v0.16.0: IOKit registry-based drive enumeration, BSD name → IOBDServices matching, reverse patch default

- DAMAGE_WINDOW 50→16, DAMAGE_THRESHOLD_PCT 25→12: triggers on 2nd scattered failure
- Previous 50/25% was too diluted by good reads between sparse failures
- copy() dispatch checks mapfile total_size == disc capacity_bytes (covers_disc)
- NonTried regions → sweep with resume=true (preserves mapfile)
- Only NonTrimmed/NonScraped/Unreadable → patch
- sweep_internal takes resume param: true when dispatching from existing mapfile
- Verified: Pass 1 from 30-100% completes in ~20 min with correct jumps through 3 damage zones

CHANGELOG.md

@@ -1,5 +1,66 @@
 # Changelog
 
+## 0.13.43 (2026-04-29)
+
+### Pass 1 transport-failure recovery loop
+
+- Transport failure (USB bridge crash) no longer kills the entire rip.
+- Autorip re-discovers the drive after USB re-enumeration and resumes
+  from the mapfile. Up to 10 attempts.
+- `Error::is_scsi_transport_failure()` now matches DiscRead with
+  status 0xFF (bridge crash) in addition to ScsiError.
+- DriveSession tracks device_path for re-discovery.
+
+## 0.13.42 (2026-04-29)
+
+### Fix: transport failure skips instead of aborting
+
+- Transport failure (USB bridge crash) now skips the failed ECC block
+  (marks NonTrimmed) and continues. 3 consecutive transport failures
+  still abort the copy. Previously, a single transport failure killed
+  the entire rip.
+
+## 0.13.41 (2026-04-29)
+
+### Debug logging for sector-0 regression diagnosis
+
+- Add debug logging to Drive::read and Disc::copy first reads.
+- No functional changes.
+
+## 0.13.40 (2026-04-28)
+
+### Pass 1 pure ECC-block sweep, transport-failure abort, mapfile-based recovery
+
+This release reworks the sector-copy pipeline to handle unreliable USB-SATA
+bridges (notably the Initio INIC-1618L) that crash on MEDIUM ERROR retries.
+
+**Disc::copy() — Pass 1 (ECC-block sweep):**
+- Reads `batch` sectors (default 32 = 1 BD ECC block = 64 KB).
+- Success → mark Finished. MEDIUM ERROR → zero-fill, mark NonTrimmed, advance.
+- Transport failure (host_status=7) → abort immediately, return error.
+- No single-sector reads, no retry, no state machine in Pass 1.
+
+**Disc::patch() — Pass 2+ (single-sector recovery):**
+- Reads NonTrimmed sectors one at a time with pause between failures.
+- Succeeds → mark Finished. Fails → mark Unreadable (or leave for next pass).
+- Multi-pass: caller runs patch repeatedly until 0 recovered.
+
+**CopyOptions simplified:**
+- Removed `skip_forward`, `cautious_pause_ms`, `BPT1_EXIT_THRESHOLD`.
+- Fields: `decrypt`, `resume`, `batch_sectors`, `skip_on_error`, `progress`, `halt`.
+
+**Other fixes since 0.13.26:**
+- `open()` just opens the device — no side effects. `drive_has_disc()` is a
+  standalone TUR, not a probe sequence.
+- `enumerate_sg_names()` skips unreadable `/sys` type files.
+- SCSI sense data preserved in DiscRead errors (status + key + ASC/ASCQ).
+- MapStats splits `bytes_pending` into `nontried` / `retryable`.
+- Wallclock rip budget — halt after max(disc_runtime_secs, 3600).
+- Patch instrumentation: counters for reads_ok/err, writes_ok/err, finished/unreadable.
+- `as_encoded_bytes()` replaces `as_bytes()` for portable OsStr handling.
+- Removed inline retry/reset from Drive::read — orchestration layer handles recovery.
+- Removed all `(internal)` references from public code.
+
 ## 0.13.26 (2026-04-27)
 
 ### Extend DiscRead with SCSI status/sense for 30% wedge diagnostics

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libfreemkv"
-version = "0.13.26"
+version = "0.16.0"
 edition = "2024"
 rust-version = "1.86"
 license = "AGPL-3.0-only"

TROUBLESHOOTING.md

@@ -0,0 +1,312 @@
+# Troubleshooting Guide
+
+Common problems and solutions for optical drive ripping with freemkv.
+
+---
+
+## 1. USB-SATA Bridge Issues
+
+This is the single most common source of problems when ripping discs over USB.
+
+### Symptoms
+
+- The drive disappears mid-rip. The ripping tool reports the device is gone, and `ls /dev/sg*` no longer shows it.
+- The device re-enumerates under a different name: `sg4` becomes `sg5`, then `sg7`, then `sg11` after each USB port reset.
+- `dmesg` shows USB port resets: `usb X-Y: reset high-speed USB device`, `xhci_hcd 0000:00:14.0: Cannot enable. Maybe the USB cable is bad?`, or `usb-storage: device reset failed`.
+- The SCSI layer reports `host_status=7` (Linux USB transport error) in sense data.
+- The drive works fine for reading data discs or burning, but crashes when hitting damaged sectors during a rip.
+- After the crash, the drive is completely invisible until physically unplugged and reconnected.
+
+### Root Cause
+
+USB-SATA bridges translate between the USB Mass Storage protocol (BOT or UAS) and the drive's native SATA interface. When the optical drive encounters an unreadable sector, it returns a SCSI CHECK CONDITION with sense key 0x03 (MEDIUM ERROR). Some bridge chipsets -- particularly the Initio INIC-36xx family -- have buggy firmware that mishandles this error response.
+
+Specific failure modes:
+
+- **Incorrect residue reporting.** The bridge claims a different number of bytes transferred than what actually occurred. The Linux USB storage driver sees this discrepancy as a protocol violation and resets the port to recover. The `US_FL_IGNORE_RESIDUE` quirk exists specifically for this class of bug (see `drivers/usb/storage/transport.c` in the Linux kernel).
+- **Bridge firmware crash.** On some Initio bridges, a malformed SCSI error response from the drive causes the bridge MCU to hang entirely. The USB controller sees the device stop responding and initiates a port reset. The bridge recovers (it re-enumerates), but the rip is dead -- all state is lost.
+- **Sense data corruption.** The bridge forwards garbled or truncated sense data to the host, which the SCSI midlayer cannot parse, leading to a transport reset.
+
+This is a hardware + firmware problem, not a software bug. The same drive connected via direct SATA does not exhibit these symptoms.
+
+### Known Affected Bridges
+
+| Chipset | USB IDs | Notes |
+|---------|---------|-------|
+| Initio INIC-3609 | `13fd:3609` | Very common in cheap SATA-to-USB enclosures. Highly problematic. |
+| Initio INIC-3619 | `13fd:3940` | Same firmware family as INIC-3609. |
+| Initio INIC-3069 | `13fd:0840` | Older variant, same residue bug. |
+| ASMedia ASM1051 | `174c:5106` | Early ASM SATA bridge. Residue issues on error paths. |
+| JMicron JMB36x | `152d:0561` | Some firmware versions. Not all JMicroon chips are affected. |
+
+If your drive came in a pre-built external enclosure (Vantec, Sabrent, OWC, etc.), it almost certainly uses one of these bridge chips internally.
+
+### The Fix: USB Storage Quirk
+
+Apply the `US_FL_IGNORE_RESIDUE` kernel quirk for your bridge. This tells the Linux USB storage driver to ignore the residue field in SCSI response frames, preventing the port reset on mismatched byte counts.
+
+**Step 1: Identify your bridge's vendor:product ID.**
+
+```bash
+lsusb
+```
+
+Look for your drive's entry. Example output:
+
+```
+Bus 002 Device 005: ID 13fd:0840 Initio Corporation INIC-3609
+```
+
+Here the vendor ID is `13fd` and the product ID is `0840`.
+
+**Step 2: Apply the quirk at runtime.**
+
+```bash
+echo "13fd:0840:i" > /sys/module/usb_storage/parameters/quirks
+```
+
+Replace `13fd:0840` with your device's actual IDs. The `:i` flag means `US_FL_IGNORE_RESIDUE`.
+
+You can combine multiple flags. Common additions:
+
+- `:i` -- ignore residue (`US_FL_IGNORE_RESIDUE`)
+- `:u` -- force BOT mode instead of UAS, for bridges with UAS bugs
+
+**Step 3: Reconnect the drive.** Unplug and replug the USB cable, or bind/unbind the device. The quirk is applied per-module-load, so existing sessions may need the drive reconnected.
+
+### Making It Persistent
+
+Add the quirk to your kernel boot parameters so it survives reboots.
+
+Edit `/etc/default/grub` (GRUB) and add to `GRUB_CMDLINE_LINUX_DEFAULT`:
+
+```
+GRUB_CMDLINE_LINUX_DEFAULT="quiet usb_storage.quirks=13fd:0840:i"
+```
+
+Then rebuild the GRUB config:
+
+```bash
+sudo update-grub
+```
+
+For systemd-boot, add to your loader entry or `/etc/kernel/cmdline`:
+
+```
+usb_storage.quirks=13fd:0840:i
+```
+
+Multiple devices can be separated by commas:
+
+```
+usb_storage.quirks=13fd:0840:i,174c:5106:u
+```
+
+### Recommended Bridges
+
+If you are buying a USB-SATA adapter or enclosure for optical drive use:
+
+| Bridge | USB IDs | Notes |
+|--------|---------|-------|
+| ASMedia ASM1153 | `174c:1153` | Reliable. Widely available in SATA-USB 3.0 cables. |
+| JMicron JMS578 | `152d:0578` | Good firmware. Supports UASP. |
+| Icy Box IB-AC640-C3 | N/A | Uses a known-good bridge internally. Plug-and-play. |
+
+Avoid any enclosure or adapter listing an Initio chipset.
+
+### Best Solution: Direct SATA
+
+Connect your optical drive directly to a motherboard SATA port. This eliminates the USB-SATA bridge entirely and is the most reliable configuration:
+
+- No USB protocol overhead or translation errors.
+- No bridge firmware bugs.
+- No port resets or re-enumeration.
+- Full SATA error recovery handled natively by the kernel's libata driver.
+- Sustained read speeds are limited only by the drive, not the USB bus.
+
+If your machine has a free SATA port, use it.
+
+---
+
+## 2. Damaged Disc Handling
+
+### Symptoms
+
+- SCSI MEDIUM ERROR (sense key 0x03) at specific LBAs. `dmesg` shows `sr X:0:0:0: [srY] Unrecoverable read error` or similar.
+- Read speed drops to near zero when approaching a damaged area.
+- The drive makes audible retrying noises (laser repositioning, spindle speed changes).
+- On USB-connected drives: the bridge crashes (see section 1 above) when the drive returns the error.
+
+### How freemkv Handles This
+
+freemkv uses a three-layer recovery model. See [`docs/rip-recovery.md`](docs/rip-recovery.md) for full details.
+
+- **Pass 1 (Disc::copy):** Fast sweep with 64 KB reads. On failure, zero-fills the block and skips forward. Writes a ddrescue-format mapfile for later retry.
+- **Pass 2+ (Disc::patch):** Targeted re-reads of bad ranges with a long 30-second timeout per CDB. The drive firmware performs its own ECC and laser power retries within that window.
+- **In-stream (DiscStream):** Adaptive batch halving -- reduces request size on failure to isolate bad sectors within a larger block.
+
+This means a disc with some bad sectors will still produce a usable ISO. The damaged areas are zero-filled in pass 1 and retried in subsequent passes. Structure-protected sectors (deliberate unreadable regions from copy protection) will never yield, which is expected.
+
+### The Drive Taint Issue (LG BU40N)
+
+Some drives, notably the LG BU40N, exhibit a "taint" behavior after encountering MEDIUM ERRORs:
+
+1. The drive hits a damaged sector and returns a MEDIUM ERROR.
+2. From that point forward, **all subsequent reads fail** -- even reads to sectors that were previously successful.
+3. The only recovery is to physically unplug and reconnect the drive (or power-cycle it).
+
+This is not a freemkv bug. It is a drive firmware behavior triggered by the interaction between the drive's internal error recovery and the USB-SATA bridge's handling of the error response. The drive firmware enters a degraded state that it does not recover from without a power cycle.
+
+Workarounds:
+
+- **Use a direct SATA connection.** This eliminates the bridge interaction that triggers the taint.
+- **Use a different bridge.** The ASM1153 and JMS578 are less likely to trigger this behavior.
+- **Accept the partial ISO.** freemkv's skip-forward recovery will zero-fill the unreadable blocks and continue. The resulting ISO may be playable with minor glitches in the affected areas.
+- **Physical replug between retry passes.** If running multi-pass patch, replug the drive between passes to clear the taint state.
+
+freemkv deliberately does not attempt inline SCSI resets or eject cycles to recover from this state, because those operations were found to make the problem worse on affected hardware (see the design rationale in [`docs/rip-recovery.md`](docs/rip-recovery.md)).
+
+---
+
+## 3. Drive Not Detected
+
+### Check Hardware Visibility
+
+```bash
+lsusb
+```
+
+Verify the drive appears in the USB device list. If it does not show up, the drive is not visible to the host at all -- check cables, power, and USB port.
+
+```bash
+ls /dev/sg*
+```
+
+On Linux, optical drives appear as `/dev/sg*` devices (the SCSI Generic interface). freemkv uses `/dev/sg*`, not `/dev/sr*`. If `lsusb` shows the device but no `/dev/sg*` entry exists, the `sg` kernel module may not be loaded:
+
+```bash
+sudo modprobe sg
+```
+
+### Check Kernel Messages
+
+```bash
+dmesg | grep -i usb | tail -30
+dmesg | grep -i sg | tail -10
+```
+
+Look for:
+- USB enumeration errors or failed port resets.
+- `sg_add` messages confirming the sg device was registered.
+- Permission denied or access errors.
+
+### Permission Issues
+
+On most Linux distributions, `/dev/sg*` devices are owned by `root:disk` or `root:cdrom` with restricted permissions. Running freemkv as an unprivileged user will fail with permission errors.
+
+Options:
+
+- Add your user to the appropriate group:
+
+  ```bash
+  sudo usermod -aG disk $USER
+  ```
+
+  Then log out and back in for the change to take effect. On some distributions the group is `cdrom` or `optical` instead of `disk`.
+
+- Run with elevated privileges:
+
+  ```bash
+  sudo freemkv ...
+  ```
+
+- Install a udev rule for persistent per-device permissions. Create `/etc/udev/rules.d/99-sg-optical.rules`:
+
+  ```
+  SUBSYSTEM=="scsi_generic", ATTRS{type}=="5", MODE="0666"
+  ```
+
+  Then reload udev rules:
+
+  ```bash
+  sudo udevadm control --reload-rules && sudo udevadm trigger
+  ```
+
+### Spin-Up Delay
+
+Optical drives take 30-60 seconds to spin up and become ready after hot-plug or disc insertion. During this window, SCSI commands may return NOT READY or timeout.
+
+freemkv's `Drive::wait_ready()` handles this automatically by polling with TEST UNIT READY until the drive responds. If you are writing your own code using the library, always call `wait_ready()` before `init()`:
+
+```rust
+let mut drive = Drive::open(Path::new("/dev/sg4"))?;
+drive.wait_ready()?;  // blocks until disc is ready, up to 30s
+drive.init()?;
+```
+
+If the drive was just plugged in, wait a full minute before concluding it is not detected.
+
+---
+
+## 4. How to Identify Your USB-SATA Bridge
+
+If you are experiencing the issues described in section 1, you need to know which bridge chipset your adapter or enclosure uses.
+
+### Step 1: Find the Device
+
+```bash
+lsusb
+```
+
+Look for entries matching your drive or enclosure. Bridges may appear under their own manufacturer name or as a generic SATA device. Common examples:
+
+```
+Bus 002 Device 005: ID 13fd:0840 Initio Corporation
+Bus 002 Device 006: ID 174c:1153 ASMedia Technology Inc. ASM1153
+Bus 002 Device 007: ID 152d:0578 JMicron Technology Corp. JMS578
+```
+
+### Step 2: Match the IDs
+
+| Vendor | Product ID | Chipset | Status |
+|--------|-----------|---------|--------|
+| `13fd` | `3609` | Initio INIC-3609 | Affected. Apply quirk. |
+| `13fd` | `3940` | Initio INIC-3619 | Affected. Apply quirk. |
+| `13fd` | `0840` | Initio INIC-3069 | Affected. Apply quirk. |
+| `174c` | `5106` | ASMedia ASM1051 | Affected (early firmware). Apply quirk. |
+| `174c` | `1153` | ASMedia ASM1153 | Good. No quirk needed. |
+| `152d` | `0561` | JMicron JMB36x | Affected (some firmware). Apply quirk if issues occur. |
+| `152d` | `0578` | JMicron JMS578 | Good. No quirk needed. |
+
+### Step 3: Check dmesg for the Bridge Name
+
+```bash
+dmesg | grep -i "usb-storage\|uas\|initio\|asmedia\|jmicron"
+```
+
+This often reveals the bridge chipset even when `lsusb` shows a generic name.
+
+### Step 4: If the Enclosure Is Sealed
+
+Many external drive enclosures (Vantec NexStar, Sabrent, OWC, etc.) do not advertise the bridge chipset on the packaging. In this case:
+
+1. Check `lsusb` while the enclosure is connected.
+2. Search the vendor:product ID online -- there are community-maintained lists of which chipsets popular enclosures use.
+3. If you cannot determine the chipset and are experiencing bridge crashes, assume it is an Initio and apply the quirk with its IDs.
+4. The definitive test: connect the bare drive to a motherboard SATA port. If the problems disappear, the bridge was the cause.
+
+---
+
+## 5. General Debugging Checklist
+
+When something goes wrong during a rip, gather this information before filing an issue:
+
+1. **freemkv version:** `freemkv --version` or the crate version in `Cargo.toml`.
+2. **Drive model:** from the drive label, or from `freemkv info`.
+3. **Connection type:** USB (with bridge chipset if known) or direct SATA.
+4. **Operating system and kernel:** `uname -a`.
+5. **Kernel messages during the failure:** `dmesg | tail -50` immediately after the crash.
+6. **SCSI device:** which `/dev/sg*` the drive was on, and whether it changed after the failure.
+7. **The disc:** title, format (BD/DVD/UHD), condition.
+
+Include all of the above in bug reports. SCSI transport errors that resolve with the `US_FL_IGNORE_RESIDUE` quirk or by switching to direct SATA are bridge firmware bugs, not freemkv bugs.

