# Diagnose a Hanging or Long-Running WebAssembly Command with Atlas in 2026 > Atlas diagnoses hanging WebAssembly commands by detecting if `wasm-pack test` or `cargo (wasm-bindgen)` is blocked on interactive input or genuinely slow, offering precise next steps. Atlas helps WebAssembly developers diagnose hanging or long-running commands by running them through its `bash` tool, which races every command against a timeout and explicitly identifies if a `wasm-pack test` or `cargo (wasm-bindgen)` build is genuinely slow or silently blocked on interactive input, providing clear instructions to resolve the issue. ## Key takeaways - Atlas's `bash` tool diagnoses hanging `wasm-pack` commands by racing them against a timeout. - The `shell_metadata` block explicitly distinguishes between genuinely slow WebAssembly operations and those blocked on interactive input. - Unblock interactive `wasm-pack` commands by using flags like `--no-input` or `-y`. - For genuinely slow `wasm-pack` builds or tests, Atlas instructs you to retry with an increased timeout in milliseconds. - Atlas ensures safety with permission-gated tool calls and unified diffs for all WebAssembly code changes. - Atlas reads `Cargo.toml` and `#[wasm_bindgen]` exports to understand your WebAssembly project context. ## How does Atlas diagnose hanging WebAssembly commands? Atlas diagnoses hanging WebAssembly commands by executing them through its `bash` tool, which races every command against a configurable timeout. In 2026, this mechanism provides immediate feedback, telling you exactly what happened when a `wasm-pack` operation exceeds its time limit, distinguishing between genuine slowness and silent blocking. When you run a WebAssembly command like `wasm-pack test --node` or `wasm-pack build --target web` using `atlas bash "your command"`, Atlas monitors its execution. If the command does not complete within the specified timeout, Atlas terminates it and provides a detailed `shell_metadata` block in its output. This metadata explicitly states whether the command was genuinely slow and simply needed more time, or if it was silently blocked, most commonly waiting for interactive input. This clear diagnosis is crucial for WebAssembly developers working with complex build processes or test suites that might unexpectedly halt. ## How to identify if a WebAssembly build is blocked on input? Identifying a WebAssembly build blocked on input is straightforward with Atlas's `shell_metadata` output. If a `cargo (wasm-bindgen)` or `wasm-pack` command hangs, Atlas's diagnosis will explicitly call out the interactive-input case, preventing you from waiting indefinitely for a prompt that never appears in a non-interactive environment, a common issue in 2026 CI/CD pipelines. The most common reason for a WebAssembly command to hang without apparent progress is that it is silently blocked on interactive input. This means the command is waiting for a 'yes/no' confirmation or other user interaction that is not being provided. Atlas's `bash` tool is designed to detect this specific scenario. When a `wasm-pack build` or `wasm-pack test` command is killed due to a timeout, the `shell_metadata` block will contain a message explicitly stating that the command was waiting for interactive input. To resolve this, you would typically re-run the command with non-interactive flags such as `--no-input` or `-y`, ensuring the WebAssembly toolchain proceeds without user intervention. ## What to do when a WebAssembly command is genuinely slow? When Atlas diagnoses a WebAssembly command as genuinely slow, rather than blocked, the solution is to retry it with a larger timeout value. The `shell_metadata` block will provide clear instructions, including the timeout in milliseconds, allowing you to adjust for complex `wasm-pack build` processes or extensive `wasm-pack test` suites that legitimately require more than a few seconds to complete in 2026. If Atlas's `bash` tool determines that your `wasm-pack` command, such as `wasm-pack build --target web` or a lengthy `wasm-pack test` run, is genuinely slow and not blocked on input, the `shell_metadata` output will instruct you to retry the command with an increased timeout. This is common for operations involving significant compilation, optimization, or extensive test execution within the WebAssembly ecosystem. Atlas's message will specify the timeout in milliseconds, allowing you to easily adjust the `bash` tool's parameters for subsequent runs, ensuring