fix(runner): soft workspace boundary + per-target throttle (#3493 #3599 #3605)

Replaces PR #3493's blanket fatal abort with a "tell the model + throttle
the bypass loop" policy.  Workspace-bound rejections are now ordinary
recoverable tool errors enriched with a structured "this is a hard policy
boundary" instruction; SSRF stays the only marker that aborts the turn.

Why the fatal-abort approach broke
----------------------------------
PR #3493 promoted every shell `_guard_command` and filesystem path-resolution
rejection to a turn-fatal RuntimeError.  Two of those messages (`path
outside working dir` and `path traversal detected`) are heuristic substring
scans on the raw command, so legitimate commands like `rm <ws>/x.txt
2>/dev/null` or `find . -type f` killed the user's turn (#3599).  On
channels with outbound dedupe (Telegram) the user just saw silence (#3605),
and the noise polluted the LLM's context until it started hallucinating
guard rejections on plain relative paths (#3597).

Why we still need *some* throttle
---------------------------------
The original #3493 pain point was real: the LLM, refused once, would
swap tools and try again -- read_file -> exec cat -> exec cp -> bash -c
-> ln -sf -> python -c open(...).  Just removing the fatal escape lets
that loop run wild until max_iterations.

What this commit does
---------------------
- `nanobot/utils/runtime.py`: add `workspace_violation_signature` and
  `repeated_workspace_violation_error`.  The signature normalizes
  filesystem `path` arguments and the first absolute path inside an
  exec command, so swapping tools against the same outside target hits
  the same throttle bucket.  Two soft attempts are allowed; the third
  attempt's tool result is replaced with a hard "stop trying to bypass"
  message that quotes the target path and tells the model to ask the
  user for help.

- `nanobot/agent/runner.py`: split classification into `_is_ssrf_violation`
  (still fatal) and `_is_workspace_violation` (now soft).  All three
  failure branches in `_run_tool` (prep_error / exception / Error
  result) route through a shared `_classify_violation` that bumps the
  per-turn workspace_violation_counts dict and either keeps the tool's
  own message or substitutes the throttle escalation.  `_execute_tools`
  now threads that dict alongside the existing external_lookup_counts.

- `nanobot/agent/tools/shell.py`: append a structured boundary note to
  every workspace-bound guard rejection (`working_dir could not be
  resolved`, `working_dir is outside`, `path outside working dir`,
  `path traversal detected`).  SSRF errors stay short and direct so the
  model doesn't try to "phrase around" them.  Existing `2>/dev/null`
  allow-list and benign device passthrough from the previous commit
  remain.

- `nanobot/agent/tools/filesystem.py`: append the same boundary note to
  the `outside allowed directory` PermissionError so read_file / write_file
  / list_dir errors give the LLM the same explicit hint.

Tests
-----
- `tests/utils/test_workspace_violation_throttle.py` (new): signature
  collapses across read_file/exec/python -c against the same path,
  different paths get independent budgets, escalation only fires after
  the third attempt.

- `tests/agent/test_runner.py`:
  - `test_runner_does_not_abort_on_workspace_violation_anymore` -- v2
    contract: filesystem PermissionError is now soft, runner moves to
    the next iteration and finalizes cleanly.
  - `test_is_ssrf_violation_remains_fatal` + the existing
    `test_runner_aborts_on_ssrf_violation` -- SSRF still aborts on the
    first attempt.
  - `test_runner_lets_llm_recover_from_shell_guard_path_outside` -- end
    to end recovery from `path outside working dir`.
  - `test_runner_throttles_repeated_workspace_bypass_attempts` -- four
    bypass attempts against the same outside target produce at least
    one `workspace_violation_escalated` event and the run completes
    naturally without aborting the turn.
  - The two `_execute_tools` direct-call tests now pass the new
    workspace_violation_counts dict.

- `tests/tools/test_tool_validation.py`: relax three `==` assertions
  to `startswith` + "hard policy boundary" substring check to match
  the new structured error messages.

- `tests/tools/test_exec_security.py` keeps the prior `2>/dev/null`
  regression and the `> /etc/issue` negative case from the previous
  commit on this branch -- they still pass under the new policy.

Coverage status: full pytest 2648 passed / 2 skipped (was 2638 / 2
on origin/main).  Ruff is clean for every file touched in this commit.

Co-authored-by: Cursor <cursoragent@cursor.com>

nanobot/agent/runner.py

@@ -33,6 +33,7 @@ from nanobot.utils.runtime import (
     ensure_nonempty_tool_result,
     is_blank_text,
     repeated_external_lookup_error,
+    repeated_workspace_violation_error,
 )
 
