diff --git a/server/routes.js b/server/routes.js
index 0c6f334..4658f79 100644
--- a/server/routes.js
+++ b/server/routes.js
@@ -4140,6 +4140,32 @@ function reseedAgentsMd(existingContent, freshContent) {
   };
 }
 
+// #966: Distinctive H2 headings that only appear in QuadWork's seeded
+// `templates/CLAUDE.md`. A worktree CLAUDE.md is treated as QuadWork-seeded
+// (and therefore safe to refresh) ONLY when it contains ALL of these — a
+// project's own hand-authored CLAUDE.md (e.g. this repo's, whose H2s are
+// "What is QuadWork", "Tech Stack", …) won't, so it is never clobbered. These
+// three headings have been stable across template versions, so a file seeded
+// by an older template is still recognized.
+const SEEDED_CLAUDE_SIGNATURE = Object.freeze([
+  "Multi-Agent System",
+  "GitHub Workflow",
+  "Communication Rules",
+]);
+
+// #966: True only when `content` is a QuadWork-seeded CLAUDE.md — i.e. it
+// carries every heading in SEEDED_CLAUDE_SIGNATURE (case-insensitive,
+// whitespace-normalized, same comparison the merger uses). Empty/foreign
+// content returns false so reseed leaves it untouched. Pure — no I/O.
+function _isSeededClaudeMd(content) {
+  if (!content || !content.trim()) return false;
+  const norm = (s) => s.toLowerCase().replace(/\s+/g, " ").trim();
+  const headings = new Set(
+    _splitAgentsMdSections(content).blocks.map((b) => norm(b.heading))
+  );
+  return SEEDED_CLAUDE_SIGNATURE.every((h) => headings.has(norm(h)));
+}
+
 // #854: Extract the reviewer token path from a worktree's existing AGENTS.md
 // so the re-seed substitution preserves a custom path instead of resetting
 // it to the default. The re1/re2 seed renders:
@@ -4360,6 +4386,36 @@ function _performReseedWrites(project, cfg, opts = {}) {
     if (merged.preservedHeadings.length > 0) {
       preserved[agentKey] = merged.preservedHeadings;
     }
+
+    // #966: Refresh the worktree CLAUDE.md too — but ONLY when it is provably
+    // QuadWork-seeded, so a project's own hand-authored CLAUDE.md is never
+    // clobbered. Uses the same reseedAgentsMd merge (fresh template wins
+    // per-H2, operator-added H2 sections preserved). Missing or foreign
+    // CLAUDE.md is left byte-identical and recorded in `skipped`.
+    const claudeMd = path.join(wtDir, "CLAUDE.md");
+    if (!fs.existsSync(claudeMd)) {
+      skipped.push(`${agentKey}/CLAUDE.md (none)`);
+    } else {
+      let claudeExisting = "";
+      try { claudeExisting = fs.readFileSync(claudeMd, "utf-8"); } catch { claudeExisting = ""; }
+      if (!_isSeededClaudeMd(claudeExisting)) {
+        skipped.push(`${agentKey}/CLAUDE.md (not QuadWork-seeded)`);
+      } else {
+        const claudeSrc = path.join(TEMPLATES_DIR, "CLAUDE.md");
+        if (!fs.existsSync(claudeSrc)) {
+          skipped.push(`${agentKey}/CLAUDE.md (no template)`);
+        } else {
+          const freshClaude = fs.readFileSync(claudeSrc, "utf-8")
+            .replace(/\{\{project_name\}\}/g, dirName);
+          const mergedClaude = reseedAgentsMd(claudeExisting, freshClaude);
+          fs.writeFileSync(claudeMd, mergedClaude.content);
+          reseeded.push(`${agentKey}/CLAUDE.md`);
+          if (mergedClaude.preservedHeadings.length > 0) {
+            preserved[`${agentKey}/CLAUDE.md`] = mergedClaude.preservedHeadings;
+          }
+        }
+      }
+    }
   }
   return { reseeded, skipped, preserved };
 }
@@ -5101,6 +5157,8 @@ module.exports.isBatchActiveFromProgress = isBatchActiveFromProgress;
 // custom-section preservation contract is exercisable without spinning up a
 // real worktree. Pure function; no production callers outside this file.
 module.exports.reseedAgentsMd = reseedAgentsMd;
+// #966: expose the QuadWork-seeded CLAUDE.md predicate for unit tests.
+module.exports._isSeededClaudeMd = _isSeededClaudeMd;
 // #855: expose the per-agent target resolver + legacy-key map so the legacy
 // config (`reviewer1` / `reviewer2` / `t1..t3`) → canonical-template mapping
 // is exercisable without spinning up a real worktree. Pure helpers; no
diff --git a/server/routes.reseedClaudeMd.test.js b/server/routes.reseedClaudeMd.test.js
new file mode 100644
index 0000000..30219a3
--- /dev/null
+++ b/server/routes.reseedClaudeMd.test.js
@@ -0,0 +1,181 @@
+// #966: reseed must refresh a worktree's QuadWork-seeded CLAUDE.md alongside
+// AGENTS.md, but must NEVER clobber a project's own hand-authored CLAUDE.md.
