refactor(web): dock chat inline below the summary, integrated view (ADR-027)

The chat was a separate page — opening it left the summary behind, the very
context you're asking about. Now the chat docks open IN PLACE below the summary:
"Dig deeper" reveals the chat section (HTMX, outerHTML over the closed dock) so
the summary stays on screen above it; no navigation. The no-JS fallback renders
the full summary AND the open chat on one page (the same integrated view), so
progressive enhancement holds.

Extracts a shared summaryBody templ so the detail page and the chat page render
one identical summary, not two divergent ones. GET /v/{id}/chat returns just the
open chat section as a fragment for the inline reveal, or the full summary+chat
page for a no-JS navigation; POST swaps the panel inline or re-renders the whole
page. Tests assert summary+chat coexist on the page and the reveal is a fragment.

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

DECISIONS.md

@@ -827,10 +827,18 @@ The fix is resilience around it, not replacing it.
 **Decision.**
 1. **Ordered endpoint chain (`summarizer.NewChain`).** Endpoints are tried in order; the first to
    return a *parseable* summary wins. Default chain:
-   `koala/phi4-mini` (primary, local) → `koala/phi4-14b` (fallback, local) →
+   `koala/phi4-mini` (primary, local) → `iguana/gemma4-26b` (fallback, local on a
-   `berget/mistral-small` (worst-case, external). All three are reached through the **one** LiteLLM
+   *different host*) → `berget/mistral-small` (worst-case, external). All three are reached through
-   gateway by alias — the gateway already fronts both llama-swap and berget — so a fallback is a
+   the **one** LiteLLM gateway by alias — the gateway already fronts both llama-swap and berget — so
-   different alias, not a second client config.
+   a fallback is a different alias, not a second client config.
+
+   **Update 2026-06-11:** the local fallback moved from `koala/phi4-14b` to `iguana/gemma4-26b`.
+   koala now carries other GPU loads, so keeping the fallback on koala competed with them; iguana
+   (M2 Ultra) has the headroom, and a different host is also a different egress IP for the rare
+   fallback fetch. `gemma4-26b` is the brain-validated homelab general-purpose model (agentsquad
+   H2/H3 executor) and returned valid summary JSON on the real prompt in a smoke test
+   (~37s incl. cold-load — fine for a path hit only when the fast primary fails). Pure config:
+   `TAPIR_FALLBACK_MODEL`.
 2. **A parse failure advances the chain, same as a transport error.** "Reliably summarized" means
    *parseable summary returned*, not *HTTP 200*. This is the behaviour the old Primary→Fallback
    shape missed.
@@ -855,6 +863,203 @@ reply still parses; a transcript within budget is unchanged).
 
 ---
 
+## ADR-023 — Drop Shorts/livestreams at discovery to protect the caption budget
+
+**Status:** Accepted (2026-06-10). **Builds on ADR-014** (per-IP caption rate limit is the
+binding constraint) and the ADR-022 live-run findings.
+
+**Context.** The scarce resource is the unofficial timedtext caption fetch (per-egress-IP
+429, ~3 successful/pass). The first multi-user run showed the candidate set was mostly noise —
+Shorts, sub-minute clips, and live broadcasts — each of which still consumes a caption-fetch
+attempt (and a "none" result is a *completed* fetch, so it costs budget even when it yields
+nothing). Spending the rate-limited budget on content the user will not read is the waste to
+cut first; it is cheaper and lower-risk than raising the ceiling (multi-IP, Whisper).
+
+Duration and live status are NOT in the playlistItems discovery response, but they ARE in the
+Data API `videos.list` (contentDetails.duration + snippet.liveBroadcastContent) — the official
+**quota-based** API (1 unit/call, 50 ids/call), which is a *different* limit from the timedtext
+429. So one cheap quota call buys a filter that saves many expensive throttled fetches.
+
+**Decision.**
+1. `NewVideos` enriches its candidates with a single `videos.list` call and drops, before
+   returning: videos shorter than `TAPIR_MIN_VIDEO_SECONDS` (default 60) and any `live`/
+   `upcoming` broadcast. Dropped videos are never persisted, so they also declutter the list.
+2. The filter is **degrade-open**: `MinVideoSeconds=0` disables it (no quota call), and a
+   `videos.list` error returns the candidates unfiltered — discovery must never break because a
+   metadata call hiccuped (worst case = pre-ADR-023 behaviour).
+3. The paste-a-URL path (`VideoByID`) is **not** filtered — an explicit user request for a
+   specific video (even a Short) is honoured.
+
+**Reversibility.** Pure discovery-time filter + config. `TAPIR_MIN_VIDEO_SECONDS=0` restores
+the old behaviour. No schema change, no effect on already-stored videos.
+
+**Quota note.** Per-channel enrichment adds ~1 unit/channel/pass. At pilot scale (≤3 users)
+this is well under the 10k/day cap; at larger scale, batch `videos.list` across channels
+(50 ids/call) by collecting all discovered ids per pass before enriching.
+
+---
+
+## ADR-024 — Per-channel caption-availability memory
+
+**Status:** Accepted (2026-06-10). **Builds on ADR-014** (per-IP caption budget), **ADR-021**
+(shared transcript cache), **ADR-023** (Shorts filter).
+
+**Context.** After ADR-021 caches transcripts and ADR-023 drops Shorts, the remaining caption
+waste is the *first* fetch on every new video of a channel that never publishes English captions
+(foreign-language news, music, etc.). Each costs one rate-limited fetch to resolve to "none" —
+and on a throttled IP that fetch may 429 and churn the backoff machinery before it ever gets a
+verdict. A pilot user's feed had several such channels.
+
+**Decision.** Remember, per `(user, channel)`, a streak of consecutive no-caption outcomes
+(`channel_caption_state`, migration 016, RLS-scoped like the rest of the user-owned schema).
+Once the streak reaches `TAPIR_CHANNEL_CAPTIONLESS_THRESHOLD` (default 5) the channel is
+suppressed — its videos are discovered/listed but not caption-fetched — for
+`TAPIR_CHANNEL_CAPTIONLESS_WINDOW` (default 14d), after which one video is re-probed
+(auto-recovery for a channel that starts adding captions). A successful fetch resets the streak;
+a fresh 429 does NOT count (transient, not a caption verdict). An explicit manual request
+bypasses suppression. `threshold = 0` disables the feature.
+
+**Why per-user, not global.** Caption availability is really a channel property (public), so a
+global table would let users share the learning. But subscriptions are per-user (ADR-012) and at
+pilot scale users' channel sets barely overlap, so per-user + RLS keeps it consistent with the
+existing isolation model with no new non-RLS exception to justify. Promoting to a shared table
+(like transcripts, ADR-021) is a future optimisation if channel overlap grows.
+
+**Reversibility.** Migration 016 is a clean drop; `threshold = 0` disables at runtime. The
+memory only ever *suppresses fetches* — it never deletes content or affects already-stored
+summaries.
+
+---
+
+## ADR-025 — Honest, state-aware foreground summarization status
+
+**Status:** Accepted (2026-06-10). **Pillar B of the manual-mode UX work** (Pillar A, foreground
+fetch priority, is a separate follow-up). Builds on ADR-014 (the rate limit the UX must make
+legible).
+
+**Context.** Clicking "Summarize" spawned a background goroutine and polled `/status`, which
+returned only two states: the spinner (in-flight) or the normal card (done). But the web
+`ProcessVideo` only recorded an outcome on *success* — a 429'd or caption-less click left
+`transcript_status` unset, so the next poll silently reverted to the "Summarize" button. The
+user saw either an endless spinner or a button that did nothing useful when clicked again. The
+binding constraint (YouTube's caption rate limit) was completely invisible.
+
+**Decision.**
+1. **Record every outcome on the web path**, mirroring the runner: `ProcessVideo` stamps
+   `rate_limited` / `none` / `fetched`. A rate-limited video keeps its requested flag so the
+   background sweep retries it; `none` and `fetched` are terminal.
+2. **`/status` is state-aware**: summarized → summary card; in-flight → working spinner;
+   `rate_limited` → a calm "waiting, will retry" card that keeps polling (every 30s) so the
+   summary appears on its own when the retry lands — the user never clicks again;
+   `none` → a terminal "no captions" card with no poll and no dead-end button.
+3. **Charm status text** (Claude-Code / Crush inspired): the working spinner cycles playful,
+   tapir-themed gerunds ("Chewing the cud…", "Munching leaves…", "Distilling the gist…") via
+   CSS only — no JS, keeping the HTMX/no-JS ethos. Decorative (aria-hidden) with a stable
+   `role=status` line for assistive tech.
+
+**Principle.** When the system cannot be fast (throttled IP), it is at least honest, and it
+self-resolves without making the user retry. Honesty is the load-bearing half — Pillar A's
+priority lane only improves the odds of a fast slot; it cannot beat an already-hot IP.
+
+**Reversibility.** Pure transport-layer + view change over the unchanged engine/ports. No
+schema change (reuses `transcript_status` from migration 007).
+
+---
+
+## ADR-026 — Foreground caption fetches take priority; the credentials probe is dead
+
+**Status:** Accepted (2026-06-10). **Pillar A of the manual-mode UX work** (Pillar B was
+ADR-025). Builds on ADR-014 (the shared per-IP gate).
+
+**Context.** Every caption fetch — the background sweep and the web click-path — shared one
+process-wide rate gate equally. So a user waiting on a "Summarize" click competed with the
+firehose for both pacing and the scarce pre-429 window; on a busy IP the click was slow or
+429'd while the background churned.
+
+**Decision.** A context-marked priority lane. The web path
+(`engineProcessor.ProcessVideo`) wraps its context with `ForegroundContext`; the gate gives
+foreground fetches a token immediately, while **background fetches yield** — they wait until no
+foreground fetch is pending before taking a token. Threaded via a context value (not new
+signatures) and a process-wide `foregroundPending` counter. Clicks are rare and bursty, so the
+background barely loses throughput; the waiting human gets the next (and cleanest) slot.
+
+**Credentials probe — rejected, not built.** The idea was to fetch captions with the user's
+auth in manual mode to dodge 429s. It is a dead end, already settled by ADR-010 and the code:
+the caption path is *deliberately anonymous* because the InnerTube/timedtext endpoints **reject
+or break on authenticated requests** (`captions.go`: "no OAuth token — it can break the
+timedtext endpoint"). The user's OAuth (a Data API credential) does not authenticate InnerTube
+at all, and the official `captions.download` is owner-only (403 on third-party). So auth cannot
+help here and can actively hurt. No probe needed — building one would only re-confirm the ADR.
+
+**Reversibility.** Context-marker + a yield loop in the gate; removing the marker collapses to
+the prior equal-share behaviour. No schema or API change.
+
+---
+
+## ADR-027 — Chat with a video's stored transcript (deeper-dive, on an already-summarized video)
+
+**Status:** Accepted (2026-06-11). **Consumes ADR-021** (the shared, video-keyed transcript
+store) for the first time beyond summarization; **uses the ADR-022 chain models**; relates to
+ADR-012 (isolation) and ADR-016 (the Stage-0 gate).
+
+**Context — observed demand, not hypothetical.** The maintainer read 10+ real pilot summaries
+and reported the reactions: *many good; some he wanted to dig deeper into; some less useful*
+(the "less useful" split between weak-*model* output and uninteresting-*video* content). The
+middle reaction is the signal: a good summary that makes the reader want *more* is the summary
+succeeding at triage and then hitting a wall — there is nowhere to go deeper short of watching
+the video. That want is the feature. It is also the cheapest possible feature to satisfy
+honestly, because ADR-021 already persists the transcript: the deeper-dive runs entirely on
+stored public-content text + local models, touching **no** caption fetch and **no** YouTube.
+
+**Decision.** Add a per-video chat that lets the user ask questions against a video's stored
+transcript.
+1. **Entry from the summary view only.** A "dig deeper / ask" affordance on a summarized video —
+   the chat lives exactly where the "I want more" reaction happens. No standalone chat surface.
+2. **Stored-transcript-only (load-bearing constraint).** Chat is available **only** for videos
+   that already have a stored transcript. It never triggers a caption fetch, so it cannot touch
+   the rate gate, the 429 surface, or YouTube at all — the entire account-safety constraint that
+   governs the rest of Tapir is satisfied *by construction* here, not by careful gating. (Entry
+   being "from a summary" guarantees the transcript exists.) On-demand fetch for un-stored videos
+   is explicitly deferred.
+3. **Model = the summary's model by default; user-switchable among the ADR-022 chain models**
+   (`phi4-mini` / `gemma4-26b` / `mistral-small` to start). This is deliberate: it doubles as
+   live model-comparison instrumentation — ask the same question of the same transcript under two
+   models and the difference is directly felt. This is the mechanism by which the maintainer
+   learns *which* model is worth defaulting to, and it is the multi-model-analysis direction
+   ADR-021 anticipated, arriving as a user-facing capability.
+   - Chat is a **read-bounded retrieval/QA task** (the user supplies the focus), which is
+     *easier* than summarization (the model must decide what matters). So a model that summarizes
+     mediocrely may chat well — chat is plausibly a partial remedy for the weak-summary case, not
+     an inheritor of it.
+4. **Ephemeral chat (v1).** No persisted history; chat is per-session. Persisting per-user,
+   RLS-scoped history is deferred until there is evidence anyone wants to revisit a conversation.
+5. **Chat-only, trust-the-model (v1) — with a recorded limitation.** The chat does not expose the
+   raw transcript for verification in v1 (kept simple). **Known limitation:** because some
+   summaries were weak-model output, the user has reason not to fully trust a chat answer's
+   fidelity to the transcript, and v1 gives no in-UI way to check. The model-switcher partially
+   compensates (two models disagreeing on the same question is itself a signal). A
+   "show source / view transcript" verification path is the natural **v2** and is *not*
+   foreclosed — ADR-021's stored transcript already makes it cheap. Recorded so v2 is a known
+   next step, not a rediscovery.
+
+**Why this is safe and in-scope.** It adds no caption-fetch surface (stored-only), no new
+non-RLS table (transcripts already shared per ADR-021; ephemeral chat stores nothing), and no
+auth change. It is additive to the read path. The one genuine product expansion — Tapir becomes
+an interactive transcript-QA tool, not only a summarizer — is justified by *observed* demand from
+real reading, which is exactly the kind of evidence the Stage-0 discipline asks for before
+building.
+
+**Relation to the Stage-0 gate.** This is **not** a return-nudge (those stay deferred, ADR-020) —
+it adds nothing that prompts the user to return; it deepens the value *once they are already
+reading*. It does not contaminate the unprompted-return signal. If anything it strengthens the
+"useful to me" case the gate measures, by giving a good summary somewhere to lead.
+
+**Reversibility.** Additive read-path feature over the unchanged engine + the ADR-021 store.
+Removing the summary-view affordance removes the feature; nothing else depends on it. Ephemeral =
+no migration, no stored state to unwind. Spec: `docs/specs/chat-with-transcript.md`.
+
+---
+
 ## Rejected alternatives
 
 Approaches considered during the 2026-06-02 planning + grill session and **deliberately not

cmd/tapir/chat_test.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"gitea.d-ma.be/mathias/tapir/internal/config"
+)
+
+// TestChatModelsReuseTheChainLocalFirst: the switcher offers the ADR-022 chain in
+// order, deduped — primary, local fallback, cloud.
+func TestChatModelsReuseTheChainLocalFirst(t *testing.T) {
+	got := chatModels(config.Config{
+		SummarizerModel:    "koala/phi4-mini",
+		FallbackModel:      "iguana/gemma4-26b",
+		CloudFallbackModel: "berget/mistral-small",
+	})
+	want := []string{"koala/phi4-mini", "iguana/gemma4-26b", "berget/mistral-small"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Fatalf("chatModels = %v, want %v", got, want)
+	}
+}
+
+// TestChatCloudModelAbsentWhenDisabled: the local-first / NDA lever — with the
+// cloud fallback empty (TAPIR_CLOUD_FALLBACK_MODEL=""), no external model is
+// offered in the switcher, so chat content never leaves the local stack (ADR-027,
+// honouring ADR-022's "content stays local" guarantee).
+func TestChatCloudModelAbsentWhenDisabled(t *testing.T) {
+	got := chatModels(config.Config{
+		SummarizerModel:    "koala/phi4-mini",
+		FallbackModel:      "iguana/gemma4-26b",
+		CloudFallbackModel: "",
+	})
+	for _, m := range got {
+		if strings.HasPrefix(m, "berget/") || strings.Contains(m, "mistral") {
+			t.Fatalf("cloud model %q offered though the cloud fallback is disabled", m)
+		}
+	}
+	want := []string{"koala/phi4-mini", "iguana/gemma4-26b"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Fatalf("chatModels = %v, want %v", got, want)
+	}
+}
+
+// TestChatModelsDedup: a config that reuses one alias across slots collapses to a
+// single switcher entry (no duplicate options).
+func TestChatModelsDedup(t *testing.T) {
+	got := chatModels(config.Config{
+		SummarizerModel:    "koala/phi4-mini",
+		FallbackModel:      "koala/phi4-mini",
+		CloudFallbackModel: "",
+	})
+	if len(got) != 1 || got[0] != "koala/phi4-mini" {
+		t.Fatalf("chatModels = %v, want a single deduped entry", got)
+	}
+}
+
+// TestBuildChatNilWithoutGateway: no gateway → no chat backend (routes unmounted,
+// read path unaffected).
+func TestBuildChatNilWithoutGateway(t *testing.T) {
+	if c := buildChat(config.Config{GatewayURL: ""}); c != nil {
+		t.Fatal("buildChat must return nil without a gateway URL")
+	}
+}

cmd/tapir/main.go

@@ -136,7 +136,8 @@ func cmdRun(ctx context.Context, log *slog.Logger) error {
 
 	r := runner.New(engine.Source, st, engine, cfg.UserID, log,
 		runner.WithBackoff(cfg.FetchBackoff),
-		runner.WithAutoWindow(cfg.AutoSummarizeWindow))
+		runner.WithAutoWindow(cfg.AutoSummarizeWindow),
+		runner.WithCaptionMemory(cfg.ChannelCaptionlessThreshold, cfg.ChannelCaptionlessWindow))
 
 	log.Info("starting run", "user", cfg.UserID, "model", cfg.SummarizerModel,
 		"gateway", cfg.GatewayURL, "poll_interval", cfg.PollInterval, "fetch_backoff", cfg.FetchBackoff,
@@ -196,6 +197,15 @@ func cmdServe(ctx context.Context, log *slog.Logger) error {
 	secretStore := secrets.NewFileStore(cfg.SecretsFile)
 	app := &web.App{Store: st, Identity: st, Auth: authn, Secrets: secretStore, Log: log, RecencyWindow: cfg.AutoSummarizeWindow}
 
