perf: cache doctor beads dir resolution

cmd/bd/doctor/backend.go

@@ -5,11 +5,14 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/steveyegge/beads/internal/configfile"
 	"github.com/steveyegge/beads/internal/utils"
 )
 
+var resolveBeadsDirCache sync.Map
+
 // getBackendAndBeadsDir resolves the effective .beads directory (following redirects)
 // and returns the configured storage backend ("dolt" by default).
 func getBackendAndBeadsDir(repoPath string) (backend string, beadsDir string) {
@@ -23,10 +26,17 @@ func getBackendAndBeadsDir(repoPath string) (backend string, beadsDir string) {
 }
 
 func ResolveBeadsDirForRepo(repoPath string) string {
-	return resolveDoctorBeadsDir(repoPath)
+	cacheKey := utils.CanonicalizePath(repoPath)
+	if resolved, ok := resolveBeadsDirCache.Load(cacheKey); ok {
+		return resolved.(string)
+	}
+
+	resolved := resolveBeadsDirForRepoUncached(repoPath)
+	resolveBeadsDirCache.Store(cacheKey, resolved)
+	return resolved
 }
 
-func resolveDoctorBeadsDir(repoPath string) string {
+func resolveBeadsDirForRepoUncached(repoPath string) string {
 	localBeadsDir := filepath.Join(repoPath, ".beads")
 	if info, err := os.Stat(localBeadsDir); err == nil && info.IsDir() {
 		return resolveBeadsDir(localBeadsDir)
@@ -39,6 +49,10 @@ func resolveDoctorBeadsDir(repoPath string) string {
 	return resolveBeadsDir(localBeadsDir)
 }
 
+func clearResolveBeadsDirCache() {
+	resolveBeadsDirCache = sync.Map{}
+}
+
 func worktreeFallbackBeadsDir(repoPath string) string {
 	cmd := exec.Command("git", "-C", repoPath, "rev-parse", "--git-dir", "--git-common-dir")
 	output, err := cmd.Output()

cmd/bd/doctor/bare_parent_fallback_test.go

@@ -11,6 +11,9 @@ import (
 )
 
 func TestResolveBeadsDirForRepo_BareParentWorktreeFallback(t *testing.T) {
+	clearResolveBeadsDirCache()
+	t.Cleanup(clearResolveBeadsDirCache)
+
 	bareDir, featureWorktreeDir := setupBareParentWorktreeForDoctorTest(t)
 	bareBeadsDir := filepath.Join(bareDir, ".beads")
 	if err := os.MkdirAll(bareBeadsDir, 0o750); err != nil {
@@ -23,7 +26,66 @@ func TestResolveBeadsDirForRepo_BareParentWorktreeFallback(t *testing.T) {
 	}
 }
 
+func TestResolveBeadsDirForRepo_CachesFallbackResult(t *testing.T) {
+	clearResolveBeadsDirCache()
+	t.Cleanup(clearResolveBeadsDirCache)
+
+	tmpDir := t.TempDir()
+	repoPath := filepath.Join(tmpDir, "feature")
+	bareDir := filepath.Join(tmpDir, "repo.git")
+	bareBeadsDir := filepath.Join(bareDir, ".beads")
+	gitBinDir := filepath.Join(tmpDir, "bin")
+	gitLogPath := filepath.Join(tmpDir, "git.log")
+	gitScriptPath := filepath.Join(gitBinDir, "git")
+
+	for _, dir := range []string{repoPath, bareBeadsDir, gitBinDir} {
+		if err := os.MkdirAll(dir, 0o750); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	gitScript := strings.Join([]string{
+		"#!/bin/sh",
+		"printf 'called\n' >> \"$FAKE_GIT_LOG\"",
+		"printf '%s\\n%s\\n' \"$FAKE_GIT_DIR\" \"$FAKE_GIT_COMMON_DIR\"",
+		"",
+	}, "\n")
+	if err := os.WriteFile(gitScriptPath, []byte(gitScript), 0o750); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Setenv("PATH", gitBinDir)
+	t.Setenv("FAKE_GIT_LOG", gitLogPath)
+	t.Setenv("FAKE_GIT_DIR", filepath.Join(bareDir, "worktrees", "feature"))
+	t.Setenv("FAKE_GIT_COMMON_DIR", bareDir)
+
+	first := ResolveBeadsDirForRepo(repoPath)
+	if first != utils.CanonicalizePath(bareBeadsDir) {
+		t.Fatalf("first ResolveBeadsDirForRepo() = %q, want %q", first, utils.CanonicalizePath(bareBeadsDir))
+	}
+
+	if err := os.Remove(gitScriptPath); err != nil {
+		t.Fatal(err)
+	}
+
+	second := ResolveBeadsDirForRepo(repoPath)
+	if second != first {
+		t.Fatalf("second ResolveBeadsDirForRepo() = %q, want cached %q", second, first)
+	}
+
+	logData, err := os.ReadFile(gitLogPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if calls := strings.Count(string(logData), "called\n"); calls != 1 {
+		t.Fatalf("git fallback call count = %d, want 1", calls)
+	}
+}
+
 func TestCheckMetadataVersionTracking_BareParentWorktreeFallback(t *testing.T) {
+	clearResolveBeadsDirCache()
+	t.Cleanup(clearResolveBeadsDirCache)
+
 	bareDir, featureWorktreeDir := setupBareParentWorktreeForDoctorTest(t)
 	bareBeadsDir := filepath.Join(bareDir, ".beads")
 	if err := os.MkdirAll(bareBeadsDir, 0o750); err != nil {
@@ -40,6 +102,9 @@ func TestCheckMetadataVersionTracking_BareParentWorktreeFallback(t *testing.T) {
 }
 
 func TestCheckLockHealth_BareParentWorktreeFallback(t *testing.T) {
+	clearResolveBeadsDirCache()
+	t.Cleanup(clearResolveBeadsDirCache)
+
 	bareDir, featureWorktreeDir := setupBareParentWorktreeForDoctorTest(t)
 	bareBeadsDir := filepath.Join(bareDir, ".beads")
 	if err := os.MkdirAll(filepath.Join(bareBeadsDir, "dolt"), 0o750); err != nil {
@@ -56,6 +121,9 @@ func TestCheckLockHealth_BareParentWorktreeFallback(t *testing.T) {
 }
 
 func TestCheckDoltLocks_BareParentWorktreeFallback(t *testing.T) {
+	clearResolveBeadsDirCache()
+	t.Cleanup(clearResolveBeadsDirCache)
+
 	bareDir, featureWorktreeDir := setupBareParentWorktreeForDoctorTest(t)
 	bareBeadsDir := filepath.Join(bareDir, ".beads")
 	if err := os.MkdirAll(bareBeadsDir, 0o750); err != nil {

default.nix

@@ -16,7 +16,7 @@ buildGoModule {
   doCheck = false;
 
   # Go module dependencies hash - if build fails with hash mismatch, update with the "got:" value
-  vendorHash = "sha256-1BJsEPP5SYZFGCWHLn532IUKlzcGDg5nhrqGWylEHgY=";
+  vendorHash = "sha256-wcFAvGoDR9IYckWRMqPqCgPSUKmoYYyYg0dfNGDI6Go=";
 
   # Relax go.mod version for Nix: nixpkgs Go may lag behind the latest
   # patch release, and GOTOOLCHAIN=auto can't download in the Nix sandbox.