fix: kimi-for-coding provider gets 429 engine overloaded due to missing User-Agent header

Description

The built-in kimi-for-coding provider uses @ai-sdk/anthropic, which sends Anthropic/JS x.x.x as the User-Agent on every request. Kimi's /coding gateway intermittently returns HTTP 429 engine overloaded for requests from non-whitelisted agents — even with a valid paid API key and available quota.

Setting User-Agent: KimiCLI/1.5 (a whitelisted coding agent UA) significantly reduces these 429s in practice. The same fix is documented for other clients using the Anthropic SDK against Kimi's endpoint.

Plugins

none (built-in provider)

OpenCode version

1.15.3

Steps to reproduce

Set up the built-in kimi-for-coding provider with a valid KIMI_API_KEY
Send messages using a kimi-for-coding model (k2p6, k2p5, kimi-k2-thinking)
Observe intermittent 429 {"error":{"type":"rate_limit_error","message":"The engine is currently overloaded, please try again later"}}

The 429s are intermittent but noticeably reduced after overriding the User-Agent to KimiCLI/1.5.

Operating System

macOS 26.0

This issue might be a duplicate of existing issues. Please check:

[BUG] Custom provider headers (User-Agent) from opencode.json not applied to fetch requests #22608: Custom provider headers (User-Agent) from opencode.json not applied to fetch requests — reports the same User-Agent header issue for Kimi's coding API
User-Agent in custom provider options.headers is overridden #24594: User-Agent in custom provider options.headers is overridden — reports that opencode hardcodes its own User-Agent, overriding any user-set value, which would also affect the built-in kimi-for-coding provider

Not a duplicate — these are related but distinct:

[BUG] Custom provider headers (User-Agent) from opencode.json not applied to fetch requests #22608 is about user-configured custom provider headers not reaching the wire. Our issue is about the built-in kimi-for-coding provider having no User-Agent set at all.
User-Agent in custom provider options.headers is overridden #24594 actually informed the fix here. It correctly identifies that options.headers is overridden by the hardcoded opencode/${version} UA in llm.ts — this was broken by the revert in fix: revert change that caused headers to be double merged if provider was authed in multiple places #12072. Our fix sets the UA in model.headers instead, which is spread at llm.ts:382 after the default UA at line 380, so it wins.

In other words, #24594 is why the fix cannot go in custom() via options.headers (the pattern used by Cloudflare and GitLab providers, which are also silently broken for UA today). The PR uses model.headers in fromModelsDevModel specifically to work around this.

I experienced this issue between 5/11 - 5/13 using both anthropic and openai-compatible. On 5/13, I manually patched OpenCode 1.14.50 to use a KimiCLI User-Agent:

perl -i -pe 's/"User-Agent": `opencode\/\$\{InstallationVersion\}`/"User-Agent": (process.env.OPENCODE_USER_AGENT || "KimiCLI\/1.37.0")/g' opencode/packages/opencode/src/session/llm.ts

That fixed the issue and I have not received the error since. Others on the Kimi Discord continue to report the error. Those that apply the patch also report that replacing the User-Agent resolves the issue.

Is there any workaround for this? I can no longer use my Kimi coding plan.

Is there any workaround for this? I can no longer use my Kimi coding plan.

The workaround has been mentioned right above your reply. You can ask Kimi on web to help you implement the patch.

Is there any workaround for this? I can no longer use my Kimi coding plan.

Try add this to opencode config

"kimi-for-coding": {
      "models": {
        "k2p6":             { "headers": { "User-Agent": "KimiCLI/1.5" } },
        "k2p5":             { "headers": { "User-Agent": "KimiCLI/1.5" } },
        "kimi-k2-thinking": { "headers": { "User-Agent": "KimiCLI/1.5" } }
      }
    },

Is there any workaround for this? I can no longer use my Kimi coding plan.

Try add this to opencode config

"kimi-for-coding": {
      "models": {
        "k2p6":             { "headers": { "User-Agent": "KimiCLI/1.5" } },
        "k2p5":             { "headers": { "User-Agent": "KimiCLI/1.5" } },
        "kimi-k2-thinking": { "headers": { "User-Agent": "KimiCLI/1.5" } }
      }
    },

This did not work for me due to the open defects: #27902 (comment).

Use plugin opencode-kimi-full can workaround this, even better than native.

When will this issue be fixed? It's been almost a week already.

To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.

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fix: kimi-for-coding provider gets 429 engine overloaded due to missing User-Agent header #27902

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fix: kimi-for-coding provider gets 429 engine overloaded due to missing User-Agent header #27902

Description

Description

Plugins

OpenCode version

Steps to reproduce

Operating System

Activity

github-actions commented on May 16, 2026

bzqzheng commented on May 16, 2026

BrianJM commented on May 16, 2026

CrazyTomatoOo commented on May 18, 2026

tapcrapioca commented on May 18, 2026

bzqzheng commented on May 18, 2026

BrianJM commented on May 19, 2026

CrazyTomatoOo commented on May 19, 2026

CrazyTomatoOo commented on May 21, 2026

github-actions commented on Jul 21, 2026

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