CLI and exit codes

The jj-acp binary is the only executable in this repository. It composes the crates and owns nothing else: argument parsing, launch configuration assembly, signal handling and the process exit code.

The first delivery is the one-shot prepared task runner. A persistent service mode is specified but not implemented, and the ledger records it as deferred rather than implying parity.

Requirements

Commands

Exit code 0 means the turn returned normally. It is not proof that the task succeeded; the caller MUST inspect stopReason. A refusal is a normal completion with stopReason set to refusal, which is why the two are separate signals.

Working directory and inheritance

The working directory is the launch working directory. A task document cannot change it, and no option in the document is consulted for it. This keeps the untrusted input away from the one decision that determines which files an agent can touch.

The inherited environment is preserved and extended, never replaced. Existing variables that the harness needs to control are overridden deliberately and the override is recorded; everything else passes through so a controlling application can configure provider credentials the way it already does.

Implemented surface

Every launch option has a flag and a matching JJ_ACP_* variable, and the flag wins. Defaults for the idle window and the absolute cap are 620 and 7200 seconds, inherited from the upstream harness; the cancellation grace and reap bounds default to five seconds each.

Installing a signal handler replaces the default terminate-immediately behaviour, so an interruption now produces bounded cleanup and a record instead of an orphaned agent and silence. A failure to install is reported rather than ignored, because running without cancellation handling would silently weaken that guarantee.

Stdout contract

Stdout carries terminal records, and for --help, --version and agents the output those commands exist to produce. Nothing else is ever written there. Usage for a malformed command line goes to stderr, so a controlling application that mis-invokes the binary still sees empty stdout rather than prose it cannot parse.

A record is emitted on every path that reaches an invocation, including a spawn failure and an agent error. A broken stdout is the one case with no record, and it exits 1; the record is not a durable ledger and a killed harness can leave none.

Failure classification

The exit code distinguishes causes a controlling application must treat differently. 1 with agent_exited means the agent is gone and a new one can safely be started. 124 means a bound elapsed and the agent’s state is unknown, so starting another one risks two agents working the same task. 2 means nothing was started at all, so the same document can be corrected and resubmitted.

130 and 143 mean the run was interrupted and bounded cleanup ran. Cleanup being bounded is not the same as cleanup being complete, and the record says cancelled with interrupted rather than claiming the agent stopped.

Subcommand option handling

agents parses the same launch options as run, because it inspects a catalog. Building it from defaults instead reported a smaller runner set than the operator configured and looked like a correct answer, which is the worst shape for this class of bug: a catalog file that silently does nothing.

Arguments that no subcommand would read are refused rather than ignored. --help --catalog x is a mistake, and accepting it teaches an operator that unparsed flags are harmless.

Session configuration flags

--model, --effort and --mode request session settings, each with a matching JJ_ACP_MODEL, JJ_ACP_EFFORT and JJ_ACP_MODE variable and the flag winning. All three are requests, not requirements: a value the adapter does not offer is reported on stderr and the adapter’s own default is kept, and the run still completes normally with exit 0.

That asymmetry is intentional. Failing a task because an adapter lacks a preference would make the flags dangerous to pass, and a controlling application that targets several adapters could not set a preference at all. The record schema is unchanged by configuration, so shortfalls travel on stderr where an operator reads them and never in the record a machine parses.

The serve command

jj-acp serve parses the same launch options as run and refuses --task, because a task arrives per control frame and a launch-time document would be meaningless. Sharing the option parser is what stops a flag from meaning one thing in run and something else in serve; the trusted launch configuration is built by one function both commands call.

A signal ends the loop rather than cancelling one task. A controlling application that has stopped reading has nobody to receive a record, so the honest outcome is a bounded drain followed by the signal’s own exit code. Reaching end of input is a clean exit 0, because a closed stdin is how a controlling application says it is finished.

Unusable launch configuration exits 2 with the reason on stderr and nothing on stdout. There is no loop to serve and no peer to frame a refusal for, so the exit code is the only machine-readable signal available.

Pool sizing

--workers sets how many submissions serve executes at once and --queue-capacity how many may wait, each with a matching JJ_ACP_WORKERS and JJ_ACP_QUEUE_CAPACITY variable. Workers default to one, which preserves the serial behaviour from before scopes existed, so raising concurrency is an explicit choice rather than a surprise. Both are validated: zero is refused, and workers are capped at 32.

The one-shot path ignores both, because a process that runs one task and exits has nothing to size.

Interactive session integration

The additive –control-version option accepts 1 or 2 and defaults to 1. Version 2 requires an explicit –runner. Signal and owner EOF request bounded interactive cleanup.

Queued prompt cancellation in explicit control v2 reports sessionUsable while retaining the warm session. The next explicit follow-up reuses it; connection shutdown still closes it. Version-1 command and terminal record shapes remain unchanged. E-M11-003 records the binary regression and source gates.

Warm worker integration explicitly selects –control-version 3 and a fixed managed cwd root. The flag default remains version 1; version 2 remains a single interactive session with no request-supplied paths.

A version-3 adapter rejection of open/configure remains request-scoped. Other opened sessions stay usable on the initialized process. Protocol errors, timeouts and process exits retain worker-wide invalidation (E-M12-004).

Serve controls v2/v3 accept optional prepared context independently of text. This adds no launch flag, filesystem selection or credential surface. The CLI preserves caller session/request fencing and emits one terminal outcome per real prompt; warming and context preparation do not submit preliminary turns.

Interactive v2/v3 callers may submit a comments-only turn using empty text and nonblank prepared context. The CLI retains both fields without inventing user text; an entirely empty prompt remains invalid (E-M12-003).

Trusted coding-tool declarations

The controlling application may select a bounded JSON file of stdio MCP declarations through --tools or JJ_ACP_TOOLS. This is trusted launch configuration, independent of tasks and v2/v3 control input. Session creation and supported loading receive the same declarations. Warm initialization does not start a tool session. The file is bounded to 64 KiB and eight unique stdio servers; only absolute executable paths are accepted, with bounded arguments/environment and no reserved harness identity names. Errors disclose stable codes, not file contents or credentials. ACP continues to own no tool policy, authentication, network or durable settings.

Public release packaging

The public Cargo package name is jj-acp, retaining the jj-acp executable and jj_acp_cli library. Source paths stay under crates/jj-acp-cli. The README covers one-shot tasks, persistent control, trusted tool declarations and installation. Packaging changes do not change the control protocol.

Parallel CLI fixtures allocate process-local serials with exclusive directory creation. Timestamp collisions must never share state, and peer teardown must preserve live test directories. The scratch regression reproduced 31 directories for 32 simultaneous callers before this fix. Signal exit-code and record assertions remain unchanged.

The deadline containment regression allows interpreter startup before testing cleanup of a real descendant. Its configured absolute deadline is ten seconds; the test verifies exit 124, a deadline-exceeded terminal record, exactly one prompt dispatch, bounded completion and disappearance of the recorded process. A two-second delayed interpreter reproduces the previous premature timeout and passes the corrected setup. This is fixture timing, not a runtime limit change.

Changesets version preparation refreshes the root installation example and packaged CLI README together. The CLI Cargo package continues to inherit the coordinated workspace version; version preparation adds no command or protocol.