Reasoning blockPro

• Type: Component (special)
• Access: Xzero Pro
• Page: https://ui.xzero.co.uk/components/reasoning-block
• Markdown: https://ui.xzero.co.uk/components/reasoning-block/markdown
• Source file: registry/components/reasoning-block/reasoning-block.tsx
• Dependencies: motion, lucide-react
• Keywords: special, ai, new, reasoning, thinking, thought for, extended thinking, chain of thought, reasoning summary, collapsible, ai reply, claude, streaming, llm

When to use

• Showing a reasoning model's thinking above its answer in a chat or agent transcript.
• Letting people audit why an assistant reached a recommendation without crowding the reply.
• Restoring past messages where the reasoning should stay folded with its original thinking time.

When not to use

• Tool or function calls with inputs and outputs: use ToolCall.
• A multi step agent plan with checkable tasks: use Agent plan.
• A one line busy indicator with no reasoning to show: use TextShimmer on its own.

Installation

Register both Xzero UI namespaces in your project's components.json:

{
  "registries": {
    "@xzero-ui": "https://mcp.xzero.co.uk/r/{name}.json",
    "@xzero-ui-pro": "https://mcp.xzero.co.uk/r/pro/{name}.json"
  }
}

npx shadcn@4.23.0 add @xzero-ui-pro/reasoning-block

Install xzero-foundation once, and import @/components/xzero/foundation.css in your app root. No Xzero token is used by this snapshot. For sample portraits, photos, fonts, or logos, download https://mcp.xzero.co.uk/install-assets.mjs and run node xzero-install-assets.mjs <receiving-project>.

Usage

import { ReasoningBlock } from "@/components/xzero/reasoning-block/reasoning-block";

// While streaming: pass the growing text, then flip status when the answer starts.
<ReasoningBlock
  reasoning={thinkingText}
  status={done ? "done" : "thinking"}
  onStop={() => controller.abort()}
/>

// A finished message from history.
<ReasoningBlock reasoning={message.reasoning} status="done" seconds={message.thinkingSeconds} />

API reference

ReasoningBlock

The collapsible thinking block of an AI reply. While the model thinks, a shimmering "Thinking" label counts the seconds and the latest reasoning streams under it in muted text, two lines tall. When it finishes it collapses to "Thought for 7s" with a chevron; opening it shows the full reasoning as steps with headings on a quiet rail. With no props it plays a simulated Claude session on a loop.

Prop	Type	Default	Description
reasoning	string | ReasoningStep[]	–	The reasoning so far. Pass the growing string while the model streams: blank lines split paragraphs, and a line written as Heading or ## Heading starts a new step (a half streamed heading never shows raw asterisks). Or pass { title?, text }[] steps.
status	"thinking" | "done" | "stopped" | "error"	"done" when reasoning is passed	thinking shimmers the label, counts seconds and streams the latest line; done collapses to "Thought for 7s"; stopped reads "Stopped after 4s"; error shows an alert icon with "Thinking interrupted" and the reason inside.
seconds	number	–	Seconds spent thinking, shown as 7s or 1m 12s. Left out, the block measures from the moment status turns thinking. Done without a measurement reads "Thought process".
model	{ name: string; mark?: ReactNode }	{ name: "Claude Opus 5.5" }	Who is thinking. The name labels the block for assistive technology; the mark is an 18px glyph at the left and defaults to the Claude mark in its brand color.
open	boolean	–	Controls whether the full reasoning shows. Pair with onOpenChange.
defaultOpen	boolean	false	Opens the full reasoning on first render.
onOpenChange	(open: boolean) => void	–	Called when the header is pressed.
onStop	() => void	–	Shows a compact Stop action while thinking. Abort your request, then set status to stopped.
onRetry	() => void	–	Shows Retry in the header when status is error.
error	string	–	The reason shown at the end of the reasoning when status is error.
variant	"card" | "plain"	"card"	card draws a quiet bordered surface; plain drops the border and padding so the block sits flush inside a message bubble.
className	string	–	Class on the root.

parseReasoning

The parser the block uses, exported for tests or for showing a step count elsewhere. Turns a streamed string into { title?, text }[] steps.

Prop	Type	Default	Description
reasoning (required)	string | ReasoningStep[] | undefined	–	Raw streamed reasoning or steps.

ClaudeMark

The Claude mark (Simple Icons, CC0) in its brand color. Pass mono to draw it with currentColor.

Prop	Type	Default	Description
title	string	"Claude"	Accessible name.
mono	boolean	false	Draws with currentColor instead of #D97757.

Keyboard interactions

Keys	Action
Tab	Moves to the header, then to Stop or Retry when shown, then to Copy reasoning inside the open block.
Enter / Space	Opens or closes the full reasoning from the header.

