<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>crimson-crab — the production-grade Rust SDK for Claude</title>
<meta name="description" content="crimson-crab is the production-grade Rust SDK for Anthropic's Claude API. Wire-faithful types, streaming, tool use, adaptive thinking, prompt caching, batches — first-class, not adapted.">
<meta name="color-scheme" content="light dark">
<style>
/* ------------------------------------------------------------------ *
* crimson-crab — "Carapace" · the Crimson Crab landing page *
* Palette: oxidized iron + crimson + rust-oxide + terracotta clay *
* ------------------------------------------------------------------ */
/* --- Tokens: light (default) --- */
:root {
--ink: #F6EDE5; /* clay paper background */
--ink-2: #EFE3D8; /* recessed background */
--carapace: #FBF4EC; /* raised panel */
--carapace-2: #F3E7DB; /* panel alt */
--line: #E1CDBE; /* hairline */
--line-soft: #EBDCCF;
--text: #2B1A12; /* near-black warm oxide */
--text-2: #6A5142; /* secondary */
--muted: #8A7061; /* captions */
--crimson: #B5352A; /* primary accent */
--crimson-lo: #C74A38;
--rust: #A6521F; /* rust-oxide */
--clay: #C6753E; /* terracotta */
--clay-soft: #E7CDB6;
--on-accent: #FBF1E9;
--focus: #B5352A;
/* crab mark */
--shell: #B5352A;
--shell-edge: #7E2018;
--claw: #A6521F;
--claw-edge: #6E340F;
--limb: #C6753E;
--eye: #2B1A12;
/* code */
--code-bg: #FCF5ED;
--code-line: #E7D7C8;
--c-text: #43301F;
--c-kw: #B5352A;
--c-type: #A6521F;
--c-str: #4F6B34;
--c-fn: #7A4A2E;
--c-num: #A6521F;
--c-com: #9C8474;
--c-punc: #6A5142;
--maxw: 1120px;
--font-display: "Iowan Old Style","Palatino Linotype",Palatino,"Book Antiqua","URW Palladio L",Georgia,"Times New Roman",serif;
--font-body: -apple-system,"Seravek","Segoe UI",system-ui,"Helvetica Neue",Arial,sans-serif;
--font-mono: ui-monospace,"SF Mono","JetBrains Mono","Cascadia Code",Menlo,Consolas,"Liberation Mono",monospace;
}
/* --- Tokens: dark (primary identity) --- */
@media (prefers-color-scheme: dark) {
:root {
--ink: #150E0B;
--ink-2: #1B1310;
--carapace: #221713;
--carapace-2: #2A1C16;
--line: #3A281F;
--line-soft: #2E1F19;
--text: #F3E7DC;
--text-2: #C6AC9C;
--muted: #9E8375;
--crimson: #E4655A;
--crimson-lo: #D33B2C;
--rust: #D98A5B;
--clay: #E0A06A;
--clay-soft: #4A3223;
--on-accent: #1A0E0A;
--focus: #E9A98F;
--shell: #CB3A2C;
--shell-edge: #7E2018;
--claw: #C87A4A;
--claw-edge: #5E2E12;
--limb: #D98A5B;
--eye: #F3E7DC;
--code-bg: #1C1310;
--code-line: #33231B;
--c-text: #E7D6C7;
--c-kw: #E96D62;
--c-type: #E3A56E;
--c-str: #A6BE84;
--c-fn: #F0D9C1;
--c-num: #E3A56E;
--c-com: #9A8272;
--c-punc: #B49E90;
}
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
margin: 0;
background: var(--ink);
color: var(--text);
font-family: var(--font-body);
font-size: clamp(15px, 0.6vw + 14px, 17px);
line-height: 1.6;
-webkit-font-smoothing: antialiased;
text-rendering: optimizeLegibility;
overflow-x: hidden;
}
/* ambient ferrous plate texture */
body::before {
content: "";
position: fixed;
inset: 0;
z-index: -1;
pointer-events: none;
background:
radial-gradient(120% 90% at 82% -10%, color-mix(in srgb, var(--crimson) 12%, transparent), transparent 55%),
radial-gradient(100% 80% at -10% 110%, color-mix(in srgb, var(--rust) 10%, transparent), transparent 55%);
}
a { color: var(--crimson); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--crimson-lo); }
:focus-visible {
outline: 2px solid var(--focus);
outline-offset: 3px;
border-radius: 3px;
}
h1, h2, h3 { font-family: var(--font-display); font-weight: 600; line-height: 1.08; letter-spacing: -0.01em; margin: 0; }
.wrap { width: 100%; max-width: var(--maxw); margin-inline: auto; padding-inline: clamp(20px, 5vw, 48px); }
.eyebrow {
font-family: var(--font-mono);
font-size: 0.72rem;
letter-spacing: 0.14em;
text-transform: uppercase;
color: var(--muted);
margin: 0;
}
.skip {
position: absolute; left: 12px; top: -60px;
background: var(--crimson); color: var(--on-accent);
padding: 10px 16px; border-radius: 8px; z-index: 100;
font-family: var(--font-mono); font-size: 0.8rem;
transition: top .15s ease;
}
