v0.16.6

Added

• Type classes now accept hash construction with mixed key shapes — symbols or strings, snake_case or camelCase — and support bracket access (obj[:field], obj['field']). UserMessage.new({"sessionId" => "abc"}) works the same as UserMessage.new(session_id: "abc"). Type.from_hash(nil) and Type.wrap(nil) are nil-safe.
• ClaudeAgentOptions.new(nil) is accepted and yields an options object populated with configured defaults.

Changed

• Discriminator fields on type classes (type on SystemPromptFile/McpStdioServerConfig/etc., behavior on PermissionResultAllow/Deny, hook_event_name on every hook input/output) are now attr_reader-only, set authoritatively in initialize. They cannot be overwritten externally.
• ClaudeAgentOptions continues to raise ArgumentError on unknown keys (constructor, dup_with, and []=); other type subclasses silently drop unknown keys for forward-compatibility with newer CLI output.

Internal

• Unified ~50 type classes (messages, hook inputs/outputs, MCP configs, system prompt configs, sandbox settings) under a shared Type base class. lib/claude_agent_sdk/types.rb shrank from 1510 to 588 lines; MessageParser's system-message dispatch went from 215 lines to a 14-entry lookup table.

What's changed

• #30 Unify types under Type base class — @songjiz

Full Changelog: v0.16.5...v0.16.6

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gem install claude-agent-sdk -v 0.16.6