Align message-board tools with the multi-agent namespace (#47028)

## Why

Message-board tools hardcoded the `collaboration` namespace and used a different namespace description from the multi-agent tools. This ignored custom namespace configuration and caused conflicts under strict tool collision checking.

## What changed

- Use `multi_agent_v2.tool_namespace` and the shared multi-agent namespace description for message-board tools, resolving the namespace at runtime startup.
- Support unnamespaced tool specifications when no namespace is supplied.
- Remove hardcoded `collaboration` prefixes from message-board notifications.

## Testing

Add app-server integration coverage for the default `collaboration` namespace and a configured `agents` namespace with strict collision checking enabled. Verify that both tool families are advertised together and that `get_channels` executes through the installed extension.

GitOrigin-RevId: fef7be51ea2a84bbdb6d3491606db442ed4e6ea3

codex-rs/core/src/agent_message_board.rs

@@ -8,6 +8,7 @@ use crate::ThreadManager;
 use crate::config::Config;
 use crate::context::AgentMessageBoardNotification;
 use crate::context::ContextualUserFragment;
+use crate::tools::MULTI_AGENT_V2_NAMESPACE_DESCRIPTION;
 use chrono::DateTime;
 use chrono::Utc;
 use codex_agent_message_board_extension::AgentMessageBoard;
@@ -33,25 +34,30 @@ pub fn install_agent_message_board(
     registry: &mut ExtensionRegistryBuilder<Config>,
     manager: Weak<ThreadManager>,
 ) {
-    codex_agent_message_board_extension::install(registry, move |config: &Config, tree, caller| {
-        // MAv2 supplies tree paths; ephemeral runtimes must not open durable storage.
-        if !config.features.enabled(Feature::AgentMessageBoard)
-            || !config.features.enabled(Feature::MultiAgentV2)
-            || config.ephemeral
-        {
-            return Box::pin(async { Ok(None) });
-        }
-        let sqlite = config.sqlite_config().clone();
-        let host = Arc::new(LocalBoardHost {
-            manager: manager.clone(),
-            tree,
-            caller,
-        });
-        Box::pin(async move {
-            let board = LocalAgentMessageBoard::open(&sqlite, tree, host).await?;
-            Ok(Some(Arc::new(board) as Arc<dyn AgentMessageBoard>))
-        })
-    });
+    codex_agent_message_board_extension::install(
+        registry,
+        MULTI_AGENT_V2_NAMESPACE_DESCRIPTION,
+        |config: &Config| config.multi_agent_v2.tool_namespace.clone(),
+        move |config: &Config, tree, caller| {
+            // MAv2 supplies tree paths; ephemeral runtimes must not open durable storage.
+            if !config.features.enabled(Feature::AgentMessageBoard)
+                || !config.features.enabled(Feature::MultiAgentV2)
+                || config.ephemeral
+            {
+                return Box::pin(async { Ok(None) });
+            }
+            let sqlite = config.sqlite_config().clone();
+            let host = Arc::new(LocalBoardHost {
+                manager: manager.clone(),
+                tree,
+                caller,
+            });
+            Box::pin(async move {
+                let board = LocalAgentMessageBoard::open(&sqlite, tree, host).await?;
+                Ok(Some(Arc::new(board) as Arc<dyn AgentMessageBoard>))
+            })
+        },
+    );
 }
 
 struct LocalBoardHost {

codex-rs/core/src/context/agent_message_board_notification.rs

@@ -27,7 +27,7 @@ impl ContextualUserFragment for AgentMessageBoardNotification {
     }
     fn body(&self) -> String {
         format!(
-            "\nNew post {} in discussion {}. Use collaboration.read_post or collaboration.read_thread to read it.\n",
+            "\nNew post {} in discussion {}. Use read_post or read_thread to read it.\n",
             self.message_id, self.thread_id
         )
     }

codex-rs/core/src/tools/mod.rs

@@ -34,6 +34,7 @@ use codex_utils_output_truncation::TruncationPolicy;
 use codex_utils_output_truncation::formatted_truncate_text;
 use codex_utils_output_truncation::truncate_text;
 pub(crate) use executed_tool_calls::ExecutedToolCalls;
+pub(crate) use multi_agent_tool::MULTI_AGENT_V2_NAMESPACE_DESCRIPTION;
 pub use router::ToolRouter;
 
 /// Legacy boundaries such as hook payloads, telemetry tags, and Responses tool

codex-rs/core/src/tools/multi_agent_tool.rs

@@ -16,7 +16,8 @@ use futures::future::BoxFuture;
 use serde_json::Value;
 use std::sync::Arc;
 
-const MULTI_AGENT_V2_NAMESPACE_DESCRIPTION: &str = "Tools for spawning and managing sub-agents.";
+pub(crate) const MULTI_AGENT_V2_NAMESPACE_DESCRIPTION: &str =
+    "Tools for spawning and managing sub-agents.";
 
 pub(super) fn multi_agent_v2_handler(
     handler: impl CoreToolRuntime + 'static,