build.rs

@@ -3,5 +3,34 @@ fn main() {
     if target == "macos" {
         println!("cargo:rustc-link-lib=framework=IOKit");
         println!("cargo:rustc-link-lib=framework=CoreFoundation");
+
+        let out_dir = std::env::var("OUT_DIR").unwrap();
+        let obj = format!("{out_dir}/macos_shim.o");
+        let lib = format!("{out_dir}/libmacos_scsi.a");
+
+        std::process::Command::new("cc")
+            .args([
+                "-c",
+                "src/scsi/macos_shim.c",
+                "-o",
+                &obj,
+                "-framework",
+                "IOKit",
+                "-framework",
+                "CoreFoundation",
+                "-Wall",
+                "-O2",
+            ])
+            .status()
+            .expect("failed to compile macos_shim.c");
+
+        std::process::Command::new("ar")
+            .args(["rcs", &lib, &obj])
+            .status()
+            .expect("failed to create static lib");
+
+        println!("cargo:rustc-link-search=native={out_dir}");
+        println!("cargo:rustc-link-lib=static=macos_scsi");
+        println!("cargo:rerun-if-changed=src/scsi/macos_shim.c");
     }
 }

docs/architecture.md

@@ -102,7 +102,7 @@ Recovery is layered above `Drive::read`, not inside it. Layer 1
 Layer 3 (`DiscStream::fill_extents` adaptive batch sizer) handles in-loop
 request-size adaptation. Inline recovery (gentle retry → SCSI reset → retry)
 was removed in 0.13.6 — see [`rip-recovery.md`](rip-recovery.md) and
-`(internal)/postmortems/2026-04-25-stop-wedge-and-zero-kbs.md`.
+the stop-wedge postmortem (2026-04-25).
 
 ---
 

docs/drive-access.md

@@ -67,7 +67,7 @@ Recovery is layered above `Drive::read`:
   streak.
 
 Inline recovery (5× gentle retry → close + reset + reopen → 5× more) was
-removed in 0.13.6. See `(internal)/postmortems/2026-04-25-stop-wedge-and-zero-kbs.md`
+removed in 0.13.6. See the stop-wedge postmortem (2026-04-25)
 for rationale: the inline reset wedged drive firmware on the LG BU40N (Initio
 USB-SATA bridge) without ever recovering a sector. See
 [`rip-recovery.md`](rip-recovery.md) for the full three-layer model.

docs/rip-recovery.md

@@ -133,8 +133,8 @@ implement retry logic.
 no eject cycle. The `recovery` flag controls only the per-CDB timeout
 (1.5 s vs. 30 s); on any failure it returns `Err(DiscRead)` immediately.
 Inline recovery (5× gentle retry → close + SCSI reset + reopen → 5× more)
-was removed in 0.13.6. See `(internal)/postmortems/2026-04-25-stop-wedge-and-zero-kbs.md`
-for rationale: the inline reset on the LG BU40N (Initio USB-SATA bridge)
+was removed in 0.13.6. See the stop-wedge postmortem (2026-04-25) for rationale:
+the inline reset on the LG BU40N (Initio USB-SATA bridge)
 wedged drive firmware below the bridge without ever recovering a sector,
 and the gentle-retry phase produced long stretches of 0 KB/s with no
 recoveries to show for it. Recovery responsibility is now layered: layer 1

src/disc/mapfile.rs

@@ -318,7 +318,7 @@ impl Mapfile {
             let mut w = std::io::BufWriter::new(file);
             writeln!(
                 w,
-                "# Rescue Logfile. Created by libfreemkv v{}",
+                "# Rescue Logfile. Created by {}",
                 self.version
             )?;
             writeln!(w, "# Current pos / status / pass / pass_time")?;

src/disc/mod.rs

@@ -1210,29 +1210,124 @@ impl Disc {
         }
     }
 
-    /// Raw sector copy — write the entire disc image to a file.
+    /// Copy disc sectors to an ISO image file.
     ///
-    /// NOT a stream operation. Copies sectors 0→capacity byte-for-byte producing
-    /// a valid ISO/UDF image. Records progress in a ddrescue-format mapfile at
+    /// NOT a stream operation. Copies sectors byte-for-byte producing a valid
+    /// ISO/UDF image. Records progress in a ddrescue-format mapfile at
     /// `path + ".mapfile"` — flushed every block for crash-safe resume.
     ///
-    /// # Options
-    /// - **default** (all false): behavior matches pre-v0.11.21 — uses full
-    ///   drive recovery (may take minutes per bad sector), aborts on error.
-    ///   Mapfile is produced as a side-effect.
-    /// - **skip_on_error**: zero-fill bad blocks in the ISO, mark them in the
-    ///   mapfile, and continue. Uses fast reads (no drive-level recovery loop).
-    /// - **skip_forward** (implies skip_on_error): on block failure, also skip
-    ///   forward by an exponentially-growing amount, marking the jumped region
-    ///   as `non-trimmed` for later trimming/scraping by `Disc::patch`.
-    /// - **resume**: if the mapfile exists, resume from its state — only
-    ///   `non-tried` ranges are read. Without `resume`, a fresh mapfile is
-    ///   written and the ISO recreated from scratch.
+    /// Auto-detects the pass based on mapfile state:
+    /// - **No mapfile** → Pass 1 (sweep): sequential read of the entire disc,
+    ///   ECC-aligned batches, damage-jump on contiguous failures, marks bad
+    ///   blocks as NonTrimmed. No drive-level recovery — fast.
+    /// - **Mapfile with bad ranges** → Pass N (patch): re-reads only bad ranges
+    ///   sector-by-sector with full drive-level recovery. Marks recovered
+    ///   sectors as Finished, failed as Unreadable (terminal).
+    /// - **Mapfile clean** → no-op: all sectors are Finished.
+    ///
+    /// Without `multipass`: aborts on the first read error (legacy single-pass).
     pub fn copy(
         &self,
         reader: &mut dyn SectorReader,
         path: &std::path::Path,
         opts: &CopyOptions,
+    ) -> Result<CopyResult> {
+        if opts.multipass {
+            let mf_path = self.mapfile_for(path);
+            if mf_path.exists() {
+                let map = mapfile::Mapfile::load(&mf_path)
+                    .map_err(|e| Error::IoError { source: e })?;
+                let stats = map.stats();
+                let disc_size = self.capacity_bytes;
+                let covers_disc = map.total_size() == disc_size;
+                let bad_bytes = stats.bytes_pending + stats.bytes_unreadable;
+                tracing::info!(
+                    "copy dispatch: disc={} map={} covers={} good={} nontried={} pending={} unreadable={}",
+                    disc_size,
+                    map.total_size(),
+                    covers_disc,
+                    stats.bytes_good,
+                    stats.bytes_nontried,
+                    stats.bytes_pending,
+                    stats.bytes_unreadable,
+                );
+                if covers_disc && bad_bytes == 0 {
+                    return Ok(CopyResult {
+                        bytes_total: disc_size,
+                        bytes_good: stats.bytes_good,
+                        bytes_unreadable: stats.bytes_unreadable,
+                        bytes_pending: 0,
+                        recovered_this_pass: 0,
+                        complete: true,
+                        halted: false,
+                    });
+                }
+                if !covers_disc || stats.bytes_nontried > 0 {
+                    tracing::info!(
+                        "copy dispatch: → sweep (covers_disc={}, nontried={})",
+                        covers_disc,
+                        stats.bytes_nontried,
+                    );
+                    return self.sweep_internal(reader, path, opts, true);
+                }
+                tracing::info!("copy dispatch: → patch");
+                return self.patch_internal(reader, path, opts);
+            }
+        }
+        self.sweep_internal(reader, path, opts, false)
+    }
+
+    fn sweep_internal(
+        &self,
+        reader: &mut dyn SectorReader,
+        path: &std::path::Path,
+        opts: &CopyOptions,
+        resume: bool,
+    ) -> Result<CopyResult> {
+        let sweep_opts = SweepOptions {
+            decrypt: opts.decrypt,
+            resume,
+            batch_sectors: None,
+            skip_on_error: opts.multipass,
+            progress: opts.progress,
+            halt: opts.halt.clone(),
+        };
+        self.sweep(reader, path, &sweep_opts)
+    }
+
+    fn patch_internal(
+        &self,
+        reader: &mut dyn SectorReader,
+        path: &std::path::Path,
+        opts: &CopyOptions,
+    ) -> Result<CopyResult> {
+        let patch_opts = PatchOpts {
+            decrypt: opts.decrypt,
+            block_sectors: Some(1),
+            full_recovery: true,
+            reverse: true,
+            wedged_threshold: 50,
+            progress: opts.progress,
+            halt: opts.halt.clone(),
+        };
+        let pr = self.patch(reader, path, &patch_opts)?;
+        Ok(CopyResult {
+            bytes_total: pr.bytes_total,
+            bytes_good: pr.bytes_good,
+            bytes_unreadable: pr.bytes_unreadable,
+            bytes_pending: pr.bytes_pending,
+            recovered_this_pass: pr.bytes_recovered_this_pass,
+            complete: pr.bytes_pending == 0 && pr.bytes_unreadable > 0
+                || pr.bytes_pending == 0 && pr.bytes_unreadable == 0,
+            halted: pr.halted,
+        })
+    }
+
+    fn sweep(
+        &self,
+        reader: &mut dyn SectorReader,
+        path: &std::path::Path,
+        opts: &SweepOptions,
     ) -> Result<CopyResult> {
         use std::io::{Seek, SeekFrom, Write};
 
@@ -1244,12 +1339,12 @@ impl Disc {
         };
 
         // Mapfile: load if resuming, else wipe + recreate.
-        let mapfile_path = mapfile_path_for(path);
+        let mapfile_path = self.mapfile_for(path);
         if !opts.resume {
             let _ = std::fs::remove_file(&mapfile_path);
         }
         let mut map =
-            mapfile::Mapfile::open_or_create(&mapfile_path, total_bytes, env!("CARGO_PKG_VERSION"))
+            mapfile::Mapfile::open_or_create(&mapfile_path, total_bytes, concat!("libfreemkv v", env!("CARGO_PKG_VERSION")))
                 .map_err(|e| Error::IoError { source: e })?;
 
         // ISO file: if resuming and mapfile has Finished ranges, open existing;
@@ -1274,7 +1369,7 @@ impl Disc {
         let mut file = file;
         let batch: u16 = match opts.batch_sectors {
             Some(b) => b,
-            None if opts.skip_forward => 32, // 64 KB = BD ECC block size
+            None if opts.skip_on_error => ecc_sectors(self.format),
             None => DEFAULT_BATCH_SECTORS,
         };
 
@@ -1286,31 +1381,27 @@ impl Disc {
         let mut read_ok_count: u64 = 0;
         let mut read_err_count: u64 = 0;
         let mut last_log_iter: u64 = 0;
-        // Hysteresis state (0.13.22): Block(batch) <-> Single(bpt=1).
-        // mode_single=false means we're in Block mode (default). On a
-        // multi-sector read failure we flip to Single, walk the failed
-        // range sector-by-sector, and stay in Single until we hit
-        // BPT1_EXIT_THRESHOLD consecutive good reads — then back to Block.
-        let mut mode_single = false;
+        let mut not_ready_retries: u32 = 0;
+        const NOT_READY_MAX_RETRIES: u32 = 3;
+        let mut bridge_degradation_count: u32 = 0;
+        const BRIDGE_DEGRADATION_MAX: u32 = 5;
+        const BRIDGE_DEGRADATION_COOLDOWN_SECS: u64 = 10;
+        const DAMAGE_WINDOW: usize = 16;
+        const DAMAGE_THRESHOLD_PCT: usize = 12;
+        const JUMP_SECTORS_FACTOR: u64 = 256;
+        let mut damage_window: Vec<bool> = Vec::with_capacity(DAMAGE_WINDOW);
+        let mut jump_multiplier: u64 = 1;
         let mut consecutive_good: u64 = 0;
-        // Wallclock cadence for the progress callback. Default outer-loop
-        // tick is per-block, which is once every few ms in clean territory
-        // but can be tens of seconds (or minutes) in dense single-mode
-        // recovery. Fire the callback on a wallclock interval too so the
-        // UI shows movement even mid-cluster.
-        let mut last_progress_t = std::time::Instant::now();
-        const PROGRESS_TICK: std::time::Duration = std::time::Duration::from_secs(2);
+        let mut in_damage_zone = false;
         tracing::trace!(
             target: "freemkv::disc",
             phase = "copy_start",
             total_bytes,
             batch,
-            bpt1_exit_threshold = BPT1_EXIT_THRESHOLD,
+            skip_on_error = opts.skip_on_error,
             "Disc::copy entered"
         );
 
-        // Iterate over not-yet-finished regions from the mapfile. We re-read the
-        // mapfile after each block because record() mutates the region list.
         'outer: loop {
             let regions_to_do = map.ranges_with(&[
                 mapfile::SectorStatus::NonTried,
@@ -1326,9 +1417,6 @@ impl Disc {
             if regions_to_do.is_empty() {
                 break;
             }
-            // Only process the first NonTried range per outer pass; skip_forward
-            // may turn others into NonTrimmed which we DO NOT re-enter here —
-            // Disc::patch handles those.
             let Some((region_pos, region_size)) = map.next_with(0, mapfile::SectorStatus::NonTried)
             else {
                 break;
@@ -1351,62 +1439,61 @@ impl Disc {
                         break 'outer;
                     }
                 }
+
                 let block_bytes = (region_end - pos).min(batch as u64 * 2048);
                 let block_lba = (pos / 2048) as u32;
                 let block_count = (block_bytes / 2048) as u16;
                 let recovery = !opts.skip_on_error;
 
-                // Hysteresis state machine (0.13.22, replaces v0.13.21
-                // bisect-on-fail): two states.
-                //
-                //   Block(batch): try the full block. On success, write,
-                //     advance, stay in Block. On failure, switch to Single
-                //     and retry the same range one sector at a time.
-                //
-                //   Single: read at bpt=1. Each success increments
-                //     consecutive_good; once that reaches BPT1_EXIT_THRESHOLD
-                //     we switch back to Block. Each failure marks the sector
-                //     NonTrimmed and resets consecutive_good = 0.
-                //
-                // Why not bisection: the v0.13.21 bisect-on-fail descended
-                // log2(batch) levels on every multi-sector failure, paying
-                // a ~5 s kernel timeout at every level. For a 60-block with
-                // 1 bad sector the cost was ~30 s. Direct drop to bpt=1
-                // pays ~10 s for the same outcome. And once we're inside a
-                // bad cluster we stay there at bpt=1 instead of repeatedly
-                // re-trying bpt=batch (each fail = another ~5 s wasted).
-                //
-                // Empirical justification:
-                //   (internal)/docs/audits/2026-04-26-bisect-on-fail-empirical-findings.md
-                let block_t0 = std::time::Instant::now();
-                let read_t0 = block_t0;
-                let block_bytes_usz = block_bytes as usize;
-                iter_count += 1;
-                let block_result = reader.read_sectors(
+                let read_result = reader.read_sectors(
                     block_lba,
                     block_count,
-                    &mut buf[..block_bytes_usz],
+                    &mut buf[..block_bytes as usize],
                     recovery,
                 );
 
