diff --git a/CHANGELOG.md b/CHANGELOG.md
index b16c5b7..932261b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -130,6 +130,7 @@ This project uses a Keep a Changelog-style structure. Until a tagged release is
 - Additional WCAG requirement IDs used by `jp-public-web` are accepted by screening validation.
 - Formal claim blockers are separated from auxiliary screening candidates.
 - Public report visibility (`report --visibility public`) now withholds every target host that the Web network guard refuses, and records the reason in the redaction manifest. This adds IPv4-mapped, NAT64, 6to4 and site-local IPv6 forms, `192.88.99.0/24`, and `*.localhost` / `*.localdomain` names. Earlier builds kept some of these hosts; regenerate public reports made with them and complete publication review again.
+- Registering or validating artifact paths that differ only in letter case is now rejected as a duplicate on macOS as well as Windows, because the default macOS filesystem is case-insensitive. Symlink, junction and containment checks are unchanged. A case-sensitive macOS volume can report a false duplicate; that is deliberate.
 
 ## Compatibility notes
 
diff --git a/release-files.json b/release-files.json
index a7247ab..13cd3d6 100644
--- a/release-files.json
+++ b/release-files.json
@@ -346,6 +346,7 @@
     "tests/agent-role-contracts.test.mjs",
     "tests/architecture-doc.test.mjs",
     "tests/artifact-authoring.test.mjs",
+    "tests/artifact-path-identity.test.mjs",
     "tests/assessment-output-contract.test.mjs",
     "tests/assessment-review-provenance.test.mjs",
     "tests/attestation-verifier.test.mjs",
diff --git a/shared/skill/scripts/lib/audit-run-validation.mjs b/shared/skill/scripts/lib/audit-run-validation.mjs
index 53d47e1..8c49a4a 100644
--- a/shared/skill/scripts/lib/audit-run-validation.mjs
+++ b/shared/skill/scripts/lib/audit-run-validation.mjs
@@ -10,7 +10,7 @@ import { validateParticipantBindings, collectParticipantEvidence } from "./parti
 import { validateDeclaredChangeBindings, collectDeclaredChangeEvidence } from "./declared-change.mjs";
 import { collectFixExecutionEvidence } from "./fix-execution-evidence.mjs";
 import { targetBindingErrors } from "./run-targets.mjs";
-import { pathKey, parseJsonBytes, readStableFile, assertStableFile, resolveInside } from "./safe-file-io.mjs";
+import { artifactPathKey, parseJsonBytes, readStableFile, assertStableFile, resolveInside } from "./safe-file-io.mjs";
 import { defaultSkillRoot, loadAuditResources } from "./audit-resources.mjs";
 import { auditRunRegistryCompatibility, auditRunEnvelopeCompatibility } from "./orchestration-contracts.mjs";
 import { artifactRootFor, validateArtifact, registeredArtifactPath, canonicalPermissions, remediationPermissionError, validateRegisteredArtifactEntries, validateArtifactEnvelopeSemantics, validateHumanQueueBindings, validateScreeningProfileBindings, validateDeclaredHumanBindings, validateRemediationBindings } from "./audit-artifact-validation.mjs";
@@ -158,7 +158,7 @@ export function validateAuditRun(run, { skillRoot = defaultSkillRoot, runFile, r
     if (!artifactRoot) continue;
     try {
       const file = registeredArtifactPath(artifactRoot, entry);
-      const canonicalPath = pathKey(file);
+      const canonicalPath = artifactPathKey(file);
       if (canonicalArtifactPaths.has(canonicalPath)) errors.push(`Duplicate canonical artifact path: ${String(entry?.path)}.`);
       canonicalArtifactPaths.add(canonicalPath);
       const snapshot = readArtifactFile(file, { label: `registered artifact ${String(entry?.artifact_id)}` });
diff --git a/shared/skill/scripts/lib/audit-run.mjs b/shared/skill/scripts/lib/audit-run.mjs
index 4bfd722..78138ba 100644
--- a/shared/skill/scripts/lib/audit-run.mjs
+++ b/shared/skill/scripts/lib/audit-run.mjs
@@ -16,7 +16,7 @@ import { networkPolicyErrors } from "./network-policy.mjs";
 import { afterChangeRun } from "./declared-change.mjs";
 import { collectFixExecutionEvidence } from "./fix-execution-evidence.mjs";
 import { targetInventoryErrors, targetBindingErrors, checkLocalRunTargets, consumeRunTargetCheck, checkRunTargets } from "./run-targets.mjs";
-import { pathKey, isWithinPath, hasTraversal, inspectRealComponents, parseJsonBytes, readStableFile, assertStableFile, resolveInside } from "./safe-file-io.mjs";
+import { artifactPathKey, isWithinPath, hasTraversal, inspectRealComponents, parseJsonBytes, readStableFile, assertStableFile, resolveInside } from "./safe-file-io.mjs";
 import { defaultSkillRoot, loadAuditResources } from "./audit-resources.mjs";
 import { compareText } from "./text-order.mjs";
 import { roleFor, validateArtifact, registeredArtifactPath, canonicalPermissions, remediationPermissionError, validateFixHandoffBinding, validateChangeRecordAuthorizationBinding, assertCurrentOperationalRun } from "./audit-artifact-validation.mjs";
@@ -173,7 +173,7 @@ export function registerArtifact(run, artifact, options = {}) {
   if (relativeSegments.includes(".fix-consumption") || relativeSegments.some((segment) => segment.includes("pending-change-record"))) {
     throw new Error(`Internal fixer runtime evidence is not registerable as a completed artifact: ${relativePath}`);
   }
-  if (run.artifacts.some((entry) => pathKey(registeredArtifactPath(validation.artifactRoot, entry)) === pathKey(artifactPath))) {
+  if (run.artifacts.some((entry) => artifactPathKey(registeredArtifactPath(validation.artifactRoot, entry)) === artifactPathKey(artifactPath))) {
     throw new Error(`Duplicate artifact path: ${relativePath}`);
   }
   const snapshot = readStableFile(artifactPath, { label: "artifact file" });
diff --git a/shared/skill/scripts/lib/safe-file-io.mjs b/shared/skill/scripts/lib/safe-file-io.mjs
index b4e7dae..3bb6a30 100644
--- a/shared/skill/scripts/lib/safe-file-io.mjs
+++ b/shared/skill/scripts/lib/safe-file-io.mjs
@@ -11,6 +11,11 @@ export function pathKey(value) {
   return process.platform === "win32" ? normalized.toLowerCase() : normalized;
 }
 
