Adds AsOf to the Development & Code Tools section, alphabetically between artifacts-builder and aws-skills.

What it is

A temporal-awareness skill for tool-using LLMs. It addresses a specific failure mode: the agent treats all in-context data as if captured "now," regardless of how stale it actually is.

AsOf surfaces three categories of staleness via Claude Code hooks:

1. In-context file staleness — files Read earlier whose mtime has moved since (peer edits, user edits in another tool)
2. Dated content in user paste — stock quotes, earnings, log entries with embedded timestamps
3. Pseudo-stable factual claims — "current Python version," "typical hotel cost," etc. — compared against the model's training cutoff

The hook does all date arithmetic in Python; the model reads pre-computed verdicts. No multi-step date math in chat means no boundary errors at end-of-month or leap years.

Why it fits the list

It's a real Claude skill (with SKILL.md and YAML frontmatter), tested across Claude tiers (Opus 4.7, Sonnet 4.6, Haiku 4.5), and addresses a documented LLM failure mode. A/B tests show categorical behavior change when the verdict block is present.

Install

pip install asoftime && asof install — patches ~/.claude/settings.json idempotently. MIT.