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 guard failure
Root causeThe recorded failure was caused by the verifier's environment/tamper detection, not by a behavioral mismatch in the submitted SystemVerilog or by an underspecified task. Because simulation never ran, this trial does not reveal a task-specification problem.
RecommendationN/A - harness/runtime issue; task specification was not evaluated.
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 design this carefully. Let me think through the architecture, then write the module and verify it compiles. My plan: receive all bytes into a memory (indexed by arrival order), then emit blocks. Byte `k`'s arrival index equals `32*I + 4*p + L` for lane `L`, block `I`, position `p` , so I can compute any block's content on the fly from memory. Padding/length follow the MD-style rules. Emission is round-robin by block index, lanes 0→3. Let me write it:
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 [1:0] IDLE = 2'd0, RECV = 2'd1, EMIT = 2'd2;

  reg [1:0]  state;
  reg [12:0] n;            // accepted byte count (0..8191)
  reg [1:0]  cur_lane;     // currently presented block's lane
  reg [9:0]  cur_idx;      // currently presented block's index
  reg [12:0] nres;         // temp for f_next result

  reg [7:0]  mem [0:8191]; // bytes in arrival order

  // ---- combinational helpers (functions of n) ----

  // number of bytes routed to lane L
  function automatic [11:0] f_laneLen(input [1:0] L);
    reg [11:0] base; reg extra;
    begin
      base = {1'b0, n[12:2]};        // n / 4
      case (L)
        2'd0:    extra = (n[1:0] > 2'd0);
        2'd1:    extra = (n[1:0] > 2'd1);
        2'd2:    extra = (n[1:0] > 2'd2);
        default: extra = 1'b0;
      endcase
      f_laneLen = base + {11'b0, extra};
    end
  endfunction

  // number of emitted blocks for a lane of Lj bytes
  function automatic [9:0] f_blocks(input [11:0] Lj);
    reg [8:0] q; reg [2:0] rem; reg [9:0] extra;
    begin
      q   = Lj[11:3];               // Lj / 8
      rem = Lj[2:0];               // Lj % 8
      extra = (rem >= 3'd6) ? 10'd1 : 10'd0;
      f_blocks = {1'b0, q} + 10'd1 + extra;
    end
  endfunction

  // build 64-bit block content for lane L, block index I
  function automatic [63:0] f_block(input [1:0] L, input [9:0] I);
    reg [11:0] Lj; reg [9:0] Bj; reg [15:0] lenb;
    integer p; reg [15:0] m; reg [15:0] addr; reg [7:0] cur;
    reg [63:0] acc;
    begin
      Lj   = f_laneLen(L);
      Bj   = f_blocks(Lj);
      lenb = {1'b0, Lj, 3'b000};    // length in bits = 8 * Lj
      acc  = 64'd0;
      for (p = 0; p < 8; p = p + 1) begin
        m    = I*8 + p;             // lane byte position
        addr = I*32 + p*4 + L;      // arrival index (valid when m < Lj)
        if (m < Lj)                          cur = mem[addr];
        else if ((I == Bj - 10'd1) && (p==6)) cur = lenb[15:8];
        else if ((I == Bj - 10'd1) && (p==7)) cur = lenb[7:0];
        else if (m == Lj)                    cur = 8'h80;
        else                                 cur = 8'h00;
        acc = (acc << 8) | {56'b0, cur};
      end
      f_block = acc;                // earliest byte in [63:56]
    end
  endfunction

  // next block in emission order; returns {done, lane[1:0], idx[9:0]}
  function automatic [12:0] f_next(input [1:0] L, input [9:0] I, input [9:0] maxB);
    reg found; reg [1:0] nl; reg [9:0] ni; integer j; reg [9:0] bj;
    begin
      found = 1'b0; nl = 2'd0; ni = 10'd0;
      // same index, a higher lane
      for (j = 0; j < 4; j = j + 1) begin
        bj = f_blocks(f_laneLen(j[1:0]));
        if (!found && (j > L) && (bj > I)) begin
          found = 1'b1; nl = j[1:0]; ni = I;
        end
      end
      // otherwise advance to next index, lowest qualifying lane
      if (!found && ((I + 10'd1) < maxB)) begin
        for (j = 0; j < 4; j = j + 1) begin
          bj = f_blocks(f_laneLen(j[1:0]));
          if (!found && (bj > (I + 10'd1))) begin
            found = 1'b1; nl = j[1:0]; ni = I + 10'd1;
          end
        end
      end
      f_next = {~found, nl, ni};
    end
  endfunction

