state compaction

introduces a new topic ("state_catchup") over which a full state can be sent. currently the master sends the worker + api this new state, and they update only if they have no other events applied - otherwise usual NACK systems function ## testing manually tested on two nodes
2026-01-23 13:29:29 -05:00 · 2026-01-23 14:15:06 +00:00
27 changed files with 346 additions and 739 deletions
--- a/dashboard/parts.nix
+++ b/dashboard/parts.nix
@@ -3,45 +3,6 @@
  perSystem =
    { pkgs, lib, ... }:
    let
-      # Stub source with lockfiles and minimal files for build to succeed
-      # This allows prettier-svelte to avoid rebuilding when dashboard source changes
-      dashboardStubSrc = pkgs.runCommand "dashboard-stub-src" { } ''
-        mkdir -p $out
-        cp ${inputs.self}/dashboard/package.json $out/
-        cp ${inputs.self}/dashboard/package-lock.json $out/
-        # Minimal files so vite build succeeds (produces empty output)
-        echo '<!DOCTYPE html><html><head></head><body></body></html>' > $out/index.html
-        mkdir -p $out/src
-        touch $out/src/app.html
-      '';
-
-      # Deps-only build using stub source (for prettier-svelte)
-      # Only rebuilds when package.json or package-lock.json change
-      dashboardDeps = inputs.dream2nix.lib.evalModules {
-        packageSets.nixpkgs = pkgs;
-        modules = [
-          ./dashboard.nix
-          {
-            paths.projectRoot = inputs.self;
-            paths.projectRootFile = "flake.nix";
-            paths.package = inputs.self + "/dashboard";
-          }
-          {
-            deps.dashboardSrc = lib.mkForce dashboardStubSrc;
-          }
-          # Override build phases to skip the actual build - just need node_modules
-          {
-            mkDerivation = {
-              buildPhase = lib.mkForce "true";
-              installPhase = lib.mkForce ''
-                runHook preInstall
-                runHook postInstall
-              '';
-            };
-          }
-        ];
-      };
-
      # Filter source to only include dashboard directory
      dashboardSrc = lib.cleanSourceWith {
        src = inputs.self;
@@ -81,12 +42,11 @@
      '';

      # Prettier with svelte plugin for treefmt
-      # Uses dashboardDeps instead of dashboardFull to avoid rebuilding on source changes
      packages.prettier-svelte = pkgs.writeShellScriptBin "prettier-svelte" ''
-        export NODE_PATH="${dashboardDeps}/lib/node_modules/exo-dashboard/node_modules"
+        export NODE_PATH="${dashboardFull}/lib/node_modules/exo-dashboard/node_modules"
        exec ${pkgs.nodejs}/bin/node \
-          ${dashboardDeps}/lib/node_modules/exo-dashboard/node_modules/prettier/bin/prettier.cjs \
-          --plugin "${dashboardDeps}/lib/node_modules/exo-dashboard/node_modules/prettier-plugin-svelte/plugin.js" \
+          ${dashboardFull}/lib/node_modules/exo-dashboard/node_modules/prettier/bin/prettier.cjs \
+          --plugin "${dashboardFull}/lib/node_modules/exo-dashboard/node_modules/prettier-plugin-svelte/plugin.js" \
          "$@"
      '';
    };
--- a/dashboard/src/lib/stores/app.svelte.ts
+++ b/dashboard/src/lib/stores/app.svelte.ts
@@ -216,8 +216,6 @@ export interface Message {
  attachments?: MessageAttachment[];
  ttftMs?: number; // Time to first token in ms (for assistant messages)
  tps?: number; // Tokens per second (for assistant messages)
-  requestType?: "chat" | "image-generation" | "image-editing";
-  sourceImageDataUrl?: string; // For image editing regeneration
 }

 export interface Conversation {
@@ -1272,46 +1270,10 @@ class AppStore {

    if (lastUserIndex === -1) return;

-    const lastUserMessage = this.messages[lastUserIndex];
-    const requestType = lastUserMessage.requestType || "chat";
-    const prompt = lastUserMessage.content;
+    // Remove any messages after the user message
+    this.messages = this.messages.slice(0, lastUserIndex + 1);

-    // Remove messages after user message (including the user message for image requests
-    // since generateImage/editImage will re-add it)
-    this.messages = this.messages.slice(0, lastUserIndex);
-
-    switch (requestType) {
-      case "image-generation":
-        await this.generateImage(prompt);
-        break;
-      case "image-editing":
-        if (lastUserMessage.sourceImageDataUrl) {
-          await this.editImage(prompt, lastUserMessage.sourceImageDataUrl);
-        } else {
-          // Can't regenerate edit without source image - restore user message and show error
-          this.messages.push(lastUserMessage);
-          const errorMessage = this.addMessage("assistant", "");
-          const idx = this.messages.findIndex((m) => m.id === errorMessage.id);
-          if (idx !== -1) {
-            this.messages[idx].content =
-              "Error: Cannot regenerate image edit - source image not found";
-          }
-          this.updateActiveConversation();
-        }
-        break;
-      case "chat":
-      default:
-        // Restore the user message for chat regeneration
-        this.messages.push(lastUserMessage);
-        await this.regenerateChatCompletion();
-        break;
-    }
-  }
-
-  /**
-   * Helper method to regenerate a chat completion response
-   */
-  private async regenerateChatCompletion(): Promise<void> {
+    // Resend the message to get a new response
    this.isLoading = true;
    this.currentResponse = "";

@@ -1826,7 +1788,6 @@ class AppStore {
      role: "user",
      content: prompt,
      timestamp: Date.now(),
-      requestType: "image-generation",
    };
    this.messages.push(userMessage);

@@ -2037,8 +1998,6 @@ class AppStore {
      role: "user",
      content: prompt,
      timestamp: Date.now(),
-      requestType: "image-editing",
-      sourceImageDataUrl: imageDataUrl,
    };
    this.messages.push(userMessage);

@@ -2228,54 +2187,6 @@ class AppStore {
      this.conversations.find((c) => c.id === this.activeConversationId) || null
    );
  }
-
-  /**
-   * Start a download on a specific node
-   */
-  async startDownload(nodeId: string, shardMetadata: object): Promise<void> {
-    try {
-      const response = await fetch("/download/start", {
-        method: "POST",
-        headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({
-          targetNodeId: nodeId,
-          shardMetadata: shardMetadata,
-        }),
-      });
-      if (!response.ok) {
-        const errorText = await response.text();
-        throw new Error(
-          `Failed to start download: ${response.status} - ${errorText}`,
-        );
-      }
-    } catch (error) {
-      console.error("Error starting download:", error);
-      throw error;
-    }
-  }
-
-  /**
-   * Delete a downloaded model from a specific node
-   */
-  async deleteDownload(nodeId: string, modelId: string): Promise<void> {
-    try {
-      const response = await fetch(
-        `/download/${encodeURIComponent(nodeId)}/${encodeURIComponent(modelId)}`,
-        {
-          method: "DELETE",
-        },
-      );
-      if (!response.ok) {
-        const errorText = await response.text();
-        throw new Error(
-          `Failed to delete download: ${response.status} - ${errorText}`,
-        );
-      }
-    } catch (error) {
-      console.error("Error deleting download:", error);
-      throw error;
-    }
-  }
 }

 export const appStore = new AppStore();
@@ -2381,9 +2292,3 @@ export const setImageGenerationParams = (
 ) => appStore.setImageGenerationParams(params);
 export const resetImageGenerationParams = () =>
  appStore.resetImageGenerationParams();
-
-// Download actions
-export const startDownload = (nodeId: string, shardMetadata: object) =>
-  appStore.startDownload(nodeId, shardMetadata);
-export const deleteDownload = (nodeId: string, modelId: string) =>
-  appStore.deleteDownload(nodeId, modelId);
--- a/dashboard/src/routes/downloads/+page.svelte
+++ b/dashboard/src/routes/downloads/+page.svelte
@@ -6,8 +6,6 @@
    type DownloadProgress,
    refreshState,
    lastUpdate as lastUpdateStore,
-    startDownload,
-    deleteDownload,
  } from "$lib/stores/app.svelte";
  import HeaderNav from "$lib/components/HeaderNav.svelte";

