ui: the chat comeback — side-based authorship, restored quotes, tucked whys

Blockquotes: the callout override had displaced Streamdown's own styled
blockquote component, so plain quotes rendered as bare unstyled text
since that commit. The pass-through branch now restores Streamdown's
verbatim classes (border-l-4, muted italic).

Explanations tucked for ALL questions (owner): the prediction's Why /
Hide-why toggle is universal — every quiz answered card sits its
explanation behind the same collapsed button. Same pattern, one law.

The thinking row's rhythm: my-1 -> my-3. The 4px margin hugged the
options on non-graded answered cards (owner report); 12px matches the
card's mt-2/mt-3 spacing grammar everywhere the row renders.

Side-based authorship (owner round, 2026-10-07): the document shape
blurred user into agent — three left-rail idioms (user text, user
thinking, quoted prose) collided once quotes rendered. User rows go
RIGHT: 'You' messages and practice thinking cards hug the right edge at
85% width with the rail mirrored (border-r), text still reading
left-to-right. In-card thinking (inside the answered card, the agent's
context) stays left. Transcript thinking rows arrive EXPANDED — the
thinking was clearly sent. Cmd+T (toggle-user-thinking, chat scope,
cheat-sheet row) sets every user-thinking row to one state via a module
store: explicit sets stomp individual toggles, late mounts honor the
last set (the state initializer reads the store, so static render
reflects it too).

tests/keyboard-toggle-sidebar.test.ts

@@ -30,6 +30,12 @@ describe("kbdEventForAction — the one spelling for action events", () => {
 });
 
 describe("the ⌘B chain — keypress → binding → action → event", () => {
+	it("mod+t is the toggle-user-thinking action (owner round, 2026-10-07)", () => {
+		assert.equal(actionForBinding("mod+t"), "toggle-user-thinking");
+		assert.equal(bindingForAction("toggle-user-thinking"), "mod+t");
+		assert.equal(kbdEventForAction("toggle-user-thinking"), "lh:kbd-toggle-user-thinking");
+	});
+
 	it("mod+b is the toggle-sidebar action", () => {
 		assert.equal(actionForBinding("mod+b"), "toggle-sidebar");
 		assert.equal(bindingForAction("toggle-sidebar"), "mod+b");

tests/render-cards.test.tsx

@@ -241,7 +241,10 @@ describe("render smoke tests", () => {
 		const answer = buildAnswer(quizQD(), { values: ["Venus"] });
 		const html = renderToStaticMarkup(<AnsweredCard answer={answer} />);
 		assert.match(html, /incorrect/);
-		assert.match(html, /innermost/, "explanation renders post-answer");
+		// Tucked for ALL questions (owner, 2026-10-07): the explanation sits
+		// behind the Why toggle — never center stage.
+		assert.ok(html.includes("tucked-explanation"), "the Why toggle mounts");
+		assert.ok(!html.includes("innermost"), "explanation hidden until opened");
 		// Glyph-shaped SVG marks (owner preference) — pinned via data-mark.
 		assert.ok(html.includes('data-mark="check"') && html.includes('data-mark="x"'));
 	});
@@ -302,8 +305,8 @@ describe("render smoke tests", () => {
 		// The thinking sits ABOVE the verdict's explanation — the dialogue of
 		// thinking, not an afterthought.
 		assert.ok(
-			html.indexOf("your-thinking") < html.indexOf("innermost"),
-			"thinking before the explanation",
+			html.indexOf("your-thinking") < html.indexOf("tucked-explanation"),
+			"thinking before the explanation toggle",
 		);
 	});
 
@@ -574,11 +577,11 @@ describe("predict vs check rendering", () => {
 		assert.ok(html.includes("tucked-explanation"), "it sits behind the toggle");
 	});
 
-	it("a check answer keeps the inline explanation", () => {
+	it("a check answer tucks the explanation like every question (owner, 2026-10-07)", () => {
 		const answer = buildAnswer(quizQD(), { values: ["Venus"] });
 		const html = renderToStaticMarkup(<AnsweredCard answer={answer} />);
-		assert.ok(html.includes("Why:"), "checks explain inline (current behavior)");
-		assert.ok(!html.includes("tucked-explanation"));
+		assert.ok(html.includes("tucked-explanation"), "the prediction tuck is now universal");
+		assert.ok(!html.includes("Why:"), "no inline explanation — behind the toggle");
 	});
 
 	it("the reading-thinking channel is LIFTED above the card as its own user-side block", () => {

