OpenRouter Known Pitfalls

Overview

A curated list of real-world mistakes developers make when integrating OpenRouter, each with the specific API behavior that causes the problem and the exact fix. These are not theoretical -- they come from production incidents and support requests.

Prerequisites

• An existing (or in-progress) OpenRouter integration to audit against the 10 pitfalls below
• An OpenRouter API key (sk-or-v1-...) exported as OPENROUTERAPIKEY — see the openrouter-install-auth skill for setup
• Python 3.8+ with the OpenAI SDK (pip install openai) to run the validation snippets (e.g., the startup check against /api/v1/models)
• Grep access to the codebase to hunt hardcoded sk-or-v1- keys and scattered model IDs

Instructions

1. Audit request format first: every model ID uses the provider/model form (Pitfall 1), and model IDs live in one MODELS config validated against /api/v1/models at startup instead of being scattered through the code (Pitfall 3).
2. Check cost controls: max_tokens is set on every request (Pitfall 2) and no :free models are used in production, where the 50-1000 req/day limits will 429 you (Pitfall 5).
3. Review routing: sensitive-data requests pin provider.order with allow_fallbacks: False (Pitfall 4), and response.model is logged on every call to catch unexpected fallbacks (Pitfall 6).
4. Inspect client hygiene: one shared client instance with connection pooling (Pitfall 7) configured with timeout and max_retries (Pitfall 9).
5. Sweep for secrets: grep for hardcoded sk-or-v1- strings and move any hits to env vars or a secrets manager, rotating the exposed keys (Pitfall 8).
6. Verify caching only stores deterministic temperature=0 responses (Pitfall 10).
7. Finish by walking the Quick Checklist (PITFALL_CHECKLIST) top to bottom — it condenses all 10 pitfalls into a code-review pass.

Pitfall 1: Missing Provider Prefix on Model ID

# WRONG: Model ID without provider prefix
response = client.chat.completions.create(
    model="gpt-4o",  # ← Will fail with 400 "model not found"
    messages=[{"role": "user", "content": "Hello"}],
)

# RIGHT: Always include provider/model format
response = client.chat.completions.create(
    model="openai/gpt-4o",  # ← Correct
    messages=[{"role": "user", "content": "Hello"}],
)

Pitfall 2: No max_tokens = Runaway Costs

# WRONG: No max_tokens -- model may generate 4000+ tokens
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",  # $15/1M completion tokens
    messages=[{"role": "user", "content": "Write a story"}],
    # No max_tokens → could generate $0.06+ per request
)

# RIGHT: Always set max_tokens
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",
    messages=[{"role": "user", "content": "Write a story"}],
    max_tokens=500,  # ← Caps cost at ~$0.0075
)

Pitfall 3: Hardcoded Model IDs Break When Models Are Renamed

# WRONG: Hardcoded model ID scattered across codebase
# When "claude-3-opus" becomes "claude-3-opus-20240229", everything breaks

# RIGHT: Centralize model IDs in config
MODELS = {
    "primary": "anthropic/claude-3.5-sonnet",
    "budget": "openai/gpt-4o-mini",
    "free": "google/gemma-2-9b-it:free",
}

# Validate at startup
import requests
available = {m["id"] for m in requests.get("https://openrouter.ai/api/v1/models").json()["data"]}
for name, model_id in MODELS.items():
    if model_id not in available:
        print(f"WARNING: {name} model '{model_id}' not available!")

Pitfall 4: Fallbacks Route to Unexpected Providers

# WRONG: Default allow_fallbacks=True without controlling which providers
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",
    messages=[{"role": "user", "content": sensitive_data}],
    # OpenRouter might fall back to a different provider you didn't approve
)

# RIGHT: Control fallback behavior explicitly
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",
    messages=[{"role": "user", "content": sensitive_data}],
    extra_body={
        "provider": {
            "order": ["Anthropic"],      # Only approved provider
            "allow_fallbacks": False,     # No surprise routing
        },
    },
)

Pitfall 5: Ignoring the Free Model Daily Limit

# WRONG: Using free models in production
# Free models have limits: 50 req/day (no credits), 1000 req/day (with credits)
response = client.chat.completions.create(
    model="google/gemma-2-9b-it:free",  # Will 429 after daily limit
    messages=[{"role": "user", "content": "Hello"}],
)

# RIGHT: Use free models only for dev/testing
# Use paid models with credit limits for production

Pitfall 6: Not Checking Which Model Actually Served the Request

# WRONG: Assuming the model you requested is the model that responded
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",
    messages=[{"role": "user", "content": "Hello"}],
)
print(response.choices[0].message.content)  # Might be from a fallback model!

