fix: undo strict null widening for tool inputs

.changeset/calm-tools-return.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/openai-base': patch
+---
+
+Undo strict-mode null widening before validating and executing OpenAI-compatible tool calls.

packages/openai-base/src/adapters/chat-completions-text.ts

@@ -7,6 +7,7 @@ import {
 import { generateId } from '@tanstack/ai-utils'
 import { extractRequestOptions } from '../utils/request-options'
 import { makeStructuredOutputCompatible } from '../utils/schema-converter'
+import { createToolInputNormalizer } from '../utils/tool-input-normalizer'
 import { buildChatCompletionsUsage } from '../usage'
 import { convertToolsToChatCompletionsFormat } from './chat-completions-tool-converter'
 import type OpenAI from 'openai'
@@ -620,6 +621,7 @@ export abstract class OpenAIBaseChatCompletionsTextAdapter<
       hasEmittedRunStarted: boolean
     },
   ): AsyncIterable<StreamChunk> {
+    const normalizeToolInput = createToolInputNormalizer(options.tools)
     let accumulatedContent = ''
     let hasEmittedTextMessageStart = false
     let lastModel: string | undefined
@@ -888,8 +890,10 @@ export abstract class OpenAIBaseChatCompletionsTextAdapter<
               if (toolCall.arguments) {
                 try {
                   const parsed: unknown = JSON.parse(toolCall.arguments)
-                  parsedInput =
-                    parsed && typeof parsed === 'object' ? parsed : {}
+                  parsedInput = normalizeToolInput(
+                    toolCall.name,
+                    parsed && typeof parsed === 'object' ? parsed : {},
+                  )
                 } catch (parseError) {
                   options.logger.errors(
                     `${this.name}.processStreamChunks tool-args JSON parse failed`,
@@ -960,7 +964,10 @@ export abstract class OpenAIBaseChatCompletionsTextAdapter<
           if (toolCall.arguments) {
             try {
               const parsed: unknown = JSON.parse(toolCall.arguments)
-              parsedInput = parsed && typeof parsed === 'object' ? parsed : {}
+              parsedInput = normalizeToolInput(
+                toolCall.name,
+                parsed && typeof parsed === 'object' ? parsed : {},
+              )
             } catch (parseError) {
               // Mirror the finish_reason path's logger call — a truncated
               // stream emitting malformed tool-call JSON would otherwise

packages/openai-base/src/adapters/chat-completions-tool-converter.test.ts

@@ -0,0 +1,64 @@
+import { describe, expect, it } from 'vitest'
+import { convertFunctionToolToChatCompletionsFormat } from './chat-completions-tool-converter'
+import type { Tool } from '@tanstack/ai'
+
+describe('chat-completions tool converter', () => {
+  it('falls back from strict mode when an anyOf variant needs null widening', () => {
+    const out = convertFunctionToolToChatCompletionsFormat(
+      anyOfOptionalVariantTool,
+    )
+
+    expect(out.function.strict).toBe(false)
+  })
+
+  it('falls back from strict mode for boolean schema nodes', () => {
+    const out = convertFunctionToolToChatCompletionsFormat(booleanSchemaTool)
+
+    expect(out.function.strict).toBe(false)
+    expect(out.function.parameters).toEqual(booleanSchemaTool.inputSchema)
+  })
+})
+
+const booleanSchemaInput = {
+  type: 'object',
+  properties: {},
+  required: [],
+}
+Reflect.set(booleanSchemaInput.properties, 'acceptAnything', true)
+
+const booleanSchemaTool = {
+  name: 'accept_anything',
+  description: 'Accept any value',
+  inputSchema: booleanSchemaInput,
+} satisfies Tool
+
+const anyOfOptionalVariantTool: Tool = {
+  name: 'store_variant',
+  description: 'Store a union variant',
+  inputSchema: {
+    type: 'object',
+    properties: {
+      value: {
+        anyOf: [
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'optional' },
+              note: { type: 'string' },
+            },
+            required: ['kind'],
+          },
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'nullable' },
+              note: { type: ['string', 'null'] },
+            },
+            required: ['kind', 'note'],
+          },
+        ],
+      },
+    },
+    required: ['value'],
+  },
+}

packages/openai-base/src/adapters/responses-text.ts

@@ -7,6 +7,7 @@ import {
 import { generateId } from '@tanstack/ai-utils'
 import { extractRequestOptions } from '../utils/request-options'
 import { makeStructuredOutputCompatible } from '../utils/schema-converter'
+import { createToolInputNormalizer } from '../utils/tool-input-normalizer'
 import { buildResponsesUsage } from '../usage'
 import { convertToolsToResponsesFormat } from './responses-tool-converter'
 import type OpenAI from 'openai'
@@ -777,6 +778,7 @@ export abstract class OpenAIBaseResponsesTextAdapter<
       hasEmittedRunStarted: boolean
     },
   ): AsyncIterable<StreamChunk> {
+    const normalizeToolInput = createToolInputNormalizer(options.tools)
     let accumulatedContent = ''
     let accumulatedReasoning = ''
 
