feat: add list-meta and list-schema commands with persistent meta index

Adds Store.listMeta() and Store.listSchemas() to expose meta-schema
discovery, backed by an in-memory metaSet (memory store) and a
persistent _index/_meta file (FS store). Surfaces both via new
json-cas list-meta and list-schema CLI commands wrapped in
@output/list-meta and @output/list-schema envelope schemas.

The FS store migrates from existing nodes when _meta is absent
(scanning self-referencing nodes) and preserves _meta on subsequent
opens. delete() removes affected hashes from the meta index and
persists the change.

Closes #90

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/cli-json-cas/src/index.ts

@@ -823,6 +823,18 @@ async function cmdList(_args: string[]): Promise<void> {
   out(await wrapEnvelope(store, "@output/list", hashes));
 }
 
+async function cmdListMeta(_args: string[]): Promise<void> {
+  const store = await openStore();
+  const hashes = store.listMeta();
+  out(await wrapEnvelope(store, "@output/list-meta", hashes));
+}
+
+async function cmdListSchema(_args: string[]): Promise<void> {
+  const store = await openStore();
+  const hashes = store.listSchemas();
+  out(await wrapEnvelope(store, "@output/list-schema", hashes));
+}
+
 function printUsage(): void {
   console.log(`\
 Usage: json-cas [--store <path>] [--json] <command> [args]
@@ -842,6 +854,8 @@ Commands:
   render <hash> [options]           Render node as text with resolution decay (raw output)
   render --pipe/-p [options]        Render { type, value } from stdin (raw output)
   list --type <hash-or-alias>       List hashes for a type (value=string[])            (@output/list)
+  list-meta                         List meta-schema hashes (value=string[])           (@output/list-meta)
+  list-schema                       List all schema hashes (value=string[])            (@output/list-schema)
   var set <name> <hash> [--tag <tag>...] Create/update a variable                      (@output/var-set)
   var get <name> --schema <hash>    Get a variable by name + schema                    (@output/var-get)
   var delete <name> [--schema <hash>] Delete variable(s)                               (@output/var-delete)
@@ -912,6 +926,14 @@ switch (cmd) {
     await cmdList(rest);
     break;
 
+  case "list-meta":
+    await cmdListMeta(rest);
+    break;
+
+  case "list-schema":
+    await cmdListSchema(rest);
+    break;
+
   case "var": {
     const [sub, ...subRest] = rest;
     switch (sub) {

packages/cli-json-cas/tests/__snapshots__/edge-cases.test.ts.snap

@@ -24,6 +24,8 @@ Commands:
   render <hash> [options]           Render node as text with resolution decay (raw output)
   render --pipe/-p [options]        Render { type, value } from stdin (raw output)
   list --type <hash-or-alias>       List hashes for a type (value=string[])            (@output/list)
+  list-meta                         List meta-schema hashes (value=string[])           (@output/list-meta)
+  list-schema                       List all schema hashes (value=string[])            (@output/list-schema)
   var set <name> <hash> [--tag <tag>...] Create/update a variable                      (@output/var-set)
   var get <name> --schema <hash>    Get a variable by name + schema                    (@output/var-get)
   var delete <name> [--schema <hash>] Delete variable(s)                               (@output/var-delete)

packages/cli-json-cas/tests/alias.test.ts

@@ -1,9 +1,5 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
-import {
+import { mkdirSync, rmSync, writeFileSync } from "node:fs";
-  mkdirSync,
-  rmSync,
-  writeFileSync,
-} from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 

packages/cli-json-cas/tests/edge-cases.test.ts

@@ -75,7 +75,10 @@ describe("Phase 7: Edge Cases", () => {
     const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
     const { putSchema } = await import("@uncaged/json-cas");
     const store = await openFsStore(tmpStore);
-    typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+    typeHash = await putSchema(
+      store,
+      JSON.parse(readFileSync(schemaFile, "utf-8")),
+    );
 
     const nodeFile = join(tmpStore, "test-node.json");
     writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));
@@ -191,7 +194,10 @@ describe("Phase 3: Variable System", () => {
     const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
     const { putSchema } = await import("@uncaged/json-cas");
     const store = await openFsStore(tmpStore);
-    typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+    typeHash = await putSchema(
+      store,
+      JSON.parse(readFileSync(schemaFile, "utf-8")),
+    );
 
