diff --git a/docs/reference/sqlite-authority-store.md b/docs/reference/sqlite-authority-store.md
index 09d23bc965..bdd6674e25 100644
--- a/docs/reference/sqlite-authority-store.md
+++ b/docs/reference/sqlite-authority-store.md
@@ -310,14 +310,21 @@ The shipped version-1 database keeps one full projection per retained row, so it
 cannot be read by the version-2 provider. `sqlite_authority_migration.ts`
 migrates one Goal database in place: it reads the frozen version-1 rows, proves
 every stored commit digest, writes the checkpoint/delta log, proves that each
-written delta reconstructs its projection, requires the commit count to match,
-swaps tables and updates the schema version inside a single
+written delta reconstructs its projection, reads the not-yet-swapped tables back
+and replays them through the store's own delta decoder, requires the commit
+count to match, swaps tables and updates the schema version inside a single
 `BEGIN IMMEDIATE` transaction. Any failure rolls back and leaves version 1
 untouched; a second run reports `already_current`; a rewritten proof, a
 mismatched goal/incarnation or an existing swap target fails closed. Cursors,
 operation IDs, commit digests, provider revisions, receipts, events and scan
 pages are byte-identical after the migration.
 
+Retained projections keep every JSON object key the version-1 provider accepted,
+including an empty key and a `__proto__` key: a database the previous provider
+could read must not become one the version-2 provider cannot. The replay proof
+is what keeps that promise honest, because identical identity and digest columns
+alone would not show that a migrated state log is unreadable.
+
 A version-1 database that published only its schema and metadata — the state a
 goal leaves behind when it selected the provider and never committed — migrates
 to an equally empty version-2 database instead of failing, so the operator is
@@ -390,4 +397,8 @@ delta”：活跃头读取只用自己的行、对应提交和游标连续性自
 才写入，`--expected-identity` 可拒绝并非操作者所指的 incarnation，失败保持 v1
 原样）。只发布过 schema 与 metadata、从未提交的 v1 库会迁移成同样为空的 v2 库，
 不会让操作者落在两个 provider 都不接受的状态。迁移不改 cursor、operation id、
-commit digest、provider revision、receipt、event 或 scan 页面字节。
+commit digest、provider revision、receipt、event 或 scan 页面字节。迁移在提交前
+还会把刚写入的表读回来、用 store 自己的 delta 解码器重放一遍：只核对搬过去的
+标识与摘要无法证明新的状态日志可读。v1 能接受的 JSON key（包括空字符串和
+`__proto__`）在 v2 中保持同样的数据语义，迁移不会把原本可读的库变成读不出来的
+状态。
diff --git a/loopx/control_plane/coordination/authority_state_log.ts b/loopx/control_plane/coordination/authority_state_log.ts
index a49faf08ee..1fc4e97bb1 100644
--- a/loopx/control_plane/coordination/authority_state_log.ts
+++ b/loopx/control_plane/coordination/authority_state_log.ts
@@ -35,6 +35,10 @@ export const AUTHORITY_STATE_CHECKPOINT_INTERVAL = 64;
 /**
  * Object path inside one projection. Arrays are addressed as a whole value;
  * element identity is owned by the domain, not by this codec.
+ *
+ * Segments are JSON object keys, and strict JSON allows any string as a key:
+ * the empty string is a key, and so is `__proto__`. V1 retained whole
+ * projections, so both are legal retained data and stay legal here.
  */
 export type AuthorityStatePath = readonly string[];
 
@@ -183,7 +187,22 @@ function applyAuthorityStateOperation(root: JsonObject, operation: AuthorityStat
     if (!present) protocol("authority state delta removed a value that was never stored");
     delete container[last];
   }
-  else container[last] = structuredClone(operation.value);
+  else setOwnJsonKey(container, last, structuredClone(operation.value));
+}
+
+/**
+ * Write one decoded key as an own data property.
+ *
+ * `container[key] = value` would run the inherited `__proto__` accessor and
+ * replace the reconstructed object's prototype with the stored value, so a
+ * retained projection carrying that key would silently lose it. Decoded
+ * deltas are data, so every key is created the same way the canonicalizer
+ * creates keys, which keeps reconstruction exact for every JSON object key.
