400 UnsupportedClientVersionException since Kiro's Nov 9 2026 client EOL #138

Bug

Since November 9, 2026, every request fails with:

Kiro Error: 400 - UnsupportedClientVersionException:
This version of Kiro is no longer supported. Please update to the latest version of Kiro to continue.

Login, token refresh and usage lookups still work; only generateAssistantResponse is rejected.

Cause

Kiro ended support for IDE < 0.11.133 and CLI < 1.28.2 on 2026-11-09
(kirodotdev/Kiro#11335). The plugin identifies itself with an unversioned KiroIDE:

• dist/plugin/request.js: user-agent: ... m/E KiroIDE and x-amz-user-agent: aws-sdk-js/3.738.0 KiroIDE
• dist/constants.js: USER_AGENT: 'KiroIDE'
• dist/plugin/token.js: KiroIDE / KiroIDE-0.1.0

The backend apparently treats the missing/old version as an unsupported client.

Workaround (verified)

Sending a versioned id in the same format as the real IDE (KiroIDE-<version>-<machineId>)
fixes it, e.g. KiroIDE-1.4.178-<sha256(hostname)> in both user-agent and x-amz-user-agent,
and KiroIDE-1.4.178 in KIRO_CONSTANTS.USER_AGENT. After this change,
claude-sonnet-4-5 and claude-haiku-4-5 return 200 again.

Suggestion: keep the IDE version in one constant and allow overriding it via an env var
(e.g. KIRO_IDE_VERSION) so users can fix the next minimum-version bump without a release.

Environment

• @zhafron/opencode-kiro-auth 2.0.0
• opencode 1.18.4, macOS
• Auth: IAM Identity Center (Kiro CLI sync)