tools: foreign Effect NonEmptyString schemas reject valid input

Summary

Tools registered by a local plugin with an Effect schema created outside OpenCode's bundled Effect runtime are advertised correctly but reject valid input at execution time.

For example, Schema.NonEmptyString generates the correct minLength: 1 JSON Schema, but valid values such as "alpha" and "beta" fail runtime decoding as if they were empty.

Environment

• opencode version: 2.0.3
• OS: Darwin 25.6.0 arm64
• Terminal: Ghostty (TERM=xterm-ghostty, COLORTERM=truecolor)
• Shell: /bin/zsh
• Install/channel: latest
• Active plugins: local plugin .opencode/plugins/non-empty-array/index.ts

Reproduction

1. Create a local plugin that registers a direct tool with an Effect schema:

   import { Plugin } from "@opencode/plugin/effect";
   import { Effect, Schema } from "effect";
   
   const Input = Schema.Struct({
     values: Schema.Array(Schema.NonEmptyString),
   });
   
   export default Plugin.define({
     id: "repro.non-empty-array",
     effect: (context) =>
       context.tool.transform((editor) => {
         editor.add({
           name: "accept_non_empty_strings",
           description: "Accept an array of non-empty strings and return them unchanged.",
           input: Input,
           options: { codemode: false },
           execute: (input) =>
             Effect.succeed({
               content: `EXECUTED:${JSON.stringify(input.values)}`,
             }),
         });
       }),
   });
   

2. Start OpenCode with the plugin enabled.

3. Ask OpenCode to call accept_non_empty_strings with:

   {"values":["alpha","beta"]}
   

Expected Behavior

The tool should execute and return:

EXECUTED:["alpha","beta"]

Actual Behavior

The tool is advertised correctly, but execution fails with:

Invalid arguments for tool "accept_non_empty_strings":
- values[0]: Expected a value with a length of at least 1
- values[1]: Expected a value with a length of at least 1

Additional Context

The issue is reproducible consistently with OpenCode 2.0.3, @opencode/plugin 2.0.3, and Effect 4.0.0-rc.112.

The same values decode successfully when tested directly with the plugin's Effect runtime:

Schema.decodeUnknownSync(Schema.NonEmptyString)("alpha");

A tool using Schema.String instead of Schema.NonEmptyString succeeds. A tool using an equivalent plain JSON Schema also succeeds.

The generated model-facing JSON Schema is correct (minLength: 1). The failure occurs during runtime input decoding, suggesting that OpenCode is applying its bundled Effect decoder directly to an Effect schema created by the external plugin runtime.

A workaround is to use JSON Schema for plugin tool inputs. The likely framework fix is to normalize foreign Effect schemas before decoding them, or ensure plugin schemas are decoded using the originating Effect runtime.