SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

Serial bit-destuff framer

codex gpt-5.5 ✓ resolved GOOD_SUCCESS ↑ 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_SUCCESSLegitimate solve, implements the asked-for behavior; tests verify real functionality.
SubtypeLegitimate Solution
EvidenceTest output shows 'PASS - 672 samples, no mismatches' with reward=1.0. Agent trajectory shows systematic exploration of the module structure, understanding of the run-count state machine, compilation with iverilog -g2012, and manual testbench validation. Agent implemented unconditional always_ff block with state holding on stalls, exact threshold detection (run==STUFF_R for 5, run==FLAG_R/ABORT_R for 6), proper reset behavior, and one-clock pulse outputs (d_valid, flag, abort). Implementation matches the instruction provided in the trajectory (step 3).
Root causeThe agent correctly understood and implemented the serial bit-destuff framer according to the instruction they were given, achieving full passing validation with 672 directed and random test samples across stuff-bit removal, delimiter detection, abort detection, stall-hold behavior, and reset handling.
RecommendationN/A - task is fine. Agent successfully solved the specified problem. (Note: The instruction.md file on disk appears to be a newer version with additional complexity around transparent-stuff run-counting and post-abort resync, which differs from the instruction shown in this trial's trajectory. If the task specification has been intentionally updated, ensure test vectors are similarly updated to maintain verification coverage of the new requirements.)
Trajectory
Tool-by-tool agent trajectory
15 tool calls · 2 tool types · 26 steps
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(file: /tmp/codex-home/skills/.system/skill-installer/SKILL.md) ### How to use skills - Discovery: The list above is the skills available in this session (name + description + source locator). `file` entries live on the host filesystem, `environment resource` entries are owned by their execution environment, `orchestrator resource` entries must be accessed through `skills.list` and `skills.read`, and `custom resource` entries use their provider's access mechanism. - Trigger rules: If the user names a skill (with `$SkillName` or plain text) OR the task clearly matches a skill's description shown above, you must use that skill for that turn. Multiple mentions mean use them all. Do not carry skills across turns unless re-mentioned. - Missing/blocked: If a named skill isn't in the list or its source can't be read, say so briefly and continue with the best fallback. - How to use a skill (progressive disclosure): 1) After deciding to use a skill, the main agent must read its `SKILL.md` completely before taking task actions. For a `file` entry, open the listed path. For an `environment resource`, use the filesystem of the owning environment. For an `orchestrator resource`, call `skills.list` with `{"authority":{"kind":"orchestrator"}}`, select the matching package, and pass its `main_resource` to `skills.read`. If a read is truncated or paginated, continue until EOF. 2) When `SKILL.md` references another resource, use the same access mechanism. Resolve relative paths against a filesystem-backed skill directory. For orchestrator skills, pass the exact referenced resource identifier with the same authority and package to `skills.read`; do not treat `skill://` identifiers as filesystem paths. 3) If `SKILL.md` points to extra folders such as `references/`, use its routing instructions to identify the resources required for the task. The main agent must read each required instruction or reference file itself before acting on it. Do not delegate reading, summarizing, or interpreting skill instructions to a subagent. Subagents may still perform task work when the selected skill allows it. 4) For filesystem-backed skills, prefer running or patching provided scripts instead of retyping large code blocks. 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<environment_context> <cwd>/work</cwd> <shell>bash</shell> <current_date>2026-06-20</current_date> <timezone>Etc/UTC</timezone> <filesystem><workspace_roots><root>/work</root></workspace_roots><permission_profile type="disabled"><file_system type="unrestricted" /></permission_profile></filesystem> </environment_context>