# RIGHT: Always check response.model
response = client.chat.completions.create(
    model="anthropic/claude-3.5-sonnet",
    messages=[{"role": "user", "content": "Hello"}],
)
print(f"Served by: {response.model}")  # Log this for debugging
if response.model != "anthropic/claude-3.5-sonnet":
    log.warning(f"Fallback triggered: requested claude-3.5-sonnet, got {response.model}")

Pitfall 7: Creating New Client Instance Per Request

# WRONG: New client per request (new TCP/TLS handshake each time)
for prompt in prompts:
    client = OpenAI(base_url="https://openrouter.ai/api/v1", api_key=key)
    client.chat.completions.create(...)  # Slow!

# RIGHT: Reuse single client (connection pooling)
client = OpenAI(
    base_url="https://openrouter.ai/api/v1",
    api_key=os.environ["OPENROUTER_API_KEY"],
    default_headers={"HTTP-Referer": "https://my-app.com", "X-Title": "my-app"},
)
for prompt in prompts:
    client.chat.completions.create(...)  # Reuses HTTP connection

Pitfall 8: Storing API Keys in Source Code

# WRONG: Key in source code
client = OpenAI(
    base_url="https://openrouter.ai/api/v1",
    api_key="sk-or-v1-abc123...",  # ← Will be committed to git
)

# RIGHT: Environment variable + secrets manager
client = OpenAI(
    base_url="https://openrouter.ai/api/v1",
    api_key=os.environ["OPENROUTER_API_KEY"],  # From .env (gitignored) or secrets manager
)

Pitfall 9: Not Setting Timeouts

# WRONG: No timeout -- request hangs forever if model is slow
client = OpenAI(base_url="https://openrouter.ai/api/v1", api_key=key)

# RIGHT: Set explicit timeout
client = OpenAI(
    base_url="https://openrouter.ai/api/v1",
    api_key=os.environ["OPENROUTER_API_KEY"],
    timeout=30.0,      # 30s per request
    max_retries=3,     # Retry on 429/5xx
)

Pitfall 10: Caching Non-Deterministic Responses

# WRONG: Caching responses with temperature > 0
# Each call produces different output, so cache is meaningless
cache[key] = client.chat.completions.create(
    model="openai/gpt-4o-mini",
    messages=msgs,
    temperature=0.7,  # ← Non-deterministic!
)

# RIGHT: Only cache with temperature=0
if temperature == 0:
    cache[key] = response

Quick Checklist

PITFALL_CHECKLIST = [
    "Model IDs use provider/model format (e.g., openai/gpt-4o)",
    "max_tokens set on every request",
    "API keys in env vars or secrets manager, never in code",
    "Single client instance reused (not created per request)",
    "Timeout and max_retries configured",
    "response.model checked (may differ from requested model)",
    "Free models NOT used in production",
    "Fallback behavior explicitly controlled for sensitive data",
    "Model IDs centralized in config (not scattered in code)",
    "Only deterministic responses (temp=0) are cached",
]

Output

An audit pass with this skill produces:

• A pitfall-by-pitfall verdict on your integration — each of the 10 items either confirmed clean or flagged with the exact fix from its section
• Startup validation output from the Pitfall 3 snippet: WARNING: primary model 'anthropic/claude-3.5-sonnet' not available! for any config entry missing from /api/v1/models
• Fallback-detection log lines from Pitfall 6: Fallback triggered: requested claude-3.5-sonnet, got
• The completed PITFALL_CHECKLIST — a 10-line review artifact to attach to the integration PR

Examples

Validating your centralized model config at startup (Pitfall 3):

available = {m["id"] for m in requests.get("https://openrouter.ai/api/v1/models").json()["data"]}
for name, model_id in MODELS.items():
    if model_id not in available:
        print(f"WARNING: {name} model '{model_id}' not available!")
# WARNING: primary model 'anthropic/claude-3-opus' not available!

A warning here means a rename or removal upstream — update the one MODELS entry instead of chasing hardcoded IDs across the codebase. More worked examples: references/examples.md.

Error Handling

Enterprise Considerations

• Run the pitfall checklist during code review for any OpenRouter integration PR
• Add pre-commit hooks that scan for hardcoded sk-or-v1- patterns
• Centralize model IDs in a config file and validate against /api/v1/models at startup
• Log response.model on every request to catch unexpected fallbacks
• Set max_tokens as a team-wide policy enforced in your client wrapper

References

• Examples | Errors
• Quickstart | API Reference