Presets Guide

Presets are pre-built configuration profiles that set error rates, latency, burst patterns, and response generation for common testing scenarios. Instead of manually configuring dozens of fields, pick a preset that matches your testing goal.

Using Presets

# CLI
uv run chaosllm serve --preset=realistic
uv run chaosweb serve --preset=stress_scraping
uv run chaosblob serve --preset=stress_storage
uv run chaossmtp serve --preset=stress_delivery

# Python
from errorworks.llm.config import load_config
config = load_config(preset="realistic")

ChaosLLM Presets

Comparison Table

Preset	Rate Limit	Capacity 529	Server Errors	Connection Failures	Malformed	Burst	Latency
silent	0%	0%	0%	0%	0%	Off	10 +/- 5ms
gentle	1%	0.5%	0.5% svc unavail	0%	0%	Off	50 +/- 20ms
realistic	5%	2%	0.5% svc, 0.2% internal, 0.1% bad gw, 0.2% gw timeout	0.2% timeout, 0.1% reset, 1% slow	0.1% invalid JSON, 0.1% truncated, 0.1% missing fields	60s/5s (50% rl, 30% cap)	100 +/- 50ms
stress_aimd	15%	5%	2% svc, 0.5% internal, 0.2% bad gw, 0.3% gw timeout	0.5% slow	0%	30s/5s (80% rl, 50% cap)	30 +/- 15ms
stress_extreme	20%	10%	3% svc, 5% internal, 1% bad gw, 1% gw timeout	0%	3% invalid JSON, 2% truncated	15s/5s (90% rl, 70% cap)	10 +/- 5ms
chaos	6.25%	3.13%	1.88% svc, 1.88% internal, 1.25% bad gw, 1.25% gw timeout	1.25% timeout, 0.94% reset, 1.88% slow	1.25% invalid JSON, 0.94% truncated, 0.63% empty, 0.94% missing, 0.31% wrong ct	20s/8s (90% rl, 70% cap)	100 +/- 100ms

When to Use Each

Preset	Use When
silent	Measuring maximum pipeline throughput without noise
gentle	Verifying basic pipeline operation and debugging
realistic	Testing against production-like Azure OpenAI conditions
stress_aimd	Tuning AIMD throttle parameters and backoff behavior
stress_extreme	Verifying pipeline survives under harsh HTTP error rates
chaos	Achieving error handling coverage across every failure type

ChaosWeb Presets

Comparison Table

Preset	Rate Limit	Forbidden	Not Found	Connection Failures	Content Malform.	Redirects	Burst	Latency
silent	0%	0%	0%	0%	0%	0%	Off	200 +/- 100ms
gentle	1%	0%	1%	0%	0%	0%	Off	100 +/- 50ms
realistic	5%	3%	2%	0.5% timeout, 0.2% reset, 5% slow	1% wrong ct, 1% encoding, 0.5% truncated	0%	60s/8s (40% rl, 30% forbid)	300 +/- 150ms
stress_scraping	15%	10%	3%	5% timeout, 3% reset, 8% slow, 2% incomplete	3% wrong ct, 2% encoding, 2% truncated, 1% charset	1% SSRF	60s/10s (80% rl, 50% forbid)	500 +/- 200ms
stress_extreme	25%	15%	5%	10% timeout, 5% reset, 3% stall, 5% slow, 5% incomplete	5% wrong ct, 3% encoding, 3% truncated, 2% invalid enc, 2% charset, 1% meta	3% loop, 2% SSRF	30s/8s (90% rl, 70% forbid)	800 +/- 400ms

When to Use Each

Preset	Use When
silent	Measuring scraping throughput without error injection overhead
gentle	Verifying basic scraping functionality works before adding stress
realistic	Testing against typical web scraping production conditions
stress_scraping	Verifying retry logic, backoff, and error routing under pressure
stress_extreme	Finding failure modes and verifying graceful degradation

ChaosBlob Presets

Comparison Table

Preset	SlowDown	HTTP Errors	Connection Failures	Object Corruption	List Corruption	Burst	Latency
silent	0%	0%	0%	0%	0%	Off	50 +/- 25ms
gentle	1%	0.5% not found	0%	0%	0%	Off	100 +/- 50ms
realistic	4%	0.5% access denied, 1% not found, 0.8% svc, 0.2% internal, 0.2% bad gw, 0.3% gw timeout	0.3% timeout, 0.2% reset, 3% slow	0.5% truncated, 0.3% wrong length, 0.5% checksum, 0.3% metadata	3% stale, 0.2% malformed XML	90s/10s (35% slow, 10% svc)	150 +/- 75ms
stress_storage	8%	4% not found	8% slow	8% truncated, 6% wrong length, 8% checksum, 6% metadata	12% stale, 4% malformed XML	60s/12s (60% slow, 20% svc)	250 +/- 150ms
stress_extreme	20%	5% access denied, 5% not found, 8% svc, 4% internal, 3% bad gw, 5% gw timeout	8% timeout, 5% reset, 4% stall, 8% slow	6% truncated, 5% wrong length, 6% checksum, 4% metadata	8% stale, 4% malformed XML	30s/8s (90% slow, 60% svc)	600 +/- 300ms

