fix(credentials): require full DPAPI provider GUID signature

Accept Windows safeStorage blobs only when they start with version 01 00 00 00 plus provider GUID df9d8cd0-1501-11d1-8c7a-00c04fc297eb, so coincidental 01 00 00 00 prefixes are not treated as ciphertext. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>
fix(credentials): reject impossible v10/v11 ciphertext lengths
2026-10-29 18:11:40 +00:00 · 2026-08-06 05:05:30 +00:00 · 2026-08-06 04:58:58 +00:00 · 2026-08-06 04:53:17 +00:00 · 2026-08-06 04:47:00 +00:00 · 2026-08-06 04:39:56 +00:00
32 changed files with 1218 additions and 188 deletions
@@ -34,7 +34,7 @@ import { buildTelnetDeepLinkConnectionHost, buildTelnetDeepLinkEphemeralHostFrom
 import { buildJmsDeepLinkEphemeralHost, isSupportedJmsProtocol, parseJmsDeepLink } from './domain/jmsDeepLink';
 import { applyEphemeralHostsUpdate, splitHostsUpdateByEphemeral } from './domain/ephemeralHosts';
 import { resolveHostAuth } from './domain/sshAuth';
-import { isEncryptedCredentialPlaceholder } from './domain/credentials';
+import { isEncryptedCredentialPlaceholder, stripSyncPayloadEncryptedCredentials } from './domain/credentials';
 import {
  mergeTerminalHostUpdate,
  TERMINAL_THEME_AUTO,
@@ -664,7 +664,8 @@ function App({ settings }: { settings: SettingsState }) {
      applyProtectedSyncPayload({
        buildPreApplyPayload: () => buildCurrentSyncPayload(),
        applyPayload: async () => {
-          await applySyncPayload(payload, {
+          const portable = stripSyncPayloadEncryptedCredentials(payload);
+          await applySyncPayload(portable, {
            importVaultData: importDataFromString,
            importPortForwardingRules,
            onSettingsApplied: settings.rehydrateAllFromStorage,
@@ -189,7 +189,7 @@ test("loadDefaultKeyPassphrase removes undecryptable credential placeholders", a
  globalThis.localStorage.setItem(
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
    JSON.stringify({
-      [keyPath]: "enc:v1:djEwYWJj",
+      [keyPath]: "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==",
      "/Users/alice/.ssh/id_rsa": "still-valid",
    }),
  );
@@ -206,7 +206,7 @@ test("loadDefaultKeyPassphrase removes undecryptable credential placeholders", a
 test("export read reports unavailable encrypted passphrases without deleting them", async (t) => {
  installLocalStorage(t);
  const keyPath = "/Users/alice/.ssh/id_ed25519";
-  const encrypted = "enc:v1:djEwYWJj";
+  const encrypted = "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==";
  globalThis.localStorage.setItem(
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
    JSON.stringify({ [keyPath]: encrypted }),
@@ -225,7 +225,7 @@ test("export read reports unavailable encrypted passphrases without deleting the
 test("export read retries when the passphrase changes during decryption", async (t) => {
  installLocalStorage(t);
  const keyPath = "/Users/alice/.ssh/id_ed25519";
-  const encrypted = "enc:v1:djEwYWJj";
+  const encrypted = "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==";
  let releaseDecrypt: (() => void) | undefined;
  const decryptGate = new Promise<void>((resolve) => {
    releaseDecrypt = resolve;
@@ -286,7 +286,7 @@ test("remembered passphrase read marks encrypted Keychain placeholders unreadabl
  installLocalStorage(t);
  const key = {
    ...referenceKey(),
-    passphrase: "enc:v1:djEwYWJj",
+    passphrase: "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==",
    savePassphrase: true,
  };

@@ -311,7 +311,7 @@ test("passphrase verification reads every alias and preserves unreadable state",
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
    JSON.stringify({
      "~/.ssh/id_ed25519": "readable-secret",
-      "/Users/alice/.ssh/id_ed25519": "enc:v1:djEwYWJj",
+      "/Users/alice/.ssh/id_ed25519": "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==",
    }),
  );

@@ -455,7 +455,7 @@ test("loadDefaultKeyPassphrase cleanup preserves a passphrase saved concurrently
  });
  globalThis.localStorage.setItem(
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
-    JSON.stringify({ "/Users/alice/.ssh/id_old": "enc:v1:djEwYWJj" }),
+    JSON.stringify({ "/Users/alice/.ssh/id_old": "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==" }),
  );

  const pendingLoad = loadDefaultKeyPassphrase("/Users/alice/.ssh/id_old");
@@ -549,7 +549,7 @@ test("loadDefaultKeyPassphrase prefers an exact saved path over a stale alias",
  globalThis.localStorage.setItem(
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
    JSON.stringify({
-      "~/.ssh/id_ed25519": "enc:v1:djEwYWJj",
+      "~/.ssh/id_ed25519": "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==",
      "/Users/alice/.ssh/id_ed25519": "valid-exact-passphrase",
    }),
  );
@@ -574,7 +574,7 @@ test("loadDefaultKeyPassphrase falls back to a valid alias and removes an invali
    STORAGE_KEY_DEFAULT_KEY_PASSPHRASES,
    JSON.stringify({
      "~/.ssh/id_ed25519": "valid-alias-passphrase",
-      "/Users/alice/.ssh/id_ed25519": "enc:v1:djEwYWJj",
+      "/Users/alice/.ssh/id_ed25519": "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==",
    }),
  );

@@ -913,7 +913,7 @@ test("shouldUpdateReferenceKeyPassphrase replaces missing or undecryptable passp
  assert.equal(
    shouldUpdateReferenceKeyPassphrase({
      ...referenceKey(),
-      passphrase: "enc:v1:djEwAAAA",
+      passphrase: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    }),
    true,
  );
@@ -232,7 +232,7 @@ test("buildSftpHostCredentials rejects proxy identities with blank usernames eve
        label: "Proxy login",
        username: " ",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -285,7 +285,7 @@ test("buildSftpHostCredentials rejects incomplete proxy identities on jump hosts
        label: "Proxy login",
        username: "",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -368,7 +368,7 @@ test("buildSftpHostCredentials rejects undecryptable proxy identity passwords",
        label: "Proxy login",
        username: "proxy-user",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -434,7 +434,7 @@ test("buildSftpHostCredentials rejects undecryptable jump host proxy identity pa
        label: "Proxy login",
        username: "proxy-user",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -539,7 +539,7 @@ test("buildSftpHostCredentials rejects undecryptable saved password credentials"
    () => buildSftpHostCredentials({
      host: host({
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      }),
      hosts: [],
      keys: [],
@@ -553,7 +553,7 @@ test("buildSftpHostCredentials keeps automatic target discovery available with a
  const credentials = buildSftpHostCredentials({
    host: host({
      authMethod: "auto",
-      password: "enc:v1:djEwAAAA",
+      password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    }),
    hosts: [],
    keys: [],
@@ -569,7 +569,7 @@ test("buildSftpHostCredentials keeps automatic jump discovery available with an
    id: "jump-1",
    label: "Jump",
    authMethod: "auto",
-    password: "enc:v1:djEwAAAA",
+    password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
  });
  const credentials = buildSftpHostCredentials({
    host: host({ hostChain: { hostIds: ["jump-1"] } }),
@@ -604,7 +604,7 @@ test("buildSftpHostCredentials rejects undecryptable saved key material without
    id: "key-1",
    label: "Imported key",
    type: "ED25519",
-    privateKey: "enc:v1:djEwAAAA",
+    privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    source: "imported",
    category: "key",
    created: 1,
@@ -626,7 +626,7 @@ test("buildSftpHostCredentials does not use stale local key paths when a selecte
    id: "key-1",
    label: "Imported key",
    type: "ED25519",
-    privateKey: "enc:v1:djEwAAAA",
+    privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    source: "imported",
    category: "key",
    created: 1,
@@ -653,7 +653,7 @@ test("buildSftpHostCredentials uses the system agent when a synced key cannot be
    label: "Synced key",
    type: "ED25519",
    publicKey: "ssh-ed25519 AAAASELECTED",
-    privateKey: "enc:v1:djEwAAAA",
+    privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    source: "imported",
    category: "key",
    created: 1,
@@ -191,3 +191,48 @@ test("auto-sync skips only the exact remote-applied data hash", () => {
    "remote-apply skip hash must survive temporary sync blockers and clear only after a successful sync",
  );
 });
+
+test("startup local-wins and merge round-trips refuse device-bound credential placeholders", () => {
+  const source = readFileSync(new URL("./useAutoSync.ts", import.meta.url), "utf8");
+  const uploadLocalIndex = source.indexOf("if (conflictAction === 'upload-local')");
+  const uploadGuardIndex = source.indexOf(
+    "findSyncPayloadEncryptedCredentialPaths(localPayload)",
+    uploadLocalIndex,
+  );
+  const uploadPushIndex = source.indexOf("manager.syncAllProviders(localPayload)", uploadGuardIndex);
+  const mergeRoundTripBlockIndex = source.indexOf(
+    "stripSyncPayloadEncryptedCredentials(mergeResult.payload)",
+  );
+  const mergeLocalHealIndex = source.indexOf(
+    "healPoisonedSecretsForMerge(localPayload, remoteRaw, base)",
+  );
+  const mergeRemoteHealIndex = source.indexOf(
+    "healPoisonedSecretsForMerge(remoteRaw, localPayload, base)",
+  );
+  const mergePushIndex = source.indexOf(
+    "manager.syncAllProviders(portableMerge)",
+    mergeRoundTripBlockIndex,
+  );
+  const stripRemoteIndex = source.indexOf(
+    "stripSyncPayloadEncryptedCredentials(remoteRaw)",
+  );
+
+  assert.notEqual(uploadLocalIndex, -1);
+  assert.notEqual(uploadGuardIndex, -1);
+  assert.notEqual(uploadPushIndex, -1);
+  assert.notEqual(mergeLocalHealIndex, -1);
+  assert.notEqual(mergeRemoteHealIndex, -1);
+  assert.notEqual(mergeRoundTripBlockIndex, -1);
+  assert.notEqual(mergePushIndex, -1);
+  assert.notEqual(stripRemoteIndex, -1);
+  assert.ok(
+    uploadGuardIndex < uploadPushIndex,
+    "startup local-wins must guard placeholders before syncAllProviders",
+  );
+  assert.ok(
+    mergeLocalHealIndex < mergeRoundTripBlockIndex
+      && mergeRemoteHealIndex < mergeRoundTripBlockIndex
+      && mergeRoundTripBlockIndex < mergePushIndex,
+    "startup merge must heal local+remote secrets, then strip, then upload",
+  );
+});
@@ -14,6 +14,8 @@ import { getCloudSyncManager } from '../../infrastructure/services/CloudSyncMana
 import { netcattyBridge } from '../../infrastructure/services/netcattyBridge';
 import {
  findSyncPayloadEncryptedCredentialPaths,
+  healPoisonedSecretsForMerge,
+  stripSyncPayloadEncryptedCredentials,
 } from '../../domain/credentials';
 import { isProviderReadyForSync, type CloudProvider, type SyncPayload } from '../../domain/sync';
 import { mergeSyncPayloads } from '../../domain/syncMerge';
@@ -435,13 +437,14 @@ export const useAutoSync = (config: AutoSyncConfig) => {

      for (const result of resultList) {
        if (result.mergedPayload && !result.mergedPayloadApplied) {
-          await Promise.resolve(onApplyPayload(result.mergedPayload));
+          const portableMerged = stripSyncPayloadEncryptedCredentials(result.mergedPayload);
+          await Promise.resolve(onApplyPayload(portableMerged));
          if (result.remoteFile) {
-            await sync.commitRemoteInspection(result.provider, result.remoteFile, result.mergedPayload, {
+            await sync.commitRemoteInspection(result.provider, result.remoteFile, portableMerged, {
              recordDownload: true,
            });
          }
-          skipNextSyncHashRef.current = allProvidersSynced ? getSyncPayloadDataHash(result.mergedPayload) : null;
+          skipNextSyncHashRef.current = allProvidersSynced ? getSyncPayloadDataHash(portableMerged) : null;
          if (!allProvidersSynced) {
            console.warn('[AutoSync] Remote payload applied locally, but not every provider synced; leaving next auto-sync enabled for retry.');
          }
@@ -707,7 +710,11 @@ export const useAutoSync = (config: AutoSyncConfig) => {
      inspectedRemoteChange = true;

      const remoteFile = inspection.remoteFile;
-      const remotePayload = inspection.payload;
+      const remoteRaw = inspection.payload;
+      // Strip device-bound enc:v1 for download/apply paths so poisoned cloud
+      // snapshots restore usable host shells. Smart-merge heals from local/base
+      // separately below so good secrets are not treated as remote deletions.
+      const remotePayload = stripSyncPayloadEncryptedCredentials(remoteRaw);
      const localPayload = await buildPayloadRef.current();

