test(a4): the composite purge names its claude session by a real uuid (Issue #31, review)

claude now takes only a canonical uuid (81b6c2e), so the fixture id
'uuid-c' purged nothing. The three claude spellings in
test_purge_artifacts_composite become one uuid literal; the assertions
and the other adapters' parts are unchanged. Approved by the user.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/agents/__main__.py

@@ -155,7 +155,8 @@ def main():
         # in-use <agent> <uuid> [workspace] [--wait <sec>]  (Issue #31)
         # The purge CLI's own in-use verdict, for stop_session.sh to ask
         # before it purges. Re-checks every 0.25 s for up to --wait seconds.
-        # Prints {"agent", "in_use"}. Exit 0 free; 4 still in use; 1 bad args.
+        # Prints {"agent", "in_use"}, and while in use where to look on
+        # stderr. Exit 0 free; 4 still in use; 1 bad args.
         args = sys.argv[2:]
         wait = 0.0
         if '--wait' in args:
@@ -181,6 +182,10 @@ def main():
             time.sleep(0.25)
             in_use = adapter.conversation_in_use(uuid, ctx)
         print(json.dumps({"agent": agent_name, "in_use": in_use}))
+        if in_use:
+            print("  What may hold it:", file=sys.stderr)
+            for hint in adapter.in_use_hints(uuid, ctx):
+                print(f"    {hint}", file=sys.stderr)
         sys.exit(4 if in_use else 0)
 
     else:

.agents/skills/lib_py/agents/adapters/claude.py

@@ -1,9 +1,23 @@
-import os, re, json, glob, time, shutil, subprocess
+import os, re, json, glob, math, stat, time, shutil, calendar, subprocess
 from typing import Optional, Any
-from lib_py.agents.base import BaseAgentAdapter, DiscoveryContext, conversation_in_use, scan_names, _plausible_id
+from lib_py.agents.base import BaseAgentAdapter, DiscoveryContext, conversation_in_use, scan_names
 from lib_py.verify_session import workspace_key
 
 
+_UUID = re.compile(r"[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}", re.IGNORECASE)
+
+
+def _canonical(uuid) -> Optional[str]:
+    """The id claude itself writes, in lowercase, for any spelling of a
+    canonical uuid; None for anything else. Any other name in a session's
+    place is not one: projects/<key>/memory/ (auto memory) sits beside the
+    session dirs. Another spelling must go through the same checks as
+    claude's own: on macOS's default case-insensitive APFS it names the
+    same files, while the ids in session files and on command lines are
+    compared exactly."""
+    return uuid.lower() if isinstance(uuid, str) and _UUID.fullmatch(uuid) else None
+
+
 def _config_dir(ctx: DiscoveryContext) -> str:
     """claude's config root: CLAUDE_CONFIG_DIR moves all of it (sessions/,
     file-history/, session-env/, jobs/, projects/)."""
@@ -22,6 +36,10 @@ def _projects_dirs(ctx: DiscoveryContext) -> list:
     return dirs
 
 
+# Node's os.tmpdir() when no TMPDIR/TMP/TEMP is set; tests point it elsewhere.
+_SYSTEM_TMP = "/tmp"
+
+
 def _tmp_roots() -> list:
     """The per-uid temp roots claude may have used: ${CLAUDE_CODE_TMPDIR:-
     os.tmpdir()}/claude-<uid>. A sandboxed tool shell sets CLAUDE_CODE_TMPDIR
@@ -36,9 +54,9 @@ def _tmp_roots() -> list:
             cands.append(override)
     # Node's os.tmpdir() on POSIX, not tempfile.gettempdir() (which probes
     # writability and falls back to the cwd).
-    tmp = os.environ.get("TMPDIR") or os.environ.get("TMP") or os.environ.get("TEMP") or "/tmp"
+    tmp = os.environ.get("TMPDIR") or os.environ.get("TMP") or os.environ.get("TEMP") or _SYSTEM_TMP
     cands.append(os.path.join(tmp.rstrip("/") or "/", name))
-    cands.append(os.path.join("/tmp", name))
+    cands.append(os.path.join(_SYSTEM_TMP, name))
     roots, seen = [], set()
     for c in cands:
         real = os.path.realpath(c)
@@ -63,20 +81,47 @@ def _session_file_live(data: dict, pid) -> bool:
         return False
     except OSError:
         pass
+    # startedAt is epoch ms: a finite positive number. A bool, a string, NaN
+    # (every comparison with it is false), an infinity or an int too large
+    # for a float is no time at all.
+    started = data.get("startedAt")
+    if isinstance(started, bool) or not isinstance(started, (int, float)):
+        return True
+    try:
+        started = float(started) / 1000.0
+    except OverflowError:
+        return True
+    if not math.isfinite(started) or started <= 0:
+        return True
+    # lstart in UTC: a local time is ambiguous in the hour a DST change repeats.
     try:
         out = subprocess.run(["ps", "-p", str(pid), "-o", "lstart="], capture_output=True, text=True,
-                             timeout=5, env=dict(os.environ, LC_ALL="C")).stdout
-        lstart = time.mktime(time.strptime(" ".join(out.split()), "%a %b %d %H:%M:%S %Y"))
-        started = float(data["startedAt"]) / 1000.0
+                             timeout=5, env=dict(os.environ, LC_ALL="C", TZ="UTC0")).stdout
+        lstart = calendar.timegm(time.strptime(" ".join(out.split()), "%a %b %d %H:%M:%S %Y"))
     except Exception:
         return True
-    if started <= 0:
-        return True
     # startedAt is written 1.7-3.2 s after the process starts; 2 s covers
     # lstart's one-second resolution.
     return lstart <= started + 2
 
