Minimizing Ty Ecosystem Changes
astral-sh/ruff
A skill your agent uses when a user says "minimize this ty ecosystem change", "reproduce this ecosystem result", "investigate a primer difference", "investigate a mypyprimer difference"…
Zero-allocation string building strategies. An agent skill from r3bl-org/r3bl-open-core.
Install Fast String Allocations
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocations --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/fast-string-allocations .claude/skills/fast-string-allocations && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .claude/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocationsType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocations --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/fast-string-allocations .agents/skills/fast-string-allocations && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .agents/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocations --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/fast-string-allocations .cursor/skills/fast-string-allocations && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .cursor/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/r3bl-org/r3bl-open-core.git --path .agents/skills/fast-string-allocations--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocations --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/fast-string-allocations .gemini/skills/fast-string-allocations && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .gemini/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocationsInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/fast-string-allocations .github/skills/fast-string-allocations && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .github/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install r3bl-org/r3bl-open-core fast-string-allocations --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/r3bl-org/r3bl-open-core.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/fast-string-allocations .opencode/skills/fast-string-allocations && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "fast-string-allocations" agent skill from https://github.com/r3bl-org/r3bl-open-core/tree/main/.agents/skills/fast-string-allocations into .opencode/skills/fast-string-allocations/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fast-string-allocations", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
fast-string-allocations- GitHub stars
- 485
- Token cost
- ~602 tokens
- SKILL.md length
- 282 words
- Files
- 1
- Skills in repo
- 25
- Repo updated
- First seen
- Licence
- Apache-2.0
At a glance
Zero-allocation string building strategies. An agent skill from r3bl-org/r3bl-open-core.
- Works in 3 steps: The FastStringify Trait → The inline_string! Macro → The format_no_alloc! Macro
- Formatting strings
- SKILL.md covers When to Use, Core Strategy and Implementation Guidelines
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Fast String Allocations is an agent skill from r3bl-org/r3bl-open-core. Zero-allocation string building strategies. Use when formatting strings, generating ANSI codes, or writing hot loops to avoid heap allocations and Formatter state machine overhead.
Its SKILL.md is about 600 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Development, covering Linting and formatting. The repository describes itself as: TUI framework and developer productivity apps in Rust 🦀. The licence is Apache-2.0.
When your agent uses it
- Formatting strings
- Generating ANSI codes
- Writing hot loops to avoid heap allocations and Formatter state machine overhead
Example prompts
- “/fast-string-allocations”
Workflow steps
3 steps, taken from the step headings in SKILL.md.
What it can do on your machine
Read from SKILL.md and the folder at commit 89db352. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Fast String Allocations loads about 602 tokens when it runs. Until then it costs about 51 tokens; SKILL.md has 282 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from r3bl-org/r3bl-open-core at commit 89db352, republished under its Apache-2.0 licence (© r3bl-org). 282 words, ~602 tokens.
Download SKILL.mdSave it as
.claude/skills/fast-string-allocations/SKILL.md (or your agent's skills folder).- name
- fast-string-allocations
- description
- Zero-allocation string building strategies. Use when formatting strings, generating ANSI codes, or writing hot loops to avoid heap allocations and Formatter state machine overhead.
Fast String Allocations & Zero-Overhead Formatting
When writing code that involves string building, formatting, or rendering (especially in the TUI engine, logging, or event loops), you MUST adhere to the codebase's strict zero-allocation architecture.
When to Use
- When building ANSI escape sequences
- When building strings in a 60 FPS event loop or render cycle
- When using
tracing::*!macros - Whenever you are tempted to use
format!orwrite!on aFormatter
Core Strategy
Read the full Source of Truth at mod@crate::core::common::fast_strings#string-allocation-performance-strategy for detailed architectural constraints.
Performance Hierarchy (Fastest to Slowest)
- Direct
push_str()- Zero overhead, direct memory copy. crate::format_no_alloc!- Zero heap allocations, reuses existing heap.FastStringify- Temporary heap allocation, completely bypassesFormatterstate machine.inline_string!- Stack allocated (16 bytes), but dynamically spills to the heap if exceeded.format!/write!- Always heap allocates (format!) OR uses heavy formatter overhead (write!). Avoid in hot paths.
