feat(f6): diff-view toggle on any file — global storage, untitled in-memory (#19)

F6 no longer requires a workspace file. It gets its own diffable predicate
(any file: or untitled:) decoupled from F2 isTracked, keys baselines by a
sha256 of the document URI, and stores them in VS Code GLOBAL storage
(context.globalStorageUri) — always present, never the repo (INV-19). Untitled
buffers have no durable identity → in-memory baseline only (lost on reload).

DiffViewController is now constructed before the workspace-root check and its
commands are always live (never stubbed) — the machine-landing advance wiring
stays in the with-root branch since the seam only fires on workspace files.
BaselineStore generalized to key-by-hash (Baseline.docPath → uri).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/baselineStore.ts

@@ -1,10 +1,12 @@
 /**
  * BaselineStore — load/save one diff-view baseline JSON per document (F6 §6.3).
  * The CoauthorStore shape (src/store.ts): vscode-free (Node fs only, unit-
- * testable), one file per docPath. INV-19: the storage dir is VS Code's
- * per-workspace extension storage, NEVER the repo — so the baseline can never
- * be committed, merged, or read by another rung, and the sidecar / cross-rung
- * contract (INV-14..17) are untouched by construction.
+ * testable), one file per storage key. INV-19: the storage dir is VS Code's
+ * per-extension GLOBAL storage, NEVER the repo — so the baseline can never be
+ * committed, merged, or read by another rung. F6 works on *any* file, so the
+ * key is a hash of the document URI (the controller derives it), not a
+ * workspace-relative path; an untitled buffer has no durable identity and is
+ * never persisted here (in-memory only — see DiffViewController).
  */
 import * as fs from "node:fs";
 import * as path from "node:path";
@@ -12,7 +14,8 @@ import * as path from "node:path";
 export type BaselineReason = "opened" | "machine-landing" | "pinned";
 
 export interface Baseline {
-  docPath: string;
+  /** the document URI (the identity the key is derived from) — for round-trip/debug. */
+  uri: string;
   /** full document text captured at the epoch (from the buffer, not disk — §6.3). */
   text: string;
   capturedAt: string;
@@ -20,23 +23,23 @@ export interface Baseline {
 }
 
 export class BaselineStore {
-  /** @param storageDir absolute VS Code workspace-storage dir (context.storageUri.fsPath). */
+  /** @param storageDir absolute VS Code GLOBAL-storage dir (context.globalStorageUri.fsPath). */
   constructor(private readonly storageDir: string) {}
 
-  /** `<storageDir>/baselines/<repo-relative-docPath>.json` (§6.3). */
-  baselinePath(docPath: string): string {
-    return path.join(this.storageDir, "baselines", `${docPath}.json`);
+  /** `<storageDir>/baselines/<key>.json` — `key` is a filesystem-safe hash (§6.3). */
+  baselinePath(key: string): string {
+    return path.join(this.storageDir, "baselines", `${key}.json`);
   }
 
-  load(docPath: string): Baseline | null {
-    const p = this.baselinePath(docPath);
+  load(key: string): Baseline | null {
+    const p = this.baselinePath(key);
     if (!fs.existsSync(p)) return null;
     return JSON.parse(fs.readFileSync(p, "utf8")) as Baseline;
   }
 
   /** Newest epoch wins — overwrite in place, no history (state-not-history, the F3/F4 precedent). */
-  save(docPath: string, baseline: Baseline): void {
-    const p = this.baselinePath(docPath);
+  save(key: string, baseline: Baseline): void {
+    const p = this.baselinePath(key);
     fs.mkdirSync(path.dirname(p), { recursive: true });
     fs.writeFileSync(p, JSON.stringify(baseline, null, 2) + "\n", "utf8");
   }

src/diffViewController.ts

@@ -1,14 +1,21 @@
 /**
  * DiffViewController — F6 diff-view toggle (spec §6.2/§6.4). Owns the baseline
- * lifecycle (initialize at first track / advance at every machine landing / pin
+ * lifecycle (initialize at first sight / advance at every machine landing / pin
  * on demand), serves the baseline as a readonly `cowriting-baseline:` virtual
  * document, and toggles a native vscode.diff (baseline left, the LIVE document
  * right). A pure view: never mutates the document, sidecar, or attribution
- * state (INV-19). Baselines persist via the vscode-free BaselineStore; if
- * storage is unavailable the controller degrades to in-memory baselines + one
- * warning (reload survival is lost; the toggle still works) — §6.5 PUC-5.
+ * state (INV-19).
+ *
+ * F6 works on ANY text document, not just workspace files — it needs no
+ * `.threads/` sidecar, only a stable doc identity + a storage home. So it has
+ * its OWN diffable predicate (any `file:` or `untitled:` doc), decoupled from
+ * F2's workspace `isTracked`. Persistable docs (`file:`) keep their baseline in
+ * VS Code's per-extension GLOBAL storage keyed by a hash of the document URI;
+ * untitled buffers have no durable identity, so their baseline is in-memory
+ * only (lost on reload) — the same degrade the storage-unavailable path uses.
  */
 import * as path from "node:path";
+import { createHash } from "node:crypto";
 import * as vscode from "vscode";
 import { BaselineStore, type Baseline, type BaselineReason } from "./baselineStore";
 
