segysak

segysak is a skill for Claude Code, Codex from SteadfastAsArt/geoscience-skills. It costs 53 tokens per session (686 once invoked), scanned A, original, MIT.

A Python tool for reading SEG-Y seismic files as labelled xarray datasets. SEG-Y is a common file format for seismic traces; xarray adds named dimensions such as inline, crossline and time, while Dask can delay processing of large data.

In plain words
What is it for?
Use it to inspect SEG-Y headers, load seismic volumes with named axes, preserve survey geometry, and process large datasets lazily before exporting or analysing them.
Why use it?
It reduces the risk of assigning the wrong survey dimensions, units or coordinate meaning from ambiguous trace headers. It also helps inspect incomplete or irregular surveys without treating them as a valid rectangular cube.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to inspect SEG-Y headers, load seismic volumes with named axes, preserve survey geometry, and process large datasets lazily before exporting or analysing them.

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Install with agentmods
npx agentmods add skills/steadfastasart/geoscience-skills/segysak
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 SteadfastAsArt/geoscience-skills --skill segysak
Clone the repo
git clone --depth 1 https://github.com/SteadfastAsArt/geoscience-skills

Made for: Claude Code, Codex.

Its marketplace also offers this one on its own, as the plugin segysak — /plugin install segysak after adding the marketplace above.

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 segysak

README.md
[![agentmods](https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/segysak/github.svg)](https://agentmods.dev/skills/steadfastasart/geoscience-skills/segysak)
Your own site
<a href="https://agentmods.dev/skills/steadfastasart/geoscience-skills/segysak"><img src="https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/segysak/github.svg" alt="Measured on agentmods" height="20"></a>

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.

agentmods 80×15 button for segysak

Your own site · 80×15
<a href="https://agentmods.dev/skills/steadfastasart/geoscience-skills/segysak"><img src="https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/segysak.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 686 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 $0.00053 $0.00686
Opus 5.5 $0.00021 $0.00274
Sonnet 5.5 $0.00011 $0.00137
Haiku 4.5 $0.00005 $0.00069

Measured 1mo ago against content hash 4f9b1006469b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

segysak 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 1mo 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.

segysak/SKILL.md · 70 lines

How it starts

The opening of the file, as written. The whole thing — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SEGY-SAK

Map trace headers to labelled dimensions without losing the original survey geometry. Header byte assignments are evidence to inspect, not safe guesses.

Before opening

Inspect format/endian, trace count, sample count/interval, delay recording time, inline/crossline or CDP headers, coordinate units and scalar. SEG-Y sample intervals are stored in microseconds; the backend's vertical samples use milliseconds for ordinary time sections. A depth section needs an explicit depth convention. Confirm actual data units before labelling an axis.

Check dimension key uniqueness and missing traces. Sparse or irregular geometry may not form a complete rectangular cube. Keep the original trace index for exports. A dimension byte offset is one-based SEG-Y numbering (CDP ensemble is 21, inline is 189, crossline is 193); some upstream old examples use a wrong CDP offset. Use the actual file's header convention.

Labelled read

This fragment needs an existing, verified rectangular post-stack file. It uses the 0.5 backend API; old segy_loader tutorials describe a different interface.

# example: labelled-segy
import xarray as xr
import segysak  # registers accessors; the installed distribution provides the backend

with xr.open_dataset(
    seismic_path,
    engine="sgy_engine",
    dim_byte_fields={"iline": 189, "xline": 193},
) as seismic:
    inline_labels = seismic.iline.values.copy()
    crossline_labels = seismic.xline.values.copy()
    sample_coordinate = seismic.samples.values.copy()
    amplitudes = seismic["data"].load().copy(deep=True)

For large surveys, open with Dask chunks chosen for the access pattern and retain lazy operations until the selected result fits memory. Avoid .load() on a whole production cube. Inspect coordinate variables before .sel() and use .isel() only for integer positions.

Validation and exports

Compare several labelled traces against original trace samples using segyio, including the last sample and nonzero start time. Verify shape, orientation, missing-trace behavior and coordinate scalars. Round-trip any export and compare headers as well as amplitudes; xarray labels alone do not preserve every SEG-Y header or prove geographic CRS. Keep source hash, byte mapping and transforms.

Read the full file on GitHub · 70 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. 1mo ago First seen · 70 lines · 53 tokens per session scan A 4f9b1006469b

Subscribe to this mod's changes

segysak is a skill published in the GitHub repository SteadfastAsArt/geoscience-skills (70 stars, last pushed 1mo ago), licensed MIT. It adds 53 tokens to every session and 686 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-16.

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