diff --git a/src/cli/args.js b/src/cli/args.js
index fbbc8709..8e0a337a 100644
--- a/src/cli/args.js
+++ b/src/cli/args.js
@@ -390,6 +390,7 @@ function parseAgentsArgs(rawArgs) {
     dryRun: false,
     reviewIntervalSeconds: 30,
     cleanupIntervalSeconds: 60,
+    cleanupOnly: false,
     idleMinutes: DEFAULT_SHADOW_CLEANUP_IDLE_MINUTES,
     staleAgeMinutes: 24 * 60,
     pid: null,
@@ -551,6 +552,10 @@ function parseAgentsArgs(rawArgs) {
       index += 1;
       continue;
     }
+    if (arg === '--cleanup-only') {
+      options.cleanupOnly = true;
+      continue;
+    }
     if (arg === '--cleanup-interval') {
       const next = rest[index + 1];
       if (!next) {
@@ -1029,7 +1034,11 @@ function parseCleanupArgs(rawArgs) {
     keepRemote: false,
     keepCleanWorktrees: true,
     includeCleanLinkedWorktrees: false,
-    includePrMerged: false,
+    // Squash/rebase merges leave the branch tip off the base's history, so
+    // ancestry alone reports a merged PR's branch as unmerged and cleanup
+    // never reclaims it. Consult merged PRs by default; `gh` missing or failing
+    // disables the lookup (fail-closed: nothing is treated as merged).
+    includePrMerged: true,
     idleMinutes: 0,
     watch: false,
     intervalSeconds: 60,
@@ -1094,6 +1103,10 @@ function parseCleanupArgs(rawArgs) {
       options.includePrMerged = true;
       continue;
     }
+    if (arg === '--no-include-pr-merged') {
+      options.includePrMerged = false;
+      continue;
+    }
     if (arg === '--idle-minutes') {
       const next = rawArgs[index + 1];
       if (!next) {
diff --git a/src/cli/commands/agents.js b/src/cli/commands/agents.js
index 9934866a..08733b73 100644
--- a/src/cli/commands/agents.js
+++ b/src/cli/commands/agents.js
@@ -254,7 +254,15 @@ function agents(rawArgs) {
     const reviewRunning = processAlive(existingReviewPid);
     const cleanupRunning = processAlive(existingCleanupPid);
 
-    if (reviewRunning && cleanupRunning) {
+    // --cleanup-only: run just the cleanup bot. The review bot spends model
+    // tokens on every PR; reclaiming merged lanes should not require it.
+    const reviewWanted = !options.cleanupOnly;
+    if ((reviewRunning || !reviewWanted) && cleanupRunning) {
+      if (!reviewWanted) {
+        console.log(`[${TOOL_NAME}] Cleanup bot already running (pid=${existingCleanupPid}).`);
+        process.exitCode = 0;
+        return;
+      }
       console.log(
         `[${TOOL_NAME}] Repo agents already running (review pid=${existingReviewPid}, cleanup pid=${existingCleanupPid}).`,
       );
@@ -271,7 +279,7 @@ function agents(rawArgs) {
     let reusedAny = false;
 
     const mainScriptPath = require.resolve('../main.js');
-    if (!reviewRunning) {
+    if (reviewWanted && !reviewRunning) {
       reviewPid = spawnDetachedAgentProcess({
         command: process.execPath,
         args: [
@@ -288,7 +296,7 @@ function agents(rawArgs) {
         logPath: reviewLogPath,
       });
       startedAny = true;
-    } else {
+    } else if (reviewRunning) {
       reusedAny = true;
     }
 
@@ -333,7 +341,7 @@ function agents(rawArgs) {
       repoRoot,
       startedAt: new Date().toISOString(),
       review: {
-        pid: reviewPid,
+        pid: reviewWanted || reviewRunning ? reviewPid : null,
         intervalSeconds: reviewIntervalSeconds,
         script: mainScriptPath,
         logPath: reviewLogPath,
@@ -348,12 +356,18 @@ function agents(rawArgs) {
     });
 
