llm-speed-bench 1.0.3

Local smoke tests for live LLM models, latency, and cost

LLM Speed Bench

A local CLI for smoke-testing live LLM models before you use them in production. Run your own prompts and tests across OpenAI, Anthropic, Gemini, xAI/Grok, OpenRouter, and arbitrary OpenAI-compatible APIs, then compare pass/fail behavior, latency, token usage, and cost.

The goal is not to be a full LLM evaluation platform, tracing system, RAG framework, or public leaderboard. It is a fast model test drive for engineers who need to answer:

Does this model actually work for my task, at acceptable speed and cost?

[!WARNING] Benchmarks make paid API requests. Preview the catalog first, keep limits and repetitions small while configuring a run, and review the interactive confirmation before proceeding.

60-second local demo

Create and run a complete benchmark without an API key or network request:

With the installed CLI:

llm-bench --init
llm-bench benchmark.json --no-save

From a source checkout, use the Python module instead:

python3 -m llm_bench.cli --init
python3 -m llm_bench.cli benchmark.json --no-save

--init refuses to overwrite an existing file and creates a deterministic mock provider configuration. You can inspect the terminal report and exit behavior locally, then replace mock:local with a provider and model ID when you are ready to run paid requests. Press Ctrl-C to cancel a benchmark cleanly; the command exits with status 130 and does not save artifacts.

What it measures

• Pass/fail behavior for built-in smoke tests and your custom tests
• End-to-end request latency (p50 and p95)
• Time to first generated token (TTFT)
• Output tokens per second, when the provider reports token usage
• Success/error rate and response validation failures
• Input/output token totals and estimated cost, when pricing is configured
• Reproducibility metadata: exact request settings, prompt hash, time, host, and raw per-request observations

When to use it

• Before switching models or providers
• Before accepting a provider's latest alias in production
• When a new model appears in a provider catalog
• When you need to compare speed, cost, and output validity on your own prompts
• When you want a local, inspectable result file instead of a hosted dashboard

For deeper application evaluation, RAG metrics, tracing, annotation queues, red-teaming, or LLM-as-judge workflows, use a dedicated eval platform. This tool is intentionally narrower: quick live-model validation and cost/speed comparison.

Network distance, provider load, rate limits, and concurrency affect these numbers. Run from the same host and use at least 20 measured repetitions for meaningful comparisons. The default concurrency of one measures interactive latency; create a separate configuration with higher concurrency to measure load behavior.

Quick start

Python 3.10 or newer is required. No runtime packages are needed.

cp benchmark.example.json benchmark.json
cp .env.example .env.production
# Edit benchmark.json and add only the provider keys you use.
python3 -m llm_bench.cli benchmark.json

Alternatively, put the keys in .env.production next to the benchmark configuration. The CLI loads that file automatically and does not overwrite variables already present in the environment. Loaded values are never printed:

OPENAI_API_KEY="..."
ANTHROPIC_API_KEY="..."
GEMINI_API_KEY="..."
OPENROUTER_API_KEY="..."
XAI_API_KEY="..."

To avoid loading .env.production, pass --no-env-file:

python3 -m llm_bench.cli benchmark.json --no-env-file

To load a different file, pass --env-file:

python3 -m llm_bench.cli benchmark.json --env-file ./local.keys

Or install the local CLI:

python3 -m pip install -e ".[dev]"
llm-bench benchmark.json

Each run prints an aligned terminal table and writes full JSON plus a Markdown report under results/. Interactive terminals use color for successful, partial, and failed rows. Commit or archive the result files if you want durable trend history. The report ends with an executive summary naming the fastest model, the cheapest model, and the best value among models that pass every selected test. Models that fail a required test are explicitly excluded from recommendations rather than being promoted for speed or cost alone. Value equally weights reliability, relative speed, and relative measured cost among qualified models. New result files also record warmup usage and total estimated spend for the complete run.

Automatic model discovery

Use discovery to resolve models from provider catalogs at run time. Every source requires a positive limit; this is a cost-safety control. Optional include and exclude values are case-insensitive regular expressions.