@@ -30,7 +28,6 @@
    etaMs: number;
    status: "completed" | "downloading";
    files: FileProgress[];
-    shardMetadata?: Record<string, unknown>;
  };

  type NodeEntry = {
@@ -272,12 +269,6 @@
            }
          }

-          // Extract shard_metadata for use with download actions
-          const shardMetadata = (downloadPayload.shard_metadata ??
-            downloadPayload.shardMetadata) as
-            | Record<string, unknown>
-            | undefined;
-
          const entry: ModelEntry = {
            modelId,
            prettyName,
@@ -294,7 +285,6 @@
                ? "completed"
                : "downloading",
            files,
-            shardMetadata,
          };

          const existing = modelMap.get(modelId);
@@ -479,52 +469,6 @@
                    >
                      {pct.toFixed(1)}%
                    </span>
-                    {#if model.status !== "completed" && model.shardMetadata}
-                      <button
-                        type="button"
-                        class="text-exo-light-gray hover:text-exo-yellow transition-colors"
-                        onclick={() =>
-                          startDownload(node.nodeId, model.shardMetadata!)}
-                        title="Start download"
-                      >
-                        <svg
-                          class="w-4 h-4"
-                          viewBox="0 0 20 20"
-                          fill="none"
-                          stroke="currentColor"
-                          stroke-width="2"
-                        >
-                          <path
-                            d="M10 3v10m0 0l-3-3m3 3l3-3M3 17h14"
-                            stroke-linecap="round"
-                            stroke-linejoin="round"
-                          ></path>
-                        </svg>
-                      </button>
-                    {/if}
-                    {#if model.status === "completed"}
-                      <button
-                        type="button"
-                        class="text-exo-light-gray hover:text-red-400 transition-colors"
-                        onclick={() =>
-                          deleteDownload(node.nodeId, model.modelId)}
-                        title="Delete download"
-                      >
-                        <svg
-                          class="w-4 h-4"
-                          viewBox="0 0 20 20"
-                          fill="none"
-                          stroke="currentColor"
-                          stroke-width="2"
-                        >
-                          <path
-                            d="M4 6h12M8 6V4h4v2m1 0v10a1 1 0 01-1 1H8a1 1 0 01-1-1V6h6"
-                            stroke-linecap="round"
-                            stroke-linejoin="round"
-                          ></path>
-                        </svg>
-                      </button>
-                    {/if}
                    <button
                      type="button"
                      class="text-exo-light-gray hover:text-exo-yellow transition-colors"
--- a/src/exo/download/coordinator.py
+++ b/src/exo/download/coordinator.py
@@ -1,284 +0,0 @@
-import asyncio
-from dataclasses import dataclass, field
-from typing import Iterator
-
-import anyio
-from anyio import current_time
-from anyio.abc import TaskGroup
-from loguru import logger
-
-from exo.download.download_utils import (
-    RepoDownloadProgress,
-    delete_model,
-    map_repo_download_progress_to_download_progress_data,
-)
-from exo.download.shard_downloader import ShardDownloader
-from exo.shared.models.model_cards import ModelId
-from exo.shared.types.commands import (
-    DeleteDownload,
-    ForwarderDownloadCommand,
-    StartDownload,
-)
-from exo.shared.types.common import NodeId, SessionId
-from exo.shared.types.events import (
-    Event,
-    ForwarderEvent,
-    NodeDownloadProgress,
-)
-from exo.shared.types.worker.downloads import (
-    DownloadCompleted,
-    DownloadFailed,
-    DownloadOngoing,
-    DownloadPending,
-    DownloadProgress,
-)
-from exo.shared.types.worker.shards import ShardMetadata
-from exo.utils.channels import Receiver, Sender, channel
-
-
-@dataclass
-class DownloadCoordinator:
-    node_id: NodeId
-    session_id: SessionId
-    shard_downloader: ShardDownloader
-    download_command_receiver: Receiver[ForwarderDownloadCommand]
-    local_event_sender: Sender[ForwarderEvent]
-    event_index_counter: Iterator[int]
-
-    # Local state
-    download_status: dict[ModelId, DownloadProgress] = field(default_factory=dict)
-    active_downloads: dict[ModelId, asyncio.Task[None]] = field(default_factory=dict)
-
-    # Internal event channel for forwarding (initialized in __post_init__)
-    event_sender: Sender[Event] = field(init=False)
-    event_receiver: Receiver[Event] = field(init=False)
-    _tg: TaskGroup = field(init=False)
-
-    def __post_init__(self) -> None:
-        self.event_sender, self.event_receiver = channel[Event]()
-        self._tg = anyio.create_task_group()
-
-    async def run(self) -> None:
-        logger.info("Starting DownloadCoordinator")
-        async with self._tg as tg:
-            tg.start_soon(self._command_processor)
-            tg.start_soon(self._forward_events)
-            tg.start_soon(self._emit_existing_download_progress)
-
-    def shutdown(self) -> None:
-        self._tg.cancel_scope.cancel()
-
-    async def _command_processor(self) -> None:
-        with self.download_command_receiver as commands:
-            async for cmd in commands:
-                # Only process commands targeting this node
-                if cmd.command.target_node_id != self.node_id:
-                    continue
-
-                match cmd.command:
-                    case StartDownload(shard_metadata=shard):
-                        await self._start_download(shard)
-                    case DeleteDownload(model_id=model_id):
-                        await self._delete_download(model_id)
-
-    async def _start_download(self, shard: ShardMetadata) -> None:
-        model_id = shard.model_card.model_id
-
-        # Check if already downloading or complete
-        if model_id in self.download_status:
-            status = self.download_status[model_id]
-            if isinstance(status, (DownloadOngoing, DownloadCompleted)):
-                logger.debug(
-                    f"Download for {model_id} already in progress or complete, skipping"
-                )
-                return
-
-        # Emit pending status
-        progress = DownloadPending(shard_metadata=shard, node_id=self.node_id)
-        self.download_status[model_id] = progress
-        await self.event_sender.send(NodeDownloadProgress(download_progress=progress))
-
-        # Check initial status from downloader
-        initial_progress = (
-            await self.shard_downloader.get_shard_download_status_for_shard(shard)
-        )
-
-        if initial_progress.status == "complete":
-            completed = DownloadCompleted(
-                shard_metadata=shard,
-                node_id=self.node_id,
-                total_bytes=initial_progress.total_bytes,
-            )
-            self.download_status[model_id] = completed
-            await self.event_sender.send(
-                NodeDownloadProgress(download_progress=completed)
-            )
-            return
-
-        # Start actual download
-        self._start_download_task(shard, initial_progress)
-
-    def _start_download_task(
-        self, shard: ShardMetadata, initial_progress: RepoDownloadProgress
-    ) -> None:
-        model_id = shard.model_card.model_id
-
-        # Emit ongoing status
-        status = DownloadOngoing(
-            node_id=self.node_id,
-            shard_metadata=shard,
-            download_progress=map_repo_download_progress_to_download_progress_data(
-                initial_progress
-            ),
-        )
-        self.download_status[model_id] = status
-        self.event_sender.send_nowait(NodeDownloadProgress(download_progress=status))
-
-        last_progress_time = 0.0
-        throttle_interval_secs = 1.0
-
-        async def download_progress_callback(
-            callback_shard: ShardMetadata, progress: RepoDownloadProgress
-        ) -> None:
-            nonlocal last_progress_time
-
-            if progress.status == "complete":
-                completed = DownloadCompleted(
-                    shard_metadata=callback_shard,
-                    node_id=self.node_id,
-                    total_bytes=progress.total_bytes,
-                )
-                self.download_status[callback_shard.model_card.model_id] = completed
-                await self.event_sender.send(
-                    NodeDownloadProgress(download_progress=completed)
-                )
-                # Clean up active download tracking
-                if callback_shard.model_card.model_id in self.active_downloads:
-                    del self.active_downloads[callback_shard.model_card.model_id]
-            elif (
-                progress.status == "in_progress"
-                and current_time() - last_progress_time > throttle_interval_secs
-            ):
-                ongoing = DownloadOngoing(
-                    node_id=self.node_id,
-                    shard_metadata=callback_shard,
-                    download_progress=map_repo_download_progress_to_download_progress_data(
-                        progress
-                    ),
-                )
-                self.download_status[callback_shard.model_card.model_id] = ongoing
-                await self.event_sender.send(
-                    NodeDownloadProgress(download_progress=ongoing)
-                )
-                last_progress_time = current_time()
-
-        self.shard_downloader.on_progress(download_progress_callback)
-
-        async def download_wrapper() -> None:
-            try:
-                await self.shard_downloader.ensure_shard(shard)
-            except Exception as e:
-                logger.error(f"Download failed for {model_id}: {e}")
-                failed = DownloadFailed(
-                    shard_metadata=shard,
-                    node_id=self.node_id,
-                    error_message=str(e),
-                )
-                self.download_status[model_id] = failed
-                await self.event_sender.send(
-                    NodeDownloadProgress(download_progress=failed)
-                )
-            finally:
-                if model_id in self.active_downloads:
-                    del self.active_downloads[model_id]
-
-        task = asyncio.create_task(download_wrapper())
-        self.active_downloads[model_id] = task
-
-    async def _delete_download(self, model_id: ModelId) -> None:
-        # Cancel if active
-        if model_id in self.active_downloads:
-            logger.info(f"Cancelling active download for {model_id} before deletion")
-            self.active_downloads[model_id].cancel()
-            del self.active_downloads[model_id]
-
-        # Delete from disk
-        logger.info(f"Deleting model files for {model_id}")
-        deleted = await delete_model(model_id)
-
-        if deleted:
-            logger.info(f"Successfully deleted model {model_id}")
-        else:
-            logger.warning(f"Model {model_id} was not found on disk")
-
-        # Emit pending status to reset UI state, then remove from local tracking
-        if model_id in self.download_status:
-            current_status = self.download_status[model_id]
-            pending = DownloadPending(
-                shard_metadata=current_status.shard_metadata,
-                node_id=self.node_id,
-            )
-            await self.event_sender.send(
-                NodeDownloadProgress(download_progress=pending)
-            )
-            del self.download_status[model_id]
-
-    async def _forward_events(self) -> None:
-        with self.event_receiver as events:
-            async for event in events:
-                idx = next(self.event_index_counter)
-                fe = ForwarderEvent(
-                    origin_idx=idx,
-                    origin=self.node_id,
-                    session=self.session_id,
-                    event=event,
-                )
-                logger.debug(
-                    f"DownloadCoordinator published event {idx}: {str(event)[:100]}"
-                )
-                await self.local_event_sender.send(fe)
-
-    async def _emit_existing_download_progress(self) -> None:
-        try:
-            while True:
-                logger.info(
-                    "DownloadCoordinator: Fetching and emitting existing download progress..."
-                )
-                async for (
-                    _,
-                    progress,
-                ) in self.shard_downloader.get_shard_download_status():
-                    if progress.status == "complete":
-                        status: DownloadProgress = DownloadCompleted(
-                            node_id=self.node_id,
-                            shard_metadata=progress.shard,
-                            total_bytes=progress.total_bytes,
-                        )
-                    elif progress.status in ["in_progress", "not_started"]:
-                        if progress.downloaded_bytes_this_session.in_bytes == 0:
-                            status = DownloadPending(
-                                node_id=self.node_id, shard_metadata=progress.shard
-                            )
-                        else:
-                            status = DownloadOngoing(
-                                node_id=self.node_id,
-                                shard_metadata=progress.shard,
-                                download_progress=map_repo_download_progress_to_download_progress_data(
-                                    progress
-                                ),
-                            )
-                    else:
-                        continue
-
-                    self.download_status[progress.shard.model_card.model_id] = status
-                    await self.event_sender.send(
-                        NodeDownloadProgress(download_progress=status)
-                    )
-                logger.info(
-                    "DownloadCoordinator: Done emitting existing download progress."
-                )
-                await anyio.sleep(5 * 60)  # 5 minutes
-        except Exception as e:
-            logger.error(
-                f"DownloadCoordinator: Error emitting existing download progress: {e}"
-            )
--- a/src/exo/main.py
+++ b/src/exo/main.py
@@ -1,11 +1,10 @@
 import argparse
-import itertools
 import multiprocessing as mp
 import os
 import resource
 import signal
 from dataclasses import dataclass, field
-from typing import Iterator, Self
+from typing import Self

