feat: Add typed extensions infrastructure with auto-discovery #648
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Typed extensions provide formal JSON schemas for vendor-agnostic
extension data in `ext.{namespace}` fields. This enables SDK code
generation, schema validation, and cross-vendor interoperability.
**New features:**
- Extension meta schema defining valid_from/valid_until version bounds
- Auto-discovery of extensions during schema build
- Version-filtered extension registries per schema version
- New `extensions_supported` field in agent card adcp extension
- Comprehensive test suite for extension infrastructure
**How it works:**
1. Extensions are defined in `/schemas/source/extensions/{namespace}.json`
2. Build script auto-discovers extensions and filters by version compatibility
3. Each versioned build includes only compatible extensions in registry
4. Agents declare supported extensions via `extensions_supported` array
This is a MINOR release adding new optional capabilities without
breaking existing functionality.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <[email protected]>
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youbek
reviewed
Jan 8, 2026
youbek
reviewed
Jan 8, 2026
youbek
reviewed
Jan 8, 2026
Updates documentation to be compliant with both protocol specs: **A2A Agent Cards:** - Changed from `extensions.adcp` object to proper A2A `extensions[]` array format - Each extension now has uri, description, required, and params fields - Extension URI: https://adcontextprotocol.org/extensions/adcp **MCP Server Cards:** - Added support for declaring AdCP via `_meta['adcontextprotocol.org']` - Supports both `/.well-known/mcp.json` and `/.well-known/server.json` - Uses reverse DNS namespacing per MCP server.json spec **Extension Params Schema:** - Updated description to clarify usage in both protocols - Same params structure works for both A2A and MCP 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
The JSON schema validation test was failing because it tried to validate against https://registry.modelcontextprotocol.io/server.schema.json which is an external schema we don't have locally. Removed the $schema field from MCP server card examples since they reference an external MCP registry schema, not an AdCP schema. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
BaiyuScope3
reviewed
Jan 8, 2026
BaiyuScope3
reviewed
Jan 8, 2026
Addresses PR review feedback: **Reserved Namespaces (@BaiyuScope3)** - Added RESERVED_NAMESPACES list: adcp, core, protocol, schema, meta, ext, context - Build script now validates and rejects reserved namespaces - Documented in extensions reference **Deprecation Policy (@BaiyuScope3)** - Added "Extension Deprecation Policy" section with: - When extensions may be deprecated (superseded, promoted, low adoption, incompatible) - Standard deprecation process (valid_until + 1 minor, CHANGELOG, migration guide) - Emergency deprecation for security issues **Tests** - Added test verifying reserved namespaces are not used 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
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Summary
ext.{namespace}fieldsvalid_from/valid_untilextensions_supportedfield to agent card for declaring typed extension supportFeatures
Extension Meta Schema (
extension-meta.json)valid_from(required): Minimum AdCP version (e.g., "2.5")valid_until(optional): Maximum AdCP version for deprecationAuto-Discovery Build System
/schemas/source/extensions/{namespace}.jsonare auto-discoveredextensions/index.json) is auto-generated with valid extensionsAgent Card Extension Support
extensions_supportedarray field in adcp extensionHow It Works
/schemas/source/extensions/{namespace}.jsonvalid_fromspecifying minimum AdCP versionextensions_supported: ["namespace"]ext.{namespace}data against typed schemasTest plan
npm run test:extension-schemaspassesextensions_supportedfield🤖 Generated with Claude Code