fix(prompts): strip JSON fences at render time
Keep fenced examples readable in prompt Markdown while removing only JSON fence markers from the final assembled system prompt. Cover all bundled profiles and preserve non-JSON fences.
Alessandro committed
Jul 25, 2026 at 16:01 UTC
9f1e24a2dbc6fdb1f80f4997028ff1f3f9fc2a9e
6 files changed
+59
-7
AGENTS.md
+1
@@ -29,6 +29,7 @@
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- Use Linux paths and commands in examples.
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- When a live Dockerized Agent Zero target is explicitly named, verify that exact runtime instead of assuming a fixed localhost port.
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- Message-loop completion flows through a response tool with `break_loop`; plain or malformed Chat Completions text enters repair, and native Responses output text is normalized through the same response-tool path.
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+- Prompt Markdown may retain fenced JSON examples for readability; final system-prompt rendering removes only their JSON fence markers before model calls and preserves non-JSON fences.
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- Copy live core-plugin changes back into tracked source under `plugins/`.
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- Develop new custom plugins under ignored `usr/plugins/`; tracked bundled plugins live under `plugins/`.
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- Use the framework runtime for backend and plugin-hook verification, not the separate agent execution runtime.
agent.py
+4
-2
@@ -568,8 +568,10 @@ class Agent:
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"message_loop_prompts_after", self, loop_data=loop_data
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)
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- # concatenate system prompt
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- system_text = "\n\n".join(loop_data.system)
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+ # concatenate system prompt and remove JSON fence markers from examples
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+ system_text = files.remove_code_fences(
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+ "\n\n".join(loop_data.system), language="json"
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+ )
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# join protocol and extras
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protocol = self._build_context_message(
helpers/files.py
+8
-1
@@ -433,7 +433,14 @@ def find_existing_paths_by_pattern(pattern: str):
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return matches
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-def remove_code_fences(text):
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+def remove_code_fences(text, language: str | None = None):
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+ if language:
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+ pattern = (
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+ rf"(?ims)^[ \t]*(```|~~~)[ \t]*{re.escape(language)}[ \t]*\r?\n"
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+ r"(.*?)^[ \t]*\1[ \t]*\r?$"
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+ )
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+ return re.sub(pattern, lambda match: match.group(2), text)
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+
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# Pattern to match code fences with optional language specifier
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pattern = r"(```|~~~)(.*?\n)(.*?)(\1)"
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helpers/files.py.dox.md
+2
-2
@@ -33,7 +33,7 @@
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- `find_file_in_dirs(_filename: str, _directories: list[str])`: This function searches for a filename in a list of directories in order.
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- `get_unique_filenames_in_dirs(dir_paths: list[str], pattern: str=..., type: Literal['file', 'dir', 'any']=...)`
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- `find_existing_paths_by_pattern(pattern: str)`
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-- `remove_code_fences(text)`
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+- `remove_code_fences(text, language: str | None=...)`: Remove every code fence, or only fences for one language while preserving their contents.
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- `is_full_json_template(text)`
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- `write_file(relative_path: str, content: str, encoding: str=...)`
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- `delete_file(relative_path: str)`
@@ -55,7 +55,7 @@
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## Key Concepts
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-- Important called helpers/classes observed in the source: `os.path.dirname`, `os.path.abspath`, `find_file_in_dirs`, `is_full_json_template`, `remove_code_fences`, `evaluate_text_conditions`, `replace_placeholders_text`, `process_includes`, `re.compile`, `_process`, `get_abs_path`, `is_probably_binary_bytes`, `replace_value`, `re.sub`, `os.path.normpath`, `FileNotFoundError`, `result.sort`, `glob.glob`, `matches.sort`, `re.fullmatch`.
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+- Important called helpers/classes observed in the source: `os.path.dirname`, `os.path.abspath`, `find_file_in_dirs`, `is_full_json_template`, `remove_code_fences`, `evaluate_text_conditions`, `replace_placeholders_text`, `process_includes`, `re.compile`, `re.escape`, `_process`, `get_abs_path`, `is_probably_binary_bytes`, `replace_value`, `re.sub`, `os.path.normpath`, `FileNotFoundError`, `result.sort`, `glob.glob`, `matches.sort`, `re.fullmatch`.
