llm-route-audit

Find out whether LLM model routing saves money without hurting quality, on your own traffic.

Model routers send easy prompts to cheap models and hard prompts to strong ones. Whether that works for your workload is usually a guess. llm-route-audit replays a sample of your real requests on cheaper models, grades every answer against the original, and tells you, task by task, where a cheaper model is good enough. You get a report and a routing policy for the gateway you already run.

_{Demo run on 5 requests: using Haiku everywhere cut cost to 19% but only 58% of answers passed. Per-task routing kept every answer passing at 26% of the cost. The sample is far too small to trust, so run it on your own logs.}

Try it in one minute

No API key needed. The repository includes the results of a real run.

git clone https://github.com/good2idnan/llm-route-audit.git
cd llm-route-audit
uv sync
uv run routeaudit report examples/sample_logs.jsonl \
  --replay examples/demo/replay.jsonl --grades examples/demo/grades.jsonl --min-samples 1

Requires Python 3.11+ and uv. The command-line tool is called routeaudit.

Why

• Routers often don't beat one good model. In independent benchmarks, most learned routers fail to beat simply using the best single model.
• Cheaper per call isn't cheaper per task. A cheap model that breaks your JSON format or gets the facts wrong costs more than it saves.
• Your workload is not a benchmark. The only evidence that counts is how candidate models do on your own requests.

llm-route-audit is not a router. It measures whether routing pays off, and can tell you not to route.

Features

• Your own data. Replays your logged requests, not public benchmarks.
• Per task type. Recommends a model for each kind of request, since one cheaper model rarely fits all of them.
• Honest grading. Exact checks first (JSON, fields, required text), then an AI judge that reads each pair in both orders, with its consistency reported.
• Model and effort. Tests (model, reasoning effort) pairs, not just models.
• Spending you control. A cost estimate and confirmation before any paid call, plus a hard --max-spend limit that can't be exceeded. Answers are cached, so you never pay twice.
• Readable output. An offline HTML report, a YAML policy, or a ready-to-use LiteLLM config.
• Local first. Logs, results and reports stay on your machine.

How it works

your logs ─▶ analyze ─▶ replay a sample ─▶ grade answers ─▶ report ─▶ export policy ─▶ monitor

Command	What it does
routeaudit import	Convert LiteLLM, Langfuse or OpenTelemetry logs into routeaudit's log format
routeaudit validate	Check a log file
routeaudit analyze	Show what your traffic costs today, by task type and model
routeaudit replay	Re-run a sample of requests on candidate models (Anthropic, OpenRouter, Ollama)
routeaudit grade	Compare every answer with the original: exact checks, then an AI judge
routeaudit report	Recommend a model per task type, with cost and quality for each strategy
routeaudit export	Write the policy as YAML or as a LiteLLM proxy config
routeaudit monitor	After you switch, check that routed traffic still meets the audited quality
routeaudit check-model	Test a newly released model on your last audit's sample and see what it would change

Audit your own traffic

The commands below use the bundled synthetic sample, examples/sample_logs.jsonl. Swap in your own log file.

1. See what you spend today

uv run routeaudit analyze examples/sample_logs.jsonl

By task type (most expensive first)
  Task             Requests  Share  Avg in  Avg out     Cost  Cost share  Per 1K    p50
  review_contract        30    15%     209    1,126  $0.7005         55%  $23.35  24.1s
  summarize_call         40    20%     199      235  $0.2197         17%   $5.49   6.3s
  classify_ticket        45    22%     121       31  $0.0499          4%   $1.11   1.6s

2. Replay a sample on cheaper models

List the candidates in a YAML file (see examples/candidates.yaml), check the cost first, then run:

uv run routeaudit replay examples/sample_logs.jsonl -c examples/candidates.yaml --dry-run
uv run routeaudit replay examples/sample_logs.jsonl -c examples/candidates.yaml --max-spend 1.00

3. Grade the answers

uv run routeaudit grade examples/sample_logs.jsonl --config examples/grading.yaml --max-spend 1.00

Rules are set per task type in examples/grading.yaml. Exact checks run first and cost nothing. Answers that pass them go to the AI judge, which compares each one with the original twice, swapping the order to cancel position bias. Disagreements count as ties. Pick the judge with --judge-model.

4. Get the report

uv run routeaudit report examples/sample_logs.jsonl

For each task type, the report recommends the cheapest option that keeps at least 95% of the original's pass rate, and only once that option has at least 10 graded answers. Until then it keeps your current model and says why. The same report is saved as .routeaudit/report.html. Tune the rules with --target and --min-samples.

5. Export the policy

uv run routeaudit export examples/sample_logs.jsonl --out routing-policy.yaml
uv run routeaudit export examples/sample_logs.jsonl --format litellm --out litellm-config.yaml

The LiteLLM config gives each task type its own model alias, such as route/draft_reply. Your app sends each request to its task's alias, and LiteLLM forwards it to the chosen model with the right effort setting.

