fix(tool): support zod 3 plugin schemas

packages/opencode/src/session/tools.ts

@@ -20,6 +20,7 @@ import * as Log from "@opencode-ai/core/util/log"
 import { EffectBridge } from "@/effect/bridge"
 
 const log = Log.create({ service: "session.tools" })
+const schemaInternalKeys = new Set(["_def", "def", "_zod", "~standard", "_cached", "typeName"])
 
 export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {
   agent: Agent.Info
@@ -78,6 +79,7 @@ export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {
     agent: input.agent,
   })) {
     const schema = ProviderTransform.schema(input.model, ToolJsonSchema.fromTool(item))
+    assertNoSchemaInternals(item.id, schema)
     tools[item.id] = tool({
       description: item.description,
       inputSchema: jsonSchema(schema),
@@ -121,6 +123,7 @@ export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {
 
     const schema = yield* Effect.promise(() => Promise.resolve(asSchema(item.inputSchema).jsonSchema))
     const transformed = ProviderTransform.schema(input.model, schema)
+    assertNoSchemaInternals(key, transformed)
     item.inputSchema = jsonSchema(transformed)
     item.execute = (args, opts) =>
       run.promise(
@@ -205,4 +208,31 @@ export const resolve = Effect.fn("SessionTools.resolve")(function* (input: {
   return tools
 })
 
+function assertNoSchemaInternals(toolID: string, schema: unknown) {
+  const path = schemaInternalPath(schema)
+  if (!path) return
+  throw new Error(`Tool ${toolID} input schema contains non-JSON-Schema Zod internals at ${path}`)
+}
+
+function schemaInternalPath(value: unknown, path = "$", skipKeys = false): string | undefined {
+  if (Array.isArray(value)) {
+    return value
+      .map((item, index) => schemaInternalPath(item, `${path}[${index}]`))
+      .find((item): item is string => item !== undefined)
+  }
+  if (typeof value !== "object" || value === null) return undefined
+
+  for (const [key, item] of Object.entries(value)) {
+    const nextPath = /^[A-Za-z_$][\w$]*$/.test(key) ? `${path}.${key}` : `${path}[${JSON.stringify(key)}]`
+    if (!skipKeys && schemaInternalKeys.has(key)) return nextPath
+    const found = schemaInternalPath(
+      item,
+      nextPath,
+      key === "properties" || key === "$defs" || key === "definitions" || key === "patternProperties",
+    )
+    if (found) return found
+  }
+  return undefined
+}
+
 export * as SessionTools from "./tools"

packages/opencode/src/tool/registry.ts

@@ -55,6 +55,13 @@ import { Reference } from "@/reference/reference"
 import { BackgroundJob } from "@/background/job"
 import { SessionStatus } from "@/session/status"
 import { RuntimeFlags } from "@/effect/runtime-flags"
+import {
+  objectFromShape,
+  safeParse,
+  type AnyObjectSchema,
+  type AnySchema,
+} from "@modelcontextprotocol/sdk/server/zod-compat.js"
+import { toJsonSchemaCompat } from "@modelcontextprotocol/sdk/server/zod-json-schema-compat.js"
 
 const log = Log.create({ service: "tool.registry" })
 
@@ -150,10 +157,10 @@ export const layer: Layer.Layer<
           const args = def.args ?? {}
           const entries = Object.entries(args)
           const allZod = entries.every((entry) => isZodType(entry[1]))
-          const zodParams = allZod ? z.object(args) : undefined
+          const zodParams = allZod ? objectFromShape(args as Record<string, AnySchema>) : undefined
           const jsonSchema = zodParams ? zodJsonSchema(zodParams) : legacyJsonSchema(entries)
           const parameters = zodParams
-            ? Schema.declare<unknown>((u): u is unknown => zodParams.safeParse(u).success)
+            ? Schema.declare<unknown>((u): u is unknown => safeParse(zodParams, u).success)
             : Schema.Unknown
           return {
             id,
@@ -402,7 +409,11 @@ export const defaultLayer = Layer.suspend(() =>
     .pipe(Layer.provide(RuntimeFlags.defaultLayer)),
 )
 
-function isZodType(value: unknown): value is z.ZodType {
+function isZodType(value: unknown): value is AnySchema {
+  return typeof value === "object" && value !== null && ("_zod" in value || "_def" in value)
+}
+
+function isZod4Type(value: unknown): value is z.ZodType {
   return typeof value === "object" && value !== null && "_zod" in value
 }
 
