release(v4.0.0): Shade GA — V3.x consolidation + audit prep

V3.1 → V3.12 consolidated and tagged for the first GA release. Wire
format unchanged from 0.4.x — 4.0 peers interoperate with 0.4.x peers
byte-for-byte. The version bump is semantic: audit-cycle complete,
opt-in surface fully exposed, threat model refreshed for every new
surface.

Highlights:
- All 24 @shade/* packages bumped to 4.0.0 in lockstep.
- CHANGELOG 4.0.0 section is the canonical manifest of what landed.
- THREAT-MODEL extended (§10 fingerprint gates, §11 WebRTC P2P, §12
  Web-Worker boundary) + residual-risks table refreshed.
- OpenAPI now covers all 27 routes: prekey, transfer, KT, inbox,
  bridge, observer, /metrics, /healthz, /ready.
- MIGRATION 0.3.x → 4.0 documented + smoke-tested against
  shade migrate-storage on a real SQLite DB.
- docs/audit/REVIEW-BUNDLE.md + SCOPE.md ready for external reviewer.
- scripts/soak.ts harness for the GA-stable 2-week soak window.
- All V*.md plans archived under docs/archive/ with Status: Done.
- Voice/Video carved out into V5.0; 4.0 audit focuses on the frozen
  non-realtime stack.

Tests: TS 1000/1000 + Kotlin 11/11 cross-platform vectors green.
Docker: gt.zyon.no/stian/shade-prekey:4.0.0 builds and reports
  version 4.0.0 on /health.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-transport/package.json

@@ -1,12 +1,13 @@
 {
   "name": "@shade/transport",
-  "version": "0.3.0",
+  "version": "4.0.0",
   "type": "module",
   "main": "src/index.ts",
   "types": "src/index.ts",
   "dependencies": {
     "@shade/core": "workspace:*",
     "@shade/crypto-web": "workspace:*",
+    "@shade/key-transparency": "workspace:*",
     "@shade/proto": "workspace:*",
     "@shade/server": "workspace:*"
   }

packages/shade-transport/src/fetch-transport.ts

@@ -1,5 +1,18 @@
 import type { PreKeyBundle, OneTimePreKey, CryptoProvider } from '@shade/core';
 import { NetworkError } from '@shade/core';
+import {
+  type KTProof,
+  type KTProofWire,
+  type SignedTreeHead,
+  ktProofFromWire,
+  verifyBundleAbsence,
+  verifyBundleInclusion,
+  verifyBundleTombstone,
+} from '@shade/key-transparency';
+import {
+  KTSplitViewError,
+  KTVerificationError,
+} from '@shade/key-transparency';
 
 /**
  * HTTP transport client for the Shade Prekey Server.
@@ -19,17 +32,56 @@ import { NetworkError } from '@shade/core';
  * const bundle = await transport.fetchBundle('bob'); // anonymous
  * ```
  */
+/** Result of a KT-aware bundle fetch. */
+export interface FetchBundleResult {
+  bundle: PreKeyBundle;
+  /**
+   * Verified Signed Tree Head when KT was active and the proof verified.
+   * Callers should feed this into a `LightWitness` for split-view tracking.
+   */
+  ktSth?: SignedTreeHead;
+}
+
+/**
+ * Optional KT verifier callback. When provided to `ShadeFetchTransport`,
+ * the transport verifies every bundle proof before handing the bundle to
+ * the SDK. Missing-or-invalid proofs throw `KTVerificationError`.
+ *
+ * `mode`:
+ *   - `'observe'`     verify proof when present, do not fail when missing.
+ *   - `'observe-strict'` require a proof; throw if absent.