      // If local vault is empty but cloud has data, this almost certainly
@@ -778,6 +785,14 @@ export const useAutoSync = (config: AutoSyncConfig) => {
      }

      if (conflictAction === 'upload-local') {
+        const encryptedCredentialPaths = findSyncPayloadEncryptedCredentialPaths(localPayload);
+        if (encryptedCredentialPaths.length > 0) {
+          console.warn(
+            '[AutoSync] Startup local-wins blocked: encrypted credential placeholders found at:',
+            encryptedCredentialPaths.join(', '),
+          );
+          throw new Error(tRef.current('sync.credentialsUnavailable'));
+        }
        const pushResults = await manager.syncAllProviders(localPayload);
        const results = Array.from(pushResults.values());
        commitPluginSidecarsAfterSuccessfulSync(localPayload, results);
@@ -797,15 +812,20 @@ export const useAutoSync = (config: AutoSyncConfig) => {
        throw new Error('Startup local-wins sync failed for one or more providers');
      }

-      const mergeResult = mergeSyncPayloads(base, localPayload, remotePayload);
+      // Prefer usable secrets from the opposite side / base over enc:v1
+      // placeholders before merge. Otherwise smart-merge can pick a "changed"
+      // local entity whose only secret change is ciphertext, then strip +
+      // upload and wipe usable cloud passwords. Same for remote-side poison.
+      const localHealed = healPoisonedSecretsForMerge(localPayload, remoteRaw, base);
+      const remoteHealed = healPoisonedSecretsForMerge(remoteRaw, localPayload, base);
+      const mergeResult = mergeSyncPayloads(base, localHealed, remoteHealed);

      // Apply merged payload to local state BEFORE committing. If the apply
      // throws, the next startup will re-run the merge with fresh data.
-      await Promise.resolve(onApplyPayloadRef.current(mergeResult.payload));
-      // Base is the last-agreed remote snapshot; `commitRemoteInspection`
-      // stores remotePayload as the base so the next diff is computed
-      // against what the cloud actually has, not against the merged
-      // local-only state.
+      const portableMerge = stripSyncPayloadEncryptedCredentials(mergeResult.payload);
+      await Promise.resolve(onApplyPayloadRef.current(portableMerge));
+      // Base is the last-agreed remote snapshot; store the portable remote
+      // view so future diffs never treat device-bound enc:v1 as cloud truth.
      await manager.commitRemoteInspection(connectedProvider, remoteFile, remotePayload);
      startupConsistent = true;
      markCurrentDataSynced = false;
@@ -826,9 +846,9 @@ export const useAutoSync = (config: AutoSyncConfig) => {
      // that only approximated the correct ordering.
      if (mergeResult.payload) {
        try {
-          const roundTripResults = await manager.syncAllProviders(mergeResult.payload);
+          const roundTripResults = await manager.syncAllProviders(portableMerge);
          const roundTripResultList = Array.from(roundTripResults.values());
-          commitPluginSidecarsAfterSuccessfulSync(mergeResult.payload, roundTripResultList);
+          commitPluginSidecarsAfterSuccessfulSync(portableMerge, roundTripResultList);
          const wasShrinkBlocked = roundTripResultList.some((r) => r.shrinkBlocked === true);
          const roundTripFullySynced = roundTripResultList.length > 0
            && roundTripResultList.every((result) => result.success);
@@ -989,6 +989,10 @@ export const useVaultState = () => {
              ),
            );
            setHosts(sanitized);
+            // Always re-encrypt the batch. Stale enc:v1 placeholders are left
+            // unchanged by encryptCredentialValue (no double-wrap); plaintext
+            // siblings still need encryption when safeStorage was previously
+            // unavailable for some records.
            encryptHosts(sanitized).then((enc) => {
              if (ver === hostsWriteVersion.current)
                localStorageAdapter.write(STORAGE_KEY_HOSTS, enc);
@@ -212,13 +212,13 @@ test("buildSyncPayload includes AI configuration settings", () => {
    id: "openai-main",
    providerId: "openai",
    name: "OpenAI",
-    apiKey: "enc:v1:test",
+    apiKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    defaultModel: "gpt-test",
    enabled: true,
  }];
  const webSearch = {
    providerId: "tavily",
-    apiKey: "enc:v1:web",
+    apiKey: "enc:v1:djEwd2ViAAAAAAAAAAAAAAAAAA==",
    enabled: true,
    maxResults: 7,
  };
@@ -239,8 +239,11 @@ test("buildSyncPayload includes AI configuration settings", () => {

  const payload = buildSyncPayload(vault([]));

+  // Device-bound enc:v1 apiKeys are stripped from portable sync settings.
+  const { apiKey: _providerKey, ...providerWithoutKey } = providers[0]!;
+  const { apiKey: _webKey, ...webSearchWithoutKey } = webSearch;
  assert.deepEqual(payload.settings?.ai, {
-    providers,
+    providers: [providerWithoutKey],
    activeProviderId: "openai-main",
    activeModelId: "gpt-test",
    globalPermissionMode: "auto",
@@ -251,7 +254,7 @@ test("buildSyncPayload includes AI configuration settings", () => {
    maxIterations: 10,
    agentModelMap: { codex: "gpt-test" },
    agentProviderMap: { catty: "openai-main" },
-    webSearchConfig: webSearch,
+    webSearchConfig: webSearchWithoutKey,
    showTerminalSelectionAction: false,
  });
 });
@@ -340,12 +343,12 @@ test("buildSyncPayload omits device-bound encrypted AI API keys", () => {
    id: "openai-main",
    providerId: "openai",
    name: "OpenAI",
-    apiKey: "enc:v1:djEwAAAA",
+    apiKey: "enc:v1:djEwQUFBQQAAAAAAAAAAAAAAAA==",
    enabled: true,
  }]));
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH, JSON.stringify({
    providerId: "tavily",
-    apiKey: "enc:v1:djEwAAAA",
+    apiKey: "enc:v1:djEwQUFBQQAAAAAAAAAAAAAAAA==",
    enabled: true,
  }));

@@ -360,8 +363,8 @@ test("buildCloudSyncPayload includes decrypted AI API keys for portable cloud sy
    value: {
      netcatty: {
        credentialsDecrypt: async (value: string) => {
-          if (value === "enc:v1:djEwPROVIDER") return "sk-provider";
-          if (value === "enc:v1:djEwWEB") return "sk-web";
+          if (value === "enc:v1:djEwUFJPVklERVIAAAAAAAAAAA==") return "sk-provider";
+          if (value === "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==") return "sk-web";
          return value;
        },
      },
@@ -373,12 +376,12 @@ test("buildCloudSyncPayload includes decrypted AI API keys for portable cloud sy
    id: "openai-main",
    providerId: "openai",
    name: "OpenAI",
-    apiKey: "enc:v1:djEwPROVIDER",
+    apiKey: "enc:v1:djEwUFJPVklERVIAAAAAAAAAAA==",
    enabled: true,
  }]));
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH, JSON.stringify({
    providerId: "tavily",
-    apiKey: "enc:v1:djEwWEB",
+    apiKey: "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==",
    enabled: true,
  }));

@@ -402,7 +405,7 @@ test("buildCloudSyncPayload fails instead of deleting API keys when decrypt fail
    id: "openai-main",
    providerId: "openai",
    name: "OpenAI",
-    apiKey: "enc:v1:djEwPROVIDER",
+    apiKey: "enc:v1:djEwUFJPVklERVIAAAAAAAAAAA==",
    enabled: true,
  }]));

@@ -417,12 +420,12 @@ test("applySyncPayload restores AI configuration settings", async () => {
    id: "anthropic-main",
    providerId: "anthropic",
    name: "Anthropic",
-    apiKey: "enc:v1:test",
+    apiKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    enabled: true,
  }];
  const webSearch = {
    providerId: "exa",
-    apiKey: "enc:v1:web",
+    apiKey: "enc:v1:djEwd2ViAAAAAAAAAAAAAAAAAA==",
    enabled: true,
  };

@@ -473,7 +476,12 @@ test("applySyncPayload encrypts synced plaintext AI API keys before saving local
  Object.defineProperty(globalThis, "window", {
    value: {
      netcatty: {
-        credentialsEncrypt: async (value: string) => `enc:v1:djEwLOCAL_${value}`,
+        credentialsEncrypt: async (value: string) => {
+          const body = Buffer.alloc(19, 0);
+          Buffer.from("v10", "utf8").copy(body, 0);
+          Buffer.from(`LOCAL_${value}`.slice(0, 16), "utf8").copy(body, 3);
+          return `enc:v1:${body.toString("base64")}`;
+        },
      },
      dispatchEvent: () => true,
    },
@@ -501,8 +509,20 @@ test("applySyncPayload encrypts synced plaintext AI API keys before saving local

  const provider = JSON.parse(localStorage.getItem(storageKeys.STORAGE_KEY_AI_PROVIDERS)!)[0];
  const webSearch = JSON.parse(localStorage.getItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH)!);
-  assert.equal(provider.apiKey, "enc:v1:djEwLOCAL_sk-provider");
-  assert.equal(webSearch.apiKey, "enc:v1:djEwLOCAL_sk-web");
+  const expectedProviderKey = (() => {
+    const body = Buffer.alloc(19, 0);
+    Buffer.from("v10", "utf8").copy(body, 0);
+    Buffer.from("LOCAL_sk-provider".slice(0, 16), "utf8").copy(body, 3);
+    return `enc:v1:${body.toString("base64")}`;
+  })();
+  const expectedWebKey = (() => {
+    const body = Buffer.alloc(19, 0);
+    Buffer.from("v10", "utf8").copy(body, 0);
+    Buffer.from("LOCAL_sk-web".slice(0, 16), "utf8").copy(body, 3);
+    return `enc:v1:${body.toString("base64")}`;
+  })();
+  assert.equal(provider.apiKey, expectedProviderKey);
+  assert.equal(webSearch.apiKey, expectedWebKey);
 });

 test("applySyncPayload restores host tree sidebar visibility setting", async () => {
@@ -658,14 +678,14 @@ test("applySyncPayload preserves local AI provider apiKeys when synced payload o
      id: "openai-main",
      providerId: "openai",
      name: "OpenAI",
-      apiKey: "enc:v1:djEwLOCAL",
+      apiKey: "enc:v1:djEwTE9DQUwAAAAAAAAAAAAAAA==",
      enabled: true,
    },
    {
      id: "anthropic-main",
      providerId: "anthropic",
      name: "Anthropic",
-      apiKey: "enc:v1:djEwANTHROPIC",
+      apiKey: "enc:v1:djEwQU5USFJPUElDAAAAAAAAAA==",
      enabled: true,
    },
  ];
@@ -696,14 +716,14 @@ test("applySyncPayload preserves local AI provider apiKeys when synced payload o
      id: "openai-main",
      providerId: "openai",
      name: "OpenAI (renamed)",
-      apiKey: "enc:v1:djEwLOCAL",
+      apiKey: "enc:v1:djEwTE9DQUwAAAAAAAAAAAAAAA==",
      enabled: true,
    },
    {
      id: "anthropic-main",
      providerId: "anthropic",
      name: "Anthropic",
-      apiKey: "enc:v1:djEwANTHROPIC",
+      apiKey: "enc:v1:djEwQU5USFJPUElDAAAAAAAAAA==",
      enabled: false,
    },
  ]);
@@ -711,7 +731,7 @@ test("applySyncPayload preserves local AI provider apiKeys when synced payload o

 test("applySyncPayload prefers explicit synced apiKey over local apiKey", async () => {
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_PROVIDERS, JSON.stringify([
-    { id: "openai-main", providerId: "openai", name: "OpenAI", apiKey: "enc:v1:djEwLOCAL", enabled: true },
+    { id: "openai-main", providerId: "openai", name: "OpenAI", apiKey: "enc:v1:djEwTE9DQUwAAAAAAAAAAAAAAA==", enabled: true },
  ]));

  const payload: SyncPayload = {
@@ -739,7 +759,7 @@ test("applySyncPayload prefers explicit synced apiKey over local apiKey", async
 test("applySyncPayload preserves local web-search apiKey when synced config omits it", async () => {
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH, JSON.stringify({
    providerId: "tavily",
-    apiKey: "enc:v1:djEwWEB",
+    apiKey: "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==",
    enabled: true,
    maxResults: 7,
  }));
@@ -763,7 +783,7 @@ test("applySyncPayload preserves local web-search apiKey when synced config omit
  const stored = JSON.parse(localStorage.getItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH)!);
  assert.deepEqual(stored, {
    providerId: "tavily",
-    apiKey: "enc:v1:djEwWEB",
+    apiKey: "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==",
    enabled: false,
    maxResults: 12,
  });
@@ -772,7 +792,7 @@ test("applySyncPayload preserves local web-search apiKey when synced config omit
 test("applySyncPayload drops local web-search apiKey when synced config switches provider", async () => {
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH, JSON.stringify({
    providerId: "tavily",
-    apiKey: "enc:v1:djEwWEB",
+    apiKey: "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==",
    enabled: true,
  }));