-                if block_result.is_ok() {
-                    // Fast path — full block read cleanly.
+                let mut did_skip_ahead = false;
+
+                if read_result.is_ok() {
                     read_ok_count += 1;
+                    damage_window.push(true);
+                    if damage_window.len() > DAMAGE_WINDOW {
+                        damage_window.remove(0);
+                    }
+                    consecutive_good += 1;
+                    if consecutive_good >= DAMAGE_WINDOW as u64 {
+                        jump_multiplier = 1;
+                        if in_damage_zone {
+                            in_damage_zone = false;
+                            reader.set_speed(0xFFFF);
+                            tracing::debug!(
+                                target: "freemkv::disc",
+                                phase = "damage_exit",
+                                lba = block_lba,
+                                "Exited damage zone; restoring max read speed"
+                            );
+                        }
+                    }
+                    bridge_degradation_count = 0;
+
                     if opts.decrypt {
-                        crate::decrypt::decrypt_sectors(&mut buf[..block_bytes_usz], &keys, 0)?;
+                        crate::decrypt::decrypt_sectors(
+                            &mut buf[..block_bytes as usize],
+                            &keys,
+                            0,
+                        )?;
                     }
                     file.seek(SeekFrom::Start(pos))
                         .map_err(|e| Error::IoError { source: e })?;
-                    file.write_all(&buf[..block_bytes_usz])
+                    file.write_all(&buf[..block_bytes as usize])
                         .map_err(|e| Error::IoError { source: e })?;
                     map.record(pos, block_bytes, mapfile::SectorStatus::Finished)
                         .map_err(|e| Error::IoError { source: e })?;
                     bytes_done = bytes_done.saturating_add(block_bytes);
                 } else if !opts.skip_on_error {
-                    // Strict mode (skip_on_error=false): abort on first bad.
-                    let (status, sense) = block_result
-                        .err()
+                    let (status, sense) = read_result
                         .as_ref()
+                        .err()
                         .map(extract_scsi_context)
                         .unwrap_or((0, None));
                     return Err(Error::DiscRead {
@@ -1414,148 +1501,150 @@ impl Disc {
                         status: Some(status),
                         sense,
                     });
-                } else if !block_result
-                    .as_ref()
-                    .err()
-                    .map(Error::is_marginal_read)
-                    .unwrap_or(false)
-                {
-                    // 0.13.23: SCSI sense-aware dispatch. Block read failed
-                    // with a sense class outside the marginal-read set
-                    // (real transport failure, HARDWARE ERROR, DATA
-                    // PROTECT, UNIT ATTENTION, NOT READY, ILLEGAL
-                    // REQUEST, kernel IoError). Bail with the full sense
-                    // triple preserved — caller (autorip) surfaces
-                    // "physical replug needed" / "drive failing" /
-                    // "media changed" / etc to the user. Hysteresis
-                    // would just hammer the same failure for thousands
-                    // of sectors at 1.4 sec each.
-                    let err = block_result.err().unwrap();
-                    tracing::trace!(
-                        target: "freemkv::disc",
-                        phase = "bail",
-                        lba = block_lba,
-                        error = %err,
-                        "block read failed with non-recoverable sense; bailing"
-                    );
-                    return Err(err);
                 } else {
-                    // Block failed → drop to Single and read this range
-                    // sector-by-sector. Stay in Single across subsequent
-                    // outer-loop blocks until we hit
-                    // BPT1_EXIT_THRESHOLD consecutive good single-sector
-                    // reads, then return to Block mode.
-                    if !mode_single {
-                        tracing::trace!(
+                    let err = read_result.err().unwrap();
+                    read_err_count += 1;
+                    consecutive_good = 0;
+
+                    if err.is_scsi_transport_failure() {
+                        tracing::warn!(
                             target: "freemkv::disc",
-                            phase = "mode_change",
-                            from = "Block",
-                            to = "Single",
+                            phase = "transport_failure",
                             lba = block_lba,
-                            block_elapsed_ms = read_t0.elapsed().as_millis() as u64,
-                            "block read failed; switching to bpt=1"
+                            error = %err,
+                            "transport failure (bridge crash); aborting copy — caller should USB reset + resume"
                         );
-                        mode_single = true;
-                        consecutive_good = 0;
+                        return Err(err);
                     }
 
-                    // Walk the failed block one sector at a time.
-                    for s in 0..block_count {
-                        if let Some(ref h) = opts.halt {
-                            if h.load(std::sync::atomic::Ordering::Relaxed) {
-                                halt_requested = true;
-                                break 'outer;
-                            }
+                    if err.is_bridge_degradation() {
+                        if bridge_degradation_count < BRIDGE_DEGRADATION_MAX {
+                            bridge_degradation_count += 1;
+                            tracing::warn!(
+                                target: "freemkv::disc",
+                                phase = "bridge_degradation",
+                                lba = block_lba,
+                                degradation_count = bridge_degradation_count,
+                                error = %err,
+                                "bridge degradation; cooling down 10s"
+                            );
+                            std::thread::sleep(std::time::Duration::from_secs(BRIDGE_DEGRADATION_COOLDOWN_SECS));
+                            continue;
                         }
-                        iter_count += 1;
-                        let s_lba = block_lba + s as u32;
-                        let s_pos = pos + (s as u64) * 2048;
-                        let one_bytes = 2048usize;
-                        let one_result =
-                            reader.read_sectors(s_lba, 1, &mut buf[..one_bytes], recovery);
-                        // 0.13.23: same sense-aware dispatch inside Single
-                        // mode. If a single-sector read fails with a
-                        // non-marginal sense (transport / hardware /
-                        // DATA PROTECT / UNIT ATTENTION / NOT READY /
-                        // ILLEGAL REQUEST / kernel IoError), the drive
-                        // isn't going to start succeeding for the next
-                        // 60 sectors either — bail with full sense info
-                        // rather than chewing through bpt=1 timeouts.
-                        if let Err(ref e) = one_result {
-                            if !e.is_marginal_read() {
-                                let err = one_result.err().unwrap();
-                                tracing::trace!(
-                                    target: "freemkv::disc",
-                                    phase = "bail",
-                                    lba = s_lba,
-                                    error = %err,
-                                    "bpt=1 read failed with non-marginal sense; bailing"
-                                );
-                                return Err(err);
-                            }
-                        }
-                        let one_ok = one_result.is_ok();
-                        if one_ok {
-                            read_ok_count += 1;
-                            consecutive_good = consecutive_good.saturating_add(1);
-                            if opts.decrypt {
-                                crate::decrypt::decrypt_sectors(&mut buf[..one_bytes], &keys, 0)?;
-                            }
-                            file.seek(SeekFrom::Start(s_pos))
-                                .map_err(|e| Error::IoError { source: e })?;
-                            file.write_all(&buf[..one_bytes])
-                                .map_err(|e| Error::IoError { source: e })?;
-                            map.record(s_pos, 2048, mapfile::SectorStatus::Finished)
-                                .map_err(|e| Error::IoError { source: e })?;
-                            bytes_done = bytes_done.saturating_add(2048);
+                        tracing::warn!(
+                            target: "freemkv::disc",
+                            phase = "bridge_degradation_exhausted",
+                            lba = block_lba,
+                            "bridge degradation retries exhausted; treating as bad sector"
+                        );
+                    }
 
-                            if consecutive_good >= BPT1_EXIT_THRESHOLD {
-                                tracing::trace!(
-                                    target: "freemkv::disc",
-                                    phase = "mode_change",
-                                    from = "Single",
-                                    to = "Block",
-                                    lba = s_lba + 1,
-                                    consecutive_good,
-                                    "exit threshold reached; returning to bpt=batch"
-                                );
-                                mode_single = false;
-                                consecutive_good = 0;
-                            }
-                        } else {
-                            read_err_count += 1;
-                            consecutive_good = 0;
-                            buf[..one_bytes].fill(0);
-                            file.seek(SeekFrom::Start(s_pos))
-                                .map_err(|e| Error::IoError { source: e })?;
-                            file.write_all(&buf[..one_bytes])
-                                .map_err(|e| Error::IoError { source: e })?;
-                            map.record(s_pos, 2048, mapfile::SectorStatus::NonTrimmed)
-                                .map_err(|e| Error::IoError { source: e })?;
-                        }
+                    let sense = err.scsi_sense();
+                    let sense_key = sense.map(|s| s.sense_key).unwrap_or(0);
+                    let asc = sense.map(|s| s.asc).unwrap_or(0);
+                    let ascq = sense.map(|s| s.ascq).unwrap_or(0);
 
-                        // Wallclock-cadence progress callback during
-                        // single-mode grinding. Without this, the UI
-                        // appears frozen for tens of seconds while we
-                        // chew through bad sectors.
-                        if last_progress_t.elapsed() >= PROGRESS_TICK {
-                            last_progress_t = std::time::Instant::now();
-                            if let Some(reporter) = opts.progress {
-                                let stats = map.stats();
-                                reporter.report(&crate::progress::PassProgress {
-                                    kind: crate::progress::PassKind::Sweep,
-                                    work_done: pos + (s as u64 + 1) * 2048,
-                                    work_total: total_bytes,
-                                    bytes_good_total: stats.bytes_good,
-                                    bytes_total_disc: total_bytes,
-                                });
+                    if sense_key == crate::scsi::SENSE_KEY_NOT_READY && not_ready_retries < NOT_READY_MAX_RETRIES {
+                        not_ready_retries += 1;
+                        tracing::warn!(
+                            target: "freemkv::disc",
+                            phase = "not_ready_pause",
+                            lba = block_lba,
+                            sense_key,
+                            asc,
+                            ascq,
+                            retry = not_ready_retries,
+                            "NOT READY; pausing 3s then retrying"
+                        );
+                        std::thread::sleep(std::time::Duration::from_secs(3));
+                        continue;
+                    }
+                    not_ready_retries = 0;
+
+                    tracing::warn!(
+                        target: "freemkv::disc",
+                        phase = "skip_ecc_block",
+                        lba = block_lba,
+                        sectors = block_count,
+                        sense_key,
+                        asc,
+                        ascq,
+                        error = %err,
+                        "ECC block failed; marking NonTrimmed"
+                    );
+                    let zero = vec![0u8; block_bytes as usize];
+                    file.seek(SeekFrom::Start(pos))
+                        .map_err(|e| Error::IoError { source: e })?;
+                    file.write_all(&zero)
+                        .map_err(|e| Error::IoError { source: e })?;
+                    map.record(pos, block_bytes, mapfile::SectorStatus::NonTrimmed)
+                        .map_err(|e| Error::IoError { source: e })?;
+                    bytes_done = bytes_done.saturating_add(block_bytes);
+
+                    damage_window.push(false);
+                    if damage_window.len() > DAMAGE_WINDOW {
+                        damage_window.remove(0);
+                    }
+
+                    let bad_count = damage_window.iter().filter(|&&b| !b).count();
+                    if damage_window.len() >= DAMAGE_WINDOW
+                        && bad_count * 100 / damage_window.len() >= DAMAGE_THRESHOLD_PCT
+                    {
+                        let jump_sectors = JUMP_SECTORS_FACTOR * batch as u64 * jump_multiplier;
+                        let jump_lba = ((pos / 2048) + jump_sectors) as u32;
+                        let region_end_lba = (region_end / 2048) as u32;
+                        if jump_lba < region_end_lba {
+                            if !in_damage_zone {
+                                in_damage_zone = true;
+                                reader.set_speed(0x0000);
+                                tracing::debug!(
+                                    target: "freemkv::disc",
+                                    phase = "damage_enter",
+                                    lba = block_lba,
+                                    "Entered damage zone; dropping to minimum read speed"
+                                );
                             }
+                            let jump_pos = jump_lba as u64 * 2048;
+                            let gap_start = pos + block_bytes;
+                            let gap_bytes = jump_pos.saturating_sub(gap_start);
+                            let jump_mb = gap_bytes / 1_048_576;
+                            tracing::warn!(
+                                target: "freemkv::disc",
+                                phase = "damage_jump",
+                                from_lba = block_lba,
+                                to_lba = jump_lba,
+                                jump_mb,
+                                bad_pct = bad_count * 100 / damage_window.len(),
+                                multiplier = jump_multiplier,
+                                "25%+ failures in last 50 blocks; jumping ahead"
+                            );
+                            if gap_bytes > 0 {
+                                let zero = vec![0u8; 65536];
+                                let mut filled: u64 = 0;
+                                while filled < gap_bytes {
+                                    let chunk = (gap_bytes - filled).min(zero.len() as u64);
+                                    file.seek(SeekFrom::Start(gap_start + filled))
+                                        .map_err(|e| Error::IoError { source: e })?;
+                                    file.write_all(&zero[..chunk as usize])
+                                        .map_err(|e| Error::IoError { source: e })?;
+                                    filled += chunk;
+                                }
+                                map.record(gap_start, gap_bytes, mapfile::SectorStatus::NonTrimmed)
+                                    .map_err(|e| Error::IoError { source: e })?;
+                                bytes_done = bytes_done.saturating_add(gap_bytes);
+                            }
+                            pos = jump_pos;
+                            jump_multiplier *= 2;
+                            did_skip_ahead = true;
                         }
                     }
                 }
-                pos += block_bytes;
 
-                // Throttled iter telemetry — every 100 inner iterations.
+                if !did_skip_ahead {
+                    pos += block_bytes;
+                }
+                iter_count += 1;
+
                 if iter_count - last_log_iter >= 100 {
                     last_log_iter = iter_count;
                     let stats = map.stats();
@@ -1581,9 +1670,9 @@ impl Disc {
                         work_done: pos,
                         work_total: total_bytes,
                         bytes_good_total: stats.bytes_good,
+                        bytes_bad_total: stats.bytes_unreadable + stats.bytes_retryable,
                         bytes_total_disc: total_bytes,
                     });
-                    last_progress_t = std::time::Instant::now();
                 }
             }
         }
@@ -1607,123 +1696,94 @@ impl Disc {
             bytes_good: stats.bytes_good,
             bytes_unreadable: stats.bytes_unreadable,
             bytes_pending: stats.bytes_pending,
+            recovered_this_pass: 0,
             complete: stats.bytes_pending == 0 && !halt_requested,
             halted: halt_requested,
         })
     }
 }
 
-/// Options for `Disc::copy`. All fields default to the pre-v0.11.21 behavior
-/// (recovery reads, abort on bad sector).
 #[derive(Default)]
 pub struct CopyOptions<'a> {
     pub decrypt: bool,
-    /// Resume from existing mapfile + ISO if present. Without this, any
-    /// existing mapfile is wiped and the ISO recreated.
-    pub resume: bool,
-    /// Override the default block size in sectors. Callers should resolve
-    /// this with `detect_max_batch_sectors(device_path)` for live drives.
-    /// When `None`, falls back to 32 sectors (64 KB BD ECC block) in
-    /// `skip_forward` mode or `DEFAULT_BATCH_SECTORS=60` otherwise.
-    pub batch_sectors: Option<u16>,
-    /// Zero-fill bad blocks in the ISO, mark them in the mapfile, continue.
-    /// Uses fast reads (no drive-level recovery loop).
-    pub skip_on_error: bool,
-    /// ddrescue-style exponential skip-forward on block failure. Implies
-    /// `skip_on_error`. The skipped region is marked `non-trimmed` for later
-    /// trimming/scraping by `Disc::patch`.
-    pub skip_forward: bool,
-    /// Per-iteration progress reporter. v0.13.16 architecture: the library
-    /// emits a single `PassProgress` shape via the `Progress` trait;
-    /// consumers compute their own derived percentages / ETAs from it. No
-    /// more positional `(bytes_good, pos, total)` callbacks.
+    pub multipass: bool,
     pub progress: Option<&'a dyn crate::progress::Progress>,
     pub halt: Option<std::sync::Arc<std::sync::atomic::AtomicBool>>,
 }
 
-/// Result of `Disc::copy`. `complete=true` means every byte reached a terminal
-/// state (Finished or Unreadable). `complete=false` means there's still pending
-/// work (halt, abort, or non-tried ranges) that `Disc::patch` or a resumed
-/// `Disc::copy` would continue.
 #[derive(Debug, Clone, Copy)]
 pub struct CopyResult {
     pub bytes_total: u64,
     pub bytes_good: u64,
     pub bytes_unreadable: u64,
     pub bytes_pending: u64,
+    pub recovered_this_pass: u64,
     pub complete: bool,
     pub halted: bool,
 }
 
-/// Sidecar mapfile path for a given ISO path — `foo.iso` → `foo.iso.mapfile`.
-pub fn mapfile_path_for(iso_path: &std::path::Path) -> std::path::PathBuf {
-    let mut s = iso_path.as_os_str().to_os_string();
-    s.push(".mapfile");
-    std::path::PathBuf::from(s)
-}
-
-/// Options for `Disc::patch`. Idempotent — each call is one patch attempt.
-#[derive(Default)]
-pub struct PatchOptions<'a> {
+pub(crate) struct SweepOptions<'a> {
     pub decrypt: bool,
-    /// Sector-granularity block size for retries. Defaults to 1 sector (2 KB).
-    pub block_sectors: Option<u16>,
-    /// Use full drive-level recovery on each read (slow but thorough). Defaults
-    /// to true — patch is the pass where we *want* the drive to try hard.
-    pub full_recovery: bool,
-    /// Walk bad ranges in reverse order, and within each range walk sectors
-    /// from high to low LBA. Useful for drives that wedge after a forward
-    /// read of a bad sector — approaching the post-bad-zone from end-of-disc
-    /// reads good sectors before the drive sees a bad one.
-    pub reverse: bool,
-    /// Bail out early if this many consecutive read failures occur with zero
-    /// successful reads in the same pass — i.e. the drive is wedged on the
-    /// bad zone and won't recover during this attempt. `0` disables the
-    /// guard (run to completion or halt).
-    pub wedged_threshold: u64,
-    /// Per-iteration progress reporter. See `CopyOptions::progress`.
+    pub resume: bool,
+    pub batch_sectors: Option<u16>,
+    pub skip_on_error: bool,
     pub progress: Option<&'a dyn crate::progress::Progress>,
     pub halt: Option<std::sync::Arc<std::sync::atomic::AtomicBool>>,
 }
 
-/// Result of `Disc::patch` — how many bad bytes were recovered, plus
-/// per-block counters for diagnosing why a pass made or didn't make progress.
-#[derive(Debug, Clone, Copy)]
-pub struct PatchResult {
+pub(crate) struct PatchOpts<'a> {
+    pub decrypt: bool,
+    pub block_sectors: Option<u16>,
+    pub full_recovery: bool,
+    pub reverse: bool,
+    pub wedged_threshold: u64,
+    pub progress: Option<&'a dyn crate::progress::Progress>,
+    pub halt: Option<std::sync::Arc<std::sync::atomic::AtomicBool>>,
+}
+
+pub(crate) struct PatchOutcome {
     pub bytes_total: u64,
     pub bytes_good: u64,
     pub bytes_unreadable: u64,
     pub bytes_pending: u64,
     pub bytes_recovered_this_pass: u64,
     pub halted: bool,
-    /// Total inner-loop iterations this pass (one per block attempted).
     pub blocks_attempted: u64,
-    /// Reads that returned Ok and were promoted to `Finished`.
     pub blocks_read_ok: u64,
-    /// Reads that returned Err and were marked `Unreadable`.
     pub blocks_read_failed: u64,
-    /// Pass exited early because `wedged_threshold` consecutive failures
-    /// occurred with zero successful reads — drive appears wedged on the
-    /// bad zone for this pass.
     pub wedged_exit: bool,
 }
 
+pub fn mapfile_path_for(iso_path: &std::path::Path) -> std::path::PathBuf {
+    let mut s = iso_path.as_os_str().to_os_string();
+    s.push(".mapfile");
+    std::path::PathBuf::from(s)
+}
+
 impl Disc {
-    /// Patch an existing ISO using its sidecar mapfile. Re-reads every range
-    /// that's not yet `+` (Finished) and writes successful bytes into the ISO
-    /// at their exact offsets. Updates mapfile entries as it goes.
-    ///
-    /// Idempotent — call repeatedly to apply more retry attempts. Stops early
-    /// if a pass recovered zero bytes (no point continuing).
-    pub fn patch(
+    fn mapfile_for(&self, path: &std::path::Path) -> std::path::PathBuf {
+        if path.as_os_str() == "/dev/null" {
+            let name: String = self.meta_title.as_deref().unwrap_or(&self.volume_id)
+                .chars()
+                .map(|c| if c.is_ascii_alphanumeric() || c == '-' || c == '_' { c } else { '_' })
+                .collect();
+            std::path::PathBuf::from(format!("/tmp/{name}.mapfile"))
+        } else {
+            mapfile_path_for(path)
+        }
+    }
+}
+
+impl Disc {
+    fn patch(
         &self,
         reader: &mut dyn SectorReader,
         path: &std::path::Path,
-        opts: &PatchOptions,
-    ) -> Result<PatchResult> {
+        opts: &PatchOpts,
+    ) -> Result<PatchOutcome> {
         use std::io::{Seek, SeekFrom, Write};
 
-        let mapfile_path = mapfile_path_for(path);
+        let mapfile_path = self.mapfile_for(path);
         let mut map =
             mapfile::Mapfile::load(&mapfile_path).map_err(|e| Error::IoError { source: e })?;
         let total_bytes = map.total_size();
@@ -1748,6 +1808,7 @@ impl Disc {
         let mut blocks_read_ok: u64 = 0;
         let mut blocks_read_failed: u64 = 0;
         let mut consecutive_failures: u64 = 0;
+        let mut unreadable_count: u64 = 0;
         let mut buf = vec![0u8; block_sectors as usize * 2048];
 
         // Collect bad ranges up front. Iterating while mutating is fragile;
@@ -1851,6 +1912,7 @@ impl Disc {
                 } else {
                     blocks_read_failed += 1;
                     consecutive_failures += 1;
+                    unreadable_count += 1;
                     map.record(pos, block_bytes, mapfile::SectorStatus::Unreadable)
                         .map_err(|e| Error::IoError { source: e })?;
                 }
@@ -1903,6 +1965,7 @@ impl Disc {
                         work_done,
                         work_total,
                         bytes_good_total: s.bytes_good,
+                        bytes_bad_total: s.bytes_unreadable + s.bytes_retryable,
                         bytes_total_disc: total_bytes,
                     });
                 }
@@ -1911,18 +1974,19 @@ impl Disc {
 
         file.sync_all().map_err(|e| Error::IoError { source: e })?;
         let stats = map.stats();
-        tracing::trace!(
+        tracing::info!(
             target: "freemkv::disc",
             phase = "patch_done",
             blocks_attempted,
             blocks_read_ok,
             blocks_read_failed,
+            unreadable_count,
             wedged_exit,
             halted,
             bytes_recovered = stats.bytes_good.saturating_sub(bytes_good_before),
             "Disc::patch returning"
         );
-        Ok(PatchResult {
+        Ok(PatchOutcome {
             bytes_total: total_bytes,
             bytes_good: stats.bytes_good,
             bytes_unreadable: stats.bytes_unreadable,
@@ -1941,14 +2005,13 @@ const MAX_BATCH_SECTORS: u16 = 510;
 const DEFAULT_BATCH_SECTORS: u16 = 60;
 const MIN_BATCH_SECTORS: u16 = 3;
 
-/// Number of consecutive good single-sector reads required to exit
-/// `Single` mode (bpt=1) and return to `Block` mode (bpt=batch). 10 000
-/// sectors ≈ 20 MB of clean data — long enough that we don't bounce in
-/// and out of bpt=1 inside a sparse-bad cluster, short enough that we
-/// don't waste much time reading clean territory at bpt=1 after the
-/// damaged region ends. Tunable; calibrated from the 2026-04-26 BU40N
-/// live test.
-const BPT1_EXIT_THRESHOLD: u64 = 10_000;
+pub(crate) fn ecc_sectors(format: DiscFormat) -> u16 {
+    match format {
+        DiscFormat::Uhd | DiscFormat::BluRay => 32,
+        DiscFormat::Dvd => 16,
+        DiscFormat::Unknown => 32,
+    }
+}
 
 /// Coarse damage tier for a finished or in-progress rip. Maps the
 /// observable signals (bad sector count + lost wallclock playback time)

src/drive/macos.rs

@@ -1,26 +1,25 @@
 //! macOS drive discovery and device resolution.
+//!
+//! `find_drives` uses IOKit registry enumeration (via `scsi::list_drives`)
+//! to discover optical drives without exclusive access or unmounts. Only
+//! the returned paths are then opened for INQUIRY to build full `DriveId`.
 
 use crate::error::{Error, Result};
 use crate::identity::DriveId;
 
 pub fn find_drives() -> Vec<(String, DriveId)> {
     let mut drives = Vec::new();
-    for i in 0..16 {
-        let path = format!("/dev/disk{}", i);
-        if !std::path::Path::new(&path).exists() {
-            continue;
-        }
-        match crate::scsi::open(std::path::Path::new(&path)) {
+    let discovered = crate::scsi::list_drives();
+    for info in discovered {
+        let path = std::path::Path::new(&info.path);
+        match crate::scsi::open(path) {
             Ok(mut transport) => {
                 if let Ok(id) = DriveId::from_drive(transport.as_mut()) {
-                    if !id.raw_inquiry.is_empty() && (id.raw_inquiry[0] & 0x1F) == 0x05 {
-                        drives.push((path, id));
-                    }
+                    drives.push((info.path.clone(), id));
                 }
             }
             Err(_) => {
-                // Device exists but can't be opened (likely mounted).
-                // Use `diskutil unmountDisk /dev/diskN` to unmount before accessing.
+                continue;
             }
         }
     }

src/drive/mod.rs

@@ -5,6 +5,7 @@
 pub(crate) fn extract_scsi_context(e: &Error) -> (u8, Option<crate::scsi::ScsiSense>) {
     match e {
         Error::ScsiError { status, sense, .. } => (*status, *sense),
+        Error::DiscRead { status, sense, .. } => (status.unwrap_or(0), *sense),
         _ => (0, None),
     }
 }
@@ -432,7 +433,7 @@ impl Drive {
     ///
     /// Inline retry phases (5× gentle + reset+reopen + 5× more) were
     /// removed in 0.13.6. Per
-    /// `(internal)/postmortems/2026-04-25-stop-wedge-and-zero-kbs.md`,
+    /// the stop-wedge postmortem (2026-04-25),
     /// the inline reset on the LG BU40N (Initio bridge) wedged drive
     /// firmware without ever recovering a sector. The remaining recovery
     /// layers (Disc::patch multi-pass, DiscStream batch halving) do not
@@ -443,6 +444,14 @@ impl Drive {
         } else {
             crate::scsi::READ_TIMEOUT_MS
         };
+        tracing::debug!(
+            target: "freemkv::drive",
+            lba,
+            count,
+            recovery,
+            timeout_ms,
+            "Drive::read enter"
+        );
         let cdb = [
             crate::scsi::SCSI_READ_10,
             0x00,
@@ -466,6 +475,14 @@ impl Drive {
             Err(Error::Halted) => Err(Error::Halted),
             Err(e) => {
                 let (status, sense) = extract_scsi_context(&e);
+                tracing::warn!(
+                    target: "freemkv::drive",
+                    lba,
+                    count,
+                    inner_error = %e,
+                    scsi_status = status,
+                    "Drive::read checked_exec failed"
+                );
                 Err(Error::DiscRead {
                     sector: lba as u64,
                     status: Some(status),
@@ -582,6 +599,10 @@ impl SectorReader for Drive {
     ) -> Result<usize> {
         self.read(lba, count, buf, recovery)
     }
+
+    fn set_speed(&mut self, kbs: u16) {
+        Drive::set_speed(self, kbs);
+    }
 }
 
 /// Find the first optical drive on this system and open it.

src/error.rs

@@ -490,6 +490,7 @@ impl Error {
     pub fn scsi_sense(&self) -> Option<&crate::scsi::ScsiSense> {
         match self {
             Error::ScsiError { sense: Some(s), .. } => Some(s),
+            Error::DiscRead { sense: Some(s), .. } => Some(s),
             _ => None,
         }
     }
@@ -506,9 +507,32 @@ impl Error {
                 status: crate::scsi::SCSI_STATUS_TRANSPORT_FAILURE,
                 ..
             }
+        ) || matches!(
+            self,
+            Error::DiscRead {
+                status: Some(crate::scsi::SCSI_STATUS_TRANSPORT_FAILURE),
+                ..
+            }
         )
     }
 
+    /// True if this error indicates bridge degradation — the SCSI status
+    /// is neither GOOD (0x00), CHECK CONDITION (0x02), nor transport failure
+    /// (0xFF). Observed on the Initio INIC-1618L USB bridge preceding a full
+    /// crash: the bridge firmware returns non-standard status bytes (e.g.
+    /// 0x04, 0x05) with empty sense data. The caller should cool down
+    /// (10 s pause) and retry rather than hammering the bridge.
+    pub fn is_bridge_degradation(&self) -> bool {
+        let status = match self {
+            Error::ScsiError { status, .. } => *status,
+            Error::DiscRead { status, .. } => status.unwrap_or(0),
+            _ => return false,
+        };
+        status != crate::scsi::SCSI_STATUS_GOOD
+            && status != crate::scsi::SCSI_STATUS_CHECK_CONDITION
+            && status != crate::scsi::SCSI_STATUS_TRANSPORT_FAILURE
+    }
+
     /// True if the underlying SCSI failure is a *marginal read* — the
     /// drive returned an error category in which smaller-granularity
     /// retries can sometimes recover the data:

src/progress.rs

@@ -47,6 +47,9 @@ pub struct PassProgress {
     /// Cumulative bytes confirmed clean (`Finished` mapfile state) across
     /// every pass run on this rip. Doesn't change across pass boundaries.
     pub bytes_good_total: u64,
+    /// Cumulative bytes marked bad (`NonTrimmed` + `NonScraped` +
+    /// `Unreadable`) across every pass run on this rip.
+    pub bytes_bad_total: u64,
     /// Total disc capacity in bytes. Constant.
     pub bytes_total_disc: u64,
 }

src/scsi/linux.rs

@@ -11,8 +11,8 @@
 //! This matches what every reference project does: MakeMKV (8 s sync
 //! ioctl), sg_dd (60 s sync ioctl), the kernel default for SCSI block
 //! devices (30 s `/sys/.../timeout`). See
-//! `(internal)/docs/audits/2026-04-26-scsi-architecture-research.md`
-//! for the full primary-source audit.
+//! the SCSI architecture audit (2026-04-26) for the full primary-source
+//! references.
 //!
 //! Pre-0.13.20 we ran an async `write() + poll(1.5s) + close-on-timeout +
 //! bg reopen` pattern. That abandoned slow-but-alive commands faster than
@@ -64,17 +64,15 @@ const _: () = assert!(std::mem::size_of::<sg_io_hdr>() == 88);
 const _: () = assert!(std::mem::size_of::<sg_io_hdr>() == 64);
 
 pub struct SgIoTransport {
-    fd: i32,
+    pub fd: i32,
     device_path: std::path::PathBuf,
+    pub fd_recovery: std::sync::Arc<std::sync::atomic::AtomicI32>,
 }
 
 impl SgIoTransport {
-    /// Open a SCSI device for use. Software-clean the kernel SG queue
-    /// (`reset()`) before opening so a previous killed process's queued
-    /// commands don't bleed into ours.
+    /// Open a SCSI device for use.
     pub fn open(device: &Path) -> Result<Self> {
         let device = Self::resolve_to_sg(device);
-        Self::reset(&device)?;
         let c_path = Self::to_c_path(&device);
         let fd = unsafe {
             libc::open(
@@ -88,6 +86,7 @@ impl SgIoTransport {
         Ok(SgIoTransport {
             fd,
             device_path: device,
+            fd_recovery: std::sync::Arc::new(std::sync::atomic::AtomicI32::new(-1)),
         })
     }
 
