## Problem
When archiving an agent with subagents, the children briefly flash in
the sidebar as root-level items before disappearing. Two issues:
1. **Backend:** Archive used N+1 queries — a recursive DFS
(`archiveChatTree`, no transaction) or BFS loop (`chatd.ArchiveChat`,
N+1 queries in a tx) to walk the tree and archive each chat
individually.
2. **Frontend:** The SSE `deleted` event handler only filtered out the
parent chat from the cache. Children remained briefly, got promoted to
root-level by `buildChatTree`, then disappeared on the next re-fetch.
## Fix
**Backend:** Replace both tree-walk implementations with a single SQL
query:
```sql
UPDATE chats SET archived = true, updated_at = NOW()
WHERE id = @id OR root_chat_id = @id;
```
This leverages the existing `root_chat_id` column (already indexed) to
archive the entire tree atomically.
**Frontend:** When a `deleted` event arrives, also filter out any chats
whose `root_chat_id` matches the deleted chat, so children vanish from
the sidebar immediately with the parent.
## Changes
- `coderd/database/queries/chats.sql` — Added `ArchiveChatTreeByID`
query
- `coderd/chats.go` — Use single query, delete `archiveChatTree`
function
- `coderd/chatd/chatd.go` — Simplify `ArchiveChat` to use single query
- `coderd/database/dbauthz/dbauthz.go` — Auth wrapper for new query
- `coderd/chats_test.go` — Added `TestArchiveChat/ArchivesChildren`
subtest
- `site/src/pages/AgentsPage/AgentsPage.tsx` — Filter children in SSE
handler
- Generated files updated via `make gen`
## 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>
Adds a nullable `last_error` column to the `chats` table so error
reasons survive page reloads.
**Backend:**
- Migration adds `last_error TEXT` (nullable) to chats
- `UpdateChatStatus` writes the error reason when status transitions to
`error`, clears it (NULL) on recovery
- `convertChat` maps `sql.NullString` to `*string` in the SDK
**Frontend:**
- Sidebar falls back to `chat.last_error` when no stream error reason is
cached
- Chat detail page does the same for `persistedErrorReason`
- Fixtures updated for new required field
## Summary
The UI has always labeled the action as "Archive agent" but the backend
was performing a hard `DELETE`, permanently destroying chats and all
their messages.
This change replaces the hard delete with a soft archive, consistent
with the pattern used by template versions.
## Changes
### Database
- **Migration 000423**: Add `archived boolean DEFAULT false NOT NULL`
column to `chats` table
- Replace `DeleteChatByID` query with `ArchiveChatByID` (`UPDATE SET
archived = true`)
- Add `UnarchiveChatByID` query (`UPDATE SET archived = false`)
- Filter archived chats from `GetChatsByOwnerID` (`WHERE archived =
false`)
### API
- Remove `DELETE /api/experimental/chats/{chat}`
- Add `POST /api/experimental/chats/{chat}/archive` — archives a chat
and all its descendants
- Add `POST /api/experimental/chats/{chat}/unarchive` — unarchives a
single chat (API only, no UI yet)
### Backend
- `archiveChatTree()` recursively archives child chats (replaces
`deleteChatTree()` which hard-deleted)
- Chat daemon's `ArchiveChat()` archives the full chat tree in a
transaction
- Authorization uses `ActionUpdate` instead of `ActionDelete`
### SDK
- Replace `DeleteChat()` with `ArchiveChat()` and `UnarchiveChat()`
- Add `Archived` field to `Chat` struct
### Frontend
- `archiveChat` API call uses `POST .../archive` instead of `DELETE`
- No UI changes — the "Archive agent" button now actually archives
instead of deleting
## Design Decision
This follows the **template version archive pattern** (Pattern B in the
codebase):
- `archived boolean` column (not `deleted boolean`)
- Dedicated `POST .../archive` and `POST .../unarchive` routes (not
repurposing `DELETE`)
- Reversible — users can unarchive via the API (UI for this will come
later)
Kyle Carberry