fix(daemon): do not retry workers that finished with a final exit code

internal/daemon/pool.go

@@ -17,6 +17,28 @@ const (
 	ExitPermanent = 76
 )
 
+// Exit codes `zero exec` (internal/cli/exec.go) uses to report a run that
+// finished, or was stopped on purpose, rather than crashed. They are duplicated
+// here because the daemon cannot import the CLI package; keep them in sync.
+const (
+	exitUsage       = 2   // bad flags or arguments: a retry fails the same way
+	exitProvider    = 3   // provider failure the run already surfaced
+	exitIncomplete  = 4   // the agent ran (edits, commands) and stopped unfinished
+	exitInterrupted = 130 // SIGINT: someone stopped it on purpose
+)
+
+// isFinalExit reports whether a worker exit code means the run is over and must
+// not be retried. Retrying would repeat the agent's side effects and re-bill the
+// provider, and append a second run to the same session stream. Only crash-type
+// exits (1, signals) and launch/read errors are worth another attempt.
+func isFinalExit(code int) bool {
+	switch code {
+	case exitUsage, exitProvider, exitIncomplete, exitInterrupted:
+		return true
+	}
+	return false
+}
+
 // defaultPoolSize, defaultMaxAttempts and defaultKillTimeout are used when a
 // PoolOptions field is left zero.
 const (
@@ -176,7 +198,8 @@ type Sink interface {
 // Run leases a worker slot and dispatches spec to a worker, streaming its
 // stream-json lines to sink. It is at-least-once with bounded retries: a worker
 // that crashes (non-zero, non-permanent) is retried on a fresh worker after a
-// backoff; ExitPermanent or exhausting MaxAttempts returns ErrPermanent. Run
+// backoff; ExitPermanent, a final `zero exec` exit (usage, provider, incomplete,
+// interrupted) or exhausting MaxAttempts returns ErrPermanent. Run
 // queues when all slots are busy. The returned int is the final worker exit code.
 func (p *Pool) Run(ctx context.Context, spec WorkerSpec, sink Sink) (int, error) {
 	if err := p.acquire(ctx); err != nil {
@@ -209,6 +232,9 @@ func (p *Pool) Run(ctx context.Context, spec WorkerSpec, sink Sink) (int, error)
 		case code == ExitPermanent:
 			p.logf("worker %d exited permanently (code=%d) — not retrying", stat.id, code)
 			return code, ErrPermanent
+		case isFinalExit(code):
+			p.logf("worker %d finished with exit code %d — not retrying", stat.id, code)
+			return code, fmt.Errorf("%w: worker %d exited code=%d", ErrPermanent, stat.id, code)
 		case code == ExitTempfail:
 			lastErr = fmt.Errorf("worker %d tempfail (code=%d)", stat.id, code)
 			p.logf("worker %d tempfail — retry after %s", stat.id, p.opts.TempfailDelay)

internal/daemon/pool_test.go

@@ -3,6 +3,7 @@ package daemon
 import (
 	"context"
 	"errors"
+	"fmt"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -148,6 +149,35 @@ func TestPoolRunPermanentStopsImmediately(t *testing.T) {
 	}
 }
 
+// A `zero exec` run that ended with usage (2), provider (3), incomplete (4) or
+// interrupted (130) is over: retrying would repeat its side effects and merge a
+// second run into the same session stream.
+func TestPoolRunFinalExitCodesDoNotRetry(t *testing.T) {
+	for _, code := range []int{2, 3, 4, 130} {
+		t.Run(fmt.Sprintf("exit_%d", code), func(t *testing.T) {
+			launcher, calls := seqLauncher(
+				&fakeWorker{pid: 1, exitCode: code, out: []string{"first run"}},
+				&fakeWorker{pid: 2, exitCode: 0, out: []string{"second run"}},
+			)
+			pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher, MaxAttempts: 5, Backoff: func(int) time.Duration { return 0 }})
+			sink := &collectSink{}
+			got, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, sink)
+			if !errors.Is(err, ErrPermanent) {
+				t.Fatalf("Run err = %v, want ErrPermanent", err)
+			}
+			if got != code {
+				t.Fatalf("Run code = %d, want the worker's exit code %d", got, code)
+			}
+			if *calls != 1 {
+				t.Fatalf("launcher calls = %d, want 1 (no retry)", *calls)
+			}
+			if len(sink.lines) != 1 || sink.lines[0] != "first run" {
+				t.Fatalf("sink lines = %v, want only the first run's output", sink.lines)
+			}
+		})
+	}
+}
+
 func TestPoolRunCapExhausted(t *testing.T) {
 	launcher, calls := seqLauncher(
 		&fakeWorker{pid: 1, exitCode: 1},