+// Covers the pure `_isSeededClaudeMd` predicate plus the endpoint-level
+// behavior against temp worktrees:
+//   • seeded CLAUDE.md is refreshed and an operator-added H2 is preserved
+//   • foreign (hand-authored) CLAUDE.md is left byte-identical (skipped)
+//   • worktree with no CLAUDE.md is handled without error (skipped)
+//   • AGENTS.md reseed behavior is unchanged (still refreshed)
+//
+// Plain node:assert script — auto-discovered by the #836 runner. Run directly
+// with `node server/routes.reseedClaudeMd.test.js`.
+
+const assert = require("node:assert/strict");
+const fs = require("fs");
+const os = require("os");
+const path = require("path");
+const http = require("http");
+const crypto = require("crypto");
+
+const CONFIG_PATH = path.join(os.homedir(), ".quadwork", "config.json");
+const TEMPLATES_DIR = path.join(__dirname, "..", "templates");
+
+// ── Stub fs.readFileSync for CONFIG_PATH BEFORE requiring routes ──────────
+// (Same hermetic pattern as routes.reseedTokenPreservation.test.js.)
+const realReadFileSync = fs.readFileSync;
+let stubCfgJson = JSON.stringify({ projects: [] });
+fs.readFileSync = function stubReadFileSync(p, ...rest) {
+  if (p === CONFIG_PATH) return stubCfgJson;
+  return realReadFileSync(p, ...rest);
+};
+
+const express = require("express");
+const routes = require("./routes");
+const { _isSeededClaudeMd } = routes;
+
+async function withServer(fn) {
+  const app = express();
+  app.use(express.json());
+  app.use(routes.router || routes);
+  await new Promise((resolve, reject) => {
+    const server = app.listen(0, "127.0.0.1", async () => {
+      const { port } = server.address();
+      try { await fn(`http://127.0.0.1:${port}`); resolve(); }
+      catch (e) { reject(e); }
+      finally { server.close(); }
+    });
+  });
+}
+
+function post(url, body) {
+  return new Promise((resolve, reject) => {
+    const u = new URL(url);
+    const data = JSON.stringify(body || {});
+    const req = http.request({
+      hostname: u.hostname, port: u.port, path: u.pathname, method: "POST",
+      headers: { "Content-Type": "application/json", "Content-Length": Buffer.byteLength(data) },
+    }, (res) => {
+      let chunks = "";
+      res.on("data", (c) => chunks += c);
+      res.on("end", () => {
+        try { resolve({ status: res.statusCode, body: JSON.parse(chunks || "{}") }); }
+        catch (e) { reject(new Error(`Non-JSON response (status ${res.statusCode}): ${chunks}`)); }
+      });
+    });
+    req.on("error", reject);
+    req.write(data);
+    req.end();
+  });
+}
+
+// A minimal but genuinely QuadWork-seeded CLAUDE.md: carries the signature
+// H2 set. (We use the real template rendered for `{{project_name}}`.)
+const CLAUDE_TEMPLATE = realReadFileSync(path.join(TEMPLATES_DIR, "CLAUDE.md"), "utf-8");
+
+// A project's OWN hand-authored CLAUDE.md — none of the signature headings.
+const FOREIGN_CLAUDE = `# Cool Project — Development Rules
+
+## What is Cool Project
+
+A bespoke tool. Nothing to do with the multi-agent template.
+
+## Tech Stack
+
+- Rust + wgpu
+
+## Git
+
+- Commit format: whatever you like
+`;
+
+// ── Pure predicate tests ─────────────────────────────────────────────────
+{
+  const rendered = CLAUDE_TEMPLATE.replace(/\{\{project_name\}\}/g, "demo");
+  assert.equal(_isSeededClaudeMd(rendered), true, "rendered template is recognized as seeded");
+  assert.equal(_isSeededClaudeMd(FOREIGN_CLAUDE), false, "hand-authored CLAUDE.md is not seeded");
+  assert.equal(_isSeededClaudeMd(""), false, "empty content is not seeded");
+  assert.equal(_isSeededClaudeMd(null), false, "null content is not seeded");
+  // A seeded file with an operator-added H2 is still recognized.
+  const withOperator = rendered + "\n## Project Notes\n- run make first\n";
+  assert.equal(_isSeededClaudeMd(withOperator), true, "operator H2 doesn't hide the signature");
+  // Missing even one signature heading → not seeded (fail-closed).
+  const missingOne = rendered.replace(/^## Communication Rules$/m, "## Chatting");
+  assert.equal(_isSeededClaudeMd(missingOne), false, "missing a signature heading → not seeded");
+}
+
+function makeTempProject(label, layout) {
+  // layout: { agentKey: { cwdName, agentsMd, claudeMd } } — omit a field to
+  // skip writing that file (simulates a worktree missing it).
