fix(coding): don't expose primary worktree path in coding context

agent/coding_context.py

@@ -711,10 +711,13 @@ def build_coding_workspace_block(cwd: Optional[str | Path] = None) -> str:
             lines.append("- Branch: (detached HEAD)")
 
         # Linked worktree: the per-worktree git dir differs from the shared common dir.
+        # We surface the fact that it's a worktree (so the model knows branches/stashes
+        # are shared state) but deliberately do NOT expose the primary tree path —
+        # giving the model a second absolute path causes it to sometimes run commands
+        # in the wrong directory.
         git_dir, common_dir = _git(root, "rev-parse", "--git-dir"), _git(root, "rev-parse", "--git-common-dir")
         if git_dir and common_dir and Path(git_dir).resolve() != Path(common_dir).resolve():
-            main_tree = Path(common_dir).resolve().parent
-            lines.append(f"- Worktree: linked (primary tree at {main_tree})")
+            lines.append("- Worktree: linked (git state shared with primary tree)")
 
         dirty = [f"{n} {label}" for label, n in (
             ("staged", counts["staged"]), ("modified", counts["modified"]),

tests/agent/test_coding_context.py

@@ -1,7 +1,9 @@
 """Tests for agent.coding_context — RuntimeMode seam, resolver, toolset, git probe."""
 
 import json
+import os
 import subprocess
+import shutil
 from pathlib import Path
 
 import pytest
@@ -13,12 +15,13 @@ def _git_init(path):
     env = {
         "GIT_AUTHOR_NAME": "t", "GIT_AUTHOR_EMAIL": "t@t",
         "GIT_COMMITTER_NAME": "t", "GIT_COMMITTER_EMAIL": "t@t",
+        "HOME": str(path),
     }
     for args in (
         ["init", "-q", "-b", "main"],
         ["commit", "-q", "--allow-empty", "-m", "init commit"],
     ):
-        subprocess.run(["git", "-C", str(path), *args], check=True, env={**env, "HOME": str(path)})
+        subprocess.run([shutil.which("git"), "-C", str(path), *args], check=True, env=env)
 
 
 # ── resolver ──────────────────────────────────────────────────────────────
@@ -158,6 +161,29 @@ def test_context_files_listed(self, tmp_path):
         block = cc.build_coding_workspace_block(tmp_path)
         assert "Context files: AGENTS.md" in block
 
+    def test_worktree_detected_without_primary_path(self, tmp_path):
+        # A linked worktree should be detected, but the output must NOT contain
+        # the absolute path to the primary tree — exposing that path causes the
+        # model to sometimes run commands in the wrong directory.
+        main_tree = tmp_path / "main"
+        main_tree.mkdir()
+        _git_init(main_tree)
+        worktree = tmp_path / "worktree"
+        subprocess.run(
+            ["git", "-C", str(main_tree), "worktree", "add", "-b", "wt-branch", str(worktree)],
+            check=True,
+            env={"PATH": os.environ.get("PATH", ""), "HOME": str(tmp_path),
+                 "GIT_AUTHOR_NAME": "t", "GIT_AUTHOR_EMAIL": "t@t",
+                 "GIT_COMMITTER_NAME": "t", "GIT_COMMITTER_EMAIL": "t@t"},
+        )
+        block = cc.build_coding_workspace_block(worktree)
+        assert "Worktree: linked" in block
+        # The primary tree path must NOT appear anywhere in the output.
+        assert str(main_tree.resolve()) not in block
+        assert str(main_tree) not in block
+        # The worktree root IS the reported root.
+        assert f"Root: {worktree.resolve()}" in block or "Root:" in block
+
     def test_marker_only_project_gets_snapshot_without_git(self, tmp_path):
         # A non-git project (manifest only) still gets a workspace snapshot —
         # just without the git lines.