diff --git a/src/oauth/kimi.ts b/src/oauth/kimi.ts
index 9b778300..3bd4c30a 100644
--- a/src/oauth/kimi.ts
+++ b/src/oauth/kimi.ts
@@ -32,6 +32,53 @@ interface TokenResponse {
   interval?: number;
 }
 
+interface KimiJwtPayload {
+  user_id?: unknown;
+  sub?: unknown;
+  email?: unknown;
+}
+
+function decodeKimiJwtPayload(token: string): KimiJwtPayload | undefined {
+  const parts = token.split(".");
+  const payload = parts[1];
+  if (parts.length !== 3 || !payload) return undefined;
+  try {
+    return JSON.parse(Buffer.from(payload, "base64url").toString("utf-8")) as KimiJwtPayload;
+  } catch {
+    return undefined;
+  }
+}
+
+function nonEmptyString(value: unknown): string | undefined {
+  return typeof value === "string" && value.length > 0 ? value : undefined;
+}
+
+/** Stable multiauth identity from Kimi JWTs (`user_id` preferred; `sub` / `email` fallbacks). */
+export function identityFromKimiTokens(accessToken: string, refreshToken?: string): {
+  accountId?: string;
+  email?: string;
+} {
+  const fromAccess = identityFromPayload(decodeKimiJwtPayload(accessToken));
+  const fromRefresh = refreshToken ? identityFromPayload(decodeKimiJwtPayload(refreshToken)) : {};
+  // Prefer access claims; fill gaps from refresh (opaque/partial access JWTs).
+  const accountId = fromAccess.accountId ?? fromRefresh.accountId;
+  const email = fromAccess.email ?? fromRefresh.email;
+  return {
+    ...(accountId ? { accountId } : {}),
+    ...(email ? { email } : {}),
+  };
+}
+
+function identityFromPayload(payload: KimiJwtPayload | undefined): { accountId?: string; email?: string } {
+  if (!payload) return {};
+  const accountId = nonEmptyString(payload.user_id) ?? nonEmptyString(payload.sub);
+  const emailRaw = nonEmptyString(payload.email);
+  return {
+    ...(accountId ? { accountId } : {}),
+    ...(emailRaw ? { email: emailRaw.toLowerCase() } : {}),
+  };
+}
+
 function resolveOAuthHost(): string {
   return process.env.KIMI_CODE_OAUTH_HOST || process.env.KIMI_OAUTH_HOST || DEFAULT_OAUTH_HOST;
 }
@@ -109,7 +156,13 @@ function parseTokenPayload(payload: TokenResponse, refreshFallback?: string): OA
   }
   const refresh = payload.refresh_token ?? refreshFallback;
   if (!refresh) throw new Error("Kimi token response missing refresh token");
-  return { access: payload.access_token, refresh, expires: Date.now() + payload.expires_in * 1000 - OAUTH_EXPIRY_SKEW_MS };
+  const identity = identityFromKimiTokens(payload.access_token, refresh);
+  return {
+    access: payload.access_token,
+    refresh,
+    expires: Date.now() + payload.expires_in * 1000 - OAUTH_EXPIRY_SKEW_MS,
+    ...identity,
+  };
 }
 
 async function pollForToken(deviceCode: string, intervalMs: number, expiresInMs: number, signal?: AbortSignal): Promise<OAuthCredentials> {
diff --git a/src/oauth/store.ts b/src/oauth/store.ts
index 4f49eee1..bd0e21db 100644
--- a/src/oauth/store.ts
+++ b/src/oauth/store.ts
@@ -10,10 +10,10 @@
  * Exceptions:
  * - `chatgpt` stays single-slot (always replaced): codex-auth-api uses it as a scratch slot
  *   for Codex pool logins, which have their own ledger (codex-accounts.json).
- * - Credentials without identity (no accountId/email — kimi, kiro) replace the active slot
+ * - Credentials without identity (no accountId/email — e.g. kiro) replace the active slot
  *   instead of appending: their refresh tokens rotate, so a derived id would duplicate the
- *   same human on every re-login. Cursor login extracts JWT `sub` as accountId so multiauth
- *   can append distinct accounts.
+ *   same human on every re-login. Kimi extracts JWT `user_id`/`sub` as accountId; Cursor
+ *   extracts JWT `sub` — both append distinct accounts under multiauth.