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), `qw-966-${label}-`));
+  const workingDir = path.join(root, "proj");
+  fs.mkdirSync(workingDir, { recursive: true });
+  const agents = {};
+  for (const [agentKey, spec] of Object.entries(layout)) {
+    const cwd = path.join(root, spec.cwdName);
+    fs.mkdirSync(cwd, { recursive: true });
+    if (spec.agentsMd != null) fs.writeFileSync(path.join(cwd, "AGENTS.md"), spec.agentsMd);
+    if (spec.claudeMd != null) fs.writeFileSync(path.join(cwd, "CLAUDE.md"), spec.claudeMd);
+    agents[agentKey] = { cwd };
+  }
+  return { workingDir, agents };
+}
+
+(async () => {
+  const dirName = "proj"; // path.basename(workingDir) → what the server substitutes
+
+  // ── Endpoint test: seeded refreshed + operator H2 preserved; foreign
+  //    skipped byte-identical; missing handled without error. ──────────────
+  const projId = `p966-${crypto.randomBytes(4).toString("hex")}`;
+
+  // A stale seeded CLAUDE.md (rendered from template) with an operator H2 and
+  // a deliberately-mangled canonical section that the refresh must overwrite.
+  const rendered = CLAUDE_TEMPLATE.replace(/\{\{project_name\}\}/g, dirName);
+  const seededStale = rendered
+      .replace("QuadWork agent", "STALE-MARKER agent") // canonical body edit
+    + "\n## Project Notes\n- Local: run `make dev` before pushing.\n";
+
+  const { workingDir, agents } = makeTempProject("mix", {
+    // head: seeded CLAUDE.md → must be refreshed, operator H2 preserved
+    head: { cwdName: "proj-head", agentsMd: "# Head\n\nStale.\n", claudeMd: seededStale },
+    // re1: foreign CLAUDE.md → must be left byte-identical (skipped)
+    re1:  { cwdName: "proj-re1",  agentsMd: "# Reviewer 1\n\nStale.\n", claudeMd: FOREIGN_CLAUDE },
+    // dev: no CLAUDE.md at all → handled without error (skipped)
+    dev:  { cwdName: "proj-dev",  agentsMd: "# Dev\n\nStale.\n" },
+  });
+
+  stubCfgJson = JSON.stringify({
+    projects: [{ id: projId, name: "P966", repo: "ex/p966", working_dir: workingDir, agents }],
+  });
+
+  let resp;
+  await withServer(async (base) => {
+    resp = await post(`${base}/api/projects/${projId}/reseed-agents`, { force: true });
+  });
+  assert.equal(resp.status, 200, `expected 200, got ${resp.status} ${JSON.stringify(resp.body)}`);
+  assert.equal(resp.body.ok, true);
+
+  // AGENTS.md reseed behavior unchanged: all three still refreshed.
+  for (const k of ["head", "re1", "dev"]) {
+    assert.ok(resp.body.reseeded.includes(`${k}/AGENTS.md`), `${k}/AGENTS.md still reseeded`);
+  }
+
+  // head: seeded CLAUDE.md refreshed, stale canonical body gone, operator H2 kept.
+  const headClaude = realReadFileSync(path.join(agents.head.cwd, "CLAUDE.md"), "utf-8");
+  assert.ok(resp.body.reseeded.includes("head/CLAUDE.md"), "head/CLAUDE.md reported reseeded");
+  assert.ok(!headClaude.includes("STALE-MARKER"), "stale canonical body overwritten by fresh template");
+  assert.ok(headClaude.includes("## Multi-Agent System"), "canonical section present from fresh template");
+  assert.ok(headClaude.includes("## Project Notes"), "operator H2 heading preserved");
+  assert.ok(headClaude.includes("run `make dev` before pushing"), "operator H2 body preserved");
+  assert.deepEqual(resp.body.preserved["head/CLAUDE.md"], ["Project Notes"], "preserved reported under head/CLAUDE.md");
+
+  // re1: foreign CLAUDE.md left byte-identical and reported skipped.
+  const re1Claude = realReadFileSync(path.join(agents.re1.cwd, "CLAUDE.md"), "utf-8");
+  assert.equal(re1Claude, FOREIGN_CLAUDE, "foreign CLAUDE.md left byte-identical");
+  assert.ok(resp.body.skipped.includes("re1/CLAUDE.md (not QuadWork-seeded)"), "foreign skip reported");
+
+  // dev: no CLAUDE.md → handled without error, reported skipped, none created.
+  assert.ok(!fs.existsSync(path.join(agents.dev.cwd, "CLAUDE.md")), "no CLAUDE.md created where none existed");
+  assert.ok(resp.body.skipped.includes("dev/CLAUDE.md (none)"), "missing CLAUDE.md skip reported");
+
+  console.log("routes.reseedClaudeMd.test.js: all assertions passed");
+})().catch((err) => { console.error(err); process.exit(1); });