diff --git a/packages/opencode/script/tool-schema-compatibility-matrix.ts b/packages/opencode/script/tool-schema-compatibility-matrix.ts
new file mode 100644
index 000000000000..72a490880b56
--- /dev/null
+++ b/packages/opencode/script/tool-schema-compatibility-matrix.ts
@@ -0,0 +1,285 @@
+import { ModelV2 } from "@opencode-ai/core/model"
+import { ProviderV2 } from "@opencode-ai/core/provider"
+import type { JSONSchema7 } from "@ai-sdk/provider"
+import { Effect } from "effect"
+import { jsonSchema, streamText, tool, type LanguageModel } from "ai"
+import { AppRuntime } from "@/effect/app-runtime"
+import { InstanceRef } from "@/effect/instance-ref"
+import { Provider } from "@/provider/provider"
+import { InstanceStore } from "@/project/instance-store"
+import { MFJS } from "@/provider/mfjs"
+
+// Usage:
+// bun run script/tool-schema-compatibility-matrix.ts --models=model-a,model-b
+//   [--provider=opencode-go] [--projection=none|mfjs]
+//   [--cases=tuple items,...] [--concurrency=9] [--timeout=30000]
+
+type JsonRecord = Record<string, unknown>
+type Case = {
+  name: string
+  schema: JsonRecord
+}
+type Result = {
+  case: string
+  model: string
+  status: "accepted" | "rejected" | "rate-limited" | "error"
+  code?: number
+  error?: string
+}
+
+const projection = option("projection") ?? "none"
+if (projection !== "none" && projection !== "mfjs") throw new Error(`Unsupported projection: ${projection}`)
+const concurrency = Number(option("concurrency") ?? 9)
+const timeout = Number(option("timeout") ?? 30_000)
+const providerID = option("provider") ?? "opencode-go"
+const models = option("models")?.split(",").filter(Boolean) ?? []
+if (models.length === 0) throw new Error("--models must contain at least one model ID")
+const selectedCases = new Set(option("cases")?.split(",").filter(Boolean) ?? [])
+
+const matrix: Case[] = [
+  property("enum/type mismatch", { type: "object", enum: ["move", "copy"] }),
+  property("untyped enum", { enum: ["move", "copy"] }),
+  property("mixed untyped enum", { enum: ["move", 1, null, true] }),
+  property("const", { const: "move" }),
+  property("tuple items", { type: "array", items: [{ type: "string" }, { type: "number" }] }),
+  property("prefix items", { type: "array", prefixItems: [{ type: "string" }, { type: "number" }] }),
+  property("typed anyOf", {
+    type: "string",
+    enum: ["move"],
+    anyOf: [{ type: "string" }, { type: "null" }],
+  }),
+  property("anyOf count limit", {
+    anyOf: Array.from({ length: 501 }, (_, index) => ({ const: `value_${index}` })),
+  }),
+  property("oneOf", { oneOf: [{ type: "string" }, { type: "integer" }] }),
+  property("allOf", {
+    allOf: [
+      { type: "object", properties: { left: { type: "string" } } },
+      { type: "object", properties: { right: { type: "number" } } },
+    ],
+  }),
+  property("not", { type: "string", not: { enum: ["blocked"] } }),
+  property("if/then/else", {
+    type: "object",
+    properties: { mode: { type: "string" }, count: { type: "integer" } },
+    if: { properties: { mode: { enum: ["many"] } } },
+    then: { required: ["count"] },
+    else: { properties: { count: { maximum: 1 } } },
+  }),
+  property("contains", { type: "array", contains: { type: "string" } }),
+  objectCase("patternProperties", {
+    type: "object",
+    patternProperties: { "^extra_": { type: "number" } },
+    additionalProperties: false,
+  }),
+  objectCase("dependentSchemas", {
+    type: "object",
+    properties: { key: { type: "string" }, value: { type: "string" } },
+    dependentSchemas: { key: { required: ["value"] } },
+  }),
+  objectCase("propertyNames", {
+    type: "object",
+    propertyNames: { pattern: "^[a-z]+$" },
+  }),
+  property("uniqueItems", { type: "array", items: { type: "string" }, uniqueItems: true }),
+  property("boolean true schema", true),
+  property("boolean false schema", false),
+  objectCase("empty property name", {
+    type: "object",
+    properties: { "": { type: "string" } },
+    required: [""],
+  }),
+  objectCase("dangling required", {
+    type: "object",
+    properties: {},
+    required: ["missing"],
+  }),
+  objectCase("external ref", {
+    type: "object",
+    properties: { value: { $ref: "https://example.com/schema.json" } },
+  }),
+  objectCase("chained ref", {
+    type: "object",
+    properties: { value: { $ref: "#/$defs/A" } },
+    $defs: { A: { $ref: "#/$defs/B" }, B: { type: "string" } },
+  }),
+  objectCase("recursive ref", {
+    type: "object",
+    properties: { node: { $ref: "#/$defs/Node" } },
+    $defs: {
+      Node: {
+        type: "object",
+        properties: { value: { type: "string" }, next: { anyOf: [{ $ref: "#/$defs/Node" }, { type: "null" }] } },
+        required: ["value"],
+      },
+    },
+  }),
+  objectCase("reference depth limit", {
+    type: "object",
+    properties: { value: { $ref: "#/$defs/Value" } },
+    $defs: { Value: nested(30) },
+  }),
+  objectCase("schema size limit", {
+    type: "object",
+    description: "x".repeat(120_001),
+    properties: {},
+  }),
+  objectCase("schema depth limit", nested(35)),
+  objectCase("property count limit", {
+    type: "object",
+    properties: Object.fromEntries(
+      Array.from({ length: 3001 }, (_, index) => [`property_${index}`, { type: "string" }]),
+    ),
+  }),
+  property("enum count limit", {
+    type: "string",
+    enum: Array.from({ length: 1001 }, (_, index) => `value_${index}`),
+  }),
+]
+const cases = selectedCases.size === 0 ? matrix : matrix.filter((item) => selectedCases.has(item.name))
+
+const { store, ctx } = await AppRuntime.runPromise(
+  InstanceStore.Service.use((store) =>
+    store.load({ directory: process.cwd() }).pipe(Effect.map((ctx) => ({ store, ctx }))),
+  ),
+)
+
+try {
+  const languages = await AppRuntime.runPromise(
+    Effect.gen(function* () {
+      const provider = yield* Provider.Service
+      return yield* Effect.forEach(
+        models,
+        Effect.fnUntraced(function* (model) {
+          const info = yield* provider.getModel(ProviderV2.ID.make(providerID), ModelV2.ID.make(model))
+          return [model, yield* provider.getLanguage(info)] as const
+        }),
+        { concurrency: "unbounded" },
+      )
+    }).pipe(Effect.provideService(InstanceRef, ctx)),
+  )
+  const jobs = languages.flatMap(([model, language]) => cases.map((item) => () => run(language, model, item)))
+  const results = await parallel(jobs, concurrency)
+  print(results)
