fix(xcode-ide): add bridge proxy diagnostics and default schema handling

Add debug logging to xcode-tools-bridge proxy tool calls so the exact
arguments and responses can be inspected when diagnosing bridge-related
issues like XcodeGlob returning paths rejected by XcodeRead/RenderPreview.

Handle the JSON Schema `default` keyword in jsonSchemaToZod so remote
tool schema defaults are preserved through the proxy, preventing
potential argument loss.

Add integration test verifying argument passthrough integrity through
the full proxy pipeline (paths with spaces, unicode, extra properties).

Closes #252

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dpearson2699

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## [Unreleased]
+
+### Added
+
+- Added debug logging for xcode-tools-bridge proxy tool calls to aid diagnosis of bridge-related issues ([#252](https://github.com/getsentry/XcodeBuildMCP/issues/252)).
+
+### Fixed
+
+- Fixed `jsonSchemaToZod` converter to apply `default` values from remote tool JSON schemas, preventing potential argument loss when proxying bridge tools ([#252](https://github.com/getsentry/XcodeBuildMCP/issues/252)).
+
 ## [2.3.2]
 
 ### Fixed

src/integrations/xcode-tools-bridge/__tests__/fixtures/fake-xcode-tools-server.mjs

@@ -60,6 +60,23 @@ function registerInitialTools() {
       return { content: [{ type: 'text', text: 'changed' }], isError: false };
     },
   );
+
+  server.registerTool(
+    'Echo',
+    {
+      description: 'Echoes back received arguments as JSON',
+      inputSchema: z
+        .object({
+          filePath: z.string(),
+          tabIdentifier: z.string().optional(),
+        })
+        .passthrough(),
+    },
+    async (args) => ({
+      content: [{ type: 'text', text: JSON.stringify(args) }],
+      isError: false,
+    }),
+  );
 }
 
 function applyCatalogChange() {

src/integrations/xcode-tools-bridge/__tests__/jsonschema-to-zod.test.ts

@@ -69,4 +69,40 @@ describe('jsonSchemaToZod', () => {
     const parsed = zod.parse({ a: 'x', extra: 1 }) as Record<string, unknown>;
     expect(parsed.extra).toBe(1);
   });
+
+  it('applies default values from JSON Schema', () => {
+    const schema = {
+      type: 'object',
+      properties: {
+        name: { type: 'string' },
+        format: { type: 'string', default: 'project-relative' },
+      },
+      required: ['name'],
+    };
+
+    const zod = jsonSchemaToZod(schema);
+
+    // Default is applied when property is absent
+    const withDefault = zod.parse({ name: 'test' }) as Record<string, unknown>;
+    expect(withDefault.format).toBe('project-relative');
+
+    // Explicit value overrides the default
+    const withExplicit = zod.parse({ name: 'test', format: 'absolute' }) as Record<string, unknown>;
+    expect(withExplicit.format).toBe('absolute');
+  });
+
+  it('applies default values on primitive types', () => {
+    const stringSchema = { type: 'string', default: 'hello' };
+    expect(jsonSchemaToZod(stringSchema).parse(undefined)).toBe('hello');
+    expect(jsonSchemaToZod(stringSchema).parse('world')).toBe('world');
+
+    const numberSchema = { type: 'number', default: 42 };
+    expect(jsonSchemaToZod(numberSchema).parse(undefined)).toBe(42);
+
+    const boolSchema = { type: 'boolean', default: true };
+    expect(jsonSchemaToZod(boolSchema).parse(undefined)).toBe(true);
+
+    const intSchema = { type: 'integer', default: 7 };
+    expect(jsonSchemaToZod(intSchema).parse(undefined)).toBe(7);
+  });
 });

src/integrations/xcode-tools-bridge/__tests__/registry.integration.test.ts

@@ -132,4 +132,50 @@ describe('XcodeToolsProxyRegistry (stdio integration)', () => {
     })) as CallToolResult;
     expect(res.content[0]).toMatchObject({ type: 'text', text: 'Alpha2:hi:e' });
   });
+
+  it('passes arguments through the proxy without modification', async () => {
+    const tools = await localClient.listTools();
+    expect(tools.tools.map((t) => t.name)).toContain('xcode_tools_Echo');
+
+    const testCases = [
+      {
+        name: 'file paths with slashes and spaces',
+        args: {
+          filePath: '/Users/test/My Project/Sources/Views/MainTabView.swift',
+          tabIdentifier: 'windowtab1',
+        },
+      },
+      {
+        name: 'unicode characters in paths',
+        args: {
+          filePath: '/Users/test/Projekt/Ansichten/\u00dcbersicht.swift',
+          tabIdentifier: 'tab-2',
+        },
+      },
+      {
+        name: 'extra properties not in schema (passthrough)',
+        args: {
+          filePath: 'Sources/App.swift',
+          tabIdentifier: 'wt1',
+          extraFlag: true,
+          nested: { deep: 'value' },
+        },
+      },
+    ];
+
+    for (const tc of testCases) {
+      const res = (await localClient.callTool({
+        name: 'xcode_tools_Echo',
+        arguments: tc.args,
+      })) as CallToolResult;
+      expect(res.isError).not.toBe(true);
+      const echoed = JSON.parse((res.content[0] as { text: string }).text) as Record<
+        string,
+        unknown
+      >;
+      for (const [key, value] of Object.entries(tc.args)) {
+        expect(echoed[key]).toEqual(value);
+      }
+    }
+  });
 });

src/integrations/xcode-tools-bridge/jsonschema-to-zod.ts

@@ -5,6 +5,7 @@ type JsonSchemaEnumValue = string | number | boolean | null;
 type JsonSchema = {
   type?: string | string[];
   description?: string;
+  default?: unknown;
   enum?: unknown[];
   items?: JsonSchema;
   properties?: Record<string, JsonSchema>;
@@ -16,6 +17,11 @@ function applyDescription<T extends z.ZodTypeAny>(schema: T, description?: strin
   return schema.describe(description) as T;
 }
 
