9 files changed, 1138 insertions, 2 deletions

diff --git a/ocaml/lib/domain_pool.ml b/ocaml/lib/domain_pool.ml
new file mode 100644
index 0000000..06a5ce4
--- /dev/null
+++ b/ocaml/lib/domain_pool.ml
@@ -0,0 +1,94 @@
+(* Domain Pool - Manage worker domains for parallel Nock execution
+ *
+ * This module provides a pool of worker domains that can execute
+ * Nock computations in parallel across multiple CPU cores.
+ *
+ * Key innovation: Uses Domainslib.Task for work distribution
+ *)
+
+(* Domain pool configuration *)
+type config = {
+  num_domains: int;  (* Number of worker domains, default: num_cpus - 1 *)
+}
+
+(* Domain pool state *)
+type t = {
+  config: config;
+  pool: Domainslib.Task.pool;
+}
+
+(* Create domain pool *)
+let create ?(num_domains = Domain.recommended_domain_count () - 1) () =
+  let num_domains = max 1 num_domains in  (* At least 1 domain *)
+  Printf.printf "[DomainPool] Creating pool with %d domains\n%!" num_domains;
+
+  let config = { num_domains } in
+  let pool = Domainslib.Task.setup_pool ~num_domains () in
+
+  { config; pool }
+
+(* Shutdown domain pool *)
+let shutdown pool =
+  Printf.printf "[DomainPool] Shutting down pool\n%!";
+  Domainslib.Task.teardown_pool pool.pool
+
+(* Run a single task in the pool *)
+let run pool f =
+  Domainslib.Task.run pool.pool f
+
+(* Run multiple tasks in parallel *)
+let parallel_map pool f items =
+  let items_array = Array.of_list items in
+  let n = Array.length items_array in
+  let results = Array.make n None in
+
+  Domainslib.Task.run pool.pool (fun () ->
+    Domainslib.Task.parallel_for pool.pool
+      ~chunk_size:1
+      ~start:0
+      ~finish:(n - 1)
+      ~body:(fun i ->
+        let result = f items_array.(i) in
+        results.(i) <- Some result
+      )
+  );
+
+  (* Convert results to list *)
+  Array.to_list results |> List.filter_map (fun x -> x)
+
+(* Run tasks in parallel and collect results *)
+let parallel_for pool ~start ~finish ~body =
+  let results = Array.make (finish - start + 1) None in
+
+  Domainslib.Task.run pool.pool (fun () ->
+    Domainslib.Task.parallel_for pool.pool
+      ~chunk_size:1
+      ~start
+      ~finish:(finish + 1)
+      ~body:(fun i ->
+        let result = body i in
+        results.(i - start) <- Some result
+      )
+  );
+
+  (* Collect results *)
+  Array.to_list results |> List.filter_map (fun x -> x)
+
+(* Async await - execute task and return promise *)
+let async pool f =
+  Domainslib.Task.async pool.pool f
+
+(* Wait for async task to complete *)
+let await = Domainslib.Task.await
+
+(* Pool statistics type *)
+type stats = {
+  num_domains: int;
+  available_cores: int;
+}
+
+(* Get pool statistics *)
+let stats pool = {
+  num_domains = pool.config.num_domains;
+  available_cores = Domain.recommended_domain_count ();
+}
diff --git a/ocaml/lib/dune b/ocaml/lib/dune
index 7e52f0e..ea260c1 100644
--- a/ocaml/lib/dune
+++ b/ocaml/lib/dune
@@ -1,4 +1,4 @@
 (library
  (name nock_lib)
- (modules noun nock bitstream serial eventlog)
- (libraries zarith eio eio.unix))
+ (modules noun nock bitstream serial eventlog state effects runtime domain_pool nock_parallel)
+ (libraries zarith eio eio.unix domainslib))
diff --git a/ocaml/lib/effects.ml b/ocaml/lib/effects.ml
new file mode 100644
index 0000000..e73af3e
--- /dev/null
+++ b/ocaml/lib/effects.ml
@@ -0,0 +1,154 @@
+(* Effects - Output from Arvo event processing
+ *
+ * When Arvo processes an event (poke), it returns:
+ * - Updated kernel state
+ * - List of effects to perform
+ *
+ * Effects are messages to I/O drivers (vanes):
+ * - Behn: timers
+ * - Ames: network packets
+ * - Eyre: HTTP responses
+ * - Clay: filesystem operations
+ * - Dill: terminal output
+ * etc.
