JAM is the anticipated future protocol for Polkadot, being implemented by multiple teams across different programming languages. The JAM Gray Paper outlines the protocol, and the Web3 Foundation has shared jamtestvectors and a basic jam-conformance fuzzing process.
This repo contains the latest duna_fuzzer and duna_target (Linux + Mac) targeting 0.6.7 and some useful test banks.
After we get to 0.7.x conformance, we will get back to getting a multiclient tiny testnet going.
- Run a Fuzzer target: (see jam-conformance repo for active teams)
Example 1: JAM DUNA
% ./duna_target_mac --pvm-logging trace
2025/08/14 14:17:47 Starting target on socket: /tmp/jam_target.sock
2025/08/14 14:17:47 Target listening on /tmp/jam_target.sock
Example 2: JavaJam
% bin/javajam fuzz /tmp/jam_target.sock
❤ JavaJAM
22:00:11.265 INFO FuzzServer -- Fuzzer server listening on /tmp/jam_target.sock
22:00:11.266 INFO FuzzServer -- ChainSpec: TINY
Example 3: JamZig
% ./conformance-releases/tiny/macos/aarch64/jam_conformance_target
JAM Conformance Target Server
=============================
Socket path: /tmp/jam_conformance.sock
Starting server...
Listening on Unix socket: /tmp/jam_conformance.sock
Press Ctrl+C to stop
- Run the fuzzer with the above target socket endpoint and a test bank:
Example 1: algo (found here)
./duna_fuzzer_mac --test-dir ~/Desktop/jamtestnet/0.6.7/algo --socket=/tmp/jam_target.sock
Example 2: game_of_life (found here)
./duna_fuzzer_mac --test-dir ~/Desktop/jamtestnet/0.6.7/game_of_life --socket=/tmp/jam_target.sock
Example 3: jam-conformance (found here)
./duna_fuzzer_mac --test-dir ~/Desktop/jamtestnet/0.6.7/jam-conformance --socket=/tmp/jam_target.sock
(This is a rapidly changing dataset -- we'll try to update it every time we publish a new fuzzer/target version)
The above 3 test banks are in this repo, but others should work too.
If everything is working you should see this from the fuzzer:
If the fuzzer runs into a failure you get an execution report:
[big giant JSON object with the prestate, block, poststate]
Diff on 1 keys: [0x1000000000000000000000000000000000000000000000000000000000000000]
========================================
State Key: c16 (0x1000000000000000000000000000000000000000000000000000000000000000)
c16 | PreState : 0x0114000000ce07e7687972cccfbfe304e4217db58cde9b833750fe557d4e543771b2214db7
c16 | Expected: 0x00000000000000000000000000000000000000000000000000000000000000000000000000
c16 | Actual: 0x0114000000ce07e7687972cccfbfe304e4217db58cde9b833750fe557d4e543771b2214db7
------ c16 JSON DONE ------
If you find a discrepancy between the fuzzer and your target, please file an issue!
Teams can get PVM traces from the duna_target
(a) run duna_fuzzer and supplying a directory with .bin test files as the --test-dir parameter
(b) run duna_target with --pvm-logging debug flag or --pvm-logging trace flag
With --pvm-logging debug logs you get one line per pvm step (with pc, gas, registers):
% ./duna_target_mac --pvm-logging debug
2025/08/14 13:34:50 Starting target on socket: /tmp/jam_target.sock
2025/08/14 13:34:50 Target listening on /tmp/jam_target.sock
...
2025/08/14 13:34:54 [INCOMING REQUEST] ImportBlock
2025/08/14 13:34:54 Received ImportBlock request for block hash: 0x193f7dc1328e396932a38eb0cffb19e953ef5f23f1b924cdca426c3eef35484d
accumulate: JUMP step: 0 pc: 5386 gas:4999999 Registers:[4294901760 4278059008 0 0 0 0 0 4278124544 3 0 0 0 0]
accumulate: MOVE_REG step: 1 pc: 5388 gas:4999996 Registers:[4294901760 4278059008 0 0 0 0 0 4278124544 3 0 4278124544 0 0]
accumulate: LOAD_IMM step: 2 pc: 5393 gas:4999996 Registers:[4294901760 4278059008 0 0 0 0 0 65536 3 0 4278124544 0 0]
...
With --pvm-logging trace you get 2 lines, one like the above and another roughly matching that of polkajam.
% ./duna_target_mac --pvm-logging trace
2025/08/14 16:01:41 Starting target on socket: /tmp/jam_conformance.sock
2025/08/14 16:01:41 Target listening on /tmp/jam_conformance.sock
2025/08/14 16:01:49 Fuzzer connected.
2025/08/14 16:01:49 [INCOMING REQUEST] PeerInfo
2025/08/14 16:01:49 Received handshake from fuzzer: jam-duna-fuzzer-0.6.7.14
2025/08/14 16:01:49 [OUTGOING RESPONSE] PeerInfo
2025/08/14 16:01:49 [INCOMING REQUEST] SetState
2025/08/14 16:01:49 Received SetState request with 34 key-value pairs.
2025/08/14 16:01:49 Setting state with header: 0x3e90aa8a6ba08f64dfa589b628b63dc6ff8114582e01cfe28bc8152ee7398ada
2025/08/14 16:01:49 StateDB initialized with 34 key-value pairs. stateRoot: 0x451fab9ecf3f1eb1378211ed840cf089914c75b99fec126e67f79e00734442b7 | HeaderHash: 0x3e90aa8a6ba08f64dfa589b628b63dc6ff8114582e01cfe28bc8152ee7398ada
2025/08/14 16:01:49 [OUTGOING RESPONSE] StateRoot
...
