feat: MCP Roots support by alexhancock · Pull Request #7790 · block/goose

alexhancock · 2026-03-10T17:12:22Z

demo

demo of it with a server that has a tool which lists roots from client and returns them from the tool

alexhancock · 2026-03-10T17:12:59Z

Cargo.toml


 [patch.crates-io]
 v8 = { path = "vendor/v8" }
+rmcp = { path = "../rust-sdk/crates/rmcp" }


will update this when modelcontextprotocol/rust-sdk#742 merges and releases

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chatgpt-codex-connector · 2026-03-10T17:16:27Z

Cargo.toml


 [patch.crates-io]
 v8 = { path = "vendor/v8" }
+rmcp = { path = "../rust-sdk/crates/rmcp" }


Remove machine-local rmcp patch override

The new [patch.crates-io] entry hard-pins rmcp to ../rust-sdk/crates/rmcp, which is outside this repository and not present in a standard checkout. That makes dependency resolution fail for contributors/CI that only have this repo, so the project cannot build or test without an extra unpublished sibling directory.

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chatgpt-codex-connector · 2026-03-10T17:16:28Z

crates/goose/src/agents/extension_manager.rs

    let timeout_duration =
        Duration::from_secs(timeout.unwrap_or(crate::config::DEFAULT_EXTENSION_TIMEOUT));

+    let roots_dir = std::env::current_dir().unwrap_or_default();


Use session working dir for streamable HTTP roots

This sets MCP roots for streamable HTTP extensions from std::env::current_dir() instead of the per-session working_dir passed into ExtensionManager::add_extension. In sessions started with a different workspace path, servers that call roots/list will be given the wrong directory and may operate on the wrong files or fail to find project data.

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chatgpt-codex-connector · 2026-03-10T17:16:28Z

crates/goose/src/agents/mcp_client.rs

 }

+fn working_dir_roots(dir: &std::path::Path) -> ListRootsResult {
+    let uri = format!("file://{}", dir.display());


Build roots URI with proper file-URL encoding

Constructing the root URI via string formatting (file://{dir.display()}) does not perform file-URL normalization/escaping, so paths with spaces, #, non-UTF-8 bytes, or Windows separators produce invalid or ambiguous URIs. MCP servers consuming roots/list can misparse or reject these roots; use a file-URL constructor instead of raw formatting.

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DOsinga · 2026-03-10T21:09:18Z

the codex comments seem worth paying attention to, especially the one about the current folder

and there's the thing, we talked about this before, but should the working_dir be the root for the MCP servers? that means that technically they shouldn't have access to anything outside the working_dir. our developer extension definitely does that and would then ignore the root. ¯_(ツ)_/¯

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chatgpt-codex-connector · 2026-03-11T14:11:51Z

crates/goose/src/agents/extension_manager.rs

+    let roots_dir = effective_working_dir
+        .clone()
+        .unwrap_or_else(|| std::env::current_dir().unwrap_or_default());


Derive roots path from validated working directory

When working_dir is provided but does not exist, this function logs a warning and skips command.current_dir(dir), so the MCP process runs in the parent process directory; however, roots_dir is still taken from the invalid effective_working_dir. In that scenario, roots/list returns a non-existent root that does not match the server's actual cwd, and root-aware MCP servers can fail file operations even though the extension started successfully.

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chatgpt-codex-connector · 2026-03-11T14:46:28Z

crates/goose/src/agents/mcp_client.rs

+        &self,
+        _context: RequestContext<RoleClient>,
+    ) -> impl std::future::Future<Output = Result<ListRootsResult, ErrorData>> + Send + '_ {
+        std::future::ready(Ok(working_dir_roots(&self.working_dir)))


Update roots after working directory changes

list_roots always returns the working_dir captured when the MCP client is first connected, so roots become stale if a session's working directory is changed later (for example via ACP working_dir/update, which updates session state without recreating extension clients). In that scenario, root-aware MCP servers receive an outdated root and can resolve files against the wrong project until the extension is reconnected.

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chatgpt-codex-connector · 2026-03-11T14:55:23Z

crates/goose/src/agents/extension_manager.rs

    let timeout_duration =
        Duration::from_secs(timeout.unwrap_or(crate::config::DEFAULT_EXTENSION_TIMEOUT));

+    let roots_dir = std::env::current_dir().unwrap_or_default();


Pass session working dir to streamable HTTP MCP clients

ExtensionManager::add_extension receives a per-session working_dir, but create_streamable_http_client always derives roots_dir from std::env::current_dir() before calling McpClient::connect. In sessions where the workspace differs from the process cwd, roots/list will advertise the wrong directory to streamable HTTP servers, so root-aware tools can read/write against the wrong project tree.

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chatgpt-codex-connector · 2026-03-11T14:55:23Z

crates/goose/src/agents/extension_manager.rs

+    let roots_dir = effective_working_dir
+        .clone()
+        .unwrap_or_else(|| std::env::current_dir().unwrap_or_default());


Derive roots from the validated child-process working dir

child_process_client validates effective_working_dir before calling command.current_dir, but roots_dir is still taken from effective_working_dir even when that validation fails. If working_dir (or GOOSE_WORKING_DIR) points to a missing/non-directory path, the MCP process runs with a different cwd while roots/list advertises the invalid path, which can break root-based file operations.