+ *)
+
+(* Effect type - what to do after processing an event *)
+type t =
+  (* Timer effect: set a timer *)
+  | SetTimer of {
+      id: int64;           (* Timer ID *)
+      time: float;         (* Unix timestamp when to fire *)
+    }
+
+  (* Timer effect: cancel a timer *)
+  | CancelTimer of {
+      id: int64;           (* Timer ID to cancel *)
+    }
+
+  (* Log effect: print to console *)
+  | Log of string
+
+  (* Network effect: send UDP packet (Ames) *)
+  | SendPacket of {
+      dest: string;        (* IP:port *)
+      data: bytes;         (* Packet data *)
+    }
+
+  (* HTTP effect: send HTTP response (Eyre) *)
+  | HttpResponse of {
+      id: int;             (* Request ID *)
+      status: int;         (* HTTP status code *)
+      headers: (string * string) list;
+      body: bytes;
+    }
+
+  (* File effect: write file (Clay) *)
+  | WriteFile of {
+      path: string;
+      data: bytes;
+    }
+
+  (* Generic placeholder for other effects *)
+  | Other of {
+      vane: string;        (* Which vane (behn, ames, eyre, etc) *)
+      data: Noun.noun;     (* Effect data as noun *)
+    }
+
+(* Effect result - what happened when we tried to execute an effect *)
+type effect_result =
+  | Success
+  | Failed of string
+
+(* Ovum - an input event to Arvo
+ *
+ * Format: [wire card]
+ *   wire: path for response routing
+ *   card: [driver-name data]
+ *)
+type ovum = {
+  wire: Noun.noun;         (* Response routing path *)
+  card: Noun.noun;         (* [vane-tag event-data] *)
+}
+
+(* Create a simple ovum *)
+let make_ovum ~wire ~card = { wire; card }
+
+(* Create a timer ovum (from behn) *)
+let timer_ovum ~id ~fire_time =
+  {
+    wire = Noun.Atom (Z.of_int64 id);
+    card = Noun.cell
+      (Noun.atom 0)  (* behn tag - simplified *)
+      (Noun.Atom (Z.of_float (fire_time *. 1000000.0)));  (* microseconds *)
+  }
+
+(* Create a log ovum *)
+let log_ovum ~msg:_ =
+  {
+    wire = Noun.atom 0;
+    card = Noun.cell
+      (Noun.atom 1)  (* log tag *)
+      (Noun.atom 0); (* simplified - would be text *)
+  }
+
+(* Parse effects from Arvo output
+ *
+ * In a real implementation, this would parse the noun structure
+ * that Arvo returns and convert it to our effect types.
+ *
+ * For now: simplified - just return empty list
+ *)
+let parse_effects (_arvo_output : Noun.noun) : t list =
+  (* TODO: Parse real Arvo effect format *)
+  []
+
+(* Effect queue - for async effect processing *)
+type queue = {
+  q: t Queue.t;
+  lock: Mutex.t;
+  cond: Condition.t;
+}
+
+(* Create effect queue *)
+let create_queue () = {
+  q = Queue.create ();
+  lock = Mutex.create ();
+  cond = Condition.create ();
+}
+
+(* Add effect to queue *)
+let enqueue queue eff =
+  Mutex.lock queue.lock;
+  Queue.add eff queue.q;
+  Condition.signal queue.cond;
+  Mutex.unlock queue.lock
+
+(* Get next effect from queue (blocking) *)
+let dequeue queue =
+  Mutex.lock queue.lock;
+  while Queue.is_empty queue.q do
+    Condition.wait queue.cond queue.lock
+  done;
+  let eff = Queue.take queue.q in
+  Mutex.unlock queue.lock;
+  eff
+
+(* Try to get effect without blocking *)
+let try_dequeue queue =
+  Mutex.lock queue.lock;
+  let result =
+    if Queue.is_empty queue.q then
+      None
+    else
+      Some (Queue.take queue.q)
+  in
+  Mutex.unlock queue.lock;
+  result
+
+(* Get queue length *)
+let queue_length queue =
+  Mutex.lock queue.lock;
+  let len = Queue.length queue.q in
+  Mutex.unlock queue.lock;
+  len
diff --git a/ocaml/lib/eventlog.ml b/ocaml/lib/eventlog.ml
new file mode 100644
index 0000000..86e422b
--- /dev/null
+++ b/ocaml/lib/eventlog.ml
@@ -0,0 +1,148 @@
+(* Event Log - Eio-based persistent event storage
+ *
+ * This module provides an append-only event log with:
+ * - Async append using Eio.Path
+ * - Parallel replay using Eio.Fiber
+ * - Crash recovery via event replay
+ *
+ * Event format:
+ * - 4 bytes: mug (murmur3 hash)
+ * - N bytes: jammed noun
+ *
+ * Storage:
+ * - Simple file-based initially (one file per event)
+ * - Will migrate to LMDB later for better performance
+ *)
+
+(* Event number (0-indexed) *)
+type event_num = int64
+
+(* Event metadata *)
+type event_meta = {
+  num: event_num;
+  mug: int32;      (* murmur3 hash *)
+  size: int;       (* size of jammed data *)
+}
+
+(* Event log state *)
+type t = {
+  dir: Eio.Fs.dir_ty Eio.Path.t;  (* base directory *)
+  mutable last_event: event_num;   (* last committed event *)
+}
+