+ */
+export interface KTVerifierOptions {
+  mode: 'observe' | 'observe-strict';
+  logPublicKey: Uint8Array;
+  /** Inject `now` for tests; defaults to `Date.now()`. */
+  now?: () => number;
+  /** Override default 24h freshness. */
+  maxStaleMs?: number;
+  /** Optional hook to track every observed STH (e.g. into a LightWitness). */
+  onObserveSth?: (sth: SignedTreeHead) => void | Promise<void>;
+}
+
 export class ShadeFetchTransport {
   private readonly baseUrl: string;
   private readonly crypto: CryptoProvider;
   private readonly signingPrivateKey?: Uint8Array;
+  private readonly kt?: KTVerifierOptions;
 
-  constructor(options: { baseUrl: string; crypto: CryptoProvider; signingPrivateKey?: Uint8Array }) {
+  constructor(options: {
+    baseUrl: string;
+    crypto: CryptoProvider;
+    signingPrivateKey?: Uint8Array;
+    keyTransparency?: KTVerifierOptions;
+  }) {
     this.baseUrl = options.baseUrl;
     this.crypto = options.crypto;
     if (options.signingPrivateKey !== undefined) {
       this.signingPrivateKey = options.signingPrivateKey;
     }
+    if (options.keyTransparency !== undefined) {
+      this.kt = options.keyTransparency;
+    }
   }
 
   private headers(): Record<string, string> {
@@ -89,12 +141,45 @@ export class ShadeFetchTransport {
     if (!res.ok) throw new NetworkError(`Register failed: ${res.status}`, res.status);
   }
 
-  /** Fetch a prekey bundle for a peer (anonymous, consumes one one-time prekey) */
+  /**
+   * Fetch a prekey bundle for a peer (anonymous, consumes one one-time prekey).
+   *
+   * When the transport was created with `keyTransparency`, this also verifies
+   * the inclusion proof and (if configured) feeds the STH into the supplied
+   * `onObserveSth` hook for split-view tracking.
+   */
   async fetchBundle(address: string): Promise<PreKeyBundle> {
+    const result = await this.fetchBundleVerified(address);
+    return result.bundle;
+  }
+
+  /**
+   * Same as `fetchBundle` but returns the verified STH alongside the bundle
+   * so callers can wire it into a `LightWitness`. Use this when you want
+   * direct access to the proof side-channel.
+   */
+  async fetchBundleVerified(address: string): Promise<FetchBundleResult> {
     const res = await fetch(`${this.baseUrl}/v1/keys/bundle/${encodeURIComponent(address)}`, {
       headers: this.headers(),
     });
-    if (!res.ok) throw new NetworkError(`Fetch bundle failed: ${res.status}`, res.status);
+    if (!res.ok) {
+      // KT-aware 404: read the body for an absence/tombstone proof so the
+      // negative answer is also pinned to a tree state.
+      if (res.status === 404 && this.kt) {
+        const body = (await res.json().catch(() => null)) as
+          | { ktProof?: KTProofWire }
+          | null;
+        if (body?.ktProof) {
+          const proof = ktProofFromWire(body.ktProof);
+          await this.verifyAbsenceOrTombstone(address, proof);
+        } else if (this.kt.mode === 'observe-strict') {
+          throw new KTVerificationError(
+            `KT-strict: 404 for ${address} but no ktProof in response`,
+          );
+        }
+      }
+      throw new NetworkError(`Fetch bundle failed: ${res.status}`, res.status);
+    }
 
     const data = (await res.json()) as {
       registrationId?: number;
@@ -102,6 +187,7 @@ export class ShadeFetchTransport {
       identityDHKey: string;
       signedPreKey: { keyId: number; publicKey: string; signature: string };
       oneTimePreKey?: { keyId: number; publicKey: string };
+      ktProof?: KTProofWire;
     };
     const bundle: PreKeyBundle = {
