The scanners cap by truncating: they return findings, so reading a prefix costs
detection in the tail and nothing else. The three transform surfaces return
*content*, where the same move is not available — a shortened document is silent
data loss, and a transformed prefix followed by an untransformed tail is a
bypass, since the attacker chooses where in the document the payload sits.
So they fail secure instead. Above MAX_INPUT_CHARS (1 000 000) sanitize, fence
and neutralize raise OversizeInputError. sanitize is step 1 of prepare_input and
only ever removes, so that one refusal bounds the whole input path.
OversizeInputError subclasses ContractViolation: a pipeline already bracketing
its quarantined stage keeps failing closed rather than meeting a type it has
never heard of. It inherits the alert-routable property too — sizes in the
message, refusing surface in details, no input in either.
Invariant now pinned across all three: returned text is always fully
transformed, or not returned at all.
Still uncapped and recorded in LIMITATIONS: scan_active_content called directly
(through scan_output it inherits that cap) and the okf link graph. Both are
detection-shaped, so truncate-and-flag transfers unchanged — mechanical, not
policy.
699 tests (+23), coverage 128/128 + 6/6, ReDoS sweep 0 candidates / 150.
Pre-release hardening from an independent adversarial review; each fixed
test-first (failing test -> fix -> green). 214 tests pass.
- entropy (M1): decode-and-rescan now runs BEFORE false-positive suppression,
so an SRI/media-prefixed injection blob is still decoded and lexicon-rescanned.
Suppression gates only the entropy finding, never the decode.
- output/disposition (M3): the invisible-carrier invariant now holds on the
persist gate. scan_output flags zero-width/BIDI presence and disposition
treats those + lexicon:unicode-tags-present as any-tier carriers, so a carrier
in model output fails secure even under a trusted policy.
- contract (M2): assert_credential_allowlist catches a bare <PROVIDER>_KEY
(e.g. STRIPE_KEY) that the old regex silently missed (fail-open). Deliberately
broad: also flags PARTITION_KEY/SORT_KEY as loud, allowlistable FPs -- fail-loud
beats fail-silent for an isolation control.
- disposition (m6): guard runs decide inside its guarded block -> total
fail-closed even on a malformed report.
- output (m4): egress placeholder suppression anchors word markers (example,
todo, ...) to a word boundary, closing a fail-open where a real secret merely
containing such a word was suppressed.
Docs: CHANGELOG Security subsection; README honest-limit for lexicon dedup (m5,
documented tradeoff, not fixed).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HyRCQMocjZ6SmSQ6JidJ2k
Module 9 of the build order — the differentiator. Where the other modules
detect and report, these are pure functions that ENFORCE an invariant and
raise: the write-time analogue of runtime least-privilege. They harden the
call a pipeline makes around its quarantined transform; the library makes no
model call itself.
Three asserts, matching the reusable-contract checklist (BRIEF §6 steps 3-4):
- assert_tool_less(request): the model request carries no tool surface —
tools/functions/tool_choice/function_call/mcp_servers, populated. Covers
both Anthropic and OpenAI request shapes; empty/None is genuinely tool-less.
- assert_credential_allowlist(env, allowed): the process env holds no
credential beyond this stage's allowlist (subset = least-privilege; the
enrichment stage sees only the model key, never the publish credential).
- scoped_env(env, allowed): the isolation primitive — strips off-allowlist
credentials, keeps PATH etc.; the assert then passes by construction.
Generalized from claude-code-llm-wiki tools/wiki_ingest/enrich.py
assert_quarantine (a pipeline-specific gate) into framework-agnostic pieces.
Two deliberate safety choices inherited from the reference: credential
detection is name-based (env VALUES are never read — value-scanning is the
output module's job); and a raised ContractViolation names only the offending
KEY, never a value, so it is safe to route to an alert channel (minimal-alert,
BRIEF §6 step 8). CREDENTIAL_NAME_RE ported verbatim from the proven reference.
23 new tests; 161 green total.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HyRCQMocjZ6SmSQ6JidJ2k
