Add Perplexity integration entry (#478)

* Add Perplexity integration entry

* docs(perplexity): align with latest perplexity-haystack integration

- Remove all references to Sonar models. The integration uses the
  Agent API (OpenAI-compatible Responses) and Search API exclusively.
- Update PerplexityChatGenerator default to openai/gpt-5.4 (was sonar-pro).
- Surface the actual list of supported Agent API models
  (openai/gpt-5.5, openai/gpt-5.4, openai/gpt-4o,
   anthropic/claude-sonnet-4-6, xai/grok-4-1,
   google/gemini-3-flash-preview).
- Mention default + alternative embedding models
  (pplx-embed-v1-0.6b, pplx-embed-v1-4b).
- Add a PerplexityDocumentEmbedder example.
- Section title 'Chat Completions (Agent API)' to make the API surface
  explicit.

Author: jliounis

integrations/perplexity.md

@@ -0,0 +1,126 @@
+---
+layout: integration
+name: Perplexity
+description: Use the Perplexity Agent API, Embeddings API, and grounded Search API in Haystack pipelines.
+authors:
+    - name: deepset
+      socials:
+        github: deepset-ai
+        twitter: deepset_ai
+        linkedin: https://www.linkedin.com/company/deepset-ai/
+pypi: https://pypi.org/project/perplexity-haystack
+repo: https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/perplexity
+type: Model Provider
+report_issue: https://github.com/deepset-ai/haystack-core-integrations/issues
+logo: /logos/perplexity.png
+version: Haystack 2.0
+toc: true
+---
+
+### **Table of Contents**
+- [Overview](#overview)
+- [Installation](#installation)
+- [Usage](#usage)
+- [License](#license)
+
+## Overview
+
+The `perplexity-haystack` package lets you use Perplexity's Agent API, Embeddings API, and grounded Search API in Haystack pipelines through four components:
+
+- `PerplexityChatGenerator` — chat completions through the Perplexity Agent API (OpenAI-compatible Responses API). Defaults to `openai/gpt-5.4`; other supported models include `openai/gpt-5.5`, `openai/gpt-4o`, `anthropic/claude-sonnet-4-6`, `xai/grok-4-1`, and `google/gemini-3-flash-preview`.
+- `PerplexityTextEmbedder` and `PerplexityDocumentEmbedder` — embeddings through the Perplexity Embeddings API. Defaults to `pplx-embed-v1-0.6b`; `pplx-embed-v1-4b` is also available.
+- `PerplexityWebSearch` — grounded web search results through the Perplexity Search API.
+
+For more information about the Perplexity API, see [the Perplexity docs](https://docs.perplexity.ai).
+
+In order to follow along with this guide, you'll need a Perplexity API key. Add it as an environment variable, `PERPLEXITY_API_KEY`.
+
+## Installation
+
+```bash
+pip install perplexity-haystack
+```
+
+## Usage
+
+You can use the Perplexity components as standalone components or in Haystack pipelines.
+
+### Use Perplexity Chat Completions (Agent API)
+
+`PerplexityChatGenerator` is powered by the Perplexity Agent API and defaults to `openai/gpt-5.4`.
+
+```python
+import os
+
+from haystack.dataclasses import ChatMessage
+from haystack_integrations.components.generators.perplexity import PerplexityChatGenerator
+
+os.environ["PERPLEXITY_API_KEY"] = "YOUR_PERPLEXITY_API_KEY"
+
+client = PerplexityChatGenerator()
+response = client.run(
+    messages=[ChatMessage.from_user("What are Agentic Pipelines? Be brief.")]
+)
+
+print(response["replies"])
+```
+
+You can pick any of the supported Agent API models via the `model` parameter, for example:
+
+```python
+client = PerplexityChatGenerator(model="anthropic/claude-sonnet-4-6")
+```
+
+### Use Perplexity Embeddings
+
+```python
+import os
+
+from haystack_integrations.components.embedders.perplexity import PerplexityTextEmbedder
+
+os.environ["PERPLEXITY_API_KEY"] = "YOUR_PERPLEXITY_API_KEY"
+
+embedder = PerplexityTextEmbedder()
+response = embedder.run(text="What is Haystack by deepset?")
+
+print(response["embedding"])
+```
+
+For embedding a list of documents, use `PerplexityDocumentEmbedder`:
+
+```python
+from haystack import Document
+from haystack_integrations.components.embedders.perplexity import PerplexityDocumentEmbedder
+
+docs = [Document(content="What is Haystack by deepset?")]
+result = PerplexityDocumentEmbedder().run(documents=docs)
+
+print(result["documents"][0].embedding)
+```
+
+### Use Perplexity Web Search (Search API)
+
+```python
+import os
+
+from haystack.utils import Secret
+from haystack_integrations.components.websearch.perplexity import PerplexityWebSearch
+
+os.environ["PERPLEXITY_API_KEY"] = "YOUR_PERPLEXITY_API_KEY"
+
+websearch = PerplexityWebSearch(
+    api_key=Secret.from_env_var("PERPLEXITY_API_KEY"),
+    top_k=5,
+)
+result = websearch.run(query="What is Haystack by deepset?")
+
+documents = result["documents"]
+links = result["links"]
+
+print(documents)
+print(links)
+```
+
+### License
+
+`perplexity-haystack` is distributed under the terms of the [Apache-2.0](https://spdx.org/licenses/Apache-2.0.html) license.