     const nodeFile = join(tmpStore, "test-node.json");
     writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));
@@ -377,7 +383,10 @@ describe("Phase 4: Template System", () => {
     const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
     const { putSchema } = await import("@uncaged/json-cas");
     const store = await openFsStore(tmpStore);
-    typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+    typeHash = await putSchema(
+      store,
+      JSON.parse(readFileSync(schemaFile, "utf-8")),
+    );
   });
 
   afterAll(() => {

packages/cli-json-cas/tests/gc.test.ts

@@ -28,7 +28,10 @@ beforeAll(async () => {
   const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
   const { putSchema } = await import("@uncaged/json-cas");
   const store = await openFsStore(tmpStore);
-  typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+  typeHash = await putSchema(
+    store,
+    JSON.parse(readFileSync(schemaFile, "utf-8")),
+  );
 
   const nodeFile = join(tmpStore, "test-node.json");
   writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));
@@ -78,7 +81,16 @@ describe("Phase 6: GC", () => {
     expect(gcExit).toBe(0);
 
     const proc = Bun.spawn(
-      ["bun", entrypoint, "--store", tmpStore, "--var-db", varDbPath, "render", "--pipe"],
+      [
+        "bun",
+        entrypoint,
+        "--store",
+        tmpStore,
+        "--var-db",
+        varDbPath,
+        "render",
+        "--pipe",
+      ],
       { stdin: "pipe", stdout: "pipe", stderr: "pipe" },
     );
     proc.stdin.write(gcOut);

packages/cli-json-cas/tests/helpers.ts

@@ -1,13 +1,26 @@
-import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import {
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+} from "node:fs";
 import { tmpdir } from "node:os";
 import { join, resolve } from "node:path";
 import type { JSONSchema } from "@uncaged/json-cas";
 import { putSchema } from "@uncaged/json-cas";
 import { openStore as openFsStore } from "@uncaged/json-cas-fs";
 
-export { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync };
+export {
-export { tmpdir };
+  join,
-export { join, resolve };
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  resolve,
+  rmSync,
+  tmpdir,
+  writeFileSync,
+};
 
 export const entrypoint = resolve(import.meta.dir, "../src/index.ts");
 export const pkgPath = resolve(import.meta.dir, "../package.json");

packages/cli-json-cas/tests/list-meta-schema.test.ts

@@ -0,0 +1,113 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdirSync, mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { envValue, runCli } from "./helpers.js";
+
+let storePath: string;
+
+beforeEach(() => {
+  storePath = mkdtempSync(join(tmpdir(), "json-cas-list-meta-schema-"));
+  mkdirSync(storePath, { recursive: true });
+});
+
+afterEach(() => {
+  rmSync(storePath, { recursive: true, force: true });
+});
+
+describe("list-meta CLI command", () => {
+  test("E1. list-meta on bootstrapped store contains exactly the meta-schema hash", async () => {
+    // First, get @schema hash by calling has on it (also triggers bootstrap)
+    const { stdout: hashOut, exitCode: hashCode } = await runCli(
+      ["hash", "@schema", "--pipe"],
+      storePath,
+    );
+    // ensure bootstrap by running a no-op command:
+    void hashOut;
+    void hashCode;
+
+    // Bootstrap fully via 'list --type @schema'
+    const { stdout: schemaListOut } = await runCli(
+      ["list", "--type", "@schema"],
+      storePath,
+    );
+    const schemaList = envValue(schemaListOut) as string[];
+    expect(Array.isArray(schemaList)).toBe(true);
+
+    const { stdout, stderr, exitCode } = await runCli(["list-meta"], storePath);
+    expect(exitCode).toBe(0);
+    expect(stderr).toBe("");
+
+    const parsed = JSON.parse(stdout) as { type: string; value: string[] };
+    expect(parsed.type).toMatch(/^[0-9A-HJKMNP-TV-Z]{13}$/);
+    expect(Array.isArray(parsed.value)).toBe(true);
+    expect(parsed.value).toHaveLength(1);
+    expect(parsed.value[0]).toMatch(/^[0-9A-HJKMNP-TV-Z]{13}$/);
+  });
+
+  test("E1. --json flag yields compact JSON", async () => {
+    const { stdout, exitCode } = await runCli(
+      ["--json", "list-meta"],
+      storePath,
+    );
+    expect(exitCode).toBe(0);
+    // compact = no newlines/spaces between fields
+    expect(stdout.trim()).not.toContain("\n  ");
+  });
+});
+
+describe("list-schema CLI command", () => {
+  test("E2. list-schema on bootstrapped store includes meta-schema and built-ins", async () => {
+    const { stdout, stderr, exitCode } = await runCli(
+      ["list-schema"],
+      storePath,
+    );
+    expect(exitCode).toBe(0);
+    expect(stderr).toBe("");
+
+    const parsed = JSON.parse(stdout) as { type: string; value: string[] };
+    expect(parsed.type).toMatch(/^[0-9A-HJKMNP-TV-Z]{13}$/);
+    expect(Array.isArray(parsed.value)).toBe(true);
+    // meta + 5 primitive + 20 output = 26
+    expect(parsed.value.length).toBeGreaterThanOrEqual(6);
+  });
+});
+
+describe("usage help", () => {
+  test("E3. printing usage includes list-meta and list-schema lines", async () => {
+    const { stdout, exitCode } = await runCli([], storePath);
+    expect(exitCode).toBe(0);
+    expect(stdout).toContain("list-meta");
+    expect(stdout).toContain("list-schema");
+  });
+});
+
+describe("F1. output schemas registered", () => {
+  test("@output/list-meta and @output/list-schema schemas exist", async () => {
+    const { stdout, exitCode } = await runCli(["list-meta"], storePath);
+    expect(exitCode).toBe(0);
+    const parsed = JSON.parse(stdout) as { type: string };
+    // type hash references the @output/list-meta schema, must be retrievable
+    const { stdout: getOut, exitCode: getCode } = await runCli(
+      ["get", parsed.type],
+      storePath,
+    );
+    expect(getCode).toBe(0);
+    const node = envValue(getOut) as {
+      payload: { title?: string };
+    };
+    expect(node.payload.title).toBe("ucas list-meta result");
+
+    const { stdout: schemaOut } = await runCli(["list-schema"], storePath);
+    const schemaParsed = JSON.parse(schemaOut) as { type: string };
+    const { stdout: getSchOut, exitCode: getSchCode } = await runCli(
+      ["get", schemaParsed.type],
+      storePath,
+    );
+    expect(getSchCode).toBe(0);
+    const schNode = envValue(getSchOut) as {
+      payload: { title?: string };
+    };
+    expect(schNode.payload.title).toBe("ucas list-schema result");
+  });
+});

