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Agent Environment Variables Missing in Docker — .env File Not Loaded

Symptom

• Agent works locally but fails in Docker with missing env var errors
• os.environ.get('ANTHROPIC_API_KEY') returns None inside container
• .env file exists in the project directory
• Error: KeyError: 'ANTHROPIC_API_KEY' or Missing required environment variable
• docker run works but docker-compose up fails (or vice versa)

Root Cause

Docker doesn’t automatically load .env files into container environment. Three separate contexts need env vars:

1. Docker Compose — reads .env for its own variable substitution, but doesn’t pass to container unless specified
2. Container runtime — only sees vars explicitly passed via -e, --env-file, or docker-compose environment/env_file
3. Python dotenv — only works if load_dotenv() is called AND the .env file is accessible inside the container

Fix

Option 1: docker-compose env_file directive

# docker-compose.yml
services:
  agent:
    image: your-agent:latest
    env_file:
      - .env          # Docker reads this file and passes all vars to container
    # Note: This is DIFFERENT from docker-compose variable substitution
    # docker-compose automatically reads .env for ${VAR} substitution,
    # but env_file is required to pass those vars INTO the container

Option 2: Explicit environment vars in docker-compose

# docker-compose.yml
services:
  agent:
    environment:
      - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY}   # Pass from host env
      - DATABASE_URL=${DATABASE_URL}
      - OPENCLAW_SECRET=${OPENCLAW_SECRET}

Host must export these first:

source .env && docker-compose up
# OR
export $(cat .env | grep -v '^#' | xargs) && docker-compose up

Option 3: Pass at docker run time

# Pass single variable
docker run -e ANTHROPIC_API_KEY=sk-ant-... your-agent:latest

# Pass all variables from .env file
docker run --env-file .env your-agent:latest

# Pass from current environment
docker run -e ANTHROPIC_API_KEY your-agent:latest  # Passes from host env

Option 4: Bake in the Python dotenv call with correct path

from dotenv import load_dotenv
import os

# In Docker, .env might be at a different path than local
# Try multiple locations
for env_path in ['.env', '/workspace/.env', '/app/.env', os.path.expanduser('~/.env')]:
    if os.path.exists(env_path):
        load_dotenv(env_path)
        print(f"Loaded env from {env_path}")
        break

# Validate after loading
required = ['ANTHROPIC_API_KEY', 'DATABASE_URL']
missing = [v for v in required if not os.environ.get(v)]
if missing:
    raise EnvironmentError(f"Missing required vars: {missing}")

Option 5: Build-time ARG → ENV (not recommended for secrets)

# Only for non-sensitive config values (not API keys)
ARG NODE_ENV=production
ENV NODE_ENV=${NODE_ENV}

Never bake secrets into image — they appear in docker history and image layers.

Verification

# Check what env vars are visible inside the container
docker run --env-file .env your-agent:latest env | grep ANTHROPIC

# Check if a specific var is set
docker exec <container_id> printenv ANTHROPIC_API_KEY

Expected Token Savings

Debugging missing env vars in Docker deployment: ~6,000 tokens This fix: ~100 tokens (one line in docker-compose.yml)

Environment

• Docker and docker-compose agent deployments
• Any Python agent using python-dotenv or os.environ
• Source: direct experience, extremely common deployment issue

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