+	// Per-video deeper-dive chat over the STORED transcript (ADR-027). Enabled
+	// whenever a gateway is configured — it needs no YouTube credentials because it
+	// never fetches. Guarded so a typed-nil never lands in the interface field
+	// (which would mount the routes over a nil backend).
+	if c := buildChat(cfg); c != nil {
+		app.Chat = c
+		log.Info("web chat enabled (stored-transcript only)", "models", chatModels(cfg))
+	}
+
 	// User onboarding is handled by the IdP (Authentik invite flow), not Tapir —
 	// the Dex local-password provisioning path was removed (ADR-019). An
 	// authenticated subject with no Tapir user is routed to /register.

cmd/tapir/processor.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"strings"
 
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/chat"
 	"gitea.d-ma.be/mathias/tapir/internal/adapters/llm"
 	"gitea.d-ma.be/mathias/tapir/internal/adapters/secrets"
 	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
@@ -68,6 +69,49 @@ func buildSummarizer(cfg config.Config) *summarizer.Summarizer {
 	return summarizer.NewChain(eps, cfg.MaxTranscriptChars)
 }
 
+// chatModels is the ordered, local-first set of models offered in the chat
+// switcher (ADR-027), reusing the ADR-022 chain: primary → local fallback →
+// cloud. Empty entries are dropped and duplicates collapsed, so a client/NDA
+// deployment that sets the cloud fallback empty simply has no external model in
+// the switcher — the same local-first lever the summarizer honours.
+func chatModels(cfg config.Config) []string {
+	var models []string
+	add := func(m string) {
+		if m == "" {
+			return
+		}
+		for _, e := range models {
+			if e == m {
+				return
+			}
+		}
+		models = append(models, m)
+	}
+	add(cfg.SummarizerModel)
+	add(cfg.FallbackModel)
+	add(cfg.CloudFallbackModel)
+	return models
+}
+
+// buildChat wires the per-video chat service (ADR-027): a Completer factory over
+// the SAME LiteLLM gateway the summarizer uses (a different alias per model, not a
+// second client config) and the same transcript-truncation budget. It returns nil
+// when no gateway is configured — chat is simply not mounted, the read path is
+// unaffected. It deliberately takes NO YouTube source: chat is stored-only.
+func buildChat(cfg config.Config) *chat.Service {
+	if cfg.GatewayURL == "" {
+		return nil
+	}
+	models := chatModels(cfg)
+	if len(models) == 0 {
+		return nil
+	}
+	newClient := func(model string) chat.Completer {
+		return llm.New(cfg.GatewayURL, cfg.GatewayKey, model, cfg.SummarizerTimeout, llm.WithMaxTokens(cfg.SummaryMaxTokens))
+	}
+	return chat.New(newClient, models, cfg.MaxTranscriptChars)
+}
+
 // providerOf maps a model alias to the domain AIProvider recorded on summaries.
 // A "berget/" alias is an external provider; everything else is the local stack.
 func providerOf(model string) string {
@@ -88,6 +132,7 @@ func buildProcessor(cfg config.Config, st *store.Store) (*usecase.Engine, error)
 		ClientSecret:       cfg.YTClientSecret,
 		TokenSecretRef:     cfg.YTTokenRef,
 		PreferredLanguages: []string{"en"},
+		MinVideoSeconds:    cfg.MinVideoSeconds,
 	}, secretStore)
 
 	sum := buildSummarizer(cfg)
@@ -112,6 +157,11 @@ type engineProcessor struct {
 }
 
 func (p *engineProcessor) ProcessVideo(ctx context.Context, userID, videoID string) error {
+	// This is the user-initiated (foreground) path — a click on "Summarize",
+	// "Try now", or a pasted URL. Mark the context so the caption gate gives it
+	// priority over the background sweep (ADR-026, Pillar A).
+	ctx = youtube.ForegroundContext(ctx)
+
 	row, err := p.store.GetVideoRow(ctx, userID, videoID)
 	if err != nil {
 		return fmt.Errorf("load video %q: %w", videoID, err)
@@ -131,7 +181,28 @@ func (p *engineProcessor) ProcessVideo(ctx context.Context, userID, videoID stri
 	if err != nil {
 		return fmt.Errorf("process video %q: %w", videoID, err)
 	}
-	if res.Summary != nil {
+
+	// Record the outcome so the status endpoint can show honest state (ADR-025):
+	// a 429'd or caption-less click used to leave transcript_status unset, so the
+	// poll silently reverted to the "Summarize" button. Mirror the runner: stamp
+	// rate_limited / none / fetched. A rate-limited video keeps its requested flag
+	// so the background sweep retries it; none and fetched are terminal here.
+	switch {
+	case res.Skipped && res.TranscriptSource == string(domain.SourceRateLimited):
+		if err := p.store.SetTranscriptStatus(ctx, userID, videoID, "rate_limited"); err != nil {
+			return fmt.Errorf("set rate_limited status %q: %w", videoID, err)
+		}
+	case res.Skipped:
+		if err := p.store.SetTranscriptStatus(ctx, userID, videoID, "none"); err != nil {
+			return fmt.Errorf("set none status %q: %w", videoID, err)
+		}
+		if err := p.store.ClearSummarizeRequested(ctx, userID, videoID); err != nil {
+			return fmt.Errorf("clear summarize flag %q: %w", videoID, err)
+		}
+	case res.Summary != nil:
+		if err := p.store.SetTranscriptStatus(ctx, userID, videoID, "fetched"); err != nil {
+			return fmt.Errorf("set fetched status %q: %w", videoID, err)
+		}
 		if err := p.store.ClearSummarizeRequested(ctx, userID, videoID); err != nil {
 			return fmt.Errorf("clear summarize flag %q: %w", videoID, err)
 		}

cmd/tapir/scheduler.go

@@ -33,13 +33,20 @@ func buildUserRunner(cfg config.Config, st *store.Store, secretStore ports.Secre
 		ClientSecret:       cfg.YTClientSecret,
 		TokenSecretRef:     web.YouTubeTokenRef(userID),
 		PreferredLanguages: []string{"en"},
+		MinVideoSeconds:    cfg.MinVideoSeconds,
 	}, secretStore)
 
 	engine := usecase.NewEngine(src, buildSummarizer(cfg), st)
+	// Share the transcript cache (ADR-021) on the scheduler path too — without
+	// this every scheduled pass re-fetches transcripts it already had, burning the
+	// scarce per-IP caption budget (ADR-014) and starving other users. The web
+	// "Summarize now" path already sets this; the scheduler omitting it was a bug.
+	engine.Transcripts = st
 
 	return runner.New(src, st, engine, userID, log,
 		runner.WithBackoff(cfg.FetchBackoff),
-		runner.WithAutoWindow(cfg.AutoSummarizeWindow)), nil
+		runner.WithAutoWindow(cfg.AutoSummarizeWindow),
+		runner.WithCaptionMemory(cfg.ChannelCaptionlessThreshold, cfg.ChannelCaptionlessWindow)), nil
 }
 
 // userLister enumerates every registered user and reports a user's video
@@ -57,6 +64,7 @@ type userLister interface {
 // isolation). Returns the stats summed across users.
 func runDiscoveryPass(
 	ctx context.Context,
+	pass int,
 	lister userLister,
 	runUser func(context.Context, string) (runner.Stats, error),
 	log *slog.Logger,
@@ -67,15 +75,17 @@ func runDiscoveryPass(
 		return runner.Stats{}
 	}
 
-	log.Info("scheduler: starting discovery pass", "users", len(users))
+	// Keep only users with a video connection. A pass for a connectionless user
-	var total runner.Stats
+	// (e.g. a stale Dex-era orphan identity) only tries to resolve a token that
+	// was never minted, logging a spurious "ref not found" every tick. Filtering
+	// here — BEFORE rotation — also keeps fairness honest: rotation is over the
+	// users that actually consume the caption budget, so a dead identity can't eat
+	// a rotation slot and skew the lead share.
+	var connected []store.UserIdentity
 	for _, u := range users {
 		if ctx.Err() != nil {
-			break // shutting down: stop enumerating
+			return runner.Stats{} // shutting down
 		}
-		// Skip users with no video connection. A discovery pass for them only
-		// attempts to resolve a token that was never minted, logging a spurious
-		// "ref not found" every tick (e.g. stale Dex-era orphan identities).
 		conns, err := lister.ConnectionsForUser(ctx, u.UserID)
 		if err != nil {
 			log.Warn("scheduler: list connections failed", "user", u.UserID, "err", err)
@@ -85,6 +95,22 @@ func runDiscoveryPass(
 			log.Debug("scheduler: skipping user with no video connections", "user", u.UserID)
 			continue
 		}
+		connected = append(connected, u)
+	}
+
+	// Rotate who goes first each pass. Caption fetches share one per-egress-IP
+	// rate budget (ADR-014); whoever runs first each pass spends the pre-throttle
+	// window, so a FIXED order permanently starves whoever is last (a new pilot
+	// user got 0 fetches for 12h while the first-listed user got all of them).
+	// Rotation over the connected set gives each real user the lead in turn.
+	connected = rotateUsers(connected, pass)
+
+	log.Info("scheduler: starting discovery pass", "users", len(connected))
+	var total runner.Stats
+	for _, u := range connected {
+		if ctx.Err() != nil {
+			break // shutting down: stop enumerating
+		}
 		stats, err := runUser(ctx, u.UserID)
 		total = sumStats(total, stats)
 		if err != nil {
@@ -96,6 +122,7 @@ func runDiscoveryPass(
 		"skipped_seen", total.SkippedSeen, "skipped_no_text", total.SkippedNoText,
 		"skipped_manual", total.SkippedManual, "skipped_too_old", total.SkippedTooOld,
 		"skipped_rate_limited", total.SkippedRateLimited,
+		"skipped_no_caption_channel", total.SkippedNoCaptionChannel,
 		"channel_unavailable", total.ChannelUnavailable, "errors", total.Errors)
 	return total
 }
@@ -116,7 +143,18 @@ func runScheduler(
 		return // disabled
 	}
 
-	runDiscoveryPass(ctx, lister, runUser, log)
+	// Derive the rotation offset from wall-clock, NOT an in-memory counter. A
+	// counter reset to 0 on every pod restart always hands the lead to the
+	// first-listed user — so frequent deploys re-starve whoever is last (exactly
+	// what happened to the first pilot user during a deploy-heavy session). A
+	// time-based offset advances with real time and is identical across restarts,
+	// so the lead rotates fairly regardless of how often the pod bounces.
+	runPass := func() {
+		pass := int(time.Now().Unix() / int64(interval/time.Second))
+		runDiscoveryPass(ctx, pass, lister, runUser, log)
+	}
+
+	runPass()
 
 	ticker := time.NewTicker(interval)
 	defer ticker.Stop()
@@ -125,11 +163,31 @@ func runScheduler(
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			runDiscoveryPass(ctx, lister, runUser, log)
+			runPass()
 		}
 	}
 }
 
+// rotateUsers left-rotates users by pass positions so a different user leads each
+// pass. With n users, user i leads on every pass where pass ≡ i (mod n). A pass
+// offset that is negative or exceeds n is normalised. Order within the rotation
+// is otherwise preserved, so the set of users run is unchanged — only who is
+// first (and thus wins the scarce caption-fetch budget) rotates.
+func rotateUsers(users []store.UserIdentity, pass int) []store.UserIdentity {
+	n := len(users)
+	if n <= 1 {
+		return users
+	}
+	off := ((pass % n) + n) % n
+	if off == 0 {
+		return users
+	}
+	out := make([]store.UserIdentity, 0, n)
+	out = append(out, users[off:]...)
+	out = append(out, users[:off]...)
+	return out
+}
+
 // sumStats adds two passes' stats field-wise, so runDiscoveryPass can report a
 // per-tick aggregate across all users.
 func sumStats(a, b runner.Stats) runner.Stats {
@@ -141,6 +199,7 @@ func sumStats(a, b runner.Stats) runner.Stats {
 		SkippedManual:           a.SkippedManual + b.SkippedManual,
 		SkippedTooOld:           a.SkippedTooOld + b.SkippedTooOld,
 		SkippedRateLimited:      a.SkippedRateLimited + b.SkippedRateLimited,
+		SkippedNoCaptionChannel: a.SkippedNoCaptionChannel + b.SkippedNoCaptionChannel,
 		ChannelUnavailable:      a.ChannelUnavailable + b.ChannelUnavailable,
 		Errors:                  a.Errors + b.Errors,
 	}

cmd/tapir/scheduler_test.go

@@ -45,6 +45,7 @@ func (f fakeLister) ConnectionsForUser(_ context.Context, userID string) ([]stor
 type countingRunUser struct {
 	mu      sync.Mutex
 	calls   map[string]int
+	order   []string // userIDs in the order they were run, across all passes
 	failFor map[string]bool
 }
 
@@ -60,12 +61,19 @@ func (c *countingRunUser) run(_ context.Context, userID string) (runner.Stats, e
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	c.calls[userID]++
+	c.order = append(c.order, userID)
 	if c.failFor[userID] {
 		return runner.Stats{Errors: 1}, errors.New("boom")
 	}
 	return runner.Stats{Summarized: 1}, nil
 }
 
+func (c *countingRunUser) runOrder() []string {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return append([]string(nil), c.order...)
+}
+
 func (c *countingRunUser) count(userID string) int {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -94,7 +102,7 @@ func TestDiscoveryPassRunsEveryUserOnce(t *testing.T) {
 	lister := fakeLister{users: usersN("a", "b", "c")}
 	rc := newCountingRunUser()
 
-	stats := runDiscoveryPass(context.Background(), lister, rc.run, quietLog())
+	stats := runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
 
 	require.Equal(t, 1, rc.count("a"))
 	require.Equal(t, 1, rc.count("b"))
@@ -102,13 +110,46 @@ func TestDiscoveryPassRunsEveryUserOnce(t *testing.T) {
 	require.Equal(t, 3, stats.Summarized, "stats are summed across users")
 }
 
+// Caption fetches share one per-IP budget; a fixed user order starves whoever is
+// last. Each pass must rotate which user leads so the lead slot is shared.
+func TestDiscoveryPassRotatesLeadUser(t *testing.T) {
+	lister := fakeLister{users: usersN("a", "b", "c")}
+	rc := newCountingRunUser()
+
+	runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
+	runDiscoveryPass(context.Background(), 1, lister, rc.run, quietLog())
+	runDiscoveryPass(context.Background(), 2, lister, rc.run, quietLog())
+
+	require.Equal(t, []string{"a", "b", "c", "b", "c", "a", "c", "a", "b"}, rc.runOrder(),
+		"each pass left-rotates the user order so every user leads in turn")
+	// Fairness: over a full rotation cycle every user ran the same number of times.
+	require.Equal(t, 3, rc.count("a"))
+	require.Equal(t, 3, rc.count("b"))
+	require.Equal(t, 3, rc.count("c"))
+}
+
+// A connectionless orphan must not consume a rotation slot: rotation is over the
+// connected users only, so two real users alternate the lead 50/50 even with a
+// dead identity listed between them.
+func TestDiscoveryPassRotationIgnoresConnectionlessUsers(t *testing.T) {
+	lister := fakeLister{users: usersN("a", "orphan", "c"), noConn: map[string]bool{"orphan": true}}
+	rc := newCountingRunUser()
+
+	runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
+	runDiscoveryPass(context.Background(), 1, lister, rc.run, quietLog())
+
+	require.Equal(t, []string{"a", "c", "c", "a"}, rc.runOrder(),
+		"only connected users rotate; the orphan never runs and never holds a slot")
+	require.Equal(t, 0, rc.count("orphan"))
+}
+
 func TestDiscoveryPassSkipsUsersWithoutConnections(t *testing.T) {
 	// b never connected a video source (e.g. a stale Dex-era orphan identity).
 	// It must be skipped silently — not run and logged as a token error every pass.
 	lister := fakeLister{users: usersN("a", "b", "c"), noConn: map[string]bool{"b": true}}
 	rc := newCountingRunUser()
 
-	stats := runDiscoveryPass(context.Background(), lister, rc.run, quietLog())
+	stats := runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
 
 	require.Equal(t, 1, rc.count("a"))
 	require.Equal(t, 0, rc.count("b"), "a user with no connection must be skipped, not run")
@@ -121,7 +162,7 @@ func TestDiscoveryPassOneUserFailureDoesNotStopOthers(t *testing.T) {
 	lister := fakeLister{users: usersN("a", "b", "c")}
 	rc := newCountingRunUser("b") // user b's pass errors
 
-	stats := runDiscoveryPass(context.Background(), lister, rc.run, quietLog())
+	stats := runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
 
 	require.Equal(t, 1, rc.count("a"))
 	require.Equal(t, 1, rc.count("b"))
@@ -134,7 +175,7 @@ func TestDiscoveryPassListerErrorIsContained(t *testing.T) {
 	lister := fakeLister{err: errors.New("db down")}
 	rc := newCountingRunUser()
 
-	stats := runDiscoveryPass(context.Background(), lister, rc.run, quietLog())
+	stats := runDiscoveryPass(context.Background(), 0, lister, rc.run, quietLog())
 
 	require.Equal(t, 0, rc.total(), "no users enumerated → no passes")
 	require.Equal(t, runner.Stats{}, stats)

docs/homelab-integration.md

@@ -30,7 +30,9 @@ it** — endpoints and aliases drift, and this file is a snapshot (2026-06-06),
 - **Summarizer fallback chain (ADR-022).** The primary alias is the *first* of an ordered chain;
   on failure or unparseable output the summarizer advances to the next model. All reached through
   the same gateway by alias.
-  - `TAPIR_FALLBACK_MODEL` — local fallback. **Default `koala/phi4-14b`.** Empty disables it.
+  - `TAPIR_FALLBACK_MODEL` — local fallback. **Default `iguana/gemma4-26b`** — on iguana, NOT
+    koala, so the fallback does not compete with koala's other GPU loads (and runs from a different
+    egress IP). Empty disables it.
   - `TAPIR_CLOUD_FALLBACK_MODEL` — worst-case EXTERNAL fallback. **Default `berget/mistral-small`.**
     **Set this empty (`""`) for any client/NDA deployment** so content never leaves the local
     stack — the chain then contains only local endpoints.
@@ -39,6 +41,16 @@ it** — endpoints and aliases drift, and this file is a snapshot (2026-06-06),
   - `TAPIR_MAX_TRANSCRIPT_CHARS` — transcript truncation budget sent to the model. **Default
     `18000`** (~fits an 8k-context model). `0` disables truncation. Prevents the context-overflow
     HTTP 400 a long transcript caused on `phi4-mini`.
+- **Discovery low-value filter (ADR-023).** `TAPIR_MIN_VIDEO_SECONDS` — **default `60`**. At
+  discovery, `NewVideos` enriches candidates with one cheap `videos.list` call (quota API, NOT
+  the timedtext 429 path) and drops videos shorter than this plus any live/upcoming broadcast,
+  so the scarce caption-fetch budget isn't spent on Shorts. `0` disables the filter. The
+  paste-a-URL path is never filtered.
+- **Per-channel caption memory (ADR-024).** `TAPIR_CHANNEL_CAPTIONLESS_THRESHOLD` — **default
+  `5`** consecutive no-caption results before a channel is suppressed (its videos listed but not
+  caption-fetched). `TAPIR_CHANNEL_CAPTIONLESS_WINDOW` — **default `336h`** (14d) suppression
+  before one video is re-probed. `THRESHOLD=0` disables. A successful fetch resets the channel;
+  a 429 does not count; an explicit manual request bypasses suppression.
 - **Thinking models need an explicit `max_tokens`.** qwen3 / deepseek-r1 spend the budget on
   reasoning and return **empty content** if `max_tokens` is too low (or unset). The summarizer's
   parser treats an empty summary as an error for exactly this reason. **Done (2026-06-02, Worker F):**

docs/specs/chat-with-transcript.md

@@ -0,0 +1,89 @@
+# Spec — Chat with a video's stored transcript (ADR-027)
+
+**Repo:** tapir · **Size:** medium · **Solo session.** Implements ADR-027. Read CLAUDE.md,
+DECISIONS.md (ADR-021 transcript store, ADR-022 model chain, ADR-012 isolation, ADR-027), and
+`docs/ui-spec.md` first. TBD, conventional commits, `task check` green per commit, `templ
+generate` after view changes.
+
+## FIRST: append ADR-027 to DECISIONS.md
+ADR-027 text is provided separately (planning thread). Insert immediately before the
+`## Rejected alternatives` heading, as the first commit, so the decision precedes the build.
+
+## What this is
+A per-video chat letting the user ask questions against a video's **already-stored** transcript,
+entered from the summary view. Born from observed demand: the maintainer read real summaries and
+some made him want to dig deeper — this gives that "I want more" reaction somewhere to go, without
+watching the video.
+
+## HARD CONSTRAINT — stored-transcript-only (the safety property)
+Chat is available **ONLY** for videos that already have a stored transcript (ADR-021). It must
+**never** trigger a caption fetch, never touch the rate gate, never reach YouTube. Entry being
+"from a summarized video" guarantees the transcript exists. If somehow invoked on a video with no
+stored transcript → show "transcript not available for chat", NO fetch. This is what makes the
+feature safe by construction; do not add an on-demand-fetch path (explicitly deferred).
+
+## 1. Entry point
+- A "Dig deeper" / "Ask about this" affordance on the **summary view** of a summarized video
+  (not the list cards — the detail/summary page). Quiet, consistent with the existing card-state
+  styling.
+- Opens a chat panel/view scoped to that one video, with its stored transcript as context.
+
+## 2. The chat
+- Read the stored transcript for the video (via the ADR-021 `TranscriptStore`, keyed by
+  `(provider, provider_video_id)`). No fetch.
+- Send transcript + the user's question + minimal system framing to the chosen model via the
+  **existing LiteLLM gateway** (the same client the summarizer uses — a chat is a different
+  call, not a new integration).
+- Stream or return the answer; render in the chat panel. HTMX/no-JS ethos — match the existing
+  app (the summarize status uses HTMX polling; chat can use a simple POST-and-render or HTMX
+  streaming if clean).
+- **Transcript truncation:** reuse/respect `TAPIR_MAX_TRANSCRIPT_CHARS` (ADR-022) so a long
+  transcript fits the model context. If truncated, the chat should be honest that it's working
+  from a bounded portion (a quiet note), since answers about the tail of a long video may be
+  incomplete.
+
+## 3. Model selection (the instrumentation win)
+- **Default model = the model that produced this video's summary.** (Store/lookup which chain
+  model summarized it — if not already recorded, this is a small addition; if recording it is
+  non-trivial, default to the chain primary and note the gap.)
+- **User can switch** among the ADR-022 chain models (`phi4-mini`, `gemma4-26b`,
+  `mistral-small` to start) via a simple selector in the chat panel. Switching re-runs against
+  the same transcript — this is deliberate model-comparison instrumentation.
+- Respect the local-first / NDA posture: if `TAPIR_CLOUD_FALLBACK_MODEL=""` (cloud disabled),
+  the external model is NOT offered in the switcher — only local models. Chat must honor the same
+  "content stays local" guarantee as ADR-022.
+
+## 4. Ephemeral (v1)
+- No persisted chat history. Conversation lives for the session/page. No new table, no migration.
+- (Multi-turn within a session is fine — keep the running messages in the request/page state —
+  but nothing is written to the DB.)
+
+## 5. Isolation
+- The transcript is shared/non-RLS (ADR-021) — fine, it's public content. But the chat is invoked
+  by a user about a video **in their feed**; confirm the entry path is reachable only for the
+  requesting user's own videos (the summary view is already RLS-scoped). Chat adds no new
+  user-data surface (ephemeral), so there's nothing new to RLS — but the test should confirm a
+  user can only open chat from their own summary view, not arbitrary video ids.
+
+## Tests
+- Chat on a video with a stored transcript → answer returned; assert NO caption-fetch / no
+  YouTube call occurs (the safety property — this is the key assertion).
+- Chat invoked on a video with no stored transcript → honest "not available", NO fetch.
+- Model switch → re-runs against the same transcript with the selected model; cloud model absent
+  from the switcher when `TAPIR_CLOUD_FALLBACK_MODEL=""`.
+- Truncation honored for a long transcript; the bounded-context note shows.
+- Entry is reachable only from the user's own summary view (isolation).
+
+## Out of scope / deferred (record, don't build)
+- **Persisted chat history** (per-user, RLS-scoped) — deferred until evidence anyone revisits a
+  conversation.
+- **Show-source / transcript-verification UI** — the natural v2 (ADR-027 records it); v1 is
+  chat-only/trust-the-model. ADR-021's stored transcript makes v2 cheap when wanted.
+- **On-demand fetch** for un-stored videos — would reintroduce the caption-fetch surface the
+  stored-only constraint removes. Not now.
+- Anything that nudges the user to return (ADR-020 — gate contamination).
+
+## Boundaries
+Stored-transcript-only (HARD). No rate-gate/fetch surface. No auth changes. No new persisted
+state in v1. Reuse the existing gateway client + truncation config; don't build a new model
+integration.

docs/use-cases/chat_transcript.feature

@@ -0,0 +1,69 @@
+Feature: Chat with a video's stored transcript
+  As a reader whose summary made me want to dig deeper
+  I want to ask questions about the video without watching it
+  So that I can go further on the ones worth it, without leaving the reader
+
+  # ADR-027. The load-bearing constraint is safety-by-construction: chat runs
+  # ONLY against an already-stored transcript (ADR-021) and never fetches captions,
+  # never touches the rate gate, never reaches YouTube. Entry is from the summary
+  # view of one's OWN video; the conversation is ephemeral (no persisted history).
+
+  Background:
+    Given I have a summarized video with a stored transcript
+
+  Scenario: A summary view offers a deeper-dive into the video
+    When I view the summary
+    Then I see a "dig deeper" affordance that opens a chat about this video
+    And it opens the chat in place, below the summary, without leaving the page
+
+  Scenario: The summary and the chat are on one page
+    When I open the chat
+    Then the summary stays visible alongside the chat
+    And I can read the summary while I ask questions
+
+  Scenario: Ask a question answered from the stored transcript
+    When I ask a question in the chat
+    Then the answer is produced from the stored transcript
+    And no caption fetch and no YouTube call occurs
+
+  Scenario: Chat never fetches captions or reaches YouTube
+    When I ask a question in the chat
+    Then Tapir reads only the stored transcript
+    And the caption-fetch and video-fetch paths are never invoked
+
+  Scenario: A video with no stored transcript offers no chat
+    Given a video that has no stored transcript
+    When I open the chat for it
+    Then I am told chat is not available
+    And no fetch is attempted and no model is called
+
+  Scenario: The default model is the summary's model and is switchable
+    When I open the chat
+    Then the model defaults to the model that produced the summary
+    And I can switch among the offered chain models
+
+  Scenario: Switching models re-runs against the same transcript
+    When I ask a question with a different chain model selected
+    Then the chosen model answers
+    And it answers against the same stored transcript
+
+  Scenario: The cloud model is hidden when cloud is disabled
+    Given the cloud fallback model is disabled
+    Then the chat switcher offers only local models
+
+  Scenario: A long transcript is bounded and the chat says so
+    Given the stored transcript is longer than the model budget
+    When I ask a question
+    Then the answer is produced from a bounded portion
+    And the chat notes that it worked from a bounded portion
+
+  Scenario: A multi-turn conversation is ephemeral
+    When I ask a follow-up question
+    Then the prior turn is carried into the answer
+    And nothing about the conversation is written to the database
+
+  Scenario: Chat is reachable only from my own summary view
+    Given another user has a summarized video with a stored transcript
+    When I try to open the chat for their video
+    Then I get a not-found response
+    And no model is called

internal/adapters/chat/chat.go

@@ -0,0 +1,171 @@
+// Package chat implements the per-video deeper-dive chat (ADR-027): a read-only
+// QA over a video's ALREADY-STORED transcript (ADR-021). It is the enforcement
+// point for the feature's load-bearing safety property — stored-transcript-only:
+// the Service has NO VideoSource and NO caption-fetch dependency, only a
+// Completer factory, so it CANNOT reach YouTube or the rate gate by construction.
+// The caller supplies the stored transcript text; chat never fetches.
+//
+// It reuses the same LiteLLM gateway as the summarizer (a chat is a different
+// call, not a new integration) and the same transcript-truncation discipline
+// (TAPIR_MAX_TRANSCRIPT_CHARS) so a long transcript fits a small-context model.
+package chat
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"unicode/utf8"
+)
+
+// Completer is the minimal LLM chat surface the Service needs. *llm.Client
+// satisfies it; tests use a fake. It is the SAME surface the summarizer uses.
+type Completer interface {
+	Complete(ctx context.Context, system, user string) (string, error)
+}
+
+// Turn is one completed exchange in an ephemeral, session-only conversation
+// (ADR-027 v1: nothing is persisted).
+type Turn struct {
+	Question string
+	Answer   string
+}
+
+// Request is one chat turn: the chosen model, the stored transcript text, the
+// prior turns (for multi-turn context within the session), and the new question.
+type Request struct {
+	Model      string
+	Transcript string
+	History    []Turn
+	Question   string
+}
+
+// Reply is the model's answer plus whether the transcript was bounded to fit the
+// model context (so the UI can be honest that an answer about the tail of a long
+// video may be incomplete).
+type Reply struct {
+	Answer    string
+	Truncated bool
+}
+
+// Service answers questions against a stored transcript via a switchable set of
+// models. models is the ordered, local-first list offered to the user (the cloud
+// model is simply absent when disabled — see cmd wiring); maxChars bounds the
+// transcript sent to any model (0 = unbounded). newClient builds a Completer for
+// a chosen model alias (the same gateway, a different alias).
+type Service struct {
+	newClient func(model string) Completer
+	models    []string
+	maxChars  int
+}
+
+// New constructs a Service. models must be non-empty and already filtered to the
+// offerable set (cloud excluded when disabled) and de-duplicated by the caller.
+func New(newClient func(model string) Completer, models []string, maxChars int) *Service {
+	return &Service{newClient: newClient, models: models, maxChars: maxChars}
+}
+
+// Models returns a copy of the offerable model list (local-first order).
+func (s *Service) Models() []string {
+	out := make([]string, len(s.models))
+	copy(out, s.models)
+	return out
+}
+
+// offers reports whether model is in the offerable set — the guard that keeps an
+// arbitrary, un-offered alias (e.g. a forged form value) from reaching the gateway.
+func (s *Service) offers(model string) bool {
+	for _, m := range s.models {
+		if m == model {
+			return true
+		}
+	}
+	return false
+}
+
+// DefaultModel resolves the model a fresh chat opens with: the summary's own
+// model when it is still an offered option (the ADR-027 default — chat continues
+// in the model that produced the summary), otherwise the first offered model.
+// Returns "" only when no models are configured.
+func (s *Service) DefaultModel(summaryModel string) string {
+	if summaryModel != "" && s.offers(summaryModel) {
+		return summaryModel
+	}
+	if len(s.models) > 0 {
+		return s.models[0]
+	}
+	return ""
+}
+
+// Answer runs one chat turn. The model is forced back to a default if the request
+// names an un-offered alias, so chat can never call the gateway with an arbitrary
+// model. The transcript is truncated up front (reporting whether it was cut) and
+// passed as system context; the running conversation is the user message.
+func (s *Service) Answer(ctx context.Context, req Request) (Reply, error) {
+	if len(s.models) == 0 {
+		return Reply{}, fmt.Errorf("chat: no models configured")
+	}
+	model := req.Model
+	if !s.offers(model) {
+		model = s.DefaultModel("")
+	}
+
+	transcript, truncated := truncate(req.Transcript, s.maxChars)
+	system := buildSystem(transcript, truncated)
+	user := buildUser(req.History, req.Question)
+
+	out, err := s.newClient(model).Complete(ctx, system, user)
+	if err != nil {
+		return Reply{}, fmt.Errorf("chat: %s: %w", model, err)
+	}
+	answer := strings.TrimSpace(out)
+	if answer == "" {
+		return Reply{}, fmt.Errorf("chat: %s returned an empty answer", model)
+	}
+	return Reply{Answer: answer, Truncated: truncated}, nil
+}
+
+const systemPreamble = `You are Tapir, answering questions about ONE video using ONLY the transcript below.
+Ground every answer in the transcript. If the transcript does not contain the answer, say so plainly rather than guessing.`
+
+const truncatedNote = `
+The transcript below is truncated to fit the model — if a question seems to concern something missing, note it may be beyond the available portion.`
+
+// buildSystem frames the model as a transcript-grounded QA assistant and embeds
+// the (possibly truncated) transcript as context.
+func buildSystem(transcript string, truncated bool) string {
+	var b strings.Builder
+	b.WriteString(systemPreamble)
+	if truncated {
+		b.WriteString(truncatedNote)
+	}
+	b.WriteString("\n\nTranscript:\n")
+	b.WriteString(transcript)
+	return b.String()
+}
+
+// buildUser renders the running conversation as the user message: prior turns as
+// Q/A pairs followed by the new question. Folding history into one message keeps
+// the Completer surface (a single system+user call) unchanged — no new llm method.
+func buildUser(history []Turn, question string) string {
+	var b strings.Builder
+	for _, t := range history {
+		fmt.Fprintf(&b, "Q: %s\nA: %s\n\n", t.Question, t.Answer)
+	}
+	fmt.Fprintf(&b, "Q: %s", question)
+	return b.String()
+}
+
+// truncate caps content to max bytes on a UTF-8 rune boundary, reporting whether
+// it cut. It mirrors the summarizer's truncation discipline (ADR-022) but returns
+// the cut flag so the chat UI can be honest about a bounded transcript. A
+// non-positive max (or content already within budget) returns content unchanged.
+func truncate(content string, max int) (string, bool) {
+	if max <= 0 || len(content) <= max {
+		return content, false
+	}
+	cut := max
+	for cut > 0 && !utf8.RuneStart(content[cut]) {
+		cut--
+	}
+	return content[:cut], true
+}

internal/adapters/chat/chat_test.go

@@ -0,0 +1,164 @@
+package chat
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+)
+
+// recordingCompleter captures the system+user it was asked with and returns a
+// canned answer (or error). It also records which model alias built it.
+type recordingCompleter struct {
+	model      string
+	lastSystem string
+	lastUser   string
+	answer     string
+	err        error
+	calls      *int
+}
+
+func (c *recordingCompleter) Complete(_ context.Context, system, user string) (string, error) {
+	*c.calls++
+	c.lastSystem = system
+	c.lastUser = user
+	if c.err != nil {
+		return "", c.err
+	}
+	return c.answer, nil
+}
+
+// factory builds a recordingCompleter per model and records the last one built so
+// the test can assert which model alias was actually used for the gateway call.
+type factory struct {
+	answer string
+	err    error
+	calls  int
+	used   *recordingCompleter
+}
+
+func (f *factory) make(model string) Completer {
+	c := &recordingCompleter{model: model, answer: f.answer, err: f.err, calls: &f.calls}
+	f.used = c
+	return c
+}
+
+func TestModelsAreOfferedLocalFirstAndCopied(t *testing.T) {
+	f := &factory{answer: "ok"}
+	s := New(f.make, []string{"koala/phi4-mini", "iguana/gemma4-26b"}, 0)
+
+	got := s.Models()
+	want := []string{"koala/phi4-mini", "iguana/gemma4-26b"}
+	if len(got) != len(want) || got[0] != want[0] || got[1] != want[1] {
+		t.Fatalf("Models() = %v, want %v", got, want)
+	}
+	// Mutating the returned slice must not corrupt the Service's list.
+	got[0] = "tampered"
+	if s.Models()[0] != "koala/phi4-mini" {
+		t.Fatal("Models() leaked its backing slice")
+	}
+}
+
+func TestDefaultModelIsTheSummarysModelWhenOffered(t *testing.T) {
+	f := &factory{answer: "ok"}
+	s := New(f.make, []string{"koala/phi4-mini", "iguana/gemma4-26b", "berget/mistral-small"}, 0)
+
+	if got := s.DefaultModel("iguana/gemma4-26b"); got != "iguana/gemma4-26b" {
+		t.Fatalf("DefaultModel(summary) = %q, want the summary's model", got)
+	}
+	// A summary model no longer offered (e.g. cloud disabled) falls back to first.
+	if got := s.DefaultModel("berget/old-model"); got != "koala/phi4-mini" {
+		t.Fatalf("DefaultModel(un-offered) = %q, want the first offered model", got)
+	}
+	// No summary model recorded → first offered.
+	if got := s.DefaultModel(""); got != "koala/phi4-mini" {
+		t.Fatalf("DefaultModel(\"\") = %q, want the first offered model", got)
+	}
+}
+
+func TestAnswerGroundsOnTranscriptAndCarriesHistory(t *testing.T) {
+	f := &factory{answer: "  The video is about attention.  "}
+	s := New(f.make, []string{"koala/phi4-mini"}, 0)
+
+	reply, err := s.Answer(context.Background(), Request{
+		Model:      "koala/phi4-mini",
+		Transcript: "ATTENTION-TRANSCRIPT-MARKER",
+		History:    []Turn{{Question: "who", Answer: "the host"}},
+		Question:   "what is it about",
+	})
+	if err != nil {
+		t.Fatalf("Answer: %v", err)
+	}
+	if reply.Answer != "The video is about attention." {
+		t.Fatalf("answer not trimmed: %q", reply.Answer)
+	}
+	if reply.Truncated {
+		t.Fatal("short transcript must not report truncated")
+	}
+	// The transcript rides in the system prompt; the conversation in the user msg.
+	if !strings.Contains(f.used.lastSystem, "ATTENTION-TRANSCRIPT-MARKER") {
+		t.Fatal("transcript not grounded into the system prompt")
+	}
+	if !strings.Contains(f.used.lastUser, "Q: who") || !strings.Contains(f.used.lastUser, "A: the host") {
+		t.Fatalf("history not carried into the user message: %q", f.used.lastUser)
+	}
+	if !strings.Contains(f.used.lastUser, "what is it about") {
+		t.Fatal("new question missing from the user message")
+	}
+}
+
+func TestAnswerTruncatesLongTranscriptAndReportsIt(t *testing.T) {
+	f := &factory{answer: "answer"}
+	s := New(f.make, []string{"koala/phi4-mini"}, 10)
+
+	reply, err := s.Answer(context.Background(), Request{
+		Model:      "koala/phi4-mini",
+		Transcript: strings.Repeat("x", 500),
+		Question:   "summarize",
+	})
+	if err != nil {
+		t.Fatalf("Answer: %v", err)
+	}
+	if !reply.Truncated {
+		t.Fatal("a transcript past maxChars must report Truncated")
+	}
+	if strings.Count(f.used.lastSystem, "x") != 10 {
+		t.Fatalf("transcript not bounded to maxChars: got %d x's", strings.Count(f.used.lastSystem, "x"))
+	}
+}
+
+func TestAnswerForcesAnUnofferedModelBackToDefault(t *testing.T) {
+	f := &factory{answer: "answer"}
+	s := New(f.make, []string{"koala/phi4-mini", "iguana/gemma4-26b"}, 0)
+
+	// A forged/un-offered model must never reach the gateway as-is — it is forced
+	// to the default offered model (the cloud-absent guarantee depends on this).
+	_, err := s.Answer(context.Background(), Request{
+		Model:      "berget/secret-cloud-model",
+		Transcript: "t",
+		Question:   "q",
+	})
+	if err != nil {
+		t.Fatalf("Answer: %v", err)
+	}
+	if f.used.model != "koala/phi4-mini" {
+		t.Fatalf("un-offered model reached the gateway as %q, want the default", f.used.model)
+	}
+}
+
+func TestAnswerPropagatesCompleterError(t *testing.T) {
+	f := &factory{err: errors.New("gateway down")}
+	s := New(f.make, []string{"koala/phi4-mini"}, 0)
+
+	_, err := s.Answer(context.Background(), Request{Model: "koala/phi4-mini", Transcript: "t", Question: "q"})
+	if err == nil {
+		t.Fatal("expected the gateway error to propagate")
+	}
+}
+
+func TestAnswerRejectsEmptyModelSet(t *testing.T) {
+	s := New(func(string) Completer { return nil }, nil, 0)
+	if _, err := s.Answer(context.Background(), Request{Question: "q"}); err == nil {
+		t.Fatal("expected an error when no models are configured")
+	}
+}