     console.log(
-      `[${TOOL_NAME}] Started repo agents in ${repoRoot} (review pid=${reviewPid}, cleanup pid=${cleanupPid}).`,
+      reviewWanted
+        ? `[${TOOL_NAME}] Started repo agents in ${repoRoot} (review pid=${reviewPid}, cleanup pid=${cleanupPid}).`
+        : reviewRunning
+          ? `[${TOOL_NAME}] Started the cleanup bot in ${repoRoot} (cleanup pid=${cleanupPid}); the review bot already running (pid=${existingReviewPid}) is left as is.`
+          : `[${TOOL_NAME}] Started the cleanup bot in ${repoRoot} (cleanup pid=${cleanupPid}; review bot not started: --cleanup-only).`,
     );
     if (reusedAny && startedAny) {
       console.log(`[${TOOL_NAME}] Reused healthy bot process(es) and started only missing ones.`);
     }
-    console.log(`[${TOOL_NAME}] Logs: ${reviewLogPath}, ${cleanupLogPath}`);
+    console.log(
+      `[${TOOL_NAME}] Logs: ${reviewWanted || reviewRunning ? `${reviewLogPath}, ` : ''}${cleanupLogPath}`,
+    );
     process.exitCode = 0;
     return;
   }
diff --git a/src/context.js b/src/context.js
index 2b2ac8be..d88d68f8 100644
--- a/src/context.js
+++ b/src/context.js
@@ -674,7 +674,7 @@ const CLI_COMMAND_HELP = {
     summary: 'Repo-scoped review and cleanup bots, plus the agent inbox and lane inspection.',
     subcommands: [
       ['status', 'Show the running bots and the agent lanes (the default with no subcommand)'],
-      ['start', 'Start the review + cleanup bots for this repo'],
+      ['start', 'Start the review + cleanup bots for this repo (--cleanup-only: just the cleanup bot)'],
       ['stop', 'Stop them'],
       ['finish', 'Finish an agent lane by session or branch'],
       ['files', 'Show which files each lane has touched'],
@@ -693,8 +693,9 @@ const CLI_COMMAND_HELP = {
       ['--session <id>', 'Address one agent session'],
       ['--branch <agent/...>', 'Address one agent branch'],
       ['--dry-run', 'Print actions without applying them'],
+      ['--cleanup-only', 'start: run only the cleanup bot (no token-spending review bot)'],
     ],
-    examples: ['gx agents status --json', 'gx agents files --branch agent/claude/my-lane'],
+    examples: ['gx agents status --json', 'gx agents start --cleanup-only', 'gx agents files --branch agent/claude/my-lane'],
   },
 
   'pr-review': {
diff --git a/src/finish/index.js b/src/finish/index.js
index 552145f4..11c89151 100644
--- a/src/finish/index.js
+++ b/src/finish/index.js
@@ -235,7 +235,8 @@ OPTIONS
   --keep-clean-worktrees   Preserve clean, unmerged agent worktrees (default)
   --include-clean-linked-worktrees
                            Also prune clean linked worktrees outside managed agent directories
-  --include-pr-merged      Treat branches from merged PRs as merged
+  --include-pr-merged      Treat branches from merged PRs as merged (default; needs gh)
+  --no-include-pr-merged   Judge merged by git ancestry only (misses squash merges)
   --idle-minutes <n>       Only consider worktrees idle for at least n minutes
   --watch                  Repeat cleanup cycles (defaults idle threshold to 60)
   --interval <seconds>     Watch interval in seconds (minimum: 5; default: 60)
diff --git a/templates/scripts/agent-worktree-prune.sh b/templates/scripts/agent-worktree-prune.sh
index 91cafed2..7b6bf33f 100644
--- a/templates/scripts/agent-worktree-prune.sh
+++ b/templates/scripts/agent-worktree-prune.sh
@@ -228,14 +228,18 @@ load_merged_pr_branches() {
     return 1
   fi
 
