feat(client): inbox mechanism, write-guard, SPARQL injection hardening

Polyfill capabilities landed for Festipod's T02 features (all generic,
zero-domain — the consumer injects the domain).

- inbox: implement the previously-stubbed namespace. post(target,{from?,
  payload,ts?}) deposits {from,payload,ts} as RDF via docs.sparqlUpdate (the
  real injected ng, never makeNg); read/materialize + watch emulate the curator
  in-lib (deposits read via docs.sparqlQuery). `from` optional = anonymity.
- write-guard: caps.hasWritePolicy() + ng-proxy.sparql_update rejects when the
  target doc is under a write policy and the current user lacks its write cap;
  passthrough otherwise (no regression). Read-cap registry unchanged.
- sparql.ts (new): escapeLiteral / escapeIri / assertNuri, exported from index.
  store-registry now escapes every literal and validates/encodes every IRI-
  position value — closes a SPARQL-injection hole where an untrusted username
  could inject triples into the shim (the account→doc-NURI trust root).

Tests: inbox, sparql (incl. injection), ng-proxy write-guard, isolation-active.
68 tests pass; tsc --noEmit rc=0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/client/src/caps.ts

@@ -83,6 +83,11 @@ export class CapRegistry {
     return this.readers.size > 0 || this.publicDocs.size > 0;
   }
 
+  /** No WRITE policy declared → the write guard stays inert (passthrough). */
+  hasWritePolicy(): boolean {
+    return this.writers.size > 0;
+  }
+
   clear(): void {
     this.readers.clear();
     this.writers.clear();

packages/client/src/inbox.ts

@@ -1,29 +1,194 @@
 /**
- * Inbox — client side (deposit only). The MATERIALIZATION of deposits is the
+ * Inbox — the ONE deposit + materialization mechanism, reused for BOTH meeting-
- * curator's job (a separate package, deferred — see repo README), never the client's.
+ * point registration AND submission to the discovery index (see the discovery-
+ * model decision: same `inbox.post` API, same watcher). GENERIC by construction:
+ * this module knows no application domain (no meeting-point, no notification).
+ * The consumer supplies the inbox document NURI and interprets the `payload`.
+ *
+ * ── TARGET vs POLYFILL ────────────────────────────────────────────────────
+ * Target: `post` seals a reference into the inbox owner's native inbox
+ * (`ng.inbox_post_link(...)`), and a SEPARATE curator process (the deferred
+ * `@ng-eventually/service` package) MATERIALIZES the deposits into the owned
+ * document. Here, in the shared-wallet polyfill (everything is readable),
+ * both sides are emulated in-lib:
+ *   - `post` appends a deposit `{ from, payload, ts }` as RDF into the inbox
+ *     DOCUMENT (in the shared wallet) via the `docs.sparqlUpdate` primitive;
+ *   - `read` / `watch` play the CURATOR: they read the deposits back via
+ *     `docs.sparqlQuery` and expose them. This in-client emulation is enough
+ *     for the polyfill — at migration the real materialization moves to the
+ *     separate curator and this read side goes away.
+ *
+ * All NextGraph I/O routes through the T01.a `docs` primitives (the REAL
+ * injected `ng`, never `makeNg`), so this module imports NO `@ng-org` package.
  */
 
-import { getConfig, getCurrentUser } from "./polyfill";
+import { sparqlUpdate, sparqlQuery } from "./docs";
-import type { Nuri } from "./types";
+import { getCurrentUser, getStoreRegistryDeps } from "./polyfill";
+import { escapeLiteral } from "./sparql";
+import type { Nuri, PrincipalId } from "./types";
 