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- Keep request/response, tool, or helper semantics documented here at the same time as source changes.
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## Work Guidance
prompts/agent.system.main.communication.md
+2
@@ -18,6 +18,7 @@
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Fences in the examples below are documentation formatting only. Your actual output starts with `{` and ends with `}` — no fences, no language tag, no prose.
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### Response example
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+~~~json
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{
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"thoughts": [
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"instructions?",
@@ -32,5 +33,6 @@ Fences in the examples below are documentation formatting only. Your actual outp
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"arg2": "val2"
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}
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}
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+~~~
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{{ include "agent.system.main.communication_additions.md" }}
tests/test_default_prompt_budget.py
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-2
@@ -19,7 +19,7 @@ def _iter_prompt_files():
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yield from prompts_dir.rglob("*.md")
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-async def _build_system_text(profile: str = "agent0") -> str:
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+async def _build_system_text(profile: str = "agent0", rendered: bool = False) -> str:
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old_args = dict(runtime.args)
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runtime.args.clear()
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runtime.args["dockerized"] = "true"
@@ -34,6 +34,9 @@ async def _build_system_text(profile: str = "agent0") -> str:
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set_current=False,
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)
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try:
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+ if rendered:
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+ prompt = await ctx.agent0.prepare_prompt(ctx.agent0.loop_data)
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+ return str(prompt[0].content)
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system = await ctx.agent0.get_system_prompt(ctx.agent0.loop_data)
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return "\n\n".join(system)
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finally:
@@ -45,6 +48,7 @@ async def _build_system_text(profile: str = "agent0") -> str:
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@pytest.mark.asyncio
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async def test_default_agent0_prompt_budget_and_guardrails():
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system_text = await _build_system_text()
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+ rendered_system_text = await _build_system_text(rendered=True)
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communication_prompt = (
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PROJECT_ROOT / "prompts" / "agent.system.main.communication.md"
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).read_text(encoding="utf-8")
@@ -66,7 +70,9 @@ async def test_default_agent0_prompt_budget_and_guardrails():
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assert '"tool_name": "memory_load"' in system_text
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assert "informative but tight" in system_text
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assert "Your actual output starts with `{` and ends with `}`" in system_text
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- assert "~~~json" not in communication_prompt
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+ assert "~~~json" in communication_prompt
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+ assert "~~~json" not in rendered_system_text
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+ assert "```json" not in rendered_system_text
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assert "# code_execution_remote tool" not in system_text
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assert "# text_editor_remote tool" not in system_text
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assert "### computer_use_remote" not in system_text
@@ -76,6 +82,40 @@ async def test_default_agent0_prompt_budget_and_guardrails():
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assert "Computer Use enablement is scoped to the current CLI session" not in system_text
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+@pytest.mark.asyncio
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+@pytest.mark.parametrize(
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+ "profile", ["agent0", "default", "developer", "researcher", "tiny-local"]
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+)
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+async def test_rendered_profiles_strip_json_fences(profile: str):
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+ system_text = await _build_system_text(profile, rendered=True)
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+
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+ assert "~~~json" not in system_text
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+ assert "```json" not in system_text
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+
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+ if profile == "researcher":
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+ assert "~~~python" in system_text
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+
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+
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+def test_remove_code_fences_can_target_json_only():
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+ from helpers import files
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+
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+ prompt = """Before
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+~~~json
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+{"tool_name":"response","tool_args":{"text":"done"}}
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+~~~
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+~~~python
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+print("keep me fenced")
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+~~~
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+After
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+"""
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+
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+ rendered = files.remove_code_fences(prompt, language="json")
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+
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+ assert "~~~json" not in rendered
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+ assert '{"tool_name":"response"' in rendered
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+ assert '~~~python\nprint("keep me fenced")\n~~~' in rendered
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+
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+
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@pytest.mark.asyncio
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async def test_tiny_local_profile_prompt_is_action_first_json_contract():
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system_text = await _build_system_text("tiny-local")