diff --git a/package.json b/package.json
index 74777d68..84852cde 100644
--- a/package.json
+++ b/package.json
@@ -52,13 +52,13 @@
   },
   "resolutions": {
     "@polkadot/api": "^16.5.6",
-    "@polkadot/keyring": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.1/keyring-14.0.3-quantus.1.tgz",
-    "@polkadot/networks": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.1/networks-14.0.3-quantus.1.tgz",
+    "@polkadot/keyring": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.2/keyring-14.0.3-quantus.2.tgz",
+    "@polkadot/networks": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.2/networks-14.0.3-quantus.2.tgz",
     "@polkadot/rpc-provider": "^16.5.6",
     "@polkadot/types": "^16.5.6",
-    "@polkadot/ui-keyring": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.1/ui-keyring-3.16.7-quantus.1.tgz",
+    "@polkadot/ui-keyring": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.2/ui-keyring-3.16.7-quantus.2.tgz",
     "@polkadot/util": "^14.0.3",
-    "@polkadot/util-crypto": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.1/util-crypto-14.0.3-quantus.1.tgz",
+    "@polkadot/util-crypto": "https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.2/util-crypto-14.0.3-quantus.2.tgz",
     "@polkadot/x-fetch": "^14.0.3",
     "safe-buffer": "^5.2.1",
     "typescript": "^5.5.4"
diff --git a/packages/extension-base/package.json b/packages/extension-base/package.json
index db019c44..9cc61d9e 100644
--- a/packages/extension-base/package.json
+++ b/packages/extension-base/package.json
@@ -34,6 +34,7 @@
     "@polkadot/ui-settings": "^3.16.7",
     "@polkadot/util": "^14.0.3",
     "@polkadot/util-crypto": "^14.0.3",
+    "@quantus/codec": "^0.1.0",
     "@quantus/crypto": "^0.1.1",
     "eventemitter3": "^5.0.1",
     "rxjs": "^7.8.1",
diff --git a/packages/extension-ui/src/util/chains.ts b/packages/extension-ui/src/util/chains.ts
index fd1556e1..19c86ee1 100644
--- a/packages/extension-ui/src/util/chains.ts
+++ b/packages/extension-ui/src/util/chains.ts
@@ -3,10 +3,24 @@
 
 import type { MetadataDefBase } from '@polkadot/extension-inject/types';
 
-import { selectableNetworks } from '@polkadot/networks';
+import { isQuantumSafe, selectableNetworks } from '@polkadot/networks';
 
+// The chains this extension offers.
+//
+// Filtered here rather than in @polkadot/networks. An earlier attempt gated
+// `selectableNetworks` itself, which broke @polkadot/api at import:
+// @polkadot/types-known looks up every chain it holds upgrade history for and
+// throws when one is missing. Those lists are a library's view of what Substrate
+// networks exist; which of them a *wallet* offers is the wallet's decision, and
+// this is the wallet.
+//
+// The filter is post-quantum accounts. Everything else in the registry uses a
+// discrete-log scheme — *25519, Sr25519, Ed25519, secp256k1 — all of which Shor's
+// algorithm breaks at once, so such a chain has no quantum-safe account type to
+// offer whatever else is true of it. A null standardAccount counts as unsafe:
+// unknown is not the same as safe.
 const hashes: MetadataDefBase[] = selectableNetworks
-  .filter(({ genesisHash }) => !!genesisHash.length)
+  .filter(({ genesisHash, standardAccount }) => !!genesisHash.length && isQuantumSafe(standardAccount))
   .map((network) => ({
     chain: network.displayName,
     genesisHash: network.genesisHash[0],
diff --git a/scripts/tier1/submit.mjs b/scripts/tier1/submit.mjs
new file mode 100644
index 00000000..455a9007
--- /dev/null
+++ b/scripts/tier1/submit.mjs
@@ -0,0 +1,173 @@
+// Copyright 2019-2026 @polkadot/extension authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+// quantus/extension#7 tier 1: sign a real extrinsic with the forked keyring and
+// submit it to a real node. No browser, no extension, no dapp.
