#47 (SLICE-2, review): per-block document proposals + word-precise accept

Document-edit flow SLICE-2 (specs/coauthoring-document-edit-flow.md §7.2,
INV-39/40/41 — P1 "too much to review"). A whole-document rewrite now proposes
ONE F4 proposal per CHANGED BLOCK (the unit a human reviews), but accepting a
block reconciles attribution at WORD granularity (the unit F3 records). Block =
decision unit; word = attribution unit. Supersedes INV-37's per-word cut for
document edits; selection edits unchanged.

- trackChangesModel.ts: new pure diffToBlockHunks(current, rewritten) — block-key
  alignment (reusing diffArrays/diffBlocks keying): an isolated changed block →
  one block-aligned hunk → the rewritten block raw (a code/mermaid fence is one
  atomic whole-fence hunk, INV-23); insert/delete runs → one gap-span hunk over
  the inter-anchor region (separators included) so reconstruction stays exact; a
  zero-width gap-span is anchored (INV-41). Also split diffToHunks into the raw,
  un-anchored wordEditHunks + the anchoring wrapper (the anchoring could grow an
  insertion to overlap an adjacent hunk, corrupting a batch apply — a latent bug
  that only surfaced once hunks are applied as a batch).
- trackChangesPreview.ts: runEditAndPropose document branch uses diffToBlockHunks
  and tags each proposal granularity:"block".
- model.ts / proposalModel.ts: additive optional Proposal.granularity
  ("block"|"single"; absent ⇒ single, back-compat — no migration).
- proposalController.ts: accept of a block proposal runs an intra-block word
  sub-diff (wordEditHunks, disjoint) and applies one applyAgentEdit per changed
  run, descending offset — only the words Claude changed land Claude-attributed;
  unchanged spans keep prior authorship (INV-40).
- Tests: diffToBlockHunks unit (reconstruction + fence atomic + add/remove);
  f12Review host E2E (M blocks→M proposals, unchanged→none, fence atomic, INV-40
  attribution, INV-41 insertion accept); updated the f11 document-path E2E to
  per-block (INV-39 supersedes INV-37); MANUAL-SMOKE-F12 §2.

Seam note: pendingEdits.matchEvent resolves one registration per change event, so
INV-40's per-run attribution is sequential applyAgentEdit calls (N undo steps),
not one multi-replace WorkspaceEdit — see transcript Deferred decisions.

214 unit + 69/5 host E2E green.

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

docs/MANUAL-SMOKE-F12.md

@@ -35,3 +35,35 @@ The body and tab menus show exactly one Ask-Claude edit entry, matching the live
 selection state (selection → Edit Selection; none → Edit Document); the tab
 gesture targets the clicked tab's document, not the active editor; both are absent
 on non-markdown docs; no console errors.
+
+## SLICE-2 — #47 (review): per-block proposals + word-precise attribution (INV-39/40/41)
+
+On a markdown doc with several paragraphs, **Ask Claude to Edit Document** with a
+light copy-edit instruction (e.g. "tighten the prose, fix typos").
+
+1. **One proposal per changed block (INV-39).** Claude's pass surfaces as **one
+   ✓/✗ block per changed paragraph/header/bullet**, not a flurry of word-level
+   blocks. A paragraph with several word edits is a **single** proposal; the
+   word-level `<ins>`/`<del>` still shows *inside* it. Untouched paragraphs show no
+   proposal.
+2. **Changed fence is atomic (INV-23).** If Claude edits a code/mermaid fence, it
+   is **one** whole-fence proposal.
+3. **Accept attributes only the changed words (INV-40).** Accept a block proposal,
+   then toggle the preview to **Authorship**/colors (or re-open in the on-state):
+   only the words Claude actually changed are Claude-colored; the unchanged words
+   in that block keep their prior author. The block is the decision unit; the word
+   is the attribution unit.
+4. **Inserted block accepts cleanly (INV-41).** If Claude adds a new paragraph,
+   its proposal **accepts** (it is anchored to an adjacent block, never a
+   born-orphaned/zero-width proposal).
+5. **Undo.** Accepting a block is currently **N undo steps** (one per changed run
+   inside the block) — `Ctrl+Z` repeatedly restores it. (Spec deferred note:
+   single-undo-step grouping is a possible follow-up.)
+6. **Selection edits unchanged.** Edit *Selection* still produces exactly one
+   proposal over the selection (no block fan-out).
+
+### Pass criteria
+
+A document edit yields one in-context proposal per changed block (fences atomic);
+accepting a block lands the whole block but Claude-attributes only the words it
+changed; inserted blocks accept; selection edits are unaffected; no console errors.

