CLI/TUI/Desktop sessions were *recreated* on every POST to /api/chat/start
instead of *claimed*, because the claim/synthesis logic only ran on the GET
stub path. GET /api/session already synthesized a read-only stub from
state.db, but POST /api/chat/start unconditionally 404'd on any session_id
without a WebUI JSON sidecar — and the frontend 404 handler then ran its
empty-state self-heal, stripping the URL and silently discarding the user's
typed message.
This closes the GET/POST asymmetry by routing both endpoints through a new
shared helper, _claim_or_synthesize_cli_session, that materialises a
WebUI-owned Session on first write (via synth.save()).
Preserved guards:
- Denylist of foreign-owned sources via _is_claimable_cli_source:
{claude_code, cron, external_agent, gateway, messaging, unknown}; cli/tui/
desktop fall through to CLAIMABLE.
- The not_claimable arm returns 403 (NOT 404) and never reaches synth.save()
(ownership guard). 403-vs-404 matters: the frontend 404 handler runs the
empty-state self-heal that strips the URL, so a legitimately-listed
read-only session must surface a refusal instead of vanishing.
- created_at mapping from state.db is load-bearing (Session.save() doesn't
touch created_at), so claimed sidecars no longer sort as "Jan 1 1970".
- The 500 path uses _sanitize_error so a raw OSError can't leak the sidecar
filesystem path.
- The #2782 deleted-WebUI-session 404 self-heal contract is preserved via
_session_index_marks_was_webui.
- The GET path's _session_visible_to_active_profile gate is preserved.
Polish over the original PR:
- Test docstring rationale corrected re: updated_at — Session.save() defaults
touch_updated_at=True so the claimed sidecar's updated_at is stamped to
"now" regardless; only created_at is preserved. Assertions unchanged.
- touch_updated_at=True default kept (a claimed session jumps to "just now",
which is the desired UX); no test pins persisted updated_at to the state.db
value.
- Added a path-leak assertion to the 500-sanitisation test: the sanitized
string must not contain a '/' segment from the session-store root.
Salvage of #4153.
Co-authored-by: merodahero <merodahero@users.noreply.github.com>
Rod Boev