fix(execenv): strip [[skills.config]] from per-task codex config.toml (#1816)

Codex Desktop writes one [[skills.config]] entry per known skill into
~/.codex/config.toml. File-backed entries get path = "...", but
plugin-backed entries (e.g. name = "superpowers:brainstorming") only get
a name. Codex CLI 0.114's TOML deserializer treats path as required, so
it rejects the plugin entries with "missing field path" and fails
thread/start.

The daemon copies ~/.codex/config.toml verbatim into each task's
isolated codex-home, which propagated those broken entries into the
per-task config and blocked every Codex agent run for affected users.

Strip the whole [[skills.config]] array on copy. Multica writes the
agent's currently assigned skills directly to codex-home/skills/ and
Codex auto-discovers them from there, so the user-level skill registry
is redundant for a per-task run.

Closes #1753

server/internal/daemon/execenv/codex_home.go

@@ -89,6 +89,16 @@ func prepareCodexHomeWithOpts(codexHome string, opts CodexHomeOptions, logger *s
 		}
 	}
 
+	// Drop `[[skills.config]]` entries inherited from the user's
+	// ~/.codex/config.toml. Codex Desktop writes plugin-backed skills with a
+	// `name` and no `path`, which the CLI's stricter TOML parser rejects with
+	// `missing field path` and bails out of `thread/start`. Multica writes the
+	// agent's active skills directly to `codex-home/skills/`, so the
+	// user-level registry is redundant here. See codex_skill_strip.go.
+	if err := sanitizeCopiedCodexConfig(filepath.Join(codexHome, "config.toml")); err != nil {
+		logger.Warn("execenv: codex-home sanitize config failed", "error", err)
+	}
+
 	if err := exposeSharedCodexPluginCache(codexHome, sharedHome); err != nil {
 		logger.Warn("execenv: codex-home plugin cache exposure failed", "error", err)
 	}

server/internal/daemon/execenv/codex_skill_strip.go

@@ -0,0 +1,87 @@
+package execenv
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+// stripSkillsConfigEntries removes every `[[skills.config]]` array-of-tables
+// block from the given config.toml content.
+//
+// Background: Codex Desktop writes one `[[skills.config]]` entry per skill it
+// knows about — file-backed skills get a `path = "..."` field, while
+// plugin-backed skills (e.g. `name = "superpowers:brainstorming"`) only get a
+// `name`. Codex CLI 0.114's TOML deserializer treats `path` as a required
+// field, so it rejects the plugin entries with `missing field path` and
+// refuses to start. Multica copies the user's `~/.codex/config.toml` verbatim
+// into each task's isolated codex-home, which propagates the broken entries
+// into the per-task config and blocks `codex thread/start`.
+//
+// Stripping the whole `[[skills.config]]` array sidesteps the issue: Multica
+// writes the agent's currently assigned skills directly to
+// `codex-home/skills/<name>/SKILL.md`, and Codex auto-discovers them from
+// that directory. The user-level skill registry is irrelevant to a per-task
+// run, so dropping it is both safe and the right scope of isolation.
+//
+// Lines outside `[[skills.config]]` blocks are preserved untouched.
+func stripSkillsConfigEntries(content string) string {
+	if !strings.Contains(content, "[[skills.config]]") {
+		return content
+	}
+
+	lines := strings.Split(content, "\n")
+	out := make([]string, 0, len(lines))
+	inSkillsConfig := false
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+
+		// A new TOML header always closes the current `[[skills.config]]`
+		// block, regardless of whether it's another entry of the same array
+		// or a different table.
+		if strings.HasPrefix(trimmed, "[") {
+			if trimmed == "[[skills.config]]" {
+				inSkillsConfig = true
+				continue
+			}
+			inSkillsConfig = false
+			out = append(out, line)
+			continue
+		}
+
+		if inSkillsConfig {
+			continue
+		}
+		out = append(out, line)
+	}
+
+	stripped := strings.Join(out, "\n")
+	// Collapse the trailing blank-line cluster that the removal can leave
+	// behind so repeated copies don't grow the file unboundedly.
+	stripped = strings.TrimRight(stripped, "\n") + "\n"
+	if strings.TrimSpace(stripped) == "" {
+		return ""
+	}
+	return stripped
+}
+
+// sanitizeCopiedCodexConfig rewrites the per-task config.toml in place,
+// dropping `[[skills.config]]` entries inherited from the shared
+// `~/.codex/config.toml`. No-op if the file doesn't exist or doesn't change.
+func sanitizeCopiedCodexConfig(configPath string) error {
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("read config.toml: %w", err)
+	}
+	stripped := stripSkillsConfigEntries(string(data))
+	if stripped == string(data) {
+		return nil
+	}
+	if err := os.WriteFile(configPath, []byte(stripped), 0o644); err != nil {
+		return fmt.Errorf("write config.toml: %w", err)
+	}
+	return nil
+}

