Claude API — Rate limits

Anthropic’s reference for how the Claude API caps an organization’s usage. Routed here on 2026-06-28 from the hub: the provider-API-access lens (alongside claude-refusals-and-fallback and llm-api-pricing). The standout for this wiki is cache-aware ITPM — a rate-limit rule that turns prompt caching from a discount into a throughput multiplier.

Two limits, set at the org level

• Spend limits — a maximum monthly cost, billed per calendar month. Tiered caps: Start $500 · Build $1,000 · Scale $200,000 · Custom none (arranged with the account team). Hit the cap and usage pauses until next month unless you request more. You can also set a lower self-limit under your tier’s cap.
• Rate limits — RPM / input-tokens-per-minute (ITPM) / output-tokens-per-minute (OTPM), per model class, enforced at the org level. Exceed one and you get a 429 naming which limit blew, with a retry-after header.

Tier placement is automatic and rises with usage over time. Limits use the token-bucket algorithm — capacity replenishes continuously rather than resetting on a fixed clock — so a “60 RPM” allowance behaves like ~1 request/second and short bursts can still trip a 429. A separate acceleration limit fires on sharp usage spikes, so the docs advise ramping traffic gradually.

Cache-aware ITPM — the cost/throughput hook

Unlike a flat “tokens per minute” cap, only uncached input tokens count toward ITPM on most Claude models:

• input_tokens (after the last cache breakpoint) → counts
• cache_creation_input_tokens (writing to cache) → counts
• cache_read_input_tokens (reading from cache) → does NOT count (except Claude Haiku 3.5, marked † in the tables, which does count cache reads)

So caching does double duty: cache reads are billed at ~10% of input price and don’t consume rate limit. The docs’ example: a 2,000,000 ITPM limit at an 80% cache-hit rate effectively processes 10M total input tokens/minute (2M uncached + 8M cached). OTPM, by contrast, counts only tokens actually generated — max_tokens doesn’t factor in, so setting it high carries no rate-limit penalty.

The tier tables (mid-2026 snapshot — volatile)

Per-model RPM / ITPM / OTPM. Opus 4.x and Sonnet 4.x each share one combined limit across their point releases (Opus 4.8/4.7/4.6/4.5; Sonnet 4.6/4.5):

Above Scale is Custom (contact sales). Limits are per-model, so different models draw from separate pools simultaneously. Rate limits are currently shared across inference_geo values (us and global draw from one pool).

Separate limit pools

• Message Batches API — its own RPM (1,000 / 2,000 / 4,000 by tier) plus caps on batch requests in the processing queue (200K / 300K / 500K) and per batch (100K).
• Managed Agents — 300 RPM create / 1,200 RPM read, separate from the Messages API.
• Fast mode (speed: "fast" on Opus 4.8/4.7/4.6, research preview) — dedicated limits separate from standard Opus, surfaced via anthropic-fast-* headers.

Response headers & workspaces

Every response carries anthropic-ratelimit-{requests,tokens,input-tokens,output-tokens}-{limit, remaining,reset} (reset in RFC 3339), plus retry-after and Priority-Tier variants. The tokens-* headers report the most restrictive limit currently binding. Orgs can also set per-Workspace spend/rate limits below the org cap to stop one workspace starving the rest (org-wide limits always dominate; the default workspace can’t be limited).

Platform caveat

On Claude Platform on AWS: rate limits here apply, but spend limits don’t (billing is via AWS Marketplace, not Anthropic credits), orgs sit on Start tier and don’t auto-promote, and per-workspace config + fast mode are unavailable.

Why this lives in the providers wiki

It sharpens two of the spoke’s running threads:

• “Engineering sets real cost” (llm-api-pricing, claude-refusals-and-fallback): prompt caching isn’t only a price cut — under cache-aware ITPM it raises effective throughput without a higher limit. Caching is now a rate-limit lever, not just a billing one.
• API access as competitive surface: tiers, token-bucket pacing, per-model pools, and the AWS-reseller divergence are all part of how access is rationed, the access-and-pricing half of this wiki’s domain.

Related

anthropic · llm-api-pricing · claude-refusals-and-fallback · llm-provider