SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

hash-message-padder

claude-code claude-opus-4-8 ✗ failed BAD_FAILURE ↑ 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
BAD_FAILUREThe task is at fault, underspecified/contradictory instruction, brittle/flaky tests, or tests demanding undiscoverable behavior.
SubtypeEnvironment Issues
Evidenceverifier/test-stdout.txt reports: `FAIL: tampered GRADER_HOME/runtime detected -> failing closed (score 0)`. The failure occurs at the start of tests/test.sh in `detect_tamper` before `/app/dut.sv` is compiled or simulated. Agent trajectory shows only `/app/dut.sv` creation, `iverilog -g2012 -o /tmp/syn.out dut.sv`, and writing `/tmp/tb.sv`; there is no evidence it modified `/logs`, `H2T_GRADER_HOME`, or verifier runtime paths.
Root causeThe trial failed because the verifier's tamper-detection guard rejected the runtime environment before evaluating the submitted SystemVerilog. This is not normal agent failure on the specified design task and does not reflect the correctness of the agent's implementation.
RecommendationFix the task harness/runtime contract so `detect_tamper` does not false-fail in valid trial environments, or remove/relax the ownership/mode guard to only check paths the agent can actually tamper with. Ensure the verifier proceeds to compile and simulate `/app/dut.sv` unless there is concrete agent-caused tampering.
Trajectory
Tool-by-tool agent trajectory
3 tool calls · 2 tool types · 7 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.
Looking at this problem, I need to carefully work out the padding algorithm, block emission order, and exact handshake timing. Let me design and implement it directly. Let me first work through the key algorithm, then write the module.
write · /app/dut.sv
module TopModule(
  input  logic        clk,
  input  logic        rst,
  input  logic        start_i,
  input  logic [7:0]  byte_i,
  input  logic        byte_valid_i,
  input  logic        last_i,
  input  logic        block_ready_i,
  output logic [63:0] block_o,
  output logic        block_valid_o,
  output logic        byte_ready_o,
  output logic        done_o,
  output logic        busy_o
);

  localparam RECV = 1'b0;
  localparam SEND = 1'b1;

  // ---------------- state / storage ----------------
  reg          state;
  reg  [7:0]   mem [0:8191];
  reg  [13:0]  cnt;      // bytes accepted so far in current message
  reg  [13:0]  N;        // latched message length
  reg  [8:0]   curi;     // current block index within a lane
  reg  [1:0]   curj;     // current lane

  // ---------------- functions ----------------
  // number of blocks a lane of L bytes produces
  function automatic [10:0] nblk(input [13:0] L);
    reg [10:0] q; reg [2:0] r;
    begin
      q = L[13:3];
      r = L[2:0];
      nblk = (r <= 3'd5) ? (q + 11'd1) : (q + 11'd2);
    end
  endfunction

  // next emission pointer given current (ci,cj) and per-lane block counts
  function automatic [10:0] next_ptr(input [8:0] ci, input [1:0] cj,
                                     input [10:0] b0, input [10:0] b1,
                                     input [10:0] b2, input [10:0] b3);
    reg [10:0] arr [0:3];
    reg [8:0]  ii; reg [1:0] jj; reg fnd; integer x;
    begin
      arr[0]=b0; arr[1]=b1; arr[2]=b2; arr[3]=b3;
      ii = ci; jj = cj; fnd = 1'b0;
      // same index, higher lanes
      for (x=0; x<4; x=x+1) begin
        if (!fnd && (x > cj) && (ci < arr[x])) begin
          ii = ci; jj = x[1:0]; fnd = 1'b1;
        end
      end
      // next index, lanes 0..3
      if (!fnd) begin
        for (x=0; x<4; x=x+1) begin
          if (!fnd && ((ci + 9'd1) < arr[x])) begin
            ii = ci + 9'd1; jj = x[1:0]; fnd = 1'b1;
          end
        end
      end
      next_ptr = {ii, jj};
    end
  endfunction

  // generate the 64-bit content for block bi of lane bj, given message length Nv.
  // do_fwd forwards a byte being written this same edge (index fidx -> value fval).
  function automatic [63:0] gen_block(input [8:0]  bi, input [1:0] bj,
                                      input [13:0] Nv, input       do_fwd,
                                      input [13:0] fidx, input [7:0] fval);
    reg [13:0] base; reg [1:0] rem; reg [13:0] L;
    reg [10:0] q; reg [10:0] nb; reg [2:0] r;
    reg [15:0] lbits;
    reg [63:0] blk;
    integer    p;
    reg [16:0] m;
    reg [15:0] k;
    reg [7:0]  bval;
    begin
      base = Nv >> 2;
      rem  = Nv[1:0];
      case (bj)
        2'd0: L = base + ((rem > 2'd0) ? 14'd1 : 14'd0);
        2'd1: L = base + ((rem > 2'd1) ? 14'd1 : 14'd0);
        2'd2: L = base + ((rem > 2'd2) ? 14'd1 : 14'd0);
        default: L = base;
      endcase
      q     = L[13:3];
      r     = L[2:0];
      nb    = (r <= 3'd5) ? (q + 11'd1) : (q + 11'd2);
      lbits = L << 3;             // length in bits (16-bit)
      blk   = 64'd0;
      for (p=0; p<8; p=p+1) begin
        m = bi*8 + p;
        if ((bi == (nb - 11'd1)) && (p >= 6)) begin
          bval = (p == 6) ? lbits[15:8] : lbits[7:0];
        end else if (m < L) begin
          k    = bj + 4*m;
          bval = (do_fwd && (k == fidx)) ? fval : mem[k];
        end else if (m == L) begin
          bval = 8'h80;
        end else begin
          bval = 8'h00;
        end
        blk[(7-p)*8 +: 8] = bval;  // earliest byte in [63:56]
      end
      gen_block = blk;
    end
  endfunction