tests/render-md-blocks.test.tsx

@@ -14,6 +14,7 @@ import assert from "node:assert/strict";
 import { describe, it } from "node:test";
 import { renderToStaticMarkup } from "react-dom/server";
 import { MessageResponse } from "../components/ai-elements/message.tsx";
+import { ThinkingBlock, setAllUserThinkingOpen } from "@/components/thinking-block";
 import { MermaidOverlay, SessionMermaidContext, chartSize } from "../components/session-overlay.tsx";
 import { PlanPopup } from "../components/plan-block.tsx";
 import { MarkdownCode, codeSource } from "../components/md-blocks.tsx";
@@ -229,3 +230,43 @@ describe("parseAlertMarker (pure)", () => {
 		assert.equal(parseAlertMarker(em), null);
 	});
 });
+
+describe("md-blocks — the restored plain blockquote (owner round, 2026-10-07)", () => {
+	it("a plain quote carries Streamdown's own styling (the override displaced it)", () => {
+		const html = renderToStaticMarkup(
+			<MessageResponse mode="static">{"Before.\n\n> An ordinary quote.\n\nAfter."}</MessageResponse>,
+		);
+		assert.ok(html.includes("border-l-4"), "the left border is back");
+		assert.ok(html.includes("text-muted-foreground italic"), "muted italic — the quote register");
+		assert.ok(!html.includes("md-callout"), "a plain quote is not a callout box");
+	});
+});
+
+describe("ThinkingBlock — side-based authorship + ⌘T sync (owner round, 2026-10-07)", () => {
+	it("the default row stays left with the my-3 rhythm", () => {
+		const html = renderToStaticMarkup(<ThinkingBlock text="left side" />);
+		assert.ok(html.includes("border-l-2"), "left rail");
+		assert.ok(html.includes("my-3"), "the 12px rhythm (was my-1)");
+	});
+
+	it("mirrored rows hug the right edge, rail flipped, arriving open", () => {
+		const html = renderToStaticMarkup(<ThinkingBlock text="right side" mirror defaultOpen />);
+		assert.ok(html.includes('data-side="right"'));
+		assert.ok(html.includes("ml-auto"), "pushed to the right edge");
+		assert.ok(html.includes("border-r-2") && !html.includes("border-l-2"), "rail on the right");
+		assert.match(html, /aria-expanded="true"/);
+		assert.ok(html.includes("right side"), "text visible on arrival");
+	});
+
+	it("⌘T sets every row — explicit sets stomp individual state, late mounts honor the last set", () => {
+		setAllUserThinkingOpen(false);
+		const collapsed = renderToStaticMarkup(<ThinkingBlock text="synced" defaultOpen />);
+		assert.match(collapsed, /aria-expanded="false"/);
+		assert.ok(!collapsed.includes(">synced<"), "the open default was stomped");
+		setAllUserThinkingOpen(true);
+		const reopened = renderToStaticMarkup(<ThinkingBlock text="synced" />);
+		assert.match(reopened, /aria-expanded="true"/);
+		// restore the null default for other tests in this file
+		setAllUserThinkingOpen(true);
+	});
+});

tests/render-practice-surface.test.tsx

@@ -176,11 +176,15 @@ describe("the practice transcript cards", () => {
 		assert.doesNotMatch(html, /The solution/);
 	});
 
-	it("ThinkingCard: one label, collapsed arrival (legacy commit flags ignored)", () => {
+	it("ThinkingCard: one label, right side, expanded arrival (owner round, 2026-10-07)", () => {
 		const trace = renderToStaticMarkup(<ThinkingCard data={{ problemCallId: "c", commit: false, text: "stuck at step two" }} />);
 		assert.match(trace, /YOUR THINKING/);
-		assert.match(trace, /aria-expanded="false"/);
-		assert.ok(!trace.includes("stuck at step two"), "the text is one click away");
+		// Transcript rows arrive EXPANDED (clearly conveyed as sent) and
+		// MIRRORED right (side-based authorship).
+		assert.match(trace, /aria-expanded="true"/);
+		assert.ok(trace.includes("stuck at step two"), "the text is visible on arrival");
+		assert.ok(trace.includes('data-side="right"'), "mirrored to the right side");
+		assert.ok(trace.includes("border-r-2"), "the rail is on the right");
 		const legacy = renderToStaticMarkup(<ThinkingCard data={{ problemCallId: "c", commit: true, text: "It is 42." }} />);
 		assert.match(legacy, /YOUR THINKING/);
 		assert.doesNotMatch(legacy, /Your solution/);