 
+def _inside(root: str, path: str) -> bool:
+    """`path` is reached from `root` through real directories only: no
+    component between the two is a symlink, and its parent resolves inside
+    the resolved root. The root may be a link itself (/tmp -> /private/tmp,
+    a linked ~/.claude), and so may `path`: _remove then takes the link alone."""
+    cur = root
+    for part in os.path.relpath(os.path.dirname(path), root).split(os.sep):
+        cur = os.path.join(cur, part)
+        try:
+            if not stat.S_ISDIR(os.lstat(cur).st_mode):
+                return False
+        except OSError:
+            return False
+    real_root = os.path.realpath(root)
+    return os.path.realpath(os.path.dirname(path)).startswith(real_root.rstrip(os.sep) + os.sep)
+
+
 def _remove(path: str) -> None:
     try:
         if os.path.islink(path) or not os.path.isdir(path):
@@ -253,45 +298,66 @@ class ClaudeAgentAdapter(BaseAgentAdapter):
             pass
         return None
 
-    def _owned_paths(self, uuid: str, ctx: DiscoveryContext) -> list:
-        """Every existing path that belongs to this session alone (Issue #31).
-        Shared files that merely mention it (history.jsonl, ~/.claude.json,
-        backups, paste-cache) are not the session's and are never listed."""
+    def _candidates(self, uuid: str, ctx: DiscoveryContext) -> list:
+        """(root, path) of every existing path that belongs to this session
+        alone (Issue #31), with the root (config, projects or tmp) it was
+        found under. Shared files that merely mention it (history.jsonl,
+        ~/.claude.json, backups, paste-cache) are not the session's and are
+        never listed."""
         # Checked before any path is built: whole directories named by the id
-        # are removed, so "", "." or ".." would reach file-history/ itself.
-        if not _plausible_id(uuid):
+        # are removed, so "", "." or ".." would reach file-history/ itself,
+        # and "memory" the auto memory. Only a uuid names a session.
+        uuid = _canonical(uuid)
+        if not uuid:
             return []
         cfg = _config_dir(ctx)
-        paths = []
+        found = []
         for pdir in _projects_dirs(ctx):
             base = os.path.join(pdir, ctx.ws_key, uuid)
-            paths += [p for p in (base + ".jsonl", base) if os.path.lexists(p)]
-        paths += [p for p in (os.path.join(cfg, "file-history", uuid),
-                              os.path.join(cfg, "session-env", uuid)) if os.path.lexists(p)]
+            found += [(pdir, p) for p in (base + ".jsonl", base) if os.path.lexists(p)]
+        found += [(cfg, p) for p in (os.path.join(cfg, "file-history", uuid),
+                                     os.path.join(cfg, "session-env", uuid)) if os.path.lexists(p)]
         job = self._owned_job(uuid, ctx)
         if job:
-            paths.append(job)
+            found.append((cfg, job))
         for path, pid, data in self._session_files(uuid, ctx):
             if not _session_file_live(data, pid):
                 # Keys before the session file: the file is what ties them to
                 # this session, so it must outlive them.
-                paths += _key_files(path) + [path]
+                found += [(cfg, p) for p in _key_files(path) + [path]]
         for root in _tmp_roots():
             try:
                 keys = sorted(os.listdir(root))
             except OSError:
                 continue
-            paths.extend(p for p in (os.path.join(root, k, uuid) for k in keys) if os.path.lexists(p))
-        return paths
+            found += [(root, p) for p in (os.path.join(root, k, uuid) for k in keys) if os.path.lexists(p)]
+        return found
+
+    def _owned_paths(self, uuid: str, ctx: DiscoveryContext) -> list:
+        # What lies behind a linked dir below its root is not the session's:
+        # it is kept, and residual_artifacts reports it.
+        return [p for root, p in self._candidates(uuid, ctx) if _inside(root, p)]
 
