write-script-bunnative

CLI Commands

Place scripts in a folder.

After writing, tell the user which command fits what they want to do:

• wmill script preview <script_path> — default when iterating on a local script. Runs the local file without deploying.
• wmill script run <path> — runs the script already deployed in the workspace. Use only when the user explicitly wants to test the deployed version, not local edits.
• wmill generate-metadata — regenerate the local .script.yaml (input schema) and .lock (resolved dependencies) for scripts you changed, and refresh their content hashes in wmill-lock.yaml. Local files only — not a deploy. See "Keep metadata in sync" below.
• Deploy local changes to the workspace — via git push or wmill sync push depending on how the repo is wired (see the Deploying section in AGENTS.wmill.md). Only suggest/run a deploy when the user explicitly asks to deploy/publish/push — not when they say "run", "try", or "test".

Preview vs run — choose by intent, not habit

If the user says "run the script", "try it", "test it", "does it work" while there are local edits to the script file, use script preview. Do NOT push the script to then script run it — pushing is a deploy, and deploying just to test overwrites the workspace version with untested changes.

Only use script run when:

• The user explicitly says "run the deployed version" / "run what's on the server".
• There is no local script being edited (you're just invoking an existing script).

Only use sync push when:

• The user explicitly asks to deploy, publish, push, or ship.
• The preview has already validated the change and the user wants it in the workspace.

Keep metadata in sync after editing

wmill-lock.yaml tracks a content hash for each item. Editing a script's content — most importantly adding or removing an import or changing main's arguments — invalidates that hash and leaves the .lock, the .script.yaml input schema, and the hash row out of date. Run wmill generate-metadata (scoped to what you touched) after such edits so the resolved lock, the auto-generated args UI (driven by .script.yaml), and wmill-lock.yaml all match the code. Leaving them stale produces spurious diffs in git-sync and CI.

This only writes local files (it is not a deploy), but it re-resolves dependencies, so it can bump unpinned versions (the same as deploying from the UI; expected, not a bug). So by default offer it and run it once the user agrees, rather than running it silently after every edit — unless the project's AGENTS.md opts into running metadata automatically (see the "Keeping metadata in sync" preference there). Either way YOU run the command, not the user. After running it, diff the regenerated .lock / .script.lock files and tell the user which dependency versions changed (e.g. requests 2.31.0 → 2.32.0), so they can catch an unwanted bump before deploying — even under Metadata: auto, since it's information, not a confirmation gate. Pin versions in code to keep them fixed.

With no path argument, generate-metadata regenerates only the items whose content hash drifted — not everything. Imports propagate: editing a script that others import marks every importer stale too, so a one-line change to a shared module can regenerate many locks (by design — their locks must reflect the imported code). If it touches more than you expect, run wmill generate-metadata --dry-run — it lists each stale item with a reason (content changed or depends on <path>) without changing anything — then narrow with a path argument (wmill generate-metadata f/foo) or --strict-folder-boundaries.

If the on-disk .lock and .script.yaml are already correct and only wmill-lock.yaml needs its hashes refreshed (hash drift, or bootstrapping missing entries), use wmill generate-metadata rehash — it re-records hashes from disk with no backend round-trip and no dependency changes.

After writing — offer to test, don't wait passively

If the user hasn't already told you to run/test/preview the script, offer it as a one-sentence next step (e.g. "Want me to run wmill script preview with sample args?"). Do not present a multi-option menu.

If the user already asked to test/run/try the script in their original request, skip the offer and just execute wmill script preview <path> -d '<args>' directly — pick plausible args from the script's declared parameters. The shape varies by language: main(...) for code languages, the SQL dialect's own placeholder syntax ($1 for PostgreSQL, ? for MySQL/Snowflake, @P1 for MSSQL, @name for BigQuery, etc.), positional $1, $2, … for Bash, param(...) for PowerShell.

wmill script preview does not deploy, but it still executes script code and may cause side effects; run it yourself when the user asked to test/preview (or after confirming that execution is intended). wmill generate-metadata does not deploy either — it only writes local files (locks, schemas, hashes) — but offer it before running (or run automatically if the project's AGENTS.md opts in), per "Keep metadata in sync" above. Deploying to the workspace (git push or wmill sync push depending on how the repo is wired — see the Deploying section) is the only step that mutates remote state — do it only when the user explicitly asks to deploy/publish/push.

