Unseals the Sparkplug branch of the MQTT address-picker browser that Task 10
deliberately sealed shut, and adds the first (and only) sanctioned publish on a
browse session.
- MqttBrowseSession serves Group -> EdgeNode -> [Device] -> Metric in Sparkplug
mode, decoded from observed NBIRTH/DBIRTH certificates (the only Sparkplug
messages that name their metrics). Node-level metrics hang directly under
their edge node -- no synthesised device folder, because the authored address
tuple genuinely has deviceId = null for them. Metric node ids use a '::'
separator: a metric name may contain '/', so slash-joining would make a
node-level metric indistinguishable from a device folder.
- AttributesAsync is purely birth-derived in Sparkplug mode. The plain path's
UTF-8 inference / payload-snippet machinery does not run and no payload bytes
are retained: a Sparkplug body is protobuf and would be reported as
"(N bytes, binary)" for every metric in the plant. A datatype ToDriverDataType
cannot map is reported as the Sparkplug type name, never coerced.
- RequestRebirthAsync(scope) is the one publishing member, reached only by an
explicit operator action. It routes through the counted PublishAsync
chokepoint via a private RebirthTransport adapter, so PublishCountForTest
still proves that OpenAsync/RootAsync/ExpandAsync/AttributesAsync/Observe/
DisposeAsync publish nothing -- now in both modes. A device or metric scope
resolves up to its owning edge node (NCMD is node-addressed); group scope
enumerates observed edge nodes and is refused whole past
MaxGroupRebirthNodes = 32.
- BrowserSessionService.RequestRebirthAsync gates on the same DriverOperator
policy that gates the picker, evaluated server-side where the action happens
rather than only at render time, fails closed, and Info-logs the scope and the
published count. Exposed through the new IRebirthCapableBrowseSession contract
so "does this session write?" stays a type question.
- ToBrowseOptions' Last-Will landmine re-verified: MqttDriverOptions still
carries nothing will-shaped (an NDEATH is a broker-published will and would be
invisible to PublishCountForTest), now pinned by a reflection guard.
Falsifiability: injecting a publish into RootAsync reddens the Sparkplug and
plain passivity tests; double-publishing per target reddens all four
one-NCMD-per-node assertions. 572/572 MQTT tests, 24/24 AdminUI browsing tests.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Three review findings, all "unbounded work/memory from untrusted broker input"
rather than correctness bugs - but this points at a live plant broker.
1. InferPayload decoded the WHOLE payload on MQTTnet's dispatcher thread before
trimming to 64 chars. The node cap never engages here: a multi-MB blob on an
already-known topic creates no node, it just updates one, so the cost repeats
per message forever. Now at most PayloadInspectMaxBytes (512) are examined.
A blind slice can cut a multi-byte sequence, which the strict decoder would
report as "binary" - TrimToUtf8Boundary backs the window off to the last whole
sequence so good UTF-8 is never mislabelled. A clipped payload is String by
construction rather than inferred from a partial view.
2. The node cap bounded COUNT, not bytes. MQTT topics run to ~65KB, so 50k nodes
near that ceiling is a multi-GB tree. Topics now bounded at 1024 chars and
segments at 256, rejected whole (a truncated topic is a DIFFERENT topic the
picker would commit as a tag address) and surfaced via an __oversized__ marker
kept distinct from __truncated__ - the operator's remedy differs.
3. Control characters in a snippet would break the picker's single-line row;
Trim() only strips the ends. Now scrubbed to spaces.
Each guard was falsified independently by neutering it and confirming exactly one
test reddens. That found a real gap: the oversized-topic test was passing via the
SEGMENT bound, leaving the whole-topic bound untested - the test now uses many
short segments so only the topic bound can reject it.
Also records the .Driver project reference as a known, deliberate exception to the
.Browser -> .Contracts pattern, with its cost (AdminUI gains Core + Polly + Serilog)
and the clean fix (a leaf transport project; NOT a move into .Contracts, which is
deliberately transport-free).
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
MQTT has no discovery protocol, so the AdminUI address picker learns the topic
space the only way there is: subscribe to the wildcard and accumulate what
arrives. MqttBrowseSession serves that observation as a segment tree (split on
'/'); MqttDriverBrowser opens it with a distinct "{clientId}-browse-{guid8}"
identity under a 5-30 s clamped budget.
Browsing publishes NOTHING - the load-bearing safety property, since the picker
runs against a live plant broker. Every outbound message must route through the
single PublishAsync seam that counts into PublishCountForTest; P2's operator-
triggered Sparkplug rebirth is the one intended exception. Sparkplug mode fails
fast rather than serving a raw spBv1.0 topic tree that looks like a metric tree.
Deviation from the plan's ref list: the project also references .Driver so the
browse CONNECT reuses MqttConnection.BuildClientOptions (TLS posture, CA-pin
chain validator, credentials). A second copy would be a security divergence.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty