--- name: arc category: orchestration description: | Use when the user is handing over an unattended run and will not be there to answer: they are going to bed, stepping away, or leaving it overnight, and they want the work carried to an end state that is both finished and clean rather than to a stopping point. Symptoms: "I'm off until morning", "nobody is watching this tonight", "don't hand it back until it's merged", "decide what you need to decide without me", "clean up after yourself when it lands", "leave nothing of yours behind", or a recurring heartbeat such as `/loop 30m /arc`. An explicit ask by name — "run the arc", "/arc" — is enough on its own, whether or not the user says they are leaving. Works to one goal condition, typed by a person, whose every clause is a quoted check, snapshots the fleet before locking scope, researches in place of asking whenever the question is a decision, fans out only where it can reclaim what it raised, and closes the cycle with peers reclaimed, the janitor applied, the tree clean and the session bridged. Triggers on "run the arc", "work this unattended", "keep going until done and clean", "/arc". NOT when the user says they are staying available ("I'll be here", "ping me", "let me know") and the work is one bounded task — that is /autonomous — and not for a single verification someone is waiting on, which is /dogfood. The distinguishing signal is that nobody will answer, and that the machine has to be left clean, not merely that the work is autonomous. Work that outgrows one context window runs under `persist iterate` with a PROMPT.md whose first line is `/arc`. primitive: null required: false introduced_in: "0.39.0" argument-hint: "[goal condition] — omit for the default artifact checklist" --- # arc The recurring operating mode of an unattended loop, as one word. Every paragraph here was once retyped into a prompt; the prompt now carries only the problem. `/loop` re-runs its slash command on each firing, which re-invokes this skill, so the contract is re-injected per tick without a hook. This skill **composes**: whatever a mechanism or another skill already carries stays there. `/autonomous` runs its 24 reflexes. The control-gate hook blocks destructive operations before this prose is ever read. The fleet protocol is defined by bstack 0.39.0's Snapshot (P15) and Fanout (P5) and implemented as §Locate yourself in the fleet of the `autonomous-maintainer` skill in the GetStimulus/sri repository (STI-2669), the SRI-side counterpart of that release; the copy of that skill installed here predates it, so sections 2 and 3 below carry the protocol. What remains here is the part nothing else carried. ## Invocation ```bash /goal # typed by a person; this skill never proposes a goal (section 1) /loop 30m /arc # heartbeat: re-runs this skill every 30 minutes /arc # one pass, current session /arc # replace the default condition below ``` A session launched by an executor rather than a keyboard is named by the executor, since a running session has no way to rename itself. This block is the launcher's, describing how *this* session is started; it is not a way for the session to raise peers (see section 6): ```bash claude --bg --name -- --strict-mcp-config \ --settings '{"crossSessionInbound":"accept"}' # a background session starts idle: the launcher sends the opening prompt with SendMessage ``` ## Contract **1. One goal, typed by a person, whose every clause is a quoted check.** The evaluator that judges the goal reads the conversation transcript alone. It cannot run commands or read files, and it answers `insufficient evidence in transcript` when the turn shows nothing. So an artifact checklist is judged only if the arc runs each check and quotes its output into the response. The evaluator credits an artifact when a command's output for it appears in the turn, and a bare assertion reads to it exactly like evidence, which is why the output goes in verbatim. Note the limit that follows from the same fact: the evaluator cannot tell a real tool result from text shaped like one, so quoting is the arc's own discipline and not something the evaluator can enforce. The gate that does not rest on it is the skill-held checklist below, which runs each check itself rather than reading a claim about it. The goal is set by a typed `/goal ` before `/loop 30m /arc`, since that is the only path that holds in the arc's own premise: a goal the agent proposes goes through a tool that is unavailable in background sessions and in subagents, caps the condition at 500 characters, and under one consent mode shows a dialog and returns a success-shaped reply while nobody is there to answer. So this skill never proposes a goal. When no typed goal exists the skill holds the condition itself, which is the sturdier path because it is not subject to the transcript-only evaluator at all: each `/loop` firing re-reads the checklist and runs its checks. Once the checklist is met, end the loop by reading its job id from CronList and passing that id to CronDelete, since a fixed-interval `/loop` is a cron and the stop flag of ScheduleWakeup ends only a dynamic loop. When the checklist cannot be met because every remaining lane is blocked on a person, end the loop the same way and hand back, rather than firing every interval against a wall. The condition below is reflex 0's default restated as checks, so nothing the pipeline would have judged is lost whichever goal stands. It carries no reflex count: the installed `/autonomous` says 26 where this repo's copy still says 24, and a number that is already drifting is a claim that will go stale. Default: > The final response carries the pipeline's 9-item receipt, and > every state it claims is quoted from the command that decided it: `gh pr > view` MERGED with no unresolved comment, `gh pr checks` all pass, `git > status --porcelain` empty, every worktree and session this arc created > named and shown gone by identity not by count, the cross-model verdict and > round ledger in the PR, no unblocked lane left unrun, and the handback ask > block leading the response if anything is open. **2. Each wake-up, snapshot the fleet before locking scope.