---
title: "AI Token Router engineering blog"
canonical: "https://router.xark.io/blog"
description: "18 written explanations, each answering a question with numbers that are ours to publish."
section: "core"
updated: "2026-09-02"
source: "https://router.xark.io/blog.md"
---

# AI Token Router engineering blog

18 written explanations, each answering a question with numbers that are ours to publish.

| Article | Published | Updated | Topics | Document |
| --- | --- | --- | --- | --- |
| What a context window actually costs | 2026-09-08 | — | pricing, tokens, cost-control, open-weights | [read](https://router.xark.io/blog/choosing-a-context-window.md) |
| Tool calling on open-weight models | 2026-09-08 | — | api-contract, openai-compatible, agents, sdk | [read](https://router.xark.io/blog/tool-calling-and-structured-output.md) |
| What a spending ceiling protects you from | 2026-09-08 | — | cost-control, billing, credits, agents | [read](https://router.xark.io/blog/what-a-spending-ceiling-protects-you-from.md) |
| Reconciling an API bill, token by token | 2026-09-08 | — | billing, tokens, pricing, cost-control | [read](https://router.xark.io/blog/reconciling-an-api-bill-to-the-token.md) |
| Why a payment cannot credit you twice | 2026-09-08 | — | billing, credits, api-contract, security | [read](https://router.xark.io/blog/webhook-idempotency-and-double-credit.md) |
| Inside the request path | 2026-09-08 | — | api-contract, openai-compatible, streaming, sdk | [read](https://router.xark.io/blog/inside-the-request-path.md) |
| Open-weight or frontier: how to decide | 2026-09-07 | — | open-weights, procurement, licensing, compliance | [read](https://router.xark.io/blog/open-weight-vs-frontier-model-decision.md) |
| What it costs to run an evaluation suite | 2026-09-07 | — | evaluation, cost-control, pricing, agents | [read](https://router.xark.io/blog/what-an-eval-suite-costs.md) |
| Embeddings: dimensions and corpus cost | 2026-09-07 | — | embeddings, pricing, cost-control, open-weights | [read](https://router.xark.io/blog/embeddings-dimensions-and-corpus-cost.md) |
| Rate limits, concurrency and backoff | 2026-09-07 | — | rate-limits, api-contract, agents, sdk | [read](https://router.xark.io/blog/rate-limits-and-backoff.md) |
| What a leaked API key can actually do | 2026-09-07 | — | security, api-contract, credits, sdk | [read](https://router.xark.io/blog/api-key-security-rotation-and-leaks.md) |
| Streaming: who pays when nobody listens | 2026-09-07 | — | streaming, api-contract, sdk, billing | [read](https://router.xark.io/blog/streaming-completions-usage-and-disconnects.md) |
| Prepaid credits vs postpaid invoicing | 2026-09-07 | — | billing, pricing, credits, api-contract | [read](https://router.xark.io/blog/prepaid-credits-vs-postpaid-billing.md) |
| What open-source video generation costs | 2026-09-07 | — | pricing, video, open-weights, billing | [read](https://router.xark.io/blog/video-generation-api-pricing.md) |
| Cached input pricing and what an agent costs | 2026-09-07 | — | pricing, caching, agents, cost-control | [read](https://router.xark.io/blog/cached-input-pricing.md) |
| Open-weight licences and what you can ship | 2026-09-07 | — | licensing, open-weights, compliance, procurement | [read](https://router.xark.io/blog/open-weight-vs-closed-model-licensing.md) |
| What OpenAI compatibility does not change | 2026-09-07 | — | migration, openai-compatible, api-contract, sdk | [read](https://router.xark.io/blog/openai-compatible-api-migration.md) |
| How LLM API pricing is calculated | 2026-09-07 | — | pricing, tokens, billing, cost-control | [read](https://router.xark.io/blog/llm-api-pricing-explained.md) |