+ */
+function setOwnJsonKey(container: JsonObject, key: string, value: unknown): void {
+  Object.defineProperty(container, key, {
+    value, writable: true, enumerable: true, configurable: true,
+  });
 }
 
 function descend(container: unknown, segment: string): unknown {
@@ -233,7 +252,8 @@ function decodeAuthorityStateOperation(value: unknown, index: number): Authority
 function decodeAuthorityStatePath(value: unknown, label: string): AuthorityStatePath {
   if (!Array.isArray(value) || value.length === 0) protocol(`${label} path is invalid`);
   return value.map(segment => {
-    if (typeof segment === "string" && segment.length > 0) return segment;
+    // Any string is a legal JSON key, including the empty string.
+    if (typeof segment === "string") return segment;
     return protocol(`${label} path segment is invalid`);
   });
 }
diff --git a/loopx/control_plane/coordination/sqlite_authority_migration.ts b/loopx/control_plane/coordination/sqlite_authority_migration.ts
index 68d6fde3d1..e053876ef6 100644
--- a/loopx/control_plane/coordination/sqlite_authority_migration.ts
+++ b/loopx/control_plane/coordination/sqlite_authority_migration.ts
@@ -22,8 +22,9 @@ import type { DatabaseSync } from "node:sqlite";
 import type { JsonObject } from "../effect_program.ts";
 import { AuthorityStoreProtocolError, canonicalAuthorityObject,
   canonicalAuthorityObjectList, requireAuthorityStoreId } from "./authority_store_codec.ts";
-import { authorityStateCheckpointCursor, authorityStateDelta,
-  authorityStateDigest, isAuthorityStateCheckpoint } from "./authority_state_log.ts";
+import { applyAuthorityStateDelta, authorityStateCheckpointCursor, authorityStateDelta,
+  authorityStateDigest, decodeAuthorityStateDelta,
+  isAuthorityStateCheckpoint } from "./authority_state_log.ts";
 import {
   SQLITE_AUTHORITY_STORE_SCHEMA,
   commitDigest,
@@ -192,6 +193,13 @@ function executeSqliteAuthorityMigration(
         }
         const stateDigest = authorityStateDigest(projection);
         const delta = authorityStateDelta(previous ?? {}, projection);
+        // Prove the encoder before anything is written, exactly like a live
+        // commit: replaying the stored delta must reproduce this projection
+        // byte for byte. A retained projection the new format cannot read
+        // would otherwise be copied into V2 and only fail on a later read.
+        if (authorityStateDigest(applyAuthorityStateDelta(previous ?? {}, delta)) !== stateDigest) {
+          throw new AuthorityStoreProtocolError("V1 authority state delta does not reconstruct its commit");
+        }
         if (isAuthorityStateCheckpoint(cursor)) {
           insertCheckpoint.run(cursor.toString(), JSON.stringify(projection), stateDigest);
           checkpoints += 1;
@@ -214,6 +222,11 @@ function executeSqliteAuthorityMigration(
       db.prepare("INSERT INTO head_v2 VALUES (1, ?, ?, ?)").run(cursor.toString(),
         JSON.stringify(previous), previousDigest);
     }
+    // Prove the new format is readable before it is adopted: every retained
+    // row is read back from its stored text and replayed through the codec the
+    // store reads with, so the swap cannot publish a log only its writer can
+    // decode.
+    verifyWrittenStateLogReadable(db, commits);
     // Swap only after every retained row was proved and re-published.
     db.exec("DROP TABLE head");
     db.exec("DROP TABLE commits");
@@ -243,6 +256,78 @@ function executeSqliteAuthorityMigration(
   } finally { db?.close(); }
 }
 
+/**
+ * Read the not-yet-swapped V2 tables back and prove they reconstruct.
+ *
+ * The migration already proved each delta against its in-memory predecessor.
