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 runtime tamper check failure
Evidenceverifier/test-stdout.txt contains: "FAIL: tampered GRADER_HOME/runtime detected -> failing closed (score 0)" before any compile or simulation output. tests/test.sh exits immediately when detect_tamper fails, before checking /app/dut.sv or running iverilog. The agent did run and wrote /app/dut.sv; trajectory shows "COMPILE OK" for `iverilog -g2012 -o /tmp/dut_compile dut.sv`.
Root causeThe verified failure did not come from the task requirements or the agent's SystemVerilog implementation. The verifier's runtime integrity check rejected the grading environment before evaluating the DUT.
RecommendationFix the verifier/runtime setup or relax/correct the tamper check so valid trial environments pass detect_tamper before DUT evaluation.
Trajectory
Tool-by-tool agent trajectory
4 tool calls · 2 tool types · 8 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 analyze this carefully. This is a padding/framing pipeline (MD-style padding per lane, 8-byte blocks, 16-bit bit-length) with valid/ready handshakes and registered outputs. Let me work out the algorithm, then implement and compile-test it. Let me start by writing the module.
write · /app/dut.sv
// TopModule: split byte stream across 4 lanes, pad each lane (MD-style with a
// 16-bit big-endian bit-length), frame into 64-bit big-endian blocks, and emit
// blocks in round-robin-by-index order.  All outputs registered.
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_INPUT = 2'd0;
    localparam ST_LOAD  = 2'd1;
    localparam ST_EMIT  = 2'd2;

    // Byte storage, arrival order.  Max message length 8191.
    reg [7:0] mem [0:8190];

    reg [1:0]  st;
    reg [13:0] Ncnt;    // accepted byte count
    reg [13:0] cur_i;   // current block index
    reg [1:0]  cur_j;   // current lane

    // combinational scratch (assigned before use in the clocked block)
    reg [13:0] e0, e1, e2, e3;
    reg [13:0] s_ifin, s_ni;
    reg [1:0]  s_jfin, s_nj;
    reg        s_found;

    // Length in bytes routed to lane j given total N.
    function automatic [13:0] f_len(input [13:0] N, input [1:0] j);
        reg [13:0] base;
        reg [1:0]  rem;
        begin
            base = N >> 2;
            rem  = N[1:0];
            f_len = base + ((rem > j) ? 14'd1 : 14'd0);
        end
    endfunction

    // Number of 8-byte blocks lane j emits.
    function automatic [13:0] f_blocks(input [13:0] N, input [1:0] j);
        reg [13:0] L;
        reg [13:0] full;
        reg [2:0]  r;
        begin
            L    = f_len(N, j);
            full = L >> 3;
            r    = L[2:0];
            f_blocks = full + 14'd1 + ((r >= 3'd6) ? 14'd1 : 14'd0);
        end
    endfunction

    // Build block bi of lane j.
    function automatic [63:0] f_block(input [1:0] j, input [13:0] bi, input [13:0] N);
        reg [13:0] L, blocks, finalBlk;
        reg [15:0] lenbits;
        integer    p;
        reg [16:0] m;
        reg [18:0] idx;
        reg [7:0]  b;
        begin
            L        = f_len(N, j);
            blocks   = f_blocks(N, j);
            finalBlk = blocks - 14'd1;
            lenbits  = {2'b00, L} << 3;   // length in bits, 16-bit
            f_block  = 64'd0;
            for (p = 0; p < 8; p = p + 1) begin
                m = ({3'b000, bi} << 3) + p[16:0];   // lane byte index
                if ((bi == finalBlk) && (p == 6 || p == 7)) begin
                    b = (p == 6) ? lenbits[15:8] : lenbits[7:0];
                end else if (m < {3'b000, L}) begin
                    idx = (m << 2) + {17'b0, j};      // arrival index = j + 4*m
                    b   = mem[idx];
                end else if (m == {3'b000, L}) begin
                    b = 8'h80;                        // padding marker
                end else begin
                    b = 8'h00;
                end
                f_block[63 - 8*p -: 8] = b;
            end
        end
    endfunction

    always @(posedge clk) begin
        if (rst) begin
            st            <= ST_INPUT;
            Ncnt          <= 14'd0;
            cur_i         <= 14'd0;
            cur_j         <= 2'd0;
            block_o       <= 64'd0;
            block_valid_o <= 1'b0;
            byte_ready_o  <= 1'b1;
            done_o        <= 1'b0;
            busy_o        <= 1'b0;
        end else begin
            case (st)
                ST_INPUT: begin
                    if (byte_valid_i && byte_ready_o) begin
                        mem[Ncnt] <= byte_i;
                        Ncnt      <= Ncnt + 14'd1;
                        busy_o    <= 1'b1;
                        if (last_i) begin
                            byte_ready_o <= 1'b0;
                            st           <= ST_LOAD;
                        end
                    end
                end

