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ReAct: Reason + Act

🔄 The Agentic Control Loop⏱ 8 min⭐ 60 BASE XP⌨ HANDS-ON LAB

The ReAct Pattern

ReAct (Reasoning + Acting) is the foundational pattern for modern AI agents. Instead of just answering a question, the model emits a "Thought", then an "Action". The system runs the action and returns an "Observation".

Thought: I need to find the current price of AAPL. I will use the search_finance tool.
Action: search_finance(ticker="AAPL")
Observation: $195.50
Thought: Now I have the price. I can answer the user.
Answer: The current price of AAPL is $195.50.
💡 Key Insight: ReAct works because forcing the model to write out its "Thought" (Chain-of-Thought) before predicting the "Action" drastically reduces errors and hallucinated tool calls.
⌨ HANDS-ON LABSimulate ReAct Thought-Action-Observation Loop
⭐ +150 XP

Step through a ReAct execution cycle validating prompt parsing of Thought, Action, Action Input, and Observation.

1Simulate a ReAct trace execution.
lab-sandbox — simulated environment
INFINITY LAB SANDBOX v2.6 — simulated shell
Type the command for the current objective. Helpers: "hint", "solution", "clear".
$
OBJECTIVE 1 / 1 — type "hint" if stuck
SYNAPSE VERIFICATION
QUERY 1 // 1
In the ReAct pattern, what is the sequence of steps?
Act → Observe → Reason
Reason → Act → Observe
Observe → Answer → Quit
Think → Code → Test