`explore`

A full-screen terminal UI for browsing the address space.

Usage

opcua-cli explore <endpoint> [global-options]

One argument, no extra flags beyond the globals. Connects, starts the TUI, exits when you press q.

What it looks like

┌ Address space ──────────────────────┐┌ Details ────────────────────────────┐
│ ▾ Objects                           ││ NodeId:      ns=2;s=PLC/Speed       │
│   ▾ Server                          ││ BrowseName:  2:Speed                │
│     • ServerArray                   ││ DisplayName: Speed                  │
│     • NamespaceArray                ││ NodeClass:   Variable               │
│     • ServerStatus                  ││                                     │
│   ▾ DeviceSet                       ││ Value:       42.5                   │
│     ▾ PLC1                          ││ Type:        Double                 │
│       › Speed                       ││ Status:      Good (0x00000000)      │
│       • Mode                        ││ Source:      2026-05-15T10:30:00+00:00 │
│       • Health                      ││                                     │
└─────────────────────────────────────┘└─────────────────────────────────────┘
┌ Log — q=quit  ↑↓=move  →/Enter=expand  ←=collapse/up  r=refresh ───────────┐
│ [10:30:00] Connected. Browsing Objects folder (i=85)...                    │
│ [10:30:00] Loaded 4 root children.                                          │
│ [10:30:02] Browsed ns=2;s=PLC: 3 children.                                  │
└─────────────────────────────────────────────────────────────────────────────┘

The screen has three regions: the address-space tree (left, scrollable), the selected node's details (right), and the log pane (bottom). The pane titles are literally Address space, Details, and Log — … (the log border carries the keybinding hint).

Only browse / read / connection-level events appear in the log — moving the selection with the arrow keys doesn't log anything.

Keybindings

The TUI is keyboard-only — no mouse handler is wired up (php-tui exposes mouse events, but ExploreApp does not consume them).

What happens under the covers

explore runs on top of php-tui. The application:

1. 01

   Browses lazily.

   Only the currently-expanded folders are fetched. Expanding a folder issues a browse() for that NodeId and renders the children.

2. 02

   Caches values.

   Once a Variable node's value has been read, it's cached for the session. Reload with r to force a fresh read.

3. 03

   Logs at the bottom.

   Every action (browse, read, error) appears in the log pane. Useful for understanding what triggered each round-trip.

4. 04

   Drains input then sleeps 50 ms

   per loop iteration — effectively a ~20 Hz tick. Snappy on every modern terminal.

When to use it

• First exploration of an unfamiliar server. Faster than browse --recursive because you only descend into the parts you care about.
• Verifying a path. Click through to confirm /Objects/PLC1/Speed exists and has the value you expect.
• Demoing to non-developers. The TUI is intuitive enough that a process engineer can use it without reading docs.

Limitations

• Read-only. No write support. Use opcua-cli write for modifications.
• No subscriptions. Values are point-in-time on read. Press r to refresh; for live updates use opcua-cli watch.
• Terminal-dependent rendering. Best on a 100×30+ terminal with UTF-8 + true-color. Tiny terminals will clip the panes.
• No search. Browse manually; no global node-name search yet.

Common pitfalls

• Slow expansion on huge folders. A folder with 10 000 children fetches them all on expand. Cap your patience or prefer dump:nodeset for full-address-space work.
• Connection drops are not recovered. A network blip during exploration disconnects the session. Press q and re-launch.
• Untrusted certificates. explore follows the same trust rules as the other commands. If the server cert is not yet trusted, the session fails to open and the TUI never starts — the CLI prints the helpful trust <endpoint> hint and exits. See Trust store workflow.