feat: tab completion for citation keys

[wjiayis]

#33

In short, it'll

1. [Frontend] Recognize that user is trying to add a citation (trigger text is \cite{)
2. [Frontend] Temporarily suppress default Overleaf dropdown suggestions
3. [Frontend] Get the last sentence as context for LLM
4. [Backend] Fetch bibliography in .bib files as raw text, and remove irrelevant fields to save tokens
5. [Backend] Call XtraMCP to get paper abstract, using paper title as key
6. [Backend] Query a fast LLM (hardcoded to gpt-5.2 for now) to get at most 3 citation keys
7. [Frontend] Suppress default Overleaf tab-completion to allow users to accept citation suggestions

[Junyi-99]

Hi @wjiayis, thanks for the update. I’ve created a new issue to address the token expiration problem.

Regarding the latency issue, do we have visibility into which part of the pipeline contributes most to the high latency? For example, a rough breakdown across:

frontend → backend → LLM provider (reasoning + response)

I’ll take a look at this PR later this evening as well.

[wjiayis]

@Junyi-99 I haven't gotten to the latency breakdown yet, but I've settled everything else and I'm gonna work on this next. Thanks for helping to review when convenient, I'll update my findings when I have them too!

[Junyi-99]

@wjiayis Got it, thanks for the update. Looking forward to your findings.

[wjiayis]

Root Cause

There's a ~20s latency in the inline-suggestion loop, and >99% of the latency comes from waiting for LLM to start responding. This issues arises because I'm passing in a large (but realistic) bibliography (the bibliography of PaperDebugger: A Plugin-Based Multi-Agent System for In-Editor Academic Writing, Review, and Editing itself), and gpt-5-nano takes a while to parse it.

Solution

I think it's reasonable to expect that a regular user's max latency tolerance is ~2s. I'll implement the following 3 solutions to achieve that.

Model Selection

gpt-5-nano is takes a long time to process the long bibliography. Just swapping it out for gpt-5.2 brings latency down to 2-4s. But gpt-5.2 is expensive to call. I'll improve latency and cost with the next 2 solutions.

Prompt Caching

Since bibliography remains generally constant and takes up the bulk of the prompt, I'll use OpenAI's prompt caching - advertised to reduce latency by up to 80% and input token costs by up to 90%.

1. Place bibliography at the start of the prompt (prompt caching uses exact prefix match)
2. Run a "no-reply" LLM query at the start of each session and when database reloads, and config it to cache 24h
3. Each time \cite{ is triggered, the cached bibliography is used -> lower latency

Prompt Refinement

I'll remove info-sparse fields (eg doi, url, pages) and retain only info-rich fields (eg title, booktitle), to reduce the total size of bibliography by (hopefully) at least 40%.

cc: @Junyi-99

[Copilot]

Pull request overview

Implements a first version of citation-aware tab completion by detecting \cite{ in the editor, fetching suggested BibTeX keys from a new backend endpoint, and suppressing Overleaf’s default autocomplete/tab behavior to allow accepting inline suggestions.

Changes:

• Frontend: Adds a “citation suggestions” beta setting, detects \cite{ triggers, fetches citation keys, and intercepts Tab to accept inline suggestions.
• Backend: Adds GetCitationKeys RPC/HTTP endpoint, extracts and token-reduces .bib content, and queries an LLM for up to ~3 relevant citation keys.
• Plumbing: Updates generated proto clients/servers and ignores CLAUDE.md.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
webapp/_webapp/src/views/settings/sections/beta-feature-settings.tsx	Renames the completion toggle UI to “citation suggestions”.
webapp/_webapp/src/views/settings/index.tsx	Renders the beta features section in Settings.
webapp/_webapp/src/query/api.ts	Adds getCitationKeys() API wrapper for the new v2 endpoint.
webapp/_webapp/src/pkg/gen/apiclient/chat/v2/chat_pb.ts	Generated TS client types/service updated for GetCitationKeys.
webapp/_webapp/src/libs/inline-suggestion.ts	Adds \cite{ trigger handling and suppresses Overleaf autocomplete/tab behavior when suggestions are active.
proto/chat/v2/chat.proto	Adds GetCitationKeys RPC + request/response messages.
pkg/gen/api/chat/v2/chat_grpc.pb.go	Generated gRPC server/client updated with GetCitationKeys.
pkg/gen/api/chat/v2/chat.pb.gw.go	Generated grpc-gateway bindings for /_pd/api/v2/chats/citation-keys.
pkg/gen/api/chat/v2/chat.pb.go	Generated Go proto types updated with new messages and RPC.
internal/services/toolkit/client/get_citation_keys.go	Implements bibliography extraction and LLM prompt to suggest citation keys.
internal/api/chat/get_citation_keys.go	Implements the ChatServerV2 handler for GetCitationKeys.
.gitignore	Ignores CLAUDE.md.

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[Junyi-99]

@wjiayis Hi Jiayi, thanks for your patience. I’ve left some comments, once those are addressed, it can be merged.

[4ndrelim]

Thanks for the hardwork jiayi! Just some minor comments on top of jun yi's. Once these are resolved, let's merge to staging, do a test on the staging env endpoint (together if you'd like, and i can run you through our deployment pipeline too) and if all is working as expected, we can immediately raise to main.

[wjiayis]

All comments are resolved! I'll work with @4ndrelim tomorrow to test and merge the PR.
cc: @Junyi-99

[Junyi-99]

LGTM! Thanks for your patience and for iterating on this!

[4ndrelim]

LGTM. Thanks for the revision!