+ * This reads the rows it actually wrote, decodes them with the store's own
+ * delta decoder, replays them from the empty state, and requires every payload
+ * to match the digest the row published. Identical identity and digest columns
+ * alone would not catch a state log the new format cannot read.
+ */
+function verifyWrittenStateLogReadable(db: DatabaseSync, commits: number): void {
+  const page = db.prepare(`SELECT CAST(cursor AS TEXT) AS sequence, state_digest, parent_state_digest,
+      delta FROM commits_v2 WHERE cursor > ? ORDER BY cursor LIMIT ?`);
+  let state: JsonObject = {};
+  let digest: string | null = null;
+  let cursor = 0n;
+  let read = 0;
+  for (;;) {
+    const rows = page.all(cursor.toString(), BigInt(MIGRATION_PAGE)) as unknown as
+      Record<string, unknown>[];
+    if (rows.length === 0) break;
+    for (const row of rows) {
+      const sequence = row.sequence;
+      if (typeof sequence !== "string" || !/^[1-9]\d*$/.test(sequence)) {
+        throw new AuthorityStoreProtocolError("migrated authority store cursor is invalid");
+      }
+      cursor = BigInt(sequence);
+      read += 1;
+      if ((row.parent_state_digest === null ? null : String(row.parent_state_digest)) !== digest) {
+        throw new AuthorityStoreProtocolError("migrated authority state log parent lineage is invalid");
+      }
+      state = applyAuthorityStateDelta(state,
+        decodeAuthorityStateDelta(JSON.parse(String(row.delta)) as unknown));
+      if (authorityStateDigest(state) !== row.state_digest) {
+        throw new AuthorityStoreProtocolError("migrated authority state log digest mismatch");
+      }
+      digest = String(row.state_digest);
+    }
+  }
+  if (read !== commits) {
+    throw new AuthorityStoreProtocolError("migrated authority state log lost retained transactions");
+  }
+  const retainedDigest = db.prepare("SELECT state_digest FROM commits_v2 WHERE cursor = ?");
+  for (const row of db.prepare(`SELECT CAST(cursor AS TEXT) AS sequence, projection, projection_digest
+      FROM checkpoints_v2 ORDER BY cursor`).all() as unknown as Record<string, unknown>[]) {
+    const projection = canonicalAuthorityObject(JSON.parse(String(row.projection)) as unknown,
+      "migrated authority checkpoint projection");
+    if (authorityStateDigest(projection) !== row.projection_digest) {
+      throw new AuthorityStoreProtocolError("migrated authority checkpoint is not readable");
+    }
+    if (retainedDigest.get(String(row.sequence))?.state_digest !== row.projection_digest) {
+      throw new AuthorityStoreProtocolError("migrated authority checkpoint does not cover its cursor");
+    }
+  }
+  const head = db.prepare("SELECT CAST(cursor AS TEXT) AS sequence, projection, state_digest FROM head_v2 WHERE singleton = 1")
+    .get() as Record<string, unknown> | undefined;
+  if (read === 0) {
+    if (head !== undefined) {
+      throw new AuthorityStoreProtocolError(
+        "migrated authority head was published without a retained transaction");
+    }
+    return;
+  }
+  if (head === undefined || head.sequence !== cursor.toString() || head.state_digest !== digest) {
+    throw new AuthorityStoreProtocolError("migrated authority head does not match its state log");
+  }
+  const projection = canonicalAuthorityObject(JSON.parse(String(head.projection)) as unknown,
+    "migrated authority head projection");
+  if (authorityStateDigest(projection) !== digest) {
+    throw new AuthorityStoreProtocolError("migrated authority head is not readable");
+  }
+}
+
 /**
  * Read the migrated store back and prove that its retained transaction
  * identity sequence and authority lineage are exactly the pre-migration ones.
