SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

dualmaster-membridge

claude-code claude-opus-4-8 ✗ failed GOOD_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
GOOD_FAILUREHonest miss, the agent ran correctly but couldn't solve it. Expected for a hard task; the task is sound.
SubtypeImplementation Bugs
EvidenceThe verifier compiled and simulated the submitted RTL normally, then failed the sealed reference check: `reference_equivalence: FAIL (2323 mismatches in 3839 samples)`. The task instruction specifies a fixed E to E+5 registered transaction schedule: `m_req_o and m_addr_o carry the chosen command during E+1 only`, `m_data_i is valid during E+3`, and the winner's ack/data are high during E+4 only. The submitted design used pending/rising-edge request tracking and did not match that protocol over the randomized reference-equivalence trace, so this is an implementation miss rather than a task ambiguity.
Root causeThe agent implemented a request-capture timing policy that does not satisfy the specified fixed-latency E to E+5 bridge protocol. The harness ran successfully and the failure is attributable to candidate RTL behavior.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
3 tool calls · 2 tool types · 7 steps
A bridge shares one read-only memory port between requesters A and B, keeping neither starved. Ports: clk, rst, a_req_i, a_addr_i (8), a_ack_o, a_data_o (16), b_req_i, b_addr_i (8), b_ack_o, b_data_o (16), m_req_o, m_addr_o (8), m_data_i (16). rst is synchronous active high, clearing all state and outputs to 0. All outputs are registered. A requester holds req and addr stable through the cycle after its ack. The bridge samples on the idle edge after a request first appears, calling that edge E; a freshly-arriving request is registered one idle cycle before it is sampled as E. One request finishes before the next is sampled. m_req_o and m_addr_o carry the chosen command during E+1 only. m_data_i is valid during E+3. The winner's ack and word are high during E+4 only, the other ack 0. E+4 is the last occupied cycle; the bridge is idle again at E+5, never earlier or later. A sample after a fully idle stretch favours A when both ask. The sample at E+5 directly after an operation instead takes the requester that did not just win if it asks, else the one that did; a later idle stretch resets this, so the next cold sample favours A again. edge E E+1 E+3 E+4 E+5 E+6 m_req_o 0 1 0 0 0 1 a_ack_o 0 0 0 1 0 0 a_data_o and b_data_o matter only while the matching ack is high. Write module TopModule to /app/dut.sv. Plain ASCII synthesizable SystemVerilog only: no define, include, ifdef, system tasks, force, release, bind.
I'll analyze this timing-sensitive arbiter spec carefully, then write the module. Let me work through the timing model: - **Cold start**: request rises → registered (pending flop) → one idle cycle → sampled at edge **E**. So E is 2 edges after the request-rise cycle. - **Pipeline** after sample edge E: `[E,E+1]` decided (outputs 0), `E+1` drives `m_req_o`/`m_addr_o`, `E+3` memory data valid, `E+4` winner ack+data, `E+5` idle-or-restart. - **Fairness**: rising-edge "pending" tracking so a held-high (just-served) request doesn't spuriously re-fire; cold favors A; warm (restart directly from the ack cycle) favors the requester that did *not* just win. Let me write it:
write · /app/dut.sv
module TopModule (
    input             clk,
    input             rst,
    input             a_req_i,
    input      [7:0]  a_addr_i,
    output reg        a_ack_o,
    output reg [15:0] a_data_o,
    input             b_req_i,
    input      [7:0]  b_addr_i,
    output reg        b_ack_o,
    output reg [15:0] b_data_o,
    output reg        m_req_o,
    output reg [7:0]  m_addr_o,
    input      [15:0] m_data_i
);

    // phase: 0 = idle, 2..6 track an in-flight operation relative to sample edge E
    //   phase 2 : cycle [E ,E+1]  (decided, outputs still 0)
    //   phase 3 : cycle [E+1,E+2] (m_req_o / m_addr_o driven)
    //   phase 4 : cycle [E+2,E+3]
    //   phase 5 : cycle [E+3,E+4] (m_data_i valid)
    //   phase 6 : cycle [E+4,E+5] (winner ack + data)
    reg [2:0] phase;
    reg       win;        // current/last winner: 0 = A, 1 = B
    reg [7:0] win_addr;

    reg       a_pending, b_pending;   // rising-edge captured, unserved requests
    reg       a_req_d, b_req_d;      // previous req level for edge detect