that legitimate long-running processes are given sufficient time to complete without being prematurely terminated. ## How does Atlas ensure safety and review for WebAssembly changes? Atlas ensures safety and review for WebAssembly development through a multi-stage approval process, including permission-gated tool calls and unified diffs. Every Atlas tool call, whether it's running `rustfmt` or modifying `Cargo.toml`, is permission-gated against allow, ask, and deny rules, providing a robust safety net for developers in 2026. Atlas is built with developer safety and control as a core principle. Before any tool, including `bash` for running `wasm-pack test` or `read` for inspecting `Cargo.toml`, is executed, it is permission-gated against your configured allow, ask, and deny rules. Furthermore, Atlas drafts its plan in a read-only plan agent, asking for your approval before switching to a build agent that can make changes. For any proposed file edits, such as adjusting `#[wasm_bindgen]` exports or modifying `wasm32-wasip2` target configurations, Atlas computes a unified diff and surfaces it for your explicit approval before writing to disk. This granular control ensures that all changes to your WebAssembly codebase are transparent and intentional, preventing unexpected modifications. ## Steps 1. Run your WebAssembly command through Atlas's `bash` tool, for example: `atlas bash "wasm-pack test --node"`. 2. Examine the `shell_metadata` block in Atlas's output when the command is killed to understand the diagnosis. 3. If Atlas explicitly states the `wasm-pack` command is waiting for interactive input, re-run it with non-interactive flags like `--no-input` or `-y`, for instance: `atlas bash "wasm-pack build --target web --no-input"`. 4. If the `shell_metadata` indicates the `wasm-pack` command is genuinely slow, retry it with a larger timeout value in milliseconds, as Atlas instructs. 5. If you manually aborted the command, verify the `shell_metadata` block states "User aborted the command" to distinguish it from an Atlas-imposed timeout. ## FAQ ### How do I debug a hanging `wasm-pack test` in Atlas? Run `atlas bash "wasm-pack test --node"`. Atlas will execute the command, and if it hangs, the `shell_metadata` block in the output will diagnose whether it's blocked on input or genuinely slow, guiding your next steps. ### What does "blocked on interactive input" mean for a WebAssembly build? For a `wasm-pack build` or `cargo (wasm-bindgen)` command, it means the process is waiting for user input (like a confirmation prompt) and will not proceed. Atlas explicitly identifies this in the `shell_metadata` output, preventing indefinite waits. ### Can Atlas help with slow `wasm-bindgen` compilation? Yes, if `cargo (wasm-bindgen)` compilation is genuinely slow, Atlas's `bash` tool will time it out and suggest retrying with a larger timeout value in milliseconds, helping you manage long-running builds efficiently. ### How does Atlas prevent unwanted changes to my `Cargo.toml`? Atlas operates with permission-gated tool calls and drafts a plan in a read-only agent. Any proposed changes, such as to `Cargo.toml` or `#[wasm_bindgen]` exports, generate a unified diff for your approval before being written. ### What are the non-interactive flags for `wasm-pack`? Common non-interactive flags for `wasm-pack` commands include `--no-input` or `-y` (for "yes"). Using these prevents the command from prompting for user interaction, which can unblock a hanging process in automated environments. ### How does Atlas know if I aborted a WebAssembly command myself? If you manually interrupt a `wasm-pack` command running through Atlas's `bash` tool, the `shell_metadata` block will explicitly state "User aborted the command," distinguishing your interrupt from an Atlas-imposed timeout. ### Does Atlas support `wasm32-wasip2` target configurations? Yes, Atlas is designed to read and understand your `wasm32-wasip2` target configurations, along with `#[wasm_bindgen]` exports and generated JS glue, providing context-aware assistance for your WebAssembly projects. --- Canonical HTML: https://runatlas.sh/resources/stacks/diagnose-a-hanging-or-long-running-command-in-webassembly Source of truth: aeo_pages row `/resources/stacks/diagnose-a-hanging-or-long-running-command-in-webassembly` (segment: Stacks) (this file is generated from it, never hand-edited). Licence: Atlas is proprietary with a free core. It is not open source and there is no public source repository.