.skip:focus { top: 12px; color: var(--on-accent); }
/* ---------------------------------------------------------------- */
/* Header */
/* ---------------------------------------------------------------- */
.site-head {
position: sticky; top: 0; z-index: 50;
backdrop-filter: saturate(1.4) blur(10px);
background: color-mix(in srgb, var(--ink) 82%, transparent);
border-bottom: 1px solid var(--line-soft);
}
.site-head .bar {
display: flex; align-items: center; justify-content: space-between;
gap: 20px; height: 62px;
}
.brand { display: flex; align-items: center; gap: 11px; text-decoration: none; color: var(--text); }
.brand svg { display: block; width: 34px; height: 30px; }
.brand .name { font-family: var(--font-mono); font-weight: 600; font-size: 0.98rem; letter-spacing: -0.01em; }
.brand .name b { color: var(--crimson); font-weight: 600; }
.nav { display: flex; align-items: center; gap: 4px; font-family: var(--font-mono); font-size: 0.8rem; }
.nav a {
color: var(--text-2); text-decoration: none; padding: 8px 12px; border-radius: 8px;
letter-spacing: 0.02em;
}
.nav a:hover { color: var(--text); background: var(--carapace); }
.nav a.gh { color: var(--text); border: 1px solid var(--line); }
.nav a.gh:hover { border-color: var(--crimson); }
@media (max-width: 680px) { .nav .hide-sm { display: none; } }
/* crab hover pinch */
.brand:hover .claw-l { transform: rotate(-7deg); }
.brand:hover .claw-r { transform: rotate(7deg); }
.claw-l, .claw-r { transform-box: fill-box; transform-origin: center; transition: transform .35s cubic-bezier(.2,.9,.25,1); }
@media (prefers-reduced-motion: reduce) { .claw-l, .claw-r { transition: none; } }
/* ---------------------------------------------------------------- */
/* Hero */
/* ---------------------------------------------------------------- */
.hero { padding-top: clamp(48px, 8vw, 96px); padding-bottom: clamp(40px, 6vw, 80px); }
.hero .grid {
display: grid; grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
gap: clamp(24px, 5vw, 64px); align-items: center;
}
.hero .tag {
display: inline-flex; flex-wrap: wrap; gap: 8px 14px; align-items: center;
font-family: var(--font-mono); font-size: 0.74rem; color: var(--muted);
letter-spacing: 0.06em; margin-bottom: 22px;
}
.hero .tag .dot { width: 6px; height: 6px; border-radius: 50%; background: var(--crimson); display: inline-block; }
.hero .tag .crate { color: var(--crimson); font-weight: 600; letter-spacing: 0.02em; }
.hero .tag .sep { color: var(--line); }
.hero h1 {
font-size: clamp(2.5rem, 5.6vw, 4.4rem);
letter-spacing: -0.025em;
margin: 0 0 22px;
}
.hero h1 .accent { color: var(--crimson); font-style: italic; }
.hero .lede {
font-size: clamp(1.05rem, 1.3vw, 1.28rem);
color: var(--text-2); max-width: 40ch; margin: 0 0 30px; line-height: 1.55;
}
.hero .lede b { color: var(--text); font-weight: 600; }
/* install snippet */
.install {
display: flex; align-items: stretch; gap: 0; max-width: 420px;
border: 1px solid var(--line); border-radius: 12px; overflow: hidden;
background: var(--code-bg); box-shadow: 0 1px 0 color-mix(in srgb, var(--text) 6%, transparent);
}
.install .cmd {
flex: 1; display: flex; align-items: center; gap: 12px; padding: 14px 16px;
font-family: var(--font-mono); font-size: 0.92rem; color: var(--c-text); min-width: 0;
}
.install .cmd .prompt { color: var(--crimson); user-select: none; }
.install .cmd code { overflow-x: auto; white-space: nowrap; }
.install .cmd code b { color: var(--c-kw); font-weight: 600; }
.copy {
border: 0; border-left: 1px solid var(--line); cursor: pointer;
background: var(--carapace); color: var(--text-2);
font-family: var(--font-mono); font-size: 0.74rem; letter-spacing: 0.08em; text-transform: uppercase;
padding: 0 18px; transition: background .15s ease, color .15s ease;
}
.copy:hover { background: var(--crimson); color: var(--on-accent); }
.copy.done { background: var(--rust); color: var(--on-accent); }
.hero .links { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 22px; }
.btn {
display: inline-flex; align-items: center; gap: 8px;
font-family: var(--font-mono); font-size: 0.82rem; letter-spacing: 0.02em;