# Serial bit-destuff framer ## Context We are receiving a serial bit stream one bit at a time and need the front-end block `bds` that cleans it up for the layer above. The transmitter on the far end inserts an extra `0` into the data whenever it has just sent a long-ish run of `1`s, so that the data can never accidentally look like one of the special delimiter patterns; our job is to take those inserted bits back out, hand the real data bits onward, and raise a side flag whenever a delimiter or an error-marker pattern goes by. The bit that makes this fiddly is that there is really only *one* piece of state here -- a running count of how many `1`s in a row we have just seen -- and that single count decides all of it at once: whether the next `0` is a real data bit or a bit to throw away, whether we just saw a delimiter, and whether we just saw an error marker. Get the count or its thresholds slightly off and every one of those decisions goes wrong together. The line is not always sending. On any cycle the count of incoming bits is qualified by a strobe; on the cycles where that strobe is low there is no bit to look at and the whole block has to sit still. The package and the wrapper are in place; only `rtl/bds.sv` is a stub. Implement it. ## Interface ``` input clk // single clock input rst_n // asynchronous, active low input s_in // serial data bit in input s_valid // input-bit strobe: s_in is a real bit only when high output d_out // recovered data bit out output d_valid // output-bit strobe: high for one clock per emitted bit output flag // delimiter-seen pulse output abort // error-marker-seen pulse ``` ## What "a bit arrives" means A bit arrives on a rising edge of `clk` where `s_valid` is high; `s_in` is that bit. On a rising edge where `s_valid` is low, **nothing happens**: `s_in` is meaningless, no bit is processed, the running count holds, `d_out` holds its last value, and `d_valid`, `flag` and `abort` are all low. The block only ever advances on cycles where a bit actually arrives. ## The running count Keep a count of how many `1` bits have arrived consecutively, **up to but not including the bit you are processing right now**. It starts at zero, and any `0` that you finish processing leaves it at zero. Everything below is phrased in terms of that count -- call it the *run* -- as it stands at the moment a bit arrives. ## Behaviour When a bit arrives (`s_valid` high), classify it by its value and by the run: - **A `1` bit.** If the run is already six -- i.e. this `1` is the *seventh* in a row -- it is an **error marker**: pulse `abort`, do not emit anything, and the run goes back to zero. Otherwise this `1` is a data bit: emit it (`d_out` = 1, `d_valid` high for this one cycle) and the run grows by one. - **A `0` bit.** Look at how many `1`s preceded it: - if the run is exactly **five**, this `0` is a **stuffed bit**: drop it -- emit nothing -- and the run goes back to zero; - if the run is exactly **six**, this `0` closes a **delimiter**: pulse `flag`, emit nothing, and the run goes back to zero; - otherwise (the run is four or fewer) this `0` is an ordinary data bit: emit it (`d_out` = 0, `d_valid` high for this one cycle) and the run goes back to zero. Note the thresholds are **exact counts, not "at least"**. A `0` only gets removed when precisely five `1`s came before it; a `0` after one, two, three or four `1`s is normal data and is emitted. The sixth `1` in a row is still a data bit that you emit; it is the *seventh* `1` that is the error marker. A `0` after six `1`s is a delimiter, not a removed bit. `d_valid`, `flag` and `abort` are each **one-clock pulses**: high only on the single cycle that processes the bit that caused them, low otherwise (and low on every stalled cycle). At most one of "`d_valid`", "`flag`" and "`abort`" is ever high on the same cycle. ## Precedence There is exactly one decision per arriving bit and it is fixed by `(value of the bit, run before it)`: a `1` is an abort when the run is six and data otherwise; a `0` is a removed stuff bit when the run is exactly five, a flag when the run is exactly six, and data otherwise. A bit that is dropped, that closes a flag, or that triggers an abort is never also emitted, and none of those bits advances the run -- they reset it to zero. ## Conventions `d_out`, `d_valid`, `flag` and `abort` are all **registered**: they take their new value on the rising edge that processes a bit and are observable from just after that edge until the next processed bit. The result of the bit that arrives on