IA Agentique : 5 Patterns Architecturaux pour des Agents Autonomes Fiables

Les LLMs ont révolutionné l'IA, mais ils restent stateless et réactifs. Vous posez une question, ils répondent. Fin de l'interaction.

L'IA agentique (Agentic AI) change la donne : des agents qui planifient, agissent, utilisent des outils, et corrigent leurs erreurs de manière autonome. Selon Stanford HAI, l'IA agentique sera l'une des 3 tendances dominantes de 2026.

Le problème ? L'architecture des agents est complexe :

• Comment gérer la mémoire à long terme ?
• Comment éviter les boucles infinies ?
• Comment orchestrer plusieurs agents ?
• Dans cet article, nous explorons 5 patterns architecturaux éprouvés pour construire des agents IA fiables :
• 1. ReAct : Raisonnement + Action
• 2. Plan-and-Execute : Planification stratégique
• 3. ReWOO : Orchestration optimisée
• 4. Multi-Agent : Collaboration spécialisée
• 5. Reflection : Auto-critique et amélioration
• Pour chaque pattern, nous fournissons :
• Architecture détaillée
• Implémentation Python (LangChain/LangGraph)
• Cas d'usage réels
• Comparatif performances
• Le pattern ReAct (Yao et al., 2023) alterne entre raisonnement et action :
• L'agent explicite son raisonnement à chaque étape, ce qui améliore la traçabilité et réduit les erreurs.
• Trace d'exécution :
• ✅ Support client : Recherche docs + base de connaissances
• ✅ Analyse de données : Requêtes SQL + calculs + visualisation
• ✅ Recherche académique : Recherche papers + synthèse
• Limites :
• ❌ Pas de planification à long terme
• ❌ Une seule action à la fois (séquentiel)
• Inspiré par BabyAGI et AutoGPT, ce pattern sépare planification et exécution :
• 1. Planner : Génère un plan d'actions
• 2. Executor : Exécute chaque action
• 3. Replanner : Ajuste le plan si nécessaire
• Sortie :
• ✅ Tâches complexes multi-étapes
• ✅ Recherche approfondie (competitive intelligence)
• ✅ Workflows métier (RH, finance)
• Avantages :
• ✅ Plan explicite et modifiable
• ✅ Parallélisation possible des étapes
• ReWOO (Xu et al., 2023) optimise ReAct en planifiant toutes les actions d'un coup, puis en les exécutant en parallèle.
• Différence clé :
• ReAct : Thought → Action → Observation → Thought → ...
• ReWOO : Thought → [Action1, Action2, Action3] → [Obs1, Obs2, Obs3] → Answer
• Performances :
• ReAct : 8 secondes (séquentiel)
• ReWOO : 3 secondes (parallèle) ✅
• Au lieu d'un agent monolithique, déléguer à des agents spécialisés :
• Researcher : Recherche d'informations
• Analyst : Analyse de données
• Writer : Rédaction
• Critic : Revue qualité
• Conversation typique :
• ✅ Génération de contenu complexe (rapports, articles)
• ✅ Analyse multi-dimensionnelle (business intelligence)
• ✅ Workflows créatifs (design, marketing)
• L'agent critique son propre travail et itère jusqu'à satisfaction :
• Sortie :
• Critères de choix :
• 1. Latence : ReWOO (parallèle)
• 2. Qualité : Reflection ou Multi-Agent
• 3. Simplicité : ReAct
• 4. Complexité tâche : Plan-Execute ou Multi-Agent
• Les 5 patterns architecturaux couvrent tous les cas d'usage de l'IA agentique :
• ReAct : Le couteau suisse (80% des cas)
• Plan-Execute : Tâches complexes structurées
• ReWOO : Performance maximale
• Multi-Agent : Collaboration spécialisée
• Reflection : Qualité maximale
• Checklist implémentation :
• [ ] Choisir pattern selon use case
• [ ] Implémenter timeouts et limites
• [ ] Ajouter logging/tracing
• [ ] Monitorer coûts LLM
• [ ] Tester cas limites (boucles, erreurs)
• Maillage interne :
• Claude Agent SDK : Construire un Agent IA Autonome
• MCP : Protocole Standardisé IA Agentique
• Sécuriser Code Généré par IA : Checklist
• Optimiser Coûts LLM en Production

