Claude Code: API Configuration and Model Selection

Q: How do I know current Token usage?

Type /cost in Claude Code to see current session token usage and estimated cost.

Last updated: 2026-08-31

Claude Code uses the Anthropic API by default, but also supports connecting third-party models like DeepSeek via compatible interfaces. Proper API configuration is key to controlling cost and quality.

💡 Tip: Claude Code natively supports the Anthropic API via the ANTHROPIC_API_KEY environment variable. Third-party models require OpenAI-compatible interfaces.

📋 Prerequisites: Chapter 2 - Installation and Usage

1. What You'll Learn

Anthropic API configuration and billing
DeepSeek and third-party model integration
Model selection strategy (Sonnet vs Opus)
API cost estimation
Multi-API Key management

2. Anthropic API Configuration

(1) Getting an API Key

BASH

# Steps:
# 1. Visit https://console.anthropic.com/
# 2. Register/login to your account
# 3. Go to the API Keys page
# 4. Click "Create Key"
# 5. Copy the Key (format: sk-ant-api03-xxxxx)

(2) Configure Environment Variable

BASH

# Temporary (current terminal only)
export ANTHROPIC_API_KEY="sk-ant-api03-xxxxx"

# Permanent (add to shell config)
echo 'export ANTHROPIC_API_KEY="sk-ant-api03-xxxxx"' >> ~/.zshrc
source ~/.zshrc

# Verify
echo $ANTHROPIC_API_KEY
# sk-ant-api03-xxxxx

(3) Model Selection

Model	Context	Input Price	Output Price	Use Case
Claude Sonnet	200K	$3/MTok	$15/MTok	Daily coding, best value
Claude Opus	200K	$15/MTok	$75/MTok	Complex architecture, deep reasoning
Claude Haiku	200K	$0.25/MTok	$1.25/MTok	Quick queries, low cost

BASH

# Specify model
claude --model claude-sonnet-4-20250514
claude --model claude-opus-4-20250514

# Or via environment variable
export CLAUDE_MODEL="claude-sonnet-4-20250514"

3. DeepSeek Model Integration

(1) Configure DeepSeek API

DeepSeek provides OpenAI-compatible interfaces usable by Claude Code:

BASH

# Set DeepSeek API
export ANTHROPIC_API_KEY="your-deepseek-api-key"
export ANTHROPIC_BASE_URL="https://api.deepseek.com"

# Or use OpenAI compatible endpoint
export OPENAI_API_KEY="your-deepseek-api-key"
export OPENAI_BASE_URL="https://api.deepseek.com/v1"

(2) DeepSeek Model Comparison

Model	Context	Price (Input/Output)	Use Case
DeepSeek V3	128K	¥2/MTok / ¥8/MTok	General coding, extreme value
DeepSeek R1	128K	¥4/MTok / ¥16/MTok	Deep reasoning, math/logic

▶ Example 1: DeepSeek Configuration Complete Flow

BASH

# Alice uses DeepSeek to reduce costs

# 1. Get DeepSeek API Key
# Visit https://platform.deepseek.com/

# 2. Configure environment variables
export ANTHROPIC_API_KEY="sk-deepseek-xxxxx"
export ANTHROPIC_BASE_URL="https://api.deepseek.com"
export CLAUDE_MODEL="deepseek-chat"

# 3. Run Claude Code
claude "Help me refactor this function"

4. Cost Estimation and Control

(1) Token Consumption Patterns

Claude Code's Token consumption mainly comes from:

Source	Share	Description
Project context	40-60%	Reading project file contents
Conversation history	20-30%	Previous interaction records
Code output	10-20%	Generated code
System prompts	5-10%	CLAUDE.md and other instructions

(2) Cost Estimation

▶ Example 2: Monthly Cost Estimation Script

PYTHON

def estimate_monthly_cost(
    daily_sessions: int,
    avg_context_tokens: int,
    avg_output_tokens: int,
    model_input_price: float,
    model_output_price: float,
    working_days: int = 22
):
    daily_input = daily_sessions * avg_context_tokens
    daily_output = daily_sessions * avg_output_tokens
    monthly_input = daily_input * working_days
    monthly_output = daily_output * working_days

    cost = (
        monthly_input * model_input_price / 1_000_000
        + monthly_output * model_output_price / 1_000_000
    )
    return round(cost, 2)

# Sonnet plan
sonnet_cost = estimate_monthly_cost(
    daily_sessions=10,
    avg_context_tokens=50000,
    avg_output_tokens=5000,
    model_input_price=3,
    model_output_price=15
)
print(f"Sonnet monthly: ${sonnet_cost}")

