APIMart vs Spanlens

APIMart and Spanlens are both inference engines & infra tracked by AIDiveForge. Below is a side-by-side comparison of pricing, capabilities, platforms, and ownership — sourced from each tool's live website and verified before publishing.

APIMart

APIMart is a paid API gateway that routes requests to 500-plus models — including chat, image, video, and audio — through one OpenAI-compatible interface, with discounts the vendor states range from 30 to 70 percent off official provider pricing. You swap one base URL and keep your existing SDK. The catalog spans OpenAI, Anthropic, Google, ByteDance, Qwen, Kimi, and MiniMax, so switching between providers is a config change, not a refactor. The ceiling shows up when you need call-level control: APIMart is a passive gateway, not an orchestrator, so any branching logic, retries, or fallback chains live entirely in your own code. Teams building complex multi-step pipelines maintain that routing layer themselves.

Spanlens

Spanlens sits in front of your LLM provider via a single baseURL change, recording every call's cost, latency, tokens, and full request-response body with no SDK rewrite required. Agent runs surface as waterfall span trees so you can identify the one step consuming 80% of wall-clock time. The model recommender flags GPT-4o calls that look like classification tasks and shows the cost delta if you swap — with numbers from your own traffic, not benchmarks. The eval and experiment layer lets you replay a fixed dataset across prompt versions before you ship, so quality regressions don't surprise you in production. PII scanning and anomaly detection run at log time, which matters when sensitive data crosses the wire at 3 a.m. with nobody watching.

Attribute	APIMart	Spanlens
Pricing	Paid	Paid
Price	—	$29/mo
Free trial	No	No
Open source	No	Yes
Has API	Yes	Yes
Self-hosted option	No	Yes
Platforms	Cloud-based API service	Node.js, Python, Next.js, Edge, self-hosted
Pros	OpenAI-compatible API surface, which means your existing SDK code reaches the full 500-plus model catalog by changing one base URL — no per-provider SDK migrations when you add a new model. Per-model discount pricing displayed transparently in the marketplace, so you can calculate actual cost before committing to a model in production rather than discovering the bill after a spike. Single API key covers chat, image, video, and audio providers, which means you stop maintaining separate credentials and billing accounts for each vendor and reduce the blast radius when a key rotates. The docs provide an llms.txt prompt so AI coding agents like Cursor or Claude can instantly understand the full APIMart endpoint catalog, cutting integration time from hours to minutes for developers using AI-assisted workflows. Usage-based billing where you pay only for successful requests, so failed or errored calls do not consume budget — a material difference when you are stress-testing a new model with high failure rates.	Proxy-layer instrumentation via a single baseURL change, so existing code requires no structural rewrite and every provider call is captured from day one rather than after a manual instrumentation sprint. Per-user and per-route cost attribution, which means you can identify the specific customer or endpoint burning disproportionate budget before it compounds across a billing cycle. Agent waterfall trace trees with critical-path highlighting, so a slow or expensive step in a multi-agent run is pinpointed in seconds instead of reproduced manually in a staging environment. Experiment runner replays a fixed dataset across prompt versions and models with quality, cost, and latency compared side by side, which means you ship with evidence that v8 is better than v7 rather than finding out the hard way in production. Self-hosted deployment via Docker Compose under MIT license, so teams with data residency or audit requirements can run the full platform without sending trace data to a third-party cloud.
Cons	APIMart is a passive relay: it does not retry failed requests, fall back to an alternative model when a provider returns an error, or route based on latency or cost thresholds. Teams that need gateway-level resilience write and maintain that logic themselves — at which point they are running two systems. No self-hosted deployment option exists. Teams operating under data-residency or compliance requirements that prohibit third-party intermediaries handling request payloads cannot use APIMart at all and switch to a self-hostable alternative like LiteLLM. The discount model is a paid-only service with no documented free tier. Prototyping before committing budget requires a sign-up and funding the account, which adds friction for early-stage evaluation compared to providers offering free trial credits.	PII detection is regex-based and runs at log time as a flag — not a pre-storage redaction guarantee. Teams operating under HIPAA or SOC 2 controls where sensitive data must never reach a log store, even briefly, need a dedicated redaction layer upstream of Spanlens or a different architecture entirely. The LLM-as-judge eval scoring is a single 0–1 scalar per response. Teams needing structured, multi-criteria evaluation rubrics — for example, factual accuracy scored separately from tone and policy compliance — hit the ceiling of what the built-in scorer expresses and end up maintaining a custom eval harness alongside Spanlens. At high request volumes where the proxy layer adds measurable latency to every call, teams running latency-sensitive production paths at scale have moved to SDK-side instrumentation tools or full APM platforms with LLM plugins, where the observability path is out of band rather than in the critical path.

Bottom line

Spanlens is open source. Choose based on which difference matters most for your workflow.

Frequently asked questions

What is the difference between APIMart and Spanlens?

APIMart is Paid, while Spanlens is Paid and open source. Compare pricing, free trial, API, platforms, and pros/cons in the table above on AIDiveForge.

Is APIMart better than Spanlens?

It depends on your workflow. Use the side-by-side attributes (pricing, open source, API, self-hosted, platforms) to decide. AIDiveForge does not rank a universal winner — we publish verified facts so you can choose.