Merge: the advice tap points both ways

Claude-Session: https://claude.ai/code/session_01KGACAtTPjvZ2PipDZ5qD99

internal/llm/lang_test.go

@@ -44,7 +44,7 @@ func TestPromptsNameTheWritersLanguage(t *testing.T) {
 		t.Fatalf("collocation prompt lost its tone guidance:\n%s", collocation)
 	}
 
-	translate := TranslateMessages("Try a shorter sentence here.", pt)[0].Content
+	translate := TranslateMessages("Try a shorter sentence here.", English, pt)[0].Content
 	if !strings.Contains(translate, "European Portuguese") || strings.Contains(translate, "Chinese") {
 		t.Fatalf("translate prompt targets the wrong language:\n%s", translate)
 	}
@@ -76,7 +76,7 @@ func TestDefaultPairStillReadsAsBefore(t *testing.T) {
 	if got := CollocationMessages("x", "", EnglishTarget(zh))[0].Content; !strings.Contains(got, "Simplified Chinese (Mandarin) gloss in parentheses") {
 		t.Fatalf("zh collocation gloss changed:\n%s", got)
 	}
-	if got := TranslateMessages("x", zh)[0].Content; !strings.Contains(got, "natural, friendly Simplified Chinese (Mandarin)") {
+	if got := TranslateMessages("x", English, zh)[0].Content; !strings.Contains(got, "natural, friendly Simplified Chinese (Mandarin)") {
 		t.Fatalf("zh translate target changed:\n%s", got)
 	}
 	if got := AskPetalSystemPrompt("a", "b", "c", "d", "e", zh); !strings.Contains(got, "为什么") {

internal/llm/prompts.go

@@ -329,23 +329,29 @@ func RewriteMessages(text, style string) []Message {
 }
 
 // translateSystemPrompt drives the explanation translator: it renders a
-// suggestion's English explanation into the writer's own language so an ESL
-// reader sees the "why" in her first language. Strict about returning ONLY the
-// translation (no quotes, no romanisation, no English echo) so it can drop
-// straight into the chat bubble. Kept warm and plain — these are short, friendly
-// one-liners.
-const translateSystemPrompt = `You are Petal, a warm writing assistant. Translate the English text the user ` +
-	`sends into natural, friendly %[1]s. It is a short explanation of a writing ` +
-	`suggestion, written for a native %[1]s speaker learning English.
+// suggestion's explanation into the half of the pair the explanation is not
+// already in, so the "why" is readable from both sides. Strict about returning
+// ONLY the translation (no quotes, no romanisation, no echo of the source) so it
+// can drop straight into the chat bubble. Kept warm and plain — these are short,
+// friendly one-liners.
+//
+// Both languages are parameters because neither end is a constant. Until Phase
+// 28 the source was always English and the destination always hers; a document
+// written in her own language is explained in her own language, and then the tap
+// runs the other way, into the English she is practising.
+const translateSystemPrompt = `You are Petal, a warm writing assistant. Translate the %[1]s text the user ` +
+	`sends into natural, friendly %[2]s. It is a short explanation of a writing ` +
+	`suggestion, written for someone who is learning one of %[1]s and %[2]s and reads the other most easily.
 
-Respond with ONLY the %[1]s translation. No quotation marks, no romanisation, no English, no preamble — ` +
+Respond with ONLY the %[2]s translation. No quotation marks, no romanisation, no %[1]s, no preamble — ` +
 	`just the translated sentence.`
 
-// TranslateMessages builds the message array for translating one short English
-// explanation into the writer's own language.
-func TranslateMessages(text string, lang Lang) []Message {
+// TranslateMessages builds the message array for rendering one short
+// explanation out of the language it arrived in and into the other half of the
+// writer's pair.
+func TranslateMessages(text string, from, to Lang) []Message {
 	return []Message{
-		{Role: "system", Content: fmt.Sprintf(translateSystemPrompt, lang.Name)},
+		{Role: "system", Content: fmt.Sprintf(translateSystemPrompt, from.Name, to.Name)},
 		{Role: "user", Content: text},
 	}
 }

internal/llm/translate.go

@@ -4,13 +4,14 @@ import (
 	"context"
 )
 
-// RunTranslate renders a short English explanation into the writer's own
-// language. It is a one-shot Complete (the result seeds the Ask Petal bubble),
-// kept at a low temperature so the translation is faithful rather than creative. Output is
-// trimmed of any stray surrounding quotes the model may add.
-func RunTranslate(ctx context.Context, client LLMClient, text string, lang Lang) (string, error) {
+// RunTranslate renders a short explanation out of the language it was written
+// in and into the other half of the writer's pair. It is a one-shot Complete
+// (the result seeds the Ask Petal bubble), kept at a low temperature so the
+// translation is faithful rather than creative. Output is trimmed of any stray
+// surrounding quotes the model may add.
+func RunTranslate(ctx context.Context, client LLMClient, text string, from, to Lang) (string, error) {
 	out, err := client.Complete(ctx, CompletionRequest{
-		Messages:          TranslateMessages(text, lang),
+		Messages:          TranslateMessages(text, from, to),
 		MaxTokens:         512,
 		Temperature:       0.2,
 		TopP:              0.9,

internal/suggestions/doclang_test.go

@@ -371,10 +371,15 @@ func seedExplanation(t *testing.T, h *Handler, docID, explanation string) string
 