 import anyio
 from anyio.abc import TaskGroup
@@ -13,8 +12,6 @@ from loguru import logger
 from pydantic import PositiveInt

 import exo.routing.topics as topics
-from exo.download.coordinator import DownloadCoordinator
-from exo.download.impl_shard_downloader import exo_shard_downloader
 from exo.master.api import API  # TODO: should API be in master?
 from exo.master.main import Master
 from exo.routing.router import Router, get_node_id_keypair
@@ -24,6 +21,7 @@ from exo.shared.logging import logger_cleanup, logger_setup
 from exo.shared.types.common import NodeId, SessionId
 from exo.utils.channels import Receiver, channel
 from exo.utils.pydantic_ext import CamelCaseModel
+from exo.worker.download.impl_shard_downloader import exo_shard_downloader
 from exo.worker.main import Worker


@@ -31,7 +29,6 @@ from exo.worker.main import Worker
@dataclass
 class Node:
    router: Router
-    download_coordinator: DownloadCoordinator | None
    worker: Worker | None
    election: Election  # Every node participates in election, as we do want a node to become master even if it isn't a master candidate if no master candidates are present.
    election_result_receiver: Receiver[ElectionResult]
@@ -39,7 +36,6 @@ class Node:
    api: API | None

    node_id: NodeId
-    event_index_counter: Iterator[int]
    _tg: TaskGroup = field(init=False, default_factory=anyio.create_task_group)

    @classmethod
@@ -53,26 +49,9 @@ class Node:
        await router.register_topic(topics.COMMANDS)
        await router.register_topic(topics.ELECTION_MESSAGES)
        await router.register_topic(topics.CONNECTION_MESSAGES)
-        await router.register_topic(topics.DOWNLOAD_COMMANDS)
+        await router.register_topic(topics.STATE_CATCHUP)

        logger.info(f"Starting node {node_id}")
-
-        # Create shared event index counter for Worker and DownloadCoordinator
-        event_index_counter = itertools.count()
-
-        # Create DownloadCoordinator (unless --no-downloads)
-        if not args.no_downloads:
-            download_coordinator = DownloadCoordinator(
-                node_id,
-                session_id,
-                exo_shard_downloader(),
-                download_command_receiver=router.receiver(topics.DOWNLOAD_COMMANDS),
-                local_event_sender=router.sender(topics.LOCAL_EVENTS),
-                event_index_counter=event_index_counter,
-            )
-        else:
-            download_coordinator = None
-
        if args.spawn_api:
            api = API(
                node_id,
@@ -80,8 +59,8 @@ class Node:
                port=args.api_port,
                global_event_receiver=router.receiver(topics.GLOBAL_EVENTS),
                command_sender=router.sender(topics.COMMANDS),
-                download_command_sender=router.sender(topics.DOWNLOAD_COMMANDS),
                election_receiver=router.receiver(topics.ELECTION_MESSAGES),
+                state_catchup_receiver=router.receiver(topics.STATE_CATCHUP),
            )
        else:
            api = None
@@ -90,12 +69,12 @@ class Node:
            worker = Worker(
                node_id,
                session_id,
+                exo_shard_downloader(),
                connection_message_receiver=router.receiver(topics.CONNECTION_MESSAGES),
                global_event_receiver=router.receiver(topics.GLOBAL_EVENTS),
                local_event_sender=router.sender(topics.LOCAL_EVENTS),
                command_sender=router.sender(topics.COMMANDS),
-                download_command_sender=router.sender(topics.DOWNLOAD_COMMANDS),
-                event_index_counter=event_index_counter,
+                state_catchup_receiver=router.receiver(topics.STATE_CATCHUP),
            )
        else:
            worker = None
@@ -107,6 +86,7 @@ class Node:
            global_event_sender=router.sender(topics.GLOBAL_EVENTS),
            local_event_receiver=router.receiver(topics.LOCAL_EVENTS),
            command_receiver=router.receiver(topics.COMMANDS),
+            state_catchup_sender=router.sender(topics.STATE_CATCHUP),
        )

        er_send, er_recv = channel[ElectionResult]()
@@ -123,25 +103,13 @@ class Node:
            election_result_sender=er_send,
        )

-        return cls(
-            router,
-            download_coordinator,
-            worker,
-            election,
-            er_recv,
-            master,
-            api,
-            node_id,
-            event_index_counter,
-        )
+        return cls(router, worker, election, er_recv, master, api, node_id)

    async def run(self):
        async with self._tg as tg:
            signal.signal(signal.SIGINT, lambda _, __: self.shutdown())
            tg.start_soon(self.router.run)
            tg.start_soon(self.election.run)
-            if self.download_coordinator:
-                tg.start_soon(self.download_coordinator.run)
            if self.worker:
                tg.start_soon(self.worker.run)
            if self.master:
@@ -189,6 +157,7 @@ class Node:
                        global_event_sender=self.router.sender(topics.GLOBAL_EVENTS),
                        local_event_receiver=self.router.receiver(topics.LOCAL_EVENTS),
                        command_receiver=self.router.receiver(topics.COMMANDS),
+                        state_catchup_sender=self.router.sender(topics.STATE_CATCHUP),
                    )
                    self._tg.start_soon(self.master.run)
                elif (
@@ -206,27 +175,13 @@ class Node:
                    )
                if result.is_new_master:
                    await anyio.sleep(0)
-                    # Fresh counter for new session (buffer expects indices from 0)
-                    self.event_index_counter = itertools.count()
-                    if self.download_coordinator:
-                        self.download_coordinator.shutdown()
-                        self.download_coordinator = DownloadCoordinator(
-                            self.node_id,
-                            result.session_id,
-                            exo_shard_downloader(),
-                            download_command_receiver=self.router.receiver(
-                                topics.DOWNLOAD_COMMANDS
-                            ),
-                            local_event_sender=self.router.sender(topics.LOCAL_EVENTS),
-                            event_index_counter=self.event_index_counter,
-                        )
-                        self._tg.start_soon(self.download_coordinator.run)
                    if self.worker:
                        self.worker.shutdown()
                        # TODO: add profiling etc to resource monitor
                        self.worker = Worker(
                            self.node_id,
                            result.session_id,
+                            exo_shard_downloader(),
                            connection_message_receiver=self.router.receiver(
                                topics.CONNECTION_MESSAGES
                            ),
@@ -235,10 +190,9 @@ class Node:
                            ),
                            local_event_sender=self.router.sender(topics.LOCAL_EVENTS),
                            command_sender=self.router.sender(topics.COMMANDS),
-                            download_command_sender=self.router.sender(
-                                topics.DOWNLOAD_COMMANDS
+                            state_catchup_receiver=self.router.receiver(
+                                topics.STATE_CATCHUP
                            ),
-                            event_index_counter=self.event_index_counter,
                        )
                        self._tg.start_soon(self.worker.run)
                    if self.api:
@@ -280,7 +234,6 @@ class Args(CamelCaseModel):
    api_port: PositiveInt = 52415
    tb_only: bool = False
    no_worker: bool = False
-    no_downloads: bool = False
    fast_synch: bool | None = None  # None = auto, True = force on, False = force off