     def has_artifacts(self, uuid: str, ctx: DiscoveryContext) -> bool:
-        # Leftovers count without the transcript (a pre-#31 purge left them).
-        return bool(self._owned_paths(uuid, ctx))
+        # Leftovers count without the transcript (a pre-#31 purge left them),
+        # and so does one behind a link: the purge keeps it, but picking
+        # claude is what gets it reported as residual.
+        return bool(self._candidates(uuid, ctx))
 
     def conversation_in_use(self, uuid: str, ctx: DiscoveryContext) -> bool:
-        if conversation_in_use(uuid, [self.artifact_path(uuid, ctx)]):
+        # No claude process holds a name that is not a uuid; searching
+        # command lines for one ("a/b", "memory") only finds strangers.
+        canon = _canonical(uuid)
+        if not canon:
+            return False
+        # claude's own spelling and the one asked about, on a command line.
+        if any(conversation_in_use(u, [self.artifact_path(canon, ctx)]) for u in {canon, uuid}):
             return True
-        return any(_session_file_live(data, pid) for _, pid, data in self._session_files(uuid, ctx))
+        return any(_session_file_live(data, pid) for _, pid, data in self._session_files(canon, ctx))
+
+    def in_use_hints(self, uuid: str, ctx: DiscoveryContext) -> list:
+        return [f"a claude process whose session file under {os.path.join(_config_dir(ctx), 'sessions')}/ names it"] \
+            + super().in_use_hints(_canonical(uuid) or uuid, ctx)
 
     def purge_artifacts(self, uuid: str, ctx: DiscoveryContext) -> list:
         # Best effort: never raises (stop runs this inside its registry
@@ -299,6 +365,9 @@ class ClaudeAgentAdapter(BaseAgentAdapter):
         # shows up in residual_artifacts instead.
         # Ownership evidence (a job's state.json, a session file) is removed
         # only after what it vouches for, so a retry can still find the rest.
+        uuid = _canonical(uuid)
+        if not uuid:
+            return []
         purged = []
         job = self._owned_job(uuid, ctx)
         for path in self._owned_paths(uuid, ctx):
@@ -318,7 +387,8 @@ class ClaudeAgentAdapter(BaseAgentAdapter):
         roots (two levels), plus the content-matched jobs dir and session
         files with their (masked) key files. projects is not walked deeper;
         it can be very large."""
-        if not _plausible_id(uuid):
+        uuid = _canonical(uuid)
+        if not uuid:
             return []
         cfg = _config_dir(ctx)
         pdirs = _projects_dirs(ctx)
@@ -337,18 +407,11 @@ class ClaudeAgentAdapter(BaseAgentAdapter):
                         found.update(os.path.join(kdir, n) for n in os.listdir(kdir) if uuid in n)
                     except OSError:
                         pass
-        job = self._owned_job(uuid, ctx)
-        if job:
-            found.add(job)
+        # Every candidate, inside its root or behind a link (never purged).
+        found.update(_label(p) for _, p in self._candidates(uuid, ctx))
         for path, _, _ in self._session_files(uuid, ctx):
             found.add(path)
             found.update(_label(k) for k in _key_files(path))
-        for root in _tmp_roots():
-            try:
-                tkeys = os.listdir(root)
-            except OSError:
-                continue
-            found.update(p for p in (os.path.join(root, k, uuid) for k in tkeys) if os.path.lexists(p))
         return sorted(found)
 
     def spawn_spec(self, binary: str, session_uuid: str = "", use_wrapper: bool = False) -> str:

.agents/skills/lib_py/agents/base.py

@@ -308,6 +308,11 @@ class BaseAgentAdapter:
         """True while a live process still references the conversation."""
         return conversation_in_use(uuid, [self.artifact_path(uuid, ctx)])
 
+    def in_use_hints(self, uuid: str, ctx: DiscoveryContext) -> list:
+        """Where to look for what holds the conversation, shown when a purge
+        is refused because it is in use."""
+        return [f"any process with it on its command line (an editor, a grep, ...): ps -axww | grep {uuid}"]
+
     def spawn_spec(self, binary: str, session_uuid: str = "", use_wrapper: bool = False) -> str:
         raise NotImplementedError
 

