* feat(mcp): JSON-RPC endpoint skeleton for MCP Apps

* feat(mcp): mount /mcp handler in app handler chain when enabled

* feat(mcp): postMessage tunnel connection and _shiny_* tools

* feat(mcp): ui://shiny/app single-file resource with inlined assets

* feat(mcp): postMessage bridge bundle overriding Shiny.createSocket

* fix(mcp): use .globals for sweeper flag (assignInMyNamespace fails in later callback)

* docs(mcp): NEWS entry for experimental MCP Apps support

* docs(mcp): mirror MCP Apps plans, research notes, and demo app into mcp/

* feat(mcp): _shiny_http tool tunnels HTTP side channels in-process

* feat(mcp): inline dynamic htmlDependencies for MCP tunnel sessions

* feat(mcp): tunnel XHR side channels, downloads, host theme + context (Phase 2 client)

* docs(mcp): Phase 2 NEWS + mirror plan/demo/screenshot into mcp/

* feat(mcp): inline CSS url() assets as data URIs for the sandbox

* feat(mcp): exported session API — mcpToolInput, mcpUpdateModelContext, mcpSendMessage, mcpHostContext, isMcpSession

* feat(mcp): author-declared MCP tools via options(shiny.mcp.tools)

* feat(mcp): stdio transport for local desktop hosts

* feat(mcp): direct-connect WebSocket fast path + display mode requests

* docs(mcp): direct-connect/display-mode NEWS, mcptools upstream notes, QUESTIONS.md

* docs(mcp): use real PR number in NEWS

* docs(mcp): record decisions in QUESTIONS.md; explain direct-connect default

* fix(mcp): declare processx/pkgload test deps; run stdio subprocess against installed shiny under R CMD check

* feat(mcp): path-aware direct-connect base (shiny.mcp.origin, X-RSC-Request, rsconnect records)

* feat(mcp): discover deployed URL from Quarto _publish.yml and Posit Publisher records

* fix: pkgdown index for mcp-session; wrap-tolerant reactlog Suggests test; drop Quarto _publish.yml source

* `npm run build` (GitHub Actions)

* fix(mcp): use RStudio-Connect-App-Base-Url for the direct-connect base

Verified against a real connect.posit.it deployment: Connect does not
send X-RSC-Request to Shiny content, and rsconnect excludes its own
rsconnect/ records from the bundle. The header Connect actually sends
with every proxied request is RStudio-Connect-App-Base-Url, which is
already the app's external base URL. Honor it first (X-RSC-Request kept
for API content).

* feat(mcp): shinyapps.io direct-connect base via X-Redx-Frontend-Name

Verified against a real shinyapps.io deployment: the proxy passes
POST /mcp through unauthenticated, sends RStudio-Connect-App-Base-Url
with an EMPTY value, and identifies the external base as
X-Redx-Frontend-Name (schemeless host + path). Combine that with
X-Forwarded-Proto for the direct base, and prefer X-Forwarded-Host
over the internal Host for the generic origin fallback and
deployment-record host matching.

* feat(mcp): appId namespacing so a gateway can serve multiple apps

options(shiny.mcp.appId=) prefixes the internal _shiny_* tunnel tools
(demo_shiny_connect, ...) and publishes the UI resource as
ui://shiny/<appId>; the bridge reads appId from __shinyMcpConfig__ and
prefixes its tool calls to match. mcp/gateway/shiny-mcp-gateway.mjs
(zero-dep Node, stdio or HTTP) merges several app endpoints into one MCP
server, so a single connector exposes many Shiny apps. E2E verified in
basic-host with two apps behind one gateway, including full tunnel
reactivity.

* docs(mcp): add mcp/architecture.md describing the system as built

* docs(mcp): compare with JamesHWade/shinymcp

* fix(mcp/gateway): cookie stickiness, cold-start wake retry, drain on close

shinyapps.io rejects POST to a sleeping app with 405 (only GET
cold-starts an instance) and pins clients to an instance via a session
cookie. The gateway now keeps a per-backend cookie jar, and on a failed
POST wakes the app with a GET to its base URL and retries with backoff.
Also drain in-flight requests before exiting when stdin closes.

* chore(mcp): commit demo-app deployment records (no secrets; exercise the DCF direct-base path)

* fix(mcp): inline render-time deps from direct createWebDependency() calls

{htmlwidgets} (and friends) call createWebDependency() directly for the
dependencies attached to a widget's render payload, bypassing the
processDeps() MCP hook — so a dynamically shown plotly widget arrived
with URL-based crosstalk/CSS deps that 404 inside the sandbox
("crosstalk is not defined"). createWebDependency() now diverts
file-based deps to mcpInlineDependency() when the current reactive
domain is an MCP session; href-only deps fall through to avoid
recursion. Demo: cars app gains a checkbox-gated plotly plot,
E2E-verified in basic-host (Plotly + crosstalk load on demand, 32
points rendered).

* test(mcp): write download bytes with writeBin for Windows

writeLines() opens the file path in text mode, so on Windows the CSV's
\n bytes became \r\n and the _shiny_http download body assertion failed
(only Windows R-CMD-check was red). writeBin(charToRaw(...)) writes the
exact bytes on every platform.

* chore: ignore .playwright-mcp scratch dir (git + R build)

---------

Co-authored-by: schloerke <schloerke@users.noreply.github.com>