Conclusion

class CostTracker:
    COSTS = {
        "gpt-4o": {"input": 0.005, "output": 0.015},  # per 1K tokens
        "gpt-4o-mini": {"input": 0.0015, "output": 0.006}
    }    def __init__(self, model: str):
        self.model = model
        self.total_input_tokens = 0
        self.total_output_tokens = 0    def track(self, input_tokens: int, output_tokens: int):
        self.total_input_tokens += input_tokens
        self.total_output_tokens += output_tokens    def get_cost(self) -> float:
        costs = self.COSTS[self.model]
        input_cost = (self.total_input_tokens / 1000) * costs["input"]
        output_cost = (self.total_output_tokens / 1000) * costs["output"]
        return input_cost + output_cost    def report(self):
        return {
            "model": self.model,
            "input_tokens": self.total_input_tokens,
            "output_tokens": self.total_output_tokens,
            "total_cost_usd": round(self.get_cost(), 4)

3. Cost Tracking

import structlog
from opentelemetry import tracelogger = structlog.get_logger()
tracer = trace.get_tracer(__name__)class ObservableAgent:
    def run(self, query: str):
        with tracer.start_as_current_span("agent_run") as span:
            span.set_attribute("query", query)            logger.info("agent_started", query=query)            try:
                result = self._execute(query)                span.set_attribute("result", result)
                logger.info("agent_completed", result=result)                return result            except Exception as e:
                span.set_attribute("error", str(e))
                logger.error("agent_failed", error=str(e))

2. Logging et Observabilité

from functools import wraps
import timedef with_timeout(seconds):
    def decorator(func):
        @wraps(func)
        def wrapper(args, *kwargs):
            start = time.time()
            result = func(args, *kwargs)
            duration = time.time() - start            if duration > seconds:
                raise TimeoutError(f"Execution exceeded {seconds}s")            return result
        return wrapper
    return decoratorclass SafeAgent:
    MAX_ITERATIONS = 15
    MAX_TOOL_CALLS = 50
    TIMEOUT_SECONDS = 120    def __init__(self, base_agent):
        self.agent = base_agent
        self.iterations = 0
        self.tool_calls = 0    @with_timeout(TIMEOUT_SECONDS)
    def run(self, query: str):
        self.iterations = 0
        self.tool_calls = 0        while self.iterations < self.MAX_ITERATIONS:
            self.iterations += 1            # Exécuter agent
            result = self.agent.step(query)            # Compter appels outils
            if result.get("tool_used"):
                self.tool_calls += 1            if self.tool_calls > self.MAX_TOOL_CALLS:
                raise RuntimeError("Tool call limit exceeded")            if result.get("final_answer"):
                return result["final_answer"]

1. Limites et Timeouts

Production-Ready : Monitoring et Safeguards

Comparatif des Patterns

🔄 Iteration 1
📝 Attempt:
Quantum computing uses quantum bits (qubits) which can be 0, 1, or both...
💭 Critique:
Too technical. Avoid jargon like "qubits". Use simpler analogies.🔄 Iteration 2
📝 Attempt:
Imagine a magic coin that can be heads AND tails at the same time...
💭 Critique:
Good analogy! But explain why this is useful. Add practical example.🔄 Iteration 3
📝 Attempt:
Imagine a magic coin that can be heads AND tails simultaneously. This lets
quantum computers solve certain problems much faster, like finding the best
route for a delivery truck visiting 100 cities...
💭 Critique:
APPROVED. Clear, age-appropriate, with practical example.

