Merge pull request #6687 from ethereum-optimism/aj/cannon-first-step

op-challenger: Fix provision of pre-state, proof and oracle data from cannon proofs

op-challenger/fault/agent.go

@@ -134,21 +134,17 @@ func (a *Agent) step(ctx context.Context, claim types.Claim, game types.Game) er
 		return nil
 	}
 
-	oracleData, err := a.solver.GetOracleData(ctx, claim)
+	a.log.Info("Attempting step", "claim_depth", claim.Depth(), "maxDepth", a.maxDepth)
+	step, err := a.solver.AttemptStep(ctx, claim, agreeWithClaimLevel)
 	if err != nil {
-		a.log.Debug("Failed to get oracle data", "err", err)
-		return nil
+		return fmt.Errorf("attempt step: %w", err)
 	}
 
-	a.log.Info("Updating oracle data", "oracleKey", oracleData.OracleKey, "oracleData", oracleData.OracleData)
-	if err := a.updater.UpdateOracle(ctx, oracleData); err != nil {
+	if step.OracleData != nil {
+		a.log.Info("Updating oracle data", "oracleKey", step.OracleData.OracleKey, "oracleData", step.OracleData.OracleData)
+		if err := a.updater.UpdateOracle(ctx, step.OracleData); err != nil {
 			return fmt.Errorf("failed to load oracle data: %w", err)
 		}
-
-	a.log.Info("Attempting step", "claim_depth", claim.Depth(), "maxDepth", a.maxDepth)
-	step, err := a.solver.AttemptStep(ctx, claim, agreeWithClaimLevel)
-	if err != nil {
-		return fmt.Errorf("attempt step: %w", err)
 	}
 
 	a.log.Info("Performing step", "is_attack", step.IsAttack,

op-challenger/fault/alphabet/provider.go

@@ -30,27 +30,31 @@ func NewTraceProvider(state string, depth uint64) *AlphabetTraceProvider {
 	}
 }
 
-// GetOracleData should not return any preimage oracle data for the alphabet provider.
-func (p *AlphabetTraceProvider) GetOracleData(ctx context.Context, i uint64) (*types.PreimageOracleData, error) {
-	return &types.PreimageOracleData{}, nil
-}
-
-// GetPreimage returns the preimage for the given hash.
-func (ap *AlphabetTraceProvider) GetPreimage(ctx context.Context, i uint64) ([]byte, []byte, error) {
+func (ap *AlphabetTraceProvider) GetStepData(ctx context.Context, i uint64) ([]byte, []byte, *types.PreimageOracleData, error) {
+	if i == 0 {
+		prestate, err := ap.AbsolutePreState(ctx)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+		return prestate, []byte{}, nil, nil
+	}
+	// We want the pre-state which is the value prior to the one requested
+	i--
 	// The index cannot be larger than the maximum index as computed by the depth.
 	if i >= ap.maxLen {
-		return nil, nil, ErrIndexTooLarge
+		return nil, nil, nil, ErrIndexTooLarge
 	}
 	// We extend the deepest hash to the maximum depth if the trace is not expansive.
 	if i >= uint64(len(ap.state)) {
-		return ap.GetPreimage(ctx, uint64(len(ap.state))-1)
+		return ap.GetStepData(ctx, uint64(len(ap.state)))
 	}
-	return BuildAlphabetPreimage(i, ap.state[i]), []byte{}, nil
+	return BuildAlphabetPreimage(i, ap.state[i]), []byte{}, nil, nil
 }
 
 // Get returns the claim value at the given index in the trace.
 func (ap *AlphabetTraceProvider) Get(ctx context.Context, i uint64) (common.Hash, error) {
-	claimBytes, _, err := ap.GetPreimage(ctx, i)
+	// Step data returns the pre-state, so add 1 to get the state for index i
+	claimBytes, _, _, err := ap.GetStepData(ctx, i+1)
 	if err != nil {
 		return common.Hash{}, err
 	}

op-challenger/fault/alphabet/provider_test.go

@@ -58,20 +58,21 @@ func FuzzIndexToBytes(f *testing.F) {
 
 // TestGetPreimage_Succeeds tests the GetPreimage function
 // returns the correct pre-image for a index.
-func TestGetPreimage_Succeeds(t *testing.T) {
+func TestGetStepData_Succeeds(t *testing.T) {
 	ap := NewTraceProvider("abc", 2)
 	expected := BuildAlphabetPreimage(0, "a'")
-	retrieved, proof, err := ap.GetPreimage(context.Background(), uint64(0))
+	retrieved, proof, data, err := ap.GetStepData(context.Background(), uint64(1))
 	require.NoError(t, err)
 	require.Equal(t, expected, retrieved)
 	require.Empty(t, proof)
+	require.Nil(t, data)
 }
 
 // TestGetPreimage_TooLargeIndex_Fails tests the GetPreimage
 // function errors if the index is too large.
-func TestGetPreimage_TooLargeIndex_Fails(t *testing.T) {
+func TestGetStepData_TooLargeIndex_Fails(t *testing.T) {
 	ap := NewTraceProvider("abc", 2)
-	_, _, err := ap.GetPreimage(context.Background(), 4)
+	_, _, _, err := ap.GetStepData(context.Background(), 5)
 	require.ErrorIs(t, err, ErrIndexTooLarge)
 }
 

op-challenger/fault/cannon/provider.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"path/filepath"
 
