1 files changed, 112 insertions, 0 deletions
diff --git a/pkg/aflow/trajectory/trajectory.go b/pkg/aflow/trajectory/trajectory.go
new file mode 100644
index 000000000..12c585815
--- /dev/null
+++ b/pkg/aflow/trajectory/trajectory.go
@@ -0,0 +1,112 @@
+// Copyright 2025 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package trajectory
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+	"time"
+)
+
+// Span describes one step in an aflow workflow execution.
+// Spans can be finished/unfinished (Finished field), and nested (Nesting field).
+type Span struct {
+	// Seq is monotomically increasing for each new span in a workflow starting from 0.
+	Seq int
+	// Nesting represents hierarchical relation between spans.
+	// For example, SpanTool spans within SpanAgent have +1 nesting level.
+	Nesting  int
+	Type     SpanType
+	Name     string // flow/action/tool name
+	Started  time.Time
+	Finished time.Time
+	Error    string // relevant if Finished is set
+
+	// Args/results for actions/tools.
+	Args    map[string]any
+	Results map[string]any
+
+	// Agent invocation.
+	Instruction string
+	Prompt      string
+	Reply       string
+
+	// LLM invocation.
+	Thoughts string
+}
+
+type SpanType string
+
+const (
+	SpanFlow   = SpanType("flow") // always the first outermost span
+	SpanAction = SpanType("action")
+	SpanAgent  = SpanType("agent")
+	SpanLLM    = SpanType("llm")
+	SpanTool   = SpanType("tool")
+)
+
+func (span *Span) String() string {
+	// This is used for console logging only.
+	sb := new(strings.Builder)
+	if span.Finished.IsZero() {
+		fmt.Fprintf(sb, "starting %v %v (%v/%v)...\n",
+			span.Type, span.Name, span.Nesting, span.Seq)
+		switch span.Type {
+		case SpanFlow:
+		case SpanAction:
+		case SpanAgent:
+			fmt.Fprintf(sb, "instruction:\n%v\nprompt:\n%v\n", span.Instruction, span.Prompt)
+		case SpanLLM:
+		case SpanTool:
+			printMap(sb, span.Args, "args")
+		default:
+			panic(fmt.Sprintf("unhandled span type %v", span.Type))
+		}
+	} else {
+		fmt.Fprintf(sb, "finished %v %v (%v/%v) in %v\n",
+			span.Type, span.Name, span.Nesting, span.Seq, span.Finished.Sub(span.Started))
+		switch span.Type {
+		case SpanFlow:
+			printMap(sb, span.Results, "results")
+		case SpanAction:
+			printMap(sb, span.Results, "results")
+		case SpanAgent:
+			if span.Results != nil {
+				printMap(sb, span.Results, "results")
+			}
+			fmt.Fprintf(sb, "reply:\n%v\n", span.Reply)
+		case SpanLLM:
+			if span.Thoughts != "" {
+				fmt.Fprintf(sb, "thoughts:\n%v\n", span.Thoughts)
+			}
+		case SpanTool:
+			printMap(sb, span.Results, "results")
+		default:
+			panic(fmt.Sprintf("unhandled span type %v", span.Type))
+		}
+	}
+	if span.Error != "" {
+		fmt.Fprintf(sb, "error:\n%v\n", span.Error)
+	}
+	return sb.String()
+}
+
+func printMap(sb *strings.Builder, m map[string]any, what string) {
+	fmt.Fprintf(sb, "%v:\n", what)
+	type nameVal struct {
+		name string
+		val  any
+	}
+	var sorted []nameVal
+	for k, v := range m {
+		sorted = append(sorted, nameVal{k, v})
+	}
+	slices.SortFunc(sorted, func(a, b nameVal) int {
+		return strings.Compare(a.name, b.name)
+	})
+	for _, kv := range sorted {
+		fmt.Fprintf(sb, "\t%v: %v\n", kv.name, kv.val)
+	}
+}