@@ -425,8 +436,12 @@ function legacyJsonSchema(entries: [string, unknown][]): JSONSchema7 {
   }
 }
 
-function zodJsonSchema(schema: z.ZodType): JSONSchema7 {
-  const result = normalizeZodJsonSchema(z.toJSONSchema(schema, { io: "input", metadata: zodMetadataRegistry(schema) }))
+function zodJsonSchema(schema: AnyObjectSchema): JSONSchema7 {
+  const result = normalizeZodJsonSchema(
+    isZod4Type(schema)
+      ? z.toJSONSchema(schema, { io: "input", metadata: zodMetadataRegistry(schema) })
+      : toJsonSchemaCompat(schema, { pipeStrategy: "input" }),
+  )
   if (!isJsonSchemaObject(result)) throw new Error("plugin tool Zod schema produced a non-object JSON Schema")
   const { $defs, ...rest } = result
   return (
@@ -434,7 +449,7 @@ function zodJsonSchema(schema: z.ZodType): JSONSchema7 {
   ) as JSONSchema7
 }
 
-function zodMetadataRegistry(schema: z.ZodType) {
+function zodMetadataRegistry(schema: AnyObjectSchema) {
   const registry = z.registry<Record<string, unknown>>()
   const seen = new WeakSet<object>()
   const collect = (value: unknown) => {
@@ -442,7 +457,7 @@ function zodMetadataRegistry(schema: z.ZodType) {
     if (seen.has(value)) return
     seen.add(value)
 
-    if (isZodType(value)) {
+    if (isZod4Type(value)) {
       const metadata = typeof value.meta === "function" ? value.meta() : undefined
       const description = typeof value.description === "string" ? value.description : undefined
       const merged = {