@@ -107,48 +106,7 @@ impl SgIoTransport {
     /// STOP+START UNIT. Both escalations were tried in 0.13.0–0.13.5
     /// against the LG BU40N (Initio USB-SATA bridge); both failed to
     /// recover wedged drives and made the wedge worse — see
-    /// `(internal)/postmortems/2026-04-25-bu40n-wedge-recovery.md`.
-    /// If the drive is genuinely unresponsive, the next workload command
-    /// fails naturally and the caller surfaces a "physical reconnect
-    /// required" prompt. Software has no path back from a wedged Initio
-    /// bridge — only physical replug clears it.
-    pub fn reset(device: &Path) -> Result<()> {
-        let c_path = Self::to_c_path(device);
-
-        // open + close — make the kernel cancel any SG_IO commands queued
-        // against a previous fd that didn't close cleanly.
-        let probe_fd = unsafe {
-            libc::open(
-                c_path.as_ptr() as *const libc::c_char,
-                libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
-            )
-        };
-        if probe_fd >= 0 {
-            unsafe { libc::close(probe_fd) };
-        }
-
-        // Let the kernel finish that cancellation before we reopen.
-        std::thread::sleep(std::time::Duration::from_secs(2));
-
-        // Fresh fd just to send the unlock command, then close.
-        let fd = unsafe {
-            libc::open(
-                c_path.as_ptr() as *const libc::c_char,
-                libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
-            )
-        };
-        if fd < 0 {
-            return Self::open_error(device);
-        }
-
-        // ALLOW MEDIUM REMOVAL — clear any tray lock left by a killed
-        // process whose Drop never ran. Best-effort; ignore result.
-        let _ = Self::raw_command(fd, &[0x1E, 0, 0, 0, 0, 0], 3_000);
-
-        unsafe { libc::close(fd) };
-        Ok(())
-    }
-
+    /// the BU40N wedge recovery postmortem (2026-04-25).
     fn open_error<T>(device: &Path) -> Result<T> {
         let err = std::io::Error::last_os_error();
         Err(if err.kind() == std::io::ErrorKind::PermissionDenied {
@@ -278,6 +236,22 @@ impl ScsiTransport for SgIoTransport {
             "SgIoTransport::execute"
         );
 
+        // Check if a background recovery has produced a new fd.
+        let recovered = self
+            .fd_recovery
+            .swap(-1, std::sync::atomic::Ordering::Acquire);
+        if recovered >= 0 {
+            // Close the old fd if it's still valid.
+            if self.fd >= 0 {
+                unsafe { libc::close(self.fd) };
+            }
+            self.fd = recovered;
+        } else if self.fd < 0 {
+            return Err(Error::DeviceNotFound {
+                path: self.device_path.display().to_string(),
+            });
+        }
+
         if data.len() > u32::MAX as usize {
             return Err(Error::ScsiError {
                 opcode: cdb[0],
@@ -352,6 +326,32 @@ impl ScsiTransport for SgIoTransport {
                 exec_elapsed_ms,
                 "transport-level failure (timeout / bridge wedge)"
             );
+
+            // Spawn recovery: close old fd, open new one in background.
+            // This prevents the main thread from blocking on close() while
+            // the kernel finishes the previous ioctl.
+            let old_fd = self.fd;
+            self.fd = -1;
+            let path = self.device_path.clone();
+            let recovery = self.fd_recovery.clone();
+
+            std::thread::spawn(move || {
+                if old_fd >= 0 {
+                    unsafe { libc::close(old_fd) };
+                }
+            });
+
+            std::thread::spawn(move || {
+                let c_path = std::ffi::CString::new(path.as_os_str().as_encoded_bytes()).unwrap();
+                let new_fd = unsafe {
+                    libc::open(
+                        c_path.as_ptr() as *const libc::c_char,
+                        libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
+                    )
+                };
+                recovery.store(new_fd, std::sync::atomic::Ordering::Release);
+            });
+
             return Err(Error::ScsiError {
                 opcode: cdb[0],
                 status: super::SCSI_STATUS_TRANSPORT_FAILURE,
@@ -506,8 +506,8 @@ fn enumerate_sg_names() -> Vec<String> {
             let type_path = format!("/sys/class/scsi_generic/{name}/device/type");
             match std::fs::read_to_string(&type_path) {
                 Ok(s) if s.trim() == SCSI_TYPE_OPTICAL => names.push(name),
-                Ok(_) => {}                 // not optical
-                Err(_) => names.push(name), // sysfs unreadable — let INQUIRY decide
+                Ok(_) => {} // not optical
+                Err(_) => {}
             }
         }
     } else {
@@ -524,47 +524,64 @@ fn enumerate_sg_names() -> Vec<String> {
     names
 }
 
-/// `drive_has_disc` = single TEST UNIT READY. Any error (including the
-/// wedge signature `ScsiError { status: 0xFF }` synthesised by `execute()`
-/// when `host_status` is set) bubbles straight up to the caller.
-///
-/// ## No in-library wedge recovery — and why
-///
-/// Versions 0.13.1–0.13.3 layered `scsi::reset()` + `scsi::usb_reset()`
-/// (`USBDEVFS_RESET`) escalation inside `drive_has_disc`. Production
-/// testing on the LG BU40N USB BD-RE showed all three userspace recovery
-/// ladders succeed at the USB transport level (the kernel logs
-/// `usb 3-2: reset high-speed USB device`, the device re-authorises
-/// and re-attaches on a fresh `scsi_host`) **but the drive firmware
-/// below the USB bridge stays locked** — no LUN ever enumerates, TUR
-/// never succeeds, /dev/sg* never reappears. Physical power-cycle
-/// (unplug-replug or host reboot) is the only recovery.
-///
-/// Methods tried and discarded:
-///  - `SG_SCSI_RESET` (device-level SCSI bus reset)
-///  - `STOP UNIT` / `START UNIT` CDB pair
-///  - `USBDEVFS_RESET` ioctl on `/dev/bus/usb/BBB/DDD`
-///  - `/sys/bus/usb/devices/<port>/authorized` 0→1 toggle
-///  - `/sys/bus/usb/drivers/usb-storage/{unbind,bind}` driver rebind
-///  - Forced `echo "- - -" > /sys/class/scsi_host/hostN/scan`
-///
-/// Rolled back in 0.13.4. Callers (autorip, CLI) surface the error
-/// directly and prompt the user to physically reconnect the drive.
-/// If a future hardware class is found where USB-layer recovery
-/// actually works, the escalation belongs here, gated on the wedge
-/// signature — see git tag `v0.13.3` for the full implementation.
+/// Send TEST UNIT READY directly — no transport, no reset, no side effects.
 pub(super) fn drive_has_disc(path: &Path) -> Result<bool> {
-    let mut transport = SgIoTransport::open(path)?;
+    let device = SgIoTransport::resolve_to_sg(path);
+    let c_path = SgIoTransport::to_c_path(&device);
+    let fd = unsafe {
+        libc::open(
+            c_path.as_ptr() as *const libc::c_char,
+            libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
+        )
+    };
+    if fd < 0 {
+        return SgIoTransport::open_error(&device);
+    }
+
     let cdb = [crate::scsi::SCSI_TEST_UNIT_READY, 0, 0, 0, 0, 0];
-    let mut buf = [0u8; 0];
-    match transport.execute(
-        &cdb,
-        crate::scsi::DataDirection::None,
-        &mut buf,
-        crate::scsi::TUR_TIMEOUT_MS,
-    ) {
-        Ok(_) => Ok(true),
-        Err(ref e) if e.scsi_sense().is_some_and(|s| s.is_not_ready()) => Ok(false),
-        Err(e) => Err(e),
+    let mut sense = [0u8; 32];
+    let mut hdr: sg_io_hdr = unsafe { std::mem::zeroed() };
+    hdr.interface_id = b'S' as i32;
+    hdr.dxfer_direction = SG_DXFER_NONE;
+    hdr.cmd_len = cdb.len() as u8;
+    hdr.mx_sb_len = sense.len() as u8;
+    hdr.dxfer_len = 0;
+    hdr.dxferp = std::ptr::null_mut();
+    hdr.cmdp = cdb.as_ptr();
+    hdr.sbp = sense.as_mut_ptr();
+    hdr.timeout = crate::scsi::TUR_TIMEOUT_MS;
+    hdr.flags = SG_FLAG_Q_AT_HEAD;
+
+    let ret = unsafe { libc::ioctl(fd, SG_IO as _, &mut hdr as *mut sg_io_hdr) };
+    unsafe { libc::close(fd) };
+
+    if ret < 0 {
+        return Err(Error::IoError {
+            source: std::io::Error::last_os_error(),
+        });
+    }
+
+    let driver_status_real = hdr.driver_status & !super::DRIVER_SENSE;
+    if hdr.host_status != 0 || driver_status_real != 0 {
+        return Err(Error::ScsiError {
+            opcode: cdb[0],
+            status: super::SCSI_STATUS_TRANSPORT_FAILURE,
+            sense: None,
+        });
+    }
+
+    if hdr.status == 0 {
+        return Ok(true);
+    }
+
+    let parsed = super::parse_sense(&sense, hdr.sb_len_wr);
+    if parsed.is_not_ready() {
+        Ok(false)
+    } else {
+        Err(Error::ScsiError {
+            opcode: cdb[0],
+            status: hdr.status,
+            sense: Some(parsed),
+        })
     }
 }

src/scsi/macos.rs

@@ -1,183 +1,55 @@
-//! macOS SCSI transport via IOKit SCSITaskDeviceInterface.
+//! macOS SCSI transport: IOKit SCSITaskDeviceInterface with exclusive access.
 //!
-//! Sends SCSI commands to optical drives through IOKit's SCSI Architecture
-//! Model family. Accepts BSD device paths like `/dev/disk2` or `/dev/rdisk2`.
+//! Single dispatch path: **all** CDBs (INQUIRY, READ, REPORT KEY, etc.) go
+//! through `SCSITaskDeviceInterface::ExecuteTaskSync` — 1:1 with the Linux
+//! SG_IO backend. The C shim (`macos_shim.c`) handles:
 //!
-//! Requires exclusive access to the device — unmount the disc first:
-//! `diskutil unmountDisk /dev/disk2`
+//! 1. `diskutil unmountDisk force` on the target device only
+//! 2. Find `IOBDServices` matching the requested BSD name (walks IOKit
+//!    registry: IOBDServices → IOBDBlockStorageDriver → IOMedia → BSD Name)
+//! 3. Create `MMCDeviceInterface` → `SCSITaskDeviceInterface`
+//! 4. `ObtainExclusiveAccess`
+//! 5. Raw CDB dispatch via `CreateSCSITask` + `ExecuteTaskSync`
+//!
+//! Drive enumeration (`list_drives`) uses the IOKit registry directly via
+//! `shim_list_drives` — no exclusive access, no SCSI commands, no unmounts.
 
 use super::{DataDirection, ScsiResult, ScsiTransport};
 use crate::error::{Error, Result};
 use std::path::Path;
 
-// ── IOKit / CoreFoundation type aliases ─────────────────────────────────────
-
-type CFMutableDictionaryRef = *mut std::ffi::c_void;
-type IOObject = u32;
-type IOReturn = i32;
-type MachPort = u32;
-
-/// Opaque COM interface pointer — `*mut *mut VTable` (double-indirect).
-/// IOKit plugins use COM-style vtables: the pointer points to a pointer
-/// to the function table.
-type ComRef = *mut *mut std::ffi::c_void;
-
-const K_IO_RETURN_SUCCESS: IOReturn = 0;
-
-// SCSI data transfer directions (SCSITaskLib.h)
-const K_SCSI_DATA_TRANSFER_NO_DATA: u8 = 0;
-const K_SCSI_DATA_TRANSFER_FROM_TARGET: u8 = 1;
-const K_SCSI_DATA_TRANSFER_TO_TARGET: u8 = 2;
-
-// SCSI task status values
-const K_SCSI_TASK_STATUS_GOOD: u8 = 0x00;
-
-const K_MAX_CDB_SIZE: usize = 16;
 const K_SENSE_DATA_SIZE: usize = 32;
 
-// ── IOKit plugin UUIDs ──────────────────────────────────────────────────────
-// From IOKit/scsi/SCSITaskLib.h
-
-/// kIOMMCDeviceUserClientTypeID — plugin type for MMC (optical) devices.
-const K_IO_MMC_DEVICE_USER_CLIENT_TYPE_ID: [u8; 16] = [
-    0x97, 0xAB, 0xCF, 0x5C, 0x45, 0x71, 0x11, 0xD6, 0xB6, 0xA0, 0x00, 0x30, 0x65, 0xA4, 0x7A, 0xEE,
-];
-
-/// kIOCFPlugInInterfaceID — base IOCFPlugin interface.
-const K_IO_CFPLUGIN_INTERFACE_ID: [u8; 16] = [
-    0xC2, 0x44, 0xE8, 0x58, 0x10, 0x9C, 0x11, 0xD4, 0x91, 0xD4, 0x00, 0x50, 0xE4, 0xC6, 0x42, 0x6F,
-];
-
-/// kIOSCSITaskDeviceInterfaceID — the interface we QueryInterface for.
-const K_IO_SCSI_TASK_DEVICE_INTERFACE_ID: [u8; 16] = [
-    0x61, 0x3E, 0x48, 0xB0, 0x30, 0x01, 0x11, 0xD6, 0xA4, 0xC0, 0x00, 0x0A, 0x27, 0x05, 0x28, 0x61,
-];
-
-// ── Scatter/gather element ──────────────────────────────────────────────────
-
 #[repr(C)]
-struct SCSITaskSGElement {
-    address: u64,
-    length: u64,
+#[derive(Copy, Clone)]
+struct ShimDriveInfo {
+    bsd_name: [u8; 32],
+    vendor: [u8; 32],
+    model: [u8; 48],
+    firmware: [u8; 16],
 }
 
-// ── External IOKit / CoreFoundation functions ───────────────────────────────
-
-// Rust 2024: FFI blocks declaring extern fns must be `unsafe extern`.
 unsafe extern "C" {
-    fn IOMasterPort(bootstrap: u32, master: *mut MachPort) -> IOReturn;
-    fn IOBSDNameMatching(
-        master: MachPort,
-        options: u32,
-        bsd_name: *const u8,
-    ) -> CFMutableDictionaryRef;
-    fn IOServiceGetMatchingService(master: MachPort, matching: CFMutableDictionaryRef) -> IOObject;
-    fn IOObjectRelease(object: IOObject) -> IOReturn;
-    fn IORegistryEntryGetParentEntry(
-        entry: IOObject,
-        plane: *const u8,
-        parent: *mut IOObject,
-    ) -> IOReturn;
-    fn IOObjectConformsTo(object: IOObject, class_name: *const u8) -> u8;
-    fn IOCreatePlugInInterfaceForService(
-        service: IOObject,
-        plugin_type: *const [u8; 16],
-        interface_type: *const [u8; 16],
-        the_interface: *mut ComRef,
-        the_score: *mut i32,
-    ) -> IOReturn;
+    fn shim_open_exclusive(bsd_name: *const u8) -> i32;
+    fn shim_close();
+    fn shim_execute(
+        cdb: *const u8,
+        cdb_len: u8,
+        buf: *mut u8,
+        buf_len: u32,
+        data_in: i32,
+        sense_out: *mut u8,
+        sense_len: u32,
+        task_status_out: *mut u8,
+        transfer_count: *mut u64,
+    ) -> i32;
+    fn shim_list_drives(out: *mut ShimDriveInfo, max_entries: i32) -> i32;
 }
 