edge `E` lands on the outputs on that same edge `E` -- a single registered stage, no extra pipeline delay. `d_valid`, `flag` and `abort` are **pulses** (one clock each, as above), never levels. `d_out` is a held value: it changes only on a cycle that emits a bit and otherwise keeps whatever it last drove (its value is only meaningful on cycles where `d_valid` is high). `rst_n` is **asynchronous** and **active low**: while it is low the run count is cleared to zero and all four outputs are forced to zero, immediately on the falling edge of `rst_n` rather than waiting for a clock, and reset wins over `s_valid`. The run count holds across stalled (`s_valid` low) cycles, so a stall in the middle of a run of `1`s does not change which bit eventually trips the threshold. For an emitted bit on edge `E` with two stalled cycles after it: ``` edge E E+1 E+2 E+3 s_valid 1 0 0 1 d_valid 1 0 0 1 d_out A A A B ``` (`A` and `B` are the two emitted bits; across the stall `d_out` holds `A` and the run is unchanged.) ## Submission Write your implementation into `rtl/bds.sv`, keeping the module name, ports and parameters exactly as given. It must elaborate under Icarus Verilog 11 (`iverilog -g2012`); note that on that tool a bit- or part-select of an *expression* (a sum, a shift, a function result) is a syntax error, so keep the run count in a named register and do any such bit work inside a `function automatic` on a named value. The grader compiles your block with a held-back checker and compares `d_valid`, `flag` and `abort` every cycle, and `d_out` on the cycles you emit a bit, against a reference over directed and random stimulus.
I’ll inspect the RTL stub and surrounding package/wrapper first so the implementation matches the existing module shape exactly.
shell
sed -n '1,220p' rtl/bds.sv
output
Chunk ID: 3ff72d
Wall time: 0.0000 seconds
Process exited with code 2
Original token count: 14
Output:
sed: can't read rtl/bds.sv: No such file or directory
shell
rg -n "module bds|bds" -S .
output
Chunk ID: ad0169
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 184
Output:
./bds_core/rtl/bds_pkg.sv:2:// bds_pkg.sv
./bds_core/rtl/bds_pkg.sv:16:`ifndef BDS_PKG_SV
./bds_core/rtl/bds_pkg.sv:17:`define BDS_PKG_SV
./bds_core/rtl/bds_pkg.sv:19:package bds_pkg;
./bds_core/rtl/bds_pkg.sv:32:endpackage : bds_pkg
./bds_core/rtl/bds_pkg.sv:34:`endif // BDS_PKG_SV
./bds_core/rtl/bds_top.sv:2:// bds_top.sv
./bds_core/rtl/bds_top.sv:6:// itself. It instantiates bds with the project-default geometry from bds_pkg.
./bds_core/rtl/bds_top.sv:11:`include "bds_pkg.sv"
./bds_core/rtl/bds_top.sv:13:module bds_top (
./bds_core/rtl/bds_top.sv:26:  bds u_bds (
./bds_core/rtl/bds_top.sv:37:endmodule : bds_top
./bds_core/rtl/bds.sv:2:// bds.sv
./bds_core/rtl/bds.sv:26:module bds #(
./bds_core/rtl/bds.sv:74:endmodule : bds
shell
rg --files
output
Chunk ID: 4a2d1e
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 17
Output:
bds_core/rtl/bds.sv
bds_core/rtl/bds_top.sv
bds_core/rtl/bds_pkg.sv
The repo root contains `bds_core`, so the target file is `bds_core/rtl/bds.sv`. I’m reading the wrapper/package now to preserve any parameters or style constraints before patching.
shell
sed -n '1,180p' bds_core/rtl/bds.sv
output
Chunk ID: 963ffb
Wall time: 0.0001 seconds
Process exited with code 0
Original token count: 709
Output:
//==============================================================================
// bds.sv
//
// Serial bit-destuff framer.
//
// ---------------------------------------------------------------------------
//  >>> IMPLEMENTATION REQUIRED <<<
//
//  The module ports, parameters and the run-count register are provided. The
//  destuff / flag / abort decode and the outputs are left as a TODO and
//  currently drive constant zeros, so the block emits nothing and the verifier
//  FAILS.
//
//  Implement the behaviour described in instruction.md. Do NOT change the module
//  name, the port list, or the parameter list.
//
//  iverilog 11 note: a bit/part-select of an EXPRESSION (a sum, a shift, a
//  function-call result) is a syntax error under `iverilog -g2012`. Index only
//  named signals, and do any bit work that needs an intermediate value inside a
//  `function automatic` using named locals. Keep the run count in a named
//  register.
// ---------------------------------------------------------------------------
//==============================================================================
`timescale 1ns/1ps