packages/opencode/test/session/tools-schema.test.ts

@@ -0,0 +1,201 @@
+import { describe, expect } from "bun:test"
+import { jsonSchema } from "ai"
+import { Effect, Exit, Layer } from "effect"
+import { Agent } from "@/agent/agent"
+import { MCP } from "@/mcp"
+import { Permission } from "@/permission"
+import { ProjectID } from "@/project/schema"
+import { ModelID, ProviderID } from "@/provider/schema"
+import type { Provider } from "@/provider/provider"
+import { SessionTools } from "@/session/tools"
+import { MessageV2 } from "@/session/message-v2"
+import { MessageID, SessionID } from "@/session/schema"
+import { ToolRegistry } from "@/tool/registry"
+import { Truncate } from "@/tool/truncate"
+import { Plugin } from "@/plugin"
+import { testEffect } from "../lib/effect"
+
+const it = testEffect(
+  Layer.mergeAll(
+    Layer.succeed(
+      ToolRegistry.Service,
+      ToolRegistry.Service.of({
+        ids: () => Effect.succeed([]),
+        all: () => Effect.succeed([]),
+        named: () => Effect.die("unexpected named tool lookup"),
+        tools: () => Effect.succeed([]),
+      }),
+    ),
+    Layer.succeed(
+      MCP.Service,
+      MCP.Service.of({
+        status: () => Effect.succeed({}),
+        clients: () => Effect.succeed({}),
+        tools: () =>
+          Effect.succeed({
+            ctx_batch_execute: {
+              description: "context tool",
+              inputSchema: jsonSchema({
+                type: "object",
+                properties: {
+                  batch: {
+                    type: "array",
+                    items: schemaWithZodInternals(),
+                  },
+                },
+              }),
+              execute: () => Promise.resolve({ content: [{ type: "text" as const, text: "ok" }] }),
+            },
+          }),
+        prompts: () => Effect.succeed({}),
+        resources: () => Effect.succeed({}),
+        add: () => Effect.succeed({ status: { status: "disabled" as const } }),
+        connect: () => Effect.void,
+        disconnect: () => Effect.void,
+        getPrompt: () => Effect.succeed(undefined),
+        readResource: () => Effect.succeed(undefined),
+        startAuth: () => Effect.die("unexpected MCP auth"),
+        authenticate: () => Effect.die("unexpected MCP auth"),
+        finishAuth: () => Effect.die("unexpected MCP auth"),
+        removeAuth: () => Effect.void,
+        supportsOAuth: () => Effect.succeed(false),
+        hasStoredTokens: () => Effect.succeed(false),
+        getAuthStatus: () => Effect.succeed("not_authenticated" as const),
+      }),
+    ),
+    Layer.succeed(
+      Plugin.Service,
+      Plugin.Service.of({
+        trigger: (_name, _input, output) => Effect.succeed(output),
+        list: () => Effect.succeed([]),
+        init: () => Effect.void,
+      }),
+    ),
+    Layer.succeed(
+      Permission.Service,
+      Permission.Service.of({
+        ask: () => Effect.void,
+        reply: () => Effect.void,
+        list: () => Effect.succeed([]),
+      }),
+    ),
+    Layer.succeed(
+      Truncate.Service,
+      Truncate.Service.of({
+        cleanup: () => Effect.void,
+        write: () => Effect.succeed("/tmp/tool-output"),
+        output: (text) => Effect.succeed({ content: text, truncated: false as const }),
+        limits: () => Effect.succeed({ maxLines: 2000, maxBytes: 50 * 1024 }),
+      }),
+    ),
+  ),
+)
+
+describe("SessionTools.resolve", () => {
+  it.effect("fails locally when MCP schemas contain Zod internals", () =>
+    Effect.gen(function* () {
+      const exit = yield* SessionTools.resolve({
+        agent: agentInfo(),
+        model: kimiModel(),
+        session: sessionInfo(),
+        processor: processor(),
+        bypassAgentCheck: false,
+        messages: [],
+        promptOps: promptOps(),
+      }).pipe(Effect.exit)
+
+      expect(Exit.isFailure(exit)).toBe(true)
+      if (!Exit.isFailure(exit)) return
+
+      expect(String(exit.cause)).toContain("ctx_batch_execute")
+      expect(String(exit.cause)).toContain("non-JSON-Schema Zod internals")
+      expect(String(exit.cause)).toContain("$.properties.batch.items._zod")
+    }),
+  )
+})
+
+function agentInfo(): Agent.Info {
+  return {
+    name: "build",
+    mode: "primary",
+    permission: [],
+    options: {},
+  }
+}
+
+function schemaWithZodInternals() {
+  return JSON.parse(
+    JSON.stringify({
+      _zod: { def: { type: "object" } },
+      def: { type: "object" },
+      typeName: "ZodObject",
+      "~standard": { vendor: "zod" },
+    }),
+  )
+}
+
+function kimiModel(): Provider.Model {
+  return {
+    id: ModelID.make("kimi-k2.6"),
+    providerID: ProviderID.make("moonshotai"),
+    name: "Kimi K2.6",
+    limit: { context: 128_000, output: 32_000 },
+    cost: { input: 0, output: 0, cache: { read: 0, write: 0 } },
+    capabilities: {
+      toolcall: true,
+      attachment: false,
+      reasoning: false,
+      temperature: true,
+      input: { text: true, image: false, audio: false, video: false, pdf: false },
+      output: { text: true, image: false, audio: false, video: false, pdf: false },
+      interleaved: false,
+    },
+    api: { id: "kimi-k2.6", url: "https://api.moonshot.example/v1", npm: "@ai-sdk/openai-compatible" },
+    options: {},
+    headers: {},
+    release_date: "2026-01-01",
+    status: "active",
+  }
+}
+
+function sessionInfo() {
+  return {
+    id: SessionID.descending(),
+    slug: "test",
+    projectID: ProjectID.global,
+    directory: "/tmp/test",
+    title: "test",
+    version: "test",
+    time: { created: Date.now(), updated: Date.now() },
+  }
+}
+
+function processor() {
+  return {
+    message: {
+      id: MessageID.ascending(),
+      sessionID: SessionID.descending(),
+      role: "assistant",
+      parentID: MessageID.ascending(),
+      modelID: ModelID.make("kimi-k2.6"),
+      providerID: ProviderID.make("moonshotai"),
+      mode: "build",
+      agent: "build",
+      path: { cwd: "/tmp/test", root: "/tmp/test" },
+      cost: 0,
+      tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+      time: { created: Date.now() },
+    } satisfies MessageV2.Assistant,
+    updateToolCall: () => Effect.succeed(undefined),
+    completeToolCall: () => Effect.void,
+  }
+}
+
+function promptOps() {
+  return {
+    cancel: () => Effect.void,
+    resolvePromptParts: (template: string) => Effect.succeed([{ type: "text" as const, text: template }]),
+    prompt: () => Effect.die("unexpected prompt call"),
+    loop: () => Effect.die("unexpected loop call"),
+  }
+}

