span-coding

A guide for examining Phoenix spans, which are records of steps or events in an AI application. It supports gradually grouping observations into categories and structured notes.

In plain words
What is it for?
Use it to inspect spans, recover analysis notes, identify categories, and turn stable categories into annotations.
Why use it?
It helps find recurring failure patterns before a formal classification system exists.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/arize-ai/phoenix/span-coding
Any agent
npx skills add Arize-ai/phoenix --skill span-coding
Clone the repo
git clone --depth 1 https://github.com/Arize-ai/phoenix

Made for: Claude Code, Codex.

Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 879 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00043 $0.00879
Opus 5 $0.00022 $0.00439
Sonnet 5 $0.00009 $0.00176
Haiku 4.5 $0.00004 $0.00088

Measured 2d ago against content hash e42d4210c614, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

span-coding 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 2d 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.

src/phoenix/server/agents/prompts/skills/span-coding/SKILL.md · 102 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 2d ago First seen · 102 lines · 43 tokens per session scan A e42d4210c614

Subscribe to this mod's changes

span-coding is a skill published in the GitHub repository Arize-ai/phoenix (11,275 stars, last pushed today), with no licence file. It adds 43 tokens to every session and 879 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 2026-08-30.

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