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.
npx skills add heyAyushh/stacc --skill zero-cost-abstractionsgit clone --depth 1 https://github.com/heyAyushh/staccWrote 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/skills/heyayushh/stacc/zero-cost-abstractions)<a href="https://agentmods.dev/skills/heyayushh/stacc/zero-cost-abstractions"><img src="https://agentmods.dev/badge/skills/heyayushh/stacc/zero-cost-abstractions/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/heyayushh/stacc/zero-cost-abstractions"><img src="https://agentmods.dev/badge/skills/heyayushh/stacc/zero-cost-abstractions.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00045 | $0.00782 |
| Opus 5 | $0.00023 | $0.00391 |
| Sonnet 5 | $0.00009 | $0.00156 |
| Haiku 4.5 | $0.00005 | $0.00078 |
Grade A, and why
rust-zero-cost-abstractions 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 9d 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 — 112 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Zero-Cost Abstractions
Layer 1: Language Mechanics
Core Question
Do we need compile-time or runtime polymorphism?
Before choosing between generics and trait objects:
- Is the type known at compile time?
- Is a heterogeneous collection needed?
- What's the performance priority?
Thinking Prompt
Before adding trait bounds:
-
What abstraction is needed?
- Same behavior, different types → trait
- Different behavior, same type → enum
- No abstraction needed → concrete type
-
When is type known?
- Compile time → generics (static dispatch)
- Runtime → trait objects (dynamic dispatch)
-
What's the trade-off priority?
- Performance → generics
- Compile time → trait objects
- Flexibility → depends
Syntax Comparison
// Static dispatch — type known at compile time
fn process(x: impl Display) { } // argument position
fn process<T: Display>(x: T) { } // explicit generic
fn get() -> impl Display { } // return position
// Dynamic dispatch — type determined at runtime
fn process(x: &dyn Display) { } // reference
fn process(x: Box<dyn Display>) { } // owned
Decision Guide
| Scenario | Choose | Why |
|---|---|---|
| Performance critical | Generics | Zero runtime cost |
| Heterogeneous collection | dyn Trait |
Different types at runtime |
| Plugin architecture | dyn Trait |
Unknown types at compile time |
| Reduce compile time | dyn Trait |
Less monomorphization |
| Small, known type set | enum |
No indirection |
Cost Comparison
| Pattern | Dispatch | Code Size | Runtime Cost |
|---|---|---|---|
fn foo<T: Trait>() |
Static | +bloat | Zero |
fn foo(x: &dyn Trait) |
Dynamic | Minimal | vtable lookup |
impl Trait return |
Static | +bloat | Zero |
Box<dyn Trait> |
Dynamic | Minimal | Allocation + vtable |
Object Safety
A trait is object-safe if it:
- Doesn't have
Self: Sizedbound - Doesn't return
Self - Doesn't have generic methods
- Uses
where Self: Sizedfor non-object-safe methods
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.
- 9d ago First seen · 112 lines · 45 tokens per session scan A 0c33cf303355
rust-zero-cost-abstractions is a skill published in the GitHub repository heyAyushh/stacc (3 stars, last pushed 2mo ago), licensed MIT. It adds 45 tokens to every session and 782 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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