fix: normalize Vercel stream tool arguments by schema

internal/js/chat-stream/vercel_stream_impl.js

@@ -205,14 +205,14 @@ async function handleVercelStream(req, res, rawBody, payload) {
       if (detected.length > 0 && !toolCallsDoneEmitted) {
         toolCallsEmitted = true;
         toolCallsDoneEmitted = true;
-        sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(detected, streamToolCallIDs) });
+        sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(detected, streamToolCallIDs, payload.tools) });
       } else if (toolSieveEnabled) {
         const tailEvents = flushToolSieve(toolSieveState, toolNames);
         for (const evt of tailEvents) {
           if (evt.type === 'tool_calls' && Array.isArray(evt.calls) && evt.calls.length > 0) {
             toolCallsEmitted = true;
             toolCallsDoneEmitted = true;
-            sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(evt.calls, streamToolCallIDs) });
+            sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(evt.calls, streamToolCallIDs, payload.tools) });
             resetStreamToolCallState(streamToolCallIDs, streamToolNames);
             continue;
           }
@@ -352,14 +352,14 @@ async function handleVercelStream(req, res, rawBody, payload) {
                       const formatted = formatIncrementalToolCallDeltas(filtered, streamToolCallIDs);
                       if (formatted.length > 0) {
                         toolCallsEmitted = true;
-                        sendDeltaFrame({ tool_calls: formatted });
+                      sendDeltaFrame({ tool_calls: formatted });
                       }
                       continue;
                     }
                     if (evt.type === 'tool_calls') {
                       toolCallsEmitted = true;
                       toolCallsDoneEmitted = true;
-                      sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(evt.calls, streamToolCallIDs) });
+                      sendDeltaFrame({ tool_calls: formatOpenAIStreamToolCalls(evt.calls, streamToolCallIDs, payload.tools) });
                       resetStreamToolCallState(streamToolCallIDs, streamToolNames);
                       continue;
                     }

internal/js/helpers/stream-tool-sieve/format.js

@@ -2,11 +2,12 @@
 
 const crypto = require('crypto');
 
-function formatOpenAIStreamToolCalls(calls, idStore) {
+function formatOpenAIStreamToolCalls(calls, idStore, toolsRaw) {
   if (!Array.isArray(calls) || calls.length === 0) {
     return [];
   }
-  return calls.map((c, idx) => ({
+  const normalized = normalizeParsedToolCallsForSchemas(calls, toolsRaw);
+  return normalized.map((c, idx) => ({
     index: idx,
     id: ensureStreamToolCallID(idStore, idx),
     type: 'function',
@@ -17,6 +18,194 @@ function formatOpenAIStreamToolCalls(calls, idStore) {
   }));
 }
 