 _DEFAULT_ERROR_MESSAGE = "Sorry, I encountered an error calling the AI model."
@@ -239,6 +240,10 @@ class AgentRunner:
         stop_reason = "completed"
         tool_events: list[dict[str, str]] = []
         external_lookup_counts: dict[str, int] = {}
+        # Tracks repeated bypass attempts against the same outside-workspace
+        # target within this turn.  See ``repeated_workspace_violation_error``
+        # in ``nanobot.utils.runtime`` for the throttle policy.
+        workspace_violation_counts: dict[str, int] = {}
         empty_content_retries = 0
         length_recovery_count = 0
         had_injections = False
@@ -314,6 +319,7 @@ class AgentRunner:
                     spec,
                     tool_calls,
                     external_lookup_counts,
+                    workspace_violation_counts,
                 )
                 tool_events.extend(new_events)
                 context.tool_results = list(results)
@@ -698,20 +704,25 @@ class AgentRunner:
         spec: AgentRunSpec,
         tool_calls: list[ToolCallRequest],
         external_lookup_counts: dict[str, int],
+        workspace_violation_counts: dict[str, int],
     ) -> tuple[list[Any], list[dict[str, str]], BaseException | None]:
         batches = self._partition_tool_batches(spec, tool_calls)
         tool_results: list[tuple[Any, dict[str, str], BaseException | None]] = []
         for batch in batches:
             if spec.concurrent_tools and len(batch) > 1:
                 batch_results = await asyncio.gather(*(
-                    self._run_tool(spec, tool_call, external_lookup_counts)
+                    self._run_tool(
+                        spec, tool_call, external_lookup_counts, workspace_violation_counts,
+                    )
                     for tool_call in batch
                 ))
                 tool_results.extend(batch_results)
             else:
                 batch_results = []
                 for tool_call in batch:
-                    result = await self._run_tool(spec, tool_call, external_lookup_counts)
+                    result = await self._run_tool(
+                        spec, tool_call, external_lookup_counts, workspace_violation_counts,
+                    )
                     tool_results.append(result)
                     batch_results.append(result)
                     if isinstance(result[2], AskUserInterrupt):
@@ -734,6 +745,7 @@ class AgentRunner:
         spec: AgentRunSpec,
         tool_call: ToolCallRequest,
         external_lookup_counts: dict[str, int],
+        workspace_violation_counts: dict[str, int],
     ) -> tuple[Any, dict[str, str], BaseException | None]:
         hint = "\n\n[Analyze the error above and try a different approach.]"
         lookup_error = repeated_external_lookup_error(
@@ -763,16 +775,20 @@ class AgentRunner:
                 "status": "error",
                 "detail": prep_error.split(": ", 1)[-1][:120],
             }
-            if self._is_workspace_violation(prep_error):
+            handled = self._classify_violation(
-                logger.warning(
+                raw_text=prep_error,
-                    "Tool {} blocked by workspace/safety guard during preparation; aborting turn: {}",
+                soft_payload=prep_error + hint,
-                    tool_call.name,
+                ssrf_payload=prep_error,
-                    prep_error.replace("\n", " ").strip()[:200],
+                ssrf_error=RuntimeError(prep_error),
+                event=event,
+                tool_call=tool_call,
+                workspace_violation_counts=workspace_violation_counts,
+            )
+            if handled is not None:
+                return handled
+            return prep_error + hint, event, (
+                RuntimeError(prep_error) if spec.fail_on_tool_error else None
             )
-                event["detail"] = ("workspace_violation: "
-                                   + prep_error.replace("\n", " ").strip())[:160]
-                return prep_error, event, RuntimeError(prep_error)
-            return prep_error + hint, event, RuntimeError(prep_error) if spec.fail_on_tool_error else None
         try:
             if tool is not None:
                 result = await tool.execute(**params)
@@ -789,18 +805,25 @@ class AgentRunner:
             if isinstance(exc, AskUserInterrupt):
                 event["status"] = "waiting"
                 return "", event, exc
-            if self._is_workspace_violation(str(exc)):
+            payload = f"Error: {type(exc).__name__}: {exc}"
-                logger.warning(
+            handled = self._classify_violation(
-                    "Tool {} blocked by workspace/safety guard; aborting turn: {}",
+                raw_text=str(exc),
-                    tool_call.name,
+                # Match the legacy behavior here: the exception branch never
-                    str(exc).replace("\n", " ").strip()[:200],
+                # appended the "try a different approach" hint, even on the
+                # workspace-violation path -- preserve that for callers that
+                # eyeball the exact tool message.
+                soft_payload=payload,
+                ssrf_payload=payload,
+                ssrf_error=exc,
+                event=event,
+                tool_call=tool_call,
+                workspace_violation_counts=workspace_violation_counts,
             )
-                event["detail"] = ("workspace_violation: "
+            if handled is not None:
-                                   + str(exc).replace("\n", " ").strip())[:160]
+                return handled
-                return f"Error: {type(exc).__name__}: {exc}", event, exc
             if spec.fail_on_tool_error:
-                return f"Error: {type(exc).__name__}: {exc}", event, exc
+                return payload, event, exc
-            return f"Error: {type(exc).__name__}: {exc}", event, None
+            return payload, event, None
 
         if isinstance(result, str) and result.startswith("Error"):
             event = {
@@ -808,17 +831,17 @@ class AgentRunner:
                 "status": "error",
                 "detail": result.replace("\n", " ").strip()[:120],
             }
-
+            handled = self._classify_violation(
-            # check the outside workspace error and break loop
+                raw_text=result,
-            if self._is_workspace_violation(result):
+                soft_payload=result + hint,
-                logger.warning(
+                ssrf_payload=result,
-                    "Tool {} blocked by workspace/safety guard; aborting turn: {}",
+                ssrf_error=RuntimeError(result),
-                    tool_call.name,
+                event=event,
-                    result.replace("\n", " ").strip()[:200],
+                tool_call=tool_call,
+                workspace_violation_counts=workspace_violation_counts,
             )
-                event["detail"] = ("workspace_violation: "
+            if handled is not None:
-                                   + result.replace("\n", " ").strip())[:160]
+                return handled
-                return result, event, RuntimeError(result)
             if spec.fail_on_tool_error:
                 return result + hint, event, RuntimeError(result)
             return result + hint, event, None
@@ -831,39 +854,103 @@ class AgentRunner:
             detail = detail[:120] + "..."
         return result, {"name": tool_call.name, "status": "ok", "detail": detail}, None
 
