feat(web): inline-expand summary + Q&A in the list (ADR-031, #16)

Click a summarized card → its full summary (summaryBody) + chat dock (chatReveal)
expand in place via HTMX (GET /v/{id}/expand → expandedCard), collapse back via
GET /v/{id}/card → compact VideoCard. Same <li id>, outerHTML swap — the existing
list-fragment pattern. The card title carries href=/v/{id} as the no-JS fallback
(detail page stays for no-JS + deep links); only summarized cards expand. Reuses
summaryBody + chatReveal so the expanded card never drifts from the detail page.

BDD: inline_expand.feature un-pended + mapped. TDD: 6 handler/fragment tests
(expand/collapse fragments, chat dock, summarized-only, no-JS href, shared body).
Minimal CSS only — the TUI/charm restyle is #17.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

DECISIONS.md

@@ -1219,6 +1219,54 @@ stops scraping; the app is unaffected. No schema change.
 
 ---
 
+## ADR-031 — SPA-like reader: inline-expand summary + Q&A in the list (HTMX, no framework)
+
+**Status:** Proposed (2026-06-12). Issue #16. **Draft for review — no code yet.**
+
+**Context / requirements.** The reader is multi-page: a list of compact cards (`/`), then a
+navigation to a separate detail page (`/v/{id}`) for the full summary + the docked chat (ADR-027).
+It feels less fluid than a single integrated view. We want the full summary AND the per-video
+Q&A to open **in place in the list**, no page hop. Requirements:
+- R1: clicking a summarized card expands it in place to the full summary (summary/highlights/
+  takeaways) + the chat dock; a collapse returns it to the compact card.
+- R2: **no SPA framework** — stay HTMX + Templ (ADR-003); reuse existing fragments, not a rewrite.
+- R3: **progressive enhancement** — with JS off, the card link still navigates to `/v/{id}`
+  (the detail page stays as the no-JS + deep-link surface). Nothing becomes JS-only.
+- R4: only **summarized** cards expand; pending/rate-limited/no-caption cards keep their current
+  footer behaviour (Summarize button, waiting/none states).
+- R5: chat inside an expanded card works exactly as on the detail page (reuse `chatReveal`/
+  `chatSection` + the existing `/v/{id}/chat` endpoints, unchanged).
+
+**Decision / architecture.**
+1. **Reuse the existing fragments.** `summaryBody(r)` and `chatReveal(videoID)` already exist and
+   render the detail page; a new `expandedCard(r, chatEnabled)` composes the compact header + a
+   collapse control + `summaryBody` + `chatReveal`. `DetailPage` is refactored to also compose
+   `summaryBody` so the two never drift (DRY).
+2. **Two fragment endpoints** (mirroring the existing list/status HTMX fragment pattern):
+   `GET /v/{videoId}/expand` → `expandedCard`; collapse reuses the existing compact `VideoCard`
+   via `GET /v/{videoId}/card`. Both are list-card `<li>` fragments with the SAME `id`
+   (`video-{id}`), swapped `outerHTML` — same mechanism as `processingCard`/`VideoCard` today.
+3. **The compact card's title/"Read" affordance** becomes `hx-get=/v/{id}/expand`,
+   `hx-target=#video-{id}`, `hx-swap=outerHTML`, with `href=/v/{id}` as the no-JS fallback (R3).
+   The expanded card's collapse control is the inverse (`hx-get=/v/{id}/card`).
+4. **Only when `r.Summarized`** does the expand affordance render (R4); the other states are
+   unchanged.
+5. **v1 does NOT push the URL** (`hx-push-url`) — expand/collapse is ephemeral list UI state; the
+   detail page remains the deep-link/shareable URL. Deep-linking the open state via `hx-push-url`
+   is noted as a later option (needs list-state restore on back).
+
+**Out of scope / later.** URL push / deep-linkable open state; the visual refresh (#17) — though
+the expanded-card markup is where #17's TUI/charm styling will land, so they pair.
+
+**Reversibility.** Additive: two fragment endpoints + one templ + an affordance swap on the
+compact card. Removing the affordance reverts to plain list→detail navigation; the detail page is
+untouched. No schema change.
+
+**Next steps (gated):** on approval → BDD (`docs/use-cases/inline_expand.feature` + coverage
+map) → TDD → implement → SemVer + docs.
+
+---
+
 ## Rejected alternatives
 
