test: T-A38 root-cause proof — >768 KiB snapshot succeeds because duress rides its own frame

@@ -792,4 +792,65 @@792792     expect(Object.keys(result.entries).length).toBeLessThan(200);793793     expect(result.tombstones).toEqual({ "dead-0": 1 });794794   });795+796+  // T-A38: the single test that proves the *root-cause fix* for the frame797+  // ceiling bug, not just the new wire path. Combines the high-level798+  // end-to-end success assertion (T-A33) with the structural proof (T-A34):799+  // a payload whose combined raw exceeds the 768 KiB wire ceiling succeeds800+  // because the duress slot rides its own frame instead of piggybacking on801+  // the entries final chunk. Pre-v4.6.4, duress counted against the entries802+  // frame, so a single frame would exceed SNAPSHOT_FRAME_WIRE_CEILING and the803+  // receiver would reject the whole snapshot with ADOPT_SNAPSHOT_CHUNK_TOO_LARGE.804+  it("T-A38: >768 KiB snapshot succeeds because duress no longer counts against the entries frame", async () => {805+    const [source, receiver] = memoryPair();806+    // Single entry that is ~450 KiB on its own; combined with a ~640 KiB807+    // duress JSON, the total payload exceeds the 768 KiB wire ceiling.808+    const entries: Record<string, string> = { "id-0": "x".repeat(450 * 1024) };809+    const tombstones: Record<string, number> = { "dead-0": 1 };810+    const duressJson = JSON.stringify({811+      version: 1,812+      salt: "aa".repeat(16),813+      nonce: "bb".repeat(12),814+      ciphertext: "cc".repeat(320 * 1024),815+      tag: "dd".repeat(16),816+    });817+    const CEILING = 768 * 1024;818+819+    // Probe the wire so we can assert the structural shape alongside the820+    // end-to-end success.821+    const observed: Array<{ size: number; hasDuress: boolean; entriesKeys: number }> = [];822+    const probe: PairingTransport = {823+      async send(msg) {824+        const f = JSON.parse(new TextDecoder().decode(msg)) as Record<string, unknown>;825+        observed.push({826+          size: msg.length,827+          hasDuress: typeof f.duress_slot === "string",828+          entriesKeys: Object.keys((f.entries as Record<string, unknown>) ?? {}).length,829+        });830+        return source.send(msg);831+      },832+      receive() { return source.receive(); },833+    };834+835+    const [result] = await Promise.all([836+      receiveVaultSnapshot(receiver),837+      sendVaultSnapshot(probe, entries, tombstones, duressJson),838+    ]);839+840+    // High-level success: the receiver accepts the >768 KiB combined payload.841+    expect(result.entries).toEqual(entries);842+    expect(result.tombstones).toEqual(tombstones);843+    expect(result.duressSlot).toBe(duressJson);844+845+    // Root-cause proof: duress is on its own frame, not on the entries frame.846+    // Every frame stays under the ceiling; only the combined raw exceeds it.847+    expect(observed.length).toBe(2);848+    expect(observed[0].hasDuress).toBe(false);849+    expect(observed[0].entriesKeys).toBe(1);850+    expect(observed[0].size).toBeLessThan(CEILING);851+    expect(observed[1].hasDuress).toBe(true);852+    expect(observed[1].entriesKeys).toBe(0);853+    expect(observed[1].size).toBeLessThan(CEILING);854+    expect(observed[0].size + observed[1].size).toBeGreaterThan(CEILING);855+  });795856 });