dingtalk-workspace-cli/docs/event-subprocess-contract.md

Event consume — AI subprocess contract

Aligns dws event consume with the "AI subprocess contract" that lark-cli event consume exposes, so any orchestrator (Claude Code's Monitor, a bash bridge, systemd, an agent plugin) can drive it with zero ambiguity: know when it is ready, stop it cleanly, and machine-read why it exited.

Scope of this branch: the four contract items below. Reconnect resilience (keeping the stream alive across a transient upstream drop) is tracked separately and intentionally out of scope here.

Baseline (already present, no work)

• --max-events N — stop after N events (exit 0).
• --duration D — wall-clock budget (exit 0). Kept as --duration, NOT aliased to --timeout: the global --timeout is the HTTP request timeout (int seconds) and would collide (different type and meaning). Docs note the lark-cli name difference.
• Bus idle-shutdown fires only with zero consumers, so a connected consumer is never idle-killed.
• SIGINT/SIGTERM already cancel the run context and return cleanly.

Improvements

1. Ready marker (standardized)

On connect, emit a fixed stderr line before any stdout event:

[event] ready event_key=<key> bus_pid=<pid>

Parents block on stderr until this line, then read stdout. Suppressed under --quiet. Replaces the ad-hoc connected bus pid=... line (which omits event_key).

Verification

• T1a: stderr contains a line matching ^\[event\] ready event_key=<key>.
• T1b: that line appears before the first stdout event (ordering).
• T1c: with --quiet, the line is absent.

2. stdin EOF = graceful exit

consume watches stdin; closing stdin is a shutdown signal (wired for AI subprocess callers). To stay resident, feed a never-EOF stdin (< <(tail -f /dev/null)) or run bounded (--max-events / --duration).

Verification

• T2a: printf '' | dws event consume <key> exits ≤2s, code 0, final line reason: signal (stdin-eof classified as signal).
• T2b: dws event consume <key> < <(tail -f /dev/null) still alive after 5s, connection intact.
• T2c (unit): a controllable stdin reader hitting EOF makes Run return nil via the cleanup path.

3. Exit reason contract + exit codes

On exit, final stderr line:

[event] exited — received N event(s) in Xs (reason: <limit|timeout|signal|bus_shutdown>)

Exit codes: controlled exit (limit/timeout/signal/stdin-eof) = 0; startup or runtime failure (permissions, network, params) = non-zero, with no exited line and an Error: line instead.

Verification

• T3a: --max-events 1 + 1 event → exit 0, reason=limit, N=1.
• T3b: --duration 2s, no events → exit 0, reason=timeout.
• T3c: SIGTERM mid-run → exit 0, reason=signal.
• T3d: bad params / permission failure → exit≠0, no exited line, has Error:.
• Unit tests assert (reason string, exit code) for each path.

4. Cleanup on exit (no kill -9)

Ownership-based, matching lark-cli:

• If this run created the subscription (no --subscribe-id), a clean exit (SIGTERM / SIGINT / stdin-EOF / limit / timeout) unsubscribes it server-side and sends Bye.
• If --subscribe-id was passed (reusing an existing subscription), the subscription is left intact — the caller owns its lifecycle.
• --ephemeral remains as an explicit "always unsubscribe" override.
• Help/docs warn: avoid kill -9 (skips the unsubscribe → leaked server-side subscription: "subscription already exists" on restart, duplicate delivery). Prefer SIGTERM or closing stdin.

Verification

• T4a: start consume (self-created subscription), record subscribe_id; SIGTERM; afterwards dws event status no longer lists that subscribe_id and the server-side subscription is gone.
• T4b: start consume with --subscribe-id <existing>; SIGTERM; the subscription is still present (reuse case preserved).
• T4c (control): kill -9 leaves subscribe_id lingering (documented risk; we only guarantee SIGTERM is clean, we do not fix kill -9 itself).

Out of scope (next branch)

Reconnect resilience — today personal source retries only retryable errors (1–30s backoff); a non-retryable error tears the bus down and takes consume with it (the likely cause of the observed silent drop). Making more drops retryable, keeping the bus alive across a reconnect, and emitting reason: source_lost only after exhausting the budget — tracked on its own branch, since it needs error-classification judgement and real flaky-network testing, and would otherwise couple clean contract work with resilience work.

Test surface

• Unit: extend internal/event/consume/*_test.go with fake bus conn / stdin / stderr sink for T1c, T2c, T3 (all paths), T4 ownership branch.
• Integration/e2e: --foreground + mock source (or a short real run) for T1a/b, T2a/b, T3a–d, T4a/b/c — assert the stderr contract lines and exit codes.