src/model.ts

@@ -90,6 +90,13 @@ export interface Proposal {
   turnId?: string;
   /** what the human asked for (review context). */
   instruction?: string;
+  /**
+   * F12/#47 (INV-39/40): the review-decision unit this proposal represents.
+   * `"block"` ⇒ the anchor spans a whole document block and accept reconciles
+   * attribution per WORD inside it (INV-40); `"single"` (or absent, for
+   * back-compat with older sidecars) ⇒ a single-range proposal accepted whole.
+   */
+  granularity?: "block" | "single";
 }
 
 export interface Artifact {

src/proposalController.ts

@@ -18,7 +18,7 @@ import { addProposal, removeProposal } from "./proposalModel";
 import type { AttributionController } from "./attributionController";
 import type { VersionGuard } from "./versionGuard";
 import { isAuthorable } from "./workspacePath";
-import type { ProposalView } from "./trackChangesModel";
+import { wordEditHunks, type ProposalView } from "./trackChangesModel";
 
 /** Test-facing snapshot of what is currently rendered for a document. */
 export interface RenderedProposal {
@@ -122,7 +122,7 @@ export class ProposalController implements vscode.Disposable {
     fp: Fingerprint,
     replacement: string,
     author: Provenance,
-    opts?: { turnId?: string; instruction?: string },
+    opts?: { turnId?: string; instruction?: string; granularity?: "block" | "single" },
   ): Promise<string | undefined> {
     if (!this.isTracked(document)) return undefined;
     if (this.guard.isReadOnly(this.keyOf(document))) return undefined;
@@ -164,12 +164,19 @@ export class ProposalController implements vscode.Disposable {
       this.renderAll(document);
       return false;
     }
-    const range = new vscode.Range(document.positionAt(resolved.start), document.positionAt(resolved.end));
+    // #47 (INV-40): a BLOCK proposal applies the whole block but attributes only
+    // the words Claude actually changed; a single proposal applies its whole range.
+    const ok =
+      proposal.granularity === "block"
+        ? await this.acceptBlock(document, resolved, proposal)
+        : await this.attribution.applyAgentEdit(
+            document,
+            new vscode.Range(document.positionAt(resolved.start), document.positionAt(resolved.end)),
+            proposal.replacement,
+            proposal.author,
             // No awaits between resolve and the seam call: document.version is current.
-    const ok = await this.attribution.applyAgentEdit(document, range, proposal.replacement, proposal.author, {
+            { expectedVersion: document.version, turnId: proposal.turnId },
-      expectedVersion: document.version,
+          );
-      turnId: proposal.turnId,
-    });
     if (!ok) {
       void vscode.window.showWarningMessage(
         "Cowriting: the editor rejected the accept — the proposal is still pending.",
@@ -181,6 +188,41 @@ export class ProposalController implements vscode.Disposable {
     return true;
   }
 
+  /**
+   * #47 (INV-40): accept a BLOCK proposal — apply Claude's whole block, but
+   * attribute ONLY the runs Claude actually changed. The block is the DECISION
+   * unit; the word is the ATTRIBUTION unit. An intra-block word sub-diff
+   * (`wordEditHunks`, the raw engine INV-37 used, repurposed — un-anchored so the
+   * runs stay disjoint for a batch apply) yields the changed runs; each lands
+   * through the F4 seam (Claude-attributed), applied last-position-first so an
+   * earlier run's offsets stay valid under the later ones. Unchanged spans within
+   * the block are never touched, so their prior authorship stands. (Each run is
+   * one seam edit / one undo step — see the spec's deferred note on undo grouping.)
+   */
+  private async acceptBlock(
+    document: vscode.TextDocument,
+    resolved: OffsetRange,
+    proposal: Proposal,
+  ): Promise<boolean> {
+    const blockText = document.getText(
+      new vscode.Range(document.positionAt(resolved.start), document.positionAt(resolved.end)),
+    );
+    const subHunks = wordEditHunks(blockText, proposal.replacement);
+    if (subHunks.length === 0) return true; // block already equals the proposal — nothing to attribute
+    for (const h of [...subHunks].sort((a, b) => b.start - a.start)) {
+      const range = new vscode.Range(
+        document.positionAt(resolved.start + h.start),
+        document.positionAt(resolved.start + h.end),
+      );
+      const ok = await this.attribution.applyAgentEdit(document, range, h.replacement, proposal.author, {
+        expectedVersion: document.version,
+        turnId: proposal.turnId,
+      });
+      if (!ok) return false;
+    }
+    return true;
+  }
+
   private reject(state: DocState, proposal: Proposal): void {
     if (this.guard.isReadOnly(state.docPath)) return;
     this.store.update(state.docPath, (a) => removeProposal(a, proposal.id));