padding: 11px 16px; border-radius: 10px; text-decoration: none;
border: 1px solid var(--line); color: var(--text); background: var(--carapace);
transition: border-color .15s ease, transform .15s ease, background .15s ease;
}
.btn:hover { border-color: var(--crimson); transform: translateY(-1px); color: var(--text); }
.btn.primary { background: var(--crimson); border-color: var(--crimson); color: var(--on-accent); }
.btn.primary:hover { background: var(--crimson-lo); border-color: var(--crimson-lo); color: var(--on-accent); }
.btn svg { width: 15px; height: 15px; }
/* hero crab art */
.hero .art { display: flex; justify-content: center; align-items: center; }
.hero .art svg { width: 100%; max-width: 380px; height: auto; filter: drop-shadow(0 22px 40px color-mix(in srgb, var(--shell-edge) 40%, transparent)); }
@media (max-width: 860px) {
.hero .grid { grid-template-columns: 1fr; }
.hero .art { order: -1; }
.hero .art svg { max-width: 240px; }
}
/* ---------------------------------------------------------------- */
/* Section scaffolding */
/* ---------------------------------------------------------------- */
section { padding-block: clamp(56px, 8vw, 104px); }
.sec-head { max-width: 62ch; margin-bottom: clamp(30px, 4vw, 52px); }
.sec-head h2 { font-size: clamp(1.9rem, 3.4vw, 2.7rem); margin-top: 10px; letter-spacing: -0.02em; }
.sec-head p { color: var(--text-2); font-size: 1.05rem; margin: 14px 0 0; }
.rule { border: 0; border-top: 1px solid var(--line-soft); margin: 0; }
/* ---------------------------------------------------------------- */
/* Feature grid */
/* ---------------------------------------------------------------- */
.features { background: var(--ink-2); }
.fgrid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; background: var(--line-soft); border: 1px solid var(--line-soft); border-radius: 14px; overflow: hidden; }
@media (max-width: 820px) { .fgrid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px) { .fgrid { grid-template-columns: 1fr; } }
.feat { background: var(--carapace); padding: 26px 24px 28px; position: relative; }
.feat::before { content: ""; position: absolute; left: 24px; right: 24px; top: 0; height: 2px; background: linear-gradient(90deg, var(--crimson), var(--clay)); opacity: 0; transition: opacity .2s ease; }
.feat:hover::before { opacity: 1; }
.feat .ic { color: var(--crimson); margin-bottom: 14px; display: block; }
.feat .ic svg { width: 26px; height: 26px; display: block; }
.feat h3 { font-family: var(--font-body); font-weight: 600; font-size: 1.05rem; letter-spacing: -0.005em; margin-bottom: 7px; }
.feat p { margin: 0; color: var(--text-2); font-size: 0.93rem; line-height: 1.5; }
.feat code { font-family: var(--font-mono); font-size: 0.86em; color: var(--rust); background: color-mix(in srgb, var(--rust) 12%, transparent); padding: 1px 5px; border-radius: 4px; }
/* ---------------------------------------------------------------- */
/* Code examples */
/* ---------------------------------------------------------------- */
.tabs { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 16px; }
.tab {
font-family: var(--font-mono); font-size: 0.82rem; letter-spacing: 0.01em;
padding: 9px 15px; border-radius: 9px 9px 0 0; cursor: pointer;
background: transparent; border: 1px solid transparent; border-bottom: 0;
color: var(--text-2);
}
.tab:hover { color: var(--text); }
.tab[aria-selected="true"] { color: var(--crimson); background: var(--code-bg); border-color: var(--code-line); position: relative; }
.tab[aria-selected="true"]::after { content: ""; position: absolute; left: 0; right: 0; bottom: -1px; height: 2px; background: var(--crimson); }
.editor { border: 1px solid var(--code-line); border-radius: 14px; overflow: hidden; background: var(--code-bg); }
.editor .chrome { display: flex; align-items: center; gap: 8px; padding: 12px 16px; border-bottom: 1px solid var(--code-line); }
.editor .chrome .dots { display: flex; gap: 7px; }
.editor .chrome .dots i { width: 11px; height: 11px; border-radius: 50%; display: block; }
.editor .chrome .dots i:nth-child(1) { background: var(--crimson); }