-/**
+// --- deposit model --------------------------------------------------------
- * Deposit a reference into a document's inbox (anticipated SDK shape). Target:
+
- * `ng.inbox_post_link(...)`, sealed to the inbox owner; `from` optional → the
+/** One deposit as materialized from an inbox document. */
- * sender is identified if known, anonymous otherwise. Polyfill: append a
+export interface Deposit {
- * deposit to the emulated inbox document.
+  /** The sender, if identified; `null` when the deposit was anonymous. */
- */
+  from: PrincipalId | null;
-export async function post(
+  /** The consumer-defined payload (opaque here — JSON-serialized in storage). */
-  targetInbox: Nuri,
+  payload: unknown;
-  payload: unknown,
+  /** Deposit timestamp (ms epoch). Caller may pass one for determinism. */
-  opts?: { anonymous?: boolean },
+  ts: number;
-): Promise<void> {
+}
-  const { ng } = getConfig();
+
-  const from = opts?.anonymous ? null : getCurrentUser();
+/** Options for {@link post}. `from` and `ts` are both optional. */
-  // TODO(polyfill): append { from, payload } to the emulated inbox document
+export interface PostOptions {
-  // (targetInbox) via ng.sparql_update.
+  /**
-  void ng;
+   * Who is depositing. Omit (or pass `null`) for an ANONYMOUS deposit; pass a
-  void from;
+   * principal id to identify the sender. Defaults to the current polyfill user
-  void targetInbox;
+   * ({@link getCurrentUser}) when the property is entirely absent, so callers
-  void payload;
+   * that want anonymity must pass `from: null` explicitly.
-  throw new Error("[ng-eventually] inbox.post: polyfill emulation not yet implemented");
+   */
+  from?: PrincipalId | null;
+  /** The payload to deposit (interpreted only by the consumer). */
+  payload: unknown;
+  /** Optional deposit timestamp (ms epoch). Omitted → `Date.now()`. Passing it
+   *  keeps tests deterministic. */
+  ts?: number;
+}
+
+const SHIM = "urn:ng-eventually:inbox";
+const P = {
+  type: `${SHIM}:Deposit`,
+  from: `${SHIM}:from`,
+  payload: `${SHIM}:payload`,
+  ts: `${SHIM}:ts`,
+} as const;
+
+// --- session access (shared with the storeRegistry) -----------------------
+
+/** The inbox documents live in the shared wallet, so we reuse the registry's
+ *  injected session provider for the sessionId. Disappears at migration. */
+async function sessionId(): Promise<string> {
+  return (await getStoreRegistryDeps().getSession()).sessionId;
+}
+
+// --- SPARQL result helpers ------------------------------------------------
+
+/** Tolerant extraction of SPARQL SELECT bindings across possible shapes. */
+function readBindings(result: unknown): Array<Record<string, { value: string }>> {
+  if (!result) return [];
+  if (Array.isArray(result)) return result as Array<Record<string, { value: string }>>;
+  const anyRes = result as {
+    results?: { bindings?: Array<Record<string, { value: string }>> };
+  };
+  return anyRes.results?.bindings ?? [];
+}
+
+// --- deposit (client side) ------------------------------------------------
+
+/**
+ * Deposit a payload into `targetInbox`.
+ *
+ * Appends `{ from, payload, ts }` into the inbox document via `docs.sparqlUpdate`
+ * (the real injected `ng`). Each deposit is a fresh RDF subject in the inbox
+ * graph, so concurrent deposits don't collide. `from` is optional: pass `null`
+ * for an anonymous deposit; omit it entirely to default to the current user.
+ */
+export async function post(targetInbox: Nuri, opts: PostOptions): Promise<void> {
+  const from = opts.from === undefined ? getCurrentUser() : opts.from;
+  const ts = opts.ts ?? Date.now();
+  const sid = await sessionId();
+
+  // A unique subject per deposit (in the inbox graph) — no collisions.
+  const subject = `${SHIM}:deposit:${ts}:${Math.random().toString(36).slice(2)}`;
+  const payloadLiteral = escapeLiteral(JSON.stringify(opts.payload ?? null));
+  const fromTriple =
+    from == null ? "" : ` ;\n        <${P.from}> "${escapeLiteral(from)}"`;
+
+  const update = `
+    INSERT DATA {
+      GRAPH <${targetInbox}> {
+        <${subject}> a <${P.type}> ;
+        <${P.payload}> "${payloadLiteral}" ;
+        <${P.ts}> "${ts}"${fromTriple} .
+      }
+    }`;
+  await sparqlUpdate(sid, update, targetInbox);
+}
+
+// --- read / materialize (emulated curator) --------------------------------
+
+/**
+ * Read (materialize) every deposit currently in `targetInbox`, sorted by `ts`
+ * ascending. This is the EMULATED CURATOR: at migration a separate curator
+ * process materializes deposits and this in-client read goes away. The consumer
+ * interprets each deposit's `payload`.
+ */
+export async function read(targetInbox: Nuri): Promise<Deposit[]> {
+  const sid = await sessionId();
+  const query = `
+    SELECT ?payload ?ts ?from WHERE {
+      GRAPH <${targetInbox}> {
+        ?d a <${P.type}> ;
+           <${P.payload}> ?payload ;
+           <${P.ts}> ?ts .
+        OPTIONAL { ?d <${P.from}> ?from }
+      }
+    }`;
+  const result = await sparqlQuery(sid, query, undefined, targetInbox);
+  const deposits: Deposit[] = [];
+  for (const row of readBindings(result)) {
+    const rawPayload = row.payload?.value ?? "null";
+    let payload: unknown;
+    try {
+      payload = JSON.parse(rawPayload);
+    } catch {
+      payload = rawPayload; // tolerate a non-JSON literal
+    }
+    const tsRaw = row.ts?.value ?? "0";
+    const ts = Number.parseInt(tsRaw, 10) || 0;
+    const fromValue = row.from?.value;
+    deposits.push({ from: fromValue ? fromValue : null, payload, ts });
+  }
+  deposits.sort((a, b) => a.ts - b.ts);
+  return deposits;
+}
+
+/** Alias for {@link read} — the name that reads as "run the curator now". */
+export const materialize = read;
+
+/**
+ * Subscription over an inbox — the emulated watcher. Polls {@link read} on an
+ * interval and invokes `onDeposits` with the full current deposit list whenever
+ * it changes (grows). Returns an unsubscribe function. The polyfill has no
+ * native reactive inbox subscription, so this emulates one; at migration it is
+ * replaced by the real curator's watch. `onDeposits` fires once immediately.
+ */
+export function watch(
+  targetInbox: Nuri,
+  onDeposits: (deposits: Deposit[]) => void,
+  opts?: { intervalMs?: number },
+): () => void {
+  let stopped = false;
+  let lastCount = -1;
+  const intervalMs = opts?.intervalMs ?? 1000;
+
+  const tick = async (): Promise<void> => {
+    if (stopped) return;
+    try {
+      const deposits = await read(targetInbox);
+      if (!stopped && deposits.length !== lastCount) {
+        lastCount = deposits.length;
+        onDeposits(deposits);
+      }
+    } catch (error) {
+      console.error("[inbox] watch read failed:", error);
+    }
+  };
+
+  void tick(); // fire once immediately
+  const handle = setInterval(() => void tick(), intervalMs);
+  return () => {
+    stopped = true;
+    clearInterval(handle);
+  };
 }

packages/client/src/index.ts

@@ -23,6 +23,12 @@ export type { Connections, IsolationAccessors } from "./isolation";
 export * as accounts from "./accounts";
 export type { AccountStorage } from "./accounts";
 
+// SPARQL injection-safety helpers — so the app can reuse the same escaping /
+// validation when it builds SPARQL by interpolation. `escapeLiteral` for string
+// literals, `escapeIri` to embed untrusted values in an IRI, `assertNuri` to
+// validate trusted-shaped NURIs before embedding them in an IRI.
+export { escapeLiteral, escapeIri, assertNuri } from "./sparql";
+
 // SDK type re-exports — so the app imports these from @ng-eventually/client too,
 // not from @ng-org. `export type` is ERASED at build, so this adds NO runtime
 // @ng-org import to the lib (no risk of a duplicate SDK copy in the bundle).

packages/client/src/ng-proxy.ts

@@ -4,7 +4,8 @@
  * surface stays identical to `@ng-org/web`'s `ng`.
  */
 
-import { getConfig } from "./polyfill";
+import { getConfig, getCaps, getCurrentUser } from "./polyfill";
+import type { Nuri } from "./types";
 
 export function makeNg(): Record<string, any> {
   return new Proxy({} as Record<string, any>, {
@@ -21,10 +22,28 @@ export function makeNg(): Record<string, any> {
       }
 