internal/adapters/store/channel_caption.go

@@ -0,0 +1,83 @@
+package store
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+)
+
+// CaptionlessChannels returns the set of channel ids currently suppressed for the
+// user — channels whose recent videos all yielded no captions, within their
+// suppression window (ADR-024). The runner skips caption fetches for these
+// channels' videos. A channel whose window has expired is not returned, so its
+// next video is re-probed (auto-recovery).
+func (s *Store) CaptionlessChannels(ctx context.Context, userID string) (map[string]bool, error) {
+	out := map[string]bool{}
+	err := s.withUser(ctx, userID, func(tx pgx.Tx) error {
+		rows, err := tx.Query(ctx, `
+			SELECT channel_id FROM channel_caption_state
+			WHERE user_id = $1 AND captionless_until IS NOT NULL AND captionless_until > now()`,
+			userID)
+		if err != nil {
+			return fmt.Errorf("store: caption-less channels: %w", err)
+		}
+		defer rows.Close()
+		for rows.Next() {
+			var ch string
+			if err := rows.Scan(&ch); err != nil {
+				return fmt.Errorf("store: scan caption-less channel: %w", err)
+			}
+			out[ch] = true
+		}
+		return rows.Err()
+	})
+	return out, err
+}
+
+// RecordChannelCaptionOutcome updates a channel's caption-availability memory
+// after a fetch attempt (ADR-024). hadCaptions resets the channel (consecutive
+// count to 0, suppression cleared). Otherwise the consecutive no-caption count is
+// incremented; once it reaches threshold the channel is suppressed for window.
+// threshold <= 0 is a no-op (feature disabled). An empty channelID is ignored
+// (some sources may not carry one).
+func (s *Store) RecordChannelCaptionOutcome(ctx context.Context, userID, channelID string, hadCaptions bool, threshold int, window time.Duration) error {
+	if channelID == "" || threshold <= 0 {
+		return nil
+	}
+	return s.withUser(ctx, userID, func(tx pgx.Tx) error {
+		if hadCaptions {
+			_, err := tx.Exec(ctx, `
+				INSERT INTO channel_caption_state (user_id, channel_id, consecutive_none, captionless_until, updated_at)
+				VALUES ($1, $2, 0, NULL, now())
+				ON CONFLICT (user_id, channel_id)
+				DO UPDATE SET consecutive_none = 0, captionless_until = NULL, updated_at = now()`,
+				userID, channelID)
+			if err != nil {
+				return fmt.Errorf("store: reset channel caption state: %w", err)
+			}
+			return nil
+		}
+		// No captions: increment the streak; suppress once it reaches threshold.
+		// captionless_until is set from the NEW count inside the same statement so
+		// the decision is atomic with the increment.
+		until := time.Now().Add(window)
+		_, err := tx.Exec(ctx, `
+			INSERT INTO channel_caption_state (user_id, channel_id, consecutive_none, captionless_until, updated_at)
+			VALUES ($1, $2, 1, CASE WHEN 1 >= $3 THEN $4::timestamptz ELSE NULL END, now())
+			ON CONFLICT (user_id, channel_id)
+			DO UPDATE SET
+				consecutive_none = channel_caption_state.consecutive_none + 1,
+				captionless_until = CASE
+					WHEN channel_caption_state.consecutive_none + 1 >= $3 THEN $4::timestamptz
+					ELSE channel_caption_state.captionless_until
+				END,
+				updated_at = now()`,
+			userID, channelID, threshold, until)
+		if err != nil {
+			return fmt.Errorf("store: record channel no-caption: %w", err)
+		}
+		return nil
+	})
+}

internal/adapters/store/channel_caption_test.go

@@ -0,0 +1,67 @@
+package store_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestChannelCaptionMemory_SuppressesAfterThreshold(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	super := rawPool(t)
+	resetDB(t, super)
+	seedUser(t, super, userA)
+
+	const threshold = 3
+	window := time.Hour
+
+	// Below threshold: not yet suppressed.
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanX", false, threshold, window))
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanX", false, threshold, window))
+	got, err := s.CaptionlessChannels(ctx, userA)
+	require.NoError(t, err)
+	require.NotContains(t, got, "chanX", "2 < threshold 3: not suppressed yet")
+
+	// Crossing the threshold suppresses the channel.
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanX", false, threshold, window))
+	got, err = s.CaptionlessChannels(ctx, userA)
+	require.NoError(t, err)
+	require.Contains(t, got, "chanX", "3 consecutive no-caption results suppress the channel")
+
+	// A successful caption fetch resets it.
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanX", true, threshold, window))
+	got, err = s.CaptionlessChannels(ctx, userA)
+	require.NoError(t, err)
+	require.NotContains(t, got, "chanX", "a captioned video clears suppression")
+}
+
+func TestChannelCaptionMemory_WindowExpiryReProbes(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	super := rawPool(t)
+	resetDB(t, super)
+	seedUser(t, super, userA)
+
+	// A negative window means captionless_until lands in the past — modelling an
+	// elapsed suppression window, which must make the channel eligible again.
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanY", false, 1, -time.Hour))
+	got, err := s.CaptionlessChannels(ctx, userA)
+	require.NoError(t, err)
+	require.NotContains(t, got, "chanY", "an expired window re-enables the channel for a re-probe")
+}
+
+func TestChannelCaptionMemory_DisabledThresholdIsNoOp(t *testing.T) {
+	ctx := context.Background()
+	s := newStore(t)
+	super := rawPool(t)
+	resetDB(t, super)
+	seedUser(t, super, userA)
+
+	require.NoError(t, s.RecordChannelCaptionOutcome(ctx, userA, "chanZ", false, 0, time.Hour))
+	got, err := s.CaptionlessChannels(ctx, userA)
+	require.NoError(t, err)
+	require.Empty(t, got, "threshold 0 disables the memory — nothing recorded")
+}

internal/adapters/store/migrate_test.go

@@ -53,7 +53,9 @@ func TestMigration010LoginEventsUpDown(t *testing.T) {
 	require.True(t, loginEventsExists(t), "login_events must exist at latest migration")
 
 	m := fileMigrator(t)
-	// 011..015 sit above 010; step them down first so 010 is exercised in isolation.
+	// 011..016 sit above 010; step them down first so 010 is exercised in isolation.
+	require.NoError(t, m.Steps(-1), "down 016 drops channel_caption_state, login_events intact")
+	require.True(t, loginEventsExists(t), "016 down leaves login_events intact")
 	require.NoError(t, m.Steps(-1), "down 015 reshapes transcripts, login_events intact")
 	require.True(t, loginEventsExists(t), "015 down leaves login_events intact")
 	require.NoError(t, m.Steps(-1), "down 014 drops channel_title, login_events intact")
@@ -68,7 +70,7 @@ func TestMigration010LoginEventsUpDown(t *testing.T) {
 	require.NoError(t, m.Steps(-1), "down 010 must drop login_events")
 	require.False(t, loginEventsExists(t), "login_events must be gone after the down migration")
 
-	require.NoError(t, m.Steps(6), "up must recreate 010 then re-apply 011..015")
+	require.NoError(t, m.Steps(7), "up must recreate 010 then re-apply 011..016")
 	require.True(t, loginEventsExists(t), "login_events must be restored after the up migration")
 }
 
@@ -91,6 +93,7 @@ func TestMigration011AutoSummarizeDefaultUpDown(t *testing.T) {
 	require.Equal(t, "true", autoSummarizeDefault(t), "011 sets the default to TRUE")
 
 	m := fileMigrator(t)
+	require.NoError(t, m.Steps(-1), "down 016 drops channel_caption_state")
 	require.NoError(t, m.Steps(-1), "down 015 reshapes transcripts")
 	require.NoError(t, m.Steps(-1), "down 014 drops channel_title")
 	require.NoError(t, m.Steps(-1), "down 013 drops channel_errors")
@@ -104,6 +107,7 @@ func TestMigration011AutoSummarizeDefaultUpDown(t *testing.T) {
 	require.NoError(t, m.Steps(1), "up 013 creates channel_errors")
 	require.NoError(t, m.Steps(1), "up 014 recreates channel_title")
 	require.NoError(t, m.Steps(1), "up 015 reshapes transcripts to shared")
+	require.NoError(t, m.Steps(1), "up 016 recreates channel_caption_state (HEAD)")
 }
 
 // channelTitleExists reports whether videos.channel_title is present.
@@ -123,6 +127,8 @@ func TestMigration014VideoChannelTitleUpDown(t *testing.T) {
 	require.True(t, channelTitleExists(t), "channel_title exists at latest migration")
 
 	m := fileMigrator(t)
+	require.NoError(t, m.Steps(-1), "down 016 drops channel_caption_state, channel_title intact")
+	require.True(t, channelTitleExists(t), "016 down leaves channel_title intact")
 	require.NoError(t, m.Steps(-1), "down 015 reshapes transcripts, channel_title intact")
 	require.True(t, channelTitleExists(t), "015 down leaves channel_title intact")
 	require.NoError(t, m.Steps(-1), "down 014 must drop channel_title")
@@ -130,7 +136,8 @@ func TestMigration014VideoChannelTitleUpDown(t *testing.T) {
 
 	require.NoError(t, m.Steps(1), "up 014 must recreate channel_title")
 	require.True(t, channelTitleExists(t), "channel_title must be restored after the up migration")
-	require.NoError(t, m.Steps(1), "up 015 restores the shared transcripts shape (HEAD)")
+	require.NoError(t, m.Steps(1), "up 015 restores the shared transcripts shape")
+	require.NoError(t, m.Steps(1), "up 016 recreates channel_caption_state (HEAD)")
 }
 
 // TestMigration012FixAutoSummarizeRLS proves 012 runs cleanly and flips any

internal/adapters/store/migrations/016_channel_caption_state.down.sql

@@ -0,0 +1 @@
+DROP TABLE channel_caption_state;

internal/adapters/store/migrations/016_channel_caption_state.up.sql

@@ -0,0 +1,30 @@
+-- Migration 016: per-(user, channel) caption-availability memory (ADR-024).
+--
+-- Some channels never publish English captions (foreign-language news, music,
+-- etc.). Each of their new videos still costs ONE rate-limited caption fetch
+-- (ADR-014) before resolving to "none" — and on a throttled egress IP that fetch
+-- may 429 and churn through the backoff machinery first. This table remembers
+-- channels that repeatedly yield no captions so discovery can stop attempting
+-- their videos, freeing the scarce fetch budget for channels that do have them.
+--
+-- consecutive_none counts no-caption outcomes in a row; a successful fetch resets
+-- it to 0. Once it crosses the threshold the channel is suppressed until
+-- captionless_until, after which one video is re-probed (auto-recovery for a
+-- channel that starts adding captions). Per-user + RLS-scoped, consistent with
+-- the rest of the user-owned schema (subscriptions are per-user; ADR-012).
+CREATE TABLE channel_caption_state (
+    user_id           UUID        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    channel_id        TEXT        NOT NULL,
+    consecutive_none  INT         NOT NULL DEFAULT 0,
+    captionless_until TIMESTAMPTZ,
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_id, channel_id)
+);
+
+CREATE INDEX idx_channel_caption_state_user_id ON channel_caption_state(user_id);
+
+ALTER TABLE channel_caption_state ENABLE ROW LEVEL SECURITY;
+ALTER TABLE channel_caption_state FORCE ROW LEVEL SECURITY;
+CREATE POLICY channel_caption_state_isolation ON channel_caption_state
+    FOR ALL
+    USING (user_id = current_setting('tapir.current_user_id', true)::uuid);

internal/adapters/store/store_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"path/filepath"
 	"testing"
 
 	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
@@ -24,11 +25,22 @@ var _ ports.Sink = (*store.Store)(nil)
 var dsn string
 
 func TestMain(m *testing.M) {
-	const port = 54329
+	// Port + runtime/data dirs are per-process (PID-derived) so two concurrent
+	// `go test` invocations — e.g. a push-run and a tag-run firing together in CI —
+	// don't collide on a fixed port or a shared data dir (which silently failed
+	// both runs). CachePath is shared so the PG archive is downloaded once, not
+	// per process. Base 54000 keeps this package's range distinct from web's.
+	port := uint32(54000 + os.Getpid()%1000)
 	dsn = fmt.Sprintf("postgres://postgres:postgres@localhost:%d/postgres?sslmode=disable", port)
 
+	rt := filepath.Join(os.TempDir(), fmt.Sprintf("tapir-epg-store-%d", os.Getpid()))
 	pg := embeddedpostgres.NewDatabase(
-		embeddedpostgres.DefaultConfig().Port(port),
+		embeddedpostgres.DefaultConfig().
+			Port(port).
+			RuntimePath(rt).
+			DataPath(filepath.Join(rt, "data")).
+			BinariesPath(filepath.Join(rt, "bin")).
+			CachePath(filepath.Join(os.TempDir(), "tapir-epg-cache")),
 	)
 	if err := pg.Start(); err != nil {
 		fmt.Fprintf(os.Stderr, "embedded-postgres start: %v\n", err)
@@ -40,6 +52,7 @@ func TestMain(m *testing.M) {
 	if err := pg.Stop(); err != nil {
 		fmt.Fprintf(os.Stderr, "embedded-postgres stop: %v\n", err)
 	}
+	_ = os.RemoveAll(rt)
 	os.Exit(code)
 }
 

internal/adapters/youtube/gate.go

@@ -2,6 +2,7 @@ package youtube
 
 import (
 	"context"
+	"sync/atomic"
 	"time"
 
 	"golang.org/x/time/rate"
@@ -29,9 +30,55 @@ func SetFetchRate(interval time.Duration) {
 	globalFetchGate = rate.NewLimiter(rate.Every(interval), 1)
 }
 
+// foregroundPending counts in-flight foreground (user-initiated) caption fetches.
+// The background sweep yields the gate while this is non-zero so a human waiting
+// on a click gets the next slot — and, on a near-throttled IP, the pre-429 window
+// — instead of competing equally with the firehose (ADR-026, Pillar A). Clicks are
+// rare and bursty, so background barely notices; the win to the click is large.
+var foregroundPending atomic.Int64
+
+// fgCtxKey marks a context as foreground (user-initiated). Unexported; set via
+// ForegroundContext and read via isForeground so only this package owns the key.
+type fgCtxKey struct{}
+
+// ForegroundContext marks ctx as a user-initiated (foreground) fetch so the gate
+// gives it priority. The web "Summarize"/paste/retry path wraps its context with
+// this; the background scheduler leaves it unset.
+func ForegroundContext(ctx context.Context) context.Context {
+	return context.WithValue(ctx, fgCtxKey{}, true)
+}
+
+func isForeground(ctx context.Context) bool {
+	v, _ := ctx.Value(fgCtxKey{}).(bool)
+	return v
+}
+
+// fgYieldPoll is how often a background waiter re-checks whether a foreground
+// fetch is still pending. Short enough to feel immediate, long enough not to spin.
+const fgYieldPoll = 200 * time.Millisecond
+
 // WaitFetchGate blocks until the process-wide gate allows one timedtext fetch,
 // respecting ctx cancellation. Called from httpDo before every live outbound
 // caption fetch so the scheduler and the click-path share the same egress budget.
+//
+// Foreground (user-initiated) fetches take priority: they register as pending and
+// acquire a token immediately. Background fetches first yield — they wait until no
+// foreground fetch is pending — so a live click is never stuck behind the
+// background sweep and gets the cleaner slot against the per-IP limit (ADR-026).
 func WaitFetchGate(ctx context.Context) error {
+	if isForeground(ctx) {
+		foregroundPending.Add(1)
+		defer foregroundPending.Add(-1)
+		return globalFetchGate.Wait(ctx)
+	}
+
+	// Background: defer to any pending foreground fetch before taking a token.
+	for foregroundPending.Load() > 0 {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-time.After(fgYieldPoll):
+		}
+	}
 	return globalFetchGate.Wait(ctx)
 }

internal/adapters/youtube/gate_test.go

@@ -82,3 +82,37 @@ func TestSetFetchRateZeroIsUnlimited(t *testing.T) {
 		require.NoError(t, WaitFetchGate(context.Background()))
 	}
 }
+
+func TestForegroundContextMarker(t *testing.T) {
+	require.False(t, isForeground(context.Background()), "plain context is background")
+	require.True(t, isForeground(ForegroundContext(context.Background())), "marked context is foreground")
+}
+
+// TestWaitFetchGateForegroundProceedsImmediately: a foreground fetch acquires a
+// token without yielding, even when background callers exist.
+func TestWaitFetchGateForegroundProceedsImmediately(t *testing.T) {
+	SetFetchRate(0) // unlimited limiter — isolate the yield logic from pacing
+	foregroundPending.Store(0)
+	t.Cleanup(func() { foregroundPending.Store(0) })
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	require.NoError(t, WaitFetchGate(ForegroundContext(ctx)), "foreground proceeds immediately")
+}
+
+// TestWaitFetchGateBackgroundYieldsToForeground: while a foreground fetch is
+// pending, a background fetch yields (does not take a token) until the foreground
+// clears — proven by a background wait timing out against its own deadline, then
+// succeeding once the foreground is done.
+func TestWaitFetchGateBackgroundYieldsToForeground(t *testing.T) {
+	SetFetchRate(0)
+	foregroundPending.Store(1) // simulate a foreground fetch in flight
+	t.Cleanup(func() { foregroundPending.Store(0) })
+
+	ctx, cancel := context.WithTimeout(context.Background(), 250*time.Millisecond)
+	defer cancel()
+	require.Error(t, WaitFetchGate(ctx), "background yields (blocks) while foreground is pending")
+
+	foregroundPending.Store(0) // foreground done
+	require.NoError(t, WaitFetchGate(context.Background()), "background proceeds once foreground clears")
+}

internal/adapters/youtube/youtube.go

@@ -66,6 +66,13 @@ type Config struct {
 	// poll. Zero means defaultMaxVideos.
 	MaxVideosPerSubscription int
 
