diff --git a/internal/cloud/server-workbench-http.test.ts b/internal/cloud/server-workbench-http.test.ts
index 98bb19ec..2daf1229 100644
--- a/internal/cloud/server-workbench-http.test.ts
+++ b/internal/cloud/server-workbench-http.test.ts
@@ -115,6 +115,39 @@ test("workbench turn projection treats retryable provider stream disconnect as a
   assert.equal(completedProjection.finalResponse?.text, "retry recovered");
 });
 
+test("workbench turn projection treats legacy agentrun-unreachable as retryable AgentRun transport interruption (#1853)", () => {
+  const traceId = "trc_retryable_legacy_agentrun_unreachable";
+  const result = {
+    traceId,
+    status: "failed",
+    failureKind: "agentrun-unreachable",
+    willRetry: true,
+    agentRun: {
+      runId: "run_retryable_legacy_agentrun_unreachable",
+      commandId: "cmd_retryable_legacy_agentrun_unreachable",
+      terminalStatus: "failed",
+      failureKind: "agentrun-unreachable",
+      willRetry: true
+    },
+    providerTrace: { failureKind: "agentrun-unreachable", willRetry: true }
+  };
+  const trace = {
+    traceId,
+    status: "failed",
+    events: [
+      { seq: 1, type: "error", status: "failed", errorCode: "agentrun-unreachable", failureKind: "agentrun-unreachable", willRetry: true, terminal: true }
+    ],
+    eventCount: 1
+  };
+  const projection = createWorkbenchTurnProjection({ traceId, result, trace });
+  assert.equal(projection.status, "retrying");
+  assert.equal(projection.running, true);
+  assert.equal(projection.terminal, false);
+  assert.equal(projection.finalResponse, null);
+  assert.equal(durableTraceStatus(trace.events), "retrying");
+  assert.equal(traceTerminalEvidence(trace), null);
+});
+
 test("workbench turn projection seals final response from authoritative terminal assistant trace event (#1629)", () => {
   const traceId = "trc_workbench_terminal_assistant_final";
   const finalText = [
diff --git a/internal/cloud/workbench-turn-projection.ts b/internal/cloud/workbench-turn-projection.ts
index cd30d2c6..c7098561 100644
--- a/internal/cloud/workbench-turn-projection.ts
+++ b/internal/cloud/workbench-turn-projection.ts
@@ -313,13 +313,13 @@ const RETRYABLE_AGENTRUN_TRANSPORT_FAILURE_KINDS = new Set([
 ]);
 
 function isRetryableAgentRunTransportFailureKind(kind) {
-  return RETRYABLE_AGENTRUN_TRANSPORT_FAILURE_KINDS.has(kind);
+  return RETRYABLE_AGENTRUN_TRANSPORT_FAILURE_KINDS.has(normalizedProjectionFailureKind(kind));
 }
 
 function retryableProviderInterruptionRecord(value) {
   const record = objectValue(value);
   if (!record) return null;
-  const kind = normalizeWorkbenchStatus(record.failureKind ?? record.errorCode ?? record.code ?? record.name);
+  const kind = normalizedProjectionFailureKind(record.failureKind ?? record.errorCode ?? record.code ?? record.name);
   if ((kind === "provider-stream-disconnected" || kind === "provider-unavailable" || isRetryableAgentRunTransportFailureKind(kind)) && record.willRetry === true) {
     return {
       failureKind: kind,
@@ -340,6 +340,12 @@ function retryableProviderInterruptionRecord(value) {
   return null;
 }
 
+function normalizedProjectionFailureKind(value) {
+  const kind = normalizeWorkbenchStatus(value);
+  if (kind === "agentrun-unreachable") return "agentrun-connect-failed";
+  return kind;
+}
+
 function hasTraceProjection(trace) {
   return Boolean(trace && trace.status !== "missing" && (normalizedEventCount(trace) > 0 || traceLastEvent(trace)));
 }