fleet-worker Skill | Agent Skills

fleet-worker

Run a cheap headless Claude Code worker on a cheaper model and let an Opus orchestrator (this session) fan workers out in parallel, then verify and land their work. The worker keeps Claude Code's entire tool harness (Read/Write/Edit/Bash/Glob/Grep/Task/MCP/hooks) — only the brain is swapped to a cheaper model via env — a cheaper Anthropic model (Sonnet/Haiku) or a non-Anthropic endpoint. GLM-5.2 on z.ai is the default worked example; the mechanism is provider- and model-agnostic (any Anthropic-compatible endpoint).

This is the spawning layer. fleet-ops is the landing layer. fleet-worker produces branches cheaply; fleet-ops lands them through a test gate with your review. See references/fleet-ops-handoff.md.

The architecture crux: per-agent model = process isolation

ANTHROPIC_BASE_URL and the ANTHROPIC_DEFAULT_*_MODEL mapping vars are process-global — read once per claude process, applied to every model call it makes (including in-process Task subagents). There is no per-agent override. So you cannot keep one Opus session and have its subagents secretly run on GLM. The only way to pair a GLM-brained agent with an Opus orchestrator is a separate OS process with its own env block. That process is fleet-worker.

The load-bearing rule: auth isolation (do not skip)

On any machine also logged into a Claude.ai/Anthropic subscription, the naïve "just set ANTHROPIC_AUTH_TOKEN" launcher fails with 401 token expired or incorrect — the host's stored subscription OAuth token (~/.claude.json oauthAccount + forceLoginMethod) takes precedence and gets sent to the non-Anthropic endpoint, which rejects it. --settings overrides do not fix it. The fix is a dedicated, empty config dir:

export CLAUDE_CONFIG_DIR="$HOME/.fleet-worker/cfg"   # no inherited OAuth/hooks

The launcher sets this automatically. It also gives each worker a clean hook/permission/MCP profile so it can't trip the host's hooks. Full analysis in references/fleet-worker-spec.md §4.

Giving a worker skills

The isolated config dir starts clean — the worker inherits none of the host's skills, MCP servers, or hooks (that isolation is what keeps it off your credentials). So provision what a worker should have: drop skill dirs into the worker's own config ($FLEET_WORKER_CONFIG_DIR/skills/<name>/) or commit them to the project's .claude/skills/ in the worktree. The cheap brain then loads the same on-demand, progressively-disclosed procedural knowledge your orchestrator has — often the cheapest way to lift a weak model's output on a specialized task.

Setup

Install — these scripts ship with the skill. After scripts/install.sh they live at ~/.claude/skills/fleet-worker/scripts/. Either call them by that path, or symlink onto PATH for convenience:
```
ln -s ~/.claude/skills/fleet-worker/scripts/fleet-worker ~/.local/bin/fleet-worker
ln -s ~/.claude/skills/fleet-worker/scripts/fleet-collect.sh ~/.local/bin/fleet-collect.sh
```
Provide the key (the launcher never prints it; resolution order):
- export ANTHROPIC_AUTH_TOKEN=<key>, or
- export FLEET_WORKER_KEYRING_SERVICE=<svc> FLEET_WORKER_KEYRING_KEY=<name> (uses keyring get), or
- export ZHIPU_API_KEY=<key> (or GLM_API_KEY).
Preflight — bash scripts/fleet-doctor.sh --offline (structural) or --live (pings the endpoint; warns about the §4 oauth trap).

Config knobs (env, all optional)

| Var | Default | Purpose | |---|---|---| | FLEET_WORKER_BASE_URL | https://api.z.ai/api/anthropic | Anthropic-compatible endpoint | | FLEET_WORKER_MODEL | GLM-5.2 | main model (opus+sonnet mapping) | | FLEET_WORKER_SMALL_MODEL | GLM-4.5-Air | background/cheap model (haiku mapping) | | FLEET_WORKER_CONFIG_DIR | ~/.fleet-worker/cfg | isolated config dir — one per parallel worker | | FLEET_WORKER_EFFORT | high | seeded effortLevel in the worker's settings | | FLEET_WORKER_PERMISSION_MODE | bypassPermissions | worker --permission-mode; use dontAsk + an allowlist to spawn from an auto-mode orchestrator (see Permission posture) |

Point FLEET_WORKER_BASE_URL/FLEET_WORKER_MODEL at any other Anthropic-compatible gateway (this is the documented Claude Code custom-endpoint mechanism) to drive a different cheap model.

