docs: lock buyer-facing auto backend to fail-closed Rust by cursor[bot] · Pull Request #945 · ContextualWisdomLab/fast-mlsirm

cursor · 2026-08-16T16:22:54Z

Scope

Keep the executable Claude runtime-contract from #833, and close the remaining buyer-facing #621 defect: README and commercial-readiness still told a purchaser that backend="auto" transparently falls back to NumPy, which is the opposite of shipped resolve_backend("auto") behavior.

This branch includes the #833 CLAUDE.md TOML contract and extends the lock to customer-facing install/sales copy plus the PRD/TRD/ADR-0002 summaries that still called automatic resolution a transparent fallback.

Prefer this PR over #833. Do not merge #833 in parallel.

What a purchaser should do

Install a wheel or editable build that compiles fast_mlsirm._core.
Keep FitConfig(backend="auto") for production; it fails closed if the Rust core is missing.
Pass backend="numpy" only when you want the explicit reference/parity path.

Machine-readable contract (unchanged)

[runtime_contract]
requires_python = ">=3.12"
auto_backend = "rust_required"
numpy_role = "reference_parity_only"

Verification

Focused contract tests in tests/test_claude_runtime_contract.py passed locally (7 tests), including README, commercial-readiness, PRD, TRD, and ADR-0002 stale-claim locks. No runtime, formula, estimator, or dependency changes.

Advances #621.

Keep the Claude runtime-contract TOML, and stop README, commercial readiness, PRD, TRD, and ADR-0002 from advertising a silent NumPy fallback for backend=auto. Purchasers should install the compiled Rust core or pass explicit backend=numpy for parity testing. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com>

cursor · 2026-08-16T16:24:04Z

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Verdict: REQUEST_CHANGES (posted as COMMENT; GitHub rejects REQUEST_CHANGES on cursor[bot] PRs)

The Install rewrite, CLAUDE.md TOML contract, commercial Supported Product Surface, and the PRD/TRD/ADR-0002 auto sentences match shipped resolve_backend("auto"). Prefer this PR over #833. Do not merge #833 in parallel.

This branch does not close the buyer-facing defect it claims to close. A purchaser can still be told that auto falls back to NumPy — in the same README this PR edited, in fast-mlsirm fit --help, in the public FitConfig comments, and in commercial Operational Notes. The new tests lock exact phrases and stay green through all of that. They never import resolve_backend.

Shipped policy on this head:

python/fast_mlsirm/backend.py: auto → "rust" when fast_mlsirm._core imports; otherwise RuntimeError("compiled Rust core is required for automatic backend resolution"). Explicit numpy never inspects the core.
FitConfig.backend default is "auto".
CLI --backend default is auto.
Behavioral lock already exists in tests/test_backend.py.

No security, formula, estimator, or dependency issues.

Blocking leftovers (same defect class)

README.md CLI section (lines 378–381) — Install now says fail-closed; the later CLI examples still say fit --backend auto “falls back to NumPy otherwise.” Buyer confusion in the primary install doc.
python/fast_mlsirm/cli.py --help — still says default: auto = Rust core when available, numpy reference fallback. That is the purchaser-visible contract for fast-mlsirm fit.
python/fast_mlsirm/config.py FitConfig.backend comment — still says "auto" “transparently falls back to the pure-numpy reference implementation otherwise.”
docs/commercial_readiness.md Operational Notes — still says “Installed wheels can use the NumPy backend by default,” which contradicts the new Supported Product Surface and README (“installed wheels ship the compiled core”).
tests/test_claude_runtime_contract.py — phrase locks, not a shipped-policy bind. _STALE_AUTO_NUMPY_FALLBACK is the old Install sentence only. It does not catch “falls back to NumPy otherwise”, CLI help, FitConfig comments, or commercial Operational Notes. test_claude_machine_runtime_contract_matches_shipped_policy never imports resolve_backend.

Residual product gap (not introduced here)

Auto fail-closed errors do not tell the next action. Doctoring correctly wants a stable, non-reflective error, but a purchaser is not told to install a wheel/_core or pass backend="numpy" / --backend numpy.

Next action

A successor on this run’s branch will lock the leftover README/CLI/FitConfig/commercial surfaces, bind the contract tests to resolve_backend, and add a stable next-action suffix on the auto fail-closed error. Treat that successor as the landing vehicle. Reviewer seonghobae is already requested. Do not self-approve.

