code-style

A set of C++ coding rules covering error handling, file organization, security, performance, memory, threads, and testing.

In plain words
What is it for?
Use it when writing or reviewing C++ services that use MongoDB, Redis, HTTP APIs, smart pointers, locks, prepared statements, or CMake.
Why use it?
It gives contributors consistent ways to handle failures, organize includes, validate input, access MongoDB, manage resources, and test APIs.

Cursor rule for Cursor

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 rules/hatefsystems/search-engine-core/code-style
Clone the repo
git clone --depth 1 https://github.com/hatefsystems/search-engine-core

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 357 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 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 $0.00000 $0.00357
Opus 5 $0.00000 $0.00179
Sonnet 5 $0.00000 $0.00071
Haiku 4.5 $0.00000 $0.00036

Measured yesterday against content hash ef26d0d34c3a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-style scanned grade A with 2 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.

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.

Sends data to an external URLlowData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

- API: `curl --location 'http://localhost:3000/api/endpoint' --header 'Content-Type: application/json' --data-raw '{ ... }'`

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- API: `curl --location 'http://localhost:3000/api/endpoint' --header 'Content-Type: application/json' --data-raw '{ ... }'`
.cursor/rules/code-style.mdc · 53 lines

What it actually says

Code Style and Practices

Error Handling

try {
    mongocxx::instance& instance = MongoDBInstance::getInstance();
    // ...
} catch (const mongocxx::exception& e) {
    LOG_ERROR("MongoDB error: " + std::string(e.what()));
    serverError(res, "Database error occurred");
}

Includes Order

// System headers first
#include <string>
#include <memory>
// Project headers
#include "../../include/Logger.h"
#include "../../include/mongodb.h"
// Third-party headers
#include <mongocxx/client.hpp>
#include <nlohmann/json.hpp>

Security

Validate input; use prepared statements; rate limit APIs; sanitize URLs; validate email/mobile formats.

Performance

Connection pooling (MongoDB); Redis caching; minimize DB round trips; indexes on hot fields.

Memory and Threads

Smart pointers; RAII; mutexes for shared state; lock_guard; minimize lock scope.

Testing

  • MongoDB: docker exec mongodb_test mongosh --username admin --password password123 --eval "db.adminCommand('ping')"
  • API: curl --location 'http://localhost:3000/api/endpoint' --header 'Content-Type: application/json' --data-raw '{ ... }'
  • Verify data: docker exec mongodb_test mongosh --username admin --password password123 --eval "use('search-engine'); db.collection.find().pretty()"
  • Logs: docker logs core --tail 50, docker logs mongodb_test
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 · 53 lines · 0 tokens per session scan A ef26d0d34c3a

Subscribe to this mod's changes

code-style is a cursor rule published in the GitHub repository hatefsystems/search-engine-core (5 stars, last pushed 28d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 357 tokens. A static security scan graded it A with 2 findings (sends data to an external url, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.