Accessibility

• The header is a real button with aria-expanded and aria-controls; its name is the visible label, such as "Thought for 7s".
• A polite live region announces status changes only (thinking, thought for 7 seconds, stopped, interrupted), never each streamed chunk or each second.
• The two line live preview is aria-hidden because the same text is in the full reasoning region, which carries aria-busy while streaming.
• Status is never color alone: errors pair an alert icon with "Thinking interrupted", and the footer pairs a check, square or alert with Done, Stopped or the reason.
• The no props preview says "Simulated, nothing was sent to a model" to assistive technology.

Motion

• Streaming is chunked: each appended chunk fades in once over 140ms. No blur, slide or per word springs.
• Stop and Retry overflow a fixed 20px row, so the header is 44px in every state and never shifts when an action appears.
• The live preview stays anchored to its newest line; when a line wraps, the text glides up with a bounce free spring (0.24s) instead of jumping.
• Label swaps (Thinking to Thought for 7s) are a single crossfade: out in 100ms, in over 160ms with a 2px rise. The seconds counter rolls in tabular numerals inside a reserved width.
• Opening, closing and the preview collapsing all animate measured height with one critically damped spring (0.26s) and one opacity fade. Only what streams in while open (a new step, paragraph or chunk) fades on its own, so nothing animates twice.
• The shimmer and the self-playing loop pause off screen and in background tabs. Reduced motion keeps every end state, drops the shimmer, the glide and the chunk fades, and cuts heights instantly.

Responsive behavior

• Fills its container from 320px up; the header never wraps and long labels truncate.
• The live preview stays two lines at every width, so streaming never changes the block's height.
• Paragraphs wrap with text-wrap: pretty and break long identifiers instead of scrolling sideways.
• On touch, the whole header and live preview are one press target of at least 44px.

Performance

• Streamed text is appended as spans that never re-render once on screen; finished messages render plain text.
• Only the open block mounts its full reasoning, so long transcripts of collapsed blocks stay light.
• The preview glide is one transform on one element driven by a ResizeObserver, with no layout animation on text.

Notes for AI

• Use it above the answer in an assistant message whenever the model streams reasoning (extended thinking, reasoning summaries). Feed it the raw thinking text and switch status to done as soon as answer tokens start.
• Do not pass seconds while streaming unless your server measures it; the block counts by itself and freezes the value when status leaves thinking. Store that number with the message so history shows the same "Thought for 7s".
• Keep reasoning out of the answer text. For tool calls made during reasoning, render ToolCall rows after the block instead of inside it.
• Use variant="plain" inside a message bubble that already has its own surface, so you never nest cards.
• Swap the mark for another provider by passing model={{ name, mark }} with an 18px SVG.

Related

• Tool call: A tool call row for agent transcripts: the tool's mark and the call in plain words, a live state while it runs, and the input and output a click away, with approval and retry when needed.
• Agent status: A compact live status pill for a running AI agent: the agent's mark in a live ring, the current activity and an elapsed timer, opening into the steps so far.
• Text shimmer: Show ongoing work with a calm light across the words.
• Agent plan: The plan an agent writes before it acts: edit, reorder or add steps while it is a draft, then watch it work through them as a live checklist.

