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Michael Suchacz
e96d8646e2
Chat message ordering was derived from `created_at`, which is `now()` and therefore the transaction start time. That makes it unusable as an append-order column for two independent reasons: every row in one `InsertChatMessages` batch shares a single timestamp, and two concurrent transactions can commit in the opposite order to the one they started in. This PR gives `chat_messages.id` a real append-order guarantee and moves the history reads onto it. ## Changes **`InsertChatMessages` had no input-order guarantee.** Callers index the returned slice by input position. That only worked because PostgreSQL happens to evaluate the `BIGSERIAL` default in row order. Ids are now allocated up front and the k-th smallest is assigned to input index k, so the pairing does not depend on where the column default is evaluated. Returned rows are explicitly `ORDER BY id`. **Three history reads now order by `id`.** | Query | Was | Now | |---|---|---| | `GetChatMessagesByChatID` | `created_at ASC` | `id ASC` | | `GetChatMessagesByRevisionForStream` | `created_at ASC, id ASC` | `id ASC` | | `GetLastChatMessageByRole` | `created_at DESC, id DESC` | `id DESC` | `GetChatMessagesByChatID` paginated by `id` while ordering by `created_at`, which is incoherent on its own terms. The other two matter because of who consumes them. The stream query supplies incremental updates on the same socket that emits a full `GetChatMessagesByChatID` snapshot on history reset, so once that snapshot moved to `id` the two disagreed under timestamp skew. `GetLastChatMessageByRole` returns an id that is then used as an id cursor, both as `AfterID` when synthesizing tool cancellations and as `chats.last_read_message_id`, where a stale anchor leaves later assistant messages permanently unread. A tie-breaker would not have fixed either one. It only resolves equal timestamps; leading with `created_at` is the actual defect. **`GetLastChatMessageByRole` loses its index, so this adds one.** `ORDER BY created_at DESC, id DESC` could take an ordered scan of `idx_chat_messages_chat_created`. Nothing in the schema can supply `ORDER BY id DESC LIMIT 1` for a given `chat_id` and `role`, so the planner switches to a backward scan of the primary key and filters every newer row in the table, scanning all of it when the chat has no message in that role, which is the routine case for a fresh chat. Migration `000559` adds `(chat_id, role, id DESC) WHERE deleted = false`, the same shape as the existing `idx_chat_messages_user_prompts`. This matters because the query is hot: it runs on every stream connect and disconnect, and once per turn when synthesizing tool cancellations. `GetChatMessagesForPromptByChatID` has the same defect and is fixed in the stacked PR, because its compaction boundary change is semantic and deserves a separate review. Auto-archive stays timestamp-based deliberately: it measures activity, not order. Wrapping the insert in a CTE (needed because `INSERT` cannot take `ORDER BY`) makes sqlc synthesize `InsertChatMessagesRow`. It is structurally identical to `ChatMessage`, so the call sites use a direct struct conversion that stops compiling if the two ever diverge. ## Testing Behavior tests write `created_at` values inverted against id order, so a reader that leads with `created_at` returns the batch backwards. All three queries were verified red by reverting the `ORDER BY` and regenerating: the stream query returned `[3,2,1]` for `[1,2,3]`, and `GetLastChatMessageByRole` picked id 1 instead of id 3. `TestInsertChatMessagesOrderContract` asserts against the generated SQL, covering what a behavior test cannot: PostgreSQL evaluates the id default in row order anyway, so a batch still looks ordered once the guarantee is removed. `TestChatMessagesSequenceCacheIsOne` guards the cross-batch half of the invariant. Ids follow chat row lock order only while the sequence hands out one value at a time; sequence cache blocks are per session, so with a cache above one a backend holding stale cached values can lock second and still commit lower ids. Bumping a sequence cache is an ordinary throughput tweak, and it would silently corrupt history order. The index was checked on a 200k row fixture. Without it, the zero-match lookup filters all 200,000 rows over 2763 buffers; with it, the plan is an index scan with both `chat_id` and `role` in the index condition, no sort node, and 3 buffers. Note that the within-batch mapping does not depend on the cache size. It is established by `ROW_NUMBER() OVER (ORDER BY id)` over the allocated ids, so it holds regardless of `nextval` evaluation order. ## Note on the deleted subagent hand-sort The subagent history reader's hand-sort stays deleted, but calling it redundant was imprecise. It sorted by `created_at` then `id`, so it is only equivalent to `id` ordering when the two agree. When they disagree the old code selected a different "latest assistant". This is a deliberate behavior change to match the new invariant, not dead-code removal. > Opened by Mux on behalf of Mike.
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.