Package the message board MCP connection as a plugin (#58908)

## What changed

Add a `message-board` plugin with connection metadata for the HTTP MCP server. It defaults to `http://127.0.0.1:7777/mcp`, uses `CODEX_MESSAGE_BOARD_TOKEN` for bearer authentication, and marks the server as required.

Document installation and endpoint overrides through `mcp_servers.codex_message_board`. Installing the plugin does not start the server.

## Testing

Extend the HTTP board integration scenario to cover both direct configuration and plugin installation, verifying that a child can post a decision and its restarted parent can discover the same board and read it. Add a plugin context snapshot and include the plugin resources in Bazel test data.

GitOrigin-RevId: d6cf797caaa4dbdcd45114c2ad0a6bd695cf056f

codex-rs/core/BUILD.bazel

@@ -30,6 +30,7 @@ codex_rust_crate(
         "CARGO_MANIFEST_DIR": "codex-rs/core",
     },
     test_data_extra = [
+        "//codex-rs/message-board-mcp:package-files",
         "config.schema.json",
     ] + glob(["src/**/snapshots/**"]) + [
     ],

codex-rs/core/tests/suite/scenarios_agent_message_board_http.rs

@@ -5,8 +5,10 @@ use pretty_assertions::assert_eq;
 use std::sync::Arc;
 use tokio::io::AsyncBufReadExt;
 
+#[test_case::test_case(false; "config")]
+#[test_case::test_case(true; "plugin")]
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn http_board_is_shared_with_children() -> anyhow::Result<()> {
+async fn http_board_is_shared_with_children(plugin: bool) -> anyhow::Result<()> {
     let server = responses::start_mock_server().await;
     let home = Arc::new(tempfile::tempdir()?);
     let sqlite = codex_state::SqliteConfig::new_for_testing(home.path().to_path_buf().try_into()?);
@@ -28,6 +30,26 @@ async fn http_board_is_shared_with_children() -> anyhow::Result<()> {
         .context("server readiness")?;
     let ready: Value = serde_json::from_str(&ready)?;
     let endpoint = json!({"url":ready["url"],"http_headers":{"Authorization":"Bearer http-board-test-token","Host":"board.example"},"required":true,"default_tools_approval_mode":"approve"});
+    if plugin {
+        let manifest = codex_utils_cargo_bin::find_resource!(
+            "../message-board-mcp/plugin/.codex-plugin/plugin.json"
+        )?;
+        let declaration_path =
+            codex_utils_cargo_bin::find_resource!("../message-board-mcp/plugin/.mcp.json")?;
+        let installed = home.path().join("plugins/cache/test/message-board/local");
+        std::fs::create_dir_all(installed.join(".codex-plugin"))?;
+        std::fs::copy(manifest, installed.join(".codex-plugin/plugin.json"))?;
+        let mut declaration: Value = serde_json::from_slice(&std::fs::read(declaration_path)?)?;
+        declaration["mcpServers"]["codex_message_board"] = endpoint.clone();
+        std::fs::write(
+            installed.join(".mcp.json"),
+            serde_json::to_vec(&declaration)?,
+        )?;
+        std::fs::write(
+            home.path().join("config.toml"),
+            "[features]\nplugins = true\n[plugins.\"message-board@test\"]\nenabled = true\n",
+        )?;
+    }
     let configured_endpoint = endpoint.clone();
     let configured_sqlite = sqlite.clone();
     let configure_board = move |config: &mut codex_core::config::Config| {
@@ -37,12 +59,14 @@ async fn http_board_is_shared_with_children() -> anyhow::Result<()> {
             .features
             .disable(Feature::AgentMessageBoard)
             .expect("disable native board");
-        let mut servers = config.mcp_servers.get().clone();
-        servers.insert(
-            "codex_message_board".into(),
-            serde_json::from_value(configured_endpoint.clone()).expect("HTTP config"),
-        );
-        config.mcp_servers.set(servers).expect("configure endpoint");
+        if !plugin {
+            let mut servers = config.mcp_servers.get().clone();
+            servers.insert(
+                "codex_message_board".into(),
+                serde_json::from_value(configured_endpoint.clone()).expect("HTTP config"),
+            );
+            config.mcp_servers.set(servers).expect("configure endpoint");
+        }
     };
     let mut builder = test_codex()
         .with_home(home)
@@ -194,7 +218,11 @@ async fn http_board_is_shared_with_children() -> anyhow::Result<()> {
         }
     }
     insta::assert_snapshot!(
-        "agent_message_board_mcp_context",
+        if plugin {
+            "agent_message_board_plugin_context"
+        } else {
+            "agent_message_board_mcp_context"
+        },
         context_snapshot::format_context_snapshot(
             "A child posts through the HTTP MCP executable; its restarted parent discovers the same board and reads the decision.",
             &bodies.iter().map(SnapshotEntry::body).collect::<Vec<_>>(),

