Michael Suchacz
9d0469fc4c
## Summary
Allow root plan-mode chats to use MCP tools from external servers that
an admin has explicitly approved for plan mode. Workspace MCP and
plan-mode subagents remain blocked.
## Problem
`chatd.go` excluded every MCP tool when `isPlanModeTurn` was true, so
planning had no access to tools like docs search, ticketing, etc.
Lifting that guard wholesale was unsafe: `mcp_server_configs` already
has centralized admin governance, but workspace-local MCP (discovered
from agent `.mcp.json`) does not, and subagents use a narrower trust
boundary.
## Fix
Add an admin-controlled per-server `allow_in_plan_mode` flag (default
`false`) and gate plan-mode MCP access on it.
### Backend / schema
- New migration `000472_mcp_server_allow_in_plan_mode.{up,down}.sql` and
matching fixture update.
- `mcpserverconfigs.sql` + generated code: persist and read the new
column.
- `codersdk/mcp.go`: thread the field through `MCPServerConfig`,
`Create*`, and `Update*` request types.
- `coderd/mcp.go`: validate, persist, and return the flag in
get/list/create/update handlers.
### chatd
- `coderd/x/chatd/chatd.go`: pre-filter selected external MCP configs by
`AllowInPlanMode` before calling `mcpclient.ConnectAll` on plan-mode
root turns. Workspace MCP discovery is skipped entirely on plan-mode
turns.
- Single helper decides whether a tool is available in plan mode, used
both at construction and for active-tool filtering (defense in depth).
Plan-mode subagents, dynamic tools, provider-native tools, computer-use,
and workspace MCP stay unchanged.
- `coderd/x/chatd/prompt.go`: update the root plan-mode overlay text to
match the new boundary.
### UI
- `MCPServerAdminPanel.tsx`: add an explicit toggle ("Allow all tools
from this MCP server in root plan mode") next to the existing governance
controls.
- Regenerated `site/src/api/typesGenerated.ts`.
### Docs
- `docs/ai-coder/agents/architecture.md`: replace the blanket "MCP is
unavailable in plan mode" note with the new root-only, external-only,
admin-approved policy. Explicitly call out that workspace MCP and
plan-mode subagents are still excluded.
### Tests
- Plan-mode visibility (approved vs non-approved external server).
- Plan-mode invocation of an approved external MCP tool.
- End-to-end plan-mode workflow that uses an approved MCP tool and then
reaches `propose_plan`.
- Regressions: workspace MCP still excluded in plan mode; plan-mode
subagents still on the restricted tool boundary; existing tool
allow/deny list filtering still applies.
## Policy precedence
`allow_in_plan_mode` is an **additional** requirement on top of existing
`enabled`, availability, chat-selected / forced server IDs, and tool
allow/deny lists. It approves **all tools on that server** for root plan
mode; a per-tool plan allowlist is deliberately deferred.
## Follow-ups (explicitly out of scope)
- Whether plan-mode subagents should inherit approved external MCP
tools.
- Workspace-local MCP safety model (agent-side `.mcp.json` schema vs. a
coderd-managed workspace MCP config).
## Validation
- `go vet ./coderd/x/chatd/...`
- `go test ./coderd/x/chatd -run 'TestPlan.*|TestMCP.*' -count=1`
- `go test ./coderd/x/chatd -count=1 -timeout 5m` (full chatd suite)
- `make fmt` (no diff)
> Mux opened this PR on Mike's behalf.
About
Coder is a self-hosted, open source, cloud development environment that works with any cloud, IDE, OS, Git provider, and IDP.
Screenshots of Coder workspaces and connections
Coder is built on common development interfaces and infrastructure tools to make the process of provisioning and accessing remote workspaces approachable for organizations of various sizes and stages of cloud-native maturity.
IDE support
You can use:
-
Any Web IDE, such as
- code-server
- JetBrains Projector
- Jupyter
- And others
-
Your existing remote development environment:
-
A file sync such as Mutagen
Why remote development
Remote development offers several benefits for users and administrators, including:
-
Increased speed
- Server-grade cloud hardware speeds up operations in software development, from loading the IDE to compiling and building code, and running large workloads such as those for monolith or microservice applications.
-
Easier environment management
- Built-in infrastructure tools such as Terraform, nix, Docker, Dev Containers, and others make it easier to onboard developers with consistent environments.
-
Increased security
- Centralize source code and other data onto private servers or cloud services instead of local developers' machines.
- Manage users and groups with SSO and Role-based access controlled (RBAC).
-
Improved compatibility
- Remote workspaces can share infrastructure configurations with other development, staging, and production environments, reducing configuration drift.
-
Improved accessibility
- Connect to remote workspaces via browser-based IDEs or remote IDE extensions to enable developers regardless of the device they use, whether it's their main device, a lightweight laptop, Chromebook, or iPad.
Read more about why organizations and engineers are moving to remote development on our blog, the Slack engineering blog, or from OpenFaaS's Alex Ellis.
Why Coder
The key difference between Coder and other remote IDE platforms is the added layer of infrastructure control. This additional layer allows admins to:
- Simultaneously support ARM, Windows, Linux, and macOS workspaces.
- Modify pod/container specs, such as adding disks, managing network policies, or setting/updating environment variables.
- Use VM or dedicated workspaces, developing with Kernel features (no container knowledge required).
- Enable persistent workspaces, which are like local machines, but faster and hosted by a cloud service.
How much does it cost?
Coder is free and open source under GNU Affero General Public License v3.0. All developer productivity features are included in the Open Source version of Coder. A Premium license is available for enhanced support options and custom deployments.
How does Coder work
Coder workspaces are represented with Terraform, but you don't need to know Terraform to get started. We have a database of production-ready templates for use with AWS EC2, Azure, Google Cloud, Kubernetes, and more.
Providers and compute environments
Coder workspaces can be used for more than just compute. You can use Terraform to add storage buckets, secrets, sidecars, and more.
Visit the templates documentation to learn more.
What Coder is not
-
Coder is not an infrastructure as code (IaC) platform.
- Terraform is the first IaC provisioner in Coder, allowing Coder admins to define Terraform resources as Coder workspaces.
-
Coder is not a DevOps/CI platform.
- Coder workspaces can be configured to follow best practices for cloud-service-based workloads, but Coder is not responsible for how you define or deploy the software you write.
-
Coder is not an online IDE.
- Coder supports common editors, such as VS Code, vim, and JetBrains, all over HTTPS or SSH.
-
Coder is not a collaboration platform.
- You can use Git with your favorite Git platform and dedicated IDE extensions for pull requests, code reviews, and pair programming.
-
Coder is not a SaaS/fully-managed offering.
- Coder is a self-hosted solution. You must host Coder in a private data center or on a cloud service, such as AWS, Azure, or GCP.
Using Coder v1?
If you're a Coder v1 customer, view the v1 documentation or the v2 migration guide and FAQ.
Up next
- Template
- Installing Coder
- Quickstart to try Coder out for yourself.