from langchain.chains import LLMChain
from langchain.prompts import PromptTemplateclass ReflectionAgent:
    def __init__(self, llm):
        self.llm = llm        # Generator prompt
        self.generator_prompt = PromptTemplate.from_template("""
Task: {task}Previous attempt: {previous_attempt}
Critique: {critique}Generate an improved response:
""")        # Critic prompt
        self.critic_prompt = PromptTemplate.from_template("""
Evaluate the following response to the task:Task: {task}
Response: {response}Provide constructive criticism focusing on:
Accuracy
Completeness
Clarity
Potential improvementsIf the response is satisfactory, respond with "APPROVED".
Otherwise, provide specific feedback.Critique:
""")        self.generator = LLMChain(llm=self.llm, prompt=self.generator_prompt)
        self.critic = LLMChain(llm=self.llm, prompt=self.critic_prompt)    def run(self, task: str, max_iterations: int = 5) -> str:
        """Générer avec réflexion itérative"""
        attempt = ""
        critique = ""        for i in range(max_iterations):
            print(f"\n🔄 Iteration {i+1}")            # Générer réponse
            attempt = self.generator.run(
                task=task,
                previous_attempt=attempt,
                critique=critique
            )
            print(f"📝 Attempt:\n{attempt[:200]}...")            # Critiquer
            critique = self.critic.run(
                task=task,
                response=attempt
            )
            print(f"💭 Critique:\n{critique}")            # Vérifier si approuvé
            if "APPROVED" in critique:
                print("\n✅ Response approved!")
                return attempt        print("\n⚠️ Max iterations reached")
        return attemptExemple
from langchain_openai import ChatOpenAIllm = ChatOpenAI(model="gpt-4o", temperature=0.7)
agent = ReflectionAgent(llm)task = """
Explain quantum computing to a 10-year-old child.
"""final_answer = agent.run(task, max_iterations=3)

Implémentation

Generate → Critique → Refine → Critique → ...

Concept

Pattern 5 : Reflection

Cas d'Usage

User: Write a report on AI impact on software development in 2026Researcher: I'll gather data on AI adoption, developer productivity metrics,
and recent studies... [Searches web, compiles sources]Analyst: Based on the research, I observe 3 key trends:
1. 73% of developers use AI daily (up from 45% in 2024)
2. Code completion tools reduce development time by 35%
3. AI code review reduces bugs by 28%Writer: [Drafts report synthesizing research and analysis]Critic: The report is solid, but I suggest:
Add concrete examples of AI tools
Clarify the 35% productivity metric
Include potential risks/limitationsWriter: [Revises report based on feedback]

from autogen import AssistantAgent, UserProxyAgent, GroupChat, GroupChatManagerclass MultiAgentSystem:
    def __init__(self):
        llm_config = {
            "model": "gpt-4o",
            "temperature": 0.7
        }        # Agent 1 : Researcher
        self.researcher = AssistantAgent(
            name="Researcher",
            system_message="""
You are a research specialist. Your role is to gather information,
search the web, and compile relevant data. Be thorough and cite sources.
""",
            llm_config=llm_config
        )        # Agent 2 : Analyst
        self.analyst = AssistantAgent(
            name="Analyst",
            system_message="""
You are a data analyst. Your role is to analyze information provided
by the Researcher, identify patterns, and draw insights.
""",
            llm_config=llm_config
        )        # Agent 3 : Writer
        self.writer = AssistantAgent(
            name="Writer",
            system_message="""
You are a technical writer. Your role is to synthesize research and
analysis into clear, well-structured content. Focus on clarity.
""",
            llm_config=llm_config
        )        # Agent 4 : Critic
        self.critic = AssistantAgent(
            name="Critic",
            system_message="""
You are a quality reviewer. Your role is to review the Writer's output,
identify errors, suggest improvements, and ensure accuracy.
""",
            llm_config=llm_config
        )        # User proxy (orchestrateur)
        self.user_proxy = UserProxyAgent(
            name="User",
            human_input_mode="NEVER",
            max_consecutive_auto_reply=0
        )        # Group chat
        self.group_chat = GroupChat(
            agents=[self.researcher, self.analyst, self.writer, self.critic, self.user_proxy],
            messages=[],
            max_round=10
        )        self.manager = GroupChatManager(
            groupchat=self.group_chat,
            llm_config=llm_config
        )    def run(self, task: str) -> str:
        """Exécuter tâche avec collaboration multi-agents"""
        self.user_proxy.initiate_chat(
            self.manager,
            message=task
        )        # Récupérer résultat final
        last_message = self.group_chat.messages[-1]
        return last_message["content"]Exemple d'utilisation
system = MultiAgentSystem()task = """
Write a comprehensive report on the impact of AI on software development in 2026.
Include statistics, trends, and future predictions.
"""result = system.run(task)