@@ -1046,19 +1066,19 @@ test("buildLocalVaultPayload preserves local AI API keys for protective backups"
    id: "openai-main",
    providerId: "openai",
    name: "OpenAI",
-    apiKey: "enc:v1:djEwPROVIDER",
+    apiKey: "enc:v1:djEwUFJPVklERVIAAAAAAAAAAA==",
    enabled: true,
  }]));
  localStorage.setItem(storageKeys.STORAGE_KEY_AI_WEB_SEARCH, JSON.stringify({
    providerId: "tavily",
-    apiKey: "enc:v1:djEwWEB",
+    apiKey: "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==",
    enabled: true,
  }));

  const payload = buildLocalVaultPayload(vault([]));

-  assert.equal(payload.settings?.ai?.providers?.[0]?.apiKey, "enc:v1:djEwPROVIDER");
-  assert.equal(payload.settings?.ai?.webSearchConfig?.apiKey, "enc:v1:djEwWEB");
+  assert.equal(payload.settings?.ai?.providers?.[0]?.apiKey, "enc:v1:djEwUFJPVklERVIAAAAAAAAAAA==");
+  assert.equal(payload.settings?.ai?.webSearchConfig?.apiKey, "enc:v1:djEwV0VCAAAAAAAAAAAAAAAAAA==");
 });

 test("applySyncPayload ignores legacy cloud known hosts", async () => {
@@ -1497,6 +1517,51 @@ test("prepareLocalVaultPayloadApply does not import until the prepared callback
  assert.deepEqual(calls, ["prepare", "import", "commit"]);
 });

+test("prepareLocalVaultPayloadApply sanitizes enc:v1 before convergent prepare and apply", async () => {
+  const completeBlob = Buffer.alloc(31, 0);
+  Buffer.from("v10", "utf8").copy(completeBlob, 0);
+  const ENC = `enc:v1:${completeBlob.toString("base64")}`;
+  const preparedPayloads: SyncPayload[] = [];
+  const imported: Array<Record<string, unknown>> = [];
+
+  const applyPreparedPayload = await prepareLocalVaultPayloadApply({
+    hosts: [{
+      id: "h1",
+      label: "prod",
+      hostname: "prod.example",
+      username: "root",
+      password: ENC,
+      port: 22,
+      os: "linux",
+      group: "",
+      tags: [],
+      protocol: "ssh",
+    }],
+    keys: [],
+    identities: [],
+    snippets: [],
+    customGroups: [],
+    syncedAt: 1,
+  }, {
+    importVaultData: (json) => {
+      imported.push(JSON.parse(json) as Record<string, unknown>);
+    },
+  }, {
+    prepareConvergentRestore: async (payload) => {
+      preparedPayloads.push(payload);
+      return async () => undefined;
+    },
+  });
+
+  await applyPreparedPayload();
+
+  assert.equal(preparedPayloads.length, 1);
+  assert.equal(preparedPayloads[0]?.hosts[0]?.password, undefined);
+  assert.equal(imported.length, 1);
+  const hosts = imported[0]?.hosts as Array<{ password?: string }> | undefined;
+  assert.equal(hosts?.[0]?.password, undefined);
+});
+
 test("applyLocalVaultPayload leaves local data untouched when convergent preparation fails", async () => {
  let imported = false;
  const payload: SyncPayload = {
@@ -32,7 +32,10 @@ import {
  parseCustomKeyBindingsStorageRecord,
  serializeCustomKeyBindingsStorageRecord,
 } from '../domain/customKeyBindings';
-import { isEncryptedCredentialPlaceholder } from '../domain/credentials';
+import {
+  isEncryptedCredentialPlaceholder,
+  stripSyncPayloadEncryptedCredentials,
+} from '../domain/credentials';
 import { localStorageAdapter } from '../infrastructure/persistence/localStorageAdapter';
 import { decryptField, encryptField } from '../infrastructure/persistence/secureFieldAdapter';
 import { sanitizeQuickMessages } from '../infrastructure/ai/quickMessages';
@@ -1079,31 +1082,35 @@ function applyPayload(
    applyPluginSidecars?: PluginSyncSidecarApplier;
  },
 ): Promise<void> {
-  const legacyLineTimestampsEnabled = payload.settings?.terminalSettings?.showLineTimestamps === true;
+  // Portable payloads must never keep device-bound enc:v1 blobs. Strip them
+  // so a previously poisoned cloud/backup snapshot can still restore host
+  // shells and let the user re-enter secrets (#2702).
+  const sanitizedPayload = stripSyncPayloadEncryptedCredentials(payload);
+  const legacyLineTimestampsEnabled = sanitizedPayload.settings?.terminalSettings?.showLineTimestamps === true;
  // Build the vault import object. Cloud sync intentionally ignores
  // local-only trust records even if legacy cloud snapshots still carry them.
  const vaultImport: Record<string, unknown> = {
-    hosts: migrateHostsFromLegacyLineTimestamps(payload.hosts, legacyLineTimestampsEnabled),
-    keys: payload.keys,
-    identities: payload.identities,
-    proxyProfiles: payload.proxyProfiles,
-    snippets: payload.snippets,
-    customGroups: payload.customGroups,
+    hosts: migrateHostsFromLegacyLineTimestamps(sanitizedPayload.hosts, legacyLineTimestampsEnabled),
+    keys: sanitizedPayload.keys,
+    identities: sanitizedPayload.identities,
+    proxyProfiles: sanitizedPayload.proxyProfiles,
+    snippets: sanitizedPayload.snippets,
+    customGroups: sanitizedPayload.customGroups,
  };
-  if (payload.snippetPackages !== undefined) {
-    vaultImport.snippetPackages = payload.snippetPackages;
+  if (sanitizedPayload.snippetPackages !== undefined) {
+    vaultImport.snippetPackages = sanitizedPayload.snippetPackages;
  }
-  if (payload.notes !== undefined) {
-    vaultImport.notes = payload.notes;
+  if (sanitizedPayload.notes !== undefined) {
+    vaultImport.notes = sanitizedPayload.notes;
  }
-  if (payload.noteGroups !== undefined) {
-    vaultImport.noteGroups = payload.noteGroups;
+  if (sanitizedPayload.noteGroups !== undefined) {
+    vaultImport.noteGroups = sanitizedPayload.noteGroups;
  }
-  if (options.includeLocalOnlyData && payload.knownHosts !== undefined) {
-    vaultImport.knownHosts = payload.knownHosts;
+  if (options.includeLocalOnlyData && sanitizedPayload.knownHosts !== undefined) {
+    vaultImport.knownHosts = sanitizedPayload.knownHosts;
  }
-  if (Array.isArray(payload.groupConfigs)) {
-    vaultImport.groupConfigs = payload.groupConfigs;
+  if (Array.isArray(sanitizedPayload.groupConfigs)) {
+    vaultImport.groupConfigs = sanitizedPayload.groupConfigs;
  }

  return Promise.resolve(importers.importVaultData(JSON.stringify(vaultImport))).then(async () => {
@@ -1111,23 +1118,23 @@ function applyPayload(
    // them.  Absent field = "payload was created before this feature existed",
    // so local rules are preserved.  Explicitly present [] = "remote has no
    // rules, clear local state".
-    if (payload.portForwardingRules !== undefined && importers.importPortForwardingRules) {
-      importers.importPortForwardingRules(payload.portForwardingRules);
+    if (sanitizedPayload.portForwardingRules !== undefined && importers.importPortForwardingRules) {
+      importers.importPortForwardingRules(sanitizedPayload.portForwardingRules);
    }

    // Apply synced settings
-    if (payload.settings) {
-      await applySyncableSettings(payload.settings);
+    if (sanitizedPayload.settings) {
+      await applySyncableSettings(sanitizedPayload.settings);
      // Rehydrate in-memory bookmark snapshot after localStorage was updated
-      if (payload.settings.sftpGlobalBookmarks != null) rehydrateGlobalSftpBookmarks();
+      if (sanitizedPayload.settings.sftpGlobalBookmarks != null) rehydrateGlobalSftpBookmarks();
      importers.onSettingsApplied?.();
    }

    // Plugin encrypted sidecars: only apply when the field is present so
    // legacy payloads without pluginSidecars do not wipe installed settings.
-    if (Object.prototype.hasOwnProperty.call(payload, 'pluginSidecars')) {
+    if (Object.prototype.hasOwnProperty.call(sanitizedPayload, 'pluginSidecars')) {
      const applySidecars = options.applyPluginSidecars ?? defaultApplyPluginSyncSidecars;
-      await applySidecars(payload.pluginSidecars ?? { version: 1, entries: [] });
+      await applySidecars(sanitizedPayload.pluginSidecars ?? { version: 1, entries: [] });
    }
  });
 }
@@ -1154,11 +1161,14 @@ export async function prepareLocalVaultPayloadApply(
    ) => Promise<() => Promise<void>>;
  } = {},
 ): Promise<() => Promise<void>> {
+  // Sanitize once so vault import and convergent replica commit share the
+  // same portable secrets view (no device-bound enc:v1 leftovers).
+  const sanitizedPayload = stripSyncPayloadEncryptedCredentials(payload);
  const prepareConvergentRestore = dependencies.prepareConvergentRestore
    ?? prepareRestoredPayloadConvergentWrites;
-  const commitConvergentRestore = await prepareConvergentRestore(payload);
+  const commitConvergentRestore = await prepareConvergentRestore(sanitizedPayload);
  return async () => {
-    await applyPayload(payload, importers, { includeLocalOnlyData: true });
+    await applyPayload(sanitizedPayload, importers, { includeLocalOnlyData: true });
    await commitConvergentRestore();
  };
 }
@@ -111,7 +111,7 @@ test("CSV credentials exclude an explicitly unsaved Keychain passphrase for a di
 test("CSV credentials warn when a saved reference-key passphrase cannot be read", async () => {
  const result = await buildVaultCsvCredentialOptions(
    [host("key-1")],
-    [referenceKey({ savePassphrase: true, passphrase: "enc:v1:djEwYWJj" })],
+    [referenceKey({ savePassphrase: true, passphrase: "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==" })],
    async () => ({ values: [], unreadable: false, present: false }),
  );

@@ -19,6 +19,7 @@ import {
 import { useI18n } from '../application/i18n/I18nProvider';
 import {
    findSyncPayloadEncryptedCredentialPaths,
+    stripSyncPayloadEncryptedCredentials,
 } from '../domain/credentials';
 import {
    isProviderReadyForSync,
@@ -675,9 +676,10 @@ const SyncDashboard: React.FC<SyncDashboardProps> = ({
            // requested provider fails, another provider can verify a newer
            // joined replica that must be applied before reporting the error.
            if (result.mergedPayload && !result.mergedPayloadApplied && onApplyPayload) {
-                await Promise.resolve(onApplyPayload(result.mergedPayload));
+                const portableMerged = stripSyncPayloadEncryptedCredentials(result.mergedPayload);
+                await Promise.resolve(onApplyPayload(portableMerged));
                if (result.remoteFile) {
-                    await sync.commitRemoteInspection(result.provider, result.remoteFile, result.mergedPayload, {
+                    await sync.commitRemoteInspection(result.provider, result.remoteFile, portableMerged, {
                        recordDownload: true,
                    });
                }
@@ -703,13 +705,14 @@ const SyncDashboard: React.FC<SyncDashboardProps> = ({
                // USE_REMOTE applies cloud data over local — same data-loss
                // shape as a local backup restore, so gate auto-sync in
                // every other window the same way.
+                const portableRemote = stripSyncPayloadEncryptedCredentials(remoteResult.payload);
                await withRestoreBarrier(async () => {
-                    await Promise.resolve(onApplyPayload(remoteResult.payload));
+                    await Promise.resolve(onApplyPayload(portableRemote));
                });
                await sync.commitRemoteInspection(
                    remoteResult.provider,
                    remoteResult.remoteFile,
-                    remoteResult.payload,
+                    portableRemote,
                    { recordDownload: true },
                );
                toast.success(t('cloudSync.resolve.downloaded'));
@@ -746,9 +749,10 @@ const SyncDashboard: React.FC<SyncDashboardProps> = ({
                    // reflects what's now on cloud (in case remote changed during the merge).
                    for (const result of (results as Map<CloudProvider, SyncResult>).values()) {
                        if (result.mergedPayload && !result.mergedPayloadApplied) {
-                            await Promise.resolve(onApplyPayload(result.mergedPayload));
+                            const portableMerged = stripSyncPayloadEncryptedCredentials(result.mergedPayload);
+                            await Promise.resolve(onApplyPayload(portableMerged));
                            if (result.remoteFile) {
-                                await sync.commitRemoteInspection(result.provider, result.remoteFile, result.mergedPayload, {
+                                await sync.commitRemoteInspection(result.provider, result.remoteFile, portableMerged, {
                                    recordDownload: true,
                                });
                            }
@@ -406,7 +406,7 @@ test("validateProxyConfigForSave rejects unreadable proxy identity passwords", (
        label: "Proxy login",
        username: "proxy-user",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -459,7 +459,7 @@ test("prepareProxyConfigForSave returns identity errors before save handlers bui
        label: "Proxy login",
        username: "",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    }),
@@ -178,7 +178,7 @@ test("ProxyPanel warns when a saved proxy profile has an unreadable identity pas
      },
    }],
    selectedProxyProfileId: proxyProfile.id,
-    identities: [{ ...proxyIdentity, password: "enc:v1:djEwAAAA" }],
+    identities: [{ ...proxyIdentity, password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }],
  });