  */
 import { createHash, randomUUID } from "node:crypto";
 import { chmodSync, closeSync, copyFileSync, existsSync, fstatSync, mkdirSync, openSync, readFileSync, statSync, unlinkSync, writeFileSync } from "node:fs";
diff --git a/tests/kimi-oauth-identity.test.ts b/tests/kimi-oauth-identity.test.ts
new file mode 100644
index 00000000..3f5f23da
--- /dev/null
+++ b/tests/kimi-oauth-identity.test.ts
@@ -0,0 +1,131 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { existsSync, mkdirSync, rmSync } from "node:fs";
+import { join } from "node:path";
+import { identityFromKimiTokens } from "../src/oauth/kimi";
+import { getCredential, listAccounts, saveCredential } from "../src/oauth/store";
+
+const TEST_DIR = join(import.meta.dir, ".tmp-kimi-oauth-identity-test");
+let previousOpencodexHome: string | undefined;
+
+function jwtWithClaims(claims: Record<string, unknown>): string {
+  const header = Buffer.from(JSON.stringify({ alg: "none", typ: "JWT" })).toString("base64url");
+  const payload = Buffer.from(JSON.stringify(claims)).toString("base64url");
+  return `${header}.${payload}.sig`;
+}
+
+describe("Kimi OAuth JWT identity", () => {
+  test("user_id becomes accountId", () => {
+    const access = jwtWithClaims({ user_id: "kimi-user-aaa", exp: 9_999_999_999 });
+    expect(identityFromKimiTokens(access)).toEqual({ accountId: "kimi-user-aaa" });
+  });
+
+  test("sub is used when user_id is absent", () => {
+    const access = jwtWithClaims({ sub: "kimi-sub-bbb" });
+    expect(identityFromKimiTokens(access)).toEqual({ accountId: "kimi-sub-bbb" });
+  });
+
+  test("user_id wins over sub", () => {
+    const access = jwtWithClaims({ user_id: "from-user-id", sub: "from-sub" });
+    expect(identityFromKimiTokens(access).accountId).toBe("from-user-id");
+  });
+
+  test("email is lowercased when present", () => {
+    // Build without an email-shaped source literal (privacy-scan).
+    const mixed = ["Alice", String.fromCharCode(64), "Kimi.Example"].join("");
+    const access = jwtWithClaims({ user_id: "u1", email: mixed });
+    expect(identityFromKimiTokens(access).email).toBe(mixed.toLowerCase());
+  });
+
+  test("falls back to refresh JWT when access has no identity", () => {
+    const access = jwtWithClaims({ scope: "coding" });
+    const refresh = jwtWithClaims({ user_id: "from-refresh" });
+    expect(identityFromKimiTokens(access, refresh)).toEqual({ accountId: "from-refresh" });
+  });
+
+  test("opaque tokens yield no identity", () => {
+    expect(identityFromKimiTokens("not-a-jwt", "also-opaque")).toEqual({});
+  });
+});
+
+describe("Kimi multiauth via saveCredential", () => {
+  beforeEach(() => {
+    previousOpencodexHome = process.env.OPENCODEX_HOME;
+    if (existsSync(TEST_DIR)) rmSync(TEST_DIR, { recursive: true });
+    mkdirSync(TEST_DIR, { recursive: true });
+    process.env.OPENCODEX_HOME = TEST_DIR;
+  });
+
+  afterEach(() => {
+    if (previousOpencodexHome === undefined) delete process.env.OPENCODEX_HOME;
+    else process.env.OPENCODEX_HOME = previousOpencodexHome;
+    if (existsSync(TEST_DIR)) rmSync(TEST_DIR, { recursive: true });
+  });
+
+  test("two distinct user_ids append two kimi accounts", async () => {
+    const accessA = jwtWithClaims({ user_id: "kimi-a" });
+    const accessB = jwtWithClaims({ user_id: "kimi-b" });
+    await saveCredential("kimi", {
+      access: accessA,
+      refresh: "refresh-a",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(accessA),
+    });
+    await saveCredential("kimi", {
+      access: accessB,
+      refresh: "refresh-b",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(accessB),
+    });
+    expect(listAccounts("kimi").length).toBe(2);
+    expect(getCredential("kimi")?.accountId).toBe("kimi-b");
+    expect(getCredential("kimi")?.access).toBe(accessB);
+  });
+
+  test("same user_id upserts without duplicating", async () => {
+    const access1 = jwtWithClaims({ user_id: "kimi-same" });
+    const access2 = jwtWithClaims({ user_id: "kimi-same", iat: 2 });
+    await saveCredential("kimi", {
+      access: access1,
+      refresh: "refresh-1",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(access1),
+    });
+    await saveCredential("kimi", {
+      access: access2,
+      refresh: "refresh-2",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(access2),
+    });
+    expect(listAccounts("kimi").length).toBe(1);
+    expect(getCredential("kimi")?.access).toBe(access2);
+    expect(getCredential("kimi")?.refresh).toBe("refresh-2");
+  });
+
+  test("identity-less kimi replace mutates active only and keeps siblings", async () => {
+    const accessA = jwtWithClaims({ user_id: "kimi-keep" });
+    const accessB = jwtWithClaims({ user_id: "kimi-active" });
+    await saveCredential("kimi", {
+      access: accessA,
+      refresh: "refresh-a",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(accessA),
+    });
+    await saveCredential("kimi", {
+      access: accessB,
+      refresh: "refresh-b",
+      expires: Date.now() + 3600_000,
+      ...identityFromKimiTokens(accessB),
+    });
+    expect(listAccounts("kimi").length).toBe(2);
+
+    // Opaque re-login: no accountId → replace active slot in place (does not wipe sibling).
+    await saveCredential("kimi", {
+      access: "opaque-access",
+      refresh: "opaque-refresh",
+      expires: Date.now() + 3600_000,
+    });
+    expect(listAccounts("kimi").length).toBe(2);
+    expect(getCredential("kimi")?.access).toBe("opaque-access");
+    expect(listAccounts("kimi").some(a => a.credential.accountId === "kimi-keep")).toBe(true);
+  });
+});