  // ---------------- lane geometry (from latched N) ----------------
  wire [13:0] nbase = N >> 2;
  wire [1:0]  nrem  = N[1:0];
  wire [13:0] len0  = nbase + ((nrem > 2'd0) ? 14'd1 : 14'd0);
  wire [13:0] len1  = nbase + ((nrem > 2'd1) ? 14'd1 : 14'd0);
  wire [13:0] len2  = nbase + ((nrem > 2'd2) ? 14'd1 : 14'd0);
  wire [13:0] len3  = nbase;
  wire [10:0] nb0   = nblk(len0);
  wire [10:0] nb1   = nblk(len1);
  wire [10:0] nb2   = nblk(len2);
  wire [10:0] nb3   = nblk(len3);

  // final block = highest index (maxblocks-1), highest lane reaching it.
  // lengths are non-increasing across lanes, so nb0 is the max.
  wire [10:0] FI = nb0 - 11'd1;
  wire [1:0]  FJ = (nb3 == nb0) ? 2'd3 :
                   (nb2 == nb0) ? 2'd2 :
                   (nb1 == nb0) ? 2'd1 : 2'd0;

  wire [10:0] nxt  = next_ptr(curi, curj, nb0, nb1, nb2, nb3);
  wire [8:0]  nxti = nxt[10:2];
  wire [1:0]  nxtj = nxt[1:0];

  // ---------------- sequential ----------------
  always_ff @(posedge clk) begin
    if (rst) begin
      state         <= RECV;
      byte_ready_o  <= 1'b1;
      block_valid_o <= 1'b0;
      done_o        <= 1'b0;
      busy_o        <= 1'b0;
      block_o       <= 64'd0;
      cnt           <= 14'd0;
      N             <= 14'd0;
      curi          <= 9'd0;
      curj          <= 2'd0;
    end else begin
      case (state)
        RECV: begin
          if (byte_valid_i && byte_ready_o) begin
            mem[cnt] <= byte_i;
            busy_o   <= 1'b1;
            if (last_i) begin
              // last byte accepted -> begin emitting blocks next cycle
              N             <= cnt + 14'd1;
              state         <= SEND;
              byte_ready_o  <= 1'b0;
              curi          <= 9'd0;
              curj          <= 2'd0;
              block_valid_o <= 1'b1;
              done_o        <= 1'b0;  // first block is never the final one (>=4 blocks)
              block_o       <= gen_block(9'd0, 2'd0, cnt + 14'd1, 1'b1, cnt, byte_i);
            end else begin
              cnt <= cnt + 14'd1;
            end
          end
        end

        SEND: begin
          if (block_valid_o && block_ready_i) begin
            if (done_o) begin
              // final block accepted -> done
              state         <= RECV;
              byte_ready_o  <= 1'b1;
              block_valid_o <= 1'b0;
              busy_o        <= 1'b0;
              done_o        <= 1'b0;
              cnt           <= 14'd0;
            end else begin
              curi    <= nxti;
              curj    <= nxtj;
              block_o <= gen_block(nxti, nxtj, N, 1'b0, 14'd0, 8'd0);
              done_o  <= (({2'd0, nxti} == FI) && (nxtj == FJ));
            end
          end
        end
      endcase
    end
  end

endmodule
Let me verify it compiles with iverilog and run a quick self-check against a reference model I'll write in a testbench.