-	"github.com/ethereum-optimism/optimism/cannon/mipsevm"
 	"github.com/ethereum-optimism/optimism/op-bindings/bindings"
 	"github.com/ethereum-optimism/optimism/op-challenger/config"
 	"github.com/ethereum-optimism/optimism/op-challenger/fault/types"
@@ -47,6 +46,8 @@ type CannonTraceProvider struct {
 	// lastStep stores the last step in the actual trace if known. 0 indicates unknown.
 	// Cached as an optimisation to avoid repeatedly attempting to execute beyond the end of the trace.
 	lastStep uint64
+	// lastProof stores the proof data to use for all steps extended beyond lastStep
+	lastProof *proofData
 }
 
 func NewTraceProvider(ctx context.Context, logger log.Logger, cfg *config.Config, l1Client bind.ContractCaller) (*CannonTraceProvider, error) {
@@ -71,24 +72,11 @@ func NewTraceProvider(ctx context.Context, logger log.Logger, cfg *config.Config
 	}, nil
 }
 
-func (p *CannonTraceProvider) GetOracleData(ctx context.Context, i uint64) (*types.PreimageOracleData, error) {
-	proof, err := p.loadProofData(ctx, i)
-	if err != nil {
-		return nil, err
-	}
-	data := types.NewPreimageOracleData(proof.OracleKey, proof.OracleValue, proof.OracleOffset)
-	return &data, nil
-}
-
 func (p *CannonTraceProvider) Get(ctx context.Context, i uint64) (common.Hash, error) {
-	proof, state, err := p.loadProof(ctx, i)
+	proof, err := p.loadProof(ctx, i)
 	if err != nil {
 		return common.Hash{}, err
 	}
-	if proof == nil && state != nil {
-		// Use the hash from the final state
-		return crypto.Keccak256Hash(state.EncodeWitness()), nil
-	}
 	value := common.BytesToHash(proof.ClaimValue)
 
 	if value == (common.Hash{}) {
@@ -97,66 +85,46 @@ func (p *CannonTraceProvider) Get(ctx context.Context, i uint64) (common.Hash, e
 	return value, nil
 }
 
-func (p *CannonTraceProvider) GetPreimage(ctx context.Context, i uint64) ([]byte, []byte, error) {
-	proof, err := p.loadProofData(ctx, i)
+func (p *CannonTraceProvider) GetStepData(ctx context.Context, i uint64) ([]byte, []byte, *types.PreimageOracleData, error) {
+	proof, err := p.loadProof(ctx, i)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 	value := ([]byte)(proof.StateData)
 	if len(value) == 0 {
-		return nil, nil, errors.New("proof missing state data")
+		return nil, nil, nil, errors.New("proof missing state data")
 	}
 	data := ([]byte)(proof.ProofData)
-	if len(data) == 0 {
-		return nil, nil, errors.New("proof missing proof data")
+	if data == nil {
+		return nil, nil, nil, errors.New("proof missing proof data")
+	}
+	var oracleData *types.PreimageOracleData
+	if len(proof.OracleKey) > 0 {
+		oracleData = types.NewPreimageOracleData(proof.OracleKey, proof.OracleValue, proof.OracleOffset)
 	}
-	return value, data, nil
+	return value, data, oracleData, nil
 }
 
 func (p *CannonTraceProvider) AbsolutePreState(ctx context.Context) ([]byte, error) {
 	state, err := parseState(p.prestate)
 	if err != nil {
-		return []byte{}, fmt.Errorf("cannot load absolute pre-state: %w", err)
+		return nil, fmt.Errorf("cannot load absolute pre-state: %w", err)
 	}
 	return state.EncodeWitness(), nil
 }
 