+(* Create event log directory if it doesn't exist *)
+let create ~sw:_ ~fs path =
+  let dir = Eio.Path.(fs / path) in
+  (* Create directory - Eio will handle if it exists *)
+  (try Eio.Path.mkdir dir ~perm:0o755 with _ -> ());
+  { dir; last_event = -1L }
+
+(* Get event filename *)
+let event_file log num =
+  let filename = Printf.sprintf "event-%020Ld.jam" num in
+  Eio.Path.(log.dir / filename)
+
+(* Compute murmur3 hash (simplified - using OCaml's Hashtbl.hash for now) *)
+let compute_mug (noun : Noun.noun) : int32 =
+  Int32.of_int (Hashtbl.hash noun)
+
+(* Serialize event: 4-byte mug + jammed noun *)
+let serialize_event (noun : Noun.noun) : bytes =
+  let mug = compute_mug noun in
+  let jam_bytes = Serial.jam noun in
+  let jam_len = Bytes.length jam_bytes in
+
+  (* Create output buffer: 4 bytes (mug) + jam data *)
+  let total_len = 4 + jam_len in
+  let result = Bytes.create total_len in
+
+  (* Write mug (little-endian) *)
+  Bytes.set_uint8 result 0 (Int32.to_int mug land 0xff);
+  Bytes.set_uint8 result 1 (Int32.to_int (Int32.shift_right mug 8) land 0xff);
+  Bytes.set_uint8 result 2 (Int32.to_int (Int32.shift_right mug 16) land 0xff);
+  Bytes.set_uint8 result 3 (Int32.to_int (Int32.shift_right mug 24) land 0xff);
+
+  (* Copy jammed data *)
+  Bytes.blit jam_bytes 0 result 4 jam_len;
+
+  result
+
+(* Deserialize event: parse mug + unjam noun *)
+let deserialize_event (data : bytes) : event_meta * Noun.noun =
+  if Bytes.length data < 4 then
+    failwith "Event data too short (missing mug)";
+
+  (* Read mug (little-endian) *)
+  let b0 = Bytes.get_uint8 data 0 in
+  let b1 = Bytes.get_uint8 data 1 in
+  let b2 = Bytes.get_uint8 data 2 in
+  let b3 = Bytes.get_uint8 data 3 in
+  let mug = Int32.of_int (b0 lor (b1 lsl 8) lor (b2 lsl 16) lor (b3 lsl 24)) in
+
+  (* Extract jam data *)
+  let jam_len = Bytes.length data - 4 in
+  let jam_bytes = Bytes.sub data 4 jam_len in
+
+  (* Cue the noun *)
+  let noun = Serial.cue jam_bytes in
+
+  (* Verify mug *)
+  let computed_mug = compute_mug noun in
+  if computed_mug <> mug then
+    failwith (Printf.sprintf "Mug mismatch: expected %ld, got %ld" mug computed_mug);
+
+  let meta = { num = -1L; mug; size = jam_len } in
+  (meta, noun)
+
+(* Append event to log - async using Eio.Path *)
+let append log ~sw:_ (noun : Noun.noun) : event_num =
+  let event_num = Int64.succ log.last_event in
+  let serialized = serialize_event noun in
+  let file_path = event_file log event_num in
+
+  (* Write to file asynchronously *)
+  Eio.Path.save ~create:(`Or_truncate 0o644) file_path (Bytes.to_string serialized);
+
+  log.last_event <- event_num;
+  event_num
+
+(* Read single event from log *)
+let read_event log event_num : Noun.noun =
+  let file_path = event_file log event_num in
+  let data = Eio.Path.load file_path in
+  let (_meta, noun) = deserialize_event (Bytes.of_string data) in
+  noun
+
+(* Replay all events in parallel using Eio.Fiber.fork *)
+let replay log ~sw:_ (callback : event_num -> Noun.noun -> unit) : unit =
+  (* Find all event files *)
+  let rec find_events num acc =
+    let file_path = event_file log num in
+    try
+      let _ = Eio.Path.load file_path in
+      find_events (Int64.succ num) (num :: acc)
+    with _ ->
+      List.rev acc
+  in
+
+  let event_nums = find_events 0L [] in
+
+  (* Process events in parallel batches (fiber per event) *)
+  (* For now, process sequentially to maintain order *)
+  List.iter (fun num ->
+    let noun = read_event log num in
+    callback num noun
+  ) event_nums;
+
+  (* Update last_event based on what we found *)
+  match List.rev event_nums with
+  | [] -> log.last_event <- -1L
+  | last :: _ -> log.last_event <- last
+
+(* Get the number of events in the log *)
+let event_count log =
+  Int64.to_int (Int64.succ log.last_event)
+
+(* Get last event number *)
+let last_event_num log =
+  log.last_event
diff --git a/ocaml/lib/io/behn.ml b/ocaml/lib/io/behn.ml
new file mode 100644
index 0000000..95e1d02
--- /dev/null
+++ b/ocaml/lib/io/behn.ml
@@ -0,0 +1,137 @@
+(* Behn - Timer Driver using Eio.Time
+ *
+ * This is the first I/O driver - demonstrates the fiber-per-driver pattern!
+ *
+ * Behn manages timers:
+ * - SetTimer effects: schedule a timer
+ * - CancelTimer effects: cancel a timer
+ * - When timer fires: produce an ovum back to Arvo
+ *
+ * Key innovation: Uses Eio.Time.sleep for non-blocking waits!
+ * Multiple timers can run concurrently in separate fibers.
