Derive stable prompt sessions for CLI runs

internal/cli/session.go

@@ -0,0 +1,26 @@
+package cli
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"strings"
+)
+
+const generatedSessionIDPrefix = "notarius:v1:"
+
+func resolvePromptSessionID(explicitSessionID, inputModule string, rawInput []byte) (string, error) {
+	inputModule = strings.TrimSpace(inputModule)
+	if inputModule == "" {
+		return "", fmt.Errorf("resolve prompt session: input module key must not be empty")
+	}
+	if sessionID := strings.TrimSpace(explicitSessionID); sessionID != "" {
+		return sessionID, nil
+	}
+
+	hasher := sha256.New()
+	_, _ = hasher.Write([]byte(inputModule))
+	_, _ = hasher.Write([]byte{0})
+	_, _ = hasher.Write(rawInput)
+	return generatedSessionIDPrefix + hex.EncodeToString(hasher.Sum(nil)), nil
+}