2025/08/14 16:01:49 [INCOMING REQUEST] ImportBlock
2025/08/14 16:01:49 Received ImportBlock request for block hash: 0x193f7dc1328e396932a38eb0cffb19e953ef5f23f1b924cdca426c3eef35484d
*** jump 5386
accumulate: JUMP step: 0 pc: 5386 gas:4999999 Registers:[4294901760 4278059008 0 0 0 0 0 4278124544 3 0 0 0 0]
TRACE polkavm::interpreter a3 = 0xfeff0000
accumulate: MOVE_REG step: 1 pc: 5388 gas:4999996 Registers:[4294901760 4278059008 0 0 0 0 0 4278124544 3 0 4278124544 0 0]
TRACE polkavm::interpreter a0 = 0x10000
accumulate: LOAD_IMM step: 2 pc: 5393 gas:4999996 Registers:[4294901760 4278059008 0 0 0 0 0 65536 3 0 4278124544 0 0]
accumulate: BRANCH_EQ_IMM step: 3 pc: 5397 gas:4999996 Registers:[4294901760 4278059008 0 0 0 0 0 65536 3 0 4278124544 0 0]
TRACE polkavm::interpreter sp = 0xfefdff68
accumulate: ADD_IMM_64 step: 4 pc: 5401 gas:4999988 Registers:[4294901760 4278058856 0 0 0 0 0 65536 3 0 4278124544 0 0]
TRACE polkavm::interpreter u64 [0xfefdfff8] = ra = 0xffff0000
accumulate: STORE_IND_U64 step: 5 pc: 5405 gas:4999988 Registers:[4294901760 4278058856 0 0 0 0 0 65536 3 0 4278124544 0 0]
TRACE polkavm::interpreter u64 [0xfefdfff0] = s0 = 0x0
accumulate: STORE_IND_U64 step: 6 pc: 5409 gas:4999988 Registers:[4294901760 4278058856 0 0 0 0 0 65536 3 0 4278124544 0 0]
TRACE polkavm::interpreter u64 [0xfefdffe8] = s1 = 0x0
...
If you find a discrepancy between implementations, please create an issue with a link to a test file and your trace formatted in identical form to the debug trace.
JAM DUNA is happy to report initial recompiler performance results on game of life match up closely with that of polkajam in 0.6.7 tiny testnets:
| WP | # steps | RefineGasUsed | Compile (ms) | Execution (ms) | Total | Polkajam node 1 | Polkajam node 2 | Average 1+2 | Comparison | ChildGasUsed | ms/step | gas/step |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 73581 | 4.6 | 5.1 | 9.6 | 8.4 | 8.1 | 8.2 | 85.25% | ||||
| 2 | 760 | 73641 | 4.1 | 213.7 | 217.8 | 219.0 | 218.8 | 218.9 | 100.47% | 1,788,605,516 | 0.3 | 2,353,428 |
| 3 | 1510 | 104880 | 4.7 | 419.6 | 424.3 | 392.4 | 396.5 | 394.4 | 92.96% | 3,553,649,782 | 0.3 | 2,353,410 |
| 4 | 2260 | 104880 | 7.1 | 1167.5 | 1174.5 | 1033.3 | 1044.9 | 1039.1 | 88.47% | 5,318,666,032 | 0.5 | 2,353,392 |
| 5 | 3010 | 104880 | 4.2 | 831.7 | 835.9 | 794.2 | 796.4 | 795.3 | 95.15% | 7,083,682,282 | 0.3 | 2,353,383 |
| 6 | 3760 | 104880 | 4.3 | 1038.5 | 1042.8 | 962.4 | 973.0 | 967.7 | 92.79% | 8,848,698,532 | 0.3 | 2,353,377 |
| 7 | 4510 | 104910 | 4.2 | 1261.4 | 1265.5 | 1189.2 | 1195.0 | 1192.1 | 94.19% | 10,613,714,782 | 0.3 | 2,353,374 |
| 8 | 5260 | 104910 | 4.3 | 1446.8 | 1451.0 | 1344.8 | 1354.6 | 1349.7 | 93.02% | 12,378,731,032 | 0.3 | 2,353,371 |
| 9 | 6010 | 104910 | 4.2 | 1655.2 | 1659.3 | 1555.4 | 1568.6 | 1562.0 | 94.13% | 14,143,747,282 | 0.3 | 2,353,369 |
| 10 | 6760 | 104910 | 6.5 | 2447.9 | 2454.5 | 2295.3 | 2302.9 | 2299.1 | 93.67% | 15,908,763,532 | 0.4 | 2,353,367 |
| 11 | 7510 | 104905 | 4.6 | 2066.9 | 2071.5 | 1919.3 | 1934.3 | 1926.8 | 93.02% | 17,673,779,782 | 0.3 | 2,353,366 |
| 12606.9 | 11753.3 | 93.23% |
Nov 2024 - Dec 2025:
- initial setup of fallback/safrole datasets, now covered in this dataset
Feb - early March 2025:
Late March 2025 - Early April 2025:
May 2025:
June 2025:
- First contact with Multiclient JAM Testnet with polkajam + javajam
July 2025:
- 0.6.5 Recompiler success with Doom + Algo
August 2025:
- 0.6.7 Fuzzer + Fuzzer Target released, demonstrated approximate parity of recompiler performance on Game of Life, see Game of Life Recompiler Comparison -- JAM DUNA vs Polkajam (data above, raw data from jamduna and polkajam)
Terrific - please let everyone know in Lets JAM Matrix Room