       registrationId: data.registrationId ?? 0,
@@ -119,7 +205,68 @@ export class ShadeFetchTransport {
         publicKey: fromB64(data.oneTimePreKey.publicKey),
       };
     }
-    return bundle;
+
+    let ktSth: SignedTreeHead | undefined;
+    if (this.kt) {
+      if (data.ktProof) {
+        const proof = ktProofFromWire(data.ktProof);
+        ktSth = await this.verifyInclusion(address, bundle, proof);
+        if (this.kt.onObserveSth) await this.kt.onObserveSth(ktSth);
+      } else if (this.kt.mode === 'observe-strict') {
+        throw new KTVerificationError(
+          `KT-strict: bundle for ${address} missing ktProof`,
+        );
+      }
+    }
+
+    return ktSth ? { bundle, ktSth } : { bundle };
+  }
+
+  private async verifyInclusion(
+    address: string,
+    bundle: PreKeyBundle,
+    proof: KTProof,
+  ): Promise<SignedTreeHead> {
+    if (!this.kt) throw new Error('KT verifier not configured');
+    const opts = {
+      crypto: this.crypto,
+      logPublicKey: this.kt.logPublicKey,
+      ...(this.kt.maxStaleMs !== undefined ? { maxStaleMs: this.kt.maxStaleMs } : {}),
+      ...(this.kt.now !== undefined ? { nowMs: this.kt.now() } : {}),
+    };
+    if (proof.body.kind === 'inclusion') {
+      return verifyBundleInclusion(opts, address, bundle, proof);
+    }
+    if (proof.body.kind === 'tombstone') {
+      // A tombstone proof on a 200 response would mean the server delivered
+      // a deleted address — this is malicious.
+      throw new KTVerificationError(`server returned tombstoned bundle for ${address}`);
+    }
+    if (proof.body.kind === 'absence') {
+      throw new KTVerificationError(`server returned bundle but absence proof for ${address}`);
+    }
+    throw new KTSplitViewError(`unknown proof kind`);
+  }
+
+  private async verifyAbsenceOrTombstone(address: string, proof: KTProof): Promise<void> {
+    if (!this.kt) return;
+    const opts = {
+      crypto: this.crypto,
+      logPublicKey: this.kt.logPublicKey,
+      ...(this.kt.maxStaleMs !== undefined ? { maxStaleMs: this.kt.maxStaleMs } : {}),
+      ...(this.kt.now !== undefined ? { nowMs: this.kt.now() } : {}),
+    };
+    let sth: SignedTreeHead;
+    if (proof.body.kind === 'absence') {
+      sth = await verifyBundleAbsence(opts, address, proof);
+    } else if (proof.body.kind === 'tombstone') {
+      sth = await verifyBundleTombstone(opts, address, proof);
+    } else {
+      throw new KTVerificationError(
+        `404 with non-absence/non-tombstone proof for ${address}`,
+      );
+    }
+    if (this.kt.onObserveSth) await this.kt.onObserveSth(sth);
   }
 
   /** Upload additional one-time prekeys (signed) */

packages/shade-transport/src/index.ts

@@ -1,2 +1,3 @@
 export { ShadeFetchTransport } from './fetch-transport.js';
+export type { FetchBundleResult, KTVerifierOptions } from './fetch-transport.js';
 export { ShadeWebSocket } from './ws-adapter.js';

packages/shade-transport/tests/kt-split-view-e2e.test.ts

@@ -0,0 +1,176 @@
+/**
+ * Acceptance test for V3.12 §"End-to-end test: split-view detection".
+ *
+ * Scenario:
+ *   - One legitimate STH-signing key (the operator's pinned key).
+ *   - Two divergent log views A and B, both signed by the same key
+ *     (simulating a malicious server that hands different responses to
+ *     different clients).
+ *   - Two clients (Bob, Charlie) each fetch alice's bundle, but each is
+ *     served from a different view.
+ *   - A `LightWitness` cross-pollinates the two clients' STHs.
+ *   - The witness must reject the second STH at the same tree_size with
+ *     a `KTSplitViewError`.
