SCRIP-CORPUS-082: guard VAR replay against Header provider drift

corpus/candidates/darwin-origin-species-rachinsky-1864-ru-var-provider-drift.md

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+# Darwin/Rachinsky 1864 — `{{ВАР}}` provider-drift guard
+
+This source-free companion records why Scriptorium does **not** silently bind whatever `Module:Header` happens to be live when replaying the unresolved `{{ВАР}}` shape.
+
+The previously reviewed evidence pins Russian Wikisource `Шаблон:ВАР/Документация@5711068` and `Модуль:Дореформенная орфография@5721277`. The latter delegates non-Page title classification to `Module:Header.parse_title(..., "isPRS")` and selects one of the two arguments from that result.
+
+Fresh provider evidence on 2026-09-24 shows `Модуль:Header@5746249`, last edited 2026-09-10 — later than the pinned VAR implementation module. A Russian Wikisource forum discussion on 2026-09-08 explicitly asked whether `{{ВАР}}` had broken after Header-related work and noted that the small orthography module depends on Header for page-title parsing. Scriptorium records that as a **drift risk**, not as proof that production Wikisource was broken.
+
+For the retained Darwin mainspace title `О происхождении видов (Дарвин; Рачинский)/1864 (ВТ:Ё)`, the observed Header rule at revision `5746249` parses the edition segment as `1864 (ВТ:Ё)` and yields `isPRS=false`. If the pinned VAR module's non-Page branch is reached under that observed rule, it therefore selects the **second (modern) argument**.
+
+That narrow classification replay is not a complete `{{ВАР}}` replay. The live `Шаблон:ВАР` root is still unbound; Header's MediaWiki SHA-1 and execution-relevant nested closure are not frozen; no offline/version-pinned MediaWiki runtime is established; historical transclusion is not inferred; and the render profile/backlog is unchanged. `ВАР` remains unresolved at **388** candidate invocations.
+
+The source-free evidence contract is [`source-edition-traces/darwin-origin-species-rachinsky-1864-ru.var-provider-drift-evidence.json`](source-edition-traces/darwin-origin-species-rachinsky-1864-ru.var-provider-drift-evidence.json), SHA-256 `6126adbc966c7120ca487fb940bd0e01aafa0d7350d332e6422edbf8b3846cb8`.
+
+The next bounded replay step must deliberately choose one coherent snapshot, freeze exact `Шаблон:ВАР`, `Модуль:Дореформенная орфография` and `Module:Header` identities including MediaWiki SHA-1 plus the execution-relevant nested closure, and only then replay the candidate invocation. A later live descendant must not be substituted as if it were historical provenance.
+
+No source text, Page wikitext, template argument values, rendered prose, OCR or scan bytes are published here. Renderer/body/>=300k/FantLab-input/M2 gates remain unchanged; M2 stays **0/5**.

corpus/candidates/source-edition-traces/darwin-origin-species-rachinsky-1864-ru.var-provider-drift-evidence.json