module bds #(
    parameter RUN_W   = 3,
    parameter STUFF_R = 5,
    parameter FLAG_R  = 6,
    parameter ABORT_R = 6
) (
    input  logic clk,
    input  logic rst_n,
    input  logic s_in,
    input  logic s_valid,
    output logic d_out,
    output logic d_valid,
    output logic flag,
    output logic abort
);

  // ---------------------------------------------------------------------------
  // State (provided): running count of consecutive 1 bits seen on the input
  // stream, BEFORE the bit currently being processed.
  // ---------------------------------------------------------------------------
  logic [RUN_W-1:0] run;

  // ===========================================================================
  // TODO: IMPLEMENT THE FRAMER.
  //   * process s_in only on cycles where s_valid is high; freeze every register
  //     (the run count and the outputs) on a stall;
  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
  //     detect flags, and detect aborts;
  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
  //   * asynchronous active-low reset clears the run count and all outputs.
  //
  // The placeholder below keeps the module compilable but INCORRECT.
  // ===========================================================================
  always_ff @(posedge clk or negedge rst_n) begin
    if (!rst_n) begin
      run <= '0;
    end else begin
      // TODO: replace with the real decode + control.
      run <= run;
    end
  end

  // TODO: replace these placeholder outputs with the real ones.
  assign d_out   = 1'b0;
  assign d_valid = 1'b0;
  assign flag    = 1'b0;
  assign abort   = 1'b0;

endmodule : bds
shell
sed -n '1,140p' bds_core/rtl/bds_pkg.sv
output
Chunk ID: fe78ee
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 381
Output:
//==============================================================================
// bds_pkg.sv
//
// Shared constants for the serial bit-destuff framer. The receiver keeps a small
// running count of consecutive 1 bits seen on the input stream; that one count
// drives stuff-bit removal, flag detection, abort detection and the output
// strobe together. The threshold constants live here so the data path and the
// integration wrapper agree on the geometry.
//
// Parameters are declared without an explicit data type for broad simulator
// compatibility (Icarus Verilog 11); they default to plain integer constants,
// which is sufficient here.
//
// DO NOT change this file.
//==============================================================================
`ifndef BDS_PKG_SV
`define BDS_PKG_SV

package bds_pkg;

  // Width of the consecutive-1 run counter. It only ever needs to represent the
  // values 0..6 (a seventh consecutive 1 is consumed as an abort and resets the
  // count), so three bits is ample.
  localparam RUN_W   = 3;

  // Run-length landmarks the contract keys off (counts of consecutive 1 bits
  // already seen, i.e. the run value BEFORE the bit currently being processed).
  localparam STUFF_R = 5;   // a 0 seen with exactly this many 1s before it is a stuffed bit
  localparam FLAG_R  = 6;   // a 0 seen with exactly this many 1s before it closes a flag
  localparam ABORT_R = 6;   // a 1 seen with this many 1s before it is the seventh 1 -> abort

endpackage : bds_pkg

`endif // BDS_PKG_SV
shell
sed -n '1,120p' bds_core/rtl/bds_top.sv
output
Chunk ID: 877a0e
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 269
Output:
//==============================================================================
// bds_top.sv
//
// Thin integration wrapper. The verification environment drives this wrapper so
// that the instantiation wiring is exercised alongside the destuff framer
// itself. It instantiates bds with the project-default geometry from bds_pkg.
//
// DO NOT change this file.
//==============================================================================
`timescale 1ns/1ps
`include "bds_pkg.sv"

module bds_top (
    input  logic clk,
    input  logic rst_n,
    input  logic s_in,
    input  logic s_valid,
    output logic d_out,
    output logic d_valid,
    output logic flag,
    output logic abort
);

  // Bare instantiation: the framer carries its own default geometry, so a
  // submission needs no parameter override to elaborate correctly.
  bds u_bds (
      .clk     (clk),
      .rst_n   (rst_n),
      .s_in    (s_in),
      .s_valid (s_valid),
      .d_out   (d_out),
      .d_valid (d_valid),
      .flag    (flag),
      .abort   (abort)
  );