+ *
+ * Also asserts the *positive* path: when both clients see the same view,
+ * no error is raised.
+ */
+
+import { describe, expect, test } from 'bun:test';
+import { SubtleCryptoProvider } from '@shade/crypto-web';
+import {
+  KTLogManager,
+  KTSplitViewError,
+  LightWitness,
+  MemoryKTLogStore,
+  computeBundleHash,
+  computeLogId,
+} from '@shade/key-transparency';
+
+const crypto = new SubtleCryptoProvider();
+
+function fakeBundle(seed: number) {
+  return {
+    identitySigningKey: new Uint8Array(32).fill(seed),
+    identityDHKey: new Uint8Array(32).fill(seed + 1),
+    signedPreKey: {
+      keyId: 1,
+      publicKey: new Uint8Array(32).fill(seed + 2),
+      signature: new Uint8Array(64).fill(seed + 3),
+    },
+  };
+}
+
+describe('Split-view E2E', () => {
+  test('two divergent views at the same tree_size are caught by witness', async () => {
+    const operator = await crypto.generateEd25519KeyPair();
+
+    // View A — alice has the *real* identity (seed 0x10)
+    const viewA = await KTLogManager.create({
+      crypto,
+      store: new MemoryKTLogStore(),
+      signingPrivateKey: operator.privateKey,
+      signingPublicKey: operator.publicKey,
+    });
+    await viewA.recordRegister('alice', computeBundleHash(fakeBundle(0x10)));
+    const sthA = await viewA.publishSTH();
+
+    // View B — alice has a *malicious* identity (seed 0xff)
+    const viewB = await KTLogManager.create({
+      crypto,
+      store: new MemoryKTLogStore(),
+      signingPrivateKey: operator.privateKey,
+      signingPublicKey: operator.publicKey,
+    });
+    await viewB.recordRegister('alice', computeBundleHash(fakeBundle(0xff)));
+    const sthB = await viewB.publishSTH();
+
+    // Both STHs claim tree_size = 1 with the same logId, but with
+    // different rootHash + indexRoot. This is what a split-view attack
+    // looks like on the wire.
+    expect(sthA.treeSize).toBe(sthB.treeSize);
+    expect(Buffer.from(sthA.logId).toString('hex')).toBe(
+      Buffer.from(sthB.logId).toString('hex'),
+    );
+    expect(Buffer.from(sthA.rootHash).toString('hex')).not.toBe(
+      Buffer.from(sthB.rootHash).toString('hex'),
+    );
+
+    // Bob has been served STH A; Charlie has been served STH B.
+    // They share a witness (gossip-style):
+    const witness = new LightWitness({
+      crypto,
+      logPublicKey: operator.publicKey,
+      fetcher: {
+        async fetchLatestSTH() {
+          throw new Error('not used in this test');
+        },
+        async fetchConsistencyProof() {
+          return { proof: [] };
+        },
+      },
+    });
+
+    await witness.observe(sthA);
+    expect(witness.compare(sthA)).toBe('agree');
+    expect(witness.compare(sthB)).toBe('split-view');
+    await expect(witness.observe(sthB)).rejects.toBeInstanceOf(KTSplitViewError);
+  });
+
+  test('positive path: same view → no false alarm', async () => {
+    const operator = await crypto.generateEd25519KeyPair();
+    const view = await KTLogManager.create({
+      crypto,
+      store: new MemoryKTLogStore(),
+      signingPrivateKey: operator.privateKey,
+      signingPublicKey: operator.publicKey,
+    });
+    await view.recordRegister('alice', computeBundleHash(fakeBundle(0x10)));
+    const sth1 = await view.publishSTH();
+    await view.recordRegister('bob', computeBundleHash(fakeBundle(0x20)));
+    const sth2 = await view.publishSTH();
+
+    const witness = new LightWitness({
+      crypto,
+      logPublicKey: operator.publicKey,
+      fetcher: {
+        async fetchLatestSTH() {
+          throw new Error('not used');
+        },
+        async fetchConsistencyProof(from, to) {
+          const result = await view.buildHistoricalConsistencyProof(from, to);
+          return { proof: result.map((b) => Buffer.from(b).toString('base64')) };
+        },
+      },
+    });
+    await witness.observe(sth1);
+    await witness.observe(sth2);
+    expect(witness.compare(sth2)).toBe('agree');
+  });
+
+  test('rewriting history (forked log at tree_size 1) fails consistency from sth1 → sth2', async () => {
+    const operator = await crypto.generateEd25519KeyPair();
+    const real = await KTLogManager.create({
+      crypto,
+      store: new MemoryKTLogStore(),
+      signingPrivateKey: operator.privateKey,
+      signingPublicKey: operator.publicKey,
+    });
+    await real.recordRegister('alice', computeBundleHash(fakeBundle(0x10)));
+    const sth1 = await real.publishSTH();
+
+    // Build a divergent log that pretends 'mallory' was the first leaf,
+    // not 'alice'. The forked tree's STH at size 2 must NOT pass a
+    // consistency proof against sth1.