+//
+// Nothing here uses @polkadot/api. Its codec cannot read or write this chain —
+// quantus/api#1 has the evidence — so every byte on the wire is produced by
+// @quantus/codec against metadata the node generated by running
+// `Metadata_metadata` against the runtime WASM. `WsProvider` appears only as a
+// JSON-RPC transport; no type in this file is decoded by it.
+
+import { Runtime } from '@quantus/codec';
+import { contextForSpec } from '@quantus/crypto';
+
+import { Keyring } from '@polkadot/keyring';
+import { WsProvider } from '@polkadot/rpc-provider';
+import { u8aToHex } from '@polkadot/util';
+import { blake2AsU8a, cryptoWaitReady, decodeAddress } from '@polkadot/util-crypto';
+
+const ENDPOINT = process.env.QUANTUS_WS || 'wss://a1-heisenberg.quantus.cat';
+// crystal_alice: seed = 32 zero bytes, ML-DSA-87. Published in the chain's own
+// source, funded at dev genesis, and assumed compromised by everyone.
+const SEED = `0x${'00'.repeat(32)}`;
+const TYPE = 'dilithium87';
+// Substrate's own rule, from `unchecked_extrinsic.rs`: a signing payload longer
+// than 256 bytes is signed as its BLAKE2b-256 hash, otherwise as-is.
+const HASH_ABOVE = 256;
+
+await cryptoWaitReady();
+
+const keyring = new Keyring({ ss58Format: 189, type: TYPE });
+const pair = keyring.createFromUri(SEED, { name: 'crystal_alice' }, TYPE);
+
+console.log(`signer      ${pair.address}`);
+
+const provider = new WsProvider(ENDPOINT);
+
+await provider.isReady;
+
+const [version, genesisHash, metadataHex] = await Promise.all([
+  provider.send('state_getRuntimeVersion', []),
+  provider.send('chain_getBlockHash', ['0x0']),
+  provider.send('state_getMetadata', [])
+]);
+
+const specVersion = version.specVersion;
+const transactionVersion = version.transactionVersion;
+const runtime = Runtime.fromMetadata(Uint8Array.from(Buffer.from(metadataHex.slice(2), 'hex')));
+
+console.log(`chain       ${version.specName} spec ${specVersion} tx ${transactionVersion}`);
+console.log(`genesis     ${genesisHash}`);
+console.log(`extrinsic   v${runtime.extrinsicVersion}`);
+
+const dest = process.env.QUANTUS_DEST || 'qzkYEQv8tQsmniZYdame3Cku18RL5g9bGK9Pdydq5TMPdpE3y'; // crystal_bob
+const amount = 1_000_000_000n; // 0.001
+const destId = u8aToHex(decodeAddress(dest));
+const nonce = parseInt(await provider.send('system_accountNextIndex', [pair.address]), 10);
+
+console.log(`recipient   ${dest}`);
+console.log(`nonce       ${nonce}`);
+
+const call = runtime.encodeCall('Balances', 'transfer_keep_alive', {
+  dest: { Id: destId },
+  value: amount.toString()
+});
+
+console.log(`call        ${u8aToHex(call)}`);
+
+// An immortal era, so `CheckMortality`'s implicit is the genesis hash and there
+// is no birth block to agree with the node about. Mortality is a hardening step,
+// not part of proving the fork can spend.
+const values = runtime.standardExtensions({
+  blockHash: genesisHash,
+  genesisHash,
+  nonce,
+  specVersion,
+  transactionVersion
+});
+
+// Every extension the runtime declares as non-empty and `standardExtensions`
+// does not cover. Reported rather than skipped: skipping is the polkadot-js
+// failure mode this whole package exists to avoid.
