Discover stdio MCP servers from selected executor plugins by jif-oai · Pull Request #27870 · openai/codex

jif-oai · 2026-06-12T13:15:57Z

Why

In short: this PR discovers MCP registrations by reading a selected plugin's .mcp.json on its executor. #27884 then resolves those registrations in the shared catalog.

thread/start.selectedCapabilityRoots can select a plugin root owned by an executor, and Codex can resolve that package through the executor filesystem. MCP declarations inside the selected plugin are still ignored.

This PR adds the source-specific discovery layer on top of the selected-plugin catalog boundary in #27884:

selected capability root
        |
        v
resolve the plugin through its executor filesystem
        |
        v
read and normalize its MCP config through the same filesystem
        |
        v
contribute stdio registrations bound to that environment ID

The existing MCP launcher and connection manager remain unchanged. MCP config parsing is shared with local plugins through #27863.

What changed

Added an executor plugin MCP provider in the MCP extension.
Retained only the exact filesystem capability used for package resolution and reused it for the selected plugin's MCP config, with no host-filesystem fallback or unrelated process/HTTP authority.
Read either the manifest-declared MCP config or the default .mcp.json; a missing default file means the plugin has no MCP servers.
Accepted stdio servers only for this first vertical. Executor-owned HTTP declarations are skipped with a warning until their placement semantics are defined.
Normalized stdio registrations with the owning environment's stable logical ID and plugin-root working directory.
Resolved environment-variable names on the owning executor and rejected explicit local forwarding for non-local plugins.
Froze discovered declarations once per active thread runtime, then applied current managed plugin and MCP requirements when contributing them.
Carried the selected root ID, display name, and selection order into the catalog contribution defined by Add selected-plugin precedence and attribution to the MCP catalog #27884.

Behavior and scope

There is intentionally no production behavior change yet. This PR provides the executor provider and contribution boundary, but app-server does not install it in this change. Existing local plugin MCP loading is unchanged, and no MCP process is launched by this PR alone.

Assumptions

The selected root ID is the plugin policy identity; the manifest display name is presentation metadata.
An environment ID is a stable logical authority. Reconnection or replacement under the same ID does not change ownership.
Selected plugin packages and their manifests are trusted inputs.
The selected package and MCP discovery snapshot remain frozen for the active thread runtime.

Follow-up

The next PR installs this contributor in app-server and adds an end-to-end test proving that a selected plugin MCP tool launches on its owning executor, can be called by the model, survives an explicit MCP refresh, and is invisible when its root was not selected.

Resume, fork, environment removal or ID changes, dynamic catalog reload, and executor-owned HTTP MCP placement remain separate lifecycle decisions.

Verification

Focused tests cover executor-only filesystem reads, missing and malformed config, stdio filtering and normalization, managed requirements, package attribution, and selection order. CI owns execution of the test suite.

jif-oai · 2026-06-12T13:16:56Z

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jif-oai · 2026-06-12T14:00:17Z

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jif-oai · 2026-06-12T14:31:48Z

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chatgpt-codex-connector · 2026-06-12T14:50:57Z

@@ -39,3 +41,20 @@ impl McpServerContributor<Config> for HostedPluginRuntimeExtension {
 pub fn install(builder: &mut ExtensionRegistryBuilder<Config>) {
    builder.mcp_server_contributor(std::sync::Arc::new(HostedPluginRuntimeExtension));
 }
+
+/// Installs discovery for MCP servers declared by thread-selected executor plugins.
+pub fn install_executor_plugins(


Wire executor plugin MCP discovery into startup

When executor plugins declare MCP servers, this installer is never wired into production startup: repo-wide rg shows the app-server production registry still only calls codex_mcp_extension::install, while install_executor_plugins and initialize_executor_plugin_thread_data are only referenced by tests. That means selected plugin MCP declarations won't be discovered for real threads.

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In the next PR, calm down

…7884) ## Why **In short:** this PR resolves already-discovered MCP registrations. It does not read selected plugins or discover their MCP servers. The resolved MCP catalog currently builds config and auto-discovered plugin registrations before runtime contributors are applied. A thread-selected plugin needs a distinct precedence tier in that same initial resolution pass: otherwise a disabled lower-precedence winner can leave stale name-level state behind, and the winning MCP tools cannot be attributed to the selected package reliably. This PR adds that catalog boundary before executor discovery is connected. ## What changed - Added an explicit selected-plugin registration tier between auto-discovered plugins and explicit config. - Collected selected-plugin contributions before the initial catalog build, while leaving compatibility and generic extension overlays in their existing runtime phase. - Retained the winning plugin ID and display name directly on plugin-owned catalog registrations. - Derived MCP tool provenance from the winning catalog entry instead of joining against local-only plugin summaries. - Retained the winning selected server's tool approval policy in the running connection manager, so a selected registration cannot inherit approval behavior from a losing local plugin. - Kept remembered approval session-scoped for selected plugins until there is an authority-aware persistence contract; Codex will not write approval back to an unrelated local plugin. - Preserved existing name-level disabled vetoes for discovered plugins and config, while keeping a selected package's own disabled registration scoped to that registration. - Preserved deterministic selection order and existing config, compatibility, and extension precedence. The resulting order is: ```text auto-discovered plugin < selected plugin < explicit config < compatibility registration < extension overlay ``` ## Behavior and scope This is a catalog and provenance change only. No production host contributes selected-plugin MCP registrations yet, so existing local MCP behavior remains unchanged. The stacked follow-up, #27870, installs the executor plugin provider that produces these registrations. App-server activation remains a separate final step. ## Verification Focused tests cover precedence, deterministic selected-plugin conflicts, disabled-veto behavior across catalog phases, managed requirements before selected-plugin resolution, winning-server approval policy, and attribution when local and selected packages share an ID or server name. CI owns execution of the test suite.

jif-oai · 2026-06-15T09:42:56Z

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jif-oai requested a review from a team as a code owner June 12, 2026 13:15

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Resolve selected plugin MCP registrations

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jif-oai force-pushed the jif/selected-executor-plugin-mcp-registration branch from 642d0f2 to f6fbab9 Compare June 12, 2026 14:24

jif-oai changed the base branch from main to jif/selected-plugin-mcp-catalog June 12, 2026 14:25

jif-oai mentioned this pull request Jun 12, 2026

Add selected-plugin precedence and attribution to the MCP catalog #27884

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jif-oai changed the title ~~Register MCP servers from selected executor plugins~~ Discover stdio MCP servers from selected executor plugins Jun 12, 2026

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jif-oai added 3 commits June 12, 2026 17:16

Use selected MCP winner approval policy

a7578ad

Discover MCP servers in selected executor plugins

8b78cf4

Narrow executor plugin access to its filesystem

b718083

jif-oai force-pushed the jif/selected-executor-plugin-mcp-registration branch from f6fbab9 to b718083 Compare June 12, 2026 15:19

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Activate selected executor plugin MCPs in app-server #27893

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Comment thread codex-rs/ext/mcp/src/executor_plugin/provider.rs

Base automatically changed from jif/selected-plugin-mcp-catalog to main June 15, 2026 09:10

Merge main into jif/selected-executor-plugin-mcp-registration

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jif-oai merged commit b3c423e into main Jun 15, 2026
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jif-oai deleted the jif/selected-executor-plugin-mcp-registration branch June 15, 2026 09:52

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jif-oai commented Jun 12, 2026 •

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