feat(api): Implement debug_traceTransaction API

.config/forest.dic

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-258
+266
 Algorand/M
 API's
 API/SM
@@ -52,6 +52,7 @@ clonable
 Cloudflare
 codebase
 codec
+Coinbase
 config/S
 cron
 crypto
@@ -81,6 +82,7 @@ Enum
 enum
 enums
 env
+EOAs
 EOF
 eth
 Ethereum
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 jsonrpsee
 JWT/S
 Kademlia
+KAMT
 keypair/S
 keystore/S
 Kubernetes
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 PoC
 pointer/SM
 PoSt
+Post
+post
+Pre
+pre
 precommit
 preloaded
 pubsub
@@ -227,6 +234,7 @@ tipsetkey/S
 Tokio
 TOML
 toolchain/S
+Trie
 trie
 truthy
 TTY

docs/docs/developers/guides/debug_trace_transaction_guide.md

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+# `debug_traceTransaction` Developer Guide
+
+This guide covers testing and development workflows for Forest's `debug_traceTransaction` implementation. For API documentation and user-facing usage, see the [API guide](/knowledge_base/rpc/debug_trace_transaction).
+
+## Tracer Contract
+
+The [`Tracer.sol`](https://github.com/ChainSafe/forest/blob/963237708137e9c7388c57eba39a2f8bf12ace74/src/tool/subcommands/api_cmd/contracts/tracer/Tracer.sol) contract provides various functions to test different tracing scenarios.
+
+### Storage Layout
+
+| Slot | Variable       | Description                  |
+| ---- | -------------- | ---------------------------- |
+| 0    | `x`            | Initialized to 42            |
+| 1    | `balances`     | Mapping base slot            |
+| 2    | `storageTestA` | Starts empty (for add tests) |
+| 3    | `storageTestB` | Starts empty                 |
+| 4    | `storageTestC` | Starts empty                 |
+| 5    | `dynamicArray` | Array length slot            |
+
+### Function Reference
+
+#### Basic Operations
+
+| Function            | Selector     | Description                 |
+| ------------------- | ------------ | --------------------------- |
+| `setX(uint256)`     | `0x4018d9aa` | Write to slot 0             |
+| `deposit()`         | `0xd0e30db0` | Receive ETH, update mapping |
+| `withdraw(uint256)` | `0x2e1a7d4d` | Send ETH from contract      |
+| `doRevert()`        | `0xafc874d2` | Always reverts              |
+
+#### Call Tracing
+
+| Function                | Selector     | Description            |
+| ----------------------- | ------------ | ---------------------- |
+| `callSelf(uint256)`     | `0xa1a88595` | Single nested CALL     |
+| `delegateSelf(uint256)` | `0x8f5e07b8` | `DELEGATECALL` trace   |
+| `complexTrace()`        | `0x6659ab96` | Multiple nested calls  |
+| `deepTrace(uint256)`    | `0x0f3a17b8` | Recursive N-level deep |
+
+#### Storage Diff Testing
+
+| Function                                   | Selector     | Description          |
+| ------------------------------------------ | ------------ | -------------------- |
+| `storageAdd(uint256)`                      | `0x55cb64b4` | Add to empty slot 2  |
+| `storageChange(uint256)`                   | `0x7c8f6e57` | Modify existing slot |
+| `storageDelete()`                          | `0xd92846a3` | Set slot to zero     |
+| `storageMultiple(uint256,uint256,uint256)` | `0x310af204` | Change slots 2,3,4   |
+
+### Generating Function Selectors
+
+Use `cast` from Foundry to generate function selectors:
+
+```bash
+# Get selector for a function
+cast sig "setX(uint256)"
+# Output: 0x4018d9aa
+
+# Encode full calldata
+cast calldata "setX(uint256)" 123
+# Output: 0x4018d9aa000000000000000000000000000000000000000000000000000000000000007b
+```
+
+### Deployed Contracts
+
+Pre-deployed Tracer contracts for quick testing:
+
+| Network  | Contract Address                                                                                                                      |
+| -------- | ------------------------------------------------------------------------------------------------------------------------------------- |
+| Calibnet | [`0x73a43475aa2ccb14246613708b399f4b2ba546c7`](https://calibration.filfox.info/en/address/0x73a43475aa2ccb14246613708b399f4b2ba546c7) |
+| Mainnet  | [`0x9BB686Ba6a50D1CF670a98f522a59555d4977fb2`](https://filecoin.blockscout.com/address/0x9BB686Ba6a50D1CF670a98f522a59555d4977fb2)    |
+
+## Comparison Testing with Anvil
+
+Anvil uses the same **Geth style** tracing as `debug_traceTransaction`, making it ideal for direct comparison testing — verifying that Forest produces identical or semantically equivalent results.
