Claude Code transcript - page 1/1

{
  "type": "tool_reference",
  "tool_name": "Read"
}

{
  "type": "tool_reference",
  "tool_name": "Glob"
}

{
  "type": "tool_reference",
  "tool_name": "Agent"
}

     1→# MultiPaxos Replicated KV Store Emulation
     2→
     3→## Context
     4→The project needs a new emulation that replicates the existing `kv_store` using MultiPaxos consensus. This demonstrates how a distributed consensus protocol can be used to replicate state across multiple nodes while preserving the same client-facing semantics (put fails if key exists, get returns value or error, delete fails if key missing). The client is given a Subject pointing to the leader directly (no leader discovery).
     5→
     6→## Architecture
     7→
     8→Three actor types + client:
     9→
    10→1. **Acceptor** - Paxos voting participant (prepare/promise, accept/accepted)
    11→2. **Leader** (proposer + learner + state machine) - Receives client requests, assigns log slots, runs Paxos Phase 2, applies committed commands to local KV store, replies to clients, broadcasts commits to replicas
    12→3. **Replica** (passive learner) - Receives committed commands from leader, applies to local KV copy
    13→4. **Client** - Same as `kv_store/client.gleam` but 5 requests, targeting leader
    14→
    15→### Message Flow
    16→```
    17→Client --[ClientPut/Get/Delete]--> Leader
    18→  Leader assigns slot N
    19→  Leader --[Accept(slot N, ballot, cmd)]--> all Acceptors (synchronous calls)
    20→  Leader waits for quorum of Accepted responses
    21→  Leader applies command to local KV store
    22→  Leader --[reply]--> Client
    23→  Leader --[Commit(slot N, cmd)]--> all Replicas
    24→```
    25→
    26→### Key Design Decisions
    27→- **Phase 1 once at startup**: Leader runs prepare/promise during init. With stable leader assumption, succeeds immediately.
    28→- **Synchronous Phase 2**: Leader calls acceptors sequentially with `actor.call` during request handling. Simple, correct, educational.
    29→- **GETs go through the log**: For linearizability, reads are also assigned slots and go through consensus.
    30→- **Replicas are passive**: They receive committed commands for demonstration of replication.
    31→
    32→## File Structure
    33→```
    34→multipaxos_kv/
    35→  gleam.toml
    36→  src/
    37→    multipaxos_kv.gleam              -- main entry point
    38→    multipaxos_kv/
    39→      types.gleam                    -- shared types (Command, Ballot, OpResult)
    40→      acceptor.gleam                 -- Paxos acceptor actor
    41→      leader.gleam                   -- proposer + learner + KV state machine + client API
    42→      replica.gleam                  -- passive learner
    43→      client.gleam                   -- 5 random requests to leader
    44→  test/
    45→    multipaxos_kv_test.gleam         -- basic test
    46→```
    47→
    48→## Implementation Steps
    49→
    50→### 1. Create project
    51→```sh
    52→cd /Users/apanda/code/agent-spec-code
    53→gleam new --skip-git --skip-github multipaxos_kv
    54→cd multipaxos_kv
    55→gleam add gleam_otp gleam_erlang argv
    56→```
    57→
    58→### 2. `types.gleam` - Shared types
    59→- `Ballot(round: Int, leader_id: Int)` with comparison function
    60→- `Command` = `Put(key, value)` | `Get(key)` | `Delete(key)` | `Noop`
    61→- `OpResult` = `OpOk` | `OpError(reason: String)`
    62→
    63→### 3. `acceptor.gleam` - Paxos acceptor
    64→- **State**: `id`, `promised_ballot: Option(Ballot)`, `accepted: Dict(Int, #(Ballot, Command))`, `self`
    65→- **Messages**: `Prepare(ballot, reply_with)`, `Accept(slot, ballot, command, reply_with)`
    66→- **Responses**: `Promise(accepted_entries)` | `PrepareRejected(highest)`, `Accepted(slot)` | `AcceptRejected(slot, highest)`
    67→- Logic: standard Paxos prepare/accept with ballot comparison
    68→
    69→### 4. `leader.gleam` - Core logic (most complex file)
    70→- **State**: `id`, `ballot`, `acceptors`, `replicas`, `quorum_size`, `next_slot`, `log: Dict(Int, Command)`, `store: Dict(String, String)`, `last_applied`, `self`
    71→- **Client messages**: `ClientPut(key, value, reply_with)`, `ClientGet(key, reply_with)`, `ClientDelete(key, reply_with)` - same signatures as `kv_store/server`
    72→- **Init**: Run Phase 1 (prepare) to all acceptors, collect promises
    73→- **Request handling**: Assign slot, run Phase 2 synchronously (call each acceptor), on quorum: commit to log, apply to store, reply to client, broadcast to replicas
    74→- **Public API**: `put(leader, key, value)`, `get(leader, key)`, `delete(leader, key)` matching `kv_store/server` signatures
    75→- **KV semantics**: Identical to `kv_store/server.gleam` (put rejects existing keys, delete rejects missing keys)
    76→
    77→### 5. `replica.gleam` - Passive learner
    78→- **State**: `id`, `log: Dict(Int, Command)`, `store: Dict(String, String)`, `last_applied`, `self`
    79→- **Message**: `Commit(slot: Int, command: Command)`
    80→- Applies committed commands in log order to local store, prints state changes
    81→
    82→### 6. `client.gleam` - Adapted from kv_store
    83→- Same structure as `kv_store/client.gleam`
    84→- 5 requests instead of 10
    85→- Targets `Subject(leader.Message)` instead of `Subject(server.Message)`
    86→- Calls `leader.put`, `leader.get` (and optionally `leader.delete`)
    87→- Same random key pool ["a","b","c","d","e"], same random values
    88→
    89→### 7. `multipaxos_kv.gleam` - Main
    90→- Start 3 acceptors, 2 replicas, 1 leader, N clients (default 3)
    91→- Parse num_clients from CLI args
    92→- Send Start to all clients, sleep 3s
    93→
    94→## Reference Files
    95→- `/Users/apanda/code/agent-spec-code/kv_store/src/kv_store/server.gleam` - KV semantics to replicate
    96→- `/Users/apanda/code/agent-spec-code/kv_store/src/kv_store/client.gleam` - Client pattern to adapt
    97→- `/Users/apanda/code/agent-spec-code/kv_store/src/kv_store.gleam` - Main wiring pattern
    98→- `/Users/apanda/code/agent-spec-code/.claude/skills/gleam-otp.md` - Actor patterns
    99→
   100→## Verification
   101→1. `gleam build` - should compile without errors
   102→2. `gleam run` - should show:
   103→   - Acceptors starting
   104→   - Replicas starting
   105→   - Leader starting with Phase 1 completion
   106→   - Clients issuing 5 requests each with Paxos consensus trace
   107→   - Replicas applying committed commands
   108→3. `gleam format` - ensure code is formatted
   109→

