fix: inject version via ldflags and set model on tool spans (#54)

Author: GuyMoses

.goreleaser.yaml

@@ -7,6 +7,8 @@ builds:
   - id: on-event
     env:
       - CGO_ENABLED=0
+    ldflags:
+      - -s -w -X github.com/dash0hq/dash0-agent-plugin/internal/version.Version={{.Version}}
     goos:
       - linux
       - darwin

cmd/on-event/main.go

@@ -38,6 +38,15 @@ func sendToolTrace(event map[string]any, cfg otlp.Config, ts time.Time, dataDir
 		event["model"] = ctx.Model
 	}
 
+	// Fall back to reading model from transcript if still missing.
+	if _, hasModel := event["model"]; !hasModel {
+		if tp, _ := event["transcript_path"].(string); tp != "" {
+			if m := transcript.ReadModel(tp); m != "" {
+				event["model"] = m
+			}
+		}
+	}
+
 	// Compute start time from duration_ms (always present on PostToolUse).
 	startTime := ts
 	if durationMs, ok := event["duration_ms"].(float64); ok && durationMs > 0 {

cmd/on-event/main_test.go

@@ -692,3 +692,47 @@ func TestConversationIDOnAllSpans(t *testing.T) {
 		assert.True(t, found, "span %q should have gen_ai.conversation.id", span.Name)
 	}
 }
+
+func TestModelOnToolSpanFromTranscriptWhenSessionStartOmitsModel(t *testing.T) {
+	dataDir := t.TempDir()
+	t.Setenv("CLAUDE_PLUGIN_DATA", dataDir)
+	srv, spans, _ := collectingServer(t)
+	t.Setenv("DASH0_OTLP_URL", srv.URL)
+
+	// Create transcript with model info.
+	transcriptPath := filepath.Join(dataDir, "transcript.jsonl")
+	writeTranscript(t, transcriptPath, []string{
+		`{"type":"user","message":{"role":"user","content":[{"type":"text","text":"hello"}]}}`,
+		`{"type":"assistant","requestId":"req_001","message":{"role":"assistant","model":"claude-opus-4-7","content":[{"type":"text","text":"hi"}],"usage":{"input_tokens":10,"output_tokens":5}}}`,
+	})
+
+	// SessionStart WITHOUT model — simulates the real-world bug.
+	feed(t, `{"hook_event_name":"SessionStart","session_id":"sess-no-model"}`)
+	feed(t, `{"hook_event_name":"UserPromptSubmit","session_id":"sess-no-model","prompt":"hello"}`)
+	feed(t, fmt.Sprintf(`{"hook_event_name":"PostToolUse","session_id":"sess-no-model","tool_name":"Bash","tool_use_id":"tu1","tool_response":"ok","transcript_path":"%s"}`, transcriptPath))
+	feed(t, fmt.Sprintf(`{"hook_event_name":"Stop","session_id":"sess-no-model","transcript_path":"%s"}`, transcriptPath))
+
+	require.Len(t, *spans, 2, "expected tool span + chat span")
+
+	// Tool span should have model from transcript fallback.
+	toolSpan := findSpan(*spans, "execute_tool")
+	require.NotNil(t, toolSpan, "tool span should exist")
+	assertStringAttr(t, toolSpan.Attributes, "gen_ai.request.model", "claude-opus-4-7")
+
+	// Chat span should also have model from transcript.
+	chatSpan := findSpan(*spans, "chat")
+	require.NotNil(t, chatSpan, "chat span should exist")
+	assertStringAttr(t, chatSpan.Attributes, "gen_ai.request.model", "claude-opus-4-7")
+}
+
+func assertStringAttr(t *testing.T, attrs []otlp.Attribute, key, want string) {
+	t.Helper()
+	for _, a := range attrs {
+		if a.Key == key {
+			require.NotNil(t, a.Value.StringValue, "attribute %q should have string value", key)
+			assert.Equal(t, want, *a.Value.StringValue)
+			return
+		}
+	}
+	t.Errorf("attribute %q not found", key)
+}

internal/otlp/trace.go

@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"strconv"
 	"time"
+
+	"github.com/dash0hq/dash0-agent-plugin/internal/version"
 )
 
 // OTLP JSON wire format types for traces.
@@ -132,7 +134,7 @@ func SendTrace(span Span, event map[string]any, cfg Config) error {
 			ScopeSpans: []ScopeSpans{{
 				Scope: Scope{
 					Name:    "dash0-agent-plugin",
-					Version: "0.1.0",
+					Version: version.Version,
 				},
 				Spans: []Span{span},
 			}},

internal/otlp/trace_test.go

@@ -228,7 +228,7 @@ func TestSendTrace(t *testing.T) {
 	require.Len(t, rs.ScopeSpans, 1)
 	ss := rs.ScopeSpans[0]
 	assert.Equal(t, "dash0-agent-plugin", ss.Scope.Name)
-	assert.Equal(t, "0.1.0", ss.Scope.Version)
+	assert.Equal(t, "dev", ss.Scope.Version)
 
 	require.Len(t, ss.Spans, 1)
 	s := ss.Spans[0]

internal/version/version.go

@@ -0,0 +1,4 @@
+package version
+
+// Version is set at build time by GoReleaser via ldflags.
+var Version = "dev"