@@ -16,20 +23,17 @@ export const BASELINE_SCHEME = "cowriting-baseline";
 
 export class DiffViewController implements vscode.Disposable {
   private readonly disposables: vscode.Disposable[] = [];
-  /** Source of truth for the content provider; mirrors what the store persists. */
+  /** Source of truth for the content provider, keyed by `document.uri.toString()`. */
   private readonly baselines = new Map<string, Baseline>();
   private readonly onDidChangeEmitter = new vscode.EventEmitter<vscode.Uri>();
   private storageWarned = false;
 
-  constructor(
-    private readonly store: BaselineStore | null,
-    private readonly rootDir: string,
-  ) {
+  constructor(private readonly store: BaselineStore | null) {
     const provider: vscode.TextDocumentContentProvider = {
       onDidChange: this.onDidChangeEmitter.event,
       provideTextDocumentContent: (uri) => {
-        const docPath = this.docPathFromBaselineUri(uri);
-        return this.baselines.get(docPath)?.text ?? "";
+        // The baseline URI carries the real document URI in its query (see baselineUri).
+        return this.baselines.get(uri.query)?.text ?? "";
       },
     };
     this.disposables.push(
@@ -41,37 +45,49 @@ export class DiffViewController implements vscode.Disposable {
       vscode.commands.registerCommand("cowriting.pinDiffBaseline", () =>
         this.pinCommand(vscode.window.activeTextEditor),
       ),
+      // F6 captures a baseline for any diffable doc the moment it is first seen,
+      // independent of the workspace gate (so "opened" is the open-time text).
+      vscode.workspace.onDidOpenTextDocument((d) => this.ensureBaseline(d)),
     );
+    for (const d of vscode.workspace.textDocuments) this.ensureBaseline(d);
   }
 
-  // ---- tracking / uri helpers --------------------------------------------------------
+  // ---- diffability / identity --------------------------------------------------------
 
-  private isTracked(document: vscode.TextDocument): boolean {
-    return document.uri.scheme === "file" && document.uri.fsPath.startsWith(this.rootDir);
+  /** Any text document F6 can diff: a saved file OR an unsaved buffer. */
+  private isDiffable(document: vscode.TextDocument): boolean {
+    return document.uri.scheme === "file" || document.uri.scheme === "untitled";
   }
-  private docPathOf(uri: vscode.Uri): string {
-    return vscode.workspace.asRelativePath(uri, false);
+  /** Only `file:` docs have a durable identity to persist a baseline against. */
+  private isPersistable(document: vscode.TextDocument): boolean {
+    return document.uri.scheme === "file";
   }
-  /** The readonly virtual-doc URI whose content the provider serves for this doc. */
-  private baselineUri(docPath: string): vscode.Uri {
-    return vscode.Uri.from({ scheme: BASELINE_SCHEME, path: "/" + docPath });
+  /** In-memory map key — the full document URI. */
+  private uriKey(document: vscode.TextDocument): string {
+    return document.uri.toString();
   }
-  private docPathFromBaselineUri(uri: vscode.Uri): string {
-    return uri.path.replace(/^\//, "");
+  /** Filesystem-safe storage key for a persistable doc: sha256 of its URI. */
+  private storageKey(uriKey: string): string {
+    return createHash("sha256").update(uriKey).digest("hex");
+  }
+  /** The readonly virtual-doc URI; its query carries the real document URI. */
+  private baselineUri(document: vscode.TextDocument): vscode.Uri {
+    const name = path.basename(document.uri.path) || "untitled";
+    return vscode.Uri.from({ scheme: BASELINE_SCHEME, path: "/" + name, query: this.uriKey(document) });
   }
 
   // ---- baseline lifecycle (§6.4) -----------------------------------------------------
 
