# Run Atlas Headless in CI for WebAssembly Projects in 2026

> WebAssembly developers in 2026 can run Atlas headless in CI, leveraging `atlas run --format json` to get machine-readable output and automate tasks within their `wasm-pack` and `cargo wasm-bindgen`

In 2026, WebAssembly developers can run Atlas headless in CI pipelines to automate code modifications and receive machine-readable output by invoking `atlas run --format json` within their `Cargo.toml` configured for `cdylib` and `wasm-bindgen` dependencies, ensuring pre-approved permissions for tools like `bash` and `edit`.

## Key takeaways

- Atlas runs headless in WebAssembly CI using `atlas run --format json` for machine-readable output.
- Pre-approve `wasm-pack test` and `rustfmt` permissions for non-interactive Atlas sessions.
- Atlas understands `#[wasm_bindgen]` exports and `wasm-pack` build targets for WebAssembly.
- Session resumption with `--continue` or `--session` supports iterative WebAssembly development in CI.
- Atlas indexes WebAssembly code using AST declarations and local Ollama embeddings, keeping code off third-party servers.

## How to Run Atlas Headless in WebAssembly CI Pipelines

In 2026, WebAssembly developers can execute Atlas non-interactively within their continuous integration pipelines using the `atlas run` command. This headless mode is designed for automation, allowing Atlas to process a single prompt, stream events to stdout, and exit once its session becomes idle, integrating directly with `wasm-pack` projects.

Atlas is built for non-interactive execution in CI environments, making it ideal for WebAssembly projects. When you invoke `atlas run` without additional flags, it operates in a default non-interactive mode: it accepts a single prompt as an argument, streams all session events to standard output, and then gracefully exits once the agent session goes idle. This behavior is crucial for CI pipelines where human intervention is not possible. For WebAssembly development, this means Atlas can be integrated into a `Cargo.toml` based project where the `crate-type` is set to `cdylib` and `wasm-bindgen` is a declared dependency. Atlas is designed to read and understand your `#[wasm_bindgen]` exports, the JavaScript glue code they generate, and any `wasm32-wasip2` target configurations, allowing it to intelligently propose and implement changes that respect the WebAssembly boundary. This capability ensures that Atlas's automated modifications are contextually aware of the unique requirements of WebAssembly modules.

## Securing Headless Atlas Operations in WebAssembly with Permission Gates

Atlas ensures secure operations in WebAssembly CI environments by requiring explicit pre-approval for every tool call, preventing unauthorized actions in 2026. Headless runs, lacking an interactive user, rely on a permission configuration to allow, ask, or deny rules for tools like `bash`, `read`, `edit`, and `todowrite` before they execute.

For headless Atlas sessions within a WebAssembly CI pipeline, pre-approving tool permissions is a critical security measure. Since there is no interactive user to respond to 'ask' prompts, all necessary tools must be explicitly `allow`-listed in Atlas's permission configuration. This includes general-purpose tools like `bash` for executing shell commands, `read` for file access, `edit` for modifying code, and `todowrite` for creating new files. More specifically for WebAssembly development, you must pre-approve commands such as `wasm-pack test --node` for running tests in a Node.js environment and `rustfmt` for formatting Rust code. Atlas's architecture, which includes a read-only plan agent that drafts a plan and asks for approval before switching to a build agent, still applies. However, in a headless context, these 'ask' prompts are automatically resolved by the pre-configured permission rules. Furthermore, Atlas computes a unified diff for every file edit and surfaces it for approval, which in a headless setup, would be part of the machine-readable output for automated review.

## Capturing Machine-Readable Output from WebAssembly Atlas Sessions

To facilitate automated parsing by subsequent pipeline steps in 2026, Atlas provides machine-readable output from headless WebAssembly sessions. Developers can pass the `--format json` flag to `atlas run`, which streams raw event data to stdout, enabling programmatic analysis of Atlas's actions and generated code changes.

When integrating Atlas into a WebAssembly CI pipeline, obtaining machine-readable output is essential for automated processing and reporting. By invoking `atlas run` with the `--format json` flag, Atlas streams a raw event log to standard output in a structured JSON format. This allows subsequent pipeline steps to easily parse Atlas's actions, tool calls, generated code, and unified diffs programmatically, rather than relying on human-readable prose. This is particularly useful for automated quality gates or for generating reports on code modifications within a WebAssembly project. Additionally, Atlas supports `--command` for executing specific slash commands non-interactively, enabling precise control over the agent's behavior in CI. For scenarios requiring iteration or debugging, Atlas offers `--continue`, `--session`, and `--fork` flags. These allow a pipeline step to resume a prior session, replay a specific run, or fork a new session from an existing one, providing flexibility for complex WebAssembly development workflows that might span multiple CI jobs.