{
  "discovery": [
    {
      "provider": "openrouter",
      "sort": "newest",
      "output_modalities": "text",
      "limit": 5
    }
  ]
}

Inspect exactly what would run without making generation requests:

python3 -m llm_bench.cli benchmark.auto.example.json --catalog

Choose models, providers or provider families, tests, and repetitions interactively. After repetitions, the CLI shows a colored run plan with the selected models, tests, request estimate, response-retention mode, and request breakdown before asking for confirmation. During the run it reports the current model and request, profile/case, API status, test-validation status, input/output tokens, and estimated cost:

python3 -m llm_bench.cli benchmark.auto.example.json --interactive

Model selections accept numbers, a provider such as openai, or a provider family such as openrouter/qwen. Multiple selections are comma-separated.

Progress status separates transport from validation:

• API OK / TEST OK: the provider returned a response and the evaluator accepted it.
• API OK / TEST FAIL: the provider returned a response, but the answer failed the deterministic test.
• API FAIL: the request failed before a usable answer was produced.

The final pass/fail dashboard is based on test validity, not just API request success.

Interactive mode also asks when to stop:

• any-fail: stop after the first model with either an API error or test failure.
• api-error: stop only if the provider/request breaks; continue past weak model outputs.
• test-fail: stop after the first model output failure.
• never: run every selected model.

Named custom prompts

Define reusable prompts in the configuration when you want to benchmark your own requests rather than the built-in profiles. A prompt name is the stable selector shown in interactive mode and accepted by the non-interactive CLI:

{
  "prompts": [
    {
      "name": "csv-review",
      "system_prompt": "Return concise JSON.",
      "prompt": "Find invalid rows in this CSV:\norder_id,total\nA-1,20\nA-2,-5",
      "request": {
        "temperature": 0,
        "max_output_tokens": 500
      },
      "validation": {
        "contains": "A-2"
      }
    },
    {
      "name": "long-summary",
      "prompt": "Summarize the supplied long text in five bullets."
    }
  ],
  "models": [
    {
      "provider": "openai",
      "model": "gpt-5.4-mini"
    }
  ]
}

Run one custom prompt without interaction:

python3 -m llm_bench.cli benchmark.json --prompt csv-review

Custom prompts can also run as first-class tests beside built-in profiles. Use their names in --tests, including mixed selections. The older --profiles flag remains supported as a compatibility alias:

python3 -m llm_bench.cli benchmark.json \
  --tests classification,csv-review,long-summary

In --interactive, built-in profiles are numbered first and custom prompts continue the same numeric list. A configuration may retain the legacy top-level prompt as its default, or contain only prompts and require an explicit test selection.

For short inputs, embed the data directly in JSON using newline escapes. For longer text, CSV, JSON, or other fixture data, put the file next to the benchmark config or in a subfolder and reference it with prompt_file:

benchmarks/
  benchmark.json
  fixtures/
    orders.csv

{
  "prompts": [
    {
      "name": "csv-review",
      "system_prompt": "Return concise JSON with invalid row IDs.",
      "prompt_file": "fixtures/orders.csv",
      "request": {
        "temperature": 0,
        "max_output_tokens": 500
      },
      "validation": {
        "contains": "A-2"
      }
    }
  ],
  "models": [
    {
      "provider": "openai",
      "model": "gpt-5.4-mini"
    }
  ]
}

prompt_file is resolved relative to the configuration file, must be a relative path, and cannot escape the config directory with ... Use either prompt or prompt_file for a custom prompt, not both. If you need instructions plus data, put both in the referenced file or use system_prompt for the instructions and the file for the user prompt body. Do not place confidential data in a configuration or fixture file that will be committed to source control.

Example: source text to structured quiz

Both checked-in example configurations include a source-to-quiz prompt. It asks each selected model to turn a short source passage into exactly four questions covering multiple-choice, true-or-false, and short-answer formats. The response must be JSON and include stable question IDs, answers, plausible options, and source-grounded explanations. This exercises instruction following, constrained generation, source fidelity, and structured output in a single request.

Run the demo directly against the dynamically discovered model set:

python3 -m llm_bench.cli benchmark.auto.example.json \
  --prompt source-to-quiz

In interactive mode, select models first, then choose tests by number or name:

Tests:
  1. chat-fast — ...
  ...
  6. source-to-quiz — Custom prompt test.
Select tests (numbers/names/all) or Enter for the config prompt: 1,6

The demo's prompt-level request controls temperature and output length for this test. It also uses prompt-level presets for common provider quirks:

{
  "name": "source-to-quiz",
  "presets": ["structured"]
}

The initial presets are json, no-reasoning, low-latency, and structured. They expand into provider-specific request options for providers that support them, such as Gemini JSON MIME settings and OpenRouter no-reasoning flags. Explicit request values in your config win over preset defaults. Presets may be placed at the top level for a whole run or on an individual custom prompt/profile when only one test needs structured-output settings.

