Add Perplexity as a BYOK provider

[jliounis]

Summary

Adds Perplexity as a Bring-Your-Own-Key (BYOK) language model provider in Copilot Chat. Perplexity exposes an OpenAI-compatible Chat Completions API at https://api.perplexity.ai, so the new provider extends AbstractOpenAICompatibleLMProvider — mirroring the existing xAI and OpenRouter providers.

After merging, users with a Perplexity API key can pick Perplexity from the BYOK provider dropdown and use Sonar models from Copilot Chat.

Changes

• src/extension/byok/vscode-node/perplexityProvider.ts — new PerplexityLMProvider extending AbstractOpenAICompatibleLMProvider. Ships a curated list of currently-available models:
  • sonar-pro (default)
  • sonar
  • sonar-reasoning-pro
  • sonar-reasoning
• src/extension/byok/vscode-node/byokContribution.ts — registers the new provider alongside Anthropic / xAI / OpenRouter / OpenAI / Gemini / Ollama / Azure / customoai.
• package.json — adds the "perplexity" vendor entry under languageModelChatProviders with the standard apiKey configuration field.

Attribution header

The provider sends X-Pplx-Integration: vscode-copilot/<package-version> on every outgoing request (via BYOKModelCapabilities.requestHeaders, picked up by OpenAIEndpoint.getExtraHeaders) so Perplexity can attribute traffic to this integration. Set centrally in perplexityProvider.ts — not sprinkled across call sites.

Branding & defaults

• Default model: sonar-pro
• Branding: Perplexity in user-facing UI/docs (never "Sonar API")
• Base URL: https://api.perplexity.ai
• Auth: standard Authorization: Bearer <key> (BYOK key field)

Links

• Perplexity docs: https://docs.perplexity.ai
• Model cards: https://docs.perplexity.ai/models/model-cards

CLA

I'll sign the Microsoft CLA before merge — no blockers expected.

Test plan

• Build the extension
• Configure a Perplexity API key under the new "Perplexity" provider in BYOK settings
• Verify sonar-pro, sonar, sonar-reasoning-pro, and sonar-reasoning show up in the model picker
• Send a chat message and confirm streaming completion works
• Confirm requests include X-Pplx-Integration: vscode-copilot/<version> header

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[Copilot]

Pull request overview

Adds Perplexity as a new BYOK (Bring-Your-Own-Key) language model provider, integrating it into Copilot Chat’s existing OpenAI-compatible BYOK provider framework and surfacing it in VS Code’s BYOK provider configuration UI.

Changes:

• Introduces PerplexityLMProvider (OpenAI-compatible) with a curated set of Sonar models and an X-Pplx-Integration attribution header.
• Registers Perplexity in the BYOK contribution so it becomes an available provider at runtime.
• Adds a new perplexity vendor entry in package.json to expose API key configuration in the BYOK provider dropdown/settings.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/extension/byok/vscode-node/perplexityProvider.ts	Adds the new Perplexity BYOK provider, model metadata, and integration header wiring.
src/extension/byok/vscode-node/byokContribution.ts	Registers Perplexity provider alongside other BYOK providers.
package.json	Adds Perplexity as a configurable languageModelChatProviders vendor with an apiKey field.

[Copilot]

getModelsBaseUrl() returns a base URL, which causes AbstractOpenAICompatibleLMProvider to always call ${baseUrl}/models for discovery. That contradicts the comment/PR description that Perplexity doesn't have a stable /models endpoint, and it also means the curated PERPLEXITY_KNOWN_MODELS list will never be shown unless the discovery call succeeds and returns those IDs. Consider overriding getAllModels (like CustomOAI does) to return the curated/merged known-model list with url set to the Perplexity base URL, optionally attempting discovery as a best-effort fallback rather than a hard dependency.

Suggested change

	return 'https://api.perplexity.ai';
	// Perplexity does not provide a stable /models discovery endpoint for this provider.
	// Rely on the curated known-model list instead of enabling generic discovery.
	return undefined;

[Copilot]

The merge order for requestHeaders allows an existing caps.requestHeaders entry to override X-Pplx-Integration, which can accidentally drop or change the attribution header. If the intent is to guarantee the header on every request, apply the integration header last (so it wins) when merging curated and remote model capabilities.

Suggested change

	merged[id] = { ...caps, requestHeaders: { ...integrationHeader, ...(caps.requestHeaders ?? {}) } };
	}
	if (remote) {
	for (const [id, caps] of Object.entries(remote)) {
	merged[id] = { ...caps, requestHeaders: { ...integrationHeader, ...(caps.requestHeaders ?? {}) } };
	merged[id] = { ...caps, requestHeaders: { ...(caps.requestHeaders ?? {}), ...integrationHeader } };
	}
	if (remote) {
	for (const [id, caps] of Object.entries(remote)) {
	merged[id] = { ...caps, requestHeaders: { ...(caps.requestHeaders ?? {}), ...integrationHeader } };

[Copilot]

A new BYOK provider is introduced but there are no accompanying unit tests under src/extension/byok/vscode-node/test/ (other providers like Ollama/Gemini/Azure have coverage). Adding a Perplexity provider spec would help lock in: the curated model list shown in the picker and that X-Pplx-Integration is present in each model's requestHeaders.