feat: auto-resolve cross-rig IDs in bd dep add (bd-lfiu)

When `bd dep add` fails to resolve the dependency ID locally, it now
checks routes.jsonl for a matching prefix and auto-converts to an
external reference format (external:<project>:<id>).

This allows simpler syntax like:
  bd dep add gt-xyz bd-abc

Instead of the verbose:
  bd dep add gt-xyz external:beads:bd-abc

New functions in routing package:
- ExtractProjectFromPath: Gets project name from route path
- ResolveToExternalRef: Converts foreign ID to external ref using routes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/dep.go

@@ -5,9 +5,11 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/spf13/cobra"
+	"github.com/steveyegge/beads/internal/routing"
 	"github.com/steveyegge/beads/internal/rpc"
 	"github.com/steveyegge/beads/internal/storage/sqlite"
 	"github.com/steveyegge/beads/internal/types"
@@ -15,6 +17,14 @@ import (
 	"github.com/steveyegge/beads/internal/utils"
 )
 
+// getBeadsDir returns the .beads directory path, derived from the global dbPath.
+func getBeadsDir() string {
+	if dbPath != "" {
+		return filepath.Dir(dbPath)
+	}
+	return ""
+}
+
 // isChildOf returns true if childID is a hierarchical child of parentID.
 // For example, "bd-abc.1" is a child of "bd-abc", and "bd-abc.1.2" is a child of "bd-abc.1".
 func isChildOf(childID, parentID string) bool {
@@ -88,9 +98,15 @@ Examples:
 				resolveArgs = &rpc.ResolveIDArgs{ID: args[1]}
 				resp, err = daemonClient.ResolveID(resolveArgs)
 				if err != nil {
-					FatalErrorRespectJSON("resolving dependency ID %s: %v", args[1], err)
-				}
-				if err := json.Unmarshal(resp.Data, &toID); err != nil {
+					// Resolution failed - try auto-converting to external ref (bd-lfiu)
+					beadsDir := getBeadsDir()
+					if extRef := routing.ResolveToExternalRef(args[1], beadsDir); extRef != "" {
+						toID = extRef
+						isExternalRef = true
+					} else {
+						FatalErrorRespectJSON("resolving dependency ID %s: %v", args[1], err)
+					}
+				} else if err := json.Unmarshal(resp.Data, &toID); err != nil {
 					FatalErrorRespectJSON("unmarshaling resolved ID: %v", err)
 				}
 			}
@@ -111,7 +127,14 @@ Examples:
 			} else {
 				toID, err = utils.ResolvePartialID(ctx, store, args[1])
 				if err != nil {
-					FatalErrorRespectJSON("resolving dependency ID %s: %v", args[1], err)
+					// Resolution failed - try auto-converting to external ref (bd-lfiu)
+					beadsDir := getBeadsDir()
+					if extRef := routing.ResolveToExternalRef(args[1], beadsDir); extRef != "" {
+						toID = extRef
+						isExternalRef = true
+					} else {
+						FatalErrorRespectJSON("resolving dependency ID %s: %v", args[1], err)
+					}
 				}
 			}
 		}

internal/routing/routes.go

@@ -67,6 +67,49 @@ func ExtractPrefix(id string) string {
 	return id[:idx+1] // Include the hyphen
 }
 
+// ExtractProjectFromPath extracts the project name from a route path.
+// For "beads/mayor/rig", returns "beads".
+// For "gastown/crew/max", returns "gastown".
+func ExtractProjectFromPath(path string) string {
+	// Get the first component of the path
+	parts := strings.Split(path, "/")
+	if len(parts) > 0 && parts[0] != "" {
+		return parts[0]
+	}
+	return ""
+}
+
+// ResolveToExternalRef attempts to convert a foreign issue ID to an external reference
+// using routes.jsonl for prefix-based routing.
+//
+// If the ID's prefix matches a route, returns "external:<project>:<id>".
+// Otherwise, returns empty string (no route found).
+//
+// Example: If routes.jsonl has {"prefix": "bd-", "path": "beads/mayor/rig"}
+// then ResolveToExternalRef("bd-abc", beadsDir) returns "external:beads:bd-abc"
+func ResolveToExternalRef(id, beadsDir string) string {
+	routes, err := LoadRoutes(beadsDir)
+	if err != nil || len(routes) == 0 {
+		return ""
+	}
+
+	prefix := ExtractPrefix(id)
+	if prefix == "" {
+		return ""
+	}
+
+	for _, route := range routes {
+		if route.Prefix == prefix {
+			project := ExtractProjectFromPath(route.Path)
+			if project != "" {
+				return fmt.Sprintf("external:%s:%s", project, id)
+			}
+		}
+	}
+
+	return ""
+}
+
 // ResolveBeadsDirForID determines which beads directory contains the given issue ID.
 // It first checks the local beads directory, then consults routes.jsonl for prefix-based routing.
 //

internal/routing/routing_test.go

@@ -88,3 +88,57 @@ func TestDetectUserRole_Fallback(t *testing.T) {
 		t.Errorf("DetectUserRole() = %v, want %v (fallback)", role, Contributor)
 	}
 }
+
+func TestExtractPrefix(t *testing.T) {
+	tests := []struct {
+		id   string
+		want string
+	}{
+		{"gt-abc123", "gt-"},
+		{"bd-xyz", "bd-"},
+		{"hq-1234", "hq-"},
+		{"abc123", ""},     // No hyphen
+		{"", ""},           // Empty string
+		{"-abc", "-"},      // Starts with hyphen
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.id, func(t *testing.T) {
+			got := ExtractPrefix(tt.id)
+			if got != tt.want {
+				t.Errorf("ExtractPrefix(%q) = %q, want %q", tt.id, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestExtractProjectFromPath(t *testing.T) {
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"beads/mayor/rig", "beads"},
+		{"gastown/crew/max", "gastown"},
+		{"simple", "simple"},
+		{"", ""},
+		{"/absolute/path", ""}, // Starts with /, first component is empty
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			got := ExtractProjectFromPath(tt.path)
+			if got != tt.want {
+				t.Errorf("ExtractProjectFromPath(%q) = %q, want %q", tt.path, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestResolveToExternalRef(t *testing.T) {
+	// This test is limited since it requires a routes.jsonl file
+	// Just test that it returns empty string for nonexistent directory
+	got := ResolveToExternalRef("bd-abc", "/nonexistent/path")
+	if got != "" {
+		t.Errorf("ResolveToExternalRef() = %q, want empty string for nonexistent path", got)
+	}
+}