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+{
+  "admitted_for_calibration": false,
+  "candidate_id": "darwin-origin-species-rachinsky-1864-ru",
+  "dependency_boundary": {
+    "full_var_candidate_branch_replayed": false,
+    "historical_transclusion_proven": false,
+    "implementation_module_revision_frozen_for_this_chain": true,
+    "module_header_mediawiki_sha1_frozen": false,
+    "module_header_revision_observed": true,
+    "nested_dependency_closure_frozen": false,
+    "offline_version_pinned_runtime_proven": false,
+    "reason": "the Header revision and title-classification rule are observed, but the live template root, Header SHA-1 and complete replay-time closure are not yet bound into one executable snapshot",
+    "template_root_revision_frozen": false
+  },
+  "diagnostic_ready": false,
+  "evidence_sha256": "6126adbc966c7120ca487fb940bd0e01aafa0d7350d332e6422edbf8b3846cb8",
+  "fantlab_source_edition_match": "unknown",
+  "inter_page_composition_frozen": false,
+  "literary_body_count_and_digests_frozen": false,
+  "m2_parity_admissible": false,
+  "minimum_300k_proved": false,
+  "observed_header_rule_replay": {
+    "candidate_namespace": "mainspace",
+    "candidate_title": "О происхождении видов (Дарвин; Рачинский)/1864 (ВТ:Ё)",
+    "edition_segment": "1864 (ВТ:Ё)",
+    "function": "parse_title(..., \"isPRS\")",
+    "header_revision_id": 5746249,
+    "isPRS": false,
+    "scope": "deterministic_replay_of_the_observed_Header_title_classification_rule_only",
+    "selected_variant_if_module_branch_is_reached": "second_parameter_modern"
+  },
+  "prior_evidence": {
+    "documentation_revision_id": 5711068,
+    "evidence_sha256": "321ced32bb7ffc75829b6fbb5255bce3243641a80c21ad4e2b7bb7a25138502d",
+    "implementation_module_revision_id": 5721277,
+    "schema_version": "scriptorium-darwin-var-documentation-evidence-v1"
+  },
+  "promotion_decision": {
+    "backlog_item_removed": false,
+    "effective_backlog_changed": false,
+    "next_evidence_required": "choose one explicit coherent replay snapshot, freeze exact Шаблон:ВАР plus Модуль:Дореформенная орфография plus Module:Header identities including MediaWiki SHA-1 and the execution-relevant nested closure, then replay the candidate mainspace invocation without substituting later live descendants",
+    "reason": "provider drift evidence narrows snapshot selection but does not prove a complete deterministic VAR invocation replay",
+    "render_profile_rule_promoted": false
+  },
+  "provider_drift_observation": {
+    "community_warning": {
+      "claim_scope": "provider_drift_risk_not_a_proven_runtime_failure",
+      "discussion_date": "2026-09-08",
+      "forum_url": "https://ru.wikisource.org/wiki/Викитека:Форум",
+      "observation": "Wikisource editors explicitly raised whether template VAR had broken after Header-related changes and noted that the small pre-reform module delegates page-title parsing to Header."
+    },
+    "decision_effect": "do_not_silently_bind_a_future_live_Header_as_replay_equivalence; select_and_record_an_explicit_coherent_snapshot_before_full_VAR_replay",
+    "observed_header": {
+      "permanent_url": "https://ru.wikisource.org/w/index.php?title=Модуль:Header&oldid=5746249",
+      "relationship_to_pinned_var_module": "later_revision",
+      "revision_date": "2026-09-10",
+      "revision_id": 5746249,
+      "title": "Модуль:Header"
+    },
+    "provider": "Russian Wikisource"
+  },
+  "renderer_implementation_ready": false,
+  "renderer_semantics_complete": false,
+  "researched_on": "2026-09-24",
+  "schema_version": "scriptorium-darwin-var-provider-drift-evidence-v1",
+  "source_text_included": false
+}

project/CHANGELOG.d/SCRIP-CORPUS-082.md

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+# SCRIP-CORPUS-082 — Darwin/Rachinsky `{{ВАР}}` provider-drift guard
+
+- Re-oriented from `master@bd291227733155672f8dd6d9d3a634348615cdbe`; no open review-ready PR or interrupted unit preempted normal P2 corpus/provenance selection.
+- Fresh Russian Wikisource evidence materially changes the next `{{ВАР}}` replay decision: `Модуль:Header@5746249` is dated 2026-09-10, later than the already pinned `Модуль:Дореформенная орфография@5721277`, and a 2026-09-08 Wikisource forum discussion explicitly raised possible `{{ВАР}}` breakage after Header-related changes. This is recorded as provider-drift risk, not as proof of a runtime failure.
+- Added deterministic source-free evidence `scriptorium-darwin-var-provider-drift-evidence-v1`, SHA-256 `6126adbc966c7120ca487fb940bd0e01aafa0d7350d332e6422edbf8b3846cb8`.
+- Replayed only the observed Header title-classification rule for the retained Darwin mainspace title `О происхождении видов (Дарвин; Рачинский)/1864 (ВТ:Ё)`: edition segment `1864 (ВТ:Ё)` yields `isPRS=false`, therefore the pinned VAR module would select the second/modern argument if that non-Page branch is reached.
+- Kept `Шаблон:ВАР` root identity, Header MediaWiki SHA-1, nested replay closure, full VAR invocation replay, historical transclusion and offline/version-pinned runtime explicitly unfrozen. No render-profile/backlog promotion occurs; `ВАР` stays unresolved at 388 occurrences and effective backlog counts do not change.
+- Added focused regressions and a public source-free provider-drift companion. Renderer/body/>=300k/FantLab-input gates stay closed; M2 remains 0/5.
+- Next evidence must deliberately select one coherent replay snapshot and freeze exact template/module/Header identities plus execution-relevant closure before a full candidate invocation replay. A later live descendant must not be substituted as historical provenance.
+
+Issue: #253. Draft PR: #254 (REVIEW_PENDING).