Phases name absolute tiers (best fable>opus>sonnet, big opus>fable>sonnet,
work sonnet>opus, cheap haiku>sonnet) resolved to the first available full
id; per-model circuit breaker fed by StopFailure kinds (rate_limit,
overloaded, billing_error, model_not_found) and PostModelSwitch auto, with
episode backoff 15→300 min, cleared by a user /model or /route reload and
kept across /clear; fallback chain fable→opus→sonnet→haiku with the effort
unchanged; main loop upgrades to a phase's tier by itself under a context
cap (fails closed on unknown usage), downgrades only with the switch on,
sticky within a turn; derived orchestrate on background dispatches;
prompt default rules (plan/reflect, Unicode guards, skipped on slash
commands, floor matches and mid-turn). 58 plugin tests.
One decision helper (mainEffort) feeds the plan and every answer text;
per-axis precedence (sticky > turn route > floor > engine); a mid-turn
prompt floors the running turn and the next; per-machine kill switch
"enabled": false in ~/.claude/model-router.json, kept across /clear and
across a failed reload; typed /effort-<l> attested at prompt.submit so a
sub-agent preload cannot floor the main loop. 30 plugin tests.
Security-gate round on the wave 1-A mod: /route answers only a composer
origin; an in-agent route call can no longer change the agent's model
(effort only, model fixed at spawn); config patterns capped (200 chars,
4096-char scan), phase keys restricted, override file refused above 64 KB,
additionalProperties false on the tool schema; every .catch logs once per
session; post-next bookkeeping isolated. 14 plugin tests, verifier 11/11.
Function-hooks plugin under mods/model-router: routes effort (and, behind a
flag, the model) of every main-loop request, sets built-in sub-agents' model
at spawn with full ids, answers Skill(effort-*) itself (single writer, no
pairing rule), exposes the route tool and /route, validates the optional
~/.claude/model-router.json. 11 plugin tests, validate + tsc clean.
Contract .claude/tasks/contracts/2026-10-08-model-router-w1a-1533.md.
bchanot