feat: BYOK enhancements

[kah-seng]

Key Changes:

• Added temperature, parallel tool calls and store param as configurable options for BYOK
• Added tooltips
• Frontend prevents adding 2 custom models with same name and slug

Yet to fix bad request error for certain DeepSeek requests.

[Copilot]

Pull request overview

Adds BYOK (Bring Your Own Key) enhancements across the webapp, proto API, and backend LLM client so custom models can expose additional OpenAI-compatible parameters and be selected more reliably.

Changes:

• Extends custom model settings (temperature, parallel tool calls, store) and updates the settings UI with validation, sorting, and tooltips.
• Adds custom model identifiers to supported-model listings and includes custom_model_id in the chat streaming request path.
• Updates backend model mapping/storage and OpenAI request parameter construction to use the new custom-model fields.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
webapp/_webapp/src/views/settings/sections/api-key-settings.tsx	UI/UX for custom model CRUD; adds new BYOK fields, tooltips, validation, duplicate prevention
webapp/_webapp/src/views/chat/footer/toolbar/selection.tsx	Extends selection item metadata to carry custom model identity flags
webapp/_webapp/src/views/chat/footer/toolbar/model-selection.tsx	Selects custom models by ID (when available) to disambiguate custom entries
webapp/_webapp/src/utils/stream-request-builder.ts	Adds customModelId to the stream request builder params/payload
webapp/_webapp/src/stores/setting-store.ts	Initializes settings defaults to include customModels
webapp/_webapp/src/stores/conversation/conversation-ui-store.ts	Persists lastUsedCustomModelId in UI store
webapp/_webapp/src/pkg/gen/apiclient/user/v1/user_pb.ts	Regenerated TS client types for added custom model fields
webapp/_webapp/src/pkg/gen/apiclient/chat/v2/chat_pb.ts	Regenerated TS client types for supported model IDs + stream request customModelId
webapp/_webapp/src/hooks/useSendMessageStream.ts	Sends customModelId with message stream requests
webapp/_webapp/src/hooks/useLanguageModels.ts	Tracks/uses lastUsedCustomModelId for selecting custom models
proto/user/v1/user.proto	Adds custom model fields (temperature, parallel tool calls, store)
proto/chat/v2/chat.proto	Adds supported model id + stream request custom_model_id
pkg/gen/api/user/v1/user.pb.go	Regenerated Go proto for custom model fields
pkg/gen/api/chat/v2/chat.pb.go	Regenerated Go proto for supported model IDs + stream request custom_model_id
internal/services/toolkit/client/utils_v2.go	Uses custom model fields when building OpenAI chat completion params
internal/services/toolkit/client/get_conversation_title_v2.go	Plumbs custom model through title generation path
internal/services/toolkit/client/get_citation_keys.go	Updates call signature for ChatCompletionV2 with custom model param
internal/services/toolkit/client/completion_v2.go	Updates ChatCompletionV2/StreamV2 signatures to accept custom model
internal/models/user.go	Persists new custom model fields in MongoDB model struct
internal/api/mapper/user.go	Maps new custom model fields between proto and internal models
internal/api/chat/list_supported_models_v2.go	Includes custom model ID in supported models response
internal/api/chat/create_conversation_message_stream_v2.go	Resolves custom models by custom_model_id and passes through to LLM client

Comments suppressed due to low confidence (1)

internal/api/chat/create_conversation_message_stream_v2.go:300

• Custom models are now only resolved when custom_model_id is present. If the client omits custom_model_id (e.g., older clients, or loading an existing conversation where the UI store has no matching lastUsedCustomModelId), a custom model slug will be treated as a built-in model and the BYOK endpoint/API key won’t be applied. Consider keeping a backward-compatible fallback: when custom_model_id is empty, attempt to resolve settings.CustomModels by modelSlug (or persist custom model ID in the conversation state and always send it).

	customModelID := req.GetCustomModelId()
	if customModelID != "" {
		for i := range settings.CustomModels {
			if settings.CustomModels[i].Id.Hex() == customModelID {
				customModel = &settings.CustomModels[i]
				break
			}
		}
		if customModel == nil {
			return s.sendStreamError(stream, fmt.Errorf("custom model not found: %q", customModelID))
		}
		modelSlug = customModel.Slug
	}

	if customModel == nil {

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