8 min read
Claude Fable 5.1 Refuses Less: What Actually Changed
Fable 5.1 cuts wrong refusals 85 percent in biology, 60 percent in cyber. Plus the refusal that returns…
The Lab · Written in the open · Tagged Anthropic
Lab.
Working notes from the studio. The tools I build, the workflows I keep, the mistakes I paid for.
48 entries · latest 2026-09-02
Latest entry
Claude Fable 5.1 and Mythos 5.1: What Changed on September 1
Anthropic shipped Fable 5.1 and Mythos 5.1 on September 1. Here is what actually changes for Claude Code users this week, not just the spec sheet.
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8 min read
Claude Fable 5.1 vs Opus 5: Which One Earns Its Price
Fable 5.1 costs double what Opus 5 does. On single questions they are within 1.4 points; on long…
8 min read
Claude Fable 5.1 Benchmarks: Every Number Compared
All nine Claude Fable 5.1 benchmarks against Fable 5, Opus 5 and GPT-5.6 Sol, plus the 75 percent…
9 min read
A Federal Judge Just Blocked the Pentagon's Anthropic Ban
A federal judge ruled the Pentagon's Anthropic blacklist was illegal retaliation, and what the case means for a…
8 min read
Anthropic Pulled Fable 5 and Mythos 5: What the Ban Means
Anthropic disabled Claude Fable 5 and Mythos 5 on June 12 under a US export order over a…
8 min read
Claude Fable 5 vs Opus 4.8: Is Double the Price Worth It?
Fable 5 costs 10 dollars per million input tokens against 5 for Opus 4.8, output is 50 vs…
8 min read
Claude Fable 5 Is Here: The First Public Mythos-Class Model
Anthropic released Claude Fable 5 on June 9, 2026, the first Mythos-class model anyone can use
9 min read
From Notion to MCP Server: I Rebuilt 4 Workflows in a Weekend
Migrated 4 of 7 Notion automations to an MCP server in one weekend
10 min read
5 Claude API Errors That Cost Me Money (And How I Trapped Them)
Retry storms turned 1 timeout into 340 duplicate calls billed in 90 seconds
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The 1M Context Window vs Prompt Caching: When to Use Which
1M context costs full price on every query, caching cuts repeated tokens to 1/10
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Claude Files API in Production: 5 Patterns for Document Workflows
Files API replaced my 40KB inline blobs with reusable file IDs across requests