ChaosSMTP Presets

Comparison Table

Preset	MAIL/RCPT Failures	DATA Failures	Protocol/Connection	Burst	Latency	Capture
silent	0%	0%	0%	Off	10 +/- 5ms	metadata
gentle	1% RCPT tempfail	1% tempfail	0%	Off	50 +/- 20ms	metadata
realistic	3% rate limit, 4% RCPT tempfail	3% tempfail, 1% reject	2% slow response	60s/8s (50% tempfail, 40% rate limit)	120 +/- 60ms	metadata
stress_delivery	10% rate limit, 5% MAIL tempfail, 15% RCPT tempfail, 8% RCPT reject	12% tempfail, 8% reject, 2% accept/drop	5% slow response	45s/10s (80% tempfail, 70% rate limit)	200 +/- 100ms	metadata
stress_extreme	15% rate limit, 8% MAIL tempfail, 5% MAIL reject, 15% RCPT tempfail, 10% RCPT reject	12% tempfail, 10% reject, 5% accept/drop	4% reset, 3% stall, 8% slow, 2% malformed, 2% wrong code	30s/8s (90% tempfail, 85% rate limit)	300 +/- 200ms	metadata

When to Use Each

Preset	Use When
silent	Measuring object workflow throughput without injected failures
gentle	Verifying happy-path PUT/GET/list behavior with light throttling
realistic	Testing common object-store throttling, stale list, and rare read faults
stress_storage	Exercising body integrity, metadata validation, and stale listing recovery
stress_extreme	Finding retry, timeout, and corruption handling breakpoints

When to Use Each (SMTP)

Preset	Use When
silent	Verifying SMTP client wiring and baseline throughput with no delivery faults
gentle	Checking basic retry paths without making tests noisy
realistic	Simulating common transient delivery pressure and occasional DATA rejection
stress_delivery	Exercising retry, bounce, and alerting behavior under heavy delivery pressure
stress_extreme	Finding SMTP client failure modes across protocol, connection, and delivery errors

Use SMTP presets from either CLI entry point:

uv run chaossmtp serve --preset=realistic
uv run chaosengine smtp serve --preset=stress_delivery

Combining Presets with Overrides

Presets provide the base configuration, but you can override any setting on top. Configuration precedence (highest to lowest):

1. CLI flags -- Override individual settings
2. Config file -- --config=my-config.yaml
3. Preset -- --preset=realistic
4. Defaults -- Built-in Pydantic defaults

Example: Preset with CLI Override

# Start with realistic, but increase rate limiting
uv run chaosllm serve --preset=realistic --rate-limit-pct=20.0

Example: Preset with Config File Override

# my-overrides.yaml
error_injection:
  rate_limit_pct: 20.0
  burst:
    interval_sec: 30  # More frequent bursts

uv run chaosllm serve --preset=realistic --config=my-overrides.yaml

The config file's rate_limit_pct: 20.0 overrides the preset's 5.0, and the burst interval_sec: 30 overrides the preset's 60. All other preset values are preserved.

Example: Python with Overrides

from errorworks.llm.config import load_config

config = load_config(
    preset="realistic",
    cli_overrides={
        "error_injection": {"rate_limit_pct": 20.0},
        "latency": {"base_ms": 200},
    },
)

Tip

Deep merge means you only need to specify the fields you want to change. Nested objects are merged recursively -- you do not need to repeat the entire burst section just to change interval_sec.

Listing Available Presets

from errorworks.llm.config import list_presets as list_llm_presets
from errorworks.blob.config import list_presets as list_blob_presets
from errorworks.smtp.config import list_presets as list_smtp_presets
from errorworks.web.config import list_presets as list_web_presets

print(list_llm_presets())  # ['chaos', 'gentle', 'realistic', 'silent', 'stress_aimd', 'stress_extreme']
print(list_smtp_presets())  # ['gentle', 'realistic', 'silent', 'stress_delivery', 'stress_extreme']
print(list_web_presets())  # ['gentle', 'realistic', 'silent', 'stress_extreme', 'stress_scraping']
print(list_blob_presets())  # ['gentle', 'realistic', 'silent', 'stress_extreme', 'stress_storage']

Related Pages

• ChaosLLM -- Full ChaosLLM endpoint and error injection reference
• ChaosWeb -- Full ChaosWeb endpoint and error injection reference
• ChaosBlob -- Full ChaosBlob endpoint and error injection reference
• ChaosSMTP -- SMTP listener, error injection, and capture reference
• Configuration -- YAML config file structure and precedence details