Martin Algesten algesten

Xcode MCP and Apple skills for external coding agents

Current setup for agents such as Codex running outside Xcode. Locally verified on Xcode 27.1, build 27A9275, on October 27, 2026 using the installed CLI help, exported Codex plugin, and a live MCP connection. Changes documented for Xcode 27.2 RC are listed separately below.

mcpbridge connects a local stdio MCP client to Xcode's tools. mcp-server manages headless access, permissions, projects, and service lifecycle. Apple's skills supply instructions and reference documents; the MCP connection supplies executable tools.

1. Select the full Xcode installation

Xcode 27.1 and 27.2 RC require macOS Tahoe 26.6 or later. See Apple's system requirements.

macOS Hardened Runtime Required for CoreText Emoji Rendering

Problem

On Apple Silicon Macs (ARM64), binaries signed without hardened runtime crash with SIGBUS (EXC_BAD_ACCESS / EXC_ARM_DA_ALIGN) when CoreText attempts to render bitmap emoji glyphs (sbix table). The crash occurs inside Apple's ImageIO framework:

IIOReadPlugin::callInitialize()

macOS Data Protection Keychain: Helper Binary Inside .app Bundle

Date: 2026-02-21

Environment

Component	Version
macOS	15.6.1 (24G90)
Xcode	26.2 (17C52)

Probe Clusters in str0m

This document outlines a plan for implementing probe clusters in str0m, matching libWebRTC's bandwidth probing approach.

Scope

This plan covers probe clusters for existing media RTX/padding only. Pre-media SSRC 0 probing is out of scope and will be addressed in a separate PR that builds on this infrastructure.

Current State

Apple provides CTFontCopyDefaultCascadeListForLanguages to get a set of fallback font names for a certain ISO language code. I want to know how much these vary.

main.swift is a quick hack to dump a JSON of all codes with the fallbacks. The test assumes Menlo 12.0 as the starting point.

output.json is the full output from running the swift hack.

Finally I used nodejs to crunch the json to buckets that have different lists of fallbacks. code is in crunch.js

buckets.json has the result of running the crunch.

	//! # Proposed API Changes for str0m
	//!
	//! Type-state pattern enforcing correct API usage at compile time.
	//!
	//! ## Core Principles
	//!
	//! 1. Time is driven externally — caller provides `now: Instant`
	//! 2. Every mutation requires poll-to-timeout — type system enforces this
	//! 3. All state changes are mutations — media writes, DirectApi, SDP
	//!

	use tracing::{info_span, Span};

	pub struct Blah {
	pub span: Span,
	}

	impl Blah {
	pub fn new(name: &str) -> Self {
	Blah {
	span: info_span!(name),

	stokast v0.1.0 (/Users/martin/dev/stokast)
	├── alg v0.1.0 (/Users/martin/dev/alg)
	│ ├── gcd v2.0.1
	│ └── log v0.4.14
	│ └── cfg-if v1.0.0
	├── arrayvec v0.7.1
	├── cortex-m v0.6.7
	│ ├── aligned v0.3.5
	│ │ └── as-slice v0.1.5
	│ │ ├── generic-array v0.12.4

	use chrono::{DateTime, Utc};
	use hmac::{Hmac, Mac, NewMac};
	use once_cell::sync::Lazy;
	// notice this is percent_encoding=1.0.1 since I haven't bothered to
	// fix this for latter versions of the crate.
	use percent_encoding::{define_encode_set, utf8_percent_encode, SIMPLE_ENCODE_SET};
	use sha2::{Digest, Sha256};
	use std::env;
	use std::fmt::Write;


	# propagate titles to the window
	set -g set-titles on

	# Minimalist window title "0:bash"
	set -g set-titles-string "#I:#W"

	# show colors
	set -g default-terminal "screen-256color"