                ST_LOAD: begin
                    // Ncnt is final and mem is fully written; present block (0,0).
                    block_o       <= f_block(2'd0, 14'd0, Ncnt);
                    block_valid_o <= 1'b1;
                    cur_i         <= 14'd0;
                    cur_j         <= 2'd0;
                    done_o        <= 1'b0;   // (0,0) is never the final block
                    st            <= ST_EMIT;
                end

                ST_EMIT: begin
                    if (block_valid_o && block_ready_i) begin
                        e0 = f_blocks(Ncnt, 2'd0);
                        e1 = f_blocks(Ncnt, 2'd1);
                        e2 = f_blocks(Ncnt, 2'd2);
                        e3 = f_blocks(Ncnt, 2'd3);
                        s_ifin = e0 - 14'd1;
                        s_jfin = (e3 == e0) ? 2'd3 :
                                 (e2 == e0) ? 2'd2 :
                                 (e1 == e0) ? 2'd1 : 2'd0;

                        if ((cur_i == s_ifin) && (cur_j == s_jfin)) begin
                            // final block accepted -> back to accepting bytes
                            st            <= ST_INPUT;
                            byte_ready_o  <= 1'b1;
                            block_valid_o <= 1'b0;
                            busy_o        <= 1'b0;
                            done_o        <= 1'b0;
                            Ncnt          <= 14'd0;
                        end else begin
                            s_found = 1'b0;
                            s_ni    = cur_i;
                            s_nj    = 2'd0;
                            if (!s_found && (cur_j < 2'd1) && (e1 > cur_i)) begin
                                s_nj = 2'd1; s_ni = cur_i; s_found = 1'b1;
                            end
                            if (!s_found && (cur_j < 2'd2) && (e2 > cur_i)) begin
                                s_nj = 2'd2; s_ni = cur_i; s_found = 1'b1;
                            end
                            if (!s_found && (cur_j < 2'd3) && (e3 > cur_i)) begin
                                s_nj = 2'd3; s_ni = cur_i; s_found = 1'b1;
                            end
                            if (!s_found) begin
                                s_ni = cur_i + 14'd1; s_nj = 2'd0;
                            end
                            cur_i         <= s_ni;
                            cur_j         <= s_nj;
                            block_o       <= f_block(s_nj, s_ni, Ncnt);
                            block_valid_o <= 1'b1;
                            done_o        <= ((s_ni == s_ifin) && (s_nj == s_jfin)) ? 1'b1 : 1'b0;
                        end
                    end
                end

                default: st <= ST_INPUT;
            endcase
        end
    end

endmodule
Now let me verify it compiles with iverilog and write a quick self-check testbench to validate the functional model against my hand-derived expectations.

Compile dut.sv with iverilog

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

[stdout]
COMPILE OK
Compiles. Now let me build a self-checking testbench with an **independent** golden model (coded separately from the DUT logic) to validate the block content, ordering, and handshake behavior against my reading of the spec.
write · /tmp/tb.sv
`timescale 1ns/1ps
module tb;
    reg clk=0, rst=1, start_i=0, byte_valid_i=0, last_i=0, block_ready_i=0;
    reg [7:0] byte_i=0;
    wire [63:0] block_o;
    wire block_valid_o, byte_ready_o, done_o, busy_o;

    TopModule dut(.clk(clk), .rst(rst), .start_i(start_i), .byte_i(byte_i),
        .byte_valid_i(byte_valid_i), .last_i(last_i), .block_ready_i(block_ready_i),
        .block_o(block_o), .block_valid_o(block_valid_o), .byte_ready_o(byte_ready_o),
        .done_o(done_o), .busy_o(busy_o));

    always #5 clk = ~clk;

    // ---- independent golden model ----
    integer N;
    reg [7:0] msg [0:8191];
    // expected block stream
    reg [63:0] exp_blk [0:70000];
    integer    exp_done [0:70000]; // 1 if this emitted block is the final block
    integer    exp_cnt;

    integer laneL [0:3];
    integer laneBlocks [0:3];

    function integer blocks_of(input integer L);
        integer full; integer r;
        begin
            full = L/8; r = L%8;
            blocks_of = full + 1 + ((r>=6)?1:0);
        end
    endfunction