src/proposalModel.ts

@@ -12,7 +12,7 @@ export function addProposal(
   fp: Fingerprint,
   replacement: string,
   author: Provenance,
-  opts?: { turnId?: string; instruction?: string },
+  opts?: { turnId?: string; instruction?: string; granularity?: "block" | "single" },
 ): { proposalId: string; anchorId: string } {
   const anchorId = newId("a");
   const proposalId = newId("pr");
@@ -25,6 +25,7 @@ export function addProposal(
     createdAt: new Date().toISOString(),
     ...(opts?.turnId !== undefined ? { turnId: opts.turnId } : {}),
     ...(opts?.instruction !== undefined ? { instruction: opts.instruction } : {}),
+    ...(opts?.granularity !== undefined ? { granularity: opts.granularity } : {}),
   });
   return { proposalId, anchorId };
 }

src/trackChangesModel.ts

@@ -223,11 +223,27 @@ export interface EditHunk {
  * never part of another hunk.
  */
 export function diffToHunks(currentText: string, rewrittenText: string): EditHunk[] {
+  return wordEditHunks(currentText, rewrittenText).map((h) =>
+    h.start === h.end ? anchorInsertion(h, currentText) : h,
+  );
+}
+
+/**
+ * The raw word-level diff underlying `diffToHunks`: disjoint, ordered EditHunks
+ * that exactly partition the change (a pure insertion stays ZERO-WIDTH at its
+ * offset — not anchored). `diffToHunks` adds anchoring on top so each hunk's F4
+ * fingerprint resolves; callers that apply hunks directly through the seam
+ * (INV-40's intra-block accept) want THESE raw, non-overlapping hunks instead —
+ * anchoring can grow an insertion to absorb a token an adjacent hunk also edits,
+ * which corrupts a batch apply. Pure, vscode-free, deterministic. Applying these
+ * right→left reconstructs `rewrittenText` exactly.
+ */
+export function wordEditHunks(currentText: string, rewrittenText: string): EditHunk[] {
   const hunks: EditHunk[] = [];
   let offset = 0;
   let open: EditHunk | null = null;
   const flush = () => {
-    if (open) hunks.push(open.start === open.end ? anchorInsertion(open, currentText) : open);
+    if (open) hunks.push(open);
     open = null;
   };
   for (const part of diffWordsWithSpace(currentText, rewrittenText)) {
@@ -272,6 +288,108 @@ function anchorInsertion(hunk: EditHunk, text: string): EditHunk {
   return { start: s, end: p, replacement: text.slice(s, p) + hunk.replacement };
 }
 
+type BlockAlignKind = "unchanged" | "changed" | "removed" | "added";
+interface BlockAlignOp {
+  kind: BlockAlignKind;
+  ci?: number; // index into the current blocks
+  ni?: number; // index into the rewritten blocks
+}
+
+/**
+ * Align two block sequences by normalized key (jsdiff `diffArrays`), pairing an
+ * adjacent removed-then-added run element-wise into `changed` ops (the surplus
+ * staying `removed` / `added`) — the same pairing `diffBlocks` uses, but yielding
+ * index ops so the caller can read each side's source range. Pure.
+ */
+function alignBlocks(cur: BlockWithRange[], next: BlockWithRange[]): BlockAlignOp[] {
+  const changes = diffArrays(
+    cur.map((b) => b.key),
+    next.map((b) => b.key),
+  );
+  const ops: BlockAlignOp[] = [];
+  let bi = 0; // current index
+  let ci = 0; // rewritten index
+  for (let n = 0; n < changes.length; n++) {
+    const ch = changes[n];
+    const count = ch.count ?? ch.value.length;
+    if (!ch.added && !ch.removed) {
+      for (let k = 0; k < count; k++) ops.push({ kind: "unchanged", ci: bi++, ni: ci++ });
+      continue;
+    }
+    if (ch.removed) {
+      const nx = changes[n + 1];
+      const addCount = nx?.added ? (nx.count ?? nx.value.length) : 0;
+      const paired = Math.min(count, addCount);
+      for (let k = 0; k < paired; k++) ops.push({ kind: "changed", ci: bi++, ni: ci++ });
+      for (let k = paired; k < count; k++) ops.push({ kind: "removed", ci: bi++ });
+      for (let k = paired; k < addCount; k++) ops.push({ kind: "added", ni: ci++ });
+      if (nx?.added) n++;
+      continue;
+    }
+    for (let k = 0; k < count; k++) ops.push({ kind: "added", ni: ci++ });
+  }
+  return ops;
+}
+
+/**
+ * #47 (INV-39, §6.4): diff a whole-document rewrite into ONE EditHunk per CHANGED
+ * BLOCK — the unit a human reviews — rather than per word (which INV-37/`diffToHunks`
+ * did and this supersedes for document edits). Built by aligning both sides into
+ * the existing block units (`splitBlocksWithRanges`) and keying with the same diff
+ * as `diffBlocks`:
+ *  - an ISOLATED changed block (1:1, unchanged blocks on both sides) → a
+ *    block-aligned hunk `[block.start, block.end)` → the rewritten block's raw
+ *    text. A code/mermaid fence is one such whole-block hunk (atomic, INV-23).
+ *  - any other changed RUN (block insertions/deletions, or adjacent changes) → one
+ *    gap-span hunk covering the source between the bounding unchanged blocks → the
+ *    matching rewritten span (separators included), so reconstruction stays exact.
+ *    A zero-width gap-span (insert at a seamless boundary) is anchored to an
+ *    adjacent token (INV-41) so its F4 fingerprint resolves and it accepts.
+ *  - unchanged blocks (same key AND same raw) → no hunk.
+ * Pure, vscode-free, deterministic; same `EditHunk` shape as `diffToHunks` (which
+ * is RETAINED as the intra-block sub-diff engine for word-precise accept
+ * attribution — INV-40). Applying all hunks right→left reconstructs `rewrittenText`
+ * exactly.
+ */
+export function diffToBlockHunks(currentText: string, rewrittenText: string): EditHunk[] {
+  const cur = splitBlocksWithRanges(currentText);
+  const next = splitBlocksWithRanges(rewrittenText);
+  const ops = alignBlocks(cur, next);
+  // Same key but different raw (whitespace/case) is still a real content change.
+  for (const op of ops) {
+    if (op.kind === "unchanged" && cur[op.ci!].raw !== next[op.ni!].raw) op.kind = "changed";
+  }
+  const hunks: EditHunk[] = [];
+  let i = 0;
+  while (i < ops.length) {
+    if (ops[i].kind === "unchanged") {
+      i++;
+      continue;
+    }
+    let j = i;
+    while (j < ops.length && ops[j].kind !== "unchanged") j++;
+    const run = ops.slice(i, j);
+    if (run.length === 1 && run[0].kind === "changed") {
+      const c = cur[run[0].ci!];
+      hunks.push({ start: c.start, end: c.end, replacement: next[run[0].ni!].raw });
+    } else {
+      // A run with insertions/deletions: replace the whole inter-anchor gap so the
+      // separators reconstruct exactly. Bound by the unchanged blocks on each side
+      // (or the document edges).
+      const prev = i > 0 ? ops[i - 1] : null;
+      const after = j < ops.length ? ops[j] : null;
+      const curStart = prev ? cur[prev.ci!].end : 0;
+      const curEnd = after ? cur[after.ci!].start : currentText.length;
+      const newStart = prev ? next[prev.ni!].end : 0;
+      const newEnd = after ? next[after.ni!].start : rewrittenText.length;
+      const hunk: EditHunk = { start: curStart, end: curEnd, replacement: rewrittenText.slice(newStart, newEnd) };
+      hunks.push(hunk.start === hunk.end ? anchorInsertion(hunk, currentText) : hunk);
+    }
+    i = j;
+  }
+  return hunks;
+}
+
 const md = new MarkdownIt({ html: true, linkify: false, breaks: false });
 // mermaid fences → <pre class="mermaid">SRC</pre> for client-side rendering; all
 // other fences fall through to markdown-it's default (escaped <pre><code>).

src/trackChangesPreview.ts

@@ -13,7 +13,7 @@ import * as vscode from "vscode";
 import type { DiffViewController } from "./diffViewController";
 import type { AttributionController } from "./attributionController";
 import type { ProposalController } from "./proposalController";
-import { renderReview, renderPlain, diffBlocks, diffToHunks, type BlockOp } from "./trackChangesModel";
+import { renderReview, renderPlain, diffBlocks, diffToBlockHunks, type BlockOp } from "./trackChangesModel";
 import { buildFingerprint } from "./anchorer";
 import { isAuthorable } from "./workspacePath";
 import type { EditTurnResult } from "./liveTurn";
@@ -226,11 +226,12 @@ export class TrackChangesPreviewController implements vscode.Disposable {
   }
 