+
+### Prerequisites
+
+- [Foundry](https://book.getfoundry.sh/getting-started/installation) installed (`forge`, `cast` commands)
+- A running [Forest node](https://docs.forest.chainsafe.io/getting_started/syncing) and Anvil instance
+
+### What is Anvil?
+
+[Anvil](https://getfoundry.sh/anvil/reference/) is a local Ethereum development node included with Foundry. It provides:
+
+- Instant block mining
+- Pre-funded test accounts (10 accounts with 10,000 ETH each)
+- Support for `debug_traceTransaction` with various tracers
+- No real tokens required
+
+### Starting Anvil
+
+```bash
+# Start Anvil with tracer to allow `debug_traceTransaction` API's
+anvil --tracing
+```
+
+Anvil RPC endpoint: `http://localhost:8545`
+
+### Deploying Contract on Anvil
+
+```bash
+forge create src/tool/subcommands/api_cmd/contracts/tracer/Tracer.sol:Tracer \
+    --rpc-url http://localhost:8545 \
+    --broadcast \
+    --private-key <ANVIL_OUTPUT_PRIVATE_KEY>
+
+# Output:
+# Deployer: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
+# Deployed to: 0x5FbDB2315678afecb367f032d93F642f64180aa3
+# Transaction hash: 0x...
+```
+
+### Sending Test Transactions on Anvil
+
+Unlike `trace_call` (which simulates calls), `debug_traceTransaction` traces mined transactions. You must first send transactions to get transaction hashes:
+
+```bash
+# Set variables
+export ANVIL_RPC="http://localhost:8545"
+export ANVIL_KEY="0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80"  # Anvil default key
+export ANVIL_CONTRACT="0x5FbDB2315678afecb367f032d93F642f64180aa3"  # Deployed address
+
+# Send transactions
+cast send $ANVIL_CONTRACT "setX(uint256)" 123 \
+    --rpc-url $ANVIL_RPC --private-key $ANVIL_KEY
+
+cast send $ANVIL_CONTRACT "deposit()" \
+    --value 1ether --rpc-url $ANVIL_RPC --private-key $ANVIL_KEY
+
+cast send $ANVIL_CONTRACT "storageAdd(uint256)" 100 \
+    --rpc-url $ANVIL_RPC --private-key $ANVIL_KEY
+
+cast send $ANVIL_CONTRACT "callSelf(uint256)" 456 \
+    --rpc-url $ANVIL_RPC --private-key $ANVIL_KEY
+
+cast send $ANVIL_CONTRACT "storageMultiple(uint256,uint256,uint256)" 10 20 30 \
+    --rpc-url $ANVIL_RPC --private-key $ANVIL_KEY
+```
+
+Save the transaction hashes from the output for use in the tracing examples below.
+
+### Getting the correct transaction hash on Forest
+
+`debug_traceTransaction` expects the canonical **EthHash** (0x...). If your client returned something else, resolve it first.
+
+- **0x... value** (e.g. from `cast send`): call `eth_getTransactionByHash` and use the response's **`hash`** field for tracing. Forest resolves via the indexer or by message lookup.
+- **Literal CID** (e.g. `bafy2bzace...`): `eth_getTransactionByHash` accepts only EthHash. Use `eth_getTransactionHashByCid` to get the hash, then pass it to `debug_traceTransaction`.
+
+Example (0x... from cast):
+
+```bash
+HASH_0X="0x..."   # from cast send or block explorer
+TX_HASH=$(curl -s -X POST http://localhost:2345/rpc/v1 -H "Content-Type: application/json" \
+    -d '{"jsonrpc":"2.0","id":1,"method":"eth_getTransactionByHash","params":["'"$HASH_0X"'"]}' \
+    | jq -r '.result.hash // empty')
+
+curl -s -X POST "http://localhost:2345/rpc/v1" -H "Content-Type: application/json" \
+    -d '{"jsonrpc":"2.0","id":1,"method":"debug_traceTransaction","params":["'"$TX_HASH"'",{"tracer":"prestateTracer","tracerConfig":{"diffMode":true}}]}'
+```
+
+If you have a CID: `TX_HASH=$(curl -s ... -d '{"method":"eth_getTransactionHashByCid","params":["'"$MSG_CID"'"]}' | jq -r '.result // empty')`, then use `$TX_HASH` in the trace call above.
+
+### Comparing Forest vs Anvil Responses
+
+Both Forest and Anvil use the same `debug_traceTransaction` method and tracer format, so responses can be compared directly.