-// loadProofData loads the proof data for the specified step.
-// If the requested index is beyond the end of the actual trace, the proof data from the last step is returned.
-// Cannon will be executed a second time if required to generate the full proof data.
-func (p *CannonTraceProvider) loadProofData(ctx context.Context, i uint64) (*proofData, error) {
-	proof, state, err := p.loadProof(ctx, i)
-	if err != nil {
-		return nil, err
-	} else if proof == nil && state != nil {
-		p.logger.Info("Re-executing to generate proof for last step", "step", state.Step)
-		proof, _, err = p.loadProof(ctx, state.Step)
-		if err != nil {
-			return nil, err
-		}
-		if proof == nil {
-			return nil, fmt.Errorf("proof at step %v was not generated", i)
-		}
-		return proof, nil
-	}
-	return proof, nil
-}
-
 // loadProof will attempt to load or generate the proof data at the specified index
-// If the requested index is beyond the end of the actual trace:
-//   - When the actual trace length is known, the proof data from the last step is returned with nil state
-//   - When the actual trace length is not yet know, the state from after the last step is returned with nil proofData
-//     and the actual trace length is cached for future runs
-func (p *CannonTraceProvider) loadProof(ctx context.Context, i uint64) (*proofData, *mipsevm.State, error) {
-	if p.lastStep != 0 && i > p.lastStep {
-		// If the requested index is after the last step in the actual trace, use the last step
-		i = p.lastStep
+// If the requested index is beyond the end of the actual trace it is extended with no-op instructions.
+func (p *CannonTraceProvider) loadProof(ctx context.Context, i uint64) (*proofData, error) {
+	if p.lastProof != nil && i > p.lastStep {
+		// If the requested index is after the last step in the actual trace, extend the final no-op step
+		return p.lastProof, nil
 	}
 	path := filepath.Join(p.dir, proofsDir, fmt.Sprintf("%d.json", i))
 	file, err := os.Open(path)
 	if errors.Is(err, os.ErrNotExist) {
 		if err := p.generator.GenerateProof(ctx, p.dir, i); err != nil {
-			return nil, nil, fmt.Errorf("generate cannon trace with proof at %v: %w", i, err)
+			return nil, fmt.Errorf("generate cannon trace with proof at %v: %w", i, err)
 		}
 		// Try opening the file again now and it should exist.
 		file, err = os.Open(path)
@@ -164,27 +132,39 @@ func (p *CannonTraceProvider) loadProof(ctx context.Context, i uint64) (*proofDa
 			// Expected proof wasn't generated, check if we reached the end of execution
 			state, err := parseState(filepath.Join(p.dir, finalState))
 			if err != nil {
-				return nil, nil, fmt.Errorf("cannot read final state: %w", err)
+				return nil, fmt.Errorf("cannot read final state: %w", err)
 			}
-			if state.Exited && state.Step < i {
+			if state.Exited && state.Step <= i {
 				p.logger.Warn("Requested proof was after the program exited", "proof", i, "last", state.Step)
 				// The final instruction has already been applied to this state, so the last step we can execute
 				// is one before its Step value.
 				p.lastStep = state.Step - 1
-				return nil, state, nil
+				// Extend the trace out to the full length using a no-op instruction that doesn't change any state
+				// No execution is done, so no proof-data or oracle values are required.
+				witness := state.EncodeWitness()
+				proof := &proofData{
+					ClaimValue:   crypto.Keccak256(witness),
+					StateData:    witness,
+					ProofData:    []byte{},
+					OracleKey:    nil,
+					OracleValue:  nil,
+					OracleOffset: 0,
+				}
+				p.lastProof = proof
+				return proof, nil
 			} else {
-				return nil, nil, fmt.Errorf("expected proof not generated but final state was not exited, requested step %v, final state at step %v", i, state.Step)
+				return nil, fmt.Errorf("expected proof not generated but final state was not exited, requested step %v, final state at step %v", i, state.Step)
 			}
 		}
 	}
 	if err != nil {
-		return nil, nil, fmt.Errorf("cannot open proof file (%v): %w", path, err)
+		return nil, fmt.Errorf("cannot open proof file (%v): %w", path, err)
 	}
 	defer file.Close()
 	var proof proofData
 	err = json.NewDecoder(file).Decode(&proof)
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to read proof (%v): %w", path, err)
+		return nil, fmt.Errorf("failed to read proof (%v): %w", path, err)
 	}
-	return &proof, nil, nil
+	return &proof, nil
 }

op-challenger/fault/cannon/provider_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 
 	"github.com/ethereum-optimism/optimism/cannon/mipsevm"
+	"github.com/ethereum-optimism/optimism/op-challenger/fault/types"
 	"github.com/ethereum-optimism/optimism/op-node/testlog"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -61,21 +62,22 @@ func TestGet(t *testing.T) {
 	})
 }
 
-func TestGetOracleData(t *testing.T) {
+func TestGetStepData(t *testing.T) {
 	dataDir, prestate := setupTestData(t)
 	t.Run("ExistingProof", func(t *testing.T) {
 		provider, generator := setupWithTestData(t, dataDir, prestate)
-		oracleData, err := provider.GetOracleData(context.Background(), 420)
+		value, proof, data, err := provider.GetStepData(context.Background(), 0)
 		require.NoError(t, err)
-		require.False(t, oracleData.IsLocal)
-		expectedKey := common.Hex2Bytes("eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee")
-		require.Equal(t, expectedKey, oracleData.OracleKey)
-		expectedData := common.Hex2Bytes("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
-		require.Equal(t, expectedData, oracleData.OracleData)
+		expected := common.Hex2Bytes("b8f068de604c85ea0e2acd437cdb47add074a2d70b81d018390c504b71fe26f400000000000000000000000000000000000000000000000000000000000000000000000000")
+		require.Equal(t, expected, value)
+		expectedProof := common.Hex2Bytes("08028e3c0000000000000000000000003c01000a24210b7c00200008000000008fa40004")
+		require.Equal(t, expectedProof, proof)
+		// TODO: Need to add some oracle data
+		require.Nil(t, data)
 		require.Empty(t, generator.generated)
 	})
 