+const unmet = runtime
+  .signedExtensions()
+  .filter((e) => (e.needsExtra || e.needsAdditional) && !values[e.identifier]);
+
+if (unmet.length) {
+  throw new Error(`runtime declares extensions this harness cannot fill: ${unmet.map((e) => e.identifier).join(', ')}`);
+}
+
+const extra = runtime.encodeExtra(values);
+const payload = runtime.signerPayload(call, values);
+const toSign = payload.length > HASH_ABOVE ? blake2AsU8a(payload) : payload;
+const context = contextForSpec(specVersion);
+
+console.log(`extra       ${u8aToHex(extra)}`);
+console.log(`payload     ${payload.length} bytes -> signing ${toSign.length}`);
+console.log(`context     ${context.length ? new TextDecoder().decode(context) : '(empty)'}`);
+
+const signature = pair.sign(toSign, { context, withType: true });
+
+console.log(`signature   ${signature.length} bytes, variant 0x${signature[0].toString(16).padStart(2, '0')}`);
+
+const extrinsic = runtime.encodeExtrinsic({ Id: u8aToHex(pair.addressRaw) }, signature, extra, call);
+
+console.log(`extrinsic   ${extrinsic.length} bytes`);
+
+// Decoding what we are about to send, with the same runtime that built it. A
+// round trip that fails here is a bug in this package; one that succeeds and is
+// still rejected is a disagreement with the chain, and the two are worth telling
+// apart before the node is involved.
+const readBack = runtime.decodeExtrinsic(extrinsic);
+
+console.log(`round trip  v${readBack.version} signed=${readBack.signed} ${JSON.stringify(readBack.call)}`);
+
+const hash = await provider.send('author_submitExtrinsic', [u8aToHex(extrinsic)]);
+
+// Acceptance into the pool already means the signature verified: an extrinsic
+// the runtime cannot check is rejected right here, as `1010: Invalid
+// Transaction: Transaction has a bad signature`.
+console.log(`accepted    ${hash}`);
+
+// Inclusion, though, is the claim worth making, so wait for the chain to put it
+// in a block and then read that block back with the same runtime — which also
+// exercises the thing @polkadot/api cannot do at all: every Quantus block opens
+// with a timestamp inherent whose preamble byte is `0x05`, bare and version 5,
+// while this signed extrinsic is `0x84`, signed and version 4.
+const DEADLINE = Date.now() + 10 * 60 * 1000;
+
+let height = parseInt((await provider.send('chain_getHeader', [])).number, 16);
+let found = null;
+
+while (!found && Date.now() < DEADLINE) {
+  const head = parseInt((await provider.send('chain_getHeader', [])).number, 16);
+
+  while (height <= head && !found) {
+    const blockHash = await provider.send('chain_getBlockHash', [`0x${height.toString(16)}`]);
+    const block = await provider.send('chain_getBlock', [blockHash]);
+
+    for (const [index, raw] of block.block.extrinsics.entries()) {
+      const decoded = runtime.decodeExtrinsic(Uint8Array.from(Buffer.from(raw.slice(2), 'hex')));
+
+      if (raw === u8aToHex(extrinsic)) {
+        found = { blockHash, decoded, height, index };
+      }
+    }
+
+    height++;
+  }
+
+  if (!found) {
+    await new Promise((resolve) => setTimeout(resolve, 10_000));
+  }
+}
+
+if (!found) {
+  throw new Error('accepted into the pool but not included within ten minutes');
+}
+
+console.log(`included    block ${found.height} index ${found.index} (${found.blockHash})`);
+console.log(`decoded     ${JSON.stringify(found.decoded.call)}`);
+console.log(`signature   ${JSON.stringify(found.decoded.signature).slice(0, 60)}…`);
