Assistant citations

For maintainers. Using T3 Code? See Quote an assistant response.

Assistant citations store a selected excerpt and its source in ordinary message text. They need no database migration, citation table, or sidecar draft metadata. The saved excerpt remains available even when the source response is missing or has changed.

Serialized form

AssistantCitation defines version 1. assistantCitations.ts serializes it as a Markdown link with the literal label Assistant quote:

The formatter percent-encodes each path segment and uses URLSearchParams for the query. The environment, thread, and message IDs identify the source without a browser origin, so local, remote, and tunnel clients share one form. Opening the source still requires access to its environment.

The parser accepts only version 1 with exactly three source IDs and one of each selector field; comment is optional and links without one keep their original format. It rejects credentials, ports, malformed encoding, and extra or duplicate query fields. IDs have a 512-character limit, the quote and comment each fit in 8,000 UTF-16 code units, offsets are nonnegative safe integers with end > start, prefix and suffix each fit in 32 code units, and the URI itself is capped at 160,000 characters. Malformed or unsupported links remain ordinary prompt text everywhere: collectors, provider expansion, and readable fallbacks all skip them. Parsing validates the payload, not the existence of its source.

Selection and source matching

assistantTextSelection.ts captures one native DOM range inside one assistant response, including backward and paragraph selections. Empty range endpoints at neighboring blocks are narrowed to the first and last selected text nodes before validating the source, so triple-click selections that end at the next block still resolve. The text stream follows DOM order, inserts line breaks between blocks and at <br>, and includes displayed code and link text. Controls, hidden subtrees, CSS-generated content, and soft wrapping do not contribute.

text keeps the exact selected excerpt, including line breaks and indentation. start, end, prefix, and suffix use the rendered-text stream after each JavaScript whitespace run collapses to one space, without trimming, in UTF-16 code units. Context boundaries avoid splitting surrogate pairs.

Resolution uses the same normalization and case-sensitive matching. It checks the saved offsets against the quote and context, then searches for a context-matching occurrence if positions have moved. A unique quote can still match after its context changes. Multiple context-matching occurrences are ambiguous, even if one remains at the saved offsets; the resolver does not guess.

Composer and clients

AssistantSelectionToolbar offers Cite in composer for a selection within one response and disables it above the quote limit. It shares selectionActions.ts with the terminal's selection menu: the observer opens actions only after a primary-button release from a gesture that started inside the surface, waits out the 500 ms repeat-click window so double/triple clicks can finish, anchors to the release point (or the text end for keyboard selections), and dismisses on outside interaction, scrolling, or Escape. The toolbar registers its own element with the observer so interacting with it cannot replace the captured quote.

ChatView inserts the serialized link at the last composer cursor. A one-shot editor request then opens the comment editor beside the cited source text, carrying the live DOM range for positioning and an editing highlight; that range is transient and never becomes part of the citation. withAssistantCitationComment trims outer whitespace and removes the field when blank; it never changes the saved quote or selector. Restoring or pasting a citation does not reopen the editor.

ComposerCitationNode is an inline Lexical DecoratorNode holding the quote and comment as one atomic chip. Its label shows the comment when present, otherwise a short quote preview; the node retains the full serialized source and returns it from getTextContent(). Comment edits update the citation and serialized source together as one undoable change. The token parser, clipboard handling, and cursor mapping treat citations as inline tokens alongside mentions and skills, so drafts, stashes, and pastes reconstruct chips from the prompt string alone. Sent messages keep the same links; ChatMarkdown renders valid citation URIs as read-only AssistantCitationChips, and the whole chip supplies its serialized value to Markdown copy so the displayed label is not duplicated as text.

Source navigation

assistantCitationNavigation.ts routes to the source thread with #assistant-citation=<base64url-encoded citation URI>; the encoding keeps router hash normalization from decoding quote whitespace or source IDs. Each click adds a fresh activation ID to navigation state so the same link can reveal its source again after dismissal.

useAssistantCitationTarget loads earlier history (bounded at 20 pages or a repeated cursor, with a warning past that), expands a folded turn, and asks the virtual list to mount the source row. While positioning, the timeline disables initial end-scroll and scroll maintenance and keeps the cited row mounted until measured; the activation ID doubles as the list's data version so pinning rows recalculates a stationary Legend list without discarding measurements.

AssistantCitationSource resolves the DOM range, smoothly scrolls to it, and pulses only that text through the CSS Highlight API: two 650 ms pulses driven by a registered opacity property, with the second settling into a held highlight before fading out. Navigation owns the highlight's start time and completion state: range repairs keep the original clock, remounting resumes only the remaining time, and an expired or dismissed highlight cannot revive. Reduced motion scrolls instantly and holds the highlight without pulsing. Browsers without the Highlight API temporarily select the range and remove only that owned selection. User navigation or Escape cancels pending positioning; missing messages or unmatched text produce warnings without changing the saved quote. The separate comment-editing highlight uses the same range-repair observer while its editor is open.

Desktop shares the web implementation. Mobile's ThreadFeed uses renderAssistantCitationsAsText to show sent quotes as readable Markdown blockquotes with each user comment below its quote; it does not create citations or navigate to sources.

Provider input and titles

ProviderService.sendTurn calls expandAssistantCitationsForProvider before routing to any adapter; persisted messages keep their links. Each distinct serialized link becomes an inline [assistant-quote-N] marker, and one <assistant_citations> block carries JSON entries with an id and the complete citation. The block identifies citation.text as quoted reference material, not new instructions, and citation.comment as the user's comment about that quote. JSON encoding escapes <, >, and & so content cannot close the wrapper. The expansion is shared by all providers; there is no per-adapter citation handling or source lookup at send time.

The 120,000-character provider input limit applies both before and after expansion: composerSubmission.ts checks the larger length client-side and keeps an over-limit draft editable, and the server revalidates the expanded input before dispatch. Expansion does not apply to pending user-input answers.

assistantCitationsToPlainText supplies readable input for title seeds, stash previews, and the server's title and branch-name helpers, which see the quoted text and comment rather than an encoded URI.