-	t.Run("ProofAfterEndOfTrace", func(t *testing.T) {
+	t.Run("GenerateProof", func(t *testing.T) {
 		provider, generator := setupWithTestData(t, dataDir, prestate)
 		generator.finalState = &mipsevm.State{
 			Memory: &mipsevm.Memory{},
@@ -90,39 +92,14 @@ func TestGetOracleData(t *testing.T) {
 			OracleValue:  []byte{0xdd},
 			OracleOffset: 10,
 		}
-		oracleData, err := provider.GetOracleData(context.Background(), 7000)
-		require.NoError(t, err)
-		require.Contains(t, generator.generated, 7000, "should have tried to generate the proof")
-		require.Contains(t, generator.generated, 9, "should have regenerated proof from last step")
-		require.False(t, oracleData.IsLocal)
-		require.EqualValues(t, generator.proof.OracleKey, oracleData.OracleKey)
-		require.EqualValues(t, generator.proof.OracleValue, oracleData.OracleData)
-	})
-
-	t.Run("IgnoreUnknownFields", func(t *testing.T) {
-		provider, generator := setupWithTestData(t, dataDir, prestate)
-		oracleData, err := provider.GetOracleData(context.Background(), 421)
+		preimage, proof, data, err := provider.GetStepData(context.Background(), 4)
 		require.NoError(t, err)
-		require.False(t, oracleData.IsLocal)
-		expectedKey := common.Hex2Bytes("eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee")
-		require.Equal(t, expectedKey, oracleData.OracleKey)
-		expectedData := common.Hex2Bytes("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
-		require.Equal(t, expectedData, oracleData.OracleData)
-		require.Empty(t, generator.generated)
-	})
-}
+		require.Contains(t, generator.generated, 4, "should have tried to generate the proof")
 
-func TestGetPreimage(t *testing.T) {
-	dataDir, prestate := setupTestData(t)
-	t.Run("ExistingProof", func(t *testing.T) {
-		provider, generator := setupWithTestData(t, dataDir, prestate)
-		value, proof, err := provider.GetPreimage(context.Background(), 0)
-		require.NoError(t, err)
-		expected := common.Hex2Bytes("b8f068de604c85ea0e2acd437cdb47add074a2d70b81d018390c504b71fe26f400000000000000000000000000000000000000000000000000000000000000000000000000")
-		require.Equal(t, expected, value)
-		expectedProof := common.Hex2Bytes("08028e3c0000000000000000000000003c01000a24210b7c00200008000000008fa40004")
-		require.Equal(t, expectedProof, proof)
-		require.Empty(t, generator.generated)
+		require.EqualValues(t, generator.proof.StateData, preimage)
+		require.EqualValues(t, generator.proof.ProofData, proof)
+		expectedData := types.NewPreimageOracleData(generator.proof.OracleKey, generator.proof.OracleValue, generator.proof.OracleOffset)
+		require.EqualValues(t, expectedData, data)
 	})
 
 	t.Run("ProofAfterEndOfTrace", func(t *testing.T) {
@@ -140,30 +117,33 @@ func TestGetPreimage(t *testing.T) {
 			OracleValue:  []byte{0xdd},
 			OracleOffset: 10,
 		}
-		preimage, proof, err := provider.GetPreimage(context.Background(), 7000)
+		preimage, proof, data, err := provider.GetStepData(context.Background(), 7000)
 		require.NoError(t, err)
 		require.Contains(t, generator.generated, 7000, "should have tried to generate the proof")
-		require.Contains(t, generator.generated, 9, "should have regenerated proof from last step")
-		require.EqualValues(t, generator.proof.StateData, preimage)
-		require.EqualValues(t, generator.proof.ProofData, proof)
+
+		witness := generator.finalState.EncodeWitness()
+		require.EqualValues(t, witness, preimage)
+		require.Equal(t, []byte{}, proof)
+		require.Nil(t, data)
 	})
 
 	t.Run("MissingStateData", func(t *testing.T) {
 		provider, generator := setupWithTestData(t, dataDir, prestate)
-		_, _, err := provider.GetPreimage(context.Background(), 1)
+		_, _, _, err := provider.GetStepData(context.Background(), 1)
 		require.ErrorContains(t, err, "missing state data")
 		require.Empty(t, generator.generated)
 	})
 
 	t.Run("IgnoreUnknownFields", func(t *testing.T) {
 		provider, generator := setupWithTestData(t, dataDir, prestate)
-		value, proof, err := provider.GetPreimage(context.Background(), 2)
+		value, proof, data, err := provider.GetStepData(context.Background(), 2)
 		require.NoError(t, err)
 		expected := common.Hex2Bytes("cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc")
 		require.Equal(t, expected, value)
 		expectedProof := common.Hex2Bytes("dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd")
 		require.Equal(t, expectedProof, proof)
 		require.Empty(t, generator.generated)
+		require.Nil(t, data)
 	})
 }
 

op-challenger/fault/cannon/updater.go

@@ -87,9 +87,6 @@ func NewOracleUpdaterWithOracle(
 
 // UpdateOracle updates the oracle with the given data.
 func (u *cannonUpdater) UpdateOracle(ctx context.Context, data *types.PreimageOracleData) error {
-	if len(data.OracleKey) == 0 {
-		return nil
-	}
 	if data.IsLocal {
 		return u.sendLocalOracleData(ctx, data)
 	}

op-challenger/fault/cannon/updater_test.go

@@ -89,12 +89,6 @@ func TestCannonUpdater_UpdateOracle(t *testing.T) {
 		}))
 		require.Equal(t, 1, mockTxMgr.failedSends)
 	})
-
-	t.Run("skip empty data", func(t *testing.T) {
-		updater, mockTxMgr := newTestCannonUpdater(t, true)
-		require.NoError(t, updater.UpdateOracle(context.Background(), &types.PreimageOracleData{}))
-		require.Equal(t, 0, mockTxMgr.sends)
-	})
 }
 
