diff --git a/server/__tests__/lane-mcp.test.js b/server/__tests__/lane-mcp.test.js
new file mode 100644
index 0000000..e69816f
--- /dev/null
+++ b/server/__tests__/lane-mcp.test.js
@@ -0,0 +1,176 @@
+/**
+ * @file Tests for server/lib/lane-mcp.js: relocating a source repo's
+ * ~/.claude.json MCP server config into a lane's own .mcp.json, pinning
+ * Playwright's proof output dir, and seeding Chromium profiles. Uses a real
+ * temp $HOME (via process.env.HOME override) so the module's own
+ * os.homedir()-based path resolution is exercised, not mocked around.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const { describe, it, before, after } = require("node:test");
+const assert = require("node:assert/strict");
+const fs = require("node:fs");
+const os = require("node:os");
+const path = require("node:path");
+
+const SUITE_ROOT = fs.mkdtempSync(path.join(os.tmpdir(), "ccam-mcp-"));
+const FAKE_HOME = path.join(SUITE_ROOT, "home");
+fs.mkdirSync(FAKE_HOME, { recursive: true });
+process.env.HOME = FAKE_HOME;
+
+const laneMcp = require("../lib/lane-mcp");
+
+after(() => fs.rmSync(SUITE_ROOT, { recursive: true, force: true }));
+
+function writeClaudeJson(projects) {
+  fs.writeFileSync(path.join(FAKE_HOME, ".claude.json"), JSON.stringify({ projects }, null, 2));
+}
+
+let laneSeq = 0;
+function makeLane(sourceRepo) {
+  laneSeq += 1;
+  const cwd = path.join(SUITE_ROOT, `lane-cwd-${laneSeq}`);
+  fs.mkdirSync(cwd, { recursive: true });
+  return { cwd, source_repo: sourceRepo };
+}
+
+describe("syncMcp — reading and relocating", () => {
+  it("throws ENOMCPCONFIG when the source repo has no mcpServers", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-none");
+    fs.mkdirSync(sourceRepo, { recursive: true });
+    writeClaudeJson({ [sourceRepo]: {} });
+    await assert.rejects(() => laneMcp.syncMcp(makeLane(sourceRepo)), {
+      code: "ENOMCPCONFIG",
+    });
+  });
+
+  it("throws ENOMCPCONFIG when ~/.claude.json doesn't exist at all", async () => {
+    fs.rmSync(path.join(FAKE_HOME, ".claude.json"), { force: true });
+    await assert.rejects(() => laneMcp.syncMcp(makeLane(path.join(SUITE_ROOT, "src-missing"))), {
+      code: "ENOMCPCONFIG",
+    });
+  });
+
+  it("relocates absolute paths under source_repo to the lane's cwd", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-relocate");
+    fs.mkdirSync(sourceRepo, { recursive: true });
+    writeClaudeJson({
+      [sourceRepo]: {
+        mcpServers: {
+          playwright: {
+            command: "npx",
+            args: [
+              "-y",
+              "@playwright/mcp@latest",
+              "--user-data-dir",
+              `${sourceRepo}/.playwright-mcp/profiles/default`,
+            ],
+          },
+        },
+      },
+    });
+    const lane = makeLane(sourceRepo);
+    const result = await laneMcp.syncMcp(lane);
+    assert.deepEqual(result.servers, ["playwright"]);
+
+    const written = JSON.parse(fs.readFileSync(path.join(lane.cwd, ".mcp.json"), "utf8"));
+    assert.equal(
+      written.mcpServers.playwright.args[3],
+      `${lane.cwd}/.playwright-mcp/profiles/default`
+    );
+  });
+});
+
+describe("syncMcp — Playwright output-dir pinning", () => {
+  it("pins --output-dir only when a @playwright/mcp server doesn't already declare one", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-pin");
+    fs.mkdirSync(sourceRepo, { recursive: true });
+    writeClaudeJson({
+      [sourceRepo]: {
+        mcpServers: {
+          playwright: { command: "npx", args: ["-y", "@playwright/mcp@latest"] },
+          "playwright-custom": {
+            command: "npx",
+            args: ["-y", "@playwright/mcp@latest", "--output-dir", "/already/set"],
+          },
+          "not-playwright": { command: "npx", args: ["-y", "some-other-mcp"] },
+        },
+      },
+    });
+    const lane = makeLane(sourceRepo);
+    await laneMcp.syncMcp(lane);
+    const written = JSON.parse(fs.readFileSync(path.join(lane.cwd, ".mcp.json"), "utf8"));
+
+    assert.deepEqual(written.mcpServers.playwright.args.slice(-2), [