    @classmethod
@@ -323,11 +276,6 @@ class Args(CamelCaseModel):
            "--no-worker",
            action="store_true",
        )
-        parser.add_argument(
-            "--no-downloads",
-            action="store_true",
-            help="Disable the download coordinator (node won't download models)",
-        )
        fast_synch_group = parser.add_mutually_exclusive_group()
        fast_synch_group.add_argument(
            "--fast-synch",
--- a/src/exo/master/api.py
+++ b/src/exo/master/api.py
@@ -44,7 +44,6 @@ from exo.shared.types.api import (
    ChatCompletionResponse,
    CreateInstanceParams,
    CreateInstanceResponse,
-    DeleteDownloadResponse,
    DeleteInstanceResponse,
    ErrorInfo,
    ErrorResponse,
@@ -62,8 +61,6 @@ from exo.shared.types.api import (
    PlaceInstanceParams,
    PlacementPreview,
    PlacementPreviewResponse,
-    StartDownloadParams,
-    StartDownloadResponse,
    StreamingChoiceResponse,
    ToolCall,
 )
@@ -78,16 +75,12 @@ from exo.shared.types.commands import (
    ChatCompletion,
    Command,
    CreateInstance,
-    DeleteDownload,
    DeleteInstance,
-    DownloadCommand,
    ForwarderCommand,
-    ForwarderDownloadCommand,
    ImageEdits,
    ImageGeneration,
    PlaceInstance,
    SendInputChunk,
-    StartDownload,
    TaskFinished,
 )
 from exo.shared.types.common import CommandId, Id, NodeId, SessionId
@@ -163,16 +156,16 @@ class API:
        # Ideally this would be a MasterForwarderEvent but type system says no :(
        global_event_receiver: Receiver[ForwarderEvent],
        command_sender: Sender[ForwarderCommand],
-        download_command_sender: Sender[ForwarderDownloadCommand],
        # This lets us pause the API if an election is running
        election_receiver: Receiver[ElectionMessage],
+        state_catchup_receiver: Receiver[State],
    ) -> None:
        self.state = State()
        self._event_log: list[Event] = []
        self.command_sender = command_sender
-        self.download_command_sender = download_command_sender
        self.global_event_receiver = global_event_receiver
        self.election_receiver = election_receiver
+        self.state_catchup_receiver = state_catchup_receiver
        self.event_buffer: OrderedBuffer[Event] = OrderedBuffer[Event]()
        self.node_id: NodeId = node_id
        self.session_id: SessionId = session_id
@@ -269,8 +262,6 @@ class API:
        self.app.get("/images/{image_id}")(self.get_image)
        self.app.get("/state")(lambda: self.state)
        self.app.get("/events")(lambda: self._event_log)
-        self.app.post("/download/start")(self.start_download)
-        self.app.delete("/download/{node_id}/{model_id:path}")(self.delete_download)

    async def place_instance(self, payload: PlaceInstanceParams):
        command = PlaceInstance(
@@ -1242,6 +1233,7 @@ class API:
            tg.start_soon(self._apply_state)
            tg.start_soon(self._pause_on_new_election)
            tg.start_soon(self._cleanup_expired_images)
+            tg.start_soon(self._state_catchup)
            print_startup_banner(self.port)
            await serve(
                cast(ASGIFramework, self.app),
@@ -1252,6 +1244,22 @@ class API:
        self.command_sender.close()
        self.global_event_receiver.close()

+    async def _state_catchup(self):
+        with self.state_catchup_receiver as states:
+            async for state in states:
+                if (
+                    self.state.last_event_applied_idx == -1
+                    and state.last_event_applied_idx > self.state.last_event_applied_idx
+                ):
+                    logger.info(
+                        f"API catching up state to idx {state.last_event_applied_idx}"
+                    )
+                    self.event_buffer.store = {}
+                    self.event_buffer.next_idx_to_release = (
+                        state.last_event_applied_idx + 1
+                    )
+                    self.state = state
+
    async def _apply_state(self):
        with self.global_event_receiver as events:
            async for f_event in events:
@@ -1303,28 +1311,3 @@ class API:
        await self.command_sender.send(
            ForwarderCommand(origin=self.node_id, command=command)
        )
-
-    async def _send_download(self, command: DownloadCommand):
-        await self.download_command_sender.send(
-            ForwarderDownloadCommand(origin=self.node_id, command=command)
-        )
-
-    async def start_download(
-        self, payload: StartDownloadParams
-    ) -> StartDownloadResponse:
-        command = StartDownload(
-            target_node_id=payload.target_node_id,
-            shard_metadata=payload.shard_metadata,
-        )
-        await self._send_download(command)
-        return StartDownloadResponse(command_id=command.command_id)
-
-    async def delete_download(
-        self, node_id: NodeId, model_id: ModelId
-    ) -> DeleteDownloadResponse:
-        command = DeleteDownload(
-            target_node_id=node_id,
-            model_id=ModelId(model_id),
-        )
-        await self._send_download(command)
-        return DeleteDownloadResponse(command_id=command.command_id)
--- a/src/exo/master/main.py
+++ b/src/exo/master/main.py
@@ -68,6 +68,8 @@ class Master:
        # Send events to the forwarder to be indexed (usually from command processing)
        # Ideally these would be MasterForwarderEvents but type system says no :(
        global_event_sender: Sender[ForwarderEvent],
+        # not a fan but - send the entire state to a node so it can catchup without the whole event log.
+        state_catchup_sender: Sender[State],
    ):
        self.state = State()
        self._tg: TaskGroup = anyio.create_task_group()
@@ -77,6 +79,7 @@ class Master:
        self.command_receiver = command_receiver
        self.local_event_receiver = local_event_receiver
        self.global_event_sender = global_event_sender
+        self.state_catchup_sender = state_catchup_sender
        send, recv = channel[Event]()
        self.event_sender: Sender[Event] = send
        self._loopback_event_receiver: Receiver[Event] = recv
@@ -84,7 +87,6 @@ class Master:
            local_event_receiver.clone_sender()
        )
        self._multi_buffer = MultiSourceBuffer[NodeId, Event]()
-        # TODO: not have this
        self._event_log: list[Event] = []

    async def run(self):
@@ -291,11 +293,17 @@ class Master:
                                    command.finished_command_id
                                ]
                        case RequestEventLog():
-                            # We should just be able to send everything, since other buffers will ignore old messages
-                            for i in range(command.since_idx, len(self._event_log)):
-                                await self._send_event(
-                                    IndexedEvent(idx=i, event=self._event_log[i])
+                            if command.since_idx == 0:
+                                # This is an optimization, and should not be relied upon in theory.
+                                logger.info(
+                                    f"Master sending catchup state for index {self.state.last_event_applied_idx}"
                                )
+                                await self.state_catchup_sender.send(self.state)
+                            else:
+                                for i in range(command.since_idx, len(self._event_log)):
+                                    await self._send_event(
+                                        IndexedEvent(idx=i, event=self._event_log[i])
+                                    )
                    for event in generated_events:
                        await self.event_sender.send(event)
                except ValueError as e:
--- a/src/exo/master/tests/test_master.py
+++ b/src/exo/master/tests/test_master.py
@@ -27,6 +27,7 @@ from exo.shared.types.memory import Memory
 from exo.shared.types.profiling import (
    MemoryUsage,
 )
+from exo.shared.types.state import State
 from exo.shared.types.tasks import ChatCompletion as ChatCompletionTask
 from exo.shared.types.tasks import TaskStatus
 from exo.shared.types.worker.instances import (
@@ -47,6 +48,7 @@ async def test_master():
    ge_sender, global_event_receiver = channel[ForwarderEvent]()
    command_sender, co_receiver = channel[ForwarderCommand]()
    local_event_sender, le_receiver = channel[ForwarderEvent]()
+    st_s, _st_r = channel[State]()

    all_events: list[IndexedEvent] = []