   /**
-   * F11 (INV-35/37): run one host edit turn and record the result as F4
+   * F11/F12 (INV-35/39): run one host edit turn and record the result as F4
    * proposal(s) — a SELECTION yields one single-range proposal over the resolved
-   * block-union; a DOCUMENT rewrite is `diffToHunks`'d into one single-range
+   * block-union; a DOCUMENT rewrite is `diffToBlockHunks`'d into one proposal per
-   * proposal per changed hunk (reusing the F4 single-range model N times, no new
+   * changed BLOCK (#47, INV-39 supersedes INV-37's per-word cut), each tagged
-   * model). Never mutates the document (INV-10). Returns the created proposal ids.
+   * `granularity:"block"` so accept reconciles attribution per word (INV-40).
+   * Never mutates the document (INV-10). Returns the created proposal ids.
    */
   async runEditAndPropose(
     document: vscode.TextDocument,
@@ -253,9 +254,17 @@ export class TrackChangesPreviewController implements vscode.Disposable {
     }
     const turn = await this.editTurn(instruction, full);
     const ids: string[] = [];
-    for (const h of diffToHunks(full, turn.replacement)) {
+    // #47 (INV-39, supersedes INV-37): a document rewrite is cut at BLOCK
+    // granularity — one proposal per changed block (the unit a human reviews) —
+    // not per word. Each is tagged `granularity:"block"` so accept reconciles
+    // attribution per word inside the block (INV-40).
+    for (const h of diffToBlockHunks(full, turn.replacement)) {
       const fp = buildFingerprint(full, { start: h.start, end: h.end });
-      const id = await this.proposals.propose(document, fp, h.replacement, provenance(turn), { turnId, instruction });
+      const id = await this.proposals.propose(document, fp, h.replacement, provenance(turn), {
+        turnId,
+        instruction,
+        granularity: "block",
+      });
       if (id) ids.push(id);
     }
     return ids;

test/e2e/suite/f11Toolbar.test.ts

@@ -67,8 +67,10 @@ suite("F11 preview toolbar (host E2E — message → seam wiring, no LLM)", () =
     assert.match(entry!.when ?? "", /editorLangId == markdown/, "guarded on markdown");
   });
 
-  // SLICE-3: Edit Document → a whole-document rewrite diffed into N F4 proposals.
+  // #47 (was INV-37): Edit Document now cuts at BLOCK granularity — two word
-  test("runEditAndPropose(document) with a stubbed multi-hunk rewrite → N proposals matching the hunks (PUC-4, INV-37)", async () => {
+  // changes in ONE paragraph are ONE block proposal (INV-39 supersedes INV-37's
+  // per-word cut). Full block coverage lives in f12Review.test.ts.
+  test("runEditAndPropose(document) — two word edits in one paragraph → ONE block proposal (PUC-4, INV-39)", async () => {
     const { doc, key } = await freshDoc(
       "docs/f11doc.md",
       "# F11 doc\n\nThe quick brown fox jumps over the lazy dog.\n",
@@ -87,15 +89,16 @@ suite("F11 preview toolbar (host E2E — message → seam wiring, no LLM)", () =
 
     const ids = await ctl.runEditAndPropose(doc, { kind: "document" }, "swap brown→RED and dog→CAT");
     await settle();
-    assert.strictEqual(ids.length, 2, "two changed words → two independent proposals");
+    assert.strictEqual(ids.length, 1, "two changed words in one block → ONE block proposal (INV-39)");
 
     const views = api.proposalController.listProposals(doc);
-    assert.ok(
+    const view = views.find((v) => v.id === ids[0]);
-      ids.every((id) => views.some((v) => v.id === id)),
+    assert.ok(view, "the returned proposal id is a live pending proposal");
-      "every returned proposal id is a live pending proposal",
+    assert.strictEqual(
+      view!.replacement,
+      "The quick RED fox jumps over the lazy CAT.",
+      "the block proposal carries the whole rewritten paragraph",
     );
-    const replacements = views.map((v) => v.replacement);
-    assert.ok(replacements.includes("RED") && replacements.includes("CAT"), "proposals carry the per-hunk replacements");
     // INV-10: proposing never mutates the document.
     assert.ok(doc.getText().includes("brown fox") && doc.getText().includes("lazy dog"), "document unchanged by propose");
     void key;

