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1
rest
generic
content_negotiation
406 Not Acceptable
GET /api/data Accept: text/html
The server only produces JSON; sending Accept: text/html returns 406.
GET /api/data Accept: application/json
Match the Accept header to the media types the server advertises.
rest,content-negotiation,406
2
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.slack.com/api/chat.postMessage")
No timeout set on call to slack endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.slack.com/api/chat.postMessage", timeout=5) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,slack
3
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.slack.com/api/chat.postMessage")
No timeout set on call to slack endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.slack.com/api/chat.postMessage", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,slack
4
javascript
axios
cancel_request
CanceledError unhandled when navigating away
const source = axios.CancelToken.source(); axios.get("/slow-api", { cancelToken: source.token }); source.cancel();
Cancellation throws a CanceledError that must be caught and handled.
const controller = new AbortController(); try { const resp = await axios.get("/slow-api", { signal: controller.signal }); process(resp.data); } catch (err) { if (!axios.isCancel(err)) throw err; } // to cancel: controller.abort();
Use AbortController with axios (v1+) and filter cancellations with axios.isCancel(err).
axios,cancel,abort
5
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
The mapbox API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,mapbox
6
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
The msgraph API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,msgraph
7
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues")
No timeout set on call to github endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues", timeout=60) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,github
8
python
requests
stream_large_response
MemoryError downloading large file
resp = requests.get("https://example.com/large-file.zip") with open("large-file.zip", "wb") as f: f.write(resp.content)
resp.content loads the entire response into memory. For large files, stream the response.
resp = requests.get("https://example.com/large-file.zip", stream=True) with open("large-file.zip", "wb") as f: for chunk in resp.iter_content(chunk_size=8192): f.write(chunk)
Use stream=True and iter_content() to download large files without loading them into memory.
streaming,download,memory
9
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.slack.com/api/chat.postMessage")
The slack API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.slack.com/api/chat.postMessage", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,slack
10
python
stripe
expand_nested
AttributeError: PaymentIntent has no attribute 'customer' — got string ID
intent = stripe.PaymentIntent.retrieve("pi_...") print(intent.customer.email) # intent.customer is a string ID
By default Stripe returns nested object IDs as strings. Use expand= to include full objects.
intent = stripe.PaymentIntent.retrieve("pi_...", expand=["customer"]) print(intent.customer.email)
Use expand=['nested.field'] to retrieve full objects; by default Stripe returns only IDs.
stripe,expand,nested-objects
11
python
anthropic
system_in_messages
Response ignores instructions in messages role=system
messages = [{"role": "system", "content": "You are a concise assistant."}, {"role": "user", "content": "Explain quantum computing."}] resp = client.messages.create(model="claude-opus-4-7", max_tokens=512, messages=messages)
Anthropic Messages API has a top-level system parameter — not a message with role='system'.
resp = client.messages.create( model="claude-opus-4-7", max_tokens=512, system="You are a concise assistant.", messages=[{"role": "user", "content": "Explain quantum computing."}], )
Pass system instructions via the top-level system= parameter, not as a message with role='system'.
anthropic,system-prompt
12
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues")
The github API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,github
13
javascript
fetch
no_error_check
Silently receives 4xx/5xx without throwing
const resp = await fetch("https://api.sendgrid.com/v3/mail/send"); const data = await resp.json();
fetch() resolves even on HTTP errors from sendgrid. Status must be checked manually.
const resp = await fetch("https://api.sendgrid.com/v3/mail/send"); if (!resp.ok) throw new Error(`HTTP ${resp.status} from sendgrid`); const data = await resp.json();
fetch() only rejects on network failure; always check resp.ok for HTTP-level errors.
fetch,error-handling,sendgrid
14
python
boto3
s3_upload_large
EntityTooLarge: Your proposed upload exceeds the maximum allowed size
s3.put_object(Bucket="mybucket", Key="largefile.bin", Body=large_bytes)
put_object has a 5 GB limit. Large files require multipart upload.
from boto3.s3.transfer import TransferConfig config = TransferConfig(multipart_threshold=8 * 1024 * 1024) s3.upload_file("largefile.bin", "mybucket", "largefile.bin", Config=config)
Use upload_file with TransferConfig(multipart_threshold=...) for files > 5 GB.
aws,s3,upload,multipart
15
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.stripe.com/v1/charges")
The stripe API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.stripe.com/v1/charges", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,stripe
16
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
No timeout set on call to mapbox endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,mapbox
17
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.example.com/data") print(resp.json())
The request is missing authentication credentials. The API requires a Bearer token in the Authorization header.
headers = {"Authorization": "Bearer YOUR_TOKEN"} resp = requests.get("https://api.example.com/data", headers=headers) resp.raise_for_status() print(resp.json())
Always attach auth headers explicitly; requests does not add them automatically.
auth,http,401
18
python
boto3
region_missing
EndpointResolutionError: endpoint could not be resolved
import boto3 client = boto3.client("bedrock-runtime") # no region
Some AWS services (like Bedrock) require an explicit region.
import boto3 client = boto3.client("bedrock-runtime", region_name="us-east-1")
Always specify region_name for regional AWS services; the SDK default may not support the service.
aws,region,boto3
19
go
net/http
http_status_not_checked
Silent error: 404 treated as success
resp, _ := http.Get("https://api.example.com/users/99") defer resp.Body.Close() body, _ := io.ReadAll(resp.Body)
HTTP status code is not checked; 404 or 500 responses are silently treated as success.