 // The tap-through has to read the same decision the card was written under. On a
 // Portuguese document by a Portuguese writer the explanation already arrived in
-// Portuguese, and the old endpoint would have sent it to the model to be
-// rendered into Portuguese again.
-func TestTranslateSkipsWhenTheExplanationIsAlreadyHers(t *testing.T) {
-	client := &stubClient{response: "Não devia ser chamado."}
+// Portuguese, so the destination is the other half of the pair — the English she
+// is practising — and never Portuguese into Portuguese again.
+//
+// This pins the report that "Petal presents the Ask Petal advice in both
+// sections as Portuguese": the endpoint used to answer "" here, which left the
+// card Portuguese, the bubble beneath it the same Portuguese, and no English on
+// the card at all for a writer whose whole reason for the pair is English.
+func TestTranslateRendersHerExplanationIntoTheEnglishSheIsLearning(t *testing.T) {
+	client := &stubClient{response: "Use this one here."}
 	srv, docID, h := newDirectedServer(t, client, "pt-PT", auth.DirectionLearningEn, ptDocument)
 	setDocLang(t, h, docID, docLangPair)
 	sugID := seedExplanation(t, h, docID, "Aqui usa-se isto.")
@@ -387,11 +392,14 @@ func TestTranslateSkipsWhenTheExplanationIsAlreadyHers(t *testing.T) {
 	if err := json.Unmarshal(rec.Body.Bytes(), &out); err != nil {
 		t.Fatalf("decode: %v", err)
 	}
-	if out.Translation != "" {
-		t.Fatalf("translation = %q, want empty: the bubble seeds from the explanation itself", out.Translation)
+	if out.Translation == "" {
+		t.Fatal("a Portuguese explanation left the tap with nowhere to go")
 	}
-	if client.calls != 0 {
-		t.Fatal("the model was asked to render Portuguese into Portuguese")
+	if !strings.Contains(client.lastPrompt, "into natural, friendly English") {
+		t.Fatalf("translate didn't render into English:\n%s", client.lastPrompt)
+	}
+	if strings.Contains(client.lastPrompt, "into natural, friendly European Portuguese") {
+		t.Fatalf("the model was asked to render Portuguese into Portuguese:\n%s", client.lastPrompt)
 	}
 }
 

internal/suggestions/translate.go

@@ -30,11 +30,18 @@ type translateResponse struct {
 // this endpoint has to read the same decision back, or it round-trips Portuguese
 // into Portuguese and calls it a translation.
 //
-// So: render into whichever half the explanation is NOT already in, and when the
-// explanation already arrived in the language this bubble exists to reach her
-// in, skip the model call and answer "". The client seeds the bubble with the
-// explanation itself when the translation comes back empty, which is exactly
-// right — there is nothing to add.
+// So: render into whichever half the explanation is NOT already in — and that
+// is the whole rule, in both directions. When it first shipped this endpoint
+// answered "" for a Portuguese explanation on the reasoning that an English
+// rendering she hadn't asked for was noise. It was reported as the opposite: a
+// writer whose pair is Portuguese and English, learning English, met a
+// Portuguese card with a Portuguese bubble under it and no English anywhere on
+// the card. The tap is the one place the other language was promised, and the
+// half she is *practising* is exactly the half worth a tap.
+//
+// The bubble sits directly beneath the explanation inside the card, so between
+// the two the writer always has both languages, whichever way round the document
+// put them.
 func (h *Handler) translate(w http.ResponseWriter, r *http.Request) {
 	sugID := chi.URLParam(r, "id")
 
@@ -69,15 +76,14 @@ func (h *Handler) translate(w http.ResponseWriter, r *http.Request) {
 	// today; the alternative is a language column on every suggestion row, and the
 	// cost of being wrong is one bubble seeded in the language it was already in.
 	target := targetFor(pairLang, direction, docLang)
-	if target.Explain.Code == target.Pair.Code {
-		// Already in her language. The other half is English — the language she is
-		// practising — and an unasked-for English rendering of an explanation she
-		// can already read is not a seed, it's noise.
-		httputil.WriteJSON(w, http.StatusOK, translateResponse{Translation: ""})
-		return
+	from, to := target.Explain, target.Pair
+	if from.Code == to.Code {
+		// The explanation is already in her language, so the half this tap has to
+		// reach is the other one: the English she is practising.
+		to = llm.English
 	}
 