_{Sent by Cursor Automation: Fix Issues}

cursor · 2026-08-16T16:34:56Z

+    assert _STALE_AUTO_NUMPY_FALLBACK not in normalized
+    assert _STALE_PARITY_AND_FALLBACK not in normalized
+    assert "fails closed when that extension is unavailable" in normalized
+    assert "Automatic resolution never silently selects NumPy" in normalized


This README lock only forbids the old Install sentence. The same file still says fit --backend auto “falls back to NumPy otherwise” around lines 378–381. A purchaser who follows the CLI examples gets the opposite of shipped resolve_backend("auto"). Scan that later CLI section (or the whole README) for the leftover claim.

cursor · 2026-08-16T16:34:56Z

+    project = tomllib.loads((ROOT / "pyproject.toml").read_text(encoding="utf-8"))
+    guidance = (ROOT / "CLAUDE.md").read_text(encoding="utf-8")
+
+    assert _runtime_contract(guidance) == {


test_claude_machine_runtime_contract_matches_shipped_policy compares CLAUDE.md TOML to hardcoded rust_required / reference_parity_only. It never imports resolve_backend. The executable fail-closed bind already lives in tests/test_backend.py; this lock should call or document that shipped function so a docs-only rewrite cannot drift from runtime policy.

cursor · 2026-08-16T16:34:56Z

+
+    assert _STALE_NUMPY_DEFAULT not in readiness
+    assert "Rust/PyO3 backend as the default `auto` runtime path" in readiness
+    assert "Explicit NumPy reference backend for parity testing only" in readiness


This assertion locks the Supported Product Surface rewrite and misses Operational Notes: “Installed wheels can use the NumPy backend by default.” That leftover still tells a sales reviewer the opposite of “installed wheels ship the compiled core.” Include that sentence in the stale-claim scan.

cursor · 2026-08-16T16:34:57Z

-`backend="numpy"` to force the pure-Python reference (used for parity testing).
+The default runtime backend is `"auto"`. It uses the compiled Rust core
+(`fast_mlsirm._core`) and fails closed when that extension is unavailable.
+Automatic resolution never silently selects NumPy. Source and editable installs


Install copy is now correct. The CLI section later in this same file still says fit --backend auto uses Rust when available and falls back to NumPy otherwise. Until that paragraph is rewritten, this PR does not close the buyer-facing #621 defect.

cursor · 2026-08-16T16:34:57Z

+- Rust/PyO3 backend as the default `auto` runtime path through
+  `fast_mlsirm._core`. `auto` fails closed when the compiled core is
+  unavailable.
+- Explicit NumPy reference backend for parity testing only.


Supported Product Surface is now correct. Operational Notes still say installed wheels can use NumPy by default. A sales reviewer who reads past the surface list still gets the old ownership story.

seonghobae · 2026-08-16T16:38:23Z

Superseded by #946 after a fresh exact-head comparison. #946 is a strict descendant of this head (ahead 2 / behind 0, merge base = this exact head), retains the executable CLAUDE/runtime and buyer-facing Rust-required auto contract, and closes additional stale surfaces in README CLI guidance, fit --help, public FitConfig comments, commercial Operational Notes, and the package-owned auto error path. This PR was closed before its enabled auto-merge could integrate the incomplete predecessor contract.