resp, err := http.Get("https://api.example.com/users/99") if err != nil { log.Fatal(err) } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { log.Fatalf("unexpected status: %d", resp.StatusCode) } body, err := io.ReadAll(resp.Body)
Always check resp.StatusCode after a successful Do/Get; network success != HTTP success.
go,http,error-handling
20
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
No timeout set on call to mapbox endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", timeout=60) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,mapbox
21
javascript
fetch
credential_cookies
Cookies not sent on cross-origin requests
const resp = await fetch("https://api.example.com/profile");
By default fetch does not send cookies for cross-origin requests.
const resp = await fetch("https://api.example.com/profile", { credentials: "include" }); if (!resp.ok) throw new Error(`HTTP ${resp.status}`); const data = await resp.json();
Set credentials: 'include' to send cookies cross-origin; also requires server CORS Allow-Credentials.
fetch,cookies,credentials,cors
22
python
redis
cache_stampede
Cache stampede: all workers recompute on cache miss simultaneously
val = r.get("expensive_result") if val is None: val = compute_expensive_result() r.set("expensive_result", val, ex=300)
Many workers miss simultaneously and all start computing, overloading the backend.
import time LOCK_KEY = "expensive_result:lock" val = r.get("expensive_result") if val is None: if r.set(LOCK_KEY, "1", nx=True, ex=30): try: val = compute_expensive_result() r.set("expensive_result", val, ex=300) finally: r.delete(LOCK_KEY) else: time....
Use a Redis SETNX lock to allow only one worker to recompute on cache miss; others wait or serve stale.
redis,cache,stampede,locking
23
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
The msgraph API requires authentication via X-API-Key header.
headers = {"X-API-Key": "X-API-Key: {API_KEY}"} resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", headers=headers) resp.raise_for_status()
Attach credentials in X-API-Key header; requests does not add them automatically.
auth,401,msgraph
24
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
No timeout set on call to msgraph endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,msgraph
25
python
requests
json_body
415 Unsupported Media Type
payload = {"name": "alice", "role": "admin"} resp = requests.post("https://api.example.com/users", data=payload)
data= sends form-encoded body. The API expects JSON, so the Content-Type is wrong.
payload = {"name": "alice", "role": "admin"} resp = requests.post("https://api.example.com/users", json=payload) resp.raise_for_status()
Use json= not data= to send JSON; requests sets Content-Type automatically.
json,content-type,415
26
python
boto3
paginator_missing
Truncated results: only first 1000 S3 objects returned
resp = s3.list_objects_v2(Bucket="mybucket") objects = resp["Contents"]
list_objects_v2 returns at most 1000 objects. Use a paginator for buckets with more.
paginator = s3.get_paginator("list_objects_v2") objects = [] for page in paginator.paginate(Bucket="mybucket"): objects.extend(page.get("Contents", []))
Use boto3 paginators for any list operation that may return more than 1000 results.
aws,s3,pagination
27
python
aiohttp
concurrent_requests
Sequential async calls — no performance gain
async def fetch_all(urls): results = [] for url in urls: resp = await session.get(url) results.append(await resp.json()) return results
Sequential awaits defeat the purpose of async. Use asyncio.gather for concurrent requests.
async def fetch_all(urls, session): async def fetch_one(url): resp = await session.get(url) resp.raise_for_status() return await resp.json() return await asyncio.gather(*[fetch_one(url) for url in urls])
Use asyncio.gather() to run independent async requests concurrently.
aiohttp,async,concurrent,asyncio
28
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
No timeout set on call to twilio endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", timeout=5) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,twilio
29
python
google-auth
no_credentials
google.auth.exceptions.DefaultCredentialsError: Could not automatically determine credentials
import googleapiclient.discovery service = googleapiclient.discovery.build("calendar", "v3")
No Application Default Credentials found. Point to the service account key file explicitly.
from google.oauth2 import service_account import googleapiclient.discovery creds = service_account.Credentials.from_service_account_file( "service-account-key.json", scopes=["https://www.googleapis.com/auth/calendar.readonly"], ) service = googleapiclient.discovery.build("calendar", "v3", credentials=creds)
Use service_account.Credentials.from_service_account_file() for server-side auth.
google,auth,service-account
30
python
requests
json_body
415 Unsupported Media Type
payload = {"key": "value"} resp = requests.post("https://api.openai.com/v1/embeddings", data=payload)
data= sends form-encoded body to openai-rest. Use json= for JSON requests.
payload = {"key": "value"} resp = requests.post("https://api.openai.com/v1/embeddings", json=payload) resp.raise_for_status()
Use json= not data= to send JSON; requests sets Content-Type automatically.
json,content-type,415,openai-rest
31
python
requests
json_body
415 Unsupported Media Type
payload = {"key": "value"} resp = requests.post("https://graph.microsoft.com/v1.0/me/messages", data=payload)
data= sends form-encoded body to msgraph. Use json= for JSON requests.
payload = {"key": "value"} resp = requests.post("https://graph.microsoft.com/v1.0/me/messages", json=payload) resp.raise_for_status()
Use json= not data= to send JSON; requests sets Content-Type automatically.
json,content-type,415,msgraph
32
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
The sendgrid API requires authentication via X-API-Key header.
headers = {"X-API-Key": "X-API-Key: {API_KEY}"} resp = requests.get("https://api.sendgrid.com/v3/mail/send", headers=headers) resp.raise_for_status()
Attach credentials in X-API-Key header; requests does not add them automatically.
auth,401,sendgrid
33
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
No timeout set on call to twilio endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", timeout=30) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,twilio
34
python
requests
ssl_verify_false
requests.exceptions.SSLError: certificate verify failed
resp = requests.get("https://internal-dev.example.com/api", verify=False)
Disabling SSL verification is insecure. The dev server has a self-signed cert that should be trusted explicitly.
resp = requests.get("https://internal-dev.example.com/api", verify="/path/to/dev-ca.crt") resp.raise_for_status()
Pass verify='/path/to/ca-bundle.crt' instead of verify=False to trust self-signed certs securely.
ssl,security
35
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.openai.com/v1/embeddings")