Architecture AutoGen

Concept

Pattern 4 : Multi-Agent

import asyncio
from typing import List, Tupleclass ReWOOAgent:
    def __init__(self, llm, tools):
        self.llm = llm
        self.tools = tools    async def run(self, query: str) -> str:
        # 1. Planner : générer toutes les actions d'un coup
        plan = await self.plan(query)
        print(f"📋 Plan: {plan}")        # 2. Worker : exécuter toutes les actions en parallèle
        observations = await self.execute_parallel(plan)
        print(f"👁️ Observations: {observations}")        # 3. Solver : synthétiser la réponse
        answer = await self.solve(query, plan, observations)
        return answer    async def plan(self, query: str) -> List[Tuple[str, str]]:
        """Générer plan complet (liste d'actions)"""
        prompt = f"""
Given the query: {query}Plan all necessary actions upfront using these tools: {[t.name for t in self.tools]}Format:
#E1 = Tool[input]
#E2 = Tool[input using #E1]
...Plan:
"""
        response = await self.llm.ainvoke(prompt)
        return self.parse_plan(response.content)    def parse_plan(self, plan_text: str) -> List[Tuple[str, str]]:
        """Parser plan en liste (tool, input)"""
        actions = []
        for line in plan_text.split("\n"):
            if "=" in line and "[" in line:
                # #E1 = Search[Paris population]
                tool_part = line.split("=")[1].strip()
                tool_name = tool_part.split("[")[0].strip()
                tool_input = tool_part.split("[")[1].split("]")[0]
                actions.append((tool_name, tool_input))
        return actions    async def execute_parallel(self, plan: List[Tuple[str, str]]) -> List[str]:
        """Exécuter toutes les actions en parallèle"""
        tasks = []
        for tool_name, tool_input in plan:
            tool = next((t for t in self.tools if t.name == tool_name), None)
            if tool:
                # Créer tâche async
                task = asyncio.create_task(self.execute_tool(tool, tool_input))
                tasks.append(task)        # Attendre toutes les tâches
        results = await asyncio.gather(*tasks)
        return results    async def execute_tool(self, tool, input_str: str) -> str:
        """Exécuter un outil (async)"""
        try:
            # Si l'outil est async
            if asyncio.iscoroutinefunction(tool.func):
                return await tool.func(input_str)
            else:
                # Wrapper sync → async
                loop = asyncio.get_event_loop()
                return await loop.run_in_executor(None, tool.func, input_str)
        except Exception as e:
            return f"Error: {str(e)}"    async def solve(self, query: str, plan: List, observations: List[str]) -> str:
        """Synthétiser réponse finale"""
        prompt = f"""
Query: {query}Plan executed:
{plan}Observations:
{observations}Provide the final answer:
"""
        response = await self.llm.ainvoke(prompt)
        return response.contentExemple d'utilisation
async def main():
    from langchain_openai import ChatOpenAI    llm = ChatOpenAI(model="gpt-4o")
    tools = [
        Tool(name="Search", func=DuckDuckGoSearchRun().run, description="Web search"),
        Tool(name="Calculator", func=lambda x: str(eval(x)), description="Math")
    ]    agent = ReWOOAgent(llm, tools)
    answer = await agent.run("What is the population of Tokyo times 3?")
    print(f"\n✅ Answer: {answer}")

Architecture

Concept

Pattern 3 : ReWOO (Reasoning WithOut Observation)

Cas d'Usage

📋 Plan:
1. [Search] Find GDP of USA in 2025
2. [Search] Find GDP of China in 2025
3. [Search] Find GDP of Japan in 2025
4. [Calculator] Sum the three GDPs⚙️ Executing step 1: [Search] Find GDP of USA in 2025
✅ Result: USA GDP in 2025 is approximately $28.7 trillion⚙️ Executing step 2: [Search] Find GDP of China in 2025
✅ Result: China GDP in 2025 is approximately $19.4 trillion⚙️ Executing step 3: [Search] Find GDP of Japan in 2025
✅ Result: Japan GDP in 2025 is approximately $4.2 trillion⚙️ Executing step 4: [Calculator] Sum the three GDPs
✅ Result: 52.3📊 Final Answer:
The top 3 economies in 2025 are USA ($28.7T), China ($19.4T), and Japan ($4.2T).