     1→## Metadata
     2→name: Creating a distributed system emulation
     3→description: This is a recipe for how to build a distributed system emulation in Gleam given a human description. 
     4→
     5→
     6→## Overview
     7→In this environment we use Gleam for emulation. The goal is to produce a version that can be executed and help explain how the protocol (i.e., the algorithm implemented by the system) runs.
     8→
     9→Each type of process (or node or server, I tend to use the same word for all of them) is implemented as a Gleam actor. The Gleam OTP skill that accompanies this can help write the code. Do not try to optimize the code, but be sure to use comments to document the logic of each actor, and use print statements to record the execution of each actor.
    10→
    11→Once code for all types of processes has been written, change the main function to take a configuration file (in TOML) that specifies how many nodes of each type to start and then runs them to produce an execution schedule.
    12→
    13→Finally, use the appropriate version control system to add a commit for the emulation
    14→
    15→## Steps to Create an Emulation
    16→
    17→- Use instructions from the gleam-otop skill to create and code up the emulation.
    18→- Change the main function of the newly created emulation so that it can read a configuration file written in TOML (you can read it in gleam using the `tom` package) that specifies the number of each type of process.
    19→- Create a new commit using the appropriate version control system.
    20→
    21→## Writing a new emulation
    22→
    23→Use instructions from the gleam-otp skill.
    24→
    25→## Version Control
    26→
    27→Check if the root directory contains a `.jj` directory. If so, the project is managed using Jujutsu, and the accompanying jujutsu skill to manage things.
    28→
    29→If on the other hand the root directory contains a `.git` directory (but no `.jj` directory) use git.
    30→