@@ -67,6 +69,7 @@ async def test_master():
        global_event_sender=ge_sender,
        local_event_receiver=le_receiver,
        command_receiver=co_receiver,
+        state_catchup_sender=st_s,
    )
    logger.info("run the master")
    async with anyio.create_task_group() as tg:
--- a/src/exo/routing/topics.py
+++ b/src/exo/routing/topics.py
@@ -3,10 +3,11 @@ from enum import Enum

 from exo.routing.connection_message import ConnectionMessage
 from exo.shared.election import ElectionMessage
-from exo.shared.types.commands import ForwarderCommand, ForwarderDownloadCommand
+from exo.shared.types.commands import ForwarderCommand
 from exo.shared.types.events import (
    ForwarderEvent,
 )
+from exo.shared.types.state import State
 from exo.utils.pydantic_ext import CamelCaseModel


@@ -45,6 +46,4 @@ ELECTION_MESSAGES = TypedTopic(
 CONNECTION_MESSAGES = TypedTopic(
    "connection_messages", PublishPolicy.Never, ConnectionMessage
 )
-DOWNLOAD_COMMANDS = TypedTopic(
-    "download_commands", PublishPolicy.Always, ForwarderDownloadCommand
-)
+STATE_CATCHUP = TypedTopic("state_catchup", PublishPolicy.Always, State)
--- a/src/exo/shared/models/model_cards.py
+++ b/src/exo/shared/models/model_cards.py
@@ -621,7 +621,7 @@ class ConfigData(BaseModel):

 async def get_config_data(model_id: ModelId) -> ConfigData:
    """Downloads and parses config.json for a model."""
-    from exo.download.download_utils import (
+    from exo.worker.download.download_utils import (
        download_file_with_retry,
        ensure_models_dir,
    )
@@ -643,11 +643,11 @@ async def get_config_data(model_id: ModelId) -> ConfigData:

 async def get_safetensors_size(model_id: ModelId) -> Memory:
    """Gets model size from safetensors index or falls back to HF API."""
-    from exo.download.download_utils import (
+    from exo.shared.types.worker.downloads import ModelSafetensorsIndex
+    from exo.worker.download.download_utils import (
        download_file_with_retry,
        ensure_models_dir,
    )
-    from exo.shared.types.worker.downloads import ModelSafetensorsIndex

    target_dir = (await ensure_models_dir()) / model_id.normalize()
    await aios.makedirs(target_dir, exist_ok=True)
--- a/src/exo/shared/types/api.py
+++ b/src/exo/shared/types/api.py
@@ -7,11 +7,10 @@ from pydantic import BaseModel, Field, field_validator
 from pydantic_core import PydanticUseDefault

 from exo.shared.models.model_cards import ModelCard, ModelId
-from exo.shared.types.common import CommandId, NodeId
+from exo.shared.types.common import CommandId
 from exo.shared.types.memory import Memory
 from exo.shared.types.worker.instances import Instance, InstanceId, InstanceMeta
-from exo.shared.types.worker.shards import Sharding, ShardMetadata
-from exo.utils.pydantic_ext import CamelCaseModel
+from exo.shared.types.worker.shards import Sharding

 FinishReason = Literal[
    "stop", "length", "tool_calls", "content_filter", "function_call", "error"
@@ -353,16 +352,3 @@ class ImageListItem(BaseModel, frozen=True):

 class ImageListResponse(BaseModel, frozen=True):
    data: list[ImageListItem]
-
-
-class StartDownloadParams(CamelCaseModel):
-    target_node_id: NodeId
-    shard_metadata: ShardMetadata
-
-
-class StartDownloadResponse(CamelCaseModel):
-    command_id: CommandId
-
-
-class DeleteDownloadResponse(CamelCaseModel):
-    command_id: CommandId
--- a/src/exo/shared/types/commands.py
+++ b/src/exo/shared/types/commands.py
@@ -1,6 +1,6 @@
 from pydantic import Field

-from exo.shared.models.model_cards import ModelCard, ModelId
+from exo.shared.models.model_cards import ModelCard
 from exo.shared.types.api import (
    ChatCompletionTaskParams,
    ImageEditsInternalParams,
@@ -9,7 +9,7 @@ from exo.shared.types.api import (
 from exo.shared.types.chunks import InputImageChunk
 from exo.shared.types.common import CommandId, NodeId
 from exo.shared.types.worker.instances import Instance, InstanceId, InstanceMeta
-from exo.shared.types.worker.shards import Sharding, ShardMetadata
+from exo.shared.types.worker.shards import Sharding
 from exo.utils.pydantic_ext import CamelCaseModel, TaggedModel


@@ -62,19 +62,6 @@ class RequestEventLog(BaseCommand):
    since_idx: int


-class StartDownload(BaseCommand):
-    target_node_id: NodeId
-    shard_metadata: ShardMetadata
-
-
-class DeleteDownload(BaseCommand):
-    target_node_id: NodeId
-    model_id: ModelId
-
-
-DownloadCommand = StartDownload | DeleteDownload
-
-
 Command = (
    TestCommand
    | RequestEventLog
@@ -92,8 +79,3 @@ Command = (
 class ForwarderCommand(CamelCaseModel):
    origin: NodeId
    command: Command
-
-
-class ForwarderDownloadCommand(CamelCaseModel):
-    origin: NodeId
-    command: DownloadCommand
--- a/src/exo/utils/keyed_backoff.py
+++ b/src/exo/utils/keyed_backoff.py
@@ -1,32 +0,0 @@
-import time
-from typing import Generic, TypeVar
-
-K = TypeVar("K")
-
-
-class KeyedBackoff(Generic[K]):
-    """Tracks exponential backoff state per key."""
-
-    def __init__(self, base: float = 0.5, cap: float = 10.0):
-        self._base = base
-        self._cap = cap
-        self._attempts: dict[K, int] = {}
-        self._last_time: dict[K, float] = {}
-
-    def should_proceed(self, key: K) -> bool:
-        """Returns True if enough time has elapsed since last attempt."""
-        now = time.monotonic()
-        last = self._last_time.get(key, 0.0)
-        attempts = self._attempts.get(key, 0)
-        delay = min(self._cap, self._base * (2.0**attempts))
-        return now - last >= delay
-
-    def record_attempt(self, key: K) -> None:
-        """Record that an attempt was made for this key."""
-        self._last_time[key] = time.monotonic()
-        self._attempts[key] = self._attempts.get(key, 0) + 1
-
-    def reset(self, key: K) -> None:
-        """Reset backoff state for a key (e.g., on success)."""
-        self._attempts.pop(key, None)
-        self._last_time.pop(key, None)
--- a/src/exo/worker/download/download_utils.py
+++ b/src/exo/worker/download/download_utils.py
@@ -24,13 +24,6 @@ from pydantic import (
    TypeAdapter,
 )

-from exo.download.huggingface_utils import (
-    filter_repo_objects,
-    get_allow_patterns,
-    get_auth_headers,
-    get_hf_endpoint,
-    get_hf_token,
-)
 from exo.shared.constants import EXO_MODELS_DIR
 from exo.shared.types.common import ModelId
 from exo.shared.types.memory import Memory
@@ -42,6 +35,13 @@ from exo.shared.types.worker.downloads import (
    RepoFileDownloadProgress,
 )
 from exo.shared.types.worker.shards import ShardMetadata
+from exo.worker.download.huggingface_utils import (
+    filter_repo_objects,
+    get_allow_patterns,
+    get_auth_headers,
+    get_hf_endpoint,
+    get_hf_token,
+)


 class HuggingFaceAuthenticationError(Exception):
--- a/src/exo/worker/download/huggingface_utils.py
+++ b/src/exo/worker/download/huggingface_utils.py
--- a/src/exo/worker/download/impl_shard_downloader.py
+++ b/src/exo/worker/download/impl_shard_downloader.py
@@ -5,13 +5,13 @@ from typing import AsyncIterator, Callable

 from loguru import logger

-from exo.download.download_utils import RepoDownloadProgress, download_shard
-from exo.download.shard_downloader import ShardDownloader
 from exo.shared.models.model_cards import MODEL_CARDS, ModelCard, ModelId
 from exo.shared.types.worker.shards import (
    PipelineShardMetadata,
    ShardMetadata,
 )
+from exo.worker.download.download_utils import RepoDownloadProgress, download_shard
+from exo.worker.download.shard_downloader import ShardDownloader


 def exo_shard_downloader(max_parallel_downloads: int = 8) -> ShardDownloader:
--- a/src/exo/worker/download/shard_downloader.py
+++ b/src/exo/worker/download/shard_downloader.py
@@ -5,13 +5,13 @@ from datetime import timedelta
 from pathlib import Path
 from typing import AsyncIterator, Callable