-    # Markers identifying tool results that represent a *hard* workspace /
+    # SSRF rejections remain a hard, non-recoverable safety boundary: a single
-    # safety boundary rejection -- only these abort the agent loop.
+    # successful internal-URL fetch can leak cloud metadata, so we never let
-    #
+    # the LLM "retry" with a different phrasing of the same target.
-    # We deliberately keep this list narrow (#3599 / #3605):
+    _SSRF_MARKER: str = "internal/private url detected"
-    # - The first four come from explicit path-resolution checks in
+
-    #   ``filesystem.py`` and ``shell.py`` that cannot false-positive on user
+    # Markers that identify "tried to access something outside the workspace".
-    #   payloads -- if you see them, the LLM truly tried to escape the
+    # Unlike SSRF these are intentionally *non-fatal* (#3599 / #3605):
-    #   workspace.
+    # - The structured error message itself tells the model not to bypass.
-    # - "internal/private url detected" stays fatal because SSRF is a real
+    # - ``repeated_workspace_violation_error`` throttles the loop reported
-    #   security boundary; allowing the LLM to "retry" would just let it
+    #   in #3493 by escalating after two attempts against the same target.
-    #   poke internal infra with a different URL phrasing.
+    # - max_iterations is the ultimate ceiling, so we never need to abort.
-    # - "path traversal detected" and "path outside working dir" are
+    _WORKSPACE_VIOLATION_MARKERS: tuple[str, ...] = (
-    #   intentionally *not* listed: both come from the heuristic
-    #   ``_guard_command`` checks in ``shell.py`` which scan the raw command
-    #   string and routinely false-positive on legitimate constructs (e.g.
-    #   ``2>/dev/null`` redirects, quoted ``..`` arguments to ``sed`` /
-    #   ``find``, paths inside inline scripts).  Treating them as fatal
-    #   silently kills user turns (#3599) and prevents the agent from
-    #   self-correcting by trying a different approach (#3605).
-    _WORKSPACE_BLOCK_MARKERS: tuple[str, ...] = (
         "outside the configured workspace",
         "outside allowed directory",
         "working_dir is outside",
         "working_dir could not be resolved",
-        "internal/private url detected",
+        "path outside working dir",
+        "path traversal detected",
     )
 
+    @classmethod
+    def _is_ssrf_violation(cls, text: str) -> bool:
+        return bool(text) and cls._SSRF_MARKER in text.lower()
+
     @classmethod
     def _is_workspace_violation(cls, text: str) -> bool:
+        """True when *text* looks like *any* policy boundary rejection.
+
+        Kept as a public-ish hook for callers that need a yes/no signal
+        (logging, telemetry).  The runner itself uses the more specific
+        ``_is_ssrf_violation`` to decide what is fatal.
+        """
         if not text:
             return False
         lowered = text.lower()
-        return any(marker in lowered for marker in cls._WORKSPACE_BLOCK_MARKERS)
+        if cls._SSRF_MARKER in lowered:
+            return True
+        return any(marker in lowered for marker in cls._WORKSPACE_VIOLATION_MARKERS)
+
+    def _classify_violation(
+        self,
+        *,
+        raw_text: str,
+        soft_payload: str,
+        ssrf_payload: str,
+        ssrf_error: BaseException,
+        event: dict[str, str],
+        tool_call: ToolCallRequest,
+        workspace_violation_counts: dict[str, int],
+    ) -> tuple[Any, dict[str, str], BaseException | None] | None:
+        """Apply violation policy to a tool failure, or pass through.
+
+        Returns a fully-formed (payload, event, error) triple when *raw_text*
+        looks like a policy boundary rejection.  Returns ``None`` when the
+        caller should fall through to its generic per-branch handling.
+
+        - SSRF stays fatal -- a single successful internal fetch can leak
+          cloud metadata, so retrying with a different URL phrasing is
+          never acceptable.  We mutate ``event`` in place so the caller's
+          telemetry stays consistent.
+        - All other workspace-bound rejections become soft tool errors.
+          Each repeated attempt against the same outside target bumps a
+          per-turn counter; after the soft retry budget is exhausted we
+          replace the message body with an explicit "stop trying to bypass
+          the policy" instruction (see #3493 for the original bypass-loop
+          that motivated PR #3493's hard-abort, and #3599 / #3605 for why
+          the hard-abort backfired).
+        """
+        if self._is_ssrf_violation(raw_text):
+            logger.warning(
+                "Tool {} blocked by SSRF guard; aborting turn: {}",
+                tool_call.name,
+                raw_text.replace("\n", " ").strip()[:200],
+            )
+            event["detail"] = ("workspace_violation: "
+                               + raw_text.replace("\n", " ").strip())[:160]
+            return ssrf_payload, event, ssrf_error
+
+        if self._is_workspace_violation(raw_text):
+            escalation = repeated_workspace_violation_error(
+                tool_call.name,
+                tool_call.arguments,
+                workspace_violation_counts,
+            )
+            event["detail"] = ("workspace_violation: "
+                               + raw_text.replace("\n", " ").strip())[:160]
+            if escalation is not None:
+                logger.warning(
+                    "Tool {} hit workspace boundary repeatedly; escalating hint",
+                    tool_call.name,
+                )
+                event["detail"] = ("workspace_violation_escalated: "
+                                   + raw_text.replace("\n", " ").strip())[:160]
+                return escalation, event, None
+            return soft_payload, event, None
+
+        return None
 
     async def _emit_checkpoint(
         self,

nanobot/agent/tools/filesystem.py

@@ -14,6 +14,13 @@ from nanobot.utils.helpers import build_image_content_blocks, detect_image_mime
 from nanobot.config.paths import get_media_dir
 
 
+_FS_WORKSPACE_BOUNDARY_NOTE = (
+    " (this is a hard policy boundary, not a transient failure; "
+    "do not retry with shell tricks or alternative tools, and ask "
+    "the user how to proceed if the resource is genuinely required)"
+)
+
+
 def _resolve_path(
     path: str,
     workspace: Path | None = None,
@@ -29,7 +36,10 @@ def _resolve_path(
         media_path = get_media_dir().resolve()
         all_dirs = [allowed_dir] + [media_path] + (extra_allowed_dirs or []) 
         if not any(_is_under(resolved, d) for d in all_dirs):
-            raise PermissionError(f"Path {path} is outside allowed directory {allowed_dir}")
+            raise PermissionError(
+                f"Path {path} is outside allowed directory {allowed_dir}"
+                + _FS_WORKSPACE_BOUNDARY_NOTE
+            )
     return resolved
 
 

nanobot/agent/tools/shell.py

@@ -19,6 +19,20 @@ from nanobot.config.paths import get_media_dir
 _IS_WINDOWS = sys.platform == "win32"
 
 
+# Appended to every workspace / safety guard rejection so the LLM is told
+# explicitly that this is a policy boundary (not a transient failure) and
+# that bypass loops will not change the answer.  The throttle in
+# ``nanobot.utils.runtime.repeated_workspace_violation_error`` upgrades
+# this further once the model keeps targeting the same path.
+_WORKSPACE_BOUNDARY_NOTE = (
+    "\n\nNote: this is a hard policy boundary, not a transient failure. "
+    "Do NOT retry with shell tricks (symlinks, base64 piping, alternative "
+    "tools, working_dir overrides). If the user genuinely needs this "
+    "resource, tell them you cannot reach it under the current "
+    "restrict_to_workspace policy and ask how to proceed."
+)
+
+
 @tool_parameters(
     tool_parameters_schema(
         command=StringSchema("The shell command to execute"),
@@ -129,9 +143,15 @@ class ExecTool(Tool):
                 requested = Path(cwd).expanduser().resolve()
                 workspace_root = Path(self.working_dir).expanduser().resolve()
             except Exception:
-                return "Error: working_dir could not be resolved"
+                return (
+                    "Error: working_dir could not be resolved"
+                    + _WORKSPACE_BOUNDARY_NOTE
+                )
             if requested != workspace_root and workspace_root not in requested.parents:
-                return "Error: working_dir is outside the configured workspace"
+                return (
+                    "Error: working_dir is outside the configured workspace"
+                    + _WORKSPACE_BOUNDARY_NOTE
+                )
 
         guard_error = self._guard_command(command, cwd)
         if guard_error:
@@ -305,11 +325,18 @@ class ExecTool(Tool):
 
         from nanobot.security.network import contains_internal_url
         if contains_internal_url(cmd):
+            # SSRF: stay short and direct.  The runner classifies this
+            # marker as a hard, non-recoverable boundary, so the
+            # _WORKSPACE_BOUNDARY_NOTE policy text doesn't apply here --
+            # we don't want the model to retry at all.
             return "Error: Command blocked by safety guard (internal/private URL detected)"
 
         if self.restrict_to_workspace:
             if "..\\" in cmd or "../" in cmd:
-                return "Error: Command blocked by safety guard (path traversal detected)"
+                return (
+                    "Error: Command blocked by safety guard (path traversal detected)"
+                    + _WORKSPACE_BOUNDARY_NOTE
+                )
 
             cwd_path = Path(cwd).resolve()
 
@@ -335,7 +362,10 @@ class ExecTool(Tool):
                     and media_path not in p.parents
                     and p != media_path
                 ):
-                    return "Error: Command blocked by safety guard (path outside working dir)"
+                    return (
+                        "Error: Command blocked by safety guard (path outside working dir)"
+                        + _WORKSPACE_BOUNDARY_NOTE
+                    )
 
         return None
 

nanobot/utils/runtime.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+import re
+from pathlib import Path
 from typing import Any
 
 from loguru import logger
@@ -10,6 +12,14 @@ from nanobot.utils.helpers import stringify_text_blocks
 
