SDK Architecture

Load when: You need to understand SDK interfaces, add a new SDK, or figure out why Go SDK is different from others.

Built-in SDKs

Defined in core/sdk/consts.go:

SDK	Codegen	Notes
Go	cmd/codegen/generator/go/	Hardcoded in engine, NOT a module
Python	sdk/python/codegen/	Native Python, ~870 lines
TypeScript	cmd/codegen/generator/typescript/	Shares cmd/codegen binary
Java	sdk/java/dagger-codegen-maven-plugin/	Maven plugin
PHP	sdk/php/src/Codegen/	PHP classes
Elixir	sdk/elixir/dagger_codegen/	Elixir mix

Experimental SDK

SDK	Codegen	Notes
.NET	sdk/dotnet/sdk/Dagger.SDK.SourceGenerator/	C# Source Generator; not in consts.go

Interfaces

All at core/sdk.go:

Interface	Line	Purpose	Implementers
ClientGenerator	20	Generate standalone clients	Go, TypeScript
CodeGenerator	93	Generate in-module bindings	All 6 built-in
Runtime	145	Provide execution container	All 6 built-in
ModuleTypes	179	Extract user type definitions	All 6 built-in

Why Go is Special

Go SDK is not a module. It's hardcoded in the engine.

Implementation: core/sdk/go_sdk.go

How it works:

1. cmd/codegen binary is built
2. Packaged into container, tarball'd
3. Embedded in engine image
4. Engine calls it directly (no module invocation)

All other SDKs are modules that expose interfaces via GraphQL fields. The engine loads them dynamically.

Consequence: Code paths differ between Go and module-based SDKs. Look at both when debugging.

Key Files

File	Purpose
core/sdk/consts.go	Built-in SDK list
core/sdk.go	Interface definitions
core/sdk/go_sdk.go	Go SDK (hardcoded)
core/sdk/module.go	Module-based SDK wrapper
core/sdk/module_code_generator.go	CodeGenerator for module SDKs
core/sdk/module_client_generator.go	ClientGenerator for module SDKs