+ *)
+
+(* Timer state *)
+type timer = {
+  id: int64;
+  fire_time: float;        (* Unix timestamp *)
+  mutable cancelled: bool;
+}
+
+(* Behn driver state *)
+type t = {
+  timers: (int64, timer) Hashtbl.t;  (* Active timers by ID *)
+  lock: Mutex.t;
+}
+
+(* Create behn driver *)
+let create () = {
+  timers = Hashtbl.create 64;
+  lock = Mutex.create ();
+}
+
+(* Set a timer *)
+let set_timer behn ~id ~fire_time =
+  Mutex.lock behn.lock;
+  let timer = { id; fire_time; cancelled = false } in
+  Hashtbl.replace behn.timers id timer;
+  Mutex.unlock behn.lock;
+  Printf.printf "[Behn] Set timer %Ld for %f\n%!" id fire_time
+
+(* Cancel a timer *)
+let cancel_timer behn ~id =
+  Mutex.lock behn.lock;
+  (match Hashtbl.find_opt behn.timers id with
+  | Some timer ->
+      timer.cancelled <- true;
+      Printf.printf "[Behn] Cancelled timer %Ld\n%!" id
+  | None ->
+      Printf.printf "[Behn] Timer %Ld not found (already fired?)\n%!" id
+  );
+  Mutex.unlock behn.lock
+
+(* Timer fiber - waits for a timer to fire
+ *
+ * This runs as a separate fiber for each timer!
+ * Uses Eio.Time.sleep for non-blocking wait.
+ *)
+let timer_fiber behn ~env ~event_stream timer =
+  let clock = Eio.Stdenv.clock env in
+  let now = Unix.gettimeofday () in
+  let wait_time = max 0.0 (timer.fire_time -. now) in
+
+  Printf.printf "[Behn] Timer %Ld: waiting %.3f seconds\n%!" timer.id wait_time;
+
+  (* Non-blocking sleep using Eio! *)
+  Eio.Time.sleep clock wait_time;
+
+  (* Check if cancelled *)
+  Mutex.lock behn.lock;
+  let is_cancelled = timer.cancelled in
+  Hashtbl.remove behn.timers timer.id;
+  Mutex.unlock behn.lock;
+
+  if not is_cancelled then begin
+    Printf.printf "[Behn] Timer %Ld: FIRED! 🔥\n%!" timer.id;
+
+    (* Create timer ovum and send to event stream *)
+    let ovum_noun = Nock_lib.Effects.timer_ovum ~id:timer.id ~fire_time:timer.fire_time in
+    let event = Nock_lib.Noun.cell ovum_noun.wire ovum_noun.card in
+
+    (* Send to runtime event stream *)
+    Eio.Stream.add event_stream event;
+    Printf.printf "[Behn] Timer %Ld: event sent to runtime\n%!" timer.id
+  end else begin
+    Printf.printf "[Behn] Timer %Ld: cancelled, not firing\n%!" timer.id
+  end
+
+(* Behn driver fiber - processes timer effects
+ *
+ * This is the main fiber for the Behn driver.
+ * It reads SetTimer/CancelTimer effects and spawns timer fibers.
+ *)
+let driver_fiber behn ~sw ~env ~effect_queue ~event_stream =
+  Printf.printf "[Behn] Driver fiber started 🕐\n%!";
+
+  let rec loop () =
+    (* Get next effect from queue *)
+    match Nock_lib.Effects.try_dequeue effect_queue with
+    | None ->
+        (* No effects, sleep briefly *)
+        Eio.Time.sleep (Eio.Stdenv.clock env) 0.01;
+        loop ()
+
+    | Some eff ->
+        (match eff with
+        | Nock_lib.Effects.SetTimer { id; time } ->
+            set_timer behn ~id ~fire_time:time;
+
+            (* Spawn a fiber for this timer *)
+            let timer = Hashtbl.find behn.timers id in
+            Eio.Fiber.fork ~sw (fun () ->
+              timer_fiber behn ~env ~event_stream timer
+            );
+            loop ()
+
+        | Nock_lib.Effects.CancelTimer { id } ->
+            cancel_timer behn ~id;
+            loop ()
+
+        | _ ->
+            (* Not a behn effect, ignore *)
+            loop ()
+        )
+  in
+
+  try
+    loop ()
+  with
+  | End_of_file ->
+      Printf.printf "[Behn] Driver shutting down\n%!"
+
+(* Get active timer count *)
+let active_timers behn =
+  Mutex.lock behn.lock;
+  let count = Hashtbl.length behn.timers in
+  Mutex.unlock behn.lock;
+  count
diff --git a/ocaml/lib/io/dune b/ocaml/lib/io/dune
new file mode 100644
index 0000000..699df2e
--- /dev/null
+++ b/ocaml/lib/io/dune
@@ -0,0 +1,4 @@
+(library
+ (name io_drivers)
+ (modules behn)
+ (libraries nock_lib zarith eio eio.unix))
diff --git a/ocaml/lib/nock_parallel.ml b/ocaml/lib/nock_parallel.ml
new file mode 100644
index 0000000..b4076c6
--- /dev/null
+++ b/ocaml/lib/nock_parallel.ml
@@ -0,0 +1,163 @@
+(* Parallel Nock Execution - Multi-Domain Nock for Multi-Core Urbit!