 _MAX_REPEAT_EXTERNAL_LOOKUPS = 2
 
+# Workspace-violation throttle: how many times the LLM is allowed to bump
+# against the same outside-workspace target *within a single turn* before the
+# tool result is escalated with a hard "stop trying to bypass the policy"
+# instruction.  Two free attempts give the model room to e.g. read_file then
+# fall back to exec without immediately escalating; the third attempt at the
+# same target is treated as a clear bypass loop.
+_MAX_REPEAT_WORKSPACE_VIOLATIONS = 2
+
 EMPTY_FINAL_RESPONSE_MESSAGE = (
     "I completed the tool steps but couldn't produce a final answer. "
     "Please try again or narrow the task."
@@ -95,3 +105,108 @@ def repeated_external_lookup_error(
         "Error: repeated external lookup blocked. "
         "Use the results you already have to answer, or try a meaningfully different source."
     )
+
+
+# --- Workspace-violation throttle --------------------------------------------
+#
+# When ``restrict_to_workspace`` is on and the LLM tries to read or exec
+# something outside of the workspace, we want to *tell* the model that it
+# hit a hard policy boundary -- not silently abort the whole turn and not
+# allow it to spin forever swapping ``read_file`` for ``exec cat`` for
+# ``python -c open(...)`` (the actual loop reported in #3493).  The strategy
+# is two-fold:
+#
+# 1. Each individual guard error already includes structured instructions
+#    that tell the model "don't try to bypass this; ask the user for help".
+# 2. We additionally count how many times the *same outside target* has
+#    been refused within the current turn.  After two free attempts the
+#    third refusal swaps in a much more forceful message that quotes the
+#    target path and explicitly orders the model to stop and surface the
+#    boundary back to the user.  The model is still free to do something
+#    else (different target, different question) -- only the bypass loop
+#    is interrupted.
+#
+# This intentionally does *not* fatal-abort the turn: max_iterations and
+# the empty-final-response retries already provide the ultimate ceiling
+# for runaway loops, and aborting is what produced the silent-hang bug
+# in #3605 in the first place.
+
+_OUTSIDE_PATH_PATTERN = re.compile(r"(?:^|[\s|>'\"])((?:/[^\s\"'>;|<]+)|(?:~[^\s\"'>;|<]+))")
+
+
+def workspace_violation_signature(
+    tool_name: str,
+    arguments: dict[str, Any],
+) -> str | None:
+    """Return a stable signature for the outside-workspace target a tool tried.
+
+    The signature is shared across tool names so that the LLM cannot bypass
+    the throttle by switching from ``read_file`` to ``exec cat`` to
+    ``python -c open(...)`` against the same path.  Returns ``None`` when
+    the call has no obvious outside target (e.g. SSRF rejections, deny
+    pattern hits, or tools whose argument shape we don't understand).
+    """
+    for key in ("path", "file_path", "target", "source", "destination"):
+        val = arguments.get(key)
+        if isinstance(val, str) and val.strip():
+            return _normalize_violation_target(val.strip())
+
+    if tool_name in {"exec", "shell"}:
+        cmd = str(arguments.get("command") or "").strip()
+        if cmd:
+            match = _OUTSIDE_PATH_PATTERN.search(cmd)
+            if match:
+                return _normalize_violation_target(match.group(1))
+        cwd = str(arguments.get("working_dir") or "").strip()
+        if cwd:
+            return _normalize_violation_target(cwd)
+
+    return None
+
+
+def _normalize_violation_target(raw: str) -> str:
+    """Normalize *raw* path so that equivalent spellings collide on the same key."""
+    try:
+        normalized = str(Path(raw).expanduser().resolve())
+    except Exception:
+        normalized = raw
+    return f"violation:{normalized}".lower()
+
+
+def repeated_workspace_violation_error(
+    tool_name: str,
+    arguments: dict[str, Any],
+    seen_counts: dict[str, int],
+) -> str | None:
+    """Return an escalated error string after repeated bypass attempts.
+
+    Returns ``None`` while the LLM is still within the soft retry budget --
+    callers should fall back to the tool's own error message in that case.
+    Once the budget is exceeded, returns a hard "stop trying" instruction
+    that quotes the offending target.  Throttle state lives in
+    *seen_counts* (a per-turn dict), so the budget naturally resets across
+    turns without persisting LLM-controlled keys.
+    """
+    signature = workspace_violation_signature(tool_name, arguments)
+    if signature is None:
+        return None
+    count = seen_counts.get(signature, 0) + 1
+    seen_counts[signature] = count
+    if count <= _MAX_REPEAT_WORKSPACE_VIOLATIONS:
+        return None
+    logger.warning(
+        "Escalating repeated workspace bypass attempt {} (attempt {})",
+        signature[:160],
+        count,
+    )
+    target = signature.split("violation:", 1)[1] if "violation:" in signature else signature
+    return (
+        "Error: refusing repeated workspace-bypass attempts.\n"
+        f"You have tried to access '{target}' (or an equivalent path) "
+        f"{count} times in this turn. This is a hard policy boundary -- "
+        "switching tools, shell tricks, working_dir overrides, symlinks, "
+        "or base64 piping will NOT change the answer. Stop retrying. "
+        "If the user genuinely needs this resource, tell them you cannot "
+        "access it and ask how they want to proceed (e.g. copy the file "
+        "into the workspace, or disable restrict_to_workspace for this run)."
+    )

tests/agent/test_runner.py

@@ -313,21 +313,33 @@ async def test_runner_returns_structured_tool_error():
 
 
 @pytest.mark.asyncio
-async def test_runner_stops_on_workspace_violation_without_fail_on_tool_error():
+async def test_runner_does_not_abort_on_workspace_violation_anymore():
+    """v2 behavior: workspace-bound rejections are *soft* tool errors.
+
+    Previously (PR #3493) any workspace boundary error became a fatal
+    RuntimeError that aborted the turn. That silently killed legitimate
+    workspace commands once the heuristic guard misfired (#3599 #3605), so
+    we now hand the error back to the LLM as a recoverable tool result and
+    rely on ``repeated_workspace_violation_error`` to throttle bypass loops.
+    """
     from nanobot.agent.runner import AgentRunSpec, AgentRunner
 
     provider = MagicMock()
     provider.chat_with_retry = AsyncMock(side_effect=[
         LLMResponse(
-            content="working",
+            content="trying outside",
-            tool_calls=[ToolCallRequest(id="call_1", name="read_file", arguments={"path": "/tmp/outside.md"})],
+            tool_calls=[ToolCallRequest(
+                id="call_1", name="read_file", arguments={"path": "/tmp/outside.md"},
+            )],
         ),
-        LLMResponse(content="should not continue", tool_calls=[]),
+        LLMResponse(content="ok, telling the user instead", tool_calls=[]),
     ])
     tools = MagicMock()
     tools.get_definitions.return_value = []
     tools.execute = AsyncMock(
-        side_effect=PermissionError("Path /tmp/outside.md is outside allowed directory /workspace")
+        side_effect=PermissionError(
+            "Path /tmp/outside.md is outside allowed directory /workspace"
+        )
     )
 
     runner = AgentRunner(provider)
@@ -336,71 +348,92 @@ async def test_runner_stops_on_workspace_violation_without_fail_on_tool_error():
         initial_messages=[],
         tools=tools,
         model="test-model",
-        max_iterations=2,
+        max_iterations=3,
         max_tool_result_chars=_MAX_TOOL_RESULT_CHARS,
     ))
 