+  # Name -> space-separated merged PR head SHAs. The SHA is what makes the
+  # name match safe: a reused branch name, or commits pushed after the PR
+  # merged, must not read as "merged" (see branch_has_merged_pr).
   local merged_branches=""
   merged_branches="$(
-    "$GH_BIN" pr list --state merged --base "$BASE_BRANCH" --limit 200 --json headRefName --jq '.[].headRefName' 2>/dev/null || true
+    "$GH_BIN" pr list --state merged --base "$BASE_BRANCH" --limit 200 --json headRefName,headRefOid --jq '.[] | "\(.headRefName) \(.headRefOid)"' 2>/dev/null || true
   )"
   if [[ -n "$merged_branches" ]]; then
-    while IFS= read -r merged_branch; do
-      [[ -z "$merged_branch" ]] && continue
-      MERGED_PR_BRANCHES["$merged_branch"]=1
+    local merged_branch merged_oid
+    while IFS=' ' read -r merged_branch merged_oid; do
+      [[ -z "$merged_branch" || -z "$merged_oid" ]] && continue
+      MERGED_PR_BRANCHES["$merged_branch"]="${MERGED_PR_BRANCHES[$merged_branch]:-} ${merged_oid}"
     done <<< "$merged_branches"
   fi
   PR_MERGED_LOOKUP_LOADED=1
@@ -288,7 +292,31 @@ branch_has_merged_pr() {
     return 1
   fi
   load_merged_pr_branches || return 1
-  [[ -n "${MERGED_PR_BRANCHES[$branch]:-}" ]]
+  local merged_oids="${MERGED_PR_BRANCHES[$branch]:-}"
+  [[ -n "$merged_oids" ]] || return 1
+  # Merged only if every tip we can see — the local branch AND origin's —
+  # IS a merged PR's head or is contained in one. Anything newer (commits
+  # pushed after the merge, locally or to origin; a reused name) is unmerged
+  # work — fail closed. A PR head we do not have locally cannot prove
+  # containment, so only the exact-SHA match applies then.
+  local tips=() ref resolved
+  for ref in "refs/heads/${branch}" "refs/remotes/origin/${branch}"; do
+    resolved="$(git -C "$repo_root" rev-parse --verify --quiet "${ref}^{commit}" 2>/dev/null || true)"
+    [[ -n "$resolved" ]] && tips+=("$resolved")
+  done
+  [[ ${#tips[@]} -gt 0 ]] || return 1
+  local tip oid contained
+  for tip in "${tips[@]}"; do
+    contained=0
+    for oid in $merged_oids; do
+      if [[ "$tip" == "$oid" ]] || git -C "$repo_root" merge-base --is-ancestor "$tip" "$oid" >/dev/null 2>&1; then
+        contained=1
+        break
+      fi
+    done
+    [[ "$contained" -eq 1 ]] || return 1
+  done
+  return 0
 }
 
 load_lane_pr_metadata() {
diff --git a/test/agents.test.js b/test/agents.test.js
index cb24f970..6cd797eb 100644
--- a/test/agents.test.js
+++ b/test/agents.test.js
@@ -275,6 +275,160 @@ test('agents command starts review+cleanup bots for the target repo and stops th
 });
 
