Claude Haiku 4.5 vs Claude Sonnet 5

The scale of contextual data each model handles represents an immediate structural boundary. Claude Haiku 4.5 provides a 200K-token context window with a maximum output limit of 64K tokens, which amounts to roughly 150,000 words of working memory. This capacity accommodates everyday conversational threads, short-to-medium business documents, and scoped programmatic tasks. Claude Sonnet 5 expands this capacity fivefold, supplying a 1M-token context window alongside a 128K-token synchronous output limit. For asynchronous workloads, Sonnet 5 supports up to 300K output tokens using the Message Batches API beta header. This allows Sonnet 5 to ingest entire source repositories, extensive legal libraries, or multi-hour transcripts in a single inference call. Systems handling high-density analytical inputs or massive codebases will hit hard input limits with Haiku 4.5, making Sonnet 5 an absolute requirement when large inputs cannot be chunked.

The two models implement distinct approaches to thinking controls and inference parameters. Claude Haiku 4.5 uses manual extended thinking where engineers define a static token budget via thinking.type enabled. Haiku 4.5 does not support the newer effort parameter, leaving inference duration tied to explicit token allocations. Claude Sonnet 5 transitions entirely to adaptive thinking, which is enabled by default with a baseline effort set to high. It adjusts reasoning dynamically across effort levels spanning from low to max. Teams migrating legacy prompts must note that Sonnet 5 actively rejects manual thinking budgets and non-default sampling parameters such as temperature, top_p, and top_k with a 400 error. Prompts tuned for previous generations require code refactoring to remove hardcoded sampling controls when targeting Sonnet 5, whereas Haiku 4.5 retains backwards-compatible manual budget controls.

While both models support function calling, tool use, and computer interaction, their execution capabilities target different workflows. Anthropic positions Claude Haiku 4.5 for responsive pair programming and quick tool invocation, noting agentic coding capabilities at 90% of Sonnet 4.5. It handles scripted operations, predictable API integrations, and quick user-facing automations with minimal latency. Claude Sonnet 5 is built for long-horizon autonomous agency, approaching the task performance of Opus 4.8. Sonnet 5 formulates multi-step execution plans, navigates web browsers, executes terminal commands, and resolves complex multi-file engineering problems independently. For sensitive operational domains, buyers must note that Sonnet 5 comes with automated cyber safeguards active by default, resulting in intentionally reduced capabilities for cybersecurity tasks compared to Opus-class models, whereas Haiku 4.5 operates under the standard ASL-2 safety specification.

Pricing and runtime characteristics diverge significantly across the two models. Claude Haiku 4.5 costs $1 per million input tokens and $5 per million output tokens, dropping to $0.50 input and $2.50 output on the Batch API, with cache reads priced at $0.10 per million tokens. Combined with Anthropic's Fastest comparative latency rating, it minimizes per-interaction spend for real-time customer channels. Claude Sonnet 5 costs $2 per million input tokens and $10 per million output tokens, with batch rates at $1 and $5, and cache reads at $0.20. Token cost estimates are further impacted by Sonnet 5's modern tokenizer, which produces roughly 30% more tokens for identical text compared to legacy models like Sonnet 4.6. Regarding deployment, Haiku 4.5 uniquely supports legacy Amazon Bedrock InvokeModel endpoints alongside standard cloud integrations, but carries an older reliable knowledge cutoff of February 2025 and a retirement guarantee ending October 15, 2026. Sonnet 5 offers knowledge through January 2026 and a retirement guarantee extending through at least June 30, 2027.