endmodule : bds_top
shell
find . -maxdepth 3 -type f -name '*tb*' -o -name '*test*'
output
Chunk ID: 3ab467
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
I have enough context. I’m going to replace the placeholder with one registered process: reset clears everything, stalled cycles hold only `run` and `d_out` while clearing pulse outputs, and valid cycles classify from the pre-bit `run` value.
apply_patch
*** Begin Patch
*** Update File: /work/bds_core/rtl/bds.sv
@@
-  // ===========================================================================
-  // TODO: IMPLEMENT THE FRAMER.
-  //   * process s_in only on cycles where s_valid is high; freeze every register
-  //     (the run count and the outputs) on a stall;
-  //   * maintain the consecutive-1 run count and use it to remove stuffed bits,
-  //     detect flags, and detect aborts;
-  //   * drive d_out / d_valid / flag / abort per the contract in instruction.md;
-  //   * asynchronous active-low reset clears the run count and all outputs.
-  //
-  // The placeholder below keeps the module compilable but INCORRECT.
-  // ===========================================================================
+  // ===========================================================================
+  // Destuff / flag / abort decode.
+  // ===========================================================================
   always_ff @(posedge clk or negedge rst_n) begin
     if (!rst_n) begin
-      run <= '0;
+      run     <= '0;
+      d_out   <= 1'b0;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
     end else begin
-      // TODO: replace with the real decode + control.
-      run <= run;
+      d_valid <= 1'b0;
+      flag    <= 1'b0;
+      abort   <= 1'b0;
+
+      if (s_valid) begin
+        if (s_in) begin
+          if (run == ABORT_R) begin
+            abort <= 1'b1;
+            run   <= '0;
+          end else begin
+            d_out   <= 1'b1;
+            d_valid <= 1'b1;
+            run     <= run + 1'b1;
+          end
+        end else begin
+          run <= '0;
+
+          if (run == STUFF_R) begin
+            d_valid <= 1'b0;
+          end else if (run == FLAG_R) begin
+            flag <= 1'b1;
+          end else begin
+            d_out   <= 1'b0;
+            d_valid <= 1'b1;
+          end
+        end
+      end
     end
   end
-
-  // TODO: replace these placeholder outputs with the real ones.
-  assign d_out   = 1'b0;
-  assign d_valid = 1'b0;
-  assign flag    = 1'b0;
-  assign abort   = 1'b0;
 
 endmodule : bds
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
M /work/bds_core/rtl/bds.sv
The implementation is patched. I’m compiling it with Icarus now, then I’ll run a small focused simulation to check the exact thresholds and stall behavior since those are the likely failure points.
shell
iverilog -g2012 -Wall -o /tmp/bds_compile.vvp bds_core/rtl/bds.sv bds_core/rtl/bds_top.sv
output
Chunk ID: 148bf7
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 16
Output:
bds_core/rtl/bds_top.sv:12: Include file bds_pkg.sv not found
shell
git diff -- bds_core/rtl/bds.sv
output
Chunk ID: 16dff4
Wall time: 0.0000 seconds
Process exited with code 127
Original token count: 11
Output:
/bin/bash: line 1: git: command not found
The first compile used no include path, so `bds_top.sv` could not resolve `bds_pkg.sv`. The environment also does not have `git`, so I’ll verify with `sed`/compiler output instead of `git diff`.
shell
iverilog -g2012 -Wall -I bds_core/rtl -o /tmp/bds_compile.vvp bds_core/rtl/bds.sv bds_core/rtl/bds_top.sv
output
Chunk ID: 0ad905
Wall time: 0.0001 seconds
Process exited with code 0
Original token count: 39
Output:
bds_core/rtl/bds_pkg.sv:19: warning: timescale for bds_pkg inherited from another file.
bds_core/rtl/bds_top.sv:10: ...: The inherited timescale is here.
shell
sed -n '1,150p' bds_core/rtl/bds.sv
output
Chunk ID: c18068
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 710
Output:
//==============================================================================
// bds.sv
//
// Serial bit-destuff framer.
//
// ---------------------------------------------------------------------------
//  >>> IMPLEMENTATION REQUIRED <<<
//
//  The module ports, parameters and the run-count register are provided. The
//  destuff / flag / abort decode and the outputs are left as a TODO and
//  currently drive constant zeros, so the block emits nothing and the verifier
//  FAILS.
//
//  Implement the behaviour described in instruction.md. Do NOT change the module
//  name, the port list, or the parameter list.
//
//  iverilog 11 note: a bit/part-select of an EXPRESSION (a sum, a shift, a
//  function-call result) is a syntax error under `iverilog -g2012`. Index only
//  named signals, and do any bit work that needs an intermediate value inside a
//  `function automatic` using named locals. Keep the run count in a named
//  register.
// ---------------------------------------------------------------------------
//==============================================================================
`timescale 1ns/1ps

module bds #(
    parameter RUN_W   = 3,
    parameter STUFF_R = 5,
    parameter FLAG_R  = 6,
    parameter ABORT_R = 6
) (
    input  logic clk,
    input  logic rst_n,
    input  logic s_in,
    input  logic s_valid,
    output logic d_out,
    output logic d_valid,
    output logic flag,
    output logic abort
);