.agents/skills/multi-agent-mux-stop/SKILL.md

@@ -62,7 +62,7 @@ bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh \
 | 1 | From the checks before the stop, nothing was changed: YAML not found, or the session is not registered. **The registry update after the stop also exits 1** (the row disappeared from the YAML during the run) |
 | 2 | Bad arguments (including the retired `--mode` / `--capture-id` / `--graceful`), or `--agent` omitted and not resolvable |
 | 3 | `--purge-conversation` without `--yes` |
-| 4 | Purge aborted: the herdr session, or an agent process still holding the conversation, survived the kill chain (nothing was changed) |
+| 4 | Purge aborted: the herdr session, or an agent process still holding the conversation, survived the kill chain. Records preserved: the registry row and the conversation files are untouched, though the session itself may already be down |
 | other | The registry update after the stop (YAML / DB write) failed and its code is passed through |
 
 Exits 2 and 3, and exit 1 from the pre-stop checks, come before anything is stopped, so nothing was changed. On exit 1 from the registry update, or an `other` exit, the session may already be down while its row still says `running`: check with `multi-agent-mux-status`, then run the stop again (it is idempotent).

.agents/skills/multi-agent-mux-stop/scripts/stop_session.sh

@@ -289,12 +289,12 @@ fi
 # registry lock. Any answer but "free" (0) keeps everything.
 if [ "$PURGE" = "1" ] && [ -n "$PURGE_UUID" ]; then
   inuse_rc=0
-  "$(_delegate_py_bin)" -m lib_py.agents in-use "$AGENT" "$PURGE_UUID" "$TARGET_CWD" --wait 5 >/dev/null || inuse_rc=$?
+  inuse_hints="$("$(_delegate_py_bin)" -m lib_py.agents in-use "$AGENT" "$PURGE_UUID" "$TARGET_CWD" --wait 5 2>&1 >/dev/null)" || inuse_rc=$?
   if [ "$inuse_rc" != "0" ]; then
     echo "ERROR: conversation $PURGE_UUID is still held by a live agent process (rc=$inuse_rc)." >&2
-    echo "  Refusing purge — records preserved (no state was modified)." >&2
-    echo "  For claude, see the session files naming it under ~/.claude/sessions/." >&2
-    delegate_publish_event "$DELEGATE_JOB_ID" cancelled "purge aborted: conversation still in use; no state was modified" "$DELEGATE_JOB_TOKEN" "$DELEGATE_JOB_ATTEMPT"
+    echo "  Refusing purge — records preserved: the registry row and the conversation files are untouched (the session itself may already be down)." >&2
+    [ -n "$inuse_hints" ] && printf '%s\n' "$inuse_hints" >&2
+    delegate_publish_event "$DELEGATE_JOB_ID" cancelled "purge aborted: conversation still in use; records preserved" "$DELEGATE_JOB_TOKEN" "$DELEGATE_JOB_ATTEMPT"
     exit 4
   fi
 fi

tests/test_a4_adapter_contract.py

@@ -209,12 +209,12 @@ def test_purge_artifacts_composite(tmp_path):
     # 1. Claude
     claude_adapter = get_adapter('claude')
     claude_ctx = DiscoveryContext(workspace=ws, agent_name='claude', home_dir=home)
-    c_path = claude_adapter.artifact_path('uuid-c', claude_ctx)
+    c_path = claude_adapter.artifact_path('0c1a5f3e-6b2d-4c8e-9a7f-1d2e3f4a5b6c', claude_ctx)
     os.makedirs(os.path.dirname(c_path), exist_ok=True)
     with open(c_path, 'w') as f:
-        f.write('{"sessionId": "uuid-c"}')
+        f.write('{"sessionId": "0c1a5f3e-6b2d-4c8e-9a7f-1d2e3f4a5b6c"}')
     assert os.path.exists(c_path)
-    purged_c = claude_adapter.purge_artifacts('uuid-c', claude_ctx)
+    purged_c = claude_adapter.purge_artifacts('0c1a5f3e-6b2d-4c8e-9a7f-1d2e3f4a5b6c', claude_ctx)
     assert len(purged_c) == 1
     assert not os.path.exists(c_path)
 