  assert.match(markup, /Proxy identity password cannot be read/);
@@ -193,7 +193,7 @@ test("prepareProxyProfileForSave rejects unreadable proxy identity passwords", (
          identityId: proxyIdentity.id,
        },
      },
-      [{ ...proxyIdentity, password: "enc:v1:djEwAAAA" }],
+      [{ ...proxyIdentity, password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }],
    ).error,
    "unreadableIdentity",
  );
@@ -2,6 +2,7 @@ import React, { type Dispatch, type MutableRefObject, type SetStateAction } from
 import { AlertTriangle, Cloud, Database, Download, History, Key, Loader2, ShieldCheck, Trash2 } from 'lucide-react';
 import type { CloudProvider, ConflictResolution, SyncPayload, SyncResult, WebDAVAuthType } from '../../domain/sync';
 import type { ShrinkFinding } from '../../domain/syncGuards';
+import { stripSyncPayloadEncryptedCredentials } from '../../domain/credentials';
 import type { useCloudSync } from '../../application/state/useCloudSync';
 import { cn } from '../../lib/utils';
 import { Button } from '../ui/button';
@@ -901,9 +902,10 @@ export const CloudSyncDialogs: React.FC<CloudSyncDialogsProps> = ({
                                        // re-deleting the remote additions we just merged in.
                                        for (const result of results.values()) {
                                            if (result.mergedPayload && !result.mergedPayloadApplied) {
-                                                await Promise.resolve(onApplyPayload(result.mergedPayload));
+                                                const portableMerged = stripSyncPayloadEncryptedCredentials(result.mergedPayload);
+                                                await Promise.resolve(onApplyPayload(portableMerged));
                                                if (result.remoteFile) {
-                                                    await sync.commitRemoteInspection(result.provider, result.remoteFile, result.mergedPayload, {
+                                                    await sync.commitRemoteInspection(result.provider, result.remoteFile, portableMerged, {
                                                        recordDownload: true,
                                                    });
                                                }
@@ -6,7 +6,7 @@ import {
 } from "./createTerminalSessionStarters";

 const noop = () => undefined;
-const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwAAAA";
+const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==";

 const armSudoPrompt = (
  autofill: { armForCommand: (command: string) => void } | null,
@@ -618,7 +618,7 @@ test("startMosh asks for credential re-entry when saved key material cannot be d
    keys: [{
      id: "key-1",
      label: "Deploy key",
-      privateKey: "enc:v1:djEwAAAA",
+      privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    }],
    resolvedChainHosts: [],
    sessionId: "session-1",
@@ -699,7 +699,7 @@ test("startMosh does not use stale local key paths when selected key material is
    keys: [{
      id: "key-1",
      label: "Deploy key",
-      privateKey: "enc:v1:djEwAAAA",
+      privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    }],
    resolvedChainHosts: [],
    sessionId: "session-1",
@@ -8,7 +8,7 @@ import {
 } from "./createTerminalSessionStarters";

 const noop = () => undefined;
-const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwAAAA";
+const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==";

 test("startTelnet rejects missing saved proxy profiles", async () => {
  let started = false;
@@ -11,7 +11,7 @@ import { pasteTextIntoTerminal } from "./terminalUserPaste";
 import { shouldSuppressHostStartupCommandOnReconnect } from "../restoredSessionGate";

 const noop = () => undefined;
-const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwAAAA";
+const ENCRYPTED_CREDENTIAL_PLACEHOLDER = "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==";

 const armSudoPrompt = (
  autofill: { armForCommand: (command: string) => void } | null,
@@ -665,7 +665,7 @@ test("startSSH uses the system agent when a synced vault key cannot be decrypted
      label: "Synced key",
      type: "ED25519",
      publicKey: "ssh-ed25519 AAAASELECTED",
-      privateKey: "enc:v1:djEwAAAA",
+      privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      source: "imported",
      category: "key",
      created: 1,
@@ -132,6 +132,29 @@ test('envelope creation and hydration reject a materialized snapshot that disagr
  );
 });

+test('poisoned enc:v1 secrets still round-trip through convergent envelope validation', () => {
+  // Materialize must preserve device-bound ciphertext that already lives in the
+  // CRDT + v1 snapshot pair. Stripping here would make decrypt/hydrate reject
+  // the exact poisoned v2 clouds #2702 needs to recover from.
+  const completeBlob = Buffer.alloc(19, 0);
+  Buffer.from('v10', 'utf8').copy(completeBlob, 0);
+  const ENC = `enc:v1:${completeBlob.toString('base64')}`;
+  const poisoned = payload();
+  poisoned.hosts = [{ ...poisoned.hosts[0]!, password: ENC }];
+  poisoned.keys = [{ ...poisoned.keys[0]!, privateKey: ENC }];
+
+  const state = createConvergentSyncStateFromPayload(poisoned, 'device-a', NOW);
+  const materialized = materializeSyncPayloadFromConvergentState(state, { syncedAt: NOW });
+  assert.equal(materialized.hosts[0]?.password, ENC);
+  assert.equal(materialized.keys[0]?.privateKey, ENC);
+
+  const envelope = createConvergentSyncEnvelope(state, materialized);
+  assert.equal(
+    serializeConvergentSyncState(hydrateConvergentSyncEnvelope(envelope, materialized)),
+    serializeConvergentSyncState(state),
+  );
+});
+
 test('envelope maps preserve prototype-like entity, field, setting, and string identifiers', () => {
  const specialObject = JSON.parse('{"id":"__proto__","constructor":"safe"}') as {
    id: string;
@@ -0,0 +1,158 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import {
+  findSyncPayloadEncryptedCredentialPaths,
+  healPoisonedSecretsForMerge,
+  isEncryptedCredentialPlaceholder,
+  stripSyncPayloadEncryptedCredentials,
+} from "./credentials.ts";
+import type { SyncPayload } from "./sync.ts";
+
+const completeBlob = Buffer.alloc(19, 0);
+Buffer.from("v10", "utf8").copy(completeBlob, 0);
+const ENC = `enc:v1:${completeBlob.toString("base64")}`;
+
+function samplePayload(overrides: Partial<SyncPayload> = {}): SyncPayload {
+  return {
+    hosts: [
+      {
+        id: "h1",
+        label: "prod",
+        hostname: "prod.example",
+        username: "root",
+        password: ENC,
+        port: 22,
+        os: "linux",
+        group: "",
+        tags: [],
+        protocol: "ssh",
+      },
+    ],
+    keys: [
+      {
+        id: "k1",
+        label: "key",
+        type: "ED25519",
+        privateKey: ENC,
+        source: "imported",
+        category: "key",
+        created: 1,
+      },
+    ],
+    identities: [],
+    snippets: [],
+    customGroups: [],
+    syncedAt: 1,
+    ...overrides,
+  };
+}
+
+test("isEncryptedCredentialPlaceholder detects complete v10 device-bound ciphertext", () => {
+  assert.equal(isEncryptedCredentialPlaceholder(ENC), true);
+});
+
+test("isEncryptedCredentialPlaceholder rejects intermediate v10 lengths that are neither CBC nor GCM", () => {
+  const body = Buffer.alloc(24, 0);
+  Buffer.from("v10", "utf8").copy(body, 0);
+  assert.equal(isEncryptedCredentialPlaceholder(`enc:v1:${body.toString("base64")}`), false);
+});
+
+test("isEncryptedCredentialPlaceholder detects real Windows DPAPI base64 prefixes", () => {
+  const body = Buffer.from([
+    0x01, 0x00, 0x00, 0x00,
+    0xd0, 0x8c, 0x9d, 0xdf, 0x01, 0x15, 0xd1, 0x11,
+    0x8c, 0x7a, 0x00, 0xc0, 0x4f, 0xc2, 0x97, 0xeb,
+    0xaa,
+  ]);
+  const encoded = body.toString("base64");
+  assert.equal(encoded.startsWith("AQAAANCMnd8"), true);
+  assert.equal(isEncryptedCredentialPlaceholder(`enc:v1:${encoded}`), true);
+});
+
+test("isEncryptedCredentialPlaceholder rejects header-only enc:v1 payloads", () => {
+  assert.equal(isEncryptedCredentialPlaceholder("enc:v1:djEw"), false);
+});
+
+test("findSyncPayloadEncryptedCredentialPaths reports host and key secrets", () => {
+  const paths = findSyncPayloadEncryptedCredentialPaths(samplePayload());
+  assert.deepEqual(paths, ["hosts[0].password", "keys[0].privateKey"]);
+});
+
+test("stripSyncPayloadEncryptedCredentials clears device-bound placeholders for recovery", () => {
+  const stripped = stripSyncPayloadEncryptedCredentials(samplePayload());
+  assert.equal(stripped.hosts[0]?.password, undefined);
+  assert.equal(stripped.keys[0]?.privateKey, "");
+  assert.equal(findSyncPayloadEncryptedCredentialPaths(stripped).length, 0);
+});
+
+test("healPoisonedSecretsForMerge keeps usable preferred passwords over poisoned enc:v1", () => {
+  const poisoned = samplePayload();
+  const preferred = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      password: "preferred-secret",
+    }],
+    keys: [{
+      ...samplePayload().keys[0]!,
+      privateKey: "PREFERRED_PRIVATE_KEY",
+    }],
+  });
+  const fallback = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      password: "base-secret",
+    }],
+  });
+  const healed = healPoisonedSecretsForMerge(poisoned, preferred, fallback);
+  assert.equal(healed.hosts[0]?.password, "preferred-secret");
+  assert.equal(healed.keys[0]?.privateKey, "PREFERRED_PRIVATE_KEY");
+});
+
+test("healPoisonedSecretsForMerge heals local poison from remote then base", () => {
+  const local = samplePayload();
+  const remote = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      password: "remote-secret",
+    }],
+    keys: [{
+      ...samplePayload().keys[0]!,
+      privateKey: ENC,
+    }],
+  });
+  const base = samplePayload({
+    keys: [{
+      ...samplePayload().keys[0]!,
+      privateKey: "BASE_PRIVATE_KEY",
+    }],
+  });
+  const healed = healPoisonedSecretsForMerge(local, remote, base);
+  assert.equal(healed.hosts[0]?.password, "remote-secret");
+  assert.equal(healed.keys[0]?.privateKey, "BASE_PRIVATE_KEY");
+});
+
+test("healPoisonedSecretsForMerge preserves explicit preferred credential deletions", () => {
+  const poisoned = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      label: "renamed-on-poisoned-device",
+      password: ENC,
+    }],
+  });
+  const preferred = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      label: "renamed-on-poisoned-device",
+      password: undefined,
+    }],
+  });
+  const fallback = samplePayload({
+    hosts: [{
+      ...samplePayload().hosts[0]!,
+      password: "base-secret",
+    }],
+  });
+  const healed = healPoisonedSecretsForMerge(poisoned, preferred, fallback);
+  assert.equal(healed.hosts[0]?.password, undefined);
+  assert.equal(healed.hosts[0]?.label, "renamed-on-poisoned-device");
+});
@@ -12,21 +12,78 @@ const BASE64_RE = /^[A-Za-z0-9+/]+=*$/;
 * - macOS/Linux: plaintext bytes start with "v10" or "v11"
 * - Windows (legacy DPAPI blob): leading bytes are 0x01 0x00 0x00 0x00
 *
- * We validate the base64 payload starts with one of these header signatures
- * instead of relying only on prefix+length heuristics. This greatly reduces
- * false positives for plaintext credentials that happen to start with "enc:v1:".
+ * Detect headers on *decoded* bytes. A four-byte DPAPI version alone is not
+ * enough — real blobs continue with provider GUID
+ * {df9d8cd0-1501-11d1-8c7a-00c04fc297eb} (base64 `AQAAANCMnd8...`).
+ *
+ * We require a known header AND a complete-enough decoded blob. v10/v11 CBC
+ * blobs are at least header(3) + one AES block(16) = 19 bytes. Header-only
+ * base64 such as `enc:v1:djEw` must not be treated as ciphertext.
+ *
+ * Keep in sync with electron/bridges/credentialBridge.cjs.
 *
 * References:
 * - components/os_crypt/sync/os_crypt_mac.mm (kObfuscationPrefixV10 = "v10")
 * - components/os_crypt/sync/os_crypt_linux.cc (kObfuscationPrefixV10/V11)
 * - components/os_crypt/sync/os_crypt_win.cc (DPAPI legacy path)
 */
-const SAFE_STORAGE_BASE64_HEADER_PREFIXES = [
-  "djEw", // "v10"
-  "djEx", // "v11"
-  "AQAAAA", // 0x01 0x00 0x00 0x00 (DPAPI blob header)
+const V10_HEADER = [0x76, 0x31, 0x30] as const; // "v10"
+const V11_HEADER = [0x76, 0x31, 0x31] as const; // "v11"
+// Version (4) + provider GUID {df9d8cd0-1501-11d1-8c7a-00c04fc297eb} (16).
+const DPAPI_BLOB_PREFIX = [
+  0x01, 0x00, 0x00, 0x00,
+  0xd0, 0x8c, 0x9d, 0xdf, 0x01, 0x15, 0xd1, 0x11,
+  0x8c, 0x7a, 0x00, 0xc0, 0x4f, 0xc2, 0x97, 0xeb,
 ] as const;

