OpenRouter Upgrade & Migration
Current State
!npm list openai 2>/dev/null | head -5
!pip show openai 2>/dev/null | head -5
Overview
Migrating to OpenRouter from a direct provider API (OpenAI, Anthropic) is minimal: change base_url and api_key, add two headers. The OpenAI SDK works natively with OpenRouter. This skill covers migrating from direct APIs, switching between models, upgrading SDK versions, and running comparison tests.
Prerequisites
- An existing direct OpenAI or Anthropic integration to migrate — the Current State block above checks your installed
openai SDK via npm list openai / pip show openai
- An OpenRouter API key (
sk-or-v1-...) exported as OPENROUTER_API_KEY — see the openrouter-install-auth skill for setup
- Python 3.8+ or Node.js 18+ with the OpenAI SDK (Anthropic SDK users switch to the OpenAI SDK as part of the migration)
- The old provider key (
OPENAI_API_KEY / ANTHROPIC_API_KEY) kept active during migration for comparison tests and quick rollback
Instructions
- Confirm your installed SDK versions from the Current State output at the top of this skill.
- Apply the 3-line change per Migration from Direct OpenAI, Migration from Direct Anthropic, or TypeScript Migration: swap
base_url to https://openrouter.ai/api/v1, switch to OPENROUTER_API_KEY, and add the HTTP-Referer / X-Title headers. Anthropic migrations also change response parsing to .choices[0].message.content.
- Prefix every model ID with its provider per the Model ID Migration Map (e.g.
gpt-4o → openai/gpt-4o).
- Work through the Migration Checklist — config, code, testing, and operations items — before flipping traffic.
- Run the Comparison Test Script on your critical prompts (
temperature=0) to compare content, tokens, and latency against the old backend.
- Roll out gradually with the Feature Flag Migration pattern (
USE_OPENROUTER env var plus get_model_id mapping), moving 10% → 50% → 100%.
- Watch for post-migration failures (401,
model_not_found, response-format drift, +50–100ms latency) per the Error Handling table.
Migration from Direct OpenAI
from openai import OpenAI
client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])
response = client.chat.completions.create(
model="gpt-4o",
messages=[{"role": "user", "content": "Hello"}],
max_tokens=200,
)
from openai import OpenAI
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",
},
)
response = client.chat.completions.create(
model="openai/gpt-4o",
messages=[{"role": "user", "content": "Hello"}],
max_tokens=200,
)
Migration from Direct Anthropic
import anthropic
client = anthropic.Anthropic(api_key=os.environ["ANTHROPIC_API_KEY"])
response = client.messages.create(
model="claude-3-5-sonnet-20241022",
max_tokens=200,
messages=[{"role": "user", "content": "Hello"}],
)
content = response.content[0].text
from openai import OpenAI
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",
},
)
response = client.chat.completions.create(
model="anthropic/claude-3.5-sonnet",
messages=[{"role": "user", "content": "Hello"}],
max_tokens=200,
)
content = response.choices[0].message.content
TypeScript Migration
import OpenAI from "openai";
const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
const client = new OpenAI({
baseURL: "https://openrouter.ai/api/v1",
apiKey: process.env.OPENROUTER_API_KEY,
defaultHeaders: {
"HTTP-Referer": "https://my-app.com",
"X-Title": "my-app",
},
});
Migration Checklist
MIGRATION_CHECKLIST = {
"config": [
"base_url changed to https://openrouter.ai/api/v1",
"API key changed to OPENROUTER_API_KEY (sk-or-v1-...)",
"HTTP-Referer and X-Title headers added",
"Model IDs prefixed with provider/ (e.g., openai/gpt-4o)",
],
"code": [
"All client initialization updated",
"Model IDs updated in all routes/configs",
"Error handling covers OpenRouter-specific codes (402, 408)",
"Streaming still works with new endpoint",
"Tool/function calling still works",
],
"testing": [
"Same prompts produce comparable quality output",
"Latency within acceptable range (expect +50-100ms)",
"Token counts match expectations",
"Cost tracking updated for OpenRouter pricing",
"Fallback chain tested",
],
"operations": [
"Credit balance sufficient for expected usage",
"Per-key credit limits configured",
"Monitoring updated to track OpenRouter metrics",
"Alerting on new error codes (402, 408)",
"Rollback plan documented",
],
}
Model ID Migration Map
| Direct Provider | OpenRouter ID |
|---|
gpt-4o | openai/gpt-4o |
gpt-4o-mini | openai/gpt-4o-mini |
o1 | openai/o1 |
claude-3-5-sonnet-20241022 | anthropic/claude-3.5-sonnet |
claude-3-haiku-20240307 | anthropic/claude-3-haiku |
gemini-2.0-flash | google/gemini-2.0-flash-001 |
llama-3.1-8b-instruct | meta-llama/llama-3.1-8b-instruct |
Comparison Test Script
def compare_migration(prompt: str, old_model: str, new_model: str):
"""Run same prompt through old and new configurations to compare."""