       // sparql_update → write guard (emulated write-cap check).
+      // Mirrors the target broker/verifier: a write is refused unless the wallet
+      // holds the document's WRITE cap. Emulated per-document via CapRegistry.
+      // args = (session_id, query, anchor?) — `anchor` is the target doc NURI.
       if (prop === "sparql_update") {
         return (...args: any[]) => {
-          // TODO(polyfill): reject when getCurrentUser() lacks the write grant
+          const anchor = args[2] as Nuri | undefined;
-          // on the target document (see access.canWrite). For now, passthrough.
+          const caps = getCaps();
+          // Passthrough (no regression) unless a WRITE policy exists AND this
+          // specific document is governed by it. Ungoverned docs (mono-store
+          // default, no cap declared) flow through exactly as before.
+          if (
+            typeof anchor === "string" &&
+            caps.hasWritePolicy() &&
+            caps.governsWrite(anchor) &&
+            !caps.canWrite(anchor, getCurrentUser())
+          ) {
+            return Promise.reject(
+              new Error(
+                `[ng-eventually] write denied: current user lacks the write cap for ${anchor}`,
+              ),
+            );
+          }
           return ng.sparql_update!(...args);
         };
       }

packages/client/src/sparql.ts

@@ -0,0 +1,102 @@
+/**
+ * SPARQL string-building safety helpers — shared by every module that builds
+ * SPARQL by interpolation (inbox, store-registry).
+ *
+ * WHY THIS EXISTS: SPARQL injection. When an untrusted value (a username, a
+ * payload) is spliced verbatim into a query, a `"` closes a literal and a `>`
+ * closes an IRI, letting the value inject arbitrary triples (or wreck the shim
+ * graph, which is the trust root mapping accounts → document NURIs). Every
+ * value that reaches a query MUST pass through one of these helpers first.
+ *
+ * TWO POSITIONS, TWO STRATEGIES:
+ *  - LITERAL position (`"..."`): {@link escapeLiteral}. We *escape* rather than
+ *    reject because literals legitimately carry arbitrary text (JSON payloads,
+ *    display names). Escaping is lossless and reversible.
+ *  - IRI position (`<...>`): two cases.
+ *      · Trusted-SHAPED NURIs coming back from `ng` (`did:ng:...`): validate
+ *        with {@link assertNuri} — they should never contain IRI-breaking
+ *        chars; if one does, something upstream is wrong, so we throw rather
+ *        than silently build a broken/injected query.
+ *      · UNTRUSTED values embedded into an IRI (a username used to mint an
+ *        account-subject IRI): {@link escapeIri} percent-encodes every
+ *        IRI-hostile character. We *encode* rather than reject so any username
+ *        (spaces, unicode, punctuation) stays usable, while `<`, `>`, `"`,
+ *        whitespace and control chars can never break out of the IRI.
+ */
+
+/**
+ * Escape a value for embedding inside a SPARQL string literal (`"..."`).
+ * Escapes backslash, double-quote and the C0 whitespace controls that would
+ * otherwise terminate or corrupt the literal. Lossless / reversible.
+ */
+export function escapeLiteral(value: string): string {
+  return value
+    .replace(/\\/g, "\\\\")
+    .replace(/"/g, '\\"')
+    .replace(/\n/g, "\\n")
+    .replace(/\r/g, "\\r")
+    .replace(/\t/g, "\\t");
+}
+
+/**
+ * Delimiter characters that must never appear raw inside a SPARQL/Turtle IRI
+ * ref (`<...>`): the space plus `< > " { } | ^ backtick \`. Whitespace beyond
+ * the space and all C0/C1 control characters are handled by the code-point
+ * check in {@link isIriForbidden}. Any of these would let a value break out of
+ * the `<...>` and inject arbitrary syntax.
+ */
+const IRI_FORBIDDEN_DELIMS = /[<>"{}|^`\\ ]/;
+
+/** True if `ch` (a single code point) may not appear raw inside an IRI ref. */
+function isIriForbidden(ch: string): boolean {
+  const code = ch.codePointAt(0)!;
+  return IRI_FORBIDDEN_DELIMS.test(ch) || code < 0x20 || code === 0x7f;
+}
+
+/**
+ * Percent-encode every IRI-hostile character in `value` so it is safe to embed
+ * inside a SPARQL IRI ref (`<PREFIX:${escapeIri(value)}>`). Use this for
+ * UNTRUSTED values (e.g. a username minted into an account-subject IRI):
+ * encoding keeps every username usable while making breakout impossible.
+ *
+ * NOTE: this encodes only the delimiter/whitespace/control set, so ordinary
+ * printable characters (including `:` `/` `.` `-` `_` and unicode letters) pass
+ * through unchanged and the resulting IRI stays human-readable.
+ */
+export function escapeIri(value: string): string {
+  let out = "";
+  for (const ch of value) {
+    if (isIriForbidden(ch)) {
+      // Percent-encode each UTF-8 byte of the offending character. Also encode
+      // the chars encodeURIComponent leaves alone but which are IRI-hostile.
+      out += encodeURIComponent(ch).replace(
+        /[!'()*]/g,
+        (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
+      );
+    } else {
+      out += ch;
+    }
+  }
+  return out;
+}
+
+/**
+ * Assert that `nuri` is safe to embed verbatim inside a SPARQL IRI ref. NURIs
+ * that come back from `ng` are trusted-SHAPED (`did:ng:...` or `urn:...`) and
+ * should never carry IRI-breaking characters; if one does, we throw rather than
+ * emit a query that could be malformed or injected. Returns the value unchanged
+ * so it can be used inline: `<${assertNuri(doc)}>`.
+ */
+export function assertNuri(nuri: string): string {
+  if (typeof nuri !== "string" || nuri.length === 0) {
+    throw new Error(`[sparql] invalid NURI (empty): ${JSON.stringify(nuri)}`);
+  }
+  for (const ch of nuri) {
+    if (isIriForbidden(ch)) {
+      throw new Error(
+        `[sparql] NURI contains IRI-forbidden characters, refusing to embed: ${JSON.stringify(nuri)}`,
+      );
+    }
+  }
+  return nuri;
+}

packages/client/src/store-registry.ts

@@ -34,6 +34,7 @@
 
 import { docCreate, sparqlUpdate, sparqlQuery } from "./docs";
 import { getStoreRegistryDeps } from "./polyfill";
+import { escapeLiteral, escapeIri, assertNuri } from "./sparql";
 import type { Nuri, Scope } from "./types";
 
 // --- sharedWalletShim model ----------------------------------------------
@@ -61,7 +62,11 @@ const P = {
 const INDEX_SUBJECT = `${SHIM}:index`;
 
 function accountSubject(username: string): string {
-  return `${SHIM}:account:${normalize(username)}`;
+  // The username is UNTRUSTED and lands in an IRI position. Percent-encode it
+  // (escapeIri) so no `>` / `"` / whitespace / control char can break out of
+  // the `<...>` and inject triples into the shim graph (the account→doc trust
+  // root). normalize() runs first so the subject stays stable per shim key.
+  return `${SHIM}:account:${escapeIri(normalize(username))}`;
 }
 
