| name | write-script-bun |
| description | MUST use when writing Bun/TypeScript scripts. |
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 — generate .script.yaml and .lock files for the script you modified.wmill sync push — deploy local changes to the workspace. Only suggest/run this 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.
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 sync push and wmill generate-metadata modify workspace state or local files — only run these when the user explicitly asks; otherwise tell them which to run.
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)
Bun runtime with full npm ecosystem and fastest execution.
Structure
Export a single async function called main:
export async function main(param1: string, param2: number) {
return { result: param1, count: param2 };
}
Do not call the main function. Libraries are installed automatically.
Resource Types
On Windmill, credentials and configuration are stored in resources and passed as parameters to main.
Use the RT namespace for resource types:
export async function main(stripe: RT.Stripe) {
}
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
import Stripe from "stripe";
import { someFunction } from "some-package";
Prefer //native when the runtime allows it
If a script only needs fetch and the JavaScript standard library — including when it uses windmill-client — prefer making it a native script: add //native as the first line and write it with the write-script-bunnative skill. Native scripts run on a lightweight V8 isolate, start faster, and parallelize heavily. windmill-client works on the native worker (its calls go over fetch), so needing the Windmill client is not a reason to avoid //native. Use the regular bun language only when the code (or a dependency) needs Node/Bun runtime APIs — node:* modules, the filesystem, child processes, or native addons.
Windmill Client
Import the windmill client for platform interactions:
import * as wmill from "windmill-client";
Prefer windmill-client over raw fetch for anything that talks to Windmill — reading resources/variables/states, running scripts and flows, S3 object operations, etc. It handles auth, the workspace, and the base URL for you, so you don't hand-roll URLs or tokens. Reserve 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 to use instead of guessing or falling back to fetch.
Preprocessor Scripts
For preprocessor scripts, the function should be named preprocessor and receives an event parameter:
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
import * as wmill from "windmill-client";
export async function main(file: wmill.S3Object) {
const content = await wmill.loadS3File(file);
}
S3 operations
import * as wmill from "windmill-client";
const content: Uint8Array = await wmill.loadS3File(s3object);
const blob: Blob = await wmill.loadS3FileStream(s3object);
const result: wmill.S3Object = await wmill.writeS3File(
s3object,
fileContent,
s3ResourcePath
);
TypeScript SDK (windmill-client)
Import: import * as wmill from 'windmill-client'
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
/**
- @deprecated Use runScriptByPath or runScriptByHash instead
*/
async runScript(path: string | null = null, hash_: string | null = null, args: Record<string, any> | null = null, verbose: boolean = false): 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
- @returns Script execution result
*/
async runScriptByPath(path: string, args: Record<string, any> | null = null, verbose: boolean = false): 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
- @returns Script execution result
*/
async runScriptByHash(hash_: string, args: Record<string, any> | null = null, verbose: boolean = false): 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
- @returns Flow execution result
*/
async runFlow(path: string | null = null, args: Record<string, any> | null = null, verbose: boolean = false): 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
/**
- @deprecated Use runScriptByPathAsync or runScriptByHashAsync instead
*/
async runScriptAsync(path: string | null, hash_: string | null, args: Record<string, any> | null, scheduledInSeconds: number | null = null): 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)
- @returns Job ID of the created job
*/
async runScriptByPathAsync(path: string, args: Record<string, any> | null = null, scheduledInSeconds: number | 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)
- @returns Job ID of the created job
*/
async runScriptByHashAsync(hash_: string, args: Record<string, any> | null = null, scheduledInSeconds: number | 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)
- @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): 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
- @deprecated use setState instead
*/
async setInternalState(state: any): 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 internal state
- @deprecated use getState instead
*/
async getInternalState(): 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
- @returns signed s3 objects
*/
async signS3Objects(s3objects: S3Object[]): Promise<S3Object[]>
/**
- Sign S3 object to be used by anonymous users in public apps
- @param s3object s3 object to sign
- @returns signed s3 object
*/
async signS3Object(s3object: S3Object): 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
- @returns list of signed public URLs
*/
async getPresignedS3PublicUrls(s3Objects: S3Object[], { baseUrl }: { baseUrl?: string } = {}): Promise<string[]>
/**
- Generate a presigned public URL for an S3 object. If the S3 object is not signed yet, it will be signed first.