test/e2e/suite/f12Review.test.ts

@@ -0,0 +1,134 @@
+import * as assert from "assert";
+import * as fs from "fs";
+import * as path from "path";
+import * as vscode from "vscode";
+import type { CowritingApi } from "../../../src/extension";
+
+const WS = process.env.E2E_WORKSPACE!;
+const settle = () => new Promise((r) => setTimeout(r, 400));
+
+async function getApi(): Promise<CowritingApi> {
+  const ext = vscode.extensions.getExtension("benstull.vscode-cowriting-plugin")!;
+  const api = (await ext.activate()) as CowritingApi;
+  assert.ok(api?.trackChangesPreviewController && api?.proposalController, "exports controllers");
+  return api;
+}
+
+async function freshDoc(rel: string, body: string): Promise<vscode.TextDocument> {
+  const abs = path.join(WS, rel);
+  fs.mkdirSync(path.dirname(abs), { recursive: true });
+  fs.writeFileSync(abs, body, "utf8");
+  const doc = await vscode.workspace.openTextDocument(vscode.Uri.file(abs));
+  await vscode.window.showTextDocument(doc);
+  await settle();
+  return doc;
+}
+
+// #47 SLICE-2 (review, P1): a document rewrite proposes ONE F4 proposal per
+// CHANGED BLOCK (INV-39 supersedes INV-37's per-word cut), but accepting a block
+// reconciles attribution at WORD granularity (INV-40 — block = decision unit,
+// word = attribution unit). Host E2E, no LLM (the edit turn is stubbed).
+suite("F12 SLICE-2 — block-granularity document proposals (#47, INV-39/40/41)", () => {
+  // PUC-4: M changed blocks → M proposals; unchanged blocks → none.
+  test("edits across two paragraphs → two proposals; the untouched paragraph yields none (INV-39)", async () => {
+    const doc = await freshDoc(
+      "docs/f12-multi.md",
+      "# Doc\n\nFirst paragraph alpha.\n\nSecond paragraph beta.\n\nThird paragraph gamma.\n",
+    );
+    const api = await getApi();
+    const ctl = api.trackChangesPreviewController;
+    ctl.setEditTurnForTest(async () => ({
+      replacement: "# Doc\n\nFirst paragraph ALPHA.\n\nSecond paragraph beta.\n\nThird paragraph GAMMA.\n",
+      model: "sonnet",
+      sessionId: "e2e-f12-multi",
+    }));
+    const ids = await ctl.runEditAndPropose(doc, { kind: "document" }, "uppercase the first/last nouns");
+    await settle();
+    assert.strictEqual(ids.length, 2, "two changed blocks → two proposals; the unchanged middle block → none");
+
+    // each proposal's anchor spans a whole block, and the replacement is that block's rewrite
+    const views = api.proposalController.listProposals(doc);
+    const replacements = views.map((v) => v.replacement).sort();
+    assert.deepStrictEqual(replacements, ["First paragraph ALPHA.", "Third paragraph GAMMA."]);
+  });
+
+  // PUC-4 + INV-23: a changed code fence is ONE atomic whole-fence proposal.
+  test("a changed code fence → one atomic proposal over the whole fence (INV-23)", async () => {
+    const doc = await freshDoc(
+      "docs/f12-fence.md",
+      "# Code\n\n```js\nconst a = 1;\nconst b = 2;\n```\n",
+    );
+    const api = await getApi();
+    const ctl = api.trackChangesPreviewController;
+    ctl.setEditTurnForTest(async () => ({
+      replacement: "# Code\n\n```js\nconst a = 10;\nconst b = 2;\n```\n",
+      model: "sonnet",
+      sessionId: "e2e-f12-fence",
+    }));
+    const ids = await ctl.runEditAndPropose(doc, { kind: "document" }, "bump a to 10");
+    await settle();
+    assert.strictEqual(ids.length, 1, "a changed fence is one atomic proposal");
