How does Atlas understand my Expo project structure and `expo-router` routes?

Atlas automatically indexes your Expo project by reading `app.json` or `app.config.ts`, the `app/` directory, and `expo-router` routes. It uses AST declarations via tree-sitter to build a semantic understanding of your code, including how `config plugins` are used.

Can Atlas find code in my Expo app even if I don't know the exact function name?

Yes, Atlas's `codebase_search` tool uses hybrid semantic and keyword retrieval. You can describe the behavior in natural language, and Atlas will return relevant code declarations from your Expo project, even if your words don't appear verbatim in the source.

What if Atlas suggests a wrong file or path in my Expo application?

When you use `atlas read `, if the file is not found, Atlas will explicitly state 'File not found' and provide a 'Did you mean' list of similar paths. This prevents you from pursuing incorrect leads and helps you quickly correct the path.

How does Atlas ensure safety when suggesting changes or running commands in my Expo codebase?

Atlas employs several safety mechanisms: every tool call is permission-gated, it drafts plans in a read-only agent for approval, and all proposed file edits are presented as unified diffs for your explicit review. It also snapshots changes as git patches for easy rollback.

Can Atlas help with `config plugins` or `EAS builds` in Expo?

Yes, Atlas is designed to understand and interact with Expo's `config plugins` and `eas.json` build profiles. It can be asked to add native capabilities through a config plugin, ensuring your `prebuild` process remains reproducible without manual `ios/` or `android/` edits.

Does Atlas integrate with Expo's package manager and test runner?

Absolutely. Atlas can install packages using `npx expo install`, ensuring versions are pinned to your SDK release. It can also run your test suite with `jest-expo` behind a permission prompt, and format code changes with `prettier` on the generated diffs.

Locate Expo Behavior Implementations with Atlas in 2026

In 2026, Atlas helps Expo developers find the exact file and symbol responsible for a behavior by combining semantic code search, precise text matching with `grep`, and symbol graph navigation via `lsp`, all while respecting your project's `app.json` or `app.config.ts` and `expo-router` conventions. This integrated approach ensures you can locate code even when you only know what the software does, not what the code is called.

How Atlas Pinpoints Expo Behaviors: Semantic Search and `grep`

Locating a specific behavior in an Expo application in 2026 begins with Atlas's hybrid search capabilities, which fuse semantic understanding with keyword retrieval. This approach allows developers to describe a behavior in natural language, even if the exact code terms are unknown, and Atlas will return relevant declarations from your `app/` directory.

Atlas initiates the search for a behavior's implementation in your Expo project by using its `codebase_search` tool. This tool leverages a semantic index built from your code's Abstract Syntax Tree (AST) declarations, ensuring that it understands the structure and meaning of your JavaScript/TypeScript files, not just raw text. For instance, if you describe 'the logic for user onboarding after first launch,' Atlas will semantically identify candidate declarations across your `app/` directory, including those related to `expo-router` routes or specific UI components. Once `codebase_search` provides initial candidates, you can confirm these findings with the `grep` tool. Atlas's `grep` is powered by `ripgrep` and allows for precise regex patterns, along with include and path filters, to narrow down results within your Expo project. This is crucial for verifying semantic matches against exact text occurrences, such as specific string literals or variable names found in your `app.json` or `app.config.ts`.

Navigating Expo Code with Atlas `lsp` Tool

After identifying potential code locations, the Atlas `lsp` tool becomes indispensable for navigating the symbol graph of your Expo application. This tool allows you to jump directly to a declaration by name using `workspaceSymbol` or trace every callsite of a function with `findReferences`, providing a comprehensive view of how a behavior is implemented across your project's 2026 codebase.

When `codebase_search` and `grep` have surfaced a promising file, you can open it directly within Atlas using the `read` tool. For example, if Atlas suggests `app/screens/OnboardingScreen.tsx`, you would use `atlas read app/screens/OnboardingScreen.tsx`. If the path is incorrect, Atlas provides a 'File not found' error with a 'Did you mean' list, preventing wasted effort. Once you have a candidate file open, the `lsp` tool is critical for deeper investigation. You can use `atlas lsp workspaceSymbol <symbolName>` to jump directly to the definition of a function or component, such as an `onPress` handler within an Expo UI component. To understand how a specific function or method contributes to the overall behavior, `atlas lsp findReferences <symbolName>` will list every location where that symbol is called throughout your Expo project, including within `expo-router` route files or utility modules. This allows you to trace the full call path of a behavior, providing concrete file and line references back to the user.

Ensuring Safety and Reproducibility in Expo with Atlas

Atlas prioritizes safety and reproducibility when interacting with your Expo project, especially in 2026, by implementing a multi-layered approval process. Every Atlas tool call is permission-gated, and all proposed code changes are presented as unified diffs for explicit user approval, ensuring your `app.json` or `app.config.ts` remains consistent.

Atlas operates with a strong emphasis on user control and safety. Before any tool call, such as running `jest-expo` tests or installing packages with `npx expo install`, Atlas consults permission-gated allow, ask, and deny rules. This means you always have the final say on what actions Atlas takes. When Atlas drafts a plan to modify your Expo codebase, it first does so in a read-only plan agent, presenting the proposed steps for your review before switching to a build agent. For any file edits, Atlas computes a unified diff, which is then surfaced for your approval before being written to disk. This allows you to review every line change, ensuring that modifications align with your intentions and respect Expo's idioms, such as updates to `app.json` or `app.config.ts` or `eas.json` build profiles. Furthermore, Atlas snapshots file changes as git patches, enabling easy diffing and rollback of edits, maintaining the integrity and reproducibility of your Expo project.

Setting Up Atlas for Expo Development

Integrating Atlas into your Expo development workflow in 2026 is straightforward, requiring only a few initial steps to ensure it understands your project's unique structure. Atlas automatically reads your `app.json` or `app.config.ts` and `app/` directory, along with `expo-router` routes and `config plugins`, to build its comprehensive code index.

To begin using Atlas for locating behaviors in your Expo application, simply run `atlas` within your project's root directory. Atlas will automatically detect your Expo project by looking for an `app.json` or `app.config.ts` file and an `app/` directory. It then proceeds to read your `expo-router` routes, the `plugins` array in your configuration, and your `eas.json` build profiles. This initial indexing allows Atlas to build a robust understanding of your project's architecture, including how native capabilities are added via `config plugins` rather than manual `ios/` and `android/` edits. Atlas can also install packages using `npx expo install`, ensuring that dependencies remain pinned to your SDK release. for testing, Atlas can run `jest-expo` behind a permission prompt, and it can automatically format code changes using `prettier` on the generated diffs, maintaining code consistency across your Expo team.

Step by step

01Start Atlas in your Expo project's root directory, ensuring it can read your `app.json` or `app.config.ts` and `app/` structure.
02Describe the behavior you want to locate using `atlas codebase_search "<description of behavior>"`. For example, `atlas codebase_search "handle user login after submitting credentials"`.
03Review the candidate declarations returned by `codebase_search`. If a specific text string is known, confirm with `atlas grep -e "<regex pattern>" --include "*.tsx"`.
04Open the most promising candidate file with `atlas read <path/to/file.tsx>`. Atlas will loudly fail if the path is incorrect, offering suggestions.
05Use `atlas lsp findReferences <symbolName>` to trace all callsites of a key function or component within the file, such as an `onPress` handler in an Expo UI component.
06Alternatively, use `atlas lsp workspaceSymbol <symbolName>` to jump directly to the definition of a related symbol, like a `useAuth` hook, anywhere in your Expo project.
07Summarize the identified call path and implementation details, including concrete file and line references, back to the user.

Frequently asked questions

How does Atlas understand my Expo project structure and `expo-router` routes?: Atlas automatically indexes your Expo project by reading `app.json` or `app.config.ts`, the `app/` directory, and `expo-router` routes. It uses AST declarations via tree-sitter to build a semantic understanding of your code, including how `config plugins` are used.
Can Atlas find code in my Expo app even if I don't know the exact function name?: Yes, Atlas's `codebase_search` tool uses hybrid semantic and keyword retrieval. You can describe the behavior in natural language, and Atlas will return relevant code declarations from your Expo project, even if your words don't appear verbatim in the source.
What if Atlas suggests a wrong file or path in my Expo application?: When you use `atlas read <path>`, if the file is not found, Atlas will explicitly state 'File not found' and provide a 'Did you mean' list of similar paths. This prevents you from pursuing incorrect leads and helps you quickly correct the path.
How does Atlas ensure safety when suggesting changes or running commands in my Expo codebase?: Atlas employs several safety mechanisms: every tool call is permission-gated, it drafts plans in a read-only agent for approval, and all proposed file edits are presented as unified diffs for your explicit review. It also snapshots changes as git patches for easy rollback.
Can Atlas help with `config plugins` or `EAS builds` in Expo?: Yes, Atlas is designed to understand and interact with Expo's `config plugins` and `eas.json` build profiles. It can be asked to add native capabilities through a config plugin, ensuring your `prebuild` process remains reproducible without manual `ios/` or `android/` edits.
Does Atlas integrate with Expo's package manager and test runner?: Absolutely. Atlas can install packages using `npx expo install`, ensuring versions are pinned to your SDK release. It can also run your test suite with `jest-expo` behind a permission prompt, and format code changes with `prettier` on the generated diffs.

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