bio-alignment-validation

A bioinformatics guide for checking the quality of sequencing alignments after reads have been mapped to a reference genome. It covers measures such as mapping rate, paired-read agreement, insert size, GC bias, and strand balance.

In plain words
What is it for?
Checking file integrity and calculating post-alignment quality metrics with samtools, Picard, or Python.
Why use it?
It helps reveal damaged or biased alignment data before variant calling or measuring gene quantities.

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/gptomics/bioskills/alignment-validation
Any agent
npx skills add GPTomics/bioSkills --skill alignment-validation
Clone the repo
git clone --depth 1 https://github.com/GPTomics/bioSkills

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 4,213 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00043 $0.04213
Opus 5 $0.00022 $0.02107
Sonnet 5 $0.00009 $0.00843
Haiku 4.5 $0.00004 $0.00421

Measured yesterday against content hash 748b149783ea, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

bio-alignment-validation 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 yesterday.

The scan reads SKILL.md. This mod also ships 2 executable files (examples/validate_alignment.py, examples/validate_alignment.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

alignment-files/alignment-validation/SKILL.md · 398 lines

How it starts

The opening of the file, as written. The whole thing — 398 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Version Compatibility

Reference examples tested with: matplotlib 3.8+, numpy 1.26+, picard 3.1+, pysam 0.22+, samtools 1.19+

Before using code patterns, verify installed versions match. If versions differ:

  • Python: pip show <package> then help(module.function) to check signatures
  • CLI: <tool> --version then <tool> --help to confirm flags

If code throws ImportError, AttributeError, or TypeError, introspect the installed package and adapt the example to match the actual API rather than retrying.

Alignment Validation

Post-alignment quality control to verify alignment quality and identify issues.

"Check alignment quality" -> Compute post-alignment QC metrics (mapping rate, pairing, insert size, strand balance) to identify issues before downstream analysis.

  • CLI: samtools flagstat, samtools stats, Picard CollectAlignmentSummaryMetrics
  • Python: pysam.AlignmentFile iteration with metric calculations

Two Different Validations

Concern Tools What it catches
File integrity samtools quickcheck, picard ValidateSamFile Truncation, missing EOF, malformed records, wrong CIGAR, MAPQ out of range
Sequence dictionary identity samtools dict + M5 diff BAM aligned to wrong reference flavor / different decoy / chr vs no-chr
QC metrics samtools stats, flagstat, mosdepth, Picard CollectMultipleMetrics / CollectHsMetrics / CollectWgsMetrics Are the data biologically reasonable for the assay?
Contamination / sample swap verifybamid2, somalier, Picard CrosscheckFingerprints Cross-sample contamination, tumor-normal swap, mislabeled sample

A file can pass quickcheck and still be malformed in ways that crash GATK three hours into HaplotypeCaller. Conversely, a QC-poor BAM can be structurally valid.

File Integrity

# Fast: header + EOF block check (misses mid-file truncation, invalid CIGAR)
samtools quickcheck -v in.bam || echo "QUICKCHECK FAILED"
samtools quickcheck -v *.bam > bad_bams.fofn   # one fail-line per bad file

# Slow but thorough: structural validation
picard ValidateSamFile I=in.bam MODE=SUMMARY R=ref.fa

# Production: ignore expected-but-noisy
picard ValidateSamFile I=in.bam MODE=SUMMARY R=ref.fa \
    IGNORE=INVALID_MAPPING_QUALITY \
    IGNORE=MISMATCH_FLAG_MATE_NEG_STRAND

Read the full file on GitHub · 398 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. yesterday First seen · 398 lines · 43 tokens per session scan A 748b149783ea

Subscribe to this mod's changes

bio-alignment-validation is a skill published in the GitHub repository GPTomics/bioSkills (1,198 stars, last pushed 16d ago), licensed MIT. It adds 43 tokens to every session and 4,213 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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