No timeout set on call to openai-rest endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.openai.com/v1/embeddings", timeout=30) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,openai-rest
36
java
okhttp
network_on_main_thread
NetworkOnMainThreadException on Android
OkHttpClient client = new OkHttpClient(); Request request = new Request.Builder().url("https://api.example.com/data").build(); Response response = client.newCall(request).execute();
Synchronous HTTP calls on Android main thread throw NetworkOnMainThreadException.
OkHttpClient client = new OkHttpClient(); Request request = new Request.Builder().url("https://api.example.com/data").build(); client.newCall(request).enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { /* handle */ } @Override public void onResponse(Call call, Response response...
Use .enqueue() for async HTTP on Android; never block the main thread with .execute().
java,android,okhttp,main-thread
37
python
anthropic
prompt_caching
High latency on repeated identical system prompts
resp = client.messages.create( model="claude-opus-4-7", max_tokens=512, system="You are a helpful assistant. " + LONG_CONTEXT, messages=messages, )
Large repeated system prompts incur full processing cost each time. Use prompt caching.
resp = client.messages.create( model="claude-opus-4-7", max_tokens=512, system=[{"type": "text", "text": "You are a helpful assistant. " + LONG_CONTEXT, "cache_control": {"type": "ephemeral"}}], messages=messages, )
Add cache_control: {type: ephemeral} to large static system prompt blocks to enable Anthropic prompt caching.
anthropic,prompt-caching,performance
38
python
aiohttp
session_per_request
DeprecationWarning: Unclosed client session
async def fetch(url): session = aiohttp.ClientSession() resp = await session.get(url) return await resp.json()
Creating a new ClientSession per request opens new connections and leaks resources.
async def main(): async with aiohttp.ClientSession() as session: resp = await session.get("https://api.example.com/data") resp.raise_for_status() return await resp.json()
Create one aiohttp.ClientSession for the app lifetime; use async with to close it properly.
aiohttp,async,session,resource-leak
39
python
httpx
client_not_closed
ResourceWarning: unclosed <AsyncClient>
client = httpx.AsyncClient() resp = await client.get("https://api.example.com/data")
The AsyncClient is never closed, leaking connection resources.
async with httpx.AsyncClient() as client: resp = await client.get("https://api.example.com/data") resp.raise_for_status()
Always use httpx.AsyncClient as an async context manager to ensure connections are released.
httpx,resource-leak,async
40
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.stripe.com/v1/charges")
The stripe API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.stripe.com/v1/charges", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,stripe
41
go
net/http
custom_transport
All connections share the same idle timeout unexpectedly
client := &http.Client{}
The default Transport uses global settings. For per-client control, create a custom Transport.
client := &http.Client{ Timeout: 30 * time.Second, Transport: &http.Transport{ MaxIdleConns: 100, IdleConnTimeout: 90 * time.Second, TLSHandshakeTimeout: 10 * time.Second, }, }
Configure a custom http.Transport per client for fine-grained control over connection pooling and TLS.
go,http,transport,performance
42
javascript
axios
transformResponse
Response data not parsed as expected type
const resp = await axios.get("https://api.example.com/count"); console.log(typeof resp.data); // "string" not "number"
axios parses JSON by default but may fail for unusual content types. Use transformResponse.
const resp = await axios.get("https://api.example.com/count", { transformResponse: [(data) => parseInt(data, 10)] }); console.log(typeof resp.data); // "number"
Use transformResponse to post-process the raw response string into the desired type.
axios,transformResponse,types
43
rest
generic
http_verbs_misuse
State change via GET causes side effects on caching/replay
GET /api/users/42/delete # Logs out user when link is prefetched by browser
GET must be safe and idempotent; side effects via GET break caching, prefetch, and crawlers.
DELETE /api/users/42 # Or: POST /api/users/42/deactivate
Use DELETE/POST/PUT for state-changing operations; GET must be safe and idempotent.
rest,http-verbs,semantics
44
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.openai.com/v1/embeddings")
No timeout set on call to openai-rest endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.openai.com/v1/embeddings", timeout=5) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,openai-rest
45
go
net/http
no_context_timeout
http.Get blocks forever on slow server
resp, err := http.Get("https://slow-api.example.com/data")
The default http.Get has no timeout. Use a context with deadline.
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) defer cancel() req, _ := http.NewRequestWithContext(ctx, http.MethodGet, "https://slow-api.example.com/data", nil) resp, err := http.DefaultClient.Do(req) if err != nil { log.Fatal(err) } defer resp.Body.Close()
Use http.NewRequestWithContext with context.WithTimeout; bare http.Get has no deadline.
go,http,timeout,context
46
python
stripe
idempotency_key_retry
Duplicate charge on network retry
stripe.PaymentIntent.create(amount=1000, currency="usd")
Without an idempotency key a retried request creates a second PaymentIntent.
import uuid stripe.PaymentIntent.create( amount=1000, currency="usd", idempotency_key=str(uuid.uuid4()), )
Generate a UUID per payment action and reuse it on retries; Stripe deduplicates by this key.
stripe,idempotency,payments
47
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
No timeout set on call to sendgrid endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.sendgrid.com/v3/mail/send", timeout=60) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,sendgrid
48
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
No timeout set on call to sendgrid endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.sendgrid.com/v3/mail/send", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,sendgrid
49
python
stripe
webhook_raw_bytes
stripe.error.SignatureVerificationError: No signatures found matching
payload = request.data sig = request.headers["Stripe-Signature"] event = stripe.Webhook.construct_event(payload, sig, "whsec_...")
The raw bytes must be passed, not a parsed JSON string.
payload = request.get_data(as_text=False) # raw bytes sig = request.headers["Stripe-Signature"] try: event = stripe.Webhook.construct_event(payload, sig, os.environ["STRIPE_WEBHOOK_SECRET"]) except stripe.error.SignatureVerificationError: return "Invalid signature", 400
Stripe webhook validation requires raw request bytes; never pass a decoded/parsed body.
stripe,webhook,signature
50
python
boto3
no_credentials
