cucapra · ekiwi · Jul 20, 2026 · Jul 11, 2026 · Jul 11, 2026 · Jul 11, 2026
diff --git a/.cargo/config.toml b/.cargo/config.toml
@@ -1,5 +1,4 @@
 [alias]
 interp = "run --quiet --offline --package protocols-interp --"
-monitor = "run --quiet --offline --package protocols-monitor --"
 bi = "run --quiet --package bi --"
 parse = "run --quiet --package protocols-cli -- -p"
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
@@ -34,8 +34,8 @@ jobs:
       run: runt runt/interp
     - name: Run Runt tests for graph-interpreter
       run: runt runt/graph_interp
-    - name: Run Runt tests for monitor
-      run: runt runt/monitor
+    - name: Run Runt tests for bi
+      run: runt runt/bi
     - name: Run Runt tests for waveform
       run: runt runt/waveform
     - name: Run Runt tests for fail
@@ -120,30 +120,7 @@ jobs:
       - name: Use ruff (via uv) to format Python files
         # We pass in `--preview-features format` to suppress 
         # uv's warning messages about the formatter being experimental
-        run: uv format --check --preview-features format      
-
-  # benchmark:
-  #   name: Performance Benchmarks
-  #   runs-on: ubuntu-24.04
-  #   timeout-minutes: 30
-
-  #   steps:
-  #     - uses: actions/checkout@v4
-  #       with:
-  #         fetch-depth: 0  # Fetch all history to access baseline
-  #     - uses: ./.github/actions/setup-test-environment
-  #       with:
-  #         github_token: ${{ secrets.GITHUB_TOKEN }}
-  #     - name: Install hyperfine
-  #       run: |
-  #         wget https://github.com/sharkdp/hyperfine/releases/download/v1.19.0/hyperfine_1.19.0_amd64.deb
-  #         sudo dpkg -i hyperfine_1.19.0_amd64.deb
-  #     - name: Build monitor (release)
-  #       run: cargo build --release --package protocols-monitor
-  #     - name: Run benchmarks
-  #       run: uv run scripts/benchmark_monitor.py
-  #     - name: Check for performance regressions
-  #       run: uv run scripts/check_performance_regression.py
+        run: uv format --check --preview-features format
 
 
   verilog:

diff --git a/Cargo.toml b/Cargo.toml
@@ -1,6 +1,6 @@
 [workspace]
 resolver = "3"
-members = ["bi", "interp", "monitor", "protocols", "cli", "graph-interp"]
+members = ["bi", "interp", "protocols", "cli", "graph-interp"]
 
 
 [workspace.package]

diff --git a/README.md b/README.md
@@ -11,9 +11,9 @@ A protocol is described using an `prot` definition containing a sequence of stat
 
 This repository contains:
 - An *interpreter* for the DSL
-- A *monitor* tool, which given a specification of a hardware module's communication behavior (written in our DSL)
+- A *backwards interpreter* (BI) tool, which given a specification of a hardware module's communication behavior (written in our DSL)
   and a `.fst` waveform file, infers a transaction-level trace that is consistent with the waveform data 
-- Common infrastructure shared between the interpreter & the monitor, such as a parser, type-checker and pretty-printer for our DSL
+- Common infrastructure shared between the interpreter & the BI, such as a parser, type-checker and pretty-printer for our DSL
 These tools are all implemented in Rust, with some auxiliary benchmarking scripts written in Python.
 
 ## Installation + Build Instructions
@@ -29,17 +29,7 @@ Note: the instructions below assume a macOS environment.
 - (Optional) Run `brew install hyperfine` to install [Hyperfine](https://github.com/sharkdp/hyperfine), a command-line benchmarking tool 
 - Run `brew install just` to install [Just](https://github.com/casey/just), a command runner
 - Run `cargo install --git https://github.com/Nikil-Shyamsunder/runt.git` to install our fork of [Runt](https://github.com/rachitnigam/runt), a command-line tool we use for snapshot tests. Runt compares the output of our tools to expected outputs stored in dedicated files. 
-
-**Dependencies for benchmarking the monitor**:
 - Run `uv sync` to install the Python dependencies specified in `pyproject.toml` 
-- Then, from the top-level directory, run the following scripts (note that they take ~3 minutes to run):
-```bash
-$ uv run scripts/benchmark_monitor.py      
-$ uv run scripts/plot_benchmark_results.py 
-```
-- This produces a CSV and a scatter plot measuring the performance of the monitor in 
-  `benchmark_results/benchmark_results.csv` and `benchmark_results/benchmark_plot.png` respectively
-
 - Some of the benchmarks correspond to real-world bugs taken from the [artifact for *Debugging in the Brave New World of Reconfigurable Hardware* (Ma et al. ASPLOS '22)](https://github.com/efeslab/asplos22-hardware-debugging-artifact) -- these can be found in the `tests/fpga-debugging` sub-directory 
   (more details in the `README` of the sub-directories corresponding to each bug)
 