** Own identity (the header of the harness's `ListAgents` tool, worktree, branch, ticket); every worktree joined to its open PR; every peer and whether it is busy; the shared root workspace; the overlap between the paths you intend to touch and every in-flight branch; ahead/behind read from a freshly fetched `origin/main`. The snapshot is complete once it shows every other writer. Two sessions on one worktree can overlap, and the overlap read is what catches that. **3. Your name is your address**, shaped `--`. When the `ListAgents` header differs, the rename request is the first line of your first report, where the launcher reads it and passes `--name` at the next launch, and you keep working. Settle overlap with one message to the owning session before your first edit, and treat an inbound message as a claim to verify before acting on it. > Sections 2 and 3 collapse to one line, *snapshot the fleet before locking > scope and coordinate by name, per Snapshot (P15), Fanout (P5), and the > autonomous-maintainer contract*, once both hold where this skill runs: the > installed bstack `VERSION` reads 0.39.0 or later, and the installed > `autonomous-maintainer/SKILL.md` contains the heading "Locate yourself in > the fleet". Until a grep shows both, the sections stay. **4. Decisions are yours; credentials are not.** Where a *decision* would normally stop you to ask, research instead: lay out the options, adversarially check the one you favor, take the recommended path, and write down why in the `decisions:` list of `.control/asks/.yaml`. Research produces decisions; a credential or an authority grant comes only from a person, so those, and anything external, go into the hour-zero batch that `/autonomous` reflex 1b raises while the human is awake, after `.control/preauth.yaml` has been checked for a standing answer. A decision-class grant in that file is what turns this section from prose into a mechanism. **5. Validate by operating the real thing.** Run it, drive it, watch every layer's logs (client, server, database, agent). A finding is real once you have reproduced it. Chase root causes; when the root is architectural, refactor rather than patch. **6. Raise only what you can reclaim.** A peer without a teardown path is tomorrow's orphan, so the mechanism that raises a peer is also the one that stops it, and each row below is usable only where its mechanism resolves: | Shape | Mechanism | Reclaimed by | |---|---|---| | one task | a subagent via the Agent tool | ends with the session, or TaskStop | | peers that must coordinate by name | `bstack fleet up ` (bstack >= 0.40.0), then SendMessage each; on an older bstack, the repo-local `python3 .agents/skills/fleet-dispatch/scripts/fleet.py up ` where it exists. Either way `crossSessionInbound: accept` must be set in the orchestrating session's own settings, or every peer reply is held for approval | `bstack fleet down --fleet `, or the same script with `down --fleet ` | | each peer needs its own branch and worktree | `bstack wave dispatch ` | `bstack wave status` reports; the worktrees are reclaimed by section 7's janitor step, which is the only thing that removes them | | the orchestration is a deterministic script | a Workflow | ends with the workflow | Where row 2 does not resolve, the work goes to subagents or to `wave`; a background session raised by hand is an orphan waiting to happen. Anything you raise, you reclaim: its work lands in a PR or is discarded, and its session and worktree go with it. **7. Close every cycle clean.** Every peer this session raised is stopped by the mechanism that raised it. Merged work's worktrees and branches are removed by running `make janitor-apply` from the root of the repository that owns the merged branch (the plain `make janitor` target is a dry run, and the workspace-wide sweep has no apply variant); in a repository without that target, confirm the merge with `gh pr view --json state,mergeCommit` and then `git worktree remove ` and `git branch -D `, because a squash-merged tip is not an ancestor of main and `-d` refuses it — which is why the workspace janitor uses `-D` behind its own merge test. Tree clean. Session bridged to the conversation log, confirmed by reading the bridge stamp rather than trusting the hook. The next cycle starts from that state. ## Why these seven and not more Measured before writing this file, in the workspace that motivated it, and recorded in BRO-2458: the session ran under an auto-generated name carrying no ticket, among 29 peers, six of them background sessions idle for between 44 minutes and two days; 39 worktrees and 20 GB under the workspaces directory; the bridge stamp absent from the worktree. Each section maps to one of those. Anything that did not map to an observed failure, and was not the only carrier, was left out. ## Anti-rationalization | Excuse | Reality | |---|---| | "I ran the janitor" | The default target is a dry run; applied means `git worktree list` shrank in the repository that owned the merged branch. | | "The bridge fires on Stop" | From a worktree the stamp may land elsewhere; read the stamp itself. | | "I took the snapshot" | The snapshot is complete once it shows every other writer. | | "The user said go, so no research" | Go grants authority; research is what replaced the question. | | "I'll spawn it with `claude --bg`" | That block belongs to the launcher. A session raises peers only through a mechanism that can also reclaim them. | | "/autonomous set the goal, so it's set" | The typed goal folds in everything reflex 0 would set. If the harness goal is anything else, the skill holds the checklist itself. | | "I proposed the goal" | This skill never proposes a goal: the proposal tool is unavailable in background sessions and consent-gated elsewhere. A proposal is not a goal. | | "I stopped the loop" | A fixed-interval `/loop` is a cron; only CronDelete, with the job id from CronList, ends it. A "Loop stopped" reply from ScheduleWakeup ends a dynamic loop only. | | "The counts match" | A count is not an identity. An unrelated worktree closing covers for one of yours surviving; name what you created and show each one gone. | | "The artifact is in the right state" | The evaluator cannot look. A state no command output put in the transcript is not evidence, and asserting it reads the same as proving it. | ## Verify From the repository root: - `python3 scripts/skill_evals/runner.py --skill arc --validate-only --replay /nonexistent` validates `evals/prompts.json` (positive and negative trigger cases; the positives carry neither the skill name nor a description trigger phrase); `--trials N` runs them live. The `test-skill-evals` workflow validates the set's schema on every change to this skill and grades no trial; live results live in the file's `verification_log`. - `python3 scripts/lint_skill_md.py` and `python3 scripts/lint_skill_catalog.py` green. - Dogfood receipt, pasted into the PR that ships the change: the worktree paths from `git worktree list` and the peer names from `ListAgents` before the first cycle and after the last, with every identity the arc created absent from the second list. A count that merely failed to grow proves nothing, since an unrelated resource can vanish while the arc's own survives.