refactor: remove ModelProviderRegistry.default and require ModelConfig.provider (#590)

Final cleanup after the #589 deprecation cycle. Providers are now a
named list referenced by name end-to-end — no hidden registry default,
no YAML default leaking into DataDesigner construction (#588), and no
ambiguity about which provider wins.

ModelConfig.provider becomes a required str. ModelProviderRegistry.default
and the associated validators, get_default_provider_name() helper, CLI
"Change default provider" workflow, and the "Default" column in
`data-designer config list` are removed. resolve_model_provider_registry()
drops its default_provider_name kwarg, and DataDesigner.__init__ no
longer threads a YAML default through registry construction.

Pydantic v2's extra="ignore" default lets existing on-disk YAMLs with
default: keys load cleanly, so users on the deprecation cycle migrate
without breakage.

Author: nabinchha

docs/concepts/models/configure-model-settings-with-the-cli.md

@@ -65,14 +65,6 @@ data-designer config providers
 
 **Delete all providers**: Remove all providers and their associated models.
 
-**Change default provider**: Set which provider is used by default. This option is only available when multiple providers are configured.
-
-!!! warning "Deprecated: 'Change default provider' workflow"
-    The "Change default provider" workflow is **deprecated** and will be removed in a future
-    release alongside the registry-level default. Specify `provider=` explicitly on each
-    `ModelConfig` instead — the workflow now emits a `DeprecationWarning` when entered.
-    See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-
 ## Managing Model Configurations
 
 Run the interactive model configuration command:
@@ -117,7 +109,6 @@ data-designer config list
 This command displays:
 
 - **Model Providers**: All configured providers with their endpoints (API keys are masked)
-- **Default Provider**: The currently selected default provider _(deprecated; see issue #589)_
 - **Model Configurations**: All configured models with their settings
 
 ## Resetting Configurations

docs/concepts/models/custom-model-settings.md

@@ -90,13 +90,6 @@ preview_result.display_sample_record()
 !!! note "Default Providers Always Available"
     When you only specify `model_configs`, the default model providers (NVIDIA, OpenAI, and OpenRouter) are still available. You only need to create custom providers if you want to connect to different endpoints or modify provider settings.
 
-!!! warning "Always specify `provider=` on `ModelConfig`"
-    Leaving `provider` unset (or passing `provider=None`) on `ModelConfig` is **deprecated**.
-    The legacy "implicit default provider" routing — used when `provider` is omitted — emits
-    a `DeprecationWarning` and will be removed in a future release. Always reference the
-    intended provider by name, as the examples below do. See
-    [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-
 !!! tip "Mixing Custom and Default Models"
     When you provide custom `model_configs` to `DataDesignerConfigBuilder`, they **replace** the defaults entirely. To use custom model configs in addition to the default configs, use the add_model_config method:
 

docs/concepts/models/default-model-settings.md

@@ -110,13 +110,6 @@ Both methods operate on the same files, ensuring consistency across your entire
 !!! warning "Hosted Provider Data Handling"
     The default model providers call hosted endpoints operated by NVIDIA, OpenAI, OpenRouter, or their upstream providers. Provider terms and privacy practices apply independently of Data Designer, and free or trial endpoints may log request data for security, operations, or product improvement. Do not submit confidential information or personal data, including faces, voices, screenshots, regulated data, or other sensitive content, unless the selected provider and endpoint are approved for your use case.
 
-!!! warning "Deprecated: implicit default provider routing"
-    The `default:` key in `~/.data-designer/model_providers.yaml` and the registry-level
-    "default provider" concept are **deprecated** and will be removed in a future release.
-    Specify `provider=` explicitly on every `ModelConfig` instead — the built-in defaults
-    above already do this, and a `DeprecationWarning` is now emitted whenever the legacy
-    routing is exercised. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-
 !!! tip "Environment Variables"
     Store your API keys in environment variables rather than hardcoding them in your scripts:
 

