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Kyle Carberry
b65c0766d2
## Summary Adds a new line-based file reading endpoint to the workspace agent, replacing the unbounded byte-based approach for the `read_file` chat tool and `coder_workspace_read_file` MCP tool. **Problem**: The current `read_file` tool returns the entire file contents with no limits, which can blow up LLM context windows and cause OOM issues with large files. **Solution**: Inspired by [`coder/mux`](https://github.com/coder/mux) and [`openai/codex`](https://github.com/openai/codex), implement a line-based reader with safety limits. ## Changes ### Agent (`agent/agentfiles/`) - New `/read-file-lines` endpoint with `HandleReadFileLines` handler - Line-based `offset` (1-based line number, default: 1) and `limit` (line count, default: 2000) - Safety constants: | Constant | Value | Purpose | |---|---|---| | `MaxFileSize` | 1 MB | Reject files larger than this at stat | | `MaxLineBytes` | 1,024 | Per-line truncation with `... [truncated]` marker | | `MaxResponseLines` | 2,000 | Max lines per response | | `MaxResponseBytes` | 32 KB | Max total response size | | `DefaultLineLimit` | 2,000 | Default when no limit specified | - Line numbering format: `1\tcontent` (tab-separated) - Structured JSON response: `{ success, file_size, total_lines, lines_read, content, error }` - Hard errors when limits exceeded — tells the LLM to use `offset`/`limit` - Existing byte-based `/read-file` endpoint preserved (used by `instruction.go`) ### SDK (`codersdk/workspacesdk/`) - `ReadFileLinesResponse` type added - `ReadFileLines` method added to `AgentConn` interface - Mock regenerated ### Chat tool (`coderd/chatd/chattool/`) - `read_file` tool now uses `conn.ReadFileLines()` instead of `conn.ReadFile()` - Updated tool description to document line-based parameters - Response includes `file_size`, `total_lines`, `lines_read` metadata ### MCP tool (`codersdk/toolsdk/`) - `coder_workspace_read_file` updated to use line-based reading - Schema descriptions updated for line-based offset/limit - Removed `maxFileLimit` constant (agent handles limits now) ### Tests - 13 new test cases for `TestReadFileLines`: - Path validation (empty, relative, non-existent, directory, no permissions) - Empty file handling - Basic read, offset, limit, offset+limit combinations - Offset beyond file length - Long line truncation (>1024 bytes) - Large file rejection (>1MB) - All existing tests pass unchanged ## Design decisions | Decision | Rationale | |---|---| | Line-based, not byte-based | Both coder/mux and openai/codex use line-based — matches how LLMs reason about code | | Default limit of 2000 | Matches codex; prevents accidental full-file dumps while being generous | | 32 KB response cap | Compromise between mux (16 KB) and codex (no cap) | | 1024 byte/line truncation with marker | More generous than codex (500), marker helps LLM know data is missing | | Hard errors on overflow | Matches mux; forces LLM to paginate rather than getting partial data | | Preserve byte-based endpoint | `instruction.go` needs raw byte access for AGENTS.md |
Coder enables organizations to set up development environments in their public or private cloud infrastructure. Cloud development environments are defined with Terraform, connected through a secure high-speed Wireguard® tunnel, and automatically shut down when not used to save on costs. Coder gives engineering teams the flexibility to use the cloud for workloads most beneficial to them.
- 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
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 our
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. Use our install guides for a complete walkthrough.
Documentation
Browse our docs here or visit a specific section below:
- Templates: Templates are written in Terraform and describe the infrastructure for workspaces
- Workspaces: Workspaces contain the IDEs, dependencies, and configuration information needed for software development
- IDEs: Connect your existing editor to a workspace
- Administration: Learn how to operate Coder
- Premium: Learn about our paid features built for large teams
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
We are always working on new integrations. Please feel free to open an issue and ask for an integration. Contributions are welcome in any official or community repositories.
Official
- 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 Container Builder: Build development environments using
devcontainer.jsonon Docker, Kubernetes, and OpenShift - Coder Registry: Build and extend development environments with common use-cases
- 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.
- Setup Coder: An action to setup coder CLI in GitHub workflows.
Community
- 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
Contributing
We are always happy to see new contributors to Coder. If you are new to the Coder codebase, we have a guide on how to get started. We'd love to see your contributions!
Hiring
Apply here if you're interested in joining our team.