Michael Suchacz d5bb35a49a fix(coderd): deflake TestChatMessageWithFiles/FileCapExceeded (#28091)
Fixes the flake tracked in
[CODAGT-926](https://linear.app/codercom/issue/CODAGT-926/flake-testchatmessagewithfilesfilecapexceeded).

## Problem

`TestChatMessageWithFiles/FileCapExceeded` asserted the rollback of a
rejected over-cap send by comparing message counts taken before and
after the send. `CreateChat` starts assistant generation asynchronously,
so the assistant reply can be persisted between the two reads, making
the count check fail even though the rejected message was correctly
rolled back ("should have 1 item(s), but has 2").

## Fix

Replace the count comparison with a semantic assertion that the rejected
`one too many` message was not persisted, hardened through Codex review
rounds:

- Scan message history for the rejected marker instead of comparing
counts.
- Also scan `QueuedMessages`: a busy chat queues the send before
file-link validation, so a rollback regression could leave the rejected
message queued rather than in history.
- Close the queue-promotion race: `getChatMessages` reads history and
the queue in two separate database reads, so the assertion first waits
for the queue to observe empty; a promoted message must then appear in a
fresh history read.

## Verification

- Deterministic repro of the exact CI failure signature: waiting for the
async assistant reply before the old count assertion reproduced `should
have 1 item(s), but has 2` every run.
- The new assertion passes under that same forced condition.
- Assertion liveness (all temporary red checks reverted): persisting the
marker in history fails the history scan; queuing the marker fails the
queued scan; queuing the marker and letting it promote fails the
post-drain history scan 3/3.
- `go test ./coderd -run 'TestChatMessageWithFiles/FileCapExceeded'
-count=100` and the full `TestChatMessageWithFiles` parent both pass.

> Mux acted on Mike's behalf to create this PR.
2026-08-13 21:07:26 +02:00

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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
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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:

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