For a visual open-the-script-in-the-dev-page preview (rather than script preview's run-and-print-result), use the preview skill.

Use wmill resource-type list --schema to discover available resource types.

TypeScript (Bun Native)

Native TypeScript execution. Native scripts are Bun scripts that run on the native worker — a lightweight V8 isolate that exposes fetch and the JavaScript standard library — and can be heavily parallelized. Every script MUST start with //native on its first line so Windmill routes it to the native worker; without it the exact same script runs on the regular Bun worker. You may import npm packages and other Windmill scripts (e.g. ./helper.ts) — imports are resolved and bundled just like a regular Bun script — as long as everything (your code and its dependencies) relies only on fetch and the standard library. Libraries that need Node/Bun runtime APIs (filesystem, node:* modules, child processes, native addons) will not work on the native worker; use the regular bun language for those.

Structure

Export a single async function called main:

//native
export async function main(param1: string, param2: number) {
  // Your code here
  return { result: param1, count: param2 };
}

Do not call the main function.

Resource Types

On Windmill, credentials and configuration are stored in resources and passed as parameters to main.

Use the RT namespace for resource types:

//native
export async function main(stripe: RT.Stripe) {
  // stripe contains API key and config from the resource
}

Only use resource types if you need them to satisfy the instructions. Always use the RT namespace.

Before using a resource type, check the rt.d.ts file in the project root to see all available resource types and their fields. This file is generated by wmill resource-type generate-namespace.

Imports

The constraint is the runtime, not the import list. You may import npm packages and relative Windmill scripts; they are resolved and bundled exactly like a regular Bun script. But the native worker only provides fetch and the JavaScript standard library, so any imported code must work using only those. Anything requiring Node/Bun built-ins (node:fs, child_process, the Bun API, native modules) belongs in a regular bun script instead. Use the globally available fetch for HTTP:

//native
export async function main(url: string) {
  const response = await fetch(url);
  return await response.json();
}

Windmill Client

windmill-client works on the native worker (its calls go over fetch), so use it as the preferred way to talk to Windmill — reading resources/variables/states, running scripts and flows, and the S3 helpers below (loadS3File, loadS3FileStream, writeS3File, S3Object). It handles auth, the workspace, and the base URL for you. Reserve raw fetch for calling external HTTP APIs that aren't Windmill.

The full windmill-client API reference (every exported function and its signature) is included in this skill below — consult it for the exact method instead of hand-rolling a fetch against the Windmill API.

Preprocessor Scripts

For preprocessor scripts, the function should be named preprocessor and receives an event parameter:

//native
type Event = {
  kind:
    | "webhook"
    | "http"
    | "websocket"
    | "kafka"
    | "email"
    | "nats"
    | "postgres"
    | "sqs"
    | "mqtt"
    | "gcp";
  body: any;
  headers: Record<string, string>;
  query: Record<string, string>;
};

export async function preprocessor(event: Event) {
  return {
    param1: event.body.field1,
    param2: event.query.id,
  };
}

S3 Object Operations

Windmill provides built-in support for S3-compatible storage operations. The wmill.S3Object type covers both the s3://storage/key URI form (s3:///key for the workspace default storage) and the { s3, storage? } record form — always use it instead of redefining your own.