+  if (projection !== "none" && results.some((result) => result.status !== "accepted")) process.exitCode = 1
+} finally {
+  await AppRuntime.runPromise(store.dispose(ctx))
+}
+process.exit(process.exitCode ?? 0)
+
+async function run(language: LanguageModel, model: string, item: Case): Promise<Result> {
+  const schema = projection === "mfjs" ? MFJS.sanitize(item.schema) : item.schema
+  let providerError: unknown
+  try {
+    const response = streamText({
+      model: language,
+      prompt: "Reply with exactly OK without calling tools.",
+      maxOutputTokens: 16,
+      abortSignal: AbortSignal.timeout(timeout),
+      onError(event) {
+        providerError = event.error
+      },
+      tools: {
+        probe: tool({
+          description: `Tool schema probe: ${item.name}`,
+          inputSchema: jsonSchema(schema as JSONSchema7),
+          execute: async () => "ok",
+        }),
+      },
+    })
+    await response.text
+    if (providerError) throw providerError
+    console.error(`accepted: ${model} / ${item.name}`)
+    return { case: item.name, model, status: "accepted" }
+  } catch (error) {
+    const failure = providerError ?? error
+    const code = statusCode(failure)
+    const message = failure instanceof Error ? failure.message : String(failure)
+    const status = code === 429 || /rate limit/i.test(message) ? "rate-limited" : code === 400 ? "rejected" : "error"
+    console.error(`${status}: ${model} / ${item.name}`)
+    return {
+      case: item.name,
+      model,
+      status,
+      code,
+      error: message,
+    }
+  }
+}
+
+async function parallel<T>(jobs: Array<() => Promise<T>>, limit: number) {
+  const output = new Array<T>(jobs.length)
+  let next = 0
+  await Promise.all(
+    Array.from({ length: Math.min(limit, jobs.length) }, async () => {
+      while (true) {
+        const index = next++
+        const job = jobs[index]
+        if (!job) return
+        output[index] = await job()
+      }
+    }),
+  )
+  return output
+}
+
+function print(results: Result[]) {
+  const byCase = new Map<string, Map<string, Result>>()
+  results.forEach((result) => {
+    const row = byCase.get(result.case) ?? new Map<string, Result>()
+    row.set(result.model, result)
+    byCase.set(result.case, row)
+  })
+  console.log(`Projection: ${projection}`)
+  console.log(`Provider: ${providerID}`)
+  console.log(`| Case | ${models.join(" | ")} |`)
+  console.log(`| --- | ${models.map(() => "---").join(" | ")} |`)
+  cases.forEach((item) => {
+    const row = byCase.get(item.name)
+    const values = models.map((model) => {
+      const result = row?.get(model)
+      if (!result) return "missing"
+      return result.status === "accepted" ? "accepted" : `${result.status}${result.code ? ` (${result.code})` : ""}`
+    })
+    console.log(`| ${item.name} | ${values.join(" | ")} |`)
+  })
+  const rejected = results.filter((result) => result.status !== "accepted")
+  if (rejected.length > 0) {
+    console.log("\nRejected details:")
+    rejected.forEach((result) => console.log(`- ${result.model} / ${result.case}: ${result.error}`))
+  }
+}
+
+function property(name: string, schema: unknown): Case {
+  return objectCase(name, { type: "object", properties: { value: schema }, required: ["value"] })
+}
+
+function objectCase(name: string, schema: JsonRecord): Case {
+  return { name, schema }
+}
+
+function nested(depth: number): JsonRecord {
+  return Array.from({ length: depth }).reduce<JsonRecord>(
+    (schema) => ({ type: "object", properties: { next: schema }, required: ["next"] }),
+    { type: "string" },
+  )
+}
+
+function option(name: string) {
+  const prefix = `--${name}=`
+  return process.argv.find((arg) => arg.startsWith(prefix))?.slice(prefix.length)
+}
+
+function statusCode(error: unknown, seen = new Set<object>()): number | undefined {
+  if (!isRecord(error) || seen.has(error)) return
+  seen.add(error)
+  if (typeof error.statusCode === "number") return error.statusCode
+  for (const value of Object.values(error)) {
+    const nested = statusCode(value, seen)
+    if (nested !== undefined) return nested
+  }
+}
+
+function isRecord(value: unknown): value is JsonRecord {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}
diff --git a/packages/opencode/src/provider/mfjs.ts b/packages/opencode/src/provider/mfjs.ts
new file mode 100644
index 000000000000..e976df317fc0
--- /dev/null
+++ b/packages/opencode/src/provider/mfjs.ts
@@ -0,0 +1,651 @@
+export * as MFJS from "./mfjs"
+
+import type { JSONSchema7 } from "@ai-sdk/provider"
+
+/**
+ * Kimi tool-schema compatibility projection.
+ *
+ * Principles:
+ * - Preserve schema features accepted by Kimi without rewriting them.
+ * - Apply model-agnostic adaptations only for reproduced provider rejections.
+ * - Keep explicit types authoritative; lossy fallbacks may widen but never narrow.
+ *
+ * Adapted families include enum/type conflicts, untyped enums, tuple `items`,
+ * typed `anyOf`, boolean schemas, dangling `required`, references, and observed
+ * enum/union/property/size/depth limits. Accepted keywords such as `const`,
+ * `oneOf`, `allOf`, conditionals, `prefixItems`, and other constraints pass
+ * through recursively.
+ *
+ * `script/tool-schema-compatibility-matrix.ts` compares raw and MFJS-projected
+ * schemas across configured providers and models. Keep this projection
+ * evidence-driven as provider behavior evolves.
+ *
+ * MFJS specification and reference implementation:
+ * https://github.com/MoonshotAI/walle
+ */
+
+type JsonRecord = Record<string, unknown>
+type Context = {
+  root: JsonRecord
+  definitions: JsonRecord
+  legacy: Record<string, string>
+  properties: number
+}
+type Projection = {
+  schema: JsonRecord
+  // Unsafe projections cannot stay under non-monotonic applicators without risking narrowing.
+  unsafe: boolean
+}
+
+const TYPES = new Set(["string", "number", "boolean", "integer", "object", "array", "null"])
+const SCHEMA_MAPS = new Set(["patternProperties", "dependentSchemas"])
+const SCHEMA_NODES = new Set([
+  "additionalProperties",
+  "not",
+  "if",
+  "then",
+  "else",
+  "contains",
+  "propertyNames",
+  "unevaluatedProperties",
+])
+const SCHEMA_LISTS = new Set(["allOf", "prefixItems"])
+const MAX_ANY_OF = 500
+const MAX_DEPTH = 30
+const MAX_ENUM = 1000
+const MAX_PROPERTIES = 3000
+const MAX_RECURSION = 1000
+const MAX_SCHEMA_SIZE = 120_000
+
+/**
+ * Projects tool schemas only where Kimi rejects otherwise valid requests.
