## Why
#28529 proves OAuth discovery uses the selected executor, but its
end-to-end test stops before the callback and token exchange.
## What changed
- add an executor-only mock token endpoint
- complete the OAuth callback using the authorization URL's `state` and
`redirect_uri`
- assert the PKCE token exchange reaches the executor-only endpoint
- assert the completion notification reports the selected thread and
succeeds
Depends on #28529.
## Why
#28522 routes selected-plugin HTTP MCP traffic through the owning
executor, but OAuth bootstrap and refresh still used host-local clients.
Executor-only servers therefore cannot complete discovery or login
through the same network boundary as the MCP connection.
## What changed
- adapt `codex_exec_server::HttpClient` to RMCP 1.8's `OAuthHttpClient`
contract
- let RMCP own discovery, dynamic registration, PKCE, token exchange,
and refresh
- route auth status, persisted-token startup, and app-server login
through the server runtime while preserving the existing local discovery
path
- add optional `threadId` to `mcpServer/oauth/login` and echo it in the
completion notification
- implement RMCP's redirect policy and 1 MiB OAuth response limit over
executor HTTP
- cover selected-thread OAuth discovery and login through an
executor-only route
Depends on #28522.
## Why
Selected executor plugins can declare both stdio and Streamable HTTP MCP
servers, but only stdio registrations were retained. That silently drops
part of the plugin's tool surface and prevents HTTP traffic from using
the owning executor's network.
## What changed
- retain selected-plugin Streamable HTTP MCP declarations alongside
stdio declarations
- route their HTTP clients through the owning executor environment
- preserve local auth-header environment references while rejecting them
for executor-hosted declarations
- cover thread isolation, refresh, and an executor-only HTTP route end
to end
## Why
Selected capability roots belong to the executor filesystem, not the
app-server host. Converting their path strings into the host's native
`Path` breaks whenever the two machines use different path conventions,
such as a Windows executor behind a Unix app-server.
This PR establishes `PathUri` as the selected-plugin boundary so the
executor remains authoritative for its paths.
## What changed
- Require `selectedCapabilityRoots[].location.path` to be a canonical
`file:` URI and deserialize it directly as `PathUri`; native path
strings are rejected.
- Update the app-server schema, generated TypeScript, examples, and
request coverage for the URI contract.
- Keep selected roots, resolved plugin locations, manifest paths, and
manifest resources as `PathUri`.
- Inspect and read plugin roots and manifests only through the selected
environment's `ExecutorFileSystem`.
- Parse executor manifests with the shared URI-native parser from #29620
instead of projecting them onto the host filesystem.
- Enforce resource containment lexically and preserve the root URI's
POSIX or Windows path convention.
- Cover foreign Windows plugin roots and URI-native manifest resources.
```text
thread/start
selectedCapabilityRoots[].location.path = "file:///C:/plugins/demo"
| PathUri
v
ExecutorFileSystem
|
+--> plugin.json
+--> manifest resources
```
This PR stops at the shared selected-plugin representation. The next two
PRs remove the remaining host-path projections in the skill and MCP
consumers.
## Stack
1. #29614 — add lexical `PathUri` containment.
2. #29620 — share URI-native manifest path resolution.
3. **This PR** — keep selected plugin roots and resources URI-native.
4. #29626 — load executor skills without host path conversion.
5. #29628 — resolve executor MCP working directories without host path
conversion.
## Why
#27870 teaches the MCP extension how to discover stdio MCP servers
declared by a selected executor plugin, but app-server does not yet
install that contributor or initialize its per-thread state. As a
result, `thread/start.selectedCapabilityRoots` can select the plugin
while its MCP servers remain inactive.
This PR closes that app-server wiring gap:
```text
thread/start(selectedCapabilityRoots)
-> initialize the thread's selected-plugin MCP snapshot
-> read the selected plugin's .mcp.json through its environment
-> start declared stdio servers in that environment
-> expose their tools only on the selected thread
```
## What changed
- Install the selected-executor-plugin MCP contributor in app-server
using the existing shared `EnvironmentManager`.
- Initialize its frozen thread snapshot when `thread/start` includes
selected capability roots.
- Document that selected plugin stdio MCPs are activated in their owning
environment.
- Add an app-server E2E covering the complete selection-to-tool-call
path.
The E2E verifies that:
- the selected MCP process receives an executor-only environment value,
proving the tool runs through the selected environment;
- the MCP tool is advertised to the model and can be called;
- a normal MCP config reload does not discard the thread's frozen
selected-plugin registration;
- another thread without the selected root does not see the MCP server.
## Scope
- Existing sessions without `selectedCapabilityRoots` are unchanged.
- Only stdio MCP declarations are activated. HTTP declarations remain
inactive.
- This does not change selected-root persistence across resume/fork or
add hosted-plugin behavior.
## Verification
- Focused app-server E2E:
`selected_executor_plugin_exposes_its_stdio_mcp_only_to_that_thread`
## Stack
Stacked on #27870.
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