Corvus

A multi-agent AI research system built on a supervisor architecture. A top-level supervisor routes between specialized subagents — a Paper Finding Agent for academic search and citation discovery, and a Q&A Agent for evidence-based question answering over the papers you select.

https://github.com/user-attachments/assets/bfd8e9bc-2266-42f7-9a8e-5412029f08fc

Live demo → corvus-agent.vercel.app | MCP server — use Corvus's search tools directly in Claude Desktop

Stack

| Layer | Technology | | ------------------------ | --------------------------------------------------------------- | | Agent orchestration | LangGraph (supervisor + subgraph pattern) | | LLM inference | Google Gemini 3 Flash (preview) via LangChain | | API server | FastAPI | | Async task queue | Celery + Redis | | Frontend | React 19 + Vite + TypeScript | | Vector database | Qdrant | | Relational / checkpoints | Postgres | | PDF extraction | Grobid | | Paper search | Semantic Scholar API (200M+ papers) | | Web search | Tavily | | Reranking | Cohere | | Embeddings | OpenAI text-embedding-3-small (1536-dim) | | Auth | Clerk (optional) |

Agent Architecture

Corvus is built around three LangGraph agents: a Supervisor that plans and routes, a Paper Finding Agent that searches and discovers papers, and a Q&A Agent that retrieves evidence and answers questions.

Supervisor (graph.py)

Every user message enters the supervisor, which runs a four-node pipeline before invoking any tool:

query_evaluation → planner → executor → supervisor_tools → post_tool
                                                                ↓
                                                    replanner (interrupt)
                                                                ↓
                                                           executor …

**query_evaluation** — Classifies the query before any search is attempted. Uses structured output to return one of five decisions: clear, needs_clarification, unselected_paper, irrelevant, or inappropriate. Only clear queries proceed; all others generate an inline response explaining what Corvus needs.

**planner** — Chooses one of three execution plans based on intent:

• find_only — discover new papers
• qa_only — answer a question using papers already in context
• find_then_qa — find papers first, then answer a question about them

**executor** — Pops the next step from the plan and issues the corresponding tool call (find_papers or retrieve_and_answer_question) as a structured AIMessage with a tool call.

**post_tool** — Runs after every tool result to commit side effects (paper list UI, final answer) to state before any interrupt is issued, ensuring the checkpoint is consistent.

**replanner** — Issues a LangGraph interrupt("select_papers") so the user can choose which papers to carry into Q&A. On resume, the selected paper IDs and an optional follow-up message are extracted from the resume payload and committed to state.

---

Paper Finding Agent (paper_finder.py)

Invoked by the supervisor's find_papers tool. Runs an iterative search loop (max 3 iterations) using a combination of search tools:

planner ──→ executor ──→ replan_agent
   ↑                          │
   └──── (goal not met) ──────┘
                              │
                        (goal met) ──→ END

**planner** — Analyses the search task and generates a concrete multi-step search plan. Each step must be an actionable search operation (web search, academic database query, or citation chasing). The planner is given today's date so temporal constraints like "recent" resolve correctly.

**executor** — Runs a nested ReAct-style search agent for the current plan step. The search agent has access to four tools:

| Tool | Description | | -------------------------- | ----------------------------------------------------------------------------------- | | s2_search_papers | Keyword and filter search over Semantic Scholar (year, venue, citation count, etc.) | | tavily_research_overview | Web search for broader context, seminal papers, and author profiles | | forward_snowball | Find papers that cite a given seed paper (surfaces recent follow-on work) | | backward_snowball | Find papers cited by a given seed paper (surfaces foundational references) |

After the search agent finishes its step, all accumulated papers are reranked with Cohere against a keyword-optimised query derived from the original task. Only the top-35 most relevant papers are kept, preventing the list from growing unboundedly across iterations.

**replan_agent** — Evaluates whether the goal is achieved by inspecting the actual paper list (not just what appeared in web search summaries). If the goal is not yet met, it rewrites the remaining plan steps with explicit retrieval targets, then loops back to the executor.

All three nodes emit finder_status custom events that the frontend renders as a real-time Research Agent status card.

---

Q&A Agent (qa.py)

Invoked after paper selection. Performs iterative evidence retrieval scoped to the user-selected paper IDs (max 3 iterations):

qa_retrieve ──→ tools ──→ qa_evaluate ──→ qa_answer
                               │
                   (insufficient evidence)
                               │
                          qa_retrieve …

**qa_retrieve** — On the first iteration, checks Qdrant for each selected paper and records which ones have no indexed full text (e.g. ingestion failed or paper not on arXiv). These unindexed_paper_ids are carried in state so downstream nodes can handle thin evidence gracefully. Then generates focused retrieval queries and calls retrieve_evidence_from_selected_papers, which performs vector search over the Qdrant collection filtered to the selected paper IDs only. This scoping ensures answers are grounded exclusively in the papers the user chose.

**qa_evaluate** — Uses structured output to decide between two outcomes: AnswerQuestion (evidence is sufficient) or AskForMoreEvidence (evidence is weak — includes a limitation string that seeds the next retrieval attempt with a better query strategy).

**qa_answer** — Synthesises a final answer from all accumulated evidence chunks. Always leads with the answer; if any selected papers were unindexed, a single caveat sentence is appended at the end noting that only the abstract was available for those papers.

All three nodes emit qa_status events rendered as a real-time Q&A Agent status card.

---

Paper Ingestion Pipeline (Celery)

When a user adds a paper to their list, two things happen simultaneously: the paper is added to the agent's context (so it knows which papers the Q&A should be scoped to), and an ingestion task is pushed to the Redis queue for background processing.

The vector store is shared across all users. The Celery worker checks whether the paper is already indexed before doing any work — if another user ingested it earlier, the task skips straight to done. This significantly reduces average ingestion time across the platform.

If the paper is not yet indexed, the worker runs the full pipeline:

1. arXiv lookup — searches arXiv by title to find a PDF URL
2. PDF download — fetches the PDF to a temp file (PDF_DOWNLOAD_DIR)
3. Grobid parsing — sends the PDF to a local Grobid container for structured, section-aware full-text extraction
4. Chunking & embedding — splits extracted text using a parent indexing strategy: smaller chunks are embedded for accurate vector retrieval; larger parent chunks are stored for richer LLM context at answer time. Embeddings use OpenAI text-embedding-3-small.
5. Qdrant upsert — stores vectors with paper ID and section metadata for scoped retrieval
6. Cleanup — the temp PDF is deleted regardless of success or failure

If no arXiv PDF is found, the task returns a clean failure with a specific error message. No partial data is written to Qdrant, so re-ingestion can be attempted cleanly.

---

UI Features

• Real-time subagent status cards — live in-place updates as the Research Agent and Q&A Agent run (planning, searching, evaluating, generating)
• Paper selection interrupt — after search completes, a structured interrupt pauses execution so the user can choose which papers to bring into Q&A
• Ingestion progress panel — per-paper status tracking with a progress bar as the Celery worker processes each PDF in the background
• Streaming AI responses — token-by-token streaming via the LangGraph SDK
• Persistent thread history — conversation threads are stored in Postgres and restored across sessions

Quick Start

1. Clone

git clone https://github.com/YS0meone/Corvus.git
cd Corvus

2. Configure environment

cp backend/.env_example backend/.env.local

Edit backend/.env.local and fill in at minimum:

• OPENAI_API_KEY — for