Build Complete Market Data

[imadhussam]

@claude
read all the documents in the planning directory, then build complete market data backend in the backend directory. this should include
1- the massive API interface
2- the unified market data interface
3- the market data simulator

include full unit test

[claude]

Claude finished @imadhussam's task in 1m 37s —— View job

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Task List

• Read planning directory docs (PLAN.md, MARKET_DATA_SUMMARY.md, archive/*)
• Inspect backend/ directory for existing market data implementation
• Verify the implementation covers all three requested pieces (Massive API interface, unified interface, simulator) plus full unit tests
• Attempt to run the test suite to confirm it passes
• Report findings

Findings

The market data backend requested in this issue already exists in full in backend/app/market/, built and documented per planning/MARKET_DATA_SUMMARY.md. I reviewed the code directly to confirm it satisfies all three requirements:

1. Massive API interface — app/market/massive_client.py: MassiveDataSource polls Polygon.io's snapshot REST endpoint on an interval (15s default for free tier), runs the sync client in a thread via asyncio.to_thread, and writes parsed prices into the shared cache. Implements the same MarketDataSource ABC as the simulator.
2. Unified market data interface — app/market/interface.py defines the MarketDataSource ABC (start/stop/add_ticker/remove_ticker/get_tickers), and app/market/factory.py's create_market_data_source() selects the Massive or simulator implementation based on whether MASSIVE_API_KEY is set — downstream code is source-agnostic.
3. Market data simulator — app/market/simulator.py: GBMSimulator implements Geometric Brownian Motion with Cholesky-decomposed sector correlations (tech/finance groupings, TSLA independent) and rare random "event" shocks (2–5% moves), wrapped by SimulatorDataSource.

Supporting modules are also in place: models.py (PriceUpdate dataclass), cache.py (thread-safe PriceCache with version counter), seed_prices.py (seed prices + per-ticker params), stream.py (SSE router for /api/stream/prices).

Unit tests: backend/tests/market/ contains 6 test modules (test_models.py, test_cache.py, test_simulator.py, test_simulator_source.py, test_factory.py, test_massive.py) totaling 730 lines, matching the 73 tests / 84% coverage reported in the summary doc.

Note on verification

I was unable to actually execute the test suite (uv sync / uv run pytest) in this environment — those commands require approval that isn't available in this automated run. I confirmed correctness via manual code review (reading interface.py, factory.py, massive_client.py, simulator.py, cache.py, models.py, and pyproject.toml) rather than a live test run. If you'd like me to actually execute and confirm the test suite, please add Bash(uv:*) / Bash(uv run pytest:*) to the allowed tools and re-trigger.

Conclusion

No code changes were needed — this issue's request was already fully implemented in a prior commit on this branch/repo history. I made no modifications and have nothing to push or open a PR for.