+/** Minimum decoded sizes for complete Chromium OSCrypt blobs. */
+const MIN_V10_V11_CIPHERTEXT_BYTES = 19; // CBC: header(3) + one AES block(16)
+const MIN_V10_V11_GCM_CIPHERTEXT_BYTES = 31; // header(3) + nonce(12) + tag(16)
+const MIN_DPAPI_CIPHERTEXT_BYTES = DPAPI_BLOB_PREFIX.length + 1;
+
+/**
+ * Renderer-safe base64 decode. Avoids Node `Buffer` which is unavailable
+ * in Electron windows with `nodeIntegration: false`.
+ */
+const decodeBase64Bytes = (payload: string): Uint8Array | null => {
+  try {
+    if (typeof atob === "function") {
+      const binary = atob(payload);
+      const out = new Uint8Array(binary.length);
+      for (let i = 0; i < binary.length; i += 1) {
+        out[i] = binary.charCodeAt(i);
+      }
+      return out;
+    }
+  } catch {
+    // fall through
+  }
+  // Node / test environments without atob.
+  if (typeof Buffer !== "undefined") {
+    try {
+      return new Uint8Array(Buffer.from(payload, "base64"));
+    } catch {
+      return null;
+    }
+  }
+  return null;
+};
+
+const startsWithBytes = (
+  decoded: Uint8Array,
+  prefix: readonly number[],
+): boolean => {
+  if (decoded.byteLength < prefix.length) return false;
+  return prefix.every((byte, index) => decoded[index] === byte);
+};
+
+/** CBC is header(3) + 16-byte blocks; GCM is at least header+nonce+tag (31). */
+const isValidV10V11CiphertextLength = (byteLength: number): boolean => {
+  if (byteLength >= MIN_V10_V11_GCM_CIPHERTEXT_BYTES) return true;
+  return byteLength >= MIN_V10_V11_CIPHERTEXT_BYTES
+    && (byteLength - 3) % 16 === 0;
+};
+
 export const isEncryptedCredentialPlaceholder = (
  value: string | undefined | null,
 ): value is string => {
@@ -35,8 +92,15 @@ export const isEncryptedCredentialPlaceholder = (
  }
  const payload = value.slice(CREDENTIAL_ENCRYPTION_PREFIX.length);
  if (!payload || !BASE64_RE.test(payload)) return false;
-
-  return SAFE_STORAGE_BASE64_HEADER_PREFIXES.some((prefix) => payload.startsWith(prefix));
+  const decoded = decodeBase64Bytes(payload);
+  if (!decoded) return false;
+  if (startsWithBytes(decoded, V10_HEADER) || startsWithBytes(decoded, V11_HEADER)) {
+    return isValidV10V11CiphertextLength(decoded.byteLength);
+  }
+  if (startsWithBytes(decoded, DPAPI_BLOB_PREFIX)) {
+    return decoded.byteLength >= MIN_DPAPI_CIPHERTEXT_BYTES;
+  }
+  return false;
 };

 /**
@@ -108,3 +172,267 @@ export const findSyncPayloadEncryptedCredentialPaths = (

  return issues;
 };
+
+/**
+ * Clear device-bound enc:v1 placeholders from a portable sync payload.
+ *
+ * Cloud / backup payloads must carry plaintext secrets (protected by the
+ * master key envelope). If a previous bug uploaded undecryptable local
+ * ciphertext, stripping placeholders lets download restore a usable vault
+ * shell so the user can re-enter credentials instead of looping forever.
+ */
+export const stripSyncPayloadEncryptedCredentials = (
+  payload: SyncPayload,
+): SyncPayload => {
+  const hosts = payload.hosts.map((host) => {
+    const next = { ...host };
+    if (isEncryptedCredentialPlaceholder(next.password)) delete next.password;
+    if (isEncryptedCredentialPlaceholder(next.telnetPassword)) delete next.telnetPassword;
+    if (next.proxyConfig && isEncryptedCredentialPlaceholder(next.proxyConfig.password)) {
+      const { password: _removed, ...proxyRest } = next.proxyConfig;
+      next.proxyConfig = proxyRest;
+    }
+    return next;
+  });
+
+  const keys = payload.keys.map((key) => {
+    const next = { ...key };
+    if (isEncryptedCredentialPlaceholder(next.privateKey)) next.privateKey = "";
+    if (isEncryptedCredentialPlaceholder(next.passphrase)) delete next.passphrase;
+    return next;
+  });
+
+  const identities = payload.identities?.map((identity) => {
+    if (!isEncryptedCredentialPlaceholder(identity.password)) return identity;
+    const next = { ...identity };
+    delete next.password;
+    return next;
+  });
+
+  const proxyProfiles = payload.proxyProfiles?.map((profile) => {
+    if (!isEncryptedCredentialPlaceholder(profile.config.password)) return profile;
+    const { password: _removed, ...configRest } = profile.config;
+    return { ...profile, config: configRest };
+  });
+
+  const groupConfigs = payload.groupConfigs?.map((config) => {
+    const next = { ...config };
+    if (isEncryptedCredentialPlaceholder(next.password)) delete next.password;
+    if (isEncryptedCredentialPlaceholder(next.telnetPassword)) delete next.telnetPassword;
+    if (next.proxyConfig && isEncryptedCredentialPlaceholder(next.proxyConfig.password)) {
+      const { password: _removed, ...proxyRest } = next.proxyConfig;
+      next.proxyConfig = proxyRest;
+    }
+    return next;
+  });
+
+  return {
+    ...payload,
+    hosts,
+    keys,
+    identities: identities ?? payload.identities,
+    proxyProfiles: proxyProfiles ?? payload.proxyProfiles,
+    groupConfigs: groupConfigs ?? payload.groupConfigs,
+  };
+};
+
+const usableCredential = (value: string | undefined): string | undefined => {
+  if (typeof value !== "string" || value.length === 0) return undefined;
+  if (isEncryptedCredentialPlaceholder(value)) return undefined;
+  return value;
+};
+
+/**
+ * Resolve a poisoned secret against preferred then fallback.
+ *
+ * If the preferred *entity* exists, an empty/missing preferred secret is an
+ * explicit deletion and must win over fallback/base. Only when preferred is
+ * also poisoned (or the preferred entity is absent) may we revive from base.
+ */
+const healPoisonedCredential = (
+  preferredEntity: unknown,
+  preferredValue: string | undefined,
+  fallbackValue: string | undefined,
+): string | undefined => {
+  if (preferredEntity) {
+    if (isEncryptedCredentialPlaceholder(preferredValue)) {
+      return usableCredential(fallbackValue);
+    }
+    return usableCredential(preferredValue);
+  }
+  return usableCredential(fallbackValue);
+};
+
+/**
+ * Before three-way merge, replace device-bound enc:v1 secrets on `poisoned`
+ * with usable values from `preferred` then `fallback`. Used for both remote
+ * and local sides so a poisoned field cannot win the entity-level merge and
+ * delete a still-usable secret from the other side / base.
+ *
+ * Explicit preferred-side deletions (empty/absent secrets on a present entity)
+ * are authoritative and are not revived from base.
+ */
+export const healPoisonedSecretsForMerge = (
+  poisoned: SyncPayload,
+  preferred: SyncPayload,
+  fallback: SyncPayload | null | undefined,
+): SyncPayload => {
+  const preferredHosts = new Map(preferred.hosts.map((host) => [host.id, host]));
+  const fallbackHosts = new Map((fallback?.hosts ?? []).map((host) => [host.id, host]));
+  const hosts = poisoned.hosts.map((host) => {
+    const preferredHost = preferredHosts.get(host.id);
+    const fallbackHost = fallbackHosts.get(host.id);
+    const next = { ...host };
+    if (isEncryptedCredentialPlaceholder(next.password)) {
+      const healed = healPoisonedCredential(
+        preferredHost,
+        preferredHost?.password,
+        fallbackHost?.password,
+      );
+      if (healed !== undefined) next.password = healed;
+      else delete next.password;
+    }
+    if (isEncryptedCredentialPlaceholder(next.telnetPassword)) {
+      const healed = healPoisonedCredential(
+        preferredHost,
+        preferredHost?.telnetPassword,
+        fallbackHost?.telnetPassword,
+      );
+      if (healed !== undefined) next.telnetPassword = healed;
+      else delete next.telnetPassword;
+    }
+    if (next.proxyConfig && isEncryptedCredentialPlaceholder(next.proxyConfig.password)) {
+      const healed = healPoisonedCredential(
+        preferredHost,
+        preferredHost?.proxyConfig?.password,
+        fallbackHost?.proxyConfig?.password,
+      );
+      if (healed !== undefined) {
+        next.proxyConfig = { ...next.proxyConfig, password: healed };
+      } else {
+        const { password: _removed, ...proxyRest } = next.proxyConfig;
+        next.proxyConfig = proxyRest;
+      }
+    }
+    return next;
+  });
+
+  const preferredKeys = new Map(preferred.keys.map((key) => [key.id, key]));
+  const fallbackKeys = new Map((fallback?.keys ?? []).map((key) => [key.id, key]));
+  const keys = poisoned.keys.map((key) => {
+    const preferredKey = preferredKeys.get(key.id);
+    const fallbackKey = fallbackKeys.get(key.id);
+    const next = { ...key };
+    if (isEncryptedCredentialPlaceholder(next.privateKey)) {
+      next.privateKey = healPoisonedCredential(
+        preferredKey,
+        preferredKey?.privateKey,
+        fallbackKey?.privateKey,
+      ) ?? "";
+    }
+    if (isEncryptedCredentialPlaceholder(next.passphrase)) {
+      const healed = healPoisonedCredential(
+        preferredKey,
+        preferredKey?.passphrase,
+        fallbackKey?.passphrase,
+      );
+      if (healed !== undefined) next.passphrase = healed;
+      else delete next.passphrase;
+    }
+    return next;
+  });
+
+  const preferredIdentities = new Map((preferred.identities ?? []).map((identity) => [identity.id, identity]));
+  const fallbackIdentities = new Map((fallback?.identities ?? []).map((identity) => [identity.id, identity]));
+  const identities = poisoned.identities?.map((identity) => {
+    if (!isEncryptedCredentialPlaceholder(identity.password)) return identity;
+    const preferredIdentity = preferredIdentities.get(identity.id);
+    const healed = healPoisonedCredential(
+      preferredIdentity,
+      preferredIdentity?.password,
+      fallbackIdentities.get(identity.id)?.password,
+    );
+    if (healed !== undefined) return { ...identity, password: healed };
+    const next = { ...identity };
+    delete next.password;
+    return next;
+  });
+
+  const preferredProfiles = new Map((preferred.proxyProfiles ?? []).map((profile) => [profile.id, profile]));
+  const fallbackProfiles = new Map((fallback?.proxyProfiles ?? []).map((profile) => [profile.id, profile]));
+  const proxyProfiles = poisoned.proxyProfiles?.map((profile) => {
+    if (!isEncryptedCredentialPlaceholder(profile.config.password)) return profile;
+    const preferredProfile = preferredProfiles.get(profile.id);
+    const healed = healPoisonedCredential(
+      preferredProfile,
+      preferredProfile?.config.password,
+      fallbackProfiles.get(profile.id)?.config.password,
+    );
+    if (healed !== undefined) {
+      return { ...profile, config: { ...profile.config, password: healed } };
+    }
+    const { password: _removed, ...configRest } = profile.config;
+    return { ...profile, config: configRest };
+  });
+
+  const preferredGroupConfigs = new Map((preferred.groupConfigs ?? []).map((config) => [config.path, config]));
+  const fallbackGroupConfigs = new Map((fallback?.groupConfigs ?? []).map((config) => [config.path, config]));
+  const groupConfigs = poisoned.groupConfigs?.map((config) => {
+    const preferredConfig = preferredGroupConfigs.get(config.path);
+    const fallbackConfig = fallbackGroupConfigs.get(config.path);
+    const next = { ...config };
+    let changed = false;
+    if (isEncryptedCredentialPlaceholder(next.password)) {
+      const healed = healPoisonedCredential(
+        preferredConfig,
+        preferredConfig?.password,
+        fallbackConfig?.password,
+      );
+      if (healed !== undefined) next.password = healed;
+      else delete next.password;
+      changed = true;
+    }
+    if (isEncryptedCredentialPlaceholder(next.telnetPassword)) {
+      const healed = healPoisonedCredential(
+        preferredConfig,
+        preferredConfig?.telnetPassword,
+        fallbackConfig?.telnetPassword,
+      );
+      if (healed !== undefined) next.telnetPassword = healed;
+      else delete next.telnetPassword;
+      changed = true;
+    }
+    if (next.proxyConfig && isEncryptedCredentialPlaceholder(next.proxyConfig.password)) {
+      const healed = healPoisonedCredential(
+        preferredConfig,
+        preferredConfig?.proxyConfig?.password,
+        fallbackConfig?.proxyConfig?.password,
+      );
+      if (healed !== undefined) {
+        next.proxyConfig = { ...next.proxyConfig, password: healed };
+      } else {
+        const { password: _removed, ...proxyRest } = next.proxyConfig;
+        next.proxyConfig = proxyRest;
+      }
+      changed = true;
+    }
+    return changed ? next : config;
+  });
+
+  return {
+    ...poisoned,
+    hosts,
+    keys,
+    identities: identities ?? poisoned.identities,
+    proxyProfiles: proxyProfiles ?? poisoned.proxyProfiles,
+    groupConfigs: groupConfigs ?? poisoned.groupConfigs,
+  };
+};
+
+/** @deprecated Prefer healPoisonedSecretsForMerge(remote, local, base). */
+export const healPoisonedRemoteSecretsForMerge = (
+  remote: SyncPayload,
+  local: SyncPayload,
+  base: SyncPayload | null | undefined,
+): SyncPayload => healPoisonedSecretsForMerge(remote, local, base);
+
@@ -0,0 +1,22 @@
+/**
+ * Shared complete enc:v1 fixtures for tests.
+ *
+ * Production detectors require a full platform-shaped safeStorage blob
+ * (v10/v11 CBC >= 19 bytes, or DPAPI >= 20). Short strings like
+ * `enc:v1:djEwAAAA` are no longer treated as ciphertext.
+ */
+
+export const MIN_V10_TEST_CIPHERTEXT_BYTES = 19;
+
+export function makeEncryptedCredentialPlaceholder(seed = "fixture"): string {
+  const body = Buffer.alloc(MIN_V10_TEST_CIPHERTEXT_BYTES, 0);
+  Buffer.from("v10", "utf8").copy(body, 0);
+  Buffer.from(String(seed).slice(0, 16), "utf8").copy(body, 3);
+  return `enc:v1:${body.toString("base64")}`;
+}
+
+/** Stable complete placeholder used by most auth/SFTP/proxy tests. */
+export const ENCRYPTED_CREDENTIAL_PLACEHOLDER = makeEncryptedCredentialPlaceholder("test");
+
+/** Alternate complete placeholder (historically `enc:v1:djEwYWJj`). */
+export const ENCRYPTED_CREDENTIAL_PLACEHOLDER_ABC = makeEncryptedCredentialPlaceholder("abc");
@@ -69,11 +69,11 @@ test("listPasswordPromptFillCandidates includes password identities", () => {

