diff --git a/cmd/bd/config.go b/cmd/bd/config.go
index 07a34e12..e3c7045e 100644
--- a/cmd/bd/config.go
+++ b/cmd/bd/config.go
@@ -3,10 +3,13 @@ package main
 import (
 	"fmt"
 	"os"
+	"regexp"
 	"sort"
 	"strings"
 
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+	"github.com/steveyegge/beads/cmd/bd/doctor"
 	"github.com/steveyegge/beads/internal/config"
 	"github.com/steveyegge/beads/internal/syncbranch"
 )
@@ -268,10 +271,195 @@ var configUnsetCmd = &cobra.Command{
 	},
 }
 
+var configValidateCmd = &cobra.Command{
+	Use:   "validate",
+	Short: "Validate sync-related configuration",
+	Long: `Validate sync-related configuration settings.
+
+Checks:
+  - sync.mode is a valid value (local, git-branch, external)
+  - conflict.strategy is valid (lww, manual, ours, theirs)
+  - federation.sovereignty is valid (if set)
+  - federation.remote is set when sync.mode requires it
+  - Remote URL format is valid (dolthub://, gs://, s3://, file://)
+  - sync.branch is a valid git branch name
+  - routing.mode is valid (auto, maintainer, contributor)
+
+Examples:
+  bd config validate
+  bd config validate --json`,
+	Run: func(cmd *cobra.Command, args []string) {
+		cwd, err := os.Getwd()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+
+		// Find repo root by walking up to find .beads directory
+		repoPath := findBeadsRepoRoot(cwd)
+		if repoPath == "" {
+			fmt.Fprintf(os.Stderr, "Error: not in a beads repository (no .beads directory found)\n")
+			os.Exit(1)
+		}
+
+		// Run the existing doctor config values check
+		doctorCheck := doctor.CheckConfigValues(repoPath)
+
+		// Run additional sync-related validations
+		syncIssues := validateSyncConfig(repoPath)
+
+		// Combine results
+		allIssues := []string{}
+		if doctorCheck.Detail != "" {
+			allIssues = append(allIssues, strings.Split(doctorCheck.Detail, "\n")...)
+		}
+		allIssues = append(allIssues, syncIssues...)
+
+		// Output results
+		if jsonOutput {
+			result := map[string]interface{}{
+				"valid":  len(allIssues) == 0,
+				"issues": allIssues,
+			}
+			outputJSON(result)
+			return
+		}
+
+		if len(allIssues) == 0 {
+			fmt.Println("✓ All sync-related configuration is valid")
+			return
+		}
+
+		fmt.Println("Configuration validation found issues:")
+		for _, issue := range allIssues {
+			if issue != "" {
+				fmt.Printf("  • %s\n", issue)
+			}
+		}
+		fmt.Println("\nRun 'bd config set <key> <value>' to fix configuration issues.")
+		os.Exit(1)
+	},
+}
+
+// validateSyncConfig performs additional sync-related config validation
+// beyond what doctor.CheckConfigValues covers.
+func validateSyncConfig(repoPath string) []string {
+	var issues []string
+
+	// Load config.yaml directly from the repo path
+	configPath := repoPath + "/.beads/config.yaml"
+	v := viper.New()
+	v.SetConfigType("yaml")
+	v.SetConfigFile(configPath)
+
+	// Try to read config, but don't error if it doesn't exist
+	if err := v.ReadInConfig(); err != nil {
+		// Config file doesn't exist or is unreadable - nothing to validate
+		return issues
+	}
+
+	// Get config from yaml
+	syncMode := v.GetString("sync.mode")
+	conflictStrategy := v.GetString("conflict.strategy")
+	federationSov := v.GetString("federation.sovereignty")
+	federationRemote := v.GetString("federation.remote")
+
+	// Validate sync.mode
+	validSyncModes := map[string]bool{
+		"":           true, // not set is valid (uses default)
+		"local":      true,
+		"git-branch": true,
+		"external":   true,
+	}
+	if syncMode != "" && !validSyncModes[syncMode] {
+		issues = append(issues, fmt.Sprintf("sync.mode: %q is invalid (valid values: local, git-branch, external)", syncMode))
+	}
+
+	// Validate conflict.strategy
+	validConflictStrategies := map[string]bool{
+		"":       true, // not set is valid (uses default lww)
+		"lww":    true, // last-write-wins (default)
+		"manual": true, // require manual resolution
+		"ours":   true, // prefer local changes
+		"theirs": true, // prefer remote changes
+	}
+	if conflictStrategy != "" && !validConflictStrategies[conflictStrategy] {
+		issues = append(issues, fmt.Sprintf("conflict.strategy: %q is invalid (valid values: lww, manual, ours, theirs)", conflictStrategy))
