bounded-collections

A coding rule for collections such as hash maps, ordered maps, and lists kept in memory for a whole session. Each collection must have a maximum size and a way to remove older or less useful entries.

In plain words
What is it for?
Use it when implementing session state, caches, pipeline data, or usage counters that receive entries over time.
Why use it?
An unbounded collection can keep growing during a long-running session, eventually using too much memory.

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/beardfaceguy/daimonos/bounded-collections
Clone the repo
git clone --depth 1 https://github.com/beardfaceguy/daimonos

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 316 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 $0.00000 $0.00316
Opus 5 $0.00000 $0.00158
Sonnet 5 $0.00000 $0.00063
Haiku 4.5 $0.00000 $0.00032

Measured yesterday against content hash 4677996b2a13, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

bounded-collections 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.

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.

.cursor/rules/bounded-collections.mdc · 42 lines

What it actually says

Bounded Collections in Long-Lived State

Every HashMap, BTreeMap, or Vec stored in a struct that lives for the duration of a session (e.g. Session, plugin caches, pipeline state) must have a maximum size with an eviction strategy.

What went wrong

Four separate caches (read_cache, exec_usage, decl_cache, pipeline_cache.entries) were implemented as plain HashMap::insert() with no size check. Over a long session, each could grow without bound.

Rule

  1. When adding a collection to a long-lived struct, decide the max size at design time and make it configurable (via Config) where possible.
  2. Before every .insert(), check len() >= max and evict.
  3. Prefer the simplest eviction that fits: arbitrary eviction (.keys().next()) for caches, least-used eviction for frequency counters.

Example

// BAD: unbounded insert
self.cache.insert(key, value);

// GOOD: bounded insert with eviction
if self.cache.len() >= self.cfg.max_cache_entries {
    let evict = self.cache.keys().next().cloned();
    if let Some(k) = evict {
        self.cache.remove(&k);
    }
}
self.cache.insert(key, value);
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 · 42 lines · 0 tokens per session scan A 4677996b2a13

Subscribe to this mod's changes

bounded-collections is a cursor rule published in the GitHub repository beardfaceguy/daimonos (2 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 316 tokens. 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.