.editor .chrome .dots i:nth-child(2) { background: var(--clay); }
.editor .chrome .dots i:nth-child(3) { background: var(--rust); }
.editor .chrome .file { font-family: var(--font-mono); font-size: 0.78rem; color: var(--muted); margin-left: 4px; }
.editor .chrome .file b { color: var(--text-2); font-weight: 500; }
.panel { display: none; }
.panel.active { display: block; }
pre { margin: 0; overflow-x: auto; }
pre code {
display: block; padding: 22px clamp(16px, 3vw, 26px);
font-family: var(--font-mono); font-size: clamp(0.8rem, 0.4vw + 0.72rem, 0.9rem);
line-height: 1.75; color: var(--c-text); white-space: pre; tab-size: 4;
}
.k { color: var(--c-kw); }
.t { color: var(--c-type); }
.s { color: var(--c-str); }
.fn { color: var(--c-fn); }
.n { color: var(--c-num); }
.c { color: var(--c-com); font-style: italic; }
.m { color: var(--c-kw); }
.pu { color: var(--c-punc); }
/* ---------------------------------------------------------------- */
/* Comparison */
/* ---------------------------------------------------------------- */
.why { background: var(--ink-2); }
.cmp {
border: 1px solid var(--line); border-radius: 14px; overflow: hidden;
background: var(--carapace);
}
.cmp .row { display: grid; grid-template-columns: minmax(0,1.5fr) minmax(0,1fr) minmax(0,1fr); }
.cmp .row + .row { border-top: 1px solid var(--line-soft); }
.cmp .cell { padding: 16px 20px; font-size: 0.94rem; }
.cmp .cell:not(:first-child) { border-left: 1px solid var(--line-soft); }
.cmp .head .cell { background: var(--carapace-2); font-family: var(--font-mono); font-size: 0.78rem; letter-spacing: 0.03em; text-transform: uppercase; color: var(--muted); }
.cmp .head .cell.ours { color: var(--crimson); }
.cmp .aspect { color: var(--text); font-weight: 500; }
.cmp .v { display: inline-flex; align-items: baseline; gap: 8px; color: var(--text-2); }
.cmp .v .mark { font-family: var(--font-mono); font-size: 0.8rem; flex: none; }
.cmp .v.yes .mark { color: var(--rust); }
.cmp .v.part .mark { color: var(--muted); }
.cmp .v.no .mark { color: var(--muted); }
.cmp .v.yes.ours .mark { color: var(--crimson); }
.cmp-note { margin-top: 18px; color: var(--muted); font-size: 0.9rem; font-style: italic; max-width: 68ch; }
.cmp-note b { color: var(--text-2); font-style: normal; font-weight: 600; }
@media (max-width: 640px) {
.cmp .cell { padding: 12px 14px; font-size: 0.88rem; }
.cmp .head .cell { font-size: 0.68rem; }
}
/* ---------------------------------------------------------------- */
/* Footer */
/* ---------------------------------------------------------------- */
.site-foot { border-top: 1px solid var(--line-soft); padding-block: 48px 40px; }
.foot-grid { display: flex; flex-wrap: wrap; gap: 32px; justify-content: space-between; align-items: flex-start; }
.foot-brand { display: flex; align-items: center; gap: 12px; }
.foot-brand svg { width: 40px; height: 35px; }
.foot-brand .txt .name { font-family: var(--font-mono); font-weight: 600; font-size: 1rem; }
.foot-brand .txt .name b { color: var(--crimson); }
.foot-brand .txt small { display: block; color: var(--muted); font-size: 0.82rem; margin-top: 2px; }
.foot-cols { display: flex; flex-wrap: wrap; gap: 40px; }
.foot-col h4 { font-family: var(--font-mono); font-size: 0.72rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--muted); margin: 0 0 12px; font-weight: 600; }
.foot-col a { display: block; color: var(--text-2); text-decoration: none; font-size: 0.9rem; padding: 4px 0; }
.foot-col a:hover { color: var(--crimson); }
.foot-legal { margin-top: 40px; padding-top: 24px; border-top: 1px solid var(--line-soft); color: var(--muted); font-size: 0.85rem; display: flex; flex-wrap: wrap; gap: 8px 20px; align-items: center; }
.foot-legal .lic { font-family: var(--font-mono); color: var(--text-2); }
.foot-legal .disc { max-width: 62ch; }
.reveal { opacity: 0; transform: translateY(14px); }
.reveal.in { opacity: 1; transform: none; transition: opacity .6s ease, transform .6s cubic-bezier(.2,.7,.3,1); }
@media (prefers-reduced-motion: reduce) { .reveal { opacity: 1; transform: none; transition: none; } }