tests/test_issue31_purge_residual.py

@@ -47,6 +47,29 @@ def _fresh_id() -> str:
     return ident
 
 
+@pytest.fixture(autouse=True)
+def own_tmp_roots(tmp_path, monkeypatch):
+    """Every tmp root the claude adapter may look in stays inside the test:
+    TMP/TEMP/TMPDIR and the fixed /tmp fallback, here and in every python a
+    test starts (a sitecustomize on PYTHONPATH sets the fallback there)."""
+    from lib_py.agents.adapters import claude as claude_mod
+    sys_tmp, tmpdir, shim = tmp_path / "systmp", tmp_path / "tmpdir", tmp_path / "pyshim"
+    for d in (sys_tmp, tmpdir, shim):
+        d.mkdir()
+    monkeypatch.setattr(claude_mod, "_SYSTEM_TMP", str(sys_tmp))
+    monkeypatch.setenv("TMPDIR", str(tmpdir))
+    monkeypatch.delenv("TMP", raising=False)
+    monkeypatch.delenv("TEMP", raising=False)
+    (shim / "sitecustomize.py").write_text(
+        "try:\n"
+        "    from lib_py.agents.adapters import claude\n"
+        f"    claude._SYSTEM_TMP = {str(sys_tmp)!r}\n"
+        "except Exception:\n"
+        "    pass\n")
+    monkeypatch.setenv("PYTHONPATH", f"{shim}:{os.environ.get('PYTHONPATH', '')}")
+    return sys_tmp
+
+
 @pytest.fixture
 def conv() -> str:
     return _fresh_id()
@@ -239,18 +262,187 @@ def test_claude_residual_lists_leftovers_then_nothing(home, tmp_path, conv, othe
     assert adapter.residual_artifacts(conv, ctx) == [str(stray)]
 
 
-@pytest.mark.parametrize("bad", ["", ".", "..", "*", "../x", "a/b"])
+@pytest.mark.parametrize("bad", ["", ".", "..", "*", "../x", "a/b", "memory", " ", "notes",
+                                 "12345678-1234-1234-1234-12345678901g", "{conv} ", "x{conv}"])
 def test_claude_rejects_malformed_uuid(home, tmp_path, conv, bad):
+    bad = bad.format(conv=conv)
     ws = tmp_path / "ws"
     ws.mkdir()
     t = _tree(home, ws, conv, tmp_path / "ctmp")
+    # Claude Code's auto memory sits beside the session dirs, under the one
+    # non-uuid name there.
+    memory = home / ".claude" / "projects" / workspace_key(str(ws)) / "memory" / "MEMORY.md"
+    memory.parent.mkdir()
+    memory.write_text("m")
+    named = [home / ".claude" / d / bad / "x" for d in ("file-history", "session-env")
+             if bad.strip(". ") and "/" not in bad and "*" not in bad]
+    for p in named:
+        p.parent.mkdir(parents=True)
+        p.write_text("x")
     adapter = get_adapter("claude")
     ctx = _ctx(ws, home)
 
