diff --git a/backend/apps/agents/manager/prompt/attachments.py b/backend/apps/agents/manager/prompt/attachments.py
index 14e61e51..01233a02 100644
--- a/backend/apps/agents/manager/prompt/attachments.py
+++ b/backend/apps/agents/manager/prompt/attachments.py
@@ -148,11 +148,11 @@ def _resolve_attachments(context_paths: list | None, api_type: str, model: str)
     # refused with concrete recovery actions.
     b64_total = 0
 
-    # Combined char budget across inline TEXT attachments. The per-file
-    # 512K read cap doesn't stop a user dropping 20 huge txt files in one
-    # turn and silently blowing the context window; this caps total inline
-    # text chars and truncates the tail when we'd cross it. Picked to roughly
-    # match 1M-window models (~375K tokens at 4 chars/token) while still
+    # Combined char budget across inline TEXT attachments. Per-file 512K read
+    # cap doesn't stop a user dropping 20 huge txt files in one turn and
+    # silently blowing the context window. Whole-file or refuse: partial files
+    # confuse the model and the user can't tell what's missing. Sized to
+    # roughly fit 1M-window models (~375K tokens at 4 chars/token) while
     # leaving room for prior conversation, the prompt, and tool turns.
     text_total_chars = 0
     text_total_cap = 1_500_000
@@ -179,25 +179,19 @@ def _resolve_attachments(context_paths: list | None, api_type: str, model: str)
             kind, media_type = _sniff_file_kind(head, os.path.basename(path))
 
             if kind == "text":
-                room = max(0, text_total_cap - text_total_chars)
-                if room <= 0:
+                with open(path, "r", errors="replace") as f:
+                    content = f.read(512_000)
+                if text_total_chars + len(content) > text_total_cap:
+                    room = max(0, text_total_cap - text_total_chars)
                     refusals.append(
-                        f"[Attached text file {os.path.basename(path)} skipped: combined inline-text "
-                        f"budget of {text_total_cap // 1000}K chars already used by earlier attachments this turn. "
-                        f"Detach a file or split into separate turns.]"
+                        f"[Attached text file {os.path.basename(path)} ({len(content) // 1000}K chars) "
+                        f"skipped: would exceed combined text-attachment cap of {text_total_cap // 1000}K chars "
+                        f"this turn (~{room // 1000}K left). Detach a file or split into separate turns.]"
                     )
                     continue
-                with open(path, "r", errors="replace") as f:
-                    content = f.read(min(512_000, room))
-                truncated_note = ""
-                if len(content) >= room and os.path.getsize(path) > room:
-                    truncated_note = (
-                        f"\n[truncated: only first {room} chars included; "
-                        f"combined text-attachment cap of {text_total_cap // 1000}K chars reached.]"
-                    )
                 text_total_chars += len(content)
                 sections.append(
-                    f"<context_file path=\"{path}\">\n{content}{truncated_note}\n</context_file>"
+                    f"<context_file path=\"{path}\">\n{content}\n</context_file>"
                 )
                 continue