diff --git a/workspace-server/internal/handlers/a2a_proxy_helpers.go b/workspace-server/internal/handlers/a2a_proxy_helpers.go
index bd406b4f..4932de31 100644
--- a/workspace-server/internal/handlers/a2a_proxy_helpers.go
+++ b/workspace-server/internal/handlers/a2a_proxy_helpers.go
@@ -58,24 +58,27 @@ func (h *WorkspaceHandler) handleA2ADispatchError(ctx context.Context, workspace
 	// Issue #110.
 	//
 	// #1870 Phase 1: before returning 503, enqueue the request for drain
-	// on next heartbeat. Returning 202 Accepted {queued:true} means the
-	// caller records "dispatched — queued" not "failed", eliminating the
-	// fan-out-storm drop pattern.
+	// on next heartbeat. Returning 202 Accepted {queued:true} as a SUCCESS
+	// (not an error) means callers record this as "dispatched — queued"
+	// not "failed", eliminating the fan-out-storm drop pattern.
+	//
+	// Critical: must return (status, body, NIL ERROR) so the caller's
+	// `if proxyErr != nil` branch doesn't fire. Returning a proxyA2AError
+	// with 202 status here was the original cycle 53 bug — callers saw
+	// proxyErr != nil and logged "delegation failed: proxy a2a error".
 	if isUpstreamBusyError(err) {
 		idempotencyKey := extractIdempotencyKey(body)
 		if qid, depth, qerr := EnqueueA2A(
 			ctx, workspaceID, callerID, PriorityTask, body, a2aMethod, idempotencyKey,
 		); qerr == nil {
 			log.Printf("ProxyA2A: target %s busy — enqueued as %s (depth=%d)", workspaceID, qid, depth)
-			return http.StatusAccepted, nil, &proxyA2AError{
-				Status: http.StatusAccepted,
-				Response: gin.H{
-					"queued":      true,
-					"queue_id":    qid,
-					"queue_depth": depth,
-					"message":     "workspace agent busy — request queued, will dispatch when capacity available",
-				},
-			}
+			respBody, _ := json.Marshal(gin.H{
+				"queued":      true,
+				"queue_id":    qid,
+				"queue_depth": depth,
+				"message":     "workspace agent busy — request queued, will dispatch when capacity available",
+			})
+			return http.StatusAccepted, respBody, nil
 		} else {
 			// Queue insert failed — fall through to legacy 503 behavior
 			// so callers still retry. We don't want a queue DB hiccup to
diff --git a/workspace-server/internal/handlers/a2a_queue.go b/workspace-server/internal/handlers/a2a_queue.go
index 177d6b82..dadc9256 100644
--- a/workspace-server/internal/handlers/a2a_queue.go
+++ b/workspace-server/internal/handlers/a2a_queue.go
@@ -16,6 +16,7 @@ import (
 	"encoding/json"
 	"errors"
 	"log"
+	"net/http"
 
 	"github.com/Molecule-AI/molecule-monorepo/platform/internal/db"
 )
@@ -233,11 +234,34 @@ func (h *WorkspaceHandler) DrainQueueForWorkspace(ctx context.Context, workspace
 	}
 	// logActivity=false: the original EnqueueA2A callsite already logged
 	// the dispatch attempt; re-logging here would double-count events.
-	_, _, proxyErr := h.proxyA2ARequest(ctx, workspaceID, item.Body, callerID, false)
+	status, _, proxyErr := h.proxyA2ARequest(ctx, workspaceID, item.Body, callerID, false)
+
+	// 202 Accepted = the dispatch was itself queued again (target still busy).
+	// That's not a failure — the queued item just stays queued naturally on
+	// the next drain tick. Mark this attempt completed so we don't double-
+	// count attempts; the new (re-)queue row already exists.
+	if status == http.StatusAccepted {
+		MarkQueueItemCompleted(ctx, item.ID)
+		log.Printf("A2AQueue drain: %s re-queued (target still busy)", item.ID)
+		return
+	}
+
 	if proxyErr != nil {
-		MarkQueueItemFailed(ctx, item.ID, proxyErr.Response["error"].(string))
-		log.Printf("A2AQueue drain: dispatch for %s failed (attempt=%d): %v",
-			item.ID, item.Attempts, proxyErr.Response["error"])
+		// Defensive: proxyErr.Response is gin.H (map[string]interface{}). The
+		// "error" key is conventionally a string but can be missing or non-
+		// string in edge paths (e.g. a future error builder using a typed
+		// struct). Cast safely so a missing key doesn't crash the platform —
+		// today's outage was caused by an unchecked .(string) here.
+		errMsg, _ := proxyErr.Response["error"].(string)
+		if errMsg == "" {
+			errMsg = http.StatusText(proxyErr.Status)
+			if errMsg == "" {
+				errMsg = "unknown drain dispatch error"
+			}
+		}
+		MarkQueueItemFailed(ctx, item.ID, errMsg)
+		log.Printf("A2AQueue drain: dispatch for %s failed (attempt=%d): %s",
+			item.ID, item.Attempts, errMsg)
 		return
 	}
 	MarkQueueItemCompleted(ctx, item.ID)