Michael Suchacz
b6d7653231
## Problem
Editing a user message in an Agent chat silently dropped the MCP server
selection. The composer renders the MCP picker in edit mode and toggles
update local client state, so the picker displayed the new selection,
but the edit request omitted `mcp_server_ids` at every layer (frontend
request builder, `codersdk.EditChatMessageRequest`, the `PATCH
/chats/{chat}/messages/{message}` handler, and `chatd.EditMessage`). The
chat's persisted selection never changed and the regenerated turn ran
without the newly enabled MCP tools. Two dogfood users hit this within
hours; there is no error anywhere and the UI shows the opposite of the
server state.
## Changes
- `codersdk`: add `MCPServerIDs *[]uuid.UUID` to
`EditChatMessageRequest`, mirroring `CreateChatMessageRequest` (nil
preserves the current selection).
- `chatd`: extract the send path's MCP update block into one shared
`applyRequestedMCPServerIDs` helper (explore-subagent snapshot
immutability guard plus Force On enforcement, Cure53 CDM-02-010) and
call it from both `SendMessage` and `EditMessage`, so enforcement cannot
drift between the two paths.
- `coderd`: extract the send handler's request validation (dedupe,
enabled-in-organization check, persisted-ID exemption) into
`normalizeRequestedChatMCPServerIDs` and wire it into the edit handler,
which now threads the selection into `EditMessageOptions`.
- Frontend: the edit request now includes `mcp_server_ids:
[...effectiveMCPServerIds]`, exactly like the send path, making the
picker's displayed state real.
- `make gen` artifacts (swagger, API docs, `typesGenerated.ts`).
## Tests
Each layer is covered and was proven with independent red toggles
(removing one layer's wiring fails only that layer's tests):
- chatd (`TestEditMessage_MCPServerIDs`): edit applies a provided
selection, nil preserves it, an emptied list cannot remove a `force_on`
server, and explore subagent chats keep the spawn-time snapshot.
- API (`TestPatchChatMessage/MCPServerIDsApplied`,
`MCPServerIDsInvalidRejected`): persistence via the endpoint, omission
preserves, unknown IDs get the same 400 as the send path.
- Storybook (`EditAppliesMCPServerSelection`): toggling a server on
during an edit puts it in the edit request payload.
Note: the `AgentChatPage.stories.tsx` story "Queued For Capacity After
Polling" fails locally on current main as well (verified against the
main baseline with this branch's changes reverted); it is unrelated to
this diff.
Remote dogfood UAT ran on the exact head and passed, including proof
that the regenerated turn actually gains the newly enabled MCP server's
tools.
> 🤖 Xum acted on Mike's (@ibetitsmike) behalf. • Model:
`anthropic:claude-fable-5`
<!-- xum-attribution: model=anthropic:claude-fable-5 -->
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About
Coder is a self-hosted platform for running AI coding agents and cloud development environments on infrastructure you control. It works with any cloud, IDE, OS, Git provider, and IDP.
Coder Workspaces
Coder Workspaces are cloud development environments defined with Terraform, connected through a secure Wireguard tunnel, and automatically shut down when not in use. Agents and developers share the same workspace infrastructure.
- Defined in Terraform: Templates describe the infrastructure for each workspace, from EC2 VMs and Kubernetes Pods to Docker containers.
- Any architecture and OS: Support ARM and x86-64 across Windows, Linux, and macOS from a single deployment.
- Managed by admins: Platform teams create and maintain templates that enforce approved images, resource limits, and security policies.
- Accessed from any IDE: Connect through VS Code, JetBrains, Cursor, a web terminal, remote desktop, or SSH.
- Automatic shutdown: Idle workspaces stop automatically to reduce cloud spend, and restart in seconds when needed.
Coder Agents
Coder Agents is a native AI coding agent built into Coder. The agent loop runs in the Coder control plane on your infrastructure, not in the workspace and not in a vendor's cloud. Developers interact with agents through the web UI or the REST API for programmatic and CI-driven workflows.
- Self-hosted agent loop: The control plane handles planning, model calls, and tool dispatch. Workspaces have zero AI awareness.
- No API keys in workspaces: LLM credentials stay in the control plane.
- Any model: Anthropic, OpenAI, Google, Bedrock, or self-hosted endpoints. Switching is a configuration change.
- Governance and cost controls: Centralized model approval, per-user spend limits, and audit logging.
- Open source and inspectable: The full platform is available to audit and extend.
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
Provisioning consistent development environments for a large engineering team is difficult. Each developer has preferences for operating systems, editors, and toolchains, and ensuring a reliable build environment across all of them is a maintenance burden. A missed step during onboarding or an unsupported local configuration can cost hours of debugging.
Remote development solves this by moving the environment off the developer's machine and into managed infrastructure. The developer's laptop becomes a portal into the actual compute where work happens. If a device is lost or replaced, access is simply revoked; no source code or credentials are stored locally.
This approach provides:
- Speed: Server-grade hardware accelerates builds, tests, and large workloads without requiring expensive local machines.
- Consistency: Infrastructure tools such as Terraform, nix, Docker, and Dev Containers produce identical environments for every developer.
- Security: Source code stays on private servers. Users and groups are managed through SSO and RBAC.
- Compatibility: Workspaces share infrastructure configurations with staging and production, reducing configuration drift.
- Accessibility: Browser-based IDEs and remote IDE extensions let developers work from any device, including lightweight laptops, Chromebooks, and tablets.
Read more on the Coder blog, the Slack engineering blog, or from Alex Ellis at OpenFaaS.
Why Coder
The key difference between Coder and other platforms is that the entire system, agent loop, control plane, model routing, and workspace provisioning, runs on infrastructure you control.
For agents, this means platform teams can:
- Run the entire agent loop on their infrastructure, with no SaaS dependency for orchestration.
- Define MCP servers, skills, and system prompts centrally so every agent session starts with the same tools, policies, and context.
- Keep LLM credentials out of workspaces entirely.
- Tie every agent action to an authenticated user identity.
- Support air-gapped and restricted-network deployments with self-hosted models.
For workspaces, this means admins can:
- Support any architecture (ARM, x86-64) and operating system (Windows, Linux, macOS).
- 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.
Pricing
Coder is free and open source under the GNU Affero General Public License v3.0. All developer productivity features are included in the open source version. A Premium license is available for enhanced support and custom deployments.
How Coder works
Coder workspaces are represented with Terraform, but you do not need to know Terraform to get started. The Coder Registry provides production-ready templates for AWS EC2, Azure, Google Cloud, Kubernetes, and other providers.
Providers and compute environments
Workspaces can include more than just compute. Terraform can add storage buckets, secrets, sidecars, and other resources.
See the templates documentation for details.
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.