fix(windows): suppress the console window on the last spawn site (#1427)

scripts/test.sh

@@ -230,6 +230,9 @@ bash "$ROOT/tests/test_parallel_harness_contract.sh"
 echo "=== Step 0j: venue parity contract (one harness, every venue) ==="
 bash "$ROOT/tests/test_venue_parity_contract.sh"
 
+echo "=== Step 0k: spawn console-window contract (#1427) ==="
+bash "$ROOT/tests/test_spawn_no_window_contract.sh"
+
 # Verify compiler supports target arch
 verify_compiler "$CC"
 

src/foundation/compat_fs.c

@@ -686,7 +686,14 @@ int cbm_exec_no_shell(const char *const *argv) {
     memset(&pi, 0, sizeof(pi));
     si.cb = sizeof(si);
 
-    if (!CreateProcessW(NULL, cmdline, NULL, NULL, FALSE, 0, NULL, NULL, &si, &pi)) {
+    /* CREATE_NO_WINDOW: the third and last spawn site that still needed it
+     * (#1427). Without it every helper routed through here — git, codesign,
+     * open — flashes a console window, and under a stdio MCP session with
+     * auto_watch those steal focus while the user is typing. The other three
+     * CreateProcessW sites already set it: subprocess.c and cbm_popen_isolated
+     * via #1448, and the detached daemon spawn in daemon/bootstrap.c, which has
+     * had it since it was written. */
+    if (!CreateProcessW(NULL, cmdline, NULL, NULL, FALSE, CREATE_NO_WINDOW, NULL, NULL, &si, &pi)) {
         free(cmdline);
         return CBM_NOT_FOUND;
     }

tests/test_spawn_no_window_contract.sh

@@ -0,0 +1,125 @@
+#!/usr/bin/env bash
+# Contract: every CreateProcessW spawn must suppress its console window.
+#
+# This exists because the fix for #1427 was applied THREE times and still missed
+# a site. The reported symptom is a console window stealing focus mid-typing on a
+# stdio MCP session with auto_watch. The flag that prevents it, CREATE_NO_WINDOW,
+# has to be set at each spawn independently, and the sites do not look alike:
+#
+#   daemon/bootstrap.c   had it from the start   (DETACHED_PROCESS | ... | CREATE_NO_WINDOW)
+#   subprocess.c         added by #1448          (flags variable)
+#   compat_fs.c :313     added by #1448          (inline literal, popen path)
+#   compat_fs.c :689     MISSED by #1448         (dwCreationFlags was a bare 0)
+#
+# The missed one is the helper that runs git / codesign / open, i.e. the one a
+# user meets most often. Nobody was wrong to miss it: it is a different function
+# from the popen site in the same file, and reviewing "does the PR add the flag"
+# says nothing about the sites the PR does not touch. Only a whole-tree property
+# catches that, so this asserts the property rather than any one call.
+#
+# Python, not shell: this needs the 6th argument of a call spanning lines, and
+# the enclosing function's flags variable when that argument is not a literal.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$ROOT"
+
+python3 - "$ROOT" <<'PY'
+import pathlib
+import re
+import sys
+
+root = pathlib.Path(sys.argv[1])
+
+
+def strip_comments(text):
+    """Blank out C comments, preserving line count and column positions.
+
+    Mandatory, not tidiness: the first version of this contract matched the flag
+    name anywhere near the call, so the explanatory COMMENT sitting above the
+    fixed call site satisfied it — the test passed with the fix reverted. A
+    contract that can be satisfied by prose about the contract is a false guard.
+    """
+    out = []
+    i, n = 0, len(text)
+    while i < n:
+        two = text[i:i + 2]
+        if two == "/*":
+            j = text.find("*/", i + 2)
+            j = n if j < 0 else j + 2
+            out.append("".join(c if c == "\n" else " " for c in text[i:j]))
+            i = j
+        elif two == "//":
+            j = text.find("\n", i)
+            j = n if j < 0 else j
+            out.append(" " * (j - i))
+            i = j
+        else:
+            out.append(text[i])
+            i += 1
+    return "".join(out)
+
+# A site may opt out only with a justified, at-the-case entry (O10): the exact
+# "file:function" plus WHY. Empty on purpose — every current site sets the flag.
+ALLOWLIST = {
+    # "src/foo/bar.c:some_function": "why a console window is required here",
+}
+
+FLAG = "CREATE_NO_WINDOW"
+failures = []
+checked = 0
+
+for path in sorted(root.glob("src/**/*.c")):
+    raw = path.read_text(encoding="utf-8", errors="replace")
+    if "CreateProcessW(" not in raw:
+        continue
+    # Comments are blanked FIRST, so neither the call scan nor the flag check can
+    # be satisfied by prose. Line numbers still map to the real file.
+    text = strip_comments(raw)
+    lines = text.splitlines()
+    for idx, line in enumerate(lines):
+        if "CreateProcessW(" not in line:
+            continue
+        checked += 1
+
+        # Enclosing function: nearest preceding line that starts in column 0 and
+        # looks like a definition. Good enough — these files are plain C.
+        func = "<unknown>"
+        for back in range(idx, -1, -1):
+            m = re.match(r"^(?:static\s+)?[A-Za-z_][\w \t*]*\b(\w+)\s*\(", lines[back])
+            if m and not lines[back].lstrip().startswith(("*", "//", "/*")):
+                func = m.group(1)
+                break
+        rel = path.relative_to(root).as_posix()
+        key = f"{rel}:{func}"
+        if key in ALLOWLIST:
+            continue
+
+        # The call may wrap across lines; take a window around it, plus the
+        # enclosing function body, so a `DWORD flags = ...` assignment counts.
+        call_window = "\n".join(lines[idx:idx + 4])
+        body_start = max(0, idx - 60)
+        body_window = "\n".join(lines[body_start:idx + 4])
+
+        if FLAG in call_window or FLAG in body_window:
+            continue
+        failures.append(
+            f"{rel}:{idx + 1} ({func}) spawns without {FLAG}\n"
+            f"      {line.strip()}"
+        )
+
+if checked == 0:
+    print("FAIL: no CreateProcessW call sites found — this contract has stopped "
+          "checking anything (did the spawn layer move?)")
+    sys.exit(1)
+
+if failures:
+    print(f"FAIL: {len(failures)} CreateProcessW site(s) can pop a console window (#1427):\n")
+    for f in failures:
+        print(f"  - {f}")
+    print(f"\nAdd {FLAG} to dwCreationFlags. If a site genuinely needs a console, "
+          "add it to ALLOWLIST in this file with the reason.")
+    sys.exit(1)
+
+print(f"OK: all {checked} CreateProcessW site(s) set {FLAG}")
+PY