Also in ai

• Agent timeline: A compact timeline of one orchestrated agent run: the orchestrator and its subagents share a time axis, handoffs draw in between rows, and a playhead replays thinking, tool calls and waiting while the header counts time, tokens and cost. Hover a span for what it did, or click it to trace its handoff path.
• Context window: An AI context window as a grid of 200 cells: the system prompt, tools, files, summary and messages fill it in order, a threshold row marks where compaction starts, and sending a message, attaching a file or compacting shows exactly how much still fits.
• Source cards: A row of cited sources under an AI answer where cards stream in with real site marks while the model searches, the overflow collapses into a stack of favicons, hovering lifts a preview with the passage, and an inline [n] citation highlights its card.
• Model card: A model details card where switching models rolls every price, limit and score in place, a token slider estimates monthly cost live, and benchmark bars show each model's rank on hover. Compare crossfades to a side-by-side table against any rival with the better values marked, and the card never changes size.
• AI workflow: A Linear-style AI workflow card where a Gmail trigger, a Claude step, a branch and Slack and Linear actions sit on one hairline rail, and a test run glides down it, opening each step's output inline. Steps are added from a compact command menu with real app marks.
• Code suggestion: An AI code edit suggestion where the model's proposed changes stream into a small editor panel as inline diff hunks, and you accept or reject each one, or all at once with Cmd+Enter. Accepted hunks fold into the file with a smooth height change.
• Ghost text: An inline AI autocomplete where muted ghost text continues your sentence exactly at the caret and Tab turns it solid in place. Cmd+Right takes it one word at a time, Escape fades it away, and a calm chip shows the model behind it.
• Image generation: An image generation card where four images resolve as a pixel mosaic, from coarse colour blocks to full detail under a soft shimmer, each with its own progress ring. Pick one to upscale with a sweeping pixel band, vary or download it, with real provider marks and a built-in simulation.
• Dictation button: A chat composer with voice input, where the mic springs into a recording pill with a smooth live waveform, a timer, and cancel and insert buttons. Words stream into the field as you speak, muted until the recognizer settles them.
• Speech player: A read-aloud player for AI replies. The Read aloud button in the message's action row turns into a compact player with play, a scrubbable progress bar, speed and a voice picker, and a highlight follows the spoken word through the reply, karaoke style.
• Meeting summary: An AI meeting notes card: the header shows the Google Meet or Zoom mark, the attendees and the duration. Summary, Decisions and Action items stream in after a short summarizing pass. Hover any line to see the transcript quote it came from, then check off action items or send them to Linear or Notion.
• Reply draft: An AI email reply drafter where Claude streams a reply under a received Gmail message. Quick replies steer a fresh draft, tone and length rewrite it with a single crossfade, and you can edit the finished draft before you insert it.
• Agent handoff: A support conversation where an AI assistant hands off to a person. When it transfers, a card shows the summary it passes to the team and the typical wait. The person then joins and takes over, and a thin timeline on the left marks each step.
• PII redaction: A guardrail card where personal data is redacted before the prompt reaches the model. Scan marks each name, email, phone number and card with its type and swaps it for a placeholder like [EMAIL_1]. The safe prompt travels to Claude, and the reply comes back with the original values put back for the person.
• Response feedback: A feedback control for AI replies where thumbs down opens an inline panel with reason chips and an optional note, thumbs up fills and asks what was good, and a submit shows a short thank-you before folding back into the row.
• LLM cost calculator: A pricing calculator for LLM workloads. Set tokens per request, requests per day and prompt caching, and eight current models re-rank by monthly cost. Bars glide and prices roll as you drag.
• Provider keys: A settings card for bring-your-own-key AI products. Each provider row shows its real mark, the masked key, a status and when the key was last used. You can reveal a key for five seconds, copy, rotate or remove it with undo. Adding or rotating a key opens an inline form that checks the format as you type, then tests the connection before saving.
• Generation stats: A live stats strip for a streaming LLM response where time to first token, speed with a sparkline, output tokens and cost count up in tabular numerals beside the model's real mark, then settle and open into a latency and token cost breakdown.
• AI translate: A message card where picking a language streams the AI translation in place, sentence by sentence over the dimmed original, with a detected-language chip, a Show original toggle and a status line credited to the model's mark.
• TL;DR toggle: An article card with a Full, Summary and Key points switch and a length slider. Switching streams an AI summary in place of the article as the card's height springs to fit, and each key point links back to the paragraph it came from, which gets scrolled to and highlighted.
• Connector setup: A "Connect your tools" card for an AI assistant. Each app connects inline: it redirects, authorizes and runs a first sync with a progress hairline, then lists the scopes it was granted and offers Disconnect with an inline confirm.
• Smart form fill: A paste-to-fill form card where AI reads an email signature or messy notes and fills a contact field by field. Each value flashes in with a confidence dot, its source lights up in the pasted text, low-confidence guesses ask for review, and Undo puts the old values back.
• Enrich column: An AI enrichment column for a data table, where one prompt runs down every row and each cell shimmers while it works, then settles into a value with its source or a failure you can retry.
• Ticket router: A support ticket router where messages from Gmail, Intercom, Slack and Zendesk come in one at a time. An AI classifier labels each one with intent, sentiment and confidence, and the ticket moves into a team lane with an assignee. Low confidence tickets wait in a review lane, and one click there routes them to the suggested team.