+	// MinVideoSeconds drops videos shorter than this from discovery (Shorts/clips,
+	// ADR-023). NewVideos enriches candidates with a single cheap videos.list call
+	// (contentDetails.duration + snippet.liveBroadcastContent) and filters before
+	// returning, so the scarce caption-fetch budget is never spent on them. Live
+	// and upcoming broadcasts are dropped too. Zero disables the filter.
+	MinVideoSeconds int
+
 	// BaseURL overrides the Data API root. Empty means defaultBaseURL.
 	BaseURL string
 
@@ -242,7 +249,97 @@ func (a *Adapter) NewVideos(ctx context.Context, sub domain.Subscription) ([]dom
 			break
 		}
 	}
-	return videos, nil
+
+	// Drop Shorts/sub-minute clips and live/upcoming broadcasts before they ever
+	// reach the rate-limited caption path (ADR-023). One cheap videos.list call
+	// (quota API, not the timedtext throttle) supplies duration + live status.
+	return a.filterLowValue(ctx, client, videos), nil
+}
+
+// filterLowValue removes videos shorter than cfg.MinVideoSeconds and any live or
+// upcoming broadcast, using a single videos.list lookup for duration +
+// liveBroadcastContent. The filter is best-effort: if MinVideoSeconds is 0 (off)
+// or the lookup fails, the input is returned unfiltered — discovery must not break
+// because a metadata call hiccuped; the worst case is the pre-ADR-023 behaviour.
+func (a *Adapter) filterLowValue(ctx context.Context, client *http.Client, videos []domain.Video) []domain.Video {
+	if a.cfg.MinVideoSeconds <= 0 || len(videos) == 0 {
+		return videos
+	}
+
+	ids := make([]string, 0, len(videos))
+	for _, v := range videos {
+		ids = append(ids, v.ProviderVideoID)
+	}
+	q := url.Values{
+		"part": {"contentDetails,snippet"},
+		"id":   {strings.Join(ids, ",")},
+	}
+	var resp videoListResponse
+	if err := a.getJSON(ctx, client, "/videos", q, &resp); err != nil {
+		// Degrade open: keep the candidates rather than lose discovery.
+		return videos
+	}
+
+	type meta struct {
+		seconds int
+		live    string
+	}
+	byID := make(map[string]meta, len(resp.Items))
+	for _, it := range resp.Items {
+		byID[it.ID] = meta{seconds: parseISO8601Seconds(it.ContentDetails.Duration), live: it.Snippet.LiveBroadcastContent}
+	}
+
+	kept := videos[:0]
+	for _, v := range videos {
+		m, ok := byID[v.ProviderVideoID]
+		if !ok {
+			kept = append(kept, v) // unknown metadata: keep, let the fetch decide
+			continue
+		}
+		if m.live != "" && m.live != "none" {
+			continue // live or upcoming broadcast
+		}
+		if m.seconds > 0 && m.seconds < a.cfg.MinVideoSeconds {
+			continue // Short / sub-threshold clip
+		}
+		kept = append(kept, v)
+	}
+	return kept
+}
+
+// parseISO8601Seconds parses an ISO 8601 duration as returned by the YouTube Data
+// API (e.g. "PT1H2M3S", "PT45S", "PT3M") into seconds. Only the hour/minute/second
+// components YouTube emits are handled; an unparseable or zero value returns 0,
+// which the caller treats as "unknown" (not filtered on duration).
+func parseISO8601Seconds(d string) int {
+	if !strings.HasPrefix(d, "PT") {
+		return 0
+	}
+	d = d[2:]
+	total, num := 0, 0
+	seen := false
+	for _, r := range d {
+		switch {
+		case r >= '0' && r <= '9':
+			num = num*10 + int(r-'0')
+			seen = true
+		case r == 'H':
+			total += num * 3600
+			num, seen = 0, false
+		case r == 'M':
+			total += num * 60
+			num, seen = 0, false
+		case r == 'S':
+			total += num
+			num, seen = 0, false
+		default:
+			return 0 // unexpected component (days/weeks) — treat as unknown
+		}
+	}
+	if seen {
+		return 0 // trailing digits without a unit: malformed
+	}
+	return total
 }
 
 // VideoByID fetches a single video's metadata (videos.list, snippet) for an
@@ -377,11 +474,16 @@ type playlistItemListResponse struct {
 
 type videoListResponse struct {
 	Items []struct {
+		ID      string `json:"id"`
 		Snippet struct {
 			Title                string    `json:"title"`
 			ChannelTitle         string    `json:"channelTitle"`
 			PublishedAt          time.Time `json:"publishedAt"`
+			LiveBroadcastContent string    `json:"liveBroadcastContent"`
 		} `json:"snippet"`
+		ContentDetails struct {
+			Duration string `json:"duration"` // ISO 8601, e.g. "PT1M30S"
+		} `json:"contentDetails"`
 	} `json:"items"`
 }
 

internal/adapters/youtube/youtube_test.go

@@ -186,6 +186,91 @@ func TestNewVideosCapsAtMax(t *testing.T) {
 	}
 }
 
+// TestNewVideosFiltersShortsAndLive: with MinVideoSeconds set, discovery enriches
+// candidates via videos.list and drops sub-threshold clips (Shorts) and
+// live/upcoming broadcasts before they reach the rate-limited caption path.
+func TestNewVideosFiltersShortsAndLive(t *testing.T) {
+	a, _ := newTestAdapter(t, func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/playlistItems":
+			_, _ = w.Write([]byte(`{
+				"items": [
+					{"snippet": {"title": "Real Talk", "publishedAt": "2026-06-03T10:00:00Z", "resourceId": {"videoId": "long1"}}},
+					{"snippet": {"title": "A Short", "publishedAt": "2026-06-03T09:00:00Z", "resourceId": {"videoId": "short1"}}},
+					{"snippet": {"title": "Live Now", "publishedAt": "2026-06-03T08:00:00Z", "resourceId": {"videoId": "live1"}}}
+				]
+			}`))
+		case "/videos":
+			if got := r.URL.Query().Get("part"); got != "contentDetails,snippet" {
+				t.Errorf("videos.list part=%q, want contentDetails,snippet", got)
+			}
+			_, _ = w.Write([]byte(`{
+				"items": [
+					{"id": "long1", "contentDetails": {"duration": "PT12M30S"}, "snippet": {"liveBroadcastContent": "none"}},
+					{"id": "short1", "contentDetails": {"duration": "PT45S"}, "snippet": {"liveBroadcastContent": "none"}},
+					{"id": "live1", "contentDetails": {"duration": "PT0S"}, "snippet": {"liveBroadcastContent": "live"}}
+				]
+			}`))
+		default:
+			t.Errorf("unexpected path %q", r.URL.Path)
+		}
+	})
+	a.cfg.MinVideoSeconds = 60
+
+	vids, err := a.NewVideos(context.Background(), domain.Subscription{ID: "s1", UserID: "u1", ChannelID: "UC_acme"})
+	if err != nil {
+		t.Fatalf("NewVideos: %v", err)
+	}
+	if len(vids) != 1 || vids[0].ProviderVideoID != "long1" {
+		t.Fatalf("expected only long1 to survive the filter, got %+v", vids)
+	}
+}
+
+// TestNewVideosNoFilterWhenDisabled: MinVideoSeconds=0 keeps the pre-ADR-023
+// behaviour — no videos.list call, no filtering.
+func TestNewVideosNoFilterWhenDisabled(t *testing.T) {
+	a, _ := newTestAdapter(t, func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/videos" {
+			t.Errorf("videos.list must not be called when MinVideoSeconds is 0")
+		}
+		_, _ = w.Write([]byte(`{"items": [
+			{"snippet": {"title": "A Short", "publishedAt": "2026-06-03T09:00:00Z", "resourceId": {"videoId": "short1"}}}
+		]}`))
+	})
+	a.cfg.MinVideoSeconds = 0
+
+	vids, err := a.NewVideos(context.Background(), domain.Subscription{ID: "s1", UserID: "u1", ChannelID: "UC_acme"})
+	if err != nil {
+		t.Fatalf("NewVideos: %v", err)
+	}
+	if len(vids) != 1 {
+		t.Fatalf("filter disabled must keep all videos, got %d", len(vids))
+	}
+}
+
+func TestParseISO8601Seconds(t *testing.T) {
+	cases := []struct {
+		in   string
+		want int
+	}{
+		{"PT45S", 45},
+		{"PT1M30S", 90},
+		{"PT3M", 180},
+		{"PT1H2M3S", 3723},
+		{"PT2H", 7200},
+		{"PT0S", 0},
+		{"", 0},
+		{"garbage", 0},
+		{"P1D", 0},  // days component not handled → unknown
+		{"PT10", 0}, // trailing digits without a unit → malformed
+	}
+	for _, c := range cases {
+		if got := parseISO8601Seconds(c.in); got != c.want {
+			t.Errorf("parseISO8601Seconds(%q) = %d, want %d", c.in, got, c.want)
+		}
+	}
+}
+
 // TestUploadsPlaylistID covers the zero-cost UC->UU derivation, including
 // non-standard ids that must fall through unchanged (handled via fallback).
 func TestUploadsPlaylistID(t *testing.T) {

internal/config/config.go

@@ -33,7 +33,10 @@ type Config struct {
 	SummarizerModel string
 	// FallbackModel is the LOCAL fallback alias tried when the primary fails or
 	// returns unparseable output (ADR-022). Kept local so content stays on the
-	// homelab stack. Empty disables it. Default a bigger-context local model.
+	// homelab stack. Default is an IGUANA model (not koala) so the fallback runs
+	// on a different host than the koala primary — koala carries other loads, and
+	// a different host also means a different egress IP for the (rare) fallback.
+	// Empty disables it.
 	FallbackModel string
 	// CloudFallbackModel is the worst-case EXTERNAL fallback alias, tried only
 	// after every local endpoint has failed (ADR-022). For client deployments set
@@ -46,6 +49,20 @@ type Config struct {
 	// MaxTranscriptChars bounds the transcript text sent to the model so a long
 	// transcript does not overflow a small-context primary. 0 disables truncation.
 	MaxTranscriptChars int
+
+	// MinVideoSeconds drops videos shorter than this from discovery (Shorts and
+	// other sub-minute clips that are noise and waste the scarce caption-fetch
+	// budget, ADR-014/ADR-023). Enforced via a cheap Data API videos.list lookup at
+	// discovery, never the rate-limited caption path. 0 disables the filter.
+	MinVideoSeconds int
+
+	// ChannelCaptionlessThreshold is how many consecutive no-caption results a
+	// channel may yield before its videos are suppressed from caption fetching
+	// (ADR-024). 0 disables the per-channel caption memory entirely.
+	ChannelCaptionlessThreshold int
+	// ChannelCaptionlessWindow is how long a suppressed channel stays suppressed
+	// before one video is re-probed (auto-recovery for a channel that adds captions).
+	ChannelCaptionlessWindow time.Duration
 	// SummarizerTimeout bounds a single completion call. Thinking models are
 	// slow, so the default is generous.
 	SummarizerTimeout time.Duration
@@ -134,10 +151,13 @@ func (c Config) DexConfigured() bool { return strings.TrimSpace(c.OIDCIssuer) !=
 const (
 	defaultGatewayURL            = "http://koala:30401/v1"
 	defaultSummarizerModel       = "koala/phi4-mini"
-	defaultFallbackModel         = "koala/phi4-14b"
+	defaultFallbackModel         = "iguana/gemma4-26b"
 	defaultCloudFallbackModel    = "berget/mistral-small"
 	defaultSummaryMaxTokens      = 1500
 	defaultMaxTranscriptChars    = 18000
+	defaultMinVideoSeconds       = 60
+	defaultCaptionlessThreshold  = 5
+	defaultCaptionlessWindow     = 14 * 24 * time.Hour
 	defaultSummarizerTimeout     = 5 * time.Minute
 	defaultYTTokenRef            = "youtube/refresh_token"
 	defaultYTConnectRedirectURL  = "https://tapir.d-ma.be/oauth/youtube/callback"
@@ -230,6 +250,30 @@ func Load() (Config, error) {
 	}
 	c.MaxTranscriptChars = maxChars
 
+	minVideo, err := intOr("TAPIR_MIN_VIDEO_SECONDS", defaultMinVideoSeconds)
+	if err != nil {
+		return Config{}, err
+	}
+	if minVideo < 0 {
+		minVideo = 0
+	}
+	c.MinVideoSeconds = minVideo
+
+	captionThreshold, err := intOr("TAPIR_CHANNEL_CAPTIONLESS_THRESHOLD", defaultCaptionlessThreshold)
+	if err != nil {
+		return Config{}, err
+	}
+	if captionThreshold < 0 {
+		captionThreshold = 0
+	}
+	c.ChannelCaptionlessThreshold = captionThreshold
+
+	captionWindow, err := durationOr("TAPIR_CHANNEL_CAPTIONLESS_WINDOW", defaultCaptionlessWindow)
+	if err != nil {
+		return Config{}, err
+	}
+	c.ChannelCaptionlessWindow = captionWindow
+
 	onboard, err := intOr("TAPIR_ONBOARD_SUMMARIZE_COUNT", defaultOnboardSummarizeCount)
 	if err != nil {
 		return Config{}, err

internal/runner/runner.go

@@ -28,6 +28,7 @@ import (
 // and is queued for transcript fetch + summarization in this pass.
 type passCandidate struct {
 	v         domain.Video
+	channelID string // owning channel — keys the caption-availability memory (ADR-024)
 	pos       int    // discovery position — used as a stable tiebreak when published_at ties
 }
 
@@ -74,6 +75,14 @@ type VideoStore interface {
 	// Called when NewVideos returns domain.ErrChannelUnavailable; best-effort, errors
 	// are logged and never abort the pass.
 	UpsertChannelError(ctx context.Context, userID, channelID, channelTitle string) error
+	// CaptionlessChannels returns channel ids currently suppressed because their
+	// recent videos all yielded no captions (ADR-024). The loop skips caption
+	// fetches for these channels' (non-requested) videos.
+	CaptionlessChannels(ctx context.Context, userID string) (map[string]bool, error)
+	// RecordChannelCaptionOutcome updates a channel's caption memory after a fetch:
+	// hadCaptions resets it, otherwise the no-caption streak grows and the channel
+	// is suppressed for window once it reaches threshold. A no-op when threshold<=0.
+	RecordChannelCaptionOutcome(ctx context.Context, userID, channelID string, hadCaptions bool, threshold int, window time.Duration) error
 }
 
 // Processor runs the core use case for a single video. *usecase.Engine
@@ -93,6 +102,9 @@ type Runner struct {
 	backoff    time.Duration    // rate-limit retry window; 0 = always retry
 	autoWindow time.Duration    // recency bound for auto-summarize; 0 = no bound
 	now        func() time.Time // injectable clock (tests); defaults to time.Now
+
+	captionThreshold int           // consecutive no-caption results before a channel is suppressed; 0 = feature off
+	captionWindow    time.Duration // how long a caption-less channel stays suppressed before re-probe
 }
 
 // Option configures a Runner at construction. Variadic so existing call sites
@@ -114,6 +126,14 @@ func WithClock(now func() time.Time) Option { return func(r *Runner) { r.now = n
 // bypasses the bound. 0 (the default) disables it (summarize every unseen video).
 func WithAutoWindow(d time.Duration) Option { return func(r *Runner) { r.autoWindow = d } }
 
+// WithCaptionMemory enables per-channel caption-availability suppression
+// (ADR-024): after threshold consecutive no-caption results a channel's videos
+// are skipped (no caption fetch) for window, then one is re-probed. threshold<=0
+// (the default) disables the feature entirely.
+func WithCaptionMemory(threshold int, window time.Duration) Option {
+	return func(r *Runner) { r.captionThreshold = threshold; r.captionWindow = window }
+}
+
 // New builds a Runner. A nil logger falls back to slog.Default.
 func New(src ports.VideoSource, store VideoStore, engine Processor, userID string, log *slog.Logger, opts ...Option) *Runner {
 	if log == nil {
@@ -138,6 +158,7 @@ type Stats struct {
 	SkippedManual           int // discovered but not queued, in manual mode
 	SkippedTooOld           int // auto mode: published outside the recency window (not requested)
 	SkippedRateLimited      int // 429'd previously and still inside the backoff window
+	SkippedNoCaptionChannel int // channel suppressed as caption-less (ADR-024)
 	Errors                  int
 	ChannelUnavailable      int // channels that returned HTTP 404 (deleted/private)
 }
@@ -213,6 +234,17 @@ func (r *Runner) RunOnce(ctx context.Context) (Stats, error) {
 		}
 	}
 
+	// Per-channel caption memory (ADR-024): channels whose recent videos all
+	// yielded no captions are suppressed so their new videos don't burn the scarce
+	// fetch budget. Loaded only when the feature is enabled (threshold > 0).
+	var captionless map[string]bool
+	if r.captionThreshold > 0 {
+		captionless, err = r.store.CaptionlessChannels(ctx, r.userID)
+		if err != nil {
+			return stats, fmt.Errorf("runner: load caption-less channels: %w", err)
+		}
+	}
+
 	subs, err := r.src.ListSubscriptions(ctx, r.userID)
 	if err != nil {
 		return stats, fmt.Errorf("runner: list subscriptions: %w", err)
@@ -273,6 +305,14 @@ func (r *Runner) RunOnce(ctx context.Context) (Stats, error) {
 				continue
 			}
 
+			// Caption-less channel (ADR-024): its recent videos all returned no
+			// captions, so skip the fetch entirely. The video is still listed
+			// (UpsertVideo above); an explicit manual request bypasses the skip.
+			if !requested[id] && captionless[sub.ChannelID] {
+				stats.SkippedNoCaptionChannel++
+				continue
+			}
+
 			// Still inside the rate-limit backoff window: skip without fetching.
 			if at, ok := rateLimited[id]; ok && r.now().Sub(at) < r.backoff {
 				stats.SkippedRateLimited++
@@ -280,7 +320,7 @@ func (r *Runner) RunOnce(ctx context.Context) (Stats, error) {
 				continue
 			}
 