</style>
</head>
<body>
<a class="skip" href="#main">Skip to content</a>
<!-- ============================ HEADER ============================ -->
<header class="site-head">
<div class="wrap bar">
<a class="brand" href="#top" aria-label="crimson-crab home">
<!-- crab mark (small) -->
<svg viewBox="0 0 120 104" role="img" aria-hidden="true">
<g class="crab-mark">
<!-- legs -->
<g stroke="var(--limb)" stroke-width="4" stroke-linecap="round" fill="none">
<path d="M40 66 Q22 70 14 84"/>
<path d="M42 74 Q26 82 22 96"/>
<path d="M80 66 Q98 70 106 84"/>
<path d="M78 74 Q94 82 98 96"/>
</g>
<!-- claws -->
<g class="claw-l">
<path d="M40 50 Q22 42 16 30" stroke="var(--claw)" stroke-width="5" fill="none" stroke-linecap="round"/>
<path d="M16 30 q-9 -9 -1 -18 q10 -3 12 8 q-6 -2 -8 3 q4 3 9 1 q3 8 -4 12 q-6 2 -8 -6z" fill="var(--claw)" stroke="var(--claw-edge)" stroke-width="1.5"/>
</g>
<g class="claw-r">
<path d="M80 50 Q98 42 104 30" stroke="var(--claw)" stroke-width="5" fill="none" stroke-linecap="round"/>
<path d="M104 30 q9 -9 1 -18 q-10 -3 -12 8 q6 -2 8 3 q-4 3 -9 1 q-3 8 4 12 q6 2 8 -6z" fill="var(--claw)" stroke="var(--claw-edge)" stroke-width="1.5"/>
</g>
<!-- eyestalks -->
<line x1="50" y1="40" x2="47" y2="24" stroke="var(--shell-edge)" stroke-width="3"/>
<line x1="70" y1="40" x2="73" y2="24" stroke="var(--shell-edge)" stroke-width="3"/>
<circle cx="47" cy="22" r="5" fill="var(--eye)"/>
<circle cx="73" cy="22" r="5" fill="var(--eye)"/>
<!-- carapace -->
<path d="M60 40 C34 40 26 54 28 66 C30 80 44 88 60 88 C76 88 90 80 92 66 C94 54 86 40 60 40 Z" fill="var(--shell)" stroke="var(--shell-edge)" stroke-width="2"/>
<path d="M40 58 Q60 50 80 58" stroke="var(--shell-edge)" stroke-width="2" fill="none" opacity="0.55"/>
</g>
</svg>
<span class="name"><b>crimson</b>-crab</span>
</a>
<nav class="nav" aria-label="Primary">
<a href="#features" class="hide-sm">Features</a>
<a href="#examples" class="hide-sm">Examples</a>
<a href="#why" class="hide-sm">Why</a>
<a href="https://docs.rs/crimson-crab">docs.rs</a>
<a href="https://github.com/singhpratech/crimson-crab" class="gh">GitHub ↗</a>
</nav>
</div>
</header>
<main id="main">
<span id="top"></span>
<!-- ============================= HERO ============================= -->
<section class="hero">
<div class="wrap grid">
<div class="hero-copy reveal">
<p class="tag">
<span class="dot" aria-hidden="true"></span>
<span class="crate">crimson-crab</span>
<span class="sep" aria-hidden="true">/</span> v0.1
<span class="sep" aria-hidden="true">/</span> MIT OR Apache-2.0
<span class="sep" aria-hidden="true">/</span> MSRV 1.75
</p>
<h1>The production-grade Rust SDK for <span class="accent">Claude</span>.</h1>
<p class="lede">The definitive Rust client for Anthropic's Claude API, engineered to first-party SDK standards: the complete API surface, identical retry semantics, and <b>same-week support for every Claude release</b>. Streaming, tool use, thinking, prompt caching and batches are <b>first-class, not adapted</b>.</p>
<div class="install" role="group" aria-label="Install command">
<div class="cmd">
<span class="prompt" aria-hidden="true">$</span>
<code id="install-cmd"><b>cargo</b> add crimson-crab</code>
</div>
<button class="copy" id="copy-btn" type="button" aria-label="Copy install command">Copy</button>
</div>
<div class="links">
<a class="btn primary" href="https://github.com/singhpratech/crimson-crab">
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<!-- =========================== FEATURES =========================== -->
<section class="features" id="features">
<div class="wrap">
<div class="sec-head reveal">
<p class="eyebrow">Spec fidelity, not surface area</p>
<h2>The complete Claude API. Nothing lost in translation.</h2>
<p>Streaming, tool use, adaptive thinking, prompt caching, batches — every Claude capability is a first-class Rust type that mirrors the wire exactly. And when Anthropic ships something new, you’re covered from day one: new models, new features, and new content types flow through without breaking a single build.</p>