@@ -1287,7 +1289,10 @@ export abstract class OpenAIBaseResponsesTextAdapter<
           if (chunk.arguments) {
             try {
               const parsed = JSON.parse(chunk.arguments)
-              parsedInput = parsed && typeof parsed === 'object' ? parsed : {}
+              parsedInput = normalizeToolInput(
+                name,
+                parsed && typeof parsed === 'object' ? parsed : {},
+              )
             } catch (parseError) {
               options.logger.errors(
                 `${this.name}.processStreamChunks tool-args JSON parse failed`,
@@ -1361,8 +1366,10 @@ export abstract class OpenAIBaseResponsesTextAdapter<
               if (rawArgs) {
                 try {
                   const parsed = JSON.parse(rawArgs)
-                  parsedInput =
-                    parsed && typeof parsed === 'object' ? parsed : {}
+                  parsedInput = normalizeToolInput(
+                    name,
+                    parsed && typeof parsed === 'object' ? parsed : {},
+                  )
                 } catch (parseError) {
                   options.logger.errors(
                     `${this.name}.processStreamChunks tool-args JSON parse failed (output_item.done backfill)`,
@@ -1438,8 +1445,10 @@ export abstract class OpenAIBaseResponsesTextAdapter<
               if (rawArgs) {
                 try {
                   const parsed = JSON.parse(rawArgs)
-                  parsedInput =
-                    parsed && typeof parsed === 'object' ? parsed : {}
+                  parsedInput = normalizeToolInput(
+                    name,
+                    parsed && typeof parsed === 'object' ? parsed : {},
+                  )
                 } catch (parseError) {
                   options.logger.errors(
                     `${this.name}.processStreamChunks tool-args JSON parse failed (response.completed backfill)`,

packages/openai-base/src/adapters/responses-tool-converter.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it } from 'vitest'
+import { convertFunctionToolToResponsesFormat } from './responses-tool-converter'
+import type { Tool } from '@tanstack/ai'
+
+describe('responses tool converter', () => {
+  it('falls back from strict mode when an anyOf variant needs null widening', () => {
+    const out = convertFunctionToolToResponsesFormat(anyOfOptionalVariantTool)
+
+    expect(out.strict).toBe(false)
+    expect(out.parameters).toMatchObject({
+      properties: {
+        value: {
+          anyOf: [
+            { required: ['kind'] },
+            { required: ['kind', 'note'] },
+          ],
+        },
+      },
+    })
+  })
+
+  it('falls back from strict mode for boolean schema nodes', () => {
+    const out = convertFunctionToolToResponsesFormat(booleanSchemaTool)
+
+    expect(out.strict).toBe(false)
+    expect(out.parameters).toEqual(booleanSchemaTool.inputSchema)
+  })
+})
+
+const booleanSchemaInput = {
+  type: 'object',
+  properties: {},
+  required: [],
+}
+Reflect.set(booleanSchemaInput.properties, 'acceptAnything', true)
+
+const booleanSchemaTool = {
+  name: 'accept_anything',
+  description: 'Accept any value',
+  inputSchema: booleanSchemaInput,
+} satisfies Tool
+
+const anyOfOptionalVariantTool: Tool = {
+  name: 'store_variant',
+  description: 'Store a union variant',
+  inputSchema: {
+    type: 'object',
+    properties: {
+      value: {
+        anyOf: [
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'optional' },
+              note: { type: 'string' },
+            },
+            required: ['kind'],
+          },
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'nullable' },
+              note: { type: ['string', 'null'] },
+            },
+            required: ['kind', 'note'],
+          },
+        ],
+      },
+    },
+    required: ['value'],
+  },
+}

packages/openai-base/src/tools/function-tool.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from 'vitest'
+import { convertFunctionToolToAdapterFormat } from './function-tool'
+import type { Tool } from '@tanstack/ai'
+
+describe('function-tool adapter converter', () => {
+  it('falls back from strict mode when an anyOf variant needs null widening', () => {
+    const out = convertFunctionToolToAdapterFormat(anyOfOptionalVariantTool)
+
+    expect(out.strict).toBe(false)
+  })
+
+  it('falls back from strict mode for boolean schema nodes', () => {
+    const out = convertFunctionToolToAdapterFormat(booleanSchemaTool)
+
+    expect(out.strict).toBe(false)
+    expect(out.parameters).toEqual(booleanSchemaTool.inputSchema)
+  })
+})
+
+const booleanSchemaInput = {
+  type: 'object',
+  properties: {},
+  required: [],
+}
+Reflect.set(booleanSchemaInput.properties, 'acceptAnything', true)
+
+const booleanSchemaTool = {
+  name: 'accept_anything',
+  description: 'Accept any value',
+  inputSchema: booleanSchemaInput,
+} satisfies Tool
+
+const anyOfOptionalVariantTool: Tool = {
+  name: 'store_variant',
+  description: 'Store a union variant',
+  inputSchema: {
+    type: 'object',
+    properties: {
+      value: {
+        anyOf: [
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'optional' },
+              note: { type: 'string' },
+            },
+            required: ['kind'],
+          },
+          {
+            type: 'object',
+            properties: {
+              kind: { const: 'nullable' },
+              note: { type: ['string', 'null'] },
+            },
+            required: ['kind', 'note'],
+          },
+        ],
+      },
+    },
+    required: ['value'],
+  },
+}