# DeepSeek plan
deepseek_cost = estimate_monthly_cost(
    daily_sessions=10,
    avg_context_tokens=50000,
    avg_output_tokens=5000,
    model_input_price=0.27,
    model_output_price=1.1
)
print(f"DeepSeek monthly: ${deepseek_cost}")

Output:

TEXT 📖 Display only

Sonnet monthly: $46.2
DeepSeek monthly: $3.74

5. Multi-API Key Management

▶ Example 3: Switch API Config Per Project

BASH

# Configure per project in .env files
# project-a/.env
ANTHROPIC_API_KEY=sk-ant-project-a-key
CLAUDE_MODEL=claude-sonnet-4-20250514

# project-b/.env
ANTHROPIC_API_KEY=sk-deepseek-key
ANTHROPIC_BASE_URL=https://api.deepseek.com
CLAUDE_MODEL=deepseek-chat

# Use direnv for auto-switching
# .envrc
source .env
export ANTHROPIC_API_KEY
export ANTHROPIC_BASE_URL
export CLAUDE_MODEL

(2) API Quota Monitoring

BASH

# Check Anthropic API usage
curl https://api.anthropic.com/v1/usage \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01"

# Claude Code built-in stats
claude /cost
# Current session token usage: 125,430
# Estimated cost: $2.34

6. Comprehensive Example: Cost Optimization Configuration

BASH

# Alice's cost optimization plan

# Core projects: Use Sonnet (quality first)
export PROJECT_CORE_API_KEY="sk-ant-api03-xxxxx"
export PROJECT_CORE_MODEL="claude-sonnet-4-20250514"

# Auxiliary projects: Use DeepSeek (cost first)
export PROJECT_AUX_API_KEY="sk-deepseek-xxxxx"
export PROJECT_AUX_BASE_URL="https://api.deepseek.com"
export PROJECT_AUX_MODEL="deepseek-chat"

# Configure in shell aliases
alias claude-core='ANTHROPIC_API_KEY=$PROJECT_CORE_API_KEY CLAUDE_MODEL=$PROJECT_CORE_MODEL claude'
alias claude-aux='ANTHROPIC_API_KEY=$PROJECT_AUX_API_KEY ANTHROPIC_BASE_URL=$PROJECT_AUX_BASE_URL CLAUDE_MODEL=$PROJECT_AUX_MODEL claude'

# Usage
cd core-project && claude-core "Refactor authentication module"
cd side-project && claude-aux "Add logging feature"

❓ FAQ

Q How does DeepSeek's quality compare to Claude?

A DeepSeek V3 reaches about 80-90% of Claude Sonnet's level on coding tasks, but still falls short on complex reasoning and long context understanding. Sufficient for daily coding; critical tasks should use Claude.

Q What if my API Key is leaked?

A Immediately revoke the Key in the console and generate a new one. Check git history for accidentally committed Keys.

Q How long do free credits last?

A Anthropic gives new accounts $5 in credits, supporting about 50-100 medium-complexity coding sessions at Sonnet pricing.

Q Can I configure multiple APIs simultaneously?

A Yes. Switch between projects via environment variables, or use direnv for auto-switching.

Q Is DeepSeek's context length enough?

A DeepSeek V3 supports 128K context, sufficient for most projects. Very large projects (100+ files) may need Claude's 200K.

Q How do I know current Token usage?

A Type /cost in Claude Code to see current session token usage and estimated cost.

📖 Summary

Anthropic API configured via ANTHROPIC_API_KEY environment variable
Sonnet offers best value, Opus for complex reasoning, Haiku for quick queries
DeepSeek connects via OpenAI-compatible interface at 1/10 the cost of Claude
Token consumption mainly from project context (40-60%)
Multi-API configuration switching via environment variables and aliases

📝 Exercises

Basic (⭐): Configure Anthropic API Key, run Claude Code and confirm connection success.
Intermediate (⭐⭐): Estimate your team's monthly Claude Code API cost (using the script in the example).
Advanced (⭐⭐⭐): Set up DeepSeek integration, compare the same task's quality and cost between Claude Sonnet and DeepSeek V3.

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Claude Code: API Configuration and Model Selection

1. What You'll Learn

2. Anthropic API Configuration

(1) Getting an API Key

(2) Configure Environment Variable

(3) Model Selection

3. DeepSeek Model Integration

(1) Configure DeepSeek API

(2) DeepSeek Model Comparison

▶ Example 1: DeepSeek Configuration Complete Flow

4. Cost Estimation and Control

(1) Token Consumption Patterns

(2) Cost Estimation

▶ Example 2: Monthly Cost Estimation Script

5. Multi-API Key Management

▶ Example 3: Switch API Config Per Project

(2) API Quota Monitoring

6. Comprehensive Example: Cost Optimization Configuration

❓ FAQ

📖 Summary

📝 Exercises

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