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<h3>Streaming SSE</h3>
<p>A hand-rolled SSE parser yields fine-grained <code>StreamEvent</code>s and accumulates a final <code>Message</code> for you — no eventsource dependency.</p>
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<h3>Tool use</h3>
<p>Define tools with raw JSON schemas, drive the agentic loop yourself, and pass any server-tool through <code>ToolUnion::Raw</code>.</p>
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<h3>Adaptive thinking</h3>
<p><code>ThinkingConfig</code> covers adaptive, budgeted and disabled modes, with effort and display controls surfaced directly.</p>
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<h3>Prompt caching</h3>
<p>Attach <code>CacheControl</code> to any block with an optional 5m/1h TTL, and read cache hits back off <code>Usage</code>.</p>
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<h3>Message Batches</h3>
<p>Create, poll and cancel batches, then stream results back with a JSONL-decoding <code>Stream<BatchResult></code>.</p>
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<h3>Token counting</h3>
<p>Turn any request into a count request and get exact <code>input_tokens</code> before you spend on generation.</p>
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<h3>Typed errors & retries</h3>
<p>Every non-2xx maps to a precise <code>Error</code> variant with <code>request_id</code>. Backoff with jitter honors <code>retry-after</code> automatically.</p>
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<h3>Forward compatible</h3>
<p>Unknown block types, stream events and stop reasons deserialize into <code>Unknown</code> catch-alls — new API surface never breaks a build.</p>
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<h3>Runtime-light & WASM-ready</h3>
<p>The public API exposes <code>futures_core::Stream</code>, not tokio types. <code>reqwest</code> underneath means it also checks on <code>wasm32-unknown-unknown</code>.</p>
</div>
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</div>
</section>
<hr class="rule">
<!-- =========================== EXAMPLES =========================== -->
<section id="examples">
<div class="wrap">
<div class="sec-head reveal">
<p class="eyebrow">From zero to streaming in one screen</p>
<h2>Ergonomic, but nothing hidden.</h2>
<p>A builder for every request, helpers for the common paths, and full command of <code style="font-family:var(--font-mono);color:var(--rust)">stop_reason</code>. Here it is end to end.</p>
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<button class="tab" role="tab" id="tab-basic" aria-controls="p-basic" aria-selected="true">Basic message</button>
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<span class="file">examples/<b id="file-name">basic.rs</b></span>
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<pre><code><span class="k">use</span> crimson_crab::{<span class="t">Client</span>, <span class="t">MessagesRequest</span>, <span class="t">MessageParam</span>, models_ids};
<span class="c">// Reads ANTHROPIC_API_KEY from the environment.</span>
<span class="k">let</span> client = <span class="t">Client</span>::<span class="fn">from_env</span>()<span class="pu">?</span>;
<span class="k">let</span> req = <span class="t">MessagesRequest</span>::<span class="fn">builder</span>()
.<span class="fn">model</span>(models_ids::<span class="t">CLAUDE_OPUS_4_8</span>)
.<span class="fn">max_tokens</span>(<span class="n">1024</span>)
.<span class="fn">system</span>(<span class="s">"You are terse."</span>)
.<span class="fn">messages</span>(<span class="m">vec!</span>[<span class="t">MessageParam</span>::<span class="fn">user</span>(<span class="s">"Hello, Claude"</span>)])
.<span class="fn">build</span>()<span class="pu">?</span>; <span class="c">// validates required fields</span>
<span class="k">let</span> msg = client.<span class="fn">messages</span>().<span class="fn">create</span>(<span class="pu">&</span>req).<span class="k">await</span><span class="pu">?</span>;