-			candidates = append(candidates, passCandidate{v: v, pos: pos})
+			candidates = append(candidates, passCandidate{v: v, channelID: sub.ChannelID, pos: pos})
 			pos++
 		}
 	}
@@ -320,6 +360,11 @@ func (r *Runner) RunOnce(ctx context.Context) (Stats, error) {
 				errs = append(errs, fmt.Errorf("set none status %q: %w", c.v.ProviderVideoID, err))
 				stats.Errors++
 			}
+			// No captions: grow this channel's no-caption streak (ADR-024).
+			if err := r.store.RecordChannelCaptionOutcome(ctx, r.userID, c.channelID, false, r.captionThreshold, r.captionWindow); err != nil {
+				errs = append(errs, fmt.Errorf("record no-caption %q: %w", c.v.ProviderVideoID, err))
+				stats.Errors++
+			}
 			r.log.Info("skipped video (no transcript)", "video", c.v.ProviderVideoID, "title", c.v.Title)
 		case res.Summary != nil:
 			stats.Summarized++
@@ -327,6 +372,11 @@ func (r *Runner) RunOnce(ctx context.Context) (Stats, error) {
 				errs = append(errs, fmt.Errorf("set fetched status %q: %w", c.v.ProviderVideoID, err))
 				stats.Errors++
 			}
+			// Captions present: reset this channel's caption memory (ADR-024).
+			if err := r.store.RecordChannelCaptionOutcome(ctx, r.userID, c.channelID, true, r.captionThreshold, r.captionWindow); err != nil {
+				errs = append(errs, fmt.Errorf("record has-caption %q: %w", c.v.ProviderVideoID, err))
+				stats.Errors++
+			}
 			// In manual mode the video was explicitly queued; clear the flag so
 			// it is not re-summarized and the UI drops the "Queued" chip.
 			if !auto {
@@ -354,6 +404,7 @@ func (r *Runner) Loop(ctx context.Context, interval time.Duration) error {
 			"skipped_seen", stats.SkippedSeen, "skipped_no_text", stats.SkippedNoText,
 			"skipped_manual", stats.SkippedManual, "skipped_too_old", stats.SkippedTooOld,
 			"skipped_rate_limited", stats.SkippedRateLimited,
+			"skipped_no_caption_channel", stats.SkippedNoCaptionChannel,
 			"channel_unavailable", stats.ChannelUnavailable, "errors", stats.Errors)
 		if err != nil {
 			r.log.Warn("run pass had errors", "err", err)

internal/runner/runner_test.go

@@ -51,6 +51,13 @@ type fakeStore struct {
 	cleared     []string
 	rateLimited map[string]time.Time // id -> when 429'd (seeds the backoff window)
 	statuses    map[string]string    // id -> last SetTranscriptStatus value
+	captionless map[string]bool      // channel ids currently suppressed (ADR-024)
+	captionRecs []captionRec         // RecordChannelCaptionOutcome calls, in order
+}
+
+type captionRec struct {
+	channelID string
+	had       bool
 }
 
 func (f *fakeStore) UpsertVideo(_ context.Context, v domain.Video) (string, error) {
@@ -93,6 +100,22 @@ func (f *fakeStore) RateLimitedVideoIDs(_ context.Context, _ string) (map[string
 
 func (f *fakeStore) UpsertChannelError(_ context.Context, _, _, _ string) error { return nil }
 
+func (f *fakeStore) CaptionlessChannels(_ context.Context, _ string) (map[string]bool, error) {
+	cp := make(map[string]bool, len(f.captionless))
+	for k, v := range f.captionless {
+		cp[k] = v
+	}
+	return cp, nil
+}
+
+func (f *fakeStore) RecordChannelCaptionOutcome(_ context.Context, _, channelID string, hadCaptions bool, threshold int, _ time.Duration) error {
+	if threshold <= 0 {
+		return nil
+	}
+	f.captionRecs = append(f.captionRecs, captionRec{channelID: channelID, had: hadCaptions})
+	return nil
+}
+
 func (f *fakeStore) SetTranscriptStatus(_ context.Context, _, videoID, status string) error {
 	if f.statuses == nil {
 		f.statuses = map[string]string{}
@@ -284,6 +307,55 @@ func TestRunOnce_AutoMode_OldVideoRequestedBypassesWindow(t *testing.T) {
 	require.Len(t, sink.delivered, 1)
 }
 
+// TestRunOnce_CaptionlessChannelSkipped: a channel flagged caption-less (ADR-024)
+// has its videos skipped from fetching but still discovered/listed, while a
+// normal channel's video is summarized.
+func TestRunOnce_CaptionlessChannelSkipped(t *testing.T) {
+	src := &fakeSource{
+		subs: []domain.Subscription{sub("dead", "Dead Channel"), sub("live", "Live Channel")},
+		videos: map[string][]domain.Video{
+			"dead": {vid("d1", "Dead One")},
+			"live": {vid("l1", "Live One")},
+		},
+	}
+	st := &fakeStore{seen: map[string]bool{}, auto: true, captionless: map[string]bool{"dead": true}}
+	sink := &recordingSink{}
+	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
+	r := runner.New(src, st, eng, testUser, quietLogger(),
+		runner.WithCaptionMemory(5, 14*24*time.Hour))
+
+	stats, err := r.RunOnce(context.Background())
+	require.NoError(t, err)
+	require.Equal(t, 1, stats.SkippedNoCaptionChannel, "dead channel's video skipped from fetch")
+	require.Equal(t, 1, stats.Summarized, "live channel's video still summarized")
+	require.Len(t, st.upserted, 2, "both videos are still discovered and listed")
+}
+
+// TestRunOnce_RecordsCaptionOutcomes: a no-caption result grows the channel's
+// streak (had=false); a successful summary resets it (had=true).
+func TestRunOnce_RecordsCaptionOutcomes(t *testing.T) {
+	src := &fakeSource{
+		subs: []domain.Subscription{sub("c1", "Has Caps"), sub("c2", "No Caps")},
+		videos: map[string][]domain.Video{
+			"c1": {vid("good", "Good")},
+			"c2": {vid("bad", "Bad")},
+		},
+		transcripts: map[string]domain.Transcript{
+			"bad": {Source: domain.SourceNone}, // no usable text → engine skips
+		},
+	}
+	st := &fakeStore{seen: map[string]bool{}, auto: true}
+	sink := &recordingSink{}
+	eng := usecase.NewEngine(src, fakeSummarizer{}, sink)
+	r := runner.New(src, st, eng, testUser, quietLogger(),
+		runner.WithCaptionMemory(5, 14*24*time.Hour))
+
+	_, err := r.RunOnce(context.Background())
+	require.NoError(t, err)
+	require.Contains(t, st.captionRecs, captionRec{channelID: "c1", had: true}, "captioned channel reset")
+	require.Contains(t, st.captionRecs, captionRec{channelID: "c2", had: false}, "no-caption channel streak grown")
+}
+
 // TestRunOnce_AutoWindowZero_SummarizesOld: a zero window disables the bound —
 // the pre-recency behaviour (summarize every unseen video) is preserved.
 func TestRunOnce_AutoWindowZero_SummarizesOld(t *testing.T) {

internal/web/chat.go

@@ -0,0 +1,227 @@
+package web
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/chat"
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
+)
+
+// Chatter is the per-video chat backend (ADR-027). *chat.Service satisfies it;
+// tests substitute a fake. It carries NO caption-fetch dependency — the chat
+// handlers reach it only after reading an already-stored transcript, so an
+// enabled chat cannot trigger a fetch, touch the rate gate, or reach YouTube.
+type Chatter interface {
+	// Models returns the offerable models, local-first (cloud absent when disabled).
+	Models() []string
+	// DefaultModel resolves the model a fresh chat opens with given the summary's
+	// model (the ADR-027 default), falling back to the first offered model.
+	DefaultModel(summaryModel string) string
+	// Answer runs one chat turn against the supplied stored transcript text.
+	Answer(ctx context.Context, req chat.Request) (chat.Reply, error)
+}
+
+// maxHistoryTurns bounds the ephemeral conversation carried per request, so a long
+// back-and-forth cannot grow the prompt without limit (the transcript already
+// dominates the budget). Older turns drop off the front.
+const maxHistoryTurns = 8
+
+// chatView is everything the chat templates render: the video identity for links
+// and titles, the model switcher state, the running (ephemeral) conversation, and
+// the honest flags — Available is false when no usable transcript is stored
+// (ADR-027: honest "not available", never a fetch), Truncated when the transcript
+// was bounded to fit the model, Error for a transient model failure.
+type chatView struct {
+	VideoID   string
+	Title     string
+	Available bool
+	Models    []string
+	Selected  string
+	History   []chat.Turn
+	Truncated bool
+	Error     string
+}
+
+// handleChat renders the chat page for a summarized video (GET). Entry is scoped
+// through GetSummaryByVideo, which is RLS/user-scoped: a video that is not the
+// requesting user's own resolves to ErrNotFound → 404, so chat is reachable only
+// from the user's own summary view (ADR-027 isolation). The transcript is read
+// from the SHARED store (ADR-021) — a pure DB read, never a caption fetch; an
+// absent/text-less transcript renders the honest "not available" state, no fetch.
+func (a *App) handleChat(w http.ResponseWriter, r *http.Request) {
+	userID, ok := a.currentUserID(w, r)
+	if !ok {
+		return
+	}
+	row, ok := a.loadOwnedSummary(w, r, userID)
+	if !ok {
+		return
+	}
+	_, hasText, ok := a.readTranscript(w, r, *row)
+	if !ok {
+		return
+	}
+	view := chatView{
+		VideoID:   row.VideoID,
+		Title:     displayTitle(*row),
+		Available: hasText,
+		Models:    a.Chat.Models(),
+		Selected:  a.Chat.DefaultModel(row.AIModel),
+	}
+	// HTMX (the in-place reveal from the summary) gets just the open chat section,
+	// swapped over the closed dock so the summary above it stays put. A no-JS
+	// navigation gets the full page: the whole summary plus the open chat.
+	if isHTMX(r) {
+		a.render(w, r, chatSection(view))
+		return
+	}
+	a.render(w, r, ChatPage(*row, view))
+}
+
+// handleChatMessage answers one question against the stored transcript (POST).
+// It reads the transcript from the store (no fetch), runs the chosen model over
+// it plus the prior turns, appends the answer, and returns the refreshed chat
+// panel (HTMX) or the whole page (no-JS). A model failure is surfaced inline,
+// not as a 500 — the conversation and the question are preserved for a retry.
+func (a *App) handleChatMessage(w http.ResponseWriter, r *http.Request) {
+	userID, ok := a.currentUserID(w, r)
+	if !ok {
+		return
+	}
+	row, ok := a.loadOwnedSummary(w, r, userID)
+	if !ok {
+		return
+	}
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "bad form", http.StatusBadRequest)
+		return
+	}
+	transcript, hasText, ok := a.readTranscript(w, r, *row)
+	if !ok {
+		return
+	}
+
+	model := a.resolveModel(r.FormValue("model"), row.AIModel)
+	history := parseHistory(r.Form["hq"], r.Form["ha"])
+	question := strings.TrimSpace(r.FormValue("question"))
+
+	view := chatView{
+		VideoID:   row.VideoID,
+		Title:     displayTitle(*row),
+		Available: hasText,
+		Models:    a.Chat.Models(),
+		Selected:  model,
+		History:   history,
+	}
+
+	switch {
+	case !hasText:
+		// Honest "not available" — no fetch, no model call (ADR-027).
+	case question == "":
+		// A model switch with no text just re-renders — no wasted round-trip.
+	default:
+		reply, err := a.Chat.Answer(r.Context(), chat.Request{
+			Model:      model,
+			Transcript: transcript,
+			History:    history,
+			Question:   question,
+		})
+		if err != nil {
+			a.logger().Error("chat answer", "video", row.VideoID, "model", model, "err", err)
+			view.Error = "That model couldn't answer just now. Try again, or switch models."
+		} else {
+			view.History = appendTurn(history, chat.Turn{Question: question, Answer: reply.Answer})
+			view.Truncated = reply.Truncated
+		}
+	}
+	a.renderChatTurn(w, r, *row, view)
+}
+
+// loadOwnedSummary fetches the summary for the path's video scoped to userID, or
+// writes the right response (404 on not-found/not-owned, 500 on error) and reports
+// false. It is the single isolation gate for both chat handlers.
+func (a *App) loadOwnedSummary(w http.ResponseWriter, r *http.Request, userID string) (*store.SummaryRow, bool) {
+	videoID := r.PathValue("videoId")
+	row, err := a.Store.GetSummaryByVideo(r.Context(), userID, videoID)
+	if errors.Is(err, store.ErrNotFound) {
+		http.NotFound(w, r)
+		return nil, false
+	}
+	if err != nil {
+		a.serverError(w, r, "chat get summary", err)
+		return nil, false
+	}
+	return row, true
+}
+
+// readTranscript reads the shared stored transcript for a row (ADR-021) and
+// reports whether it carries usable text. It is a pure DB read — NO caption fetch,
+// the property the whole feature's safety rests on. ok is false only on a store
+// error (after a 500 is written); a missing/text-less transcript is (",", false,
+// true) — the honest "not available" case, handled by the caller, not an error.
+func (a *App) readTranscript(w http.ResponseWriter, r *http.Request, row store.SummaryRow) (content string, hasText, ok bool) {
+	t, found, err := a.Store.GetTranscript(r.Context(), row.Channel, row.ProviderVideoID)
+	if err != nil {
+		a.serverError(w, r, "chat get transcript", err)
+		return "", false, false
+	}
+	if !found || !t.HasText() {
+		return "", false, true
+	}
+	return t.Content, true, true
+}
+
+// renderChatTurn returns the chat panel fragment for an HTMX answer (swapped in
+// place within the open dock), or the full chat page otherwise — the no-JS POST
+// re-renders the whole summary + open chat with the new turn.
+func (a *App) renderChatTurn(w http.ResponseWriter, r *http.Request, row store.SummaryRow, v chatView) {
+	if isHTMX(r) {
+		a.render(w, r, chatPanel(v))
+		return
+	}
+	a.render(w, r, ChatPage(row, v))
+}
+
+// resolveModel keeps the posted model only when it is an offered option; anything
+// else (a forged value, or a model dropped because cloud is disabled) falls back
+// to the default. The chat.Service enforces the same guard before the gateway;
+// this keeps the rendered switcher honest too.
+func (a *App) resolveModel(posted, summaryModel string) string {
+	for _, m := range a.Chat.Models() {
+		if m == posted {
+			return posted
+		}
+	}
+	return a.Chat.DefaultModel(summaryModel)
+}
+
+// parseHistory zips the parallel hidden hq/ha fields back into ordered turns,
+// keeping only the most recent maxHistoryTurns. net/url preserves the submission
+// order of repeated fields, so the pairing is stable.
+func parseHistory(qs, as []string) []chat.Turn {
+	n := len(qs)
+	if len(as) < n {
+		n = len(as)
+	}
+	turns := make([]chat.Turn, 0, n)
+	for i := 0; i < n; i++ {
+		turns = append(turns, chat.Turn{Question: qs[i], Answer: as[i]})
+	}
+	return capHistory(turns)
+}
+
+// appendTurn adds a completed exchange and re-bounds the conversation.
+func appendTurn(history []chat.Turn, t chat.Turn) []chat.Turn {
+	return capHistory(append(history, t))
+}
+
+// capHistory keeps the last maxHistoryTurns turns (drops the oldest).
+func capHistory(turns []chat.Turn) []chat.Turn {
+	if len(turns) <= maxHistoryTurns {
+		return turns
+	}
+	return turns[len(turns)-maxHistoryTurns:]
+}

