Models & Algorithms•SOTAAZ Lab•January 6, 2026•KR

Multi-hop RAG: Why It Still Fails After Temporal RAG

You added Temporal RAG, but "who is my boss's boss?" still returns wrong answers. RAG now understands time, but it still doesn't know "what to search for next."

Multi-hop RAG: Why It Still Fails After Temporal RAG

You added Temporal RAG, but "who is my boss's boss?" still returns wrong answers. RAG now understands time, but it still doesn't know "what to search for next."

Redefining the Problem: Single-hop vs Multi-hop

The conventional explanation goes:

"Single-hop is easy, Multi-hop is hard"

But this describes the symptom, not the cause. A more precise definition:

Single-hop is a 'document selection problem.'

Multi-hop is a 'search sequence planning problem.'

Single-hop: Query → Retrieve → Answer
Multi-hop:  Query → Retrieve₁ → Reasoning → Retrieve₂ → ... → Answer

Temporal RAG narrows down 'when,' but it still can't reason about 'what to search next.'

The rest of this series is paid

✓ The whole “Advanced RAG” series: 7 posts in English, 7 in Korean
✓ 7 Jupyter notebooks
✓ One payment, no expiry. Opens when you sign in with the email you pay with.

The series pass needs no account to pay. The subscription needs a free account.

Multi-hop RAG: Why It Still Fails After Temporal RAG

Redefining the Problem: Single-hop vs Multi-hop

The rest of this series is paid

Files for this post