-  /** First sight of a tracked doc: load the stored baseline, else capture `opened`. */
+  /** First sight of a diffable doc: load the stored baseline, else capture `opened`. */
   ensureBaseline(document: vscode.TextDocument): void {
-    if (!this.isTracked(document)) return;
-    const docPath = this.docPathOf(document.uri);
-    if (this.baselines.has(docPath)) return;
-    if (this.store) {
+    if (!this.isDiffable(document)) return;
+    const key = this.uriKey(document);
+    if (this.baselines.has(key)) return;
+    if (this.store && this.isPersistable(document)) {
       try {
-        const stored = this.store.load(docPath);
+        const stored = this.store.load(this.storageKey(key));
         if (stored) {
-          this.baselines.set(docPath, stored);
+          this.baselines.set(key, stored);
           return;
         }
       } catch {
@@ -83,35 +99,30 @@ export class DiffViewController implements vscode.Disposable {
 
   /** Machine landing (INV-18): re-capture so landed text never shows as a change. */
   advance(document: vscode.TextDocument): void {
-    if (!this.isTracked(document)) return;
+    if (!this.isDiffable(document)) return;
     this.capture(document, "machine-landing");
   }
 
   /** Human pin: baseline := now; the open diff visibly empties (left = right). */
   pin(document: vscode.TextDocument): void {
-    if (!this.isTracked(document)) return;
+    if (!this.isDiffable(document)) return;
     this.capture(document, "pinned");
   }
 
-  /** Capture buffer text at this epoch, persist, and refresh any open diff's left side. */
+  /** Capture buffer text at this epoch, persist (if persistable), refresh any open diff. */
   private capture(document: vscode.TextDocument, reason: BaselineReason): void {
-    const docPath = this.docPathOf(document.uri);
-    const baseline: Baseline = {
-      docPath,
-      text: document.getText(),
-      capturedAt: new Date().toISOString(),
-      reason,
-    };
-    this.baselines.set(docPath, baseline);
-    if (this.store) {
+    const key = this.uriKey(document);
+    const baseline: Baseline = { uri: key, text: document.getText(), capturedAt: new Date().toISOString(), reason };
+    this.baselines.set(key, baseline);
+    if (this.store && this.isPersistable(document)) {
       try {
-        this.store.save(docPath, baseline);
+        this.store.save(this.storageKey(key), baseline);
       } catch {
         this.warnStorageOnce();
       }
     }
     // An open diff re-requests the left side when its baseline URI changes.
-    this.onDidChangeEmitter.fire(this.baselineUri(docPath));
+    this.onDidChangeEmitter.fire(this.baselineUri(document));
   }
 
   private warnStorageOnce(): void {
@@ -122,44 +133,21 @@ export class DiffViewController implements vscode.Disposable {
     );
   }
 
-  // ---- commands (toggle implemented in SLICE-3, Task 4) ------------------------------
-
-  private pinCommand(editor: vscode.TextEditor | undefined): void {
-    if (!editor || !this.isTracked(editor.document)) {
-      void vscode.window.showWarningMessage("Cowriting: open a tracked workspace document to pin its diff baseline.");
-      return;
-    }
-    this.pin(editor.document);
-  }
-
-  // ---- test-facing surface (§6.4) ----------------------------------------------------
-
-  getBaseline(docPath: string): { text: string; reason: BaselineReason; capturedAt: string } | undefined {
-    const b = this.baselines.get(docPath);
-    return b ? { text: b.text, reason: b.reason, capturedAt: b.capturedAt } : undefined;
-  }
-  /** Absolute on-disk path of this doc's persisted baseline, or undefined if in-memory. */
-  baselineFilePath(docPath: string): string | undefined {
-    return this.store?.baselinePath(docPath);
-  }
-
   // ---- toggle UX (§6.5 PUC-1) --------------------------------------------------------
 
   /**
-   * If this doc's baseline diff is the active/open tab → close it and reveal the
-   * normal editor; if the active editor is a tracked doc with no diff open →
-   * open vscode.diff (baseline left, the live document right). Untracked → warn,
-   * no diff.
+   * If this doc's baseline diff is open → close it and reveal the normal editor;
+   * else open vscode.diff (baseline left, the live document right). Warns only
+   * when there is no active text editor (or a non-diffable scheme).
    */
   private async toggle(editor: vscode.TextEditor | undefined): Promise<void> {
-    if (!editor || !this.isTracked(editor.document)) {
+    if (!editor || !this.isDiffable(editor.document)) {
       void vscode.window.showWarningMessage(
-        "Cowriting: open a tracked workspace document to toggle its diff view.",
+        "Cowriting: focus a text editor to toggle its diff view.",
       );
       return;
     }
     const document = editor.document;
-    const docPath = this.docPathOf(document.uri);
     const openTab = this.findDiffTab(document.uri);
     if (openTab) {
       await vscode.window.tabGroups.close(openTab);
@@ -167,11 +155,13 @@ export class DiffViewController implements vscode.Disposable {
       return;
     }
     this.ensureBaseline(document);
-    const baseline = this.baselines.get(docPath)!;
-    const title = `${path.basename(docPath)} — my changes since ${this.epochLabel(baseline)}`;
+    const baseline = this.baselines.get(this.uriKey(document))!;
+    const name = path.basename(document.uri.path) || "untitled";
+    const unsaved = this.isPersistable(document) ? "" : " (unsaved)";
+    const title = `${name} — my changes since ${this.epochLabel(baseline)}${unsaved}`;
     await vscode.commands.executeCommand(
       "vscode.diff",
-      this.baselineUri(docPath),
+      this.baselineUri(document),
       document.uri,
       title,
       { preview: false },
@@ -208,12 +198,28 @@ export class DiffViewController implements vscode.Disposable {
     }
   }
 