-from exo.download.download_utils import RepoDownloadProgress
 from exo.shared.models.model_cards import ModelCard, ModelId, ModelTask
 from exo.shared.types.memory import Memory
 from exo.shared.types.worker.shards import (
    PipelineShardMetadata,
    ShardMetadata,
 )
+from exo.worker.download.download_utils import RepoDownloadProgress


 # TODO: the PipelineShardMetadata getting reinstantiated is a bit messy. Should this be a classmethod?
--- a/src/exo/worker/engines/image/distributed_model.py
+++ b/src/exo/worker/engines/image/distributed_model.py
@@ -6,10 +6,10 @@ import mlx.core as mx
 from mflux.models.common.config.config import Config
 from PIL import Image

-from exo.download.download_utils import build_model_path
 from exo.shared.types.api import AdvancedImageParams
 from exo.shared.types.worker.instances import BoundInstance
 from exo.shared.types.worker.shards import PipelineShardMetadata
+from exo.worker.download.download_utils import build_model_path
 from exo.worker.engines.image.config import ImageModelConfig
 from exo.worker.engines.image.models import (
    create_adapter_for_model,
--- a/src/exo/worker/engines/mlx/utils_mlx.py
+++ b/src/exo/worker/engines/mlx/utils_mlx.py
@@ -41,7 +41,6 @@ import mlx.nn as nn
 from mlx_lm.utils import load_model
 from pydantic import RootModel

-from exo.download.download_utils import build_model_path
 from exo.shared.types.api import ChatCompletionMessageText
 from exo.shared.types.common import Host
 from exo.shared.types.memory import Memory
@@ -56,6 +55,7 @@ from exo.shared.types.worker.shards import (
    ShardMetadata,
    TensorShardMetadata,
 )
+from exo.worker.download.download_utils import build_model_path
 from exo.worker.engines.mlx import Model
 from exo.worker.engines.mlx.auto_parallel import (
    TimeoutCallback,
--- a/src/exo/worker/main.py
+++ b/src/exo/worker/main.py
@@ -1,9 +1,8 @@
 from datetime import datetime, timezone
 from random import random
-from typing import Iterator

 import anyio
-from anyio import CancelScope, create_task_group, fail_after
+from anyio import CancelScope, create_task_group, current_time, fail_after
 from anyio.abc import TaskGroup
 from loguru import logger

@@ -11,12 +10,7 @@ from exo.routing.connection_message import ConnectionMessage, ConnectionMessageT
 from exo.shared.apply import apply
 from exo.shared.models.model_cards import ModelId
 from exo.shared.types.api import ImageEditsInternalParams
-from exo.shared.types.commands import (
-    ForwarderCommand,
-    ForwarderDownloadCommand,
-    RequestEventLog,
-    StartDownload,
-)
+from exo.shared.types.commands import ForwarderCommand, RequestEventLog
 from exo.shared.types.common import CommandId, NodeId, SessionId
 from exo.shared.types.events import (
    Event,
@@ -24,6 +18,7 @@ from exo.shared.types.events import (
    ForwarderEvent,
    IndexedEvent,
    InputChunkReceived,
+    NodeDownloadProgress,
    NodeGatheredInfo,
    TaskCreated,
    TaskStatusUpdated,
@@ -41,12 +36,23 @@ from exo.shared.types.tasks import (
    TaskStatus,
 )
 from exo.shared.types.topology import Connection, SocketConnection
+from exo.shared.types.worker.downloads import (
+    DownloadCompleted,
+    DownloadFailed,
+    DownloadOngoing,
+    DownloadPending,
+    DownloadProgress,
+)
 from exo.shared.types.worker.runners import RunnerId
+from exo.shared.types.worker.shards import ShardMetadata
 from exo.utils.channels import Receiver, Sender, channel
 from exo.utils.event_buffer import OrderedBuffer
 from exo.utils.info_gatherer.info_gatherer import GatheredInfo, InfoGatherer
 from exo.utils.info_gatherer.net_profile import check_reachable
-from exo.utils.keyed_backoff import KeyedBackoff
+from exo.worker.download.download_utils import (
+    map_repo_download_progress_to_download_progress_data,
+)
+from exo.worker.download.shard_downloader import RepoDownloadProgress, ShardDownloader
 from exo.worker.plan import plan
 from exo.worker.runner.runner_supervisor import RunnerSupervisor

@@ -56,29 +62,31 @@ class Worker:
        self,
        node_id: NodeId,
        session_id: SessionId,
+        shard_downloader: ShardDownloader,
        *,
        connection_message_receiver: Receiver[ConnectionMessage],
        global_event_receiver: Receiver[ForwarderEvent],
        local_event_sender: Sender[ForwarderEvent],
-        # This is for requesting updates. It doesn't need to be a general command sender right now,
-        # but I think it's the correct way to be thinking about commands
        command_sender: Sender[ForwarderCommand],
-        download_command_sender: Sender[ForwarderDownloadCommand],
-        event_index_counter: Iterator[int],
+        state_catchup_receiver: Receiver[State],
    ):
        self.node_id: NodeId = node_id
        self.session_id: SessionId = session_id

+        self.shard_downloader: ShardDownloader = shard_downloader
+        self._pending_downloads: dict[RunnerId, ShardMetadata] = {}
+
        self.global_event_receiver = global_event_receiver
        self.local_event_sender = local_event_sender
-        self.event_index_counter = event_index_counter
+        self.state_catchup_receiver = state_catchup_receiver
+        self.local_event_index = 0
        self.command_sender = command_sender
-        self.download_command_sender = download_command_sender
        self.connection_message_receiver = connection_message_receiver
        self.event_buffer = OrderedBuffer[Event]()
        self.out_for_delivery: dict[EventId, ForwarderEvent] = {}

        self.state: State = State()
+        self.download_status: dict[ModelId, DownloadProgress] = {}
        self.runners: dict[RunnerId, RunnerSupervisor] = {}
        self._tg: TaskGroup = create_task_group()

@@ -93,8 +101,6 @@ class Worker:
        self.input_chunk_buffer: dict[CommandId, dict[int, str]] = {}
        self.input_chunk_counts: dict[CommandId, int] = {}

-        self._download_backoff: KeyedBackoff[ModelId] = KeyedBackoff(base=0.5, cap=10.0)
-
    async def run(self):
        logger.info("Starting Worker")

@@ -105,16 +111,17 @@ class Worker:
            tg.start_soon(info_gatherer.run)
            tg.start_soon(self._forward_info, info_recv)
            tg.start_soon(self.plan_step)
+            tg.start_soon(self._emit_existing_download_progress)
            tg.start_soon(self._connection_message_event_writer)
            tg.start_soon(self._resend_out_for_delivery)
            tg.start_soon(self._event_applier)
            tg.start_soon(self._forward_events)
            tg.start_soon(self._poll_connection_updates)
+            tg.start_soon(self._check_catchup_state)

        # Actual shutdown code - waits for all tasks to complete before executing.
        self.local_event_sender.close()
        self.command_sender.close()
-        self.download_command_sender.close()
        for runner in self.runners.values():
            runner.shutdown()

@@ -129,6 +136,22 @@ class Worker:
                    )
                )

+    async def _check_catchup_state(self):
+        with self.state_catchup_receiver as states:
+            async for state in states:
+                if (
+                    self.state.last_event_applied_idx == -1
+                    and state.last_event_applied_idx > self.state.last_event_applied_idx
+                ):
+                    logger.info(
+                        f"Worker catching up state to idx {state.last_event_applied_idx}"
+                    )
+                    self.event_buffer.store = {}
+                    self.event_buffer.next_idx_to_release = (
+                        state.last_event_applied_idx + 1
+                    )
+                    self.state = state
+
    async def _event_applier(self):
        with self.global_event_receiver as events:
            async for f_event in events:
@@ -173,9 +196,11 @@ class Worker:
    async def plan_step(self):
        while True:
            await anyio.sleep(0.1)
+            # 3. based on the updated state, we plan & execute an operation.
            task: Task | None = plan(
                self.node_id,
                self.runners,
+                self.download_status,
                self.state.downloads,
                self.state.instances,
                self.state.runners,
@@ -199,26 +224,42 @@ class Worker:
                        )
                    )
                case DownloadModel(shard_metadata=shard):
-                    model_id = shard.model_card.model_id
-                    if not self._download_backoff.should_proceed(model_id):
-                        continue
-
-                    self._download_backoff.record_attempt(model_id)
-
-                    await self.download_command_sender.send(
-                        ForwarderDownloadCommand(
-                            origin=self.node_id,
-                            command=StartDownload(
-                                target_node_id=self.node_id,
-                                shard_metadata=shard,
-                            ),
+                    if shard.model_card.model_id not in self.download_status:
+                        progress = DownloadPending(
+                            shard_metadata=shard, node_id=self.node_id
+                        )
+                        self.download_status[shard.model_card.model_id] = progress
+                        await self.event_sender.send(
+                            NodeDownloadProgress(download_progress=progress)
+                        )
+                    initial_progress = (
+                        await self.shard_downloader.get_shard_download_status_for_shard(
+                            shard
                        )
                    )
-                    await self.event_sender.send(
-                        TaskStatusUpdated(
-                            task_id=task.task_id, task_status=TaskStatus.Running
+                    if initial_progress.status == "complete":
+                        progress = DownloadCompleted(
+                            shard_metadata=shard,
+                            node_id=self.node_id,
+                            total_bytes=initial_progress.total_bytes,
                        )
-                    )
+                        self.download_status[shard.model_card.model_id] = progress
+                        await self.event_sender.send(
+                            NodeDownloadProgress(download_progress=progress)
+                        )
+                        await self.event_sender.send(
+                            TaskStatusUpdated(
+                                task_id=task.task_id,
+                                task_status=TaskStatus.Complete,
+                            )
+                        )
+                    else:
+                        await self.event_sender.send(
+                            TaskStatusUpdated(
+                                task_id=task.task_id, task_status=TaskStatus.Running
+                            )
+                        )
+                        self._handle_shard_download_process(task, initial_progress)
                case Shutdown(runner_id=runner_id):
                    try:
                        with fail_after(3):
@@ -318,10 +359,7 @@ class Worker:
        # We request all events after (and including) the missing index.
        # This function is started whenever we receive an event that is out of sequence.
        # It is cancelled as soon as we receiver an event that is in sequence.
-
-        if since_idx < 0:
-            logger.warning(f"Negative value encountered for nack request {since_idx=}")
-            since_idx = 0
+        assert since_idx >= 0

