Multi-agent Self-RAG: grade, rethink, retrieve again

Simple RAG retrieves once and hopes. Self-RAG style systems add loops: grade whether documents help, invent better questions when they do not, retrieve again, and only then answer. Multi-agent framing makes those loops explicit as collaborating roles instead of a single opaque chain.

Why one-shot retrieval fails in real cases

Consider a support question that mixes product names, version pins, and a vague symptom. The first embedding hit may land on an old changelog. A generator that trusts that hit will sound sure and still be wrong. A grader that can reject weak context—and a planner that can ask a sharper follow-up query—turns RAG into an iterative search rather than a lottery.

Iteration path

1st iteration — simple RAG. Embed the question, pull top-k, answer. Useful baseline; fragile under ambiguity.

2nd iteration — grade documents. A grader agent scores each chunk for relevance and support. Irrelevant context is dropped before generation.

3rd iteration — brainstorm new questions. If grades are weak, a question agent proposes alternate queries that target missing facets (version, error code, component).

Final iteration — retrieve with new questions. Run retrieval again with the expanded query set, merge evidence, then answer with citations.

Implementation sketch

State

Carry the original question, candidate documents, grades, follow-up queries, and the final answer in a shared state object the graph nodes read and write:

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Overview of US Flight Compensation Policies To get compensation for delayed flights, you should contact your airline via their customer service or go to the customer service desk. At the same time, you should bear in mind that you will only receive compensation if the delay is not weather-related and is within the carrier`s control. According to the US Department of Transportation, US airlines are not required to compensate you if a flight is cancelled or delayed. You can be compensated if you are bumped or moved from an overbooked flight. If your provider cancels your flight less than two weeks before departure and you decide to cancel your trip entirely, you can receive a refund of both pre-paid baggage fees and your plane ticket. There will be no refund if you choose to continue your journey. In the case of a delayed flight, the airline will rebook you on a different flight. According to federal law, you will not be provided with money or other compensation. Comparative Analysis of EU vs. US Flight Compensation Policies
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(AUTHOR-ADDED NOTE: IMPORTANT, PAY ATTENTION TO THIS)
Short-distance flight delays - if it is up to 1,500 km, you are due 250 Euro compensation.
Medium distance flight delays - for all the flights between 1,500 and 3,500 km, the compensation should be 400 Euro.
Long-distance flight delays - if it is over 3,500 km, you are due 600 Euro compensation. To receive this kind of compensation, the following conditions must be met; Your flight starts in a non-EU member state or in an EU member state and finishes in an EU member state and is organised by an EU airline. Your flight reaches the final destination with a delay that exceeds three hours. There is no force majeure.
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Compensation policies in the EU and US are not the same, which implies that it is worth knowing more about them. While you can always count on Skycop flight cancellation compensation, you should still get acquainted with the information below.
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Compensation for flight regulations EU: The EU does regulate flight delay compensation, which is known as EU261. US: According to the US Department of Transportation, every airline has its own policies about what should be done for delayed passengers. Compensation for flight delays EU: Just like in the United States, compensation is not provided when the flight is delayed due to uncontrollable reasons. However, there is a clear approach to compensation calculation based on distance. For example, if your flight was up to 1,500 km, you can receive 250 euros. US: There are no federal requirements. That is why every airline sets its own limits for compensation in terms of length. However, it is usually set at three hours. Overbooking EU: In the EU, they call for volunteers if the flight is overbooked. These people are entitled to a choice of: Re-routing to their final destination at the earliest opportunity. Refund of their ticket cost within a week if not travelling. Re-routing at a later date at the person`s convenience.

Graph definition

Wire nodes for retrieve, grade, rewrite, retrieve-again, and generate, with conditional edges that skip rewrite when grades already clear a threshold:

from typing import List, Annotated
from typing_extensions import TypedDict

def append_to_list(original: list, new: list) -> list:
    original.append(new)
    return original

def combine_list(original: list, new: list) -> list:
    return original + new

class GraphState(TypedDict):
    """
    Represents the state of our graph.

    Attributes:
        question: question
        generation: LLM generation
        new_documents: newly retrieved documents for the current iteration
        useful_documents: documents that are considered useful
        graded_documents: documents that have been graded
        new_queries: newly generated questions
        hypothesis: hypothesis
    """

    question: str
    generation: str
    new_documents: List[str]
    useful_documents: Annotated[List[str], combine_list]
    graded_documents: List[str]
    new_queries: Annotated[List[str], append_to_list]
    hypothesis: str

from langgraph.graph import END, StateGraph, START
from langgraph.checkpoint.memory import MemorySaver
from IPython.display import Image, display

workflow = StateGraph(GraphState)

# Define the nodes
workflow.add_node("retrieve", retrieve)  # retrieve
workflow.add_node("grade_documents", grade_documents)  # grade documents
workflow.add_node("generate", generate)  # generatae
workflow.add_node("transform_query", transform_query)  # transform_query