docs/concepts/models/model-configs.md

@@ -15,9 +15,12 @@ The `ModelConfig` class has the following fields:
 | `alias` | `str` | Yes | Unique identifier for this model configuration (e.g., `"my-text-model"`, `"reasoning-model"`) |
 | `model` | `str` | Yes | Model identifier as recognized by the provider (e.g., `"nvidia/nemotron-3-nano-30b-a3b"`, `"gpt-4"`) |
 | `inference_parameters` | `InferenceParamsT` | No | Controls model behavior during generation. Use `ChatCompletionInferenceParams` for text/code/structured generation or `EmbeddingInferenceParams` for embeddings. Defaults to `ChatCompletionInferenceParams()` if not provided. The generation type is automatically determined by the inference parameters type. See [Inference Parameters](inference-parameters.md) for details. |
-| `provider` | `str` | No | Reference to the name of the Provider to use (e.g., `"nvidia"`, `"openai"`, `"openrouter"`). If not specified, one set as the default provider, which may resolve to the first provider if there are more than one |
+| `provider` | `str` | Yes | Reference to the name of the Provider to use (e.g., `"nvidia"`, `"openai"`, `"openrouter"`). |
 | `skip_health_check` | `bool` | No | Whether to skip the health check for this model. Defaults to `False`. Set to `True` to skip health checks when you know the model is accessible or want to defer validation. |
 
+!!! warning "Upgrade note"
+    Every `ModelConfig` must now specify `provider`. Existing `model_configs.yaml` entries from older releases that omit `provider` or set it to `null` must be updated with an explicit provider name before loading. Agent tooling that parses `data-designer agent context` should read the `provider` field for each model alias; `default_provider`, `configured_provider`, and `effective_provider` are no longer emitted.
+
 
 ## Examples
 

docs/concepts/models/model-providers.md

@@ -6,14 +6,6 @@ Model providers are external services that host and serve models. Data Designer
 
 A `ModelProvider` defines how Data Designer connects to a provider's API endpoint. When you create a `ModelConfig`, you reference a provider by name, and Data Designer uses that provider's settings to make API calls to the appropriate endpoint.
 
-!!! warning "Deprecated: implicit default provider routing"
-    Earlier versions of Data Designer let you omit `provider=` on `ModelConfig` and
-    fall back to a registry-level default — including the `default:` key in
-    `~/.data-designer/model_providers.yaml`. That implicit routing is **deprecated**
-    and will be removed in a future release. Always reference a provider by name on
-    every `ModelConfig`. A `DeprecationWarning` is now emitted when the legacy path
-    is exercised. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-
 ## ModelProvider Configuration
 
 The `ModelProvider` class has the following fields:

fern/versions/latest/pages/concepts/models/configure-model-settings-with-the-cli.mdx

@@ -74,12 +74,6 @@ data-designer config providers
 
 **Delete all providers**: Remove all providers and their associated models.
 
-**Change default provider**: Set which provider is used by default. This option is only available when multiple providers are configured.
-
-<Warning title="Deprecated: 'Change default provider' workflow">
-  The "Change default provider" workflow is **deprecated** and will be removed in a future release alongside the registry-level default. Specify `provider=` explicitly on each `ModelConfig` instead — the workflow now emits a `DeprecationWarning` when entered. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-</Warning>
-
 ## Managing Model Configurations
 
 Run the interactive model configuration command:
@@ -128,7 +122,6 @@ data-designer config list
 This command displays:
 
 - **Model Providers**: All configured providers with their endpoints (API keys are masked)
-- **Default Provider**: The currently selected default provider _(deprecated; see [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589))_
 - **Model Configurations**: All configured models with their settings
 
 ## Resetting Configurations

fern/versions/latest/pages/concepts/models/custom-model-settings.mdx

@@ -94,9 +94,9 @@ preview_result.display_sample_record()
   When you only specify `model_configs`, the default model providers (NVIDIA, OpenAI, and OpenRouter) are still available. You only need to create custom providers if you want to connect to different endpoints or modify provider settings.
 </Note>
 
-<Warning title="Always specify `provider=` on `ModelConfig`">
-  Leaving `provider` unset (or passing `provider=None`) on `ModelConfig` is **deprecated**. The legacy "implicit default provider" routing — used when `provider` is omitted — emits a `DeprecationWarning` and will be removed in a future release. Always reference the intended provider by name, as the examples below do. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-</Warning>
+<Note title="Provider is required">
+  Every custom `ModelConfig` must reference the intended provider by name. The examples below use the built-in `nvidia` provider.
+</Note>
 