 Approaches considered during the 2026-06-02 planning + grill session and **deliberately not

docs/homelab-integration.md

@@ -227,6 +227,12 @@ knobs plus one load-bearing deployment constraint:
 - `TAPIR_USAGE_GATE_START` — `YYYY-MM-DD`, default **`2026-06-11`** (the morning the pilot was
   unblocked and summaries started flowing). `tapir report` counts return-usage (distinct active
   weeks, ADR-016) only from this date, so pre-launch testing and the blocked period are excluded.
+- `TAPIR_METRICS_ADDR` — listen address for the Prometheus `/metrics` endpoint (ADR-030).
+  **Default `:9090`** — a SEPARATE port from `TAPIR_HTTP_ADDR` so metrics are never on the public
+  app; scraped in-cluster only (PodMonitor). Empty disables the metrics server. Key series:
+  `tapir_summarize_duration_seconds{model,outcome,fallback}`, `tapir_caption_fetch_duration_seconds{outcome}`,
+  `tapir_chat_duration_seconds{model}`, `tapir_llm_tokens_total{model,kind}`,
+  `tapir_http_request_duration_seconds{method,route}`, `tapir_logins_total`.
 - `TAPIR_FETCH_RATE` — Go duration, default `2s`. The **process-wide per-egress-IP caption-fetch
   rate gate** (ADR-014 item 2). Every caption fetch — scheduler runners *and* the web "Summarize"
   click-path — serialises through this one limiter so the pod cannot collectively trip 429s. `0`

docs/use-cases/inline_expand.feature

@@ -0,0 +1,37 @@
+Feature: Inline-expand summary + Q&A in the list (ADR-031, #16)
+  As a reader skimming my summaries
+  I want to open a summary and its Q&A in place in the list
+  So that I get the full read and follow-up without leaving the list (SPA-like, no page hop)
+
+  # HTMX inline-expand, no SPA framework (ADR-031). Each scenario maps to a Go test
+  # in scenario_coverage_test.go (the BDD name-coverage gate).
+
+  Scenario: A summarized card expands to the full summary in place
+    Given a summarized video in my list
+    When I expand its card
+    Then the full summary, highlights, and takeaways are returned as an in-place card fragment, not a full page
+
+  Scenario: An expanded card collapses back to the compact card
+    Given an expanded card
+    When I collapse it
+    Then the compact card fragment is returned in its place
+
+  Scenario: The expanded card offers the Q&A dock
+    Given chat is enabled
+    When a summarized card is expanded
+    Then the expanded card includes the deeper-dive chat affordance for that video
+
+  Scenario: Only a summarized card offers expand
+    Given a discovered but not-yet-summarized card
+    When the card is rendered
+    Then it shows its summarize/queue footer and no expand affordance
+
+  Scenario: With JS off the card still reaches the full summary
+    Given a summarized card
+    When it is rendered
+    Then its expand affordance carries an href to the detail page as a no-JS fallback
+
+  Scenario: The detail page and the expanded card show the same summary
+    Given a summarized video
+    When I view it on the detail page and as an expanded card
+    Then both render the same summary body (one shared fragment, no drift)

