Put the user request last in the planner prompt (#7773)

Two changes to the `pdf_edit` selection prompt.

**The user's request moves to the end.** When a prompt exceeds the
model's context, Ollama keeps the tail and discards the head. The
request was the second line, so it was the first thing thrown away.
Ending with it makes the most important line the most likely to survive.

Reproduced on a local qwen3:8b before the change: five completely
different requests - convert to Word, merge two files, run OCR, add a
password, add a watermark - run sequentially at temperature 0 through
the production prompt shape all returned `COMPRESS_PDF`, and every one
reported `prompt_tokens: 2050` against a much larger prompt. The model
was not choosing badly; it was answering a question it had never been
shown.

This is defensive rather than a fix on its own - the real repair is
giving the model a context window large enough, and a prompt small
enough, to avoid truncation entirely. But the ordering is free and
correct regardless of context size.

**The duplicated unavailable-operations list is removed from the user
prompt.** It was rendered twice, once in the system prompt and again in
the user prompt. It is also counterproductive: it spends tokens teaching
the model names it must not use, and `handle()` already rejects a plan
referencing an unavailable operation in Python afterwards. The
system-prompt copy stays, so the model can still explain that an
operation exists but is not available here.

The existing test that asserted the list appears in the user prompt now
asserts it appears in the system prompt and not the user prompt.

Author: Frooodle

engine/src/stirling/agents/pdf_edit.py

@@ -282,9 +282,7 @@ async def _select_plan(
             unavailable_operations,
             allow_need_content=can_request_content,
         )
-        return await agent.select(
-            self._build_selection_prompt(request, supported_operations, unavailable_operations, repair_note)
-        )
+        return await agent.select(self._build_selection_prompt(request, supported_operations, repair_note))
 
     def _build_selection_agent(
         self,
@@ -330,7 +328,6 @@ def _build_selection_prompt(
         self,
         request: PdfEditRequest,
         supported_operations: Iterable[ToolEndpoint],
-        unavailable_operations: Iterable[ToolEndpoint],
         repair_note: str = "",
     ) -> str:
         repair_line = (
@@ -343,36 +340,20 @@ def _build_selection_prompt(
             if repair_note
             else ""
         )
-        unavailable_line = (
-            "Unavailable operations (exist but not currently usable): "
-            f"{self._get_operations_prompt(unavailable_operations)}\n"
-            if unavailable_operations
-            else ""
-        )
         return (
-            f"Conversation history:\n{format_conversation_history(request.conversation_history)}\n"
-            f"User request: {request.user_message}\n"
-            f"Files: {format_file_names(request.files)}\n"
             f"Supported operations:\n{self._get_supported_operations_prompt(supported_operations)}\n"
-            f"{unavailable_line}"
             f"{repair_line}"
-            f"Extracted page text:\n{format_page_text(request.page_text)}"
-            f"\n{language_directive()}"
+            f"Conversation history:\n{format_conversation_history(request.conversation_history)}\n"
+            f"Files: {format_file_names(request.files)}\n"
+            f"Extracted page text:\n{format_page_text(request.page_text)}\n"
+            f"{language_directive()}\n"
+            f"User request: {request.user_message}"
         )
 
-    # Endpoints that exist on the server and are callable via the direct API or the manual UI,
-    # but are never offered to the AI agent as a routing option.
-    #
-    # Why: REDACT_EXECUTE is the preferred AI-driven redaction route. AUTO_REDACT and REDACT are
-    # legacy endpoints that remain fully functional for human callers (the manual redact UI, direct
-    # API consumers, pipelines) but would produce a worse experience if the AI routed to them —
-    # they accept a simpler, less expressive schema and pre-date the unified operation model.
-    # Hiding them here channels all AI redaction traffic through REDACT_EXECUTE without disabling
-    # the legacy endpoints for anyone else.
-    #
-    # How to reuse: add an endpoint here whenever a legacy endpoint has a preferred replacement
-    # that the AI should use exclusively. The endpoint remains live on the server; only the AI
-    # planner is prevented from selecting it.
+    # Hidden from the AI planner only; still live for the manual UI, direct API and pipelines.
+    # AUTO_REDACT and REDACT pre-date the unified operation model and take a less expressive
+    # schema, so AI redaction is channelled through REDACT_EXECUTE. Add an endpoint here when a
+    # legacy one has a preferred replacement the AI should use exclusively.
     _AGENT_HIDDEN_ENDPOINTS: frozenset[ToolEndpoint] = frozenset({ToolEndpoint.AUTO_REDACT, ToolEndpoint.REDACT})
 
     def _classify_operations(self, request: PdfEditRequest) -> tuple[list[ToolEndpoint], list[ToolEndpoint]]:

engine/tests/test_pdf_edit_agent.py

@@ -144,7 +144,7 @@ def test_selection_prompt_says_nothing_about_output_formats(runtime: AppRuntime)
     # Compatibility is only raised once a plan has actually failed, so the operation list stays
     # about what each tool does. Leaking format hints here re-inflates an already large prompt.
     agent = StubPdfEditAgent(runtime, _ANY_SELECTION)
-    prompt = agent._build_selection_prompt(PdfEditRequest(user_message="anything", files=[]), list(OPERATIONS), [])
+    prompt = agent._build_selection_prompt(PdfEditRequest(user_message="anything", files=[]), list(OPERATIONS))
     assert "outputs:" not in prompt
     assert "IMAGE (several files)" not in prompt
 
@@ -156,7 +156,6 @@ def test_repair_prompt_offers_reorder_or_telling_the_user(runtime: AppRuntime) -
     prompt = agent._build_selection_prompt(
         PdfEditRequest(user_message="anything", files=[]),
         list(OPERATIONS),
-        [],
         "step 3 (SANITIZE_PDF) accepts PDF but the previous step produces IMAGE.",
     )
     assert "SANITIZE_PDF" in prompt
@@ -494,11 +493,13 @@ def test_pdf_edit_selection_prompt_includes_unavailable_operations(runtime: AppR
     )
     supported, unavailable = agent._classify_operations(request)
 
-    prompt = agent._build_selection_prompt(request, supported, unavailable)
+    selection_agent = agent._build_selection_agent(supported, unavailable, allow_need_content=False)
+    system_prompt = "".join(selection_agent.agent._system_prompts)
+    prompt = agent._build_selection_prompt(request, supported)
 
-    assert "Unavailable operations" in prompt
-    assert "OCR_PDF" in prompt
-    assert ToolEndpoint.OCR_PDF.value in prompt
+    assert "NOT currently available" in system_prompt
+    assert "OCR_PDF" in system_prompt
+    assert "OCR_PDF" not in prompt
 
 
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