packages/cli-json-cas/tests/pipe.test.ts

@@ -28,7 +28,10 @@ beforeAll(async () => {
   const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
   const { putSchema } = await import("@uncaged/json-cas");
   const store = await openFsStore(tmpStore);
-  typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+  typeHash = await putSchema(
+    store,
+    JSON.parse(readFileSync(schemaFile, "utf-8")),
+  );
 
   const nodeFile = join(tmpStore, "test-node.json");
   writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));
@@ -143,7 +146,6 @@ describe("Phase 8: Pipe Composition", () => {
     expect(exitCode).toBe(0);
     expect(stdout).toBe("Person: Carol (25)");
   });
-
 });
 
 // ---- Phase 9: Put/Hash Pipe Input ----

packages/cli-json-cas/tests/render.test.ts

@@ -104,7 +104,10 @@ describe("Phase 5: Render", () => {
     const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
     const { putSchema } = await import("@uncaged/json-cas");
     const store = await openFsStore(tmpStore);
-    typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+    typeHash = await putSchema(
+      store,
+      JSON.parse(readFileSync(schemaFile, "utf-8")),
+    );
 
     const nodeFile = join(tmpStore, "test-node.json");
     writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));

packages/cli-json-cas/tests/schema-validation.test.ts

@@ -579,12 +579,25 @@ describe("Phase 2: Schema Validation", () => {
     const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
     const { putSchema } = await import("@uncaged/json-cas");
     const store = await openFsStore(tmpStore);
-    typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+    typeHash = await putSchema(
+      store,
+      JSON.parse(readFileSync(schemaFile, "utf-8")),
+    );
 