     1→# Gleam OTP Development
     2→
     3→## Metadata
     4→name: Gleam OTP Development
     5→description: This is a skill to help with developing Gleam OTP applications.
     6→
     7→## Creating a Gleam project
     8→
     9→```sh
    10→	gleam new --skip-git --skip-github <project name> # Create a project. Project name can only contain alphanumeric characters and `_`
    11→  cd <project name> # Change directory into the project
    12→  gleam add gleam_otp # Add gleam_otp as a dependency
    13→  gleam add gleam_erlang # Add gleam_erlang as a dependency.
    14→```
    15→
    16→## Build Commands
    17→
    18→```sh
    19→gleam build       # Compile the project
    20→gleam run         # Run the project
    21→gleam test        # Run all tests
    22→gleam add <pkg>   # Add a dependency
    23→gleam format      # Format code
    24→```
    25→
    26→## Actor Pattern with gleam_otp
    27→
    28→### Basic Actor Structure
    29→
    30→```gleam
    31→import gleam/otp/actor
    32→import gleam/erlang/process.{type Subject}
    33→
    34→// 1. Define state type
    35→pub type State {
    36→  State(value: Int, self: Subject(Message))
    37→}
    38→
    39→// 2. Define message type
    40→pub type Message {
    41→  Set(value: Int)                      // Fire-and-forget
    42→  Get(reply_with: Subject(Int))        // Request-response
    43→}
    44→
    45→// 3. Implement handler
    46→fn handle_message(state: State, message: Message) -> actor.Next(State, Message) {
    47→  case message {
    48→    Set(value) -> actor.continue(State(..state, value: value))
    49→    Get(client) -> {
    50→      process.send(client, state.value)
    51→      actor.continue(state)
    52→    }
    53→  }
    54→}
    55→
    56→// 4. Start function
    57→pub fn start() -> Result(Subject(Message), actor.StartError) {
    58→  actor.new_with_initialiser(1000, fn(self) {
    59→    actor.initialised(State(value: 0, self: self))
    60→    |> actor.returning(self)
    61→    |> Ok
    62→  })
    63→  |> actor.on_message(handle_message)
    64→  |> actor.start
    65→  |> result.map(fn(started) { started.data })
    66→}
    67→```
    68→
    69→### Key Patterns
    70→
    71→**Fire-and-forget message:**
    72→```gleam
    73→pub fn set(subject: Subject(Message), value: Int) -> Nil {
    74→  actor.send(subject, Set(value))
    75→}
    76→```
    77→
    78→**Request-response (blocking call):**
    79→```gleam
    80→pub fn get(subject: Subject(Message)) -> Int {
    81→  actor.call(subject, 1000, Get)  // 1000ms timeout
    82→}
    83→```
    84→
    85→**Self-messaging (for periodic tasks):**
    86→```gleam
    87→// In initialiser or handler:
    88→process.send_after(state.self, 100, Sync)  // Send Sync message after 100ms
    89→```
    90→
    91→**Capturing self reference:**
    92→Use `actor.new_with_initialiser` instead of `actor.new` to get access to the actor's own Subject in the initialiser callback.
    93→
    94→### Handler Return Values
    95→
    96→- `actor.continue(new_state)` - Keep running with new state
    97→- `actor.stop()` - Stop the actor gracefully
    98→
    99→### Common Imports
   100→
   101→```gleam
   102→import gleam/otp/actor
   103→import gleam/erlang/process.{type Subject}
   104→import gleam/result
   105→import gleam/list
   106→import gleam/int
   107→import gleam/io
   108→```
   109→
   110→## Testing
   111→
   112→Test functions must end with `_test` suffix:
   113→
   114→```gleam
   115→import gleeunit
   116→
   117→pub fn main() -> Nil {
   118→  gleeunit.main()
   119→}
   120→
   121→pub fn my_feature_test() {
   122→  assert some_condition == True
   123→}
   124→```
   125→
   126→## Common Patterns in This Codebase
   127→
   128→### Peer-to-peer Synchronization
   129→
   130→Servers maintain a list of peers and periodically broadcast their state:
   131→
   132→```gleam
   133→Sync -> {
   134→  list.each(state.peers, fn(peer) {
   135→    process.send(peer, Set(state.value))
   136→  })
   137→  process.send_after(state.self, 100, Sync)
   138→  actor.continue(state)
   139→}
   140→```
   141→
   142→### Convergence Check
   143→
   144→Poll until all actors have the same value:
   145→
   146→```gleam
   147→fn wait_for_convergence(servers: List(Subject(Message))) -> Nil {
   148→  let values = list.map(servers, get)
   149→  case values {
   150→    [first, ..rest] -> {
   151→      let all_same = list.all(rest, fn(v) { v == first })
   152→      case all_same && first > 0 {
   153→        True -> io.println("Converged!")
   154→        False -> {
   155→          process.sleep(100)
   156→          wait_for_convergence(servers)
   157→        }
   158→      }
   159→    }
   160→    [] -> Nil
   161→  }
   162→}
   163→```
   164→
   165→## Gleam Syntax Quick Reference
   166→
   167→**Pattern matching:**
   168→```gleam
   169→case value {
   170→  Some(x) -> x
   171→  None -> 0
   172→}
   173→```
   174→
   175→**Record update:**
   176→```gleam
   177→State(..state, value: new_value)
   178→```
   179→
   180→**Pipe operator:**
   181→```gleam
   182→value
   183→|> transform1
   184→|> transform2
   185→```
   186→
   187→**Assert (panics on failure):**
   188→```gleam
   189→let assert Ok(result) = maybe_fails()
   190→```
   191→
   192→**List operations:**
   193→```gleam
   194→list.map(items, fn(x) { x + 1 })
   195→list.each(items, fn(x) { io.println(x) })
   196→list.all(items, fn(x) { x > 0 })
   197→list.flat_map(items, fn(x) { [x, x] })
   198→```
   199→

/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv/acceptor.gleam
/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv/client.gleam
/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv/leader.gleam
/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv/replica.gleam
/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv/types.gleam
/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv.gleam

     1→import gleam/int
     2→import gleam/order.{type Order}
     3→
     4→/// A Paxos ballot number, consisting of a round and leader ID.
     5→/// Higher round wins; ties broken by leader_id.
     6→pub type Ballot {
     7→  Ballot(round: Int, leader_id: Int)
     8→}
     9→
    10→/// Compare two ballots. Higher round wins; ties broken by leader_id.
    11→pub fn compare_ballots(a: Ballot, b: Ballot) -> Order {
    12→  case a.round == b.round {
    13→    True -> int.compare(a.leader_id, b.leader_id)
    14→    False -> int.compare(a.round, b.round)
    15→  }
    16→}
    17→
    18→/// A command to be replicated through Paxos.
    19→pub type Command {
    20→  Put(key: String, value: String)
    21→  Get(key: String)
    22→  Delete(key: String)
    23→  Noop
    24→}
    25→
    26→/// Result of applying a command to the KV store.
    27→pub type OpResult {
    28→  OpOk
    29→  OpError(reason: String)
    30→}
    31→

