The runtime says no lost compare-and-set as a failed operation, and its test waits on a channel, never a sleep (review round 1)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

node-tools/internal/launch/launch.go

@@ -482,8 +482,9 @@ func Start(module, entry string, env []string, mesh Bus, logf func(string, ...an
 						}
 						// A state or log operation the bus refused or let time out reaches a caller as a call that
 						// does not answer: say it here, with how long it took, so the next hang is readable.
-						if err != nil && (strings.HasPrefix(m.Method, "mesh/state.") || strings.HasPrefix(m.Method, "mesh/log.") ||
-							busStateCalls[m.Method]) {
+						// A lost compare-and-set is the normal answer of two writers to one key, retried by its caller: not said.
+						if err != nil && errorCode(err) != CodeChanged && (strings.HasPrefix(m.Method, "mesh/state.") ||
+							strings.HasPrefix(m.Method, "mesh/log.") || busStateCalls[m.Method]) {
 							logf("[mesh-tools] %s's bundle asked %s and it failed after %s: %v", module, m.Method,
 								time.Since(asked).Round(time.Millisecond), err)
 						}

node-tools/internal/launch/state_failed_test.go

@@ -7,58 +7,69 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 	"testing"
 	"time"
 )
 
+// changedError is a lost compare-and-set as the bus answers it: told by its code (novox/hq ADR 0259).
+type changedError struct{}
+
+func (changedError) Error() string  { return "the key changed since revision 3" }
+func (changedError) ErrorCode() int { return CodeChanged }
+
+// refusingState answers the state "lost" with a lost compare-and-set and every other state with a time-out.
 type refusingState struct{ subscribing }
 
-func (*refusingState) State(string, json.RawMessage) (json.RawMessage, error) {
+func (*refusingState) State(_ string, params json.RawMessage) (json.RawMessage, error) {
+	if strings.Contains(string(params), `"state":"lost"`) {
+		return nil, changedError{}
+	}
 	return nil, errors.New("the bus did not answer in 10s")
 }
 
-// A bundle that asks the runtime for a state once it is started, as a tool does.
+// A bundle that asks the runtime for the state "lost" once it is started, and for the state "copied" once that is
+// answered, so the first answer's handling has ended before the second is asked.
 const askingBundle = `#!/bin/sh
 while IFS= read -r line; do
   id=$(printf '%s' "$line" | sed -n 's/.*"id":\([0-9]*\)[,}].*/\1/p')
   case "$line" in
     *'"method":"initialize"'*) printf '{"jsonrpc":"2.0","id":%s,"result":{}}\n' "$id" ;;
     *'"method":"tools/list"'*) printf '{"jsonrpc":"2.0","id":%s,"result":{"tools":[]}}\n' "$id"
-       printf '{"jsonrpc":"2.0","id":"q1","method":"mesh/state.get","params":{"state":"copied","key":"k"}}\n' ;;
+       printf '{"jsonrpc":"2.0","id":"q1","method":"mesh/state.update","params":{"state":"lost","key":"k"}}\n' ;;
+    *'"id":"q1"'*) printf '{"jsonrpc":"2.0","id":"q2","method":"mesh/state.get","params":{"state":"copied","key":"k"}}\n' ;;
   esac
 done
 `
 
 // A state operation the bus refuses or lets time out is said in the runtime's log with its method, its bundle and its
-// time (issue 1966: a hand-act seat whose calls hung said nothing).
+// time (issue 1966: a hand-act seat whose calls hung said nothing); a lost compare-and-set, asked first, is not.
 func TestAFailedStateOperationIsSaidInTheRuntimesLog(t *testing.T) {
 	dir := t.TempDir()
 	entry := filepath.Join(dir, "bundle")
 	if err := os.WriteFile(entry, []byte(askingBundle), 0o755); err != nil {
 		t.Fatal(err)
 	}
-	var mu sync.Mutex
-	var lines []string
-	logf := func(f string, a ...any) {
-		mu.Lock()
-		defer mu.Unlock()
-		lines = append(lines, fmt.Sprintf(f, a...))
-	}
+	said := make(chan string, 16)
+	logf := func(f string, a ...any) { said <- fmt.Sprintf(f, a...) }
 	l, err := Start("asker", entry, os.Environ(), &refusingState{}, logf)
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(l.Stop)
-	deadline := time.Now().Add(5 * time.Second)
-	for time.Now().Before(deadline) {
-		mu.Lock()
-		all := strings.Join(lines, "\n")
-		mu.Unlock()
-		if strings.Contains(all, "asker's bundle asked mesh/state.get and it failed after") && strings.Contains(all, "did not answer in 10s") {
-			return
+	var heard []string
+	timeout := time.After(5 * time.Second)
+	for {
+		select {
+		case line := <-said:
+			heard = append(heard, line)
+			if strings.Contains(line, "mesh/state.update") {
+				t.Fatalf("a lost compare-and-set was said as a failure: %q", line)
+			}
+			if strings.Contains(line, "asker's bundle asked mesh/state.get and it failed after") && strings.Contains(line, "did not answer in 10s") {
+				return
+			}
+		case <-timeout:
+			t.Fatalf("the failed state operation was not said; the log: %v", heard)
 		}
-		time.Sleep(20 * time.Millisecond)
 	}
-	t.Fatalf("the failed state operation was not said; the log: %v", lines)
 }