     assert adapter.purge_artifacts(bad, ctx) == []
     assert adapter.residual_artifacts(bad, ctx) == []
     assert adapter.has_artifacts(bad, ctx) is False
+    assert adapter.conversation_in_use(bad, ctx) is False
     assert all(p.exists() for p in t.values())
+    assert memory.exists() and all(p.exists() for p in named)
+
+
+@pytest.mark.parametrize("spell", [str.upper, lambda u: u[:18].upper() + u[18:]], ids=["upper", "mixed"])
+def test_any_spelling_of_the_uuid_is_the_lowercase_session(home, tmp_path, conv, live, spell):
+    """claude writes its ids in lowercase, and on macOS's default
+    case-insensitive APFS another spelling names the very same files. Every
+    check then uses the lowercase id: the live holder is seen, by its session
+    file or its command line, and a purge takes the session's own paths."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    t = _tree(home, ws, conv, tmp_path / "ctmp", pid=live.pid)
+    other = spell(conv)
+    assert other != conv
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert adapter.conversation_in_use(other, ctx) is True
+    for args in (["purge", "claude", other, str(ws)], ["in-use", "claude", other, str(ws)]):
+        res = _agents_cli(args, ws)
+        assert res.returncode == 4, res.stdout + res.stderr
+    assert all(p.exists() for p in t.values())
+
+    live.kill()
+    live.wait()
+    named = subprocess.Popen(["sh", "-c", "sleep 120", conv])
+    try:
+        time.sleep(0.05)
+        assert adapter.conversation_in_use(other, ctx) is True, "a command line naming the lowercase id"
+    finally:
+        named.kill()
+        named.wait()
+
+    assert adapter.has_artifacts(other, ctx) is True
+    purged = adapter.purge_artifacts(other, ctx)
+    assert not any(p.exists() for p in t.values()), {k: str(p) for k, p in t.items() if p.exists()}
+    assert purged and all(other not in p for p in purged)
+    assert adapter.residual_artifacts(other, ctx) == []
+
+
+def test_claude_purge_never_follows_a_linked_dir_below_a_root(home, tmp_path, conv):
+    """A symlinked <key> (tmp, projects) or file-history/ below its root is
+    not followed: what lies behind it stays and is reported as residual."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    cfg = home / ".claude"
+    key = workspace_key(str(ws))
+    out = tmp_path / "outside"
+    victims = [out / "tmp" / conv / "keep.txt", out / "proj" / f"{conv}.jsonl", out / "proj" / conv / "keep.txt",
+               out / "fh" / conv / "keep.txt"]
+    for v in victims:
+        v.parent.mkdir(parents=True, exist_ok=True)
+        v.write_text("keep")
+    troot = tmp_path / "ctmp" / f"claude-{UID}"
+    troot.mkdir(parents=True)
+    links = [troot / "linked-workspace", cfg / "projects" / key, cfg / "file-history"]
+    for link, target in zip(links, (out / "tmp", out / "proj", out / "fh")):
+        link.symlink_to(target)
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert adapter.purge_artifacts(conv, ctx) == []
+    assert all(v.exists() for v in victims) and all(link.is_symlink() for link in links)
+    assert adapter.residual_artifacts(conv, ctx) == sorted(
+        [str(troot / "linked-workspace" / conv), str(cfg / "projects" / key / f"{conv}.jsonl"),
+         str(cfg / "projects" / key / conv), str(cfg / "file-history" / conv)])
+
+
+def test_purge_cli_reports_a_linked_orphan_it_will_not_remove(home, tmp_path, conv):
+    """A candidate behind a link is all that is left: the CLI still picks
+    claude, so its residual names it, and removes nothing."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    keep = tmp_path / "outside" / conv / "keep.txt"
+    keep.parent.mkdir(parents=True)
+    keep.write_text("keep")
+    troot = tmp_path / "ctmp" / f"claude-{UID}"
+    troot.mkdir(parents=True)
+    (troot / "linked-workspace").symlink_to(tmp_path / "outside")
+
+    res = _agents_cli(["purge", "claude", conv, str(ws)], ws)
+
+    assert res.returncode == 0, res.stdout + res.stderr
+    assert json.loads(res.stdout) == {"agent": "claude", "purged": [],
+                                      "residual": [str(troot / "linked-workspace" / conv)], "in_use": False}
+    assert keep.exists()
+
+
+def test_claude_purge_removes_only_the_link_at_the_leaf(home, tmp_path, conv):
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    key = workspace_key(str(ws))
+    out = tmp_path / "outside"
+    keep = [out / "tmp" / "keep.txt", out / "proj" / "keep.txt"]
+    for k in keep:
+        k.parent.mkdir(parents=True)
+        k.write_text("keep")
+    leaves = [tmp_path / "ctmp" / f"claude-{UID}" / key / conv, home / ".claude" / "projects" / key / conv]
+    for leaf, target in zip(leaves, (out / "tmp", out / "proj")):
+        leaf.parent.mkdir(parents=True)
+        leaf.symlink_to(target)
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert set(adapter.purge_artifacts(conv, ctx)) == {str(p) for p in leaves}
+    assert not any(os.path.lexists(p) for p in leaves)
+    assert all(k.exists() for k in keep)
+    assert adapter.residual_artifacts(conv, ctx) == []
+
+
+def test_claude_roots_may_be_links(home, tmp_path, monkeypatch, conv):
+    """A root that is itself a link (/tmp -> /private/tmp on macOS, a linked
+    ~/.claude) is the boundary, not a way out of it."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    real_cfg, real_tmp = tmp_path / "real-cfg", tmp_path / "real-tmp"
+    real_cfg.mkdir()
+    real_tmp.mkdir()
+    (tmp_path / "cfg-link").symlink_to(real_cfg)
+    (tmp_path / "tmp-link").symlink_to(real_tmp)
+    monkeypatch.setenv("CLAUDE_CONFIG_DIR", str(tmp_path / "cfg-link"))
+    monkeypatch.delenv("CLAUDE_PROJECT_DIR")
+    monkeypatch.setenv("CLAUDE_CODE_TMPDIR", str(tmp_path / "tmp-link"))
+    t = _tree(home, ws, conv, tmp_path / "tmp-link", cfg=tmp_path / "cfg-link")
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    adapter.purge_artifacts(conv, ctx)
+
+    assert not any(p.exists() for p in t.values()), {k: str(p) for k, p in t.items() if p.exists()}
+    assert adapter.residual_artifacts(conv, ctx) == []
+
+
+@pytest.mark.parametrize("name", ["uuid-c", "memory", "notes"])
+def test_a_non_uuid_id_reaches_nothing(home, tmp_path, name):
+    """Only a uuid names a claude session: no path is built for any other id,
+    not even the `<id>.jsonl` the adapter took before #31."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    proj = home / ".claude" / "projects" / workspace_key(str(ws))
+    proj.mkdir()
+    jsonl = proj / f"{name}.jsonl"
+    jsonl.write_text(json.dumps({"sessionId": name, "cwd": os.path.realpath(str(ws))}) + "\n")
+    kept = [jsonl, proj / name / "a", home / ".claude" / "file-history" / name / "b"]
+    for p in kept[1:]:
+        p.parent.mkdir(parents=True)
+        p.write_text("x")
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert adapter.has_artifacts(name, ctx) is False
+    assert adapter.residual_artifacts(name, ctx) == []
+    assert adapter.purge_artifacts(name, ctx) == []
+    res = _agents_cli(["purge", "claude", name, str(ws)], ws)
+    assert json.loads(res.stdout)["purged"] == [], res.stdout + res.stderr
+    assert all(p.exists() for p in kept)
 