  // per-lane block counts and the global maxima
  wire [11:0] llen0 = f_laneLen(2'd0);
  wire [11:0] llen1 = f_laneLen(2'd1);
  wire [11:0] llen2 = f_laneLen(2'd2);
  wire [11:0] llen3 = f_laneLen(2'd3);
  wire [9:0]  blk0  = f_blocks(llen0);
  wire [9:0]  blk1  = f_blocks(llen1);
  wire [9:0]  blk2  = f_blocks(llen2);
  wire [9:0]  blk3  = f_blocks(llen3);
  wire [9:0]  mx01  = (blk0 > blk1) ? blk0 : blk1;
  wire [9:0]  mx23  = (blk2 > blk3) ? blk2 : blk3;
  wire [9:0]  w_maxB = (mx01 > mx23) ? mx01 : mx23;
  wire [1:0]  w_finalLane = (blk3 == w_maxB) ? 2'd3 :
                            (blk2 == w_maxB) ? 2'd2 :
                            (blk1 == w_maxB) ? 2'd1 : 2'd0;

  always @(posedge clk) begin
    if (rst) begin
      state         <= IDLE;
      n             <= 13'd0;
      cur_lane      <= 2'd0;
      cur_idx       <= 10'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 (state)
        IDLE: begin
          if (byte_valid_i && byte_ready_o) begin
            mem[0] <= byte_i;
            n      <= 13'd1;
            busy_o <= 1'b1;
            if (last_i) begin
              state        <= EMIT;
              byte_ready_o <= 1'b0;   // block_valid_o stays 0 -> load next cycle
            end else begin
              state <= RECV;
            end
          end
        end

        RECV: begin
          if (byte_valid_i && byte_ready_o) begin
            mem[n] <= byte_i;
            n      <= n + 13'd1;
            if (last_i) begin
              state        <= EMIT;
              byte_ready_o <= 1'b0;
            end
          end
        end

        EMIT: begin
          if (block_valid_o) begin
            if (block_ready_i) begin
              if ((cur_idx == w_maxB - 10'd1) && (cur_lane == w_finalLane)) begin
                // final block accepted
                state         <= IDLE;
                block_valid_o <= 1'b0;
                done_o        <= 1'b0;
                busy_o        <= 1'b0;
                byte_ready_o  <= 1'b1;
              end else begin
                nres     = f_next(cur_lane, cur_idx, w_maxB);
                cur_lane <= nres[11:10];
                cur_idx  <= nres[9:0];
                block_o  <= f_block(nres[11:10], nres[9:0]);
                done_o   <= (nres[9:0] == w_maxB - 10'd1) &&
                            (nres[11:10] == w_finalLane);
              end
            end
          end else begin
            // load the very first block (lane 0, index 0)
            cur_lane      <= 2'd0;
            cur_idx       <= 10'd0;
            block_o       <= f_block(2'd0, 10'd0);
            block_valid_o <= 1'b1;
            done_o        <= (10'd0 == w_maxB - 10'd1) && (2'd0 == w_finalLane);
          end
        end

        default: state <= IDLE;
      endcase
    end
  end

endmodule
Now let me verify it compiles with iverilog and test it against my own reference model with randomized stimulus.

Compile dut.sv standalone

shell
iverilog -g2012 -o /tmp/dut_only.out dut.sv 2>&1 && echo "COMPILE_OK" || echo "COMPILE_FAIL"
output
COMPILE_OK

[stdout]
COMPILE_OK
Compiles cleanly. Now let me build a self-checking testbench with an independent golden model to validate block content, ordering, and handshake behavior across many randomized runs.
write · /tmp/tb.sv
module tb;
  reg clk=0, rst=0, 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;

  // storage for one message
  integer N;
  reg [7:0] msg [0:8191];

  // golden emitted blocks
  reg [63:0] gexp [0:5000];
  integer gcount;

  integer errors;
  integer seed;

  // compute lane length
  function integer laneLen(input integer NN, input integer L);
    laneLen = (NN/4) + (((NN%4) > L) ? 1 : 0);
  endfunction
  function integer laneBlocks(input integer Lj);
    integer q, rem;
    begin
      q = Lj/8; rem = Lj%8;
      laneBlocks = q + 1 + ((rem>=6)?1:0);
    end
  endfunction
  // build golden block for lane L idx I
  function [63:0] goldBlock(input integer L, input integer I);
    integer Lj, Bj, p, m, addr, lenb; reg [7:0] cur; reg [63:0] acc;
    begin
      Lj = laneLen(N,L); Bj = laneBlocks(Lj); lenb = 8*Lj; acc=0;
      for (p=0;p<8;p=p+1) begin
        m = I*8+p; addr = I*32+p*4+L;
        if (m < Lj) cur = msg[addr];
        else if ((I==Bj-1)&&(p==6)) cur = (lenb>>8)&8'hFF;
        else if ((I==Bj-1)&&(p==7)) cur = lenb&8'hFF;
        else if (m==Lj) cur = 8'h80;
        else cur = 8'h00;
        acc = (acc<<8)|cur;
      end
      goldBlock = acc;
    end
  endfunction

