SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

hash-message-padder

claude-code claude-opus-4-8 ✗ failed HARNESS_ERROR ↑ View task
Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.
Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.
Classification , post-hoc; cannot change the reward
HARNESS_ERRORInfrastructure failure, the agent never ran properly. Not a signal about agent or task.
SubtypeVerifier environment/tamper-detection failure
Root causeThe trial failed before the SystemVerilog DUT was compiled against the reference or simulated; the verifier's runtime tamper check rejected the grading environment. This does not reveal an underspecified instruction or brittle behavioral test for the task.
RecommendationN/A - task is fine; investigate the verifier runtime/GRADER_HOME ownership setup and rerun the trial.
Trajectory
Tool-by-tool agent trajectory
2 tool calls · 2 tool types · 5 steps
Design a SystemVerilog module named TopModule that splits a stream of message bytes across four parallel lanes, pads each lane independently, and frames the result into 64-bit blocks, with valid/ready handshakes on both the byte input and the block output. Ports, one bit each unless noted: inputs clk, rst, start_i, byte_i [7:0], byte_valid_i, last_i, block_ready_i; outputs block_o [63:0], block_valid_o, byte_ready_o, done_o, busy_o. All five outputs are registered. rst is synchronous active high: every output clears to 0 except byte_ready_o which clears to 1. block_o is compared only while block_valid_o is high. A byte is accepted on a rising edge where byte_valid_i and byte_ready_o are both high. start_i accompanies the first accepted byte, last_i the final one. The message length is its accepted-byte count, 1 to 8191. Number the accepted bytes from zero in arrival order. Byte k belongs to lane k mod 4. Within a lane the bytes keep their arrival order and pack eight per block, big-endian, the earliest byte in block_o[63:56]. Each lane is padded on its own byte stream. Append 0x80 in the byte position immediately after that lane's last byte, fill the rest with zero, and place that lane's length in bits, which is eight times the number of bytes routed to the lane, as a 16-bit big-endian value in byte6 and byte7 of the lane's final block. Emit the fewest blocks per lane that hold the lane's bytes, the marker, the fill and the length. When a lane's byte count is a multiple of eight, its 0x80 and length occupy one additional all-padding block. When the block holding a lane's last byte has six or seven byte positions filled, the length does not share it: that block carries the bytes, 0x80 and zero fill, and a following block holds only the length. A lane with no bytes still emits one block holding 0x80, zero fill and a zero length. Index the blocks of each lane from zero. Emit all four lanes' block 0, then all four lanes' block 1, and so on; within an index emit lane 0 first through lane 3. Skip a lane at indices beyond its block count. block_valid_o is high while a block is presented and a block is accepted on a rising edge where block_valid_o and block_ready_i are both high; while it is stalled block_o and block_valid_o hold. Present one block at a time. byte_ready_o is high while bytes are accepted and low while blocks are leaving. busy_o is high from the first accepted byte until the final block is accepted, low otherwise. The final block is the highest index reached by any lane, taken in the highest-numbered lane that reaches it. done_o is high for the cycles that block is presented, so on its accepting edge block_valid_o, block_ready_i and done_o are all high. Put the implementation in /app/dut.sv with the module named TopModule and exactly this port list. It is compiled with iverilog -g2012 against a held-back reference and simulated under randomized stimulus that drives the byte side and randomly stalls the block side; the design must match the reference on every output on every clock edge for every sample. Use plain synthesizable SystemVerilog: module/endmodule, always/assign, localparam, reg, wire, logic and functions. Do not use preprocessor directives (include, define, ifdef, ifndef, undef, the token-paste operator), do not call simulator system tasks ($display, $write, $finish, $stop, $system, $fopen, $fwrite, $fdisplay, $fread, $fgets, $feof, $readmem, $writemem, $dumpfile, $dumpvars, $fatal, $exit, $error, $warning, $assert), do not use force or release, and do not import DPI-C; the verifier rejects the submission before simulation if any of these appear in /app/dut.sv.
I'll design this carefully. Let me first work through the key algorithm, then implement it. The core insight: each lane independently does MD-style padding (0x80 marker + zero fill + 16-bit length in bytes 6,7 of its final block). Let me verify my block-count and byte-placement logic, then implement.
write · /app/dut.sv
module TopModule (
    input  wire        clk,
    input  wire        rst,
    input  wire        start_i,
    input  wire [7:0]  byte_i,
    input  wire        byte_valid_i,
    input  wire        last_i,
    input  wire        block_ready_i,
    output reg  [63:0] block_o,
    output reg         block_valid_o,
    output reg         byte_ready_o,
    output reg         done_o,
    output reg         busy_o
);

    localparam ST_RECV = 1'b0;
    localparam ST_EMIT = 1'b1;

