✨ Symlink skills dir for native goose discovery

changes/unreleased/70-skill-symlink-for-goose-discovery.yaml

@@ -0,0 +1,8 @@
+kind: feature
+description: >
+  Symlink $HOME/.agents/skills to the skills directory (default /opt/skills,
+  configurable via HARNESS_SKILLS_DIR) so goose discovers mounted SkillCard
+  content via its native skill platform. The link is placed in the home
+  directory rather than the clone to avoid touching the repo tree. Skills
+  are no longer injected into the prompt; the agent runtime handles
+  progressive disclosure.

harness/cmd/migration-harness/main.go

@@ -8,7 +8,6 @@ import (
 	"os/signal"
 	"path/filepath"
 	"strconv"
-	"strings"
 	"sync/atomic"
 	"syscall"
 	"time"
@@ -126,7 +125,7 @@ func runStage(cmd *cobra.Command, args []string) error {
 	logging.Ok("cloned to %s, branch %s", cloneDir, creds.Branch)
 
 	// 4. Discover skills early — controls which setup steps run
-	skillContent, skillPaths, err := discoverSkills()
+	skillPaths, err := discoverSkills()
 	if err != nil {
 		return fmt.Errorf("discover skills: %w", err)
 	}
@@ -145,6 +144,15 @@ func runStage(cmd *cobra.Command, args []string) error {
 		}); err != nil {
 			logging.Warn("gitignore: %v", err)
 		}
+
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return fmt.Errorf("resolve home dir: %w", err)
+		}
+		if err := symlinkSkillsDir(home, skillsDir()); err != nil {
+			return fmt.Errorf("skill symlink: %w", err)
+		}
+		logging.Ok("symlinked %s/.agents/skills → %s", home, skillsDir())
 	}
 
 	if hasSkills {
@@ -281,7 +289,6 @@ func runStage(cmd *cobra.Command, args []string) error {
 	stagePrompt := prompt.Build(prompt.Layers{
 		AgentPrompt:   cfg.AgentPrompt,
 		WorkflowGuide: cfg.WorkflowGuide,
-		Skill:         skillContent,
 		StageTask:     cfg.StageInstructions,
 	})
 
@@ -373,6 +380,34 @@ func runStage(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+func symlinkSkillsDir(homeDir, skillsSrc string) error {
+	skillsSrc, err := filepath.Abs(skillsSrc)
+	if err != nil {
+		return fmt.Errorf("resolve skills source: %w", err)
+	}
+
+	agentsDir := filepath.Join(homeDir, ".agents")
+	if err := os.MkdirAll(agentsDir, 0o755); err != nil {
+		return err
+	}
+
+	link := filepath.Join(agentsDir, "skills")
+	if info, err := os.Lstat(link); err == nil {
+		if info.Mode()&os.ModeSymlink != 0 {
+			if target, err := os.Readlink(link); err == nil && target == skillsSrc {
+				return nil
+			}
+			if err := os.Remove(link); err != nil {
+				return fmt.Errorf("remove stale symlink %s: %w", link, err)
+			}
+		} else {
+			return fmt.Errorf("%s already exists and is not a symlink", link)
+		}
+	}
+
+	return os.Symlink(skillsSrc, link)
+}
+
 const defaultSkillsDir = "/opt/skills"
 
 func skillsDir() string {
@@ -382,30 +417,21 @@ func skillsDir() string {
 	return defaultSkillsDir
 }
 
-func discoverSkills() (string, []string, error) {
+func discoverSkills() ([]string, error) {
 	pattern := filepath.Join(skillsDir(), "*/SKILL.md")
 	matches, err := filepath.Glob(pattern)
 	if err != nil {
-		return "", nil, err
+		return nil, err
 	}
 	if len(matches) == 0 {
 		logging.Info("no skills found at %s — proceeding without skills", pattern)
-		return "", nil, nil
+		return nil, nil
 	}
 
-	var combined strings.Builder
-	for i, m := range matches {
-		content, err := os.ReadFile(m)
-		if err != nil {
-			return "", nil, fmt.Errorf("read skill %s: %w", m, err)
-		}
+	for _, m := range matches {
 		logging.Info("discovered skill: %s", m)
-		if i > 0 {
-			combined.WriteString("\n\n---\n\n")
-		}
-		combined.Write(content)
 	}
-	return combined.String(), matches, nil
+	return matches, nil
 }
 
 func resolveFromHub(cfg *config.Config, hubClient *hub.Client) (*git.Credentials, error) {

harness/cmd/migration-harness/main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/konveyor/migration-harness/internal/config"
@@ -12,13 +13,10 @@ func TestDiscoverSkills_NoSkills(t *testing.T) {
 	dir := t.TempDir()
 	t.Setenv("HARNESS_SKILLS_DIR", dir)
 
-	content, paths, err := discoverSkills()
+	paths, err := discoverSkills()
 	if err != nil {
 		t.Fatalf("expected no error, got: %v", err)
 	}
-	if content != "" {
-		t.Errorf("expected empty content, got: %q", content)
-	}
 	if len(paths) != 0 {
 		t.Errorf("expected no paths, got: %v", paths)
 	}
@@ -36,13 +34,10 @@ func TestDiscoverSkills_WithSkills(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	content, paths, err := discoverSkills()
+	paths, err := discoverSkills()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if content != "do the thing" {
-		t.Errorf("expected skill content, got: %q", content)
-	}
 	if len(paths) != 1 {
 		t.Errorf("expected 1 path, got: %v", paths)
 	}
@@ -60,18 +55,129 @@ func TestDiscoverSkills_EmptySkillFile(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	content, paths, err := discoverSkills()
+	paths, err := discoverSkills()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if content != "" {
-		t.Errorf("expected empty content, got: %q", content)
-	}
 	if len(paths) != 1 {
 		t.Errorf("expected 1 path (skill is mounted), got: %v", paths)
 	}
 }
 
