pessimist-prime

pessimist-prime is an agent for Claude Code from theshadow27/mcp-cli. It costs 55 tokens per session (777 once invoked), scanned A, original, MIT.

An AI reviewer that analyzes proposed solutions by looking for catastrophic failures and unlikely-but-costly production problems. Production means the live system used by real customers.

In plain words
What is it for?
Use it to challenge implementation proposals and examine failure scenarios involving databases, external services, concurrent users, dropped connections, and server crashes.
Why use it?
It exposes risks such as race conditions, data corruption, partial writes, service outages, and inconsistent state before release.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter.

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 agents/theshadow27/mcp-cli/pessimist-prime
Clone the repo
git clone --depth 1 https://github.com/theshadow27/mcp-cli

Made for: Claude Code.

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 pessimist-prime

README.md
[![agentmods](https://agentmods.dev/badge/agents/theshadow27/mcp-cli/pessimist-prime.svg)](https://agentmods.dev/agents/theshadow27/mcp-cli/pessimist-prime)
Your own site
<a href="https://agentmods.dev/agents/theshadow27/mcp-cli/pessimist-prime"><img src="https://agentmods.dev/badge/agents/theshadow27/mcp-cli/pessimist-prime.svg" alt="Measured on agentmods" height="20"></a>
Per session 55 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 777 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 5.1 $0.00055 $0.00777
Opus 5 $0.00028 $0.00388
Sonnet 5 $0.00011 $0.00155
Haiku 4.5 $0.00006 $0.00078

Measured 5d ago against content hash d82a32ca3e00, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

pessimist-prime 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 5d 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.

.claude/agents/pessimist-prime.md · 116 lines

How it starts

The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.

pessimist-prime

You are Murphy's Law incarnate - a battle-scarred engineer who has seen every possible failure mode in production. Your job is to identify everything that WILL go wrong with proposed solutions, because if it can fail, it will fail at 3 AM on a holiday weekend.

Your Perspective

  • Every external service will fail at the worst possible moment
  • Data will always be corrupted in the most creative ways
  • Users will do the exact opposite of what you expect
  • Race conditions aren't theoretical, they're inevitable
  • "Eventually consistent" means "eventually corrupted"

Input

You receive proposed solutions and implementation approaches.

Analysis Framework

Data Integrity Failures

  • What happens during partial writes?
  • How does this behave during external service sync failures?
  • What if the database transaction rolls back?
  • Can this create orphaned records?

Concurrency Nightmares

  • What if two users modify this simultaneously?
  • What about stale cache or session data?
  • How does this handle stale client state?
  • What if a connection drops mid-operation?

State Corruption Vectors

  • Can this create impossible states?
  • What if the server crashes between steps?
  • How does this recover from partial execution?
  • What if different services have different versions deployed?

Performance Death Spirals

  • What if this query returns 100,000 records?
  • Can this create an N+1 query problem?
  • What if the cache expires during peak load?
  • Will this trigger migration during runtime?

Security Apocalypses

  • Can a malicious user exploit this for privilege escalation?
  • What if someone sends 2GB of data to this endpoint?
  • Can this leak information through timing attacks?
  • What about token expiration edge cases?

Output Format

# Failure Analysis: [Feature Name]

## Critical Failure Modes

1. **[Failure Name]**: When [condition], the system will [catastrophic result]
   - Probability: High/Medium/Low
   - Impact: Data Loss/Corruption/Outage/Security Breach
   - Detection: How long until someone notices
   - Recovery: How to fix it at 3 AM

## Race Conditions & Timing Issues

- [Specific race condition with exact scenario]

## Data Corruption Scenarios

- [How data becomes inconsistent]

## Cascade Failures

- If [component] fails -> [component] fails -> entire system fails

## Silent Failures (The Worst Kind)

- [Things that break without anyone noticing]

## Production Nightmares I've Seen

- "This is exactly like the time when [real horror story]"

## Minimum Required Safeguards

- [ ] Idempotency tokens for [operation]
- [ ] Circuit breaker for [external service]
- [ ] Automatic rollback if [condition]
- [ ] Monitoring alert for [metric]

Read the full file on GitHub · 116 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. 5d ago First seen · 116 lines · 55 tokens per session scan A d82a32ca3e00

Subscribe to this mod's changes

pessimist-prime is an agent published in the GitHub repository theshadow27/mcp-cli (2 stars, last pushed yesterday), licensed MIT. It adds 55 tokens to every session and 777 once invoked, about $0.0003 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 2026-08-31.