fix(yield): prepare fresh Go scaffolds

labs/22-yield/yield/cmd/yskill/main_test.go

@@ -53,8 +53,17 @@ func TestParseOnePositionalKeepsFlagFirstOrder(t *testing.T) {
 
 func TestScaffoldSkillWritesLanguageSpecificEntrypoints(t *testing.T) {
 	previousVersion := version
+	previousTidyGoModule := tidyGoModule
 	version = "0.1.9"
-	t.Cleanup(func() { version = previousVersion })
+	tidyCalls := 0
+	tidyGoModule = func(string) error {
+		tidyCalls++
+		return nil
+	}
+	t.Cleanup(func() {
+		version = previousVersion
+		tidyGoModule = previousTidyGoModule
+	})
 
 	tests := []struct {
 		language string
@@ -64,7 +73,7 @@ func TestScaffoldSkillWritesLanguageSpecificEntrypoints(t *testing.T) {
 	}{
 		{"typescript", []string{"main.ts", "package.json", "skill.json"}, "npm exec -- yskill run .", `"@operatorstack/yield": "0.1.9"`},
 		{"python", []string{"main.py", "requirements.txt", "skill.json"}, "python -m yieldskill run .", "yieldskill==0.1.9"},
-		{"go", []string{"main.go", "go.mod"}, "yskill run .", "github.com/operatorstack/yield v0.1.9"},
+		{"go", []string{"main.go", "go.mod", "skill.json"}, "yskill run .", "github.com/operatorstack/yield v0.1.9"},
 		{"rust", []string{"src/main.rs", "Cargo.toml", ".cargo/config.toml", "skill.json"}, "yskill run .", `version = "=0.1.9"`},
 	}
 	for _, tt := range tests {
@@ -98,6 +107,28 @@ func TestScaffoldSkillWritesLanguageSpecificEntrypoints(t *testing.T) {
 			}
 		})
 	}
+	if tidyCalls != 1 {
+		t.Fatalf("go mod tidy calls = %d, want 1", tidyCalls)
+	}
+}
+
+func TestGoScaffoldCanResolveItsPinnedModuleOnFirstRun(t *testing.T) {
+	previousVersion := version
+	previousTidyGoModule := tidyGoModule
+	version = "0.1.9"
+	tidyGoModule = func(string) error { return nil }
+	t.Cleanup(func() {
+		version = previousVersion
+		tidyGoModule = previousTidyGoModule
+	})
+	dir := filepath.Join(t.TempDir(), "go-skill")
+	if err := scaffoldSkill(dir, "go", ""); err != nil {
+		t.Fatal(err)
+	}
+	manifest := readTestFile(t, filepath.Join(dir, "skill.json"))
+	if manifest != "{\"run\":[\"go\",\"run\",\"-mod=readonly\",\".\"]}\n" {
+		t.Fatalf("skill.json = %q", manifest)
+	}
 }
 
 func TestPythonScaffoldUsesInvokingInterpreter(t *testing.T) {

labs/22-yield/yield/cmd/yskill/scaffold.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -11,6 +12,16 @@ import (
 
 var releaseVersionPattern = regexp.MustCompile(`^\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$`)
 var unsafePackageCharacter = regexp.MustCompile(`[^a-z0-9_-]+`)
+var tidyGoModule = func(dir string) error {
+	cmd := exec.Command("go", "mod", "tidy")
+	cmd.Dir = dir
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("prepare Go scaffold dependencies: %w", err)
+	}
+	return nil
+}
 
 func defaultLanguage() string {
 	if language := strings.TrimSpace(os.Getenv("YIELD_LANGUAGE")); language != "" {
@@ -69,6 +80,11 @@ func scaffoldSkill(dir, language, sdkPath string) error {
 			return err
 		}
 	}
+	if language == "go" {
+		if err := tidyGoModule(dir); err != nil {
+			return err
+		}
+	}
 	fmt.Printf("init: %s skill %q scaffolded in %s\n", language, name, dir)
 	return nil
 }
@@ -109,7 +125,11 @@ func scaffoldFiles(name, language, sdkPath string) map[string]string {
 		if sdkPath != "" {
 			gomod += fmt.Sprintf("\nreplace github.com/operatorstack/yield => %s\n", sdkPath)
 		}
-		return map[string]string{"main.go": mainGo, "go.mod": gomod}
+		return map[string]string{
+			"main.go":    mainGo,
+			"go.mod":     gomod,
+			"skill.json": "{\"run\":[\"go\",\"run\",\"-mod=readonly\",\".\"]}\n",
+		}
 	}
 }
 

labs/22-yield/yield/evals/results/latest.json

@@ -1,8 +1,8 @@
 {
   "schema_version": 2,
   "methodology_version": "1.0",
-  "generated_at": "2026-08-01T21:57:38.190Z",
-  "source_digest": "8fba9d25376a73e2a2230d8d10cfe8364a9b2db73e61b6974fa39928956ea9ef",
+  "generated_at": "2026-08-01T22:15:26.319Z",
+  "source_digest": "18c4620bc76291a4e8580b488f746cfb0085bf06629cf73ac38c5dbbec4bf099",
   "status": "passed",
   "workflow_conformance": {
     "passed": 40,