        with CancelScope() as scope:
            self._nack_cancel_scope = scope
@@ -363,17 +401,104 @@ class Worker:
        self._tg.start_soon(runner.run)
        return runner

+    def _handle_shard_download_process(
+        self,
+        task: DownloadModel,
+        initial_progress: RepoDownloadProgress,
+    ):
+        """Manages the shard download process with progress tracking."""
+        status = DownloadOngoing(
+            node_id=self.node_id,
+            shard_metadata=task.shard_metadata,
+            download_progress=map_repo_download_progress_to_download_progress_data(
+                initial_progress
+            ),
+        )
+        self.download_status[task.shard_metadata.model_card.model_id] = status
+        self.event_sender.send_nowait(NodeDownloadProgress(download_progress=status))
+
+        last_progress_time = 0.0
+        throttle_interval_secs = 1.0
+
+        async def download_progress_callback(
+            shard: ShardMetadata, progress: RepoDownloadProgress
+        ) -> None:
+            nonlocal self
+            nonlocal last_progress_time
+            if progress.status == "complete":
+                status = DownloadCompleted(
+                    shard_metadata=shard,
+                    node_id=self.node_id,
+                    total_bytes=progress.total_bytes,
+                )
+                self.download_status[shard.model_card.model_id] = status
+                await self.event_sender.send(
+                    NodeDownloadProgress(download_progress=status)
+                )
+                await self.event_sender.send(
+                    TaskStatusUpdated(
+                        task_id=task.task_id, task_status=TaskStatus.Complete
+                    )
+                )
+            elif (
+                progress.status == "in_progress"
+                and current_time() - last_progress_time > throttle_interval_secs
+            ):
+                status = DownloadOngoing(
+                    node_id=self.node_id,
+                    shard_metadata=shard,
+                    download_progress=map_repo_download_progress_to_download_progress_data(
+                        progress
+                    ),
+                )
+                self.download_status[shard.model_card.model_id] = status
+                await self.event_sender.send(
+                    NodeDownloadProgress(download_progress=status)
+                )
+                last_progress_time = current_time()
+
+        self.shard_downloader.on_progress(download_progress_callback)
+
+        async def download_with_error_handling() -> None:
+            try:
+                await self.shard_downloader.ensure_shard(task.shard_metadata)
+            except Exception as e:
+                error_message = str(e)
+                logger.error(
+                    f"Download failed for {task.shard_metadata.model_card.model_id}: {error_message}"
+                )
+                failed_status = DownloadFailed(
+                    node_id=self.node_id,
+                    shard_metadata=task.shard_metadata,
+                    error_message=error_message,
+                )
+                self.download_status[task.shard_metadata.model_card.model_id] = (
+                    failed_status
+                )
+                await self.event_sender.send(
+                    NodeDownloadProgress(download_progress=failed_status)
+                )
+                await self.event_sender.send(
+                    TaskStatusUpdated(
+                        task_id=task.task_id, task_status=TaskStatus.Failed
+                    )
+                )
+
+        self._tg.start_soon(download_with_error_handling)
+
    async def _forward_events(self) -> None:
        with self.event_receiver as events:
            async for event in events:
-                idx = next(self.event_index_counter)
                fe = ForwarderEvent(
-                    origin_idx=idx,
+                    origin_idx=self.local_event_index,
                    origin=self.node_id,
                    session=self.session_id,
                    event=event,
                )
-                logger.debug(f"Worker published event {idx}: {str(event)[:100]}")
+                logger.debug(
+                    f"Worker published event {self.local_event_index}: {str(event)[:100]}"
+                )
+                self.local_event_index += 1
                await self.local_event_sender.send(fe)
                self.out_for_delivery[event.event_id] = fe

@@ -421,3 +546,42 @@ class Worker:
                    await self.event_sender.send(TopologyEdgeDeleted(conn=conn))

            await anyio.sleep(10)
+
+    async def _emit_existing_download_progress(self) -> None:
+        try:
+            while True:
+                logger.debug("Fetching and emitting existing download progress...")
+                async for (
+                    _,
+                    progress,
+                ) in self.shard_downloader.get_shard_download_status():
+                    if progress.status == "complete":
+                        status = DownloadCompleted(
+                            node_id=self.node_id,
+                            shard_metadata=progress.shard,
+                            total_bytes=progress.total_bytes,
+                        )
+                    elif progress.status in ["in_progress", "not_started"]:
+                        if progress.downloaded_bytes_this_session.in_bytes == 0:
+                            status = DownloadPending(
+                                node_id=self.node_id, shard_metadata=progress.shard
+                            )
+                        else:
+                            status = DownloadOngoing(
+                                node_id=self.node_id,
+                                shard_metadata=progress.shard,
+                                download_progress=map_repo_download_progress_to_download_progress_data(
+                                    progress
+                                ),
+                            )
+                    else:
+                        continue
+
+                    self.download_status[progress.shard.model_card.model_id] = status
+                    await self.event_sender.send(
+                        NodeDownloadProgress(download_progress=status)
+                    )
+                logger.debug("Done emitting existing download progress.")
+                await anyio.sleep(5 * 60)  # 5 minutes
+        except Exception as e:
+            logger.error(f"Error emitting existing download progress: {e}")
--- a/src/exo/worker/plan.py
+++ b/src/exo/worker/plan.py
@@ -2,6 +2,7 @@

 from collections.abc import Mapping, Sequence

+from exo.shared.models.model_cards import ModelId
 from exo.shared.types.common import CommandId, NodeId
 from exo.shared.types.tasks import (
    ChatCompletion,
@@ -44,6 +45,9 @@ def plan(
    node_id: NodeId,
    # Runners is expected to be FRESH and so should not come from state
    runners: Mapping[RunnerId, RunnerSupervisor],
+    # DL_status is expected to be FRESH and so should not come from state
+    download_status: Mapping[ModelId, DownloadProgress],
+    # gdls is not expected to be fresh
    global_download_status: Mapping[NodeId, Sequence[DownloadProgress]],
    instances: Mapping[InstanceId, Instance],
    all_runners: Mapping[RunnerId, RunnerStatus],  # all global
@@ -55,7 +59,7 @@ def plan(
    return (
        _kill_runner(runners, all_runners, instances)
        or _create_runner(node_id, runners, instances)
-        or _model_needs_download(node_id, runners, global_download_status)
+        or _model_needs_download(runners, download_status)
        or _init_distributed_backend(runners, all_runners)
        or _load_model(runners, all_runners, global_download_status)
        or _ready_to_warmup(runners, all_runners)
@@ -111,15 +115,9 @@ def _create_runner(


 def _model_needs_download(
-    node_id: NodeId,
    runners: Mapping[RunnerId, RunnerSupervisor],
-    global_download_status: Mapping[NodeId, Sequence[DownloadProgress]],
+    download_status: Mapping[ModelId, DownloadProgress],
 ) -> DownloadModel | None:
-    local_downloads = global_download_status.get(node_id, [])
-    download_status = {
-        dp.shard_metadata.model_card.model_id: dp for dp in local_downloads
-    }
-
    for runner in runners.values():
        model_id = runner.bound_instance.bound_shard.model_card.model_id
        if isinstance(runner.status, RunnerIdle) and (
--- a/src/exo/worker/tests/unittests/test_mlx/test_tokenizers.py
+++ b/src/exo/worker/tests/unittests/test_mlx/test_tokenizers.py
@@ -11,12 +11,12 @@ from pathlib import Path

