diff --git a/docs/specs/2026-08-04-async-report-validation-reads.md b/docs/specs/2026-08-04-async-report-validation-reads.md
new file mode 100644
index 0000000..956bd49
--- /dev/null
+++ b/docs/specs/2026-08-04-async-report-validation-reads.md
@@ -0,0 +1,105 @@
+# Read report validation artifacts asynchronously
+
+## Traceability
+
+- Spec ID: async-report-validation-reads
+- Status: Implemented
+
+## Intent
+
+Keep report validation non-blocking while it loads generated Markdown, findings,
+and HTML artifacts. The renderer already exposes an asynchronous validation
+pipeline, so independent artifact reads should use the promise-based filesystem
+API and complete together without changing report contents or validation
+decisions.
+
+## Acceptance Scenarios
+
+- **ARV-AC-1 (asynchronous reads):** Markdown and HTML report validation reads
+  generated artifacts through the promise-based filesystem API, with no
+  synchronous file reads remaining in `render-report.mjs`.
+- **ARV-AC-2 (bounded concurrency):** The independent findings, Markdown, and
+  optional HTML reads begin through one bounded `Promise.all` operation; Markdown
+  mode does not require an HTML artifact.
+- **ARV-AC-3 (output compatibility):** Rendering preserves the existing artifact
+  names, contents, ordering in the renderer result, and selected validation
+  checks for Markdown and HTML modes.
+- **ARV-AC-4 (failure safety):** An unreadable required artifact still rejects
+  validation before the staged run is published, retaining the existing atomic
+  publication boundary.
+
+## Non-goals
+
+- Change report schemas, renderer output, validation rules, or reader-visible
+  copy.
+- Parallelize artifact writes, Canvas validation, or publication and rollback.
+- Change CLI arguments, output locations, run-directory allocation, or supported
+  hosts.
+- Add caching, streaming, or performance claims that are not measured by this
+  change.
+
+## Plan and Tasks
+
+1. Update `scripts/harness-analysis/render-report.mjs` to import `readFile` from
+   `node:fs/promises` and remove its synchronous read dependency.
+2. Read findings, Markdown, and the optional HTML artifact through one
+   `Promise.all` while preserving the current validation calls and artifact
+   ordering.
+3. Run focused HTML coverage and the complete report-render test file.
+4. Run the full repository suite, separately verify loopback preview tests when
+   sandbox networking blocks them, and check the final diff for whitespace
+   errors.
+
+## Test and Review Evidence
+
+- **ARV-AC-1/ARV-AC-2:** focused diff review confirms `readFileSync` is removed
+  from `render-report.mjs` and the three independent reads share one
+  `Promise.all` operation.
+- **ARV-AC-3:** run
+  `node --test --test-name-pattern="render command writes disk-openable HTML artifacts|HTML mode validates canonical compact" test/harness-report-render-cli.test.mjs`.
+- **ARV-AC-3:** run
+  `node --test test/harness-report-render-cli.test.mjs`; its staging,
+  validation, output-location, Markdown, HTML, and publication coverage must
+  remain green.
+- **ARV-AC-4:** focused control-flow review must confirm artifact reads remain
+  inside staged validation and `publishStagedRun` is reached only after
+  validation succeeds.
+- Regression gate: run `npm test`. If sandbox loopback restrictions produce
+  `listen EPERM`, rerun `node --test test/preview-servers.test.mjs` with local
+  loopback permission and record both results without presenting the sandbox
+  result as a product failure.
+- Documentation gate: regenerate the routing graph with
+  `node scripts/doc-link-graph/cli.mjs skills/better-harness`, then run
+  `node --test test/doc-link-graph.test.mjs`.
+- Diff gate: run `git diff --check` and confirm the change remains limited to
+  the renderer and this Spec.
+- Primary risk: concurrent reads can change which filesystem error is observed
+  first when multiple required staged artifacts are simultaneously unreadable.
+  Normal rendering creates all required artifacts before validation, and the
+  staged publication boundary prevents partial output from replacing a prior
+  run.
+
+### Observed Evidence (2026-08-04)
+
+- **ARV-AC-1/ARV-AC-2:** `render-report.mjs` now imports `readFile` from
+  `node:fs/promises`; `readFileSync` is absent, and findings, Markdown, and the
+  optional HTML artifact are read by one `Promise.all`.
+- **ARV-AC-3:** the two focused HTML tests passed 2/2, and
+  `node --test test/harness-report-render-cli.test.mjs` passed 32/32 across
+  Canvas, Markdown, and HTML rendering contracts.
+- **ARV-AC-4:** the existing control flow still writes into `stageDir`, validates
+  that staging directory, throws on failed validation, and invokes
+  `publishStagedRun` only after the validation gate passes.
+- Full regression: `npm test` ran 1,148 tests; 1,145 passed and three loopback
+  preview tests failed with sandbox-only `listen EPERM`. The bounded rerun
+  `node --test test/preview-servers.test.mjs` passed 8/8 with loopback
+  permission.
+- Documentation gate: the routing graph generator reported 35 files and 51
+  links with no generated diff; `node --test test/doc-link-graph.test.mjs`
+  passed 6/6.
+- Package gate: the default `npm run pack:verify` attempt was blocked by an
+  unwritable user npm cache. Re-running with the isolated task cache
+  `/tmp/better-harness-npm-cache-20260804` passed with 395 npm entries and 417
+  runtime ZIP entries; no user cache permissions were changed.
+- `git diff --check` passed. The working tree remains unstaged so the reviewer
+  can inspect the renderer and Spec together before commit.
diff --git a/scripts/harness-analysis/render-report.mjs b/scripts/harness-analysis/render-report.mjs
index 3c8f3dc..4d76848 100644
--- a/scripts/harness-analysis/render-report.mjs
+++ b/scripts/harness-analysis/render-report.mjs
@@ -1,7 +1,7 @@
 #!/usr/bin/env node
 
-import { existsSync, readFileSync } from "node:fs";
-import { mkdir, mkdtemp, readdir, realpath, rename, rm, writeFile } from "node:fs/promises";
+import { existsSync } from "node:fs";
+import { mkdir, mkdtemp, readFile, readdir, realpath, rename, rm, writeFile } from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
 
@@ -288,9 +288,13 @@ async function validateArtifacts({ reportData, artifactDir, runDir, artifacts, o
     checks.push(...result.checks);
   } else {
     const findingsPath = path.join(artifactDir, "findings.json");
-    const findingsText = readFileSync(findingsPath, "utf8");
     const reportPath = path.join(artifactDir, "report.md");
-    const reportText = readFileSync(reportPath, "utf8");
+    const htmlPath = reportData.mode === "html" ? path.join(artifactDir, "report.html") : null;
+    const [findingsText, reportText, htmlText] = await Promise.all([
+      readFile(findingsPath, "utf8"),
+      readFile(reportPath, "utf8"),
+      htmlPath ? readFile(htmlPath, "utf8") : Promise.resolve(null),
+    ]);
     if (!isAgentWorkLoopReport(reportData)) {
       const reportQuality = evaluateHarnessReportQuality(reportText);
       checks.push(checkResult("report-quality", reportQuality.status, reportQuality.errors, reportQuality.warnings, reportQuality.summary));
@@ -300,7 +304,7 @@ async function validateArtifacts({ reportData, artifactDir, runDir, artifacts, o
     }));
     if (reportData.mode === "html") {
       checks.push(evaluateHtmlReport(
-        readFileSync(path.join(artifactDir, "report.html"), "utf8"),
+        htmlText,
         reportData,
         { findingsPath: path.join(runDir, "findings.json") },
       ));