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Essentially, creating a companion out of LLMs is as simple as a loop. But these loops work great for one type of character without personalization and fall short as soon as you restart the chat. Problem: LLMs are stateless. GPT doesn’t remember conversations. You could stuff everything inside the context window, but that becomes slow, expensive, and breaks at scale. The solution: Mem0. It extracts and stores what matters from conversations, then retrieves it when needed. Your companion remembers user preferences, past events, and history. In this cookbook we’ll build a fitness companion that:
  • Remembers user goals across sessions
  • Recalls past workouts and progress
  • Adapts its personality based on user preferences
  • Handles both short-term context (today’s chat) and long-term memory (months of history)
By the end, you’ll have a working fitness companion and know how to handle common production challenges.

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The Basic Loop with Memory

Max wants to train for a marathon. He starts chatting with Ray, an AI running coach. 
from openai import OpenAI
from mem0 import MemoryClient

openai_client = OpenAI(api_key="your-openai-key")
mem0_client = MemoryClient(api_key="your-mem0-key")

def chat(user_input, user_id):
    # Retrieve relevant memories
    memories = mem0_client.search(user_input, user_id=user_id, limit=5)
    context = "\\n".join(m["memory"] for m in memories["results"])

    # Call LLM with memory context
    response = openai_client.chat.completions.create(
        model="gpt-4o-mini",
        messages=[
            {"role": "system", "content": f"You're Ray, a running coach. Memories:\\n{context}"},
            {"role": "user", "content": user_input}
        ]
    ).choices[0].message.content

    # Store the exchange
    mem0_client.add([
        {"role": "user", "content": user_input},
        {"role": "assistant", "content": response}
    ], user_id=user_id)

    return response
Session 1: 
chat("I want to run a marathon in under 4 hours", user_id="max")
# Output: "That's a solid goal. What's your current weekly mileage?"
# Stored in Mem0: "Max wants to run sub-4 marathon"
Session 2 (next day, app restarted): 
chat("What should I focus on today?", user_id="max")
# Output: "Based on your sub-4 marathon goal, let's work on building your aerobic base..."
Ray remembers Max’s goal across sessions. The app restarted, but the memory persisted. This is the core pattern: retrieve memories, pass them as context, store new exchanges.
Ray remembers. Restart the app, and the goal persists. From here on, we’ll focus on just the Mem0 API calls.

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Organizing Memory by Type

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Separating Temporary from Permanent

Max mentions his knee hurts. That’s different from his marathon goal - one is temporary, the other is long-term. Categories vs Metadata:
  • Categories: AI-assigned by Mem0 based on content (you can’t force them)
  • Metadata: Manually set by you for forced tagging
Define custom categories at the project level. Mem0 will automatically tag memories with relevant categories based on content: 
mem0_client.project.update(custom_categories=[
    {"goals": "Race targets and training objectives"},
    {"constraints": "Injuries, limitations, recovery needs"},
    {"preferences": "Training style, surfaces, schedules"}
])
Categories vs Metadata: Categories are AI-assigned by Mem0 based on content semantics. You define the palette, Mem0 picks which ones apply. If you need guaranteed tagging, use metadata instead.
Now when you add memories, Mem0 automatically assigns the appropriate categories: 
# Add goal - Mem0 automatically tags it as "goals"
mem0_client.add(
    [{"role": "user", "content": "Sub-4 marathon is my A-race"}],
    user_id="max"
)

# Add constraint - Mem0 automatically tags it as "constraints"
mem0_client.add(
    [{"role": "user", "content": "My right knee flares up on downhills"}],
    user_id="max"
)
Mem0 reads the content and intelligently picks which categories apply. You define the palette, it handles the tagging. Important: You cannot force specific categories. Mem0’s platform decides which categories are relevant based on content. If you need to force-tag something, use metadata instead: 
# Force tag using metadata (not categories)
mem0_client.add(
    [{"role": "user", "content": "Some workout note"}],
    user_id="max",
    metadata={"workout_type": "speed", "forced_tag": "custom_label"}
)

​
Filtering by Category

Retrieve just constraints for workout planning: 
constraints = mem0_client.search(
    "injury concerns",
    user_id="max",
    filters={"categories": {"in": ["constraints"]}}
)
print([m["memory"] for m in constraints["results"]])
# Output: ["Max's right knee flares up on downhills"]
Ray can plan workouts that avoid aggravating Max’s knee, without pulling in race goals or other unrelated memories.

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Filtering What Gets Stored

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The Problem

Run the basic loop for a week and check what’s stored: 
memories = mem0_client.get_all(user_id="max")
print([m["memory"] for m in memories["results"]])
# Output: ["Max wants to run marathon under 4 hours", "hey", "lol ok", "cool thanks", "gtg bye"]
Without filters, Mem0 stores everything—greetings, filler, and casual chat. This pollutes retrieval: instead of pulling “marathon goal,” you get “lol ok.” Set custom instructions to keep memory clean.
Noise. Greetings and filler clutter the memory.

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Custom Instructions

Tell Mem0 what matters: 
mem0_client.project.update(custom_instructions="""
Extract from running coach conversations:
- Training goals and race targets
- Physical constraints or injuries
- Training preferences (time of day, surfaces, weather)
- Progress milestones

Exclude:
- Greetings and filler
- Casual chatter
- Hypotheticals unless planning related
""")
Now chat again: 
chat("hey how's it going", user_id="max")
chat("I prefer trail running over roads", user_id="max")

memories = mem0_client.get_all(user_id="max")
print([m["memory"] for m in memories["results"]])
# Output: ["Max wants to run marathon under 4 hours", "Max prefers trail running over roads"]
Expected output: Only 2 memories stored—the marathon goal and trail preference. The greeting “hey how’s it going” was filtered out automatically. Custom instructions are working.
Only meaningful facts. Filler gets dropped automatically.

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Agent Memory for Personality

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Why Agents Need Memory Too

Max prefers direct feedback, not motivational fluff. Ray needs to remember how to communicate - that’s agent memory, separate from user memory. Store agent personality: 
mem0_client.add(
    [{"role": "system", "content": "Max wants direct, data-driven feedback. Skip motivational language."}],
    agent_id="ray_coach"
)
Retrieve agent style alongside user memories: 
# Get coach personality
agent_memories = mem0_client.search("coaching style", agent_id="ray_coach")
# Output: ["Max wants direct, data-driven feedback. Skip motivational language."]

# Store conversations with agent_id
mem0_client.add([
    {"role": "user", "content": "How'd my run look today?"},
    {"role": "assistant", "content": "Pace was 8:15/mile. Heart rate 152, zone 2."}
], user_id="max", agent_id="ray_coach")
Expected behavior: Ray’s responses are now data-driven and direct. The agent memory stored the coaching style preference, so future responses adapt automatically without Max having to repeat his preference.
No “Great job!” or “Keep it up!” - just data. Ray adapts to Max’s preference.

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Managing Short-Term Context

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When to Store in Mem0

Don’t send every single message to Mem0. Keep recent context in memory, let Mem0 handle the important long-term facts. 
# Store only meaningful exchanges in Mem0
mem0_client.add([
    {"role": "user", "content": "I want to run a marathon"},
    {"role": "assistant", "content": "Let's build a training plan"}
], user_id="max")

# Skip storing filler
# "hey" → don't store
# "cool thanks" → don't store

# Or rely on custom_instructions to filter automatically
Last 10 messages in your app’s buffer. Important facts in Mem0. Faster, cheaper, still works.

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Time-Bound Memories

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Auto-Expiring Facts

Max tweaks his ankle. It’ll heal in two weeks - the memory should expire too. 
from datetime import datetime, timedelta

expiration = (datetime.now() + timedelta(days=14)).strftime("%Y-%m-%d")

mem0_client.add(
    [{"role": "user", "content": "Rolled my left ankle, needs rest"}],
    user_id="max",
    expiration_date=expiration
)
In 14 days, this memory disappears automatically. Ray stops asking about the ankle.