+export function artifactPathKey(value, platform = process.platform) {
+  const normalized = path.normalize(path.resolve(value));
+  return platform === "win32" || platform === "darwin" ? normalized.toLowerCase() : normalized;
+}
+
 export function samePath(left, right) {
   return pathKey(left) === pathKey(right);
 }
diff --git a/tests/artifact-path-identity.test.mjs b/tests/artifact-path-identity.test.mjs
new file mode 100644
index 0000000..cb7f3db
--- /dev/null
+++ b/tests/artifact-path-identity.test.mjs
@@ -0,0 +1,31 @@
+import assert from "node:assert/strict";
+import path from "node:path";
+import test from "node:test";
+import { artifactPathKey, pathKey, samePath } from "../codex/skills/information-accessibility-practice/scripts/lib/safe-file-io.mjs";
+
+for (const platform of ["darwin", "win32", "linux"]) {
+  test(`artifact path identity ${platform === "linux" ? "preserves" : "folds"} case on ${platform}`, () => {
+    const upper = artifactPathKey("artifacts/Report.json", platform);
+    const lower = artifactPathKey("artifacts/report.json", platform);
+    if (platform === "linux") assert.notEqual(upper, lower);
+    else assert.equal(upper, lower);
+    assert.equal(upper, artifactPathKey(path.resolve("artifacts/Report.json"), platform));
+  });
+}
+
+test("artifact path identity defaults to the current platform", () => {
+  assert.equal(artifactPathKey("artifacts/Report.json"), artifactPathKey("artifacts/Report.json", process.platform));
+});
+
+test("path safety comparisons preserve case on darwin", () => {
+  const descriptor = Object.getOwnPropertyDescriptor(process, "platform");
+  try {
+    Object.defineProperty(process, "platform", { value: "darwin" });
+    assert.notEqual(pathKey("artifacts/Report.json"), pathKey("artifacts/report.json"));
+    assert.equal(samePath("artifacts/Report.json", "artifacts/report.json"), false);
+    assert.equal(samePath("artifacts/Report.json", path.resolve("artifacts/Report.json")), true);
+    assert.equal(artifactPathKey("artifacts/Report.json"), artifactPathKey("artifacts/report.json"));
+  } finally {
+    Object.defineProperty(process, "platform", descriptor);
+  }
+});