Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/davidmatousek/tachinpx agentmods add rules/davidmatousek/tachi/data-poisoningWrote 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.
[](https://agentmods.dev/rules/davidmatousek/tachi/data-poisoning)<a href="https://agentmods.dev/rules/davidmatousek/tachi/data-poisoning"><img src="https://agentmods.dev/badge/rules/davidmatousek/tachi/data-poisoning.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00041 | $0.02029 |
| Opus 5 | $0.00020 | $0.01014 |
| Sonnet 5 | $0.00008 | $0.00406 |
| Haiku 4.5 | $0.00004 | $0.00203 |
Grade A, and why
data-poisoning 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 3d 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.
How it starts
The opening of the file, as written. The whole thing — 168 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Metadata
category: llm
threat_class: LLM
dfd_targets: [Data Store, Data Flow]
owasp_references: [OWASP LLM04:2026, OWASP LLM05:2026, OWASP LLM09:2026]
output_schema: ../../../schemas/finding.yaml
Data Poisoning Threat Agent
Purpose
Detects threats where an attacker manipulates the data that an LLM relies on for training, fine-tuning, or runtime context retrieval. Data poisoning undermines the integrity of model outputs at the source: corrupted training data produces systematically biased or unsafe model behavior, poisoned RAG knowledge bases cause the model to return attacker-controlled content as authoritative answers, and contaminated fine-tuning datasets embed persistent backdoors that activate on specific trigger inputs. This agent identifies training data manipulation, RAG index poisoning, knowledge base corruption, and fine-tuning supply chain attacks.
Detection Scope
Trigger Keywords
This agent activates when a DFD element name or description matches any of the following patterns (case-insensitive):
LLMmodelGPTClaudetrainingfine-tuningfine tuningRAGretrievalknowledge basevector storeembeddingcorpus
Applicable DFD Element Types
- Data Store: Databases, vector stores, document repositories, embedding indexes, training data lakes, fine-tuning datasets, and knowledge bases that feed content into LLM pipelines.
- Data Flow: Data pipelines that transport training data, retrieval results, embeddings, or context documents between storage and model inference processes.
Detection Patterns
- Training Data Manipulation: Unauthorized modification of training or fine-tuning datasets to embed biased, incorrect, or backdoored content. Look for:
- Training datasets sourced from public or user-contributed repositories without integrity verification
- Absence of data provenance tracking (who contributed what, when, from where)
- No checksum or hash validation on training data files between collection and use
- Fine-tuning pipelines that pull data from mutable shared storage without snapshot isolation
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.
- 3d ago First seen · 168 lines · 41 tokens per session scan A d9a2f4877f1e
data-poisoning is a cursor rule published in the GitHub repository davidmatousek/tachi (90 stars, last pushed 25d ago), licensed Apache-2.0. It adds 41 tokens to every session and 2,029 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 2026-09-03.
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