The recursive implementation of findArrayTypePaths can be inefficient due to the use of append(slice, anotherSlice...) within the recursion. Each call creates a new slice, leading to multiple allocations. A more performant and arguably clearer approach is to use a closure to append to a single paths slice, avoiding the overhead of repeated slice allocations.

// findArrayTypePaths recursively finds all paths where type="array".
func findArrayTypePaths(node gjson.Result, path string) []string {
	var paths []string
	var find func(gjson.Result, string)

	find = func(n gjson.Result, p string) {
		if n.IsObject() {
			if isArrayType(n) {
				paths = append(paths, p)
			}
			n.ForEach(func(key, value gjson.Result) bool {
				childPath := key.String()
				if p != "" {
					childPath = p + "." + childPath
				}
				find(value, childPath)
				return true
			})
		} else if n.IsArray() {
			for i, elem := range n.Array() {
				childPath := strconv.Itoa(i)
				if p != "" {
					childPath = p + "." + childPath
				}
				find(elem, childPath)
			}
		}
	}

	find(node, path)
	return paths
}

fix: add missing 'items' to array schemas in Codex tool parameters #1275

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huynguyen03dev wants to merge 1 commit into router-for-me:main from huynguyen03dev:fix/codex-array-schema-missing-items

internal/runtime/executor/codex_executor.go

-Original file line number
+Diff line change
@@ Expand Up @@
     	requestedModel := payloadRequestedModel(opts, req.Model)
     	body = applyPayloadConfigWithRoot(e.cfg, baseModel, to.String(), "", body, originalTranslated, requestedModel)
+    	body = util.FixCodexToolSchemas(body)
     	body, _ = sjson.SetBytes(body, "model", baseModel)
     	body, _ = sjson.SetBytes(body, "stream", true)
     	body, _ = sjson.DeleteBytes(body, "previous_response_id")
@@ Expand Down Expand Up @@
     	requestedModel := payloadRequestedModel(opts, req.Model)
     	body = applyPayloadConfigWithRoot(e.cfg, baseModel, to.String(), "", body, originalTranslated, requestedModel)
+    	body = util.FixCodexToolSchemas(body)
     	body, _ = sjson.DeleteBytes(body, "previous_response_id")
     	body, _ = sjson.DeleteBytes(body, "prompt_cache_retention")
     	body, _ = sjson.DeleteBytes(body, "safety_identifier")
@@ Expand Down @@

internal/util/codex_schema.go

-Original file line number
+Diff line change
@@ -0,0 +1,104 @@
+    // Package util provides utility functions for the CLI Proxy API server.
+    package util
+    import (
+    	"strconv"
+    	"github.com/tidwall/gjson"
+    	"github.com/tidwall/sjson"
+    )
+    // FixCodexToolSchemas fixes tool schemas in a Codex API request body.
+    // It adds missing "items" to array-type schemas which OpenAI's strict validation requires.
+    func FixCodexToolSchemas(body []byte) []byte {
+    	tools := gjson.GetBytes(body, "tools")
+    	if !tools.IsArray() {
+    		return body
+    	}
+    	for i, tool := range tools.Array() {
+    		if tool.Get("type").String() != "function" {
+    			continue
+    		}
+    		var params gjson.Result
+    		var setPath string
+    		// Support both Chat Completions (function.parameters) and Responses API (parameters)
+    		if tool.Get("function.parameters").Exists() {
+    			params = tool.Get("function.parameters")
+    			setPath = "tools." + strconv.Itoa(i) + ".function.parameters"
+    		} else if tool.Get("parameters").Exists() {
+    			params = tool.Get("parameters")
+    			setPath = "tools." + strconv.Itoa(i) + ".parameters"
+    		} else {
+    			continue
+    		}
+    		fixed := addMissingArrayItems(params.Raw)
+    		if fixed != params.Raw {
+    			body, _ = sjson.SetRawBytes(body, setPath, []byte(fixed))
+    		}
+    	}
+    	return body
+    }
+    // addMissingArrayItems adds a default "items" schema to arrays that are missing it.
+    func addMissingArrayItems(jsonStr string) string {
+    	paths := findArrayTypePaths(gjson.Parse(jsonStr), "")
+    	for _, p := range paths {
+    		itemsPath := p + ".items"
+    		if p == "" {
+    			itemsPath = "items"
+    		}
+    		items := gjson.Get(jsonStr, itemsPath)
+    		// Add items if missing or null
+    		if !items.Exists() || items.Type == gjson.Null {
+    			jsonStr, _ = sjson.SetRaw(jsonStr, itemsPath, `{}`)
+    		}
+    	}
+    	return jsonStr
+    }
+    // isArrayType checks if a node's type indicates an array (string or array containing "array").
+    func isArrayType(node gjson.Result) bool {
+    	typeVal := node.Get("type")
+    	if typeVal.IsArray() {
+    		for _, t := range typeVal.Array() {
+    			if t.String() == "array" {
+    				return true
+    			}
+    		}
+    		return false
+    	}
+    	return typeVal.String() == "array"
+    }
+    // findArrayTypePaths recursively finds all paths where type="array".
+    func findArrayTypePaths(node gjson.Result, path string) []string {
+    	var paths []string
+    	if node.IsObject() {
+    		if isArrayType(node) {
+    			paths = append(paths, path)
+    		}
+    		node.ForEach(func(key, value gjson.Result) bool {
+    			newPath := key.String()
+    			if path != "" {
+    				newPath = path + "." + key.String()
+    			}
+    			paths = append(paths, findArrayTypePaths(value, newPath)...)
+    			return true
+    		})
+    	} else if node.IsArray() {
+    		for i, elem := range node.Array() {
+    			newPath := strconv.Itoa(i)
+    			if path != "" {
+    				newPath = path + "." + strconv.Itoa(i)
+    			}
+    			paths = append(paths, findArrayTypePaths(elem, newPath)...)
+    		}
+    	}
+    	return paths
+    }

