calesthio/OptionsCanvas

Four related fixes for trader-facing weirdness uncovered during live use today.

What's in this release

Smart error when a contract can't be found

/api/open_position used to return a single unhelpful string ('Could not find suitable option contract') when something was wrong. Now it distinguishes the failure modes:

• DTE not in chain → "DTE=6 not available for MU. Valid DTEs: 3, 10, 17, 23."
• Strike not at this DTE → "Strike $885 not available for MU CALL DTE=10. Nearest valid: $880."
• No options for this symbol → "No options found for SYMBOL."

Backend also returns structured valid_dtes + valid_strikes fields so future UI can auto-correct.

Frontend DTE pre-flight

When you click Buy, the panel now validates the selected DTE against the current symbol's actual chain before sending the order. If your selection is stale (carried over from a previous symbol that had it but the current one doesn't), you get an immediate toast naming valid DTEs and the nearest one — no 10-second timeout, no broker-rejected order.

Stale-response guard on symbol switching

TradingPanel.loadValidContracts now captures the requested symbol at request time and discards the response if you switched symbols mid-fetch. Stops the previous symbol's options leaking into the new symbol's dropdown during fast switching.

Ref-counted stream subscriptions

The big perf fix:

• Backend now tracks subscriptions per-client (sid → set of (symbol, timeframe)). handle_disconnect releases all of the disconnecting client's claims; if no other client wants the same (symbol, timeframe), the streaming loop stops polling that symbol.
• Frontend unsubscribeChart now updates its local subscription set even when the WebSocket is disconnected, so a reconnect-then-resubscribe doesn't replay stale subscriptions.

Previously: every closed browser tab leaked entries into streaming_symbols permanently. The background loop kept fetching bars for symbols nobody was watching. Verified by inspecting logs: on a clean boot you should now only see Fetching bars for <current_symbol>, no orphaned symbols accumulating.

How to upgrade

git pull
# restart the launcher, refresh the browser tab

The streaming-symbol cleanup needs a backend restart to clear the in-memory leaked entries from the previous session.

What's next

A proper refactor is queued for v0.2.0: applying AbortController + correlation-ID guards uniformly across every symbol-scoped async path (frontend ApiClient, TradingPanel, ChartManager, OrderPanelOnChart), plus splitting the backend's strike-increment cache so heuristic fallbacks don't poison the long-TTL verified cache. That's the architectural fix for the entire class of "I switched symbols and the panel showed stale data" bugs — these v0.1.x patches reduce the surface area, v0.2.0 eliminates the class.