 // TestCannonUpdater_BuildLocalOracleData tests the [cannonUpdater]

op-challenger/fault/service_test.go

@@ -67,10 +67,7 @@ func newMockTraceProvider(prestateErrors bool, prestate []byte) *mockTraceProvid
 func (m *mockTraceProvider) Get(ctx context.Context, i uint64) (common.Hash, error) {
 	panic("not implemented")
 }
-func (m *mockTraceProvider) GetOracleData(ctx context.Context, i uint64) (*types.PreimageOracleData, error) {
-	panic("not implemented")
-}
-func (m *mockTraceProvider) GetPreimage(ctx context.Context, i uint64) (preimage []byte, proofData []byte, err error) {
+func (m *mockTraceProvider) GetStepData(ctx context.Context, i uint64) (prestate []byte, proofData []byte, preimageData *types.PreimageOracleData, err error) {
 	panic("not implemented")
 }
 func (m *mockTraceProvider) AbsolutePreState(ctx context.Context) ([]byte, error) {

op-challenger/fault/solver/solver.go

@@ -28,12 +28,6 @@ func NewSolver(gameDepth int, traceProvider types.TraceProvider) *Solver {
 	}
 }
 
-// GetOracleData returns the oracle data for the provided claim.
-// It passes through to the [TraceProvider] by finding the trace index for the claim.
-func (s *Solver) GetOracleData(ctx context.Context, claim types.Claim) (*types.PreimageOracleData, error) {
-	return s.trace.GetOracleData(ctx, claim.TraceIndex(s.gameDepth))
-}
-
 // NextMove returns the next move to make given the current state of the game.
 func (s *Solver) NextMove(ctx context.Context, claim types.Claim, agreeWithClaimLevel bool) (*types.Claim, error) {
 	if agreeWithClaimLevel {
@@ -58,7 +52,7 @@ type StepData struct {
 	IsAttack   bool
 	PreState   []byte
 	ProofData  []byte
-	OracleData types.PreimageOracleData
+	OracleData *types.PreimageOracleData
 }
 
 // AttemptStep determines what step should occur for a given leaf claim.
@@ -77,35 +71,30 @@ func (s *Solver) AttemptStep(ctx context.Context, claim types.Claim, agreeWithCl
 	index := claim.TraceIndex(s.gameDepth)
 	var preState []byte
 	var proofData []byte
-	// If we are attacking index 0, we provide the absolute pre-state, not an intermediate state
-	if index == 0 && !claimCorrect {
-		state, err := s.trace.AbsolutePreState(ctx)
+	var oracleData *types.PreimageOracleData
+
+	if !claimCorrect {
+		// Attack the claim by executing step index, so we need to get the pre-state of that index
+		preState, proofData, oracleData, err = s.trace.GetStepData(ctx, index)
 		if err != nil {
 			return StepData{}, err
 		}
-		preState = state
 	} else {
-		// If attacking, get the state just before, other get the state after
-		if !claimCorrect {
-			index = index - 1
-		}
-		preState, proofData, err = s.trace.GetPreimage(ctx, index)
+		// We agree with the claim so Defend and use this claim as the starting point to execute the step after
+		// Thus we need the pre-state of the next step
+		// Note: This makes our maximum depth 63 because we need to add 1 without overflowing.
+		preState, proofData, oracleData, err = s.trace.GetStepData(ctx, index+1)
 		if err != nil {
 			return StepData{}, err
 		}
 	}
 
-	oracleData, err := s.trace.GetOracleData(ctx, index)
-	if err != nil {
-		return StepData{}, err
-	}
-
 	return StepData{
 		LeafClaim:  claim,
 		IsAttack:   !claimCorrect,
 		PreState:   preState,
 		ProofData:  proofData,
-		OracleData: *oracleData,
+		OracleData: oracleData,
 	}, nil
 }
 

op-challenger/fault/solver/solver_test.go

@@ -113,9 +113,6 @@ func TestAttemptStep(t *testing.T) {
 
 	ctx := context.Background()
 