    // sequential state
    reg        state;
    reg [12:0] write_ptr;      // number of bytes stored (0..8191)
    reg [1:0]  lane_ptr;       // lane for next byte
    reg [11:0] cnt  [0:3];     // per-lane byte counts during receive

    reg [11:0] nLr  [0:3];     // final per-lane byte counts
    reg [8:0]  BLr  [0:3];     // per-lane block counts
    reg [8:0]  maxB;           // max block index+1
    reg [1:0]  finalL;         // lane of final emitted block
    reg [8:0]  finalI;         // index of final emitted block

    reg [1:0]  cur_L;          // currently presented block: lane
    reg [8:0]  cur_i;          // currently presented block: index

    reg [7:0]  mem [0:8191];   // stored message bytes (global index)

    // combinational scratch (used with blocking assigns inside clocked block)
    integer    li;
    reg [11:0] nfin [0:3];
    reg [8:0]  cbv  [0:3];
    reg [8:0]  tmaxB;
    reg [1:0]  tfinalL;
    reg [8:0]  tfinalI;
    reg [8:0]  ni_try;
    reg [1:0]  nxtL;
    reg [8:0]  nxtI;
    reg        found;
    reg [11:0] selN;
    reg [8:0]  selB;

    // number of 64-bit blocks a lane with n bytes produces
    function [8:0] calcB(input [11:0] n);
        reg [8:0] q;
        reg [2:0] r;
        begin
            q = n[11:3];
            r = n[2:0];
            // r in 0..5 -> q+1 (marker+len fit / extra block for multiple of 8)
            // r in 6..7 -> q+2 (length pushed to its own trailing block)
            calcB = (r <= 3'd5) ? (q + 9'd1) : (q + 9'd2);
        end
    endfunction

    // build the 64-bit block for lane L, block index bi.
    // nL = lane byte count, BL = lane block count.
    // bypass allows reading the byte currently being written (index bp_idx).
    function [63:0] gen_block(input [1:0]  L,
                              input [8:0]  bi,
                              input [11:0] nL,
                              input [8:0]  BL,
                              input        use_bp,
                              input [12:0] bp_idx,
                              input [7:0]  bp_val);
        integer p;
        integer j;
        integer gidx;
        reg [7:0]  bb;
        reg [15:0] lenbits;
        begin
            lenbits = {1'b0, nL, 3'b000}; // 8 * nL, in bits
            gen_block = 64'd0;
            for (p = 0; p < 8; p = p + 1) begin
                j = bi * 8 + p;
                if ((bi == (BL - 9'd1)) && (p >= 6)) begin
                    // length occupies bytes 6,7 of a lane's final block
                    bb = (p == 6) ? lenbits[15:8] : lenbits[7:0];
                end else if (j < nL) begin
                    gidx = 4 * j + L;
                    if (use_bp && (gidx == bp_idx))
                        bb = bp_val;
                    else
                        bb = mem[gidx];
                end else if (j == nL) begin
                    bb = 8'h80;              // padding marker
                end else begin
                    bb = 8'h00;              // zero fill
                end
                // p==0 is the earliest byte -> block_o[63:56]
                gen_block[(7 - p) * 8 +: 8] = bb;
            end
        end
    endfunction

    always @(posedge clk) begin
        if (rst) begin
            block_o       <= 64'd0;
            block_valid_o <= 1'b0;
            byte_ready_o  <= 1'b1;
            done_o        <= 1'b0;
            busy_o        <= 1'b0;
            state         <= ST_RECV;
            write_ptr     <= 13'd0;
            lane_ptr      <= 2'd0;
            cur_L         <= 2'd0;
            cur_i         <= 9'd0;
            maxB          <= 9'd0;
            finalL        <= 2'd0;
            finalI        <= 9'd0;
            cnt[0] <= 12'd0; cnt[1] <= 12'd0; cnt[2] <= 12'd0; cnt[3] <= 12'd0;
            nLr[0] <= 12'd0; nLr[1] <= 12'd0; nLr[2] <= 12'd0; nLr[3] <= 12'd0;
            BLr[0] <= 9'd0;  BLr[1] <= 9'd0;  BLr[2] <= 9'd0;  BLr[3] <= 9'd0;
        end else begin
            case (state)
            ST_RECV: begin
                if (byte_valid_i && byte_ready_o) begin
                    // accept the byte
                    mem[write_ptr] <= byte_i;
                    write_ptr      <= write_ptr + 13'd1;
                    cnt[lane_ptr]  <= cnt[lane_ptr] + 12'd1;
                    lane_ptr       <= (lane_ptr == 2'd3) ? 2'd0 : (lane_ptr + 2'd1);
                    busy_o         <= 1'b1;