 import pytest

-from exo.download.download_utils import (
+from exo.shared.models.model_cards import MODEL_CARDS, ModelCard, ModelId
+from exo.worker.download.download_utils import (
    download_file_with_retry,
    ensure_models_dir,
    fetch_file_list_with_cache,
 )
-from exo.shared.models.model_cards import MODEL_CARDS, ModelCard, ModelId
 from exo.worker.engines.mlx.utils_mlx import (
    get_eos_token_ids_for_model,
    load_tokenizer_for_model_id,
--- a/src/exo/worker/tests/unittests/test_plan/test_download_and_loading.py
+++ b/src/exo/worker/tests/unittests/test_plan/test_download_and_loading.py
@@ -1,5 +1,5 @@
 import exo.worker.plan as plan_mod
-from exo.shared.types.common import NodeId
+from exo.shared.types.common import ModelId, NodeId
 from exo.shared.types.memory import Memory
 from exo.shared.types.tasks import LoadModel
 from exo.shared.types.worker.downloads import DownloadCompleted, DownloadProgress
@@ -45,9 +45,13 @@ def test_plan_requests_download_when_waiting_and_shard_not_downloaded():
    instances = {INSTANCE_1_ID: instance}
    all_runners = {RUNNER_1_ID: RunnerIdle()}

+    # No entry for this shard -> should trigger DownloadModel
+    download_status: dict[ModelId, DownloadProgress] = {}
+
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status=download_status,
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -88,6 +92,14 @@ def test_plan_loads_model_when_all_shards_downloaded_and_waiting():
        RUNNER_2_ID: RunnerConnected(),
    }

+    # Local node has already marked its shard as downloaded (not actually used by _load_model)
+    local_download_status = {
+        MODEL_A_ID: DownloadCompleted(
+            shard_metadata=shard1, node_id=NODE_A, total_bytes=Memory()
+        )
+    }
+
+    # Global view has completed downloads for both nodes
    global_download_status = {
        NODE_A: [
            DownloadCompleted(
@@ -104,6 +116,7 @@ def test_plan_loads_model_when_all_shards_downloaded_and_waiting():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status=local_download_status,
        global_download_status=global_download_status,
        instances=instances,
        all_runners=all_runners,
@@ -135,19 +148,23 @@ def test_plan_does_not_request_download_when_shard_already_downloaded():
    instances = {INSTANCE_1_ID: instance}
    all_runners = {RUNNER_1_ID: RunnerIdle()}

-    # Global state shows shard is downloaded for NODE_A
+    # Local status claims the shard is downloaded already
+    local_download_status = {
+        MODEL_A_ID: DownloadCompleted(
+            shard_metadata=shard, node_id=NODE_A, total_bytes=Memory()
+        )
+    }
+
+    # Global view hasn't caught up yet (no completed shards recorded for NODE_A)
    global_download_status: dict[NodeId, list[DownloadProgress]] = {
-        NODE_A: [
-            DownloadCompleted(
-                shard_metadata=shard, node_id=NODE_A, total_bytes=Memory()
-            )
-        ],
+        NODE_A: [],
        NODE_B: [],
    }

    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status=local_download_status,
        global_download_status=global_download_status,
        instances=instances,
        all_runners=all_runners,
@@ -185,6 +202,12 @@ def test_plan_does_not_load_model_until_all_shards_downloaded_globally():
        RUNNER_2_ID: RunnerConnected(),
    }

+    # Only NODE_A's shard is recorded as downloaded globally
+    local_download_status = {
+        MODEL_A_ID: DownloadCompleted(
+            shard_metadata=shard1, node_id=NODE_A, total_bytes=Memory()
+        )
+    }
    global_download_status = {
        NODE_A: [
            DownloadCompleted(
@@ -197,6 +220,7 @@ def test_plan_does_not_load_model_until_all_shards_downloaded_globally():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status=local_download_status,
        global_download_status=global_download_status,
        instances=instances,
        all_runners=all_runners,
@@ -221,6 +245,7 @@ def test_plan_does_not_load_model_until_all_shards_downloaded_globally():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status=local_download_status,
        global_download_status=global_download_status,
        instances=instances,
        all_runners=all_runners,
--- a/src/exo/worker/tests/unittests/test_plan/test_runner_lifecycle.py
+++ b/src/exo/worker/tests/unittests/test_plan/test_runner_lifecycle.py
@@ -47,7 +47,8 @@ def test_plan_kills_runner_when_instance_missing():

    result = plan_mod.plan(
        node_id=NODE_A,
-        runners=runners,  # type: ignore[arg-type]
+        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -86,7 +87,8 @@ def test_plan_kills_runner_when_sibling_failed():

    result = plan_mod.plan(
        node_id=NODE_A,
-        runners=runners,  # type: ignore[arg-type]
+        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -118,6 +120,7 @@ def test_plan_creates_runner_when_missing_for_node():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -155,7 +158,8 @@ def test_plan_does_not_create_runner_when_supervisor_already_present():

    result = plan_mod.plan(
        node_id=NODE_A,
-        runners=runners,  # type: ignore[arg-type]
+        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -185,6 +189,7 @@ def test_plan_does_not_create_runner_for_unassigned_node():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
--- a/src/exo/worker/tests/unittests/test_plan/test_task_forwarding.py
+++ b/src/exo/worker/tests/unittests/test_plan/test_task_forwarding.py
@@ -65,6 +65,7 @@ def test_plan_forwards_pending_chat_completion_when_runner_ready():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -112,6 +113,7 @@ def test_plan_does_not_forward_chat_completion_if_any_runner_not_ready():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
@@ -156,6 +158,7 @@ def test_plan_does_not_forward_tasks_for_other_instances():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -218,6 +221,7 @@ def test_plan_ignores_non_pending_or_non_chat_tasks():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
@@ -257,6 +261,7 @@ def test_plan_returns_none_when_nothing_to_do():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
--- a/src/exo/worker/tests/unittests/test_plan/test_warmup.py
+++ b/src/exo/worker/tests/unittests/test_plan/test_warmup.py
@@ -57,6 +57,7 @@ def test_plan_starts_warmup_for_accepting_rank_when_all_loaded_or_warming():
    result = plan_mod.plan(
        node_id=NODE_B,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -98,6 +99,7 @@ def test_plan_starts_warmup_for_rank_zero_after_others_warming():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -138,6 +140,7 @@ def test_plan_does_not_start_warmup_for_non_zero_rank_until_all_loaded_or_warmin
    result = plan_mod.plan(
        node_id=NODE_B,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
@@ -182,6 +185,7 @@ def test_plan_does_not_start_warmup_for_rank_zero_until_others_warming():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -198,6 +202,7 @@ def test_plan_does_not_start_warmup_for_rank_zero_until_others_warming():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: []},
        instances=instances,
        all_runners=all_runners,
@@ -241,6 +246,7 @@ def test_plan_starts_warmup_for_connecting_rank_after_others_warming():
    result = plan_mod.plan(
        node_id=NODE_B,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_B: []},
        instances=instances,
        all_runners=all_runners,
@@ -283,6 +289,7 @@ def test_plan_does_not_start_warmup_for_accepting_rank_until_all_loaded_or_warmi
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
@@ -324,6 +331,7 @@ def test_plan_does_not_start_warmup_for_connecting_rank_until_others_warming():
    result = plan_mod.plan(
        node_id=NODE_A,
        runners=runners,  # type: ignore
+        download_status={},
        global_download_status={NODE_A: [], NODE_B: []},
        instances=instances,
        all_runners=all_runners,
--- a/tests/headless_runner.py
+++ b/tests/headless_runner.py
@@ -11,10 +11,6 @@ from hypercorn.asyncio import serve  # pyright: ignore[reportUnknownVariableType
 from loguru import logger
 from pydantic import BaseModel

-from exo.download.impl_shard_downloader import (
-    build_full_shard,
-    exo_shard_downloader,
-)
 from exo.shared.logging import InterceptLogger, logger_setup
 from exo.shared.models.model_cards import MODEL_CARDS, ModelId
 from exo.shared.types.api import ChatCompletionMessage, ChatCompletionTaskParams
@@ -40,6 +36,10 @@ from exo.shared.types.worker.runners import RunnerId, ShardAssignments
 from exo.shared.types.worker.shards import PipelineShardMetadata, TensorShardMetadata
 from exo.utils.channels import MpReceiver, MpSender, channel, mp_channel
 from exo.utils.info_gatherer.info_gatherer import GatheredInfo, InfoGatherer
+from exo.worker.download.impl_shard_downloader import (
+    build_full_shard,
+    exo_shard_downloader,
+)
 from exo.worker.runner.bootstrap import entrypoint