+    const fork = await KTLogManager.create({
+      crypto,
+      store: new MemoryKTLogStore(),
+      signingPrivateKey: operator.privateKey,
+      signingPublicKey: operator.publicKey,
+    });
+    await fork.recordRegister('mallory', computeBundleHash(fakeBundle(0xee)));
+    await fork.recordRegister('bob', computeBundleHash(fakeBundle(0x20)));
+    const forkedSth2 = await fork.publishSTH();
+    const forkedConsistency = await fork.buildConsistencyProof(sth1.treeSize);
+
+    const witness = new LightWitness({
+      crypto,
+      logPublicKey: operator.publicKey,
+      fetcher: {
+        async fetchLatestSTH() {
+          throw new Error('not used');
+        },
+        async fetchConsistencyProof() {
+          return { proof: forkedConsistency.proof.map((b) => Buffer.from(b).toString('base64')) };
+        },
+      },
+    });
+    await witness.observe(sth1);
+    await expect(witness.observe(forkedSth2)).rejects.toThrow();
+
+    // sanity: logId pinning still valid
+    expect(Buffer.from(forkedSth2.logId).toString('hex')).toBe(
+      Buffer.from(computeLogId(operator.publicKey)).toString('hex'),
+    );
+  });
+});

packages/shade-transport/tests/kt-transport.test.ts

@@ -0,0 +1,230 @@
+import { describe, test, expect } from 'bun:test';
+import { SubtleCryptoProvider, MemoryStorage } from '@shade/crypto-web';
+import { ShadeSessionManager } from '@shade/core';
+import {
+  createPrekeyServerWithKT,
+  MemoryPrekeyStore,
+} from '@shade/server';
+import {
+  KTVerificationError,
+  LightWitness,
+  MemoryKTLogStore,
+  computeLogId,
+  signSth,
+  type SignedTreeHead,
+} from '@shade/key-transparency';
+import { ShadeFetchTransport } from '../src/fetch-transport.js';
+
+const crypto = new SubtleCryptoProvider();
+
+describe('ShadeFetchTransport with KT verifier', () => {
+  test('fetch verifies inclusion proof against pinned log key', async () => {
+    const logKp = await crypto.generateEd25519KeyPair();
+    const { app, kt } = await createPrekeyServerWithKT({
+      crypto,
+      store: new MemoryPrekeyStore(),
+      disableRateLimit: true,
+      keyTransparency: {
+        store: new MemoryKTLogStore(),
+        signingPrivateKey: logKp.privateKey,
+        signingPublicKey: logKp.publicKey,
+      },
+    });
+
+    const port = 20100 + Math.floor(Math.random() * 500);
+    const handle = Bun.serve({ port, fetch: app.fetch });
+    try {
+      const baseUrl = `http://localhost:${port}`;
+
+      // Bob registers
+      const bobStorage = new MemoryStorage();
+      const bobManager = new ShadeSessionManager(crypto, bobStorage);
+      await bobManager.initialize();
+      const bobIdentity = await bobStorage.getIdentityKeyPair();
+      const bobTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        signingPrivateKey: bobIdentity!.signingPrivateKey,
+      });
+      const bobOTPKs = await bobManager.generateOneTimePreKeys(3);
+      const bobBundle = await bobManager.createPreKeyBundle();
+      await bobTransport.register('bob', bobManager.getPublicIdentity(), bobBundle.signedPreKey, bobOTPKs);
+
+      // Alice fetches with KT verifier — should succeed
+      const observed: SignedTreeHead[] = [];
+      const aliceTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        keyTransparency: {