     1→import gleam/dict.{type Dict}
     2→import gleam/erlang/process.{type Subject}
     3→import gleam/int
     4→import gleam/io
     5→import gleam/order
     6→import gleam/otp/actor
     7→import gleam/result
     8→import multipaxos_kv/types.{type Ballot, type Command}
     9→
    10→/// Acceptor state
    11→pub type State {
    12→  State(
    13→    id: Int,
    14→    promised_ballot: Ballot,
    15→    accepted: Dict(Int, #(Ballot, Command)),
    16→    self: Subject(Message),
    17→  )
    18→}
    19→
    20→/// Response to a Prepare request
    21→pub type PrepareResponse {
    22→  /// Promise not to accept lower ballots; includes previously accepted entries
    23→  Promise(accepted: Dict(Int, #(Ballot, Command)))
    24→  /// Rejected because a higher ballot was already promised
    25→  PrepareRejected(highest: Ballot)
    26→}
    27→
    28→/// Response to an Accept request
    29→pub type AcceptResponse {
    30→  /// Successfully accepted the value for this slot
    31→  Accepted(slot: Int)
    32→  /// Rejected because a higher ballot was already promised
    33→  AcceptRejected(slot: Int, highest: Ballot)
    34→}
    35→
    36→/// Messages the acceptor handles
    37→pub type Message {
    38→  /// Phase 1: Prepare request from a proposer
    39→  Prepare(ballot: Ballot, reply_with: Subject(PrepareResponse))
    40→  /// Phase 2: Accept request from a proposer
    41→  Accept(
    42→    slot: Int,
    43→    ballot: Ballot,
    44→    command: Command,
    45→    reply_with: Subject(AcceptResponse),
    46→  )
    47→}
    48→
    49→/// Handle incoming messages
    50→fn handle_message(state: State, message: Message) -> actor.Next(State, Message) {
    51→  let id_str = int.to_string(state.id)
    52→  case message {
    53→    Prepare(ballot, reply_with) -> {
    54→      // Accept if ballot >= promised_ballot
    55→      case types.compare_ballots(ballot, state.promised_ballot) {
    56→        order.Lt -> {
    57→          io.println(
    58→            "[acceptor "
    59→            <> id_str
    60→            <> "] PREPARE rejected (higher ballot promised)",
    61→          )
    62→          process.send(reply_with, PrepareRejected(state.promised_ballot))
    63→          actor.continue(state)
    64→        }
    65→        _ -> {
    66→          io.println(
    67→            "[acceptor "
    68→            <> id_str
    69→            <> "] PREPARE accepted, promising ballot ("
    70→            <> int.to_string(ballot.round)
    71→            <> ","
    72→            <> int.to_string(ballot.leader_id)
    73→            <> ")",
    74→          )
    75→          process.send(reply_with, Promise(state.accepted))
    76→          actor.continue(State(..state, promised_ballot: ballot))
    77→        }
    78→      }
    79→    }
    80→
    81→    Accept(slot, ballot, command, reply_with) -> {
    82→      // Accept if ballot >= promised_ballot
    83→      case types.compare_ballots(ballot, state.promised_ballot) {
    84→        order.Lt -> {
    85→          io.println(
    86→            "[acceptor "
    87→            <> id_str
    88→            <> "] ACCEPT rejected for slot "
    89→            <> int.to_string(slot),
    90→          )
    91→          process.send(reply_with, AcceptRejected(slot, state.promised_ballot))
    92→          actor.continue(state)
    93→        }
    94→        _ -> {
    95→          io.println(
    96→            "[acceptor "
    97→            <> id_str
    98→            <> "] ACCEPT for slot "
    99→            <> int.to_string(slot)
   100→            <> " -> accepted",
   101→          )
   102→          let new_accepted =
   103→            dict.insert(state.accepted, slot, #(ballot, command))
   104→          process.send(reply_with, Accepted(slot))
   105→          actor.continue(
   106→            State(..state, promised_ballot: ballot, accepted: new_accepted),
   107→          )
   108→        }
   109→      }
   110→    }
   111→  }
   112→}
   113→
   114→/// Start an acceptor actor with the given ID
   115→pub fn start(id: Int) -> Result(Subject(Message), actor.StartError) {
   116→  actor.new_with_initialiser(1000, fn(self) {
   117→    io.println("[acceptor " <> int.to_string(id) <> "] Starting")
   118→    let state =
   119→      State(
   120→        id: id,
   121→        promised_ballot: types.Ballot(round: 0, leader_id: 0),
   122→        accepted: dict.new(),
   123→        self: self,
   124→      )
   125→    actor.initialised(state)
   126→    |> actor.returning(self)
   127→    |> Ok
   128→  })
   129→  |> actor.on_message(handle_message)
   130→  |> actor.start
   131→  |> result.map(fn(started) { started.data })
   132→}
   133→

