Add support for "use step" functions in class instance methods

[TooTallNate]

Added support for "use step" directive in class instance methods, allowing instance methods to be used as workflow steps.

What changed?

• Modified the SWC plugin to recognize and transform instance methods with the "use step" directive
• Added registration logic for instance method steps using ClassName.prototype.methodName
• Implemented proper serialization of class instances to preserve the this context across workflow/step boundaries
• Added comprehensive end-to-end tests for instance method steps
• Updated error handling to allow "use step" in instance methods while still preventing "use workflow" in instance methods

How to test?

The PR includes a new end-to-end test instanceMethodStepWorkflow that demonstrates the functionality:

1. Run the e2e tests to verify the new instance method step functionality
2. The test creates a Counter class with instance methods marked as steps
3. It verifies that the instance methods can be called as steps with proper serialization of the this context
4. It also verifies that multiple instances of the same class can be used independently

Why make this change?

This change enables a more natural object-oriented programming model when working with workflows. Previously, only static methods, standalone functions, and object methods could be marked as steps. Now, developers can create classes with instance methods that are steps, allowing for better encapsulation and more intuitive code organization. This is particularly useful for complex workflows that need to maintain state across multiple step invocations.

[changeset-bot]

🦋 Changeset detected

Latest commit: 16dd859

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 16 packages

Name	Type
@workflow/swc-plugin	Patch
@workflow/astro	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/nest	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
workflow	Patch
@workflow/vite	Patch
@workflow/world-testing	Patch
@workflow/docs-typecheck	Patch
@workflow/nuxt	Patch
@workflow/core	Patch
@workflow/web-shared	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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Project	Deployment	Actions	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
example-nextjs-workflow-webpack	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
example-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-astro-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-express-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-fastify-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-hono-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-nitro-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-nuxt-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-sveltekit-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workbench-vite-workflow	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workflow-docs	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am
workflow-nest	Ready	Preview, Comment, Open in v0	Feb 3, 2026 8:00am

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	479	0	38	517
✅ 💻 Local Development	438	0	32	470
✅ 📦 Local Production	438	0	32	470
✅ 🐘 Local Postgres	438	0	32	470
✅ 🪟 Windows	47	0	0	47
❌ 🌍 Community Worlds	31	169	0	200
✅ 📋 Other	129	0	12	141
Total	2000	169	146	2315

❌ Failed Tests

🌍 Community Worlds (169 failed)

mongodb (42 failed):

• addTenWorkflow
• addTenWorkflow
• should work with react rendering in step
• promiseAllWorkflow
• promiseRaceWorkflow
• promiseAnyWorkflow
• readableStreamWorkflow
• hookWorkflow
• webhookWorkflow
• sleepingWorkflow
• nullByteWorkflow
• workflowAndStepMetadataWorkflow
• outputStreamWorkflow
• outputStreamInsideStepWorkflow - getWritable() called inside step functions
• fetchWorkflow
• promiseRaceStressTestWorkflow
• error handling error propagation workflow errors nested function calls preserve message and stack trace
• error handling error propagation workflow errors cross-file imports preserve message and stack trace
• error handling error propagation step errors basic step error preserves message and stack trace
• error handling error propagation step errors cross-file step error preserves message and function names in stack
• error handling retry behavior regular Error retries until success
• error handling retry behavior FatalError fails immediately without retries
• error handling retry behavior RetryableError respects custom retryAfter delay
• error handling retry behavior maxRetries=0 disables retries
• error handling catchability FatalError can be caught and detected with FatalError.is()
• hookCleanupTestWorkflow - hook token reuse after workflow completion
• concurrent hook token conflict - two workflows cannot use the same hook token simultaneously
• stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars)
• stepFunctionWithClosureWorkflow - step function with closure variables passed as argument
• closureVariableWorkflow - nested step functions with closure variables
• spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step
• pathsAliasWorkflow - TypeScript path aliases resolve correctly
• Calculator.calculate - static workflow method using static step methods from another class
• AllInOneService.processNumber - static workflow method using sibling static step methods
• ChainableService.processWithThis - static step methods using this to reference the class
• thisSerializationWorkflow - step function invoked with .call() and .apply()
• customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE
• instanceMethodStepWorkflow - instance methods with "use step" directive
• crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context
• pages router addTenWorkflow via pages router
• pages router promiseAllWorkflow via pages router
• pages router sleepingWorkflow via pages router

redis (42 failed):