internal/web/chat_handler_test.go

@@ -0,0 +1,375 @@
+package web_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/stretchr/testify/require"
+
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/chat"
+	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
+	"gitea.d-ma.be/mathias/tapir/internal/domain"
+	"gitea.d-ma.be/mathias/tapir/internal/web"
+)
+
+// videoZ is a video id used by the isolation test for a DIFFERENT user's video.
+const videoZ = "33333333-3333-3333-3333-333333333333"
+
+// --- chat test doubles -----------------------------------------------------
+
+// fakeChatter is a web.Chatter that records the request it received and returns a
+// canned reply. It performs NO network and NO fetch — it stands in for the real
+// chat.Service so the handler behaviour is what's under test.
+type fakeChatter struct {
+	models    []string
+	reply     chat.Reply
+	err       error
+	gotReq    chat.Request
+	callCount int
+}
+
+func (f *fakeChatter) Models() []string { return f.models }
+
+func (f *fakeChatter) DefaultModel(summaryModel string) string {
+	for _, m := range f.models {
+		if m == summaryModel {
+			return summaryModel
+		}
+	}
+	if len(f.models) > 0 {
+		return f.models[0]
+	}
+	return ""
+}
+
+func (f *fakeChatter) Answer(_ context.Context, req chat.Request) (chat.Reply, error) {
+	f.callCount++
+	f.gotReq = req
+	if f.err != nil {
+		return chat.Reply{}, f.err
+	}
+	return f.reply, nil
+}
+
+// tripwireProcessor and tripwireFetcher are the YouTube-reaching collaborators
+// (summarize → caption fetch, and the paste metadata fetch). Wired into the App
+// for the safety test, they fail it the instant chat routes into either — the
+// behavioural proof that chat never triggers a fetch (ADR-027).
+type tripwireProcessor struct{ t *testing.T }
+
+func (p tripwireProcessor) ProcessVideo(context.Context, string, string) error {
+	p.t.Fatal("chat triggered summarization (→ caption fetch) — must never happen (ADR-027)")
+	return nil
+}
+
+type tripwireFetcher struct{ t *testing.T }
+
+func (f tripwireFetcher) FetchVideo(context.Context, string, string) (domain.Video, error) {
+	f.t.Fatal("chat triggered a YouTube video fetch — must never happen (ADR-027)")
+	return domain.Video{}, nil
+}
+
+// --- helpers ---------------------------------------------------------------
+
+// newChatApp builds the App under test as the registered stub user, with a Chat
+// backend wired. Mirrors newApp but adds chat (and any extra wiring via mutate).
+func newChatApp(t *testing.T, chatter web.Chatter, mutate func(*web.App)) *web.App {
+	t.Helper()
+	s := newStore(t)
+	app := &web.App{
+		Store:    s,
+		Identity: s,
+		Auth:     web.StubAuth{U: web.User{Subject: stubSubject}},
+		Chat:     chatter,
+	}
+	if mutate != nil {
+		mutate(app)
+	}
+	return app
+}
+
+// seededProviderVideoID mirrors seedVideo's derivation so the chat path's
+// (provider, providerVideoID) transcript key matches the seeded video row.
+func seededProviderVideoID(videoID string) string { return "pv-" + videoID[:8] }
+
+// seedTranscript stores a shared (provider, providerVideoID) transcript — the
+// ADR-021 stored content the chat reads. Captions source = usable text.
+func seedTranscript(t *testing.T, s *store.Store, videoID, content string) {
+	t.Helper()
+	err := s.SaveTranscript(context.Background(), "youtube", seededProviderVideoID(videoID),
+		domain.Transcript{Source: domain.SourceCaptions, Language: "en", Content: content})
+	require.NoError(t, err)
+}
+
+func getChat(t *testing.T, app *web.App, videoID string) *httptest.ResponseRecorder {
+	t.Helper()
+	return do(t, app, httptest.NewRequest(http.MethodGet, "/v/"+videoID+"/chat", nil))
+}
+
+func postChat(t *testing.T, app *web.App, videoID string, form url.Values, htmx bool) *httptest.ResponseRecorder {
+	t.Helper()
+	req := httptest.NewRequest(http.MethodPost, "/v/"+videoID+"/chat", strings.NewReader(form.Encode()))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	if htmx {
+		req.Header.Set("HX-Request", "true")
+	}
+	return do(t, app, req)
+}
+
+// --- scenarios -------------------------------------------------------------
+
+// The "dig deeper" affordance appears on a summary detail view only when chat is
+// enabled, and links to that video's chat — the single entry point (ADR-027 §1).
+func TestChatEntryAffordanceOnSummaryView(t *testing.T) {
+	ctx := context.Background()
+	withChat := newChatApp(t, &fakeChatter{models: []string{"phi4-mini"}}, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, withChat, videoX, "body x"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+
+	html := body(t, do(t, withChat, httptest.NewRequest(http.MethodGet, "/v/"+videoX, nil)))
+	require.Contains(t, html, "Dig deeper", "the deeper-dive affordance is shown when chat is enabled")
+	require.Contains(t, html, "/v/"+videoX+"/chat", "it links to this video's chat")
+	require.Contains(t, html, `id="chat-section"`, "the dock lives on the detail page")
+	require.Contains(t, html, `hx-get="/v/`+videoX+`/chat"`, "it opens the chat in place (HTMX), not a navigation")
+
+	// With no chat backend wired the affordance is absent (routes unmounted).
+	noChat := newApp(t)
+	require.NoError(t, deliver(ctx, noChat, videoX, "body x"))
+	html = body(t, do(t, noChat, httptest.NewRequest(http.MethodGet, "/v/"+videoX, nil)))
+	require.NotContains(t, html, "Dig deeper", "no affordance when chat is disabled")
+}
+
+// The summary and the chat live together (the integrated UX): the no-JS chat page
+// renders the full summary alongside the chat, and the HTMX reveal returns just
+// the open chat section as a fragment so it docks in below the summary already on
+// screen — the summary is never navigated away from.
+func TestChatIntegratedWithSummaryOnSamePage(t *testing.T) {
+	ctx := context.Background()
+	chatter := &fakeChatter{models: []string{"phi4-mini", "gemma4-26b"}}
+	app := newChatApp(t, chatter, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "SUMMARY-BODY-MARKER"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	seedTranscript(t, app.Store.(*store.Store), videoX, "the transcript")
+
+	// No-JS full page: the summary payload and the chat are on one page.
+	html := body(t, getChat(t, app, videoX))
+	require.Contains(t, html, "SUMMARY-BODY-MARKER", "the summary text is shown on the chat page")
+	require.Contains(t, html, "takeaway one", "takeaways shown alongside the chat")
+	require.Contains(t, html, "highlight one", "highlights shown alongside the chat")
+	require.Contains(t, html, "Ask about this video", "the chat sits on the same page as the summary")
+	require.Contains(t, html, `name="question"`, "the ask form is present")
+
+	// HTMX reveal: the open chat section ONLY (a fragment) — no full-page chrome and
+	// no duplicated summary, so it swaps in below the summary already rendered.
+	req := httptest.NewRequest(http.MethodGet, "/v/"+videoX+"/chat", nil)
+	req.Header.Set("HX-Request", "true")
+	frag := body(t, do(t, app, req))
+	require.NotContains(t, frag, "<html", "the reveal is a fragment, not a full page")
+	require.NotContains(t, frag, "SUMMARY-BODY-MARKER", "the reveal does not re-send the summary (it's already on screen)")
+	require.Contains(t, frag, `id="chat-section"`, "the fragment replaces the dock in place")
+	require.Contains(t, frag, `name="question"`, "the ask form is in the revealed section")
+}
+
+// THE KEY SAFETY ASSERTION (ADR-027): a chat answer is produced entirely from the
+// stored transcript — the model receives the stored text, and neither the
+// summarize→fetch path nor the YouTube fetch path is ever touched. The tripwire
+// collaborators t.Fatal the test if chat reaches them.
+func TestChatAnswersFromStoredTranscriptWithoutAnyFetch(t *testing.T) {
+	ctx := context.Background()
+	const transcript = "STORED-TRANSCRIPT-MARKER: the host explains attention budgets."
+	chatter := &fakeChatter{
+		models: []string{"phi4-mini"},
+		reply:  chat.Reply{Answer: "It is about attention budgets."},
+	}
+	app := newChatApp(t, chatter, func(a *web.App) {
+		a.Processor = tripwireProcessor{t} // fails the test if chat summarizes/fetches
+		a.Fetcher = tripwireFetcher{t}     // fails the test if chat fetches video metadata
+	})
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	seedTranscript(t, app.Store.(*store.Store), videoX, transcript)
+
+	form := url.Values{"question": {"what is it about?"}, "model": {"phi4-mini"}}
+	rec := postChat(t, app, videoX, form, true)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Contains(t, body(t, rec), "It is about attention budgets.", "the answer is rendered")
+	require.Equal(t, 1, chatter.callCount, "the model was asked exactly once")
+	require.Equal(t, transcript, chatter.gotReq.Transcript,
+		"the model answered from the STORED transcript, not a fetched one")
+	// The tripwires never firing IS the no-fetch / no-YouTube proof.
+}
+
+// A video with no stored transcript yields an honest "not available" — and never
+// a fetch, never a model call (ADR-027 §2: do not add an on-demand-fetch path).
+func TestChatUnavailableWhenNoStoredTranscript(t *testing.T) {
+	ctx := context.Background()
+	chatter := &fakeChatter{models: []string{"phi4-mini"}}
+	app := newChatApp(t, chatter, func(a *web.App) {
+		a.Processor = tripwireProcessor{t}
+		a.Fetcher = tripwireFetcher{t}
+	})
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	// NB: no seedTranscript — the transcript is absent.
+
+	rec := getChat(t, app, videoX)
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Contains(t, body(t, rec), "isn't available", "honest not-available copy")
+
+	// Asking anyway still triggers nothing: no model call, no fetch.
+	rec = postChat(t, app, videoX, url.Values{"question": {"hi"}, "model": {"phi4-mini"}}, true)
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, 0, chatter.callCount, "no model call without a stored transcript")
+}
+
+// Chat is reachable ONLY from the user's own summary view: opening chat for a
+// video that belongs to another user 404s (the summary read is RLS-scoped), so a
+// guessed/arbitrary video id is not a chat surface (ADR-027 §5 isolation).
+func TestChatOnlyReachableForOwnVideo(t *testing.T) {
+	chatter := &fakeChatter{models: []string{"phi4-mini"}}
+	app := newChatApp(t, chatter, func(a *web.App) {
+		a.Processor = tripwireProcessor{t}
+		a.Fetcher = tripwireFetcher{t}
+	})
+	p := rawPool(t)
+	resetDB(t, p)
+
+	// A summarized video with a stored transcript owned by ANOTHER user.
+	const other = "22222222-2222-2222-2222-222222222222"
+	seedForeignSummaryWithTranscript(t, p, other, videoZ, "Foreign Title")
+
+	rec := getChat(t, app, videoZ)
+	require.Equal(t, http.StatusNotFound, rec.Code, "cannot open chat for another user's video")
+	require.Equal(t, 0, chatter.callCount, "no model call for a non-owned video")
+
+	rec = postChat(t, app, videoZ, url.Values{"question": {"hi"}, "model": {"phi4-mini"}}, true)
+	require.Equal(t, http.StatusNotFound, rec.Code, "cannot post chat to another user's video")
+}
+
+// The switcher offers exactly the backend's models, defaults to the summary's own
+// model, and a switch re-runs against the SAME transcript with the chosen model
+// (ADR-027 §3 — model-comparison instrumentation). A model dropped from the offer
+// set (e.g. cloud disabled) is not rendered.
+func TestChatModelSwitcherDefaultAndSwitch(t *testing.T) {
+	ctx := context.Background()
+	// The seeded summary's model is "phi4-mini" (see handlers_test summary()).
+	chatter := &fakeChatter{
+		models: []string{"phi4-mini", "gemma4-26b"}, // note: no cloud model offered
+		reply:  chat.Reply{Answer: "answer"},
+	}
+	app := newChatApp(t, chatter, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	seedTranscript(t, app.Store.(*store.Store), videoX, "the transcript text")
+
+	html := body(t, getChat(t, app, videoX))
+	require.Contains(t, html, "gemma4-26b", "every offered model is in the switcher")
+	require.NotContains(t, html, "mistral", "a non-offered (cloud-disabled) model is absent")
+	require.Contains(t, html, `value="phi4-mini" selected`, "defaults to the summary's own model")
+
+	// Switching to gemma re-runs against the same stored transcript.
+	form := url.Values{"question": {"q"}, "model": {"gemma4-26b"}}
+	rec := postChat(t, app, videoX, form, true)
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Equal(t, "gemma4-26b", chatter.gotReq.Model, "the chosen model answers")
+	require.Equal(t, "the transcript text", chatter.gotReq.Transcript, "against the same transcript")
+}
+
+// A truncated transcript surfaces the honest bounded-context note (ADR-027 §2).
+func TestChatTruncationNoteShown(t *testing.T) {
+	ctx := context.Background()
+	chatter := &fakeChatter{
+		models: []string{"phi4-mini"},
+		reply:  chat.Reply{Answer: "answer", Truncated: true},
+	}
+	app := newChatApp(t, chatter, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	seedTranscript(t, app.Store.(*store.Store), videoX, "long transcript")
+
+	rec := postChat(t, app, videoX, url.Values{"question": {"q"}, "model": {"phi4-mini"}}, true)
+	require.Contains(t, body(t, rec), "bounded portion", "the truncation note is shown")
+}
+
+// A multi-turn conversation is carried in the request (hidden fields), not the DB:
+// prior turns ride back into the next answer, and nothing is persisted (ADR-027 §4).
+func TestChatMultiTurnHistoryIsEphemeral(t *testing.T) {
+	ctx := context.Background()
+	chatter := &fakeChatter{models: []string{"phi4-mini"}, reply: chat.Reply{Answer: "second answer"}}
+	app := newChatApp(t, chatter, nil)
+	p := rawPool(t)
+	resetDB(t, p)
+	require.NoError(t, deliver(ctx, app, videoX, "summary body"))
+	seedVideo(t, p, videoX, "X Title", "https://x", time.Time{})
+	seedTranscript(t, app.Store.(*store.Store), videoX, "the transcript")
+
+	// Second turn posts the prior exchange as hidden history fields.
+	form := url.Values{
+		"question": {"follow-up question"},
+		"model":    {"phi4-mini"},
+		"hq":       {"first question"},
+		"ha":       {"first answer"},
+	}
+	rec := postChat(t, app, videoX, form, true)
+	require.Equal(t, http.StatusOK, rec.Code)
+
+	require.Len(t, chatter.gotReq.History, 1, "the prior turn was carried into the request")
+	require.Equal(t, "first question", chatter.gotReq.History[0].Question)
+	require.Equal(t, "first answer", chatter.gotReq.History[0].Answer)
+
+	html := body(t, rec)
+	require.Contains(t, html, "second answer", "the new answer renders")
+	require.Contains(t, html, "first question", "the conversation persists in page state")
+
+	// Nothing was written to the DB — there is no chat table; the summaries/actions
+	// are unchanged by a chat turn.
+	row, err := app.Store.GetSummaryByVideo(ctx, userID, videoX)
+	require.NoError(t, err)
+	require.Equal(t, "summary body", row.Summary, "chat never mutates stored data")
+}
+
+// --- foreign-user seeding (isolation) --------------------------------------
+
+// seedForeignSummaryWithTranscript creates a fully-summarized, transcript-backed
+// video owned by a DIFFERENT user via the raw pool (which bypasses RLS), so the
+// isolation test can confirm the requesting user cannot open chat for it.
+func seedForeignSummaryWithTranscript(t *testing.T, p *pgxpool.Pool, otherUserID, videoID, title string) {
+	t.Helper()
+	ctx := context.Background()
+	_, err := p.Exec(ctx, `INSERT INTO users (id) VALUES ($1) ON CONFLICT (id) DO NOTHING`, otherUserID)
+	require.NoError(t, err)
+	_, err = p.Exec(ctx,
+		`INSERT INTO videos (id, user_id, provider, provider_video_id, title, url)
+		 VALUES ($1, $2, 'youtube', $3, $4, 'https://z')`,
+		videoID, otherUserID, seededProviderVideoID(videoID), title)
+	require.NoError(t, err)
+	_, err = p.Exec(ctx,
+		`INSERT INTO summaries (user_id, video_id, summary, ai_provider, ai_model)
+		 VALUES ($1, $2, 'foreign summary', 'local', 'phi4-mini')`,
+		otherUserID, videoID)
+	require.NoError(t, err)
+	_, err = p.Exec(ctx,
+		`INSERT INTO transcripts (provider, provider_video_id, source, language, content)
+		 VALUES ('youtube', $1, 'captions', 'en', 'foreign transcript')`,
+		seededProviderVideoID(videoID))
+	require.NoError(t, err)
+}

internal/web/handlers.go

@@ -26,6 +26,10 @@ type Store interface {
 	DistinctChannels(ctx context.Context, userID string) ([]string, error)
 	GetSummaryByVideo(ctx context.Context, userID, videoID string) (*store.SummaryRow, error)
 	GetVideoRow(ctx context.Context, userID, videoID string) (*store.SummaryRow, error)
+	// GetTranscript reads the shared, stored transcript keyed by (provider,
+	// providerVideoID) — ADR-021. It is a pure DB read: it never fetches captions,
+	// so the chat path (ADR-027) reaches it without any caption-fetch surface.
+	GetTranscript(ctx context.Context, provider, providerVideoID string) (domain.Transcript, bool, error)
 	ActionsFor(ctx context.Context, userID string, videoIDs []string) (map[string][]string, error)
 	SetAction(ctx context.Context, userID, videoID, action string) error
 	ClearAction(ctx context.Context, userID, videoID, action string) error
@@ -91,6 +95,11 @@ type App struct {
 	// Fetcher, when non-nil, resolves an arbitrary YouTube video id to metadata for
 	// the paste-a-URL flow (Feature 2). Nil = the /paste route is not mounted.
 	Fetcher VideoFetcher
+	// Chat, when non-nil, answers per-video questions against a video's STORED
+	// transcript (ADR-027). Nil = the /v/{id}/chat routes are not mounted and the
+	// summary view shows no "dig deeper" affordance. It holds no caption-fetch
+	// dependency, so an enabled chat cannot reach YouTube or the rate gate.
+	Chat Chatter
 	// Processing tracks in-flight immediate summarizations so the status endpoint
 	// shows the animation until the summary lands. The zero value is ready to use.
 	Processing ProcessingSet
@@ -149,6 +158,12 @@ func (a *App) Router() http.Handler {
 		app.HandleFunc("POST /paste", a.handlePaste)
 	}
 	app.HandleFunc("GET /v/{videoId}/status", a.handleStatus)
+	// Per-video deeper-dive chat over the STORED transcript (ADR-027). Mounted only
+	// when a Chat backend is wired; it never fetches captions.
+	if a.Chat != nil {
+		app.HandleFunc("GET /v/{videoId}/chat", a.handleChat)
+		app.HandleFunc("POST /v/{videoId}/chat", a.handleChatMessage)
+	}
 	app.HandleFunc("GET /register", a.handleRegisterForm)
 	app.HandleFunc("POST /register", a.handleRegister)
 
@@ -265,7 +280,7 @@ func (a *App) handleDetail(w http.ResponseWriter, r *http.Request) {
 		a.serverError(w, r, "get summary", err)
 		return
 	}
-	a.render(w, r, DetailPage(*row))
+	a.render(w, r, DetailPage(*row, a.Chat != nil))
 }
 
 // handleAction toggles one action: re-clicking an active verb clears it, else it
@@ -495,11 +510,22 @@ func (a *App) handleStatus(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if row.Summarized || !a.Processing.Has(processingKey(userID, videoID)) {
+	// Honest, state-aware status (ADR-025). Order matters: a finished summary wins;
+	// an in-flight goroutine shows the working spinner; a recorded rate-limit shows
+	// the calm "waiting, will retry" card that keeps polling; a recorded "none" is
+	// terminal; anything else falls back to the normal card.
+	switch {
+	case row.Summarized:
 		a.render(w, r, VideoCard(*row))
-		return
+	case a.Processing.Has(processingKey(userID, videoID)):
-	}
 		a.render(w, r, processingCard(*row))
+	case row.TranscriptStatus == "rate_limited":
+		a.render(w, r, waitingCard(*row))
+	case row.TranscriptStatus == "none":
+		a.render(w, r, noCaptionsCard(*row))
+	default:
+		a.render(w, r, VideoCard(*row))
+	}
 }
 
 // handleSummarizeMode toggles the user's auto/manual summarization mode. The form

internal/web/handlers_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -26,10 +27,22 @@ import (
 var dsn string
 
 func TestMain(m *testing.M) {
-	const port = 54330 // distinct from the store package's embedded PG (54329)
+	// Per-process port + dirs so concurrent `go test` runs (e.g. a push-run and a
+	// tag-run in CI) never collide on a fixed port or shared data dir. Base 55000
+	// keeps web's range distinct from the store package (54000). Shared CachePath
+	// downloads the PG archive once.
+	port := uint32(55000 + os.Getpid()%1000)
 	dsn = fmt.Sprintf("postgres://postgres:postgres@localhost:%d/postgres?sslmode=disable", port)
 
-	pg := embeddedpostgres.NewDatabase(embeddedpostgres.DefaultConfig().Port(port))
+	rt := filepath.Join(os.TempDir(), fmt.Sprintf("tapir-epg-web-%d", os.Getpid()))
+	pg := embeddedpostgres.NewDatabase(
+		embeddedpostgres.DefaultConfig().
+			Port(port).
+			RuntimePath(rt).
+			DataPath(filepath.Join(rt, "data")).
+			BinariesPath(filepath.Join(rt, "bin")).
+			CachePath(filepath.Join(os.TempDir(), "tapir-epg-cache")),
+	)
 	if err := pg.Start(); err != nil {
 		fmt.Fprintf(os.Stderr, "embedded-postgres start: %v\n", err)
 		os.Exit(1)
@@ -38,6 +51,7 @@ func TestMain(m *testing.M) {
 	if err := pg.Stop(); err != nil {
 		fmt.Fprintf(os.Stderr, "embedded-postgres stop: %v\n", err)
 	}
+	_ = os.RemoveAll(rt)
 	os.Exit(code)
 }
 

internal/web/processing_handler_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/stretchr/testify/require"
 