@@ -49,51 +39,55 @@ $ uv run scripts/plot_benchmark_results.py
 **Building the source code**:
 - Run `cargo build` to build the Rust code
 - Run `just test` to execute all unit tests (`cargo test`) + snapshot tests (via Runt)
-  - To only run the subset of tests for the monitor, run `just monitor` 
 - To generate HTML documentation, run `just doc` (this opens Cargo-generated docs in your browser)
 
-## Monitor CLI
-The CLI for the monitor can be used as follows:
+## Backwards Interpreter CLI
+The CLI for the BI can be used as follows:
 ```bash 
-$ cargo monitor --help
+$ cargo bi --help
+analyze signal traces to extract transactions
 
-Usage: protocols-monitor [OPTIONS] --protocol <PROTOCOLS_FILE> --wave <WAVE_FILE>
+Usage: bi [OPTIONS] --wave <WAVE_FILE>
 
 Options:
   -p, --protocol <PROTOCOLS_FILE>
-          Path to a Protocol (.prot) file
+          One or several protocol files.
   -w, --wave <WAVE_FILE>
           Path to a waveform trace (.fst, .vcd, .ghw) file
   -i, --instances <INSTANCES>...
-          A mapping of DUT struct in the protocol file to an instance in the signal trace. Multiple arguments can be passed if they're seperated by whitespace. Format is: `${instance_name}:${dut_struct_name}`
+          A mapping of DUT struct in the protocol file to an instance in the signal trace. Can be used multiple times. Format is: `${instance_name}:${dut_struct_name}
   -v, --verbose...
           Increase logging verbosity
   -q, --quiet...
           Decrease logging verbosity
-      --color <COLOR_CHOICE>
-          To suppress colors in error messages, pass in `--color never` Otherwise, by default, error messages are displayed w/ ANSI colors [default: auto] [possible values: auto, always, never]
-  -d, --display-hex
-          If enabled, displays integer literals using hexadecimal notation
       --sample-posedge <SIGNAL_TO_SAMPLE_ON_RISING_EDGE>
           Optional argument which specifies the name of the signal to sample on a rising edge (posedge). If enabled, this flag acts as the "clock" signal for the monitor. Note: the full path to the signal should be passed as this argument, e.g. `uut_rx.clk`, where `uut_rx` is an instance in the signal trace
-      --show-waveform-time
-          If enabled, displays the start & end waveform time for each inferred transaction
-      --show-thread-ids
-          If enabled, displays the thread ID corresponding to each inferred transaction
-      --time-unit <TIME_UNIT>
-          Specifies the time unit for displaying waveform times. Can only be used with --show-waveform-time. Valid options: fs, ps, ns, us, ms, s, auto Default is 'auto' which selects the unit based on the maximum time in the waveform
-      --print-num-steps
-          Optional flag: if enabled, prints the no. of (logical) steps (i.e. clock cycles) taken by the montior
       --include-idle
           Optional flag: if enabled, always prints out idle transcations regardless of whether the protocol has been annotated with `#[idle]`
+      --show-steps
+          If enabled, displays the start & end step for each inferred transaction
+      --include-in-progress
+          This flag will make the bi append any in-progress transactions to the trace
+      --show-waveform-time
+
+      --time-unit <TIME_UNIT>
+
+      --max-traces <MAX_TRACES>
+          Limit the number of traces written to stdout
+      --color <COLOR_CHOICE>
+          To suppress colors in error messages, pass in `--color never`. Otherwise, by default, error messages are displayed with colors [default: auto] [possible values: auto, always, never]
+  -d, --display-hex
+          If enabled, displays integer literals using hexadecimal notation
+  -r, --rename <RENAME>...
+          Rename pins of the DUT. &{field name in the struct} = ${verilog name}
   -h, --help
           Print help
 ```
 
 Example usage:
 ```bash
 $ cd tests
-$ cargo monitor -p adders/add_d1.prot --wave adders/add_d1.fst --instances add_d1:Adder
+$ cargo bi -p adders/add_d1.prot --wave adders/add_d1.fst --instances add_d1:Adder
 ```
 
 ## Interpreter CLI

diff --git a/benchmark_results/baseline_results.csv b/benchmark_results/baseline_results.csv
diff --git a/benchmark_results/benchmark_results.csv b/benchmark_results/benchmark_results.csv
diff --git a/bi/src/bi.rs b/bi/src/bi.rs
@@ -632,11 +632,15 @@ impl Thread {
                     }
                 }
                 Stmt::Fork => {
-                    assert!(self.step > 0, "[{}] Cannot fork at step zero!", self.name);
-                    self.has_forked = true;
-                    self.next_stmt = ti.next_stmt[&stmt];
-                    self.effectful_stmt_in_step = true;
-                    Fork
+                    if self.step > 0 {
+                        self.has_forked = true;
+                        self.next_stmt = ti.next_stmt[&stmt];
+                        self.effectful_stmt_in_step = true;
+                        Fork
+                    } else {
+                        eprintln!("[{}] Cannot fork at step zero!", self.name);
+                        std::process::exit(1);
+                    }
                 }
                 Stmt::While(cond, body) => {
                     let cond_value = self