-    assert provider.chat_with_retry.await_count == 1
+    assert provider.chat_with_retry.await_count == 2, (
-    assert result.stop_reason == "tool_error"
+        "workspace violation must NOT short-circuit the loop"
-    assert "outside allowed directory" in (result.error or "")
+    )
-    assert result.tool_events == [
+    assert result.stop_reason != "tool_error"
-        {
+    assert result.error is None
-            "name": "read_file",
+    assert result.final_content == "ok, telling the user instead"
-            "status": "error",
+    assert result.tool_events and result.tool_events[0]["status"] == "error"
-            "detail": "workspace_violation: Path /tmp/outside.md is outside allowed directory /workspace",
+    # Detail still carries the workspace_violation breadcrumb for telemetry,
-        }
+    # but the runner did not raise.
-    ]
+    assert "workspace_violation" in result.tool_events[0]["detail"]
 
 
-def test_is_workspace_violation_recognizes_ssrf_block():
+def test_is_ssrf_violation_remains_fatal():
-    """Internal/private URL block must be classified as a fatal workspace violation.
+    """SSRF rejections are the only marker that stays turn-fatal.
 
-    Regression guard: the deny/allowlist filter messages were intentionally split
+    A single successful internal-URL fetch can leak cloud metadata, so we
-    out of `_WORKSPACE_BLOCK_MARKERS` so the LLM can retry, but SSRF rejections
+    never let the LLM "retry" with a different URL phrasing -- contrast
-    are a hard security boundary and must remain fatal.
+    this with workspace-bound rejections which are soft + throttled in v2.
     """
     from nanobot.agent.runner import AgentRunner
 
     ssrf_msg = "Error: Command blocked by safety guard (internal/private URL detected)"
-    assert AgentRunner._is_workspace_violation(ssrf_msg) is True
+    assert AgentRunner._is_ssrf_violation(ssrf_msg) is True
 
-    # Sanity: deny/allowlist filter messages are deliberately *not* fatal.
+    # Workspace-bound markers are NOT classified as SSRF.
-    assert AgentRunner._is_workspace_violation(
+    assert AgentRunner._is_ssrf_violation(
-        "Error: Command blocked by deny pattern filter"
-    ) is False
-    assert AgentRunner._is_workspace_violation(
-        "Error: Command blocked by allowlist filter (not in allowlist)"
-    ) is False
-
-
-def test_is_workspace_violation_does_not_fatal_on_shell_guard_heuristics():
-    """#3599 / #3605 regression: shell guard heuristics must NOT be fatal.
-
-    ``path outside working dir`` and ``path traversal detected`` are produced
-    by best-effort string scans inside ``ExecTool._guard_command`` -- they
-    routinely false-positive on idiomatic constructs (``2>/dev/null``,
-    ``sed 's|x|../y|g'``) and should be surfaced to the LLM as recoverable
-    tool errors so it can switch tactics, not abort the whole turn.
-    """
-    from nanobot.agent.runner import AgentRunner
-
-    assert AgentRunner._is_workspace_violation(
         "Error: Command blocked by safety guard (path outside working dir)"
     ) is False
-    assert AgentRunner._is_workspace_violation(
+    assert AgentRunner._is_ssrf_violation(
-        "Error: Command blocked by safety guard (path traversal detected)"
+        "Path /tmp/x is outside allowed directory /ws"
+    ) is False
+    # Deny / allowlist filter messages stay non-fatal too.
+    assert AgentRunner._is_ssrf_violation(
+        "Error: Command blocked by deny pattern filter"
     ) is False
 
 
 @pytest.mark.asyncio
-async def test_runner_lets_llm_recover_from_shell_guard_path_outside():
+async def test_runner_aborts_on_ssrf_violation():
-    """End-to-end: a guard-blocked exec is a soft tool error, not a turn-fatal.
+    """SSRF still fatal-aborts the turn even though workspace ones are soft."""
+    from nanobot.agent.runner import AgentRunSpec, AgentRunner
 