Receiving an S3Object as a script parameter

//native
import * as wmill from "windmill-client";

export async function main(file: wmill.S3Object) {
  const content = await wmill.loadS3File(file);
  // ...
}

S3 operations

//native
import * as wmill from "windmill-client";

// Load file content from S3
const content: Uint8Array = await wmill.loadS3File(s3object);

// Load file as stream
const blob: Blob = await wmill.loadS3FileStream(s3object);

// Write file to S3
const result: wmill.S3Object = await wmill.writeS3File(
  s3object, // Target path (or undefined to auto-generate)
  fileContent, // string or Blob
  s3ResourcePath // Optional: specific S3 resource to use
);

TypeScript SDK (windmill-client)

Import: import * as wmill from 'windmill-client'

The client configures itself from the job's environment — base URL, token and credentials mode are all set before your code runs, so there is nothing to initialize and no reason to read WM_TOKEN or BASE_INTERNAL_URL and build an API URL yourself. Reconstructing that by hand only reintroduces details the client already handles. Call the SDK for anything Windmill, and use raw HTTP for third-party APIs.

The helpers below are the surface to prefer. For an endpoint none of them covers, import the generated service classes (JobService, ScriptService, ...) from 'windmill-client' — they are not listed here but they do exist. What does not exist is a helper name you guessed at: if it is neither listed below nor a service method, do not call it.

To know who is running the script, read the contextual variables rather than calling the API: process.env.WM_END_USER_EMAIL || process.env.WM_EMAIL. WM_END_USER_EMAIL is the app viewer when the run was triggered from an app and empty otherwise (both variables are always defined), WM_EMAIL is the user the job is permissioned as. WM_USERNAME is the matching username.

workerHasInternalServer(): boolean

/**

• Initialize the Windmill client with authentication token and base URL
• @param token - Authentication token (defaults to WM_TOKEN env variable)
• @param baseUrl - API base URL (defaults to BASE_INTERNAL_URL or BASE_URL env variable) */ setClient(token?: string, baseUrl?: string): void

/**

• Create a client configuration from env variables
• @returns client configuration */ getWorkspace(): string

/**

• Get a resource value by path
• @param path path of the resource, default to internal state path
• @param undefinedIfEmpty if the resource does not exist, return undefined instead of throwing an error
• @returns resource value */ async getResource(path?: string, undefinedIfEmpty?: boolean): Promise

/**

• Get the true root job id
• @param jobId job id to get the root job id from (default to current job)
• @returns root job id */ async getRootJobId(jobId?: string): Promise

/**

• Run a script synchronously by its path and wait for the result
• @param path - Script path in Windmill
• @param args - Arguments to pass to the script
• @param verbose - Enable verbose logging
• @param tag - Override the worker tag the job runs on
• @returns Script execution result */ async runScriptByPath(path: string, args: Record<string, any> | null = null, verbose: boolean = false, tag: string | null = null): Promise

/**

• Run a script synchronously by its hash and wait for the result
• @param hash_ - Script hash in Windmill
• @param args - Arguments to pass to the script
• @param verbose - Enable verbose logging
• @param tag - Override the worker tag the job runs on
• @returns Script execution result */ async runScriptByHash(hash_: string, args: Record<string, any> | null = null, verbose: boolean = false, tag: string | null = null): Promise

/**

• Append a text to the result stream
• @param text text to append to the result stream */ appendToResultStream(text: string): void

/**

• Stream to the result stream
• @param stream stream to stream to the result stream */ async streamResult(stream: AsyncIterable): Promise

/**

• Run a flow synchronously by its path and wait for the result
• @param path - Flow path in Windmill
• @param args - Arguments to pass to the flow
• @param verbose - Enable verbose logging
• @param tag - Override the worker tag the job runs on
• @returns Flow execution result */ async runFlow(path: string | null = null, args: Record<string, any> | null = null, verbose: boolean = false, tag: string | null = null): Promise

/**

• Wait for a job to complete and return its result
• @param jobId - ID of the job to wait for
• @param verbose - Enable verbose logging
• @returns Job result when completed */ async waitJob(jobId: string, verbose: boolean = false): Promise

/**

• Get the result of a completed job
• @param jobId - ID of the completed job
• @returns Job result */ async getResult(jobId: string): Promise

/**

• Get the result of a job if completed, or its current status
• @param jobId - ID of the job
• @returns Object with started, completed, success, and result properties */ async getResultMaybe(jobId: string): Promise

