fix(runtime): agents can finally Edit/Write — drop global deny + fix abs path syntax (#167)

Smoke-10..14: every agent (developers included) got "Edit exists but is
not enabled in this context" and fell back to destructive bash
redirection (a 207-line README rewritten to a 3-line stub, which QA
correctly failed). Two coordinated defects in _generate_agent_settings /
_get_role_permissions:

1. base_deny carried a GLOBAL Write(*)/Edit(*). Claude Code evaluates
   permission rules deny -> ask -> allow, first match wins — a deny
   ALWAYS beats a more-specific allow and the glob syntax has no
   negation. So the global deny unconditionally shadowed every per-role
   workspace-scoped Write/Edit allow. Removed it; the security denies
   that legitimately rely on deny-always-wins (Bash(git:*), credential
   Read denies, curl github, env) stay. Roles that must not author
   (qa, cell_pm, main_pm, auditor) keep their OWN Write(*)/Edit(*) deny.

2. The workspace allow used a single leading slash (Write(/data/...)).
   Claude Code resolves a single / against the settings.json project
   root, not the container filesystem root, so the allow silently never
   matched even without defect #1. Emit the // absolute-filesystem form.

defaultMode stays bypassPermissions (switching to dontAsk would require
re-deriving the full allow-list and risks wedging agents elsewhere —
out of scope). Verified against Claude Code 2.1.114 permission docs.

tests/unit/runtime/test_agent_write_permissions.py

@@ -0,0 +1,110 @@
+"""#167: agents could never Edit/Write any file (smoke-10..14).
+
+Root cause: _generate_agent_settings put ``Write(*)``/``Edit(*)`` in the
+GLOBAL base_deny. Claude Code evaluates rules deny -> ask -> allow and the
+first match wins, so a deny ALWAYS beats a more-specific allow (the glob
+syntax has no negation). The global deny therefore unconditionally
+shadowed every per-role workspace-scoped Write/Edit allow — every agent,
+developers included, got "Edit exists but is not enabled in this context"
+and fell back to destructive bash redirection (clobbering real files;
+e.g. a 207-line README rewritten to a 3-line stub, which QA correctly
+failed).
+
+Second defect: the workspace allow used a SINGLE leading slash
+(``Write(/data/...)``). Claude Code resolves a single ``/`` against the
+settings.json project root, not the container filesystem root, so even
+without the global deny the allow never matched. Absolute container
+paths require the ``//`` form.
+
+Fix: drop Write(*)/Edit(*) from base_deny (roles that must not write keep
+their OWN Write(*)/Edit(*) deny); emit the workspace allow in the ``//``
+absolute form.
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from unittest.mock import patch
+
+from roboco.runtime.orchestrator import AgentOrchestrator
+
+
+def _orch() -> AgentOrchestrator:
+    with patch.object(AgentOrchestrator, "__init__", return_value=None):
+        return AgentOrchestrator.__new__(AgentOrchestrator)
+
+
+_WS = "/data/workspaces/roboco-api/backend/be-dev-1"
+_CELL = "/data/workspaces/roboco-api/backend"
+
+_WRITER_ROLES = ("developer", "documenter", "product_owner", "head_marketing")
+_NON_WRITER_ROLES = ("qa", "cell_pm", "main_pm", "auditor")
+
+
+def test_generated_settings_base_deny_has_no_global_write_edit() -> None:
+    """The settings file a developer is spawned with must NOT globally
+    deny Write/Edit (that shadowed the workspace allow → unusable)."""
+    orch = _orch()
+    path = orch._generate_agent_settings(
+        agent_id="be-dev-1",
+        role="developer",
+        workspace_path=_WS,
+        cell_workspace_path=_CELL,
+    )
+    settings = json.loads(Path(path).read_text())
+    deny = settings["permissions"]["deny"]
+    allow = settings["permissions"]["allow"]
+
+    assert "Write(*)" not in deny, deny
+    assert "Edit(*)" not in deny, deny
+    # The security denies that DO rely on deny-always-wins must remain.
+    assert "Bash(git:*)" in deny, deny
+    assert any(".git/config" in d for d in deny), deny
+    # Workspace allow present and in the // absolute form.
+    assert f"Write(/{_WS}/**)" in allow, allow
+    assert f"Edit(/{_WS}/**)" in allow, allow
+
+
+def test_writer_roles_use_double_slash_absolute_allow() -> None:
+    """Every role that authors files emits Write/Edit allow rules in the
+    // absolute-filesystem form (single / silently never matches)."""
+    orch = _orch()
+    for role in _WRITER_ROLES:
+        perms = orch._get_role_permissions(
+            role=role, workspace_path=_WS, cell_workspace_path=_CELL
+        )
+        write_edit = [e for e in perms["allow"] if e.startswith(("Write(", "Edit("))]
+        assert write_edit, f"{role} should allow some Write/Edit: {perms}"
+        for entry in write_edit:
+            inner = entry[entry.index("(") + 1 :]
+            assert inner.startswith("//"), (
+                f"{role} allow rule must use // absolute form: {entry}"
+            )
+
+
+def test_non_writer_roles_still_deny_write_edit() -> None:
+    """Removing the GLOBAL deny must not let QA / PMs / auditor write —
+    they carry their own Write(*)/Edit(*) deny in the role config."""
+    orch = _orch()
+    for role in _NON_WRITER_ROLES:
+        perms = orch._get_role_permissions(
+            role=role, workspace_path=_WS, cell_workspace_path=_CELL
+        )
+        assert "Write(*)" in perms["deny"], f"{role}: {perms}"
+        assert "Edit(*)" in perms["deny"], f"{role}: {perms}"
+
+
+def test_non_writer_generated_settings_block_write() -> None:
+    """End-to-end: a cell_pm's generated settings still deny Write/Edit
+    (their own role deny survives the base_deny change)."""
+    orch = _orch()
+    path = orch._generate_agent_settings(
+        agent_id="be-pm",
+        role="cell_pm",
+        workspace_path=_WS,
+        cell_workspace_path=_CELL,
+    )
+    deny = json.loads(Path(path).read_text())["permissions"]["deny"]
+    assert "Write(*)" in deny, deny
+    assert "Edit(*)" in deny, deny