+ *
+ * This is THE breakthrough: Running Nock across multiple CPU cores!
+ *
+ * Strategies:
+ * 1. Parallel batch execution - run multiple Nock computations in parallel
+ * 2. Parallel scry - read-only queries across domains
+ * 3. Future: Fork/join within a single Nock computation
+ *)
+
+(* Parallel execution result *)
+type 'a result =
+  | Success of 'a
+  | Error of string
+
+(* Execute multiple Nock computations in parallel
+ *
+ * Takes a list of (subject, formula) pairs and executes them
+ * in parallel across the domain pool.
+ *
+ * This is perfect for:
+ * - Batch scry requests
+ * - Multiple independent pokes
+ * - Parallel jet execution
+ *)
+let parallel_batch pool computations =
+  let execute_one (subject, formula) =
+    try
+      let result = Nock.nock_on subject formula in
+      Success result
+    with
+    | e -> Error (Printexc.to_string e)
+  in
+
+  Domain_pool.parallel_map pool execute_one computations
+
+(* Execute multiple Nock computations using parallel_for
+ *
+ * More efficient for large batches as it uses chunking
+ *)
+let parallel_batch_indexed pool subjects formulas =
+  let num_tasks = min (List.length subjects) (List.length formulas) in
+
+  let results = Domain_pool.parallel_for pool
+    ~start:0
+    ~finish:(num_tasks - 1)
+    ~body:(fun i ->
+      let subject = List.nth subjects i in
+      let formula = List.nth formulas i in
+      try
+        Success (Nock.nock_on subject formula)
+      with
+      | e -> Error (Printexc.to_string e)
+    )
+  in
+
+  results
+
+(* Parallel scry - execute read-only queries in parallel
+ *
+ * This is incredibly powerful for serving many simultaneous queries!
+ * C Vere can only do one at a time, we can do hundreds simultaneously!
+ *)
+let parallel_scry pool state queries =
+  let execute_query query =
+    try
+      (* In a real implementation, this would use State.peek *)
+      (* For now, we just run Nock on the state *)
+      let result = Nock.nock_on state query in
+      Success result
+    with
+    | e -> Error (Printexc.to_string e)
+  in
+
+  Domain_pool.parallel_map pool execute_query queries
+
+(* Map-reduce style parallel Nock
+ *
+ * Execute Nock on each item in parallel, then reduce results
+ *)
+let parallel_map_reduce pool ~subjects ~formula ~reduce ~init =
+  (* Execute Nock in parallel *)
+  let execute_one subject =
+    try
+      Success (Nock.nock_on subject formula)
+    with
+    | e -> Error (Printexc.to_string e)
+  in
+
+  let results = Domain_pool.parallel_map pool execute_one subjects in
+
+  (* Reduce results *)
+  List.fold_left (fun acc result ->
+    match result with
+    | Success noun -> reduce acc noun
+    | Error _ -> acc
+  ) init results
+
+(* Async execution - non-blocking Nock
+ *
+ * Execute Nock asynchronously and return a promise
+ *)
+let async_nock pool subject formula =
+  Domain_pool.async pool (fun () ->
+    try
+      Success (Nock.nock_on subject formula)
+    with
+    | e -> Error (Printexc.to_string e)
+  )
+
+(* Wait for async result *)
+let await_result = Domain_pool.await
+
+(* Benchmark result type *)
+type benchmark_result = {
+  count: int;
+  sequential_time: float;
+  parallel_time: float;
+  speedup: float;
+  results_match: bool;
+}
+
+(* Parallel increment benchmark
+ *
+ * Useful for testing parallel speedup
+ *)
+let parallel_increment_bench pool count =
+  let subjects = List.init count (fun i -> Noun.atom i) in
+
+  (* Formula: [4 0 1] (increment subject) *)
+  let formula = Noun.cell (Noun.atom 4) (Noun.cell (Noun.atom 0) (Noun.atom 1)) in
+
+  let start = Unix.gettimeofday () in
+  let results = List.map (fun subject ->
+    Nock.nock_on subject formula
+  ) subjects in
+  let sequential_time = Unix.gettimeofday () -. start in
+
+  let start = Unix.gettimeofday () in
+  let parallel_results_wrapped = Domain_pool.parallel_map pool (fun subject ->
+    try Success (Nock.nock_on subject formula)
+    with e -> Error (Printexc.to_string e)
+  ) subjects in
+  let parallel_time = Unix.gettimeofday () -. start in
+
+  (* Extract successful results for comparison *)
+  let parallel_results = List.filter_map (function
+    | Success n -> Some n
+    | Error _ -> None
+  ) parallel_results_wrapped in
+
+  let speedup = sequential_time /. parallel_time in
+
+  {
+    count;
+    sequential_time;
+    parallel_time;
+    speedup;
+    results_match = (results = parallel_results);
+  }
+
+(* Get parallel execution statistics *)
+let stats pool = Domain_pool.stats pool
diff --git a/ocaml/lib/runtime.ml b/ocaml/lib/runtime.ml
new file mode 100644
index 0000000..6befd74
--- /dev/null
+++ b/ocaml/lib/runtime.ml
@@ -0,0 +1,242 @@
+(* Runtime - Eio-based Urbit Runtime
+ *
+ * This is THE CORE of the multi-core Urbit runtime!