 
+test('agents start --cleanup-only starts only the cleanup bot', () => {
+  const repoDir = initRepo();
+  seedCommit(repoDir);
+  const scriptsDir = path.join(repoDir, 'scripts');
+  fs.mkdirSync(scriptsDir, { recursive: true });
+  const reviewScriptPath = path.join(scriptsDir, 'review-bot-watch.sh');
+  fs.writeFileSync(reviewScriptPath, fakeReviewBotDaemonScript(), 'utf8');
+  fs.chmodSync(reviewScriptPath, 0o755);
+  const pruneScriptPath = path.join(scriptsDir, 'agent-worktree-prune.sh');
+  fs.writeFileSync(
+    pruneScriptPath,
+    '#!/usr/bin/env bash\n' +
+      'set -euo pipefail\n' +
+      'exit 0\n',
+    'utf8',
+  );
+  fs.chmodSync(pruneScriptPath, 0o755);
+
+  let result = runNode(
+    ['agents', 'start', '--target', repoDir, '--cleanup-only', '--cleanup-interval', '47', '--idle-minutes', '12'],
+    repoDir,
+  );
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.match(result.stdout, /Started the cleanup bot/);
+  assert.match(result.stdout, /review bot not started: --cleanup-only/);
+
+  const statePath = path.join(repoDir, '.omx', 'state', 'agents-bots.json');
+  const state = JSON.parse(fs.readFileSync(statePath, 'utf8'));
+  assert.equal(state.review.pid, null, 'no review bot under --cleanup-only');
+  assert.equal(isPidAlive(state.cleanup.pid), true, 'cleanup bot pid should be alive after start');
+  assert.equal(
+    fs.existsSync(path.join(repoDir, '.omx', 'logs', 'agent-review.log')),
+    false,
+    'no review log under --cleanup-only',
+  );
+
+  // A second start is a no-op while the cleanup bot runs.
+  result = runNode(['agents', 'start', '--target', repoDir, '--cleanup-only'], repoDir);
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.match(result.stdout, /Cleanup bot already running/);
+
+  result = runNode(['agents', 'stop', '--target', repoDir], repoDir);
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.equal(waitForPidExit(state.cleanup.pid), true, 'cleanup bot pid should exit after stop');
+});
+
+test('gx cleanup consults merged PRs by default and skips them under --no-include-pr-merged', () => {
+  const repoDir = initRepo();
+  seedCommit(repoDir);
+  const execGit = (dir, args) => {
+    const out = runCmd('git', args, dir);
+    assert.equal(out.status, 0, out.stderr || out.stdout);
+    return String(out.stdout || '').trim();
+  };
+  const base = execGit(repoDir, ['rev-parse', '--abbrev-ref', 'HEAD']);
+  // An agent lane whose tip is NOT an ancestor of the base — what a squash
+  // merge leaves behind — so only the PR lookup can call it merged.
+  execGit(repoDir, ['checkout', '-q', '-b', 'agent/claude/squashed-lane']);
+  fs.writeFileSync(path.join(repoDir, 'lane.txt'), 'lane\n', 'utf8');
+  execGit(repoDir, ['add', 'lane.txt']);
+  execGit(repoDir, ['commit', '-q', '-m', 'lane work']);
+  execGit(repoDir, ['checkout', '-q', base]);
+
+  const ghLog = path.join(repoDir, '.gh-calls.log');
+  const fakeGh = path.join(repoDir, 'fake-gh.sh');
+  fs.writeFileSync(fakeGh, `#!/usr/bin/env bash\necho "$*" >> ${JSON.stringify(ghLog)}\nexit 0\n`, 'utf8');
+  fs.chmodSync(fakeGh, 0o755);
+
+  let result = runNodeWithEnv(
+    ['cleanup', '--target', repoDir, '--base', base, '--dry-run'],
+    repoDir,
+    { GUARDEX_GH_BIN: fakeGh },
+  );
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  const calls = fs.existsSync(ghLog) ? fs.readFileSync(ghLog, 'utf8') : '';
+  assert.match(calls, /pr list --state merged/, 'default cleanup must ask for merged PRs');
+
+  fs.rmSync(ghLog, { force: true });
+  result = runNodeWithEnv(
+    ['cleanup', '--target', repoDir, '--base', base, '--dry-run', '--no-include-pr-merged'],
+    repoDir,
+    { GUARDEX_GH_BIN: fakeGh },
+  );
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  const optOut = fs.existsSync(ghLog) ? fs.readFileSync(ghLog, 'utf8') : '';
+  assert.doesNotMatch(optOut, /--state merged/, 'opt-out must not query merged PRs');
+});
+
+test('gx cleanup treats a lane as PR-merged only when its tip matches the merged PR head', () => {
+  const repoDir = initRepo();
+  seedCommit(repoDir);
+  const execGit = (dir, args) => {
+    const out = runCmd('git', args, dir);
+    assert.equal(out.status, 0, out.stderr || out.stdout);
+    return String(out.stdout || '').trim();
+  };
+  const base = execGit(repoDir, ['rev-parse', '--abbrev-ref', 'HEAD']);
+  const lane = 'agent/claude/squashed-lane';
+  execGit(repoDir, ['checkout', '-q', '-b', lane]);
+  fs.writeFileSync(path.join(repoDir, 'lane.txt'), 'lane\n', 'utf8');
+  execGit(repoDir, ['add', 'lane.txt']);
+  execGit(repoDir, ['commit', '-q', '-m', 'lane work']);
+  const prHead = execGit(repoDir, ['rev-parse', 'HEAD']);
+  execGit(repoDir, ['checkout', '-q', base]);
+
+  const fakeGhFor = (oid) => {
+    const fakeGh = path.join(repoDir, 'fake-gh.sh');
+    fs.writeFileSync(
+      fakeGh,
+      '#!/usr/bin/env bash\n' +
+        `if [[ "$*" == *"--state merged"* ]]; then echo "${lane} ${oid}"; fi\n` +
+        'exit 0\n',
+      'utf8',
+    );
+    fs.chmodSync(fakeGh, 0o755);
+    return fakeGh;
+  };
+  const dryRun = (fakeGh) =>
+    runNodeWithEnv(['cleanup', '--target', repoDir, '--base', base, '--dry-run'], repoDir, {
+      GUARDEX_GH_BIN: fakeGh,
+    });
+
+  // Tip == merged PR head: the squash-merged lane is reclaimed.
+  let result = dryRun(fakeGhFor(prHead));
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.match(`${result.stdout}${result.stderr}`, new RegExp(`merged PR branch: ${lane}`));
+
+  // Work pushed after the PR merged: the tip is past the PR head — keep it.
+  execGit(repoDir, ['checkout', '-q', lane]);
+  fs.writeFileSync(path.join(repoDir, 'later.txt'), 'later\n', 'utf8');
+  execGit(repoDir, ['add', 'later.txt']);
+  execGit(repoDir, ['commit', '-q', '-m', 'work after merge']);
+  execGit(repoDir, ['checkout', '-q', base]);
+  result = dryRun(fakeGhFor(prHead));
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.doesNotMatch(`${result.stdout}${result.stderr}`, new RegExp(`merged PR branch: ${lane}`));
+
+  // Local branch at the PR head, but origin moved past it after the merge:
+  // the remote carries unmerged work — keep it.
+  execGit(repoDir, ['branch', '-f', lane, prHead]);
+  const laterOnOrigin = execGit(repoDir, ['rev-parse', `${lane}@{1}`]);
+  execGit(repoDir, ['update-ref', `refs/remotes/origin/${lane}`, laterOnOrigin]);
+  result = dryRun(fakeGhFor(prHead));
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.doesNotMatch(`${result.stdout}${result.stderr}`, new RegExp(`merged PR branch: ${lane}`));
+  execGit(repoDir, ['update-ref', '-d', `refs/remotes/origin/${lane}`]);
+  execGit(repoDir, ['branch', '-f', lane, laterOnOrigin]);
+
+  // A reused name whose merged PR head is unrelated to this tip — keep it.
+  result = dryRun(fakeGhFor('0123456789abcdef0123456789abcdef01234567'));
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  assert.doesNotMatch(`${result.stdout}${result.stderr}`, new RegExp(`merged PR branch: ${lane}`));
+});
+
 test('agents start reuses running review bot when only cleanup bot is missing', () => {
   const repoDir = initRepo();
   seedCommit(repoDir);
diff --git a/test/cli-args-dispatch.test.js b/test/cli-args-dispatch.test.js
index c4d286c0..015ed3d0 100644
--- a/test/cli-args-dispatch.test.js
+++ b/test/cli-args-dispatch.test.js
@@ -136,6 +136,7 @@ test('parseAgentsArgs applies interval overrides and validates the subcommand',
     dryRun: false,
     reviewIntervalSeconds: 15,
     cleanupIntervalSeconds: 45,
+    cleanupOnly: false,
     idleMinutes: 12,
     staleAgeMinutes: 1440,
     pid: null,
@@ -328,6 +329,18 @@ test('parseCleanupArgs defaults idle minutes when watch mode is enabled', () =>
   assert.equal(options.idleMinutes, DEFAULT_SHADOW_CLEANUP_IDLE_MINUTES);
 });
 