+func TestSymlinkSkillsDir(t *testing.T) {
+	homeDir := t.TempDir()
+	skillsSrc := t.TempDir()
+
+	if err := symlinkSkillsDir(homeDir, skillsSrc); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	link := filepath.Join(homeDir, ".agents", "skills")
+	target, err := os.Readlink(link)
+	if err != nil {
+		t.Fatalf("expected symlink at %s: %v", link, err)
+	}
+	if target != skillsSrc {
+		t.Errorf("symlink target = %q, want %q", target, skillsSrc)
+	}
+}
+
+func TestSymlinkSkillsDir_AlreadyExistsDir(t *testing.T) {
+	homeDir := t.TempDir()
+	skillsSrc := t.TempDir()
+
+	if err := os.MkdirAll(filepath.Join(homeDir, ".agents", "skills"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	err := symlinkSkillsDir(homeDir, skillsSrc)
+	if err == nil {
+		t.Fatal("expected error when .agents/skills already exists as a directory")
+	}
+	if !strings.Contains(err.Error(), "not a symlink") {
+		t.Errorf("error should mention 'not a symlink', got: %v", err)
+	}
+}
+
+func TestSymlinkSkillsDir_Idempotent(t *testing.T) {
+	homeDir := t.TempDir()
+	skillsSrc := t.TempDir()
+
+	if err := symlinkSkillsDir(homeDir, skillsSrc); err != nil {
+		t.Fatalf("first call: %v", err)
+	}
+	if err := symlinkSkillsDir(homeDir, skillsSrc); err != nil {
+		t.Fatalf("second call (same target) should be idempotent: %v", err)
+	}
+
+	link := filepath.Join(homeDir, ".agents", "skills")
+	target, err := os.Readlink(link)
+	if err != nil {
+		t.Fatalf("expected symlink at %s: %v", link, err)
+	}
+	if target != skillsSrc {
+		t.Errorf("symlink target = %q, want %q", target, skillsSrc)
+	}
+}
+
+func TestSymlinkSkillsDir_RelinksOnDifferentTarget(t *testing.T) {
+	homeDir := t.TempDir()
+	oldSrc := t.TempDir()
+	newSrc := t.TempDir()
+
+	if err := symlinkSkillsDir(homeDir, oldSrc); err != nil {
+		t.Fatalf("first call: %v", err)
+	}
+	if err := symlinkSkillsDir(homeDir, newSrc); err != nil {
+		t.Fatalf("second call (different target): %v", err)
+	}
+
+	link := filepath.Join(homeDir, ".agents", "skills")
+	target, err := os.Readlink(link)
+	if err != nil {
+		t.Fatalf("expected symlink at %s: %v", link, err)
+	}
+	if target != newSrc {
+		t.Errorf("symlink target = %q, want %q", target, newSrc)
+	}
+}
+
+func TestSymlinkSkillsDir_ResolvesRelativePath(t *testing.T) {
+	parent := t.TempDir()
+	homeDir := filepath.Join(parent, "home")
+	skillsSrc := filepath.Join(parent, "skills")
+	if err := os.MkdirAll(homeDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(skillsSrc, 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	relPath, err := filepath.Rel(parent, skillsSrc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	oldWd, _ := os.Getwd()
+	if err := os.Chdir(parent); err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(oldWd)
+
+	if err := symlinkSkillsDir(homeDir, relPath); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	link := filepath.Join(homeDir, ".agents", "skills")
+	target, err := os.Readlink(link)
+	if err != nil {
+		t.Fatalf("expected symlink at %s: %v", link, err)
+	}
+	if !filepath.IsAbs(target) {
+		t.Errorf("symlink target should be absolute, got %q", target)
+	}
+}
+
 func TestParseHubTokenID(t *testing.T) {
 	tests := []struct {
 		name       string

harness/internal/prompt/prompt.go

@@ -28,14 +28,12 @@ not say where to put something.
 `
 
 // Layers are the context layers composed into a stage prompt, ordered from
-// least to most specific. Any of them may be empty except Skill.
+// least to most specific.
 type Layers struct {
 	// AgentPrompt is the Agent's standing prompt.
 	AgentPrompt string
 	// WorkflowGuide is the workflow's ambient guide.
 	WorkflowGuide string
-	// Skill is the content discovered from the mounted SkillCards.
-	Skill string
 	// StageTask is the task for this stage.
 	StageTask string
 }
@@ -59,16 +57,8 @@ func Build(l Layers) string {
 		b.WriteString("\n\n")
 	}
 
-	// Skills are optional (#82): with none mounted the agent still needs to be
-	// told to commit, since nothing else in the prompt says so.
-	if l.Skill != "" {
-		b.WriteString("## Skill Instructions\n\n")
-		b.WriteString(l.Skill)
-		b.WriteString("\n\n")
-	} else {
-		b.WriteString("## Working Guidelines\n\n")
-		b.WriteString("Commit your changes to git with a descriptive message when your work is complete.\n\n")
-	}
+	b.WriteString("## Working Guidelines\n\n")
+	b.WriteString("Commit your changes to git with a descriptive message when your work is complete.\n\n")
 
 	if l.StageTask != "" {
 		b.WriteString("## Stage Task\n\n")