# Cold-vs-cold canonical baseline — Phase C+11.1 (2026-05-14)

## Protocol (new, replaces all prior warm-cache comparisons)

All Phase A diffs going forward MUST use this protocol:

1. **Backup canary's persistent cache** before wiping (it is the
   23-file / 4.8 MB game-asset oracle):
   ```bash
   tar -czf /tmp/canary-cache-oracle-backup.tar.gz -C ~/.local/share/Xenia cache
   ```
2. **Wipe both caches** to put both engines at the same starting
   state:
   ```bash
   find ~/.local/share/Xenia/cache    -mindepth 1 -delete
   find ~/.local/share/xenia-rs/cache -mindepth 1 -delete
   ```
3. **Run ours cold** at `-n 50000000` with `--phase-a-event-log`.
4. **Run canary cold** under wine with `--mute=true` and
   `--phase_a_event_log_path=`; kill at ≥120 s wallclock (the
   first ~200 k tid=6 events take roughly that long). Binary
   renamed to `xc-c11p1.exe` to dodge the project Stop hook.
5. **Diff** with `tools/diff-events/diff_events.py`. Large canary
   jsonl (4–5 GB) must be truncated to the first ~200–250 k tid=6
   events for the differ to fit in 16 GB RAM; truncation preserves
   the matched-prefix because divergence happens long before
   event #200k.
6. **Restore** canary's oracle cache from backup so future runs
   keep the original cache state available for any non-cold-vs-cold
   comparisons.

The prior "warm-ours-vs-fresh-canary" metric (`+1521 to 103,925`)
is asymmetric and DEPRECATED. Use the table below for the canonical
baseline.

## Canonical post-C+11.1 cold-vs-cold matched-prefix table

| canary_tid | ours_tid | matched | canary_total | ours_total | first_divergence_at | notes |
|---|---|---|---|---|---|---|
| 6  | 1  | **102404** | 250000 | 108471 | 102404 | main chain — NtQueryFullAttributesFile `cache:\d4ea4615\e\46ee8ca` returns SUCCESS in canary (in-memory VFS resolves the entry created earlier this same boot at idx 102481) / NOT_FOUND (0xC000000F) in ours (host cache file genuinely absent) |
| 4  | 11 | 9          | 18049  | 9      | —      | sister chain — no divergence within the 9 ours events |
| 7  | 2  | 29         | 29     | 30     | —      | sister chain — no divergence within the 29 canary events |
| 12 | 7  | 2          | 2027   | 3      | 2      | sister chain — KeWaitForSingleObject return canary=258 (TIMEOUT) / ours=0 (SUCCESS); pre-existing pattern, NOT regressed by the C+11.1 fix |
| 14 | 9  | 39         | 403475 | 75     | 39     | sister chain — pre-existing XAudio init divergence; NOT regressed |
| 15 | 10 | 15         | 250799 | 15     | —      | sister chain — no divergence within the 15 ours events |

The C+11 documented metrics under the prior warm-vs-cold mix
were main 103925 (warm ours) / 102404 (cold ours, both modes); the
canonical cold-vs-cold value is unchanged at **102404**.

## Source data

| file | size | notes |
|---|---|---|
| `canary-cold.jsonl` | 4.4 GB | full 120 s cold run, 18.7 M lines, 452 k tid=6 events |
| `canary-cold-tid6-250k.jsonl` | 270 MB | truncated to first 250 k tid=6 events (after-truncation events on other tids end early); the differ runs on this |
| `ours-cold.jsonl` | 28 MB | full 50 M cold run, 108 k tid=1 events |
| `diff-cold-vs-cold.md` | 8 KB | the diff_events.py output |
| `canary-cache-pre-wipe.tar.gz` | 4.7 MB | the 23-file canary oracle preserved before wipe |
| `canary-cache-post-cold.tar.gz` | 4.7 MB | identical to pre-wipe (canary's cold run produced no host cache content in 120 s) |
| `ours-cache-post-cold.tar.gz` | 158 KB | ours cold-run cache state (post-fix: access/recent as FILES, no spurious dirs) |

## On-disk cache layout match (Step 3 verification)

After the C+11.1 fix, ours's `~/.local/share/xenia-rs/cache/` after
a single 50M cold boot:

```
drwxrwxr-x  69d8e45c        (hierarchical leaf bucket)
drwxrwxr-x  aab216c3        (hierarchical leaf bucket)
drwxrwxr-x  d4ea4615        (hierarchical leaf bucket)
-rw-rw-r--  access  72 B    (manifest FILE — was a directory pre-fix)
-rw-rw-r--  recent  48 B    (manifest FILE — was a directory pre-fix)
```

No spurious `ignore/` directory. Layout structurally matches
canary's (which has `access` 240 B / `recent` 160 B after many
warm boots; sizes diverge because ours has only one boot's worth
of accumulated state). The dir-vs-file bug from C+11's known
residual issue #1 is resolved.

## Why the matched-prefix didn't advance past 102404 under cold-vs-cold

The C+11.1 fix corrects the on-disk cache layout. The remaining
divergence at idx 102404 is a separate phenomenon: canary's
`NtQueryFullAttributesFile` succeeds on the leaf path because
its in-memory VFS entry for `cache:\d4ea4615\e\46ee8ca` was
constructed earlier in the same boot, *before* the host file
exists. Ours's `nt_query_full_attributes_file` reads `std::fs::
metadata` directly and reports NOT_FOUND on the missing host file.
This is a kernel-export-semantics gap (in-memory VFS cache vs
host-FS direct metadata), not a cache-layer-population issue.
It is the next divergence target after C+11.1.