Its validation regex checks that the response contains a questions JSON array. That is a basic structural gate, not a full assessment of quiz correctness or JSON Schema compliance; review saved responses when comparing content quality. Failed summaries include common diagnosis hints, for example reasoning/commentary before JSON, fenced Markdown, unsupported provider parameters, rate limits, or empty billable responses. Set top-level "save_responses": true temporarily if you want raw model output in the result, and avoid doing so with sensitive source material.

Then benchmark the dynamically selected set:

python3 -m llm_bench.cli benchmark.auto.example.json

Run the complete mixed benchmark suite:

python3 -m llm_bench.cli benchmark.auto.example.json --tests all

Or select a subset:

python3 -m llm_bench.cli benchmark.auto.example.json \
  --tests chat-fast,classification,reasoning

Custom prompts can be included in the same selector:

python3 -m llm_bench.cli benchmark.auto.example.json \
  --tests chat-fast,classification,source-to-quiz

The built-in profiles are chat-fast, classification, structured-extraction, reasoning, and load. The load profile runs at concurrency 1, 5, and 10. Coding is intentionally excluded. Set "profiles": "all" in the configuration to make the built-in suite the default, and use "suite_repetitions" to repeat each deterministic case.

When you select --tests all, the load profile expands its single load-short case into multiple requests: one at concurrency 1, five at concurrency 5, and ten at concurrency 10 by default. Dry runs and interactive confirmation show this request breakdown before any paid calls are made, and live progress labels load requests as load/load-short@c1, load/load-short@c5, or load/load-short@c10.

Fast testing workflows

Use smoke mode for a reduced live benchmark. It sets one repetition, disables warmups, and keeps normal concurrency at one:

python3 -m llm_bench.cli benchmark.json --smoke

Smoke mode still makes paid provider requests. Selected profiles can include multiple deterministic cases, and the load profile retains its explicit concurrency expansion. Always inspect the exact request count first:

python3 -m llm_bench.cli benchmark.json --smoke --dry-run

Check a configuration without generation requests:

python3 -m llm_bench.cli benchmark.json --doctor

Preview the exact run plan without generation requests:

python3 -m llm_bench.cli benchmark.json --tests source-to-quiz --dry-run

The dry run prints a terminal-friendly plan with resolved models, selected tests, request count, retry maximum, estimated cost, stop mode, and response retention behavior. Add --json for the full machine-readable plan in CI.

Check only pricing confidence without generation requests:

python3 -m llm_bench.cli benchmark.json --pricing-check

The command exits non-zero when pricing is unknown or stale according to the configured freshness threshold.

Run an ad hoc prompt without creating a config file:

python3 -m llm_bench.cli \
  --quick "Return only valid JSON with a status field." \
  --models openai:gpt-5.4-mini,anthropic:claude-opus-4-8

Quick mode loads .env.production from the current working directory by default. Use --no-env-file or --env-file PATH for the same credential-file control available to config-based runs.

Compare a new result with a previous baseline:

python3 -m llm_bench.cli --diff results/old.json results/new.json
python3 -m llm_bench.cli benchmark.json --baseline results/old.json --ci

Replay a saved run exactly when the result contains source_config:

python3 -m llm_bench.cli --replay results/run.json

For test-suite runs, print a model-by-test quality matrix:

python3 -m llm_bench.cli benchmark.json --tests all --matrix

Use --changed-since catalog.json with discovery configs to run only models not present in a previous catalog snapshot. Use "max_requests" and "max_estimated_cost_usd" in a config to stop accidental expensive runs before requests are made. A cost ceiling requires complete pricing for every selected model; the command refuses to run when it cannot calculate the estimate.