+test('parseCleanupArgs consults merged PRs by default so squash-merged lanes are reclaimed', () => {
+  assert.equal(parseCleanupArgs([]).includePrMerged, true);
+  assert.equal(parseCleanupArgs(['--include-pr-merged']).includePrMerged, true);
+  assert.equal(parseCleanupArgs(['--no-include-pr-merged']).includePrMerged, false);
+  assert.equal(parseCleanupArgs(['--watch']).includePrMerged, true);
+});
+
+test('parseAgentsArgs accepts --cleanup-only for a cleanup bot without the review bot', () => {
+  assert.equal(parseAgentsArgs(['start']).cleanupOnly, false);
+  assert.equal(parseAgentsArgs(['start', '--cleanup-only']).cleanupOnly, true);
+});
+
 test('parseCleanupArgs preserves clean worktrees unless pruning is explicitly requested', () => {
   assert.equal(parseCleanupArgs([]).keepCleanWorktrees, true);
   assert.equal(parseCleanupArgs(['--prune-clean-worktrees']).keepCleanWorktrees, false);
diff --git a/test/finish.test.js b/test/finish.test.js
index 807901d7..7bfdee1f 100644
--- a/test/finish.test.js
+++ b/test/finish.test.js
@@ -1834,9 +1834,11 @@ test('cleanup command can remove squash-merged agent branches via merged PR dete
   result = runCmd('git', ['-C', worktreePath, 'commit', '-m', 'feature commit'], repoDir);
   assert.equal(result.status, 0, result.stderr || result.stdout);
 
+  // A squash-merged PR's head is the lane tip; gh reports name + head SHA.
+  const laneTip = runCmd('git', ['-C', worktreePath, 'rev-parse', 'HEAD'], repoDir).stdout.trim();
   const { fakePath: fakeGhPath } = createFakeGhScript(
     'if [[ "$1" == "pr" && "$2" == "list" ]]; then\n' +
-      '  printf \'%s\\n\' "agent/test-cleanup-pr-merged"\n' +
+      `  printf '%s %s\\n' "agent/test-cleanup-pr-merged" "${laneTip}"\n` +
       '  exit 0\n' +
       'fi\n' +
       'exit 1',