diff --git a/src/adapters/kiro-errors.ts b/src/adapters/kiro-errors.ts
index 7c475f321e..1595f1b1f4 100644
--- a/src/adapters/kiro-errors.ts
+++ b/src/adapters/kiro-errors.ts
@@ -109,6 +109,17 @@ function classifyKiroFailure(
       retryable: false,
     };
   }
+  // #993: a gated model demanding a profileArn gets a stable, actionable code
+  // instead of the generic validation bucket. Non-retryable by definition.
+  if (evidence.includes("profilearn") && evidence.includes("required")) {
+    return {
+      message: "kiro_profile_required: Kiro requires a CodeWhisperer profileArn for this account and model. Re-login or re-import the matching Kiro account (ocx account login kiro --reauth) so the profile is captured, then retry.",
+      status: 400,
+      errorType: "invalid_request_error",
+      code: "kiro_profile_required",
+      retryable: false,
+    };
+  }
   if (
     evidence.includes("insufficient_quota")
     || evidence.includes("quota exhausted")
diff --git a/src/oauth/kiro.ts b/src/oauth/kiro.ts
index ebbbaa9aa5..716e6cbfa3 100644
--- a/src/oauth/kiro.ts
+++ b/src/oauth/kiro.ts
@@ -172,13 +172,37 @@ async function defaultKiroCliRunner(args: string[], signal?: AbortSignal): Promi
   }
 }
 
-async function readKiroCliIdentity(runner: KiroCliRunner, signal?: AbortSignal): Promise<{ email?: string }> {
+/** Kiro profile ARN structure: arn:<partition>:codewhisperer:<region>:<account>:profile/<id> */
+const KIRO_PROFILE_ARN_PATTERN = /^arn:[a-z0-9-]+:codewhisperer:[a-z0-9-]+:\d{12}:profile\/[A-Za-z0-9-]+$/;
+const KIRO_PROFILE_ARN_MAX_LENGTH = 256;
+
+function parseKiroProfileArn(value: unknown): string | undefined {
+  if (typeof value !== "string") return undefined;
+  const trimmed = value.trim();
+  if (trimmed.length === 0 || trimmed.length > KIRO_PROFILE_ARN_MAX_LENGTH) return undefined;
+  return KIRO_PROFILE_ARN_PATTERN.test(trimmed) ? trimmed : undefined;
+}
+
+function profileArnFromWhoami(parsed: Record<string, unknown>): string | undefined {
+  // Only narrowly-named documented-ish shapes; never invent an ARN (#993).
+  return parseKiroProfileArn(parsed.profileArn)
+    ?? parseKiroProfileArn(parsed.profile_arn)
+    ?? (parsed.profile && typeof parsed.profile === "object" && !Array.isArray(parsed.profile)
+      ? parseKiroProfileArn((parsed.profile as Record<string, unknown>).arn)
+      : undefined);
+}
+
+async function readKiroCliIdentity(runner: KiroCliRunner, signal?: AbortSignal): Promise<{ email?: string; profileArn?: string }> {
   try {
     const result = await runner(["whoami", "--format", "json"], signal);
     if (result.exitCode !== 0) return {};
-    const parsed = JSON.parse(result.stdout) as { email?: unknown };
+    const parsed = JSON.parse(result.stdout) as Record<string, unknown>;
     const email = typeof parsed.email === "string" ? parsed.email.trim().toLowerCase() : "";
-    return email && email.length <= 320 ? { email } : {};
+    const profileArn = profileArnFromWhoami(parsed);
+    return {
+      ...(email && email.length <= 320 ? { email } : {}),
+      ...(profileArn ? { profileArn } : {}),
+    };
   } catch {
     return {};
   }
@@ -251,14 +275,34 @@ async function oauthCredentialFromImported(
   runner: KiroCliRunner,
   signal?: AbortSignal,
 ): Promise<OAuthCredentials> {
-  const identity = imported.source === "sqlite" ? await readKiroCliIdentity(runner, signal) : {};
-  const metadata = metadataFromImported(imported);
+  let identity: { email?: string; profileArn?: string } = {};
+  if (imported.source === "sqlite") {
+    identity = await readKiroCliIdentity(runner, signal);
+    // Session-switch race (#993 review): another process may have switched the
+    // active Kiro CLI session between the SQLite read and whoami. Accept
+    // whoami's identity only when the session token STILL matches the import —
+    // refresh token, or access token when refresh is absent.
+    if (identity.profileArn !== undefined) {
+      const current = readKiroCliSqliteCredential();
+      const importedKey = imported.refresh || imported.access;
+      const currentKey = current ? current.refresh || current.access : "";
+      if (!current || currentKey !== importedKey) identity = {};
+    }
+  }
+  // Builder ID imports often lack a profileArn in SQLite; whoami against the
+  // SAME active CLI session can supply it (#993). Imported stays authoritative.
