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Michael Suchacz
cc958b73be
## Problem
During the Aug 19 dev.coder.com incident, chats stalled for up to ~15
minutes per turn. chatd reconnects to every configured MCP server on
every generation step, and one configured server
(`registry.coder.com/mcp`) was black-holing requests from the
deployment's egress IPs: TCP/requests were silently dropped, and each
connect attempt hung until the kernel gave up (~125s), far past the
nominal 10s connect budget.
The budget does not hold because go-sdk v1.7.0 detaches the context
inside `StreamableClientTransport.Connect`, and its error paths block on
HTTP work bound to that detached context. Reproduced in a test: a bare
`Connect` with a 2s deadline against a black-holed server returns after
**12s**. Step-end session cleanup (`session.Close()`) runs synchronously
in the generation loop and blocks on the same detached requests, so a
server that wedges mid-turn stalls every step boundary too.
## Changes
- **Enforce the connect budget externally** (`connectOne`): run
`Connect` + `ListTools` in a goroutine and select on the budget context.
On timeout, abandon the goroutine and leave a reaper that drains its
late result and closes any session that still materialized, so nothing
leaks and the caller returns within the budget.
- **Stop using bare `http.DefaultTransport`**: MCP traffic now rides a
cloned transport with a 5s dial timeout (converts SYN black-holes into
fast errors) and a 60s `ResponseHeaderTimeout`. `http.Client.Timeout`
stays unset so long-lived SSE streams are unaffected.
- **Close sessions in detached goroutines during cleanup**
(`ConnectAll`'s cleanup func): the sessions are discarded regardless,
and a wedged `Close` (DELETE bound to the SDK's detached context) must
not stall the generation loop at step boundaries.
One deliberate deviation from the incident plan: `ResponseHeaderTimeout`
is 60s (matching `toolCallTimeout`) instead of ~10s. The same HTTP
client serves tool-call POSTs, and a JSON-response MCP server sends no
headers until the tool finishes, so a 10s bound would falsely kill
legitimate 10-60s tools that fit today's tool-call budget. The real 10s
connect budget is enforced by the external select, not the transport.
## Tests
- Acceptance: with a black-holed server plus a healthy one configured,
`ConnectAll` returns within the budget and the healthy server's tools
are present; closing the black-holed connections makes the reaper exit
(red without the fix: 1s budget took 11s).
- A slow-but-alive server (300ms/request) still connects.
- A server that only responds after the budget: `ConnectAll` returns
promptly, the late result is reaped.
- Cleanup returns promptly while the session-teardown DELETE is wedged
server-side, and the teardown still happens in the background (red
without the fix: cleanup blocked 60s).
- Transport guard test pinning the dial/response-header bounds.
`go test ./coderd/x/chatd/...` passes (including goleak in `chatd`).
Part of the MCP connect-stall incident follow-up; observability (connect
durations in logs/debug runs) comes in a stacked follow-up PR.
> 🤖 Mux authored this PR on Mike's behalf.
<!-- mux-attribution: model=anthropic:claude-opus-4-6 thinking=high -->
Coder is a self-hosted platform for cloud development environments and AI coding agents. Workspaces are defined with Terraform, connected through a secure Wireguard® tunnel, and automatically shut down when not used. Coder Agents runs a native AI coding agent whose loop executes in the control plane on your infrastructure, with no API keys in workspaces.
- Define cloud development environments in Terraform
- EC2 VMs, Kubernetes Pods, Docker Containers, etc.
- Automatically shutdown idle resources to save on costs
- Onboard developers in seconds instead of days
- Delegate coding work to AI agents on your infrastructure
- Bring any model (Anthropic, OpenAI, Google, Bedrock, self-hosted)
- No LLM credentials in workspaces, user identity on every action
- Centralized model governance, cost tracking, and audit logging
Quickstart
Check out our install guides for other methods and a complete tutorial.
Try Coder with the install script on Linux and macOS, or grab the latest binary or installer from GitHub Releases on Windows:
curl -L https://coder.com/install.sh | sh
Start the server and open http://localhost:3000 to create your initial user, create a Docker template, and provision your first workspace:
coder server
For a production deployment, add a PostgreSQL database (version 13 or later) and an external access URL, and see our validated architectures for sizing and infrastructure guidance:
coder server --postgres-url <url> --access-url <url>
Without these flags, Coder uses a built-in database and sets up a *.try.coder.app access URL for evaluation. Use coder --help for the full list of flags and environment variables.
Documentation
Browse the documentation or visit a specific section below:
- Workspaces: Workspaces contain the IDEs, dependencies, and configuration information needed for software development
- Templates: Templates are written in Terraform and describe the infrastructure for workspaces
- Coder Agents: Delegate coding work to AI agents running on your self-hosted infrastructure
- AI Gateway: Centralize authentication, auditing, and cost controls for AI tooling
- Administration: Learn how to operate Coder
- Premium: Learn about paid features built for large teams
- IDEs: Connect your existing editor to a workspace
Support
Open an issue for bugs and feature requests.
For community support, showcasing what you built, and feedback on in-progress features, join our Discord or GitHub Discussions.
Dedicated support is included in Coder Premium. For more information, visit coder.com/pricing.
Integrations
New integrations are always in progress. Open an issue to request one. Contributions are welcome in any official or community repository.
Official
- Coder Registry: Templates, modules, and integrations for common development environments
- Coding Agents: Run agents like Claude Code, Codex, and OpenCode isolated in Coder workspaces
- coderd Terraform Provider: Declaratively manage your Coder deployment configuration as code
- VS Code Extension: Open any Coder workspace in VS Code with a single click
- JetBrains Toolbox Plugin: Open any Coder workspace from JetBrains Toolbox with a single click
- Dev Containers: Build development environments using
devcontainer.jsonon Docker, Kubernetes, and OpenShift - Kubernetes Log Stream: Stream Kubernetes Pod events to the Coder startup logs
- Self-Hosted VS Code Extension Marketplace: A private extension marketplace that works in restricted or airgapped networks integrating with code-server.
- GitHub Actions: An action to set up the Coder CLI in GitHub workflows
Community
- Coder Discord: Chat with the community, get support, and hear about new product updates first
- Community Templates: Community-contributed workspace templates in the Coder Registry
- Community Modules: Community-contributed modules to extend Coder templates
- Coder Template GitHub Action: A GitHub Action that updates Coder templates
- Coder Agents Chat Action: A GitHub Action that starts a Coder Agents chat against a GitHub issue or pull request
Contributing
New contributors are always welcome. If you are new to the Coder codebase, see the contribution guide to get started.
Hiring
Apply on the careers page if you are interested in joining the team.