 <Tip title="Mixing Custom and Default Models">
 When you provide custom `model_configs` to `DataDesignerConfigBuilder`, they **replace** the defaults entirely. To use custom model configs in addition to the default configs, use the add_model_config method:

fern/versions/latest/pages/concepts/models/default-model-settings.mdx

@@ -116,10 +116,6 @@ Both methods operate on the same files, ensuring consistency across your entire
   The default model providers call hosted endpoints operated by NVIDIA, OpenAI, OpenRouter, or their upstream providers. Provider terms and privacy practices apply independently of Data Designer, and free or trial endpoints may log request data for security, operations, or product improvement. Do not submit confidential information or personal data, including faces, voices, screenshots, regulated data, or other sensitive content, unless the selected provider and endpoint are approved for your use case.
 </Warning>
 
-<Warning title="Deprecated: implicit default provider routing">
-  The `default:` key in `~/.data-designer/model_providers.yaml` and the registry-level "default provider" concept are **deprecated** and will be removed in a future release. Specify `provider=` explicitly on every `ModelConfig` instead — the built-in defaults above already do this, and a `DeprecationWarning` is now emitted whenever the legacy routing is exercised. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-</Warning>
-
 <Tip title="Environment Variables">
   Store your API keys in environment variables rather than hardcoding them in your scripts:
 

fern/versions/latest/pages/concepts/models/model-configs.mdx

@@ -18,9 +18,13 @@ The `ModelConfig` class has the following fields:
 | `alias` | `str` | Yes | Unique identifier for this model configuration (e.g., `"my-text-model"`, `"reasoning-model"`) |
 | `model` | `str` | Yes | Model identifier as recognized by the provider (e.g., `"nvidia/nemotron-3-nano-30b-a3b"`, `"gpt-4"`) |
 | `inference_parameters` | `InferenceParamsT` | No | Controls model behavior during generation. Use `ChatCompletionInferenceParams` for text/code/structured generation or `EmbeddingInferenceParams` for embeddings. Defaults to `ChatCompletionInferenceParams()` if not provided. The generation type is automatically determined by the inference parameters type. See [Inference Parameters](/concepts/models/inference-parameters) for details. |
-| `provider` | `str` | No | Reference to the name of the Provider to use (e.g., `"nvidia"`, `"openai"`, `"openrouter"`). If not specified, one set as the default provider, which may resolve to the first provider if there are more than one |
+| `provider` | `str` | Yes | Reference to the name of the Provider to use (e.g., `"nvidia"`, `"openai"`, `"openrouter"`). |
 | `skip_health_check` | `bool` | No | Whether to skip the health check for this model. Defaults to `False`. Set to `True` to skip health checks when you know the model is accessible or want to defer validation. |
 
+<Warning title="Upgrade note">
+Every `ModelConfig` must now specify `provider`. Existing `model_configs.yaml` entries from older releases that omit `provider` or set it to `null` must be updated with an explicit provider name before loading. Agent tooling that parses `data-designer agent context` should read the `provider` field for each model alias; `default_provider`, `configured_provider`, and `effective_provider` are no longer emitted.
+</Warning>
+
 
 ## Examples
 

fern/versions/latest/pages/concepts/models/model-providers.mdx

@@ -9,10 +9,6 @@ Model providers are external services that host and serve models. Data Designer
 
 A `ModelProvider` defines how Data Designer connects to a provider's API endpoint. When you create a `ModelConfig`, you reference a provider by name, and Data Designer uses that provider's settings to make API calls to the appropriate endpoint.
 
-<Warning title="Deprecated: implicit default provider routing">
-  Earlier versions of Data Designer let you omit `provider=` on `ModelConfig` and fall back to a registry-level default — including the `default:` key in `~/.data-designer/model_providers.yaml`. That implicit routing is **deprecated** and will be removed in a future release. Always reference a provider by name on every `ModelConfig`. A `DeprecationWarning` is now emitted when the legacy path is exercised. See [issue #589](https://github.com/NVIDIA-NeMo/DataDesigner/issues/589).
-</Warning>
-
 ## ModelProvider Configuration
 
 The `ModelProvider` class has the following fields: