fix(fuse): a file read just as its create lands has its bytes (B179)

docs/BUGS.md

@@ -12,6 +12,29 @@ Conventions:
 
 ---
 
+## B179 — A file read just as its create lands reads empty
+
+**Status:** Fixed (unverified).
+**Found:** 2026-10-04, by the account run on 378667f, on on-demand sync folders: the unusual
+names case read `<angle>|pipe` back as 0 bytes instead of 12, and B70's completed download as 0
+bytes instead of 147456. Both files had a write that landed during their create, which the
+daemon queued as a revision.
+
+**Where:** `Core::read_range` in `crates/pdfs-fuse/src/reads.rs`.
+
+**Cause.** A read takes the file's uid from the tree and reads on a transfer worker. A file made
+on the mount has its stand-in uid there until its create lands. When it lands, the queued write
+moves to the uid Drive gave the file. A read that still asked by the stand-in found no write
+queued under it, took the file for one created and never written, and returned nothing. The
+read waits on the transfer lane, which a run keeps busy, so the window is not small.
+
+**Fix.** A stand-in with no queued write is looked up by its local id. Once its create has
+landed, the read goes on under the uid Drive gave it.
+
+**Test:** `a_file_read_as_its_create_lands_has_its_bytes` in `crates/pdfs-fuse/src/sim/daemon.rs`.
+
+---
+
 ## B178 — Trashing a folder while sync is paused keeps a create in it as a trash
 
 **Status:** Fixed (unverified).

docs/CHANGELOG.md

@@ -83,6 +83,7 @@ by its local id, in the queue, the stored tree and pins alike.
   (B177).
 - **Deleting a folder while sync is paused no longer leaves a queued change behind** for a
   file in it that was never uploaded (B178).
+- **A file read just as it reaches Drive no longer reads empty** (B179).
 - **A file renamed just as its upload finished keeps its new name.** The mount no longer showed
   the old name, and a second rename no longer failed with "No such file or directory" (B152,
   B172).

docs/MILESTONE-3.0.0-STATUS.md

@@ -9,7 +9,7 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
 - **Phase 2**: local ids, inode = local id, one tree for every mount (2.10.0).
 - **Phase 3, first part**: mkdir, create, rename, unlink and rmdir on the mount are recorded
   locally and sent from the queue; `"local_first": false` brings back the old path (5e0f30c).
-- Fixes from the simulation and account runs since then: B127 and B141 to B178.
+- Fixes from the simulation and account runs since then: B127 and B141 to B179.
 - **Sync issues, first cut** (§6.2): refusals sorted into issues, shown at once in the app,
   tray and CLI; Export button and `pdfs sync export`; `pdfs sync issues`.
 
@@ -124,7 +124,7 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
          The account run on 378667f: a folder listed as its create landed asked Drive by
          its stand-in and answered `EIO` (B177, fixed). A folder trashed while sync was
          paused kept a create below it as a trash: a paused drain worker had claimed it
-         (B178, fixed).
+         (B178, fixed). A file read as its create landed read empty (B179, fixed).
 5. **Release**: 2.10.0 is tagged; the 2.9.0 tag still waits for the user's go-ahead.
 
 ## After 3.0.0