 // --- session / normalization access (injected by the consumer) ------------
@@ -123,7 +128,7 @@ export async function loadShim(): Promise<Map<string, AccountRecord>> {
   const anchor = await anchorNuri();
   const query = `
     SELECT ?username ?docPublic ?docProtected ?docPrivate WHERE {
-      GRAPH <${anchor}> {
+      GRAPH <${assertNuri(anchor)}> {
         ?acc a <${P.type}> ;
              <${P.username}> ?username ;
              <${P.docPublic}> ?docPublic ;
@@ -184,14 +189,18 @@ export async function ensureAccount(username: string): Promise<AccountRecord> {
   const s = await session();
   const anchor = await anchorNuri();
   const subj = accountSubject(username);
+  // `subj` is already IRI-safe (accountSubject → escapeIri). `anchor` is a
+  // trusted-shaped NURI → assertNuri. `username` is UNTRUSTED text in a LITERAL
+  // position → escapeLiteral. The doc NURIs come from `ng` but are stored as
+  // literals here, so they are escaped as literals too (defence in depth).
   const update = `
     INSERT DATA {
-      GRAPH <${anchor}> {
+      GRAPH <${assertNuri(anchor)}> {
         <${subj}> a <${P.type}> ;
-          <${P.username}> "${username}" ;
+          <${P.username}> "${escapeLiteral(username)}" ;
-          <${P.docPublic}> "${docPublic}" ;
+          <${P.docPublic}> "${escapeLiteral(docPublic)}" ;
-          <${P.docProtected}> "${docProtected}" ;
+          <${P.docProtected}> "${escapeLiteral(docProtected)}" ;
-          <${P.docPrivate}> "${docPrivate}" .
+          <${P.docPrivate}> "${escapeLiteral(docPrivate)}" .
       }
     }`;
   try {
@@ -246,7 +255,9 @@ export async function createEntityDoc(username: string, scope: Scope): Promise<N
   try {
     await sparqlUpdate(
       s.sessionId,
-      `INSERT DATA { GRAPH <${indexDoc}> { <${INDEX_SUBJECT}> <${P.contains}> "${entityNuri}" } }`,
+      // indexDoc is a NURI in IRI position → assertNuri; entityNuri is a NURI
+      // stored as a literal → escapeLiteral.
+      `INSERT DATA { GRAPH <${assertNuri(indexDoc)}> { <${INDEX_SUBJECT}> <${P.contains}> "${escapeLiteral(entityNuri)}" } }`,
       indexDoc,
     );
   } catch (error) {
@@ -269,7 +280,7 @@ export async function listEntityDocs(scope: Scope): Promise<Nuri[]> {
     try {
       const res = await sparqlQuery(
         s.sessionId,
-        `SELECT ?e WHERE { GRAPH <${indexDoc}> { <${INDEX_SUBJECT}> <${P.contains}> ?e } }`,
+        `SELECT ?e WHERE { GRAPH <${assertNuri(indexDoc)}> { <${INDEX_SUBJECT}> <${P.contains}> ?e } }`,
         undefined,
         indexDoc,
       );

packages/client/test/caps.test.ts

@@ -48,3 +48,17 @@ test("governsRead / hasReadPolicy distinguish governed from ungoverned documents
   expect(caps.governsRead("did:ng:o:doc1")).toBe(true);
   expect(caps.governsRead("did:ng:o:unknown")).toBe(false); // not declared → not enforced
 });
+
+test("governsWrite / hasWritePolicy distinguish governed from ungoverned documents", () => {
+  const caps = new CapRegistry();
+  expect(caps.hasWritePolicy()).toBe(false);
+  caps.open("did:ng:o:doc1", "private", "alice"); // owner gets the write cap
+  expect(caps.hasWritePolicy()).toBe(true);
+  expect(caps.governsWrite("did:ng:o:doc1")).toBe(true);
+  expect(caps.governsWrite("did:ng:o:unknown")).toBe(false); // not declared → not enforced
+  // A public doc grants read to all but its write cap is still owner-only.
+  const pub = new CapRegistry();
+  pub.open("did:ng:o:pub", "public", "alice");
+  expect(pub.hasWritePolicy()).toBe(true);
+  expect(pub.governsWrite("did:ng:o:pub")).toBe(true);
+});