+ * Accepted keywords are preserved, explicit types remain authoritative, and
+ * lossy fallbacks only widen what the model may emit.
+ */
+export function sanitize(value: unknown): JSONSchema7 {
+  const root = isRecord(value) ? value : {}
+  const sourceDefinitions = definitions(root)
+  const context = { root, definitions: sourceDefinitions.schemas, legacy: sourceDefinitions.legacy, properties: 0 }
+  const projected = project(root, context, 0, 0).schema
+  const defs = Object.fromEntries(
+    Object.entries(context.definitions)
+      .filter(([name, schema]) => name.length > 0 && !name.includes("/") && isRecord(schema))
+      .map(([name, schema]) => [name, containsSlashKey(schema) ? {} : project(schema, context, 0, 0).schema]),
+  )
+  if (Object.keys(defs).length > 0) projected.$defs = defs
+  const resolved = dropDanglingRefs(projected, projected)
+  const bounded =
+    (containsRef(resolved) && !terminates(resolved, resolved, new Set())) ||
+    schemaDepth(resolved, resolved, new Set()) > MAX_DEPTH
+      ? { type: "object", properties: {} }
+      : resolved
+  return fitSize(bounded) as JSONSchema7
+}
+
+function project(value: unknown, context: Context, depth: number, recursion: number): Projection {
+  if (depth >= MAX_DEPTH || recursion >= MAX_RECURSION) return { schema: {}, unsafe: true }
+  if (!isRecord(value) || Object.keys(value).length === 0) {
+    return { schema: {}, unsafe: !isRecord(value) }
+  }
+
+  const ref = canonicalRef(value.$ref, context)
+  if (ref) {
+    const schema = value.nullable === true ? { anyOf: [{ $ref: ref }, { type: "null" }] } : { $ref: ref }
+    return {
+      schema,
+      // References are conservative here because their projected targets may widen later.
+      unsafe: true,
+    }
+  }
+
+  const declaredTypes = schemaTypes(value.type)
+  const inferredTypes =
+    declaredTypes.length > 0
+      ? declaredTypes
+      : hasUnprojectableEnumValue("const" in value ? [value.const] : value.enum, [])
+        ? []
+        : groupEnum(enumValues("const" in value ? [value.const] : value.enum)).map((group) => group.type)
+  if (Array.isArray(value.anyOf) && inferredTypes.length > 0) {
+    return projectTypedAnyOf(
+      { ...value, type: inferredTypes.length === 1 ? inferredTypes[0] : inferredTypes },
+      context,
+      depth,
+      recursion,
+    )
+  }
+
+  const result: JsonRecord = {}
+  let unsafe = "$ref" in value || "$defs" in value || "definitions" in value
+  let truncatedProperties = false
+  let widenedContains = false
+  const child = (item: unknown, nextDepth = depth, nextContext = context) =>
+    project(item, nextContext, nextDepth, recursion + 1)
+  const keep = (projection: Projection) => {
+    unsafe ||= projection.unsafe
+    return projection.schema
+  }
+  const condition = (() => {
+    if (!isRecord(value.if)) return
+    const nested = { ...context }
+    const projection = child(value.if, depth, nested)
+    if (!projection.unsafe) context.properties = nested.properties
+    return projection
+  })()
+  for (const [key, item] of Object.entries(value)) {
+    if (key === "$defs" || key === "definitions") continue
+    if (key === "$ref") continue
+    if (key === "items" && Array.isArray(item)) {
+      unsafe = true
+      continue
+    }
+    if (key === "items" && (item === true || item === false)) {
+      result.items = {}
+      unsafe = true
+      continue
+    }
+    if (key === "anyOf" && Array.isArray(item)) {
+      if (item.length > 0 && item.length <= MAX_ANY_OF) {
+        result.anyOf = item.map((branch) => keep(child(branch)))
+      } else {
+        unsafe = true
+      }
+      continue
+    }
+    if (key === "oneOf" && Array.isArray(item)) {
+      const nested = { ...context }
+      const branches = item.map((branch) => child(branch, depth, nested))
+      const risky = branches.some((branch) => branch.unsafe)
+      const useBranches =
+        !risky || (!Array.isArray(value.anyOf) && branches.length > 0 && branches.length <= MAX_ANY_OF)
+      if (!risky) result.oneOf = branches.map((branch) => branch.schema)
+      if (risky && useBranches) result.anyOf = branches.map((branch) => branch.schema)
+      if (useBranches) context.properties = nested.properties
+      unsafe ||= risky
+      continue
+    }
+    if (SCHEMA_LISTS.has(key) && Array.isArray(item)) {
+      result[key] = item.map((schema) => keep(child(schema)))
+      continue
+    }
+    if (key === "not" && isRecord(item)) {
+      const nested = { ...context }
+      const schema = child(item, depth, nested)
+      if (!schema.unsafe) {
+        result.not = schema.schema
+        context.properties = nested.properties
+      } else {
+        unsafe = true
+      }
+      continue
+    }
+    if (key === "if" || key === "then" || key === "else") {
+      if (condition?.unsafe) {
+        unsafe = true
+        continue
+      }
+      if (key === "if" && condition) {
+        result.if = condition.schema
+        continue
+      }
+      if (isRecord(item)) {
+        result[key] = keep(child(item))
+        continue
+      }
+      result[key] = item
+      continue
+    }
+    if (key === "properties" && isRecord(item)) {
+      const remaining = Math.max(0, MAX_PROPERTIES - context.properties)
+      const entries = Object.entries(item).slice(0, remaining)
+      context.properties += entries.length
+      truncatedProperties = entries.length !== Object.keys(item).length
+      result.properties = Object.fromEntries(entries.map(([name, schema]) => [name, keep(child(schema, depth + 1))]))
+      unsafe ||= truncatedProperties
+      continue
+    }
+    if (SCHEMA_MAPS.has(key) && isRecord(item)) {
+      const schemas = Object.entries(item).map(([name, schema]) => [name, child(schema)] as const)
+      result[key] = Object.fromEntries(
+        schemas.map(([name, schema]) => [name, typeof schema.schema.$ref === "string" ? {} : schema.schema]),
+      )
+      unsafe ||= schemas.some(([, schema]) => schema.unsafe)
+      continue
+    }
+    if (key === "contains" && isRecord(item)) {
+      const schema = child(item)
+      result.contains = schema.schema