- @param s3Object s3 object to sign
- @returns signed public URL
*/
async getPresignedS3PublicUrl(s3Objects: S3Object, { baseUrl }: { baseUrl?: string } = {}): Promise
/**
/**
- @deprecated use getResumeUrls instead
*/
getResumeEndpoints(approver?: string): Promise<{
approvalPage: string;
resume: string;
cancel: string;
}>
/**
- Get an OIDC jwt token for auth to external services (e.g: Vault, AWS) (ee only)
- @param audience audience of the token
- @param expiresIn Optional number of seconds until the token expires
- @returns jwt token
*/
async getIdToken(audience: string, expiresIn?: number): Promise
/**
- Convert a base64-encoded string to Uint8Array
- @param data - Base64-encoded string
- @returns Decoded Uint8Array
*/
base64ToUint8Array(data: string): Uint8Array
/**
- Convert a Uint8Array to base64-encoded string
- @param arrayBuffer - Uint8Array to encode
- @returns Base64-encoded string
*/
uint8ArrayToBase64(arrayBuffer: Uint8Array): string
/**
- Get email from workspace username
- This method is particularly useful for apps that require the email address of the viewer.
- Indeed, in the viewer context, WM_USERNAME is set to the username of the viewer but WM_EMAIL is set to the email of the creator of the app.
- @param username
- @returns email address
*/
async usernameToEmail(username: string): Promise
/**
- Sends an interactive approval request via Slack, allowing optional customization of the message, approver, and form fields.
- [Enterprise Edition Only] To include form fields in the Slack approval request, go to Advanced -> Suspend -> Form
- and define a form. Learn more at Windmill Documentation.
- @param {Object} options - The configuration options for the Slack approval request.
- @param {string} options.slackResourcePath - The path to the Slack resource in Windmill.
- @param {string} options.channelId - The Slack channel ID where the approval request will be sent.
- @param {string} [options.message] - Optional custom message to include in the Slack approval request.
- @param {string} [options.approver] - Optional user ID or name of the approver for the request.
- @param {DefaultArgs} [options.defaultArgsJson] - Optional object defining or overriding the default arguments to a form field.
- @param {Enums} [options.dynamicEnumsJson] - Optional object overriding the enum default values of an enum form field.
- @param {string} [options.resumeButtonText] - Optional text for the resume button.
- @param {string} [options.cancelButtonText] - Optional text for the cancel button.
- @returns {Promise} Resolves when the Slack approval request is successfully sent.
- @throws {Error} If the function is not called within a flow or flow preview.
- @throws {Error} If the
JobService.getSlackApprovalPayload call fails.
- Usage Example:
-
- await requestInteractiveSlackApproval({
- slackResourcePath: "/u/alex/my_slack_resource",
- channelId: "admins-slack-channel",
- message: "Please approve this request",
- approver: "approver123",
- defaultArgsJson: { key1: "value1", key2: 42 },
- dynamicEnumsJson: { foo: ["choice1", "choice2"], bar: ["optionA", "optionB"] },
- resumeButtonText: "Resume",
- cancelButtonText: "Cancel",
- });
-
- Note: This function requires execution within a Windmill flow or flow preview.
*/
async requestInteractiveSlackApproval({ slackResourcePath, channelId, message, approver, defaultArgsJson, dynamicEnumsJson, resumeButtonText, cancelButtonText, }: SlackApprovalOptions): Promise
/**
- Sends an interactive approval request via Teams, allowing optional customization of the message, approver, and form fields.
- [Enterprise Edition Only] To include form fields in the Teams approval request, go to Advanced -> Suspend -> Form
- and define a form. Learn more at Windmill Documentation.
- @param {Object} options - The configuration options for the Teams approval request.
- @param {string} options.teamName - The Teams team name where the approval request will be sent.