packages/client/test/inbox.test.ts

@@ -0,0 +1,206 @@
+import { test, expect, mock, beforeEach, afterAll } from "bun:test";
+import { post, read, materialize, watch } from "../src/inbox";
+import type { Deposit } from "../src/inbox";
+import {
+  configure,
+  configureStoreRegistry,
+  resetStoreRegistry,
+  resetConfig,
+  setCurrentUser,
+} from "../src/polyfill";
+import type { RegistrySession } from "../src/store-registry";
+
+// This suite injects a fake `ng` via configure() and reuses the storeRegistry's
+// injected session provider (inbox docs live in the shared wallet). Restore the
+// un-configured state at the end so docs.test.ts's guard still sees null config.
+afterAll(() => {
+  resetConfig();
+  resetStoreRegistry();
+  setCurrentUser(null);
+});
+
+// NOTE ORDER: the "not configured → throw" case runs first — it exercises the
+// registry-deps guard before any configureStoreRegistry() call.
+
+test("throws a clear error when configureStoreRegistry() was not called", async () => {
+  resetStoreRegistry();
+  await expect(post("did:ng:o:inbox", { payload: { hi: 1 } })).rejects.toThrow(
+    /configureStoreRegistry\(\) must be called before use/,
+  );
+  await expect(read("did:ng:o:inbox")).rejects.toThrow(
+    /configureStoreRegistry\(\) must be called before use/,
+  );
+});
+
+// --- A stateful fake `ng`: parses the inbox INSERT DATA and answers the read
+// SELECT over an in-memory quad store.
+
+interface Quad { g: string; s: string; p: string; o: string }
+
+const INBOX = "urn:ng-eventually:inbox";
+
+/** Reverse of the lib's escapeLiteral: single left-to-right pass over `\x`. */
+function unescapeLiteral(s: string): string {
+  let out = "";
+  for (let i = 0; i < s.length; i++) {
+    if (s[i] === "\\" && i + 1 < s.length) {
+      const next = s[++i];
+      out +=
+        next === "n" ? "\n" : next === "r" ? "\r" : next === "t" ? "\t" : next;
+    } else {
+      out += s[i];
+    }
+  }
+  return out;
+}
+
+function makeFakeNg() {
+  const quads: Quad[] = [];
+
+  const doc_create = mock(async (..._a: unknown[]) => "did:ng:o:new");
+
+  // Parses one deposit: `<subj> a <Deposit> ; <payload> "..." ; <ts> "..." [; <from> "..."] .`
+  const sparql_update = mock(async (...a: unknown[]) => {
+    const query = a[1] as string;
+    const gm = query.match(/GRAPH <([^>]+)>\s*\{([\s\S]*)\}/);
+    if (!gm) return undefined;
+    const g = gm[1]!;
+    const body = gm[2]!;
+    const sm = body.match(/<([^>]+)>/);
+    if (!sm) return undefined;
+    const s = sm[1]!;
+    const after = body.slice(body.indexOf(sm[0]) + sm[0].length);
+    // predicate/object pairs: `a <type>` or `<p> "literal"`.
+    const pairRe = /(?:a|<([^>]+)>)\s+(?:"((?:[^"\\]|\\.)*)"|<([^>]+)>)/g;
+    let m: RegExpExecArray | null;
+    while ((m = pairRe.exec(after)) !== null) {
+      const p = m[1] ?? `${INBOX}:Deposit`; // `a` → rdf:type-ish
+      // Un-escape the SPARQL literal so payload JSON round-trips. Single pass
+      // over `\x` sequences (reverses the lib's escapeLiteral without the
+      // double-processing that chained .replace() would cause).
+      const rawLit = m[2];
+      const o = rawLit !== undefined ? unescapeLiteral(rawLit) : (m[3] ?? "");
+      quads.push({ g, s, p, o });
+    }
+    return undefined;
+  });
+
+  const sparql_query = mock(async (...a: unknown[]) => {
+    const anchor = a[3] as string | undefined;
+    const bySubject = new Map<string, Record<string, string>>();
+    for (const q of quads) {
+      if (q.g !== anchor) continue;
+      if (q.p === `${INBOX}:Deposit`) {
+        // rdf:type marker — ensure the subject exists.
+        if (!bySubject.has(q.s)) bySubject.set(q.s, {});
+        continue;
+      }
+      const rec = bySubject.get(q.s) ?? {};
+      if (q.p === `${INBOX}:payload`) rec.payload = q.o;
+      if (q.p === `${INBOX}:ts`) rec.ts = q.o;
+      if (q.p === `${INBOX}:from`) rec.from = q.o;
+      bySubject.set(q.s, rec);
+    }
+    const bindings = [...bySubject.values()]
+      .filter((r) => r.payload !== undefined && r.ts !== undefined)
+      .map((r) => {
+        const row: Record<string, { value: string }> = {
+          payload: { value: r.payload! },
+          ts: { value: r.ts! },
+        };
+        if (r.from !== undefined) row.from = { value: r.from };
+        return row;
+      });
+    return { results: { bindings } };
+  });
+
+  return { doc_create, sparql_update, sparql_query, _quads: quads };
+}
+
+const SESSION: RegistrySession = { sessionId: "sid-1", privateStoreId: "PRIV" };
+const TARGET = "did:ng:o:host-inbox";
+
+function inject() {
+  const ng = makeFakeNg();
+  configure({ ng: ng as any, useShape: (() => {}) as any });
+  configureStoreRegistry({ getSession: async () => SESSION });
+  setCurrentUser(null);
+  return ng;
+}
+
+let fake: ReturnType<typeof makeFakeNg>;
+beforeEach(() => {
+  fake = inject();
+});
+
+test("post writes via the real injected ng.sparql_update (not makeNg), scoped to the inbox", async () => {
+  await post(TARGET, { from: "alice", payload: { kind: "join" }, ts: 100 });
+  expect(fake.sparql_update).toHaveBeenCalledTimes(1);
+  const call = fake.sparql_update.mock.calls[0]!;
+  expect(call[0]).toBe("sid-1"); // sessionId from the injected session
+  expect(call[2]).toBe(TARGET); // anchored to the target inbox
+  expect(call[1] as string).toContain(`GRAPH <${TARGET}>`);
+});
+
+test("post → read round-trips payload, from and ts", async () => {
+  await post(TARGET, { from: "alice", payload: { kind: "join", n: 3 }, ts: 100 });
+  const deposits = await read(TARGET);
+  expect(deposits).toHaveLength(1);
+  expect(deposits[0]).toEqual({ from: "alice", payload: { kind: "join", n: 3 }, ts: 100 });
+});
+
+test("from is optional — omitting it defaults to the current user", async () => {
+  setCurrentUser("bob");
+  await post(TARGET, { payload: { hi: 1 }, ts: 200 });
+  const deposits = await read(TARGET);
+  expect(deposits[0]!.from).toBe("bob");
+});
+
+test("from: null makes an anonymous deposit even when a current user is set", async () => {
+  setCurrentUser("bob");
+  await post(TARGET, { from: null, payload: { hi: 1 }, ts: 200 });
+  const deposits = await read(TARGET);
+  expect(deposits[0]!.from).toBeNull();
+});
+
+test("read returns deposits sorted by ts ascending and materialize is an alias", async () => {
+  await post(TARGET, { from: null, payload: "second", ts: 300 });
+  await post(TARGET, { from: null, payload: "first", ts: 100 });
+  await post(TARGET, { from: null, payload: "third", ts: 500 });
+  const deposits = await materialize(TARGET);
+  expect(deposits.map((d) => d.payload)).toEqual(["first", "second", "third"]);
+});
+
+test("read is scoped to one inbox — deposits in another inbox are not returned", async () => {
+  await post(TARGET, { from: null, payload: "mine", ts: 1 });
+  await post("did:ng:o:other-inbox", { from: null, payload: "theirs", ts: 2 });
+  const deposits = await read(TARGET);
+  expect(deposits.map((d) => d.payload)).toEqual(["mine"]);
+});
+
+test("payload with quotes/newlines/backslashes survives the round-trip", async () => {
+  const payload = { text: 'a "quoted"\nline\\path\ttab' };
+  await post(TARGET, { from: null, payload, ts: 1 });
+  const deposits = await read(TARGET);
+  expect(deposits[0]!.payload).toEqual(payload);
+});
+
+test("watch fires immediately then on each new deposit, and unsubscribe stops it", async () => {
+  const seen: Deposit[][] = [];
+  const stop = watch(TARGET, (d) => seen.push(d), { intervalMs: 5 });
+  // Give the immediate tick a chance to run (empty inbox → still fires once).
+  await new Promise((r) => setTimeout(r, 20));
+  expect(seen.length).toBeGreaterThanOrEqual(1);
+  expect(seen[seen.length - 1]).toEqual([]);
+
+  await post(TARGET, { from: null, payload: "x", ts: 1 });
+  await new Promise((r) => setTimeout(r, 20));
+  const last = seen[seen.length - 1]!;
+  expect(last.map((d) => d.payload)).toEqual(["x"]);
+
+  stop();
+  const countAfterStop = seen.length;
+  await post(TARGET, { from: null, payload: "y", ts: 2 });
+  await new Promise((r) => setTimeout(r, 20));
+  expect(seen.length).toBe(countAfterStop); // no more callbacks after unsubscribe
+});

