- Add `chattest.OpenAI(t)` convenience wrapper around `NewOpenAI` with
sensible defaults (JSON title response for non-streaming, text chunk for
streaming)
- Update `seedChatDependencies` to use it instead of an empty base URL,
preventing title generation from hitting real `api.openai.com` with a
fake key:
```
t.go:111: 2026-04-20 19:23:31.885 [debu] coderd.chatd.processor: title model candidate failed chat_id=edb43454-f23d-4163-9974-d101b8091de6 chat_id=edb43454-f23d-4163-9974-d101b8091de6 ...
error= generate structured title:
github.com/coder/coder/v2/coderd/x/chatd.generateStructuredTitleWithUsage
/home/coder/src/coder/coder/coderd/x/chatd/quickgen.go:443
- unauthorized: Incorrect API key provided: test-api-key. You can find your API key at https://platform.openai.com/account/api-keys.
```
> 🤖
Chat title generation used free-form text completion, which let models
respond conversationally instead of producing a title. Review chats
started with GitHub URLs were especially affected — models would say "I
don't have the ability to browse external links" and that string became
the persisted title.
Replace the raw-text `generateShortText` path with structured output via
`object.Generate[generatedTitle]`. Both auto-title and manual retitle
now go through the same typed contract: the model must return a JSON
object with a `title` field, validated and normalized before
persistence. Invalid outputs (empty, too long) are rejected and retried
through the existing candidate-model fallback loop.
OpenAI Responses follow-up turns were replaying full assistant/tool
history even when `store=true`, which breaks after reasoning +
provider-executed `web_search` output.
This change persists the OpenAI response ID on assistant messages, then
in `coderd/x/chatd` switches `store=true` follow-ups to
`previous_response_id` chaining with a system + new-user-only prompt.
`store=false` and missing-ID cases still fall back to manual replay.
It also updates the fake OpenAI server and integration coverage for the
chaining contract, and carries the rebased path move to `coderd/x/chatd`
plus the migration renumber needed after rebasing onto `main`.
- 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. 🧑💻
Cian Johnston