- @param {string} options.channelName - The Teams channel name where the approval request will be sent.
- @param {string} [options.message] - Optional custom message to include in the Teams approval request.
- @param {string} [options.approver] - Optional user ID or name of the approver for the request.
- @param {DefaultArgs} [options.defaultArgsJson] - Optional object defining or overriding the default arguments to a form field.
- @param {Enums} [options.dynamicEnumsJson] - Optional object overriding the enum default values of an enum form field.
- @returns {Promise} Resolves when the Teams approval request is successfully sent.
- @throws {Error} If the function is not called within a flow or flow preview.
- @throws {Error} If the
JobService.getTeamsApprovalPayload call fails.
- Usage Example:
-
- await requestInteractiveTeamsApproval({
- teamName: "admins-teams",
- channelName: "admins-teams-channel",
- message: "Please approve this request",
- approver: "approver123",
- defaultArgsJson: { key1: "value1", key2: 42 },
- dynamicEnumsJson: { foo: ["choice1", "choice2"], bar: ["optionA", "optionB"] },
- });
-
- Note: This function requires execution within a Windmill flow or flow preview.
*/
async requestInteractiveTeamsApproval({ teamName, channelName, message, approver, defaultArgsJson, dynamicEnumsJson, }: TeamsApprovalOptions): Promise
/**
- Parse an S3 object from URI string or record format
- @param s3Object - S3 object as URI string (s3://storage/key) or record
- @returns S3 object record with storage and s3 key
*/
parseS3Object(s3Object: S3Object): S3ObjectRecord
setWorkflowCtx(ctx: WorkflowCtx | null): void
async sleep(seconds: number): Promise
async step(name: string, fn: () => T | Promise): Promise
/**
- Create a task that dispatches to a separate Windmill script.
- @example
- const extract = taskScript("f/data/extract");
- // inside workflow: await extract({ url: "https://..." })
*/
taskScript(path: string, options?: TaskOptions): (...args: any[]) => PromiseLike
/**
- Create a task that dispatches to a separate Windmill flow.
- @example
- const pipeline = taskFlow("f/etl/pipeline");
- // inside workflow: await pipeline({ input: data })
*/
taskFlow(path: string, options?: TaskOptions): (...args: any[]) => PromiseLike
/**
- Mark an async function as a workflow-as-code entry point.
- The function must be deterministic: given the same inputs it must call
- tasks in the same order on every replay. Branching on task results is fine
- (results are replayed from checkpoint), but branching on external state
- (current time, random values, external API calls) must use
step() to
- checkpoint the value so replays see the same result.
*/
workflow(fn: (...args: any[]) => Promise): void
/**
- Suspend the workflow and wait for an external approval.
- Use
getResumeUrls() (wrapped in step()) to obtain resume/cancel/approvalPage
- URLs before calling this function.
- @example
- const urls = await step("urls", () => getResumeUrls());
- await step("notify", () => sendEmail(urls.approvalPage));
- const { value, approver } = await waitForApproval({ timeout: 3600 });
*/
waitForApproval(options?: { timeout?: number; form?: object; selfApproval?: boolean; }): PromiseLike<{ value: any; approver: string; approved: boolean }>
/**
- Process items in parallel with optional concurrency control.
- Each item is processed by calling
fn(item), which should be a task().
- Items are dispatched in batches of
concurrency (default: all at once).
- @example
- const process = task(async (item: string) => { ... });
- const results = await parallel(items, process, { concurrency: 5 });
*/
async parallel<T, R>(items: T[], fn: (item: T) => PromiseLike | R, options?: { concurrency?: number },): Promise<R[]>
/**
- Commit Kafka offsets for a trigger with auto_commit disabled.
- @param triggerPath - Path to the Kafka trigger (from event.wm_trigger.trigger_path)
- @param topic - Kafka topic name (from event.topic)
- @param partition - Partition number (from event.partition)
- @param offset - Message offset to commit (from event.offset)
*/
async commitKafkaOffsets(triggerPath: string, topic: string, partition: number, offset: number,): Promise
/**
/**
