app/engine/localBackend.ts

 // Today's behavior, unchanged, behind the Backend interface -- a real

 // local clone plus flat/SQLite files under app/state/, exactly as

 // before. The only thing that moves is who resolves a repo slug into

 // paths: that logic used to live in cli/lib/repo.ts and get threaded

 // through every call site by the caller; it lives here now, since a

 // path is something only a *local* backend has at all.

 import { existsSync, readdirSync } from "node:fs";

 import { execFileSync } from "node:child_process";

 import { dirname, join } from "node:path";

 import { fileURLToPath } from "node:url";

 import type { Backend, LadderSearchHit } from "./backend.js";

 import type { Lane } from "./types.js";

 import type { Rung, RungKind } from "./ladder.js";

 import type { EmbeddedRung } from "./ladderNotes.js";

 import { writeLadder, appendRepoChildren as appendRepoChildrenImpl, readAnchor as readAnchorImpl } from "./ladderNotes.js";

 import { collectLadder, type ResolvedRung } from "./ladderRender.js";

 import { listCommitsChronological, commitFileChanges, fileContentAtCommit, type CommitRow, type FileChangeRow } from "./ingest.js";

 import { commitChangeset as commitChangesetImpl, type ChangesetFile, type CommitAuthor } from "./changeset.js";

 import { readLane as readLaneImpl, writeLane as writeLaneImpl, listLanes as listLanesImpl, withLane as withLaneImpl } from "./store.js";

 const here = dirname(fileURLToPath(import.meta.url));

 const appRoot = join(here, "..");

 /** Every "file"/"repo" kind rung in an already-resolved tree -- same filter as cloudflareBackend.ts's collectSearchableRungs (a changeset/filechange rung is a historical per-commit entry, not a holistic current-state description), just over ResolvedRung (local, children already resolved from notes refs) instead of SimpleRung (remote, embedded inline). */

 function collectSearchableRungs(rung: ResolvedRung, out: ResolvedRung[]): void {

  if (rung.kind === "file" || rung.kind === "repo") out.push(rung);

  for (const child of rung.children) collectSearchableRungs(child, out);

 }

 function parseSlug(slug: string): { name: string } {

  if (typeof slug !== "string" || !slug) {

  throw new Error(`expected a repo slug shaped "owner/repo", got ${JSON.stringify(slug)}.`);

  }

  const parts = slug.split("/");

  if (parts.length !== 2 || !parts[0] || !parts[1]) {

  throw new Error(`expected "owner/repo", got "${slug}"`);

  }

  return { name: parts[1] };

 }

 function repoDirOf(slug: string): string {

  return join(appRoot, "demo-repos", parseSlug(slug).name);

 }

 function stateDirOf(slug: string): string {

  return join(appRoot, "state", parseSlug(slug).name);

 }

 export function createLocalBackend(): Backend {

  return {

  name: "local",

  async ensureCloned(repo) {

  const repoDir = repoDirOf(repo);

  if (existsSync(repoDir)) return;

  execFileSync("git", ["clone", "--quiet", `https://github.com/${repo}.git`, repoDir], { stdio: "inherit" });

  },

  async listCommits(repo): Promise<CommitRow[]> {

  return listCommitsChronological(repoDirOf(repo));

  },

  async diffCommit(repo, commit): Promise<FileChangeRow[]> {

  return commitFileChanges(repoDirOf(repo), commit);

  },

  async readFileAtCommit(repo, sha, path): Promise<string> {

  return fileContentAtCommit(repoDirOf(repo), sha, path);

  },

  async commitChangeset(repo, input: { files: ChangesetFile[]; message: string; author: CommitAuthor }): Promise<string> {

  return commitChangesetImpl(repoDirOf(repo), input);

  },

  async readAnchor(repo, path): Promise<EmbeddedRung | null> {

  return readAnchorImpl(repoDirOf(repo), stateDirOf(repo), path);

  },

  // No network cost here to begin with (git notes in a real local

  // clone) -- resolve fresh every call, same as the Ladder tab

  // already did before this method existed, just now reachable

  // through one interface method instead of collectLadder directly.

  async readLadderTree(repo): Promise<ResolvedRung | null> {

  const { tree } = await collectLadder(repoDirOf(repo), stateDirOf(repo));

  return tree;

  },

  async writeLadder(repo, rung: Rung | Rung[]): Promise<void> {

  const rungs = Array.isArray(rung) ? rung : [rung];

  for (const one of rungs) await writeLadder(repoDirOf(repo), stateDirOf(repo), one);

  },

  async appendRepoChildren(repo, children: { path: string; kind: RungKind }[]): Promise<void> {

  await appendRepoChildrenImpl(repoDirOf(repo), stateDirOf(repo), children);

  },

  // No D1/FTS5 here -- a plain multi-term substring match (every

  // query word must appear in the summary, case-insensitive) over

  // every repo currently cloned under demo-repos/, scanned fresh on

  // every call rather than kept in a maintained index. Not as sharp

  // as the remote backend's BM25 ranking, but the same feature,

  // genuinely working locally -- not a stub. "repo" in each hit is

  // just the directory name (demo-repos/<name>), not a real

  // "owner/repo" slug: local mode has no account/ownership concept

  // to reconstruct one from, only ever the bare name a repo was

  // cloned under.

  async searchLadder(query, limit): Promise<LadderSearchHit[]> {

  const demoReposDir = join(appRoot, "demo-repos");

  if (!existsSync(demoReposDir)) return [];

  const terms = query.toLowerCase().split(/\s+/).filter(Boolean);

  const hits: LadderSearchHit[] = [];

  for (const entry of readdirSync(demoReposDir, { withFileTypes: true })) {

  if (!entry.isDirectory()) continue;

  try {

  const { tree } = await collectLadder(join(demoReposDir, entry.name), join(appRoot, "state", entry.name));

  const candidates: ResolvedRung[] = [];

  collectSearchableRungs(tree, candidates);

  for (const c of candidates) {

  const haystack = c.summary.toLowerCase();

  if (terms.every((t) => haystack.includes(t))) {

  // Unlike cloudflareLadderBackend.ts's SimpleRung (already

  // commit-only by construction), a local ResolvedRung's

  // sources can include pr/issue kinds too -- filter before

  // taking the most recent one.

  const commitSources = c.sources.filter((s) => s.kind === "commit");

  const commitSha = commitSources.length ? commitSources[commitSources.length - 1].ref : null;

  hits.push({ repo: entry.name, path: c.path, kind: c.kind, commitSha, summary: c.summary });

  }

  }

  } catch {

  // repo not onboarded/bootstrapped yet -- skip rather than fail the whole search

  }

  }

  return hits.slice(0, limit);

  },

  // No persisted index here to go stale -- searchLadder above scans

  // every repo's CURRENT Ladder tree fresh on every call, so there's

  // nothing to backfill (unlike the remote backend's D1 index,

  // populated incrementally as writes happen).

  async reindexLadder(): Promise<number> {

  return 0;

  },

  async readLane(repo, laneId): Promise<Lane | null> {

  return readLaneImpl(stateDirOf(repo), laneId);

  },

  async writeLane(repo, lane: Lane): Promise<void> {

  writeLaneImpl(stateDirOf(repo), lane);

  },

  async listLanes(repo): Promise<Lane[]> {

  return listLanesImpl(stateDirOf(repo));

  },

  async withLane(repo, laneId, mutate): Promise<Lane> {

  return withLaneImpl(stateDirOf(repo), laneId, mutate);

  },

  };

 }