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Kyle Carberry
32217259b7
## Problem
Local tool results were persisted and replayed to the model verbatim,
with no size cap. A single oversized result, most often a multi-megabyte
response from an MCP tool, overflows the prompt on the next request.
Every retry rebuilds the same history and fails the same way, leaving
the chat wedged in `error`. Auto-compaction is reactive (token usage is
only known after a response), so it can't catch a single result that
blows the very next request.
## Fix
Cap every locally-executed tool result at its single choke point,
`executeSingleTool` in `chatloop`, so the cap covers built-in tools,
**global (deployment-pinned) MCP**, **workspace MCP**, and provider
runners uniformly. Because this runs before the result is published to
the live stream and before it is committed, the SSE preview, the
persisted message, and the model replay all see the same bounded output.
The budget is token-aware: a single tool result may use at most half the
model's context window (`~4 bytes/token`), with a `16KB` floor and a
`64KB` default when the window is unknown. Truncation keeps the head and
tail of the output and replaces the middle with a marker telling the
model how much was removed and to narrow its query; it is UTF-8 safe and
never exceeds the budget. Binary media `Data` is passed through
untouched (only the text payload is bounded).
A `coderd_chatd_tool_result_truncated_total{provider,model,tool_name}`
counter and a warning log record each truncation.
## Out of scope
- Provider-executed results (e.g. web search) arrive via the stream, not
`executeSingleTool`.
- Dynamic/external tool results submitted through the `/tool-results`
API are validated as JSON elsewhere.
- Cumulative growth across many results is still handled by context
compaction; this change only bounds any single result.
<details>
<summary>Implementation notes</summary>
- New `coderd/x/chatd/chatloop/tooltruncate.go`:
`toolResultByteBudget(contextLimitTokens)` and
`truncateToolResultText(text, maxBytes)` (pure, unit-tested).
- `chatloop.go`: added `ContextLimit` to `ExecuteLocalToolsOptions`;
threaded a computed byte budget through `executeTools` into
`executeSingleTool`, where `resp.Content` is capped for the text,
media-text, and error branches.
- `generation.go`: passes `ContextLimit: prepared.ContextLimitFallback`
(the model's configured context limit).
- `metrics.go`: new `ToolResultTruncatedTotal` counter +
`RecordToolResultTruncated`.
- Tunable knobs live as constants in `tooltruncate.go`
(`toolResultContextDivisor = 2`, `bytesPerTokenEstimate`,
`minToolResultBytes`, `defaultToolResultBytes`).
Verified: `go build ./coderd/x/chatd/...`, `go test
./coderd/x/chatd/chatloop/...`, and the `chatd` test binary compiles.
</details>
---
Resolves CODAGT-678
Generated by Coder Agents on behalf of @kylecarbs.
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.