+  const resolvedProfileArn = imported.profileArn ?? identity.profileArn;
+  const metadata: KiroOAuthMetadata | undefined = (() => {
+    const base = metadataFromImported(imported) ?? {};
+    if (resolvedProfileArn && !base.profileArn) base.profileArn = resolvedProfileArn;
+    return Object.keys(base).length > 0 ? base : undefined;
+  })();
   return {
     access: imported.access,
     refresh: imported.refresh,
     expires: imported.expires,
     source: imported.source === "json" ? "credential-file" : "local-cli",
-    ...(imported.profileArn ? { accountId: imported.profileArn } : {}),
+    ...(resolvedProfileArn ? { accountId: resolvedProfileArn } : {}),
     ...(identity.email ? { email: identity.email } : {}),
     ...(metadata ? { kiro: metadata } : {}),
   };
diff --git a/tests/kiro-oauth.test.ts b/tests/kiro-oauth.test.ts
index 348eb0207c..d9487386ce 100644
--- a/tests/kiro-oauth.test.ts
+++ b/tests/kiro-oauth.test.ts
@@ -425,6 +425,131 @@ describe("kiro oauth — import-first", () => {
     expect(existsSync(kiroCliRecoveryPath())).toBe(false);
   });
 
+  test("whoami supplies a valid profileArn when the SQLite import lacks one (#993)", async () => {
+    const arn = "arn:aws:codewhisperer:us-east-1:123456789012:profile/ABCD1234";
+    seedKiroCliDb({ access_token: "aoa-builder", refresh_token: "rt-builder" });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        return { exitCode: 0, stdout: JSON.stringify({ email: "builder@example.com", profileArn: arn }) };
+      }
+      throw new Error(`unexpected Kiro CLI command: ${args[0]}`);
+    };
+
+    const cred = await loginKiro({}, { cliRunner: runner });
+
+    expect(cred).toMatchObject({
+      access: "aoa-builder",
+      accountId: arn,
+      kiro: { profileArn: arn },
+    });
+  });
+
+  test("a nested profile.arn shape is accepted (#993)", async () => {
+    const arn = "arn:aws:codewhisperer:eu-west-1:123456789012:profile/XY-99";
+    seedKiroCliDb({ access_token: "aoa-nested", refresh_token: "rt-nested" });
+    const nestedRunner = async (args: string[]) => {
+      if (args[0] === "whoami") return { exitCode: 0, stdout: JSON.stringify({ profile: { arn } }) };
+      throw new Error("unexpected");
+    };
+    const nested = await loginKiro({}, { cliRunner: nestedRunner });
+    expect(nested.accountId).toBe(arn);
+  });
+
+  test("a malformed whoami ARN is ignored without breaking the login (#993)", async () => {
+    seedKiroCliDb({ access_token: "aoa-bad", refresh_token: "rt-bad" });
+    const badRunner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        return { exitCode: 0, stdout: JSON.stringify({ profileArn: "not-an-arn", email: "bad@example.com" }) };
+      }
+      throw new Error("unexpected");
+    };
+    const bad = await loginKiro({}, { cliRunner: badRunner });
+    // Malformed ARN: login still succeeds for ungated models, but no ARN is borrowed.
+    expect(bad.accountId).toBeUndefined();
+    expect(bad.kiro?.profileArn).toBeUndefined();
+  });
+
+  test("an imported SQLite profileArn stays authoritative over whoami (#993)", async () => {
+    const sqliteArn = "arn:aws:codewhisperer:us-east-1:123456789012:profile/SQLITE";
+    const whoamiArn = "arn:aws:codewhisperer:us-east-1:123456789012:profile/WHOAMI";
+    seedKiroCliDb({ access_token: "aoa-both", refresh_token: "rt-both", profile_arn: sqliteArn });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") return { exitCode: 0, stdout: JSON.stringify({ profileArn: whoamiArn }) };
+      throw new Error("unexpected");
+    };
+    const cred = await loginKiro({}, { cliRunner: runner });
+    expect(cred.accountId).toBe(sqliteArn);
+  });
+
+  test("a session switch between the SQLite read and whoami discards whoami's ARN (#993)", async () => {
+    const arnB = "arn:aws:codewhisperer:us-east-1:123456789012:profile/OTHER-ACCOUNT";
+    seedKiroCliDb({ access_token: "aoa-accountA", refresh_token: "rt-accountA" });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        // Another process switches the active CLI session mid-flight.
+        removeKiroCliDb();
+        seedKiroCliDb({ access_token: "aoa-accountB", refresh_token: "rt-accountB" });
+        return { exitCode: 0, stdout: JSON.stringify({ email: "b@example.com", profileArn: arnB }) };
+      }
+      throw new Error("unexpected");
+    };
+    const cred = await loginKiro({}, { cliRunner: runner });
+    // Account A's token must never carry account B's ARN.
+    expect(cred.accountId).toBeUndefined();
+    expect(cred.kiro?.profileArn).toBeUndefined();
+  });
+
+  test("the discarded whoami identity takes the email with it, not just the ARN (#993)", async () => {
+    // Review finding: asserting only that the ARN is absent also passes against
+    // pre-fix code, which ignored whoami's ARN entirely. The email is the part
+    // that pre-fix code WOULD have kept, so it is the assertion that actually
+    // proves the mismatch path clears the whole identity.
