[WIP] Make OnyxUtils get functions synchronous

.claude/skills/coding-standards/SKILL.md

@@ -16,6 +16,7 @@ Coding standards for the Expensify App. Each standard is a standalone file in `r
 | Consistency | `CONSISTENCY-*` | Platform checks, magic values, unused props, ESLint discipline, localization, file naming, JSDoc |
 | Clean React Patterns | `CLEAN-REACT-PATTERNS-*` | Composition, component ownership, state structure, prop typing, function components |
 | UI | `UI-*` | Loading indicators, scrollable pages, styling conventions |
+| Onyx | `ONYX-*` | Reading Onyx data outside render, and off a tick that wrote |
 
 ## Quick Reference
 
@@ -74,6 +75,9 @@ Coding standards for the Expensify App. Each standard is a standalone file in `r
 - [UI-2](rules/ui-2-new-page-scrollview.md) — New pages must be scrollable
 - [UI-3](rules/ui-3-no-inline-styles.md) — Do not use inline style objects
 
+### Onyx
+- [ONYX-1](rules/onyx-1-no-render-reachable-onyx-read.md) — Keep synchronous Onyx reads off the render path and out of a written tick
+
 ## Usage
 
 **During development**: When writing or modifying `src/` files, consult the relevant standard files for detailed conditions, examples, and exceptions.

.claude/skills/onyx-get/SKILL.md

@@ -0,0 +1,12 @@
+---
+name: onyx-get
+description: Onyx.get() reads the Onyx cache synchronously and never subscribes. Use when writing or reviewing an Onyx read outside render, when a component or hook gains a call into a library function, or when converting a function off forwarded Onyx parameters or module-level caches.
+---
+
+`Onyx.get(key)` returns what is in the cache right now and never subscribes, so it belongs only in code that runs on an event: action creators, libraries, network handlers, and callbacks such as `useCallback`, `useEffect` and event handlers. Before reaching for it, prefer a pure function that takes the data as a parameter. `Onyx.get()` is the answer when threading the value through every caller is the only thing that parameter buys.
+
+**The rules are in [ONYX-DATA-MANAGEMENT.md](../../../contributingGuides/philosophies/ONYX-DATA-MANAGEMENT.md#reading-onyx-data-useonyx-onyxget-and-onyxconnectwithoutview).** Read that section before writing or converting a read. Every rule there has to hold at the call site.
+
+`npm run lint-changed` runs `no-unsafe-onyx-read`, which checks three of them: not during render, not at module scope, and not after an un-awaited write in the same body. A clean run is not a verdict on the rest.
+
+The rest are in `ONYX-1` (`.claude/skills/coding-standards/rules/onyx-1-no-render-reachable-onyx-read.md`), which carries the caller sweep and the two shapes lint structurally cannot see: a read reached from render through a caller, and a write in the caller with the read one call away. Apply it when writing the read, not only when reviewing it.

CLAUDE.md

@@ -157,12 +157,13 @@ Major action categories:
 - `Search.ts`: Search operations
 - `Travel.ts`: Travel features
 
-### Reading Onyx data (`useOnyx` vs `Onyx.connectWithoutView`)
-There are only two ways to read Onyx data:
+### Reading Onyx data (`useOnyx`, `Onyx.get()`, `Onyx.connectWithoutView`)
+There are three ways to read Onyx data:
 1. **`useOnyx`** (`@hooks/useOnyx`) — the default for anything a component renders.
 2. **`Onyx.connectWithoutView`** — only for non-render logic (module-level state in actions/libraries) that genuinely can't use `useOnyx`.
+3. **`Onyx.get()`**: a synchronous, non-subscribing read of the cache, for non-render code that needs a value when it runs. Never during render, never at module scope, and never after an un-awaited write to the same key in that tick.
 
-Before either, prefer a **pure function** that receives the data as parameters: it does not read Onyx itself — the caller reads (with `useOnyx` or `Onyx.connectWithoutView`) and passes the data in. Do not add a new `Onyx.connectWithoutView` by copying existing usage — justify each one on its own with a comment explaining why it is needed. Using it in a component for performance requires `@frontend-performance` approval on Slack (link it in the PR description). See [Onyx Data Management](contributingGuides/philosophies/ONYX-DATA-MANAGEMENT.md#reading-onyx-data-useonyx-vs-onyxconnectwithoutview).
+Before any of them, prefer a **pure function** that receives the data as parameters: it does not read Onyx itself — the caller reads and passes the data in. Do not add a new `Onyx.connectWithoutView` by copying existing usage — justify each one on its own with a comment explaining why it is needed. Using it in a component for performance requires `@frontend-performance` approval on Slack (link it in the PR description). The full rules for all three, including the conditions a read must meet before it moves into the function that uses it, are in [Onyx Data Management](contributingGuides/philosophies/ONYX-DATA-MANAGEMENT.md#reading-onyx-data-useonyx-onyxget-and-onyxconnectwithoutview).
 
 ## Build & Deployment
 

config/eslint/eslint.config.mjs

@@ -335,6 +335,10 @@ const config = defineConfig([
             'rulesdir/require-live-region-for-status-updates': 'error',
             'rulesdir/require-a11y-disable-justification': 'error',
             'rulesdir/no-direct-pre-insert-fullscreen-under-rhp': 'error',
+            // Position and order for the synchronous Onyx read: not during render, where the read does not subscribe; not at module
+            // scope, where it runs at import time, before Onyx.init() has hydrated the cache; and not after an un-awaited write in
+            // the same body, where Onyx.merge() and Onyx.update() apply in a later microtask so the read returns the pre-write value.
+            'rulesdir/no-unsafe-onyx-read': 'error',
             'rulesdir/require-locale-for-localized-date-format': 'error',
             'rulesdir/prefer-narrow-hook-dependencies': [
                 'error',

contributingGuides/philosophies/DATA-BINDING.md

@@ -42,7 +42,7 @@ function getReportName(reportID: string): string {
 ### - Library files that are not connected or associated to any UI SHOULD use `Onyx.connectWithoutView()` to subscribe to changes in Onyx data
 Library files are located in `/src/lib` but excluding the actions in `/src/lib/actions` which have their own rule above.
 
-`useOnyx()` is the standard for accessing Onyx data for React components. Non-React library files should always prefer using pure functions that receive all data as parameters. `Onyx.connectWithoutView()` should only be used when a library file is unable to get the data with `useOnyx()` (eg. non-React code, network layer, etc.). Never add a reference to `Onyx.connectWithoutView()` just because nearby code uses it. See [Reading Onyx data: `useOnyx` vs `Onyx.connectWithoutView`](/contributingGuides/philosophies/ONYX-DATA-MANAGEMENT.md#reading-onyx-data-useonyx-vs-onyxconnectwithoutview) for the full rules.
+`useOnyx()` is the standard for accessing Onyx data for React components. Non-React library files should always prefer using pure functions that receive all data as parameters. `Onyx.connectWithoutView()` should only be used when a library file is unable to get the data with `useOnyx()` (eg. non-React code, network layer, etc.). Never add a reference to `Onyx.connectWithoutView()` just because nearby code uses it. See [Reading Onyx data: `useOnyx`, `Onyx.get()` and `Onyx.connectWithoutView`](/contributingGuides/philosophies/ONYX-DATA-MANAGEMENT.md#reading-onyx-data-useonyx-onyxget-and-onyxconnectwithoutview) for the full rules.
 
 ```ts
 // GOOD ✅ — non-React network layer keeps the auth token in module state