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Kyle Carberry
376fc80451
## Problem In `coderd/x/chatd/chatd.go` `runChat`, workspace MCP discovery is gated on `chat.WorkspaceID.Valid` at the start of each turn. New chats that bind their workspace mid-turn (via `create_workspace` or `start_workspace`) get an empty workspace tool list on the first step, and the model falls back to `execute` (bash) because no workspace MCP tools are advertised. **Repro:** new chat → "create a workspace and use MCP tools". No `/api/v0/mcp/tools` request hits the agent on turn 1; turn 2 in the same chat works fine. ## Fix - Add a `PrepareTools` callback to `chatloop.RunOptions`, analogous to `PrepareMessages`. It is invoked once before each LLM step with the current tool list. When it returns non-nil, the chatloop replaces `opts.Tools`, rebuilds the per-step tool definitions, and appends new tool names to `opts.ActiveTools` so newly injected tools are callable immediately. - Wire `PrepareTools` in `runChat` to trigger workspace MCP discovery the first time the chat snapshot reports a valid `WorkspaceID`. The previous top-of-turn discovery path is unchanged for chats that start with a workspace. - Extract the discovery logic into `Server.discoverWorkspaceMCPTools` so the top-of-turn and mid-turn paths share identical behavior (cache, agent resolution, `ListMCPTools` timeout, invalidation). Mid-turn discovery stays disabled in plan-mode turns and Explore subagents, matching the existing top-of-turn gate. The `workspaceMCPDiscovered` flag prevents redundant dials after the first successful discovery. ## Tests - `coderd/x/chatd/chatloop/chatloop_test.go`: two new `TestRun_PrepareTools*` cases covering injection on the next step and active-set merging when `ActiveTools` is non-empty. - `coderd/x/chatd/chatd_test.go`: `TestRunChat_WorkspaceMCPDiscoveryAfterMidTurnCreateWorkspace` drives `runChat` through a `create_workspace` tool call against a real Postgres + mocked agent conn and asserts the second streamed LLM request advertises the workspace MCP tool. Verified that the test fails (and pinpoints the missing tool) when the `PrepareTools` wiring is disabled. ## Validation ``` go test ./coderd/x/chatd/chatloop/... -count=1 go test ./coderd/x/chatd/... -count=1 make lint/emdash ``` <details> <summary>Decision log</summary> - Chose a per-step `PrepareTools` callback over mutating `opts.Tools` in place because `chatloop.Run` builds the `fantasy.Tool` definitions once at start; a hook is required to let the LLM see new tools on the next step. - Returned `[]fantasy.AgentTool` (not also active-tool-names) and let the chatloop derive name merges via `mergeNewToolNames`. This avoids leaking plan-mode gating decisions into the callback contract. - Kept the existing top-of-turn discovery path so chats that already have a workspace at turn start pay no extra latency. - Skipped reusing `ReloadMessages` (history reload) since this is purely a tool-availability concern; coupling it to a history reload would defeat the chatloop cache prefix optimizations. </details> --- _This pull request was generated by Coder Agents._