+	}
+
+	// Validate federation.sovereignty
+	validSovereignties := map[string]bool{
+		"":          true, // not set is valid
+		"none":      true, // no sovereignty restrictions
+		"isolated":  true, // fully isolated, no federation
+		"federated": true, // participates in federation
+	}
+	if federationSov != "" && !validSovereignties[federationSov] {
+		issues = append(issues, fmt.Sprintf("federation.sovereignty: %q is invalid (valid values: none, isolated, federated)", federationSov))
+	}
+
+	// Validate federation.remote when required
+	if syncMode == "external" && federationRemote == "" {
+		issues = append(issues, "federation.remote: required when sync.mode is 'external'")
+	}
+
+	// Validate remote URL format
+	if federationRemote != "" {
+		if !isValidRemoteURL(federationRemote) {
+			issues = append(issues, fmt.Sprintf("federation.remote: %q is not a valid remote URL (expected dolthub://, gs://, s3://, file://, or standard git URL)", federationRemote))
+		}
+	}
+
+	return issues
+}
+
+// isValidRemoteURL validates remote URL formats for sync configuration
+func isValidRemoteURL(url string) bool {
+	// Valid URL schemes for beads remotes
+	validSchemes := []string{
+		"dolthub://",
+		"gs://",
+		"s3://",
+		"file://",
+		"https://",
+		"http://",
+		"ssh://",
+	}
+
+	for _, scheme := range validSchemes {
+		if strings.HasPrefix(url, scheme) {
+			return true
+		}
+	}
+
+	// Also allow standard git remote patterns (user@host:path)
+	// The host must have at least one character before the colon
+	// Pattern: username@hostname:path where hostname has at least 2 chars
+	gitSSHPattern := regexp.MustCompile(`^[a-zA-Z0-9._-]+@[a-zA-Z0-9][a-zA-Z0-9._-]*:.+$`)
+	return gitSSHPattern.MatchString(url)
+}
+
+// findBeadsRepoRoot walks up from the given path to find the repo root (containing .beads)
+func findBeadsRepoRoot(startPath string) string {
+	path := startPath
+	for {
+		beadsDir := path + "/.beads"
+		if info, err := os.Stat(beadsDir); err == nil && info.IsDir() {
+			return path
+		}
+		parent := path[:strings.LastIndex(path, "/")]
+		if parent == path || parent == "" {
+			return ""
+		}
+		path = parent
+	}
+}
+
 func init() {
 	configCmd.AddCommand(configSetCmd)
 	configCmd.AddCommand(configGetCmd)
 	configCmd.AddCommand(configListCmd)
 	configCmd.AddCommand(configUnsetCmd)
+	configCmd.AddCommand(configValidateCmd)
 	rootCmd.AddCommand(configCmd)
 }
diff --git a/cmd/bd/config_test.go b/cmd/bd/config_test.go
index 7a753f81..6e4ab172 100644
--- a/cmd/bd/config_test.go
+++ b/cmd/bd/config_test.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/steveyegge/beads/internal/config"
@@ -224,3 +225,230 @@ func setupTestDB(t *testing.T) (*sqlite.SQLiteStorage, func()) {
 
 	return store, cleanup
 }
+
+// TestIsValidRemoteURL tests the remote URL validation function
+func TestIsValidRemoteURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		url      string
+		expected bool
+	}{
+		// Valid URLs
+		{"dolthub scheme", "dolthub://org/repo", true},
+		{"gs scheme", "gs://bucket/path", true},
+		{"s3 scheme", "s3://bucket/path", true},
+		{"file scheme", "file:///path/to/repo", true},
+		{"https scheme", "https://github.com/user/repo", true},
+		{"http scheme", "http://github.com/user/repo", true},
+		{"ssh scheme", "ssh://git@github.com/user/repo", true},
+		{"git ssh format", "git@github.com:user/repo.git", true},
+		{"git ssh with underscore", "git@gitlab.example_host.com:user/repo.git", true},
+
+		// Invalid URLs
+		{"empty string", "", false},
+		{"no scheme", "github.com/user/repo", false},
+		{"invalid scheme", "ftp://server/path", false},
+		{"malformed git ssh", "git@:repo", false},
+		{"just path", "/path/to/repo", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isValidRemoteURL(tt.url)
+			if got != tt.expected {
+				t.Errorf("isValidRemoteURL(%q) = %v, want %v", tt.url, got, tt.expected)
+			}
+		})
+	}
+}
+
+// TestValidateSyncConfig tests the sync config validation function
+func TestValidateSyncConfig(t *testing.T) {
+	// Create a temp directory for testing
