payload.json by statusline-tee.sh.
No credentials involved. If you replace the statusline script, keep the tee.
- Modes:
auto (default — thresholds decide) · on / off (manual, outranks auto).
- Auto thresholds (in the state file): ON when 5h ≥ 60% or 7d ≥ 75%;
back OFF only when 5h < 40% and 7d < 65% (hysteresis, no flapping).
Reading stale >30 min → hold last state.
- Trigger:
low-power-mode.sh announces ON at session start and
mid-session flips at prompt boundaries. Announcements instruct the session
to invoke this skill.
Subcommands (when invoked as /fable-low-power …)
| Args | Do |
|---|
(none) / status | bash ~/.claude/skills/fable-low-power/limit-sense.sh → report effective state, mode, 5h/7d %, resets, thresholds, and frontier burn (fable_today / fable_7d / workers_today) — one screen. |
on | bash ~/.claude/skills/fable-low-power/limit-sense.sh set-mode on → confirm, then APPLY the profile below immediately in this session. |
off | bash ~/.claude/skills/fable-low-power/limit-sense.sh set-mode off → confirm normal routing resumed. |
auto | bash ~/.claude/skills/fable-low-power/limit-sense.sh set-mode auto → report what auto currently decides. |
Usage tracking
The statusline tee also writes a per-session ledger:
~/.claude/cache/usage-sessions/<session_id>.json — cumulative model, cost,
and main-loop token totals, atomically overwritten per tick (last write =
session totals). limit-sense.sh aggregates it into:
fable_today — sessions whose main loop matches model_match (default
"fable", editable in the state file), active today: count, cost_usd,
in/out tokens. out_tokens is the main loop only, so it's the closest
proxy for "what the frontier model itself generated"; cost_usd includes
in-session subagents.fable_7d — same over the trailing 7 days (matches the weekly limit window).workers_today — interactive sessions on other models. Headless -p runs
never tick a statusline, so they don't appear.
The low-power banner surfaces this as "📈 Frontier burn: …". Ledger files
older than 8 days are pruned by the reader. Day attribution = a session's
last-active day (sessions spanning midnight count once, on the later day).
The profile — what ON changes
ON hardens "the frontier model orchestrates, cheaper models execute" from
default to hard rail:
- The frontier model's token budget buys judgment only: routing
decisions, task specs, verdicts, taste calls, plans, and the reply to the
user. Nothing else.
- No inline execution. Searches, greps, probes, bulk file reads, builds,
test runs, fixes, doc/deliverable drafting — ALL go to subagents on
cheaper models (e.g. Sonnet for well-specified work, Haiku for scans).
Agents return digests; bulk artifacts travel as file paths — the frontier
model never pages through raw content it can have summarized.
- Supervision stays on: task specs written junior-clear (exact paths,
commands, expected output, "on ANY surprise stop and report"), and
load-bearing claims spot-verified — via a cheap verify agent, not by the
frontier model re-reading everything.
- One-screen replies, batched judgment. Accumulate small rulings and
deliver them together; one fix-worker per findings list, never one per
finding; no long syntheses in chat — files.
- Park what doesn't need frontier judgment. If a task needs no frontier
call at all, dispatch it whole or park it with a one-line note.
- Floor, not theater: if a dispatch would plainly cost more total tokens
than a trivial inline action (a one-line edit, a
date), do it inline.
Low power saves tokens, not ceremony.
Unchanged — these outrank the profile
- The quality bar never drops: if no affordable model clears a task's bar,
stop and tell the user — never silently ship degraded work.
- Your project's own workflow rules (review gates, PR rituals, approval
steps) keep their routing; this profile only governs everything else.
