Observed Signal · May 11, 2026 · Technical Release · Source: Linas Newsletter · Impact: 3/5 · Sentiment: Positive
Guide to Anthropic's Claude Opus 4.7 Prompting
A May 11, 2026 guide by Linas Beliūnas explains how to maximize results from Anthropic’s Claude Opus 4.7, Anthropic’s flagship generally available model released April 16, 2026. The playbook describes Opus 4.7’s stricter literalism, its new effort parameter that controls how much intelligence the model applies, and its adaptive thinking mode. It compares Opus 4.7 with Claude Sonnet 4.6 (balanced) and Claude Haiku 4.5 (speed specialist), provides a practical framework (set effort first, be specific, use XML-like tags, show examples, force reasoning steps, load rich context, specify output format, define constraints, control verbosity), includes an API example (model="claude-opus-4-7" with output_config.effort), and offers 10 ready-to-use Mega Prompts for founders, operators and investors.
A new flagship LLM release with a novel 'effort' control and prompting best practices can materially affect how teams integrate LLMs into product workflows, automation and creative processes used across marketing and ad operations, though it is not a platform-level policy change.
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Key Takeaways & Evidence Grounding
- Anthropic released Claude Opus 4.7 on April 16, 2026 as its flagship generally available model.
- Opus 4.7 introduces an effort parameter that strictly controls the model's intelligence allocation (examples: high/xhigh effort).
- Anthropic’s current lineup referenced: Claude Opus 4.7 (flagship), Claude Sonnet 4.6 (balanced), Claude Haiku 4.5 (speed specialist).
- The guide lists API pricing cited for Opus 4.7: $5 per MTok input and $25 per MTok output in the article.
- Linas Beliūnas published the prompting playbook on Substack on 2026-05-11 and provided 10 Mega Prompts calibrated for Opus 4.7.
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How to Fix Claude Opus 5’s Agentic Behavior
The author describes problems encountered using Anthropic's Claude Opus 5 — despite strong benchmark scores — and offers concrete CLAUDE.md prompt blocks that correct recurring failure modes. They report that Anthropic substantially reduced the model’s system prompt (from 2,686 words to 514) and that training emphasis on long-horizon agent behavior led the model to act autonomously in undesirable ways. After iterating for two weeks and keeping eight effective prompt blocks, the author says Opus 5 performs best for their workflows when given explicit guardrails (e.g., act vs. ask rules, do-not-implement-on-question rules, and completion guarantees).
Guide to Anthropic's Claude Fable 5 and Workflow
A Substack guide by Linas explains practical prompting and operational workflows for Anthropic’s Claude Fable 5. The article notes a limited window — through July 7, 2026 — when Fable 5 is included in Pro, Max, Team and select Enterprise plans for up to 50% of weekly usage; after that Fable sessions will consume paid usage credits. The piece highlights a field guide by Thariq Shihipar from Anthropic’s Claude Code team, details an 8-technique playbook and prompt structure, warns about fallback models (Opus 4.8), pricing math and geopolitical availability risks, and includes a downloadable “Claude Skill” implementing the recommended workflow.
How to Prompt Anthropic's Claude Fable 5
This guide explains how to prompt Anthropic’s Claude Fable 5 for high-value, long-running tasks and warns that Fable 5 requires a different prompting approach than prior Claude models. The author synthesizes Anthropic documentation and week-one community patterns, offering 12 prompting patterns, an effort-level framework, an orchestrator-and-worker routing pattern, an AI-OS framework, and reusable prompt blocks. Critically, Fable 5 is available in Pro, Max, Team, and seat-based Enterprise plans only until 22 June 2026; after that continued use will be billed at API rates ($10 per million input tokens, $50 per million output tokens). The piece recommends extracting reusable assets (prompts, agent scaffolds, memories, migration notes) during the free-access window and preparing fallback plans (Claude Opus 4.8) to manage cost and safety routing.
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