+function applyDefault(schema: z.ZodTypeAny, defaultValue: unknown): z.ZodTypeAny {
+  if (defaultValue === undefined) return schema;
+  return schema.default(defaultValue);
+}
+
 function isObjectSchema(schema: JsonSchema): boolean {
   const types =
     schema.type === undefined ? [] : Array.isArray(schema.type) ? schema.type : [schema.type];
@@ -74,21 +80,21 @@ export function jsonSchemaToZod(schema: JsonSchema | unknown): z.ZodTypeAny {
 
   switch (primaryType) {
     case 'string':
-      return applyDescription(z.string(), s.description);
+      return applyDefault(applyDescription(z.string(), s.description), s.default);
     case 'integer':
-      return applyDescription(z.number().int(), s.description);
+      return applyDefault(applyDescription(z.number().int(), s.description), s.default);
     case 'number':
-      return applyDescription(z.number(), s.description);
+      return applyDefault(applyDescription(z.number(), s.description), s.default);
     case 'boolean':
-      return applyDescription(z.boolean(), s.description);
+      return applyDefault(applyDescription(z.boolean(), s.description), s.default);
     case 'array': {
       const itemSchema = jsonSchemaToZod(s.items ?? {});
-      return applyDescription(z.array(itemSchema), s.description);
+      return applyDefault(applyDescription(z.array(itemSchema), s.description), s.default);
     }
     case 'object':
     default: {
       if (!isObjectSchema(s)) {
-        return applyDescription(z.any(), s.description);
+        return applyDefault(applyDescription(z.any(), s.description), s.default);
       }
       const required = new Set(s.required ?? []);
       const props = s.properties ?? {};
@@ -98,7 +104,10 @@ export function jsonSchemaToZod(schema: JsonSchema | unknown): z.ZodTypeAny {
         shape[key] = required.has(key) ? propSchema : propSchema.optional();
       }
       // Use passthrough to avoid breaking when Apple adds new fields.
-      return applyDescription(z.object(shape).passthrough(), s.description);
+      return applyDefault(
+        applyDescription(z.object(shape).passthrough(), s.description),
+        s.default,
+      );
     }
   }
 }

src/integrations/xcode-tools-bridge/registry.ts

@@ -1,6 +1,7 @@
 import type { McpServer, RegisteredTool } from '@modelcontextprotocol/sdk/server/mcp.js';
 import type { CallToolResult, Tool, ToolAnnotations } from '@modelcontextprotocol/sdk/types.js';
 import * as z from 'zod';
+import { log } from '../../utils/logger.ts';
 import { jsonSchemaToZod } from './jsonschema-to-zod.ts';
 
 export type CallRemoteTool = (
@@ -114,7 +115,16 @@ export class XcodeToolsProxyRegistry {
       },
       async (args: unknown) => {
         const params = (args ?? {}) as Record<string, unknown>;
-        return callRemoteTool(tool.name, params);
+        log(
+          'debug',
+          `[xcode-tools-bridge] Proxy call: ${tool.name} args=${JSON.stringify(params)}`,
+        );
+        const result = await callRemoteTool(tool.name, params);
+        log(
+          'debug',
+          `[xcode-tools-bridge] Proxy result: ${tool.name} contentItems=${result.content.length} isError=${result.isError ?? false}`,
+        );
+        return result;
       },
     );
   }

src/integrations/xcode-tools-bridge/tool-service.ts

@@ -1,4 +1,5 @@
 import type { CallToolResult, Tool } from '@modelcontextprotocol/sdk/types.js';
+import { log } from '../../utils/logger.ts';
 import {
   XcodeToolsBridgeClient,
   type XcodeToolsBridgeClientOptions,
@@ -95,12 +96,18 @@ export class XcodeIdeToolService {
     opts: { timeoutMs?: number } = {},
   ): Promise<CallToolResult> {
     await this.ensureConnected();
+    log('debug', `[xcode-tools-bridge] invokeTool: ${name} args=${JSON.stringify(args)}`);
     try {
       const response = await this.client.callTool(name, args, opts);
       this.lastError = null;
+      log(
+        'debug',
+        `[xcode-tools-bridge] invokeTool result: ${name} contentItems=${response.content.length} isError=${response.isError ?? false}`,
+      );
       return response;
     } catch (error) {
       this.lastError = toErrorMessage(error);
+      log('debug', `[xcode-tools-bridge] invokeTool error: ${name} error=${this.lastError}`);
       throw error;
     }
   }