-  /**
-   * Test-facing (§6.4): is this doc's baseline diff currently open in any tab
-   * group? The diff's `modified` side is the document's own file: URI.
-   */
-  isDiffOpen(docPath: string): boolean {
-    return this.findDiffTab(vscode.Uri.file(path.join(this.rootDir, docPath))) !== undefined;
+  private pinCommand(editor: vscode.TextEditor | undefined): void {
+    if (!editor || !this.isDiffable(editor.document)) {
+      void vscode.window.showWarningMessage("Cowriting: focus a text editor to pin its diff baseline.");
+      return;
+    }
+    this.pin(editor.document);
+  }
+
+  // ---- test-facing surface (§6.4) ----------------------------------------------------
+
+  getBaseline(uriString: string): { text: string; reason: BaselineReason; capturedAt: string } | undefined {
+    const b = this.baselines.get(uriString);
+    return b ? { text: b.text, reason: b.reason, capturedAt: b.capturedAt } : undefined;
+  }
+  /** Is this doc's baseline diff currently open in any tab group? */
+  isDiffOpen(uriString: string): boolean {
+    return this.findDiffTab(vscode.Uri.parse(uriString)) !== undefined;
+  }
+  /** Absolute on-disk path of this doc's persisted baseline, or undefined (untitled/in-memory). */
+  baselineFilePath(uriString: string): string | undefined {
+    if (!this.store || vscode.Uri.parse(uriString).scheme !== "file") return undefined;
+    return this.store.baselinePath(this.storageKey(uriString));
   }
 
   dispose(): void {

src/extension.ts

@@ -44,6 +44,18 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     }),
   );
 
+  // --- F6: diff-view toggle (Features #17 + #19) — workspace-INDEPENDENT ---
+  // F6 works on ANY diffable doc (file or untitled), so it is constructed
+  // regardless of whether a folder is open, and its commands are always live
+  // (never stubbed). Baseline lives in VS Code's per-extension GLOBAL storage
+  // (always present), never the repo (INV-19). The machine-landing advance is
+  // wired in the with-root branch below (landings only occur on workspace files
+  // through the seam). The controller self-wires baseline capture on open.
+  const baselineStorageDir = context.globalStorageUri?.fsPath;
+  const baselineStore = baselineStorageDir ? new BaselineStore(baselineStorageDir) : null;
+  const diffViewController = new DiffViewController(baselineStore);
+  context.subscriptions.push(diffViewController);
+
   // --- F2: region-anchored threads (Feature #4) ---
   const root = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath;
   if (!root) {
@@ -66,11 +78,12 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
       "cowriting.acceptProposal",
       "cowriting.rejectProposal",
       "cowriting.proposeAgentEdit",
-      "cowriting.toggleDiffView",
-      "cowriting.pinDiffBaseline",
     ]) {
       context.subscriptions.push(vscode.commands.registerCommand(command, stub));
     }
+    // F6 (toggleDiffView / pinDiffBaseline) is NOT stubbed here — it works
+    // without a folder (on untitled buffers and out-of-folder files); its real
+    // commands were registered above by DiffViewController.
     return undefined;
   }
   const store = new CoauthorStore(root);
@@ -88,14 +101,10 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   const proposalController = new ProposalController(store, attributionController, root, versionGuard);
   context.subscriptions.push(proposalController);
 