  // build the golden emission sequence
  task buildGolden;
    integer b0,b1,b2,b3,maxB,I,L,bj;
    begin
      b0=laneBlocks(laneLen(N,0)); b1=laneBlocks(laneLen(N,1));
      b2=laneBlocks(laneLen(N,2)); b3=laneBlocks(laneLen(N,3));
      maxB=b0; if(b1>maxB)maxB=b1; if(b2>maxB)maxB=b2; if(b3>maxB)maxB=b3;
      gcount=0;
      for (I=0;I<maxB;I=I+1)
        for (L=0;L<4;L=L+1) begin
          bj=laneBlocks(laneLen(N,L));
          if (I<bj) begin gexp[gcount]=goldBlock(L,I); gcount=gcount+1; end
        end
    end
  endtask

  integer collected;
  integer i, msglen;
  integer trial;
  integer gap;
  integer busy_seen_hi;

  // send one message and collect emitted blocks, checking on the fly
  task runMessage(input integer L);
    integer sent;
    begin
      N = L;
      for (i=0;i<N;i=i+1) msg[i] = $random(seed) & 8'hFF;
      buildGolden;
      collected = 0;
      sent = 0;

      // drive bytes with random gaps while randomly allowing blocks
      // (blocks won't appear until reception done, but keep ready random)
      while (sent < N || collected < gcount) begin
        @(negedge clk);
        // byte side
        if (sent < N && byte_ready_o) begin
          if (($random(seed)%3)!=0) begin
            byte_valid_i = 1;
            byte_i = msg[sent];
            start_i = (sent==0);
            last_i = (sent==N-1);
          end else begin
            byte_valid_i = 0; start_i=0; last_i=0;
          end
        end else begin
          byte_valid_i = 0; start_i=0; last_i=0;
        end
        // block side ready random
        block_ready_i = ($random(seed)%2);

        @(posedge clk);
        // observe acceptances that just happened at this edge
        if (byte_valid_i && byte_ready_o) sent = sent + 1;
        if (block_valid_o && block_ready_i) begin
          if (collected < gcount) begin
            if (block_o !== gexp[collected]) begin
              errors = errors + 1;
              $display("MISMATCH msglen=%0d block#%0d got=%h exp=%h", N, collected, block_o, gexp[collected]);
            end
            // done_o must be high exactly on the final block accept
            if ((collected==gcount-1) !== done_o) begin
              errors=errors+1;
              $display("DONE mismatch msglen=%0d block#%0d done=%b", N, collected, done_o);
            end
          end else begin
            errors=errors+1; $display("EXTRA block msglen=%0d", N);
          end
          collected = collected + 1;
        end
      end
      // small idle gap
      byte_valid_i=0; start_i=0; last_i=0; block_ready_i=0;
      repeat (($random(seed)%4)) @(negedge clk);
      if (collected != gcount) begin
        errors=errors+1; $display("COUNT mismatch msglen=%0d got=%0d exp=%0d", N, collected, gcount);
      end
    end
  endtask

  initial begin
    seed = 32'hDEAD1234;
    errors = 0;
    rst = 1; @(negedge clk); @(negedge clk); rst = 0;
    @(negedge clk);

    // directed small lengths
    for (trial=1; trial<=40; trial=trial+1) runMessage(trial);
    // multiples of 8 and boundaries per lane
    runMessage(32); runMessage(24); runMessage(23); runMessage(48);
    runMessage(1); runMessage(2); runMessage(3); runMessage(4);
    runMessage(5); runMessage(6); runMessage(7); runMessage(8);
    // random larger
    for (trial=0; trial<60; trial=trial+1) begin
      msglen = 1 + ($random(seed) % 2000);
      if (msglen<1) msglen = 1;
      runMessage(msglen);
    end
    // max
    runMessage(8191);

    if (errors==0) $display("ALL_TESTS_PASSED");
    else $display("FAILED with %0d errors", errors);
    $finish;
  end

  // watchdog
  initial begin
    #50000000 $display("TIMEOUT"); $finish;
  end
endmodule

Compile and run testbench

shell
cd /tmp && iverilog -g2012 -o /tmp/sim.out /app/dut.sv /tmp/tb.sv 2>&1 && vvp /tmp/sim.out 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_8c90b5677d734c75. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_8c90b5677d734c75 · verifier authoritative; classifier explanatory.