 test("listPasswordPromptFillCandidates skips key-only identities and placeholders", () => {
  const candidates = listPasswordPromptFillCandidates({
-    host: baseHost({ password: "enc:v1:djEwAAAA" }),
+    host: baseHost({ password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }),
    keys: [],
    identities: [
      identity({ id: "key", authMethod: "key", password: undefined }),
-      identity({ id: "bad", password: "enc:v1:djEwAAAA" }),
+      identity({ id: "bad", password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }),
      identity({ id: "ok", password: "ok-secret" }),
    ],
  });
@@ -50,7 +50,7 @@ test('plugin credentials are selectable only after secure catalog publication',
  assert.equal(isPluginCredentialCatalogEntryAvailable(credentialId, 'secret', published), true);
  assert.equal(isPluginCredentialCatalogEntryAvailable(credentialId, 'secret', new Set()), false);
  assert.equal(
-    isPluginCredentialCatalogEntryAvailable(credentialId, 'enc:v1:djEwAAAA', published),
+    isPluginCredentialCatalogEntryAvailable(credentialId, 'enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==', published),
    false,
  );
  assert.equal(
@@ -352,7 +352,7 @@ test("findIncompleteProxyIdentityId treats blank usernames as incomplete even wi
        label: "Proxy login",
        username: " ",
        authMethod: "password",
-        password: "enc:v1:djEwAAAA",
+        password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
        created: 1,
      }],
    ),
@@ -37,7 +37,7 @@ test("resolveBridgeKeyAuth ignores undecryptable passphrase placeholders", () =>
    resolveBridgeKeyAuth({
      key: {
        ...referenceKey,
-        passphrase: "enc:v1:djEwAAAA",
+        passphrase: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      },
    }).passphrase,
    undefined,
@@ -51,7 +51,7 @@ test("resolveBridgeKeyAuth ignores undecryptable private key placeholders", () =
        ...referenceKey,
        source: "imported",
        filePath: undefined,
-        privateKey: "enc:v1:djEwAAAA",
+        privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      },
    }).privateKey,
    undefined,
@@ -767,7 +767,7 @@ test("resolveHostAutofillPassword returns undefined when no password is availabl

 test("resolveHostAutofillPassword ignores undecryptable password placeholders", () => {
  assert.equal(
-    resolveHostAutofillPassword({ host: { ...autofillBaseHost, password: "enc:v1:djEwAAAA" }, keys: [] }),
+    resolveHostAutofillPassword({ host: { ...autofillBaseHost, password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }, keys: [] }),
    undefined,
  );
 });
@@ -438,7 +438,7 @@ test("CSV import ignores a passphrase without a key path", () => {
 });

 test("CSV import rejects encrypted passphrase placeholders", () => {
-  const placeholder = "enc:v1:djEwYWJj";
+  const placeholder = "enc:v1:djEwYWJjAAAAAAAAAAAAAAAAAA==";
  for (const value of [placeholder, encodeCsvPassphrase(placeholder)]) {
    const result = importVaultHostsFromText(
      "csv",
@@ -15,8 +15,147 @@

 const ENC_PREFIX = "enc:v1:";

+/**
+ * Chromium/Electron safeStorage ciphertext carries known platform headers:
+ * - macOS/Linux: plaintext bytes start with "v10" or "v11"
+ * - Windows (legacy DPAPI blob): leading bytes are 0x01 0x00 0x00 0x00
+ *
+ * Detect headers on *decoded* bytes. A four-byte DPAPI version alone is not
+ * enough — real blobs continue with provider GUID
+ * {df9d8cd0-1501-11d1-8c7a-00c04fc297eb} (base64 `AQAAANCMnd8...`).
+ *
+ * Keep in sync with domain/credentials.ts.
+ *
+ * v10/v11 CBC blobs are at least header(3) + one AES block(16) = 19 bytes.
+ * AES-GCM blobs are larger (nonce+tag), but CBC is the lower bound we must
+ * accept so short credentials are not mistaken for plaintext coincidences.
+ */
+const V10_HEADER = Buffer.from("v10", "utf8");
+const V11_HEADER = Buffer.from("v11", "utf8");
+// Version (4) + provider GUID {df9d8cd0-1501-11d1-8c7a-00c04fc297eb} (16).
+const DPAPI_BLOB_PREFIX = Buffer.from([
+  0x01, 0x00, 0x00, 0x00,
+  0xd0, 0x8c, 0x9d, 0xdf, 0x01, 0x15, 0xd1, 0x11,
+  0x8c, 0x7a, 0x00, 0xc0, 0x4f, 0xc2, 0x97, 0xeb,
+]);
+
+const MIN_V10_V11_CIPHERTEXT_BYTES = 19;
+const MIN_V10_V11_GCM_CIPHERTEXT_BYTES = 31; // header(3) + nonce(12) + tag(16)
+// Header alone is 20 bytes; require at least one trailing payload byte.
+const MIN_DPAPI_CIPHERTEXT_BYTES = DPAPI_BLOB_PREFIX.byteLength + 1;
+
+const BASE64_RE = /^[A-Za-z0-9+/]+=*$/;
+
 let safeStorage = null;

+function startsWithBytes(buffer, prefix) {
+  if (buffer.byteLength < prefix.byteLength) return false;
+  return buffer.subarray(0, prefix.byteLength).equals(prefix);
+}
+
+/** CBC is header(3) + 16-byte blocks; GCM is at least header+nonce+tag (31). */
+function isValidV10V11CiphertextLength(byteLength) {
+  if (byteLength >= MIN_V10_V11_GCM_CIPHERTEXT_BYTES) return true;
+  return byteLength >= MIN_V10_V11_CIPHERTEXT_BYTES
+    && (byteLength - 3) % 16 === 0;
+}
+
+function looksLikeEncryptedCredential(value) {
+  if (typeof value !== "string" || !value.startsWith(ENC_PREFIX)) {
+    return false;
+  }
+  const payload = value.slice(ENC_PREFIX.length);
+  if (!payload || !BASE64_RE.test(payload)) return false;
+  // Reject header-only / truncated base64 that is not a full platform blob.
+  let decoded;
+  try {
+    decoded = Buffer.from(payload, "base64");
+  } catch {
+    return false;
+  }
+  if (startsWithBytes(decoded, V10_HEADER) || startsWithBytes(decoded, V11_HEADER)) {
+    return isValidV10V11CiphertextLength(decoded.byteLength);
+  }
+  if (startsWithBytes(decoded, DPAPI_BLOB_PREFIX)) {
+    return decoded.byteLength >= MIN_DPAPI_CIPHERTEXT_BYTES;
+  }
+  return false;
+}
+
+/**
+ * Encrypt a credential field. Never wraps an existing complete device-bound
+ * enc:v1 blob again — even when trial decrypt fails (e.g. OSCrypt key
+ * rotated). Ambiguous `enc:v1:` prefixes that are not full ciphertext are
+ * treated as coincidental plaintext and encrypted normally.
+ *
+ * @param {string} plaintext
+ * @param {{ isEncryptionAvailable?: () => boolean, encryptString?: (v: string) => Buffer, decryptString?: (b: Buffer) => string } | null} storage
+ */
+function encryptCredentialValue(plaintext, storage = safeStorage) {
+  if (typeof plaintext !== "string" || plaintext.length === 0) {
+    return plaintext ?? "";
+  }
+  if (!storage?.isEncryptionAvailable?.()) {
+    return plaintext;
+  }
+
+  // Complete device-bound ciphertext: return as-is. Do not trial-decrypt then
+  // fall through to encryptString — that double-wraps when decrypt fails.
+  if (looksLikeEncryptedCredential(plaintext)) {
+    return plaintext;
+  }
+
+  // Ambiguous enc:v1: prefix (header-only / short coincidence): try decrypt.
+  // Success means a real blob we failed to classify — keep it. Failure means
+  // plaintext that happens to look prefixed — encrypt it.
+  if (plaintext.startsWith(ENC_PREFIX) && typeof storage.decryptString === "function") {
+    try {
+      const base64 = plaintext.slice(ENC_PREFIX.length);
+      const buf = Buffer.from(base64, "base64");
+      storage.decryptString(buf);
+      return plaintext;
+    } catch {
+      // coincidental plaintext — fall through
+    }
+  }
+
+  try {
+    const encrypted = storage.encryptString(plaintext);
+    return ENC_PREFIX + encrypted.toString("base64");
+  } catch (err) {
+    console.warn("[Credentials] encrypt failed, returning plaintext:", err?.message || err);
+    return plaintext;
+  }
+}
+
+/**
+ * Decrypt a credential field. On failure returns the ciphertext unchanged so
+ * callers can detect enc:v1 placeholders via looksLikeEncryptedCredential /
+ * isEncryptedCredentialPlaceholder.
+ *
+ * @param {string} value
+ * @param {{ isEncryptionAvailable?: () => boolean, decryptString?: (b: Buffer) => string } | null} storage
+ */
+function decryptCredentialValue(value, storage = safeStorage) {
+  if (typeof value !== "string" || value.length === 0) {
+    return value ?? "";
+  }
+  if (!value.startsWith(ENC_PREFIX)) {
+    return value;
+  }
+  if (!storage?.isEncryptionAvailable?.()) {
+    return value;
+  }
+  try {
+    const base64 = value.slice(ENC_PREFIX.length);
+    const buf = Buffer.from(base64, "base64");
+    return storage.decryptString(buf);
+  } catch (err) {
+    console.warn("[Credentials] decrypt failed:", err?.message || err);
+    return value;
+  }
+}
+
 /**
 * Register IPC handlers for credential encryption/decryption
 * @param {Electron.IpcMain} ipcMain
@@ -30,56 +169,20 @@ function registerHandlers(ipcMain, electronModule) {
  });