internal/web/handlers.go

@@ -151,6 +151,8 @@ func (a *App) Router() http.Handler {
 	app := http.NewServeMux()
 	app.HandleFunc("GET /{$}", a.handleList)
 	app.HandleFunc("GET /v/{videoId}", a.handleDetail)
+	app.HandleFunc("GET /v/{videoId}/expand", a.handleExpand)
+	app.HandleFunc("GET /v/{videoId}/card", a.handleCard)
 	app.HandleFunc("POST /v/{videoId}/action", a.handleAction)
 	app.HandleFunc("POST /v/{videoId}/summarize", a.handleRequestSummarize)
 	app.HandleFunc("POST /v/{videoId}/retry-now", a.handleRetryNow)
@@ -283,6 +285,48 @@ func (a *App) handleDetail(w http.ResponseWriter, r *http.Request) {
 	a.render(w, r, DetailPage(*row, a.Chat != nil))
 }
 
+// handleExpand returns the inline-expanded card fragment — the full summary +
+// chat dock swapped into the list card in place (ADR-031). Only summarized videos
+// have a summary to expand; a non-summarized id is a 404 (the compact card never
+// offers expand for it).
+func (a *App) handleExpand(w http.ResponseWriter, r *http.Request) {
+	userID, ok := a.currentUserID(w, r)
+	if !ok {
+		return
+	}
+	videoID := r.PathValue("videoId")
+	row, err := a.Store.GetSummaryByVideo(r.Context(), userID, videoID)
+	if errors.Is(err, store.ErrNotFound) {
+		http.NotFound(w, r)
+		return
+	}
+	if err != nil {
+		a.serverError(w, r, "get summary", err)
+		return
+	}
+	a.render(w, r, expandedCard(*row, a.Chat != nil))
+}
+
+// handleCard returns the compact card fragment — the collapse target that returns
+// an expanded card to its compact form in the list (ADR-031).
+func (a *App) handleCard(w http.ResponseWriter, r *http.Request) {
+	userID, ok := a.currentUserID(w, r)
+	if !ok {
+		return
+	}
+	videoID := r.PathValue("videoId")
+	row, err := a.Store.GetVideoRow(r.Context(), userID, videoID)
+	if errors.Is(err, store.ErrNotFound) {
+		http.NotFound(w, r)
+		return
+	}
+	if err != nil {
+		a.serverError(w, r, "get video", err)
+		return
+	}
+	a.render(w, r, VideoCard(*row))
+}
+
 // handleAction toggles one action: re-clicking an active verb clears it, else it
 // is set (the store enforces watched↔skipped exclusion atomically). It returns
 // the refreshed button-group fragment for HTMX; without JS it redirects back to