6. Keep watching after you switch

Models change and traffic drifts, so a cheaper route that passed the audit can get worse later. Once the policy is live, point monitor at fresh production logs:

uv run routeaudit monitor production-logs.jsonl --policy routing-policy.yaml --config examples/grading.yaml

For each task that switched to a cheaper model, it samples recent requests (--per-task 20) and replays them on the model the route replaced. It then grades the production answer against that reference answer and compares the pass rate with what the audit measured:

Status	Meaning
OK	At or above the audited pass rate, minus a small tolerance (--tolerance 0.05)
WAIT	No problem so far, but too few checks to be sure (--min-checks 10)
WARN	Below the line, but the sample can't rule out bad luck yet
ALERT	95% sure quality dropped. The command exits with code 2, so cron or CI can flag it.

Monitoring uses the same cost estimate, confirmation, --max-spend and cache as replay.

7. Test a new model in one command

When a new model comes out, test it on the same requests as your last audit:

uv run routeaudit check-model examples/sample_logs.jsonl -m claude-sonnet-5-5 --effort low --config examples/grading.yaml

It replays and grades only the new model, adds its results to your audit files, and shows which tasks it would take over and how projected savings change. To test the "one strong model at lower effort" alternative, check your current model at --effort low.

Providers and spending

Name each candidate (and the judge) after where it runs, and put the key in a .env file:

Provider	Model name	Key in .env
Anthropic	claude-haiku-4-5	ANTHROPIC_API_KEY
OpenRouter	openrouter/anthropic/claude-haiku-4.5	OPENROUTER_API_KEY
Ollama (local, free)	ollama/llama3.2	none

Effort levels (low to max) go next to the model in the candidates file. OpenRouter prices are looked up automatically, and the real cost of each call is recorded.

Three spending controls work on both replay and grade:

• Confirmation. routeaudit shows the estimate and asks before spending (--yes skips the question).
• --budget 1.00 refuses to start if the estimate is above $1.00.
• --max-spend 1.00 is a hard limit on actual spend. Each call reserves its worst-case cost first, so even parallel calls can't push the total over. Calls that don't fit are held back and reported.

Logs

Already logging somewhere? Import from the tool you use. Point import at one file or a folder:

Source	Command	Task type comes from
LiteLLM logging callbacks (JSON/JSONL)	routeaudit import litellm-logs/ --format litellm	request tag task:<name>
Langfuse observations (UI export or /api/public/v2/observations)	routeaudit import observations.json --format langfuse	trace tag task:<name>, or --task-from-name
OpenTelemetry GenAI spans (OTLP JSON, e.g. the Collector's file exporter)	routeaudit import traces.jsonl --format otel	span attribute task_type (--task-attribute)

Only real model calls are imported. Requests that can't be replayed faithfully yet are skipped and counted: failed calls, cache hits, images and tool calls. For OpenTelemetry, turn on GenAI message capture so the spans include the prompts and answers. API keys and other metadata are not copied.

Writing your own logs? Use one JSON object per line:

{"id": "req_0001", "timestamp": "2026-09-28T09:14:03Z", "model": "claude-opus-5-5",
 "task_type": "classify_ticket",
 "messages": [{"role": "system", "content": "..."}, {"role": "user", "content": "..."}],
 "response": "{\"category\": \"billing\", \"priority\": \"high\"}",
 "input_tokens": 180, "output_tokens": 32, "latency_ms": 1610}

Field	Required	Notes
id, timestamp, model, response	Yes	id must be unique
messages or prompt	Yes	Use either one
input_tokens, output_tokens	No	input_tokens counts uncached input only; estimated from text if missing
cache_read_tokens, cache_write_tokens	No	For cache-aware pricing
task_type	No	Strongly recommended: recommendations are per task type
latency_ms, outcome, metadata	No	Unknown fields are ignored

Prices. A starter table for Claude models is built in. Pass your own with --prices my-prices.yaml (USD per 1M tokens: input, output, cache_read, cache_write). Requests whose model has no price are reported, not silently dropped.

FAQ

When should I not route? When traffic is low, when every request is equally hard, or in long agent sessions where switching models throws away the prompt cache. Also whenever cheaper models fail your checks. "Keep your current model" is a normal result.

How much does an audit cost? Mostly the replay and judge calls. The demo in this repo (5 requests, 2 candidates, a Sonnet judge) cost $0.11. Costs grow roughly in line with requests × candidates. --dry-run shows the estimate, --max-spend caps it, and local Ollama models are free.

Does my data leave my machine? Only the requests you choose to replay, sent to the providers you configure. Logs, answers, grades and reports stay in your project folder, and the HTML report loads nothing from the internet.

Can I trust an AI judge? Treat it as one signal. Exact checks come first and settle formats and facts for free. The judge sees each pair in both orders, and the report shows how often its two verdicts agree. Use a strong judge model, and spot-check .routeaudit/grades.jsonl.

How many requests do I need? At least 10 graded answers per task type before anything is recommended, and 30 or more for confident numbers. The report shows a 95% range for every pass rate.

Does it handle agents and tool calls? Not yet. Version 0.1 covers single requests, such as chat, extraction, classification and drafting. Agent turns are skipped on import.

Is this a router? No. It audits routing and produces a policy. Put the policy in the gateway you already use, for example with the LiteLLM export.

Development

uv sync
uv run pytest
uv run ruff check . && uv run ruff format --check .

Issues and pull requests are welcome. See CONTRIBUTING.md.

License

MIT © 2026 Muhammad Idnan