+      widenedContains = schema.unsafe
+      keep(schema)
+      continue
+    }
+    if ((key === "items" || SCHEMA_NODES.has(key)) && isRecord(item)) {
+      result[key] = keep(child(item))
+      continue
+    }
+    result[key] = item
+  }
+  unsafe ||= projectRequired(result, context)
+  if (truncatedProperties) delete result.additionalProperties
+  if (widenedContains && "maxContains" in result) {
+    delete result.maxContains
+    unsafe = true
+  }
+  const projected = projectEnum(result)
+  unsafe ||= projected.unsafe
+  if ("unevaluatedProperties" in projected.schema && unsafe) {
+    delete projected.schema.unevaluatedProperties
+    unsafe = true
+  }
+  return { schema: projected.schema, unsafe }
+}
+
+function projectTypedAnyOf(source: JsonRecord, context: Context, depth: number, recursion: number): Projection {
+  const base = omit(source, ["anyOf", "type", "enum", "const", "$defs", "definitions"])
+  const parentTypes = schemaTypes(source.type)
+  const parentValues = "const" in source ? [source.const] : source.enum
+  const parentEnum = hasUnprojectableEnumValue(parentValues, parentTypes) ? [] : enumValues(parentValues)
+  const variants = Array.isArray(source.anyOf) ? source.anyOf : []
+  if (variants.length > MAX_ANY_OF) {
+    const projected = project(omit(source, ["anyOf", "unevaluatedProperties"]), context, depth, recursion + 1)
+    return { ...projected, unsafe: true }
+  }
+  const branches = variants.flatMap((branch) => {
+    if (branch === false) return []
+    const item = branch === true ? {} : isRecord(branch) ? branch : undefined
+    if (!item) return []
+    const types = intersectTypes(parentTypes, schemaTypes(item.type))
+    if (types.length === 0) return []
+    const branchValues = "const" in item ? [item.const] : item.enum
+    const branchEnum = hasUnprojectableEnumValue(branchValues, types) ? [] : enumValues(branchValues)
+    const values = intersectEnums(parentEnum, branchEnum).filter((value) =>
+      types.some((type) => matchesType(value, type)),
+    )
+    if ((parentEnum.length > 0 || branchEnum.length > 0) && values.length === 0) return []
+    const merged = omit({ ...base, ...item }, ["type", "enum", "const"])
+    const projected = project(
+      {
+        ...merged,
+        type: types.length === 1 ? types[0] : types,
+        ...(values.length > 0 ? { enum: values } : {}),
+      },
+      context,
+      depth,
+      recursion + 1,
+    )
+    return [projected.schema]
+  })
+  return { schema: collapse(branches), unsafe: true }
+}
+
+function projectEnum(source: JsonRecord): Projection {
+  const result = { ...source }
+  const types = schemaTypes(result.type)
+  if (hasUnprojectableEnumValue(result.enum, types)) {
+    delete result.enum
+    return { schema: result, unsafe: true }
+  }
+  const values = enumValues(result.enum)
+  if (values.length === 0) {
+    const unsafe = "enum" in result
+    delete result.enum
+    return { schema: result, unsafe }
+  }
+
+  if (types.length > 0) {
+    const compatible = values.filter((value) => types.some((type) => matchesType(value, type)))
+    if (compatible.length === 0) {
+      delete result.enum
+      return { schema: result, unsafe: true }
+    }
+    const nullable =
+      types.length === 2 && types.includes("null") && !types.includes("object") && !types.includes("array")
+    if (types.length === 1 || nullable) {
+      result.enum = compatible
+      return { schema: result, unsafe: !same(result.enum, source.enum) }
+    }
+    const base = omit(result, ["enum", "type"])
+    return {
+      schema: collapse(groupEnum(compatible).map((group) => ({ ...base, type: group.type, enum: group.values }))),
+      unsafe: true,
+    }
+  }
+
+  const groups = groupEnum(values)
+  if (groups.length === 1) {
+    result.type = groups[0]?.type
+    result.enum = groups[0]?.values
+    return { schema: result, unsafe: true }
+  }
+  const base = omit(result, ["enum", "type"])
+  return {
+    schema: { anyOf: groups.map((group) => ({ ...base, type: group.type, enum: group.values })) },
+    unsafe: true,
+  }
+}
+
+function projectRequired(schema: JsonRecord, context: Context) {
+  if (!Array.isArray(schema.required)) return false
+  const types = schemaTypes(schema.type)
+  if (types.length > 0 && !types.includes("object")) {
+    delete schema.required
+    return true
+  }
+  const sourceProperties = isRecord(schema.properties) ? schema.properties : undefined
+  const properties = { ...sourceProperties }
+  const sourceRequired = schema.required
+  const required = [...new Set(schema.required.filter((item): item is string => typeof item === "string"))].filter(
+    (name) => {
+      if (Object.hasOwn(properties, name)) return true
+      if (context.properties >= MAX_PROPERTIES) return false
+      context.properties++
+      properties[name] = {}
+      return true
+    },
+  )
+  schema.properties = properties
+  schema.required = required
+  return (
+    !sourceProperties ||
+    !same(Object.keys(sourceProperties), Object.keys(properties)) ||
+    !same(sourceRequired, required)
+  )
+}
+
+function fitSize(schema: JsonRecord) {
+  if (schemaSize(schema) <= MAX_SCHEMA_SIZE) return schema
+  const compact = stripAnnotations(schema)
+  if (schemaSize(compact) <= MAX_SCHEMA_SIZE) return compact
+  return {}
+}
+
+function stripAnnotations(schema: JsonRecord): JsonRecord {
+  return Object.fromEntries(
+    Object.entries(schema).flatMap(([key, value]) => {
+      if (["description", "title", "default", "examples", "$comment"].includes(key)) return []
+      if ((key === "properties" || key === "$defs" || SCHEMA_MAPS.has(key)) && isRecord(value)) {
+        return [
+          [
+            key,
+            Object.fromEntries(
+              Object.entries(value).map(([name, item]) => [name, isRecord(item) ? stripAnnotations(item) : item]),
+            ),
+          ],
+        ]
+      }
+      if ((key === "anyOf" || key === "oneOf" || SCHEMA_LISTS.has(key)) && Array.isArray(value)) {
+        return [[key, value.map((item) => (isRecord(item) ? stripAnnotations(item) : item))]]
+      }