Compile dut.sv for syntax check

shell
iverilog -g2012 -o /tmp/syn.out dut.sv 2>&1 | head -40 && echo "COMPILE_EXIT=$?"
output
COMPILE_EXIT=0

[stdout]
COMPILE_EXIT=0
Compiles clean. Now let me write a self-checking testbench with an independent golden reference model to validate the padding, block ordering, and handshake behavior.
write · /tmp/tb.sv
module tb;
  logic clk=0, rst=1, start_i=0, byte_valid_i=0, last_i=0, block_ready_i=0;
  logic [7:0] byte_i=0;
  logic [63:0] block_o;
  logic block_valid_o, byte_ready_o, done_o, busy_o;

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

  always #5 clk = ~clk;

  integer errors = 0;
  integer seed = 1;

  // golden reference for one message
  reg [7:0] msg [0:20000];
  reg [63:0] exp [0:8191];
  integer nexp;
  integer exp_final; // index of final block in exp

  // per-lane scratch
  reg [7:0] padded [0:3][0:9000];
  integer padlen [0:3];
  integer lblocks [0:3];

  task build_golden(input integer N);
    integer j,k,m,L,idx,i,maxb;
    reg [15:0] lbits;
    begin
      for (j=0;j<4;j=j+1) begin
        // gather lane bytes then pad
        idx=0;
        for (k=0;k<N;k=k+1) begin
          if ((k%4)==j) begin
            padded[j][idx]=msg[k]; idx=idx+1;
          end
        end
        L=idx;
        padded[j][idx]=8'h80; idx=idx+1;
        while ((idx%8)!=6) begin padded[j][idx]=8'h00; idx=idx+1; end
        lbits = L*8;
        padded[j][idx]=lbits[15:8]; idx=idx+1;
        padded[j][idx]=lbits[7:0];  idx=idx+1;
        padlen[j]=idx;
        lblocks[j]=idx/8;
      end
      maxb=lblocks[0];
      for (j=1;j<4;j=j+1) if (lblocks[j]>maxb) maxb=lblocks[j];
      // interleave
      nexp=0;
      for (i=0;i<maxb;i=i+1) begin
        for (j=0;j<4;j=j+1) begin
          if (i<lblocks[j]) begin
            exp[nexp] = { padded[j][i*8+0],padded[j][i*8+1],padded[j][i*8+2],padded[j][i*8+3],
                          padded[j][i*8+4],padded[j][i*8+5],padded[j][i*8+6],padded[j][i*8+7] };
            nexp=nexp+1;
          end
        end
      end
      exp_final=nexp-1;
    end
  endtask

  // drive one message and check
  integer got;
  integer busy_seen_first;
  task run_msg(input integer N);
    integer k;
    integer safety;
    begin
      build_golden(N);
      got=0;
      // feed bytes with random gaps
      k=0;
      while (k<N) begin
        // randomly deassert valid
        if (($random(seed)%3)==0) begin
          byte_valid_i<=0; @(posedge clk);
        end else begin
          byte_i<=msg[k];
          byte_valid_i<=1;
          start_i<=(k==0);
          last_i<=(k==N-1);
          @(posedge clk);
          if (byte_ready_o) begin
            k=k+1;
          end
        end
      end
      byte_valid_i<=0; start_i<=0; last_i<=0;
      // now receive blocks with random stalls
      safety=0;
      while (got<nexp && safety<200000) begin
        block_ready_i<=($random(seed)%2);
        @(posedge clk);
        safety=safety+1;
        if (block_valid_o && block_ready_i) begin
          if (block_o !== exp[got]) begin
            errors=errors+1;
            $display("MISMATCH N=%0d block#%0d got=%h exp=%h",N,got,block_o,exp[got]);
          end
          // done_o must be high exactly when accepting final block
          if ((got==nexp-1) && !done_o) begin
            errors=errors+1; $display("DONE not high on final N=%0d",N);
          end
          if ((got!=nexp-1) && done_o) begin
            errors=errors+1; $display("DONE high early N=%0d got=%0d",N,got);
          end
          got=got+1;
        end
      end
      block_ready_i<=0;
      if (got!=nexp) begin errors=errors+1; $display("BLOCKCOUNT N=%0d got=%0d exp=%0d",N,got,nexp); end
      // a couple idle cycles, busy should drop
      @(posedge clk);
      if (busy_o) begin errors=errors+1; $display("BUSY stuck after N=%0d",N); end
      if (!byte_ready_o) begin errors=errors+1; $display("byte_ready low idle after N=%0d",N); end
    end
  endtask

  integer t, N, b;
  initial begin
    rst<=1; @(posedge clk); @(posedge clk); rst<=0; @(posedge clk);
    // directed small lengths
    for (N=1;N<=40;N=N+1) begin
      for (b=0;b<N;b=b+1) msg[b]=($random(seed))&8'hff;
      run_msg(N);
    end
    // random lengths incl larger
    for (t=0;t<60;t=t+1) begin
      N = 1 + ({$random(seed)}%800);
      for (b=0;b<N;b=b+1) msg[b]=($random(seed))&8'hff;
      run_msg(N);
    end
    // boundary lengths around multiples/6-7 mod
    for (N=8188;N<=8191;N=N+1) begin
      for (b=0;b<N;b=b+1) msg[b]=($random(seed))&8'hff;
      run_msg(N);
    end
    if (errors==0) $display("ALL_PASS");
    else $display("FAILED errors=%0d",errors);
    $finish;
  end
endmodule
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_0fce56bc7f294495. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_0fce56bc7f294495 · verifier authoritative; classifier explanatory.