 
 def test_purge_cli_resolves_claude_from_leftovers_only(home, tmp_path, conv):
@@ -314,6 +506,60 @@ def test_session_file_liveness_fails_safe(monkeypatch, live):
     assert claude_mod._session_file_live({"startedAt": hour_ago}, live.pid) is True, "ps unavailable: live"
 
 
+def test_liveness_reads_lstart_as_utc(tmp_path, monkeypatch, live):
+    """2026-11-01 01:30 happens twice in EST5EDT. A process that started at
+    the second one (06:30 UTC) shows lstart 01:30 to a local-time ps; read as
+    the first (05:30 UTC) it predates a session file written at 05:45. ps
+    runs with TZ=UTC0 instead, which BSD ps and procps both honour."""
+    import calendar
+    from lib_py.agents.adapters import claude as claude_mod
+    fake = tmp_path / "fakebin"
+    fake.mkdir()
+    (fake / "ps").write_text('#!/bin/sh\nif [ "$TZ" = UTC0 ]; then echo "Sun Nov  1 06:30:00 2026"; '
+                             'else echo "Sun Nov  1 01:30:00 2026"; fi\n')
+    (fake / "ps").chmod(0o755)
+    utc = lambda hhmmss: calendar.timegm(time.strptime(f"2026-11-01 {hhmmss}", "%Y-%m-%d %H:%M:%S")) * 1000  # noqa: E731
+    try:
+        with monkeypatch.context() as m:
+            m.setenv("PATH", f"{fake}:{os.environ['PATH']}")
+            m.setenv("TZ", "EST5EDT,M3.2.0,M11.1.0")
+            time.tzset()
+            assert claude_mod._session_file_live({"startedAt": utc("05:45:00")}, live.pid) is False, "reused pid"
+            assert claude_mod._session_file_live({"startedAt": utc("06:30:02")}, live.pid) is True
+    finally:
+        time.tzset()
+
+
+@pytest.mark.parametrize("started", ["NaN", float("nan"), float("inf"), float("-inf"), "inf", "1760000000000",
+                                     "soon", True, False, None, [1], pytest.param(10 ** 400, id="10**400"),
+                                     "<missing>"])
+def test_an_unusable_started_at_means_live(live, started):
+    from lib_py.agents.adapters import claude as claude_mod
+    data = {} if started == "<missing>" else {"startedAt": started}
+    assert claude_mod._session_file_live(data, live.pid) is True
+    assert claude_mod._session_file_live(data, _dead_pid()) is False, "a dead pid holds nothing"
+
+
+@pytest.mark.parametrize("raw", ["NaN", '"NaN"', "Infinity", "true",
+                                 pytest.param("1" + "0" * 400, id="10**400")])
+def test_a_live_holder_with_an_unusable_started_at_blocks_the_purge(home, tmp_path, conv, live, raw):
+    """json.load turns a bare NaN or Infinity into a float that every
+    comparison fails, which once made a live holder look stale, and a huge
+    integer into an int no float can hold."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    sfile, key = _session_file(home / ".claude", live.pid, conv)
+    sfile.write_text(f'{{"pid": {live.pid}, "sessionId": "{conv}", "cwd": "/x", "startedAt": {raw}}}')
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert adapter.conversation_in_use(conv, ctx) is True
+    res = _agents_cli(["in-use", "claude", conv, str(ws)], ws)
+    assert res.returncode == 4, res.stdout + res.stderr
+    assert adapter.purge_artifacts(conv, ctx) == []
+    assert sfile.exists() and key.exists()
+
+
 def test_claude_purge_takes_the_stale_key_with_its_session_file(home, tmp_path, conv, other, live):
     ws = tmp_path / "ws"
     ws.mkdir()
@@ -349,6 +595,7 @@ def test_claude_config_dir_moves_the_config_root(home, tmp_path, monkeypatch, co
     ctx = _ctx(ws, home)
 