-    Reporter scenario: a previous PR turned ``path outside working dir`` into
+    provider = MagicMock()
-    a turn-fatal RuntimeError, so when the false-positive guard fired the
+    provider.chat_with_retry = AsyncMock(side_effect=[
-    user got no further iterations and (depending on channel) a silent hang.
+        LLMResponse(
-    After narrowing the marker list, the runner must hand the error back to
+            content="curl-ing metadata",
-    the LLM and let the next iteration succeed normally.
+            tool_calls=[ToolCallRequest(
+                id="call_ssrf",
+                name="exec",
+                arguments={"command": "curl http://169.254.169.254"},
+            )],
+        ),
+        LLMResponse(content="should NOT be reached", tool_calls=[]),
+    ])
+    tools = MagicMock()
+    tools.get_definitions.return_value = []
+    tools.execute = AsyncMock(return_value=(
+        "Error: Command blocked by safety guard (internal/private URL detected)"
+    ))
+
+    runner = AgentRunner(provider)
+    result = await runner.run(AgentRunSpec(
+        initial_messages=[],
+        tools=tools,
+        model="test-model",
+        max_iterations=3,
+        max_tool_result_chars=_MAX_TOOL_RESULT_CHARS,
+    ))
+
+    assert provider.chat_with_retry.await_count == 1, "SSRF must abort immediately"
+    assert result.stop_reason == "tool_error"
+    assert "internal/private url detected" in (result.error or "").lower()
+
+
+@pytest.mark.asyncio
+async def test_runner_lets_llm_recover_from_shell_guard_path_outside():
+    """Reporter scenario for #3599 / #3605 -- guard hit, agent recovers.
+
+    The shell `_guard_command` heuristic fires on `2>/dev/null`-style
+    redirects and other shell idioms. Before v2 that abort'd the whole
+    turn (silent hang on Telegram per #3605); now the LLM gets the soft
+    error back and can finalize on the next iteration.
     """
     from nanobot.agent.runner import AgentRunSpec, AgentRunner
 
@@ -443,7 +476,66 @@ async def test_runner_lets_llm_recover_from_shell_guard_path_outside():
     assert result.error is None
     assert result.final_content == "recovered final answer"
     assert result.tool_events and result.tool_events[0]["status"] == "error"
-    assert "workspace_violation" not in result.tool_events[0]["detail"]
+    # v2: detail keeps the breadcrumb but the runner did not raise.
+    assert "workspace_violation" in result.tool_events[0]["detail"]
+
+
+@pytest.mark.asyncio
+async def test_runner_throttles_repeated_workspace_bypass_attempts():
+    """#3493 motivation: stop the LLM bypass loop without aborting the turn.
+
+    LLM keeps switching tools (read_file -> exec cat -> python -c open(...))
+    against the same outside path. After the soft retry budget is exhausted
+    the runner replaces the tool result with a hard "stop trying" message
+    so the model finally gives up and surfaces the boundary to the user.
+    """
+    from nanobot.agent.runner import AgentRunSpec, AgentRunner
+
+    bypass_attempts = [
+        ToolCallRequest(
+            id=f"a{i}", name="exec",
+            arguments={"command": f"cat /Users/x/Downloads/01.md  # try {i}"},
+        )
+        for i in range(4)
+    ]
+    responses: list[LLMResponse] = [
+        LLMResponse(content=f"try {i}", tool_calls=[bypass_attempts[i]])
+        for i in range(4)
+    ]
+    responses.append(LLMResponse(content="ok telling user", tool_calls=[]))
+
+    provider = MagicMock()
+    provider.chat_with_retry = AsyncMock(side_effect=responses)
+    tools = MagicMock()
+    tools.get_definitions.return_value = []
+    tools.execute = AsyncMock(
+        return_value="Error: Command blocked by safety guard (path outside working dir)"
+    )
+
+    runner = AgentRunner(provider)
+    result = await runner.run(AgentRunSpec(
+        initial_messages=[],
+        tools=tools,
+        model="test-model",
+        max_iterations=10,
+        max_tool_result_chars=_MAX_TOOL_RESULT_CHARS,
+    ))
+
+    # All 4 bypass attempts surface to the LLM (no fatal abort), and the
+    # runner finally completes once the LLM stops asking.
+    assert result.stop_reason != "tool_error"
+    assert result.error is None
+    assert result.final_content == "ok telling user"
+    # The third+ attempts must have been escalated -- look at the events.
+    escalated = [
+        ev for ev in result.tool_events
+        if ev["status"] == "error"
+        and ev["detail"].startswith("workspace_violation_escalated:")
+    ]
+    assert escalated, (
+        "expected at least one escalated workspace_violation event, got: "
+        f"{result.tool_events}"
+    )
 
 
 @pytest.mark.asyncio
@@ -924,6 +1016,7 @@ async def test_runner_batches_read_only_tools_before_exclusive_work():
             ToolCallRequest(id="rw1", name="write_a", arguments={}),
         ],
         {},
+        {},
     )
 
     assert shared_events[0:2] == ["start:read_a", "start:read_b"]
@@ -968,6 +1061,7 @@ async def test_runner_does_not_batch_exclusive_read_only_tools():
             ToolCallRequest(id="ro2", name="read_b", arguments={}),
         ],
         {},
+        {},
     )
 
     assert shared_events[0] == "start:read_a"

tests/tools/test_tool_validation.py

@@ -242,13 +242,21 @@ def test_exec_extract_absolute_paths_captures_quoted_paths() -> None:
 def test_exec_guard_blocks_home_path_outside_workspace(tmp_path) -> None:
     tool = ExecTool(restrict_to_workspace=True)
     error = tool._guard_command("cat ~/.nanobot/config.json", str(tmp_path))
-    assert error == "Error: Command blocked by safety guard (path outside working dir)"
+    assert error is not None
+    assert error.startswith(
+        "Error: Command blocked by safety guard (path outside working dir)"
+    )
+    assert "hard policy boundary" in error
 
 
 def test_exec_guard_blocks_quoted_home_path_outside_workspace(tmp_path) -> None:
     tool = ExecTool(restrict_to_workspace=True)
     error = tool._guard_command('cat "~/.nanobot/config.json"', str(tmp_path))
-    assert error == "Error: Command blocked by safety guard (path outside working dir)"
+    assert error is not None
+    assert error.startswith(
+        "Error: Command blocked by safety guard (path outside working dir)"
+    )
+    assert "hard policy boundary" in error
 
 
 def test_exec_guard_allows_media_path_outside_workspace(tmp_path, monkeypatch) -> None:
@@ -300,7 +308,11 @@ def test_exec_guard_blocks_windows_drive_root_outside_workspace(monkeypatch) ->
 
     tool = ExecTool(restrict_to_workspace=True)
     error = tool._guard_command("dir E:\\", "E:\\workspace")
-    assert error == "Error: Command blocked by safety guard (path outside working dir)"
+    assert error is not None
+    assert error.startswith(
+        "Error: Command blocked by safety guard (path outside working dir)"
+    )
+    assert "hard policy boundary" in error
 