internal/web/inline_expand_test.go

@@ -0,0 +1,107 @@
+package web_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestExpandReturnsSummaryBodyFragment: GET /v/{id}/expand returns the full
+// summary as an in-place card fragment (not a full page) — ADR-031.
+func TestExpandReturnsSummaryBodyFragment(t *testing.T) {
+	ctx := context.Background()
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "the full summary text"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	html := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/expand", nil)))
+	require.Contains(t, html, "the full summary text")
+	require.Contains(t, html, "Takeaways")
+	require.Contains(t, html, "highlight one")
+	require.Contains(t, html, "card-expanded", "rendered as the expanded card")
+	require.Contains(t, html, "/v/"+videoX+"/card", "carries a collapse affordance")
+	require.NotContains(t, html, "<html", "fragment, not a full page")
+}
+
+// TestCollapseReturnsCompactCard: GET /v/{id}/card returns the compact card with
+// the expand affordance — the collapse target.
+func TestCollapseReturnsCompactCard(t *testing.T) {
+	ctx := context.Background()
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary text"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	html := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/card", nil)))
+	require.Contains(t, html, `class="card"`, "compact card")
+	require.Contains(t, html, "/v/"+videoX+"/expand", "compact card offers expand")
+	require.NotContains(t, html, "card-expanded")
+	require.NotContains(t, html, "<html", "fragment, not a full page")
+}
+
+// TestExpandedCardOffersChatDock: with chat enabled, the expanded card includes
+// the deeper-dive chat affordance.
+func TestExpandedCardOffersChatDock(t *testing.T) {
+	ctx := context.Background()
+	app := newChatApp(t, &fakeChatter{models: []string{"m"}}, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary text"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	html := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/expand", nil)))
+	require.Contains(t, html, "/v/"+videoX+"/chat", "expanded card wires the chat dock")
+}
+
+// TestCompactCardExpandOnlyWhenSummarized: a not-yet-summarized card shows its
+// summarize footer and no expand affordance.
+func TestCompactCardExpandOnlyWhenSummarized(t *testing.T) {
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	seedVideo(t, p, videoX, "Pending Title", "https://x", time.Time{}) // no summary
+
+	html := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/card", nil)))
+	require.Contains(t, html, "Not summarized")
+	require.NotContains(t, html, "/v/"+videoX+"/expand", "pending card offers no expand")
+}
+
+// TestCompactCardHasNoJSDetailFallback: the expand affordance carries an href to
+// the detail page, so JS-off users still reach the full summary.
+func TestCompactCardHasNoJSDetailFallback(t *testing.T) {
+	ctx := context.Background()
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary text"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	html := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/card", nil)))
+	require.Contains(t, html, `href="/v/`+videoX+`"`, "no-JS fallback to the detail page")
+	require.Contains(t, html, "/v/"+videoX+"/expand", "and the HTMX expand for JS users")
+}
+
+// TestDetailAndExpandShareSummaryBody: the detail page and the expanded card render
+// the same summary body (one shared fragment, no drift).
+func TestDetailAndExpandShareSummaryBody(t *testing.T) {
+	ctx := context.Background()
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "shared summary text"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	detail := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX, nil)))
+	expand := body(t, do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/expand", nil)))
+	for _, want := range []string{"shared summary text", "Takeaways", "highlight one"} {
+		require.Contains(t, detail, want)
+		require.Contains(t, expand, want)
+	}
+}

internal/web/view.go

@@ -190,6 +190,18 @@ func chatURL(videoID string) templ.SafeURL {
 	return templ.SafeURL("/v/" + videoID + "/chat")
 }
 
+// expandURL builds the inline-expand fragment path (GET) — the full summary + chat
+// dock swapped into the list card in place (ADR-031).
+func expandURL(videoID string) templ.SafeURL {
+	return templ.SafeURL("/v/" + videoID + "/expand")
+}
+
+// cardURL builds the compact-card fragment path (GET) — the collapse target that
+// returns an expanded card to its compact form (ADR-031).
+func cardURL(videoID string) templ.SafeURL {
+	return templ.SafeURL("/v/" + videoID + "/card")
+}
+
 // Charmbracelet-inspired palette for the summarizing animation (TapirSpinner) —
 // a charm purple box, pink tapir, mint snout/eyes/progress. Kept as named consts
 // so the inline span colours and the CSS track/fill share one source of truth.
@@ -618,6 +630,10 @@ a.btn, a.btn:visited { color: var(--accent-fg); }
 .card-meta { color: var(--muted); font-size: .85rem; }
 .card-preview { color: var(--muted); font-size: .9rem; line-height: 1.5; display: -webkit-box; -webkit-line-clamp: 1; line-clamp: 1; -webkit-box-orient: vertical; overflow: hidden; }
 .card-foot { display: flex; gap: var(--s2); align-items: center; flex-wrap: wrap; margin-top: var(--s1); }
+/* Inline-expanded card (ADR-031). Minimal layout only — the TUI/charm restyle is #17. */
+.card-expanded { border-color: var(--accent, #7653fc); }
+.card-expanded-head { display: flex; justify-content: space-between; align-items: baseline; gap: var(--s2); }
+.card-collapse { font-size: .85rem; white-space: nowrap; }
 .chip { display: inline-block; padding: .15rem .55rem; border-radius: 999px; background: var(--accent-weak); color: var(--accent); font-size: .72rem; font-weight: 600; }
 /* passive "retrying later" chip: dim/grey (CharmDim), not the accent — it is a
    status, not an action the user can take. */