    // combinational scratch (single clocked block)
    reg       a_rise, b_rise;
    reg       do_sample, cold, sel, valid_sel;
    reg       a_serv, b_serv;

    always @(posedge clk) begin
        if (rst) begin
            phase     <= 3'd0;
            win       <= 1'b0;
            win_addr  <= 8'd0;
            a_pending <= 1'b0;
            b_pending <= 1'b0;
            a_req_d   <= 1'b0;
            b_req_d   <= 1'b0;
            a_ack_o   <= 1'b0;
            a_data_o  <= 16'd0;
            b_ack_o   <= 1'b0;
            b_data_o  <= 16'd0;
            m_req_o   <= 1'b0;
            m_addr_o  <= 8'd0;
        end else begin
            // ---- edge detection (registered one cycle before use) ----
            a_rise = a_req_i & ~a_req_d;
            b_rise = b_req_i & ~b_req_d;
            a_req_d <= a_req_i;
            b_req_d <= b_req_i;

            // ---- registered outputs default to 0 each cycle ----
            a_ack_o  <= 1'b0;
            a_data_o <= 16'd0;
            b_ack_o  <= 1'b0;
            b_data_o <= 16'd0;
            m_req_o  <= 1'b0;
            m_addr_o <= 8'd0;

            // ---- control defaults ----
            do_sample = 1'b0;
            cold      = 1'b0;
            sel       = 1'b0;
            valid_sel = 1'b0;
            a_serv    = 1'b0;
            b_serv    = 1'b0;

            case (phase)
                3'd0: begin // idle: a pending request registered last cycle -> sample now (cold)
                    if (a_pending | b_pending) begin
                        do_sample = 1'b1;
                        cold      = 1'b1;
                    end
                end
                3'd2: begin // drive the chosen command during E+1 only
                    phase    <= 3'd3;
                    m_req_o  <= 1'b1;
                    m_addr_o <= win_addr;
                end
                3'd3: phase <= 3'd4;
                3'd4: phase <= 3'd5;
                3'd5: begin // m_data_i valid this cycle: capture and drive ack next cycle
                    phase <= 3'd6;
                    if (win == 1'b0) begin
                        a_ack_o  <= 1'b1;
                        a_data_o <= m_data_i;
                    end else begin
                        b_ack_o  <= 1'b1;
                        b_data_o <= m_data_i;
                    end
                end
                3'd6: begin // last occupied cycle: restart directly (warm) or fall idle
                    if (a_pending | b_pending) begin
                        do_sample = 1'b1;
                        cold      = 1'b0;
                    end else begin
                        phase <= 3'd0;
                    end
                end
                default: phase <= 3'd0;
            endcase

            // ---- arbitration at a sample edge ----
            if (do_sample) begin
                if (cold) begin
                    // fully-idle stretch: favour A
                    if (a_pending)      begin sel = 1'b0; valid_sel = 1'b1; end
                    else if (b_pending) begin sel = 1'b1; valid_sel = 1'b1; end
                end else begin
                    // directly after an op: favour the one that did NOT just win
                    if (win == 1'b0) begin
                        if (b_pending)      begin sel = 1'b1; valid_sel = 1'b1; end
                        else if (a_pending) begin sel = 1'b0; valid_sel = 1'b1; end
                    end else begin
                        if (a_pending)      begin sel = 1'b0; valid_sel = 1'b1; end
                        else if (b_pending) begin sel = 1'b1; valid_sel = 1'b1; end
                    end
                end

                if (valid_sel) begin
                    phase    <= 3'd2;
                    win      <= sel;
                    win_addr <= (sel == 1'b0) ? a_addr_i : b_addr_i;
                    a_serv   = (sel == 1'b0);
                    b_serv   = (sel == 1'b1);
                end else begin
                    phase <= 3'd0;
                end
            end

            // ---- pending update: a fresh rising edge outranks being served ----
            a_pending <= a_rise ? 1'b1 : (a_serv ? 1'b0 : a_pending);
            b_pending <= b_rise ? 1'b1 : (b_serv ? 1'b0 : b_pending);
        end
    end

endmodule
Let me sanity-check that it compiles:

Compile/lint the module

shell
(iverilog -g2012 -o /tmp/dut_test dut.sv 2>&1 && echo "COMPILE OK") || (verilator --lint-only -Wall dut.sv 2>&1 | head -20) || echo "no simulator available"
output
COMPILE OK

[stdout]
COMPILE OK
Compiles. Let me verify the timing against the spec with a quick testbench:

Run timing testbench

shell
cat > /tmp/tb.sv << 'EOF'
module tb;
  reg clk=0, rst=1;
  reg a_req_i=0, b_req_i=0;
  reg [7:0] a_addr_i=0, b_addr_i=0;
  wire a_ack_o, b_ack_o, m_req_o;
  wire [15:0] a_data_o, b_data_o;
  wire [7:0] m_addr_o;
  reg [15:0] m_data_i=0;

