Published by Voxgig, which makes one of the two tools compared here. Facts checked against the first-party sources linked below. Corrections go to info@voxgig.com. Every page in this section follows the same scope and method.
On 17 September 2026 Speakeasy and Google published the Speakeasy generator as open source under AGPL-3.0, at github.com/speakeasy-api/openapi-generation. Google wrote that the provider behind its Gemini SDKs was acquired and abruptly announced its shutdown in May 2026, and that the open-source release now generates those SDKs. Speakeasy's own site leads with an AI control plane for enterprises; SDK generation continues as a product with a free account tier and quoted enterprise pricing.
Speakeasy is a commercial SDK generation company. You run a single CLI binary locally or in CI, authenticated against a workspace, and it produces SDKs into repositories you own. Since 17 September 2026 the generator behind that CLI is open source under AGPL-3.0. Speakeasy describes the repository as the development home for the generator and its templates, and points end users back to the CLI for everyday generation.
The SDK targets are C#, Go, Java, PHP, Python, Ruby, TypeScript and Unity. Beside them the generator produces Terraform providers, CLI applications, Postman collections and MCP servers in TypeScript, plus documentation, code samples and test suites.
Its design position is that OpenAPI is the source of truth and there should be no second definition format. Where the spec is not shaped the way you want the SDK shaped, you write an OpenAPI Overlay. An Overlay is an OpenAPI Initiative specification for a document of targeted edits applied over another document. Generation settings live in a gen.yaml, the pipeline in a workflow.yaml, and the usual deployment is a GitHub Action that regenerates and opens a pull request when the spec changes.
The license of the generated code is an election you make before generation runs. Under the free election the output is AGPL-3.0-only, and the generator writes a LICENSE and a NOTICE covering Speakeasy-authored material into it. With a commercial license token the SDK is yours to license on your own terms, and Speakeasy's documentation says SDKs generated through its platform are MIT by default. A free account generates one SDK of up to 50 API methods, a new account gets a fourteen-day trial of the business tier, and the pricing page lists one enterprise plan, priced on request.
Capabilities Speakeasy has that Voxgig does not, in enough detail to evaluate them.
This is the headline, and it deserves to be. If your API provisions anything, your larger customers want a Terraform provider. Hand-writing one is a specialized job most API teams have nobody for: resource and data-source schemas, plan and apply semantics, import, state upgrades, drift. Speakeasy generates one from the same description as the SDK. Voxgig does not generate a provider at all. If you need one, that alone is a complete reason to choose Speakeasy.
Most tools solve the my spec does not describe the library I want problem with a proprietary config file. Speakeasy uses Overlay, which is a published OpenAPI Initiative specification. The practical difference is that your customizations are a standard document other tools can read, and they stay useful if you leave. It is the better-behaved answer to that problem, and it is useful to understand even if you never buy the product.
The AGPL release changes what Speakeasy is. You can read the generator, fork it and run it from source with no account. If you change it and offer it as a service, the AGPL obliges you to publish the changes. The part to read twice is the output. Under the free election the SDK it generates is AGPL-3.0-only, with a LICENSE and NOTICE written in for Speakeasy's material. Only a commercial license token makes the SDK yours to license as you choose. For an API provider handing a library to customers, that election is the price of the product, and it is a clearer price than a seat count. Voxgig's generator is MIT and its output carries whatever license your repository does, with no election and no token in the pipeline.
Their TypeScript output validates responses at runtime with Zod rather than casting the JSON and hoping. When a server returns a field the spec did not promise, or omits one it did, you get an error at the boundary instead of a missing value three frames away. Voxgig's validate feature checks requests, and optionally responses, against the model's own field types, but it is opt-in and emits no schema. Speakeasy's validation is on by default, typed with Zod, and costs a runtime dependency, which is the trade they have chosen to make.
The CLI ships as a single binary rather than a Node or JVM dependency chain. That makes it usable in locked-down and air-gapped build environments, where most Node-based tooling, Voxgig included, needs work first. Running the open-source generator from source is a different matter: it needs Go, Node, npm, Docker and each target's own toolchain, which is why Speakeasy points end users at the CLI.
Their documentation on OpenAPI itself, linting rules, spec hygiene, the parts of the specification that generators actually choke on, is a genuine public good, widely cited, and useful whether or not you ever pay them. It is not a product feature, but it is a common route by which teams find the tool.
No partial ticks and no asterisks. If a tool has a feature, the table says it has it. Where a row would need a paragraph to be true, it is a paragraph somewhere else on this page instead of a row here.
| Speakeasy | Voxgig | |
|---|---|---|
| License | Generator AGPL-3.0. Generated SDKs AGPL-3.0-only under the free election, yours under a commercial license | Generator MIT. Generated SDKs are yours |
| Cost | Free under AGPL. A free account for one SDK of up to 50 methods, then a quoted enterprise plan | Free |
| Account needed | No for AGPL output from source. Yes for the CLI and for a commercial license | No |
| Language targets | 8, including Unity | 23 language targets, 20 bundled plus Dart, Haskell and Lean from the langpack |
| Terraform provider | Yes | No |
| MCP server | Yes, in TypeScript | Yes |
| CLI and REPL over your API | A CLI. No REPL | Both |
| Customization | OpenAPI Overlays, gen.yaml, custom code regions | Model, templates, components, features, targets, packages, all in your repo |
| Support | Commercial, with an SLA on paid plans | Community, or a paid API Experience engagement |
Novu publishes an SDK made with Speakeasy from version 3.19.0 of its definition. Voxgig built one from version 3.19.2, as Novu served it on 28 September 2026, and both were run against a mock of 3.19.2 on the same four steps: list, load, create, and remove. Voxgig's features are in the build and stay off until a client switches them on; the rows describe them switched on. Last measured 29 September 2026.