     const nodeFile = join(tmpStore, "test-node.json");
     writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));
     const proc = Bun.spawn(
-      ["bun", entrypoint, "--store", tmpStore, "--var-db", varDbPath, "put", typeHash, nodeFile],
+      [
+        "bun",
+        entrypoint,
+        "--store",
+        tmpStore,
+        "--var-db",
+        varDbPath,
+        "put",
+        typeHash,
+        nodeFile,
+      ],
       { stdout: "pipe", stderr: "pipe" },
     );
     await proc.exited;
@@ -600,7 +613,17 @@ describe("Phase 2: Schema Validation", () => {
     const badFile = join(tmpStore, "bad-node.json");
     writeFileSync(badFile, JSON.stringify({ name: 123 }));
     const proc = Bun.spawn(
-      ["bun", entrypoint, "--store", tmpStore, "--var-db", varDbPath, "put", typeHash, badFile],
+      [
+        "bun",
+        entrypoint,
+        "--store",
+        tmpStore,
+        "--var-db",
+        varDbPath,
+        "put",
+        typeHash,
+        badFile,
+      ],
       { stdout: "pipe", stderr: "pipe" },
     );
     const exitCode = await proc.exited;
@@ -615,7 +638,17 @@ describe("Phase 2: Schema Validation", () => {
   test("2.3 put against non-existent schema hash fails", async () => {
     const nodeFile = join(tmpStore, "test-node.json");
     const proc = Bun.spawn(
-      ["bun", entrypoint, "--store", tmpStore, "--var-db", varDbPath, "put", "AAAAAAAAAAAAA", nodeFile],
+      [
+        "bun",
+        entrypoint,
+        "--store",
+        tmpStore,
+        "--var-db",
+        varDbPath,
+        "put",
+        "AAAAAAAAAAAAA",
+        nodeFile,
+      ],
       { stdout: "pipe", stderr: "pipe" },
     );
     const exitCode = await proc.exited;

packages/cli-json-cas/tests/verify-refs-walk.test.ts

@@ -28,7 +28,10 @@ beforeAll(async () => {
   const { openStore: openFsStore } = await import("@uncaged/json-cas-fs");
   const { putSchema } = await import("@uncaged/json-cas");
   const store = await openFsStore(tmpStore);
-  typeHash = await putSchema(store, JSON.parse(readFileSync(schemaFile, "utf-8")));
+  typeHash = await putSchema(
+    store,
+    JSON.parse(readFileSync(schemaFile, "utf-8")),
+  );
 
   const nodeFile = join(tmpStore, "test-node.json");
   writeFileSync(nodeFile, JSON.stringify({ name: "Alice", age: 30 }));

packages/json-cas-fs/src/store.test.ts

@@ -3,6 +3,7 @@ import {
   existsSync,
   mkdtempSync,
   readdirSync,
+  readFileSync,
   rmSync,
   writeFileSync,
 } from "node:fs";
@@ -10,6 +11,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import type { CasNode } from "@uncaged/json-cas";
 import {
+  BOOTSTRAP_STORE,
   bootstrap,
   computeHash,
   computeSelfHash,
@@ -65,7 +67,7 @@ describe("createFsStore – init and bootstrap", () => {
     const h2 = await bootstrap(store);
 
     expect(h1).toEqual(h2);
-    expect(store.listByType(h1["@schema"] ?? "")).toHaveLength(24);
+    expect(store.listByType(h1["@schema"] ?? "")).toHaveLength(26);
   });
 });
 
