- Use t.Errorf in chattest non-streaming helpers so encoding
failures fail the test
- Thread testing.TB into writeResponsesAPIStreaming and log
SSE write errors instead of silently dropping them
- Bump createworkspace DB error log from Warn to Error
- Use errors.Join for timeout + output error in execute.go
Implement the backend for the desktop feature for agents.
- Adds a new `/api/experimental/chats/$id/desktop` endpoint to coderd
which exposes a VNC stream from a
[portabledesktop](https://github.com/coder/portabledesktop) process
running inside the workspace
- Adds a new `spawn_computer_use_agent` tool to chatd, which spawns a
subagent that has access to the `computer` tool which lets it interact
with the `portabledesktop` process running inside the workspace
- Adds the plumbing to make the above possible
There's a follow up frontend PR here:
https://github.com/coder/coder/pull/23006
Handle previously ignored error return values in coderd:
- coderd/chats.go: check sendEvent errors, log on failure
- coderd/chatd/chattest: thread testing.TB through server structs,
replace log.Printf with t.Logf, check writeSSEEvent errors
- coderd/chatd/chattool/createworkspace.go: log UpdateChatWorkspace
failure instead of discarding both return values
- coderd/chatd/chattool/execute.go: surface ProcessOutput error in
the timeout message returned to the caller
- coderd/provisionerdserver: log stream.Send failure in the
DownloadFile error helper
## Problem
Both `start_workspace` and `create_workspace` chattool tools failed to
handle soft-deleted workspaces correctly.
Coder uses soft-delete for workspaces (`deleted = true` on the row).
Both tools called `GetWorkspaceByID`, which queries
`workspaces_expanded` with **no** `deleted = false` filter — so it
returns the workspace row even when soft-deleted. The only deletion
check was for `sql.ErrNoRows`, which never fires because the row still
exists.
### `start_workspace` behavior (before fix)
1. Loads the soft-deleted workspace successfully
2. Finds the latest build (a delete transition)
3. Falls through to attempt to **start** the deleted workspace
4. Produces a confusing downstream error
### `create_workspace` behavior (before fix)
1. `checkExistingWorkspace` loads the soft-deleted workspace
2. If a delete build is **in-progress**: waits for it, then falsely
reports `already_exists` — blocks new workspace creation
3. If the delete build **succeeded**: accidentally allows creation
(because no agents are found), but via fragile logic rather than an
explicit check
## Fix
Add `ws.Deleted` checks immediately after `GetWorkspaceByID` succeeds in
both tools:
- **`startworkspace.go`**: Returns `"workspace was deleted; use
create_workspace to make a new one"`
- **`createworkspace.go`** (`checkExistingWorkspace`): Returns `(nil,
false, nil)` to allow new workspace creation
## Tests
- `TestStartWorkspace/DeletedWorkspace` — verifies `start_workspace`
returns deleted error and never calls `StartFn`
- `TestCheckExistingWorkspace_DeletedWorkspace` — verifies
`checkExistingWorkspace` allows creation for soft-deleted workspaces
## Summary
When a chat's workspace is stopped, the LLM previously had no way to
start it — `create_workspace` would either create a duplicate workspace
or fail. This adds a dedicated `start_workspace` tool to the agent flow.
## Changes
### New: `start_workspace` tool
(`coderd/chatd/chattool/startworkspace.go`)
- Detects if the chat's workspace is stopped and starts it via a new
build with `transition=start`
- Reuses the existing `waitForBuild` and `waitForAgent` helpers (shared
logic)
- Shares the workspace mutex with `create_workspace` to prevent races
- Idempotent: returns immediately if the workspace is already running or
building
- Returns a `no_agent` / `not_ready` status if the agent isn't available
yet (non-fatal)
### Updated: `create_workspace` stopped-workspace hint
- `checkExistingWorkspace` now returns a `stopped` status with message
`"use start_workspace to start it"` when it detects the chat's workspace
is stopped, instead of falling through to create a new workspace
### Wiring
- `chatd.Config` / `chatd.Server`: new `StartWorkspace` /
`startWorkspaceFn` field
- `coderd/chats.go`: new `chatStartWorkspace` method that calls
`postWorkspaceBuildsInternal` with proper RBAC context
- `coderd/coderd.go`: passes `chatStartWorkspace` into chatd config
- Tool registered alongside `create_workspace` for root chats only (not
subagents)
### Tests (`startworkspace_test.go`)
- `NoWorkspace`: error when chat has no workspace
- `AlreadyRunning`: idempotent return for workspace with successful
start build
- `StoppedWorkspace`: verifies StartFn is called, build is waited on,
and success response returned
The `create_workspace` tool waited for the workspace build to succeed
and the agent to become connectable, but did not wait for the agent's
startup scripts (e.g. git clone) to finish. This caused agents to
attempt file operations on repositories that hadn't been cloned yet.
Add a waitForStartupScripts step that polls the agent's lifecycle_state
via GetWorkspaceAgentLifecycleStateByID until it transitions out of
created/starting into a terminal state (ready, start_error, or
start_timeout). The tool now only returns success once the workspace is
fully initialized.
If the scripts fail or time out, the tool still returns (non-fatal) with
an appropriate agent_status so the model knows something went wrong.
Created using thingies (Opus 4.6 Max)
## Problem
When the git askpass flow triggered diff status refreshes, it updated
**every chat** connected to the workspace. This was wasteful and could
cause confusing status updates on unrelated chats.