-	out, err := llm.RunTranslate(r.Context(), h.Client, explanation, target.Pair)
+	out, err := llm.RunTranslate(r.Context(), h.Client, explanation, from, to)
 	if err != nil {
 		httputil.UpstreamError(w, "translate", err)
 		return

web/src/components/Editor/AskPetal.tsx

@@ -5,12 +5,11 @@ import { splitBilingual } from './bilingualReply'
 import { fromIME } from '../../lib/ime'
 
 interface Props {
+  // The card's explanation is deliberately NOT passed in. Petal's opening
+  // bubble is that explanation rendered into the other half of the pair,
+  // fetched on open from this id — and when that can't be had, the panel has
+  // nothing to say rather than a second copy of the card.
   suggestionId: string
-  // The English explanation (shown in the card body). Petal's opening bubble is
-  // its translation into the pair language, fetched on open — so the panel
-  // doesn't just repeat the same English text twice. Falls back to this on
-  // failure.
-  explanation: string
 }
 
 // CJK fallback stack — Nunito has no Chinese glyphs, and on the zh pair both
@@ -44,10 +43,11 @@ const CHAT_MIN_PX = 160
 // conversation lives in this component's state — nothing is persisted; closing
 // the card (unmounting) clears it. Each send streams Petal's reply token-by-
 // token into the latest assistant bubble.
-export function AskPetal({ suggestionId, explanation }: Props) {
+export function AskPetal({ suggestionId }: Props) {
   const t = usePack()
-  // Opening bubble starts empty (caret-only) and fills with the pair-language
-  // translation once it lands; `seeding` drives that loading caret.
+  // Opening bubble starts empty (caret-only) and fills with the other half of
+  // the pair once it lands; `seeding` drives that loading caret, and the bubble
+  // goes away entirely if there turns out to be nothing to put in it.
   const [messages, setMessages] = useState<ChatMessage[]>([{ role: 'assistant', content: '' }])
   const [seeding, setSeeding] = useState(true)
   const [input, setInput] = useState('')
@@ -82,23 +82,31 @@ export function AskPetal({ suggestionId, explanation }: Props) {
     inputRef.current?.focus({ preventScroll: true })
   }, [])
 
-  // Fetch the pair-language translation of the explanation to seed the first
-  // bubble.
+  // Fetch the explanation rendered into the other half of her pair to seed the
+  // first bubble — English under a Portuguese card, her language under an
+  // English one; the server decides which way round (suggestions/translate.go).
   // Only replaces the seed bubble if the user hasn't started chatting yet (the
-  // conversation always opens with this one assistant turn). Falls back to the
-  // English explanation if the translation can't be fetched.
+  // conversation opens with this one assistant turn and nothing else).
+  //
+  // When it can't be fetched the panel opens empty rather than falling back to
+  // the explanation, which sits two lines higher in the card: a bubble that
+  // repeats the card verbatim reads as Petal answering in the language the tap
+  // was pressed to escape. Nothing to add, nothing shown.
   useEffect(() => {
     let cancelled = false
+    const seed = (text: string) =>
+      setMessages((prev) =>
+        prev.length !== 1 ? prev : text === '' ? [] : [{ role: 'assistant', content: text }],
+      )
     api
       .translateSuggestion(suggestionId)
       .then((res) => {
         if (cancelled) return
-        const text = res.translation.trim() || explanation
-        setMessages((prev) => (prev.length === 1 ? [{ role: 'assistant', content: text }] : prev))
+        seed(res.translation.trim())
       })
       .catch(() => {
         if (cancelled) return
-        setMessages((prev) => (prev.length === 1 ? [{ role: 'assistant', content: explanation }] : prev))
+        seed('')
       })
       .finally(() => {
         if (!cancelled) setSeeding(false)
@@ -106,7 +114,7 @@ export function AskPetal({ suggestionId, explanation }: Props) {
     return () => {
       cancelled = true
     }
-  }, [suggestionId, explanation])
+  }, [suggestionId])
 
   async function send() {
     const text = input.trim()

web/src/components/Editor/SuggestionCard.tsx

@@ -197,7 +197,7 @@ export function SuggestionCard({
         {asking ? 'Hide Petal' : 'Ask Petal ✨'}
       </button>
 
-      {asking && <AskPetal suggestionId={suggestion.id} explanation={suggestion.explanation} />}
+      {asking && <AskPetal suggestionId={suggestion.id} />}
 
       <div className="mt-3 flex items-center gap-2">
         {hasReplacement && (

web/src/components/Editor/SuggestionRail.tsx

@@ -217,7 +217,7 @@ const RailCard = forwardRef<HTMLDivElement, CardProps>(function RailCard(
         </span>
       </button>
 
-      {expanded && <AskPetal suggestionId={suggestion.id} explanation={suggestion.explanation} />}
+      {expanded && <AskPetal suggestionId={suggestion.id} />}
 
       <div className="mt-2.5 flex items-center gap-2">
         {hasReplacement && (