-	preState, err := builder.CorrectTraceProvider().AbsolutePreState(ctx)
-	require.NoError(t, err)
-
 	tests := []struct {
 		name               string
 		claim              types.Claim
@@ -124,63 +121,55 @@ func TestAttemptStep(t *testing.T) {
 		expectAttack       bool
 		expectPreState     []byte
 		expectProofData    []byte
-		expectedLocal      bool
-		expectedOracleKey  []byte
-		expectedOracleData []byte
+		expectedOracleData *types.PreimageOracleData
 	}{
 		{
 			name:               "AttackFirstTraceIndex",
 			claim:              builder.CreateLeafClaim(0, false),
 			expectAttack:       true,
-			expectPreState:     preState,
-			expectProofData:    nil,
-			expectedOracleKey:  []byte{byte(0)},
-			expectedOracleData: []byte{byte(0)},
+			expectPreState:     builder.CorrectPreState(0),
+			expectProofData:    builder.CorrectProofData(0),
+			expectedOracleData: builder.CorrectOracleData(0),
 		},
 		{
 			name:               "DefendFirstTraceIndex",
 			claim:              builder.CreateLeafClaim(0, true),
 			expectAttack:       false,
-			expectPreState:     builder.CorrectPreState(0),
-			expectProofData:    builder.CorrectProofData(0),
-			expectedOracleKey:  []byte{byte(0)},
-			expectedOracleData: []byte{byte(0)},
+			expectPreState:     builder.CorrectPreState(1),
+			expectProofData:    builder.CorrectProofData(1),
+			expectedOracleData: builder.CorrectOracleData(1),
 		},
 		{
 			name:               "AttackMiddleTraceIndex",
 			claim:              builder.CreateLeafClaim(4, false),
 			expectAttack:       true,
-			expectPreState:     builder.CorrectPreState(3),
-			expectProofData:    builder.CorrectProofData(3),
-			expectedOracleKey:  []byte{byte(3)},
-			expectedOracleData: []byte{byte(3)},
+			expectPreState:     builder.CorrectPreState(4),
+			expectProofData:    builder.CorrectProofData(4),
+			expectedOracleData: builder.CorrectOracleData(4),
 		},
 		{
 			name:               "DefendMiddleTraceIndex",
 			claim:              builder.CreateLeafClaim(4, true),
 			expectAttack:       false,
-			expectPreState:     builder.CorrectPreState(4),
-			expectProofData:    builder.CorrectProofData(4),
-			expectedOracleKey:  []byte{byte(4)},
-			expectedOracleData: []byte{byte(4)},
+			expectPreState:     builder.CorrectPreState(5),
+			expectProofData:    builder.CorrectProofData(5),
+			expectedOracleData: builder.CorrectOracleData(5),
 		},
 		{
 			name:               "AttackLastTraceIndex",
 			claim:              builder.CreateLeafClaim(lastLeafTraceIndex, false),
 			expectAttack:       true,
-			expectPreState:     builder.CorrectPreState(lastLeafTraceIndex - 1),
-			expectProofData:    builder.CorrectProofData(lastLeafTraceIndex - 1),
-			expectedOracleKey:  []byte{byte(5)},
-			expectedOracleData: []byte{byte(5)},
+			expectPreState:     builder.CorrectPreState(lastLeafTraceIndex),
+			expectProofData:    builder.CorrectProofData(lastLeafTraceIndex),
+			expectedOracleData: builder.CorrectOracleData(lastLeafTraceIndex),
 		},
 		{
 			name:               "DefendLastTraceIndex",
 			claim:              builder.CreateLeafClaim(lastLeafTraceIndex, true),
 			expectAttack:       false,
-			expectPreState:     builder.CorrectPreState(lastLeafTraceIndex),
-			expectProofData:    builder.CorrectProofData(lastLeafTraceIndex),
-			expectedOracleKey:  []byte{byte(6)},
-			expectedOracleData: []byte{byte(6)},
+			expectPreState:     builder.CorrectPreState(lastLeafTraceIndex + 1),
+			expectProofData:    builder.CorrectProofData(lastLeafTraceIndex + 1),
+			expectedOracleData: builder.CorrectOracleData(lastLeafTraceIndex + 1),
 		},
 		{
 			name:        "CannotStepNonLeaf",
@@ -199,24 +188,6 @@ func TestAttemptStep(t *testing.T) {
 			agreeWithLevel: true,
 			expectedErr:    solver.ErrStepNonLeafNode,
 		},
-		{
-			name:               "AttackLocalOracleData",
-			claim:              builder.Seq(false).Attack(false).Attack(true).Defend(false).Get(),
-			expectAttack:       true,
-			agreeWithLevel:     false,
-			expectPreState:     builder.CorrectPreState(1),
-			expectProofData:    builder.CorrectProofData(1),
-			expectedLocal:      true,
-			expectedOracleKey:  []byte{0x01},
-			expectedOracleData: []byte{0x01},
-			expectedErr:        nil,
-		},
-		{
-			name:           "AttackStepOracleError",
-			claim:          builder.Seq(false).Attack(false).Attack(false).Attack(false).Get(),
-			agreeWithLevel: false,
-			expectedErr:    errProvider,
-		},
 	}
 
 	for _, tableTest := range tests {
@@ -235,9 +206,10 @@ func TestAttemptStep(t *testing.T) {
 				require.Equal(t, tableTest.expectAttack, step.IsAttack)
 				require.Equal(t, tableTest.expectPreState, step.PreState)
 				require.Equal(t, tableTest.expectProofData, step.ProofData)
-				require.Equal(t, tableTest.expectedLocal, step.OracleData.IsLocal)
-				require.Equal(t, tableTest.expectedOracleKey, step.OracleData.OracleKey)
-				require.Equal(t, tableTest.expectedOracleData, step.OracleData.OracleData)
+				require.Equal(t, tableTest.expectedOracleData.IsLocal, step.OracleData.IsLocal)
+				require.Equal(t, tableTest.expectedOracleData.OracleKey, step.OracleData.OracleKey)
+				require.Equal(t, tableTest.expectedOracleData.OracleData, step.OracleData.OracleData)
+				require.Equal(t, tableTest.expectedOracleData.OracleOffset, step.OracleData.OracleOffset)
 			} else {
 				require.ErrorIs(t, err, tableTest.expectedErr)
 				require.Equal(t, solver.StepData{}, step)

op-challenger/fault/test/alphabet.go

@@ -25,18 +25,11 @@ type alphabetWithProofProvider struct {
 	OracleError error
 }
 