<span class="k">if</span> msg.stop_reason == <span class="t">Some</span>(<span class="t">StopReason</span>::<span class="t">Refusal</span>) {
<span class="c">// handle a declined response</span>
}
<span class="m">println!</span>(<span class="s">"{}"</span>, msg.<span class="fn">text</span>()); <span class="c">// concat of all text blocks</span></code></pre>
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<pre><code><span class="k">use</span> futures_util::<span class="t">StreamExt</span>;
<span class="k">use</span> crimson_crab::{<span class="t">StreamEvent</span>, <span class="t">ContentDelta</span>};
<span class="k">let</span> <span class="k">mut</span> stream = client.<span class="fn">messages</span>().<span class="fn">stream</span>(<span class="pu">&</span>req).<span class="k">await</span><span class="pu">?</span>;
<span class="k">while</span> <span class="k">let</span> <span class="t">Some</span>(event) = stream.<span class="fn">next</span>().<span class="k">await</span> {
<span class="k">if</span> <span class="k">let</span> <span class="t">StreamEvent</span>::<span class="t">ContentBlockDelta</span> { delta, .. } = event<span class="pu">?</span> {
<span class="k">if</span> <span class="k">let</span> <span class="t">ContentDelta</span>::<span class="t">TextDelta</span> { text } = delta {
<span class="m">print!</span>(<span class="s">"{text}"</span>); <span class="c">// tokens as they arrive</span>
}
}
}
<span class="k">let</span> final_msg = stream.<span class="fn">final_message</span>(); <span class="c">// fully accumulated Message</span>
<span class="c">// ...or collapse the whole stream into a single line:</span>
<span class="k">let</span> msg = client.<span class="fn">messages</span>().<span class="fn">stream</span>(<span class="pu">&</span>req).<span class="k">await</span><span class="pu">?</span>.<span class="fn">collect_final</span>().<span class="k">await</span><span class="pu">?</span>;</code></pre>
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<pre><code><span class="k">use</span> crimson_crab::{<span class="t">Tool</span>, <span class="t">MessagesRequest</span>, <span class="t">StopReason</span>, models_ids};
<span class="k">let</span> weather = <span class="t">Tool</span>::<span class="fn">new</span>(
<span class="s">"get_weather"</span>,
<span class="s">"Look up the current weather for a city"</span>,
<span class="m">serde_json::json!</span>({
<span class="s">"type"</span>: <span class="s">"object"</span>,
<span class="s">"properties"</span>: { <span class="s">"city"</span>: { <span class="s">"type"</span>: <span class="s">"string"</span> } },
<span class="s">"required"</span>: [<span class="s">"city"</span>],
}),
);
<span class="k">let</span> req = <span class="t">MessagesRequest</span>::<span class="fn">builder</span>()
.<span class="fn">model</span>(models_ids::<span class="t">CLAUDE_SONNET_5</span>)
.<span class="fn">max_tokens</span>(<span class="n">1024</span>)
.<span class="fn">tools</span>(<span class="m">vec!</span>[weather.<span class="fn">into</span>()])
.<span class="fn">messages</span>(messages.<span class="fn">clone</span>())
.<span class="fn">build</span>()<span class="pu">?</span>;
<span class="k">let</span> msg = client.<span class="fn">messages</span>().<span class="fn">create</span>(<span class="pu">&</span>req).<span class="k">await</span><span class="pu">?</span>;
<span class="k">if</span> msg.stop_reason == <span class="t">Some</span>(<span class="t">StopReason</span>::<span class="t">ToolUse</span>) {
<span class="c">// dispatch each ToolUse block, append its ToolResult, and loop</span>
}</code></pre>
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<hr class="rule">
<!-- ============================= WHY ============================= -->
<section class="why" id="why">
<div class="wrap">
<div class="sec-head reveal">
<p class="eyebrow">Depth beats breadth</p>
<h2>Why a dedicated client?</h2>
<p>Multi-provider frameworks like <b>rig</b> and <b>genai</b> are genuinely great — if you need one interface across many model vendors, use them. <code style="font-family:var(--font-mono);color:var(--rust)">crimson-crab</code> makes the winning bet for Claude builders: go deep on one API and track it relentlessly — so every new Claude capability lands here first, typed and tested.</p>