+      if ((key === "items" || SCHEMA_NODES.has(key)) && isRecord(value)) {
+        return [[key, stripAnnotations(value)]]
+      }
+      return [[key, value]]
+    }),
+  )
+}
+
+function schemaSize(schema: JsonRecord) {
+  const json = JSON.stringify(schema).replace(/[<>&\u2028\u2029]/g, (char) => {
+    return `\\u${char.charCodeAt(0).toString(16).padStart(4, "0")}`
+  })
+  return new TextEncoder().encode(json).byteLength
+}
+
+function schemaDepth(schema: JsonRecord, root: JsonRecord, refs: Set<string>): number {
+  const properties = isRecord(schema.properties)
+    ? Math.max(
+        0,
+        ...Object.values(schema.properties).map((item) => (isRecord(item) ? 1 + schemaDepth(item, root, refs) : 0)),
+      )
+    : 0
+  const nodes = [schema.items, schema.additionalProperties].flatMap((item) =>
+    isRecord(item) ? [schemaDepth(item, root, refs)] : [],
+  )
+  const lists = [schema.anyOf, schema.oneOf, schema.allOf, schema.prefixItems].flatMap((items) =>
+    Array.isArray(items) ? items.flatMap((item) => (isRecord(item) ? [schemaDepth(item, root, refs)] : [])) : [],
+  )
+  const definitions = isRecord(schema.$defs)
+    ? Object.values(schema.$defs).flatMap((item) => (isRecord(item) ? [schemaDepth(item, root, refs)] : []))
+    : []
+  const ref = (() => {
+    if (typeof schema.$ref !== "string" || refs.has(schema.$ref)) return 0
+    const target = resolveOutputRef(schema.$ref, root)
+    if (!target) return 0
+    const next = new Set(refs)
+    next.add(schema.$ref)
+    return schemaDepth(target, root, next)
+  })()
+  return [...nodes, ...lists, ...definitions, ref].reduce((max, value) => Math.max(max, value), properties)
+}
+
+function dropDanglingRefs(schema: JsonRecord, root: JsonRecord): JsonRecord {
+  if (typeof schema.$ref === "string" && !resolveOutputRef(schema.$ref, root)) return {}
+  return Object.fromEntries(
+    Object.entries(schema).map(([key, value]) => {
+      if ((key === "properties" || key === "$defs" || SCHEMA_MAPS.has(key)) && isRecord(value)) {
+        return [
+          key,
+          Object.fromEntries(
+            Object.entries(value).map(([name, item]) => [name, isRecord(item) ? dropDanglingRefs(item, root) : item]),
+          ),
+        ]
+      }
+      if ((key === "anyOf" || key === "oneOf" || SCHEMA_LISTS.has(key)) && Array.isArray(value)) {
+        return [key, value.map((item) => (isRecord(item) ? dropDanglingRefs(item, root) : item))]
+      }
+      if ((key === "items" || SCHEMA_NODES.has(key)) && isRecord(value)) {
+        return [key, dropDanglingRefs(value, root)]
+      }
+      return [key, value]
+    }),
+  )
+}
+
+function resolveOutputRef(ref: string, root: JsonRecord): JsonRecord | undefined {
+  if (ref === "#") return root
+  const defs = isRecord(root.$defs) ? root.$defs : undefined
+  if (!ref.startsWith("#/$defs/") || !defs) return
+  return ref
+    .slice("#/$defs/".length)
+    .split("/")
+    .map((part) => part.replaceAll("~1", "/").replaceAll("~0", "~"))
+    .reduce<JsonRecord | undefined>((current, part, index) => {
+      const value = index === 0 ? defs[part] : current?.[part]
+      return isRecord(value) ? value : undefined
+    }, undefined)
+}
+
+function terminates(schema: JsonRecord, root: JsonRecord, refs: Set<string>): boolean {
+  const types = schemaTypes(schema.type)
+  if (types.some((type) => type !== "object" && type !== "array")) return true
+  if (types.includes("array")) {
+    if (!isRecord(schema.items) || Object.keys(schema.items).length === 0) return true
+    if (terminates(schema.items, root, refs)) return true
+  }
+  if (types.includes("object")) {
+    if (!Array.isArray(schema.required) || schema.required.length === 0) return true
+    const properties = isRecord(schema.properties) ? schema.properties : undefined
+    if (!properties || Object.keys(properties).length === 0) return true
+    if (
+      schema.required.every((name) => {
+        const property = typeof name === "string" ? properties[name] : undefined
+        return !isRecord(property) || terminates(property, root, refs)
+      })
+    ) {
+      return true
+    }
+  }
+  if (
+    Array.isArray(schema.anyOf) &&
+    (schema.anyOf.length === 0 || schema.anyOf.some((item) => isRecord(item) && terminates(item, root, new Set(refs))))
+  ) {
+    return true
+  }
+  if (typeof schema.$ref === "string") {
+    if (refs.has(schema.$ref)) return false
+    const target = resolveOutputRef(schema.$ref, root)
+    if (!target) return true
+    const next = new Set(refs)
+    next.add(schema.$ref)
+    return terminates(target, root, next)
+  }
+  return Object.keys(schema).length === 0
+}
+
+function canonicalRef(value: unknown, context: Context) {
+  if (typeof value !== "string") return
+  if (value.includes("~0") || value.includes("~1")) return
+  const ref = (() => {
+    if (!value.startsWith("#/definitions/")) return value
+    const parts = value.slice("#/definitions/".length).split("/")
+    const name = parts[0]?.replaceAll("~1", "/").replaceAll("~0", "~")
+    if (!name || !context.legacy[name]) return
+    return `#/$defs/${context.legacy[name]?.replaceAll("~", "~0").replaceAll("/", "~1")}${
+      parts.length > 1 ? `/${parts.slice(1).join("/")}` : ""
+    }`
+  })()
+  if (!ref) return
+  if (ref === "#") return ref
+  if (!ref.startsWith("#/$defs/") || ref === "#/$defs/") return
+  const name = ref.slice("#/$defs/".length).split("/", 1)[0]?.replaceAll("~1", "/").replaceAll("~0", "~")
+  if (!name || name.includes("/")) return
+  return isRecord(resolveRef(ref, context)) ? ref : undefined
+}
+
+function resolveRef(ref: string, context: Context): unknown {
+  if (ref === "#") return context.root
+  return ref
+    .slice("#/$defs/".length)
+    .split("/")
+    .map((part) => part.replaceAll("~1", "/").replaceAll("~0", "~"))
+    .reduce<unknown>((current, part, index) => {
+      if (index === 0) return context.definitions[part]
+      return isRecord(current) ? current[part] : undefined
+    }, undefined)
+}
+
+function definitions(root: JsonRecord) {
+  const modern = isRecord(root.$defs) ? root.$defs : {}
+  const schemas = { ...modern }
+  const legacy = Object.fromEntries(
