diff --git a/apps/harness/lib/harness/session_manager.ex b/apps/harness/lib/harness/session_manager.ex
index b3eca46f90..b5d51a5049 100644
--- a/apps/harness/lib/harness/session_manager.ex
+++ b/apps/harness/lib/harness/session_manager.ex
@@ -37,6 +37,8 @@ defmodule Harness.SessionManager do
   end
 
   defp start_session_with_module(session_module, thread_id, provider, params) do
+    params = maybe_inject_resume_cursor(params, thread_id, provider)
+
     child_spec =
       {session_module,
        %{
@@ -258,6 +260,38 @@ defmodule Harness.SessionManager do
     SnapshotServer.apply_event(event)
   end
 
+  @doc false
+  # Inject resumeCursor from SQLite binding if one exists and the provider matches.
+  # If the caller already supplied a resumeCursor, respect it (don't overwrite).
+  def maybe_inject_resume_cursor(%{"resumeCursor" => _} = params, _thread_id, _provider) do
+    params
+  end
+
+  def maybe_inject_resume_cursor(params, thread_id, provider) do
+    case Harness.Storage.get_binding(thread_id) do
+      %{provider: ^provider, resume_cursor_json: cursor_json} when is_binary(cursor_json) ->
+        case Jason.decode(cursor_json) do
+          {:ok, cursor} ->
+            normalized = normalize_resume_cursor(cursor)
+            Logger.info("Injecting resumeCursor from binding for #{thread_id} (#{provider})")
+            Map.put(params, "resumeCursor", normalized)
+
+          {:error, reason} ->
+            Logger.warning("Failed to decode binding cursor for #{thread_id}: #{inspect(reason)}")
+            params
+        end
+
+      _ ->
+        # No binding, provider mismatch, or nil cursor — start fresh
+        params
+    end
+  end
+
+  # Codex stores {"threadId": "..."} but CodexSession expects the raw string.
+  # Other providers store richer objects their session modules know how to parse.
+  defp normalize_resume_cursor(%{"threadId" => tid}) when is_binary(tid), do: tid
+  defp normalize_resume_cursor(cursor), do: cursor
+
   defp provider_module("codex"), do: {:ok, CodexSession}
   defp provider_module("claudeAgent"), do: {:ok, ClaudeSession}
   defp provider_module("opencode"), do: {:ok, OpenCodeSession}
diff --git a/apps/harness/test/harness/storage_test.exs b/apps/harness/test/harness/storage_test.exs
index 96b26b9149..5a924d0838 100644
--- a/apps/harness/test/harness/storage_test.exs
+++ b/apps/harness/test/harness/storage_test.exs
@@ -338,6 +338,85 @@ defmodule Harness.StorageTest do
     assert Storage.get_binding("t3").provider == "opencode"
   end
 
+  # --- Resume cursor injection tests (SessionManager.maybe_inject_resume_cursor) ---
+
+  alias Harness.SessionManager
+
+  test "injects resumeCursor when binding exists and provider matches" do
+    cursor = Jason.encode!(%{"threadId" => "codex-abc"})
+    :ok = Storage.upsert_binding("t1", "codex", cursor)
+
+    params = %{"threadId" => "t1", "provider" => "codex"}
+    result = SessionManager.maybe_inject_resume_cursor(params, "t1", "codex")
+
+    # Codex cursors are normalized: {"threadId":"abc"} → "abc" (raw string)
+    assert result["resumeCursor"] == "codex-abc"
+  end
+
+  test "does NOT inject resumeCursor when provider mismatches" do
+    cursor = Jason.encode!(%{"threadId" => "codex-abc"})
+    :ok = Storage.upsert_binding("t1", "codex", cursor)
+
+    params = %{"threadId" => "t1", "provider" => "cursor"}
+    result = SessionManager.maybe_inject_resume_cursor(params, "t1", "cursor")
+
+    refute Map.has_key?(result, "resumeCursor")
+  end
+
+  test "does NOT inject resumeCursor when no binding exists" do
+    params = %{"threadId" => "t1", "provider" => "codex"}
+    result = SessionManager.maybe_inject_resume_cursor(params, "t1", "codex")
+
+    refute Map.has_key?(result, "resumeCursor")
+  end
+
+  test "does NOT overwrite caller-supplied resumeCursor" do
+    cursor = Jason.encode!(%{"threadId" => "codex-abc"})
+    :ok = Storage.upsert_binding("t1", "codex", cursor)
+
+    params = %{"threadId" => "t1", "provider" => "codex", "resumeCursor" => %{"threadId" => "explicit"}}
+    result = SessionManager.maybe_inject_resume_cursor(params, "t1", "codex")
+
+    assert result["resumeCursor"] == %{"threadId" => "explicit"}
+  end
+
+  test "does NOT inject resumeCursor when cursor_json is nil" do
+    :ok = Storage.upsert_binding("t1", "codex", nil)
+
+    params = %{"threadId" => "t1", "provider" => "codex"}
+    result = SessionManager.maybe_inject_resume_cursor(params, "t1", "codex")
+
+    refute Map.has_key?(result, "resumeCursor")
+  end
+
+  test "multi-session: concurrent bindings for different threads don't cross-contaminate" do
+    :ok = Storage.upsert_binding("t1", "codex", Jason.encode!(%{"threadId" => "codex-1"}))
+    :ok = Storage.upsert_binding("t2", "cursor", Jason.encode!(%{"cursorChatId" => "cursor-1"}))
+    :ok = Storage.upsert_binding("t3", "opencode", Jason.encode!(%{"sessionId" => "oc-1"}))
+
+    r1 = SessionManager.maybe_inject_resume_cursor(%{}, "t1", "codex")
+    r2 = SessionManager.maybe_inject_resume_cursor(%{}, "t2", "cursor")
+    r3 = SessionManager.maybe_inject_resume_cursor(%{}, "t3", "opencode")
+
+    # Codex cursor normalized to raw string; others kept as maps
+    assert r1["resumeCursor"] == "codex-1"
+    assert r2["resumeCursor"] == %{"cursorChatId" => "cursor-1"}
+    assert r3["resumeCursor"] == %{"sessionId" => "oc-1"}
+  end
+
+  test "multi-session: same thread_id with different provider ignores stale binding" do
+    # Codex wrote a binding for t1
+    :ok = Storage.upsert_binding("t1", "codex", Jason.encode!(%{"threadId" => "codex-abc"}))
+
+    # Cursor tries to start on same thread — should NOT get Codex's cursor
+    result = SessionManager.maybe_inject_resume_cursor(%{}, "t1", "cursor")
+    refute Map.has_key?(result, "resumeCursor")
+
+    # Codex should still get its own cursor (normalized to raw string)
+    result = SessionManager.maybe_inject_resume_cursor(%{}, "t1", "codex")
+    assert result["resumeCursor"] == "codex-abc"
+  end
+
   # --- Integration: SnapshotServer recovery ---
 
