fix(agent): fall back to first AGENT line for discovery

pkg/agent/discovery.go

@@ -99,14 +99,28 @@ func descriptorIdentity(agentID string, definition AgentContextDefinition) (stri
 	}
 
 	if description == "" &&
-		definition.Source == AgentDefinitionSourceAgents &&
 		definition.Agent != nil {
-		description = firstMeaningfulParagraph(definition.Agent.Body)
+		if definition.Source == AgentDefinitionSourceAgent {
+			description = firstNonEmptyLine(definition.Agent.Body)
+		} else if definition.Source == AgentDefinitionSourceAgents {
+			description = firstMeaningfulParagraph(definition.Agent.Body)
+		}
 	}
 
 	return name, description
 }
 
+func firstNonEmptyLine(content string) string {
+	content = strings.ReplaceAll(content, "\r\n", "\n")
+	for _, line := range strings.Split(content, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if trimmed != "" {
+			return trimmed
+		}
+	}
+	return ""
+}
+
 func firstMeaningfulParagraph(content string) string {
 	content = strings.ReplaceAll(content, "\r\n", "\n")
 	paragraphs := strings.Split(content, "\n\n")

pkg/agent/discovery_test.go

@@ -178,3 +178,30 @@ Generalist.
 		t.Fatalf("did not expect discovery section for singleton registry, got %q", systemPrompt)
 	}
 }
+
+func TestAgentRegistry_ListAgentsFallsBackToFirstNonEmptyAgentLine(t *testing.T) {
+	workspace := setupWorkspace(t, map[string]string{
+		"AGENT.md": `---
+name: Research Agent
+---
+
+
+First useful line.
+Second line.
+`,
+	})
+	defer cleanupWorkspace(t, workspace)
+
+	cfg := testCfg([]config.AgentConfig{
+		{ID: "research", Default: true, Workspace: workspace},
+	})
+
+	registry := NewAgentRegistry(cfg, &mockRegistryProvider{})
+	descriptor, ok := registry.GetAgentDescriptor("research")
+	if !ok || descriptor == nil {
+		t.Fatal("expected research descriptor lookup to succeed")
+	}
+	if descriptor.Description != "First useful line." {
+		t.Fatalf("descriptor.Description = %q, want %q", descriptor.Description, "First useful line.")
+	}
+}