diff --git a/tests/control_plane_ts/authority_state_log.test.ts b/tests/control_plane_ts/authority_state_log.test.ts
index 2a1b0f3227..05e475f133 100644
--- a/tests/control_plane_ts/authority_state_log.test.ts
+++ b/tests/control_plane_ts/authority_state_log.test.ts
@@ -12,6 +12,8 @@ import {
   decodeAuthorityStateDelta,
   isAuthorityStateCheckpoint,
 } from "../../loopx/control_plane/coordination/authority_state_log.ts";
+import {canonicalAuthorityBytes} from
+  "../../loopx/control_plane/coordination/authority_store_codec.ts";
 
 test("authority state deltas reconstruct every committed projection exactly", () => {
   const previous = {
@@ -108,3 +110,43 @@ test("authority state digests and checkpoint windows are stable and bounded", ()
   assert.equal(isAuthorityStateCheckpoint(64n), false);
   assert.throws(() => authorityStateCheckpointCursor(0n), /checkpoint cursor/u);
 });
+
+test("authority state deltas keep every JSON key the stored projection could carry", () => {
+  // V1 retained a whole projection per commit, so every JSON object key was
+  // legal legacy input. The delta codec inherits that contract: an empty key
+  // is an ordinary key, and a `__proto__` key is stored data instead of the
+  // inherited accessor. Keys that only existed in V1 data would otherwise be
+  // copied into the new format and fail on the first read.
+  const text = (value: unknown): string => canonicalAuthorityBytes(value).toString("utf8");
+  const stored = (previous: unknown, next: unknown): unknown => JSON.parse(
+    JSON.stringify(authorityStateDelta(previous as never, next as never))) as unknown;
+
+  const previous = JSON.parse('{"": {"empty": true}, "__proto__": {"own": 1}, "todos": []}') as
+    Record<string, unknown>;
+  const next = JSON.parse('{"": {"empty": false}, "__proto__": {"own": 2},' +
+    ' "nested": {"__proto__": {"deep": true}}, "todos": [{"todo_id": "todo-0"}]}') as
+    Record<string, unknown>;
+  const applied = applyAuthorityStateDelta(previous, decodeAuthorityStateDelta(stored(previous, next)));
+  assert.equal(text(applied), text(next));
+  // The reconstruction is an ordinary JSON object: `__proto__` stayed a key.
+  assert.equal(Object.getPrototypeOf(applied), Object.prototype);
+  assert.deepEqual(Object.keys(applied).sort(), ["", "__proto__", "nested", "todos"]);
+  assert.deepEqual(applied[""], {empty: false});
+  assert.deepEqual(applied["__proto__"], {own: 2});
+  assert.deepEqual(applied["nested"], {["__proto__"]: {deep: true}});
+
+  // Removing a legacy key is legal too, including the empty key and a key that
+  // the previous state only carried inside a nested object.
+  const trimmed = JSON.parse('{"nested": {}, "todos": []}') as Record<string, unknown>;
+  const removal = applyAuthorityStateDelta(next, decodeAuthorityStateDelta(stored(next, trimmed)));
+  assert.equal(text(removal), text(trimmed));
+  assert.deepEqual(Object.keys(removal).sort(), ["nested", "todos"]);
+  assert.equal(Object.hasOwn(removal, "__proto__"), false);
+
+  // A legacy key the delta has to create is an own data property as well.
+  const legacyText = '{"__proto__": {"own": 1}, "": 0}';
+  const created = applyAuthorityStateDelta({},
+    decodeAuthorityStateDelta(stored({}, JSON.parse(legacyText) as Record<string, unknown>)));
+  assert.equal(text(created), text(JSON.parse(legacyText)));
+  assert.equal(Object.getPrototypeOf(created), Object.prototype);
+});
diff --git a/tests/control_plane_ts/sqlite_authority_migration.test.ts b/tests/control_plane_ts/sqlite_authority_migration.test.ts
index 7327682863..0edd906499 100644
--- a/tests/control_plane_ts/sqlite_authority_migration.test.ts
+++ b/tests/control_plane_ts/sqlite_authority_migration.test.ts
@@ -232,6 +232,74 @@ function runMigrationCli(args: readonly string[]): {status: number | null; stdou
     "--experimental-strip-types", script, ...args], {encoding: "utf8"});
 }
 
+/**
+ * Retained V1 history that used only JSON object keys V1 never restricted.
