feat(summarizer): move local fallback off koala to iguana/gemma4-26b

koala now carries other GPU loads, so the first fallback should not run there.
Change the default chain to koala/phi4-mini → iguana/gemma4-26b → berget/mistral-small:
the local fallback now runs on iguana (M2 Ultra headroom, different host = 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 fallback path).

Pure config default (TAPIR_FALLBACK_MODEL); chain mechanism (ADR-022) unchanged.

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.
@@ -958,6 +966,36 @@ 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.
+
+---
+
 ## Rejected alternatives
 
 Approaches considered during the 2026-06-02 planning + grill session and **deliberately not

cmd/tapir/processor.go

@@ -113,6 +113,11 @@ 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)

cmd/tapir/scheduler.go

@@ -143,8 +143,18 @@ func runScheduler(
 		return // disabled
 	}
 
-	pass := 0
+	// Derive the rotation offset from wall-clock, NOT an in-memory counter. A
-	runDiscoveryPass(ctx, pass, lister, runUser, log)
+	// 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()
@@ -153,8 +163,7 @@ func runScheduler(
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			pass++
+			runPass()
-			runDiscoveryPass(ctx, pass, lister, runUser, log)
 		}
 	}
 }

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.

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/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
@@ -148,7 +151,7 @@ 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

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)
 }