packages/opencode/test/tool/registry.test.ts

@@ -34,6 +34,7 @@ import { ProviderID, ModelID } from "@/provider/schema"
 import { ToolJsonSchema } from "@/tool/json-schema"
 import { MessageID, SessionID } from "@/session/schema"
 import { RuntimeFlags } from "@/effect/runtime-flags"
+import z3 from "zod/v3"
 
 const node = CrossSpawnSpawner.defaultLayer
 const configLayer = TestConfig.layer({
@@ -80,7 +81,7 @@ const brokenPluginLayer = Layer.succeed(
     init: () => Effect.void,
     trigger: ((_name: unknown, _input: unknown, output: unknown) =>
       Effect.succeed(output)) as Plugin.Interface["trigger"],
-    list: () =>
+    list: (() =>
       Effect.succeed([
         {
           tool: {
@@ -91,7 +92,41 @@ const brokenPluginLayer = Layer.succeed(
             },
           },
         },
-      ]),
+      ])) as unknown as Plugin.Interface["list"],
+  }),
+)
+
+const zod3PluginLayer = Layer.succeed(
+  Plugin.Service,
+  Plugin.Service.of({
+    init: () => Effect.void,
+    trigger: ((_name: unknown, _input: unknown, output: unknown) =>
+      Effect.succeed(output)) as Plugin.Interface["trigger"],
+    list: (() =>
+      Effect.succeed([
+        {
+          tool: {
+            ctx_batch_execute: {
+              description: "context-mode batch executor",
+              args: {
+                batch: z3
+                  .preprocess(
+                    (value) => (typeof value === "string" ? JSON.parse(value) : value),
+                    z3
+                      .array(
+                        z3.object({
+                          command: z3.string().describe("Command to execute"),
+                        }),
+                      )
+                      .min(1),
+                  )
+                  .describe("Commands to execute as a batch"),
+              },
+              execute: async () => "ok",
+            },
+          },
+        },
+      ])) as unknown as Plugin.Interface["list"],
   }),
 )
 
@@ -105,6 +140,7 @@ const background = testEffect(
 const withBrokenPlugin = testEffect(
   Layer.mergeAll(registryLayer({ plugin: brokenPluginLayer }), node, Agent.defaultLayer),
 )
+const withZod3Plugin = testEffect(Layer.mergeAll(registryLayer({ plugin: zod3PluginLayer }), node, Agent.defaultLayer))
 
 afterEach(async () => {
   await disposeAllInstances()
@@ -349,6 +385,52 @@ describe("tool.registry", () => {
     }),
   )
 
+  withZod3Plugin.instance("loads plugin tools with Zod 3 args as JSON Schema", () =>
+    Effect.gen(function* () {
+      const registry = yield* ToolRegistry.Service
+      const loaded = (yield* registry.all()).find((tool) => tool.id === "ctx_batch_execute")
+      if (!loaded) throw new Error("ctx_batch_execute tool was not loaded")
+
+      expect(loaded.jsonSchema).toMatchObject({
+        type: "object",
+        properties: {
+          batch: {
+            type: "array",
+            description: "Commands to execute as a batch",
+            items: {
+              type: "object",
+              properties: {
+                command: { type: "string", description: "Command to execute" },
+              },
+            },
+            minItems: 1,
+          },
+        },
+        required: ["batch"],
+      })
+      expect(JSON.stringify(loaded.jsonSchema)).not.toContain("_def")
+      expect(JSON.stringify(loaded.jsonSchema)).not.toContain("_zod")
+      expect(Result.isSuccess(Schema.decodeUnknownResult(loaded.parameters)({ batch: [{ command: "pwd" }] }))).toBe(
+        true,
+      )
+      expect(Result.isSuccess(Schema.decodeUnknownResult(loaded.parameters)({}))).toBe(false)
+    }),
+  )
+
+  withZod3Plugin.instance("validates plugin tools with Zod 3 preprocessors", () =>
+    Effect.gen(function* () {
+      const registry = yield* ToolRegistry.Service
+      const loaded = (yield* registry.all()).find((tool) => tool.id === "ctx_batch_execute")
+      if (!loaded) throw new Error("ctx_batch_execute tool was not loaded")
+
+      expect(
+        Result.isSuccess(
+          Schema.decodeUnknownResult(loaded.parameters)({ batch: JSON.stringify([{ command: "pwd" }]) }),
+        ),
+      ).toBe(true)
+    }),
+  )
+
   it.instance(
     "preserves Zod arg descriptions from older config-scoped plugin packages",
     () =>