Staying all-Anthropic? The same separate-process trick runs a cheaper Claude model as the worker — an Opus orchestrator with Sonnet/Haiku workers, no third-party account. Point FLEET_WORKER_BASE_URL at Anthropic's API and set FLEET_WORKER_MODEL/ FLEET_WORKER_SMALL_MODEL to a Claude model, authenticating with an Anthropic API key. The defaults target z.ai/GLM only because that's the cheapest brain; the mechanism doesn't care which model answers.

When to delegate (and when not)

| Delegate to a worker | Keep on the orchestrator | |---|---| | Independent, well-scoped, tool-using subtasks | Tasks needing this conversation's context | | Refactors, test-writing, doc edits, mechanical multi-file changes | Judgment calls, architecture, ambiguous specs | | Work where Opus-quality isn't required and a wrong edit is cheap to discard | Anything expensive-if-wrong and unreviewed |

The safety comes from the cage, not the model: isolated worktree (blast radius), isolated config dir (no host creds/hooks), and the orchestrator's merge gate (nothing lands without review).

Model routing convention (hybrid: in-process tiers + provider workers)

"Delegate or not" has a third axis: which model, and where. One taxonomy answers both — for the in-process Workflow-tool agents and the fleet-worker provider workers — so a fan-out routes models intentionally instead of defaulting every agent to the orchestrator's model.

It rests on the architecture crux above: model alias slots (opus｜sonnet｜haiku) vary per agent within one process (set via a Workflow agent()'s opts.model), but the provider (ANTHROPIC_BASE_URL) is process-global — so cross-provider routing needs a separate process, which is fleet-worker. Hence two loci:

| Work class | Locus | Model | Effort | |---|---|---|---| | mechanical | fleet-worker (GLM) or in-proc | haiku / GLM-4.5-Air | low | | scout | in-proc (fleet-worker if wide) | sonnet / GLM-5.2 | low | | build | in-proc | sonnet→opus | medium | | synthesize | in-proc only | inherit (session = Fable/Opus) | high | | judge | in-proc only | inherit (session = Fable/Opus) | high–max |

Locus rule: shell out to fleet-worker only for a large (≈12+), independent, file-mutating, cost-dominant fan-out you can gate before landing; everything else — and always synthesize/judge — stays in-process. Two guardrails: never under-power a judge (a cheap rubber-stamp verifier is worse than none), and reach for the effort lever before the model lever (it's finer-grained, no quality cliff).

Drop-in helper + worked examples (review→verify, hybrid migrate, budget-aware degradation): assets/route.js and references/model-routing.md.

Single-worker recipe

cd <target-worktree>
fleet-worker --output-format json "Refactor src/parser.py to use the visitor pattern" \
  > result.json
fleet-collect.sh result.json && echo "succeeded — review the diff"

fleet-collect.sh gates on is_error (the real success signal — subtype lies) and prints the worker's final text. Exit 0 = success, 10 = worker failed.

Fan-out recipe (parallel workers)

Each task gets its own git worktree + branch and its own config dir so N workers never clobber each other. Spawn from the orchestrator's Bash tool with run_in_background: true, then collect by output file.

delegate() {                     # $1 = task-id, $2 = prompt
  local id="$1" prompt="$2" wt=".fleet-work/$1"
  git worktree add -q -b "fleet/$id" "$wt" HEAD
  ( cd "$wt"
    FLEET_WORKER_CONFIG_DIR="$HOME/.fleet-worker/cfg-$id" \
      fleet-worker --output-format json "$prompt" > "../$id.result.json" 2> "../$id.err"
  )
}
delegate task-a "Add tests for the auth module"      &
delegate task-b "Update the README install section"  &
delegate task-c "Refactor utils.py duplications"     &
wait                                                  # barrier

for id in task-a task-b task-c; do
  if fleet-collect.sh ".fleet-work/$id.result.json" >/dev/null; then echo "fleet/$id OK"; fi
done

Keep concurrency modest (≤ 4–6) — the binding constraint is endpoint quota, not local CPU. .gitignore the scratch dirs (.fleet-work/, .fleet-worker/).

Hand off to fleet-ops (test-gated landing)

The winning branches are ordinary git branches — land them with the sibling skill instead of merging by hand:

fleet track fleet/task-a fleet/task-b fleet/task-c   # register as lanes
fleet land  fleet/task-a                          # sequential, test-gated, you review each diff

Full walkthrough + recovery in references/fleet-ops-handoff.md.

Permission posture

Headless -p can't answer a permission prompt — it would stall, so the worker runs in a non-interactive mode. The default is --permission-mode bypassPermissions (set FLEET_WORKER_PERMISSION_MODE to override); safety comes from the cage (isolated worktree + isolated config + merge gate), not the prompt. Optionally constrain further with --disallowedTools (e.g. block WebFetch) or --add-dir.