Model aliases and environment overlays keep daily tests short:

{
  "aliases": {
    "fast": {"provider": "openai", "model": "gpt-5.4-mini"}
  },
  "environments": {
    "ci": {"repetitions": 1, "warmups": 0},
    "deep": {"profiles": "all", "suite_repetitions": 20}
  },
  "models": ["fast"]
}

Then run:

python3 -m llm_bench.cli benchmark.json --env ci

Set "save_responses": "failures" to retain only failed outputs for review. Interactive and smoke runs default to this failure-only retention mode unless you set save_responses explicitly. Use --stop-on api-error, --stop-on test-fail, or --stop-on any-fail when you want a command to stop early. The older --fail-fast flag remains as an alias for --stop-on any-fail. Use --no-save in CI when stdout, the exit code, and an optional JSON result are sufficient and no result artifacts should be written. The deterministic evaluator supports exact matches, numeric answers, JSON subsets, regular expressions, contains checks, and a dependency-free structural json_schema subset. For no-network development checks, use the mock provider:

{
  "prompt": "Reply ok.",
  "models": [{"provider": "mock", "model": "local", "response": "ok"}]
}

Built-in test prompts

These are the exact prompts the built-in profiles send to models, together with the response shape each case expects:

Profile	Case	Prompt	Expected response
chat-fast	chat-capital	Answer in one short sentence: What is the capital of France?	Any non-empty response
chat-fast	chat-summary	Summarize in one sentence: A customer changed their email address and can no longer log in.	Any non-empty response
chat-fast	chat-rewrite	Rewrite politely in one sentence: Send the report today.	Any non-empty response
classification	class-billing	Classify as billing, technical, or account: I was charged twice.	Exactly billing
classification	class-technical	Classify as billing, technical, or account: The mobile app crashes on startup.	Exactly technical
classification	class-account	Classify as billing, technical, or account: I need to change my login email.	Exactly account
structured-extraction	extract-ticket	Extract product and priority as high, medium, or low; map "Urgent" to high: "Urgent: payments are failing in Checkout."	JSON containing {"priority":"high","product":"Checkout"}
structured-extraction	extract-person	Extract name and city: "Marta Novak lives in Bratislava."	JSON containing {"name":"Marta Novak","city":"Bratislava"}
structured-extraction	extract-order	Extract order_id and quantity: "Order A-104 contains 7 units."	JSON containing {"order_id":"A-104","quantity":7}
reasoning	reason-percent	A price of 80 increases by 25%. What is the new price? Return only the numeric answer. Do not include units, words, or explanation.	Numeric answer 100
reasoning	reason-rate	A car travels 150 km in 3 hours. What is its average speed in km/h? Return only the numeric answer. Do not include units, words, or explanation.	Numeric answer 50
reasoning	reason-sequence	What is the next number: 2, 6, 12, 20, 30? Return only the numeric answer. Do not include units, words, or explanation.	Numeric answer 42
load	load-short	Reply with exactly: benchmark	Exactly benchmark

Use a config-level profiles field when you want to run specific test groups. This works with a single built-in profile, a custom prompt name, or a comma-separated mixed subset:

{
  "profiles": "classification"
}

{
  "profiles": "chat-fast,reasoning"
}

{
  "profiles": "chat-fast,source-to-quiz"
}

If you want the built-in suite in a config file, set "profiles": "all". If you need exactly one legacy request instead of a test suite, keep the normal top-level prompt and skip profiles entirely.

The catalog response is snapshotted into each result. Gemini discovery records token limits, supported methods, and its thinking flag. OpenRouter records pricing, context, modalities, tool/structured-output support, and reasoning support. OpenAI and Anthropic discovery records the catalog data those APIs actually return; missing capabilities remain null rather than being guessed. Explicit models and discovered models can be used together.

Development

The repository follows a strict red/green/refactor workflow:

1. Write a focused test for the next behavior.
2. Run it and confirm the expected failure.
3. Add the smallest implementation that makes it pass.
4. Run the entire suite.
5. Refactor only while the suite remains green.

# Focused red/green cycle
make test-one TEST=tests/test_catalog.py::test_openrouter_normalization_and_limit

# Complete verification
make test
make coverage

Live provider credentials are not needed by the deterministic unit tests.

Providers and configuration

Every entry in models uses the same interface:

{
  "name": "label-in-reports",
  "provider": "openai",
  "model": "provider-model-id",
  "input_cost_per_million": 0,
  "output_cost_per_million": 0
}

Supported provider values and default credentials:

Provider	Native interface	Default API key variable
openai	OpenAI chat completions	OPENAI_API_KEY
anthropic	Anthropic messages	ANTHROPIC_API_KEY
gemini	Gemini generate content	GEMINI_API_KEY
xai	xAI OpenAI-compatible chat completions	XAI_API_KEY
openrouter	OpenAI-compatible chat completions	OPENROUTER_API_KEY
openai_compatible	Configurable chat completions URL	configured with api_key_env

Provider defaults can be overridden per model using base_url, api_key_env, and headers. This supports proxies, regional gateways, local inference servers, and OpenRouter attribution headers. provider_options inside the shared request object passes provider-specific body fields when the normalized temperature, system_prompt, and max_output_tokens settings are insufficient. If a provider/model rejects temperature, set "supports_temperature": false or "capabilities": {"temperature": false} on that model so the normalized request omits it.

