ark-sdk-development

Types flow through the ARK stack:

```

CRD YAML (ark/config/crd/)

↓ make ark-sdk-build (automatic)

ark-sdk Python types + overlay utilities

↓

ark-api Pydantic models (manual updates if exposing new fields)

↓ make ark-api-build → generates openapi.json

ark-dashboard TypeScript types

↓ npm run generate:api → generates types.ts

```

CRD types are automatically generated from Kubernetes CRD YAML files.

```bash

make ark-sdk-build

```

This runs:

1. crd_to_openapi.py - converts CRDs to OpenAPI schema
2. openapi-generator-cli - generates Python types from schema
3. Copies overlay files on top of generated code
4. Builds wheel package

Adding Custom SDK Functionality (Overlays)

The lib/ark-sdk/gen_sdk/overlay/python/ark_sdk/ directory contains custom Python modules that are copied on top of generated code. This is how utilities like client.py, k8s.py, and executor.py are added.

To add custom SDK functionality:

1. Add Python files to lib/ark-sdk/gen_sdk/overlay/python/ark_sdk/
2. Run make ark-sdk-build

The ark-api has manually written Pydantic models in services/ark-api/ark-api/src/ark_api/models/.

When to update ark-api models:

• When exposing new CRD fields via the HTTP API
• When adding new API response types

```bash

make ark-api-build

```

This generates services/ark-api/openapi.json from FastAPI routes and Pydantic models.

Pydantic Model Naming (CRITICAL)

Pydantic model class names MUST be globally unique across all model files. When multiple files define classes with the same name (e.g., ConfigMapKeyRef, Header, ValueFrom), FastAPI generates non-deterministic OpenAPI schema names like ark_api__models__agents__Header-Input. These names depend on import order and cause CI failures when types.ts differs between environments.

Solution: Prefix class names with their domain context:

| File | Naming Pattern | Examples |

|------|---------------|----------|

| agents.py | Agent* | AgentHeader, AgentValueFrom, AgentParameter |

| evaluators.py | Evaluator* | EvaluatorParameter, EvaluatorValueSource |

| mcp_servers.py | MCPServer* | MCPServerHeader, MCPServerValueSource |

| queries.py | Query* | QueryParameter, QueryLabelSelector |

| models.py | Model* | ModelValueSource |

Safety net: generate_openapi.py fails if any schema name contains __models__, catching collisions at build time.

See: https://github.com/mckinsey/agents-at-scale-ark/issues/656

```bash

cd services/ark-dashboard/ark-dashboard

cp ../../ark-api/openapi.json ../out/

npm run generate:api

npm run build # verify types compile

```

When you see:

```

Property 'SomeSchema' does not exist on type

```

1. Regenerate types.ts from latest openapi.json
2. Find the correct schema name:

```bash

grep "SomeSchema" services/ark-dashboard/ark-dashboard/lib/api/generated/types.ts

```

1. Update service files to use correct schema names

If you see schema names with __models__ pattern (e.g., ark_api__models__agents__Header-Input):

• This indicates a Pydantic model naming collision
• Fix by renaming the Python class to be unique (see naming convention above)
• Do NOT work around by using the __models__ name - fix the root cause

| File | Purpose |

|------|---------|

| ark/config/crd/bases/*.yaml | Source of truth - Kubernetes CRDs |

| lib/ark-sdk/gen_sdk/overlay/ | Custom SDK utilities (copied on top of generated) |

| services/ark-api/ark-api/src/ark_api/models/ | Manually written Pydantic models |

| services/ark-api/ark-api/generate_openapi.py | Generates openapi.json with collision safety net |

| services/ark-api/openapi.json | Generated OpenAPI spec from FastAPI |

| services/ark-dashboard/out/openapi.json | Copy used for dashboard type generation |

| services/ark-dashboard/ark-dashboard/lib/api/generated/types.ts | Generated TypeScript types |