browser/openspec/changes/implement-plugin-bridge-and-sdk/proposal.md

Why

Validated plugin manifests can now register game management plugins, but plugin pages still lack a safe runtime bridge and authors lack a typed SDK for calling platform-mediated abilities. This change establishes the browser-side plugin boundary needed before the plugin marketplace and server workflows can host real plugin UI.

What Changes

• Add a plugin page bridge contract that exposes only scoped platform abilities to plugin UI code.
• Add a TypeScript plugin SDK with bridge message types, permission checks, request/response helpers, and safe error handling.
• Add platform API support for validating plugin bridge sessions and evaluating requested actions against manifest permissions.
• Update the example development plugin to declare bridge requirements and exercise the SDK without direct run, host path, socket, credential, or raw AI key access.
• Add focused tests for bridge permission decisions, SDK type/runtime behavior, and platform validators.

Capabilities

New Capabilities

• plugin-bridge-and-sdk: Defines the platform-mediated plugin page bridge, SDK contract, permission enforcement, and safe capability surface for game management plugin pages.

Modified Capabilities

• None.

Impact

• plugins/: SDK source, bridge contracts, manifest/schema additions, example plugin declarations, and TypeScript tests.
• platform/: bridge session/action DTOs, domain types, validators, service logic, API route, and Go tests.
• platform_web/: bridge host contracts/utilities and tests that can later be used by plugin marketplace pages.
• OpenSpec artifacts and validation for the new plugin-bridge-and-sdk capability.