## Context Follow-up fix from live UAT of the merged chat lifecycle hooks stack (#27430). Its companion UAT fix (#27655) has merged, so this targets `main` directly. ## Why? UAT measured a burst of 1,500 concurrent chat creations against a consumer with 1.2s latency. 255 were admitted and 1,245 got `502 hook_dispatch_failed (over_capacity)`, which is correct fail-closed behavior. The collateral wasn't: the same burst failed 24 `stop` dispatches, parking chats that had already been admitted and had already executed tools. One 256-slot semaphore served every event, so new-work admission could take every slot and kill turns in flight. Callers now classify each dispatch as admission or generation, and admission draws from a 192-slot gate held *before* the shared pool. At least 64 shared slots stay reachable only by dispatches for work a chat already admitted. The dispatcher is per `coderd` replica, so these limits are per replica, not deployment-wide, and the docs say so. **The caller classifies, not the event type.** Event type isn't a reliable proxy in either direction: a subagent spawn dispatches `user_prompt_submit` from inside a running turn, and the edit path dispatches `session_start` at admission time. `CapacityClassUnset` is rejected in `Dispatch`, so a new call site fails closed rather than silently inheriting a share. **Acquisition order is load-bearing.** Admission takes its own gate first. Taking a shared slot first would let admissions queued on the gate occupy the very capacity the reserve protects. `acquireCapacity` is the only path that takes either pool, so the order can't be bypassed. ## What this does not guarantee Nothing bounds how many turns generate concurrently, so the 192/64 split is a judgement call, not a derived ceiling. This stops an *admission* burst from consuming every slot; it does not make the remainder sufficient. A large enough generation load can still exhaust the reserve and error a running chat. The docs say so explicitly rather than promising a guarantee the code doesn't deliver. Generation can now take all 256 slots, so generation traffic starves admission harder than before. That's the intended priority: rejecting a new prompt is recoverable, ending a turn that already ran tools is not. ## Testing Red-green proved both new tests. Removing the release-on-failure path fails `RefusedSharedAcquireReleasesAdmission` deterministically; removing the expired-deadline check fails `ExpiredDeadlineRefusesFreeSlot` in 18/30 runs. That deadline check fixes a real race found in review. `acquire` previously shared one `time.Timer` across both acquires. Because `select` picks a ready case at random, an admission dispatch could take a slot after its capacity deadline had passed. Measured over 300 trials: 135 late acquisitions, worst overshoot 2.1ms. `acquire` now takes an absolute deadline and refuses an expired one before selecting, which measures 0/300. Go: `coderd/x/agenthooks/...` and `coderd/x/chatd/...`, plus `-race -count=3` on the dispatcher. > Mux opened this PR on Mike's behalf.
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
The most convenient way to try Coder is to install it on your local machine and experiment with provisioning cloud development environments using Docker (works on Linux, macOS, and Windows).
# First, install Coder
curl -L https://coder.com/install.sh | sh
# Start the Coder server (caches data in ~/.cache/coder)
coder server
# Navigate to http://localhost:3000 to create your initial user,
# create a Docker template and provision a workspace
Install
The easiest way to install Coder is to use the
install script for Linux
and macOS. For Windows, use the latest ..._installer.exe file from GitHub
Releases.
curl -L https://coder.com/install.sh | sh
You can run the install script with --dry-run to see the commands that will be used to install without executing them. Run the install script with --help for additional flags.
See install for additional methods.
Once installed, you can start a production deployment with a single command:
# Automatically sets up an external access URL on *.try.coder.app
coder server
# Requires a PostgreSQL instance (version 13 or higher) and external access URL
coder server --postgres-url <url> --access-url <url>
Use coder --help to get a list of flags and environment variables. See the install guides for a complete tutorial.
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
- Administration: Learn how to operate Coder
- Premium: Learn about paid features built for large teams
- IDEs: Connect your existing editor to a workspace
Support
Feel free to open an issue if you have questions, run into bugs, or have a feature request.
Join our Discord to provide feedback on in-progress features and chat with the community using Coder!
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
- 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
- JetBrains Gateway Plugin: Open any Coder workspace in JetBrains Gateway 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
- Community Templates: Community-contributed workspace templates in the Coder Registry
- Community Modules: Community-contributed modules to extend Coder templates
- Provision Coder with Terraform: Provision Coder on Google GKE, Azure AKS, AWS EKS, DigitalOcean DOKS, IBMCloud K8s, OVHCloud K8s, and Scaleway K8s Kapsule with Terraform
- Coder Template GitHub Action: A GitHub Action that updates Coder templates
- Discord: Chat with the community and provide feedback on in-progress features
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.
