What is gpui-fast CLAUDE.md?

Project instructions for developing gpui-fast, a Rust fork of Zed's GPUI user-interface toolkit. They define where custom code and tests belong and how it should connect to upstream code.

Use them when adding or changing gpui-fast code, writing tests, and preparing changes for upstream synchronization.

They reduce merge conflicts when bringing changes from the upstream project and prevent custom logic from being mixed into upstream files.

How longbridge/gpui-fast configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to longbridge/gpui-fast. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/longbridge/gpui-fast/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/longbridge/gpui-fast

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/longbridge/gpui-fast/claude-md/github.svg)](https://agentmods.dev/instructions/longbridge/gpui-fast/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/longbridge/gpui-fast/claude-md"><img src="https://agentmods.dev/badge/instructions/longbridge/gpui-fast/claude-md/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.

Your own site · 80×15

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Per session 691 This file is loaded in full into every session.

When invoked 691 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00691	$0.00691
Opus 5.5	$0.00276	$0.00276
Sonnet 5.5	$0.00138	$0.00138
Haiku 4.5	$0.00069	$0.00069

Measured 3d ago against content hash a371f1333329, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

gpui-fast CLAUDE.md 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 3d 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.md · 43 lines

What it actually says

gpui-fast

A fork of Zed's GPUI (crates/gpui and the Zed crates it depends on) that we keep merging upstream changes into. To keep those merges easy:

Put gpui-fast's code in crates/<crate>/src/fast/, one file per topic. New work goes in a new crates/gpui/src/fast/<topic>.rs (or fast/<topic>/); its tests go in crates/gpui/src/fast/tests/<topic>.rs, or at the bottom of the topic's file when they need its private items.
Upstream files only get small hooks: one field holding a fast/ struct, one-line calls or forwarding method bodies, pub(crate) visibility bumps, mod lines, or a #[path = "fast/<file>.rs"] redirect to a rewrite. No new types, algorithms, tests or explanatory comments in upstream files, and no reformatting of upstream code. Methods on upstream types live in impl blocks in fast/.
Outside fast/, name fast code by its full path where it is used: crate::fast::<topic>::Name, never a use crate::fast::… line, so every hook shows where its code lives. The one exception is gpui.rs exporting a test-support item (pub use fast::stats::LayoutStats;). Inside fast/, use lines are fine; globs never are, use super::* included. Call a method of a fast/ type by its path too, crate::fast::layout_key::WindowLayout::end_frame(&mut self.fast_layout), not self.fast_layout.end_frame().
No new public API. The public API stays upstream's. What tests and gpui_perf need (LayoutStats, Window::layout_stats, set_view_retention) is #[cfg(any(test, feature = "test-support"))]. The few forced differences are listed in docs/upstream-sync.md ("Where our API differs from upstream's"), fast::dynamic_textures included.
New files only inside fast/ or in our own crates (crates/gpui_perf).
Run script/check-upstream before committing. It fails when a change to an upstream file is more than a hook.
Never commit to main directly; every change goes through a pull request. Work on a topic branch off origin/main, and when the change is ready to merge, push the branch and open a PR.
Prefix PR titles with the area they change, not gpui:: fast: for gpui-fast's own retained layout and performance work, composition: for window composition (e.g. composition: route pointer input to the correct composition surface).

Upstream directories and the commit they came from are in UPSTREAM. The full rules, the check and the upstream sync procedure are in docs/upstream-sync.md.

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.

3d ago Changed · +1 lines · +10 tokens per session a371f1333329
22d ago Changed · +4 lines · +61 tokens per session 08039216fdc4
1mo ago Changed · +6 lines · +98 tokens per session 0b1e228aab4a
1mo ago First seen · 32 lines · 522 tokens per session scan A 586988278279

Subscribe to this mod's changes

gpui-fast CLAUDE.md is an instructions file published in the GitHub repository longbridge/gpui-fast (393 stars, last pushed yesterday), licensed Apache-2.0. It adds 691 tokens to every session, about $0.0028 per session on Opus 5.5. 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 2026-09-29.

Frontend

gpui-fast CLAUDE.md next to 6 instructions from other repositories
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gpui-fast: Instructions file for Claude Code