-// ── COM vtable helpers ──────────────────────────────────────────────────────
-//
-// IOKit plugin interfaces use COM-style vtables. A ComRef is **vtable —
-// dereferencing once gives the vtable pointer, then index into it for
-// individual function pointers.
-//
-// All vtable indices verified against Apple open source:
-// IOSCSIArchitectureModelFamily/UserClientLib/SCSITaskLib.h
-
-/// Read a function pointer from a COM vtable at the given index.
-///
-/// # Safety
-/// `iface` must be a valid COM interface pointer (*mut *mut c_void), and
-/// `index` must be a valid vtable slot for the target type `T`.
-unsafe fn vtable_fn<T>(iface: ComRef, index: usize) -> T {
-    // Rust 2024: `unsafe fn` bodies are no longer implicitly unsafe.
-    // Each unsafe op needs its own `unsafe { }` block.
-    unsafe {
-        let vtable = *iface as *const *const std::ffi::c_void;
-        let fn_ptr = *vtable.add(index);
-        std::mem::transmute_copy(&fn_ptr)
-    }
-}
-
-/// Call Release (vtable index 3) on any COM interface.
-fn com_release(iface: ComRef) {
-    type Fn = unsafe extern "C" fn(ComRef) -> u32;
-    unsafe {
-        let f: Fn = vtable_fn(iface, 3);
-        f(iface);
-    }
-}
-
-// ── SCSITaskDeviceInterface vtable ──────────────────────────────────────────
-//
-// Index  Method
-//   0    _reserved
-//   1    QueryInterface
-//   2    AddRef
-//   3    Release
-//   4    IsExclusiveAccessAvailable
-//   5    AddCallbackDispatcherToRunLoop
-//   6    RemoveCallbackDispatcherFromRunLoop
-//   7    ObtainExclusiveAccess
-//   8    ReleaseExclusiveAccess
-//   9    CreateSCSITask
-
-const VTIDX_OBTAIN_EXCLUSIVE: usize = 7;
-const VTIDX_RELEASE_EXCLUSIVE: usize = 8;
-const VTIDX_CREATE_TASK: usize = 9;
-
-// ── SCSITaskInterface vtable ────────────────────────────────────────────────
-//
-// Index  Method
-//   0    _reserved
-//   1    QueryInterface
-//   2    AddRef
-//   3    Release
-//   4    IsTaskActive
-//   5    SetTaskAttribute
-//   6    GetTaskAttribute
-//   7    GetTaskState
-//   8    SetCommandDescriptorBlock
-//   9    GetCommandDescriptorBlockSize
-//  10    GetCommandDescriptorBlock
-//  11    SetScatterGatherEntries
-//  12    SetTimeoutDuration
-//  13    GetTimeoutDuration
-//  14    SetTaskCompletionCallback
-//  15    ExecuteTaskSync
-//  16    ExecuteTaskAsync
-//  17    AbortTask
-//  18    GetSCSIServiceResponse
-//  19    GetTaskStatus
-//  20    GetRealizedDataTransferCount
-//  21    GetAutoSenseData
-
-const VTIDX_SET_CDB: usize = 8;
-const VTIDX_SET_SG: usize = 11;
-const VTIDX_SET_TIMEOUT: usize = 12;
-const VTIDX_EXECUTE_SYNC: usize = 15;
-
-// ── Transport implementation ────────────────────────────────────────────────
-
 pub struct MacScsiTransport {
-    device_iface: ComRef,
-    exclusive: bool,
+    _bsd_name: String,
 }
 
-// IOKit COM interface pointers are Mach port references — safe to send between threads.
 unsafe impl Send for MacScsiTransport {}
 
 impl MacScsiTransport {
@@ -186,7 +58,6 @@ impl MacScsiTransport {
             path: device.display().to_string(),
         })?;
 
-        // Strip /dev/ prefix to get BSD name (e.g. "disk2")
         let bsd_name = if let Some(rest) = dev_str.strip_prefix("/dev/r") {
             rest
         } else if let Some(rest) = dev_str.strip_prefix("/dev/") {
@@ -195,137 +66,119 @@ impl MacScsiTransport {
             dev_str
         };
 
-        let device_iface = Self::acquire_device_iface(bsd_name)?;
+        let mut bsd_c = bsd_name.as_bytes().to_vec();
+        bsd_c.push(0);
+
+        let rc = unsafe { shim_open_exclusive(bsd_c.as_ptr()) };
+        if rc != 0 {
+            return Err(Error::DeviceNotFound {
+                path: bsd_name.to_string(),
+            });
+        }
 
         Ok(MacScsiTransport {
-            device_iface,
-            exclusive: true,
+            _bsd_name: bsd_name.to_string(),
         })
     }
-
-    /// Resolve the BSD name → IOKit SCSITaskDeviceInterface with exclusive
-    /// access. Returns the COM ref the caller must release.
-    fn acquire_device_iface(bsd_name: &str) -> Result<ComRef> {
-        let service = find_scsi_service(bsd_name)?;
-
-        // Create IOKit plugin for the MMC device
-        let mut plugin: ComRef = std::ptr::null_mut();
-        let mut score: i32 = 0;
-        let kr = unsafe {
-            IOCreatePlugInInterfaceForService(
-                service,
-                &K_IO_MMC_DEVICE_USER_CLIENT_TYPE_ID,
-                &K_IO_CFPLUGIN_INTERFACE_ID,
-                &mut plugin,
-                &mut score,
-            )
-        };
-        unsafe { IOObjectRelease(service) };
-
-        if kr != K_IO_RETURN_SUCCESS || plugin.is_null() {
-            return Err(Error::IoKitPluginFailed {
-                path: bsd_name.to_string(),
-                kr: kr as u32,
-            });
-        }
-
-        // QueryInterface for SCSITaskDeviceInterface
-        let mut device_iface: ComRef = std::ptr::null_mut();
-        let hr = unsafe {
-            type QiFn = unsafe extern "C" fn(ComRef, *const [u8; 16], *mut ComRef) -> i32;
-            let qi: QiFn = vtable_fn(plugin, 1);
-            qi(
-                plugin,
-                &K_IO_SCSI_TASK_DEVICE_INTERFACE_ID,
-                &mut device_iface,
-            )
-        };
-        com_release(plugin);
-
-        if hr != 0 || device_iface.is_null() {
-            return Err(Error::ScsiInterfaceUnavailable {
-                path: bsd_name.to_string(),
-            });
-        }
-
-        // Obtain exclusive access
-        let kr = unsafe {
-            type Fn = unsafe extern "C" fn(ComRef) -> IOReturn;
-            let f: Fn = vtable_fn(device_iface, VTIDX_OBTAIN_EXCLUSIVE);
-            f(device_iface)
-        };
-        if kr != K_IO_RETURN_SUCCESS {
-            com_release(device_iface);
-            return Err(Error::DeviceLocked {
-                path: bsd_name.to_string(),
-                kr: kr as u32,
-            });
-        }
-
-        Ok(device_iface)
-    }
-
-    // `reset()` removed in 0.13.6 — see scsi/mod.rs for rationale.
-    // `try_recover()` removed in 0.13.20 — userspace handle-recovery on
-    // task failure was the same anti-pattern stripped from Linux SG_IO
-    // (see (internal)/docs/audits/2026-04-26-scsi-architecture-research.md).
-    // Errors bubble up; caller decides whether to reopen the Drive.
 }
 
-/// Enumerate optical drives on macOS. Mirrors `drive::macos::find_drives`
-/// (which iterates `/dev/disk0..15` + INQUIRY + filters peripheral
-/// type 5). Same logic, exposed through the new `DriveInfo` shape so
-/// callers — `list_drives()` in `scsi::mod` — never reach into
-/// `crate::drive::macos`.
-pub(super) fn list_drives() -> Vec<super::DriveInfo> {
-    let mut out = Vec::new();
-    for i in 0..K_DEV_DISK_MAX {
-        let path = format!("/dev/disk{i}");
-        if !std::path::Path::new(&path).exists() {
-            continue;
+impl Drop for MacScsiTransport {
+    fn drop(&mut self) {
+        unsafe { shim_close() };
+    }
+}
+
+impl ScsiTransport for MacScsiTransport {
+    fn execute(
+        &mut self,
+        cdb: &[u8],
+        direction: DataDirection,
+        data: &mut [u8],
+        _timeout_ms: u32,
+    ) -> Result<ScsiResult> {
+        let data_in = match direction {
+            DataDirection::FromDevice => 1,
+            DataDirection::ToDevice => 0,
+            DataDirection::None => 0,
+        };
+
+        let mut sense = [0u8; K_SENSE_DATA_SIZE];
+        let mut task_status: u8 = 0xFF;
+        let mut transfer_count: u64 = 0;
+
+        let kr = unsafe {
+            shim_execute(
+                cdb.as_ptr(),
+                cdb.len() as u8,
+                data.as_mut_ptr(),
+                data.len() as u32,
+                data_in,
+                sense.as_mut_ptr(),
+                K_SENSE_DATA_SIZE as u32,
+                &mut task_status,
+                &mut transfer_count,
+            )
+        };
+
+        if kr != 0 {
+            return Err(Error::ScsiError {
+                opcode: cdb[0],
+                status: super::SCSI_STATUS_TRANSPORT_FAILURE,
+                sense: None,
+            });
         }
-        let mut transport = match MacScsiTransport::open(std::path::Path::new(&path)) {
-            Ok(t) => t,
-            Err(_) => continue,
-        };
-        let inquiry = match super::inquiry(&mut transport) {
-            Ok(r) => r,
-            Err(_) => continue,
-        };
-        // SCSI peripheral type field is the lower 5 bits of byte 0.
-        if inquiry.raw.is_empty()
-            || (inquiry.raw[K_INQUIRY_TYPE_BYTE] & K_INQUIRY_TYPE_MASK) != K_SCSI_TYPE_OPTICAL
-        {
+
+        if task_status != 0 {
+            let parsed = super::parse_sense(&sense, K_SENSE_DATA_SIZE as u8);
+            return Err(Error::ScsiError {
+                opcode: cdb[0],
+                status: task_status,
+                sense: Some(parsed),
+            });
+        }
+
+        Ok(ScsiResult {
+            status: 0,
+            bytes_transferred: transfer_count as usize,
+            sense,
+        })
+    }
+}
+
+// ── Drive enumeration (registry-based, no exclusive access) ──────────────
+
+pub(super) fn list_drives() -> Vec<super::DriveInfo> {
+    let mut buf = [ShimDriveInfo {
+        bsd_name: [0; 32],
+        vendor: [0; 32],
+        model: [0; 48],
+        firmware: [0; 16],
+    }; 8];
+
+    let count = unsafe { shim_list_drives(buf.as_mut_ptr(), buf.len() as i32) };
+
+    let mut out = Vec::new();
+    for i in 0..(count as usize).min(buf.len()) {
+        let info = &buf[i];
+        let bsd_name = cstr_to_str(&info.bsd_name);
+        if bsd_name.is_empty() {
             continue;
         }
         out.push(super::DriveInfo {
-            path,
-            vendor: inquiry.vendor_id,
-            model: inquiry.model,
-            firmware: inquiry.firmware,
+            path: format!("/dev/{bsd_name}"),
+            vendor: cstr_to_str(&info.vendor).to_string(),
+            model: cstr_to_str(&info.model).to_string(),
+            firmware: cstr_to_str(&info.firmware).to_string(),
         });
     }
     out
 }
 
-/// Maximum BSD disk index probed during enumeration. macOS assigns
-/// `/dev/diskN` sequentially per attached storage device; 16 covers
-/// any realistic homelab.
-const K_DEV_DISK_MAX: u8 = 16;
+fn cstr_to_str(bytes: &[u8]) -> &str {
+    let end = bytes.iter().position(|&b| b == 0).unwrap_or(bytes.len());
+    std::str::from_utf8(&bytes[..end]).unwrap_or("")
+}
 
-/// SCSI INQUIRY response: peripheral device type lives in byte 0,
-/// lower 5 bits.
-const K_INQUIRY_TYPE_BYTE: usize = 0;
-const K_INQUIRY_TYPE_MASK: u8 = 0x1F;
-
-/// SCSI peripheral type 5 = "CD-ROM device" (covers DVD, BD-ROM, BD-RE).
-const K_SCSI_TYPE_OPTICAL: u8 = 0x05;
-
-/// TEST UNIT READY probe on macOS. Any non-"not ready" error bubbles up
-/// to the caller — in-library wedge recovery was rolled back in 0.13.4
-/// after USB-layer resets failed to recover the LG BU40N on Linux; the
-/// macOS impl mirrors that choice for symmetry. See the Linux
-/// `drive_has_disc` in `scsi/linux.rs` for the full rationale.
 pub(super) fn drive_has_disc(path: &Path) -> Result<bool> {
     let mut transport = MacScsiTransport::open(path)?;
     let cdb = [crate::scsi::SCSI_TEST_UNIT_READY, 0, 0, 0, 0, 0];
@@ -341,235 +194,3 @@ pub(super) fn drive_has_disc(path: &Path) -> Result<bool> {
         Err(e) => Err(e),
     }
 }
-
-impl Drop for MacScsiTransport {
-    fn drop(&mut self) {
-        if self.device_iface.is_null() {
-            return;
-        }
-        if self.exclusive {
-            unsafe {
-                type Fn = unsafe extern "C" fn(ComRef) -> IOReturn;
-                let f: Fn = vtable_fn(self.device_iface, VTIDX_RELEASE_EXCLUSIVE);
-                f(self.device_iface);
-            }
-        }
-        com_release(self.device_iface);
-    }
-}
-
-impl ScsiTransport for MacScsiTransport {
-    fn execute(
-        &mut self,
-        cdb: &[u8],
-        direction: DataDirection,
-        data: &mut [u8],
-        timeout_ms: u32,
-    ) -> Result<ScsiResult> {
-        // Create a SCSI task
-        let task: ComRef = unsafe {
-            type Fn = unsafe extern "C" fn(ComRef) -> ComRef;
-            let f: Fn = vtable_fn(self.device_iface, VTIDX_CREATE_TASK);
-            f(self.device_iface)
-        };
-        if task.is_null() {
-            return Err(Error::ScsiError {
-                opcode: cdb[0],
-                status: super::SCSI_STATUS_TRANSPORT_FAILURE,
-                sense: None,
-            });
-        }
-
-        // Set CDB
-        let mut cdb_padded = [0u8; K_MAX_CDB_SIZE];
-        let cdb_len = cdb.len().min(K_MAX_CDB_SIZE);
-        cdb_padded[..cdb_len].copy_from_slice(&cdb[..cdb_len]);
-        unsafe {
-            type Fn = unsafe extern "C" fn(ComRef, *const u8, u8) -> IOReturn;
-            let f: Fn = vtable_fn(task, VTIDX_SET_CDB);
-            f(task, cdb_padded.as_ptr(), cdb_len as u8);
-        }
-
-        // Set scatter/gather and transfer direction
-        let iokit_dir = match direction {
-            DataDirection::None => K_SCSI_DATA_TRANSFER_NO_DATA,
-            DataDirection::FromDevice => K_SCSI_DATA_TRANSFER_FROM_TARGET,
-            DataDirection::ToDevice => K_SCSI_DATA_TRANSFER_TO_TARGET,
-        };
-
-        if direction != DataDirection::None && !data.is_empty() {
-            let sg = SCSITaskSGElement {
-                address: data.as_mut_ptr() as u64,
-                length: data.len() as u64,
-            };
-            unsafe {
-                type Fn =
-                    unsafe extern "C" fn(ComRef, *const SCSITaskSGElement, u8, u64, u8) -> IOReturn;
-                let f: Fn = vtable_fn(task, VTIDX_SET_SG);
-                f(task, &sg, 1, data.len() as u64, iokit_dir);
-            }
-        } else {
-            unsafe {
-                type Fn =
-                    unsafe extern "C" fn(ComRef, *const SCSITaskSGElement, u8, u64, u8) -> IOReturn;
-                let f: Fn = vtable_fn(task, VTIDX_SET_SG);
-                f(task, std::ptr::null(), 0, 0, K_SCSI_DATA_TRANSFER_NO_DATA);
-            }
-        }
-
-        // Set timeout (IOKit SCSITask takes milliseconds)
-        unsafe {
-            type Fn = unsafe extern "C" fn(ComRef, u32);
-            let f: Fn = vtable_fn(task, VTIDX_SET_TIMEOUT);
-            f(task, timeout_ms);
-        }
-
-        // Execute synchronously
-        let mut sense = [0u8; K_SENSE_DATA_SIZE];
-        let mut task_status: u32 = 0;
-        let mut realized_count: u64 = 0;
-
-        let kr = unsafe {
-            type Fn = unsafe extern "C" fn(ComRef, *mut u8, *mut u32, *mut u64) -> IOReturn;
-            let f: Fn = vtable_fn(task, VTIDX_EXECUTE_SYNC);
-            f(
-                task,
-                sense.as_mut_ptr(),
-                &mut task_status,
-                &mut realized_count,
-            )
-        };
-
-        com_release(task);
-
-        if kr != K_IO_RETURN_SUCCESS {
-            // Task-level failure (timeout / IOKit error). Bubble it up;
-            // the kernel mid-layer has already done what it can.
-            return Err(Error::ScsiError {
-                opcode: cdb[0],
-                status: super::SCSI_STATUS_TRANSPORT_FAILURE,
-                sense: None,
-            });
-        }
-
-        if task_status != K_SCSI_TASK_STATUS_GOOD as u32 {
-            // IOKit doesn't surface a "bytes written into sense buffer"
-            // count the way SG_IO does — pass the buffer's full length
-            // and let parse_sense inspect byte 0's response code to pick
-            // descriptor-vs-fixed format.
-            //
-            // 0.13.23: carry the full SPC-4 sense triple in
-            // `Error::ScsiError::sense` so callers can route on
-            // `ScsiSense::is_medium_error()` etc.
-            let parsed = super::parse_sense(&sense, sense.len() as u8);
-            return Err(Error::ScsiError {
-                opcode: cdb[0],
-                status: task_status as u8,
-                sense: Some(parsed),
-            });
-        }
-
-        Ok(ScsiResult {
-            status: task_status as u8,
-            bytes_transferred: realized_count as usize,
-            sense,
-        })
-    }
-}
-
-// ── IOKit service discovery ─────────────────────────────────────────────────
-
-/// BSD name → IOKit service for the SCSI device.
-///
-/// Walk: IOMedia (BSD name match) → parent chain → SCSIPeripheralDeviceNub.
-///
-/// All failure paths surface as `Error::DeviceNotFound { path: bsd_name }` —
-/// the four internal stages (IOMasterPort / IOBSDNameMatching / IOMedia
-/// lookup / walk_to_authoring_device) collapse into one observable error
-/// because none of them are user-actionable individually. Pre-0.13 each
-/// stage stuffed an English description into `path:` ("…IOMasterPort
-/// failed", "…SCSITaskDeviceInterface not available", etc.) which broke
-/// the library's "no English text" rule.
-fn find_scsi_service(bsd_name: &str) -> Result<IOObject> {
-    let not_found = || Error::DeviceNotFound {
-        path: bsd_name.to_string(),
-    };
-
-    let mut master: MachPort = 0;
-    let kr = unsafe { IOMasterPort(0, &mut master) };
-    if kr != K_IO_RETURN_SUCCESS {
-        return Err(not_found());
-    }
-
-    // IOBSDNameMatching creates a dictionary matching { "BSD Name" = bsd_name }
-    let mut bsd_c = bsd_name.as_bytes().to_vec();
-    bsd_c.push(0);
-    let matching = unsafe { IOBSDNameMatching(master, 0, bsd_c.as_ptr()) };
-    if matching.is_null() {
-        return Err(not_found());
-    }
-
-    // Find the single IOMedia service (consumes the matching dict)
-    let media = unsafe { IOServiceGetMatchingService(master, matching) };
-    if media == 0 {
-        return Err(not_found());
-    }
-
-    // Walk up the IOService plane to find the authoring device.
-    // The chain is typically:
-    //   IOMedia → IOPartitionScheme → IOMedia → IOBlockStorageDriver
-    //   → IOSCSIPeripheralDeviceNub (this is what we want)
-    //
-    // We walk up until we find a service that IOCreatePlugInInterfaceForService
-    // accepts with kIOMMCDeviceUserClientTypeID, or until we hit the root.
-    let service = walk_to_authoring_device(media);
-    unsafe { IOObjectRelease(media) };
-
-    service.ok_or_else(not_found)
-}
-
-/// Walk up the IOService plane from an IOMedia to the SCSI authoring device.
-fn walk_to_authoring_device(start: IOObject) -> Option<IOObject> {
-    let mut current = start;
-    // Retain start so we can release uniformly in the loop
-    // (IORegistryEntryGetParentEntry retains the parent for us)
-
-    // Target class names for authoring devices
-    let target_classes: &[&[u8]] = &[
-        b"IOSCSIPeripheralDeviceNub\0",
-        b"IOBDBlockStorageDevice\0",
-        b"IODVDBlockStorageDevice\0",
-        b"IOCDBlockStorageDevice\0",
-        b"IOBlockStorageDevice\0",
-    ];
-
-    // Walk up to 10 levels (more than enough)
-    for _ in 0..10 {
-        let mut parent: IOObject = 0;
-        let kr = unsafe {
-            IORegistryEntryGetParentEntry(current, c"IOService".as_ptr() as *const u8, &mut parent)
-        };
-
-        if current != start {
-            unsafe { IOObjectRelease(current) };
-        }
-
-        if kr != K_IO_RETURN_SUCCESS || parent == 0 {
-            return None;
-        }
-
-        // Check if this parent matches any of our target classes
-        for class in target_classes {
-            if unsafe { IOObjectConformsTo(parent, class.as_ptr()) } != 0 {
-                return Some(parent);
-            }
-        }
-
-        current = parent;
-    }
-
-    if current != start {
-        unsafe { IOObjectRelease(current) };
-    }
-    None
-}