packages/client/test/isolation-active.test.ts

@@ -0,0 +1,81 @@
+/**
+ * ReadCap ACTIVE — end-to-end proof that isolation is enforced by the emulated
+ * cap registry (not merely by the app's social isolation filter).
+ *
+ * This mirrors exactly what the app's storeRegistry wrapper does: create an
+ * entity document through the REAL registry (`createEntityDoc`), then declare
+ * its cap policy via `getCaps().open(doc, scope, owner)`. The read filter then
+ * hides one owner's private document from another principal — the faithful
+ * per-DOCUMENT NextGraph behavior.
+ */
+import { test, expect, mock, afterAll } from "bun:test";
+import { createEntityDoc, resetRegistryCache } from "../src/store-registry";
+import type { RegistrySession } from "../src/store-registry";
+import {
+  configure,
+  configureStoreRegistry,
+  resetStoreRegistry,
+  resetConfig,
+  getCaps,
+  resetCaps,
+} from "../src/polyfill";
+import { filterReadable } from "../src/read-filter";
+
+afterAll(() => {
+  resetConfig();
+  resetStoreRegistry();
+  resetCaps();
+});
+
+const SESSION: RegistrySession = { sessionId: "sid", privateStoreId: "PRIV" };
+
+function inject() {
+  let n = 0;
+  const ng = {
+    doc_create: mock(async () => `did:ng:o:doc${++n}`),
+    sparql_update: mock(async () => undefined),
+    sparql_query: mock(async () => ({ results: { bindings: [] } })),
+  };
+  configure({ ng: ng as any, useShape: (() => {}) as any });
+  configureStoreRegistry({ getSession: async () => SESSION, normalizeUser: (u) => u.trim() });
+  resetRegistryCache();
+  resetCaps();
+  return ng;
+}
+
+test("ReadCap active: a private entity doc created via the real registry is hidden from another principal", async () => {
+  inject();
+
+  // Alice creates a PRIVATE entity document via the REAL store-registry, then
+  // (as the app wrapper does) declares its cap policy: owner-only read.
+  const aliceDoc = await createEntityDoc("alice", "private");
+  getCaps().open(aliceDoc, "private", "alice");
+
+  // Bob creates a PUBLIC entity document (world-readable).
+  const bobDoc = await createEntityDoc("bob", "public");
+  getCaps().open(bobDoc, "public", "bob");
+
+  // The reactive set as the broker would deliver it (mono-store: items carry
+  // their @graph = the document they live in).
+  const items = [
+    { "@graph": aliceDoc, "@id": "a1", label: "alice-private" },
+    { "@graph": bobDoc, "@id": "b1", label: "bob-public" },
+  ];
+
+  // Bob cannot read alice's private doc; he CAN read the public one and, since
+  // the read filter is now under a policy, alice's private item is filtered out.
+  const bobView = filterReadable(items, getCaps(), "bob").map((i) => i["@id"]);
+  expect(bobView).toEqual(["b1"]);
+
+  // Alice reads her own private doc AND the public one.
+  const aliceView = filterReadable(items, getCaps(), "alice").map((i) => i["@id"]);
+  expect(aliceView.sort()).toEqual(["a1", "b1"]);
+
+  // Anonymous sees only the public doc.
+  const anonView = filterReadable(items, getCaps(), null).map((i) => i["@id"]);
+  expect(anonView).toEqual(["b1"]);
+
+  // Sanity: this is the REGISTRY talking, not app-level isolation — the caps
+  // registry has an active read policy.
+  expect(getCaps().hasReadPolicy()).toBe(true);
+});

packages/client/test/ng-proxy.test.ts

@@ -0,0 +1,88 @@
+import { test, expect, mock, afterEach } from "bun:test";
+import { makeNg } from "../src/ng-proxy";
+import {
+  configure,
+  resetConfig,
+  getCaps,
+  resetCaps,
+  setCurrentUser,
+} from "../src/polyfill";
+
+// This suite injects a fake `ng` via configure() and declares write caps. Reset
+// both after each test so the docs.test.ts "not configured" guard still holds
+// and no cap policy leaks into another suite.
+afterEach(() => {
+  resetConfig();
+  resetCaps();
+  setCurrentUser(null);
+});
+
+function fakeNg() {
+  return { sparql_update: mock(async (..._a: unknown[]) => undefined) };
+}
+
+function inject() {
+  const ng = fakeNg();
+  configure({ ng: ng as any, useShape: (() => {}) as any });
+  return ng;
+}
+
+const DOC = "did:ng:o:doc";
+const UPDATE = `INSERT DATA { GRAPH <${DOC}> { <s> <p> <o> } }`;
+
+test("write guard: passthrough when NO write policy is declared (no regression)", async () => {
+  const ng = inject();
+  setCurrentUser("bob"); // not a writer, but there's no policy at all
+  const proxy = makeNg();
+  await proxy.sparql_update("sid", UPDATE, DOC);
+  expect(ng.sparql_update).toHaveBeenCalledTimes(1);
+});
+
+test("write guard: passthrough for an UNGOVERNED doc even when a policy exists elsewhere", async () => {
+  const ng = inject();
+  getCaps().open("did:ng:o:other", "private", "alice"); // policy on another doc
+  setCurrentUser("bob");
+  const proxy = makeNg();
+  await proxy.sparql_update("sid", UPDATE, DOC); // DOC itself is ungoverned
+  expect(ng.sparql_update).toHaveBeenCalledTimes(1);
+});
+
+test("write guard: REJECTS when the doc is governed and the user lacks the write cap", async () => {
+  const ng = inject();
+  getCaps().open(DOC, "private", "alice"); // alice holds write cap
+  setCurrentUser("bob"); // bob does not
+  const proxy = makeNg();
+  await expect(proxy.sparql_update("sid", UPDATE, DOC)).rejects.toThrow(
+    /write denied/,
+  );
+  expect(ng.sparql_update).toHaveBeenCalledTimes(0); // never reached the real ng
+});
+
+test("write guard: REJECTS an anonymous (null) user on a governed doc", async () => {
+  const ng = inject();
+  getCaps().open(DOC, "public", "alice");
+  setCurrentUser(null);
+  const proxy = makeNg();
+  await expect(proxy.sparql_update("sid", UPDATE, DOC)).rejects.toThrow(
+    /write denied/,
+  );
+  expect(ng.sparql_update).toHaveBeenCalledTimes(0);
+});
+
+test("write guard: ALLOWS the write-cap holder", async () => {
+  const ng = inject();
+  getCaps().open(DOC, "private", "alice");
+  setCurrentUser("alice"); // owner always holds the write cap
+  const proxy = makeNg();
+  await proxy.sparql_update("sid", UPDATE, DOC);
+  expect(ng.sparql_update).toHaveBeenCalledTimes(1);
+});
+
+test("write guard: passthrough when anchor is omitted (cannot scope the guard)", async () => {
+  const ng = inject();
+  getCaps().open(DOC, "private", "alice");
+  setCurrentUser("bob");
+  const proxy = makeNg();
+  await proxy.sparql_update("sid", "INSERT DATA {}"); // no anchor → passthrough
+  expect(ng.sparql_update).toHaveBeenCalledTimes(1);
+});