…faces (#951) * test(docs): pin Claude runtime support contract * docs: align Claude guidance with fail-closed runtime * test(docs): normalize Markdown wrapping in runtime contract * test(docs): reject marginal fallback claim * revert: keep runtime guidance lane scoped * test(docs): require machine-readable runtime contract * docs: publish machine-readable runtime contract * test(config): expose integer callback trust gap * fix(config): reject caller-controlled integer coercion * test(config): cover bounded integer trust controls * docs(changelog): record config integer boundary hardening * docs(doctoring): record config integer trust boundary * fix(config): validate simulation and fit controls at construction Strix VULN-0001 failed the current head because MLS2PLMConfig and FitConfig could be constructed with values that bypass memory-safety bounds until a later explicit validate() call. Run the existing validators from __post_init__ so invalid objects cannot exist, and keep validate() public and idempotent. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * fix(config): store trusted integers and harden seed controls Write admitted NumPy integers back as built-in ints so n_items and seed + restart cannot wrap, and reject untrusted seed/verbose values before construction returns. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * docs: lock buyer-facing auto backend to fail-closed Rust Keep the Claude runtime-contract TOML, and stop README, commercial readiness, PRD, TRD, and ADR-0002 from advertising a silent NumPy fallback for backend=auto. Purchasers should install the compiled Rust core or pass explicit backend=numpy for parity testing. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * fix: lock leftover auto-backend surfaces to fail-closed Rust Close the buyer-facing leftovers that #945 missed: README CLI examples, fit --help, FitConfig comments, commercial Operational Notes, and the auto fail-closed error now name the next action. Contract tests bind to resolve_backend and scan those surfaces. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * test: tolerate wrapped fit --help and reference/parity wording The auto-unavailable message uses "reference/parity" as policy language, not a filesystem path. fit --help wraps the next-action clause, so the lock now compares whitespace-normalized help text. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * fix: lock leftover demo and acceptance auto surfaces to Rust Buyer demo copy, README layout, sales --check-import help, and release-acceptance still treated Rust as optional or accepted NumPy as an automatic fit outcome. Fail those surfaces closed and lock them. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * test(sales): expose automatic backend authority gap * test(sales): defer backend authority to owning PR * test(backend): cover unloadable Rust core * fix(backend): fail closed before untrusted controls and loader errors * test(backend): enforce callback-safe controls * docs(backend): record loader and control hardening * docs(backend): unify loader and selector trust boundary * test(config): align resource-limit regressions with constructor validation * test(config): keep bifactor objective fixture valid * fix(test): match auto-fit Rust authority error text The merge with main kept the pre-helper regex from #865 after _require_auto_fit_resolved_to_rust started raising "fit auto backend must resolve to rust". Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * fix(diagnostics): trust fold counts before budget products dimensionality_diagnostics still multiplied untrusted NumPy k_folds and added untrusted seed offsets, so uint8(32)*32 wrapped past the fit-budget cap and uint8(250)+6 wrapped to 0. Store built-in ints the same way seed/verbose already do. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * test(config): use raw regex literals in compatibility checks * fix(diagnostics): trust fit-diagnostic integer controls fit_diagnostics still coerced parameter_count with int() and left m2_q_* untrusted, so a hostile __index__ object could execute during AIC/BIC arithmetic. Marshal those controls through _trusted_integer the same way seed/verbose already do. Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> * test(backend): document import failure fixture * test(backend): lock reference guidance contract * fix(adr): preserve accepted backend decision * fix(docs): distinguish CLI and Python reference paths * fix(cli): point NumPy parity users to --reference * test(runtime): align fail-closed reference contract --------- Co-authored-by: Cursor Agent <cursoragent@cursor.com> Co-authored-by: Seongho Bae <seonghobae@users.noreply.github.com> Co-authored-by: opencode-agent[bot] <219766164+opencode-agent[bot]@users.noreply.github.com> Co-authored-by: Claude <noreply@anthropic.com>

seonghobae and others added 9 commits August 14, 2026 10:13

test(docs): pin Claude runtime support contract

154c644

docs: align Claude guidance with fail-closed runtime

2de7ef1

test(docs): normalize Markdown wrapping in runtime contract

65f2f0c

test(docs): reject marginal fallback claim

2640398

revert: keep runtime guidance lane scoped

1193778

test(docs): require machine-readable runtime contract

bad0e9f

docs: publish machine-readable runtime contract

09dcd09

Merge branch 'main' into fix/claude-runtime-contract-621

5c349bc

cursor Bot requested a review from seonghobae August 16, 2026 16:23

seonghobae marked this pull request as ready for review August 16, 2026 16:24

seonghobae enabled auto-merge (squash) August 16, 2026 16:33

cursor Bot commented Aug 16, 2026

View reviewed changes

cursor Bot mentioned this pull request Aug 16, 2026

fix: lock leftover auto-backend surfaces to fail-closed Rust #946

Closed

seonghobae closed this Aug 16, 2026

auto-merge was automatically disabled August 16, 2026 16:38
Pull request was closed

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docs: lock buyer-facing auto backend to fail-closed Rust - #945

docs: lock buyer-facing auto backend to fail-closed Rust#945
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cursor Bot commented Aug 16, 2026

Scope

What a purchaser should do

Machine-readable contract (unchanged)

Verification

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Verdict: REQUEST_CHANGES (posted as COMMENT; GitHub rejects REQUEST_CHANGES on cursor[bot] PRs)

Blocking leftovers (same defect class)

Residual product gap (not introduced here)

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