Fleet telemetry showed "unknown" as the single largest execution_surface
bucket. Two construction paths were mis-attributed, both silently:
1. ACP editor sessions (VS Code / Zed / JetBrains) declare platform="acp",
but "acp" was absent from EXECUTION_SURFACES, so the contract's
closed-schema fallback folded every editor session into "other" --
the bucket meant for genuinely unclassifiable traffic.
2. batch_runner built agents from _AGENT_PASSTHROUGH, which omitted
"platform" entirely, so every batch task run reported "unknown"
despite "batch" already being a first-class surface.
Neither is a reporting bug in the exporter: both are declaration gaps at
the construction site. "unknown" must mean "this run genuinely could not
be attributed", not "a construction site forgot to say who it was".
Changes:
- add "acp" to EXECUTION_SURFACES and map it to the "interactive"
entrypoint alongside cli/desktop/tui
- add "acp" to the v2 wire schema enum (kept in sync by an existing test)
- pass platform through batch_runner: added to _AGENT_PASSTHROUGH, set
self.platform = "batch" on the runner, and defaulted at the worker call
site so callers that build a config without it stay attributable
Wire compatibility: the ingest service validates the envelope only and
stores metric bodies verbatim, so packages carrying the new value are
accepted by the already-deployed server. No coordinated deploy needed.
Tests: 12 new behavioural tests. Verified red before the fix (4 failed),
green after. Three fix-mutants confirmed killed:
M1 revert acp from EXECUTION_SURFACES -> 3 failed
M2 revert acp entrypoint mapping only -> 1 failed
M3 revert batch passthrough -> 1 failed
No source-text assertions; every test is a contract between the surfaces
the schema accepts and the surface each path declares. A guard test pins
that a genuinely undeclared run still reports "unknown", so attribution
cannot be "fixed" by inventing a default that hides real gaps.
Ben Barclay
5a1246f830