@@ -429,3 +431,130 @@ describe("openStore – async with auto-bootstrap", () => {
     expect(store2.listByType(typeHash)).toHaveLength(1);
   });
 });
+
+// ──────────────────────────────────────────────────────────────────────────────
+// listMeta and listSchemas (FS persistence)
+// ──────────────────────────────────────────────────────────────────────────────
+describe("createFsStore – listMeta and listSchemas", () => {
+  let dir: string;
+  beforeEach(() => {
+    dir = mkdtempSync(join(tmpdir(), "json-cas-fs-meta-"));
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  test("C1. _index/_meta exists and contains hash after self-referencing put", async () => {
+    const store = createFsStore(dir);
+    const hash = await store[BOOTSTRAP_STORE]({ type: "object" });
+
+    const metaPath = join(dir, "_index", "_meta");
+    expect(existsSync(metaPath)).toBe(true);
+    const content = readFileSync(metaPath, "utf8");
+    expect(content).toBe(`${hash}\n`);
+  });
+
+  test("C2. multiple meta puts append, no duplicates", async () => {
+    const store = createFsStore(dir);
+    const h1 = await store[BOOTSTRAP_STORE]({ type: "object", v: 1 });
+    const h2 = await store[BOOTSTRAP_STORE]({ type: "object", v: 2 });
+    // re-put first (idempotent)
+    await store[BOOTSTRAP_STORE]({ type: "object", v: 1 });
+
+    const content = readFileSync(join(dir, "_index", "_meta"), "utf8");
+    const lines = content.split("\n").filter((l) => l.length > 0);
+    expect(lines).toHaveLength(2);
+    expect(lines).toContain(h1);
+    expect(lines).toContain(h2);
+  });
+
+  test("C3. reload from disk preserves listMeta", async () => {
+    const store1 = createFsStore(dir);
+    const h1 = await store1[BOOTSTRAP_STORE]({ type: "object", v: "a" });
+    const h2 = await store1[BOOTSTRAP_STORE]({ type: "object", v: "b" });
+
+    const store2 = createFsStore(dir);
+    const meta = store2.listMeta();
+    expect(meta).toContain(h1);
+    expect(meta).toContain(h2);
+    expect(meta).toHaveLength(2);
+  });
+
+  test("C4. migrates from existing nodes when _meta is missing", async () => {
+    const store1 = createFsStore(dir);
+    const h1 = await store1[BOOTSTRAP_STORE]({ type: "object", v: "mig" });
+    const t = await computeSelfHash({ name: "regular" });
+    await store1.put(h1, { type: "string" });
+
+    // Remove _index/_meta but keep _index/* and .bin files
+    const metaPath = join(dir, "_index", "_meta");
+    rmSync(metaPath, { force: true });
+    expect(existsSync(metaPath)).toBe(false);
+
+    const store2 = createFsStore(dir);
+    expect(store2.listMeta()).toContain(h1);
+    expect(existsSync(metaPath)).toBe(true);
+    const content = readFileSync(metaPath, "utf8");
+    expect(content).toContain(h1);
+
+    // unrelated type hash not in meta
+    expect(store2.listMeta()).not.toContain(t);
+  });
+
+  test("C5. existing _meta is not overwritten", async () => {
+    const store1 = createFsStore(dir);
+    const h1 = await store1[BOOTSTRAP_STORE]({ type: "object", v: "keep" });
+
+    const metaPath = join(dir, "_index", "_meta");
+    const before = readFileSync(metaPath, "utf8");
+
+    // Reopen and confirm content unchanged
+    const _store2 = createFsStore(dir);
+    const after = readFileSync(metaPath, "utf8");
+    expect(after).toBe(before);
+    expect(after).toContain(h1);
+  });
+
+  test("C6. listSchemas returns union of typeIndex[m] for m in metaSet", async () => {
+    const store = createFsStore(dir);
+    const m = await store[BOOTSTRAP_STORE]({ type: "object" });
+    const s1 = await store.put(m, { type: "string" });
+    const s2 = await store.put(m, { type: "number" });
+    const s3 = await store.put(m, { type: "array" });
+
+    const schemas = store.listSchemas();
+    expect(schemas).toHaveLength(4);
+    expect(schemas).toContain(m);
+    expect(schemas).toContain(s1);
+    expect(schemas).toContain(s2);
+    expect(schemas).toContain(s3);
+  });
+
+  test("C7. delete persists removal from _meta", async () => {
+    const store1 = createFsStore(dir);
+    const h1 = await store1[BOOTSTRAP_STORE]({ type: "object", v: 1 });
+    const h2 = await store1[BOOTSTRAP_STORE]({ type: "object", v: 2 });
+
+    store1.delete(h1);
+
+    const metaPath = join(dir, "_index", "_meta");
+    const content = readFileSync(metaPath, "utf8");
+    expect(content).not.toContain(h1);
+    expect(content).toContain(h2);
+
+    const store2 = createFsStore(dir);
+    expect(store2.listMeta()).not.toContain(h1);
+    expect(store2.listMeta()).toContain(h2);
+  });
+
+  test("C8. fresh store with no self-ref puts has empty listMeta", () => {
+    const store = createFsStore(dir);
+    expect(store.listMeta()).toEqual([]);
+    // _meta may be absent; that's fine
+    const metaPath = join(dir, "_index", "_meta");
+    if (existsSync(metaPath)) {
+      const content = readFileSync(metaPath, "utf8");
+      expect(content).toBe("");
+    }
+  });
+});

packages/json-cas-fs/src/store.ts

@@ -22,6 +22,7 @@ import {
 import { decode } from "cborg";
 
 const INDEX_DIR = "_index";
+const META_FILE = "_meta";
 
 function loadDir(dir: string, data: Map<Hash, CasNode>): void {
   let entries: string[];
@@ -100,6 +101,61 @@ function loadOrMigrateTypeIndex(
   return loadTypeIndex(indexDir);
 }
 
+function loadOrMigrateMetaSet(
+  dir: string,
+  data: Map<Hash, CasNode>,
+): Set<Hash> {
+  const indexDir = join(dir, INDEX_DIR);
+  const metaPath = join(indexDir, META_FILE);
+  if (existsSync(metaPath)) {
+    try {
+      const content = readFileSync(metaPath, "utf8");
+      return new Set(parseIndexFile(content));
+    } catch {
+      return new Set();
+    }
+  }
+  // Migration: scan loaded nodes for self-referencing nodes (type === hash)
+  const metaSet = new Set<Hash>();
+  for (const [hash, node] of data) {
+    if (node.type === hash) {
+      metaSet.add(hash);
+    }
+  }
+  if (metaSet.size > 0) {
+    mkdirSync(indexDir, { recursive: true });
+    const body = `${[...metaSet].join("\n")}\n`;
+    writeFileSync(metaPath, body, "utf8");
+  }
+  return metaSet;
+}
+
+function appendToMetaSet(
+  indexDir: string,
+  metaSet: Set<Hash>,
+  hash: Hash,
+): void {
+  if (metaSet.has(hash)) return;
+  metaSet.add(hash);
+  mkdirSync(indexDir, { recursive: true });
+  appendFileSync(join(indexDir, META_FILE), `${hash}\n`, "utf8");
+}
+
+function rewriteMetaSet(indexDir: string, metaSet: Set<Hash>): void {
+  const metaPath = join(indexDir, META_FILE);
+  if (metaSet.size === 0) {
+    try {
+      unlinkSync(metaPath);
+    } catch {
+      // ignore
+    }
+    return;
+  }
+  mkdirSync(indexDir, { recursive: true });
+  const body = `${[...metaSet].join("\n")}\n`;
+  writeFileSync(metaPath, body, "utf8");
+}
+
 function appendToTypeIndex(
   indexDir: string,
   typeIndex: Map<Hash, Hash[]>,
@@ -118,6 +174,7 @@ export function createFsStore(dir: string): BootstrapCapableStore {
   loadDir(dir, data);
   const indexDir = join(dir, INDEX_DIR);
   const typeIndex = loadOrMigrateTypeIndex(dir, data);
+  const metaSet = loadOrMigrateMetaSet(dir, data);
 
   async function putSelfReferencing(payload: unknown): Promise<Hash> {
     const hash = await computeSelfHash(payload);
@@ -136,6 +193,7 @@ export function createFsStore(dir: string): BootstrapCapableStore {
 
       appendToTypeIndex(indexDir, typeIndex, hash, hash);
     }
+    appendToMetaSet(indexDir, metaSet, hash);
     return hash;
   }
 
@@ -182,6 +240,22 @@ export function createFsStore(dir: string): BootstrapCapableStore {
       return Array.from(data.keys());
     },
 
+    listMeta(): Hash[] {
+      return Array.from(metaSet);
+    },
+
+    listSchemas(): Hash[] {
+      const result = new Set<Hash>();
+      for (const meta of metaSet) {
+        result.add(meta);
+        const list = typeIndex.get(meta);
+        if (list) {
+          for (const h of list) result.add(h);
+        }
+      }
+      return Array.from(result);
+    },
+
     delete(hash: Hash): void {
       const node = data.get(hash);
       if (node) {
@@ -213,6 +287,11 @@ export function createFsStore(dir: string): BootstrapCapableStore {
             writeFileSync(join(indexDir, node.type), body, "utf8");
           }
         }
+        // Remove from meta set if applicable
+        if (metaSet.has(hash)) {
+          metaSet.delete(hash);
+          rewriteMetaSet(indexDir, metaSet);
+        }
       }
     },
 

packages/json-cas/src/bootstrap.test.ts

@@ -13,6 +13,8 @@ const OUTPUT_ALIASES = [
   "@output/refs",
   "@output/walk",
   "@output/list",
+  "@output/list-meta",
+  "@output/list-schema",
   "@output/var-set",
   "@output/var-get",
   "@output/var-delete",
@@ -30,11 +32,11 @@ const OUTPUT_ALIASES = [
 // ──────────────────────────────────────────────────────────────────────────────
 
 describe("bootstrap - Built-in Schemas", () => {
-  test("should return map of 24 built-in schema aliases to hashes", async () => {
+  test("should return map of 26 built-in schema aliases to hashes", async () => {
     const store = createMemoryStore();
     const builtinSchemas = await bootstrap(store);
 
-    // Should return object with 6 primitive + 18 output aliases = 24
+    // Should return object with 6 primitive + 20 output aliases = 26
     expect(builtinSchemas).toHaveProperty("@schema");
     expect(builtinSchemas).toHaveProperty("@string");
     expect(builtinSchemas).toHaveProperty("@number");
@@ -46,7 +48,7 @@ describe("bootstrap - Built-in Schemas", () => {
       expect(builtinSchemas).toHaveProperty(alias);
     }
 
-    expect(Object.keys(builtinSchemas)).toHaveLength(24);
+    expect(Object.keys(builtinSchemas)).toHaveLength(26);
 
     // All values should be valid hashes
     for (const [_alias, hash] of Object.entries(builtinSchemas)) {
@@ -316,3 +318,23 @@ describe("bootstrap - @output/* Schemas", () => {
     expect(uniqueHashes.size).toBe(OUTPUT_ALIASES.length);
   });
 });
+
+describe("bootstrap - meta and schemas indexes (D1)", () => {
+  test("listMeta contains the bootstrap meta-schema hash", async () => {
+    const store = createMemoryStore();
+    const aliases = await bootstrap(store);
+    const metaHash = aliases["@schema"];
+    expect(store.listMeta()).toContain(metaHash as string);
+  });
+
+  test("listSchemas contains meta-schema and all built-in schemas", async () => {
+    const store = createMemoryStore();
+    const aliases = await bootstrap(store);
+    const schemas = store.listSchemas();
+
+    for (const [, hash] of Object.entries(aliases)) {
+      expect(schemas).toContain(hash);
+    }
+    expect(schemas.length).toBeGreaterThanOrEqual(6);
+  });
+});

packages/json-cas/src/bootstrap.ts

@@ -172,6 +172,22 @@ const OUTPUT_SCHEMAS: ReadonlyArray<
       title: "ucas list result",
     },
   ],
+  [
+    "@output/list-meta",
+    {
+      type: "array",
+      items: { type: "string", format: "cas_ref" },
+      title: "ucas list-meta result",
+    },
+  ],
+  [
+    "@output/list-schema",
+    {
+      type: "array",
+      items: { type: "string", format: "cas_ref" },
+      title: "ucas list-schema result",
+    },
+  ],
   [
     "@output/var-set",
     {

packages/json-cas/src/index.test.ts

@@ -264,7 +264,7 @@ describe("bootstrap", () => {
     );
   });
 
-  test("returns a map with 24 built-in schema aliases", async () => {
+  test("returns a map with 26 built-in schema aliases", async () => {
     const store = createMemoryStore();
     const builtinSchemas = await bootstrap(store);
 
@@ -281,7 +281,7 @@ describe("bootstrap", () => {
       expect(hash).toMatch(/^[0-9A-HJKMNP-TV-Z]{13}$/);
     }
 
-    expect(Object.keys(builtinSchemas)).toHaveLength(24);
+    expect(Object.keys(builtinSchemas)).toHaveLength(26);
   });
 
   test("meta-schema node is stored and retrievable", async () => {
@@ -318,7 +318,7 @@ describe("bootstrap", () => {
     const h2 = await bootstrap(store);
 
     expect(h1).toEqual(h2);
-    // All 24 built-in schemas should be typed by the meta-schema
+    // All 26 built-in schemas should be typed by the meta-schema
-    expect(store.listByType(h1["@schema"] ?? "")).toHaveLength(24);
+    expect(store.listByType(h1["@schema"] ?? "")).toHaveLength(26);
   });
 });

packages/json-cas/src/mem-store.ts

@@ -31,6 +31,14 @@ export class MemStore implements BootstrapCapableStore {
     return this.#inner.listAll();
   }
 
+  listMeta(): Hash[] {
+    return this.#inner.listMeta();
+  }
+
+  listSchemas(): Hash[] {
+    return this.#inner.listSchemas();
+  }
+
   delete(hash: Hash): void {
     this.#inner.delete(hash);
   }