  TopModule dut(.clk(clk),.rst(rst),
    .a_req_i(a_req_i),.a_addr_i(a_addr_i),.a_ack_o(a_ack_o),.a_data_o(a_data_o),
    .b_req_i(b_req_i),.b_addr_i(b_addr_i),.b_ack_o(b_ack_o),.b_data_o(b_data_o),
    .m_req_o(m_req_o),.m_addr_o(m_addr_o),.m_data_i(m_data_i));

  always #5 clk=~clk;
  integer cyc=0;

  // model memory: when m_req_o seen at some cycle, data valid 2 cycles later handled by dut timing.
  // Provide m_data_i = addr-based value continuously (dut samples at E+3).
  always @(*) m_data_i = {8'hAB, m_addr_o}; // simplistic

  always @(posedge clk) begin
    cyc = cyc+1;
    $display("cyc=%0d rst=%b areq=%b breq=%b | m_req=%b m_addr=%02x | a_ack=%b a_data=%04x b_ack=%b b_data=%04x",
      cyc, rst, a_req_i, b_req_i, m_req_o, m_addr_o, a_ack_o, a_data_o, b_ack_o, b_data_o);
  end

  initial begin
    @(negedge clk); rst=1; @(negedge clk); rst=0;
    $display("--- COLD A-only: a_req rises ---");
    a_addr_i=8'h11; a_req_i=1;
    repeat(8) @(negedge clk);
    a_req_i=0;
    repeat(4) @(negedge clk);
    $display("--- WARM: A and B both request continuously ---");
    a_addr_i=8'h22; b_addr_i=8'h33; a_req_i=1; b_req_i=1;
    repeat(14) @(negedge clk);
    a_req_i=0; b_req_i=0;
    repeat(4) @(negedge clk);
    $finish;
  end
endmodule
EOF
iverilog -g2012 -o /tmp/sim /app/dut.sv /tmp/tb.sv && vvp /tmp/sim
output
cyc=1 rst=1 areq=0 breq=0 | m_req=x m_addr=xx | a_ack=x a_data=xxxx b_ack=x b_data=xxxx
cyc=2 rst=1 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
--- COLD A-only: a_req rises ---
cyc=3 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=4 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=5 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=6 rst=0 areq=1 breq=0 | m_req=1 m_addr=11 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=7 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=8 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=9 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=1 a_data=ab00 b_ack=0 b_data=0000
cyc=10 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=11 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=12 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=13 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=14 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
--- WARM: A and B both request continuously ---
cyc=15 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=16 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=17 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=18 rst=0 areq=1 breq=1 | m_req=1 m_addr=22 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=19 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=20 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=21 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=1 a_data=ab00 b_ack=0 b_data=0000
cyc=22 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=23 rst=0 areq=1 breq=1 | m_req=1 m_addr=33 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=24 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=25 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=26 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=1 b_data=ab00
cyc=27 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=28 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=29 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=30 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=31 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=32 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
/tmp/tb.sv:40: $finish called at 320 (1s)

[stdout]
cyc=1 rst=1 areq=0 breq=0 | m_req=x m_addr=xx | a_ack=x a_data=xxxx b_ack=x b_data=xxxx
cyc=2 rst=1 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
--- COLD A-only: a_req rises ---
cyc=3 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=4 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=5 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=6 rst=0 areq=1 breq=0 | m_req=1 m_addr=11 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=7 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=8 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=9 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=1 a_data=ab00 b_ack=0 b_data=0000
cyc=10 rst=0 areq=1 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=11 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=12 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=13 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=14 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
--- WARM: A and B both request continuously ---
cyc=15 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=16 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=17 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=18 rst=0 areq=1 breq=1 | m_req=1 m_addr=22 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=19 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=20 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=21 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=1 a_data=ab00 b_ack=0 b_data=0000
cyc=22 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=23 rst=0 areq=1 breq=1 | m_req=1 m_addr=33 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=24 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=25 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=26 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=1 b_data=ab00
cyc=27 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=28 rst=0 areq=1 breq=1 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=29 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=30 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=31 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
cyc=32 rst=0 areq=0 breq=0 | m_req=0 m_addr=00 | a_ack=0 a_data=0000 b_ack=0 b_data=0000
/tmp/tb.sv:40: $finish called at 320 (1s)
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
TEST dut_present: PASS (/app/dut.sv exists)
TEST dut_forbidden: PASS (no forbidden constructs)
TEST dut_compiles: PASS (compiled with held-back reference/testbench)
TEST simulation_completed: PASS (Mismatches: 2323 in 3839 samples)
TEST reference_equivalence: FAIL (2323 mismatches in 3839 samples)
{"score": 0.000000, "results_file": "/tmp/h2t-grader-home.vqYqzr/runtime/cb_verifier_312-18329-26366-28507_312/results.jsonl"}

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_18d01ba9329f4eba. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_18d01ba9329f4eba · verifier authoritative; classifier explanatory.