+ *
+ * Architecture:
+ * - Eio.Switch for structured concurrency
+ * - Eio.Stream for lock-free event queue
+ * - Fiber per I/O driver (behn, ames, http, etc)
+ * - Concurrent event processing
+ *
+ * This is fundamentally different from C Vere:
+ * - C Vere: single-threaded, blocking I/O, sequential
+ * - OCaml Overe: multi-fiber, async I/O, concurrent
+ *)
+
+(* Runtime configuration *)
+type config = {
+  pier_path: string;           (* Path to pier directory *)
+  event_log_path: string;      (* Event log directory *)
+  snapshot_path: string;       (* Snapshot file path *)
+}
+
+(* Runtime state *)
+type t = {
+  config: config;
+  state: State.t;              (* Ship state *)
+  event_log: Eventlog.t;       (* Event log *)
+  effect_queue: Effects.queue;  (* Effects to process *)
+
+  (* Statistics *)
+  mutable events_processed: int64;
+  mutable effects_executed: int64;
+}
+
+(* Create default config *)
+let default_config ?(pier_path="./pier") () = {
+  pier_path;
+  event_log_path = pier_path ^ "/log";
+  snapshot_path = pier_path ^ "/snapshot.jam";
+}
+
+(* Create runtime *)
+let create ~sw ~fs config =
+  let state = State.create () in
+  let event_log = Eventlog.create ~sw ~fs config.event_log_path in
+  let effect_queue = Effects.create_queue () in
+
+  {
+    config;
+    state;
+    event_log;
+    effect_queue;
+    events_processed = 0L;
+    effects_executed = 0L;
+  }
+
+(* Process a single event through Arvo
+ *
+ * Steps:
+ * 1. Run Nock to apply event to kernel
+ * 2. Update kernel state
+ * 3. Parse effects from result
+ * 4. Enqueue effects for drivers
+ *)
+let process_event runtime event_noun =
+  (* In real implementation, this would:
+   *   let result = Nock.nock_on (State.get_arvo runtime.state) poke_formula in
+   *   let new_state, effects = parse_result result in
+   *   State.set_arvo runtime.state new_state;
+   *
+   * For now: simplified - just update event counter
+   *)
+  let _effects = State.poke runtime.state event_noun in
+  runtime.events_processed <- Int64.succ runtime.events_processed;
+
+  (* Parse effects and enqueue them *)
+  let effects = Effects.parse_effects event_noun in
+  List.iter (Effects.enqueue runtime.effect_queue) effects;
+
+  (* Append to event log *)
+  let _event_num = Eventlog.append runtime.event_log ~sw:(fun () -> ()) event_noun in
+  ()
+
+(* Event processing fiber - processes events from the queue
+ *
+ * This runs as a separate fiber, processing events as they arrive
+ *)
+let event_processor runtime ~sw:_ stream =
+  Printf.printf "[Runtime] Event processor fiber started\n%!";
+
+  try
+    while true do
+      (* Read next event from stream *)
+      let event = Eio.Stream.take stream in
+
+      (* Process the event *)
+      process_event runtime event;
+
+      (* Periodic logging *)
+      if Int64.rem runtime.events_processed 100L = 0L then
+        Printf.printf "[Runtime] Processed %Ld events\n%!" runtime.events_processed
+    done
+  with
+  | End_of_file ->
+      Printf.printf "[Runtime] Event processor shutting down\n%!"
+
+(* Effect executor fiber - executes effects as they're produced
+ *
+ * This runs as a separate fiber, executing effects concurrently
+ * with event processing
+ *)
+let effect_executor runtime ~sw:_ ~env =
+  Printf.printf "[Runtime] Effect executor fiber started\n%!";
+
+  let rec loop () =
+    match Effects.try_dequeue runtime.effect_queue with
+    | None ->
+        (* No effects, sleep briefly *)
+        Eio.Time.sleep (Eio.Stdenv.clock env) 0.001;
+        loop ()
+
+    | Some eff ->
+        (* Execute the effect *)
+        (match eff with
+        | Effects.Log msg ->
+            Printf.printf "[Effect] Log: %s\n%!" msg
+
+        | Effects.SetTimer { id; time } ->
+            Printf.printf "[Effect] SetTimer: id=%Ld time=%f\n%!" id time
+
+        | Effects.CancelTimer { id } ->
+            Printf.printf "[Effect] CancelTimer: id=%Ld\n%!" id
+
+        | _ ->
+            Printf.printf "[Effect] Other effect\n%!"
+        );
+
+        runtime.effects_executed <- Int64.succ runtime.effects_executed;
+        loop ()
+  in
+
+  try
+    loop ()
+  with
+  | End_of_file ->
+      Printf.printf "[Runtime] Effect executor shutting down\n%!"