-func (a *alphabetWithProofProvider) GetPreimage(ctx context.Context, i uint64) ([]byte, []byte, error) {
-	preimage, _, err := a.AlphabetTraceProvider.GetPreimage(ctx, i)
+func (a *alphabetWithProofProvider) GetStepData(ctx context.Context, i uint64) ([]byte, []byte, *types.PreimageOracleData, error) {
+	preimage, _, _, err := a.AlphabetTraceProvider.GetStepData(ctx, i)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
-	return preimage, []byte{byte(i)}, nil
-}
-
-func (a *alphabetWithProofProvider) GetOracleData(ctx context.Context, i uint64) (*types.PreimageOracleData, error) {
-	if a.OracleError != nil {
-		return &types.PreimageOracleData{}, a.OracleError
-	}
-	data := types.NewPreimageOracleData([]byte{byte(i)}, []byte{byte(i)}, uint32(i))
-	return &data, nil
+	data := types.NewPreimageOracleData([]byte{byte(i)}, []byte{byte(i - 1)}, uint32(i-1))
+	return preimage, []byte{byte(i - 1)}, data, nil
 }

op-challenger/fault/test/claim_builder.go

@@ -38,20 +38,26 @@ func (c *ClaimBuilder) CorrectClaim(idx uint64) common.Hash {
 	return value
 }
 
-// CorrectPreState returns the pre-image of the canonical claim at the specified trace index
+// CorrectPreState returns the pre-state (not hashed) required to execute the valid step at the specified trace index
 func (c *ClaimBuilder) CorrectPreState(idx uint64) []byte {
-	preimage, _, err := c.correct.GetPreimage(context.Background(), idx)
+	preimage, _, _, err := c.correct.GetStepData(context.Background(), idx)
 	c.require.NoError(err)
 	return preimage
 }
 
-// CorrectProofData returns the proof-data for the canonical claim at the specified trace index
+// CorrectProofData returns the proof-data required to execute the valid step at the specified trace index
 func (c *ClaimBuilder) CorrectProofData(idx uint64) []byte {
-	_, proof, err := c.correct.GetPreimage(context.Background(), idx)
+	_, proof, _, err := c.correct.GetStepData(context.Background(), idx)
 	c.require.NoError(err)
 	return proof
 }
 
+func (c *ClaimBuilder) CorrectOracleData(idx uint64) *types.PreimageOracleData {
+	_, _, data, err := c.correct.GetStepData(context.Background(), idx)
+	c.require.NoError(err)
+	return data
+}
+
 func (c *ClaimBuilder) incorrectClaim(idx uint64) common.Hash {
 	return common.BigToHash(new(big.Int).SetUint64(idx))
 }

op-challenger/fault/types/types.go

@@ -45,8 +45,8 @@ func (p *PreimageOracleData) GetPreimageWithoutSize() []byte {
 }
 
 // NewPreimageOracleData creates a new [PreimageOracleData] instance.
-func NewPreimageOracleData(key []byte, data []byte, offset uint32) PreimageOracleData {
-	return PreimageOracleData{
+func NewPreimageOracleData(key []byte, data []byte, offset uint32) *PreimageOracleData {
+	return &PreimageOracleData{
 		IsLocal:      len(key) > 0 && key[0] == byte(1),
 		OracleKey:    key,
 		OracleData:   data,
@@ -74,17 +74,14 @@ type TraceProvider interface {
 	// Get(i) = Keccak256(GetPreimage(i))
 	Get(ctx context.Context, i uint64) (common.Hash, error)
 
-	// GetOracleData returns preimage oracle data that can be submitted to the pre-image
-	// oracle and the dispute game contract. This function accepts a trace index for
-	// which the provider returns needed preimage data.
-	GetOracleData(ctx context.Context, i uint64) (*PreimageOracleData, error)
-
-	// GetPreimage returns the pre-image for a claim at the specified trace index, along
-	// with any associated proof data to assist in its verification.
-	GetPreimage(ctx context.Context, i uint64) (preimage []byte, proofData []byte, err error)
+	// GetStepData returns the data required to execute the step at the specified trace index.
+	// This includes the pre-state of the step (not hashed), the proof data required during step execution
+	// and any pre-image data that needs to be loaded into the oracle prior to execution (may be nil)
+	// The prestate returned from GetStepData for trace 10 should be the pre-image of the claim from trace 9
+	GetStepData(ctx context.Context, i uint64) (prestate []byte, proofData []byte, preimageData *PreimageOracleData, err error)
 
 	// AbsolutePreState is the pre-image value of the trace that transitions to the trace value at index 0
-	AbsolutePreState(ctx context.Context) ([]byte, error)
+	AbsolutePreState(ctx context.Context) (preimage []byte, err error)
 }
 
 // ClaimData is the core of a claim. It must be unique inside a specific game.

op-e2e/e2eutils/disputegame/cannon_helper.go

@@ -9,6 +9,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-challenger/config"
 	"github.com/ethereum-optimism/optimism/op-e2e/e2eutils/challenger"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
 )
 