+    const view = api.proposalController.listProposals(doc).find((v) => v.id === ids[0])!;
+    assert.strictEqual(view.replacement, "```js\nconst a = 10;\nconst b = 2;\n```", "whole-fence replacement");
+  });
+
+  // PUC-5 / INV-40: accepting a block attributes ONLY the words Claude changed —
+  // unchanged words in the block are NOT swept into Claude's authorship.
+  test("accepting a block proposal attributes only the changed words to Claude (INV-40)", async () => {
+    const doc = await freshDoc("docs/f12-attr.md", "# T\n\nThe quick brown fox jumps lazily.\n");
+    const api = await getApi();
+    const ctl = api.trackChangesPreviewController;
+    const key = api.proposalController.keyFor(doc);
+
+    ctl.setEditTurnForTest(async () => ({
+      replacement: "# T\n\nThe quick RED fox jumps SLOWLY.\n",
+      model: "sonnet",
+      sessionId: "e2e-f12-attr",
+    }));
+    const ids = await ctl.runEditAndPropose(doc, { kind: "document" }, "change two words");
+    await settle();
+    assert.strictEqual(ids.length, 1, "one changed paragraph → one block proposal");
+
+    const ok = await api.proposalController.acceptById(key, ids[0]);
+    assert.ok(ok, "the block proposal accepts");
+    await settle();
+
+    assert.strictEqual(doc.getText(), "# T\n\nThe quick RED fox jumps SLOWLY.\n", "the whole block landed");
+
+    const agentTexts = api.attributionController
+      .getSpans(key)
+      .filter((s) => s.authorKind === "agent")
+      .map((s) => doc.getText().slice(s.range.start, s.range.end).trim())
+      .filter((t) => t.length > 0);
+    // Only the two words Claude actually changed are Claude-attributed.
+    const joined = agentTexts.join(" ");
+    assert.ok(joined.includes("RED"), "the changed word RED is Claude-attributed");
+    assert.ok(joined.includes("SLOWLY"), "the changed word SLOWLY is Claude-attributed");
+    assert.ok(!/\bquick\b/.test(joined), "the unchanged word 'quick' is NOT swept into Claude's authorship");
+    assert.ok(!/\bfox\b/.test(joined), "the unchanged word 'fox' is NOT swept into Claude's authorship");
+  });
+
+  // PUC-4 / INV-41: a block-insertion rewrite produces acceptable proposals and
+  // accepting them all reconstructs the intended document (no born-orphaned hunk).
+  test("a rewrite that inserts a paragraph → acceptable proposals; accept-all reaches the rewrite (INV-41)", async () => {
+    const original = "# Ins\n\nAlpha block.\n\nBeta block.\n";
+    const rewrite = "# Ins\n\nAlpha block.\n\nBrand new middle block.\n\nBeta block.\n";
+    const doc = await freshDoc("docs/f12-insert.md", original);
+    const api = await getApi();
+    const ctl = api.trackChangesPreviewController;
+    const key = api.proposalController.keyFor(doc);
+
+    ctl.setEditTurnForTest(async () => ({ replacement: rewrite, model: "sonnet", sessionId: "e2e-f12-insert" }));
+    const ids = await ctl.runEditAndPropose(doc, { kind: "document" }, "insert a paragraph");
+    await settle();
+    assert.ok(ids.length >= 1, "the insertion produced at least one proposal");
+
+    for (const id of ids) {
+      const ok = await api.proposalController.acceptById(key, id);
+      assert.ok(ok, `proposal ${id} is acceptable (not born-orphaned, INV-41)`);
+      await settle();
+    }
+    assert.strictEqual(doc.getText(), rewrite, "accepting all proposals reconstructs the intended rewrite");
+    assert.strictEqual(api.proposalController.listProposals(doc).length, 0, "no proposals left pending");
+  });
+});

