The catalog Discuss button never worked

apps/mobile/app/book/[slug].tsx

@@ -552,6 +552,11 @@ export default function BookDetailScreen() {
             title={book.title}
             author={book.authors.map(a => a.name).join(', ') || null}
             editionId={book.id}
+            // Both identifiers: the read tools are slug-keyed, the insight tools are editionId-keyed.
+            slug={book.slug}
+            // Already fetched for Continue Reading; the assistant was told none of it until now.
+            progressFraction={continuePct}
+            chapterTitle={book.chapters.find(c => c.slug === continueSlug)?.title ?? null}
           />
         )}
 

apps/web/src/components/library/__tests__/DiscussWithAssistant.test.tsx

@@ -31,15 +31,20 @@ describe('DiscussWithAssistant', () => {
     }
   })
 
-  it('names an upload by bookId and a catalog book by editionId, never both', () => {
+  it('names an upload by bookId, and a catalog book by BOTH slug and editionId', () => {
     const { unmount } = render(<DiscussWithAssistant title="D" bookId="b-1" />)
     expect(decodeURIComponent(hrefOf('library.discuss.claude'))).toContain('bookId b-1')
     expect(decodeURIComponent(hrefOf('library.discuss.claude'))).not.toContain('editionId')
     unmount()
 
-    render(<DiscussWithAssistant title="D" editionId="e-1" />)
-    expect(decodeURIComponent(hrefOf('library.discuss.claude'))).toContain('editionId e-1')
-    expect(decodeURIComponent(hrefOf('library.discuss.claude'))).not.toContain('bookId')
+    // A catalog book needs both: get_book/get_chapter are slug-keyed, the insight tools are
+    // editionId-keyed. Sending only the id named tools that reject every call made from it, which
+    // is why the catalog button did not work at all until 2026-09-10.
+    render(<DiscussWithAssistant title="D" editionId="e-1" slug="dracula" />)
+    const brief = decodeURIComponent(hrefOf('library.discuss.claude'))
+    expect(brief).toContain('editionId e-1')
+    expect(brief).toContain('"dracula"')
+    expect(brief).not.toContain('bookId')
   })
 
   it('reads progress as a fraction, not as a percentage', () => {

apps/web/src/pages/BookDetailPage.tsx

@@ -363,6 +363,12 @@ export function BookDetailPage() {
           title={book.title}
           author={book.authors.map(a => a.name).join(', ') || null}
           editionId={book.id}
+          // A catalog book needs BOTH: get_book/get_chapter take the slug, the insight tools take
+          // the editionId. Sending only the id named tools that would reject every call.
+          slug={book.slug}
+          // The screen already knows where the reader stopped — the Continue Reading button above
+          // is built from it — and used to hand the assistant none of it.
+          chapterTitle={book.chapters.find(c => c.slug === continueSlug)?.title ?? null}
         />
       )}
 

packages/shared/src/lib/assistantHandoff.test.ts

@@ -31,16 +31,90 @@ describe('buildHandoffBrief', () => {
     expect(brief).not.toContain('editionId')
   })
 
-  it('names a catalog book by editionId and points at the catalog tools', () => {
+  /**
+   * Which identifier each tool actually accepts, mirroring the JSON schemas in
+   * `McpToolCatalog` — all of which set `additionalProperties: false`, so passing the wrong one is
+   * a rejected call rather than an ignored field.
+   *
+   * This table is the point of the test below. The previous version asserted that the brief string
+   * contained the substring "get_book" — prose checked against prose — and therefore passed happily
+   * while the brief handed `get_book` an editionId it cannot take. The catalog Discuss button did
+   * not work at all, and no test noticed. Keep this in step with the schemas.
+   */
+  const TOOL_IDENTIFIER: Record<string, ReadonlyArray<'slug' | 'editionId' | 'bookId'>> = {
+    get_book: ['slug'],
+    get_chapter: ['slug'],
+    get_my_book: ['bookId'],
+    get_my_chapter: ['bookId'],
+    // The insight tools take EITHER, XOR, keyed by book type: bookId for an upload, editionId for a
+    // catalog book. So they are satisfied by whichever one the brief is carrying.
+    get_my_insights: ['bookId', 'editionId'],
+    save_insight: ['bookId', 'editionId'],
+  }
+
+  /** Every tool the brief names, in order of appearance. */
+  const toolsNamedIn = (brief: string) =>
+    Object.keys(TOOL_IDENTIFIER).filter(name => brief.includes(name))
+
+  it('gives a catalog book BOTH identifiers, each next to the tools that take it', () => {
     const brief = buildHandoffBrief({
       title: 'Dracula',
       editionId: '33333333-3333-3333-3333-333333333333',
+      slug: 'dracula',
     })
+
+    // Read tools are slug-keyed; insight tools are editionId-keyed. A brief carrying only one of
+    // the two names tools that would reject every call made from it.
+    expect(brief).toContain('"dracula"')
     expect(brief).toContain('editionId 33333333-3333-3333-3333-333333333333')
-    expect(brief).toContain('get_book')
+    expect(toolsNamedIn(brief)).toContain('get_book')
+    expect(toolsNamedIn(brief)).toContain('save_insight')
     expect(brief).not.toContain('bookId')
   })
 