@@ -49,3 +50,7 @@ func (g *CannonGameHelper) StartChallenger(ctx context.Context, rollupCfg *rollu
 	})
 	return c
 }
+
+func (g *FaultGameHelper) Address() common.Address {
+	return g.addr
+}

op-e2e/e2eutils/disputegame/game_helper.go

@@ -122,3 +122,29 @@ func (g *FaultGameHelper) Attack(ctx context.Context, claimIdx int64, claim comm
 	_, err = utils.WaitReceiptOK(ctx, g.client, tx.Hash())
 	g.require.NoError(err, "Attack transaction was not OK")
 }
+
+func (g *FaultGameHelper) Defend(ctx context.Context, claimIdx int64, claim common.Hash) {
+	tx, err := g.game.Defend(g.opts, big.NewInt(claimIdx), claim)
+	g.require.NoError(err, "Defend transaction did not send")
+	_, err = utils.WaitReceiptOK(ctx, g.client, tx.Hash())
+	g.require.NoError(err, "Defend transaction was not OK")
+}
+
+func (g *FaultGameHelper) LogGameData(ctx context.Context) {
+	opts := &bind.CallOpts{Context: ctx}
+	maxDepth := int(g.MaxDepth(ctx))
+	claimCount, err := g.game.ClaimDataLen(opts)
+	info := fmt.Sprintf("Claim count: %v\n", claimCount)
+	g.require.NoError(err, "Fetching claim count")
+	for i := int64(0); i < claimCount.Int64(); i++ {
+		claim, err := g.game.ClaimData(opts, big.NewInt(i))
+		g.require.NoErrorf(err, "Fetch claim %v", i)
+
+		pos := types.NewPositionFromGIndex(claim.Position.Uint64())
+		info = info + fmt.Sprintf("%v - Position: %v, Depth: %v, IndexAtDepth: %v Trace Index: %v, Value: %v, Countered: %v\n",
+			i, claim.Position.Int64(), pos.Depth(), pos.IndexAtDepth(), pos.TraceIndex(maxDepth), common.Hash(claim.Claim).Hex(), claim.Countered)
+	}
+	status, err := g.game.Status(opts)
+	g.require.NoError(err, "Load game status")
+	g.t.Logf("Game %v:\n%v\nCurrent status: %v\n", g.addr, info, Status(status))
+}

op-e2e/faultproof_test.go

@@ -147,6 +147,19 @@ func TestChallengerCompleteDisputeGame(t *testing.T) {
 func TestCannonDisputeGame(t *testing.T) {
 	InitParallel(t)
 
+	tests := []struct {
+		name          string
+		defendAtClaim int64
+	}{
+		{"StepFirst", 0},
+		{"StepMiddle", 28},
+		{"StepInExtension", 2},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			InitParallel(t)
+
 			ctx := context.Background()
 			sys, l1Client := startFaultDisputeSystem(t)
 			t.Cleanup(sys.Close)
@@ -154,6 +167,7 @@ func TestCannonDisputeGame(t *testing.T) {
 			disputeGameFactory := disputegame.NewFactoryHelper(t, ctx, sys.cfg.L1Deployments, l1Client)
 			game := disputeGameFactory.StartCannonGame(ctx, common.Hash{0xaa})
 			require.NotNil(t, game)
+			game.LogGameData(ctx)
 
 			game.StartChallenger(ctx, sys.RollupConfig, sys.L2GenesisCfg, sys.NodeEndpoint("l1"), sys.NodeEndpoint("sequencer"), "Challenger", func(c *config.Config) {
 				c.AgreeWithProposedOutput = true // Agree with the proposed output, so disagree with the root claim
@@ -162,21 +176,33 @@ func TestCannonDisputeGame(t *testing.T) {
 
 			maxDepth := game.MaxDepth(ctx)
 			for claimCount := int64(1); claimCount < maxDepth; {
+				game.LogGameData(ctx)
 				claimCount++
 				// Wait for the challenger to counter
 				game.WaitForClaimCount(ctx, claimCount)
 
 				// Post our own counter to the latest challenger claim
+				if claimCount == test.defendAtClaim {
+					// Defend one claim so we don't wind up executing from the absolute pre-state
+					game.Defend(ctx, claimCount-1, common.Hash{byte(claimCount)})
+				} else {
 					game.Attack(ctx, claimCount-1, common.Hash{byte(claimCount)})
+				}
 				claimCount++
 				game.WaitForClaimCount(ctx, claimCount)
 			}
-	game.WaitForClaimAtMaxDepth(ctx, false)
+
+			game.LogGameData(ctx)
+			// Wait for the challenger to call step and counter our invalid claim
+			game.WaitForClaimAtMaxDepth(ctx, true)
 
 			sys.TimeTravelClock.AdvanceTime(game.GameDuration(ctx))
 			require.NoError(t, utils.WaitNextBlock(ctx, l1Client))
 
 			game.WaitForGameStatus(ctx, disputegame.StatusChallengerWins)
+			game.LogGameData(ctx)
+		})
+	}
 }
 
 func startFaultDisputeSystem(t *testing.T) (*System, *ethclient.Client) {

packages/contracts-bedrock/deploy-config/devnetL1.json

@@ -44,7 +44,7 @@
   "l1GenesisBlockTimestamp": "0x64c811bf",
   "l2GenesisRegolithTimeOffset": "0x0",
   "faultGameAbsolutePrestate": "0x41c7ae758795765c6664a5d39bf63841c71ff191e9189522bad8ebff5d4eca98",
-  "faultGameMaxDepth": 31,
+  "faultGameMaxDepth": 30,
   "faultGameMaxDuration": 300,
   "systemConfigStartBlock": 0
 }