codex-rs/core/tests/suite/snapshots/all__suite__scenarios__agent_message_board__http__agent_message_board_plugin_context.snap

@@ -0,0 +1,104 @@
+---
+source: core/tests/suite/scenarios_agent_message_board_http.rs
+expression: "context_snapshot::format_context_snapshot(\"A child posts through the HTTP MCP executable; its restarted parent discovers the same board and reads the decision.\",\n&bodies.iter().map(SnapshotEntry::body).collect::<Vec<_>>(),\n&ContextSnapshotOptions::default().rewrite_known_segments(),)"
+---
+Scenario: A child posts through the HTTP MCP executable; its restarted parent discovers the same board and reads the decision.
+
+## Window 1
+-- request 1 (request) --
+00:message/developer:
+    <MODEL_INSTRUCTIONS>
+01:message/developer[3]:
+    [01] <PERMISSIONS_INSTRUCTIONS>
+    [02] <PLUGINS_INSTRUCTIONS>
+    [03] <tools>
+        Deferred tool namespaces:
+        - mcp__codex_message_board
+        </tools>
+02:message/developer:
+    You are an agent in a team of agents collaborating to complete a task.
+
+    You can spawn sub-agents to handle subtasks, and those sub-agents can spawn their own sub-agents. All ag...nd capable, and have access to the same set of tools. [hash=876a93c54d3f61d6]
+
+    You can use `spawn_agent` to create a new agent, `followup_task` to give an existing agent a new task an... `send_message` to pass a message to a running agent. [hash=824c12425c7626dc]
+    Child agents can also spawn their own sub-agents.
+
+    When you provide a response in the final channel, that content is immediately delivered back to your parent agent.
+    <OMITTED 15 LINES; ~225 TOKENS; hash=fa366829bdb214be>
+    - All agents use the same current working directory.
+    - As a result, edits made by one agent are immediately visible to all other agents.
+
+    When calling `wait_agent`, prefer longer waits (minutes) to avoid busy polling.
+
+    There are 4 available concurrency slots, meaning that up to 4 agents can be active at once, including you.
+
+    Full-history forks (`fork_turns` omitted or `"all"`) inherit the parent model and reasoning effort and d...uctions; when doing so, set `fork_turns` to `"none"`. [hash=18ccf7e93ecabab9]
+03:message/developer:
+    <MULTI_AGENT_MODE>
+04:message/user:
+    <ENVIRONMENT_CONTEXT>
+05:agent_message
+06:message/assistant:
+    Done.
+07:message/user:
+    Find the board tools and post your decision.
+-- request 2 (request) --
+08:tool_search_call
+09:tool_search_output
+-- request 3 (request) --
+10:function_call/mcp__codex_message_board.post:{"new_channel_name":"design","text":"Worker's durable decision."}
+11:function_call_output:Wall time: <DURATION> seconds
+    Output:
+    {"author":"/root/worker","channel_name":"design","created_at":"<TIMESTAMP>","message_id":"<UUID 1>","thread_id":"<UUID 1>"}
+
+## Window 2 (after request 3: input diverged at item 02, settings changed (tools))
+-- request 4 (request) --
+00:message/developer:
+    <MODEL_INSTRUCTIONS>
+01:message/developer[3]:
+    [01] <PERMISSIONS_INSTRUCTIONS>
+    [02] <PLUGINS_INSTRUCTIONS>
+    [03] <tools>
+        Deferred tool namespaces:
+        - mcp__codex_message_board
+        </tools>
+02:message/developer:
+    You are `/root`, the primary agent in a team of agents collaborating to fulfill the user's goals.
+
+    At the start of your turn, you are the active agent.
+    You can spawn sub-agents to handle subtasks, and those sub-agents can spawn their own sub-agents.
+    All agents in the team, including the agents that you can assign tasks to, are equally intelligent and capable, and have access to the same set of tools.
+
+    You can use `spawn_agent` to create a new agent, `followup_task` to give an existing agent a new task an...message to a running agent without triggering a turn. [hash=7d40ff8b58977202]
+    Child agents can also spawn their own sub-agents.
+    <OMITTED 16 LINES; ~234 TOKENS; hash=b2e94283a8c22327>
+    - All agents use the same current working directory.
+    - As a result, edits made by one agent are immediately visible to all other agents.
+
+    When calling `wait_agent`, prefer longer waits (minutes) to avoid busy polling.
+
+    There are 4 available concurrency slots, meaning that up to 4 agents can be active at once, including you.
+
+    Full-history forks (`fork_turns` omitted or `"all"`) inherit the parent model and reasoning effort and d...uctions; when doing so, set `fork_turns` to `"none"`. [hash=18ccf7e93ecabab9]
+03:message/developer:
+    <MULTI_AGENT_MODE>
+04:message/user:
+    <ENVIRONMENT_CONTEXT>
+05:message/user:
+    Spawn a worker and finish your turn.
+06:function_call/collaboration.spawn_agent:{"fork_turns":"none","message":"Say ready.","task_name":"worker"}
+07:function_call_output:{"task_name":"/root/worker"}
+08:message/assistant:
+    Done.
+09:message/user:
+    <ENVIRONMENT_CONTEXT>
+10:message/user:
+    Find the board tools and read the worker's decision.
+-- request 5 (request) --
+11:tool_search_call
+12:tool_search_output
+-- request 6 (request) --
+13:function_call/mcp__codex_message_board.search_posts:{"channel_name":"design"}
+14:function_call_output:Wall time: <DURATION> seconds
+    Output:
+    {"has_more":false,"n_returned":1,"next_cursor":null,"results":[{"author":"/root/worker","channel_name":"...ecision.","thread_id":"<UUID 1>","truncated":false}]} [hash=0322071c1fb9baa5]