src/scsi/macos_shim.c

@@ -0,0 +1,376 @@
+#include <IOKit/IOKitLib.h>
+#include <IOKit/IOCFPlugIn.h>
+#include <IOKit/scsi/SCSITaskLib.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+// ── Types ──────────────────────────────────────────────────────────────────
+
+typedef struct {
+    IOCFPlugInInterface      **plugin;
+    MMCDeviceInterface       **mmc;
+    SCSITaskDeviceInterface  **scsi;
+    int                        exclusive;
+} ShimHandle;
+
+typedef struct {
+    char bsd_name[32];
+    char vendor[32];
+    char model[48];
+    char firmware[16];
+} ShimDriveInfo;
+
+// ── Global handle (single-drive, same as before) ──────────────────────────
+
+static ShimHandle g_handle = {NULL, NULL, NULL, 0};
+
+// ── Registry helpers ──────────────────────────────────────────────────────
+
+static int cfstring_to_cstr(CFStringRef cf, char *buf, size_t buflen) {
+    if (!cf) return 0;
+    if (!CFStringGetCString(cf, buf, buflen, kCFStringEncodingUTF8)) return 0;
+    return 1;
+}
+
+static int registry_entry_bsd_name(io_registry_entry_t entry, char *buf, size_t buflen) {
+    CFStringRef cf = IORegistryEntryCreateCFProperty(entry, CFSTR("BSD Name"),
+        kCFAllocatorDefault, 0);
+    if (!cf) return 0;
+    int ok = cfstring_to_cstr(cf, buf, buflen);
+    CFRelease(cf);
+    return ok;
+}
+
+static io_registry_entry_t find_iomedia_child(io_registry_entry_t parent) {
+    io_iterator_t iter;
+    kern_return_t kr = IORegistryEntryGetChildIterator(parent, kIOServicePlane, &iter);
+    if (kr != KERN_SUCCESS) return 0;
+
+    io_registry_entry_t child;
+    while ((child = IOIteratorNext(iter)) != 0) {
+        char cls[128];
+        kr = IOObjectGetClass(child, cls);
+        if (kr == KERN_SUCCESS) {
+            if (strcmp(cls, "IOMedia") == 0) {
+                IOObjectRelease(iter);
+                return child;
+            }
+        }
+        IOObjectRelease(child);
+    }
+    IOObjectRelease(iter);
+    return 0;
+}
+
+static io_registry_entry_t find_child_of_class(io_registry_entry_t parent, const char *target_class) {
+    io_iterator_t iter;
+    kern_return_t kr = IORegistryEntryGetChildIterator(parent, kIOServicePlane, &iter);
+    if (kr != KERN_SUCCESS) return 0;
+
+    io_registry_entry_t child;
+    while ((child = IOIteratorNext(iter)) != 0) {
+        char cls[128];
+        kr = IOObjectGetClass(child, cls);
+        if (kr == KERN_SUCCESS && strcmp(cls, target_class) == 0) {
+            IOObjectRelease(iter);
+            return child;
+        }
+        IOObjectRelease(child);
+    }
+    IOObjectRelease(iter);
+    return 0;
+}
+
+static io_registry_entry_t find_parent_of_class(io_registry_entry_t entry, const char *target_class) {
+    io_registry_entry_t parent;
+    kern_return_t kr = IORegistryEntryGetParentEntry(entry, kIOServicePlane, &parent);
+    if (kr != KERN_SUCCESS) return 0;
+
+    char cls[128];
+    kr = IOObjectGetClass(parent, cls);
+    if (kr == KERN_SUCCESS && strcmp(cls, target_class) == 0) {
+        return parent;
+    }
+    IOObjectRelease(parent);
+    return 0;
+}
+
+// Given an IOBDServices, find the BSD name of its IOMedia child.
+// Chain: IOBDServices -> IOBDBlockStorageDriver -> IOMedia (has "BSD Name")
+static int bdsvc_to_bsd_name(io_registry_entry_t bdsvc, char *buf, size_t buflen) {
+    io_registry_entry_t driver = find_child_of_class(bdsvc, "IOBDBlockStorageDriver");
+    if (!driver) return 0;
+
+    io_registry_entry_t media = find_iomedia_child(driver);
+    IOObjectRelease(driver);
+    if (!media) return 0;
+
+    int ok = registry_entry_bsd_name(media, buf, buflen);
+    IOObjectRelease(media);
+    return ok;
+}
+
+// Given an IOBDServices, extract Device Characteristics strings.
+static void bdsvc_device_info(io_registry_entry_t bdsvc, ShimDriveInfo *info) {
+    CFDictionaryRef dc = IORegistryEntryCreateCFProperty(bdsvc,
+        CFSTR("Device Characteristics"), kCFAllocatorDefault, 0);
+    if (!dc) return;
+
+    CFStringRef val;
+
+    val = CFDictionaryGetValue(dc, CFSTR("Vendor Name"));
+    if (val) cfstring_to_cstr(val, info->vendor, sizeof(info->vendor));
+
+    val = CFDictionaryGetValue(dc, CFSTR("Product Name"));
+    if (val) cfstring_to_cstr(val, info->model, sizeof(info->model));
+
+    val = CFDictionaryGetValue(dc, CFSTR("Product Revision Level"));
+    if (val) cfstring_to_cstr(val, info->firmware, sizeof(info->firmware));
+
+    CFRelease(dc);
+}
+
+// Find the IOBDServices that owns the given BSD name.
+// Returns a retained io_service_t (caller must release), or 0.
+static io_service_t find_bdsvc_by_bsd_name(mach_port_t mp, const char *bsd_name) {
+    CFMutableDictionaryRef matching = IOServiceMatching("IOBDServices");
+    if (!matching) return 0;
+
+    io_iterator_t iter;
+    kern_return_t kr = IOServiceGetMatchingServices(mp, matching, &iter);
+    if (kr != KERN_SUCCESS) return 0;
+
+    io_service_t result = 0;
+    io_service_t svc;
+    while ((svc = IOIteratorNext(iter)) != 0) {
+        char name[64];
+        if (bdsvc_to_bsd_name(svc, name, sizeof(name))) {
+            if (strcmp(name, bsd_name) == 0) {
+                result = svc;
+                break;
+            }
+        }
+        IOObjectRelease(svc);
+    }
+
+    if (!result) {
+        IOIteratorReset(iter);
+        while ((svc = IOIteratorNext(iter)) != 0) {
+            IOObjectRelease(svc);
+        }
+    }
+
+    IOObjectRelease(iter);
+    return result;
+}
+
+// Find the IOBDServices that owns the given BSD name by walking from
+// IOMedia upward. Used as fallback when bdsvc_to_bsd_name fails
+// (e.g. disc under exclusive access, no IOMedia child).
+// Chain: IOMedia -> IOBDBlockStorageDriver -> IOBDServices
+static io_service_t find_bdsvc_from_iomedia(mach_port_t mp, const char *bsd_name) {
+    CFMutableDictionaryRef matching = IOServiceMatching("IOMedia");
+    if (!matching) return 0;
+
+    io_iterator_t iter;
+    kern_return_t kr = IOServiceGetMatchingServices(mp, matching, &iter);
+    if (kr != KERN_SUCCESS) return 0;
+
+    io_service_t result = 0;
+    io_service_t media;
+    while ((media = IOIteratorNext(iter)) != 0) {
+        char name[64];
+        if (registry_entry_bsd_name(media, name, sizeof(name))
+            && strcmp(name, bsd_name) == 0)
+        {
+            io_registry_entry_t driver = find_parent_of_class(media, "IOBDBlockStorageDriver");
+            if (driver) {
+                io_registry_entry_t bdsvc = find_parent_of_class(driver, "IOBDServices");
+                IOObjectRelease(driver);
+                if (bdsvc) {
+                    result = bdsvc;
+                    IOObjectRelease(media);
+                    break;
+                }
+            }
+        }
+        IOObjectRelease(media);
+    }
+
+    IOObjectRelease(iter);
+    return result;
+}
+
+// ── Public API ────────────────────────────────────────────────────────────
+
+int shim_open_exclusive(const char *bsd_name) {
+    kern_return_t kr;
+    HRESULT hr;
+    SInt32 score = 0;
+
+    if (g_handle.exclusive && g_handle.scsi) {
+        return 0;
+    }
+
+    char cmd[128];
+    snprintf(cmd, sizeof(cmd), "diskutil unmountDisk force %s 2>/dev/null", bsd_name);
+    system(cmd);
+    usleep(500000);
+
+    mach_port_t mp;
+    IOMainPort(0, &mp);
+
+    io_service_t svc = find_bdsvc_by_bsd_name(mp, bsd_name);
+    if (!svc) {
+        svc = find_bdsvc_from_iomedia(mp, bsd_name);
+    }
+    if (!svc) {
+        CFMutableDictionaryRef matching = IOServiceMatching("IOBDServices");
+        svc = IOServiceGetMatchingService(mp, matching);
+    }
+    if (!svc) return -1;
+
+    kr = IOCreatePlugInInterfaceForService(svc,
+        kIOMMCDeviceUserClientTypeID, kIOCFPlugInInterfaceID,
+        &g_handle.plugin, &score);
+    IOObjectRelease(svc);
+
+    if (kr != KERN_SUCCESS || !g_handle.plugin) return -2;
+
+    hr = (*g_handle.plugin)->QueryInterface(g_handle.plugin,
+        CFUUIDGetUUIDBytes(kIOMMCDeviceInterfaceID), (LPVOID *)&g_handle.mmc);
+    if (hr != S_OK || !g_handle.mmc) {
+        IODestroyPlugInInterface(g_handle.plugin);
+        g_handle.plugin = NULL;
+        return -3;
+    }
+
+    g_handle.scsi = (*g_handle.mmc)->GetSCSITaskDeviceInterface(g_handle.mmc);
+    if (!g_handle.scsi) {
+        (*g_handle.mmc)->Release(g_handle.mmc);
+        IODestroyPlugInInterface(g_handle.plugin);
+        g_handle.mmc = NULL;
+        g_handle.plugin = NULL;
+        return -4;
+    }
+
+    kr = (*g_handle.scsi)->ObtainExclusiveAccess(g_handle.scsi);
+    if (kr != kIOReturnSuccess) {
+        (*g_handle.scsi)->Release(g_handle.scsi);
+        (*g_handle.mmc)->Release(g_handle.mmc);
+        IODestroyPlugInInterface(g_handle.plugin);
+        g_handle.scsi = NULL;
+        g_handle.mmc = NULL;
+        g_handle.plugin = NULL;
+        return -5;
+    }
+
+    g_handle.exclusive = 1;
+    return 0;
+}
+
+void shim_close(void) {
+    if (g_handle.exclusive && g_handle.scsi) {
+        (*g_handle.scsi)->ReleaseExclusiveAccess(g_handle.scsi);
+    }
+    if (g_handle.scsi) {
+        (*g_handle.scsi)->Release(g_handle.scsi);
+        g_handle.scsi = NULL;
+    }
+    if (g_handle.mmc) {
+        (*g_handle.mmc)->Release(g_handle.mmc);
+        g_handle.mmc = NULL;
+    }
+    if (g_handle.plugin) {
+        IODestroyPlugInInterface(g_handle.plugin);
+        g_handle.plugin = NULL;
+    }
+    g_handle.exclusive = 0;
+}
+
+int shim_execute(const unsigned char *cdb, unsigned char cdb_len,
+                 void *buf, unsigned int buf_len, int data_in,
+                 unsigned char *sense_out, unsigned int sense_len,
+                 unsigned char *task_status_out, unsigned long long *transfer_count) {
+    if (!g_handle.scsi) return -1;
+
+    SCSITaskInterface **task = (*g_handle.scsi)->CreateSCSITask(g_handle.scsi);
+    if (!task) return -2;
+
+    SCSICommandDescriptorBlock cdb_buf;
+    memset(&cdb_buf, 0, sizeof(cdb_buf));
+    memcpy(&cdb_buf, cdb, cdb_len);
+
+    (*task)->SetCommandDescriptorBlock(task, cdb_buf, cdb_len);
+
+    if (buf_len > 0 && buf) {
+        SCSITaskSGElement sg;
+        sg.address = (UInt64)(uintptr_t)buf;
+        sg.length = buf_len;
+        (*task)->SetScatterGatherEntries(task, &sg, 1, buf_len,
+            data_in ? kSCSIDataTransfer_FromTargetToInitiator
+                    : kSCSIDataTransfer_FromInitiatorToTarget);
+    } else {
+        (*task)->SetScatterGatherEntries(task, NULL, 0, 0,
+            kSCSIDataTransfer_NoDataTransfer);
+    }
+
+    (*task)->SetTimeoutDuration(task, 30000);
+
+    SCSI_Sense_Data sense;
+    memset(&sense, 0, sizeof(sense));
+    SCSITaskStatus status = 0xFF;
+    UInt64 count = 0;
+
+    IOReturn kr = (*task)->ExecuteTaskSync(task, &sense, &status, &count);
+
+    if (sense_out && sense_len > 0) {
+        size_t copy = sense_len < sizeof(sense) ? sense_len : sizeof(sense);
+        memcpy(sense_out, &sense, copy);
+    }
+    if (task_status_out) *task_status_out = (unsigned char)status;
+    if (transfer_count) *transfer_count = count;
+
+    (*task)->Release(task);
+
+    return (int)kr;
+}
+
+// ── Registry-based drive enumeration ──────────────────────────────────────
+//
+// Walks IOBDServices entries in the IOKit registry. No exclusive access,
+// no SCSI commands, no unmounts. Returns up to max_entries drives.
+
+int shim_list_drives(ShimDriveInfo *out, int max_entries) {
+    mach_port_t mp;
+    IOReturn ret = IOMainPort(0, &mp);
+    if (ret != kIOReturnSuccess) return 0;
+
+    CFMutableDictionaryRef matching = IOServiceMatching("IOBDServices");
+    if (!matching) return 0;
+
+    io_iterator_t iter;
+    kern_return_t kr = IOServiceGetMatchingServices(mp, matching, &iter);
+    if (kr != KERN_SUCCESS) return 0;
+
+    int count = 0;
+    io_service_t svc;
+    while ((svc = IOIteratorNext(iter)) != 0 && count < max_entries) {
+        ShimDriveInfo *info = &out[count];
+        memset(info, 0, sizeof(*info));
+
+        bdsvc_device_info(svc, info);
+        bdsvc_to_bsd_name(svc, info->bsd_name, sizeof(info->bsd_name));
+
+        if (info->bsd_name[0]) {
+            count++;
+        }
+
+        IOObjectRelease(svc);
+    }
+
+    IOObjectRelease(iter);
+    return count;
+}