botocore.exceptions.NoCredentialsError: Unable to locate credentials
import boto3 s3 = boto3.client("s3") s3.list_buckets()
No AWS credentials configured. boto3 searches env vars, ~/.aws/credentials, and IAM roles.
import boto3, os s3 = boto3.client( "s3", aws_access_key_id=os.environ["AWS_ACCESS_KEY_ID"], aws_secret_access_key=os.environ["AWS_SECRET_ACCESS_KEY"], region_name="us-east-1", ) s3.list_buckets()
Provide credentials via environment variables or ~/.aws/credentials; never hard-code them in source.
aws,credentials,boto3
51
typescript
react-query
error_boundary
Unhandled error crashes the whole React tree
const { data } = useQuery(["posts"], fetchPosts); return <PostList posts={data} />;
Query errors are not surfaced; if fetchPosts throws, data is undefined and the component crashes.
const { data, isError, error } = useQuery(["posts"], fetchPosts); if (isError) return <ErrorMessage message={error.message} />; return <PostList posts={data ?? []} />;
Always destructure isError and error from useQuery and render an error state; don't assume data is defined.
react-query,typescript,error-handling
52
python
redis
new_connection_per_call
redis.exceptions.ConnectionError: max number of clients reached
def handler(event): r = redis.Redis(host="localhost", port=6379) r.set("key", "value")
Creating a new Redis client per request creates a new connection each time.
pool = redis.ConnectionPool(host="localhost", port=6379, max_connections=20) def handler(event): r = redis.Redis(connection_pool=pool) r.set("key", "value")
Create one ConnectionPool at startup and share it across handlers.
redis,connection-pool,performance
53
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
The msgraph API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,msgraph
54
python
openai
function_calling_history
openai.BadRequestError: messages does not contain assistant turn after tool_call
messages = [{"role": "user", "content": "What is the weather?"}] resp = client.chat.completions.create(model="gpt-4o", messages=messages, tools=tools) tool_call = resp.choices[0].message.tool_calls[0] result_msg = {"role": "tool", "content": json.dumps(weather), "tool_call_id": tool_call.id} resp2 = client.chat.complet...
The tool result turn must include the full prior conversation including the assistant tool_calls message.
messages = [{"role": "user", "content": "What is the weather?"}] resp = client.chat.completions.create(model="gpt-4o", messages=messages, tools=tools) messages.append(resp.choices[0].message) # keep assistant turn tool_call = resp.choices[0].message.tool_calls[0] messages.append({"role": "tool", "content": json.dumps(...
Always append the assistant message (with tool_calls) to history before adding the tool result.
openai,function-calling,tool-use
55
python
grpc
insecure_channel
grpc._channel._InactiveRpcError: StatusCode.UNAVAILABLE — TLS required
channel = grpc.insecure_channel("api.example.com:443") stub = MyServiceStub(channel)
The server requires TLS but an insecure channel was used.
creds = grpc.ssl_channel_credentials() channel = grpc.secure_channel("api.example.com:443", creds) stub = MyServiceStub(channel)
Use grpc.secure_channel() with ssl_channel_credentials() for TLS-required gRPC endpoints.
grpc,tls,ssl
56
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
No timeout set on call to twilio endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,twilio
57
python
httpx
follow_redirects_off
301 response returned instead of final destination
import httpx resp = httpx.get("http://api.example.com/data")
httpx does not follow redirects by default (unlike requests).
import httpx resp = httpx.get("http://api.example.com/data", follow_redirects=True) resp.raise_for_status()
httpx requires follow_redirects=True explicitly; requests follows redirects by default.
redirect,httpx
58
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.stripe.com/v1/charges")
No timeout set on call to stripe endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.stripe.com/v1/charges", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,stripe
59
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.openai.com/v1/embeddings")
The openai-rest API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.openai.com/v1/embeddings", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,openai-rest
60
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
The twilio API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,twilio
61
javascript
fetch
json_body_wrong
415 Unsupported Media Type when POSTing JSON
const resp = await fetch("https://api.example.com/users", { method: "POST", body: { name: "alice" }, // object, not string });
The body must be a JSON string and Content-Type must be set explicitly.
const resp = await fetch("https://api.example.com/users", { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ name: "alice" }), }); if (!resp.ok) throw new Error(`HTTP ${resp.status}`); const data = await resp.json();
Stringify the body with JSON.stringify() and set Content-Type: application/json header manually.
fetch,json,content-type,415
62
rest
generic
breaking_versioning
Breaking change: v1 clients crash after API field rename
GET /api/users -> {"username": "alice"} # Changed to: GET /api/users -> {"login": "alice"} # breaks all clients
Field renaming without versioning breaks all existing clients.
GET /api/v1/users -> {"username": "alice"} # unchanged GET /api/v2/users -> {"login": "alice"} # new version
Never rename or remove fields without bumping the API version; prefer additive changes.
rest,versioning,backward-compat
63
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.stripe.com/v1/charges")
No timeout set on call to stripe endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.stripe.com/v1/charges", timeout=30) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,stripe
64
python
openai
json_mode
json.JSONDecodeError when parsing model output
resp = client.chat.completions.create(model="gpt-4o", messages=[{"role":"user","content":"Return JSON with name and age"}]) data = json.loads(resp.choices[0].message.content)
Without json mode, the model may include markdown fences or explanatory text around the JSON.
resp = client.chat.completions.create( model="gpt-4o", messages=[{"role":"user","content":"Return JSON with name and age"}], response_format={"type": "json_object"}, ) data = json.loads(resp.choices[0].message.content)
Use response_format={'type': 'json_object'} to guarantee the model returns valid JSON without extra text.
openai,json-mode,structured-output
65
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
No timeout set on call to mapbox endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,mapbox
66
python
gql
n_plus_one_queries
N+1 queries: fetching list then querying each item individually
users = client.execute(gql("query { users { id } }")) for u in users["users"]: detail = client.execute(gql(f'query {{ user(id: {u["id"]}) {{ name email }} }}'))