+
+const after = parseInt(await provider.send('system_accountNextIndex', [pair.address]), 10);
+
+console.log(`nonce       ${nonce} -> ${after}`);
+
+if (after !== nonce + 1) {
+  throw new Error(`nonce did not advance: expected ${nonce + 1}, got ${after}`);
+}
+
+await provider.disconnect();
diff --git a/tsconfig.eslint.json b/tsconfig.eslint.json
index 64ace445..ed014e31 100644
--- a/tsconfig.eslint.json
+++ b/tsconfig.eslint.json
@@ -10,7 +10,8 @@
     ".prettierrc.cjs",
     "eslint.config.js",
     "i18next-scanner.config.cjs",
-    "rollup.config.js"
+    "rollup.config.js",
+    "scripts/**/*.mjs"
   ],
   "exclude": [
     "**/node_modules/**/*"
diff --git a/yarn.lock b/yarn.lock
index 257dc7d8..0efbee8e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -982,6 +982,7 @@ __metadata:
     "@polkadot/ui-settings": "npm:^3.16.7"
     "@polkadot/util": "npm:^14.0.3"
     "@polkadot/util-crypto": "npm:^14.0.3"
+    "@quantus/codec": "npm:^0.1.0"
     "@quantus/crypto": "npm:^0.1.1"
     eventemitter3: "npm:^5.0.1"
     rxjs: "npm:^7.8.1"
@@ -1151,29 +1152,29 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"@polkadot/keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.1/keyring-14.0.3-quantus.1.tgz":
-  version: 14.0.3-quantus.1
-  resolution: "@polkadot/keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.1/keyring-14.0.3-quantus.1.tgz"
+"@polkadot/keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.2/keyring-14.0.3-quantus.2.tgz":
+  version: 14.0.3-quantus.2
+  resolution: "@polkadot/keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fkeyring/-/14.0.3-quantus.2/keyring-14.0.3-quantus.2.tgz"
   dependencies:
     "@polkadot/util": "npm:14.0.3"
-    "@polkadot/util-crypto": "npm:14.0.3-quantus.1"
+    "@polkadot/util-crypto": "npm:14.0.3-quantus.2"
     "@quantus/crypto": "npm:^0.1.0"
     tslib: "npm:^2.8.0"
   peerDependencies:
     "@polkadot/util": 14.0.3
     "@polkadot/util-crypto": 14.0.3
-  checksum: 10/513818828aebd066ec618e114441bbd2aa9cb83527fce4a78867d3b9f982e4bb17527090642d704a2a8b1fd047276b30ce8c22efcdc10c81d3e318f4b42c7059
+  checksum: 10/e3885d6a75b4c006887d24dadbfc25fff562baae84d42fd2125878af60daecbf789deed12c975edfef0884a3caff4dd469dcdcd8b63eacbd1a5fbf8bbfe48815
   languageName: node
   linkType: hard
 
-"@polkadot/networks@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.1/networks-14.0.3-quantus.1.tgz":
-  version: 14.0.3-quantus.1
-  resolution: "@polkadot/networks@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.1/networks-14.0.3-quantus.1.tgz"
+"@polkadot/networks@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.2/networks-14.0.3-quantus.2.tgz":
+  version: 14.0.3-quantus.2
+  resolution: "@polkadot/networks@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fnetworks/-/14.0.3-quantus.2/networks-14.0.3-quantus.2.tgz"
   dependencies:
     "@polkadot/util": "npm:14.0.3"
     "@substrate/ss58-registry": "npm:^1.51.0"
     tslib: "npm:^2.8.0"
-  checksum: 10/5d93c35908eec5b41f29ffd4a5a79234c7329264e61d6b4346398e5b495b80109c5ce35a2f2bb95e9f6fc4eb22b9da047b9ca4191ec73a668c43da73861d7122
+  checksum: 10/3d2f0a08cde4be418d073f63587bed451a6ce4c91a8872a5e0c4191ff3e62d57a7942c1a1b6c183ed9c22742f5b95b7496fe4e32e3565baf2093d879ac51a55e
   languageName: node
   linkType: hard
 
@@ -1362,14 +1363,14 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@polkadot/ui-keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.1/ui-keyring-3.16.7-quantus.1.tgz":