    // build expected block for lane j, block index bi
    function [63:0] mkblk(input integer j, input integer bi);
        integer L, blk, finalBlk, lenbits, p, m, idx;
        reg [7:0] b; reg [63:0] r;
        begin
            L = laneL[j]; blk = laneBlocks[j]; finalBlk = blk-1; lenbits = 8*L;
            r = 0;
            for (p=0;p<8;p=p+1) begin
                m = 8*bi + p;
                if (bi==finalBlk && (p==6||p==7)) b = (p==6)? lenbits[15:8] : lenbits[7:0];
                else if (m < L) begin idx = j + 4*m; b = msg[idx]; end
                else if (m == L) b = 8'h80;
                else b = 8'h00;
                r[63 - 8*p -: 8] = b;
            end
            mkblk = r;
        end
    endfunction

    task build_expected;
        integer j, i, maxB, ifin, jfin;
        begin
            for (j=0;j<4;j=j+1) begin
                laneL[j] = (N/4) + (((N%4) > j)?1:0);
                laneBlocks[j] = blocks_of(laneL[j]);
            end
            maxB = laneBlocks[0];
            ifin = maxB-1;
            jfin = (laneBlocks[3]==maxB)?3:(laneBlocks[2]==maxB)?2:(laneBlocks[1]==maxB)?1:0;
            exp_cnt = 0;
            for (i=0;i<maxB;i=i+1)
                for (j=0;j<4;j=j+1)
                    if (i < laneBlocks[j]) begin
                        exp_blk[exp_cnt] = mkblk(j,i);
                        exp_done[exp_cnt] = ((i==ifin)&&(j==jfin))?1:0;
                        exp_cnt = exp_cnt+1;
                    end
        end
    endtask

    integer got_cnt;
    integer errors;
    integer trial;
    integer k;
    integer r;

    // drive one message, collect blocks, compare
    task run_msg(input integer len, input integer seed);
        integer bi;
        begin
            N = len;
            for (k=0;k<len;k=k+1) msg[k] = $random;
            build_expected;
            got_cnt = 0;

            // ---- input phase ----
            bi = 0;
            while (bi < len) begin
                // randomly present a byte
                @(negedge clk);
                if (($random % 3) != 0) begin
                    byte_valid_i = 1;
                    byte_i = msg[bi];
                    start_i = (bi==0);
                    last_i  = (bi==len-1);
                end else begin
                    byte_valid_i = 0; start_i=0; last_i=0;
                end
                @(posedge clk);
                #1;
                if (byte_valid_i && byte_ready_o) bi = bi + 1;
            end
            @(negedge clk); byte_valid_i=0; start_i=0; last_i=0;

            // ---- output phase: randomly stall, collect blocks ----
            block_ready_i = 0;
            while (got_cnt < exp_cnt) begin
                @(negedge clk);
                block_ready_i = (($random % 3) != 0);
                @(posedge clk);
                #1;
                if (block_valid_o && block_ready_i) begin
                    if (block_o !== exp_blk[got_cnt]) begin
                        errors = errors+1;
                        $display("MISMATCH len=%0d blk#%0d got=%h exp=%h", len, got_cnt, block_o, exp_blk[got_cnt]);
                    end
                    if (done_o !== (exp_done[got_cnt]?1'b1:1'b0)) begin
                        errors = errors+1;
                        $display("DONE mismatch len=%0d blk#%0d got_done=%b exp=%0d", len, got_cnt, done_o, exp_done[got_cnt]);
                    end
                    // busy must be high while presenting/accepting blocks
                    if (busy_o !== 1'b1) begin
                        errors=errors+1; $display("BUSY low during block accept len=%0d blk#%0d", len, got_cnt);
                    end
                    got_cnt = got_cnt + 1;
                end
            end
            @(negedge clk); block_ready_i=0;
            // after final accept, expect busy low, ready high eventually
            @(posedge clk); #1;
            if (busy_o !== 1'b0) begin errors=errors+1; $display("BUSY not cleared len=%0d", len); end
            if (byte_ready_o !== 1'b1) begin errors=errors+1; $display("READY not restored len=%0d", len); end
        end
    endtask

    initial begin
        errors = 0;
        block_ready_i=0; byte_valid_i=0;
        @(negedge clk); rst=1; @(negedge clk); @(negedge clk); rst=0;
        @(negedge clk);

        // directed small lengths
        for (trial=1; trial<=40; trial=trial+1) run_msg(trial, trial);
        // some multiples of 32 and boundaries
        run_msg(32, 100); run_msg(31,101); run_msg(33,102);
        run_msg(64,103); run_msg(63,104); run_msg(48,105);
        // random larger
        for (trial=0; trial<30; trial=trial+1) begin
            r = ($random % 4000); if (r<1) r=1; if(r<0) r=-r; if(r<1)r=1;
            run_msg((r%8191)+1, trial+200);
        end
        run_msg(8191, 999);

        if (errors==0) $display("ALL TESTS PASSED (%0d checks)", got_cnt);
        else $display("FAILED with %0d errors", errors);
        $finish;
    end
endmodule

Compile and run self-checking testbench

shell
cd /tmp && iverilog -g2012 -o /tmp/sim /app/dut.sv /tmp/tb.sv 2>&1 && vvp /tmp/sim 2>&1 | tail -40
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_98c0bddd44a746c4. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_98c0bddd44a746c4 · verifier authoritative; classifier explanatory.