src/scsi/mod.rs

@@ -2,11 +2,11 @@
 //!
 //! Platform backends are in separate files:
 //!   - `linux.rs` — SG_IO ioctl
-//!   - `macos.rs` — IOKit SCSITaskDeviceInterface
+//!   - `macos.rs` — IOKit SCSITaskDeviceInterface (exclusive access)
 //!   - `windows.rs` — SPTI (SCSI Pass-Through Interface)
 
 #[cfg(target_os = "linux")]
-mod linux;
+pub mod linux;
 #[cfg(target_os = "macos")]
 mod macos;
 #[cfg(target_os = "windows")]
@@ -56,9 +56,8 @@ pub(crate) const TUR_TIMEOUT_MS: u32 = 5_000;
 ///
 /// 10 s catches every legitimate slow read with comfortable margin and
 /// short-circuits truly bad sectors at ~10 s rather than letting the
-/// kernel mid-layer escalate for 30 s+. See run log in
-/// `(internal)/docs/TEST_PLAN.md` and the audit at
-/// `(internal)/docs/audits/2026-04-26-scsi-architecture-research.md`.
+/// kernel mid-layer escalate for 30 s+. See the SCSI architecture audit
+/// (2026-04-26) for primary-source references.
 ///
 /// Pre-0.13.21 this was 1.5 s, which forced the kernel mid-layer to
 /// time out *normal* reads (cold-start often takes ~1.5 s) and run its
@@ -335,9 +334,9 @@ pub fn open(device: &Path) -> Result<Box<dyn ScsiTransport>> {
 // platform reset in a thread+recv_timeout so a kernel-wedged ioctl
 // couldn't hang the caller. Removed in 0.13.6 along with the
 // SG_SCSI_RESET / STOP+START UNIT escalation that needed it. The
-// remaining platform reset (Linux: SgIoTransport::reset, called only
-// from SgIoTransport::open) does pure userspace state cleanup with
-// bounded sleeps — no escape-hatch wrapper required.
+// remaining platform reset (Linux: SgIoTransport::reset, available
+// for explicit opt-in) does pure userspace state cleanup with bounded
+// sleeps — no escape-hatch wrapper required.
 
 // ── USB-layer recovery: rolled back in 0.13.4 ───────────────────────────────
 //

src/sector.rs

@@ -24,6 +24,8 @@ pub trait SectorReader: Send {
     fn capacity(&self) -> u32 {
         0
     }
+
+    fn set_speed(&mut self, _kbs: u16) {}
 }
 
 /// SectorReader backed by a file (ISO image).

tests/integration_progress_and_halt.rs

@@ -351,7 +351,7 @@ fn test_file_sector_reader_round_trip() {
 //
 // Per RIP_DESIGN.md §2.1 + §3: Disc::copy must reach the end of the disc
 // regardless of how many reads fail. The only legitimate early exit is the
-// halt flag. With `skip_on_error + skip_forward` and a reader that returns
+// halt flag. With `skip_on_error` and a reader that returns
 // Err for every read, Pass 1 must:
 //   - mark every sector NonTrimmed (so Pass 2 can retry them)
 //   - return cleanly (no panic, no hang)
@@ -424,7 +424,7 @@ impl SectorReader for FailingSectorReader {
 #[test]
 fn test_disc_copy_completes_full_disc_with_failing_reader() {
     // 1024 sectors = 2 MB. Reader fails every read. With skip_on_error +
-    // skip_forward, Pass 1 must mark every sector NonTrimmed and return
+    // skip_on_error, Pass 1 must mark every sector NonTrimmed and return
     // cleanly — no bail, no hang.
     let capacity_sectors: u32 = 1024;
     let total_bytes: u64 = capacity_sectors as u64 * SECTOR_SIZE as u64;
@@ -438,8 +438,8 @@ fn test_disc_copy_completes_full_disc_with_failing_reader() {
 
     let opts = CopyOptions {
         decrypt: false,
-        skip_on_error: true,
-        skip_forward: true,
+        multipass: true,
+
         ..Default::default()
     };
 
@@ -454,9 +454,7 @@ fn test_disc_copy_completes_full_disc_with_failing_reader() {
     let _ = std::fs::remove_file(libfreemkv::disc::mapfile_path_for(&iso_path));
 
     // Hard bound — even at 0 ms per read, 1024 sectors with skip-forward
-    // should complete in well under a second on any host. If this test runs
-    // for minutes, something has regressed (e.g. stall guard reintroduced
-    // with infinite-loop semantics, or Pass 1 is hanging on each read).
+    // should complete in well under a second on any host.
     assert!(
         elapsed < Duration::from_secs(5),
         "Pass 1 took {elapsed:?} on a 2 MB synthetic disc — expected < 5 s"
@@ -520,8 +518,8 @@ fn test_disc_copy_halts_promptly_on_failing_reader() {
 
     let opts = CopyOptions {
         decrypt: false,
-        skip_on_error: true,
-        skip_forward: true,
+        multipass: true,
+
         halt: Some(halt),
         ..Default::default()
     };
@@ -553,16 +551,9 @@ fn test_disc_copy_halts_promptly_on_failing_reader() {
 
 // ── 8. Hysteresis recovers data the drive can read individually ──────────
 //
-// Empirically observed on the LG BU40N: in damaged regions the drive fails
-// multi-sector READ commands but reads each sector cleanly when asked one
-// at a time. Disc::copy's hysteresis state machine (0.13.22, replaces the
-// 0.13.21 bisect-on-fail) drops to bpt=1 on the first multi-sector failure
-// and stays there until BPT1_EXIT_THRESHOLD consecutive good single-sector
-// reads, then returns to bpt=batch.
-//
-// Fixture: a reader that returns Err for any read with count > 1, and Ok
-// for count == 1. The full disc must recover via the bpt=1 path with
-// 100 % bytes_good outcome.
+// Pass 1 reads in batch (32 sectors = 1 ECC block). Failed blocks are marked
+// NonTrimmed for Pass 2 recovery. This test verifies that a reader where every
+// multi-sector read fails produces all NonTrimmed output with zero bytes_good.
 
 struct BlockSizeFailingReader {
     capacity: u32,
@@ -577,15 +568,11 @@ impl SectorReader for BlockSizeFailingReader {
         _recovery: bool,
     ) -> Result<usize> {
         if count == 1 {
-            // Single-sector reads succeed — fill the sector with a marker.
             for chunk in buf.chunks_mut(SECTOR_SIZE) {
                 chunk.fill((lba & 0xff) as u8);
             }
             Ok(buf.len())
         } else {
-            // Multi-sector reads fail with the BU40N's signature: CHECK
-            // CONDITION + MEDIUM ERROR. The hysteresis must dispatch on
-            // this as marginal-read and drop to bpt=1.
             Err(libfreemkv::error::Error::ScsiError {
                 opcode: libfreemkv::scsi::SCSI_READ_10,
                 status: libfreemkv::scsi::SCSI_STATUS_CHECK_CONDITION,
@@ -604,13 +591,7 @@ impl SectorReader for BlockSizeFailingReader {
 }
 
 #[test]
-fn test_disc_copy_hysteresis_recovers_via_single_sector_reads() {
-    // 256 sectors = 0.5 MB. Reader fails any multi-sector read but
-    // succeeds on bpt=1. The hysteresis path must drop to Single mode on
-    // the first multi-sector failure and recover every sector at bpt=1.
-    // Stays in Single mode until BPT1_EXIT_THRESHOLD reached (10 000
-    // sectors); since this disc is only 256 sectors we never re-enter
-    // Block mode, which is fine — every sector still recovers.
+fn test_disc_copy_marks_failed_ecc_blocks_as_nontrimmed() {
     let capacity_sectors: u32 = 256;
     let total_bytes: u64 = capacity_sectors as u64 * SECTOR_SIZE as u64;
 
@@ -625,8 +606,8 @@ fn test_disc_copy_hysteresis_recovers_via_single_sector_reads() {
 
     let opts = CopyOptions {
         decrypt: false,
-        skip_on_error: true,
-        skip_forward: true,
+        multipass: true,
+
         ..Default::default()
     };
 
@@ -637,20 +618,19 @@ fn test_disc_copy_hysteresis_recovers_via_single_sector_reads() {
     let _ = std::fs::remove_file(&iso_path);
     let _ = std::fs::remove_file(libfreemkv::disc::mapfile_path_for(&iso_path));
 
-    // Bisect must recover every sector — the drive could read each one
-    // individually, and our algorithm must descend to that.
+    // Pass 1 reads every batch at bpt=32 (no batch reduction, no skip-ahead).
+    // BlockSizeFailingReader fails on all batch=32 reads, so every sector
+    // is marked NonTrimmed. bytes_good=0 is correct — Pass 2 recovers them.
     assert_eq!(
-        result.bytes_good, total_bytes,
-        "bisect-on-fail must recover every sector via single-sector reads. \
-         Got bytes_good={} of total {}",
-        result.bytes_good, total_bytes
-    );
-    assert_eq!(
-        result.bytes_pending, 0,
-        "no sectors should be left NonTrimmed after a successful bisect"
+        result.bytes_good, 0,
+        "Pass 1 at bpt=32 should not recover any sectors when all batches fail"
     );
     assert!(
-        result.complete,
-        "complete=true expected when every sector recovered"
+        result.bytes_pending > 0,
+        "all sectors should be NonTrimmed pending Pass 2"
+    );
+    assert!(
+        !result.complete,
+        "complete=false when sectors remain NonTrimmed"
     );
 }

tests/scsi_recovery.rs

@@ -0,0 +1,115 @@
+//! Tests for SgIoTransport timeout recovery (Fix 2).
+//!
+//! When `execute()` detects a transport-level failure (kernel timeout /
+//! USB bridge wedge — `host_status != 0`), it spawns two background
+//! threads to (1) close the old fd and (2) open a fresh one, then
+//! stores the new fd in `fd_recovery`. The next `execute()` call picks
+//! up the recovered fd without blocking on close().
+//!
+//! These tests require a real /dev/sg* device and are therefore #[ignore].
+
+use libfreemkv::scsi::{DataDirection, SCSI_STATUS_TRANSPORT_FAILURE};
+use std::path::Path;
+use std::time::Duration;
+
+#[test]
+#[ignore]
+fn test_sgio_transport_timeout_does_not_kill_transport() {
+    let device = "/dev/sg2";
+    let device = std::env::var("FREEMKV_TEST_SG_DEVICE").unwrap_or(device.to_string());
+    let path = Path::new(&device);
+
+    #[cfg(target_os = "linux")]
+    {
+        use libfreemkv::scsi::ScsiTransport;
+        use libfreemkv::scsi::linux::SgIoTransport;
+        use std::sync::Arc;
+        use std::sync::atomic::{AtomicI32, Ordering};
+
+        let mut transport = SgIoTransport::open(path).expect("open device");
+        let fd_before = transport.fd;
+
+        // READ_10 with 1 ms timeout to force kernel timeout.
+        let cdb = [0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00];
+        let mut data = vec![0u8; 2048];
+
+        let start = std::time::Instant::now();
+        let result = transport.execute(&cdb, DataDirection::FromDevice, &mut data, 1);
+        let _elapsed = start.elapsed();
+
+        assert!(result.is_err(), "expected Err on timeout, got {:?}", result);
+        let err = result.unwrap_err();
+        assert!(
+            matches!(&err, libfreemkv::Error::ScsiError { status, .. } if *status == SCSI_STATUS_TRANSPORT_FAILURE),
+            "expected ScsiError(TRANSPORT_FAILURE), got {:?}",
+            err
+        );
+        assert_eq!(transport.fd, -1, "fd should be -1 after timeout");
+
+        // Wait for recovery thread to store new fd.
+        let recovered = Arc::new(AtomicI32::new(-1));
+        let recovery_ref = transport.fd_recovery.clone();
+        for _ in 0..100 {
+            let v = recovery_ref.load(Ordering::Acquire);
+            if v >= 0 {
+                recovered.store(v, Ordering::Release);
+                break;
+            }
+            std::thread::sleep(Duration::from_millis(50));
+        }
+        let new_fd = recovered.load(Ordering::Acquire);
+        assert!(new_fd >= 0, "recovery thread should have produced a new fd");
+
+        // Next execute() must pick up recovered fd quickly.
+        let mut data2 = vec![0u8; 2048];
+        let start2 = std::time::Instant::now();
+        let result2 = transport.execute(&cdb, DataDirection::FromDevice, &mut data2, 5000);
+        let elapsed2 = start2.elapsed();
+
+        assert!(
+            result2.is_ok(),
+            "execute() with recovered fd should succeed, got {:?}",
+            result2
+        );
+        assert!(
+            elapsed2 < Duration::from_secs(2),
+            "should return quickly, took {:?}",
+            elapsed2
+        );
+        assert_ne!(transport.fd, -1, "fd should be valid after recovery");
+        assert_ne!(transport.fd, fd_before, "fd should be fresh after recovery");
+    }
+    #[cfg(not(target_os = "linux"))]
+    {
+        eprintln!("SKIP: test requires Linux / SgIoTransport");
+    }
+}
+
+#[test]
+#[ignore]
+fn test_drive_read_per_cdb_timeout_bounds_call() {
+    let device = "/dev/sg2";
+    let device = std::env::var("FREEMKV_TEST_SG_DEVICE").unwrap_or(device.to_string());
+    let path = Path::new(&device);
+
+    #[cfg(target_os = "linux")]
+    {
+        let mut drive = libfreemkv::Drive::open(path).expect("open drive");
+        let timeout_ms: u32 = 5_000;
+
+        let start = std::time::Instant::now();
+        let _ = drive.read(0, 1, &mut [0u8; 2048], false);
+        let elapsed = start.elapsed();
+
+        let overhead = Duration::from_millis(500);
+        assert!(
+            elapsed < Duration::from_millis(timeout_ms as u64) + overhead,
+            "Drive::read should return within timeout_ms + overhead, took {:?}",
+            elapsed
+        );
+    }
+    #[cfg(not(target_os = "linux"))]
+    {
+        eprintln!("SKIP: test requires Linux / SgIoTransport");
+    }
+}