One query per user makes N+1 round trips. Request nested fields in one query instead.
result = client.execute(gql("query { users { id name email } }")) for user in result["users"]: process(user)
Fetch nested fields in a single GraphQL query; avoid N+1 query patterns.
graphql,n-plus-one,performance
67
go
net/http
post_no_content_type
415 Unsupported Media Type on POST
body := strings.NewReader(`{"name":"alice"}`) resp, err := http.Post("https://api.example.com/users", "", body)
The Content-Type argument is empty. The API expects application/json.
body := strings.NewReader(`{"name":"alice"}`) resp, err := http.Post("https://api.example.com/users", "application/json", body) if err != nil { log.Fatal(err) } defer resp.Body.Close()
Always pass "application/json" as the content-type argument to http.Post.
go,http,json,content-type
68
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.slack.com/api/chat.postMessage")
The slack API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.slack.com/api/chat.postMessage", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,slack
69
python
requests
pagination_keyerror
KeyError: 'next'
url = "https://api.example.com/items" while True: resp = requests.get(url).json() process(resp["items"]) url = resp["next"] # KeyError on last page
The last page has no 'next' key but the code accesses it unconditionally.
url = "https://api.example.com/items" while url: resp = requests.get(url).json() process(resp["items"]) url = resp.get("next") # None on last page -> loop ends
Use .get('next') which returns None when the key is absent, terminating the loop cleanly.
pagination,KeyError
70
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
No timeout set on call to msgraph endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,msgraph
71
javascript
fetch
no_error_check
Silently receives 4xx/5xx without throwing
const resp = await fetch("https://graph.microsoft.com/v1.0/me/messages"); const data = await resp.json();
fetch() resolves even on HTTP errors from msgraph. Status must be checked manually.
const resp = await fetch("https://graph.microsoft.com/v1.0/me/messages"); if (!resp.ok) throw new Error(`HTTP ${resp.status} from msgraph`); const data = await resp.json();
fetch() only rejects on network failure; always check resp.ok for HTTP-level errors.
fetch,error-handling,msgraph
72
javascript
axios
token_refresh_interceptor
401 after token expiry — user sees error instead of auto-refresh
const resp = await api.get("/protected");
The token expired mid-session. An axios response interceptor can refresh it transparently.
api.interceptors.response.use( res => res, async err => { if (err.response?.status === 401 && !err.config._retry) { err.config._retry = true; const token = await refreshAccessToken(); api.defaults.headers.common["Authorization"] = `Bearer ${token}`; return...
Axios response interceptors can catch 401, refresh the token, and replay the original request.
axios,interceptor,auth,refresh-token
73
python
requests
json_body
415 Unsupported Media Type
payload = {"key": "value"} resp = requests.post("https://api.sendgrid.com/v3/mail/send", data=payload)
data= sends form-encoded body to sendgrid. Use json= for JSON requests.
payload = {"key": "value"} resp = requests.post("https://api.sendgrid.com/v3/mail/send", json=payload) resp.raise_for_status()
Use json= not data= to send JSON; requests sets Content-Type automatically.
json,content-type,415,sendgrid
74
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.openai.com/v1/embeddings")
The openai-rest API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.openai.com/v1/embeddings", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,openai-rest
75
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.openai.com/v1/embeddings")
No timeout set on call to openai-rest endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.openai.com/v1/embeddings", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,openai-rest
76
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
No timeout set on call to msgraph endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", timeout=5) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,msgraph
77
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
The mapbox API requires authentication via X-API-Key header.
headers = {"X-API-Key": "X-API-Key: {API_KEY}"} resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", headers=headers) resp.raise_for_status()
Attach credentials in X-API-Key header; requests does not add them automatically.
auth,401,mapbox
78
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.stripe.com/v1/charges")
No timeout set on call to stripe endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.stripe.com/v1/charges", timeout=5) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,stripe
79
python
anthropic
streaming_await_error
TypeError: object Message cannot be used in await expression
async with client.messages.stream(model="claude-opus-4-7", max_tokens=512, messages=msgs) as stream: resp = await stream # wrong
The stream context manager yields an event stream; you iterate it, not await the whole object.
async with client.messages.stream( model="claude-opus-4-7", max_tokens=512, messages=[{"role": "user", "content": "Tell me a story."}], ) as stream: async for text in stream.text_stream: print(text, end="", flush=True)
Use async for text in stream.text_stream to consume streaming tokens; do not await the stream itself.
anthropic,streaming,async
80
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
No timeout set on call to sendgrid endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.sendgrid.com/v3/mail/send", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,sendgrid
81
python
boto3
dynamodb_decimal
TypeError: Float types are not supported. Use Decimal types instead.
table.put_item(Item={"id": "1", "score": 9.5})
DynamoDB does not accept Python float; use Decimal from the decimal module.
from decimal import Decimal table.put_item(Item={"id": "1", "score": Decimal("9.5")})
DynamoDB requires Decimal (not float) for numeric values; convert floats with Decimal(str(value)).
aws,dynamodb,decimal,types
82
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
No timeout set on call to mapbox endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", timeout=30) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,mapbox
83
python
requests
multipart_upload
400 Bad Request: expected multipart/form-data
with open("image.png", "rb") as f: resp = requests.post("https://api.example.com/upload", data=f)
Sending raw bytes via data= doesn't set multipart boundaries. Use files= for multipart upload.
with open("image.png", "rb") as f: resp = requests.post("https://api.example.com/upload", files={"file": ("image.png", f, "image/png")}) resp.raise_for_status()