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chatgpt-codex-connector · 2026-03-11T14:55:23Z

crates/goose/src/agents/mcp_client.rs

 }

+fn working_dir_roots(dir: &std::path::Path) -> ListRootsResult {
+    let uri = format!("file://{}", dir.display());


Build roots URI via proper file-URL conversion

working_dir_roots creates the root URI with raw string formatting (file://{dir.display()}), which skips file-URL escaping/normalization. Paths containing spaces, #, non-UTF8 bytes, Windows separators, or relative segments can produce malformed or ambiguous URIs, and MCP servers that parse roots as URLs may reject or misresolve them.

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fixes #6556

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chatgpt-codex-connector · 2026-03-11T17:25:24Z

crates/goose-acp/src/server.rs

+        if let Some(session) = self.sessions.lock().await.get(&req.session_id) {
+            session
+                .agent
+                .extension_manager
+                .update_working_dir(&path)


Drop sessions lock before awaiting roots update

on_update_working_dir borrows a session from self.sessions.lock().await.get(...) and then awaits extension_manager.update_working_dir, which keeps the sessions mutex held for the entire async update path. If any extension is slow or blocked while handling roots/list_changed, other ACP requests that need session lookup will block behind this lock, making the agent appear hung after a working-dir change.

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unclear to me how to test this in an ACP client, but if anything is bad in the UX we can followup.

@codefromthecrypt do you know how to trigger the working dir change in an example ACP client?

chatgpt-codex-connector · 2026-03-11T17:25:24Z

crates/goose/src/agents/extension_manager.rs

+        let extensions = self.extensions.lock().await;
+        for (name, ext) in extensions.iter() {
+            if let Err(e) = ext.client.update_working_dir(new_dir.to_path_buf()).await {


Release extensions mutex before notifying MCP clients

ExtensionManager::update_working_dir holds self.extensions.lock() while awaiting each ext.client.update_working_dir(...) call. Because those calls perform network I/O (notify_roots_list_changed), one slow extension can block the extensions map lock and stall concurrent extension operations (tool listing/calls, add/remove) until the await completes.

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* main: (270 commits) test(acp): align provider and server test parity (#7822) fix(acp): register MCP extensions when resuming a session (#7806) fix(goose): load .gitignore in prompt_manager for hint file filtering (#7795) fix: remap max_completion_tokens to max_tokens for OpenAI-compatible providers (#7765) fix(openai): preserve Responses API tool call/output linkage (#7759) chore(deps): bump @hono/node-server from 1.19.9 to 1.19.11 in /evals/open-model-gym/mcp-harness (#7687) fix: return ContextLengthExceeded when prompt exceeds effective KV cache size (#7815) feat: MCP Roots support (#7790) fix(google): use `includeThoughts/part.thought` for thinking handling (#7593) refactor: simplify tokenizer initialization — remove unnecessary Result wrapper (#7744) Fix model selector showing wrong model in tabs (#7784) Stop collecting goosed stderr after startup (#7814) fix: avoid word splitting by space for windows shell commands (#7781) (#7810) Simplify and make it not break on linux (#7813) Add preferred microphone selection (#7805) Remove dependency on posthog-rs (#7811) feat: load hints in nested subdirs (#7772) feat(acp): add read tool and delegate filesystem I/O to ACP clients (#7668) Support secret interpolation in streamable HTTP extension URLs (#7782) More logging for command injection classifier model training (#7779) ...

alexhancock requested review from DOsinga and jamadeo March 10, 2026 17:12

alexhancock commented Mar 10, 2026

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alexhancock force-pushed the alexhancock/issue-6556-mcp-roots branch from 3d68b49 to b5cda10 Compare March 11, 2026 14:06

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alexhancock force-pushed the alexhancock/issue-6556-mcp-roots branch from b5cda10 to 3d64f80 Compare March 11, 2026 14:37

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alexhancock force-pushed the alexhancock/issue-6556-mcp-roots branch from 3d64f80 to 255956e Compare March 11, 2026 14:47

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alexhancock force-pushed the alexhancock/issue-6556-mcp-roots branch 2 times, most recently from 06f1483 to 997499c Compare March 11, 2026 16:39

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feat: MCP Roots support

49492a4

fixes #6556

alexhancock force-pushed the alexhancock/issue-6556-mcp-roots branch from 997499c to 49492a4 Compare March 11, 2026 17:15

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alexhancock added this pull request to the merge queue Mar 11, 2026

Merged via the queue into main with commit f2de8b5 Mar 11, 2026
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alexhancock deleted the alexhancock/issue-6556-mcp-roots branch March 11, 2026 19:14

github-actions bot mentioned this pull request Mar 16, 2026

chore(release): release version 1.28.0 (minor) #7780

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alexhancock commented Mar 10, 2026 •

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