+    Object.entries(isRecord(root.definitions) ? root.definitions : {}).map(([name, schema]) => {
+      const target =
+        !Object.hasOwn(schemas, name) || same(schemas[name], schema) ? name : uniqueDefinition(name, schemas)
+      schemas[target] = schema
+      return [name, target]
+    }),
+  )
+  return { schemas, legacy }
+}
+
+function uniqueDefinition(name: string, schemas: JsonRecord, index = 1): string {
+  const candidate = `${name}__definitions${index === 1 ? "" : `_${index}`}`
+  if (!Object.hasOwn(schemas, candidate)) return candidate
+  return uniqueDefinition(name, schemas, index + 1)
+}
+
+function containsSlashKey(value: unknown): boolean {
+  if (Array.isArray(value)) return value.some(containsSlashKey)
+  if (!isRecord(value)) return false
+  return Object.entries(value).some(([key, item]) => key.includes("/") || containsSlashKey(item))
+}
+
+function schemaTypes(value: unknown) {
+  if (typeof value === "string" && TYPES.has(value)) return [value]
+  if (!Array.isArray(value)) return []
+  return [...new Set(value.filter((item): item is string => typeof item === "string" && TYPES.has(item)))]
+}
+
+function intersectTypes(parent: string[], child: string[]) {
+  if (child.length === 0) return parent
+  return [
+    ...new Set([
+      ...parent.filter((type) => child.includes(type)),
+      ...((parent.includes("number") && child.includes("integer")) ||
+      (parent.includes("integer") && child.includes("number"))
+        ? ["integer"]
+        : []),
+    ]),
+  ]
+}
+
+function enumValues(value: unknown) {
+  if (!Array.isArray(value)) return []
+  const values = unique(value.filter((item) => valueType(item) !== undefined))
+  return values.length > MAX_ENUM ? [] : values
+}
+
+function hasUnprojectableEnumValue(value: unknown, types: string[]) {
+  if (!Array.isArray(value)) return false
+  return value.some((item) => {
+    if (valueType(item)) return false
+    const type = Array.isArray(item) ? "array" : isRecord(item) ? "object" : undefined
+    return type !== undefined && (types.length === 0 || types.includes(type))
+  })
+}
+
+function intersectEnums(parent: unknown[], child: unknown[]) {
+  if (parent.length === 0) return child
+  if (child.length === 0) return parent
+  return parent.filter((value) => child.some((item) => Object.is(value, item)))
+}
+
+function groupEnum(values: unknown[]) {
+  const hasDecimal = values.some((item) => typeof item === "number" && !Number.isInteger(item))
+  return values.reduce<{ type: string; values: unknown[] }[]>((groups, item) => {
+    const actual = valueType(item)
+    if (!actual) return groups
+    const type = hasDecimal && actual === "integer" ? "number" : actual
+    const group = groups.find((entry) => entry.type === type)
+    if (group) group.values.push(item)
+    else groups.push({ type, values: [item] })
+    return groups
+  }, [])
+}
+
+function valueType(value: unknown) {
+  if (value === null) return "null"
+  if (typeof value === "string" || typeof value === "boolean") return typeof value
+  if (typeof value === "number" && Number.isFinite(value)) return Number.isInteger(value) ? "integer" : "number"
+}
+
+function matchesType(value: unknown, type: string) {
+  const actual = valueType(value)
+  if (type === "number") return actual === "number" || actual === "integer"
+  return actual === type
+}
+
+function collapse(branches: JsonRecord[]) {
+  const projected = unique(branches)
+  if (projected.length === 0) return {}
+  if (projected.length === 1) return projected[0] ?? {}
+  return { anyOf: projected }
+}
+
+function unique<T>(values: T[]) {
+  return [...new Map(values.map((value) => [JSON.stringify(value), value])).values()]
+}
+
+function same(left: unknown, right: unknown) {
+  return JSON.stringify(left) === JSON.stringify(right)
+}
+
+function containsRef(value: unknown): boolean {
+  if (!isRecord(value)) return false
+  if (typeof value.$ref === "string") return true
+  const maps = [value.properties, value.$defs, value.definitions, ...[...SCHEMA_MAPS].map((key) => value[key])]
+  if (maps.some((map) => isRecord(map) && Object.values(map).some(containsRef))) return true
+  const nodes = [value.items, ...[...SCHEMA_NODES].map((key) => value[key])]
+  if (nodes.some(containsRef)) return true
+  return [value.anyOf, value.oneOf, ...[...SCHEMA_LISTS].map((key) => value[key])].some(
+    (items) => Array.isArray(items) && items.some(containsRef),
+  )
+}
+
+function omit(source: JsonRecord, keys: string[]) {
+  const omitted = new Set(keys)
+  return Object.fromEntries(Object.entries(source).filter(([key]) => !omitted.has(key)))
+}
+
+function isRecord(value: unknown): value is JsonRecord {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}
diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index d6f817b50e4f..5a01d8d92b3c 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -2,6 +2,7 @@ import type { ModelMessage, ToolResultPart } from "ai"
 import { mergeDeep, unique } from "remeda"
 import type { JSONSchema7 } from "@ai-sdk/provider"
 import type * as Provider from "./provider"
+import { MFJS } from "./mfjs"
 import type * as ModelsDev from "@opencode-ai/core/models-dev"
 import { iife } from "@/util/iife"
 
@@ -1462,22 +1463,12 @@ export function schema(model: Provider.Model, schema: JSONSchema7): JSONSchema7
     // Codex also applies lossy compaction above 4 KB; defer that until OpenCode needs the same schema budget.
   }
 
-  if (model.providerID === "moonshotai" || model.api.id.toLowerCase().includes("kimi")) {
-    const sanitizeMoonshot = (obj: unknown): unknown => {
-      if (obj === null || typeof obj !== "object") return obj
-      if (Array.isArray(obj)) return obj.map(sanitizeMoonshot)
-      // Moonshot expands $ref before validation and rejects sibling keywords like description on the same node.
-      if ("$ref" in obj && typeof obj.$ref === "string") return { $ref: obj.$ref }
-      const result = Object.fromEntries(Object.entries(obj).map(([key, value]) => [key, sanitizeMoonshot(value)]))
-      // MFJS does not support tuple-style `items` arrays; it requires one schema object for all array items.
