Adds an admin-configurable deployment-wide setting that controls which
model is used for chat title generation. Admins can pick any enabled
chat model config from the Agents settings page, or leave the setting
unset to keep the existing fast-models-then-chat-model fallback
algorithm.
When a model is selected, both automatic and manual title generation use
only that model, with no silent fallback. When the configured model is
disabled, missing credentials, or otherwise unusable, automatic title
generation skips entirely (best-effort) and manual title regeneration
returns a clear error, so admins notice the misconfiguration instead of
silently routing title traffic through another provider.
## Surface
- New deployment-wide setting stored as a `site_configs` row
(`agents_chat_title_generation_model_override`).
- New experimental endpoint `GET/PUT
/api/experimental/chats/config/model-override/{context}`.
- Frontend: title generation now appears as a third dropdown on the
Agents admin settings page alongside the existing general and explore
context overrides.
## DRY refactors folded in
Title generation is integrated as a third value of the existing
`ChatModelOverrideContext` type alongside `general` and `explore`,
sharing the parameterized HTTP route, SDK methods, generated types, and
frontend API plumbing rather than introducing a parallel surface. The
`Agent` prefix was dropped from the type and route since title
generation is not a delegated agent.
The chatd model-override resolver is also shared.
`resolveConfiguredModelOverride` now takes a `failureMode` parameter:
- Subagent overrides use soft failure: misconfigured overrides are
logged and the parent model is used.
- Title generation uses hard failure: misconfigured overrides return an
explicit error so manual title regeneration surfaces the
misconfiguration and automatic title generation skips instead of
silently falling back.
> Mux is acting on Mike's behalf.
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.
Short prompts were producing title-generation meta responses such as "I
am a title generator" and prompt-echo titles. This rewrites the
automatic and manual title prompts to be shorter, less self-referential,
and more focused on returning only the title text.
The change also removes the broader post-generation guard layer, updates
manual regeneration to send real conversation text instead of a meta
instruction, and keeps regression coverage focused on the slimmer prompt
contract.
## Summary
Adds a "Generate new title" action that lets users manually regenerate a
chat's title using richer conversation context than the automatic
first-message title path.
## Changes
### Backend
- **New endpoint:** `POST
/api/experimental/chats/{chatID}/title/regenerate` returns the updated
Chat with a regenerated title
- **Manual title algorithm:** Extracts useful user/assistant text turns
→ selects first user turn + last 3 turns → builds context with gap
markers → renders prompt with anti-recency guidance → calls lightweight
model → normalizes output
- **Helpers:** `extractManualTitleTurns`,
`selectManualTitleTurnIndexes`, `buildManualTitleContext`,
`renderManualTitlePrompt`, `generateManualTitle` — all private, with the
public `Server.RegenerateChatTitle` method
- **SDK:** `ExperimentalClient.RegenerateChatTitle(ctx, chatID) (Chat,
error)`
- Persists title via existing `UpdateChatByID` and broadcasts
`ChatEventKindTitleChange`
### Frontend
- API client method + React Query mutation with cache invalidation
- "Generate new title" menu item (with wand icon) in both TopBar and
Sidebar dropdown menus
- Loading/disabled state while regeneration is in-flight
- Error toast on failure
- Stories updated for both menus
### Tests
- `quickgen_test.go`: Table-driven tests for all 4 helper functions
(turn extraction, index selection, context building, prompt rendering)
- `exp_chats_test.go`: Handler tests (ChatNotFound,
NotFoundForDifferentUser, NoDaemon)
## Design notes
- The existing auto-title path (`maybeGenerateChatTitle`, `titleInput`)
is completely unchanged
- Manual regeneration uses richer context (first user turn + last 3
turns + gap markers) vs the auto path's single first message
- Endpoint is experimental and marked with `@x-apidocgen {"skip": true}`
- Add `X-Coder-Owner-Id`, `X-Coder-Chat-Id`, `X-Coder-Subchat-Id`,
`X-Coder-Workspace-Id` headers to all outgoing LLM API requests from
chatd
- Extend `ModelFromConfig` with `extraHeaders` param, forwarded via
Fantasy `WithHeaders` on all 8 providers
- Add `CoderHeaders(database.Chat)` helper to build the header map from
chat state
- Update all 4 `ModelFromConfig` call sites (resolveChatModel,
computer-use override, title gen, push summary)
- Thread `database.Chat` into `generatePushSummary` (was `chatTitle
string`)
- Tests: `TestCoderHeaders` (4 subtests),
`TestModelFromConfig_ExtraHeaders` (OpenAI + Anthropic),
`TestModelFromConfig_NilExtraHeaders`
- Refactor existing `TestModelFromConfig_UserAgent` to use channel-based
signaling
> 🤖 This PR was generated by Coder Agents and self-reviewed by a human.
- 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. 🧑💻
Michael Suchacz