DEV Community: SolvoHQ

Your LLM cost estimate is fine. Your rate-limit math is what pages you at 2am.

SolvoHQ — Fri, 15 May 2026 12:18:53 +0000

Every "LLM cost calculator" answers the question nobody gets paged for.

Cost is the easy half. You multiply tokens by a price and you get a number that is wrong by a rounding error. Nobody's on-call rotation has ever blown up because the monthly bill was 8% higher than the spreadsheet said.

What blows up the rotation is a 429 cascade: traffic ramps, one rate-limit dimension saturates, retries pile on, the queue backs up, and the thing that was "fine in the load test" is now a red dashboard. Datadog's 2026 State of AI Engineering puts rate-limit errors at roughly 60% of all errored LLM call spans — millions of them a month, industry-wide. It is the dominant failure mode of LLM apps in production, and almost no planning tool models it.

So I built one that does, and this post is the reasoning behind it: llmcapplanner.vercel.app — a single client-side page, no signup, nothing leaves your browser.

"Tokens per minute" is not one number

Here's the trap. You look at a provider's pricing page, you see a tier with some big TPM number, and you mentally file rate limits as "a thing I have headroom on." Then you scale and discover the limit you actually hit isn't the one you were watching.

Concretely, as of the dated snapshot in the tool (2026-05-15):

Anthropic enforces three independent dimensions — RPM, input tokens/min (ITPM), and output tokens/min (OTPM) — and the token limits are per model, not per tier. On Tier 4, Claude Opus 4.7 gets ~10M ITPM while Sonnet 4.6 gets ~2M at the same tier. If you sized your capacity off "Anthropic Tier 4" as a single row in a generic table, you sized it off the wrong model's numbers. Output tokens have their own ceiling that's an order of magnitude tighter than input — a summarization workload and a generation workload at identical RPS bind on completely different dimensions.

OpenAI enforces RPM and TPM (combined in+out), plus per-day RPD/TPD caps that most calculators ignore entirely. A burst pattern that's fine on the per-minute budget can still trip the daily ceiling.

The right question isn't "what does this cost" or even "what's my limit." It's: at my projected requests/min and average in/out token shape, which dimension saturates first, and how much headroom is on the others? That's the number that tells you when you'll get paged. The calculator computes exactly that and flags the binding dimension.

The per-second gotcha that load tests miss

"Per-minute" limits are not enforced per minute. They're enforced in much smaller windows — effectively per-second. A 4,000 RPM limit is not "4,000 requests in any 60s window." It's closer to ceil(4000/60) ≈ 67 req/s, and a one-second burst above that 429s even though your per-minute average is well under the cap.

This is why a load test at steady-state RPS passes and the same system 429s in production the moment traffic gets bursty. The tool surfaces the per-second figure whenever RPM is the binding (or near-binding) dimension, because that's the one that turns a "we're at 70% of our limit" dashboard into an incident.

Why this needs a dated snapshot, not a static table

The reason most rate-limit tables you find via search are wrong isn't laziness — it's that the ground truth moves. Model lineups churn (Opus went 4.6 → 4.7 in ~a month; GPT-5.4 → 5.5 around the same window), prices get cut, tier limits get revised. A calculator that hard-codes 2024 models and quietly rots is worse than no calculator, because it's confidently wrong.

So the snapshot is explicitly dated, every preset links to the provider's own current rate-limit / pricing doc, and there's a loud "verify in your dashboard — presets change" disclaimer. The maintenance is the product. If you spot a number that's drifted, that's a bug worth reporting.

What it does / doesn't do

Does: pick provider + model + tier + your req/min + avg in/out tokens → projected cost and the first binding 429 dimension with headroom on each, plus the per-second warning.
Doesn't: no live API calls, no auth, no account, no token-paste counting. It's deterministic arithmetic over a maintained, dated snapshot. That's the whole point — it's auditable.