-      if (Array.isArray(result.items)) result.items = result.items[0] ?? {}
-      return result
-    }
-
-    const sanitized = sanitizeMoonshot(schema)
-    if (typeof sanitized === "object" && sanitized !== null && !Array.isArray(sanitized)) {
-      schema = sanitized
-    }
+  if (
+    model.providerID === "moonshotai" ||
+    model.family?.toLowerCase().startsWith("kimi") ||
+    model.api.id.toLowerCase().includes("kimi")
+  ) {
+    schema = MFJS.sanitize(schema)
   }
 
   // Convert integer enums to string enums for Google/Gemini
diff --git a/packages/opencode/test/provider/mfjs.test.ts b/packages/opencode/test/provider/mfjs.test.ts
new file mode 100644
index 000000000000..f6cd04fc71a1
--- /dev/null
+++ b/packages/opencode/test/provider/mfjs.test.ts
@@ -0,0 +1,354 @@
+import { describe, expect, test } from "bun:test"
+import { MFJS } from "@/provider/mfjs"
+
+function expectProjection(input: unknown, expected: unknown) {
+  expect(JSON.stringify(MFJS.sanitize(input))).toBe(JSON.stringify(expected))
+}
+
+function asObject(value: unknown) {
+  if (typeof value === "object" && value !== null && !Array.isArray(value)) return value as Record<string, unknown>
+  throw new Error("expected object")
+}
+
+describe("MFJS.sanitize", () => {
+  test("removes reference siblings and normalizes draft-07 definitions", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          value: { $ref: "#/definitions/Value", description: "drop me" },
+        },
+        definitions: {
+          Value: { type: "object", description: "keep me" },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: { $ref: "#/$defs/Value" } },
+      $defs: { Value: { type: "object", description: "keep me" } },
+    })
+  })
+
+  test("preserves nullable reference semantics", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { value: { $ref: "#/$defs/Value", nullable: true } },
+        $defs: { Value: { type: "object" } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: { anyOf: [{ $ref: "#/$defs/Value" }, { type: "null" }] } },
+      $defs: { Value: { type: "object" } },
+    })
+  })
+
+  test("keeps explicit types and removes incompatible enum values", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { operation: { type: "object", enum: ["move", "copy"] } },
+        required: ["operation"],
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { operation: { type: "object" } },
+      required: ["operation"],
+    })
+  })
+
+  test("removes only enum values excluded by an explicit type", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { operation: { type: "string", enum: ["move", null] } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { operation: { type: "string", enum: ["move"] } },
+    })
+  })
+
+  test("infers a type for homogeneous untyped enums", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { operation: { enum: ["move", "copy"] } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { operation: { type: "string", enum: ["move", "copy"] } },
+    })
+  })
+
+  test("splits mixed untyped enums into homogeneous branches", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { value: { enum: ["move", 1] } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: {
+        value: {
+          anyOf: [
+            { type: "string", enum: ["move"] },
+            { type: "integer", enum: [1] },
+          ],
+        },
+      },
+    })
+  })
+
+  test("widens enums when structured values remain possible", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          untyped: { enum: ["text", { kind: "legacy" }] },
+          excluded: { type: "string", enum: ["text", { kind: "legacy" }] },
+          union: {
+            type: ["string", "object"],
+            enum: ["text", { kind: "legacy" }],
+            anyOf: [{ type: "string" }, { type: "object" }],
+          },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: {
+        untyped: {},
+        excluded: { type: "string", enum: ["text"] },
+        union: { anyOf: [{ type: "string" }, { type: "object" }] },
+      },
+    })
+  })
+
+  test("drops tuple items instead of narrowing positional schemas", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          values: {
+            type: "array",
+            items: [{ type: "string" }, { type: "number" }],
+            minItems: 2,
+          },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { values: { type: "array", minItems: 2 } },
+    })
+  })
+
+  test("preserves prefixItems accepted by Kimi", () => {
+    expectProjection(
+      {
+        type: "object",
+        properties: {
+          values: { type: "array", prefixItems: [{ type: "string" }, { type: "number" }] },
+        },
+      },
+      {
+        type: "object",
+        properties: {
+          values: { type: "array", prefixItems: [{ type: "string" }, { type: "number" }] },
+        },
+      },
+    )
+  })
+
+  test("moves parent types into compatible anyOf branches", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          value: {
+            type: "string",
+            enum: ["move"],
+            anyOf: [{ type: "string" }, { type: "null" }],
+          },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: { type: "string", enum: ["move"] } },
+    })
+  })
+
+  test("preserves type arrays and nullable accepted by Kimi", () => {
+    expectProjection(
+      {
+        type: "object",
+        properties: {
+          typed: { type: ["string", "null"], enum: ["move", null] },
+          nullable: { type: "string", nullable: true },
+        },
+      },
+      {
+        type: "object",
+        properties: {
+          typed: { type: ["string", "null"], enum: ["move", null] },
+          nullable: { type: "string", nullable: true },
+        },
+      },
+    )
+  })
+
+  test("preserves oneOf, allOf, and other keywords accepted by Kimi", () => {
+    const value = {
+      oneOf: [
+        { type: "string", format: "uri" },
+        { type: "integer", multipleOf: 2 },
+      ],
+      examples: ["https://example.com"],
+    }
+    const all = {
+      allOf: [
+        { type: "object", properties: { left: { type: "string" } } },
+        { type: "object", properties: { right: { type: "number" } } },
+      ],
+    }
+    expectProjection(
+      { type: "object", properties: { value, all }, unevaluatedProperties: false },
+      { type: "object", properties: { value, all }, unevaluatedProperties: false },
+    )
+  })
+
+  test("preserves const accepted by Kimi", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { operation: { const: "move" } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { operation: { const: "move" } },
+    })
+  })
+
+  test("drops unresolved references", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { value: { $ref: "#/definitions/Missing" } },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: {} },
+    })
+  })
+
+  test("drops recursive schemas with no finite instance", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { node: { $ref: "#/$defs/Node" } },
+        required: ["node"],
+        $defs: {
+          Node: {
+            type: "object",
+            properties: {
+              value: { type: "string" },
+              next: { $ref: "#/$defs/Node" },
+            },
+            required: ["value", "next"],
+          },
+        },
+      }),
+    ).toEqual({ type: "object", properties: {} })
+  })
+
+  test("adds unconstrained schemas for dangling required properties", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {},
+        required: ["missing"],
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { missing: {} },
+      required: ["missing"],
+    })
+  })
+
+  test("preserves unconstrained schemas", () => {
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { empty: {}, truthy: true, falsy: false },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { empty: {}, truthy: {}, falsy: {} },
+    })
+  })
+
+  test("widens schemas that exceed Kimi limits", () => {