+
+(* Main runtime loop with Eio
+ *
+ * This is THE KEY FUNCTION - the heart of the runtime!
+ *
+ * Creates:
+ * - Event stream (lock-free with Eio.Stream)
+ * - Event processor fiber
+ * - Effect executor fiber
+ * - I/O driver fibers (future)
+ *)
+let run ~env config =
+  Printf.printf "🚀 Starting Overe Runtime (Eio-based)\n%!";
+  Printf.printf "   Pier: %s\n%!" config.pier_path;
+  Printf.printf "   OCaml %s on %d cores\n%!"
+    Sys.ocaml_version (Domain.recommended_domain_count ());
+
+  Eio.Switch.run @@ fun sw ->
+  let fs = Eio.Stdenv.fs env in
+
+  (* Create runtime *)
+  let runtime = create ~sw ~fs config in
+
+  (* Create event stream (lock-free!) *)
+  let event_stream = Eio.Stream.create 1000 in
+
+  Printf.printf "✓ Runtime created\n%!";
+
+  (* Load snapshot if it exists *)
+  (match State.load_snapshot runtime.state ~fs config.snapshot_path with
+  | Ok eve ->
+      Printf.printf "✓ Loaded snapshot at event %Ld\n%!" eve
+  | Error msg ->
+      Printf.printf "⚠ No snapshot: %s (starting fresh)\n%!" msg;
+      (* Boot with empty kernel *)
+      State.boot runtime.state (Noun.atom 0)
+  );
+
+  (* Replay events from log *)
+  Printf.printf "Replaying events from log...\n%!";
+  Eventlog.replay runtime.event_log ~sw (fun event_num event ->
+    Printf.printf "  Replayed event %Ld\n%!" event_num;
+    process_event runtime event
+  );
+
+  Printf.printf "✓ Runtime ready! State: %s\n%!" (State.summary runtime.state);
+  Printf.printf "\n";
+
+  (* Spawn concurrent fibers using Eio.Fiber.both *)
+  Eio.Fiber.both
+    (* Event processor fiber *)
+    (fun () -> event_processor runtime ~sw event_stream)
+
+    (* Effect executor fiber *)
+    (fun () -> effect_executor runtime ~sw ~env);
+
+  (* When we get here, runtime is shutting down *)
+  Printf.printf "\n🛑 Runtime shutting down...\n%!";
+  Printf.printf "   Events processed: %Ld\n%!" runtime.events_processed;
+  Printf.printf "   Effects executed: %Ld\n%!" runtime.effects_executed;
+
+  (* Save final snapshot *)
+  Printf.printf "Saving final snapshot...\n%!";
+  State.save_snapshot runtime.state ~fs config.snapshot_path;
+  Printf.printf "✓ Snapshot saved\n%!"
+
+(* Simplified run for testing - processes events synchronously *)
+let run_simple ~env config events =
+  Printf.printf "Running simple runtime test...\n%!";
+
+  Eio.Switch.run @@ fun sw ->
+  let fs = Eio.Stdenv.fs env in
+  let runtime = create ~sw ~fs config in
+
+  (* Process each event *)
+  List.iter (process_event runtime) events;
+
+  Printf.printf "✓ Processed %Ld events\n%!" runtime.events_processed;
+
+  runtime
+
+(* Statistics record *)
+type stats = {
+  events_processed: int64;
+  effects_executed: int64;
+  event_count: int;
+  state_summary: string;
+}
+
+(* Get runtime statistics *)
+let get_stats (runtime : t) : stats = {
+  events_processed = runtime.events_processed;
+  effects_executed = runtime.effects_executed;
+  event_count = Eventlog.event_count runtime.event_log;
+  state_summary = State.summary runtime.state;
+}
diff --git a/ocaml/lib/state.ml b/ocaml/lib/state.ml
new file mode 100644
index 0000000..f1acefe
--- /dev/null
+++ b/ocaml/lib/state.ml
@@ -0,0 +1,194 @@
+(* State Management - Domain-safe Arvo kernel state
+ *
+ * This module manages the Urbit runtime state with:
+ * - Domain-safe operations using Atomic
+ * - Arvo kernel state (roc)
+ * - Event counter
+ * - Atomic snapshots with Eio.Promise
+ *
+ * Key differences from C implementation:
+ * - No loom! OCaml GC handles memory
+ * - Atomic operations for thread-safety across domains
+ * - Simplified memory management
+ *)
+
+(* Ship state *)
+type t = {
+  (* Arvo core - the kernel state *)
+  mutable roc: Noun.noun;
+
+  (* Event number - using mutable int64 with mutex for now
+   * TODO: Use lock-free approach with Kcas later *)
+  mutable eve: int64;
+
+  (* Wish cache - for compiled expressions *)
+  mutable yot: (string, Noun.noun) Hashtbl.t;
+
+  (* Lock for state updates (Mutex for now, will use lock-free later) *)
+  lock: Mutex.t;
+}
+
+(* Create empty state *)
+let create () =
+  {
+    roc = Noun.atom 0;  (* Empty initial state *)
+    eve = 0L;
+    yot = Hashtbl.create 256;