+          mode: 'observe-strict',
+          logPublicKey: logKp.publicKey,
+          onObserveSth: async (sth) => {
+            observed.push(sth);
+          },
+        },
+      });
+      const result = await aliceTransport.fetchBundleVerified('bob');
+      expect(result.bundle.identityDHKey).toEqual(bobManager.getPublicIdentity().dhKey);
+      expect(result.ktSth).toBeDefined();
+      expect(result.ktSth!.treeSize).toBe(1);
+      expect(observed.length).toBe(1);
+
+      // Sanity: server-side latest STH matches what client observed
+      const serverSth = await kt.getLatestSTH();
+      expect(Buffer.from(serverSth.rootHash).toString('hex')).toBe(
+        Buffer.from(result.ktSth!.rootHash).toString('hex'),
+      );
+    } finally {
+      handle.stop();
+    }
+  });
+
+  test('observe-strict throws KTVerificationError on missing proof', async () => {
+    // Plain server (no KT)
+    const { createPrekeyServer, MemoryPrekeyStore } = await import('@shade/server');
+    const app = createPrekeyServer({
+      crypto,
+      store: new MemoryPrekeyStore(),
+      disableRateLimit: true,
+    });
+    const port = 20800 + Math.floor(Math.random() * 200);
+    const handle = Bun.serve({ port, fetch: app.fetch });
+    try {
+      const baseUrl = `http://localhost:${port}`;
+
+      const bobStorage = new MemoryStorage();
+      const bobManager = new ShadeSessionManager(crypto, bobStorage);
+      await bobManager.initialize();
+      const bobIdentity = await bobStorage.getIdentityKeyPair();
+      const bobTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        signingPrivateKey: bobIdentity!.signingPrivateKey,
+      });
+      const bobOTPKs = await bobManager.generateOneTimePreKeys(2);
+      const bobBundle = await bobManager.createPreKeyBundle();
+      await bobTransport.register('bob', bobManager.getPublicIdentity(), bobBundle.signedPreKey, bobOTPKs);
+
+      const logKp = await crypto.generateEd25519KeyPair();
+      const aliceTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        keyTransparency: { mode: 'observe-strict', logPublicKey: logKp.publicKey },
+      });
+      await expect(aliceTransport.fetchBundle('bob')).rejects.toBeInstanceOf(KTVerificationError);
+    } finally {
+      handle.stop();
+    }
+  });
+
+  test('forged STH (server signed with wrong key) is rejected', async () => {
+    const realLogKp = await crypto.generateEd25519KeyPair();
+    const evilLogKp = await crypto.generateEd25519KeyPair();
+    const { app } = await createPrekeyServerWithKT({
+      crypto,
+      store: new MemoryPrekeyStore(),
+      disableRateLimit: true,
+      keyTransparency: {
+        store: new MemoryKTLogStore(),
+        // Operator signs with the EVIL key
+        signingPrivateKey: evilLogKp.privateKey,
+        signingPublicKey: evilLogKp.publicKey,
+      },
+    });
+    const port = 21100 + Math.floor(Math.random() * 200);
+    const handle = Bun.serve({ port, fetch: app.fetch });
+    try {
+      const baseUrl = `http://localhost:${port}`;
+
+      const bobStorage = new MemoryStorage();
+      const bobManager = new ShadeSessionManager(crypto, bobStorage);
+      await bobManager.initialize();
+      const bobIdentity = await bobStorage.getIdentityKeyPair();