                    if (last_i) begin
                        // compute final per-lane counts (including this byte)
                        for (li = 0; li < 4; li = li + 1)
                            nfin[li] = cnt[li] + ((lane_ptr == li[1:0]) ? 12'd1 : 12'd0);
                        for (li = 0; li < 4; li = li + 1)
                            cbv[li] = calcB(nfin[li]);

                        tmaxB = cbv[0];
                        for (li = 1; li < 4; li = li + 1)
                            if (cbv[li] > tmaxB) tmaxB = cbv[li];

                        tfinalL = 2'd0;
                        for (li = 0; li < 4; li = li + 1)
                            if (cbv[li] == tmaxB) tfinalL = li[1:0]; // highest such lane

                        tfinalI = tmaxB - 9'd1;

                        // store schedule
                        for (li = 0; li < 4; li = li + 1) begin
                            nLr[li] <= nfin[li];
                            BLr[li] <= cbv[li];
                        end
                        maxB   <= tmaxB;
                        finalL <= tfinalL;
                        finalI <= tfinalI;

                        // present first block (lane 0, index 0) immediately;
                        // bypass the byte just accepted (not yet in mem)
                        cur_L         <= 2'd0;
                        cur_i         <= 9'd0;
                        block_o       <= gen_block(2'd0, 9'd0, nfin[0], cbv[0],
                                                   1'b1, write_ptr, byte_i);
                        done_o        <= ((tfinalL == 2'd0) && (tfinalI == 9'd0));
                        block_valid_o <= 1'b1;
                        byte_ready_o  <= 1'b0;
                        state         <= ST_EMIT;
                    end
                end
            end

            ST_EMIT: begin
                if (block_valid_o && block_ready_i) begin
                    // find the next (lane,index) in emission order
                    found = 1'b0;
                    nxtL  = 2'd0;
                    nxtI  = 9'd0;
                    for (li = 0; li < 4; li = li + 1)
                        if (!found && (li[1:0] > cur_L) && (cur_i < BLr[li])) begin
                            nxtL = li[1:0]; nxtI = cur_i; found = 1'b1;
                        end
                    if (!found) begin
                        ni_try = cur_i + 9'd1;
                        if (ni_try < maxB)
                            for (li = 0; li < 4; li = li + 1)
                                if (!found && (ni_try < BLr[li])) begin
                                    nxtL = li[1:0]; nxtI = ni_try; found = 1'b1;
                                end
                    end

                    if (found) begin
                        cur_L  <= nxtL;
                        cur_i  <= nxtI;
                        selN    = nLr[nxtL];
                        selB    = BLr[nxtL];
                        block_o <= gen_block(nxtL, nxtI, selN, selB,
                                             1'b0, 13'd0, 8'd0);
                        done_o <= ((nxtL == finalL) && (nxtI == finalI));
                    end else begin
                        // final block accepted; return to receive
                        block_valid_o <= 1'b0;
                        done_o        <= 1'b0;
                        busy_o        <= 1'b0;
                        byte_ready_o  <= 1'b1;
                        state         <= ST_RECV;
                        write_ptr     <= 13'd0;
                        lane_ptr      <= 2'd0;
                        cnt[0] <= 12'd0; cnt[1] <= 12'd0;
                        cnt[2] <= 12'd0; cnt[3] <= 12'd0;
                    end
                end
            end
            endcase
        end
    end

endmodule
Now let me verify it compiles with iverilog and run a quick self-check testbench.

Compile dut.sv with iverilog

shell
iverilog -g2012 -o /tmp/dut_test dut.sv 2>&1 && echo "COMPILE OK"
output
COMPILE OK

[stdout]
COMPILE OK
Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward
tests/test.sh
FAIL: tampered GRADER_HOME/runtime detected -> failing closed (score 0)

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_d744c19eb086458f. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_d744c19eb086458f · verifier authoritative; classifier explanatory.