Use files={} for multipart/form-data uploads; it sets the correct Content-Type with boundary automatically.
multipart,upload,requests
84
typescript
react-query
mutation_invalidation
Stale data shown after successful mutation
const mutation = useMutation(updateUser); mutation.mutate(payload); // cache not refreshed
After a mutation, query cache must be invalidated to trigger a refetch.
const queryClient = useQueryClient(); const mutation = useMutation(updateUser, { onSuccess: () => { queryClient.invalidateQueries(["user"]); }, }); mutation.mutate(payload);
Use onSuccess + queryClient.invalidateQueries() to refresh stale data after mutations.
react-query,typescript,mutation,invalidation
85
javascript
fetch
cors_blocked
Access blocked by CORS policy
const resp = await fetch("https://api.example.com/data"); const data = await resp.json();
CORS is enforced by the browser. The fix is server-side or proxy via your backend.
// Proxy through your backend: const resp = await fetch("/api/proxy/data"); const data = await resp.json();
CORS cannot be fixed client-side; configure the target server or proxy via your own backend.
cors,browser,fetch
86
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues")
No timeout set on call to github endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,github
87
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/")
The mapbox API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.mapbox.com/geocoding/v5/mapbox.places/", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,mapbox
88
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues")
The github API requires authentication via Authorization header.
headers = {"Authorization": "Token {API_KEY}"} resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,github
89
typescript
openai
structured_output
json.JSONDecodeError: model returned prose instead of JSON
const resp = await client.chat.completions.create({ model: "gpt-4o", messages: [{role:"user", content:"Extract: " + text}] }); const data = JSON.parse(resp.choices[0].message.content!);
Without JSON mode or structured output, the model may include markdown or prose.
import { zodResponseFormat } from "openai/helpers/zod"; import { z } from "zod"; const schema = z.object({ name: z.string(), age: z.number() }); const resp = await client.beta.chat.completions.parse({ model: "gpt-4o", messages: [{ role: "user", content: "Extract: " + text }], response_format: zodResponseFo...
Use zodResponseFormat with client.beta.chat.completions.parse() for type-safe structured output.
typescript,openai,structured-output,zod
90
python
boto3
waiter_usage
Checking EC2 instance state in a polling loop manually
import time ec2.start_instances(InstanceIds=[instance_id]) while True: state = ec2.describe_instances(InstanceIds=[instance_id])["Reservations"][0]["Instances"][0]["State"]["Name"] if state == "running": break time.sleep(5)
Manual polling is fragile. boto3 provides built-in waiters for common state transitions.
ec2.start_instances(InstanceIds=[instance_id]) waiter = ec2.get_waiter("instance_running") waiter.wait(InstanceIds=[instance_id])
Use boto3 waiters instead of manual polling loops; they handle retries and timeouts correctly.
aws,ec2,waiter
91
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
The twilio API requires authentication via X-API-Key header.
headers = {"X-API-Key": "X-API-Key: {API_KEY}"} resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", headers=headers) resp.raise_for_status()
Attach credentials in X-API-Key header; requests does not add them automatically.
auth,401,twilio
92
typescript
react-query
stale_time_missing
Excessive refetches on every component mount
const { data } = useQuery(["user", id], () => fetchUser(id));
Without staleTime, react-query refetches on every mount and window focus.
const { data } = useQuery( ["user", id], () => fetchUser(id), { staleTime: 5 * 60 * 1000 } // 5 minutes );
Set staleTime to match the data freshness requirement; default 0 causes aggressive refetching.
react-query,typescript,stale-time,performance
93
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
No timeout set on call to sendgrid endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.sendgrid.com/v3/mail/send", timeout=30) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,sendgrid
94
python
requests
json_body
415 Unsupported Media Type
payload = {"key": "value"} resp = requests.post("https://api.stripe.com/v1/charges", data=payload)
data= sends form-encoded body to stripe. Use json= for JSON requests.
payload = {"key": "value"} resp = requests.post("https://api.stripe.com/v1/charges", json=payload) resp.raise_for_status()
Use json= not data= to send JSON; requests sets Content-Type automatically.
json,content-type,415,stripe
95
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.sendgrid.com/v3/mail/send")
The sendgrid API requires authentication via Authorization header.
headers = {"Authorization": "Bearer {TOKEN}"} resp = requests.get("https://api.sendgrid.com/v3/mail/send", headers=headers) resp.raise_for_status()
Attach credentials in Authorization header; requests does not add them automatically.
auth,401,sendgrid
96
python
requests
auth_missing
401 Unauthorized
resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues")
The github API requires authentication via X-API-Key header.
headers = {"X-API-Key": "X-API-Key: {API_KEY}"} resp = requests.get("https://api.github.com/repos/{owner}/{repo}/issues", headers=headers) resp.raise_for_status()
Attach credentials in X-API-Key header; requests does not add them automatically.
auth,401,github
97
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.openai.com/v1/embeddings")
No timeout set on call to openai-rest endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.openai.com/v1/embeddings", timeout=10) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,openai-rest
98
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
No timeout set on call to twilio endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", timeout=60) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,twilio
99
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages")
No timeout set on call to twilio endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://api.twilio.com/2010-04-01/Accounts/{AccountSid}/Messages", timeout=15) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,twilio
100
python
requests
timeout_missing
requests.exceptions.ReadTimeout: HTTPSConnectionPool: Read timed out.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages")
No timeout set on call to msgraph endpoint. Slow or down servers block indefinitely.
resp = requests.get("https://graph.microsoft.com/v1.0/me/messages", timeout=60) resp.raise_for_status()
Always set a timeout on requests to external APIs; the default is None (wait forever).
timeout,requests,msgraph
End of preview. Expand in Data Studio

