diff --git a/docs/plans/2026-03-09-spar-wasm-browser-rendering.md b/docs/historical/2026-03-09-spar-wasm-browser-rendering.md
similarity index 100%
rename from docs/plans/2026-03-09-spar-wasm-browser-rendering.md
rename to docs/historical/2026-03-09-spar-wasm-browser-rendering.md
diff --git a/docs/plans/2026-03-10-commit-traceability-design.md b/docs/historical/2026-03-10-commit-traceability-design.md
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rename from docs/plans/2026-03-10-commit-traceability-design.md
rename to docs/historical/2026-03-10-commit-traceability-design.md
diff --git a/docs/plans/2026-03-10-commit-traceability-plan.md b/docs/historical/2026-03-10-commit-traceability-plan.md
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rename from docs/plans/2026-03-10-commit-traceability-plan.md
rename to docs/historical/2026-03-10-commit-traceability-plan.md
diff --git a/docs/plans/2026-03-10-cross-repo-linking-design.md b/docs/historical/2026-03-10-cross-repo-linking-design.md
similarity index 100%
rename from docs/plans/2026-03-10-cross-repo-linking-design.md
rename to docs/historical/2026-03-10-cross-repo-linking-design.md
diff --git a/docs/plans/2026-03-10-cross-repo-linking-plan.md b/docs/historical/2026-03-10-cross-repo-linking-plan.md
similarity index 100%
rename from docs/plans/2026-03-10-cross-repo-linking-plan.md
rename to docs/historical/2026-03-10-cross-repo-linking-plan.md
diff --git a/docs/plans/2026-03-10-unidirectional-externals-design.md b/docs/historical/2026-03-10-unidirectional-externals-design.md
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rename from docs/plans/2026-03-10-unidirectional-externals-design.md
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diff --git a/docs/plans/2026-03-10-unidirectional-externals-plan.md b/docs/historical/2026-03-10-unidirectional-externals-plan.md
similarity index 100%
rename from docs/plans/2026-03-10-unidirectional-externals-plan.md
rename to docs/historical/2026-03-10-unidirectional-externals-plan.md
diff --git a/docs/plans/2026-03-14-phase3-parallel-workstreams-design.md b/docs/historical/2026-03-14-phase3-parallel-workstreams-design.md
similarity index 100%
rename from docs/plans/2026-03-14-phase3-parallel-workstreams-design.md
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diff --git a/docs/plans/2026-03-15-release-v0.1.0-plan.md b/docs/historical/2026-03-15-release-v0.1.0-plan.md
similarity index 100%
rename from docs/plans/2026-03-15-release-v0.1.0-plan.md
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diff --git a/docs/plans/2026-03-16-coverage-gap-analysis.md b/docs/historical/2026-03-16-coverage-gap-analysis.md
similarity index 100%
rename from docs/plans/2026-03-16-coverage-gap-analysis.md
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diff --git a/docs/plans/2026-03-16-formal-verification-completion.md b/docs/historical/2026-03-16-formal-verification-completion.md
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rename from docs/plans/2026-03-16-formal-verification-completion.md
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diff --git a/docs/plans/2026-03-16-rowan-salsa-completion.md b/docs/historical/2026-03-16-rowan-salsa-completion.md
similarity index 100%
rename from docs/plans/2026-03-16-rowan-salsa-completion.md
rename to docs/historical/2026-03-16-rowan-salsa-completion.md
diff --git a/docs/plans/2026-03-16-stpa-sec-analysis.md b/docs/historical/2026-03-16-stpa-sec-analysis.md
similarity index 100%
rename from docs/plans/2026-03-16-stpa-sec-analysis.md
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diff --git a/docs/plans/2026-03-21-baseline-scoped-validation-design.md b/docs/historical/2026-03-21-baseline-scoped-validation-design.md
similarity index 100%
rename from docs/plans/2026-03-21-baseline-scoped-validation-design.md
rename to docs/historical/2026-03-21-baseline-scoped-validation-design.md
diff --git a/docs/plans/2026-03-21-lsp-salsa-architecture-design.md b/docs/historical/2026-03-21-lsp-salsa-architecture-design.md
similarity index 100%
rename from docs/plans/2026-03-21-lsp-salsa-architecture-design.md
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diff --git a/docs/audit-report.md b/docs/historical/audit-report.md
similarity index 100%
rename from docs/audit-report.md
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diff --git a/docs/design/rivet-cli-gaps-2026-04.md b/docs/historical/rivet-cli-gaps-2026-04.md
similarity index 100%
rename from docs/design/rivet-cli-gaps-2026-04.md
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diff --git a/docs/what-is-rivet.md b/docs/what-is-rivet.md
index 44ae95e6..ced52270 100644
--- a/docs/what-is-rivet.md
+++ b/docs/what-is-rivet.md
@@ -382,8 +382,9 @@ server-side-validated before it lands.
 - **Polarion / ReqIF fidelity audit.**
   [docs/design/polarion-reqif-fidelity.md](design/polarion-reqif-fidelity.md).
 - **Roadmap.** [docs/roadmap.md](roadmap.md).
-- **Audit report.** [docs/audit-report.md](audit-report.md) — state
-  of doc-vs-reality after PR #171's audit.
+- **Audit report.** [docs/historical/audit-report.md](historical/audit-report.md)
+  — archived doc-vs-reality snapshot (2026-03-09). Superseded by
+  [docs/research/2026-05-19-docs-audit.md](research/2026-05-19-docs-audit.md).
 
 ---
 
diff --git a/rivet-core/src/doc_check.rs b/rivet-core/src/doc_check.rs
index 5cd3cb76..b0ef5fa5 100644
--- a/rivet-core/src/doc_check.rs
+++ b/rivet-core/src/doc_check.rs
@@ -134,10 +134,15 @@ pub struct DocFile {
 
 impl DocFile {
     pub fn new(rel_path: PathBuf, content: String) -> Self {
+        // `plans/` and `design/` are forward-looking; `historical/` is
+        // frozen archive (REQ-073/074). All three legitimately reference
+        // subcommands / artifact counts / IDs that have since changed,
+        // so they opt out of the existence-based invariants.
         let is_design_doc = content.contains("rivet-docs-check: design-doc-aspirational-ok")
-            || rel_path
-                .components()
-                .any(|c| c.as_os_str() == "plans" || c.as_os_str() == "design");
+            || rel_path.components().any(|c| {
+                let s = c.as_os_str();
+                s == "plans" || s == "design" || s == "historical"
+            });
         Self {
             rel_path,
             content,
@@ -1586,6 +1591,27 @@ mod tests {
         assert_eq!(v[0].file, PathBuf::from("README.md"));
     }
 
+    /// REQ-073/074: a file under `docs/historical/` is a frozen archive
+    /// snapshot and opts out of the existence-based invariants — same as
+    /// `plans/` and `design/` — without needing the explicit marker.
+    ///
+    /// rivet: verifies REQ-074
+    #[test]
+    fn historical_dir_is_design_doc_without_marker() {
+        assert!(
+            doc("docs/historical/old-plan.md", "Run `rivet discover`.").is_design_doc,
+            "docs/historical/ must be exempt from existence invariants"
+        );
+        assert!(
+            doc("docs/plans/p.md", "x").is_design_doc,
+            "docs/plans/ exemption must still hold"
+        );
+        assert!(
+            !doc("docs/getting-started.md", "x").is_design_doc,
+            "a normal reference doc must NOT be auto-exempt"
+        );
+    }
+
     #[test]
     fn subcommand_references_skip_design_doc() {
         let content = "<!-- rivet-docs-check: design-doc-aspirational-ok -->\n\