+    const arnB = "arn:aws:codewhisperer:us-east-1:123456789012:profile/OTHER-ACCOUNT";
+    seedKiroCliDb({ access_token: "aoa-accountA", refresh_token: "rt-accountA" });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        removeKiroCliDb();
+        seedKiroCliDb({ access_token: "aoa-accountB", refresh_token: "rt-accountB" });
+        return { exitCode: 0, stdout: JSON.stringify({ email: "b@example.com", profileArn: arnB }) };
+      }
+      throw new Error("unexpected");
+    };
+    const cred = await loginKiro({}, { cliRunner: runner });
+    expect(cred.email).toBeUndefined();
+    expect(cred.kiro?.profileArn).toBeUndefined();
+  });
+
+  test("with no refresh token the access token is the revalidation key (#993)", async () => {
+    // The implementation falls back to the access token when refresh is absent.
+    // Without this case that branch is unexercised in either direction.
+    const arn = "arn:aws:codewhisperer:us-east-1:123456789012:profile/BUILDER";
+    seedKiroCliDb({ access_token: "aoa-only" });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        return { exitCode: 0, stdout: JSON.stringify({ email: "a@example.com", profileArn: arn }) };
+      }
+      throw new Error("unexpected");
+    };
+    const cred = await loginKiro({}, { cliRunner: runner });
+    expect(cred.kiro?.profileArn).toBe(arn);
+  });
+
+  test("an access-token-only session that changes under whoami is rejected (#993)", async () => {
+    const arnB = "arn:aws:codewhisperer:us-east-1:123456789012:profile/OTHER-ACCOUNT";
+    seedKiroCliDb({ access_token: "aoa-accountA" });
+    const runner = async (args: string[]) => {
+      if (args[0] === "whoami") {
+        removeKiroCliDb();
+        seedKiroCliDb({ access_token: "aoa-accountB" });
+        return { exitCode: 0, stdout: JSON.stringify({ email: "b@example.com", profileArn: arnB }) };
+      }
+      throw new Error("unexpected");
+    };
+    const cred = await loginKiro({}, { cliRunner: runner });
+    expect(cred.kiro?.profileArn).toBeUndefined();
+    expect(cred.email).toBeUndefined();
+  });
+
   test("invalid recovery data names the file the operator must remove", async () => {
     seedKiroCliDb({ access_token: "aoa-prior", refresh_token: "rt-prior" });
     writeFileSync(kiroCliRecoveryPath(), "not a recovery database", { mode: 0o600 });
diff --git a/tests/kiro-retry.test.ts b/tests/kiro-retry.test.ts
index 113e6c900c..df4285546b 100644
--- a/tests/kiro-retry.test.ts
+++ b/tests/kiro-retry.test.ts
@@ -330,6 +330,22 @@ describe("kiro retry fetch", () => {
     expect(mock.calls).toHaveLength(1);
   });
 
+  test("a profileArn-required 400 classifies as kiro_profile_required with actionable copy (#993)", async () => {
+    const mock = mockFetch([
+      new Response(JSON.stringify({
+        __type: "ValidationException",
+        message: "profileArn is required for this account",
+      }), { status: 400 }),
+    ]);
+    const res = await fetchKiroWithRetry(request, { timeoutMs: 5_000 });
+    const text = await res.text();
+    expect(res.status).toBe(400);
+    expect(text).toContain("kiro_profile_required");
+    expect(text).toContain("ocx account login kiro --reauth");
+    // Non-retryable: exactly one upstream call.
+    expect(mock.calls).toHaveLength(1);
+  });
+
   test("normalizes final transient 429 after bounded adapter retries", async () => {
     const mock = mockFetch([
       new Response("rate limited", { status: 429, headers: { "Retry-After": "0" } }),
diff --git a/tests/kiro-stream.test.ts b/tests/kiro-stream.test.ts
index b2a92bdf17..744fa8ab1f 100644
--- a/tests/kiro-stream.test.ts
+++ b/tests/kiro-stream.test.ts
@@ -1096,6 +1096,21 @@ describe("kiro adapter — parseStream", () => {
     expect(errors[0]).not.toContain("{");
   });
 
+  test("an event-stream profileArn-required exception classifies as kiro_profile_required (#993)", async () => {
+    const payload = JSON.stringify({
+      __type: "ValidationException",
+      message: "profileArn is required for this account",
+    });
+    const frame = encodeMessage({ ":message-type": "exception", ":exception-type": "ValidationException" }, enc.encode(payload));
+    const errors: string[] = [];
+    for await (const e of createKiroAdapter(provider).parseStream(new Response(streamOf(frame)))) {
+      if (e.type === "error") errors.push(e.message);
+    }
+    expect(errors).toHaveLength(1);
+    expect(errors[0]).toContain("kiro_profile_required");
+    expect(errors[0]).toContain("ocx account login kiro --reauth");
+  });
+
   test("auth and model exceptions become actionable Kiro errors", async () => {
     const authFrame = encodeMessage(
       { ":message-type": "exception", ":exception-type": "AccessDeniedException" },