     1→import gleam/dict.{type Dict}
     2→import gleam/erlang/process.{type Subject}
     3→import gleam/int
     4→import gleam/io
     5→import gleam/list
     6→import gleam/otp/actor
     7→import gleam/result
     8→import multipaxos_kv/acceptor
     9→import multipaxos_kv/replica
    10→import multipaxos_kv/types.{type Ballot, type Command}
    11→
    12→/// Leader state: proposer + learner + KV state machine
    13→pub type State {
    14→  State(
    15→    id: Int,
    16→    ballot: Ballot,
    17→    acceptors: List(Subject(acceptor.Message)),
    18→    replicas: List(Subject(replica.Message)),
    19→    quorum_size: Int,
    20→    next_slot: Int,
    21→    log: Dict(Int, Command),
    22→    store: Dict(String, String),
    23→    last_applied: Int,
    24→    self: Subject(Message),
    25→  )
    26→}
    27→
    28→/// Messages the leader handles
    29→pub type Message {
    30→  /// Client request to insert a key-value pair
    31→  ClientPut(key: String, value: String, reply_with: Subject(types.OpResult))
    32→  /// Client request to get a value by key
    33→  ClientGet(key: String, reply_with: Subject(Result(String, String)))
    34→  /// Client request to delete a key
    35→  ClientDelete(key: String, reply_with: Subject(types.OpResult))
    36→}
    37→
    38→/// Run Phase 1 (prepare) against all acceptors. Panics if quorum not reached.
    39→fn run_phase1(
    40→  ballot: Ballot,
    41→  acceptors: List(Subject(acceptor.Message)),
    42→  quorum_size: Int,
    43→) -> Nil {
    44→  io.println(
    45→    "[leader] Phase 1: sending Prepare("
    46→    <> int.to_string(ballot.round)
    47→    <> ","
    48→    <> int.to_string(ballot.leader_id)
    49→    <> ") to "
    50→    <> int.to_string(list.length(acceptors))
    51→    <> " acceptors",
    52→  )
    53→  let promises =
    54→    list.filter_map(acceptors, fn(acc) {
    55→      let response = actor.call(acc, 1000, acceptor.Prepare(ballot, _))
    56→      case response {
    57→        acceptor.Promise(_accepted) -> Ok(Nil)
    58→        acceptor.PrepareRejected(_) -> Error(Nil)
    59→      }
    60→    })
    61→  let num_promises = list.length(promises)
    62→  io.println(
    63→    "[leader] Phase 1 complete: "
    64→    <> int.to_string(num_promises)
    65→    <> " promises received (need "
    66→    <> int.to_string(quorum_size)
    67→    <> ")",
    68→  )
    69→  case num_promises >= quorum_size {
    70→    True -> Nil
    71→    False -> panic as "Failed to get quorum in Phase 1"
    72→  }
    73→}
    74→
    75→/// Run Phase 2 (accept) for a single slot. Returns True if quorum accepted.
    76→fn run_phase2(
    77→  slot: Int,
    78→  ballot: Ballot,
    79→  command: Command,
    80→  acceptors: List(Subject(acceptor.Message)),
    81→  quorum_size: Int,
    82→) -> Bool {
    83→  let accepted_count =
    84→    list.filter_map(acceptors, fn(acc) {
    85→      let response =
    86→        actor.call(acc, 1000, acceptor.Accept(slot, ballot, command, _))
    87→      case response {
    88→        acceptor.Accepted(_) -> Ok(Nil)
    89→        acceptor.AcceptRejected(_, _) -> Error(Nil)
    90→      }
    91→    })
    92→    |> list.length
    93→  io.println(
    94→    "[leader] Phase 2 for slot "
    95→    <> int.to_string(slot)
    96→    <> ": "
    97→    <> int.to_string(accepted_count)
    98→    <> "/"
    99→    <> int.to_string(quorum_size)
   100→    <> " accepted",
   101→  )
   102→  accepted_count >= quorum_size
   103→}
   104→
   105→/// Apply a command to the KV store, returning the result and updated store
   106→fn apply_command(
   107→  command: Command,
   108→  store: Dict(String, String),
   109→) -> #(Dict(String, String), Command, types.OpResult, Result(String, String)) {
   110→  case command {
   111→    types.Put(key, value) -> {
   112→      case dict.has_key(store, key) {
   113→        True -> {
   114→          io.println("[leader] PUT \"" <> key <> "\" -> REJECTED (key exists)")
   115→          #(
   116→            store,
   117→            command,
   118→            types.OpError("key already exists: " <> key),
   119→            Error(""),
   120→          )
   121→        }
   122→        False -> {
   123→          io.println(
   124→            "[leader] PUT \"" <> key <> "\" = \"" <> value <> "\" -> OK",
   125→          )
   126→          #(dict.insert(store, key, value), command, types.OpOk, Error(""))
   127→        }
   128→      }
   129→    }
   130→    types.Get(key) -> {
   131→      case dict.get(store, key) {
   132→        Ok(value) -> {
   133→          io.println("[leader] GET \"" <> key <> "\" -> \"" <> value <> "\"")
   134→          #(store, command, types.OpOk, Ok(value))
   135→        }
   136→        Error(_) -> {
   137→          io.println("[leader] GET \"" <> key <> "\" -> NOT FOUND")
   138→          #(store, command, types.OpOk, Error("key not found: " <> key))
   139→        }
   140→      }
   141→    }
   142→    types.Delete(key) -> {
   143→      case dict.has_key(store, key) {
   144→        True -> {
   145→          io.println("[leader] DELETE \"" <> key <> "\" -> OK")
   146→          #(dict.delete(store, key), command, types.OpOk, Error(""))
   147→        }
   148→        False -> {
   149→          io.println("[leader] DELETE \"" <> key <> "\" -> NOT FOUND")
   150→          #(store, command, types.OpError("key not found: " <> key), Error(""))
   151→        }
   152→      }
   153→    }
   154→    types.Noop -> #(store, command, types.OpOk, Error(""))
   155→  }
   156→}
   157→
   158→/// Broadcast a committed command to all replicas
   159→fn broadcast_commit(
   160→  replicas: List(Subject(replica.Message)),
   161→  slot: Int,
   162→  command: Command,
   163→) -> Nil {
   164→  list.each(replicas, fn(r) { process.send(r, replica.Commit(slot, command)) })
   165→}
   166→
   167→/// Handle a client request: assign slot, run Phase 2, apply, reply, broadcast
   168→fn handle_client_request(
   169→  state: State,
   170→  command: Command,
   171→  reply_put: fn(types.OpResult) -> Nil,
   172→  reply_get: fn(Result(String, String)) -> Nil,
   173→) -> actor.Next(State, Message) {
   174→  let slot = state.next_slot
   175→  io.println(
   176→    "[leader] Assigning slot " <> int.to_string(slot) <> " for client request",
   177→  )
   178→
   179→  // Run Phase 2 for this slot
   180→  let committed =
   181→    run_phase2(slot, state.ballot, command, state.acceptors, state.quorum_size)
   182→
   183→  case committed {
   184→    True -> {
   185→      // Apply to local KV store
   186→      let #(new_store, cmd, op_result, get_result) =
   187→        apply_command(command, state.store)
   188→      let new_log = dict.insert(state.log, slot, cmd)
   189→
   190→      // Reply to client
   191→      reply_put(op_result)
   192→      reply_get(get_result)
   193→
   194→      // Broadcast commit to replicas
   195→      broadcast_commit(state.replicas, slot, cmd)
   196→
   197→      actor.continue(
   198→        State(
   199→          ..state,
   200→          next_slot: slot + 1,
   201→          log: new_log,
   202→          store: new_store,
   203→          last_applied: slot,
   204→        ),
   205→      )
   206→    }
   207→    False -> {
   208→      io.println("[leader] Phase 2 FAILED for slot " <> int.to_string(slot))
   209→      reply_put(types.OpError("consensus failed"))
   210→      reply_get(Error("consensus failed"))
   211→      actor.continue(state)
   212→    }
   213→  }
   214→}
   215→
   216→/// Handle incoming messages
   217→fn handle_message(state: State, message: Message) -> actor.Next(State, Message) {
   218→  case message {
   219→    ClientPut(key, value, reply_with) -> {
   220→      handle_client_request(
   221→        state,
   222→        types.Put(key, value),
   223→        fn(r) { process.send(reply_with, r) },
   224→        fn(_) { Nil },
   225→      )
   226→    }
   227→    ClientGet(key, reply_with) -> {
   228→      handle_client_request(state, types.Get(key), fn(_) { Nil }, fn(r) {
   229→        process.send(reply_with, r)
   230→      })
   231→    }
   232→    ClientDelete(key, reply_with) -> {
   233→      handle_client_request(
   234→        state,
   235→        types.Delete(key),
   236→        fn(r) { process.send(reply_with, r) },
   237→        fn(_) { Nil },
   238→      )
   239→    }
   240→  }
   241→}
   242→
   243→/// Start a leader actor. Runs Phase 1 during initialization.
   244→pub fn start(
   245→  id: Int,
   246→  acceptors: List(Subject(acceptor.Message)),
   247→  replicas: List(Subject(replica.Message)),
   248→) -> Result(Subject(Message), actor.StartError) {
   249→  let ballot = types.Ballot(round: 1, leader_id: id)
   250→  let quorum_size = list.length(acceptors) / 2 + 1
   251→
   252→  actor.new_with_initialiser(5000, fn(self) {
   253→    io.println("[leader] Starting with id " <> int.to_string(id))
   254→
   255→    // Run Phase 1 to establish leadership
   256→    run_phase1(ballot, acceptors, quorum_size)
   257→    io.println("[leader] Phase 1 complete — leader established")
   258→
   259→    let state =
   260→      State(
   261→        id: id,
   262→        ballot: ballot,
   263→        acceptors: acceptors,
   264→        replicas: replicas,
   265→        quorum_size: quorum_size,
   266→        next_slot: 1,
   267→        log: dict.new(),
   268→        store: dict.new(),
   269→        last_applied: 0,
   270→        self: self,
   271→      )
   272→    actor.initialised(state)
   273→    |> actor.returning(self)
   274→    |> Ok
   275→  })
   276→  |> actor.on_message(handle_message)
   277→  |> actor.start
   278→  |> result.map(fn(started) { started.data })
   279→}
   280→
   281→/// Put a key-value pair. Returns error if the key already exists.
   282→pub fn put(
   283→  leader: Subject(Message),
   284→  key: String,
   285→  value: String,
   286→) -> types.OpResult {
   287→  actor.call(leader, 5000, ClientPut(key, value, _))
   288→}
   289→
   290→/// Get the value for a key. Returns Error if not found.
   291→pub fn get(leader: Subject(Message), key: String) -> Result(String, String) {
   292→  actor.call(leader, 5000, ClientGet(key, _))
   293→}
   294→
   295→/// Delete a key. Returns error if the key doesn't exist.
   296→pub fn delete(leader: Subject(Message), key: String) -> types.OpResult {
   297→  actor.call(leader, 5000, ClientDelete(key, _))
   298→}
   299→