 
 # --- cast_params tests ---

tests/utils/test_workspace_violation_throttle.py

@@ -0,0 +1,120 @@
+"""Tests for repeated_workspace_violation throttle and signature."""
+
+from __future__ import annotations
+
+from nanobot.utils.runtime import (
+    repeated_workspace_violation_error,
+    workspace_violation_signature,
+)
+
+
+def test_signature_for_filesystem_tools_uses_path_argument():
+    sig_a = workspace_violation_signature(
+        "read_file", {"path": "/Users/x/Downloads/01.md"}
+    )
+    sig_b = workspace_violation_signature(
+        "write_file", {"path": "/Users/x/Downloads/01.md"}
+    )
+    sig_c = workspace_violation_signature(
+        "edit_file", {"file_path": "/Users/x/Downloads/01.md"}
+    )
+
+    assert sig_a is not None
+    assert sig_a == sig_b == sig_c, (
+        "the throttle must collapse equivalent paths across different tools "
+        "so the LLM cannot bypass it by switching tool"
+    )
+    assert "/users/x/downloads/01.md" in sig_a
+
+
+def test_signature_for_exec_extracts_first_absolute_path_in_command():
+    sig = workspace_violation_signature(
+        "exec",
+        {"command": "cat /Users/x/Downloads/01.md && echo done"},
+    )
+    assert sig is not None
+    assert "/users/x/downloads/01.md" in sig
+
+
+def test_signature_collides_across_filesystem_and_exec_for_same_target():
+    """LLM bypass loops jump tools (read_file -> exec cat). Throttle must
+    treat both attempts as targeting the same outside resource."""
+    fs_sig = workspace_violation_signature(
+        "read_file", {"path": "/Users/x/Downloads/01.md"}
+    )
+    exec_sig = workspace_violation_signature(
+        "exec", {"command": "cat /Users/x/Downloads/01.md"}
+    )
+    assert fs_sig == exec_sig
+
+
+def test_signature_falls_back_to_working_dir_when_no_absolute_in_command():
+    sig = workspace_violation_signature(
+        "exec",
+        {"command": "ls -la", "working_dir": "/etc"},
+    )
+    assert sig is not None
+    assert "/etc" in sig
+
+
+def test_signature_is_none_for_unknown_tool_with_no_path():
+    assert workspace_violation_signature("web_search", {"query": "anything"}) is None
+    assert workspace_violation_signature("exec", {"command": "echo hello"}) is None
+
+
+def test_repeated_workspace_violation_returns_none_within_budget():
+    counts: dict[str, int] = {}
+    arguments = {"path": "/Users/x/Downloads/01.md"}
+
+    assert repeated_workspace_violation_error("read_file", arguments, counts) is None
+    assert repeated_workspace_violation_error("read_file", arguments, counts) is None
+
+
+def test_repeated_workspace_violation_escalates_after_third_attempt():
+    counts: dict[str, int] = {}
+    arguments = {"path": "/Users/x/Downloads/01.md"}
+
+    repeated_workspace_violation_error("read_file", arguments, counts)
+    repeated_workspace_violation_error("read_file", arguments, counts)
+    third = repeated_workspace_violation_error("read_file", arguments, counts)
+
+    assert third is not None
+    assert "refusing repeated workspace-bypass" in third
+    assert "/users/x/downloads/01.md" in third
+    assert "ask how they want to proceed" in third
+
+
+def test_repeated_workspace_violation_independent_per_target():
+    """Different outside paths must each get their own retry budget."""
+    counts: dict[str, int] = {}
+
+    repeated_workspace_violation_error(
+        "read_file", {"path": "/Users/x/Downloads/01.md"}, counts,
+    )
+    repeated_workspace_violation_error(
+        "read_file", {"path": "/Users/x/Downloads/01.md"}, counts,
+    )
+    # Different target, fresh budget.
+    assert repeated_workspace_violation_error(
+        "read_file", {"path": "/Users/x/Documents/notes.md"}, counts,
+    ) is None
+
+
+def test_repeated_workspace_violation_collapses_tool_switching():
+    """LLM switches from read_file to exec cat then to python -c open(...)
+    against the same path; the throttle must escalate on the third attempt."""
+    counts: dict[str, int] = {}
+
+    repeated_workspace_violation_error(
+        "read_file", {"path": "/Users/x/Downloads/01.md"}, counts,
+    )
+    repeated_workspace_violation_error(
+        "exec", {"command": "cat /Users/x/Downloads/01.md"}, counts,
+    )
+    third = repeated_workspace_violation_error(
+        "exec",
+        {"command": "python3 -c \"open('/Users/x/Downloads/01.md').read()\""},
+        counts,
+    )
+    assert third is not None
+    assert "refusing repeated workspace-bypass" in third