Bobby Ho
209d1ca498
The token endpoint accepted any non-empty `code_verifier`, so a one-character verifier was enough to authenticate. RFC 7636 §4.1 requires 43 to 128 characters from the unreserved set. That fix plus the related gaps review surfaced in the same path: - Enforce the length and charset floor on the verifier before the S256 comparison runs. - Validate the challenge at the authorize endpoint too. It was only checked for non-emptiness, so a malformed challenge was stored and then failed late at token exchange, blaming the wrong parameter. - A malformed verifier now returns `invalid_request` (RFC 6749 §5.2); a well-formed but wrong one still returns `invalid_grant` (RFC 7636 §4.6). Both looked identical before, so a client had no way to tell a syntax error from a hash mismatch and would retry the same bad verifier forever. - Revoke the authorization code when a PKCE check fails. Without that, a leaked code could be replayed with unlimited verifier guesses for its remaining lifetime, and RFC 6749 §10.5 requires codes to be single use. - Fix verifier generation in `scripts/oauth2/*.sh` and the docs example. They deleted reserved base64 characters instead of translating them to the URL-safe alphabet, so most runs produced verifiers under the new floor. Also carries #28041, which merged into this branch: public clients may register bare custom schemes such as `vscode://` again, with `mailto`, `tel`, and `sms` rejected. Split out of #27873 (public OAuth2 client support). PKCE is already mandatory for every client, so this stands on its own. <details> <summary>Manual verification</summary> Ran against a local dev server on this branch, using a session token and a throwaway app from `scripts/oauth2/setup-test-app.sh`. 1. Happy path unchanged: HTTP 200, verifier length 43. 2. `code_verifier=short`, and a 43-character verifier ending in `!`: both HTTP 400 `invalid_request`, so charset is enforced and not just length. 3. `code_challenge=tooshort` at authorize: HTTP 400 `invalid_request`, no code issued. An empty challenge still hits the older "required and cannot be empty" message. 4. Well-formed but wrong verifier: HTTP 400 `invalid_grant`, distinct from the cases above. 5. Retrying that same code with the correct verifier: HTTP 400, code already revoked by the failed check. 6. `generate-pkce.sh` produces a 43-character verifier (20 out of 20 runs); the docs example produces 128. 7. `scripts/oauth2/test-mcp-oauth2.sh` passes end to end. The two bearer-token failures in its output are a pre-existing script bug (`09c50559f3`, July 2025) that reuses a resource-scoped token against the real API, not a regression here. </details>
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:
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Any Web IDE, such as
- code-server
- JetBrains Projector
- Jupyter
- And others
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Your existing remote development environment:
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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
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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.
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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.
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Coder is not an online IDE.
- Coder supports common editors, such as VS Code, vim, and JetBrains, all over HTTPS or SSH.
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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.
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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.