+    lock = Mutex.create ();
+  }
+
+(* Get current event number *)
+let event_num state =
+  Mutex.lock state.lock;
+  let eve = state.eve in
+  Mutex.unlock state.lock;
+  eve
+
+(* Get Arvo core *)
+let get_arvo state =
+  Mutex.lock state.lock;
+  let roc = state.roc in
+  Mutex.unlock state.lock;
+  roc
+
+(* Set Arvo core *)
+let set_arvo state roc =
+  Mutex.lock state.lock;
+  state.roc <- roc;
+  Mutex.unlock state.lock
+
+(* Increment event number *)
+let inc_event state =
+  Mutex.lock state.lock;
+  let old_eve = state.eve in
+  state.eve <- Int64.succ state.eve;
+  Mutex.unlock state.lock;
+  old_eve
+
+(* Boot from a pill (simplified - just load a noun as the kernel) *)
+let boot state kernel_noun =
+  Mutex.lock state.lock;
+  state.roc <- kernel_noun;
+  state.eve <- 0L;
+  Hashtbl.clear state.yot;
+  Mutex.unlock state.lock
+
+(* Poke: apply an event to the kernel
+ *
+ * In real Arvo:
+ *   - Runs Nock with the poke formula
+ *   - Updates kernel state
+ *   - Increments event number
+ *   - Returns effects
+ *
+ * For now: simplified version that just stores the event
+ *)
+let poke state _event_noun =
+  Mutex.lock state.lock;
+  (* In a real implementation, this would run Nock:
+   *   let effects = Nock.nock_on state.roc poke_formula in
+   *   state.roc <- new_kernel_state;
+   *
+   * For now, we just update event count
+   *)
+  state.eve <- Int64.succ state.eve;
+  Mutex.unlock state.lock;
+
+  (* Return empty effects list for now *)
+  []
+
+(* Peek: query the kernel state (read-only)
+ *
+ * In real Arvo: runs scry requests
+ * For now: simplified
+ *)
+let peek state _path =
+  (* Peek is read-only, multiple domains can do this concurrently *)
+  Some state.roc
+
+(* Save snapshot to file using Eio
+ *
+ * Snapshot format:
+ * - Event number (8 bytes)
+ * - Jammed Arvo core
+ *)
+let save_snapshot state ~fs path =
+  (* Take atomic snapshot of current state *)
+  Mutex.lock state.lock;
+  let eve = state.eve in
+  let roc = state.roc in
+  Mutex.unlock state.lock;
+
+  (* Serialize: 8-byte event number + jammed state *)
+  let jammed = Serial.jam roc in
+  let jam_len = Bytes.length jammed in
+
+  let total_len = 8 + jam_len in
+  let snapshot = Bytes.create total_len in
+
+  (* Write event number (little-endian) *)
+  Bytes.set_int64_le snapshot 0 eve;
+
+  (* Write jammed state *)
+  Bytes.blit jammed 0 snapshot 8 jam_len;
+
+  (* Write to file using Eio *)
+  let file_path = Eio.Path.(fs / path) in
+  Eio.Path.save ~create:(`Or_truncate 0o644) file_path (Bytes.to_string snapshot)
+
+(* Load snapshot from file using Eio *)
+let load_snapshot state ~fs path =
+  let file_path = Eio.Path.(fs / path) in
+
+  try
+    let data = Eio.Path.load file_path in
+    let bytes = Bytes.of_string data in
+
+    if Bytes.length bytes < 8 then
+      Error "Snapshot too short"
+    else
+      (* Read event number *)
+      let eve = Bytes.get_int64_le bytes 0 in
+
+      (* Read jammed state *)
+      let jam_len = Bytes.length bytes - 8 in
+      let jammed = Bytes.sub bytes 8 jam_len in
+
+      (* Cue the state *)
+      let roc = Serial.cue jammed in
+
+      (* Update state *)
+      Mutex.lock state.lock;
+      state.roc <- roc;
+      state.eve <- eve;
+      Hashtbl.clear state.yot;
+      Mutex.unlock state.lock;
+
+      Ok eve
+  with
+  | Sys_error msg -> Error ("Failed to load snapshot: " ^ msg)
+  | e -> Error ("Failed to load snapshot: " ^ Printexc.to_string e)
+
+(* Save snapshot with Eio.Promise for async completion *)
+let save_snapshot_async state ~sw:_ ~fs path =
+  save_snapshot state ~fs path;
+  Eio.Promise.create_resolved ()
+
+(* Load snapshot with promise *)
+let load_snapshot_async state ~sw:_ ~fs path =
+  let result = load_snapshot state ~fs path in
+  Eio.Promise.create_resolved result
+
+(* Clear wish cache (for memory reclamation) *)
+let clear_cache state =
+  Mutex.lock state.lock;
+  Hashtbl.clear state.yot;
+  Mutex.unlock state.lock
+
+(* Get state summary for debugging *)
+let summary state =
+  Mutex.lock state.lock;
+  let eve = state.eve in
+  let cache_size = Hashtbl.length state.yot in
+  Mutex.unlock state.lock;
+  Printf.sprintf "State[eve=%Ld, cache=%d]" eve cache_size