  // ---------------------------------------------------------------------------
  // State (provided): running count of consecutive 1 bits seen on the input
  // stream, BEFORE the bit currently being processed.
  // ---------------------------------------------------------------------------
  logic [RUN_W-1:0] run;

  // ===========================================================================
  // Destuff / flag / abort decode.
  // ===========================================================================
  always_ff @(posedge clk or negedge rst_n) begin
    if (!rst_n) begin
      run     <= '0;
      d_out   <= 1'b0;
      d_valid <= 1'b0;
      flag    <= 1'b0;
      abort   <= 1'b0;
    end else begin
      d_valid <= 1'b0;
      flag    <= 1'b0;
      abort   <= 1'b0;

      if (s_valid) begin
        if (s_in) begin
          if (run == ABORT_R) begin
            abort <= 1'b1;
            run   <= '0;
          end else begin
            d_out   <= 1'b1;
            d_valid <= 1'b1;
            run     <= run + 1'b1;
          end
        end else begin
          run <= '0;

          if (run == STUFF_R) begin
            d_valid <= 1'b0;
          end else if (run == FLAG_R) begin
            flag <= 1'b1;
          end else begin
            d_out   <= 1'b0;
            d_valid <= 1'b1;
          end
        end
      end
    end
  end

endmodule : bds
The code elaborates under `iverilog -g2012` with only the package timescale warning. I’m adding a temporary checker in `/tmp` to exercise data zeros, stuffed zeros, flags, aborts, and stalls against the observable outputs.
apply_patch
*** Begin Patch
*** Add File: /tmp/bds_tb.sv
+`timescale 1ns/1ps
+
+module bds_tb;
+  logic clk;
+  logic rst_n;
+  logic s_in;
+  logic s_valid;
+  logic d_out;
+  logic d_valid;
+  logic flag;
+  logic abort;
+
+  int errors;
+
+  bds dut (
+      .clk(clk),
+      .rst_n(rst_n),
+      .s_in(s_in),
+      .s_valid(s_valid),
+      .d_out(d_out),
+      .d_valid(d_valid),
+      .flag(flag),
+      .abort(abort)
+  );
+
+  initial clk = 1'b0;
+  always #5 clk = ~clk;
+
+  task automatic drive_check(
+      input logic valid,
+      input logic bit_in,
+      input logic exp_d_valid,
+      input logic exp_d_out,
+      input logic exp_flag,
+      input logic exp_abort
+  );
+    begin
+      s_valid = valid;
+      s_in = bit_in;
+      @(posedge clk);
+      #1;
+      if (d_valid !== exp_d_valid || flag !== exp_flag || abort !== exp_abort ||
+          (exp_d_valid && d_out !== exp_d_out)) begin
+        $display("FAIL valid=%0b bit=%0b got dv=%0b dout=%0b flag=%0b abort=%0b exp dv=%0b dout=%0b flag=%0b abort=%0b",
+                 valid, bit_in, d_valid, d_out, flag, abort,
+                 exp_d_valid, exp_d_out, exp_flag, exp_abort);
+        errors++;
+      end
+    end
+  endtask
+
+  initial begin
+    errors = 0;
+    s_in = 1'b0;
+    s_valid = 1'b0;
+    rst_n = 1'b0;
+    #2;
+    if (d_out !== 1'b0 || d_valid !== 1'b0 || flag !== 1'b0 || abort !== 1'b0) begin
+      $display("FAIL async reset outputs");
+      errors++;
+    end
+    @(posedge clk);
+    #1;
+    rst_n = 1'b1;
+
+    drive_check(1'b1, 1'b0, 1'b1, 1'b0, 1'b0, 1'b0);
+    drive_check(1'b0, 1'b1, 1'b0, 1'b0, 1'b0, 1'b0);
+
+    repeat (4) drive_check(1'b1, 1'b1, 1'b1, 1'b1, 1'b0, 1'b0);
+    drive_check(1'b0, 1'b0, 1'b0, 1'b1, 1'b0, 1'b0);
+    drive_check(1'b1, 1'b0, 1'b1, 1'b0, 1'b0, 1'b0);
+
+    repeat (5) drive_check(1'b1, 1'b1, 1'b1, 1'b1, 1'b0, 1'b0);
+    drive_check(1'b1, 1'b0, 1'b0, 1'b1, 1'b0, 1'b0);
+
+    repeat (6) drive_check(1'b1, 1'b1, 1'b1, 1'b1, 1'b0, 1'b0);
+    drive_check(1'b1, 1'b0, 1'b0, 1'b1, 1'b1, 1'b0);
+
+    repeat (6) drive_check(1'b1, 1'b1, 1'b1, 1'b1, 1'b0, 1'b0);
