Add GET /lean/v0/fork_choice JSON endpoint to leanSpec#418
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tcoratger merged 3 commits intoleanEthereum:mainfrom Feb 25, 2026
Merged
Add GET /lean/v0/fork_choice JSON endpoint to leanSpec#418tcoratger merged 3 commits intoleanEthereum:mainfrom
GET /lean/v0/fork_choice JSON endpoint to leanSpec#418tcoratger merged 3 commits intoleanEthereum:mainfrom
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…e endpoint already available in ethlambdas Rust implementation.
tcoratger
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Feb 25, 2026
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tcoratger
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Just left a minor comment for testing, otherwise, looks good to me.
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| class TestForkChoiceEndpoint: | ||
| """Tests for the /lean/v0/fork_choice endpoint error handling.""" | ||
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| async def test_returns_503_when_store_not_initialized(self) -> None: | ||
| """Endpoint returns 503 Service Unavailable when store is not set.""" | ||
| config = ApiServerConfig(port=15058) | ||
| server = ApiServer(config=config) | ||
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| await server.start() | ||
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| try: | ||
| async with httpx.AsyncClient() as client: | ||
| response = await client.get("http://127.0.0.1:15058/lean/v0/fork_choice") | ||
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| assert response.status_code == 503 | ||
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| finally: | ||
| server.stop() | ||
| await asyncio.sleep(0.1) |
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Can't we have a test with a 200 OK code as well to test the validity?
Addresses review feedback requesting a test that validates the endpoint returns correct fork choice data when the store is initialized.
from_validator_indices expects ValidatorIndices (SSZModel with .data), not a plain list. This caused an AttributeError in CI.
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🗒️ Description
Add
GET /lean/v0/fork_choiceJSON endpoint to leanSpec, matching the endpoint already available in ethlambda's Rust implementation.The endpoint returns a snapshot of the fork choice tree:
Changes
New
compute_block_weightsmethod on Store (store.py): extracts the weight computation loop from_compute_lmd_ghost_headinto a public method. Walks backward from each validator's latest head vote, accumulating weight per block above the finalized slot.New endpoint handler (
endpoints/fork_choice.py): follows the same pattern ascheckpoints.py. Returns 503 when the store is not initialized.Route registration (
routes.py,endpoints/__init__.py): wires up/lean/v0/fork_choice.Tests:
test_server.py: 503 test for the new endpoint (port 15058)test_compute_block_weights.py: genesis-only (empty weights), linear chain (upward accumulation), and multiple attestations (weight stacking)🔗 Related Issues or PRs
N/A
✅ Checklist
toxchecks to avoid unnecessary CI fails:uvx tox