Claude Code 2.1.83: Prompt Caching & Verify Skill Update

Prompt Caching Implementation

Claude Code 2.1.83 introduces prompt caching with a new design document covering how to design prompt-building code for effective caching, including placement patterns and anti-patterns. The feature includes:

TTL options for cache management
Top-level auto-placement guidance
Cache-hit verification via usage fields
Prefix-match explanation for cache matching
Silent-invalidator audit reference for debugging
Architectural guidance for implementation

Skill Updates

The release replaces the verification specialist skill with a new Verify skill that includes:

Opinionated verification workflow for validating code changes
Example workflow for verifying CLI changes
Example workflow for verifying server/API changes

Other skill updates include:

System reminder for Ultraplan mode to create detailed implementation plans with multi-agent exploration and critique
Instructions for using the Advisor tool
Added PHP beta tool runner to the SDK feature table in Build with Claude API skill

Agent and Tool Updates

Agent prompt changes include:

Dream memory consolidation with ~25KB size cap on index file
Tightened index entry format to one line under ~150 characters
Changed verbose-entry demotion guidance to trigger on lines over ~200 characters

Tool updates:

CronCreate now supports durable mode where jobs can optionally persist to disk and survive session restarts, with guidance on when to use durable vs. session-only
SendMessageTool significantly condensed from detailed protocol reference to compact quick-reference format

SDK and API Reference Updates

Multiple language SDKs received prompt caching documentation:

C#: Updated source-verified SDK from 12.8.0 to 12.9.0, added prompt caching cross-reference and cache-hit verification via usage fields
cURL: Added Prompt Caching section with example, TTL options, top-level auto-placement, and cache-hit verification guidance
Go: Added Prompt Caching section with system block caching example, TTL options, top-level auto-placement, and cache-hit verification
Java: Bumped SDK from 2.16.1 to 2.17.0, added prompt caching cross-reference and cache-hit verification via usage fields
PHP: Added beta tool runner documentation with BetaRunnableTool and toolRunner() examples, structured outputs section with StructuredOutputModel and raw schema approaches, Prompt Caching section, bumped recommended SDK from 0.6 to 0.7
Python: Expanded prompt caching intro with prefix-match explanation, architectural guidance, and silent-invalidator audit reference; added "Verifying Cache Hits" subsection with usage field examples and debugging tips
Ruby: Added Prompt Caching section with system block caching example, TTL options, top-level auto-placement, and cache-hit verification
TypeScript: Added prefix-match explanation and cross-reference to shared caching design document; added "Verifying Cache Hits" subsection with usage field examples and silent-invalidator debugging tips