fix-build

fix-build is a command for Claude Code from CharlesWiltgen/Axiom. It costs 19 tokens per session (156 once invoked), scanned A, original, MIT.

An agent that investigates and fixes Xcode build failures, including problems involving build processes, cached build data, and simulators.

In plain words
What is it for?
Use it when Xcode reports a failed build, a missing module, an unexplained `BUILD FAILED` result, or a simulator that will not start.
Why use it?
A failed build may have an environmental cause rather than a code error, and the important details can be hard to find. The agent checks common causes, applies fixes, and verifies the result.

Command for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter.

Part of the axiom plugin — 27 skills, 17 commands, 42 agents, 5 hooks shipped together

Good fit Use it when Xcode reports a failed build, a missing module, an unexplained BUILD FAILED result, or a simulator that will not start.

Compare 6 commands from other repositories ↓
Install with agentmods
npx agentmods add commands/charleswiltgen/axiom/fix-build
About the project

Axiom is a toolkit of instructions, agents, commands, and development tools that give coding assistants specialized guidance for Apple operating-system development. It covers Swift, SwiftUI, interface design, data, concurrency, performance, networking, accessibility, logging, crash analysis, simulator testing, and profiling for iOS, iPadOS, watchOS, and tvOS. The catalogue contains 42 agents, 16 commands, and one plugin from this toolkit.

CharlesWiltgen/Axiom · 1,148 stars · on GitHub · charleswiltgen.github.io

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/CharlesWiltgen/Axiom

Made for: Claude Code.

Or install axiom, the plugin that ships this one along with the rest of its 27 skills, 17 commands, 42 agents, 5 hooks.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for fix-build

README.md
[![agentmods](https://agentmods.dev/badge/commands/charleswiltgen/axiom/fix-build.svg)](https://agentmods.dev/commands/charleswiltgen/axiom/fix-build)
Your own site
<a href="https://agentmods.dev/commands/charleswiltgen/axiom/fix-build"><img src="https://agentmods.dev/badge/commands/charleswiltgen/axiom/fix-build.svg" alt="Measured on agentmods" height="20"></a>
Per session 19 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 156 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00019 $0.00156
Opus 5 $0.00010 $0.00078
Sonnet 5 $0.00004 $0.00031
Haiku 4.5 $0.00002 $0.00016

Measured 8d ago against content hash e9b81614a7be, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

fix-build scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude-plugin/plugins/axiom/commands/fix-build.md · 27 lines

What it actually says

Fix Build Issues

Launches the build-fixer agent to diagnose and fix Xcode build failures using environment-first diagnostics.

What It Does

The agent will:

  1. Check for zombie xcodebuild processes
  2. Verify Derived Data size
  3. Check simulator state
  4. Apply appropriate fixes automatically
  5. Verify the fixes worked

Prefer Natural Language?

You can also trigger this agent by saying:

  • "My build is failing"
  • "BUILD FAILED but no error details"
  • "Xcode says 'No such module'"
  • "Getting 'Unable to boot simulator' error"
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 27 lines · 19 tokens per session scan A e9b81614a7be

Subscribe to this mod's changes

fix-build is a command published in the GitHub repository CharlesWiltgen/Axiom (1,148 stars, last pushed 2d ago), licensed MIT. It adds 19 tokens to every session and 156 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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