+function normalizeParsedToolCallsForSchemas(calls, toolsRaw) {
+  if (!Array.isArray(calls) || calls.length === 0) {
+    return calls;
+  }
+  const schemas = buildToolSchemaIndex(toolsRaw);
+  if (!schemas) {
+    return calls;
+  }
+  let changedAny = false;
+  const out = calls.map((call) => {
+    const name = String(call && call.name || '').trim().toLowerCase();
+    const schema = schemas[name];
+    if (!schema || !call || !call.input || typeof call.input !== 'object' || Array.isArray(call.input)) {
+      return call;
+    }
+    const [normalized, changed] = normalizeToolValueWithSchema(call.input, schema);
+    if (!changed || !normalized || typeof normalized !== 'object' || Array.isArray(normalized)) {
+      return call;
+    }
+    changedAny = true;
+    return { ...call, input: normalized };
+  });
+  return changedAny ? out : calls;
+}
+
+function buildToolSchemaIndex(toolsRaw) {
+  if (!Array.isArray(toolsRaw) || toolsRaw.length === 0) {
+    return null;
+  }
+  const out = {};
+  for (const item of toolsRaw) {
+    if (!item || typeof item !== 'object' || Array.isArray(item)) {
+      continue;
+    }
+    const [name, schema] = extractToolNameAndSchema(item);
+    if (!name || !schema || typeof schema !== 'object' || Array.isArray(schema)) {
+      continue;
+    }
+    out[name.toLowerCase()] = schema;
+  }
+  return Object.keys(out).length > 0 ? out : null;
+}
+
+function extractToolNameAndSchema(tool) {
+  const fn = tool && typeof tool.function === 'object' && !Array.isArray(tool.function) ? tool.function : null;
+  const name = firstNonEmptyString(tool.name, fn && fn.name);
+  const schema = firstNonNil(
+    tool.parameters,
+    tool.input_schema,
+    tool.inputSchema,
+    tool.schema,
+    fn && fn.parameters,
+    fn && fn.input_schema,
+    fn && fn.inputSchema,
+    fn && fn.schema,
+  );
+  return [name, schema];
+}
+
+function normalizeToolValueWithSchema(value, schema) {
+  if (value == null || !schema || typeof schema !== 'object' || Array.isArray(schema)) {
+    return [value, false];
+  }
+  if (shouldCoerceSchemaToString(schema)) {
+    return stringifySchemaValue(value);
+  }
+  if (looksLikeObjectSchema(schema)) {
+    if (!value || typeof value !== 'object' || Array.isArray(value)) {
+      return [value, false];
+    }
+    const properties = schema.properties && typeof schema.properties === 'object' && !Array.isArray(schema.properties) ? schema.properties : null;
+    const additional = schema.additionalProperties;
+    let changed = false;
+    const out = {};
+    for (const [key, current] of Object.entries(value)) {
+      let next = current;
+      let fieldChanged = false;
+      if (properties && Object.prototype.hasOwnProperty.call(properties, key)) {
+        [next, fieldChanged] = normalizeToolValueWithSchema(current, properties[key]);
+      } else if (additional != null) {
+        [next, fieldChanged] = normalizeToolValueWithSchema(current, additional);
+      }
+      out[key] = next;
+      changed = changed || fieldChanged;
+    }
+    return changed ? [out, true] : [value, false];
+  }
+  if (looksLikeArraySchema(schema)) {
+    if (!Array.isArray(value) || value.length === 0 || schema.items == null) {
+      return [value, false];
+    }
+    let changed = false;
+    const out = value.map((item, idx) => {
+      const itemSchema = Array.isArray(schema.items) ? schema.items[idx] : schema.items;
+      if (itemSchema == null) {
+        return item;
+      }
+      const [next, itemChanged] = normalizeToolValueWithSchema(item, itemSchema);
+      changed = changed || itemChanged;
+      return next;
+    });
+    return changed ? [out, true] : [value, false];
+  }
+  return [value, false];
+}
+
+function shouldCoerceSchemaToString(schema) {
+  if (!schema || typeof schema !== 'object' || Array.isArray(schema)) {
+    return false;
+  }
+  if (typeof schema.const === 'string') {
+    return true;
+  }
+  if (Array.isArray(schema.enum) && schema.enum.length > 0 && schema.enum.every((item) => typeof item === 'string')) {
+    return true;
+  }
+  if (typeof schema.type === 'string') {
+    return schema.type.trim().toLowerCase() === 'string';
+  }
+  if (Array.isArray(schema.type) && schema.type.length > 0) {
+    let hasString = false;
+    for (const item of schema.type) {
+      if (typeof item !== 'string') {
+        return false;
+      }
+      const typ = item.trim().toLowerCase();
+      if (typ === 'string') {
+        hasString = true;
+      } else if (typ !== 'null') {
+        return false;
+      }
+    }
+    return hasString;
+  }
+  return false;
+}
+
+function looksLikeObjectSchema(schema) {
+  return !!schema && typeof schema === 'object' && !Array.isArray(schema) && (
+    (typeof schema.type === 'string' && schema.type.trim().toLowerCase() === 'object') ||
+    (schema.properties && typeof schema.properties === 'object' && !Array.isArray(schema.properties)) ||
+    schema.additionalProperties != null
+  );
+}
+
+function looksLikeArraySchema(schema) {
+  return !!schema && typeof schema === 'object' && !Array.isArray(schema) && (
+    (typeof schema.type === 'string' && schema.type.trim().toLowerCase() === 'array') ||
+    schema.items != null
+  );
+}
+
+function stringifySchemaValue(value) {
+  if (value == null) {
+    return [value, false];
+  }
+  if (typeof value === 'string') {
+    return [value, false];
+  }
+  try {
+    return [JSON.stringify(value), true];
+  } catch {
+    return [value, false];
+  }
+}
+
+function firstNonNil(...values) {
+  for (const value of values) {
+    if (value != null) {
+      return value;
+    }
+  }
+  return null;
+}
+
+function firstNonEmptyString(...values) {
+  for (const value of values) {
+    if (typeof value !== 'string') {
+      continue;
+    }
+    const trimmed = value.trim();
+    if (trimmed) {
+      return trimmed;
+    }
+  }
+  return '';
+}
+
 function ensureStreamToolCallID(idStore, index) {
   if (!(idStore instanceof Map)) {
     return `call_${newCallID()}`;

tests/node/stream-tool-sieve.test.js

@@ -188,6 +188,30 @@ test('parseToolCalls treats single-item CDATA body as array', () => {
   assert.deepEqual(calls[0].input.todos, ['one']);
 });
 
+test('formatOpenAIStreamToolCalls normalizes camelCase inputSchema string fields', () => {
+  const formatted = formatOpenAIStreamToolCalls([
+    { name: 'Write', input: { content: { message: 'hi' }, taskId: 1 } },
+  ], new Map(), [
+    { name: 'Write', inputSchema: { type: 'object', properties: { content: { type: 'string' }, taskId: { type: 'string' } } } },
+  ]);
+  assert.equal(formatted.length, 1);
+  const args = JSON.parse(formatted[0].function.arguments);
+  assert.equal(args.content, '{"message":"hi"}');
+  assert.equal(args.taskId, '1');
+});
+
+test('formatOpenAIStreamToolCalls preserves arrays when schema says array', () => {
+  const todos = [{ content: 'x', status: 'pending', priority: 'high' }];
+  const formatted = formatOpenAIStreamToolCalls([
+    { name: 'todowrite', input: { todos } },
+  ], new Map(), [
+    { name: 'todowrite', inputSchema: { type: 'object', properties: { todos: { type: 'array', items: { type: 'object' } } } } },
+  ]);
+  assert.equal(formatted.length, 1);
+  const args = JSON.parse(formatted[0].function.arguments);
+  assert.deepEqual(args.todos, todos);
+});
+
 test('parseToolCalls treats CDATA object fragment as object', () => {
   const fragment = '<question><![CDATA[Pick one]]></question><options><item><label><![CDATA[A]]></label></item><item><label><![CDATA[B]]></label></item></options>';
   const payload = `<tool_calls><invoke name="AskUserQuestion"><parameter name="questions"><![CDATA[${fragment}]]></parameter></invoke></tool_calls>`;