packages/client/test/sparql.test.ts

@@ -0,0 +1,78 @@
+import { test, expect } from "bun:test";
+import { escapeLiteral, escapeIri, assertNuri } from "../src/sparql";
+
+// --- escapeLiteral --------------------------------------------------------
+
+test("escapeLiteral escapes backslash, quote and whitespace controls", () => {
+  expect(escapeLiteral('a"b')).toBe('a\\"b');
+  expect(escapeLiteral("a\\b")).toBe("a\\\\b");
+  expect(escapeLiteral("a\nb")).toBe("a\\nb");
+  expect(escapeLiteral("a\rb")).toBe("a\\rb");
+  expect(escapeLiteral("a\tb")).toBe("a\\tb");
+});
+
+test("escapeLiteral backslash-then-quote order does not double-escape", () => {
+  // `\` first so a raw `"` never becomes `\"` before the quote pass mangles it.
+  expect(escapeLiteral('\\"')).toBe('\\\\\\"');
+});
+
+test("escapeLiteral output can no longer close a SPARQL literal", () => {
+  const injected = '" ; <urn:evil> "pwn';
+  const escaped = escapeLiteral(injected);
+  // No RAW double-quote survives — every `"` is preceded by a backslash.
+  expect(/(^|[^\\])"/.test(escaped)).toBe(false);
+});
+
+// --- escapeIri ------------------------------------------------------------
+
+test("escapeIri passes ordinary printable identifier chars through unchanged", () => {
+  expect(escapeIri("alice")).toBe("alice");
+  expect(escapeIri("a.b-c_d:e/f")).toBe("a.b-c_d:e/f");
+});
+
+test("escapeIri percent-encodes every IRI-breaking character", () => {
+  expect(escapeIri("a>b")).toBe("a%3Eb");
+  expect(escapeIri("a<b")).toBe("a%3Cb");
+  expect(escapeIri('a"b')).toBe("a%22b");
+  expect(escapeIri("a b")).toBe("a%20b");
+  expect(escapeIri("a\nb")).toBe("a%0Ab");
+  expect(escapeIri("a\tb")).toBe("a%09b");
+  expect(escapeIri("a\\b")).toBe("a%5Cb");
+});
+
+test("escapeIri neutralises a full breakout attempt", () => {
+  const attack = 'x> <urn:evil> "pwn';
+  const encoded = escapeIri(attack);
+  // The encoded username cannot contain a raw `>`, `<`, `"` or space, so it
+  // cannot escape the surrounding <PREFIX:...> IRI.
+  expect(encoded).not.toMatch(/[<>" ]/);
+});
+
+test("escapeIri handles unicode without corrupting it (round-trips via decode)", () => {
+  const u = "élan";
+  // "é" is a printable letter → left as-is; a space would be encoded.
+  expect(escapeIri(u)).toBe("élan");
+  expect(escapeIri("é ")).toBe("é%20");
+});
+
+// --- assertNuri -----------------------------------------------------------
+
+test("assertNuri returns valid NURIs unchanged", () => {
+  expect(assertNuri("did:ng:o:doc1")).toBe("did:ng:o:doc1");
+  expect(assertNuri("urn:ng-eventually:shim")).toBe("urn:ng-eventually:shim");
+  expect(assertNuri("did:ng:PRIV")).toBe("did:ng:PRIV");
+});
+
+test("assertNuri throws on empty / non-string", () => {
+  expect(() => assertNuri("")).toThrow(/invalid NURI/);
+  // @ts-expect-error deliberately wrong type
+  expect(() => assertNuri(null)).toThrow(/invalid NURI/);
+});
+
+test("assertNuri throws on IRI-breaking characters", () => {
+  expect(() => assertNuri("did:ng:o> <urn:evil")).toThrow(/IRI-forbidden/);
+  expect(() => assertNuri('did:ng:"x')).toThrow(/IRI-forbidden/);
+  expect(() => assertNuri("did:ng: x")).toThrow(/IRI-forbidden/);
+  expect(() => assertNuri("did:ng:\nx")).toThrow(/IRI-forbidden/);
+  expect(() => assertNuri("did:ng:\tx")).toThrow(/IRI-forbidden/);
+});

packages/client/test/store-registry.test.ts

@@ -43,13 +43,31 @@ test("throws a clear error when configureStoreRegistry() was not called", async
 
 interface Quad { g: string; s: string; p: string; o: string }
 
+/** Reverse of the lib's escapeLiteral: single left-to-right pass over `\x`. */
+function unescapeLiteral(s: string): string {
+  let out = "";
+  for (let i = 0; i < s.length; i++) {
+    if (s[i] === "\\" && i + 1 < s.length) {
+      const next = s[++i];
+      out +=
+        next === "n" ? "\n" : next === "r" ? "\r" : next === "t" ? "\t" : next;
+    } else {
+      out += s[i];
+    }
+  }
+  return out;
+}
+
 function makeFakeNg() {
   const quads: Quad[] = [];
   let docCounter = 0;
 
   const doc_create = mock(async (..._a: unknown[]) => `did:ng:o:doc${++docCounter}`);
 