from typing import List, Dict
from langchain.chains import LLMChain
from langchain.prompts import PromptTemplateclass PlanAndExecuteAgent:
    def __init__(self, llm, tools):
        self.llm = llm
        self.tools = {tool.name: tool for tool in tools}        # Prompt du Planner
        self.planner_prompt = PromptTemplate.from_template("""
You are a planning agent. Given a user query, create a step-by-step plan to solve it.Available tools: {tool_names}Query: {query}Create a numbered plan with specific actions:
1. [Action] Description
2. [Action] Description
...Plan:
""")        # Prompt de l'Executor
        self.executor_prompt = PromptTemplate.from_template("""
Execute the following step using the available tools.Step: {step}
Tools: {tool_names}
Previous results: {previous_results}Execute the step and return the result.
""")        self.planner = LLMChain(llm=self.llm, prompt=self.planner_prompt)
        self.executor = LLMChain(llm=self.llm, prompt=self.executor_prompt)    def run(self, query: str) -> str:
        # 1. Générer le plan
        plan = self.planner.run(
            query=query,
            tool_names=", ".join(self.tools.keys())
        )        print(f"📋 Plan:\n{plan}\n")        # 2. Parser le plan
        steps = self.parse_plan(plan)        # 3. Exécuter chaque étape
        results = []
        for i, step in enumerate(steps, 1):
            print(f"⚙️ Executing step {i}: {step}")            # Extraire l'outil à utiliser
            tool_name, tool_input = self.parse_step(step)            if tool_name in self.tools:
                # Exécuter l'outil
                result = self.tools[tool_name].func(tool_input)
                results.append({
                    "step": step,
                    "result": result
                })
                print(f"✅ Result: {result}\n")
            else:
                # Utiliser LLM pour interpréter
                result = self.executor.run(
                    step=step,
                    tool_names=", ".join(self.tools.keys()),
                    previous_results=results
                )
                results.append({"step": step, "result": result})        # 4. Synthèse finale
        final_answer = self.synthesize(query, results)
        return final_answer    def parse_plan(self, plan: str) -> List[str]:
        """Parser le plan en étapes"""
        lines = plan.strip().split("\n")
        steps = [line.split(". ", 1)[1] if ". " in line else line
                for line in lines if line.strip()]
        return steps    def parse_step(self, step: str) -> tuple:
        """Extraire l'outil et l'input d'une étape"""
        # Exemple: "[Search] Find population of Paris"
        if "[" in step and "]" in step:
            tool = step.split("[")[1].split("]")[0]
            tool_input = step.split("]")[1].strip()
            return tool, tool_input
        return None, step    def synthesize(self, query: str, results: List[Dict]) -> str:
        """Synthétiser les résultats"""
        synthesis_prompt = PromptTemplate.from_template("""
Based on the following execution results, provide a final answer to the query.Query: {query}Results:
{results}Final Answer:
""")        results_text = "\n".join([
            f"Step: {r['step']}\nResult: {r['result']}\n"
            for r in results
        ])        chain = LLMChain(llm=self.llm, prompt=synthesis_prompt)
        return chain.run(query=query, results=results_text)Exemple d'utilisation
from langchain_openai import ChatOpenAIllm = ChatOpenAI(model="gpt-4o", temperature=0)
tools = [
    Tool(name="Search", func=DuckDuckGoSearchRun().run, description="Web search"),
    Tool(name="Calculator", func=lambda x: str(eval(x)), description="Math calculations")
]agent = PlanAndExecuteAgent(llm, tools)query = """
Compare the GDP of the top 3 economies in 2025 and calculate the total.
"""answer = agent.run(query)