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	if err := os.MkdirAll(beadsDir, 0755); err != nil {
+		t.Fatalf("Failed to create .beads dir: %v", err)
+	}
+
+	t.Run("valid empty config", func(t *testing.T) {
+		// Create minimal config.yaml
+		configContent := `prefix: test
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		if len(issues) != 0 {
+			t.Errorf("Expected no issues for valid empty config, got: %v", issues)
+		}
+	})
+
+	t.Run("invalid sync.mode", func(t *testing.T) {
+		configContent := `prefix: test
+sync:
+  mode: "invalid-mode"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		found := false
+		for _, issue := range issues {
+			if strings.Contains(issue, "sync.mode") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected issue about sync.mode, got: %v", issues)
+		}
+	})
+
+	t.Run("invalid conflict.strategy", func(t *testing.T) {
+		configContent := `prefix: test
+conflict:
+  strategy: "invalid-strategy"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		found := false
+		for _, issue := range issues {
+			if strings.Contains(issue, "conflict.strategy") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected issue about conflict.strategy, got: %v", issues)
+		}
+	})
+
+	t.Run("invalid federation.sovereignty", func(t *testing.T) {
+		configContent := `prefix: test
+federation:
+  sovereignty: "invalid-value"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		found := false
+		for _, issue := range issues {
+			if strings.Contains(issue, "federation.sovereignty") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected issue about federation.sovereignty, got: %v", issues)
+		}
+	})
+
+	t.Run("external mode without remote", func(t *testing.T) {
+		configContent := `prefix: test
+sync:
+  mode: "external"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		found := false
+		for _, issue := range issues {
+			if strings.Contains(issue, "federation.remote") && strings.Contains(issue, "required") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected issue about federation.remote being required, got: %v", issues)
+		}
+	})
+
+	t.Run("invalid remote URL", func(t *testing.T) {
+		configContent := `prefix: test
+federation:
+  remote: "invalid-url"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		found := false
+		for _, issue := range issues {
+			if strings.Contains(issue, "federation.remote") && strings.Contains(issue, "not a valid remote URL") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected issue about invalid remote URL, got: %v", issues)
+		}
+	})
+
+	t.Run("valid sync config", func(t *testing.T) {
+		configContent := `prefix: test
+sync:
+  mode: "git-branch"
+conflict:
+  strategy: "lww"
+federation:
+  sovereignty: "federated"
+  remote: "https://github.com/user/beads-data.git"
+`
+		if err := os.WriteFile(filepath.Join(beadsDir, "config.yaml"), []byte(configContent), 0644); err != nil {
+			t.Fatalf("Failed to write config.yaml: %v", err)
+		}
+
+		issues := validateSyncConfig(tmpDir)
+		if len(issues) != 0 {
+			t.Errorf("Expected no issues for valid config, got: %v", issues)
+		}
+	})
+}
+
+// TestFindBeadsRepoRoot tests the repo root finding function
+func TestFindBeadsRepoRoot(t *testing.T) {
+	// Create a temp directory structure
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	subDir := filepath.Join(tmpDir, "sub", "dir")
+
+	if err := os.MkdirAll(beadsDir, 0755); err != nil {
+		t.Fatalf("Failed to create .beads dir: %v", err)
+	}
+	if err := os.MkdirAll(subDir, 0755); err != nil {
+		t.Fatalf("Failed to create sub dir: %v", err)
+	}
+
+	t.Run("from repo root", func(t *testing.T) {
+		got := findBeadsRepoRoot(tmpDir)
+		if got != tmpDir {
+			t.Errorf("findBeadsRepoRoot(%q) = %q, want %q", tmpDir, got, tmpDir)
+		}
+	})
+
+	t.Run("from subdirectory", func(t *testing.T) {
+		got := findBeadsRepoRoot(subDir)
+		if got != tmpDir {
+			t.Errorf("findBeadsRepoRoot(%q) = %q, want %q", subDir, got, tmpDir)
+		}
+	})
+
+	t.Run("not in repo", func(t *testing.T) {
+		noRepoDir := t.TempDir()
+		got := findBeadsRepoRoot(noRepoDir)
+		if got != "" {
+			t.Errorf("findBeadsRepoRoot(%q) = %q, want empty string", noRepoDir, got)
+		}
+	})
+}