-  // Parses `INSERT DATA { GRAPH <g> { <s> <p> "o"/<o>/;-lists } }`.
+  // Parses `INSERT DATA { GRAPH <g> { <s> <p> "o"/<o>/;-lists } }`. The literal
+  // pattern honours backslash-escapes (`\"`, `\\`, `\n`…) so an escaped quote
+  // inside a value does NOT terminate the literal — this is what proves the
+  // injection escaping keeps the query well-formed.
   const sparql_update = mock(async (...a: unknown[]) => {
     const query = a[1] as string;
     const gm = query.match(/GRAPH <([^>]+)>\s*\{([\s\S]*)\}/);
@@ -60,16 +78,14 @@ function makeFakeNg() {
     const sm = body.match(/<([^>]+)>/);
     if (!sm) return undefined;
     const s = sm[1]!;
-    // Predicate/object pairs: `<p> "o"` or `<p> <o>` (a == rdf:type ignored form
+    // Predicate/object pairs: `<p> "o"` (escape-aware) or `<p> <o>`; `a <type>`.
-    // handled as literal-free; here the registry only uses <p> "literal" and
+    const pairRe = /(?:a|<([^>]+)>)\s+(?:"((?:[^"\\]|\\.)*)"|<([^>]+)>)/g;
-    // <p> <iri> and `a <type>`).
-    const pairRe = /(?:a|<([^>]+)>)\s+(?:"([^"]*)"|<([^>]+)>)/g;
     let m: RegExpExecArray | null;
     // Skip the subject token so we don't treat it as a predicate.
     const after = body.slice(body.indexOf(sm[0]) + sm[0].length);
     while ((m = pairRe.exec(after)) !== null) {
       const p = m[1] ?? "urn:ng-eventually:shim:Account"; // `a` → rdf:type-ish
-      const o = m[2] ?? m[3] ?? "";
+      const o = m[2] !== undefined ? unescapeLiteral(m[2]) : (m[3] ?? "");
       quads.push({ g, s, p, o });
     }
     return undefined;
@@ -190,6 +206,97 @@ test("allAccounts reflects every ensured account", async () => {
   expect(names).toEqual(["Gina", "Hank"]);
 });
 
+// --- SPARQL injection hardening (F1) --------------------------------------
+//
+// A malicious username must NOT be able to break out of the literal / IRI it
+// lands in and inject arbitrary triples into the shim (the account→doc trust
+// root). We inspect the exact SPARQL string the registry hands to sparql_update.
+
+/** The raw INSERT DATA string produced by ensureAccount for `username`. */
+async function insertFor(username: string): Promise<string> {
+  await ensureAccount(username);
+  const calls = fake.sparql_update.mock.calls;
+  return calls[calls.length - 1]![1] as string;
+}
+
+/** Count RAW (un-escaped) double-quotes — i.e. `"` not preceded by a `\`.
+ *  Strip escaped pairs (`\\`, `\"`, …) first so only delimiter quotes remain. */
+function rawQuoteCount(s: string): number {
+  const withoutEscapes = s.replace(/\\./g, "");
+  return (withoutEscapes.match(/"/g) ?? []).length;
+}
+
+test("injection: username with a quote cannot open extra literals", async () => {
+  const evil = 'x" ; <urn:evil> "pwn';
+  const update = await insertFor(evil);
+  // A well-formed INSERT DATA with 4 predicate literals has exactly 8 raw
+  // quotes (the delimiters). The injected `"` must have been escaped, so the
+  // count stays 8 — no extra literal was opened.
+  expect(rawQuoteCount(update)).toBe(8);
+  // The escaped username is present as a single literal value — the injected
+  // `<urn:evil>` survives only as INERT text inside that literal (its
+  // surrounding quotes are escaped `\"`), never as query syntax.
+  expect(update).toContain('"x\\" ; <urn:evil> \\"pwn"');
+});
+
+test("injection: username with '>' cannot break out of the account-subject IRI", async () => {
+  const evil = "x> <urn:evil";
+  const update = await insertFor(evil);
+  // The account subject is `<urn:ng-eventually:shim:account:...>` — the encoded
+  // username must NOT contain a raw `>` that would close the IRI early.
+  const subjMatch = update.match(/<urn:ng-eventually:shim:account:([^>]*)>/)!;
+  expect(subjMatch).not.toBeNull();
+  expect(subjMatch[1]).not.toMatch(/[<>" ]/); // fully percent-encoded
+  expect(subjMatch[1]).toContain("%3E"); // the `>` became %3E
+});
+
+test("injection: newline / control chars in username are neutralised", async () => {
+  const evil = "a\nb\tc";
+  const update = await insertFor(evil);
+  // In the literal: escaped to \n / \t (no raw control char).
+  expect(update).toContain('"a\\nb\\tc"');
+  // In the IRI subject: percent-encoded.
+  const subjMatch = update.match(/<urn:ng-eventually:shim:account:([^>]*)>/)!;
+  expect(subjMatch[1]).toContain("%0A");
+  expect(subjMatch[1]).toContain("%09");
+});
+
+test("injection: '; DELETE'-style payload stays inert inside the literal", async () => {
+  const evil = 'x"} ; DELETE WHERE { ?s ?p ?o } ; INSERT DATA { <a> <b> "';
+  const update = await insertFor(evil);
+  // The whole attack survives, escaped, as ONE literal value — the injected
+  // `"}` cannot close the literal/graph, so DELETE/second-INSERT stay text.
+  expect(update).toContain(escapeLiteralRef(evil));
+  // Quote count stays even (all delimiters balanced; the injected `"` escaped):
+  // 4 predicate literals → 8 raw delimiter quotes, nothing extra opened.
+  expect(rawQuoteCount(update)).toBe(8);
+  // The injected `"}` did not survive as raw syntax (it was escaped to `\"}`).
+  expect(update).not.toMatch(/[^\\]"} ; DELETE/);
+});
+
+// Local mirror of the lib's escapeLiteral so the assertion is self-checking.
+function escapeLiteralRef(v: string): string {
+  return `"${v
+    .replace(/\\/g, "\\\\")
+    .replace(/"/g, '\\"')
+    .replace(/\n/g, "\\n")
+    .replace(/\r/g, "\\r")
+    .replace(/\t/g, "\\t")}"`;
+}
+
+test("injection: a malicious username still round-trips through the shim", async () => {
+  const evil = 'eve" ; <urn:evil> "x';
+  const rec = await ensureAccount(evil);
+  expect(rec.username).toBe(evil);
+  resetRegistryCache();
+  const map = await loadShim();
+  // The stored username came back verbatim (escaping is lossless) under its
+  // normalized key, and exactly ONE account exists (no injected extra subject).
+  const key = evil.trim().replace(/^@+/, "").toLowerCase();
+  expect(map.get(key)?.username).toBe(evil);
+  expect(map.size).toBe(1);
+});
+
 test("normalizeUser defaults to trim when not provided", async () => {
   const ng = makeFakeNg();
   configure({ ng: ng as any, useShape: (() => {}) as any });