import time
or_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": "migration-test"},
)
start = time.monotonic()
or_response = or_client.chat.completions.create(
model=new_model,
messages=[{"role": "user", "content": prompt}],
max_tokens=200, temperature=0,
)
or_latency = (time.monotonic() - start) * 1000
return {
"openrouter": {
"model": or_response.model,
"content": or_response.choices[0].message.content[:100],
"tokens": or_response.usage.prompt_tokens + or_response.usage.completion_tokens,
"latency_ms": round(or_latency),
},
}
result = compare_migration(
"What is 2+2?",
old_model="gpt-4o",
new_model="openai/gpt-4o",
)
print(json.dumps(result, indent=2))
Feature Flag Migration
import os
USE_OPENROUTER = os.environ.get("USE_OPENROUTER", "false").lower() == "true"
def get_llm_client():
"""Feature flag for gradual migration."""
if USE_OPENROUTER:
return 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"},
)
else:
return OpenAI(api_key=os.environ["OPENAI_API_KEY"])
def get_model_id(model: str) -> str:
"""Map model IDs based on current backend."""
if USE_OPENROUTER and "/" not in model:
MODEL_MAP = {"gpt-4o": "openai/gpt-4o", "gpt-4o-mini": "openai/gpt-4o-mini"}
return MODEL_MAP.get(model, f"openai/{model}")
return model
Output
- Migrated client initialization code: 3 changed lines (
base_url, api_key, headers) plus provider-prefixed model IDs across routes/configs
- A comparison test JSON per prompt with the served
model, a content preview, combined token count, and latency_ms
- A four-category migration checklist (config / code / testing / operations) to track cutover readiness
- A feature-flagged
get_llm_client() that flips between direct OpenAI and OpenRouter via the USE_OPENROUTER env var
Examples
Verify a migrated model on the same prompt before flipping traffic:
result = compare_migration("What is 2+2?", old_model="gpt-4o", new_model="openai/gpt-4o")
print(json.dumps(result, indent=2))
Expect OpenRouter latency to run ~50-100ms above the direct API. More worked examples: references/examples.md.
Error Handling
| Error | Cause | Fix |
|---|
| 401 after migration | Using old API key with new base_url | Update to OpenRouter API key (sk-or-v1-...) |
model_not_found | Missing provider prefix | Add openai/ or anthropic/ prefix to model ID |
| Different response format | Switched from Anthropic SDK to OpenAI SDK | Update response parsing: .choices[0].message.content |
| Higher latency | OpenRouter proxy overhead | Expected: +50-100ms; use streaming to mask it |
Enterprise Considerations
- Migration from direct provider to OpenRouter requires only 3 lines of code change
- Use feature flags for gradual migration (10% -> 50% -> 100%)
- Run comparison tests on critical prompts before full migration
- OpenRouter adds ~50-100ms overhead; use streaming to mask perceived latency
- Keep direct provider keys active during migration for quick rollback
- Update monitoring dashboards for OpenRouter-specific metrics (generation_id, provider used)
References