codex-rs/message-board-mcp/README.md

@@ -73,4 +73,15 @@ for a remote hostname (repeat for multiple names); loopback hosts remain allowed
 Library callers configure this through `StreamableHttpServerConfig`. Normal MCP
 approval policy applies.
 Deduplication is scoped to MCP sessions, without guarantees across reconnects or for
-stateless clients. Plugin packaging, defaults and in-memory launching are separate.
+stateless clients.
+
+## Plugin
+
+Install `plugin/` through the normal plugin flow. Its MCP declaration defaults to
+`http://127.0.0.1:7777/mcp` and `CODEX_MESSAGE_BOARD_TOKEN`. The package contains
+connection metadata only and can be distributed independently of the server.
+Override `mcp_servers.codex_message_board` in ordinary config to point the same
+plugin at a local or deployed implementation of the contract.
+
+Installing the plugin does not start the HTTP process. Generic app-server default
+installation and local in-memory launching remain separate work.

codex-rs/message-board-mcp/plugin/.codex-plugin/plugin.json

@@ -0,0 +1,5 @@
+{
+  "name": "message-board",
+  "version": "0.1.0",
+  "description": "Shared agent discussion boards through MCP."
+}

codex-rs/message-board-mcp/plugin/.mcp.json

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "codex_message_board": {
+      "url": "http://127.0.0.1:7777/mcp",
+      "bearer_token_env_var": "CODEX_MESSAGE_BOARD_TOKEN",
+      "required": true
+    }
+  }
+}