The Problem

Our iron condor scanner picked option expirations mathematically — any Friday in the 30-45 DTE window. But Alpaca doesn’t list weekly option contracts months in advance. When the scanner chose April 3, 2026 (a Friday, 39 DTE), the symbols SPY260403P00640000 didn’t exist yet.

Result: APIError: invalid legs on every scan for weeks. Zero trades executed.

Root Cause

find_expiration_date() calculated dates without querying the broker. Weekly SPY options are only listed ~2-3 weeks before expiration. Monthly options (third Fridays) are listed months ahead.

The Fix

Two-layer defense:

Layer 1 — Smart Expiry Discovery: Query Alpaca’s OptionChainRequest API for real expirations. Only return dates where contracts actually exist. Fall back to third Fridays (monthly — always listed).

Layer 2 — Symbol Validation: Before submitting any order, verify all 4 OCC symbols exist via OptionSnapshotRequest. If any symbol is missing, abort with a clear error.

Result

First autonomous trade in weeks submitted at 17:50 UTC on Feb 23, 2026. Both Scanner and Autonomous workflows green.

Lesson

Never assume financial instrument availability from date math. Always validate against the broker’s actual listings before constructing orders.

Our North Star Strategy*