## Problem
When a template has `require_active_version` enabled and the chat agent
tries to start a workspace that is stopped on an older template version,
the agent gets stuck in an infinite loop: `start_workspace` fails with a
403 (the old version is not the active version and the user lacks
`ActionUpdate` on the template), then `create_workspace` sees the
existing stopped workspace and tells the agent to use `start_workspace`,
repeat forever.
The root cause is that `chatStartWorkspace()` passes the start build
request through without setting `TemplateVersionID`, so `wsbuilder`
defaults to the previous build's template version — which RBAC rejects
when `RequireActiveVersion` is true.
## Fix
In `chatStartWorkspace()` (`coderd/exp_chats.go`), when the template's
access control has `RequireActiveVersion` enabled, explicitly set
`req.TemplateVersionID` to `template.ActiveVersionID` before calling
`postWorkspaceBuildsInternal()`. This mirrors how the autobuild executor
handles the same scenario (`coderd/autobuild/lifecycle_executor.go`).
If the new active version introduces required parameters that cannot be
resolved automatically (no defaults, no previous values), the build
fails at parameter validation before a provisioner job is created. In
that case, a clear error message tells the user to update and start the
workspace from the UI instead of surfacing a raw internal error.
On successful auto-update, the tool response includes
`updated_to_active_version`, `update_reason`, and a human-readable
`message` so the model can explain to the user what happened.
<img width="782" height="122" alt="image"
src="https://github.com/user-attachments/assets/289430d6-066e-41cf-bc97-cd013dcf717d"
/>
### Changes
- **`coderd/exp_chats.go`**: `chatStartWorkspace()` loads the template,
checks `RequireActiveVersion` via `AccessControlStore`, and pins the
build to the active version when required. New
`isChatStartWorkspaceManualUpdateRequiredError()` classifies parameter
validation failures from both the dynamic parameters path
(`DiagnosticError`) and the classic path (`ErrParameterValidation`
sentinel).
- **`coderd/wsbuilder/wsbuilder.go`**: New `ErrParameterValidation`
sentinel error, wrapped into the classic parameter validation
`BuildError` so callers can use `errors.Is` instead of string matching.
- **`coderd/x/chatd/chattool/startworkspace.go`**:
`waitForAgentAndRespond` now returns `map[string]any` instead of
`fantasy.ToolResponse`, letting the caller annotate the result (e.g.
auto-update metadata) before converting. Error handling for `StartFn`
checks for `httperror.Responder` errors to surface clean messages for
the manual-update case.
- **`coderd/x/chatd/chattool/startworkspace_test.go`**: Two new tests —
`StoppedWorkspaceReportsAutoUpdate` (verifies auto-update fields in
response) and `ManualUpdateRequired` (verifies clean error message
without internal wrapping).
### Follow-up
The manual-update error message could include a direct link to the
workspace settings page, but the chattool layer does not currently have
access to the deployment's access URL. Plumbing it through is
straightforward but out of scope for this fix.
Closes CODAGT-192
Context files (AGENTS.md) and skills were only fetched from the
workspace on the first turn or when the agent changed. On subsequent
turns, stale content from persisted messages was used. This meant that
if AGENTS.md or skills were modified on the workspace between turns, the
agent wouldn't see the changes until the user created a new chat.
## Changes
- Extract `fetchWorkspaceContext` from `persistInstructionFiles` to
allow fetching workspace context without persisting
- On subsequent turns, re-fetch fresh context from the workspace instead
of reading stale persisted content; falls back to persisted messages if
the workspace dial fails
- Update `ReloadMessages` callback to re-derive instruction and skills
from reloaded database messages after compaction, instead of using
captured closure variables
- Add `formatSystemInstructionsFromParts` helper to build system
instructions directly from agent parts without requiring separate
OS/directory params
- Add tests for the new helper
<details><summary>Implementation Notes</summary>
### Root cause
In `runChat`, the `else if hasContextFiles` branch (subsequent turns)
called `instructionFromContextFiles(messages)` which read stale content
from persisted DB messages. The `ReloadMessages` callback
(post-compaction) also used captured `instruction`/`skills` closure
variables from the start of the turn, never re-deriving them.
### Approach
1. **Extract `fetchWorkspaceContext`** — Pure refactor of the fetch-only
part of `persistInstructionFiles` (agent connection, context config
retrieval, content sanitization, metadata stamping). Returns parts +
skills without persisting.
2. **Subsequent turns**: Instead of reading from persisted messages,
launch a `g2` goroutine that calls `fetchWorkspaceContext` to get fresh
context from the workspace. Falls back gracefully to persisted messages
if the workspace is unreachable.
3. **ReloadMessages**: Re-derive `instruction` from
`instructionFromContextFiles(reloadedMsgs)` and `skills` from
`skillsFromParts(reloadedMsgs)` using the freshly loaded messages, with
fallback to captured values if the reloaded messages don't contain
context (e.g. compacted away).
</details>
> 🤖 Generated by Coder Agents
Adds suffix-based agent selection for chatd. Template authors can direct
chat traffic to a specific root workspace agent by naming it with the
`-coderd-chat` suffix (for example, `coder_agent "dev-coderd-chat"`).
When no suffix match exists, chatd falls back to the first root agent by
`DisplayOrder`, then `Name`. Multiple suffix matches return an error.
The selection logic lives in `coderd/x/chatd/internal/agentselect` and
is shared by chatd core plus the workspace chat tools so all chat entry
points pick the same agent deterministically.
No database migrations, API contract changes, or provider changes. The
experimental sandbox template was split out to #23777.
- Moves `coderd/chatd/`, `coderd/gitsync/`, `enterprise/coderd/chatd/`
under `x/` parent directories to signal instability
- Adds `Experimental:` glue code comments in `coderd/coderd.go`
> 🤖 This PR was created with the help of Coder Agents, and was
reviewed by my human. 🧑💻
Ethan