Claude Haiku 5.5 API

Claude Haiku 5.5 is Anthropic's October 7, 2026 update to its small-model line. Anthropic positions it for latency-sensitive and cost-sensitive work such as classification, extraction, routing, live support, browser use, and focused subagent steps. It accepts text and images and returns text.

The model expands the Haiku 4.5 context window from 200K to 1M tokens and its maximum output from 64K to 128K. It is also the first Haiku model with adaptive thinking and adjustable effort. Thinking is on by default, and thinking tokens count toward max_tokens.

Anthropic's direct API uses prompt-length pricing. Requests with up to 100K input tokens use the lower tier; requests over 100K use a higher rate for the full request. This threshold matters when estimating a Claude Haiku 5.5 API cost for long documents or long-running agents. The live GPTProto pricing module is the source of truth for GPTProto billing.

Claude Haiku 5.5 API Applications

Classification, extraction, and routing. Label requests, extract fields, route tickets, or choose which model handles the next step. Keep schemas and acceptance checks in the application.

Customer support and live interfaces. Generate short answers, case summaries, query rewrites, and browser assistance. Keep retrieval, permissions, and escalation rules outside the model.

Coding subagents. Assign narrow tasks such as file discovery, change summaries, error triage, or small patches. Use Sonnet 5.5 or Opus 5.5 for more complex, open-ended coding work.

Document and image analysis. Ask questions across long documents or extract data from screenshots and charts. The larger window adds capacity, but citations and validation still matter.

Long tasks and agentic work. Increase effort when a focused step needs more reasoning. Long prompts can cross the 100K pricing threshold, while the newer tokenizer counts the same text as approximately 30% more tokens than Haiku 4.5.

Haiku 4.5 vs Haiku 5.5 vs Sonnet 5.5

Choose by workload rather than family name alone. Haiku 5.5 is the starting point for frequent, focused steps; Sonnet 5.5 remains the stronger option for difficult coding and longer chains of judgment.

The benchmark figures above are reported by Anthropic and were not independently reproduced by GPTProto. Run the same prompts, tools, time budget, and acceptance checks on your own workload before moving production traffic.

For GPT 6.1 Sol vs Claude Haiku 5.5, start with Haiku for repeated, well-scoped steps and evaluate GPT 6.1 Sol for demanding coding or agent tasks in an OpenAI-style workflow. Do not compare base token prices alone: include retries, thinking tokens, the 100K Haiku pricing threshold, latency, and accepted-task rate.

Claude Haiku 5.5 API Migration: Checks Before You Switch

Moving from Haiku 4.5 requires more than replacing the model name. Test these changes against the exact endpoint shown in GPTProto's fixed API Usage section:

1. Confirm the model string. Anthropic uses claude-haiku-5-5 with no date suffix; use the exact ID displayed by GPTProto.

2. Recount tokens. The same text can produce approximately 30% more tokens than on Haiku 4.5. Recalculate budgets and alerts.

3. Replace manual thinking budgets. budget_tokens can return a 400 error. Use adaptive thinking and control depth through effort.

4. Parse blocks by type. A response may begin with a thinking block rather than user-facing text.

5. Remove custom sampling values. Non-default temperature, top_p, or top_k settings can return a 400 error.

6. Remove assistant prefills. End messages with a user turn.

7. Handle new failure states. Add logic for refusal and model_context_window_exceeded, then test before changing the default.

If you are migrating from Anthropic to GPTProto, also verify authentication, endpoint compatibility, streaming events, tool calls, image input, and error objects. Native Anthropic parameters do not necessarily map one-to-one onto every OpenAI-compatible route.

When Should You Choose Claude Haiku 5.5?

Choose Haiku 5.5 for many short or bounded tasks: classification, extraction, routing, retrieval compression, support assistance, visual triage, or focused subagent work. It is also a candidate when Haiku 4.5 lacks enough context or reasoning control.

Choose Claude Sonnet 5.5 for deeper coding judgment or sustained multi-step execution. Keep Claude Haiku 4.5 available until token counts, response parsing, tools, and cost behavior are validated.