Architecture

Concept

Pattern 2 : Plan-and-Execute

Cas d'Usage

Thought: I need to find the capital of France first
Action: Wikipedia
Action Input: France capital
Observation: Paris is the capital and largest city of France...Thought: Now I need to find the population of Paris
Action: Search
Action Input: population of Paris 2026
Observation: The population of Paris is approximately 2.2 million...Thought: Now I need to multiply by 2
Action: Calculator
Action Input: 2.2 * 2
Observation: 4.4Thought: I now know the final answer

from langchain.agents import Tool, AgentExecutor, create_react_agent
from langchain_openai import ChatOpenAI
from langchain.prompts import PromptTemplate
from langchain_community.tools import DuckDuckGoSearchRunclass ReActAgent:
    def __init__(self, model_name="gpt-4o"):
        self.llm = ChatOpenAI(model=model_name, temperature=0)        # Définir les outils disponibles
        self.tools = [
            Tool(
                name="Search",
                func=DuckDuckGoSearchRun().run,
                description="Useful for searching information on the web. Input should be a search query."
            ),
            Tool(
                name="Calculator",
                func=self.calculator,
                description="Useful for mathematical calculations. Input should be a mathematical expression."
            ),
            Tool(
                name="Wikipedia",
                func=self.wikipedia_search,
                description="Useful for getting detailed information about topics. Input should be a topic name."
            )
        ]        # Prompt ReAct
        self.prompt = PromptTemplate.from_template("""
Answer the following questions as best you can. You have access to the following tools:{tools}Use the following format:Question: the input question you must answer
Thought: you should always think about what to do
Action: the action to take, should be one of [{tool_names}]
Action Input: the input to the action
Observation: the result of the action
... (this Thought/Action/Action Input/Observation can repeat N times)
Thought: I now know the final answer
Final Answer: the final answer to the original input questionBegin!Question: {input}
Thought: {agent_scratchpad}
""")        # Créer l'agent
        self.agent = create_react_agent(
            llm=self.llm,
            tools=self.tools,
            prompt=self.prompt
        )        # Executor avec safeguards
        self.executor = AgentExecutor(
            agent=self.agent,
            tools=self.tools,
            verbose=True,
            max_iterations=10,  # Limite boucles infinies
            max_execution_time=60,  # Timeout 60s
            handle_parsing_errors=True
        )    def calculator(self, expression: str) -> str:
        """Évaluation sécurisée d'expressions mathématiques"""
        try:
            # Whitelist de fonctions autorisées
            allowed = {
                'abs': abs, 'round': round, 'min': min, 'max': max,
                'sum': sum, 'pow': pow
            }
            result = eval(expression, {"__builtins__": {}}, allowed)
            return str(result)
        except Exception as e:
            return f"Error: {str(e)}"    def wikipedia_search(self, query: str) -> str:
        """Recherche Wikipedia"""
        import wikipedia
        try:
            return wikipedia.summary(query, sentences=3)
        except Exception as e:
            return f"Error: {str(e)}"    def run(self, query: str) -> str:
        """Exécuter l'agent sur une requête"""
        result = self.executor.invoke({"input": query})
        return result["output"]Exemple d'utilisation
agent = ReActAgent()query = """
What is the population of the capital of France multiplied by 2?
"""answer = agent.run(query)

Implémentation

┌─────────────────────────────────────────────────────┐
│                    Agent ReAct                       │
├─────────────────────────────────────────────────────┤
│                                                      │
│  ┌───────────────┐                                   │
│  │  User Query   │                                   │
│  └───────┬───────┘                                   │
│          ↓                                           │
│  ┌───────────────┐                                   │
│  │   Thought     │ "I need to search for..."        │
│  └───────┬───────┘                                   │
│          ↓                                           │
│  ┌───────────────┐                                   │
│  │    Action     │ search("query")                  │
│  └───────┬───────┘                                   │
│          ↓                                           │
│  ┌───────────────┐                                   │
│  │  Observation  │ Results: [...]                   │
│  └───────┬───────┘                                   │
│          ↓                                           │
│  ┌───────────────┐                                   │
│  │   Thought     │ "Now I need to..."               │
│  └───────┬───────┘                                   │
│          ↓                                           │
│         ...                                          │
│          ↓                                           │
│  ┌───────────────┐                                   │
│  │ Final Answer  │                                   │
│  └───────────────┘                                   │
│                                                      │

Architecture

Pensée → Action → Observation → Pensée → Action → ...

Concept

Pattern 1 : ReAct (Reason + Act)

L'IA agentique transforme les LLMs en assistants autonomes fiables. Le futur n'est plus réactif, il est proactif.

Quel pattern allez-vous implémenter en premier ?