  ipcMain.handle("netcatty:credentials:encrypt", (_event, plaintext) => {
-    if (typeof plaintext !== "string" || plaintext.length === 0) {
-      return plaintext ?? "";
-    }
-    if (!safeStorage?.isEncryptionAvailable?.()) {
-      return plaintext;
-    }
-    // If value looks like it might already be encrypted, verify by attempting
-    // to decode and decrypt.  If it succeeds the value is genuinely encrypted
-    // and we return it as-is; if it fails, the prefix was a coincidence and
-    // we proceed to encrypt the raw plaintext.
-    if (plaintext.startsWith(ENC_PREFIX)) {
-      try {
-        const base64 = plaintext.slice(ENC_PREFIX.length);
-        const buf = Buffer.from(base64, "base64");
-        safeStorage.decryptString(buf); // throws on invalid ciphertext
-        return plaintext; // verified — already encrypted
-      } catch {
-        // Not valid ciphertext — fall through to encrypt
-      }
-    }
-    try {
-      const encrypted = safeStorage.encryptString(plaintext);
-      return ENC_PREFIX + encrypted.toString("base64");
-    } catch (err) {
-      console.warn("[Credentials] encrypt failed, returning plaintext:", err?.message || err);
-      return plaintext;
-    }
+    return encryptCredentialValue(plaintext, safeStorage);
  });

  ipcMain.handle("netcatty:credentials:decrypt", (_event, value) => {
-    if (typeof value !== "string" || value.length === 0) {
-      return value ?? "";
-    }
-    // Not encrypted — pass through (supports migration from plaintext)
-    if (!value.startsWith(ENC_PREFIX)) {
-      return value;
-    }
-    if (!safeStorage?.isEncryptionAvailable?.()) {
-      // Cannot decrypt without safeStorage; return raw value
-      return value;
-    }
-    try {
-      const base64 = value.slice(ENC_PREFIX.length);
-      const buf = Buffer.from(base64, "base64");
-      return safeStorage.decryptString(buf);
-    } catch (err) {
-      console.warn("[Credentials] decrypt failed:", err?.message || err);
-      return value;
-    }
+    return decryptCredentialValue(value, safeStorage);
  });
 }

-module.exports = { registerHandlers };
+module.exports = {
+  ENC_PREFIX,
+  MIN_V10_V11_CIPHERTEXT_BYTES,
+  MIN_DPAPI_CIPHERTEXT_BYTES,
+  looksLikeEncryptedCredential,
+  encryptCredentialValue,
+  decryptCredentialValue,
+  registerHandlers,
+};
@@ -0,0 +1,136 @@
+const test = require("node:test");
+const assert = require("node:assert/strict");
+
+const {
+  ENC_PREFIX,
+  MIN_V10_V11_CIPHERTEXT_BYTES,
+  MIN_DPAPI_CIPHERTEXT_BYTES,
+  encryptCredentialValue,
+  decryptCredentialValue,
+  looksLikeEncryptedCredential,
+} = require("./credentialBridge.cjs");
+
+function fakeSafeStorage({ decryptThrows = false } = {}) {
+  const blobs = new Map();
+  let nextId = 1;
+  return {
+    isEncryptionAvailable: () => true,
+    encryptString(plaintext) {
+      const id = `cipher-${nextId++}`;
+      // Pad to a complete CBC-sized blob (header + one AES block).
+      const body = Buffer.alloc(MIN_V10_V11_CIPHERTEXT_BYTES, 0);
+      Buffer.from("v10", "utf8").copy(body, 0);
+      Buffer.from(id, "utf8").copy(body, 3);
+      blobs.set(body.toString("base64"), plaintext);
+      return body;
+    },
+    decryptString(buffer) {
+      if (decryptThrows) throw new Error("decrypt failed");
+      const key = Buffer.from(buffer).toString("base64");
+      if (!blobs.has(key)) throw new Error("unknown cipher");
+      return blobs.get(key);
+    },
+  };
+}
+
+function completeCiphertextPlaceholder(seed = "stale-key-material") {
+  const body = Buffer.alloc(MIN_V10_V11_CIPHERTEXT_BYTES, 0);
+  Buffer.from("v10", "utf8").copy(body, 0);
+  Buffer.from(seed, "utf8").copy(body, 3);
+  return `${ENC_PREFIX}${body.toString("base64")}`;
+}
+
+test("looksLikeEncryptedCredential accepts complete CBC-sized v10 payloads", () => {
+  assert.equal(looksLikeEncryptedCredential(completeCiphertextPlaceholder()), true);
+});
+
+test("looksLikeEncryptedCredential rejects impossible intermediate v10 lengths", () => {
+  // 20–30 bytes starting with v10 cannot be CBC (19+16n) or GCM (>=31).
+  const body = Buffer.alloc(24, 0);
+  Buffer.from("v10", "utf8").copy(body, 0);
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}${body.toString("base64")}`), false);
+});
+
+test("looksLikeEncryptedCredential accepts GCM-sized v10 payloads", () => {
+  const body = Buffer.alloc(31, 0);
+  Buffer.from("v10", "utf8").copy(body, 0);
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}${body.toString("base64")}`), true);
+});
+
+test("looksLikeEncryptedCredential accepts real Windows DPAPI base64 prefixes", () => {
+  // Version + provider GUID {df9d8cd0-1501-11d1-8c7a-00c04fc297eb} + payload.
+  const body = Buffer.from([
+    0x01, 0x00, 0x00, 0x00,
+    0xd0, 0x8c, 0x9d, 0xdf, 0x01, 0x15, 0xd1, 0x11,
+    0x8c, 0x7a, 0x00, 0xc0, 0x4f, 0xc2, 0x97, 0xeb,
+    0xaa,
+  ]);
+  const encoded = body.toString("base64");
+  assert.equal(encoded.startsWith("AQAAANCMnd8"), true);
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}${encoded}`), true);
+});
+
+test("looksLikeEncryptedCredential rejects version-only DPAPI-looking blobs", () => {
+  const body = Buffer.alloc(MIN_DPAPI_CIPHERTEXT_BYTES, 0);
+  body[0] = 0x01;
+  body[4] = 0xd0;
+  body[5] = 0x8c;
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}${body.toString("base64")}`), false);
+});
+
+test("looksLikeEncryptedCredential rejects header-only enc:v1 payloads", () => {
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}djEw`), false);
+  assert.equal(looksLikeEncryptedCredential(`${ENC_PREFIX}not-real-ciphertext`), false);
+  assert.equal(looksLikeEncryptedCredential("password"), false);
+});
+
+test("encrypt leaves undecryptable DPAPI enc:v1 ciphertext unchanged", () => {
+  const storage = fakeSafeStorage({ decryptThrows: true });
+  const body = Buffer.from([
+    0x01, 0x00, 0x00, 0x00,
+    0xd0, 0x8c, 0x9d, 0xdf, 0x01, 0x15, 0xd1, 0x11,
+    0x8c, 0x7a, 0x00, 0xc0, 0x4f, 0xc2, 0x97, 0xeb,
+    0xaa,
+  ]);
+  const stale = `${ENC_PREFIX}${body.toString("base64")}`;
+  assert.equal(encryptCredentialValue(stale, storage), stale);
+});
+
+test("encrypt leaves undecryptable complete enc:v1 ciphertext unchanged instead of wrapping again", () => {
+  const storage = fakeSafeStorage({ decryptThrows: true });
+  const stale = completeCiphertextPlaceholder("stale-key-material");
+  const result = encryptCredentialValue(stale, storage);
+  assert.equal(result, stale);
+});
+
+test("encrypt encrypts header-only enc:v1 coincidence instead of leaving it plaintext", () => {
+  const storage = fakeSafeStorage();
+  const coincidence = `${ENC_PREFIX}djEw`;
+  const result = encryptCredentialValue(coincidence, storage);
+  assert.notEqual(result, coincidence);
+  assert.ok(result.startsWith(ENC_PREFIX));
+  assert.equal(decryptCredentialValue(result, storage), coincidence);
+});
+
+test("encrypt still encrypts coincidental plaintext that starts with enc:v1:", () => {
+  const storage = fakeSafeStorage();
+  const coincidence = `${ENC_PREFIX}totally-plain-password`;
+  const result = encryptCredentialValue(coincidence, storage);
+  assert.notEqual(result, coincidence);
+  assert.ok(result.startsWith(ENC_PREFIX));
+  assert.equal(decryptCredentialValue(result, storage), coincidence);
+});
+
+test("encrypt round-trips plaintext and does not double-encrypt", () => {
+  const storage = fakeSafeStorage();
+  const once = encryptCredentialValue("secret", storage);
+  const twice = encryptCredentialValue(once, storage);
+  assert.equal(twice, once);
+  assert.equal(decryptCredentialValue(once, storage), "secret");
+});
+
+test("decrypt returns ciphertext unchanged when safeStorage cannot decrypt", () => {
+  const storage = fakeSafeStorage({ decryptThrows: true });
+  const stale = completeCiphertextPlaceholder("stale");
+  assert.equal(decryptCredentialValue(stale, storage), stale);
+});
@@ -4,6 +4,7 @@
 import packageJson from '../../../package.json';
 import { EncryptionService } from '../EncryptionService';
 import { mergeSyncPayloads } from '../../../domain/syncMerge';
+import { stripSyncPayloadEncryptedCredentials, healPoisonedSecretsForMerge } from '../../../domain/credentials';
 import { summarizeSyncChanges, withSyncReliabilityMeta } from '../../../domain/syncReliability';
 import { detectSuspiciousShrink, type ShrinkFinding } from '../../../domain/syncGuards';
 import { resolveCloudSyncConflictAction } from '../../../domain/syncStrategy';
@@ -467,11 +468,18 @@ export async function syncToProviderImpl(this: any,
          assertSyncSecurityGeneration(this, syncSecurityGeneration);
          const base = await this.loadSyncBase(provider);
          baseForConflict = base;
-          const mergeResult = mergeSyncPayloads(base, payload, remotePayload);
-          const mergedPayload = withSyncReliabilityMeta(mergeResult.payload, base, {
-            deviceId: this.state.deviceId,
-            now: Date.now(),
-          });
+          const localHealed = healPoisonedSecretsForMerge(payload, remotePayload, base);
+          remotePayload = healPoisonedSecretsForMerge(remotePayload, payload, base);
+          remotePayloadForConflict = remotePayload;
+          const mergeResult = mergeSyncPayloads(base, localHealed, remotePayload);
+          const mergedPayload = withSyncReliabilityMeta(
+            stripSyncPayloadEncryptedCredentials(mergeResult.payload),
+            base,
+            {
+              deviceId: this.state.deviceId,
+              now: Date.now(),
+            },
+          );
          assertConvergentSyncWriteCompatible(checkResult.remoteFile.meta, mergedPayload);

          console.info('[CloudSyncManager] Three-way merge completed', mergeResult.summary);
@@ -165,7 +165,7 @@ test("syncAllProviders uses the newest cloud payload without merging other remot
    const results = await syncAllProvidersImpl.call(manager, localPayload);