packages/json-cas/src/store.test.ts

@@ -0,0 +1,89 @@
+import { describe, expect, test } from "bun:test";
+import { BOOTSTRAP_STORE } from "./bootstrap-capable.js";
+import { createMemoryStore } from "./store.js";
+
+describe("createMemoryStore – meta and schema indexes", () => {
+  test("B1. listMeta and listSchemas are empty on a fresh store", () => {
+    const store = createMemoryStore();
+    expect(store.listMeta()).toEqual([]);
+    expect(store.listSchemas()).toEqual([]);
+  });
+
+  test("B2. self-referencing put adds hash to metaSet and listSchemas", async () => {
+    const store = createMemoryStore();
+    const hash = await store[BOOTSTRAP_STORE]({ type: "object" });
+
+    expect(store.listMeta()).toContain(hash);
+    expect(store.listSchemas()).toContain(hash);
+  });
+
+  test("B3. regular put does not add hash to metaSet", async () => {
+    const store = createMemoryStore();
+    const metaHash = await store[BOOTSTRAP_STORE]({ type: "object" });
+    const schemaHash = await store.put(metaHash, { type: "string" });
+
+    expect(store.listMeta()).not.toContain(schemaHash);
+    expect(store.listMeta()).toContain(metaHash);
+  });
+
+  test("B4. schema typed by meta-schema appears in listSchemas", async () => {
+    const store = createMemoryStore();
+    const m = await store[BOOTSTRAP_STORE]({ type: "object" });
+    const s = await store.put(m, { type: "string" });
+
+    const schemas = store.listSchemas();
+    expect(schemas).toContain(m);
+    expect(schemas).toContain(s);
+
+    const meta = store.listMeta();
+    expect(meta).toContain(m);
+    expect(meta).not.toContain(s);
+  });
+
+  test("B5. multiple meta-schemas (versioning)", async () => {
+    const store = createMemoryStore();
+    const m1 = await store[BOOTSTRAP_STORE]({ type: "object", title: "v1" });
+    const m2 = await store[BOOTSTRAP_STORE]({ type: "object", title: "v2" });
+    const s1 = await store.put(m1, { type: "string" });
+    const s2 = await store.put(m2, { type: "number" });
+
+    const meta = store.listMeta();
+    expect(meta).toContain(m1);
+    expect(meta).toContain(m2);
+    expect(meta).toHaveLength(2);
+
+    const schemas = store.listSchemas();
+    expect(schemas).toContain(m1);
+    expect(schemas).toContain(m2);
+    expect(schemas).toContain(s1);
+    expect(schemas).toContain(s2);
+  });
+
+  test("B6. idempotent self-referencing put does not duplicate", async () => {
+    const store = createMemoryStore();
+    const payload = { type: "object", title: "dup" };
+    const h1 = await store[BOOTSTRAP_STORE](payload);
+    const h2 = await store[BOOTSTRAP_STORE](payload);
+    expect(h1).toBe(h2);
+
+    const meta = store.listMeta();
+    const occurrences = meta.filter((h) => h === h1).length;
+    expect(occurrences).toBe(1);
+  });
+
+  test("B7. delete removes hash from metaSet and listSchemas", async () => {
+    const store = createMemoryStore();
+    const m = await store[BOOTSTRAP_STORE]({ type: "object" });
+    const s = await store.put(m, { type: "string" });
+
+    expect(store.listMeta()).toContain(m);
+    expect(store.listSchemas()).toContain(s);
+
+    store.delete(m);
+
+    expect(store.listMeta()).not.toContain(m);
+    // schemas typed by deleted meta no longer surface
+    expect(store.listSchemas()).not.toContain(s);
+    expect(store.listSchemas()).not.toContain(m);
+  });
+});

packages/json-cas/src/store.ts

@@ -8,6 +8,7 @@ import type { CasNode, Hash } from "./types.js";
 export function createMemoryStore(): BootstrapCapableStore {
   const data = new Map<Hash, CasNode>();
   const byType = new Map<Hash, Set<Hash>>();
+  const metaSet = new Set<Hash>();
 
   function indexHash(type: Hash, hash: Hash): void {
     let set = byType.get(type);
@@ -24,6 +25,7 @@ export function createMemoryStore(): BootstrapCapableStore {
       data.set(hash, { type: hash, payload, timestamp: Date.now() });
       indexHash(hash, hash);
     }
+    metaSet.add(hash);
     return hash;
   }
 
@@ -56,6 +58,22 @@ export function createMemoryStore(): BootstrapCapableStore {
       return Array.from(data.keys());
     },
 
+    listMeta(): Hash[] {
+      return Array.from(metaSet);
+    },
+
+    listSchemas(): Hash[] {
+      const result = new Set<Hash>();
+      for (const meta of metaSet) {
+        result.add(meta);
+        const set = byType.get(meta);
+        if (set) {
+          for (const h of set) result.add(h);
+        }
+      }
+      return Array.from(result);
+    },
+
     delete(hash: Hash): void {
       const node = data.get(hash);
       if (node) {
@@ -68,6 +86,7 @@ export function createMemoryStore(): BootstrapCapableStore {
             byType.delete(node.type);
           }
         }
+        metaSet.delete(hash);
       }
     },
 

packages/json-cas/src/types.ts

@@ -25,5 +25,7 @@ export type Store = {
   has(hash: Hash): boolean;
   listByType(typeHash: Hash): Hash[];
   listAll(): Hash[];
+  listMeta(): Hash[];
+  listSchemas(): Hash[];
   delete(hash: Hash): void;
 };