fix(opencode2): Zen free tier returns HTTP 426 for current 0.0.0 betas

[coygeek]

fix(opencode2): Zen free tier returns HTTP 426 for current 0.0.0 betas

Summary

Current OpenCode 2 betas cannot call an OpenCode Zen free model. OpenCode 1.18.31 completes the same request. OpenCode 2 0.0.0-beta-19059 and 0.0.0-beta-19271 both stop with HTTP 426 and the message OpenCode 1.18.0 or newer is required to use the free tier.

Steps to reproduce

1. Use stable OpenCode 1.18.31 and OpenCode 2 0.0.0-beta-19271. At the time of this check, npm view @opencode-ai/cli dist-tags reported beta as 0.0.0-beta-19271.
2. From an empty directory, with no plugins, run opencode run --pure --model opencode/mimo-v2.6-flash-free --format json -- 'Reply with exactly: FREE-OK'.
3. From that same directory, run opencode2 run --standalone --model opencode/mimo-v2.6-flash-free --format json -- 'Reply with exactly: FREE-OK'.
4. Omit any model variant. Passing #max fails earlier with Variant unavailable and does not reach this provider error.

Expected behavior

An official current OpenCode 2 build can call opencode/mimo-v2.6-flash-free and return the assistant text, as OpenCode 1.18.31 does.

Actual behavior

OpenCode 1.18.31 returns FREE-OK for that model, with provider opencode, model mimo-v2.6-flash-free, and cost 0. OpenCode 2 exits 1. Its JSON error event is provider.invalid-request with status 426 and message Error from provider (Console): OpenCode 1.18.0 or newer is required to use the free tier. The same 426 happens on 0.0.0-beta-19059 and on 0.0.0-beta-19271.

Affected area

OpenCode Zen free tier when the client is OpenCode 2.

Runtime or environment

• OpenCode 1.18.31
• OpenCode 2 0.0.0-beta-19271 (also reproduced on 0.0.0-beta-19059)
• Model opencode/mimo-v2.6-flash-free
• No plugins
• macOS 27.0
• Noninteractive CLI

Evidence

The stable command returns assistant text and step_finish reason stop. The OpenCode 2 command returns one error event and no assistant text. opencode2 --version prints opencode2 v0.0.0-beta-19271, which is below the 1.18.0 minimum named in the error.

Impact

OpenCode 2 cannot use the Zen free models that stable OpenCode 1.18.31 can use. Raising the beta build number from 19059 to 19271 does not change the result, because the reported version remains 0.0.0-beta-*.

Additional context

Related reports from clients that already identify as 1.18.x are #49944 and #49918. This report is the opposite case: the client is a current OpenCode 2 beta, and its own version string is below 1.18.0. The restored check is that opencode2 run --model opencode/mimo-v2.6-flash-free returns assistant text and does not return HTTP 426.

[github-actions]

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

• OpenCode V2 cannot access OpenCode Zen free models (e.g., Big Pickle) due to unsupported latest Zen authentication headers #49908: OpenCode V2 cannot access OpenCode Zen free models — same root symptom (V2 beta builds cannot use Zen free tier models)
• Server (1.18.31): Free tier zen models fail - User-Agent not forwarded to zen API #49756: Free tier zen models fail due to missing/incorrect headers forwarded to the Zen API — closely related root cause (client version/identity not properly sent)
• Error from provider (Console): OpenCode's free tier can only be used from within OpenCode #49433: "OpenCode's free tier can only be used from within OpenCode" error — same free-tier access failure, different version context

If your issue is distinct (specifically the 0.0.0-beta-* version string causing the 1.18.0 or newer is required check to fail), it may still be worth keeping open as a separate tracking issue, but please check those first.

[coygeek]

Checked the three issues named in the duplicate note.

#49908 is the same outcome: OpenCode 2 cannot call Zen free models. Its text attributes that to unsupported Zen authentication headers, and it records no version, HTTP status, or reproduction. This issue measures a different error: opencode2 0.0.0-beta-19059 and 0.0.0-beta-19271 return HTTP 426, OpenCode 1.18.0 or newer is required to use the free tier, while opencode 1.18.31 returns the assistant text for opencode/mimo-v2.6-flash-free. If the failure behind #49908 is this 426, this report is the reproduction for that issue. The header explanation in #49908 is a separate claim.

#49756 is a different failure. It uses stable OpenCode 1.18.31, opencode serve, and HTTP 403 with OpenCode's free tier can only be used from within OpenCode. The report says the server omits User-Agent.

#49433 is a different failure. It uses opencode 1.3.17 and the same 403 can only be used from within OpenCode message, not the 426 version check and not OpenCode 2.