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/repudiationWrote 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/repudiation)<a href="https://agentmods.dev/rules/davidmatousek/tachi/repudiation"><img src="https://agentmods.dev/badge/rules/davidmatousek/tachi/repudiation.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 | $0.00036 | $0.01472 |
| Opus 5 | $0.00018 | $0.00736 |
| Sonnet 5 | $0.00007 | $0.00294 |
| Haiku 4.5 | $0.00004 | $0.00147 |
Grade A, and why
repudiation 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 — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Metadata
category: stride
threat_class: R
dfd_targets: [External Entity, Process]
owasp_references:
- "OWASP Top 10 2021 A09:2021 — Security Logging and Monitoring Failures"
- "OWASP API Security 2023 API9 — Improper Inventory Management"
- "CWE-778: Insufficient Logging"
- "CWE-223: Omission of Security-Relevant Information"
- "CWE-117: Improper Output Neutralization for Logs"
- "MITRE ATT&CK T1070: Indicator Removal"
output_schema: ../../../schemas/finding.yaml
Repudiation Threat Agent
Purpose
Detects threats where a user or system can deny having performed an action, and the system lacks sufficient evidence to prove otherwise. Repudiation failures undermine accountability, forensic investigation, and compliance obligations. This agent targets External Entities (where users can deny actions they performed) and Processes (where services fail to produce tamper-evident audit trails of their operations).
Detection Scope
Targeted DFD Element Types
- External Entity: End users, API consumers, third-party integrations, administrative users, automated clients
- Process: Application services, payment processors, authorization services, data export services, administrative interfaces
Patterns and Indicators
Missing Audit Trails
- Security-sensitive operations (login, logout, permission changes) not logged
- Financial transactions without immutable audit records
- Data deletion operations without pre-deletion snapshots or tombstone records
- Administrative actions (user creation, role assignment) missing from audit logs
- API calls that modify state without recording the authenticated caller identity
Insufficient Log Detail
- Logs missing actor identity (who performed the action)
- Logs missing timestamp with sufficient precision (sub-second for high-frequency systems)
- Logs missing source context (IP address, session ID, request correlation ID)
- Logs missing the before-and-after state for data modifications
- Generic log messages that cannot distinguish between different operation types
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 · 121 lines · 36 tokens per session scan A 12895bbb8931
repudiation is a cursor rule published in the GitHub repository davidmatousek/tachi (90 stars, last pushed 25d ago), licensed Apache-2.0. It adds 36 tokens to every session and 1,472 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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