+      "--output-dir",
+      path.join(lane.cwd, ".playwright-mcp"),
+    ]);
+    assert.deepEqual(written.mcpServers["playwright-custom"].args.slice(-2), [
+      "--output-dir",
+      "/already/set",
+    ]);
+    assert.equal(written.mcpServers["not-playwright"].args.includes("--output-dir"), false);
+  });
+});
+
+describe("syncMcp — profile seeding", () => {
+  it("seeds a source profile into the lane and strips Singleton* lock files", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-profiles");
+    const srcProfileDir = path.join(sourceRepo, ".playwright-mcp", "profiles", "default");
+    fs.mkdirSync(srcProfileDir, { recursive: true });
+    fs.writeFileSync(path.join(srcProfileDir, "Cookies"), "fake-cookie-db");
+    fs.writeFileSync(path.join(srcProfileDir, "SingletonLock"), "stale-lock");
+    writeClaudeJson({
+      [sourceRepo]: { mcpServers: { playwright: { command: "npx", args: [] } } },
+    });
+
+    const lane = makeLane(sourceRepo);
+    const result = await laneMcp.syncMcp(lane);
+    assert.deepEqual(result.profilesSeeded, ["default"]);
+
+    const destDir = path.join(lane.cwd, ".playwright-mcp", "profiles", "default");
+    assert.ok(fs.existsSync(path.join(destDir, "Cookies")));
+    assert.ok(!fs.existsSync(path.join(destDir, "SingletonLock")));
+  });
+
+  it("never overwrites a profile that already exists at the destination", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-profiles-2");
+    const srcProfileDir = path.join(sourceRepo, ".playwright-mcp", "profiles", "default");
+    fs.mkdirSync(srcProfileDir, { recursive: true });
+    fs.writeFileSync(path.join(srcProfileDir, "Cookies"), "new-cookie-db");
+    writeClaudeJson({
+      [sourceRepo]: { mcpServers: { playwright: { command: "npx", args: [] } } },
+    });
+
+    const lane = makeLane(sourceRepo);
+    const destDir = path.join(lane.cwd, ".playwright-mcp", "profiles", "default");
+    fs.mkdirSync(destDir, { recursive: true });
+    fs.writeFileSync(path.join(destDir, "Cookies"), "already-logged-in-cookie-db");
+
+    const result = await laneMcp.syncMcp(lane);
+    assert.deepEqual(result.profilesSeeded, []);
+    assert.equal(
+      fs.readFileSync(path.join(destDir, "Cookies"), "utf8"),
+      "already-logged-in-cookie-db"
+    );
+  });
+});
+
+describe("syncMcp — .git/info/exclude idempotency", () => {
+  it("appends .mcp.json once and does not duplicate it on a second call", async () => {
+    const sourceRepo = path.join(SUITE_ROOT, "src-exclude");
+    fs.mkdirSync(sourceRepo, { recursive: true });
+    writeClaudeJson({
+      [sourceRepo]: { mcpServers: { playwright: { command: "npx", args: [] } } },
+    });
+    const lane = makeLane(sourceRepo);
+    fs.mkdirSync(path.join(lane.cwd, ".git"), { recursive: true });
+
+    await laneMcp.syncMcp(lane);
+    await laneMcp.syncMcp(lane);
+
+    const exclude = fs.readFileSync(path.join(lane.cwd, ".git", "info", "exclude"), "utf8");
+    const matches = exclude.split("\n").filter((line) => line === ".mcp.json");
+    assert.equal(matches.length, 1);
+  });
+});
diff --git a/server/lib/lane-mcp.js b/server/lib/lane-mcp.js
new file mode 100644
index 0000000..a11372d
--- /dev/null
+++ b/server/lib/lane-mcp.js
@@ -0,0 +1,138 @@
+/**
+ * @file Gives a lane the same MCP servers as its source repo: reads the
+ * source repo's already-configured mcpServers from ~/.claude.json (normal
+ * Claude Code project-scope config — the human sets this up once, the same
+ * way they would for any project), relocates any absolute path under the
+ * source repo to the lane's own directory, pins a Playwright server's proof
+ * output dir, and writes <lane.cwd>/.mcp.json. Also seeds the lane's
+ * Chromium browser profiles from the source repo's own (preserves saved
+ * logins — a QA account only needs to log in once per machine).
+ *
+ * Deliberately does NOT write any permission or settings.local.json content
+ * — see the F1 design spec's Scope section for why. Plain file I/O; no git
+ * calls, unlike lane-sync.js (E2) or lane-agents.js (E3).