# Build graph
workflow.add_edge(START, "retrieve")
workflow.add_edge("retrieve", "grade_documents")
workflow.add_conditional_edges(
    "grade_documents",
    decide_to_generate,
    {
        "transform_query": "transform_query",
        "generate": "generate",
    },
)
workflow.add_edge("transform_query", "retrieve")
workflow.add_conditional_edges(
    "generate",
    grade_generation_v_documents_and_question,
    {
        "useful": END,
        "not supported": "transform_query",
        "not useful": "transform_query",
    },
)

# Compile
memory = MemorySaver()
app = workflow.compile(checkpointer=memory)
display(Image(app.get_graph(xray=True).draw_mermaid_png()))

Retriever and grader nodes stay small and testable:

from pprint import pprint
config = {"configurable": {"thread_id": str(uuid4())}}

# Run
inputs = {
    "question": "how much can I receive if I am denied boarding, for flights from Delhi to Munich?",
    }
for output in app.stream(inputs, config):
    for key, value in output.items():
        # Node
        pprint(f"Node '{key}':")
        # Optional: print full state at each node
        # print(app.get_state(config).values)
    pprint("\n---\n")

# Final generation
pprint(value["generation"])

---RETRIEVE---
"Node 'retrieve':"
'\n---\n'
---CHECK DOCUMENT RELEVANCE TO QUESTION---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---ASSESS GRADED DOCUMENTS---
---DECISION: GENERATE---
"Node 'grade_documents':"
'\n---\n'
---GENERATE---
---CHECK HALLUCINATIONS---
'---DECISION: GENERATION IS NOT GROUNDED IN DOCUMENTS, RE-TRY---'
"Node 'generate':"
'\n---\n'
---TRANSFORM QUERY---
"Node 'transform_query':"
'\n---\n'
---RETRIEVE---
"Node 'retrieve':"
'\n---\n'
---CHECK DOCUMENT RELEVANCE TO QUESTION---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---GRADE: DOCUMENT NOT RELEVANT---
---ASSESS GRADED DOCUMENTS---
---DECISION: GENERATE---
"Node 'grade_documents':"
'\n---\n'
---GENERATE---
---CHECK HALLUCINATIONS---
---DECISION: GENERATION IS GROUNDED IN DOCUMENTS---
---GRADE GENERATION vs QUESTION---
---DECISION: GENERATION ADDRESSES QUESTION---
"Node 'generate':"
'\n---\n'
('Based on the context provided, the flight distance from Munich to Delhi is '
 '5,931 km, which falls into the long-distance category (over 3,500 km). '
 'Therefore, if you are denied boarding on a flight from Delhi to Munich '
 'operated by an EU airline, you would be eligible for 600 Euro compensation, '
 'provided that:\n'
 '1. The flight is operated by an EU airline\n'
 '2. There is no force majeure\n'
 '3. Other applicable conditions are met\n'
 '\n'
 "However, it's important to note that this compensation amount is only valid "
 'if all the required conditions are met as specified in the regulations.')

Question expansion and second-pass retrieval:

Based on the context provided, the flight distance from Munich to Delhi is
5,931 km, which falls into the long-distance category (over 3,500 km).
Therefore, if you are denied boarding on a flight from Delhi to Munich
operated by an EU airline, you would be eligible for 600 Euro compensation,
provided that:
1. The flight is operated by an EU airline
2. There is no force majeure
3. Other applicable conditions are met

However, it's important to note that this compensation amount is only valid
if all the required conditions are met as specified in the regulations.

print(app.get_state(config).values.get('hypothesis',""))

Final generation grounded only in surviving documents:

--- Output ---
To answer this question accurately, I need to determine:

1. Is this flight operated by an EU airline? (Since Delhi is non-EU and Munich is EU)
2. What is the flight distance between Delhi and Munich? (To determine compensation amount)
3. Are we dealing with a denied boarding situation due to overbooking? (As opposed to delay/cancellation)

From the context, I can find information about compensation amounts based on distance, but I need to verify:
- If the flight meets EU compensation eligibility criteria
- The exact distance between Delhi and Munich to determine which compensation tier applies (250€, 400€, or 600€)
- If denied boarding compensation follows the same amounts as delay compensation

The context doesn't explicitly state compensation amounts specifically for denied boarding, though it mentions overbooking situations in the EU require offering volunteers re-routing or refund options.

Would you like me to proceed with the information available, or would you need additional context about denied boarding compensation specifically?

Compile and invoke with a recursion limit so loops cannot run forever:

for questions_batch in app.get_state(config).values.get('new_queries',""):
    for q in questions_batch:
        print(q)

--- Output ---
What is the flight distance between Delhi and Munich?
Does EU denied boarding compensation follow the same amounts as flight delay compensation?
Are there specific compensation rules for denied boarding versus flight delays for flights from non-EU to EU destinations?
What are the compensation rules when flying with non-EU airlines from Delhi to Munich?
What are the specific conditions that qualify as denied boarding under EU regulations?

Conclusion

Multi-agent Self-RAG is discipline more than magic: reject weak context, ask better questions, retrieve again, then speak. Cap iterations, log grades, and evaluate whether the second pass actually improves answer faithfulness—not only whether the demo looks busier. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name. Keep fixtures green, measure each stage separately, and refuse to ship on vibes alone when the next release can reintroduce the same silent failure mode under a new name.