+    const properties = Object.fromEntries(
+      Array.from({ length: 3001 }, (_, index) => [`property_${index}`, { type: "string" }]),
+    )
+    const limited = asObject(MFJS.sanitize({ type: "object", properties }))
+    expect(Object.keys(asObject(limited.properties))).toHaveLength(3000)
+
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          value: { type: "string", enum: Array.from({ length: 1001 }, (_, index) => `value_${index}`) },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: { type: "string" } },
+    })
+
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: {
+          value: { anyOf: Array.from({ length: 501 }, (_, index) => ({ const: `value_${index}` })) },
+        },
+      }),
+    ).toEqual({
+      type: "object",
+      properties: { value: {} },
+    })
+
+    const deep = Array.from({ length: 35 }).reduce<Record<string, unknown>>(
+      (schema) => ({ type: "object", properties: { next: schema }, required: ["next"] }),
+      { type: "string" },
+    )
+    expect(JSON.stringify(MFJS.sanitize(deep)).match(/properties/g)?.length).toBe(30)
+
+    expect(MFJS.sanitize({ type: "object", description: "<".repeat(20_000), properties: {} })).toEqual({
+      type: "object",
+      properties: {},
+    })
+
+    const definition = Array.from({ length: 30 }).reduce<Record<string, unknown>>(
+      (schema) => ({ type: "object", properties: { next: schema } }),
+      { type: "string" },
+    )
+    expect(
+      MFJS.sanitize({
+        type: "object",
+        properties: { value: { $ref: "#/$defs/Value" } },
+        $defs: { Value: definition },
+      }),
+    ).toEqual({ type: "object", properties: {} })
+  })
+
+  test("is idempotent", () => {
+    const once = MFJS.sanitize({
+      type: "object",
+      properties: {
+        operation: { type: "object", enum: ["move"] },
+        values: { type: "array", items: [{ type: "string" }, { type: "number" }] },
+      },
+    })
+    expect(MFJS.sanitize(once)).toEqual(once)
+  })
+})
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index c5cea6b797fd..7d25098241dc 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -1528,148 +1528,30 @@ describe("ProviderTransform.schema - openai supported schema subset", () => {
   })
 })
 
-describe("ProviderTransform.schema - moonshot $ref siblings", () => {
-  const moonshotModel = {
-    providerID: "moonshotai",
-    api: {
-      id: "kimi-k2",
-    },
-  } as any
-
-  test("removes sibling descriptions from referenced tool parameter schemas", () => {
-    const schema = {
-      type: "object",
-      properties: {
-        deviceType: {
-          description: "Optional. The type of device that captured the screenshot, e.g. mobile or desktop.",
-          enum: ["DEVICE_TYPE_UNSPECIFIED", "MOBILE", "DESKTOP", "TABLET", "AGNOSTIC"],
-          type: "string",
-        },
-        modelId: {
-          description: "Optional. The model to use for generation.",
-          enum: ["MODEL_ID_UNSPECIFIED", "GEMINI_3_PRO", "GEMINI_3_FLASH", "GEMINI_3_1_PRO"],
-          type: "string",
-        },
-        projectId: {
-          description: "Required. The project ID of screens to generate variants for.",
-          type: "string",
-        },
-        prompt: {
-          description: "Required. The input text used to generate the variants.",
-          type: "string",
-        },
-        selectedScreenIds: {
-          description: "Required. The screen ids of screen to generate variants for.",
-          items: {
-            type: "string",
-          },
-          type: "array",
-        },
-        variantOptions: {
-          $ref: "#/$defs/VariantOptions",
-          description:
-            "Required. The variant options for generation, including the number of variants, creative range, and aspects to focus on.",
-        },
-      },
-      required: ["projectId", "selectedScreenIds", "prompt", "variantOptions"],
-      $defs: {
-        VariantOptions: {
-          description:
-            "Configuration options for design variant generation. This message captures all parameters used to generate variants, allowing the configuration to be stored, replayed, or analyzed.",
+describe("ProviderTransform.schema - MFJS selection", () => {
+  const models = [
+    ["Moonshot providers", { providerID: "moonshotai", api: { id: "kimi-k2" } }],
+    ["Kimi API IDs", { providerID: "openrouter", api: { id: "moonshotai/kimi-k2" } }],
+    ["Kimi model families", { providerID: "custom", family: "kimi-k2", api: { id: "alias" } }],
+  ] as const
+
+  for (const [name, model] of models) {
+    test(`sanitizes ${name}`, () => {
+      expect(
+        ProviderTransform.schema(model as Parameters<typeof ProviderTransform.schema>[0], {
+          type: "object",
           properties: {
-            aspects: {
-              description: "Optional. Specific aspects to focus on. If empty, all aspects may be varied.",
-              items: {
-                enum: ["VARIANT_ASPECT_UNSPECIFIED", "LAYOUT", "COLOR_SCHEME", "IMAGES", "TEXT_FONT", "TEXT_CONTENT"],
-                type: "string",
-              },
-              type: "array",
-            },
-            creativeRange: {
-              description: "Optional. Creative range for variations. Default: EXPLORE",
-              enum: ["CREATIVE_RANGE_UNSPECIFIED", "REFINE", "EXPLORE", "REIMAGINE"],
-              type: "string",
-            },
-            variantCount: {
-              description: "Optional. Number of variants to generate (1-5). Default: 3",
-              format: "int32",
-              type: "integer",
-            },
+            operation: { type: "object", enum: ["move", "copy"] },
           },
-          type: "object",
-        },
-      },
-      description: "Request message for GenerateVariants.",
-      additionalProperties: false,
-    } as any
-
-    const result = ProviderTransform.schema(moonshotModel, schema) as any
-
-    expect(result.properties.variantOptions).toEqual({
-      $ref: "#/$defs/VariantOptions",
-    })
-    expect(result.$defs.VariantOptions.description).toBe(schema.$defs.VariantOptions.description)
-  })
-
-  test("also runs for kimi models outside the moonshot provider", () => {
-    const result = ProviderTransform.schema(
-      {
-        providerID: "openrouter",
-        name: "Kimi K2",
-        api: {
-          id: "moonshotai/kimi-k2",
-        },
-      } as any,
-      {
+        }),
+      ).toEqual({
         type: "object",
         properties: {
-          value: {
-            $ref: "#/$defs/Value",
-            description: "Moonshot rejects this sibling after ref expansion.",
-          },
-        },
-        $defs: {
-          Value: {
-            description: "Referenced schema description stays here.",
-            type: "object",
-          },
-        },
-      } as any,
-    ) as any
-
-    expect(result.properties.value).toEqual({
-      $ref: "#/$defs/Value",
-    })
-  })
-
-  test("converts tuple-style array items to a single item schema", () => {
-    const result = ProviderTransform.schema(moonshotModel, {
-      type: "object",
-      properties: {
-        codeSpec: {
-          type: "object",
-          properties: {
-            accessibility: {
-              type: "object",
-              properties: {
-                renderedSize: {
-                  description: "Rendered size [width, height] in px",
-                  type: "array",
-                  items: [{ type: "number" }, { type: "number" }],
-                  minItems: 2,
-                  maxItems: 2,
-                },
-              },
-            },
-          },
+          operation: { type: "object" },
         },
-      },
-    } as any) as any
-
-    expect(result.properties.codeSpec.properties.accessibility.properties.renderedSize.items).toEqual({
-      type: "number",
+      })
     })
-  })
+  }
 })
 
 describe("ProviderTransform.message - DeepSeek reasoning content", () => {