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

[TooTallNate]

TL;DR

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: cae9a83

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

This PR includes changesets to release 13 packages

Name	Type
@workflow/swc-plugin	Patch
@workflow/astro	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
workflow	Patch
@workflow/world-testing	Patch
@workflow/docs-typecheck	Patch
@workflow/nuxt	Patch
@workflow/ai	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	Review	Updated (UTC)
example-nextjs-workflow-turbopack	Ready	Preview, Comment	Jan 14, 2026 10:28pm
example-nextjs-workflow-webpack	Ready	Preview, Comment	Jan 14, 2026 10:28pm
example-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-astro-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-express-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-fastify-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-hono-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-nitro-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-nuxt-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-sveltekit-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workbench-vite-workflow	Ready	Preview, Comment	Jan 14, 2026 10:28pm
workflow-docs	Ready	Preview, Comment	Jan 14, 2026 10:28pm

[github-actions]

🧪 E2E Test Results

❌ Some tests failed

Summary

	Passed	Failed	Skipped	Total
✅ ▲ Vercel Production	440	0	11	451
✅ 💻 Local Development	402	0	8	410
✅ 📦 Local Production	402	0	8	410
✅ 🐘 Local Postgres	402	0	8	410
❌ 🪟 Windows	40	1	0	41
❌ 🌍 Community Worlds	153	23	0	176
Total	1839	24	35	1898

❌ Failed Tests

🪟 Windows (1 failed)

nextjs-turbopack (1 failed):

• webhookWorkflow

🌍 Community Worlds (23 failed)

mongodb (1 failed):

• webhookWorkflow

redis (1 failed):

• webhookWorkflow

starter (20 failed):

• addTenWorkflow
• addTenWorkflow
• 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 catchability FatalError can be caught and detected with FatalError.is()
• hookCleanupTestWorkflow - hook token reuse after workflow completion
• stepFunctionPassingWorkflow - step function references can be passed as arguments (without closure vars)
• stepFunctionWithClosureWorkflow - step function with closure variables passed as argument
• 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

turso (1 failed):

• webhookWorkflow

Details by Category

✅ ▲ Vercel Production

App	Passed	Failed	Skipped
✅ astro	40	0	1
✅ example	40	0	1
✅ express	40	0	1
✅ fastify	40	0	1
✅ hono	40	0	1
✅ nextjs-turbopack	40	0	1
✅ nextjs-webpack	40	0	1
✅ nitro	40	0	1
✅ nuxt	40	0	1
✅ sveltekit	40	0	1
✅ vite	40	0	1

✅ 💻 Local Development

App	Passed	Failed	Skipped
✅ astro-stable	40	0	1
✅ express-stable	40	0	1
✅ fastify-stable	40	0	1
✅ hono-stable	40	0	1
✅ nextjs-turbopack-stable	41	0	0
✅ nextjs-webpack-stable	41	0	0
✅ nitro-stable	40	0	1
✅ nuxt-stable	40	0	1
✅ sveltekit-stable	40	0	1
✅ vite-stable	40	0	1

✅ 📦 Local Production

App	Passed	Failed	Skipped
✅ astro-stable	40	0	1
✅ express-stable	40	0	1
✅ fastify-stable	40	0	1
✅ hono-stable	40	0	1
✅ nextjs-turbopack-stable	41	0	0
✅ nextjs-webpack-stable	41	0	0
✅ nitro-stable	40	0	1
✅ nuxt-stable	40	0	1
✅ sveltekit-stable	40	0	1
✅ vite-stable	40	0	1

✅ 🐘 Local Postgres

App	Passed	Failed	Skipped
✅ astro-stable	40	0	1
✅ express-stable	40	0	1
✅ fastify-stable	40	0	1
✅ hono-stable	40	0	1
✅ nextjs-turbopack-stable	41	0	0
✅ nextjs-webpack-stable	41	0	0
✅ nitro-stable	40	0	1
✅ nuxt-stable	40	0	1
✅ sveltekit-stable	40	0	1
✅ vite-stable	40	0	1

❌ 🪟 Windows

App	Passed	Failed	Skipped
❌ nextjs-turbopack	40	1	0

❌ 🌍 Community Worlds

App	Passed	Failed	Skipped
✅ mongodb-dev	3	0	0
❌ mongodb	40	1	0
✅ redis-dev	3	0	0
❌ redis	40	1	0
✅ starter-dev	3	0	0
❌ starter	21	20	0
✅ turso-dev	3	0	0
❌ turso	40	1	0

---

📋 View full workflow run

---

❌ Some E2E test jobs failed:

• Vercel Prod: success
• Local Dev: success
• Local Prod: success
• Local Postgres: success
• Windows: failure

Check the workflow run for details.

[TooTallNate]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Add support for "use step" functions in class instance methods #777 👈 (View in Graphite)
• Add support for custom class instance serialization #762
• Add support for serializing this when invoking step functions #754
• Support class static methods with "use step" / "use workflow" #753
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

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🔧 Build Fix:

MDX syntax error: unexpected ! character on line 29. This appears to be invalid MDX code that should use {/* text */} for comments instead.

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Additional Suggestion:

Invalid MDX syntax: Vitepress-specific [!code highlight] comments cause MDX parsing errors and are not compatible with MDX rendering.