Claude Haiku 5.5 vs Sonnet 5

Sonnet 5 and Sonnet 5.5 are different models

This comparison is specifically about claude-haiku-5-5 and claude-sonnet-5. The Sonnet specification lists Sonnet 5 as an active legacy model released June 30, 2026. Haiku 5.5 was released October 7. For the newer Sonnet generation, use our separate Haiku 5.5 vs Sonnet 5.5 guide.

Sources: Haiku 5.5 specifications and Sonnet 5 specifications. These are model capabilities, not HaikuChat upload or output allowances. A product may impose smaller limits or configure a different effort level.

Where the rate difference matters

At the uncached base rates, 20,000 input tokens plus 2,000 billable output tokens gives a model-token estimate of $0.003 for Haiku 5.5 and $0.06 for Sonnet 5. This is an equal-token calculation, not a test result or a quote for using either through a chat product.

The twentyfold ratio only applies within Haiku's lower-price input tier. Above 100,000 input tokens, Haiku charges the entire request at $0.50 input and $2.50 output per million. At 120,000 input and 2,000 output tokens, the estimates are $0.065 and $0.26 respectively. Discounts, caching, tools and different output lengths change the actual task bill.

For a workflow repeated hundreds of times, evaluate the cost per accepted result. Include rejected answers, retries and review time. Saving token spend has little practical value if a missing constraint creates a substantial correction task. The separate HaikuChat pricing page explains this workspace's own credit packs.

Three sensible replacement candidates

Routing an incoming message: ask each model to select one label from a fixed set, using exactly the same category definitions. Include messages that fit no category. Haiku is a reasonable candidate when the labels are stable and the result is easy to check. Do not let a model invent a new label to make an uncertain input look classified.

Summarizing a known document type: compare preservation of dates, decisions and exceptions. Use a sample where the latest paragraph changes an earlier plan. A model that repeats the older date has failed the task, regardless of how concise its answer is.

Extracting a small table: fix the requested fields and check every cell against the source. Include a missing field, two currencies and a value appearing in both a subtotal and a total. If Haiku meets the same acceptance standard as the existing Sonnet process, the smaller-model option becomes concrete.

An investigation requiring several competing explanations deserves a different evaluation. Keep Sonnet in the comparison when it must reconcile ambiguous evidence or reason through dependencies; do not extrapolate a classification result to that workload.

Do not substitute a Sonnet 5.5 benchmark

A published score for Sonnet 5.5 is not a score for Sonnet 5. The release results discussed in our current-model guide compare Haiku with the newer Sonnet; they do not by themselves settle this version-specific question.

For your own comparison, freeze a small set of inputs and the acceptance criteria before testing. Record exact model identifiers, effort settings, context length and whether tools were involved. Evaluate complete answers without the model label. Count omissions and unsupported claims separately from style.

Measure time to a useful completed answer as well as time to the first token. Higher default reasoning effort can affect response length and latency. We have not measured a Haiku-versus-Sonnet-5 latency ratio and do not present a guaranteed speed multiple.

A cautious way to move an existing workflow

Start with the narrowest recurring task, keeping the existing Sonnet result as a reference. Move only the cases Haiku passes against the written rubric, and keep an escalation path for ambiguous inputs. Repeat the evaluation after changing prompts or input formats.

If you are choosing from scratch, compare current alternatives rather than treating this older pairing as the whole market. Read the Haiku, Sonnet and Opus selection guide, or compare Haiku with GPT-6 Luna for another small-model option. HaikuChat provides a Haiku workspace; it does not switch a user's existing Sonnet service automatically.

Questions about this comparison