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const fs = require("node:fs");
+const os = require("node:os");
+const path = require("node:path");
+
+/** Read the source repo's mcpServers from ~/.claude.json. Throws
+ *  ENOMCPCONFIG if the file is missing or the project has none declared —
+ *  a lane with zero MCP servers synced would silently break Stage 3/6 much
+ *  later, at a far less debuggable point, so this fails loud and early. */
+function readSourceMcpServers(sourceRepo) {
+  const claudeJsonPath = path.join(os.homedir(), ".claude.json");
+  let cfg;
+  try {
+    cfg = JSON.parse(fs.readFileSync(claudeJsonPath, "utf8"));
+  } catch {
+    cfg = null;
+  }
+  const servers = cfg?.projects?.[sourceRepo]?.mcpServers;
+  if (!servers || !Object.keys(servers).length) {
+    throw Object.assign(
+      new Error(
+        `no mcpServers configured for source repo ${sourceRepo} in ~/.claude.json — ` +
+          `configure them there first (see the ship-feature-lane skill's Setup section)`
+      ),
+      { code: "ENOMCPCONFIG" }
+    );
+  }
+  return servers;
+}
+
+/** Deep-walk a server config, replacing every occurrence of `sourceRepo`
+ *  inside a string with `laneDir`. Strings, arrays, and plain objects only
+ *  — an MCP server def never contains anything else. */
+function relocate(value, sourceRepo, laneDir) {
+  if (typeof value === "string") return value.split(sourceRepo).join(laneDir);
+  if (Array.isArray(value)) return value.map((v) => relocate(v, sourceRepo, laneDir));
+  if (value && typeof value === "object") {
+    const out = {};
+    for (const [k, v] of Object.entries(value)) out[k] = relocate(v, sourceRepo, laneDir);
+    return out;
+  }
+  return value;
+}
+
+/** Pin --output-dir for a @playwright/mcp server that doesn't already
+ *  declare one, so relative proof filenames (proof/<feature>/...) always
+ *  land under <laneDir>/.playwright-mcp — the one place the dashboard's
+ *  proof gallery reads. */
+function pinPlaywrightOutputDir(servers, laneDir) {
+  for (const server of Object.values(servers)) {
+    const args = server.args;
+    if (!Array.isArray(args)) continue;
+    const isPlaywright = args.some((a) => typeof a === "string" && a.startsWith("@playwright/mcp"));
+    if (isPlaywright && !args.includes("--output-dir")) {
+      server.args = [...args, "--output-dir", path.join(laneDir, ".playwright-mcp")];
+    }
+  }
+}
+
+/** Copy each <sourceRepo>/.playwright-mcp/profiles/<name>/ into the lane
+ *  ONLY if that name doesn't already exist there — an existing profile
+ *  means a session already logged in with it; never clobber that. Strips
+ *  Singleton* lock files from the freshly-seeded copy (stale locks from the
+ *  source's own last browser process would make the lane's browser refuse
+ *  to start, thinking another instance already holds the profile). */
+function seedProfiles(sourceRepo, laneDir) {
+  const srcProfiles = path.join(sourceRepo, ".playwright-mcp", "profiles");
+  if (!fs.existsSync(srcProfiles)) return [];
+
+  const seeded = [];
+  for (const name of fs.readdirSync(srcProfiles)) {
+    const src = path.join(srcProfiles, name);
+    if (!fs.statSync(src).isDirectory()) continue;
+    const dest = path.join(laneDir, ".playwright-mcp", "profiles", name);
+    if (fs.existsSync(dest)) continue;
+
+    fs.mkdirSync(path.dirname(dest), { recursive: true });
+    fs.cpSync(src, dest, { recursive: true });
+    for (const entry of fs.readdirSync(dest)) {
+      if (entry.startsWith("Singleton")) fs.rmSync(path.join(dest, entry), { force: true });
+    }
+    seeded.push(name);
+  }
+  return seeded;
+}
+
+/** Idempotently append a line to <laneDir>/.git/info/exclude — same
+ *  read-existing-then-append-if-missing pattern E2/E3 already use for
+ *  .git/info/attributes and .git/info/exclude. .mcp.json sits at the lane
+ *  root (not inside .git), so this needs no --git-common-dir resolution —
+ *  the exclude file itself is always local to this lane's own working copy. */
+function excludeFromGit(laneDir, line) {
+  const excludePath = path.join(laneDir, ".git", "info", "exclude");
+  fs.mkdirSync(path.dirname(excludePath), { recursive: true });
+  const existing = fs.existsSync(excludePath) ? fs.readFileSync(excludePath, "utf8") : "";
+  const lines = existing.split("\n").filter(Boolean);
+  if (!lines.includes(line)) {
+    lines.push(line);
+    fs.writeFileSync(excludePath, lines.join("\n") + "\n");
+  }
+}
+
+/**
+ * @param {{cwd: string, source_repo: string}} lane
+ * @returns {{servers: string[], profilesSeeded: string[]}}
+ */
+async function syncMcp(lane) {
+  const sourceServers = readSourceMcpServers(lane.source_repo);
+  const relocated = relocate(sourceServers, lane.source_repo, lane.cwd);
+  pinPlaywrightOutputDir(relocated, lane.cwd);
+
+  fs.writeFileSync(
+    path.join(lane.cwd, ".mcp.json"),
+    JSON.stringify({ mcpServers: relocated }, null, 2) + "\n"
+  );
+  excludeFromGit(lane.cwd, ".mcp.json");
+
+  const profilesSeeded = seedProfiles(lane.source_repo, lane.cwd);
+
+  return { servers: Object.keys(relocated), profilesSeeded };
+}
+
+module.exports = { syncMcp };