   describe "SnapshotServer recovery" do
diff --git a/apps/server/src/provider/Layers/HarnessClientAdapter.ts b/apps/server/src/provider/Layers/HarnessClientAdapter.ts
index 71442c85a2..c9fa492957 100644
--- a/apps/server/src/provider/Layers/HarnessClientAdapter.ts
+++ b/apps/server/src/provider/Layers/HarnessClientAdapter.ts
@@ -917,10 +917,9 @@ function mapHarnessEventToRuntimeEvents(
     return providerMapped;
   }
 
-  // Silently drop unrecognised events. Provider-specific notifications that
-  // pass through the GenServer (e.g. Codex app-server lifecycle events) are
-  // not bugs — they're simply events with no canonical mapping. The raw event
-  // stream still contains them for debugging.
+  // Unmapped events are already logged by codexMapToRuntimeEvents (which
+  // handles both QUIET_UNMAPPED_EVENTS suppression and console.debug for
+  // genuinely unknown methods). No additional logging needed here.
   return [];
 }
 
diff --git a/apps/server/src/provider/Layers/codexEventMapping.test.ts b/apps/server/src/provider/Layers/codexEventMapping.test.ts
index 1334b1e2cc..4041e838cf 100644
--- a/apps/server/src/provider/Layers/codexEventMapping.test.ts
+++ b/apps/server/src/provider/Layers/codexEventMapping.test.ts
@@ -2,15 +2,9 @@
  * Unit tests for codexEventMapping — calls mapToRuntimeEvents directly
  * without the full adapter/stream infrastructure.
  */
-import { describe, it, expect } from "bun:test";
+import { describe, it, expect } from "vitest";
 import { mapToRuntimeEvents } from "./codexEventMapping.ts";
-import {
-  EventId,
-  type ProviderEvent,
-  ProviderItemId,
-  ThreadId,
-  TurnId,
-} from "@t3tools/contracts";
+import { EventId, type ProviderEvent, ProviderItemId, ThreadId, TurnId } from "@t3tools/contracts";
 
 const threadId = ThreadId.makeUnsafe("thread-1");
 
diff --git a/apps/server/src/provider/Layers/codexEventMapping.ts b/apps/server/src/provider/Layers/codexEventMapping.ts
index fd2d5e1ad4..d3a1fdd916 100644
--- a/apps/server/src/provider/Layers/codexEventMapping.ts
+++ b/apps/server/src/provider/Layers/codexEventMapping.ts
@@ -514,6 +514,8 @@ const QUIET_UNMAPPED_EVENTS = new Set([
   "hook_response",
   "user",
   "thinking",
+  // Raw equivalents of item/agentMessage/delta (already mapped).
+  // Mapping these would cause duplicate deltas in the UI.
   "codex/event/agent_message_delta",
   "codex/event/agent_message",
   "codex/event/agent_message_content_delta",