internal/web/views.templ

@@ -264,7 +264,16 @@ templ summaryList(b listBuckets, hasConnected bool, autoSummarize bool) {
 templ VideoCard(r store.SummaryRow) {
 	<li class={ "card", templ.KV("card-pending", !r.Summarized) } id={ "video-" + r.VideoID }>
 		if r.Summarized {
-			<div class="card-title"><a href={ videoURL(r.VideoID) }>{ displayTitle(r) }</a></div>
+			// Expand the full summary + Q&A in place (ADR-031); href is the no-JS
+			// fallback to the detail page, so nothing becomes JS-only.
+			<div class="card-title">
+				<a
+					href={ videoURL(r.VideoID) }
+					hx-get={ string(expandURL(r.VideoID)) }
+					hx-target={ "#video-" + r.VideoID }
+					hx-swap="outerHTML"
+				>{ displayTitle(r) }</a>
+			</div>
 		} else {
 			<div class="card-title">{ displayTitle(r) }</div>
 		}
@@ -327,6 +336,32 @@ templ VideoCard(r store.SummaryRow) {
 	</li>
 }
 
+// expandedCard is a summarized list card opened IN PLACE (ADR-031): the full
+// summary body + the deeper-dive chat dock, with a collapse control back to the
+// compact card. It shares the <li id> with VideoCard so HTMX swaps it outerHTML,
+// and reuses summaryBody + chatReveal so it never drifts from the detail page.
+// Note: chatReveal uses a single #chat-section id, so this assumes one card open
+// at a time; a per-video chat id is a follow-up if simultaneous expansion is wanted.
+templ expandedCard(r store.SummaryRow, chatEnabled bool) {
+	<li class="card card-expanded" id={ "video-" + r.VideoID }>
+		<div class="card-expanded-head">
+			<span class="card-title">{ displayTitle(r) }</span>
+			<a
+				href={ videoURL(r.VideoID) }
+				hx-get={ string(cardURL(r.VideoID)) }
+				hx-target={ "#video-" + r.VideoID }
+				hx-swap="outerHTML"
+				class="card-collapse"
+				title="Collapse"
+			>collapse ↑</a>
+		</div>
+		@summaryBody(r)
+		if chatEnabled {
+			@chatReveal(r.VideoID)
+		}
+	</li>
+}
+
 // TapirSpinner is the summarizing animation: a Charmbracelet-style TUI panel —
 // three richly coloured ASCII tapir frames (inline span colours, snout wiggling
 // ∩→∪→~) cross-faded by CSS, plus a lipgloss-style progress bar whose mint fill

test/acceptance/scenario_coverage_test.go

@@ -25,6 +25,14 @@ import (
 // fails if a scenario is unmapped, a mapped test is missing, or an entry no
 // longer matches a real non-pending scenario.
 var scenarioCoverage = map[string]string{
+	// inline_expand.feature (ADR-031, #16)
+	"A summarized card expands to the full summary in place":      "TestExpandReturnsSummaryBodyFragment",
+	"An expanded card collapses back to the compact card":         "TestCollapseReturnsCompactCard",
+	"The expanded card offers the Q&A dock":                       "TestExpandedCardOffersChatDock",
+	"Only a summarized card offers expand":                        "TestCompactCardExpandOnlyWhenSummarized",
+	"With JS off the card still reaches the full summary":         "TestCompactCardHasNoJSDetailFallback",
+	"The detail page and the expanded card show the same summary": "TestDetailAndExpandShareSummaryBody",
+
 	// observability.feature (ADR-030, #15)
 	"Summarization latency is recorded per endpoint":            "TestSummarizerRecordsMetric",
 	"A failing summarizer endpoint records its failure outcome": "TestObserveSummarizeRecordsFailureOutcomes",