From 63e66ca3e6d96d9055fbd3f119bb6ece1bf29dad Mon Sep 17 00:00:00 2001
From: Kit Langton <kit.langton@gmail.com>
Date: Sun, 20 Sep 2026 18:47:56 -0700
Subject: [PATCH] fix: preserve schema compatibility on rc.115

---
 packages/ai/src/tool.ts               |  2 +-
 packages/codemode/src/tool-schema.ts  | 20 +++++++++++++-------
 packages/core/src/tool/runtime.ts     |  2 +-
 packages/httpapi-codegen/src/index.ts |  6 +++---
 4 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/packages/ai/src/tool.ts b/packages/ai/src/tool.ts
index c04b666887c..56c1f77ffec 100644
--- a/packages/ai/src/tool.ts
+++ b/packages/ai/src/tool.ts
@@ -231,7 +231,7 @@ export const toDefinitions = (tools: Tools): ReadonlyArray<ToolDefinitionClass>
   )
 
 const toJsonSchema = (schema: Schema.Top): JsonSchema.JsonSchema => {
-  const document = Schema.toJsonSchemaDocument(schema)
+  const document = Schema.toJsonSchemaDocument(schema, { onExcessProperty: "error" })
   if (Object.keys(document.definitions).length === 0) return document.schema
   return { ...document.schema, $defs: document.definitions }
 }
diff --git a/packages/codemode/src/tool-schema.ts b/packages/codemode/src/tool-schema.ts
index 80b3bc97ab0..b103ec2f033 100644
--- a/packages/codemode/src/tool-schema.ts
+++ b/packages/codemode/src/tool-schema.ts
@@ -1,4 +1,4 @@
-import { JsonPointer, Schema } from "effect"
+import { JsonPointer, Schema, SchemaAST } from "effect"
 import type { Tool, JsonSchema, SchemaType } from "./tool.js"
 
 const isEffectSchema = (schema: SchemaType): schema is Schema.Decoder<unknown> & Schema.Top => Schema.isSchema(schema)
@@ -203,7 +203,7 @@ const renderSchema = (
 export const toTypeScript = (schema: Schema.Top, decoded = false, pretty = false): string => {
   try {
     const visible = decoded ? Schema.toType(schema) : schema
-    const document = Schema.toJsonSchemaDocument(visible) as {
+    const document = Schema.toJsonSchemaDocument(visible, { onExcessProperty: "error" }) as {
       readonly schema: JsonSchema
       readonly definitions?: Readonly<Record<string, JsonSchema>>
     }
@@ -230,7 +230,7 @@ export type InputProperty = {
 export const inputProperties = <R>(tool: Tool<R>): Array<InputProperty> => {
   try {
     const document = isEffectSchema(tool.input)
-      ? (Schema.toJsonSchemaDocument(tool.input) as {
+      ? (Schema.toJsonSchemaDocument(tool.input, { onExcessProperty: "error" }) as {
           readonly schema: JsonSchema
           readonly definitions?: Readonly<Record<string, JsonSchema>>
         })
@@ -261,10 +261,16 @@ export const inputProperties = <R>(tool: Tool<R>): Array<InputProperty> => {
 export const inputTypeScript = <R>(tool: Tool<R>, pretty = false): string =>
   isEffectSchema(tool.input) ? toTypeScript(tool.input, false, pretty) : jsonSchemaToTypeScript(tool.input, pretty)
 
-// Empty object schemas render as `{}` in compact form; anything with properties,
-// an index signature, or union members renders differently, so equality is a
-// conservative emptiness test for both Effect and JSON Schema inputs.
-export const isEmptyInput = <R>(tool: Tool<R>): boolean => inputTypeScript(tool) === "{}"
+// Effect 4.0 models an empty Struct as a non-nullish object, so inspect its AST.
+// Raw JSON Schema inputs retain the compact `{}` rendering check.
+export const isEmptyInput = <R>(tool: Tool<R>): boolean => {
+  if (!isEffectSchema(tool.input)) return inputTypeScript(tool) === "{}"
+  return (
+    SchemaAST.isObjects(tool.input.ast) &&
+    tool.input.ast.propertySignatures.length === 0 &&
+    tool.input.ast.indexSignatures.length === 0
+  )
+}
 
 export const outputTypeScript = <R>(tool: Tool<R>, pretty = false): string =>
   tool.output === undefined
diff --git a/packages/core/src/tool/runtime.ts b/packages/core/src/tool/runtime.ts
index f21c67a533e..e6eb5abe412 100644
--- a/packages/core/src/tool/runtime.ts
+++ b/packages/core/src/tool/runtime.ts
@@ -170,7 +170,7 @@ const standardJsonSchema = (schema: StandardSchemaV1<any, any>, io: "input" | "o
 }
 
 const toJsonSchema = (schema: Schema.Top): JsonSchema.JsonSchema => {
-  const document = Schema.toJsonSchemaDocument(schema)
+  const document = Schema.toJsonSchemaDocument(schema, { onExcessProperty: "error" })
   // Effect emits valid JSON Schema that some inference providers handle poorly. Simplify it
   // without changing validation: `{ type: "integer", allOf: [{ minimum: 0 }] }` becomes
   // `{ type: "integer", minimum: 0 }` only when no keyword would be overwritten. Named schemas
diff --git a/packages/httpapi-codegen/src/index.ts b/packages/httpapi-codegen/src/index.ts
index ae7cd071291..b90cabad80b 100644
--- a/packages/httpapi-codegen/src/index.ts
+++ b/packages/httpapi-codegen/src/index.ts
@@ -1638,9 +1638,9 @@ function checksPortable(checks: SchemaAST.Checks | undefined): boolean {
       ? !check.aborted &&
         check.annotations?.representation !== undefined &&
         serializable(check.annotations.representation) &&
-        typeof check.annotations.arbitrary === "object" &&
-        check.annotations.arbitrary !== null &&
-        "constraint" in check.annotations.arbitrary
+        typeof check.annotations.arbitraryConstraint === "object" &&
+        check.annotations.arbitraryConstraint !== null &&
+        serializable(check.annotations.arbitraryConstraint)
       : checksPortable(check.checks),
   )
 }