+      const bobTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        signingPrivateKey: bobIdentity!.signingPrivateKey,
+      });
+      const bobOTPKs = await bobManager.generateOneTimePreKeys(2);
+      const bobBundle = await bobManager.createPreKeyBundle();
+      await bobTransport.register('bob', bobManager.getPublicIdentity(), bobBundle.signedPreKey, bobOTPKs);
+
+      // Client pinned the REAL log key — verification must fail
+      const aliceTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        keyTransparency: { mode: 'observe-strict', logPublicKey: realLogKp.publicKey },
+      });
+      await expect(aliceTransport.fetchBundle('bob')).rejects.toThrow();
+    } finally {
+      handle.stop();
+    }
+  });
+
+  test('observed STH feeds LightWitness; subsequent split-view detected', async () => {
+    const logKp = await crypto.generateEd25519KeyPair();
+    const { app, kt } = await createPrekeyServerWithKT({
+      crypto,
+      store: new MemoryPrekeyStore(),
+      disableRateLimit: true,
+      keyTransparency: {
+        store: new MemoryKTLogStore(),
+        signingPrivateKey: logKp.privateKey,
+        signingPublicKey: logKp.publicKey,
+      },
+    });
+    const port = 21500 + Math.floor(Math.random() * 200);
+    const handle = Bun.serve({ port, fetch: app.fetch });
+    try {
+      const baseUrl = `http://localhost:${port}`;
+
+      // Register Bob
+      const bobStorage = new MemoryStorage();
+      const bobManager = new ShadeSessionManager(crypto, bobStorage);
+      await bobManager.initialize();
+      const bobIdentity = await bobStorage.getIdentityKeyPair();
+      const bobTransport = new ShadeFetchTransport({
+        baseUrl,
+        crypto,
+        signingPrivateKey: bobIdentity!.signingPrivateKey,
+      });
+      const bobOTPKs = await bobManager.generateOneTimePreKeys(2);
+      const bobBundle = await bobManager.createPreKeyBundle();
+      await bobTransport.register('bob', bobManager.getPublicIdentity(), bobBundle.signedPreKey, bobOTPKs);
+
+      // Witness backed by the real /v1/kt/* endpoints
+      const witness = new LightWitness({
+        crypto,
+        logPublicKey: logKp.publicKey,
+        fetcher: {
+          async fetchLatestSTH() {
+            const res = await fetch(`${baseUrl}/v1/kt/sth`);
+            return res.json();
+          },
+          async fetchConsistencyProof(from, to) {
+            const res = await fetch(`${baseUrl}/v1/kt/consistency?from=${from}&to=${to}`);
+            return res.json();
+          },
+        },
+      });
+      const observedSth = await witness.pollOnce();
+      expect(observedSth.treeSize).toBe(1);
+
+      // Forge a divergent STH at the same tree_size and feed it to the
+      // witness (this simulates a malicious second view)
+      const realSth = await kt.getLatestSTH();
+      const tampered = new Uint8Array(realSth.rootHash);
+      tampered[0] ^= 0xff;
+      const forged = await signSth(crypto, logKp.privateKey, {
+        treeSize: realSth.treeSize,
+        timestampMs: realSth.timestampMs,
+        rootHash: tampered,
+        indexRoot: realSth.indexRoot,
+        logId: computeLogId(logKp.publicKey),
+      });
+      await expect(witness.observe(forged)).rejects.toThrow(/Split view/);
+    } finally {
+      handle.stop();
+    }
+  });
+});