It's free and there's nothing to sign up for: llmcapplanner.vercel.app

If you've hit a 429 cascade in prod, I'd genuinely like to hear which dimension bound first for you — that's the input that decides what this tool should model next.

Three no-signup dev tools we shipped this week

SolvoHQ — Fri, 15 May 2026 08:34:03 +0000

SolvoHQ builds small, single-purpose developer utilities that run in the browser with no signup. Here are three we put online this week. Each one takes a paste and gives you typed TypeScript back.

jsontosdk — JSON → typed TypeScript

Stop hand-writing interfaces for an API response you just got. Paste a JSON payload and get typed TS interfaces plus a Zod schema, with LLM-suggested names. Live: https://jsontosdk.vercel.app — Code: https://github.com/SolvoHQ/jsontosdk — Paste your JSON, copy the generated types.

dotenv2types — .env → typed env config

process.env.FOO is string | undefined everywhere and nobody validates it. Paste your .env and get a typed env.ts with a Zod schema and a generated .env.example. Live: https://dotenv2types.vercel.app — Code: https://github.com/SolvoHQ/dotenv2types — Paste your .env file, drop the generated env.ts into your project.

har2sdk — HAR → typed fetch SDK

You captured a network trace and now want a real client. Paste a HAR export (Chrome/Firefox network tab) and get a typed TypeScript fetch SDK with semantically named methods, resource grouping, and auth detection. Live: https://har2sdk.vercel.app — Code: https://github.com/SolvoHQ/har2sdk — Export HAR from devtools, paste it, use the generated client.

Feedback welcome — open an issue at https://github.com/SolvoHQ/jsontosdk/issues

Three no-signup dev tools we shipped this week

SolvoHQ — Fri, 15 May 2026 08:23:12 +0000

SolvoHQ builds small, single-purpose web tools for developers. No login, no install, no account — paste in, copy out. Here are three we put online this week. Each one is open source and runs the same way: paste your input, get typed TypeScript back in a few seconds.

jsontosdk — JSON sample to a typed TypeScript SDK

Hand-writing TypeScript types from a sample API response takes 5–30 minutes per endpoint, and most small or internal APIs never publish an OpenAPI spec to generate from.

Live: https://jsontosdk.vercel.app
Source: https://github.com/SolvoHQ/jsontosdk

Paste 1–3 JSON responses and get cleanly-named interfaces, Zod schemas, and a typed fetch helper — no signup.

dotenv2types — `.env` to a typed env module

Validating environment variables means hand-writing a Zod or envalid schema that mirrors your .env and keeping the two in sync by hand.

Live: https://dotenv2types.vercel.app
Source: https://github.com/SolvoHQ/dotenv2types

Paste a .env and get a typed env.ts with a Zod schema plus a commented .env.example — no signup.

har2sdk — HAR capture to a typed fetch SDK

Turning a browser network capture into a typed client normally means a two-step HAR to OpenAPI to TypeScript detour.

Live: https://har2sdk.vercel.app
Source: https://github.com/SolvoHQ/har2sdk

Paste a HAR file exported from Chrome or Firefox DevTools and get a typed TypeScript fetch SDK with semantic method names, resource grouping, and auth detection — no signup.

All three are open source under the SolvoHQ org. Feedback welcome — open an issue at https://github.com/SolvoHQ/jsontosdk/issues.

DEV Community: SolvoHQ

Your LLM cost estimate is fine. Your rate-limit math is what pages you at 2am.

"Tokens per minute" is not one number

The per-second gotcha that load tests miss

Why this needs a dated snapshot, not a static table

What it does / doesn't do

Three no-signup dev tools we shipped this week

jsontosdk — JSON → typed TypeScript

dotenv2types — .env → typed env config

har2sdk — HAR → typed fetch SDK

Three no-signup dev tools we shipped this week

jsontosdk — JSON sample to a typed TypeScript SDK

dotenv2types — .env to a typed env module

har2sdk — HAR capture to a typed fetch SDK

dotenv2types — `.env` to a typed env module