test/trackChangesModel.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, test, expect } from "vitest";
-import { splitBlocks, splitBlocksWithRanges, diffBlocks, diffToHunks, renderTrackChanges, colorByAuthor, type AuthorSpan } from "../src/trackChangesModel";
+import { splitBlocks, splitBlocksWithRanges, diffBlocks, diffToHunks, diffToBlockHunks, renderTrackChanges, colorByAuthor, type AuthorSpan } from "../src/trackChangesModel";
 
 describe("splitBlocks", () => {
   it("splits prose paragraphs on blank lines, dropping empties", () => {
@@ -402,6 +402,90 @@ describe("F11 diffToHunks (INV-37)", () => {
   });
 });
 
+// #47 SLICE-2 (INV-39): a whole-document rewrite is diffed into ONE EditHunk per
+// CHANGED BLOCK (the unit a human reviews), superseding INV-37's per-word hunks.
+// Built by coarsening diffToHunks to block boundaries; fences stay atomic
+// (INV-23); inserted/deleted blocks keep their anchored gap hunks (INV-41).
+// Applying all hunks right→left must still reconstruct the rewrite exactly.
+describe("#47 diffToBlockHunks (INV-39/41)", () => {
+  const applyHunks = (current: string, hunks: ReturnType<typeof diffToBlockHunks>): string => {
+    let out = current;
+    for (const h of [...hunks].sort((a, b) => b.start - a.start)) {
+      out = out.slice(0, h.start) + h.replacement + out.slice(h.end);
+    }
+    return out;
+  };
+
+  test("an identical rewrite → zero hunks", () => {
+    expect(diffToBlockHunks("# H\n\nSame body.\n", "# H\n\nSame body.\n")).toEqual([]);
+  });
+
+  test("two word edits in ONE paragraph → ONE block hunk (supersedes INV-37's two)", () => {
+    const current = "# Doc\n\nThe quick brown fox jumps over the lazy dog.\n";
+    const rewrite = "# Doc\n\nThe quick RED fox jumps over the lazy CAT.\n";
+    const hunks = diffToBlockHunks(current, rewrite);
+    expect(hunks).toHaveLength(1);
+    // the hunk spans the whole changed paragraph block
+    const para = "The quick brown fox jumps over the lazy dog.";
+    const start = current.indexOf(para);
+    expect(hunks[0].start).toBe(start);
+    expect(hunks[0].end).toBe(start + para.length);
+    expect(hunks[0].replacement).toBe("The quick RED fox jumps over the lazy CAT.");
+    expect(applyHunks(current, hunks)).toBe(rewrite);
+  });
+
+  test("edits across two paragraphs → two block hunks, one per changed block; unchanged → none", () => {
+    const current = "First para alpha.\n\nSecond para beta.\n\nThird para gamma.\n";
+    const rewrite = "First para ALPHA.\n\nSecond para beta.\n\nThird para GAMMA.\n";
+    const hunks = diffToBlockHunks(current, rewrite);
+    expect(hunks).toHaveLength(2);
+    // each hunk lands on a real block boundary in current
+    const blocks = splitBlocksWithRanges(current);
+    for (const h of hunks) {
+      expect(blocks.some((b) => b.start === h.start && b.end === h.end)).toBe(true);
+    }
+    expect(applyHunks(current, hunks)).toBe(rewrite);
+  });
+
+  test("a changed code fence → ONE atomic whole-fence hunk (INV-23)", () => {
+    const current = "# Code\n\n```js\nconst a = 1;\nconst b = 2;\n```\n";
+    const rewrite = "# Code\n\n```js\nconst a = 10;\nconst b = 2;\n```\n";
+    const hunks = diffToBlockHunks(current, rewrite);
+    expect(hunks).toHaveLength(1);
+    const fence = "```js\nconst a = 1;\nconst b = 2;\n```";
+    const start = current.indexOf(fence);
+    expect(hunks[0].start).toBe(start);
+    expect(hunks[0].end).toBe(start + fence.length);
+    expect(hunks[0].replacement).toBe("```js\nconst a = 10;\nconst b = 2;\n```");
+    expect(applyHunks(current, hunks)).toBe(rewrite);
+  });
+
+  test("every hunk is resolvable (non-zero-width, real source text) and reconstructs", () => {
+    const cases: Array<[string, string]> = [
+      ["# H\n\nThe brown fox sleeps.\n", "# H\n\nThe brown fox QUIETLY sleeps today.\n"], // insert words mid-block
+      ["A para.\n\nB para.\n\nC para.\n", "A para.\n\nC para.\n"], // delete a whole block
+      ["A para.\n\nB para.\n", "A para.\n\nNEW para.\n\nB para.\n"], // insert a whole block
+      ["Only one block here.\n", "A totally different single block.\n"], // wholesale
+      ["Keep me.\n\nDrop this one.\n", "Keep me.\n"], // delete trailing block
+      ["unchanged body\n", "unchanged body\n"], // no-op
+    ];
+    for (const [current, rewrite] of cases) {
+      const hunks = diffToBlockHunks(current, rewrite);
+      for (const h of hunks) {
+        expect(h.end).toBeGreaterThan(h.start); // non-zero-width → F4 fp resolves
+        expect(current.slice(h.start, h.end).length).toBeGreaterThan(0);
+      }
+      expect(applyHunks(current, hunks)).toBe(rewrite);
+    }
+  });
+
+  test("is deterministic — same inputs → identical hunks", () => {
+    const c = "P one.\n\nP two.\n";
+    const r = "P ONE.\n\nP two.\n";
+    expect(diffToBlockHunks(c, r)).toEqual(diffToBlockHunks(c, r));
+  });
+});
+
 // F11 SLICE-2 (INV-36): the pure render layer emits data-src-start/data-src-end
 // (source char offsets from BlockWithRange) on every LIVE-source rendered block,
 // in BOTH modes. The webview's selection→source mapping walks the DOM to the