+    drive_check(1'b1, 1'b1, 1'b0, 1'b1, 1'b0, 1'b1);
+
+    if (errors == 0) begin
+      $display("PASS");
+    end else begin
+      $display("FAIL errors=%0d", errors);
+    end
+    $finish;
+  end
+endmodule
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
A /tmp/bds_tb.sv
The temporary testbench is in place. I’m compiling and running it with the RTL directly now.
shell
iverilog -g2012 -Wall -I bds_core/rtl -o /tmp/bds_tb.vvp bds_core/rtl/bds.sv /tmp/bds_tb.sv && vvp /tmp/bds_tb.vvp
output
Chunk ID: 5e0264
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 2
Output:
PASS
shell
nl -ba bds_core/rtl/bds.sv | sed -n '35,95p'
output
Chunk ID: e89770
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 476
Output:
    35	    input  logic s_valid,
    36	    output logic d_out,
    37	    output logic d_valid,
    38	    output logic flag,
    39	    output logic abort
    40	);
    41	
    42	  // ---------------------------------------------------------------------------
    43	  // State (provided): running count of consecutive 1 bits seen on the input
    44	  // stream, BEFORE the bit currently being processed.
    45	  // ---------------------------------------------------------------------------
    46	  logic [RUN_W-1:0] run;
    47	
    48	  // ===========================================================================
    49	  // Destuff / flag / abort decode.
    50	  // ===========================================================================
    51	  always_ff @(posedge clk or negedge rst_n) begin
    52	    if (!rst_n) begin
    53	      run     <= '0;
    54	      d_out   <= 1'b0;
    55	      d_valid <= 1'b0;
    56	      flag    <= 1'b0;
    57	      abort   <= 1'b0;
    58	    end else begin
    59	      d_valid <= 1'b0;
    60	      flag    <= 1'b0;
    61	      abort   <= 1'b0;
    62	
    63	      if (s_valid) begin
    64	        if (s_in) begin
    65	          if (run == ABORT_R) begin
    66	            abort <= 1'b1;
    67	            run   <= '0;
    68	          end else begin
    69	            d_out   <= 1'b1;
    70	            d_valid <= 1'b1;
    71	            run     <= run + 1'b1;
    72	          end
    73	        end else begin
    74	          run <= '0;
    75	
    76	          if (run == STUFF_R) begin
    77	            d_valid <= 1'b0;
    78	          end else if (run == FLAG_R) begin
    79	            flag <= 1'b1;
    80	          end else begin
    81	            d_out   <= 1'b0;
    82	            d_valid <= 1'b1;
    83	          end
    84	        end
    85	      end
    86	    end
    87	  end
    88	
    89	endmodule : bds
Implemented the framer in [bds.sv](/work/bds_core/rtl/bds.sv:51). What changed: - Added registered `d_out`, `d_valid`, `flag`, and `abort` behavior. - Maintains the `run` counter only on valid input bits. - Clears pulse outputs on stalled cycles while holding `d_out` and `run`. - Handles exact thresholds for stuffed bit, delimiter flag, and abort marker. - Async active-low reset clears state and outputs. Verification: - `iverilog -g2012 -Wall -I bds_core/rtl ...` elaborates successfully. - A focused temporary simulation covering stalls, stuff removal, flag, and abort passed.
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.sh: compiling with iverilog...
----- iverilog output -----
---------------------------
test.sh: running simulation with vvp...
----- simulation output -----
INFO samples=672 dmiss=0 vmiss=0 fmiss=0 amiss=0
SAMPLES=672
ALL TESTS PASSED
-----------------------------
test.sh: PASS - 672 samples, no mismatches

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_58a44a8af850420f. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_58a44a8af850420f · verifier authoritative; classifier explanatory.