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<div class="row head" role="row">
<span class="cell aspect" role="columnheader">Capability</span>
<span class="cell ours" role="columnheader">crimson-crab · dedicated</span>
<span class="cell" role="columnheader">rig / genai · multi-provider</span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">Thinking, caching & batches</span>
<span class="cell" role="cell"><span class="v yes ours"><span class="mark">●</span> First-class types</span></span>
<span class="cell" role="cell"><span class="v part"><span class="mark">◓</span> Often lags or partial</span></span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">Wire fidelity (no renamed concepts)</span>
<span class="cell" role="cell"><span class="v yes ours"><span class="mark">●</span> Types mirror the API</span></span>
<span class="cell" role="cell"><span class="v part"><span class="mark">◓</span> Abstracted to a common shape</span></span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">New block / event types</span>
<span class="cell" role="cell"><span class="v yes ours"><span class="mark">●</span> Catch-all, never a hard error</span></span>
<span class="cell" role="cell"><span class="v part"><span class="mark">◓</span> Varies by adapter</span></span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">Fine-grained streaming events</span>
<span class="cell" role="cell"><span class="v yes ours"><span class="mark">●</span> Every delta exposed</span></span>
<span class="cell" role="cell"><span class="v part"><span class="mark">◓</span> Usually text-only</span></span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">One interface across many providers</span>
<span class="cell" role="cell"><span class="v no"><span class="mark">○</span> Claude only — by design</span></span>
<span class="cell" role="cell"><span class="v yes"><span class="mark">●</span> Their whole point</span></span>
</div>
<div class="row" role="row">
<span class="cell aspect" role="cell">Cadence tracking the Claude API</span>
<span class="cell" role="cell"><span class="v yes ours"><span class="mark">●</span> The core promise</span></span>
<span class="cell" role="cell"><span class="v part"><span class="mark">◓</span> One vendor among many</span></span>
</div>
</div>
<p class="cmp-note reveal">Straight talk: if your app talks to several model vendors, a framework will serve you better. <b>crimson-crab is for teams who have chosen Claude</b> and want the whole surface, exactly as Anthropic ships it.</p>
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<div class="name"><b>crimson</b>-crab</div>
<small>The production-grade, wire-faithful Rust SDK for Claude.</small>
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<h4>Package</h4>
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tabs.forEach(function (tab, i) {
tab.addEventListener("click", function () { select(tab); });
tab.addEventListener("keydown", function (e) {
var idx = null;
if (e.key === "ArrowRight") { idx = (i + 1) % tabs.length; }
else if (e.key === "ArrowLeft") { idx = (i - 1 + tabs.length) % tabs.length; }
else if (e.key === "Home") { idx = 0; }
else if (e.key === "End") { idx = tabs.length - 1; }
if (idx !== null) { e.preventDefault(); tabs[idx].focus(); select(tabs[idx]); }
});
});
/* --- scroll reveal --- */
var reduced = window.matchMedia && window.matchMedia("(prefers-reduced-motion: reduce)").matches;
var reveals = Array.prototype.slice.call(document.querySelectorAll(".reveal"));
if (reduced || !("IntersectionObserver" in window)) {
reveals.forEach(function (el) { el.classList.add("in"); });
} else {
var io = new IntersectionObserver(function (entries) {
entries.forEach(function (en) {
if (en.isIntersecting) { en.target.classList.add("in"); io.unobserve(en.target); }
});
}, { threshold: 0.12, rootMargin: "0px 0px -8% 0px" });
reveals.forEach(function (el) { io.observe(el); });
}
})();
</script>
</body>
</html>