     1→import gleam/dict.{type Dict}
     2→import gleam/erlang/process.{type Subject}
     3→import gleam/int
     4→import gleam/io
     5→import gleam/otp/actor
     6→import gleam/result
     7→import multipaxos_kv/types.{type Command}
     8→
     9→/// Replica state: passive learner that applies committed commands
    10→pub type State {
    11→  State(
    12→    id: Int,
    13→    log: Dict(Int, Command),
    14→    store: Dict(String, String),
    15→    last_applied: Int,
    16→    self: Subject(Message),
    17→  )
    18→}
    19→
    20→/// Messages the replica handles
    21→pub type Message {
    22→  /// A committed command from the leader
    23→  Commit(slot: Int, command: Command)
    24→}
    25→
    26→/// Apply commands from the log in order, starting from last_applied + 1
    27→fn apply_committed(state: State) -> State {
    28→  let next_slot = state.last_applied + 1
    29→  case dict.get(state.log, next_slot) {
    30→    Error(_) -> state
    31→    Ok(command) -> {
    32→      let id_str = int.to_string(state.id)
    33→      let slot_str = int.to_string(next_slot)
    34→      let new_store = case command {
    35→        types.Put(key, value) -> {
    36→          io.println(
    37→            "[replica "
    38→            <> id_str
    39→            <> "] slot "
    40→            <> slot_str
    41→            <> ": PUT \""
    42→            <> key
    43→            <> "\" = \""
    44→            <> value
    45→            <> "\"",
    46→          )
    47→          dict.insert(state.store, key, value)
    48→        }
    49→        types.Get(key) -> {
    50→          io.println(
    51→            "[replica "
    52→            <> id_str
    53→            <> "] slot "
    54→            <> slot_str
    55→            <> ": GET \""
    56→            <> key
    57→            <> "\"",
    58→          )
    59→          state.store
    60→        }
    61→        types.Delete(key) -> {
    62→          io.println(
    63→            "[replica "
    64→            <> id_str
    65→            <> "] slot "
    66→            <> slot_str
    67→            <> ": DELETE \""
    68→            <> key
    69→            <> "\"",
    70→          )
    71→          dict.delete(state.store, key)
    72→        }
    73→        types.Noop -> {
    74→          io.println("[replica " <> id_str <> "] slot " <> slot_str <> ": NOOP")
    75→          state.store
    76→        }
    77→      }
    78→      let new_state = State(..state, store: new_store, last_applied: next_slot)
    79→      // Try to apply the next slot too (in case commits arrived out of order)
    80→      apply_committed(new_state)
    81→    }
    82→  }
    83→}
    84→
    85→/// Handle incoming messages
    86→fn handle_message(state: State, message: Message) -> actor.Next(State, Message) {
    87→  case message {
    88→    Commit(slot, command) -> {
    89→      let new_log = dict.insert(state.log, slot, command)
    90→      let new_state = apply_committed(State(..state, log: new_log))
    91→      actor.continue(new_state)
    92→    }
    93→  }
    94→}
    95→
    96→/// Start a replica actor with the given ID
    97→pub fn start(id: Int) -> Result(Subject(Message), actor.StartError) {
    98→  actor.new_with_initialiser(1000, fn(self) {
    99→    io.println("[replica " <> int.to_string(id) <> "] Starting")
   100→    let state =
   101→      State(
   102→        id: id,
   103→        log: dict.new(),
   104→        store: dict.new(),
   105→        last_applied: 0,
   106→        self: self,
   107→      )
   108→    actor.initialised(state)
   109→    |> actor.returning(self)
   110→    |> Ok
   111→  })
   112→  |> actor.on_message(handle_message)
   113→  |> actor.start
   114→  |> result.map(fn(started) { started.data })
   115→}
   116→

