Add direct per-run session overrides

internal/domain/domain.go

@@ -63,6 +63,7 @@ type RunRequest struct {
 	PromptID      string
 	PromptVersion string
 	ProfileID     string
+	SessionID     string
 	APIKey        string `json:"-" yaml:"-"`
 	Inputs        map[string]ArtifactRef
 	Vars          map[string]string
@@ -79,6 +80,7 @@ type RunResult struct {
 	PromptID             string
 	PromptVersion        string
 	PromptHash           string
+	SessionID            string
 	RenderedPromptHash   string
 	SelectedProfileID    string
 	SelectedBackendID    string

internal/domain/session.go

@@ -0,0 +1,19 @@
+package domain
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf8"
+)
+
+// NormalizeSessionID applies the shared session identifier rule.
+func NormalizeSessionID(raw string) (string, error) {
+	normalized := strings.TrimSpace(raw)
+	if normalized == "" {
+		return "", nil
+	}
+	if length := utf8.RuneCountInString(normalized); length > SessionIDMaxLength {
+		return "", fmt.Errorf("session_id length %d exceeds maximum %d", length, SessionIDMaxLength)
+	}
+	return normalized, nil
+}

internal/domain/session_test.go

@@ -0,0 +1,57 @@
+package domain
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNormalizeSessionID(t *testing.T) {
+	tests := []struct {
+		name    string
+		raw     string
+		want    string
+		wantErr bool
+	}{
+		{
+			name: "trims surrounding Unicode whitespace",
+			raw:  "\u2003 session-123 \u2003",
+			want: "session-123",
+		},
+		{
+			name: "blank input is omitted",
+			raw:  " \t\u2003 ",
+			want: "",
+		},
+		{
+			name: "maximum Unicode length is accepted",
+			raw:  strings.Repeat("界", SessionIDMaxLength),
+			want: strings.Repeat("界", SessionIDMaxLength),
+		},
+		{
+			name:    "one Unicode code point over maximum is rejected",
+			raw:     strings.Repeat("界", SessionIDMaxLength+1),
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := NormalizeSessionID(tt.raw)
+			if tt.wantErr {
+				if err == nil {
+					t.Fatal("expected normalization error")
+				}
+				if !strings.Contains(err.Error(), "exceeds maximum") {
+					t.Fatalf("expected useful length diagnostic, got %v", err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("normalize session id: %v", err)
+			}
+			if got != tt.want {
+				t.Fatalf("normalized session id = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}