-  version: 3.16.7-quantus.1
-  resolution: "@polkadot/ui-keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.1/ui-keyring-3.16.7-quantus.1.tgz"
+"@polkadot/ui-keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.2/ui-keyring-3.16.7-quantus.2.tgz":
+  version: 3.16.7-quantus.2
+  resolution: "@polkadot/ui-keyring@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Fui-keyring/-/3.16.7-quantus.2/ui-keyring-3.16.7-quantus.2.tgz"
   dependencies:
-    "@polkadot/keyring": "npm:14.0.3-quantus.1"
+    "@polkadot/keyring": "npm:14.0.3-quantus.2"
     "@polkadot/ui-settings": "npm:3.16.7"
     "@polkadot/util": "npm:^14.0.3"
-    "@polkadot/util-crypto": "npm:14.0.3-quantus.1"
+    "@polkadot/util-crypto": "npm:14.0.3-quantus.2"
     mkdirp: "npm:^3.0.1"
     rxjs: "npm:^7.8.1"
     store: "npm:^2.0.12"
@@ -1378,7 +1379,7 @@ __metadata:
     "@polkadot/keyring": "*"
     "@polkadot/ui-settings": "*"
     "@polkadot/util": "*"
-  checksum: 10/8f475e2fbbf795a82513e5195ec924f4c3077cb9cf6f09205db6507a814a527b0b99ba077e44ba506e3c8120366ae1f33371653858c7ed1f291bc1fd2917cb9f
+  checksum: 10/bd62eb7fb2ad152c8f6844938af34fa75fa6b359d5414cbaca0d77c80b808f8a4e51f62b223cbbb1cbe8feefab43b42db86dd978af92dcce3bab5236cdb3a885
   languageName: node
   linkType: hard
 
@@ -1411,13 +1412,13 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@polkadot/util-crypto@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.1/util-crypto-14.0.3-quantus.1.tgz":
-  version: 14.0.3-quantus.1
-  resolution: "@polkadot/util-crypto@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.1/util-crypto-14.0.3-quantus.1.tgz"
+"@polkadot/util-crypto@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.2/util-crypto-14.0.3-quantus.2.tgz":
+  version: 14.0.3-quantus.2
+  resolution: "@polkadot/util-crypto@https://git.lair.cafe/api/packages/quantus/npm/%40polkadot%2Futil-crypto/-/14.0.3-quantus.2/util-crypto-14.0.3-quantus.2.tgz"
   dependencies:
     "@noble/curves": "npm:^1.3.0"
     "@noble/hashes": "npm:^1.3.3"
-    "@polkadot/networks": "npm:14.0.3-quantus.1"
+    "@polkadot/networks": "npm:14.0.3-quantus.2"
     "@polkadot/util": "npm:14.0.3"
     "@polkadot/wasm-crypto": "npm:^7.5.3"
     "@polkadot/wasm-util": "npm:^7.5.3"
@@ -1429,7 +1430,7 @@ __metadata:
     tslib: "npm:^2.8.0"
   peerDependencies:
     "@polkadot/util": 14.0.3
-  checksum: 10/ae364a2c47ea6033222f34766f83f3c3740966f83f380978b716013d4ab3862f03355034afe6ef84e7f28c90bda1eb347114c342acd5f4844566580d13d34341
+  checksum: 10/78f04147ddfe8ae0bca4cba2f235715615a140de9ab95f10d6e4bbabee4a2865e6f8a84f70668722ab688094a8519eeb019ed5122620b355a3ea40b0d8cfdeb8
   languageName: node
   linkType: hard
 
@@ -1602,6 +1603,16 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@quantus/codec@npm:^0.1.0":
+  version: 0.1.0
+  resolution: "@quantus/codec@npm:0.1.0::__archiveUrl=https%3A%2F%2Fgit.lair.cafe%2Fapi%2Fpackages%2Fquantus%2Fnpm%2F%2540quantus%252Fcodec%2F-%2F0.1.0%2Fcodec-0.1.0.tgz"
+  dependencies:
+    fflate: "npm:^0.8.2"
+    tslib: "npm:^2.7.0"
+  checksum: 10/90d40e0909383f5f0fea3f662772702d78f1b6fbecb9e8cac901e8a20b5adafff97782a4c13faa7e2278abd97c3c12275695d2a21d19790a359df01267febe84
+  languageName: node
+  linkType: hard
+
 "@quantus/crypto@npm:^0.1.0, @quantus/crypto@npm:^0.1.1":
   version: 0.1.1
   resolution: "@quantus/crypto@npm:0.1.1::__archiveUrl=https%3A%2F%2Fgit.lair.cafe%2Fapi%2Fpackages%2Fquantus%2Fnpm%2F%2540quantus%252Fcrypto%2F-%2F0.1.1%2Fcrypto-0.1.1.tgz"