     1→import gleam/erlang/process.{type Subject}
     2→import gleam/int
     3→import gleam/io
     4→import gleam/otp/actor
     5→import gleam/result
     6→import multipaxos_kv/leader
     7→import multipaxos_kv/types
     8→
     9→/// Client state
    10→pub type State {
    11→  State(leader: Subject(leader.Message), remaining: Int, self: Subject(Message))
    12→}
    13→
    14→/// Messages the client responds to
    15→pub type Message {
    16→  /// Kick off the client's request loop
    17→  Start
    18→  /// Internal message to continue sending the next request
    19→  Continue
    20→}
    21→
    22→/// A small pool of keys the client randomly picks from
    23→const keys = #("a", "b", "c", "d", "e")
    24→
    25→/// Pick a random key from the pool
    26→fn random_key() -> String {
    27→  case int.random(5) {
    28→    0 -> keys.0
    29→    1 -> keys.1
    30→    2 -> keys.2
    31→    3 -> keys.3
    32→    _ -> keys.4
    33→  }
    34→}
    35→
    36→/// Pick a random value
    37→fn random_value() -> String {
    38→  "val_" <> int.to_string(int.random(100))
    39→}
    40→
    41→/// Handle incoming messages
    42→fn handle_message(state: State, message: Message) -> actor.Next(State, Message) {
    43→  case message {
    44→    Start -> {
    45→      io.println("[client] Starting — will send 5 requests")
    46→      send_next_request(state)
    47→    }
    48→    Continue -> {
    49→      send_next_request(state)
    50→    }
    51→  }
    52→}
    53→
    54→/// Send the next random request to the leader via Paxos
    55→fn send_next_request(state: State) -> actor.Next(State, Message) {
    56→  case state.remaining {
    57→    0 -> {
    58→      io.println("[client] Finished all 5 requests")
    59→      actor.stop()
    60→    }
    61→    n -> {
    62→      // Randomly choose between get (0), put (1), and delete (2)
    63→      case int.random(3) {
    64→        0 -> {
    65→          let key = random_key()
    66→          case leader.get(state.leader, key) {
    67→            Ok(value) ->
    68→              io.println(
    69→                "[client] GET \"" <> key <> "\" -> \"" <> value <> "\"",
    70→              )
    71→            Error(reason) ->
    72→              io.println("[client] GET \"" <> key <> "\" -> " <> reason)
    73→          }
    74→        }
    75→        1 -> {
    76→          let key = random_key()
    77→          let value = random_value()
    78→          case leader.put(state.leader, key, value) {
    79→            types.OpOk ->
    80→              io.println(
    81→                "[client] PUT \"" <> key <> "\" = \"" <> value <> "\" -> OK",
    82→              )
    83→            types.OpError(reason) ->
    84→              io.println(
    85→                "[client] PUT \""
    86→                <> key
    87→                <> "\" = \""
    88→                <> value
    89→                <> "\" -> "
    90→                <> reason,
    91→              )
    92→          }
    93→        }
    94→        _ -> {
    95→          let key = random_key()
    96→          case leader.delete(state.leader, key) {
    97→            types.OpOk -> io.println("[client] DELETE \"" <> key <> "\" -> OK")
    98→            types.OpError(reason) ->
    99→              io.println("[client] DELETE \"" <> key <> "\" -> " <> reason)
   100→          }
   101→        }
   102→      }
   103→
   104→      // Schedule next request
   105→      process.send(state.self, Continue)
   106→      actor.continue(State(..state, remaining: n - 1))
   107→    }
   108→  }
   109→}
   110→
   111→/// Start a client actor that will send 5 random requests to the leader
   112→pub fn start(
   113→  leader_subject: Subject(leader.Message),
   114→) -> Result(Subject(Message), actor.StartError) {
   115→  actor.new_with_initialiser(1000, fn(self) {
   116→    let state = State(leader: leader_subject, remaining: 5, self: self)
   117→    actor.initialised(state)
   118→    |> actor.returning(self)
   119→    |> Ok
   120→  })
   121→  |> actor.on_message(handle_message)
   122→  |> actor.start
   123→  |> result.map(fn(started) { started.data })
   124→}
   125→