Spawning from an auto-mode orchestrator. If the session that runs fleet-worker is itself in auto mode, a bypassPermissions launch is hard-denied by the auto-mode classifier as Create Unsafe Agents (an agent spawning an ungated agent) — and no allow-rule saves it (broad/interpreter allow-rules are dropped on entry to auto mode). Two fixes, either works:

Launch from outside the auto-mode session — run the fan-out from a plain script / Task Scheduler / cron, or keep the orchestrator interactive (default/acceptEdits). With no parent classifier in the loop, the worker's own bypassPermissions is fine.
Give the worker gates — FLEET_WORKER_PERMISSION_MODE=dontAsk plus an allowlist (--allowedTools "Read Edit Write Bash(npm:*) Bash(git:*)", or permissions.allow in the worker's config). dontAsk is equally non-interactive — it auto-denies non-allowlisted calls instead of stalling — but it is not an "unsafe agent," so an auto-mode orchestrator will spawn it. The launcher warns if you select dontAsk with no allowlist (the worker would otherwise auto-deny everything). Keep bypassPermissions for the isolated-container variant.

FLEET_WORKER_PERMISSION_MODE accepts any Claude Code mode (default|acceptEdits|plan|auto|dontAsk|bypassPermissions). See ../../docs/auto-mode-classifier.md for the full classifier model (the override rules, the broad-allow-rule drop, and §7.9 on running headless sessions).

Worktree-under-.claude/ gotcha: Claude Code's sensitive-file guard runs before bypassPermissions for anything under .claude/. Keep manual worker worktrees at the repo top (e.g. .fleet-work/), not under .claude/.

Reliability & limits

Overload (429/529) is the real-world risk, worst during the model's launch-window peak hours. Retry with jittered backoff, cap attempts, prefer off-peak, and consider routing overflow to FLEET_WORKER_SMALL_MODEL.
Bound the loop: set --max-turns N and an orchestrator-side wall-clock timeout per worker. Collect via background + notification; never block.
Cost figures are notional: total_cost_usd is Claude Code's internal pricing table applied to a model it doesn't know — ignore it; account by usage.*_tokens and your provider's plan.
Re-dispatch is clean (the worktree makes retries idempotent).

Security

Key pulled at spawn time into a process-local env var, never written to the script, args (ps-safe), or logs. Isolated config dir keeps worker creds/session separate from the host — and the worker can't read the host's subscription credentials. Avoid --debug in shared logs (may print headers).

Know your terms (read before publishing or automating)

Using Claude Code with a custom ANTHROPIC_BASE_URL is a documented feature, and a non-Anthropic worker's inference never touches Anthropic's API/subscription. But terms change and vary by plan — verify both your Anthropic terms and your model provider's terms for your own use. Two specifics worth knowing:

Automated subscription access: Anthropic's Consumer Terms restrict driving a Claude.ai/Pro/Max subscription by "automated or non-human means … except when accessing via an Anthropic API Key." Keep the orchestrator interactive, or run it on an API key if you automate it. (A non-Anthropic worker isn't reached by this clause; an Anthropic-model worker driven by an API key lands in the API-key exemption.)
This skill is a tool, not legal advice. When in doubt, ask your provider.

Scripts

scripts/fleet-worker / scripts/fleet-worker.ps1 — the launcher (bash + PowerShell). fleet-worker --help for the full env/flag contract.
scripts/fleet-collect.sh — gate a --output-format json result; exit 0 success / 10 worker-failed; prints the final text. fleet-collect.sh --help.
scripts/fleet-doctor.sh — --offline structural preflight + doc-consistency (CI-safe); --live pings the endpoint to confirm the model still resolves and flags the §4 oauth trap. fleet-doctor.sh --help.

References & assets

references/fleet-worker-spec.md — full design spec: the architecture, the §4 auth-isolation finding, output-format schema, effort control, the reliability evidence, and the phased-rollout stance.
references/fleet-ops-handoff.md — fan-out → collect → fleet track → fleet land walkthrough and recovery.
references/model-routing.md — the hybrid model-routing convention: work-class taxonomy, the in-process-vs-provider locus rule, budget-aware degradation, and worked examples.
assets/route.js — paste-in route() / useFleetWorker() helper for Workflow scripts (model + effort per work class).
assets/worker-settings.json — the seed settings.json the launcher drops into a fresh config dir (effortLevel: high).

Agent Skills: fleet-worker

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