API Error Resolution Pairs

A synthetic dataset of real-world API error scenarios paired with explanations and fixes. Each example captures a broken code snippet, the error it produces, a plain-English explanation of the root cause, a corrected implementation, and a distilled key insight.

Dataset Summary

Split Examples
train 132
validation 16
test 16
Total 164

Quick Start

Load the dataset

from datasets import load_dataset

ds = load_dataset("SalutefaceAAC/api-error-resolution-pairs")
print(ds)
# DatasetDict({
#     train: Dataset({features: [...], num_rows: 132}),
#     validation: Dataset({features: [...], num_rows: 16}),
#     test: Dataset({features: [...], num_rows: 16})
# })

# Inspect a record
example = ds["train"][0]
print(example["error_type"])     # e.g. "timeout_missing"
print(example["broken_code"])    # code that triggers the error
print(example["fixed_code"])     # corrected implementation
print(example["key_insight"])    # one-sentence principle

Filter by language or error type

# All Python examples
py_examples = ds["train"].filter(lambda x: x["language"] == "python")

# Rate-limiting errors only
rate_limit = ds["train"].filter(lambda x: x["error_type"] == "rate_limit")

# Multi-filter: TypeScript + auth errors
ts_auth = ds["train"].filter(
    lambda x: x["language"] == "typescript" and "auth" in x["error_type"]
)

RAG retrieval (semantic search over error patterns)

from sentence_transformers import SentenceTransformer
import numpy as np

model = SentenceTransformer("all-MiniLM-L6-v2")

train = ds["train"]
# Embed error messages as the retrieval key
embeddings = model.encode(train["error_message"], show_progress_bar=True)

def find_similar(query: str, top_k: int = 3):
    q_emb = model.encode([query])
    scores = np.dot(embeddings, q_emb.T).squeeze()
    top_idx = np.argsort(scores)[::-1][:top_k]
    for i in top_idx:
        print(f"[{scores[i]:.3f}] {train[int(i)]['error_type']} — {train[int(i)]['key_insight']}")

find_similar("Connection refused when calling external API")