internal/util/codex_schema_test.go

-Original file line number
+Diff line change
@@ -0,0 +1,76 @@
+    package util
+    import (
+    	"testing"
+    	"github.com/tidwall/gjson"
+    )
+    func TestFixCodexToolSchemas_AddsMissingItems(t *testing.T) {
+    	input := `{"tools":[{"type":"function","parameters":{"type":"object","properties":{"options":{"type":"array"}}}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	items := gjson.GetBytes(result, "tools.0.parameters.properties.options.items")
+    	if !items.Exists() {
+    		t.Error("expected items to be added to array schema")
+    	}
+    }
+    func TestFixCodexToolSchemas_PreservesExistingItems(t *testing.T) {
+    	input := `{"tools":[{"type":"function","parameters":{"type":"object","properties":{"options":{"type":"array","items":{"type":"string"}}}}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	itemsType := gjson.GetBytes(result, "tools.0.parameters.properties.options.items.type").String()
+    	if itemsType != "string" {
+    		t.Errorf("expected existing items to be preserved, got type=%s", itemsType)
+    	}
+    }
+    func TestFixCodexToolSchemas_HandlesAnyOf(t *testing.T) {
+    	input := `{"tools":[{"type":"function","parameters":{"anyOf":[{"type":"array"}]}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	items := gjson.GetBytes(result, "tools.0.parameters.anyOf.0.items")
+    	if !items.Exists() {
+    		t.Error("expected items to be added to array schema inside anyOf")
+    	}
+    }
+    func TestFixCodexToolSchemas_NoTools(t *testing.T) {
+    	input := `{"model":"gpt-5"}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	if string(result) != input {
+    		t.Error("expected unchanged output when no tools present")
+    	}
+    }
+    func TestFixCodexToolSchemas_ChatCompletionsFormat(t *testing.T) {
+    	input := `{"tools":[{"type":"function","function":{"name":"test","parameters":{"type":"object","properties":{"items":{"type":"array"}}}}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	items := gjson.GetBytes(result, "tools.0.function.parameters.properties.items.items")
+    	if !items.Exists() {
+    		t.Error("expected items to be added to array schema in function.parameters")
+    	}
+    }
+    func TestFixCodexToolSchemas_NullableArrayType(t *testing.T) {
+    	input := `{"tools":[{"type":"function","parameters":{"type":"object","properties":{"data":{"type":["array","null"]}}}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	items := gjson.GetBytes(result, "tools.0.parameters.properties.data.items")
+    	if !items.Exists() {
+    		t.Error("expected items to be added to nullable array schema")
+    	}
+    }
+    func TestFixCodexToolSchemas_NullItems(t *testing.T) {
+    	input := `{"tools":[{"type":"function","parameters":{"type":"object","properties":{"list":{"type":"array","items":null}}}}]}`
+    	result := FixCodexToolSchemas([]byte(input))
+    	items := gjson.GetBytes(result, "tools.0.parameters.properties.list.items")
+    	if items.Type == gjson.Null {
+    		t.Error("expected null items to be replaced with empty object")
+    	}
+    }

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