/**

• Cancel a queued or running job by ID.
• @param jobId - UUID of the job to cancel
• @param reason - Optional reason for cancellation
• @returns Response message from the cancel endpoint */ async cancelJob(jobId: string, reason: string | undefined = undefined): Promise

/**

• Run a script asynchronously by its path
• @param path - Script path in Windmill
• @param args - Arguments to pass to the script
• @param scheduledInSeconds - Schedule execution for a future time (in seconds)
• @param tag - Override the worker tag the job runs on
• @returns Job ID of the created job */ async runScriptByPathAsync(path: string, args: Record<string, any> | null = null, scheduledInSeconds: number | null = null, tag: string | null = null): Promise

/**

• Run a script asynchronously by its hash
• @param hash_ - Script hash in Windmill
• @param args - Arguments to pass to the script
• @param scheduledInSeconds - Schedule execution for a future time (in seconds)
• @param tag - Override the worker tag the job runs on
• @returns Job ID of the created job */ async runScriptByHashAsync(hash_: string, args: Record<string, any> | null = null, scheduledInSeconds: number | null = null, tag: string | null = null): Promise

/**

• Run a flow asynchronously by its path
• @param path - Flow path in Windmill
• @param args - Arguments to pass to the flow
• @param scheduledInSeconds - Schedule execution for a future time (in seconds)
• @param doNotTrackInParent - If false, tracks state in parent job (only use when fully awaiting the job)
• @param tag - Override the worker tag the job runs on
• @returns Job ID of the created job */ async runFlowAsync(path: string | null, args: Record<string, any> | null, scheduledInSeconds: number | null = null, // can only be set to false if this the job will be fully await and not concurrent with any other job // as otherwise the child flow and its own child will store their state in the parent job which will // lead to incorrectness and failures doNotTrackInParent: boolean = true, tag: string | null = null): Promise

/**

• Resolve a resource value in case the default value was picked because the input payload was undefined
• @param obj resource value or path of the resource under the format $res:path
• @returns resource value */ async resolveDefaultResource(obj: any): Promise

/**

• Get the state file path from environment variables
• @returns State path string */ getStatePath(): string

/**

• Set a resource value by path
• @param path path of the resource to set, default to state path
• @param value new value of the resource to set
• @param initializeToTypeIfNotExist if the resource does not exist, initialize it with this type */ async setResource(value: any, path?: string, initializeToTypeIfNotExist?: string): Promise

/**

• Set the state
• @param state state to set
• @param path Optional state resource path override. Defaults to getStatePath(). */ async setState(state: any, path?: string): Promise

/**

• Set the progress
• Progress cannot go back and limited to 0% to 99% range
• @param percent Progress to set in %
• @param jobId? Job to set progress for */ async setProgress(percent: number, jobId?: any): Promise

/**

• Get the progress
• @param jobId? Job to get progress from
• @returns Optional clamped between 0 and 100 progress value */ async getProgress(jobId?: any): Promise<number | null>

/**

• Set a flow user state
• @param key key of the state
• @param value value of the state */ async setFlowUserState(key: string, value: any, errorIfNotPossible?: boolean): Promise

/**

• Get a flow user state
• @param path path of the variable */ async getFlowUserState(key: string, errorIfNotPossible?: boolean): Promise

/**

• Get the state shared across executions
• @param path Optional state resource path override. Defaults to getStatePath(). */ async getState(path?: string): Promise

/**

• Get a variable by path
• @param path path of the variable
• @returns variable value */ async getVariable(path: string): Promise

/**

• Set a variable by path, create if not exist
• @param path path of the variable
• @param value value of the variable
• @param isSecretIfNotExist if the variable does not exist, create it as secret or not (default: false)
• @param descriptionIfNotExist if the variable does not exist, create it with this description (default: "") */ async setVariable(path: string, value: string, isSecretIfNotExist?: boolean, descriptionIfNotExist?: string): Promise