     assert adapter.conversation_in_use(conv, ctx) is True
+    assert adapter.in_use_hints(conv, ctx)[0] == f"a claude process whose session file under {cfg / 'sessions'}/ names it"
     res = _agents_cli(["purge", "claude", conv, str(ws)], ws)
     assert res.returncode == 4, res.stdout + res.stderr
     assert all(p.exists() for p in t.values())
@@ -411,14 +658,14 @@ def test_a_job_dir_that_cannot_be_emptied_keeps_its_state_json(home, tmp_path, m
     assert adapter.residual_artifacts(conv, ctx) == []
 
 
-def test_claude_tmp_root_rules(tmp_path, monkeypatch):
+def test_claude_tmp_root_rules(tmp_path, monkeypatch, own_tmp_roots):
     from lib_py.agents.adapters.claude import _tmp_roots
     name = f"claude-{UID}"
     x, y, z = tmp_path / "x", tmp_path / "y", tmp_path / "z"
-    for d in (x / name, y / name, z / name):
+    for d in (x / name, y / name, z / name, own_tmp_roots / name):
         d.mkdir(parents=True)
     real = lambda roots: [os.path.realpath(r) for r in roots]  # noqa: E731
-    sys_tmp = [os.path.realpath(f"/tmp/{name}")] if os.path.isdir(f"/tmp/{name}") else []
+    sys_tmp = [os.path.realpath(str(own_tmp_roots / name))]
 
     monkeypatch.setenv("CLAUDE_CODE_TMPDIR", str(x))
     monkeypatch.setenv("TMPDIR", str(z) + "/")
@@ -438,6 +685,14 @@ def test_claude_tmp_root_rules(tmp_path, monkeypatch):
     assert real(_tmp_roots()) == [str(z / name)] + sys_tmp
 
 
+def test_tests_never_reach_the_real_tmp_root(tmp_path, own_tmp_roots):
+    from lib_py.agents.adapters.claude import _tmp_roots
+    assert all(os.path.realpath(r).startswith(os.path.realpath(str(tmp_path))) for r in _tmp_roots())
+    res = subprocess.run([sys.executable, "-c", "from lib_py.agents.adapters import claude; print(claude._SYSTEM_TMP)"],
+                         capture_output=True, text=True, env=_env(), timeout=30)
+    assert res.stdout.strip() == str(own_tmp_roots), res.stdout + res.stderr
+
+
 # ---------------------------------------------------------------------------
 # in-use CLI and the stop gate
 # ---------------------------------------------------------------------------
@@ -457,6 +712,8 @@ def test_in_use_cli_waits_then_answers(home, tmp_path, conv, live):
     assert res.returncode == 4, res.stdout + res.stderr
     assert json.loads(res.stdout)["in_use"] is True
     assert time.monotonic() - t0 >= 1
+    assert f"session file under {home / '.claude' / 'sessions'}/ names it" in res.stderr
+    assert f"ps -axww | grep {conv}" in res.stderr
 
     assert _agents_cli(["in-use", "nosuchagent", conv, str(ws)], ws).returncode == 1
     assert _agents_cli(["in-use", "claude"], ws).returncode == 1
@@ -540,6 +797,8 @@ def test_stop_purge_refuses_while_the_claude_process_lives(stop_box, conv):
         assert res.returncode == 4, res.stdout + res.stderr
         assert "herdr already dead" in res.stdout
         assert "records preserved" in res.stderr
+        assert f"session file under {stop_box / '.claude' / 'sessions'}/ names it" in res.stderr
+        assert f"ps -axww | grep {conv}" in res.stderr
         assert "purged: " not in res.stdout
         assert all(p.exists() for p in t.values())
         assert _row_left(stop_box, name) == (True, True)