claude-code: the sealed hand-over, the credentials write with the lineage rule, the identity read (hq to-be 40 WP2, in progress)

The parts of the agent module that hold whichever way the console is registered: X25519 +
HKDF + AES-GCM from Node's own library so the bundle carries no dependency; the predecessor's
lineage rule (rotation only if newer, a re-issue adopted, a switch regardless) with its
incidents as tests; an atomic 0600 write that strips any refresh token and keeps keys it does not
know; the account read from the agent's own state file. Manifest and renderer follow.

modules/claude-code/test/grant.test.ts

@@ -0,0 +1,54 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { mkdtempSync, readFileSync, statSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import {
+  decideApply, grantOf, holdsLogin, readCredentials, withGrant, writeCredentials, type Grant,
+} from "../dist/grant.js";
+
+const NOW = 1_700_000_000_000;
+const HOUR = 3_600_000;
+const g = (over: Partial<Grant> = {}): Grant => ({
+  accessToken: "tok-A", expiresAt: NOW + HOUR, refreshTokenExpiresAt: NOW + 30 * 24 * HOUR, ...over,
+});
+
+test("a rotation applies a newer grant of the same licence", () => {
+  assert.deepEqual(decideApply(g(), g({ accessToken: "tok-B", expiresAt: NOW + 2 * HOUR }), "rotation"), { apply: true });
+});
+
+test("a rotation refuses a grant that arrived late and is older", () => {
+  const d = decideApply(g({ accessToken: "new", expiresAt: NOW + 2 * HOUR }), g({ accessToken: "old" }), "rotation");
+  assert.equal(d.apply === false && d.reason, "not-newer");
+});
+
+test("a grant re-issued by a login is adopted even though it expires sooner (2026-09-05)", () => {
+  const local = g({ expiresAt: NOW + 8 * HOUR, refreshTokenExpiresAt: NOW + 30 * 24 * HOUR });
+  const offered = g({ accessToken: "reissued", expiresAt: NOW + HOUR, refreshTokenExpiresAt: NOW + 5 * 24 * HOUR });
+  assert.deepEqual(decideApply(local, offered, "rotation"), { apply: true, reissued: true });
+});
+
+test("a switch to another licence applies whatever the expiries say", () => {
+  const local = g({ expiresAt: NOW + 8 * HOUR });
+  assert.equal(decideApply(local, g({ accessToken: "other", expiresAt: NOW + HOUR }), "switch").apply, true);
+});
+
+test("the same token is not rewritten", () => {
+  assert.deepEqual(decideApply(g(), g(), "switch"), { apply: false, reason: "already-current" });
+});
+
+test("a full grant left by a login is seen as a login, and stripped when the node's own is written", () => {
+  const dir = mkdtempSync(join(tmpdir(), "claude-code-"));
+  const path = join(dir, ".claude", ".credentials.json");
+  writeFileSync(join(dir, "x"), "");
+  const login = { claudeAiOauth: { accessToken: "at-login", refreshToken: "rt-login", expiresAt: NOW }, other: 1 };
+  assert.equal(holdsLogin(login), true);
+  writeCredentials(path, withGrant(login, g({ accessToken: "at-mesh", scopes: ["user:inference"] })));
+  const back = readCredentials(path)!;
+  assert.equal(holdsLogin(back), false);
+  assert.equal(grantOf(back)!.accessToken, "at-mesh");
+  assert.deepEqual(back.claudeAiOauth!.scopes, ["user:inference"]);
+  assert.equal(back.other, 1, "a key the module does not know was lost");
+  assert.ok(!readFileSync(path, "utf8").includes("rt-login"));
+  assert.equal(statSync(path).mode & 0o777, 0o600);
+});

modules/claude-code/test/identity.test.ts

@@ -0,0 +1,19 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { mkdtempSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { readIdentity } from "../dist/identity.js";
+
+test("the account is read from the agent's state file", () => {
+  const p = join(mkdtempSync(join(tmpdir(), "cc-id-")), ".claude.json");
+  writeFileSync(p, JSON.stringify({ oauthAccount: { accountUuid: "u-1", emailAddress: "a@example.org" }, other: 2 }));
+  assert.deepEqual(readIdentity(p), { accountUuid: "u-1", emailAddress: "a@example.org", organizationUuid: undefined });
+});
+
+test("no state file, or no account in it, is no identity rather than a guess", () => {
+  assert.equal(readIdentity("/nonexistent/.claude.json"), null);
+  const p = join(mkdtempSync(join(tmpdir(), "cc-id-")), ".claude.json");
+  writeFileSync(p, "{}");
+  assert.equal(readIdentity(p), null);
+});

modules/claude-code/test/seal.test.ts

@@ -0,0 +1,31 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { generateKeyPair, open, seal } from "../dist/seal.js";
+
+test("a box opens with its recipient's key and yields the value", () => {
+  const k = generateKeyPair();
+  assert.equal(open(seal("at-secret", k.publicKey), k.privateKey), "at-secret");
+});
+
+test("a box sealed for one node does not open with another node's key", () => {
+  const a = generateKeyPair();
+  const b = generateKeyPair();
+  assert.throws(() => open(seal("at-secret", a.publicKey), b.privateKey));
+});
+
+test("a tampered box is refused, not opened to garbage", () => {
+  const k = generateKeyPair();
+  const box = seal("at-secret", k.publicKey);
+  const ct = Buffer.from(box.ct, "base64");
+  ct[0] ^= 0xff;
+  assert.throws(() => open({ ...box, ct: ct.toString("base64") }, k.privateKey));
+});
+
+test("two boxes of one value share nothing a reader could compare", () => {
+  const k = generateKeyPair();
+  const x = seal("at-secret", k.publicKey);
+  const y = seal("at-secret", k.publicKey);
+  assert.notEqual(x.ct, y.ct);
+  assert.notEqual(x.eph, y.eph);
+  assert.ok(!JSON.stringify(x).includes("at-secret"));
+});