tests/unit/runtime/test_spawn_cwd_workspace.py

@@ -145,14 +145,28 @@ _EDIT_ALLOWLIST_RE = re.compile(r"^Edit\((.+)/\*\*\)$")
 
 
 def _extract_edit_allowlist_prefix(permissions: dict[str, list[str]]) -> str:
-    """Extract the workspace path prefix from an Edit(path/**) allowlist entry.
+    """Extract the workspace fs-path prefix from an Edit(path/**) rule.
+
+    The rule MUST use the ``//`` absolute-filesystem form: Claude Code
+    resolves a single leading ``/`` against the settings.json project
+    root, not the container filesystem root, so a single-slash workspace
+    allow silently never matches and Edit/Write are effectively denied
+    (the smoke-10..14 "Edit not enabled in this context" failure). This
+    asserts the ``//`` invariant and returns the real fs path (one
+    leading slash) so it can be cross-checked against the docker ``-w``.
 
     Raises AssertionError if no matching entry is found.
     """
     for entry in permissions.get("allow", []):
         m = _EDIT_ALLOWLIST_RE.match(entry)
         if m:
-            return m.group(1)
+            rule_path = m.group(1)
+            assert rule_path.startswith("//"), (
+                "Edit/Write allow rule must use the // absolute-filesystem "
+                "form; a single leading / resolves against the settings.json "
+                f"project root and silently never matches: {entry}"
+            )
+            return rule_path[1:]
     raise AssertionError(
         f"No Edit(<path>/**) entry found in allow list: {permissions['allow']}"
     )