/**

• Build a PostgreSQL connection URL from a database resource
• @param path - Path to the database resource
• @returns PostgreSQL connection URL string */ async databaseUrlFromResource(path: string): Promise

async polarsConnectionSettings(s3_resource_path: string | undefined): Promise

async duckdbConnectionSettings(s3_resource_path: string | undefined): Promise

/**

• Get S3 client settings from a resource or workspace default
• @param s3_resource_path - Path to S3 resource (uses workspace default if undefined)
• @param workspace - Workspace to read from (defaults to the WM_WORKSPACE env var)
• @returns S3 client configuration settings */ async denoS3LightClientSettings(s3_resource_path: string | undefined, workspace: string | undefined = undefined): Promise

/**

• Load the content of a file stored in S3. If the s3ResourcePath is undefined, it will default to the workspace S3 resource.
• let fileContent = await wmill.loadS3FileContent(inputFile)
• // if the file is a raw text file, it can be decoded and printed directly:
• const text = new TextDecoder().decode(fileContentStream)
• console.log(text);
• @param workspace - Workspace to read from (defaults to the WM_WORKSPACE env var) */ async loadS3File(s3object: S3Object, s3ResourcePath: string | undefined = undefined, workspace: string | undefined = undefined): Promise<Uint8Array | undefined>

/**

• Load the content of a file stored in S3 as a stream. If the s3ResourcePath is undefined, it will default to the workspace S3 resource.
• let fileContentBlob = await wmill.loadS3FileStream(inputFile)
• // if the content is plain text, the blob can be read directly:
• console.log(await fileContentBlob.text());
• @param workspace - Workspace to read from (defaults to the WM_WORKSPACE env var) */ async loadS3FileStream(s3object: S3Object, s3ResourcePath: string | undefined = undefined, workspace: string | undefined = undefined): Promise<Blob | undefined>

/**

• Persist a file to the S3 bucket. If the s3ResourcePath is undefined, it will default to the workspace S3 resource.
• const s3object = await writeS3File(s3Object, "Hello Windmill!")
• const fileContentAsUtf8Str = (await s3object.toArray()).toString('utf-8')
• console.log(fileContentAsUtf8Str)
• @param workspace - Workspace to write to (defaults to the WM_WORKSPACE env var) */ async writeS3File(s3object: S3Object | undefined, fileContent: string | Blob, s3ResourcePath: string | undefined = undefined, contentType: string | undefined = undefined, contentDisposition: string | undefined = undefined, workspace: string | undefined = undefined): Promise

/**

• Permanently delete a file from S3 by key.
• await wmill.deleteS3File({ s3: "path/to/file.txt" })
• @param s3object - S3 object identifying the file to delete (must have s3 set)
• @param workspace - Workspace to delete from (defaults to the WM_WORKSPACE env var) */ async deleteS3File(s3object: S3Object, workspace: string | undefined = undefined): Promise

/**

• Sign S3 objects to be used by anonymous users in public apps
• @param s3objects s3 objects to sign
• @param expirySecs how long the signature stays valid, in seconds (default 43200 = 12h, clamped to [60, 604800])
• @returns signed s3 objects */ async signS3Objects(s3objects: S3Object[], { expirySecs }: { expirySecs?: number } = {}): Promise<S3Object[]>

/**

• Sign S3 object to be used by anonymous users in public apps
• @param s3object s3 object to sign
• @param expirySecs how long the signature stays valid, in seconds (default 43200 = 12h, clamped to [60, 604800])
• @returns signed s3 object */ async signS3Object(s3object: S3Object, { expirySecs }: { expirySecs?: number } = {}): Promise

/**

• Generate a presigned public URL for an array of S3 objects.
• If an S3 object is not signed yet, it will be signed first.
• @param s3Objects s3 objects to sign
• @param expirySecs how long the signature stays valid, in seconds (default 43200 = 12h, clamped to [60, 604800])
• @returns list of signed public URLs */ async getPresignedS3PublicUrls(s3Objects: S3Object[], { baseUrl, expirySecs }: { baseUrl?: string; expirySecs?: number } = {}): Promise<string[]>