Fine-tuning prompt template

def format_for_finetuning(example):
    """Format a record as an instruction-following prompt."""
    prompt = (
        f"Language: {example['language']}\n"
        f"Library: {example['library']}\n"
        f"Error: {example['error_message']}\n\n"
        f"Broken code:\n```\n{example['broken_code']}\n```\n\n"
        "Explain the root cause and provide the corrected implementation."
    )
    completion = (
        f"Root cause: {example['explanation']}\n\n"
        f"Fixed code:\n```\n{example['fixed_code']}\n```\n\n"
        f"Key insight: {example['key_insight']}"
    )
    return {"prompt": prompt, "completion": completion}

formatted = ds["train"].map(format_for_finetuning)

Sample Records

Example 1 — Python / requests: Large file download (MemoryError)

Field Value
language python
library requests
error_type stream_large_response
error_message MemoryError downloading large file

Broken code:

resp = requests.get("https://example.com/large-file.zip")
with open("large-file.zip", "wb") as f:
    f.write(resp.content)

Fixed code:

resp = requests.get("https://example.com/large-file.zip", stream=True)
with open("large-file.zip", "wb") as f:
    for chunk in resp.iter_content(chunk_size=8192):
        f.write(chunk)

Key insight: Use stream=True and iter_content() to download large files without loading them into memory.


Example 2 — JavaScript / axios: Unhandled cancellation

Field Value
language javascript
library axios
error_type cancel_request
error_message CanceledError unhandled when navigating away

Broken code:

const source = axios.CancelToken.source();
axios.get("/slow-api", { cancelToken: source.token });
source.cancel();

Fixed code:

const controller = new AbortController();
try {
    const resp = await axios.get("/slow-api", { signal: controller.signal });
    process(resp.data);
} catch (err) {
    if (!axios.isCancel(err)) throw err;
}
// to cancel: controller.abort();

Key insight: Use AbortController with axios (v1+) and filter cancellations with axios.isCancel(err).


Example 3 — REST: Content negotiation failure

Field Value
language rest
library generic
error_type content_negotiation
error_message 406 Not Acceptable

Broken request:

GET /api/data
Accept: text/html

Fixed request:

GET /api/data
Accept: application/json

Key insight: Match the Accept header to the media types the server advertises.

Schema

Field Type Description
id int Unique record identifier
language string Programming language (python, javascript, typescript, go, java, rest)
library string Library or framework (requests, httpx, boto3, openai, anthropic, fetch, axios, okhttp, net/http, …)
error_type string Short error category slug
error_message string The actual error message or symptom
broken_code string Snippet that triggers the error
explanation string Root cause explanation
fixed_code string Corrected implementation
key_insight string One-sentence principle to prevent this class of error
tags string Comma-separated tag list

Coverage

Languages & Libraries

Language Libraries
Python requests, httpx, boto3, openai, anthropic, aiohttp, grpc, gql, stripe, google-auth, redis
JavaScript fetch, axios
TypeScript openai, react-query
Go net/http
Java okhttp
REST Generic HTTP patterns

Error Categories

  • Auth: missing/malformed credentials, 401 flows
  • Timeout: missing timeouts, context deadlines
  • JSON body: wrong encoding, missing Content-Type
  • Error handling: unchecked 4xx/5xx, silent failures
  • Rate limiting: 429, Retry-After, backoff
  • Pagination: offset vs cursor, last-page edge cases
  • Resource leaks: unclosed bodies, sessions, connections
  • SSL/TLS: certificate verification, insecure channels
  • Performance: connection pools, pipelines, parallel requests
  • Streaming: async iteration, chunk handling
  • Function/tool calling: history management, tool result format
  • Structured output: JSON mode, Zod schemas
  • Idempotency: duplicate charges, retry safety
  • Versioning: breaking changes, additive vs destructive

Generation Methodology

Records were hand-authored one at a time, each capturing a distinct error pattern from real developer experience. A parametric augmentation layer generates variants across different API endpoints, token formats, and timeout values to increase dataset breadth without noise. All records passed MD5-based deduplication (keyed on broken_code + fixed_code).

No model was used to generate records. All broken_code / fixed_code / explanation / key_insight values were written manually.

Intended Uses

  • Fine-tuning code LLMs on error diagnosis and remediation
  • Retrieval-augmented code assistance (RAG over error patterns)
  • Benchmark evaluation for debugging models
  • Developer education tooling

Limitations

  • Augmentation depth: parametric augmentation varies endpoints and timeout values only — augmented records share structure with their base and increase breadth but not conceptual depth.
  • Language coverage: Java examples focus on Android context (OkHttp); server-side Java (Spring, Quarkus) patterns are underrepresented. Go examples cover net/http only.
  • Scenario complexity: each record is a single-error / single-fix scenario. Multi-step debugging chains and cascading failures are out of scope.
  • Domain scope: covers mainstream REST and gRPC clients; WebSocket, GraphQL subscriptions, and binary protocols are not included.
  • No runtime validation: code snippets are validated by human review, not executed; edge-case compilation issues may exist.

License

Apache 2.0

Citation

@dataset{saluteface_api_error_resolution_2026,
  title  = {API Error Resolution Pairs},
  author = {SalutefaceAAC},
  year   = {2026},
  url    = {https://huggingface.co/datasets/SalutefaceAAC/api-error-resolution-pairs}
}
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