+  it('never names a tool without the identifier that tool accepts', () => {
+    const cases = [
+      {
+        what: 'catalog',
+        book: { title: 'Dracula', editionId: '33333333-3333-3333-3333-333333333333', slug: 'dracula' },
+        present: { slug: '"dracula"', editionId: 'editionId 33333333-3333-3333-3333-333333333333' },
+      },
+      {
+        what: 'upload',
+        book: { title: 'My PDF', bookId: '22222222-2222-2222-2222-222222222222' },
+        present: { bookId: 'bookId 22222222-2222-2222-2222-222222222222' },
+      },
+    ] as const
+
+    for (const c of cases) {
+      const brief = buildHandoffBrief(c.book)
+      const named = toolsNamedIn(brief)
+      expect(named.length).toBeGreaterThan(0)
+
+      for (const tool of named) {
+        const accepts = TOOL_IDENTIFIER[tool]
+        const carried = accepts.some(id => {
+          const marker = (c.present as Record<string, string | undefined>)[id]
+          return marker !== undefined && brief.includes(marker)
+        })
+        expect(
+          carried,
+          `${c.what} brief names ${tool}, which takes ${accepts.join(' or ')}, but carries none of them`,
+        ).toBe(true)
+      }
+    }
+  })
+
+  it('says nothing about the connector when a catalog book has no slug', () => {
+    // Half the pair is worse than none: it would name slug-keyed tools with nothing to give them.
+    const brief = buildHandoffBrief({
+      title: 'Dracula',
+      editionId: '33333333-3333-3333-3333-333333333333',
+    })
+    expect(brief).not.toContain('get_book')
+    expect(brief).not.toContain('editionId')
+  })
+
   it('asks the assistant to write conclusions back', () => {
     // Without this line the conversation happens and nothing comes home, which is
     // the entire failure mode the feature exists to fix.

packages/shared/src/lib/assistantHandoff.ts

@@ -34,6 +34,15 @@ export interface HandoffBook {
   bookId?: string
   /** Edition id for a catalog book. */
   editionId?: string
+  /**
+   * The catalog book's slug. Required alongside `editionId`, not instead of it: a catalog book needs
+   * BOTH identifiers because the tools disagree about which one they take. `get_book` and
+   * `get_chapter` are keyed by slug (`"required": ["slug"]`, `additionalProperties: false`), while
+   * `save_insight` and `get_my_insights` are keyed by `editionId`. Handing an assistant only the
+   * editionId — which this did until 2026-09-10 — produced a brief naming tools that would reject
+   * every call made from it, so the catalog Discuss button never worked at all.
+   */
+  slug?: string
   /**
    * How far in, as a FRACTION of the book: 0..1, the way progress is stored
    * everywhere else in this codebase ("the server stores a book-wide fraction",
@@ -76,19 +85,22 @@ export function buildHandoffBrief(book: HandoffBook): string {
 
   // The identifier and the tool names. A connected client acts on this; an
   // unconnected one ignores it and the conversation still works.
-  const id = book.bookId
-    ? `bookId ${book.bookId}`
-    : book.editionId
-      ? `editionId ${book.editionId}`
-      : null
-  if (id) {
+  // An upload is addressed by one id everywhere. A catalog book is not: the read tools take a slug
+  // and the insight tools take an editionId, so the brief has to carry both and say which is which.
+  if (book.bookId) {
+    lines.push('')
+    lines.push(
+      `If you have the TextStack connector, this book is bookId ${book.bookId}. ` +
+      'Read it with get_my_book and get_my_chapter, and check get_my_insights first in case we have ' +
+      'discussed it before. When we are done, write the conclusions back with save_insight so I find ' +
+      'them in the book later.')
+  } else if (book.editionId && book.slug) {
     lines.push('')
     lines.push(
-      `If you have the TextStack connector, this book is ${id}. ` +
-      (book.bookId
-        ? 'Read it with get_my_book and get_my_chapter, and check get_my_insights first in case we have discussed it before. '
-        : 'Read it with get_book and get_chapter, and check get_my_insights first in case we have discussed it before. ')
-      + 'When we are done, write the conclusions back with save_insight so I find them in the book later.')
+      `If you have the TextStack connector: read this book with get_book and get_chapter using slug ` +
+      `"${book.slug}", and use editionId ${book.editionId} for get_my_insights and save_insight. ` +
+      'Check get_my_insights first in case we have discussed it before, and write the conclusions ' +
+      'back with save_insight when we are done so I find them in the book later.')
   }
 
   const brief = lines.join('\n')