## Solution
Thread the chat ID through the entire git askpass flow so only the chat
that initiated the git operation gets updated:
1. **`coderd/chatd/chattool/execute.go`** — Sets `CODER_CHAT_ID` env var
on spawned processes (alongside the existing `CODER_CHAT_AGENT`)
2. **`cli/gitaskpass.go`** — Reads `CODER_CHAT_ID` from the environment
and sends it as a `chat_id` query parameter in the `ExternalAuthRequest`
3. **`codersdk/agentsdk/agentsdk.go`** — Adds `ChatID` field to
`ExternalAuthRequest` and encodes it as a query param
4. **`coderd/workspaceagents.go`** — Parses `chat_id` query param and
passes it through to `storeChatGitRef` and
`triggerWorkspaceChatDiffStatusRefresh`
5. **`coderd/chats.go`** — `storeChatGitRef` and
`refreshWorkspaceChatDiffStatuses` now scope updates to just the
initiating chat when a chat ID is provided, falling back to
all-workspace-chats behavior for backwards compatibility (non-chat git
operations)
## Summary
Remove the `workspace_agent_id` column from the `chats` table and
dynamically look up the first workspace agent instead.
## Problem
When a workspace is stopped and restarted, the workspace agent gets a
new ID. The `workspace_agent_id` stored on the chat at creation time
becomes stale, making the agent unreachable. This caused chats to break
after workspace restarts.
## Solution
Instead of persisting the agent ID, dynamically look up the first agent
from the workspace's latest build via
`GetWorkspaceAgentsInLatestBuildByWorkspaceID` whenever an agent
connection is needed. The `workspace_id` on the chat remains stable
across restarts.
This behavior may be refined later (e.g., agent selection heuristics),
but picking the first agent resolves the immediate breakage.
## Changes
- **Migration 000425**: Drop `workspace_agent_id` column from `chats`
- **SQL queries**: Remove `workspace_agent_id` from `InsertChat` and
`UpdateChatWorkspace`
- **chatd.go**: `getWorkspaceConn` and `resolveInstructions` now look up
agents dynamically from workspace ID
- **chatd.go**: Remove `refreshChatWorkspaceSnapshot` (no longer needed)
- **createworkspace.go**: Stop persisting agent ID when associating
workspace with chat
- **subagent.go**: Stop passing agent ID to child chats
- **SDK/frontend**: Remove `WorkspaceAgentID` / `workspace_agent_id`
from Chat type
---------
Co-authored-by: Kyle Carberry <kylecarbs@gmail.com>
## Summary
Adds a new agent-side process management HTTP API and rewrites the chat
execute tool to use it instead of SSH sessions.
## What changed
### New agent/agentproc/ package
- **headtail.go** — Thread-safe io.Writer with bounded memory (16KB head
+ 16KB tail ring buffer). Provides LLM-ready output with truncation
metadata and long-line truncation at 2048 bytes.
- **headtail_test.go** — 16 tests including race detector coverage for
concurrent writes.
- **process.go** — Manager + Process types for lifecycle management
using agentexec.Execer for proper OOM/nice scores.
- **api.go** — HTTP API following the agentfiles chi router pattern. 4
endpoints: start, list, output, signal.
### Agent wiring (agent/agent.go, agent/api.go)
Mounts the process API at /api/v0/processes, mirroring how agentfiles is
mounted.
### SDK (codersdk/workspacesdk/agentconn.go)
4 new AgentConn interface methods + 7 request/response types:
- StartProcess, ListProcesses, ProcessOutput, SignalProcess
### Execute tool rewrite (coderd/chatd/chattool/execute.go)
- SSH to Agent API: conn.StartProcess() + conn.ProcessOutput() polling
- New parameters: workdir, run_in_background
- Structured response: success, exit_code, wall_duration_ms, error,
truncated, note, background_process_id
- Non-interactive env vars: GIT_EDITOR=true, TERM=dumb, NO_COLOR=1,
PAGER=cat, etc.
- Output truncation: HeadTailBuffer caps at 32KB for LLM consumption
- File-dump detection with advisory notes suggesting read_file
- Default timeout: 60s to 10s
- Foreground polling: 200ms intervals until exit or timeout
## Architecture
State lives on the agent, surviving coderd failover and instance
changes. Any coderd replica can query any agent via HTTP over tailnet.
## 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 |
## Summary
The `chattool` `list_templates` tool previously returned all templates
in a single response with no popularity signal. On deployments with many
templates (e.g. 71 on dogfood), this wastes tokens and makes it hard for
the AI to pick the right template for broad user questions.
## Changes
Single file: `coderd/chatd/chattool/listtemplates.go`
- **`page` parameter** — optional, 1-indexed, 10 results per page
- **Popularity sort** — queries
`GetWorkspaceUniqueOwnerCountByTemplateIDs` to get active developer
counts, then sorts descending (most popular first). The DB query returns
templates alphabetically, so this explicit sort is needed.
- **`active_developers`** — included on each template item so the agent
can see the signal
- **Pagination metadata** — `page`, `total_pages`, `total_count` in the
response so the agent knows there are more results
- **Updated tool description** — tells the agent that results are
ordered by popularity and paginated
## Frontend
No frontend changes needed. The renderer already reads `rec.templates`
and `rec.count` from the response — the new fields (`page`,
`total_pages`, `total_count`) are additive and safely ignored.
Mathias Fredriksson