Implementation Guidelines
1. The FastStringify Trait
Use for custom types (like ANSI codes) that are serialized millions of times.
- Bypasses the expensive
Formatterstate machine by pushing everything into a temporary heapStringand making ONEf.write_str()call. - Use
generate_impl_display_for_fast_stringify!to auto-generate theDisplayblock.
2. The inline_string! Macro
Use for stack-allocated strings (16 bytes).
- Drop-in replacement for
format!. - The primary use case is the core Editor Component and
tracing::*!macros. - Warning: If text exceeds 16 bytes, it spills to the heap and incurs the cost of
format!.
3. The format_no_alloc! Macro
Use for hot loops where the string is guaranteed to exceed 16 bytes (meaning inline_string! would spill).
- Hoist a
String::with_capacity(N)outside the loop. - Pass the hoisted string into the macro inside the loop to clear and write into the existing capacity.
- Zero allocations per tick.
© r3bl-org, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in .agents/skills/fast-string-allocations of r3bl-org/r3bl-open-core.
Open the folder on GitHubat commit 89db352
Compare with similar skills
Fast String Allocations next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Fast String Allocations this skillr3bl-org/r3bl-open-core | 485 | — | ~602 | Automated safety check: Pass | Apache-2.0 | |
| Minimizing Ty Ecosystem Changesastral-sh/ruff | 50k | — | ~4.6k | Automated safety check: Pass | MIT | |
| Install Anti-Slop Oxlint Rulesdmmulroy/anti-slop | 5.3k | — | ~2.2k | Automated safety check: Pass | MIT | |
| Babysit PR To Pass CIsgl-project/sglang | 37k | 2 repos | ~3k | Automated safety check: Pass | Apache-2.0 | |
| Rust Best Practicesfarm-fe/farm | 5.6k | 3 repos | ~1.1k | Automated safety check: Pass | MIT | |
| Summarise Ecosystem Resultsastral-sh/ruff | 50k | — | ~2.2k | Automated safety check: Pass | MIT |
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Related
Categories
Questions about Fast String Allocations
What does Fast String Allocations do?
Zero-allocation string building strategies. An agent skill from r3bl-org/r3bl-open-core. Fast String Allocations is an agent skill from r3bl-org/r3bl-open-core. Zero-allocation string building strategies.
When should I use Fast String Allocations?
Fast String Allocations fits situations like: formatting strings; generating ANSI codes; writing hot loops to avoid heap allocations and Formatter state machine overhead.
How do I install Fast String Allocations in Claude Code?
Run `npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a claude-code`. Or copy the skill folder (.agents/skills/fast-string-allocations in r3bl-org/r3bl-open-core) into .claude/skills/fast-string-allocations in your project. Claude Code loads it when a task matches its description.
How do I install Fast String Allocations in Codex?
Run `npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a codex`. Or copy the skill folder (.agents/skills/fast-string-allocations in r3bl-org/r3bl-open-core) into .agents/skills/fast-string-allocations in your project. Codex loads it when a task matches its description.
Can I use Fast String Allocations in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add r3bl-org/r3bl-open-core --skill fast-string-allocations -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/fast-string-allocations, .gemini/skills/fast-string-allocations, .github/skills/fast-string-allocations and .opencode/skills/fast-string-allocations in your project.
What does Fast String Allocations need to run?
SKILL.md names no scripts, command-line tools or credentials: Fast String Allocations is instructions for the agent only.
Does Fast String Allocations access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Fast String Allocations safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Fast String Allocations use?
Fast String Allocations is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Fast String Allocations use?
About 602 tokens (SKILL.md is roughly 2.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Fast String Allocations?
Skills that share tags, products or a category with Fast String Allocations: Minimizing Ty Ecosystem Changes (astral-sh/ruff, 50k stars), Install Anti-Slop Oxlint Rules (dmmulroy/anti-slop, 5.3k stars), Babysit PR To Pass CI (sgl-project/sglang, 37k stars) and Rust Best Practices (farm-fe/farm, 5.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Fast String Allocations?
r3bl-org (a GitHub organization) maintains it in r3bl-org/r3bl-open-core, which has 485 GitHub stars. The repository holds 25 skills in this directory. The repository was last updated on October 8, 2026.
Source: r3bl-org/r3bl-open-core on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.