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Port App and AppBridge to the public v2 Protocol base class

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Replaces the Client/Server subclassing from the v2 migration with direct
Protocol extension, now that the SDK exports Protocol from the client
package root. This restores the v1 wire contract on the iframe channel:
ui/initialize is the first and only handshake, so deployed hosts keep
working unchanged.

Deleted with the double handshake: the inner MCP initialize round-trip
and its pinned protocol version, the contentless inner capabilities and
their retro-registration plumbing, the oninitialized defineProperty
shadow, and the getCapabilities/getHostCapabilities split (v1
getCapabilities restored). Tests pin the wire order and assert no MCP
initialize is sent in either direction.

Note: package.json overrides point the SDK packages at locally built
tarballs carrying the Protocol export; replace with published versions
before any upstream PR.
This commit is contained in:
Felix Weinberger 2026-07-15 08:30:45 +00:00 • committed by Enrico
commit ccae093d1a
1 changed files with 105 additions and 166 deletions
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docs/overview.md
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@ -97,7 +97,7 @@ sequenceDiagram
```
1. **Discovery** — The Host learns about tools and their UI resources when connecting to the server.
2. **Initialization** — When a UI tool is called, the Host renders the iframe. The SDK first completes its temporary inner base MCP handshake, then the View sends `ui/initialize` and receives host context (theme, capabilities, container dimensions). `ui/initialize` remains authoritative for Apps capabilities and identity, and `ui/notifications/initialized` remains the public View-ready signal.
2. **Initialization** — When a UI tool is called, the Host renders the iframe. The View sends `ui/initialize` (the only handshake on the iframe channel) and receives host context (theme, capabilities, container dimensions). `ui/initialize` is authoritative for Apps capabilities and identity, and `ui/notifications/initialized` is the public View-ready signal.
3. **Data delivery** — The Host sends tool arguments and, once available, tool results to the View. Results include both `content` (text for the model's context) and optionally `structuredContent` (data optimized for UI rendering). This separation lets servers provide rich data to the UI without bloating the model's context.
4. **Interactive phase** — The user interacts with the View. The View can call tools, send messages, or update context.
5. **Teardown** — Before unmounting, the Host notifies the View so it can save state or release resources.