ax-foundation-models-ref

ax-foundation-models-ref is a skill for Claude Code from Kasempiternal/axiom-v2. It costs 46 tokens per session (3,125 once invoked), scanned A, original, MIT.

A reference guide for Apple’s Foundation Models framework, which lets Swift apps use language models on the device. It covers conversations, structured results, tools, streaming, and built-in model uses.

In plain words
What is it for?
Use it when building Swift features that generate text or typed data, call tools, stream model responses, check model availability, or target specific built-in uses.
Why use it?
It keeps the framework’s API details and working code patterns in one place, so developers do not have to piece them together from scattered documentation.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the axiom plugin — 40 skills, 8 commands, 12 agents, 2 hooks shipped together

Good fit Use it when building Swift features that generate text or typed data, call tools, stream model responses, check model availability, or target specific built-in uses.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/kasempiternal/axiom-v2/ax-foundation-models-ref
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.

Any agent
npx skills add Kasempiternal/axiom-v2 --skill ax-foundation-models-ref
Clone the repo
git clone --depth 1 https://github.com/Kasempiternal/axiom-v2

Made for: Claude Code.

Or install axiom, the plugin that ships this one along with the rest of its 40 skills, 8 commands, 12 agents, 2 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.

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README.md
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Your own site
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

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Your own site · 80×15
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Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,125 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 $0.00046 $0.03125
Opus 5 $0.00023 $0.01563
Sonnet 5 $0.00009 $0.00625
Haiku 4.5 $0.00005 $0.00313

Measured 10d ago against content hash 9f1ca82ba0ee, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

ax-foundation-models-ref 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 10d 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.

axiom-plugin/skills/ax-foundation-models-ref/SKILL.md · 395 lines

How it starts

The opening of the file, as written. The whole thing — 395 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Foundation Models Framework — API Reference

Quick Patterns

LanguageModelSession

import FoundationModels

// Basic
let session = LanguageModelSession()

// With instructions
let session = LanguageModelSession(instructions: "You are a helpful assistant.")

// With tools
let session = LanguageModelSession(tools: [GetWeatherTool()], instructions: "Help with weather.")

// With use case adapter
let session = LanguageModelSession(model: SystemLanguageModel(useCase: .contentTagging))

respond Methods

// Plain text
let response = try await session.respond(to: "Write a haiku")
response.content // String

// Structured output
let response = try await session.respond(to: "Generate a person", generating: Person.self)
response.content // Person

// With options
let response = try await session.respond(to: prompt, options: GenerationOptions(sampling: .greedy))

// Streaming
let stream = session.streamResponse(to: prompt, generating: Itinerary.self)
for try await partial in stream { self.itinerary = partial }

SystemLanguageModel

SystemLanguageModel.default.availability      // .available | .unavailable(reason)
SystemLanguageModel.default.supportedLanguages // [Locale.Language]
SystemLanguageModel(useCase: .contentTagging)  // Built-in adapter

Decision Tree

Looking up Foundation Models API?
|
+-- Session creation/config?   -> LanguageModelSession section
+-- Structured output?         -> @Generable + @Guide section
+-- Streaming?                 -> Streaming section
+-- External data integration? -> Tool Protocol section
+-- Runtime-defined schema?    -> Dynamic Schemas section
+-- Sampling/temperature?      -> Generation Options section
+-- Content tagging?           -> Built-in Use Cases section
+-- Error handling?            -> Error Handling section
+-- Performance tuning?        -> Performance section
+-- Availability check?        -> Availability section

Anti-Patterns

Skipping availability check before session creation

Always check SystemLanguageModel.default.availability first. Session creation on unsupported device crashes.

Read the full file on GitHub · 395 lines

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. 10d ago First seen · 395 lines · 46 tokens per session scan A 9f1ca82ba0ee

Subscribe to this mod's changes

ax-foundation-models-ref is a skill published in the GitHub repository Kasempiternal/axiom-v2 (4 stars, last pushed 6mo ago), licensed MIT. It adds 46 tokens to every session and 3,125 once invoked, about $0.0002 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 2026-08-31.

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