The childToolOmissions comparison arms ran only through the examples
snapshot suites, which the unit coverage gate does not count. Add an
authored child-omission scenario to the synthetic replay suite: one
scripted child omits the declared tool (header pin minus the omission,
prompt pin skipped), one keeps the full set (pin and prompt compared
verbatim), restoring 100% branch coverage on suite.ts.
Windows does not guarantee that an ordinary child process will continue after its parent exits. The fake ACP agent exited immediately after spawning its late-output descendant, so Windows could tear down that descendant and close the protocol stream before the delayed ACP update was written.
Launch the descendant in detached mode while continuing to inherit stdout and stderr, then unref it as before. This preserves the intended regression boundary: launcher shutdown must wait for descendant-held stdio and parse the final buffered frame after the direct ACP parent exits.
Use Node's explicit inherit stdio mode for the fake descendant instead of passing the parent process stream objects as child descriptors.
This keeps the grandchild's stdout and stderr handles open across the fake ACP parent's exit on Windows, so launcher shutdown must drain the late buffered update and stderr bytes just as it does on POSIX.
Pass the fake descendant the parent process's stdout and stderr stream handles instead of Unix-style numeric file descriptors. This lets Windows duplicate the live ACP and diagnostic pipes so launcher shutdown can prove that inherited handles, buffered frames, and stderr all drain after the parent exits.
Observe the pending update promise before initiating shutdown as well, preventing a missing late frame from becoming a transient unhandled rejection before the assertion reports the fixture failure.
The ACP bridge registers the first real approval answerer: an ask for an
agent it owns becomes session/request_permission attached to the already-
streamed tool call (one-shot allow_once/reject_once only), outcomes map
conservatively (unknown optionId never grants, client cancel → cancelled),
and foreign or call-less requests delegate down the waterfall. The snapshot
harness accepts scripted permissionAnswers (FIFO; an unscripted prompt
answers cancelled, fail closed) so recorded scenarios can drive the wire
keylessly.
A scripted fake ACP agent bin (tests/fixtures/fake-acp-agent.ts) speaks
real newline JSON-RPC through the REAL runScenario spawn path (tsx
loader, temp cwd, env plumbing); every behavior — prompt outcome,
session/new rejection, persisted logs, filesystem noise — comes from a
behavior.json beside the fixture, so specs script whole subprocess runs
from data. harness.spec.ts drives every step op, both expect-error arms,
the permission-stub default, env forwarding, workspace seeding, and the
harvest ordering/noise/fallback branches. suite.spec.ts runs the factory
for real at collection time: a replay suite over committed synthetic
fixtures and a record suite over a temp copy (write-back never touches
the committed tree; ACP_SNAPSHOT_SPEC_BOOTSTRAP=1 re-bootstraps it),
plus direct cases for the exported pure helpers. The suite factory's
pure helpers (childFixturePaths, fixtureContext, normalizedHeaders,
headerDeltaCount) are exported for those direct specs.
Two branches carry justified v8 ignores, both structurally unreachable:
the waiter in-bounds guard (noUncheckedIndexedAccess) and waitForExit's
already-exited race guard (both call sites sit one synchronous frame
after stdin.end()/kill()). The fake bin substitutes the session/new cwd,
not process.cwd(), into scripted logs — the realpath difference
(/private on darwin) is exactly what the real bin's header carries.
packages/support/acp-snapshot/src is at 100% statements, branches,
functions, and lines under the per-file gate.