• addTenWorkflow
• addTenWorkflow
• should work with react rendering in step
• promiseAllWorkflow
• promiseRaceWorkflow
• promiseAnyWorkflow
• readableStreamWorkflow
• hookWorkflow
• webhookWorkflow
• sleepingWorkflow
• nullByteWorkflow
• workflowAndStepMetadataWorkflow
• outputStreamWorkflow
• outputStreamInsideStepWorkflow - getWritable() called inside step functions
• fetchWorkflow
• promiseRaceStressTestWorkflow
• error handling error propagation workflow errors nested function calls preserve message and stack trace
• error handling error propagation workflow errors cross-file imports preserve message and stack trace
• error handling error propagation step errors basic step error preserves message and stack trace
• error handling error propagation step errors cross-file step error preserves message and function names in stack
• error handling retry behavior regular Error retries until success
• error handling retry behavior FatalError fails immediately without retries
• error handling retry behavior RetryableError respects custom retryAfter delay
• error handling retry behavior maxRetries=0 disables retries
• error handling catchability FatalError can be caught and detected with FatalError.is()
• hookCleanupTestWorkflow - hook token reuse after workflow completion
• concurrent hook token conflict - two workflows cannot use the same hook token simultaneously
• stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars)
• stepFunctionWithClosureWorkflow - step function with closure variables passed as argument
• closureVariableWorkflow - nested step functions with closure variables
• spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step
• pathsAliasWorkflow - TypeScript path aliases resolve correctly
• Calculator.calculate - static workflow method using static step methods from another class
• AllInOneService.processNumber - static workflow method using sibling static step methods
• ChainableService.processWithThis - static step methods using this to reference the class
• thisSerializationWorkflow - step function invoked with .call() and .apply()
• customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE
• instanceMethodStepWorkflow - instance methods with "use step" directive
• crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context
• pages router addTenWorkflow via pages router
• pages router promiseAllWorkflow via pages router
• pages router sleepingWorkflow via pages router

starter (43 failed):

• addTenWorkflow
• addTenWorkflow
• should work with react rendering in step
• promiseAllWorkflow
• promiseRaceWorkflow
• promiseAnyWorkflow
• readableStreamWorkflow
• hookWorkflow
• webhookWorkflow
• sleepingWorkflow
• nullByteWorkflow
• workflowAndStepMetadataWorkflow
• outputStreamWorkflow
• outputStreamInsideStepWorkflow - getWritable() called inside step functions
• fetchWorkflow
• promiseRaceStressTestWorkflow
• error handling error propagation workflow errors nested function calls preserve message and stack trace
• error handling error propagation workflow errors cross-file imports preserve message and stack trace
• error handling error propagation step errors basic step error preserves message and stack trace
• error handling error propagation step errors cross-file step error preserves message and function names in stack
• error handling retry behavior regular Error retries until success
• error handling retry behavior FatalError fails immediately without retries
• error handling retry behavior RetryableError respects custom retryAfter delay
• error handling retry behavior maxRetries=0 disables retries
• error handling catchability FatalError can be caught and detected with FatalError.is()
• hookCleanupTestWorkflow - hook token reuse after workflow completion
• concurrent hook token conflict - two workflows cannot use the same hook token simultaneously
• stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars)
• stepFunctionWithClosureWorkflow - step function with closure variables passed as argument
• closureVariableWorkflow - nested step functions with closure variables
• spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step
• health check (CLI) - workflow health command reports healthy endpoints
• pathsAliasWorkflow - TypeScript path aliases resolve correctly
• Calculator.calculate - static workflow method using static step methods from another class
• AllInOneService.processNumber - static workflow method using sibling static step methods
• ChainableService.processWithThis - static step methods using this to reference the class
• thisSerializationWorkflow - step function invoked with .call() and .apply()
• customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE
• instanceMethodStepWorkflow - instance methods with "use step" directive
• crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context
• pages router addTenWorkflow via pages router
• pages router promiseAllWorkflow via pages router
• pages router sleepingWorkflow via pages router

turso (42 failed):

• addTenWorkflow
• addTenWorkflow
• should work with react rendering in step
• promiseAllWorkflow
• promiseRaceWorkflow
• promiseAnyWorkflow
• readableStreamWorkflow
• hookWorkflow
• webhookWorkflow
• sleepingWorkflow
• nullByteWorkflow
• workflowAndStepMetadataWorkflow
• outputStreamWorkflow
• outputStreamInsideStepWorkflow - getWritable() called inside step functions
• fetchWorkflow
• promiseRaceStressTestWorkflow
• error handling error propagation workflow errors nested function calls preserve message and stack trace
• error handling error propagation workflow errors cross-file imports preserve message and stack trace
• error handling error propagation step errors basic step error preserves message and stack trace
• error handling error propagation step errors cross-file step error preserves message and function names in stack
• error handling retry behavior regular Error retries until success
• error handling retry behavior FatalError fails immediately without retries
• error handling retry behavior RetryableError respects custom retryAfter delay
• error handling retry behavior maxRetries=0 disables retries
• error handling catchability FatalError can be caught and detected with FatalError.is()
• hookCleanupTestWorkflow - hook token reuse after workflow completion
• concurrent hook token conflict - two workflows cannot use the same hook token simultaneously
• stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars)
• stepFunctionWithClosureWorkflow - step function with closure variables passed as argument
• closureVariableWorkflow - nested step functions with closure variables
• spawnWorkflowFromStepWorkflow - spawning a child workflow using start() inside a step
• pathsAliasWorkflow - TypeScript path aliases resolve correctly
• Calculator.calculate - static workflow method using static step methods from another class
• AllInOneService.processNumber - static workflow method using sibling static step methods
• ChainableService.processWithThis - static step methods using this to reference the class
• thisSerializationWorkflow - step function invoked with .call() and .apply()
• customSerializationWorkflow - custom class serialization with WORKFLOW_SERIALIZE/WORKFLOW_DESERIALIZE
• instanceMethodStepWorkflow - instance methods with "use step" directive
• crossContextSerdeWorkflow - classes defined in step code are deserializable in workflow context
• pages router addTenWorkflow via pages router
• pages router promiseAllWorkflow via pages router
• pages router sleepingWorkflow via pages router

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro	43	0	4
✅ example	43	0	4
✅ express	43	0	4
✅ fastify	43	0	4
✅ hono	43	0	4
✅ nextjs-turbopack	46	0	1
✅ nextjs-webpack	46	0	1
✅ nitro	43	0	4
✅ nuxt	43	0	4
✅ sveltekit	43	0	4
✅ vite	43	0	4

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable	43	0	4
✅ express-stable	43	0	4
✅ fastify-stable	43	0	4
✅ hono-stable	43	0	4
✅ nextjs-turbopack-stable	47	0	0
✅ nextjs-webpack-stable	47	0	0
✅ nitro-stable	43	0	4
✅ nuxt-stable	43	0	4
✅ sveltekit-stable	43	0	4
✅ vite-stable	43	0	4

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable	43	0	4
✅ express-stable	43	0	4
✅ fastify-stable	43	0	4
✅ hono-stable	43	0	4
✅ nextjs-turbopack-stable	47	0	0
✅ nextjs-webpack-stable	47	0	0
✅ nitro-stable	43	0	4
✅ nuxt-stable	43	0	4
✅ sveltekit-stable	43	0	4
✅ vite-stable	43	0	4

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable	43	0	4
✅ express-stable	43	0	4
✅ fastify-stable	43	0	4
✅ hono-stable	43	0	4
✅ nextjs-turbopack-stable	47	0	0
✅ nextjs-webpack-stable	47	0	0
✅ nitro-stable	43	0	4
✅ nuxt-stable	43	0	4
✅ sveltekit-stable	43	0	4
✅ vite-stable	43	0	4

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack	47	0	0

❌ 🌍 Community Worlds

App	Passed	Failed	Skipped
✅ mongodb-dev	3	0	0
❌ mongodb	5	42	0
✅ redis-dev	3	0	0
❌ redis	5	42	0
✅ starter-dev	3	0	0
❌ starter	4	43	0
✅ turso-dev	3	0	0
❌ turso	5	42	0

✅ 📋 Other

App	Passed	Failed	Skipped
✅ e2e-local-dev-nest-stable	43	0	4
✅ e2e-local-postgres-nest-stable	43	0	4
✅ e2e-local-prod-nest-stable	43	0	4

---

📋 View full workflow run

[TooTallNate]

• Add support for "use step" functions in class instance methods #777 : 2 dependent PRs (#876 , #899 ) 👈 (View in Graphite)
• Add discovered serializable classes in all context modes #874
• Ensure class serialization / deserialization only happens in the proper global context #873
• Fix class ID generation when class is bound to a variable #872
• Add discovery for custom classes with workflow serialization #859
• main

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