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Putting It All Together

Here’s the Mem0 setup combining everything: 
from mem0 import MemoryClient
from datetime import datetime, timedelta

mem0_client = MemoryClient(api_key="your-mem0-key")

# Configure memory filtering and categories
mem0_client.project.update(
    custom_instructions="""
    Extract: goals, constraints, preferences, progress
    Exclude: greetings, filler, casual chat
    """,
    custom_categories=[
        {"name": "goals", "description": "Training targets"},
        {"name": "constraints", "description": "Injuries and limitations"},
        {"name": "preferences", "description": "Training style"}
    ]
)
Week 1 - Store goals and preferences: 
mem0_client.add([
    {"role": "user", "content": "I want to run a sub-4 marathon"},
    {"role": "assistant", "content": "Got it. Let's build a training plan."}
], user_id="max", agent_id="ray", categories=["goals"])

mem0_client.add([
    {"role": "user", "content": "I prefer trail running over roads"}
], user_id="max", categories=["preferences"])
Week 3 - Temporary injury with expiration: 
expiration = (datetime.now() + timedelta(days=14)).strftime("%Y-%m-%d")
mem0_client.add(
    [{"role": "user", "content": "Rolled ankle, need light workouts"}],
    user_id="max",
    categories=["constraints"],
    expiration_date=expiration
)
Retrieve for context: 
memories = mem0_client.search("training plan", user_id="max", limit=5)
# Gets: marathon goal, trail preference, ankle injury (if still valid)
Ray remembers goals, preferences, and personality. Handles temporary injuries. Works across sessions.

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Common Production Patterns

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Episodic Stories with run_id

Training for Boston is different from training for New York. Separate the memory threads: 
mem0_client.add(messages, user_id="max", run_id="boston-2025")
mem0_client.add(messages, user_id="max", run_id="nyc-2025")

# Retrieve only Boston memories
boston_memories = mem0_client.search(
    "training plan",
    user_id="max",
    run_id="boston-2025"
)
Each race gets its own episodic boundary. No cross-contamination.

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Importing Historical Data

Max has 6 months of training logs to backfill: 
old_logs = [
    [{"role": "user", "content": "Completed 20-mile long run"}],
    [{"role": "user", "content": "Hit 8:00 pace on tempo run"}],
]

for log in old_logs:
    mem0_client.add(log, user_id="max")

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Handling Contradictions

Max changes his goal from sub-4 to sub-3:45: 
# Find the old memory
memories = mem0_client.get_all(user_id="max")
goal_memory = [m for m in memories["results"] if "sub-4" in m["memory"]][0]

# Update it
mem0_client.update(goal_memory["id"], "Max wants to run sub-3:45 marathon")
Update instead of creating duplicates.

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Multiple Agents

Max works with Ray for running and Jordan for strength training: 
chat("easy run today", user_id="max", agent_id="ray")
chat("leg day workout", user_id="max", agent_id="jordan")
Each coach maintains separate personality memory while sharing user context.

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Filtering by Date

Prioritize recent training over old data: 
recent = mem0_client.search(
    "training progress",
    user_id="max",
    filters={"created_at": {"gte": "2025-10-01"}}
)

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Metadata Tagging

Tag workouts by type: 
mem0_client.add(
    [{"role": "user", "content": "10x400m intervals"}],
    user_id="max",
    metadata={"workout_type": "speed", "intensity": "high"}
)

# Later, find all speed workouts
speed_sessions = mem0_client.search(
    "speed work",
    user_id="max",
    filters={"metadata": {"workout_type": "speed"}}
)

​
Pruning Old Memories

Delete irrelevant memories: 
mem0_client.delete(memory_id="mem_xyz")

# Or clear an entire run_id
mem0_client.delete_all(user_id="max", run_id="old-training-cycle")

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What You Built

A companion that:
  • Persists across sessions - Mem0 storage
  • Filters noise - custom instructions
  • Organizes by type - categories
  • Adapts personality - agent_id
  • Stays fast - short-term buffer
  • Handles temporal facts - expiration
  • Scales to production - batching, metadata, pruning
This pattern works for any companion: fitness coaches, tutors, roleplay characters, therapy bots, creative writing partners.
Start with 2-3 categories max (e.g., goals, constraints, preferences). More categories dilute tagging accuracy. You can always add more later after seeing what Mem0 extracts.

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Production Checklist

Before launching:
  • Set custom instructions for your domain
  • Define 2-3 categories (goals, constraints, preferences)
  • Add expiration strategy for time-bound facts
  • Implement error handling for API calls
  • Monitor memory quality in Mem0 dashboard
  • Clear test data from production project

Build AI with Personality

Separate user and agent memories so companions stay consistent across sessions.

Tag Support Memories

Organize customer context to keep assistants responsive at scale.