The existing single-shot autoroute leaves 1-7 nets unrouted on dense
boards in my testing. Best-of-N drives that to 0 most of the time by
running Freerouting a few times with varied --max-passes and keeping
the SES with the best routing score.
New optional parameters (all backward-compatible):
attempts: int, default 1 (unchanged behaviour). When > 1, run
Freerouting N times and pick the highest-scoring SES.
targetNets: list of critical net names. An attempt that routes all
of them earns a 50,000-point scoring bonus.
passSchedule: list of --max-passes values to cycle through across
attempts. Default: [50, 60, 65, 70, 75, 80, 85, 90, 55,
95] (wraps if attempts > len). Ignored when attempts=1
(legacy maxPasses still used).
Scoring contract (pinned by tests):
score = nets_routed * 1000 + segments
if targetNets and all routed: score += 50_000
- +1 net always beats any segment-count delta (1000 pt step).
- Segments break ties at equal net count.
- Target bonus dominates net-count gains from unrelated nets.
## Implementation notes
- When attempts > 1, each attempt runs with `-mt 1` (single-thread
optimisation). Freerouting 2.x's multi-threaded optimiser is
documented to introduce clearance violations, so forcing
single-thread during scoring keeps the comparison apples-to-apples.
- One failed attempt does not abort the whole best-of-N run. The
failure is recorded in the response under attempts[] with ok=False,
and the remaining attempts compete for best. If every attempt fails
the response surfaces a clear error.
- The winning SES is preserved as <stem>_best.ses next to the
canonical <stem>.ses so the caller can inspect it after the run.
- Response shape:
attempts == 1: unchanged (no attempts/best_attempt fields)
attempts > 1: adds attempts[], best_attempt, best_score,
best_ses_path
## Attribution
Scoring approach and default pass schedule ported from
morningfire-pcb-automation
(https://github.com/NiNjA-CodE/morningfire-pcb-automation,
scripts/routing/freeroute_runner.py). Credited in the function
docstring, the TypeScript wrapper comment, the tool description (visible
to MCP clients), and the CHANGELOG entry.
The MCP version adds: cleaner per-attempt result reporting, automatic
single-thread optimisation, graceful degradation on partial failure,
and explicit validation that surfaces clean error payloads for invalid
attempts values.
## Tests
tests/test_autoroute_score.py 8 cases, scoring contract
tests/test_autoroute_best_of_n.py 6 cases, orchestration logic
All 14 passing. Tests are pure-Python: subprocess is mocked so the
suite runs in any environment (no Java / Freerouting / KiCad required).
- Single-attempt response shape unchanged
- Best-of-three picks the highest-scoring SES
- One nonzero exit attempt doesn't abort the run
- passSchedule wraps when attempts exceeds len
- targetNets bonus wins over higher raw net count
- attempts=0 rejected with clean error before DSN export
- +1 net (1000 pts) dominates any segment delta
- Segments tiebreak at equal net count
- Quoted net names in SES are normalised vs unquoted targets
TypeScript builds clean.