## Integrating Atlas with WebAssembly Build and Test Workflows

Atlas direct integrates with the established WebAssembly build and test toolchain, understanding `wasm-pack` and `rustfmt` in 2026. It can be instructed to build projects using `wasm-pack build --target web` and check the emitted `.d.ts` files against JavaScript call sites, ensuring type safety and correct bindings.

Atlas is designed to work within the native WebAssembly development ecosystem, recognizing and utilizing tools like `wasm-pack` and `rustfmt`. When working on a WebAssembly project, Atlas can be instructed to perform build operations using `wasm-pack build --target web`, which compiles your Rust code into a WebAssembly module and generates the necessary JavaScript glue code and TypeScript declaration files. Atlas can then check these emitted `.d.ts` files against your existing JavaScript call sites, ensuring that the WebAssembly bindings are correctly typed and compatible with your frontend code. This capability is vital for maintaining type safety and preventing runtime errors at the WebAssembly boundary. Furthermore, Atlas can be configured to run `wasm-pack test --node` to execute your WebAssembly tests in a Node.js environment, verifying the functionality of your compiled module. After making code changes, Atlas can also apply `rustfmt` to the generated diff, ensuring that all modifications adhere to your project's coding style guidelines. A key optimization Atlas can perform is moving hot loops across the WebAssembly boundary in a single call, rather than incurring the overhead of chattering per element through JavaScript, directly improving performance for WebAssembly modules.

## Steps

1. Configure `Cargo.toml` for WebAssembly: Ensure your crate's `Cargo.toml` specifies `crate-type = ["cdylib"]` and includes `wasm-bindgen` as a dependency, allowing Atlas to understand your WebAssembly project structure and bindings.
2. Set the Atlas model explicitly: Invoke `atlas run` with the `--model` flag, specifying the model in `provider/model` form, for example, `--model github/copilot-gpt4`, as required for headless execution in 2026 and to avoid interactive prompts.
3. Pre-approve WebAssembly tool permissions: Configure Atlas's permission settings to `allow` necessary tools like `bash`, `read`, `edit`, `todowrite`, and specifically `wasm-pack test --node` and `rustfmt`, as headless runs cannot prompt for approval.
4. Run Atlas headless with a prompt: Execute `atlas run "Optimize the #[wasm_bindgen] export in src/lib.rs for better performance across the boundary." --format json` to send a single prompt, stream machine-readable events, and exit when idle.
5. Parse machine-readable output: In a subsequent CI step, consume the JSON event stream from `stdout` to programmatically analyze Atlas's actions, generated code, and unified diffs for automated review and reporting.
6. Build and verify WebAssembly output: Instruct Atlas to run `wasm-pack build --target web` and then check the emitted `.d.ts` files against your JavaScript call sites to ensure correct WebAssembly bindings and type definitions.
7. Run WebAssembly tests: Allow Atlas to execute `wasm-pack test --node` behind a permission prompt, verifying the functionality of the generated WebAssembly module within a Node.js environment.
8. Format generated code: Have Atlas apply `rustfmt` to any modified Rust source files, ensuring consistent code style for the WebAssembly project before committing changes.

## FAQ

### How do I run Atlas headless in a WebAssembly CI pipeline?

In 2026, run `atlas run` with your prompt and `--format json` within your WebAssembly project's CI environment. Ensure your `Cargo.toml` is configured for `cdylib` and `wasm-bindgen` dependencies to allow Atlas to understand the project.

### Can Atlas automatically build my WebAssembly project in CI?

Yes, Atlas can execute `wasm-pack build --target web` as part of its workflow, checking the emitted `.d.ts` files against your JavaScript call sites, provided the `bash` tool is pre-approved in its permission configuration.

### How does Atlas handle permissions for WebAssembly-specific tools like `wasm-pack test` in headless mode?

For headless runs, you must pre-approve tools like `wasm-pack test --node` and `rustfmt` in Atlas's permission configuration, as there is no interactive user to respond to `ask` prompts during execution.

### What kind of output does Atlas provide for automated WebAssembly CI steps?

Atlas provides a machine-readable JSON event stream via `stdout` when `atlas run` is invoked with `--format json`, allowing subsequent CI steps to parse and react to its actions and code changes programmatically.

### How does Atlas understand my WebAssembly Rust code, including `#[wasm_bindgen]` attributes?

Atlas indexes your code using AST declarations via tree-sitter, allowing it to understand `#[wasm_bindgen]` exports, the generated JavaScript glue, and `wasm32-wasip2` target configurations for precise code modifications.

### Can I resume a failed Atlas WebAssembly CI session?

Yes, you can resume or fork a prior Atlas session using the `--continue`, `--session`, or `--fork` flags with `atlas run`, allowing you to pick up where a previous WebAssembly job left off or iterate on a specific task.

### Does Atlas support local embeddings for WebAssembly code indexing?

Yes, Atlas can build its code index using local Ollama embeddings, ensuring your WebAssembly project's code remains off third-party servers during the indexing process, enhancing privacy and security.

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