Speakeasy
@novu/api 3.19.1The TypeScript SDK Novu publishes on npm, generated with Speakeasy from version 3.19.0 of the same definition.
Voxgig
voxgig-sdk/novu-sdkBuilt on 29 September 2026 from version 3.19.2 of the same definition: eight targets from one run. A repository to build from, not a published package.
The definition: Novu's SDK definition, api.novu.co/openapi.sdk.yaml at version 3.19.2: OpenAPI 3.0.0, 102 paths, 149 operations, MIT. Its source.
| Speakeasy | Voxgig | |
|---|---|---|
| Operations callable | 149 methods, generated from version 3.19.0 | 148 of 149. The workflow PATCH has no method |
| Mock scenario | 2 of 4 steps right. Load and create failed Zod validation on the mock's placeholder values, which is a limit of the mock | 4 of 4 right |
| Response validation | Zod, on every response | Not in this build. The opt-in validate feature checks payloads against the model's field types |
| Retries | Backoff from 1 to 30 seconds on 408, 409, 429 and 5xx, for up to an hour | On 408, 425, 429, 500, 502, 503 and 504, honoring Retry-After |
| Timeouts | Client-wide and per call, with none by default | 30 seconds per attempt by default |
| Pagination | Cursor arguments passed by hand. A page iterator is defined but no method uses it | Page and cursor state carried between calls in ctrl.paging, with no iterator |
| Idempotency keys | Generated for every request by a custom hook, and kept across its retries | Generated for every mutating call, and kept across its retries |
| Rate limits | 429 retried, honoring Retry-After | A client-side token bucket, and Retry-After honored on 429 |
| Logging | A debug logger that logs method, URL, headers and body | Request and response logging, with auth headers redacted |
| Offline test mode | None | A mock transport seeded with your data, which the generated tests run on |
| Metrics | None | Per-operation counts and timings, with no OpenTelemetry |
| Cancellation | An AbortSignal per call, combined with the timeout | A signal stops stream() between items. Only the timeout aborts a request in flight |
| Hooks | Before-request, error and response hooks on the HTTP client | Custom features that hook every stage of a call |
| Errors | Classes chosen per operation by status and schema, all extending NovuError | One error class per SDK, carrying the HTTP status and a notFound flag |
| Speakeasy | Voxgig | |
|---|---|---|
| Package | @novu/api on npm | Not published. You build it from the repository |
| TypeScript package size | 9.26 MB in 3,908 files | 3.63 MB in 480 files |
| Runtime dependencies | 1: zod | None |
| Languages from this build | TypeScript | TypeScript, Python, PHP, Go, Ruby and Lua, plus a Go CLI and a Go MCP server |
| Shape | Namespaces by resource, such as novu.workflows and novu.subscribers, with a function per operation beside them | 59 entities. Subscriber lists, loads, creates, and removes subscribers, but several entities are still named after response schemas, such as ListTopicSubscriptionsResponseDto for a topic's subscriptions |
| Types | A type and a Zod schema per component, for requests and responses | An interface per entity, from the response schema. Create takes the response type, so a TypeScript create needs a cast |
| Tests | Not run here: the comparison used the published package | 548 generated TypeScript tests pass, as do the generated Go, Python, Ruby, Lua, and PHP suites |
The same calls in each, in TypeScript. Both samples type-check under strict mode against the SDK they name.
import { Novu } from '@novu/api'
const novu = new Novu({ secretKey: process.env.NOVU_SECRET_KEY })
const { result: page } = await novu.workflows.list({})
const { result: workflow } = await novu.workflows.get('onboarding')
const { result: created } = await novu.workflows.create({
name: 'Onboarding',
workflowId: 'onboarding',
steps: [],
})
await novu.workflows.delete('onboarding')import { NovuSDK } from '@voxgig-sdk/novu-sdk'
const client = new NovuSDK({ apikey: process.env.NOVU_APIKEY })
const workflows = await client.Workflow().list()
const workflow = await client.Workflow().load({ id: 'onboarding' })
// WorkflowCreateData is the response schema, so without the cast TypeScript
// asks for id, createdAt and the other fields the server assigns.
const created = await client.Workflow().create({
name: 'Onboarding',
workflowId: 'onboarding',
steps: [],
} as any)
await client.Workflow().remove({ id: 'onboarding' })string in a date-time field. Against the live API that validation is a strength, and the failure belongs to the mock.novu.subscribers.search, create, retrieve and delete. Voxgig's Subscriber entity does the same for subscribers, but some entities are still named after response schemas, such as ListTopicSubscriptionsResponseDto (voxgig/apidef#97).idempotency-key header on its writes. sdkgen sent it as a query parameter until 4.32.0, which sends every header parameter as a header, so the Voxgig SDK, built on 4.32.1, sends it where Novu expects it.Corrections go to info@voxgig.com or an issue on the generator repository. A correction changes the page and moves its checked date; corrections from Speakeasy's own team carry the most weight.
First-party sources for the claims on this page. Where they disagree with it, they are the authority.
The generator is MIT and open, and the catalog holds 600+ generated SDKs readable without installing anything.