+ *
+ * V1 stored a whole projection per commit, so `""` was an ordinary key and
+ * `__proto__` was data. The migration has to carry both into the new format and
+ * prove they still read back before it commits.
+ */
+function legacyKeySeeds(): SqliteAuthorityV1Seed[] {
+  return [
+    {operation_id: "legacy-op-001",
+      projection: {authority_revision: 1, "": {empty: true}, ["__proto__"]: {own: 1}, todos: []}},
+    {operation_id: "legacy-op-002",
+      projection: {authority_revision: 2, "": {empty: true}, ["__proto__"]: {own: 1},
+        nested: {["__proto__"]: {deep: true}}, todos: [{todo_id: "todo-0", status: "open"}]}},
+    {operation_id: "legacy-op-003",
+      projection: {authority_revision: 3, "": {empty: false}, nested: {},
+        todos: [{todo_id: "todo-0", status: "done"}]}},
+  ];
+}
+
+test("SQLite V1 migration keeps every legacy JSON key readable", async t => {
+  const root = await directory(t);
+  const v1 = createSqliteAuthorityStoreV1(root, GOAL_ID, legacyKeySeeds());
+  const {DatabaseSync: Reader} = createRequire(import.meta.url)("node:sqlite");
+  const legacy = new Reader(v1.path, {readOnly: true});
+  try {
+    // The frozen V1 rows really carry the keys this test is about.
+    const text = String(legacy.prepare("SELECT projection FROM commits WHERE cursor = 2").get()?.projection);
+    assert.match(text, /"__proto__"/u);
+    assert.match(text, /""\s*:/u);
+  } finally { legacy.close(); }
+  const migrated = migrateSqliteAuthorityStoreV1ToV2(root, GOAL_ID, {execute: true});
+  assert.equal(migrated.status, "migrated", JSON.stringify(migrated));
+  assert.equal(migrated.commits, 3);
+  const store = new SqliteAuthorityStore(root, GOAL_ID, {existingOnly: true, expectedIdentity: v1.identity});
+  // The live head reads back as the exact projection the last V1 commit published.
+  const head = await store.loadAuthority();
+  assert.equal(head.status, "loaded", JSON.stringify(head));
+  if (head.status === "loaded") {
+    assert.equal(canonicalAuthorityBytes(head.head).toString("utf8"),
+      JSON.stringify(v1.rows[2]!.operation_receipt.projection));
+    // The empty key survives the migration, and the last commit really did
+    // drop `__proto__` rather than the codec silently dropping it for us.
+    assert.equal(Object.hasOwn(head.head, ""), true);
+    assert.equal(Object.hasOwn(head.head, "__proto__"), false);
+    assert.equal(Object.getPrototypeOf(head.head), Object.prototype);
+  }
+  // A retained projection keeps the legacy `__proto__` key as stored data.
+  const page = await store.scanCommitted(null, 6);
+  assert.equal(page.status, "page", JSON.stringify(page));
+  if (page.status === "page") {
+    const retained = page.transactions[1]!.projection;
+    assert.equal(Object.hasOwn(retained, "__proto__"), true);
+    assert.equal(Object.hasOwn(retained, ""), true);
+    assert.equal(Object.getPrototypeOf(retained), Object.prototype);
+    assert.deepEqual(retained["__proto__"], {own: 1});
+  }
+  // Every retained projection reads back byte-identically, not only the head.
+  const history = await logicalHistory(store);
+  for (const [index, row] of v1.rows.entries()) {
+    const parsed = JSON.parse(history[2 + index]!) as Record<string, unknown>;
+    assert.equal(parsed.cursor, row.cursor);
+    assert.equal(parsed.operation_id, row.operation_id);
+    assert.deepEqual(parsed.projection, JSON.stringify(row.operation_receipt.projection));
+  }
+  assert.equal((await store.verifyAuthorityHistory()).status, "verified");
+});
+
 test("SQLite V1 migration refuses a rewritten proof and leaves the database intact", async t => {
   const root = await directory(t);
   const v1 = createSqliteAuthorityStoreV1(root, GOAL_ID, seeds());