-  // --- F6: diff-view toggle (Feature #17) ---
-  // Baseline lives in VS Code workspace storage, never the repo (INV-19).
-  // storageUri can be undefined in odd host states → in-memory fallback (§6.5).
-  const storageDir = context.storageUri?.fsPath;
-  const baselineStore = storageDir ? new BaselineStore(storageDir) : null;
-  const diffViewController = new DiffViewController(baselineStore, root);
-  context.subscriptions.push(diffViewController);
+  // --- F6 machine-landing wiring (with-root only) ---
   // The seam's single machine-landing signal advances the baseline (INV-18).
+  // The seam fires only on workspace files, so this wiring belongs here; the
+  // DiffViewController itself was constructed above (workspace-independent).
   context.subscriptions.push(
     attributionController.onDidApplyAgentEdit((e) => diffViewController.advance(e.document)),
   );
@@ -245,7 +254,6 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
       threadController.renderAll(doc);
       attributionController.loadAll(doc);
       proposalController.renderAll(doc);
-      diffViewController.ensureBaseline(doc);
     }
   };
   vscode.workspace.textDocuments.forEach(renderIfOpen);

test/baselineStore.test.ts

@@ -13,41 +13,49 @@ afterEach(() => {
   fs.rmSync(dir, { recursive: true, force: true });
 });
 
-function sample(docPath = "notes/chapter-1.md"): Baseline {
-  return { docPath, text: "hello\nworld\n", capturedAt: "2026-06-11T00:00:00.000Z", reason: "opened" };
+const KEY = "a1b2c3"; // a stand-in for the controller's sha256(uri) key
+
+function sample(uri = "file:///ws/notes/chapter-1.md"): Baseline {
+  return { uri, text: "hello\nworld\n", capturedAt: "2026-06-11T00:00:00.000Z", reason: "opened" };
 }
 
 describe("BaselineStore", () => {
-  it("returns null for a document with no baseline", () => {
-    expect(new BaselineStore(dir).load("notes/chapter-1.md")).toBeNull();
+  it("returns null for a key with no baseline", () => {
+    expect(new BaselineStore(dir).load(KEY)).toBeNull();
   });
 
-  it("computes the baseline path as baselines/<docPath>.json", () => {
+  it("computes the baseline path as baselines/<key>.json", () => {
     const store = new BaselineStore(dir);
-    expect(store.baselinePath("notes/chapter-1.md")).toBe(
-      path.join(dir, "baselines", "notes", "chapter-1.md.json"),
-    );
+    expect(store.baselinePath(KEY)).toBe(path.join(dir, "baselines", "a1b2c3.json"));
   });
 
-  it("save then load round-trips the baseline (including nested docPaths)", () => {
+  it("save then load round-trips the baseline (including the uri identity)", () => {
     const store = new BaselineStore(dir);
     const b = sample();
-    store.save(b.docPath, b);
-    expect(store.load(b.docPath)).toEqual(b);
+    store.save(KEY, b);
+    expect(store.load(KEY)).toEqual(b);
   });
 
   it("overwrites in place: the newest epoch wins, no history kept", () => {
     const store = new BaselineStore(dir);
-    store.save("d.md", { docPath: "d.md", text: "v1", capturedAt: "2026-06-11T00:00:00.000Z", reason: "opened" });
-    store.save("d.md", { docPath: "d.md", text: "v2", capturedAt: "2026-06-11T00:01:00.000Z", reason: "pinned" });
-    expect(store.load("d.md")).toEqual({ docPath: "d.md", text: "v2", capturedAt: "2026-06-11T00:01:00.000Z", reason: "pinned" });
+    store.save(KEY, { uri: "untitled:Untitled-1", text: "v1", capturedAt: "2026-06-11T00:00:00.000Z", reason: "opened" });
+    store.save(KEY, { uri: "untitled:Untitled-1", text: "v2", capturedAt: "2026-06-11T00:01:00.000Z", reason: "pinned" });
+    expect(store.load(KEY)).toEqual({ uri: "untitled:Untitled-1", text: "v2", capturedAt: "2026-06-11T00:01:00.000Z", reason: "pinned" });
   });
 
   it("writes pretty JSON with a trailing newline", () => {
     const store = new BaselineStore(dir);
-    const b = sample("d.md");
-    store.save("d.md", b);
-    const raw = fs.readFileSync(store.baselinePath("d.md"), "utf8");
+    const b = sample();
+    store.save(KEY, b);
+    const raw = fs.readFileSync(store.baselinePath(KEY), "utf8");
     expect(raw).toBe(JSON.stringify(b, null, 2) + "\n");
   });
+
+  it("distinct keys are independent files (no collision)", () => {
+    const store = new BaselineStore(dir);
+    store.save("k1", sample("file:///a.md"));
+    store.save("k2", sample("file:///b.md"));
+    expect(store.load("k1")!.uri).toBe("file:///a.md");
+    expect(store.load("k2")!.uri).toBe("file:///b.md");
+  });
 });