• Ask your data: A natural language to chart card: you ask a question, PostgreSQL streams into a collapsible, syntax highlighted panel, the query runs with a rolling row count, and the answer builds as stacked bars, lines or a table, with a one line insight streamed in underneath.
• Agent cursor: A live document where Claude edits like a collaborator. Its labeled cursor comes out of its avatar, selects a paragraph and streams in a rewrite, adds a heading and fixes a typo, while a teammate's cursor reads along. Changes stay tinted until someone accepts or undoes them from a floating review bar.
• Provider status: A status card for the AI providers your product depends on. Each row shows the provider's real mark, its health as an icon and label, p50 latency and a 30-day uptime bar with a tooltip for each day. An incident row expands into its timeline of updates, and the card checks again on a visible countdown.
• Training run: A fine-tuning job card where a live train and validation loss curve draws across a fixed step axis that doubles as the epoch progress bar. It shows the learning rate, elapsed time, ETA and the latest evals and checkpoints, has Pause and Cancel while it runs, and ends in results with a Deploy button.
• AI command: A Cmd+K command palette with an AI mode. Search pages and actions, or press Tab to ask a question: the answer streams inside the palette with numbered sources, and the next steps it suggests, like filing a Linear issue or opening a Notion doc, run straight from the list.
• Starter prompts: A greeting and a grid of starter cards for the empty state of an AI app. The cards are grouped into Write, Code, Analyze and Plan tabs, and a shuffle swaps them with a short staggered crossfade. Picking a card fills the composer, and cards that use a connected app show its mark (Gmail, GitHub, Notion, Linear, Google Calendar).
• AI mascot: A small assistant character, a soft pebble with pill eyes and a companion dot, that shows what the AI is doing. It breathes and glances when idle, leans in to listen, looks up while the dot orbits its head, reads along the line it writes, squints with a sparkle when done and shakes once with worried brows on an error.
• Image reveal: An image generation canvas where a soft, blurred preview made from the image's own colors sharpens top to bottom behind a soft-edged band. It works the way ChatGPT, Midjourney and Gemini show images forming, with fine film grain, a translucent progress pill and calm queued and error states.
• AI spark: A brand-quality animated spark mark. Four tapered rays and four lighter diagonals breathe at rest, ripple while thinking, pulse like a heartbeat while writing, then gather and settle when done. Every status change blends from the pose the mark is already in.
• Pixel mascot: A pixel-art robot that shows what an AI assistant is doing. It idles, thinks, types, celebrates and errors in frame-stepped sprite animations, and stays crisp at every integer size from 24px to 192px.
• Ghost mascot: A floating ghost mascot whose soft sheet ripples at the hem while it hovers. It blinks when idle, turns toward you to listen, fades a little translucent while thinking, draws a tiny pen line while writing, smiles with a sparkle when done and wobbles once on an error.
• Cube mascot: An isometric cube mascot where three shaded faces and a painted-on face show what the assistant is doing. It turns a quarter turn in eased steps while thinking, prints lines onto the floor while writing, settles with a sparkle when done, and shakes once on error.
• Tone tuner: A brand voice card where two sliders (formality and detail) and Friendly, Confident and Empathetic chips rewrite a customer reply. Each changed sentence crossfades in place, new words can be highlighted against the original, and Copy takes the current version.
• Upgrade prompt: An upgrade nudge for the moment someone hits a limit. It shows a usage meter at 50 of 50 AI credits, a rolling price with a monthly and yearly toggle, three concrete unlocks with real model marks, and Upgrade or Maybe later. Upgrading leads into a success state with the new limits, and the card never changes size between states.
• Referral card: A give-and-get referral card where people copy or share their invite link, invite friends by email as chips, and watch invites move from invited to signed up to earned, with the credit total counting up and a milestone reward unlocking.
• Trial banner: A trial status banner where a ring counts down the days left, the copy names what the workspace loses, and the upgrade path is one click away. It comes as a slim banner, a sidebar card or a header pill. It shifts to a warning tone in the last days, has expired and upgraded states, and folds into the pill when dismissed or snoozed.
• Team switcher: A workspace switcher like Linear, Vercel or Slack. The trigger shows the current workspace's logo and plan. The menu has search, your role in each workspace and a Cmd+1 to 9 shortcut for each, and lets you create or join a workspace inline. A highlight glides between rows, and switching crossfades the trigger through a short loading state.
• Live visitors: A realtime visitors card where the live count rolls digit by digit, new arrivals ping in on a dotted world map, the top pages reorder with bars, and signups and upgrades tick in with country flags.
• Social proof toast: A stack of social proof notifications for landing and pricing pages, where recent trials, upgrades and verified purchases from people and companies arrive every few seconds. The stack pauses and fans out on hover, and visitors can dismiss any toast.
• Install snippet: A "get started in 30 seconds" card where framework tabs, three numbered steps and highlighted snippets take a developer from install to first event. Generate key wipes a fresh API key into the placeholder in place.

Guidance for AI tools

Reasoning block: The collapsible thinking block of an AI reply. While the model thinks, a shimmering label counts the seconds and the latest reasoning streams underneath. When it finishes, it folds to "Thought for 7s" and opens to show the full reasoning as calm steps with headings. Follow the declared prop types and do not invent props. Keep keyboard access, reduced motion support, and both light and dark themes intact when adapting it.

Full library index: https://ui.xzero.co.uk/llms.txt