 	"gitea.d-ma.be/mathias/tapir/internal/web"
@@ -129,3 +130,42 @@ func getStatus(t *testing.T, app *web.App, videoID string) *httptest.ResponseRec
 	app.Router().ServeHTTP(rec, req)
 	return rec
 }
+
+// setTranscriptStatus stamps videos.transcript_status directly (bypassing RLS via
+// the super pool) so a test can drive the status endpoint into a given state.
+func setTranscriptStatus(t *testing.T, p *pgxpool.Pool, videoID, status string) {
+	t.Helper()
+	_, err := p.Exec(context.Background(),
+		`UPDATE videos SET transcript_status = $2 WHERE id = $1`, videoID, status)
+	require.NoError(t, err)
+}
+
+// TestStatusRateLimitedShowsWaitingCard: a click that hit YouTube's rate limit
+// must surface the honest "waiting, will retry" card that keeps polling — not a
+// silent revert to the Summarize button.
+func TestStatusRateLimitedShowsWaitingCard(t *testing.T) {
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	seedVideo(t, p, videoX, "Throttled Title", "https://x", time.Time{})
+	setTranscriptStatus(t, p, videoX, "rate_limited")
+
+	html := body(t, getStatus(t, app, videoX))
+	require.Contains(t, html, "Waiting on YouTube rate limits", "honest rate-limit copy")
+	require.Contains(t, html, `hx-trigger="every 30s"`, "waiting card keeps polling so it self-resolves")
+	require.NotContains(t, html, "Summarize this video", "must not revert to the Summarize button")
+}
+
+// TestStatusNoCaptionsTerminal: a no-captions outcome is terminal — an honest
+// message, no poll, no button to click back into the same dead end.
+func TestStatusNoCaptionsTerminal(t *testing.T) {
+	app := newApp(t)
+	p := rawPool(t)
+	resetDB(t, p)
+	seedVideo(t, p, videoX, "Silent Title", "https://x", time.Time{})
+	setTranscriptStatus(t, p, videoX, "none")
+
+	html := body(t, getStatus(t, app, videoX))
+	require.Contains(t, html, "No captions available", "honest terminal copy")
+	require.NotContains(t, html, "hx-trigger", "terminal card must stop polling")
+}

internal/web/view.go

@@ -184,6 +184,12 @@ func statusURL(videoID string) templ.SafeURL {
 	return templ.SafeURL("/v/" + videoID + "/status")
 }
 
+// chatURL builds the per-video chat path (GET renders the page, POST answers) —
+// the deeper-dive over the stored transcript (ADR-027).
+func chatURL(videoID string) templ.SafeURL {
+	return templ.SafeURL("/v/" + videoID + "/chat")
+}
+
 // 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.
@@ -658,11 +664,30 @@ a.btn, a.btn:visited { color: var(--accent-fg); }
 .tapir-bar-fill { animation: tapir-fill 8s linear infinite; text-shadow: 0 0 6px rgba(14, 249, 182, .7); }
 @keyframes tapir-fill { 0% { clip-path: inset(0 100% 0 0); } 100% { clip-path: inset(0 0 0 0); } }
 .tapir-label { color: var(--muted); font-size: .9rem; margin: 0; }
+/* Cycling status verbs (Claude-Code / Crush style): five gerunds stacked, each
+   visible 1/5 of a 6s loop, cross-faded. The container reserves one line height
+   so the layout does not jump as verbs swap. */
+.tapir-verbs { position: relative; height: 1.3em; margin: .2em 0 0; color: var(--muted); font-size: .9rem; }
+.tapir-verbs span { position: absolute; left: 0; top: 0; white-space: nowrap; opacity: 0; animation: tapir-verb 6s steps(1, end) infinite; }
+.tapir-verbs .tv1 { animation-delay: 0s; }
+.tapir-verbs .tv2 { animation-delay: 1.2s; }
+.tapir-verbs .tv3 { animation-delay: 2.4s; }
+.tapir-verbs .tv4 { animation-delay: 3.6s; }
+.tapir-verbs .tv5 { animation-delay: 4.8s; }
+@keyframes tapir-verb { 0%, 19.99% { opacity: 1; } 20%, 100% { opacity: 0; } }
+/* Resting tapir for the rate-limit waiting state: the panel, one still frame, no
+   animation — calm, not busy, signalling "parked, not stuck". */
+.tapir-resting pre { position: relative; opacity: 1; animation: none; }
+.card-waiting { border-style: dashed; opacity: .92; }
+.card-no-captions .card-state { font-style: italic; }
+.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
 @media (prefers-reduced-motion: reduce) {
   .tapir-charm pre { animation: none; }
   .tapir-charm .tapir-f2, .tapir-charm .tapir-f3 { display: none; }
   .tapir-charm .tapir-f1 { opacity: 1; }
   .tapir-bar-fill { animation: none; clip-path: inset(0 35% 0 0); }
+  .tapir-verbs span { animation: none; }
+  .tapir-verbs .tv1 { opacity: 1; }
 }
 
 /* summarization mode toggle on the account page */
@@ -706,6 +731,30 @@ a.btn, a.btn:visited { color: var(--accent-fg); }
 .detail ul { margin: 0; padding-left: 1.2rem; line-height: 1.6; }
 .detail li { margin-bottom: var(--s1); }
 
+/* deeper-dive chat (ADR-027) — docks in place below the summary */
+.chat-dock { margin-top: var(--s5); border-top: 1px solid var(--line); padding-top: var(--s4); }
+.chat-dock .chat-open { display: inline-block; }
+.chat-heading { font-size: 1.1rem; margin: 0 0 var(--s2); }
+.chat-scope { margin: 0 0 var(--s3); font-size: .9rem; }
+.chat-panel { display: flex; flex-direction: column; gap: var(--s3); }
+.chat-log { display: flex; flex-direction: column; gap: var(--s3); }
+.chat-turn { border-radius: var(--radius); padding: var(--s2) var(--s3); }
+.chat-turn p { margin: 0; }
+.chat-q { background: var(--accent-weak); color: var(--fg); align-self: flex-end; max-width: 85%; }
+.chat-a { background: var(--card); border: 1px solid var(--line); }
+.chat-a .body { white-space: pre-wrap; line-height: 1.6; }
+.chat-note { margin: 0; font-size: .82rem; font-style: italic; }
+.chat-error { margin: 0; color: #8a1c10; font-size: .9rem; }
+@media (prefers-color-scheme: dark) { .chat-error { color: #f3b5ae; } }
+.chat-form { display: flex; flex-direction: column; gap: var(--s2); margin: var(--s2) 0 0; }
+.chat-model { flex-direction: column; display: flex; gap: var(--s1); font-size: .78rem; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); align-items: flex-start; }
+.chat-model select { font: inherit; text-transform: none; letter-spacing: 0; padding: .4rem .55rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); color: var(--fg); }
+.chat-model-hint { text-transform: none; letter-spacing: 0; font-size: .78rem; }
+.chat-form textarea { font: inherit; padding: .55rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); color: var(--fg); resize: vertical; }
+.chat-form textarea:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; border-color: var(--accent); }
+.chat-form .btn { align-self: flex-start; }
+.chat-thinking { font-style: italic; }
+
 /* action toggles — watched|skipped form one segmented control (they are mutually
    exclusive), "saved" sits apart as an independent toggle */
 .actions { display: flex; gap: var(--s3); margin: var(--s4) 0; flex-wrap: wrap; align-items: center; }

internal/web/views.templ

@@ -339,7 +339,17 @@ templ TapirSpinner() {
 		<pre class="tapir-f3">@templ.Raw(tapirFrameHTML3)</pre>
 		<div class="tapir-bar"><span class="tapir-bar-fill" style={ "color:" + CharmMint }>{ tapirBarFill }</span></div>
 	</div>
-	<p class="tapir-label" role="status" aria-live="polite"><em>Summarizing…</em></p>
+	// Claude-Code / Crush-style status: playful gerunds cycle in place (CSS only,
+	// no JS). Decorative — aria-hidden — with one stable status line below for
+	// assistive tech.
+	<p class="tapir-verbs" aria-hidden="true">
+		<span class="tv1"><em>Fetching captions…</em></span>
+		<span class="tv2"><em>Chewing the cud…</em></span>
+		<span class="tv3"><em>Munching leaves…</em></span>
+		<span class="tv4"><em>Distilling the gist…</em></span>
+		<span class="tv5"><em>Summarizing…</em></span>
+	</p>
+	<p class="sr-only" role="status" aria-live="polite">Summarizing…</p>
 }
 
 // processingCard is the in-flight summarization card. It replaces the Summarize
@@ -363,13 +373,48 @@ templ processingCard(r store.SummaryRow) {
 	</li>
 }
 
-// DetailPage is the full summary view: text, highlights, takeaways, metadata,
+// waitingCard is the honest rate-limited state: the click landed but YouTube is
-// and the action button group.
+// throttling the caption fetch, so the tapir rests and the card keeps polling
-templ DetailPage(r store.SummaryRow) {
+// (gently, every 30s) until the background retry lands the summary — the user
-	@Layout("Tapir — " + displayTitle(r)) {
+// never has to click again. Replaces the old silent revert to a Summarize button.
-		<article class="detail">
+templ waitingCard(r store.SummaryRow) {
-			<p class="back"><a href="/">← Summaries</a></p>
+	<li
-			<h1>{ displayTitle(r) }</h1>
+		class="card card-waiting"
+		id={ "video-" + r.VideoID }
+		hx-get={ string(statusURL(r.VideoID)) }
+		hx-trigger="every 30s"
+		hx-swap="outerHTML"
+	>
+		<div class="card-title">{ displayTitle(r) }</div>
+		if cardMeta(r) != "" {
+			<div class="card-meta">{ cardMeta(r) }</div>
+		}
+		<div class="tapir-charm tapir-resting" aria-hidden="true">
+			<pre class="tapir-f1">@templ.Raw(tapirFrameHTML2)</pre>
+		</div>
+		<p class="tapir-label" role="status" aria-live="polite">
+			Waiting on YouTube rate limits. Tapir keeps trying, slowly and politely, and the summary will appear here on its own.
+		</p>
+	</li>
+}
+
+// noCaptionsCard is the terminal no-captions state: nothing to summarize, so the
+// card stops (no poll, no button to click again into the same dead end).
+templ noCaptionsCard(r store.SummaryRow) {
+	<li class="card card-no-captions" id={ "video-" + r.VideoID }>
+		<div class="card-title">{ displayTitle(r) }</div>
+		if cardMeta(r) != "" {
+			<div class="card-meta">{ cardMeta(r) }</div>
+		}
+		<p class="card-state muted">No captions available, so Tapir cannot summarize this one.</p>
+	</li>
+}
+
+// summaryBody is the summary payload shared by the detail page and the no-JS
+// chat page (so the chat page shows the same summary, not a separate view):
+// metadata, embed, source, the action toggles, then the attention-saving order
+// Takeaways → Highlights → Summary (UX review A8).
+templ summaryBody(r store.SummaryRow) {
 	<p class="meta">
 		if detailMeta(r) != "" {
 			<span>{ detailMeta(r) }</span>
@@ -394,10 +439,6 @@ templ DetailPage(r store.SummaryRow) {
 		<p class="source"><a href={ externalURL(r.URL) } rel="noopener noreferrer">watch on source ↗</a></p>
 	}
 	@ActionButtons(r.VideoID, actionSet(r.Actions))
-			// Lead with the attention-saving payload: Takeaways ("is this worth my
-			// time?") first, then Highlights, then the full Summary last (UX review
-			// A8). Takeaways/Highlights are conditional, so a video without them falls
-			// through to the Summary leading naturally.
 	if len(r.Takeaways) > 0 {
 		<section>
 			<h2>Takeaways</h2>
@@ -422,10 +463,122 @@ templ DetailPage(r store.SummaryRow) {
 		<h2>Summary</h2>
 		<p class="body">{ r.Summary }</p>
 	</section>
+}
+
+// DetailPage is the full summary view: the summary payload, then (when chat is
+// enabled) the deeper-dive dock (ADR-027) — a reveal that opens the chat IN PLACE
+// below the summary, so the summary stays on screen as the context being asked
+// about rather than being navigated away from.
+templ DetailPage(r store.SummaryRow, chatEnabled bool) {
+	@Layout("Tapir — " + displayTitle(r)) {
+		<article class="detail">
+			<p class="back"><a href="/">← Summaries</a></p>
+			<h1>{ displayTitle(r) }</h1>
+			@summaryBody(r)
+			if chatEnabled {
+				@chatReveal(r.VideoID)
+			}
 		</article>
 	}
 }
 
+// chatReveal is the CLOSED dock at the foot of the summary: a quiet affordance,
+// not a loud CTA (it deepens value for a reader already here, never nudges). With
+// JS it swaps itself for the open chat section in place (HTMX, summary stays
+// above); without JS the same href navigates to the full chat page, which renders
+// the summary alongside the chat. Either way the summary is never lost.
+templ chatReveal(videoID string) {
+	<section id="chat-section" class="chat-dock">
+		<a
+			class="btn-secondary chat-open"
+			href={ chatURL(videoID) }
+			hx-get={ string(chatURL(videoID)) }
+			hx-target="#chat-section"
+			hx-swap="outerHTML"
+		>
+			Dig deeper — ask about this video →
+		</a>
+	</section>
+}
+
+// chatSection is the OPEN dock: heading + scope note + the chat panel, swapped in
+// over the closed reveal (same #chat-section id, outerHTML). It is the HTMX reveal
+// response AND the inline chat block on the no-JS chat page.
+templ chatSection(v chatView) {
+	<section id="chat-section" class="chat-dock chat-dock-open">
+		<h2 class="chat-heading">Ask about this video</h2>
+		<p class="chat-scope muted">Answers come only from this video's stored transcript — Tapir never fetches anything new here.</p>
+		@chatPanel(v)
+	</section>
+}
+
+// ChatPage is the no-JS full-page render of the chat: the whole summary followed
+// by the open chat dock, so a visitor without JS sees the same integrated view
+// (summary beside the conversation) that JS users get inline via the reveal.
+templ ChatPage(r store.SummaryRow, v chatView) {
+	@Layout("Tapir — " + displayTitle(r)) {
+		<article class="detail">
+			<p class="back"><a href="/">← Summaries</a></p>
+			<h1>{ displayTitle(r) }</h1>
+			@summaryBody(r)
+			@chatSection(v)
+		</article>
+	}
+}
+
+// chatPanel is the conversation + ask form, swapped in place on each answer
+// (HTMX targets #chat-panel, outerHTML). When no transcript is stored it shows the
+// honest "not available" state and no form (ADR-027: never a fetch). The prior
+// turns ride as hidden hq/ha fields so the ephemeral conversation survives the
+// round-trip without any persisted state.
+templ chatPanel(v chatView) {
+	<div id="chat-panel" class="chat-panel">
+		if !v.Available {
+			<p class="chat-unavailable muted">Chat isn't available for this video — its transcript isn't stored, and chat never fetches new captions. Summarize the video first to store its transcript.</p>
+		} else {
+			if len(v.History) > 0 {
+				<div class="chat-log">
+					for _, t := range v.History {
+						<div class="chat-turn chat-q"><p>{ t.Question }</p></div>
+						<div class="chat-turn chat-a"><p class="body">{ t.Answer }</p></div>
+					}
+				</div>
+			}
+			if v.Truncated {
+				<p class="chat-note muted">Working from a bounded portion of a long transcript — answers about the end of the video may be incomplete.</p>
+			}
+			if v.Error != "" {
+				<p class="chat-error" role="alert">{ v.Error }</p>
+			}
+			<form
+				class="chat-form"
+				method="post"
+				action={ chatURL(v.VideoID) }
+				hx-post={ string(chatURL(v.VideoID)) }
+				hx-target="#chat-panel"
+				hx-swap="outerHTML"
+			>
+				for _, t := range v.History {
+					<input type="hidden" name="hq" value={ t.Question }/>
+					<input type="hidden" name="ha" value={ t.Answer }/>
+				}
+				<label class="chat-model">
+					Model
+					<select name="model">
+						for _, m := range v.Models {
+							<option value={ m } selected?={ m == v.Selected }>{ m }</option>
+						}
+					</select>
+					<span class="chat-model-hint muted">Switch models to compare answers on the same transcript.</span>
+				</label>
+				<textarea name="question" rows="3" placeholder="Ask a question about this video…" required aria-label="Your question"></textarea>
+				<button type="submit" class="btn">Ask</button>
+				<span class="htmx-indicator chat-thinking">thinking…</span>
+			</form>
+		}
+	</div>
+}
+
 // RegisterPage is the explicit registration step (ADR-012): an authenticated Dex
 // subject with no tapir user picks a display name to create their account.
 // errMsg, when set, reports a validation problem on the prior POST.

test/acceptance/scenario_coverage_test.go

@@ -63,6 +63,19 @@ var scenarioCoverage = map[string]string{
 	"A returning subject passes straight through":                               "TestRegisteredSubjectPassesThrough",
 	"Deleting an account removes only my data and leaves other users untouched": "TestDeleteAccountWipesDataAndSecretsAndLogsOut",
 
+	// chat_transcript.feature (ADR-027)
+	"A summary view offers a deeper-dive into the video":         "TestChatEntryAffordanceOnSummaryView",
+	"The summary and the chat are on one page":                   "TestChatIntegratedWithSummaryOnSamePage",
+	"Ask a question answered from the stored transcript":         "TestChatAnswersFromStoredTranscriptWithoutAnyFetch",
+	"Chat never fetches captions or reaches YouTube":             "TestChatAnswersFromStoredTranscriptWithoutAnyFetch",
+	"A video with no stored transcript offers no chat":           "TestChatUnavailableWhenNoStoredTranscript",
+	"The default model is the summary's model and is switchable": "TestChatModelSwitcherDefaultAndSwitch",
+	"Switching models re-runs against the same transcript":       "TestChatModelSwitcherDefaultAndSwitch",
+	"The cloud model is hidden when cloud is disabled":           "TestChatCloudModelAbsentWhenDisabled",
+	"A long transcript is bounded and the chat says so":          "TestChatTruncationNoteShown",
+	"A multi-turn conversation is ephemeral":                     "TestChatMultiTurnHistoryIsEphemeral",
+	"Chat is reachable only from my own summary view":            "TestChatOnlyReachableForOwnVideo",
+
 	// summarize_new_video.feature
 	"A subscribed channel posts a video that has captions":         "TestSubscribedVideoWithCaptionsIsSummarizedAndDelivered",
 	"A subscribed channel posts a video with no usable transcript": "TestVideoWithNoTranscriptIsSkipped",