    assert.equal(results.get("github")?.action, "download");
-    assert.equal(results.get("github")?.mergedPayload, githubPayload);
+    assert.deepEqual(results.get("github")?.mergedPayload, githubPayload);
    assert.equal(results.get("github")?.remoteFile, githubRemote);
    assert.equal(uploaded.length, 1);
    assert.equal(uploaded[0].provider, "google");
@@ -816,3 +816,93 @@ test("syncToProvider preserves a merged payload discovered by a non-target provi
  assert.equal(selected.mergedPayload, mergedPayload);
  assert.equal(selected.remoteFile, undefined);
 });
+
+test("syncAllProviders smart-merge strips device-bound enc:v1 secrets before upload", async () => {
+  const originalDecryptPayload = EncryptionService.decryptPayload;
+  const originalEncryptPayload = EncryptionService.encryptPayload;
+  const completeBlob = Buffer.alloc(31, 0);
+  Buffer.from("v10", "utf8").copy(completeBlob, 0);
+  const ENC = `enc:v1:${completeBlob.toString("base64")}`;
+  const checkedRemote = remoteFile("github", 5, 500);
+  const localPayload = {
+    ...payload("shared"),
+    hosts: [{
+      ...payload("shared").hosts[0]!,
+      password: "kept-secret",
+    }],
+  };
+  const remotePoisoned: SyncPayload = {
+    ...payload("shared"),
+    hosts: [
+      {
+        ...payload("shared").hosts[0]!,
+        label: "remote-label",
+        password: ENC,
+      },
+    ],
+  };
+  const uploaded: SyncPayload[] = [];
+
+  EncryptionService.decryptPayload = async () => remotePoisoned;
+  EncryptionService.encryptPayload = async (outgoing: SyncPayload) => ({
+    ...remoteFile("github", 6, 600),
+    payload: JSON.stringify(outgoing),
+  });
+
+  try {
+    const manager = {
+      masterPassword: "pw",
+      adapters: new Map(),
+      state: {
+        securityState: "UNLOCKED",
+        providers: {
+          github: { enabled: true, connected: true, status: "connected" },
+          google: { enabled: false, connected: false, status: "disconnected" },
+          onedrive: { enabled: false, connected: false, status: "disconnected" },
+          webdav: { enabled: false, connected: false, status: "disconnected" },
+          s3: { enabled: false, connected: false, status: "disconnected" },
+        },
+        lastError: null,
+        syncState: "IDLE",
+        syncStrategy: "smartMerge",
+        localVersion: 1,
+        deviceId: "local-device",
+        deviceName: "Local",
+      },
+      getConnectedAdapter: async (provider: CloudProvider) => ({ provider }),
+      updateProviderStatus: () => {},
+      emit: () => {},
+      checkProviderConflict: async () => ({ conflict: true, remoteFile: checkedRemote }),
+      loadSyncBase: async () => ({
+        ...payload("shared"),
+        hosts: [{
+          ...payload("shared").hosts[0]!,
+          password: "kept-secret",
+        }],
+      }),
+      uploadToProvider: async (
+        _provider: CloudProvider,
+        _adapter: unknown,
+        _file: SyncedFile,
+        outgoing: SyncPayload,
+      ) => {
+        uploaded.push(outgoing);
+        return { success: true, provider: "github" as const, action: "upload" as const, version: 6 };
+      },
+      exitBlockedState: () => {},
+      notifyStateChange: () => {},
+    };
+
+    const results = await syncAllProvidersImpl.call(manager, localPayload);
+    assert.equal(results.get("github")?.success, true);
+    assert.equal(uploaded.length, 1);
+    const sharedHost = uploaded[0]?.hosts.find((host) => host.id === "shared");
+    assert.ok(sharedHost);
+    // Local/base usable secret must survive; remote non-secret edits can still apply.
+    assert.equal(sharedHost?.password, "kept-secret");
+    assert.equal(sharedHost?.label, "remote-label");
+  } finally {
+    EncryptionService.decryptPayload = originalDecryptPayload;
+    EncryptionService.encryptPayload = originalEncryptPayload;
+  }
+});
@@ -7,6 +7,7 @@ import {
 import packageJson from '../../../package.json';
 import { EncryptionService } from '../EncryptionService';
 import { mergeSyncPayloads } from '../../../domain/syncMerge';
+import { stripSyncPayloadEncryptedCredentials, healPoisonedSecretsForMerge } from '../../../domain/credentials';
 import {
  SYNC_SNAPSHOT_LIMIT,
  summarizeSyncChanges,
@@ -51,7 +52,9 @@ async function downloadRemoteForSyncAllImpl(this: any,
  syncSecurityGeneration?: number,
 ): Promise<SyncResult> {
  assertSyncSecurityGeneration(this, syncSecurityGeneration);
-  const payload = await EncryptionService.decryptPayload(remoteFile, this.masterPassword);
+  const payload = stripSyncPayloadEncryptedCredentials(
+    await EncryptionService.decryptPayload(remoteFile, this.masterPassword),
+  );
  assertSyncSecurityGeneration(this, syncSecurityGeneration);
  this.updateProviderStatus(provider, 'connected');

@@ -301,15 +304,23 @@ export async function syncAllProvidersImpl(this: any,
          let merged = payload;
          for (const c of conflicts) {
            const providerBase = await this.loadSyncBase(c.provider as CloudProvider);
-            const remotePayload = await EncryptionService.decryptPayload(
+            const remoteRaw = await EncryptionService.decryptPayload(
              c.check!.remoteFile!,
              this.masterPassword,
            );
+            const localHealed = healPoisonedSecretsForMerge(merged, remoteRaw, providerBase);
+            const remotePayload = healPoisonedSecretsForMerge(
+              remoteRaw,
+              merged,
+              providerBase,
+            );
            assertSyncSecurityGeneration(this, syncSecurityGeneration);
-            const result = mergeSyncPayloads(providerBase, merged, remotePayload);
+            const result = mergeSyncPayloads(providerBase, localHealed, remotePayload);
            merged = result.payload;
          }
-          const mergeResult = { payload: merged };
+          const mergeResult = {
+            payload: stripSyncPayloadEncryptedCredentials(merged),
+          };

          console.info('[CloudSyncManager] syncAll: three-way merge completed');

@@ -1220,7 +1220,7 @@ test("startPortForward uses the system agent when a synced key cannot be decrypt
    label: "Synced key",
    type: "ED25519",
    publicKey: "ssh-ed25519 AAAASELECTED",
-    privateKey: "enc:v1:djEwAAAA",
+    privateKey: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
    source: "imported",
    category: "key",
    created: 1,
@@ -1249,7 +1249,7 @@ test("startPortForward keeps automatic target discovery available with an unread
  const bridge = installBridgeStub();
  const result = await startPortForward(
    rule({ id: "rule-auto-unreadable" }),
-    host({ authMethod: "auto", password: "enc:v1:djEwAAAA" }),
+    host({ authMethod: "auto", password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==" }),
    [],
    [],
    [],
@@ -1267,7 +1267,7 @@ test("startPortForward keeps automatic jump discovery available with an unreadab
    id: "jump-1",
    label: "Jump",
    authMethod: "auto",
-    password: "enc:v1:djEwAAAA",
+    password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
  });
  const result = await startPortForward(
    rule({ id: "rule-auto-jump-unreadable" }),
@@ -1415,7 +1415,7 @@ test("startPortForward rejects proxy identities with blank usernames even when p
      label: "Proxy login",
      username: "",
      authMethod: "password",
-      password: "enc:v1:djEwAAAA",
+      password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      created: 1,
    }],
    (status, error) => statuses.push(error ? `${status}:${error}` : status),
@@ -1487,7 +1487,7 @@ test("startPortForward rejects target proxy identity passwords that cannot be de
      label: "Proxy login",
      username: "proxy-user",
      authMethod: "password",
-      password: "enc:v1:djEwAAAA",
+      password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      created: 1,
    }],
    (status, error) => statuses.push(error ? `${status}:${error}` : status),
@@ -1576,7 +1576,7 @@ test("startPortForward rejects incomplete jump host proxy identities before star
      label: "Proxy login",
      username: "",
      authMethod: "password",
-      password: "enc:v1:djEwAAAA",
+      password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      created: 1,
    }],
    (status, error) => statuses.push(error ? `${status}:${error}` : status),
@@ -1655,7 +1655,7 @@ test("startPortForward rejects jump host proxy identity passwords that cannot be
      label: "Proxy login",
      username: "proxy-user",
      authMethod: "password",
-      password: "enc:v1:djEwAAAA",
+      password: "enc:v1:djEwdGVzdAAAAAAAAAAAAAAAAA==",
      created: 1,
    }],
    (status, error) => statuses.push(error ? `${status}:${error}` : status),
Author	SHA1	Message	Date
Cursor Agentand陈大猫	1d3328d1e9	fix(credentials): require full DPAPI provider GUID signature Accept Windows safeStorage blobs only when they start with version 01 00 00 00 plus provider GUID df9d8cd0-1501-11d1-8c7a-00c04fc297eb, so coincidental 01 00 00 00 prefixes are not treated as ciphertext. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 05:05:30 +00:00
Cursor Agentand陈大猫	97dbacffb3	fix(credentials): reject impossible v10/v11 ciphertext lengths Accept only CBC-aligned sizes (19+16n) or GCM-sized blobs (>=31) so coincidental enc:v1 plaintext of intermediate length is encrypted instead of treated as an undecryptable placeholder. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:58:58 +00:00
Cursor Agentand陈大猫	b05e535740	fix(sync): treat preferred credential deletions as authoritative When healing enc:v1 before merge, an empty/missing secret on a present preferred entity is an intentional clear and must not be revived from base. Only fall back to base when preferred is absent or also poisoned. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:53:17 +00:00
Cursor Agentand陈大猫	f42694964c	test(credentials): use complete enc:v1 fixtures for stricter detector Short placeholders like enc:v1:djEwAAAA no longer pass the platform header + minimum-size checks. Update auth/SFTP/proxy/sync fixtures to full v10-shaped blobs so npm test matches production validation. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:47:00 +00:00
Cursor Agentand陈大猫	19575264fe	fix(credentials): detect Windows DPAPI by decoded header bytes Real DPAPI blobs start with 01 00 00 00 d0 8c... and base64-encode as AQAAANCM..., so the previous AQAAAA string prefix rejected them and allowed double-wrapping after key rotation. Match decoded headers in both the main-process bridge and renderer predicate. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:39:56 +00:00
Cursor Agentand陈大猫	835f316870	fix(sync): keep enc:v1 intact during convergent materialize Stripping device-bound secrets inside materializeSyncPayloadFromConvergentState broke envelope validation for poisoned-but-consistent v2 snapshots, so decrypt could not hydrate the clouds #2702 needs to recover. Portable stripping stays at apply/upload boundaries. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:33:44 +00:00
Cursor Agentand陈大猫	8734803475	fix(sync): heal local and remote secrets before smart-merge Smart-merge could select a locally-changed entity whose only secret delta was enc:v1 poison, then strip and upload empty secrets. Heal both sides from the opposite payload/base before merge on all sync paths. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:27:05 +00:00
Cursor Agentand陈大猫	111c77f877	fix(sync): sanitize payloads at every apply/commit boundary Codex P1: vault apply stripped enc:v1 while commitRemoteInspection and convergent materialization could keep the poison. Sanitize merged/remote payloads before apply+base commit, strip on CRDT materialization, and sanitize convergent apply inputs. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:20:39 +00:00
Cursor Agentand陈大猫	4c742486cb	fix(credentials): address Codex P1 CBC min and startup heal - Accept 19-byte v10/v11 CBC OSCrypt blobs (not only 31-byte GCM) - Heal poisoned remote secrets before startup smart-merge - Strip unresolved placeholders on merge round-trip upload Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:12:44 +00:00
Cursor Agentand陈大猫	e5f07ad24e	fix(credentials): address Codex P1 review on #2702 - Decode enc:v1 payloads with atob in the renderer-safe domain helper - Heal poisoned remote secrets from local/base before smart-merge so good credentials are not discarded as remote-only deletions - Keep post-merge strip so leftover enc:v1 never uploads Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:07:53 +00:00
Cursor Agentand陈大猫	40212dc0db	fix(credentials): address Codex P2 review on #2702 - Always re-encrypt vault init batches so plaintext siblings are not left unprotected when one record is a stale enc:v1 placeholder - Sanitize device-bound secrets before convergent restore prepare so CRDT replica commit matches vault import - Require a complete safeStorage blob (header + min 31 bytes) before treating enc:v1 as ciphertext; encrypt header-only coincidences Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 04:00:45 +00:00
Cursor Agentand陈大猫	4173b49b3a	fix(sync): strip enc:v1 secrets from smart-merge uploads Bugbot found that after local apply sanitized placeholders, legacy v1 smart-merge could still decrypt an unstripped remote, merge it, and re-upload the poison. Strip device-bound credentials on remote decrypt and again on the merged payload before upload. Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 03:48:40 +00:00
Cursor Agentand陈大猫	ae8e8a6bd9	fix(credentials): stop double-encrypting undecryptable safeStorage blobs When local decrypt failed (e.g. OSCrypt key churn after reboot), encrypt used to wrap the leftover enc:v1 ciphertext again, permanently poisoning the vault. Startup sync could also push those placeholders to cloud and make download restore the same poison. - Keep real enc:v1 blobs unchanged on encrypt (header check, no wrap) - Strip device-bound placeholders when applying portable sync payloads - Guard startup local-wins / merge round-trips before upload - Skip vault init re-encrypt writes when secrets are still undecrypted Fixes #2702 Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>	2026-08-06 03:42:59 +00:00