Adds skill discovery and tools to chatd so the agent can discover and
load `.agents/skills/` from workspaces, following the same pattern as
AGENTS.md instruction loading and MCP tool discovery.
## What changed
### `chattool/skill.go` — discovery, loading, and tools
- **DiscoverSkills** — walks `.agents/skills/` via `conn.LS()` +
`conn.ReadFile()`, parses SKILL.md frontmatter (name + description),
validates kebab-case names match directory names, silently skips
broken/missing entries.
- **FormatSkillIndex** — renders a compact `<available-skills>` XML
block for system prompt injection (~60 tokens for 3 skills). Progressive
disclosure: only names + descriptions in context, full body loaded on
demand.
- **LoadSkillBody** / **LoadSkillFile** — on-demand loading with path
traversal protection and size caps (64KB for SKILL.md, 512KB for
supporting files).
- **read_skill** / **read_skill_file** tools — `fantasy.AgentTool`
implementations following the same pattern as ReadFile and
WorkspaceMCPTool. Receive pre-discovered `[]SkillMeta` via closure to
avoid re-scanning on every call.
### `chatd.go` — integration into runChat
- Skills discovered in the `g2` errgroup parallel with instructions and
MCP tools.
- `skillsCache` (sync.Map) per chat+agent, same invalidation pattern as
MCP tools cache.
- Skill index injected via `InsertSystem` after workspace instructions.
- Re-injected in `ReloadMessages` callback so it survives compaction.
- `read_skill` + `read_skill_file` tools registered when skills are
present (for both root and subagent chats).
- Cache cleaned up in `cleanupStreamIfIdle` alongside MCP tools cache.
## Format compatibility
Uses the same `.agents/skills/<name>/SKILL.md` format as
[coder/mux](https://github.com/coder/mux) and
[openai/codex](https://github.com/openai/codex).
Coder's chat (chatd) can now discover and use MCP servers configured in
a workspace's `.mcp.json` file. This brings project-specific tooling
(GitHub, databases, docs servers, etc.) into the chat without any manual
configuration.
## How it works
The workspace agent reads `.mcp.json` from the workspace directory (same
format Claude Code uses), connects to the declared MCP servers —
spawning child processes for stdio servers and connecting over the
network for HTTP/SSE — and caches their tool lists. Two new agent HTTP
endpoints expose this:
- `GET /api/v0/mcp/tools` returns the cached tool list (supports
`?refresh=true`)
- `POST /api/v0/mcp/call-tool` proxies calls to the correct server
On each chat turn, chatd calls `ListMCPTools` through the existing
`AgentConn` tailnet connection, wraps each tool as a
`fantasy.AgentTool`, and adds them to the LLM's tool set alongside
built-in and admin-configured MCP tools. Tool names are prefixed with
the server name (`github__create_issue`) to avoid collisions.
Failed server connections are logged and skipped — they never block the
agent or break the chat. Child stdio processes are terminated on agent
shutdown.
## Summary
This change removes the steady-state "resolve the latest workspace
agent" query from chat execution.
Instead of asking the database for the latest build's agent on every
turn, a chat now persists the workspace/build/agent binding it actually
uses and reuses that binding across subsequent turns. The common path
becomes "load the bound agent by ID and dial it", with fallback paths to
repair the binding when it is missing, stale, or intentionally changed.
## What changes
- add `workspace_id`, `build_id`, and `agent_id` binding fields to
`chats`
- expose those fields through the chat API / SDK so the execution
context is explicit
- load the persisted binding first in chatd, instead of always resolving
the latest build's agent
- persist a refreshed binding when chatd has to re-resolve the workspace
agent
- keep child / subagent chats on the same bound workspace context by
inheriting the parent binding
- leave `build_id` / `agent_id` unset for flows like `create_workspace`,
then bind them lazily on the next agent-backed turn
## Runtime behavior
The binding is treated as an optimistic cache of the agent a chat should
use:
- if the bound agent still exists and dials successfully, we use it
without a latest-build lookup
- if the bound agent is missing or no longer reachable, chatd
re-resolves against the latest build and persists the new binding
- if a workspace mutation changes the chat's target workspace, the
binding is updated as part of that mutation
To avoid reintroducing a hot-path query, dialing uses lazy validation:
- start dialing the cached agent immediately
- only validate against the latest build if the dial is still pending
after a short delay
- if validation finds a different agent, cancel the stale dial, switch
to the current agent, and persist the repaired binding
## Result
The hot path stops issuing
`GetWorkspaceAgentsInLatestBuildByWorkspaceID` for every user message,
which is the source of the DB pressure this PR is addressing. At the
same time, chats still converge to the correct workspace agent when the
binding becomes stale due to rebuilds or explicit workspace changes.
The `ComputerUseProviderTool` function needed a little bit of an
adjustment because I changed `NewComputerUseTool`'s signature in
upstream fantasy a little bit.
- Stores a deployment-wide agents template allowlist in `site_configs`
(`agents_template_allowlist`)
- Adds `GET/PUT /api/experimental/chats/config/template-allowlist`
endpoints
- Filters `list_templates`, `read_template`, and `create_workspace` chat
tools by allowlist, if defined (empty=all allowed)
- Add "Templates" admin settings tab in Agents UI ([what it looks
like](https://624de63c6aacee003aa84340-sitjilsyrr.chromatic.com/?path=/story/pages-agentspage-agentsettingspageview--template-allowlist))
> 🤖 This PR was created with the help of Coder Agents, and has been
reviewed by my human. 🧑💻
create_workspace could create a replacement workspace after a single 5s
agent dial failed, even when the existing workspace agent had recently
checked in. That made temporary reachability blips look like dead
workspaces and let chatd replace a running workspace too aggressively.
Use the workspace agent's DB-backed status with the deployment's
AgentInactiveDisconnectTimeout before allowing replacement. Recently
connected and still-connecting agents now reuse the existing workspace,
while disconnected or timed-out agents still allow a new workspace. This
also threads the inactivity timeout through chatd and adds focused
coverage for the reuse and replacement branches.
Adds a `propose_plan` tool that presents a workspace markdown file as a
dedicated plan card in the agent UI.
The workflow is: the agent uses `write_file`/`edit_files` to build a
plan file (e.g. `/home/coder/PLAN.md`), then calls `propose_plan(path)`
to present it. The backend reads the file via `ReadFile` and the
frontend renders it as an expanded markdown preview card.
**Backend** (`coderd/x/chatd/chattool/proposeplan.go`): new tool
registered as root-chat-only. Validates `.md` suffix, requires an
absolute path, reads raw file content from the workspace agent. Includes
1 MiB size cap.
**Frontend** (`site/src/components/ai-elements/tool/`): dedicated
`ProposePlanTool` component with `ToolCollapsible` + `ScrollArea` +
`Response` markdown renderer, expanded by default. Custom icon
(`ClipboardListIcon`) and filename-based label.
**System prompt** (`coderd/x/chatd/prompt.go`): added `<planning>`
section guiding the agent to research → write plan file → iterate → call
`propose_plan`.
The tool descriptions pushed agents toward backgrounding anything over
5 seconds, including builds, tests, and installs where you actually
want to wait for the result. This led to unnecessary process_output
round-trips and missed the foreground timeout-to-reattach workflow
entirely.
Reframe background mode as the exception (persistent processes with
no natural exit) and foreground with an appropriate timeout as the
default. Replace "background process" with "tracked process" in
process_output, process_list, and process_signal since they work on
all tracked processes regardless of how they were started.
- 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. 🧑💻
Kyle Carberry