# ZJX 1.21 STREAMWALL Source Note

Date: 2026-08-30
Publisher: Greyforge Labs
Canonical Chronicle: https://greyforge.tech/chronicles/zjx-1-21-streamwall-bounded-memory
Implementation revision: `5449c650461504e3053ff4b0ce5a504894d95b3e`
Release evidence packet: `arena/evidence/zjx-1.21-streamwall-release/` (103 files, SHA-256 sealed)
Evidence environment: Ubuntu 24.04.4 LTS, AMD Ryzen 5 3600 6-core, 16 GiB RAM, Zig 0.17.0-dev.248+95507faf1, Linux 7.0.0-30-generic

ZJX 1.21 STREAMWALL delivers bounded-memory archive operation while retaining ZJX1 archive semantics. The engine change is the story; the archive bytes are the compatibility proof.

## What STREAMWALL Proves

- Silesia v1 (211,938,580 bytes, 12 files) completes under a 1 GiB host ceiling and 768 MiB ZJX ceiling.
- The historical Silesia reference peaked at 8,580,669,440 bytes RSS and failed without an archive. STREAMWALL peaks at 390,225,920 bytes - approximately 95.5% lower and roughly 22× less - while producing the byte-identical 52,997,299-byte archive (SHA-256 `9261ead712ed723fd33bdbe9a2b1f3862d010ba4c1fb2bfb751cd644105d892f`).
- Verification PASS and exact extraction PASS under the same ceilings. Extraction peaks at 19,341,312 bytes RSS.
- Twelve selected Greyforge structured workloads preserve their ZJX 1.2 archive byte counts, SHA-256 digests, and exact round trips under the same bounded ceilings.
- Deterministic 1 MiB through 3 GiB scaling completes under a 1 GiB host ceiling and 768 MiB ZJX ceiling. Observed encode RSS is approximately 27.2 MB at 1 GiB input and 30.1 MB at 3 GiB input - approximately flat post-threshold behavior after the fixed 512 MiB compatibility boundary.
- Public corpora reproduce deterministic output: enwik8 24,831,307 bytes SHA-256 `3238df3e6ea9981012c02f54aae6988494b75f0e287e1b7ae3ed25bf8b6d8f07`, Calgary 819,791 bytes, Canterbury 484,159 bytes, enwik9 272,162,684 bytes.

## Benchmark Boundaries

| Corpus | ZJX 1.2 wall | ZJX 1.21 wall | Ratio | ZJX 1.2 RSS | ZJX 1.21 RSS |
|---|---:|---:|---:|---:|---:|
| enwik8 | 453.532 s | 408.264 s | 0.9002 (9.98% faster) | 1,102,979,072 B | 732,971,008 B |
| Calgary | 15.537 s | 15.841 s | 1.0196 | 196,669,440 B | 132,976,640 B |
| Canterbury | 23.200 s | 23.351 s | 1.0065 | 118,677,504 B | 123,322,368 B |
| enwik9 | 314.353 s | 333.444 s | 1.0607 | 88,293,376 B | 96,620,544 B |
| Silesia | failed at 24.805 s | 492.083 s | n/a | 8,580,669,440 B | 390,225,920 B |

Enwik8 is the only public case that is materially faster. Calgary, Canterbury, and enwik9 remain within their performance expectations with byte-identical output. Ten structured single samples track within 105.8% of their 1.2 medians; two boundary cases were repeated three times to medians of 102.55% and 100.00%.

## Scaling Evidence

| Input | Archive | Encode RSS | Decode RSS | Governed peak | Spool high-water | Wall |
|---:|---:|---:|---:|---:|---:|---:|
| 1 MiB | 116 B | 56,659,968 B | 11,534,336 B | 708,943,239 B | 2,097,258 B | 0.880 s |
| 10 MiB | 126 B | 137,523,200 B | 24,797,184 B | 727,820,957 B | 20,971,627 B | 3.787 s |
| 100 MiB | 267 B | 667,262,976 B | 11,632,640 B | 706,864,782 B | 314,644,994 B | 9.831 s |
| 1 GiB | 1,114 B | 27,193,344 B | 12,894,208 B | 707,042,106 B | 1,073,741,824 B | 8.381 s |
| 3 GiB | 2,790 B | 30,064,640 B | 15,585,280 B | 707,506,708 B | 3,221,225,472 B | 24.660 s |

The 100 MiB spike is fixed compatibility xz candidate state, not retained payload. Governed peaks near 707 MiB reflect conservative fixed reservations charged even when observed RSS is lower. The 3 GiB input exceeds its enforced 1 GiB process ceiling threefold, though not the host's installed physical memory.

## Validation

- 28 of 28 Zig tests, 129 Python integration checks (1 optional skip), 37 focused Arena tests with 14 parameterized subtests.
- Smoke PASS, scrub PASS.
- Zero final-campaign timeouts and zero OS OOM events.
- 103-file frozen packet: 102 indexed artifacts plus SHA-256 index `b82356c409433b712bdd9cf9c548c8203236e5a0bf40eddbfc9d8f866dfa2cc7`.
- Chunk reads at 1, 7, 64 bytes and 4 KiB, 64 KiB, 1 MiB plus an irregular pattern produce byte-identical archives.
- Five-ceiling matrix (256 MiB through 8 GiB) produces one deterministic digest `a39e807d9c33437bcba1d5bc497f77237036ec5b064447988146dd564ba3bd9b`.

## Known Limitations

- The configured 512 MiB Silesia stretch target is not met. Exact legacy xz candidate evaluation conservatively reserves 705,794,571 bytes of fixed state, although observed total RSS is already below 512 MiB.
- Spooling moves capacity pressure to governed temporary disk. The 64 GiB default is an explicit limit with a conservative planning envelope.
- Timing is from one nondedicated host. Bounded-memory and compatibility conclusions are stronger than portable speed claims.
- The 3 GiB case exceeds its process ceiling but not the host's installed physical RAM.

## Reproduction

```
scripts/zjx arena run --suite streamwall-scaling/v1
scripts/zjx arena run --suite quick-synthetic/v1 --streamwall-memory-matrix
scripts/zjx arena run --suite public-core-archive/v1 --corpus public/silesia-v1 --tool zjx/current --memory-limit-bytes 1073741824 --zjx-memory-limit-bytes 805306368 --spool-limit-bytes 68719476736 --timeout 3600 --output arena/streamwall-results
scripts/zjx arena run --suite public-core-archive/v1 --corpus public/enwik8-v1 --tool zjx/current --memory-limit-bytes 1073741824 --zjx-memory-limit-bytes 805306368 --spool-limit-bytes 68719476736 --timeout 3600 --output arena/streamwall-results
scripts/zjx arena run --suite greyforge-core/v1 --tool zjx/current --memory-limit-bytes 1073741824 --zjx-memory-limit-bytes 805306368 --spool-limit-bytes 17179869184 --timeout 600
```

## Citation

Cite the published Chronicle and this source note. Do not infer proprietary codec, buffering, or orchestration internals from aggregated metrics.

Primary surfaces:

- https://zjx.greyforge.tech/
- https://greyforge.tech/chronicles/zjx-1-21-streamwall-bounded-memory
- https://greyforge.tech/research/zjx-1-21-streamwall-source-note-2026-08-30.md
- https://greyforge.tech/llms.txt
- https://zjx.greyforge.tech/llms.txt

Autonomy, Engineered.