prisma-risk / tsoracle / 26678761119

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fix(client): don't issue budget-squeezed seq ride-out attempts (deflake) (#586)

fix(client): don't issue budget-squeezed seq ride-out attempts

Deflakes seq_stale_epoch_hint_rides_out_then_surfaces_election (and the get_seq ride-out path generally) under CI load.

issue_seq_rpc rides out an election by re-issuing GetSeq until the overall deadline. Budget::next_attempt() has no minimum floor, so the final ride-out attempt is handed a near-zero budget squeezed by the overall deadline. On a starved runner that attempt's RPC times out post-send -> classify -> Uncertain -> an immediate 'return SeqUncertain', bypassing surface_error's sticky-election-signal precedence. The get_ts path tolerates this (its squeezed timeout is a transport last_err that surface_error already ranks below the election signal); the non-idempotent dense path cannot, since a post-send timeout is Uncertain and must return immediately to avoid a double-spend on retry.

Fix: once at least one attempt has been issued, the seq loop refuses to issue a sub-viable attempt whose budget the overall deadline has squeezed below a full per_attempt_deadline window. A never-issued RPC is unambiguous, so it breaks and lets surface_error return the recorded election FAILED_PRECONDITION. This also removes a real-world wart: a legitimate ride-out no longer manufactures a spurious SeqUncertain (forcing caller reconciliation) when the runner is briefly slow. Scoped to issue_seq_rpc; get_ts is unchanged.

Adds seq_ride_out_skips_squeezed_attempt_and_surfaces_election: a deterministic regression (server delays every reply 300ms; 500ms/500ms policy makes the second attempt structurally squeezed below the 300ms reply floor) that fails with SeqUncertain without the fix. Stressed 40x (new) and 120x incl. under induced CPU starvation (the previously-flaky test) with zero failures.

Signed-off-by: Sebastian Thiebaud <sebastian@prismarisk.com>

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