`react-doctor/r3f-no-sync-readback-in-use-frame`

Synchronous readback inside useFrame

Category: Performance
Severity: warn
Source: oxlint-plugin-react-doctor
Framework: global
Enabled when: react, r3f
Tags: r3f, webgl
Default: Enabled

Validate the diagnostic

Confirm the reported code matches this rule before you edit it.

Confirm the reported code matches react-doctor/r3f-no-sync-readback-in-use-frame. Compare it with the Before example and verify the same API, framework, and execution context. Treat it as a false positive only when one of those conditions differs.

Compare the code

The corrected pattern shows a focused way to address the diagnostic.

Reported pattern

useFrame(({ gl }) => {
  gl.readRenderTargetPixels(target, 0, 0, 1, 1, pixel);
});

Corrected pattern

const gl = useThree((state) => state.gl);
const readPixel = () => {
  gl.readRenderTargetPixels(target, 0, 0, 1, 1, pixel);
};
return <mesh onClick={readPixel} />;

How to fix

Use the corrected pattern as a reference. Preserve behavior that the rule does not require you to change.

Copyable fix prompt

Copy this self-contained prompt into your coding agent after you confirm the diagnostic.

Fix every confirmed react-doctor/r3f-no-sync-readback-in-use-frame diagnostic in the current repository. Required change: - Move readback to a discrete or serialized async path and reuse the latest completed result during frames.

Reference transformation:Before:

useFrame(({ gl }) => {
  gl.readRenderTargetPixels(target, 0, 0, 1, 1, pixel);
});

After:

const gl = useThree((state) => state.gl);
const readPixel = () => {
  gl.readRenderTargetPixels(target, 0, 0, 1, 1, pixel);
};
return <mesh onClick={readPixel} />;

Constraints: - Confirm the reported code matches the Before pattern. - Make the smallest change that fixes the root cause. - Preserve behavior and interfaces unrelated to this diagnostic. - Reuse existing project components, utilities, and conventions. - Do not introduce render-phase side effects, render-phase state updates, or Hooks rule violations. - Preserve resource ownership and cleanup. Do not move work into a hotter render or frame path. - Adapt identifiers and framework details instead of copying blindly. - Do not disable the rule or suppress matching code. - Confirm this rule is enabled for the project: react, r3f. Verification: - Run focused tests for the changed behavior. - Run React Doctor and confirm this diagnostic no longer appears. - Report the files changed and any checks you could not run.

More Performance rules from the rules reference:

react-doctor/r3f-no-unstable-args: Unstable R3F constructor args
react-doctor/r3f-prefer-use-loader: Imperative Three.js loader in a React effect
react-doctor/r3f-require-owned-texture-cleanup: Locally owned Three.js texture is not disposed
react-doctor/react-router-loader-fetch-forwards-signal: Loader fetch ignores cancellation
react-doctor/react-router-loader-parallel-fetch: Independent loader work runs sequentially

react-doctor/r3f-no-sync-readback-in-use-frame