Claude Opus 5.5

Supported Functionality

Item	Specification
Input	Text, images
Output	Text
Context	1,000,000 tokens
Max Output	128,000 tokens; 300,000 tokens in Message Batches API beta
Vision	✓ Supported
Function Calling	✓ Supported with automatic tool selection; forcing a specific tool is not supported

Description

Claude Opus 5.5 is a high-capability reasoning model released by Anthropic on September 22, 2026, and the first model in the Claude 5.5 family. Its official Claude API identifier is claude-opus-5-5. It accepts text and images, produces text, provides a one-million-token context window with up to 128,000 standard output tokens, and has a reliable knowledge cutoff of June 2026.

The model is designed for long-running agentic coding and professional knowledge work, with stronger autonomy across complex engineering, multi-application operation, and sustained execution. Adaptive Thinking is always on, the default effort is medium, and developers control reasoning depth through output_config.effort. Anthropic lists comparative latency as Moderate and supports tools, vision, PDFs, the Files API, batch processing, prompt caching, and Computer Use.

Key Capabilities

• Long-Running Coding Agents: Plans, edits, tests, and repairs substantial engineering work while maintaining execution state across extended sessions.
• Complex Code Migration: Maps dependencies, updates interfaces and configuration, creates tests, and validates migration stages.
• Professional Knowledge Work: Synthesizes research, business documents, and multiple constraints into analysis and decision support.
• Million-Token Analysis: Works across large codebases, long documents, project history, and multiple rounds of tool results.
• Visual and Document Understanding: Interprets screenshots, charts, interfaces, images, and PDFs together with written requirements.
• Sustained Tool Execution: Calls client-side or server-side tools in agent loops while preserving relevant reasoning and action state.
• Adjustable Adaptive Thinking: Uses effort to control reasoning depth while keeping Adaptive Thinking enabled on every request.

Technical Strengths

Feature	Benefit
Always-On Adaptive Thinking	Retains reasoning on every request and uses effort as the single depth control.
1M Context Window	Holds substantial code, document collections, and long project history within one analytical scope.
128K Standard Output	Supports complete code changes, extensive analysis, and large structured deliverables.
Long-Horizon Agent Optimization	Strengthens continuous planning, tool use, state tracking, and validation.
Broad Platform Features	Supports vision, PDFs, the Files API, batching, prompt caching, server tools, and client tools.
Mid-Conversation Tool Changes	Adapts tool definitions or system direction during an ongoing task.

Frequently Asked Questions

How should I set effort for Claude Opus 5.5?

The default is medium, which is a practical starting point for most evaluations. Test lower levels for routine organization or focused edits and progressively higher levels for complex migrations, deep analysis, and long-running agents. Compare completion, correctness, and observed latency on the same representative tasks.

Why can Claude Opus 5.5 not be forced to call a specific tool?

The model rejects tool_choice values of any or a named tool. Use the default auto behavior with strict tool use for schema-valid arguments, or Structured Outputs when the final response requires a fixed shape. State clearly in the prompt when a particular tool applies.

What changes when migrating from Claude Opus 5 to 5.5?

Update the model ID to claude-opus-5-5, remove disabled or manually budgeted thinking settings, and re-evaluate effort because the default changes from high to medium. Replace forced tool selection with auto, read response content by block type, and return preserved thinking blocks unchanged during tool loops.

Is the 300K output limit available on every Claude Opus 5.5 request?

No. Standard maximum output is 128K tokens; 300K is a beta capability of Anthropic's Message Batches API under its required beta configuration. Other platforms and ordinary online requests follow the limits shown in their current documentation.

How do I call Claude Opus 5.5 on LinkModel?

Claude Opus 5.5 is available on LinkModel. Open its live model page, copy the published model ID, and submit text or image input with the request structure currently shown there. Use LinkModel's live page for the platform route, context limits, and available tools instead of substituting Anthropic's official API identifier.

How do I validate Claude Opus 5.5 on LinkModel?

Complete a basic text request with the model ID shown on LinkModel, then separately test images, PDFs, long context, structured results, and multistep tool calls. Inspect the handling and replay of thinking blocks, automatic tool selection, output truncation, and errors, and confirm which options LinkModel currently exposes for effort, Computer Use, batching, and other extensions.