+
+**Forest** (use the canonical `hash` from `eth_getTransactionByHash` as described above):
+
+```bash
+curl -s -X POST "http://localhost:2345/rpc/v1" \
+    -H "Content-Type: application/json" \
+    -d '{
+        "jsonrpc": "2.0",
+        "id": 1,
+        "method": "debug_traceTransaction",
+        "params": [
+            "'$TX_HASH'",
+            {"tracer": "prestateTracer", "tracerConfig": {"diffMode": true}}
+        ]
+    }'
+```
+
+**Anvil:**
+
+```bash
+curl -s -X POST "http://localhost:8545" \
+    -H "Content-Type: application/json" \
+    -d '{
+        "jsonrpc": "2.0",
+        "id": 1,
+        "method": "debug_traceTransaction",
+        "params": [
+            "'$TX_HASH'",
+            {"tracer": "prestateTracer", "tracerConfig": {"diffMode": true}}
+        ]
+    }'
+```
+
+### Expected Differences Between Forest and Anvil
+
+When comparing `debug_traceTransaction` output from Forest and Anvil, expect these `Filecoin-specific` differences:
+
+| Aspect                 | Forest (Filecoin)                          | Anvil (Ethereum)               |
+| ---------------------- | ------------------------------------------ | ------------------------------ |
+| **Extra addresses**    | Includes `0xff00...` Filecoin ID addresses | Only EVM addresses             |
+| **Coinbase**           | Not included (gas at protocol level)       | Included as `0x0000...0000`    |
+| **Nonce format**       | Hex string (e.g., `"0x1e"`)                | Integer (e.g., `30`)           |
+| **Balance format**     | Hex string (e.g., `"0xde0b6b3a7640000"`)   | Hex string (same)              |
+| **Storage key format** | Full 32-byte padded hex                    | Full 32-byte padded hex (same) |
+
+### Test Scenarios
+
+When testing `debug_traceTransaction`, cover these categories:
+
+#### 1. `prestateTracer` Tests
+
+| Test Case                   | Function                    | What to Verify                                              |
+| --------------------------- | --------------------------- | ----------------------------------------------------------- |
+| Simple storage write        | `setX(123)`                 | `Pre-state` shows old value, `post-state` shows new value   |
+| ETH deposit                 | `deposit()` with value      | Balance changes in `pre/post` for sender and contract       |
+| Storage add (empty → value) | `storageAdd(100)`           | Storage slot absent in `pre`, present in `post` (diff mode) |
+| Storage change              | `storageChange(200)`        | Storage slot values differ between `pre` and `post`         |
+| Multiple storage writes     | `storageMultiple(10,20,30)` | Multiple storage slots change in single transaction         |
+| Default mode (no diff)      | `setX(123)`                 | Only `pre-state` returned, no post object                   |
+
+#### 2. `callTracer` Tests
+
+| Test Case       | Function            | What to Verify                               |
+| --------------- | ------------------- | -------------------------------------------- |
+| Simple call     | `setX(123)`         | Single top-level CALL frame                  |
+| Nested call     | `callSelf(456)`     | Parent CALL with child CALL in `calls` array |
+| Delegate call   | `delegateSelf(789)` | `DELEGATECALL` type in call frame            |
+| Deep recursive  | `deepTrace(3)`      | N-level nested CALL hierarchy                |
+| Complex mixed   | `complexTrace()`    | Mix of CALL, `DELEGATECALL`, `STATICCALL`    |
+| Revert at depth | `failAtDepth(3,1)`  | Error field populated in failing frame       |
+
+#### 3. `flatCallTracer` Tests
+
+| Test Case      | Function        | What to Verify                                          |
+| -------------- | --------------- | ------------------------------------------------------- |
+| Simple call    | `setX(123)`     | Single flat trace entry                                 |
+| Nested call    | `callSelf(456)` | Two entries with correct `traceAddress` and `subtraces` |
+| Deep recursive | `deepTrace(3)`  | Flat list with incrementing `traceAddress` depth        |
+
+## Official Resources
+
+- [Geth `debug_traceTransaction`](https://geth.ethereum.org/docs/interacting-with-geth/rpc/ns-debug#debugtracetransaction)
+- [Geth Built-in Tracers](https://geth.ethereum.org/docs/developers/evm-tracing/built-in-tracers)
+- [Reth debug Namespace](https://reth.rs/jsonrpc/debug)
+- [Foundry Book - Anvil](https://book.getfoundry.sh/reference/anvil/)
+- [Foundry Book - Cast](https://book.getfoundry.sh/reference/cast/)