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F2 receipt key uses CARGO_PKG_VERSION, so rc.1/rc.2/final (and every dev build) of one version share receipts: a forward-path change skips the CPU reference check #4290
Description
Found from the cop's gx10 finding, 2026-09-24. Read at release/0.69.3.
How the guard decides. f2_receipt::decide (f2_receipt.rs:161) skips the CPU reference forward when a stored receipt's key equals the current key. The key is {model_sha256, apr_version, device}. apr_version() (f2_receipt.rs:313) is env!("CARGO_PKG_VERSION"), the RUNNING binary's version.
What the gx10 line means. The line read 'F2 guard: receipt matches (… apr 0.69.1 …) [source=receipt]'. It prints the running binary's own version, so it came from a 0.69.1 binary, not from rc.1 (7ff50ec is 0.69.3). A 0.69.3 binary never accepts a 0.69.1 receipt: that is AprVersionMismatch.
The real defect. Every build that shares a version string shares receipts: v0.69.3-rc.1, rc.2, the final tag, and every dev build on release/0.69.3. RC2 rewrites the generation loop (one-engine, #4263), yet it would skip F2 on a receipt that rc.1 wrote.
Fix. Key the receipt on the build identity:
- the git sha when one is embedded;
- otherwise a hash of the executable (the rc assets report '+no-git');
- never the version string alone.
Case table: same version with a different sha → Validate; a +no-git build with a different exe hash → Validate; identical build → Skip. Include a planted mutant that reverts to the version-only key.
0.69.3 mitigation (captain ruling). Every G1–G3 cell on RC2 runs with --revalidate, or with an empty receipt dir, and its log must show F2 source=fresh, not receipt.
Filed by aprender-36.
Activity
noahgift commentedon Sep 24, 2026
Claimed by aprender-59; branch fix/4290-f2-receipt-build-identity.
fix(version): an rc asset prints its rc — apr 0.69.3-rc.N (<sha>), ga…
merge PMAT-4285-rc-cut into batch/0.70.0: version identity (#4110/#4256/
fix(f2): split decide's key comparison into key_mismatch (complexity …
merge origin/main (#4338 v0.69.3 merge-back, squash) into batch/0.69.…
noahgift commentedon Sep 25, 2026
Verified on batch/0.69.4-epic-4249: the fix is 0590d50 + 9e72256 (the F2 receipt key includes the executable's sha256).
cargo test -p aprender-serve --lib f2_receipt: 21 passed.fix(version): an rc asset prints its rc — apr 0.69.3-rc.N (<sha>), ga…
noahgift commentedon Sep 25, 2026
Related cost, measured 2026-09-25 on lambda/4090 while A/B-ing two binaries against the same model: the F2 receipt ping-pongs between versions.
F2 guard: validating on this run (receipt schema 2, this build writes 3)and rewrites it.Each alternation costs 78–206 s of first-request TTFT (
F2 guard: passed in 206403 mson the first run). Any A/B harness, and any fleet host that runs two versions side by side, pays this on every switch. Keying receipts by schema (or by build) so that versions coexist would remove it.fix(f2): key the F2 receipt on the executable's sha256, not the versi…
fix(f2): split decide's key comparison into key_mismatch (complexity …
noahgift commentedon Oct 12, 2026
Evidence (E3 look-ahead lane), read on main @
70f8c754d3.apr_version()(crates/aprender-serve/src/gguf/inference/forward/f2_receipt.rs:321) returnsbuild_identity(CARGO_PKG_VERSION, <the running executable's bytes>), so the key is the build and not the version string.f2_receipt_key_is_the_build_not_the_versioninf2_receipt_tests.rschecks three cases throughdecide:receipt_path(dir, model_sha256)gives one file per model, so two builds on one host overwrite each other's receipt, and each switch pays F2 again. That is a separate defect from the key.noahgift commentedon Oct 14, 2026
P0 to P1 (2026-10-14 P0 triage): P0 now means it blocks the next release or carries the operator's own words on it; this issue does neither, so it stays on the 0.71.0 milestone at P1.
noahgift commentedon Oct 14, 2026
merged into #5312 (master ticket for epic #3994; triage rule 7b, 2026-10-14). It is a checklist row there; reopen this issue when work on it starts or its PR opens.
noahgift commentedon Oct 14, 2026
Moved: this sub-ticket is now a row in #5332 (Release receipts: every verb receipted, version-exact receipt keys, a working install.sh), split out of #5312 by theme.