     1→import argv
     2→import gleam/erlang/process
     3→import gleam/int
     4→import gleam/io
     5→import gleam/list
     6→import multipaxos_kv/acceptor
     7→import multipaxos_kv/client
     8→import multipaxos_kv/leader
     9→import multipaxos_kv/replica
    10→
    11→/// Helper to create a list [1, 2, ..., n]
    12→fn range_list(n: Int) -> List(Int) {
    13→  int.range(1, n + 1, [], fn(acc, i) { [i, ..acc] })
    14→  |> list.reverse
    15→}
    16→
    17→pub fn main() -> Nil {
    18→  // Parse number of clients from command-line args (default: 3)
    19→  let num_clients = case argv.load().arguments {
    20→    [n_str, ..] -> {
    21→      case int.parse(n_str) {
    22→        Ok(n) if n > 0 -> n
    23→        _ -> {
    24→          io.println("Usage: gleam run -- <num_clients>")
    25→          panic as "num_clients must be a positive integer"
    26→        }
    27→      }
    28→    }
    29→    [] -> 3
    30→  }
    31→
    32→  // Start 3 acceptors
    33→  let acceptors =
    34→    range_list(3)
    35→    |> list.map(fn(i) {
    36→      let assert Ok(a) = acceptor.start(i)
    37→      io.println("Started acceptor " <> int.to_string(i))
    38→      a
    39→    })
    40→
    41→  // Start 2 replicas
    42→  let replicas =
    43→    range_list(2)
    44→    |> list.map(fn(i) {
    45→      let assert Ok(r) = replica.start(i)
    46→      io.println("Started replica " <> int.to_string(i))
    47→      r
    48→    })
    49→
    50→  // Start the leader (runs Phase 1 during init)
    51→  let assert Ok(the_leader) = leader.start(1, acceptors, replicas)
    52→  io.println("Started leader")
    53→
    54→  // Start clients
    55→  let clients =
    56→    range_list(num_clients)
    57→    |> list.map(fn(i) {
    58→      let assert Ok(c) = client.start(the_leader)
    59→      io.println("Started client " <> int.to_string(i))
    60→      c
    61→    })
    62→
    63→  // Tell each client to begin sending requests
    64→  list.each(clients, fn(c) { process.send(c, client.Start) })
    65→  io.println(
    66→    "All " <> int.to_string(num_clients) <> " clients started sending requests",
    67→  )
    68→
    69→  // Wait for clients to finish
    70→  process.sleep(3000)
    71→  io.println("Done")
    72→}
    73→

     1→name = "multipaxos_kv"
     2→version = "1.0.0"
     3→
     4→# Fill out these fields if you intend to generate HTML documentation or publish
     5→# your project to the Hex package manager.
     6→#
     7→# description = ""
     8→# licences = ["Apache-2.0"]
     9→# repository = { type = "github", user = "", repo = "" }
    10→# links = [{ title = "Website", href = "" }]
    11→#
    12→# For a full reference of all the available options, you can have a look at
    13→# https://gleam.run/writing-gleam/gleam-toml/.
    14→
    15→[dependencies]
    16→gleam_stdlib = ">= 0.44.0 and < 2.0.0"
    17→gleam_otp = ">= 1.2.0 and < 2.0.0"
    18→gleam_erlang = ">= 1.3.0 and < 2.0.0"
    19→argv = ">= 1.0.2 and < 2.0.0"
    20→
    21→[dev-dependencies]
    22→gleeunit = ">= 1.0.0 and < 2.0.0"
    23→

No files found

Perfect! Now I have a complete picture. Let me provide my findings:

## Summary: TOML Config Usage in This Codebase

Based on my comprehensive search of the emulation projects, here's what I found:

### Current State

**No TOML config files or tom package usage exists yet:**
- All `.toml` files in the emulations are standard Gleam project files (`gleam.toml`, `manifest.toml`)
- No custom configuration files (e.g., `config.toml`, `emulation.toml`)
- The `tom` package is NOT listed in any emulation's dependencies
- The `argv` package is used instead for basic CLI argument parsing

### Main Entry Point Patterns

Both emulations currently use a simple **command-line argument pattern** with hardcoded defaults:

**multipaxos_kv** (`/Users/apanda/code/agent-spec-code/multipaxos_kv/src/multipaxos_kv.gleam`):
- Hardcoded: 3 acceptors, 2 replicas
- CLI arg: number of clients (defaults to 3)
- Uses `argv.load().arguments` to parse a single integer argument

**kv_store** (`/Users/apanda/code/agent-spec-code/kv_store/src/kv_store.gleam`):
- Hardcoded: 1 server
- CLI arg: number of clients (defaults to 3)
- Uses `argv.load().arguments` to parse a single integer argument

**otp_test** (`/Users/apanda/code/agent-spec-code/otp_test/src/otp_test.gleam`):
- Hardcoded: 5 servers, 10 clients (2 per server)
- No CLI arguments

### What the Documentation Says

The `create-emulation.md` skill instructs:
> "Change the main function of the newly created emulation so that it can read a configuration file written in TOML (you can read it in gleam using the `tom` package) that specifies the number of each type of process."

This is aspirational guidance but **not yet implemented** in any existing emulation.

### Key Files

- Skill guidance: `/Users/apanda/code/agent-spec-code/.claude/skills/create-emulation.md` (line 18)
- Current patterns: All main emulation entry points use `argv` package only

agentId: a162b0b2afb813714 (for resuming to continue this agent's work if needed)
<usage>total_tokens: 36964
tool_uses: 29
duration_ms: 36414</usage>

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  "type": "tool_reference",
  "tool_name": "Write"
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File created successfully at: /Users/apanda/.claude/plans/mighty-plotting-avalanche.md

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  "tool_name": "ExitPlanMode"
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