Native Grok configuration:

{
  "provider": "xai",
  "model": "grok-4.3"
}

Native xAI discovery uses the same filtering and mandatory limit controls:

{
  "provider": "xai",
  "include": "^grok-",
  "limit": 5
}

Secrets are read only from environment variables or the selected env file. Catalog output removes custom headers. Dry-run output, saved JSON results, Markdown reports, source config snapshots, and common provider error strings are redacted for keys and values such as API_KEY, TOKEN, SECRET, PASSWORD, Authorization, X-API-Key, and every custom-header value. Prompts, model metadata, and saved failed responses can still contain business-sensitive content, so review result files before sharing them.

To add a protocol that is not OpenAI-compatible, implement ProviderClient and register it in create_client in llm_bench/client.py. The benchmark runner, validation, metrics, and output format need no changes.

Fair comparison checklist

• Keep the prompt, system instructions, temperature, and maximum output fixed.
• Compare the prompt hash and request settings in result files.
• Use validation so fast but empty or malformed responses count as failures.
• Separate cold/warm and single-user/load tests; do not mix their histories.
• Pin dated model IDs when providers offer them. Aliases may silently change.
• Treat timeout_seconds as the provider socket timeout used for connect/read operations, not a strict total wall-clock deadline for slowly streaming responses.
• Treat provider token counts as authoritative; character-based approximations are deliberately not used.
• Retryable API failures such as rate limits, selected 5xx responses, temporary network failures, and timeouts retry once by default. Set request.retry to control attempts, backoff, and bounded jitter:

{
  "request": {
    "retry": {
      "max_attempts": 3,
      "initial_delay_seconds": 0.25,
      "max_delay_seconds": 4,
      "backoff_multiplier": 2,
      "jitter_seconds": 0.1
    }
  }
}

Retries are recorded in saved JSON summaries as retry counts, retry reasons, and final failure categories. Dry runs and interactive plans show nominal requests/cost alongside the retry-expanded upper bound; configured request and cost ceilings enforce that upper bound. Retries are meant to protect smoke-test reliability, not to hide billable provider failures.

Pricing

OpenRouter prices are taken from its live model catalog. Public standard API rates for selected OpenAI, Gemini, and Anthropic models are maintained in llm_bench/pricing.py with an as_of date. Provider pricing changes over time; verify rates before relying on cost comparisons. Explicit input_cost_per_million and output_cost_per_million values in a model configuration override the registry.

Estimated spend includes measured requests and warmups. It does not include provider-specific taxes, volume agreements, data-residency premiums, tool-call fees, cache discounts, or other account-specific adjustments. Use --dry-run or --pricing-check after pricing edits to confirm the current request estimate and pricing freshness before running a live benchmark. Saved Markdown reports include pricing warnings when costs are unknown or based on stale public registry entries.

Security

• Never commit .env.production, backup environment files, raw results, or debug logs.
• Use --no-env-file in environments where credentials must only come from the parent process.
• Use --env-file PATH when a benchmark needs an explicit non-default credential file.
• Use synthetic prompts for public benchmarks.
• Treat results/ as sensitive when save_responses is enabled.
• Rotate any credential that appears in Git history or logs.
• CI runs detect-secrets-hook against publishable files using .secrets.baseline. Review new findings before updating the baseline; do not baseline real credentials.
• See SECURITY.md for private vulnerability reporting.

Release validation

Each release is validated with tests, security checks, package metadata checks, and a fresh TestPyPI installation before public publication.

Project structure

llm_bench/                  CLI, providers, discovery, profiles, metrics
tests/                      deterministic unit tests
benchmark.example.json      explicit-model configuration example
benchmark.auto.example.json discovery and profile configuration example
.env.example                credential variable template

Contributing and license

See CONTRIBUTING.md for the test-driven workflow. This project is available under the MIT License.