server/internal/daemon/execenv/codex_skill_strip_test.go

@@ -0,0 +1,199 @@
+package execenv
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestStripSkillsConfigEntries(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		in   string
+		want string
+	}{
+		{
+			name: "no skills config — returned unchanged",
+			in:   "model = \"o3\"\n",
+			want: "model = \"o3\"\n",
+		},
+		{
+			name: "drops well-formed file-backed entry",
+			in: `model = "o3"
+
+[[skills.config]]
+path = "/Users/x/SKILL.md"
+enabled = true
+`,
+			want: `model = "o3"
+`,
+		},
+		{
+			name: "drops plugin entry that lacks path",
+			in: `[[skills.config]]
+name = "superpowers:brainstorming"
+enabled = false
+
+[profiles.default]
+model = "o3"
+`,
+			want: `[profiles.default]
+model = "o3"
+`,
+		},
+		{
+			name: "drops a mix of consecutive entries and preserves surrounding tables",
+			in: `model = "o3"
+
+[[skills.config]]
+path = "/Users/x/SKILL.md"
+enabled = false
+
+[[skills.config]]
+path = "/Users/y/SKILL.md"
+enabled = false
+
+[[skills.config]]
+name = "superpowers:brainstorming"
+enabled = false
+
+[profiles.default]
+model = "o3"
+
+[mcp_servers.foo]
+command = "foo"
+`,
+			want: `model = "o3"
+
+[profiles.default]
+model = "o3"
+
+[mcp_servers.foo]
+command = "foo"
+`,
+		},
+		{
+			name: "skills.config at EOF",
+			in: `model = "o3"
+
+[[skills.config]]
+name = "superpowers:dispatching-parallel-agents"
+enabled = false
+`,
+			want: `model = "o3"
+`,
+		},
+		{
+			name: "preserves unrelated [skills] table (single brackets)",
+			in: `[skills]
+discovery_path = "skills"
+`,
+			want: `[skills]
+discovery_path = "skills"
+`,
+		},
+		{
+			name: "fully empty after strip returns empty string",
+			in: `[[skills.config]]
+name = "x"
+enabled = false
+`,
+			want: ``,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := stripSkillsConfigEntries(tt.in)
+			if got != tt.want {
+				t.Errorf("stripSkillsConfigEntries result mismatch\n--- got ---\n%s\n--- want ---\n%s", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestSanitizeCopiedCodexConfig(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.toml")
+	original := `model = "o3"
+
+[[skills.config]]
+name = "superpowers:brainstorming"
+enabled = false
+
+[[skills.config]]
+path = "/Users/x/SKILL.md"
+enabled = true
+
+[profiles.default]
+model = "o3"
+`
+	if err := os.WriteFile(configPath, []byte(original), 0o644); err != nil {
+		t.Fatalf("write fixture: %v", err)
+	}
+
+	if err := sanitizeCopiedCodexConfig(configPath); err != nil {
+		t.Fatalf("sanitizeCopiedCodexConfig failed: %v", err)
+	}
+
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		t.Fatalf("read result: %v", err)
+	}
+	got := string(data)
+	if strings.Contains(got, "[[skills.config]]") {
+		t.Errorf("expected all [[skills.config]] entries to be removed, got:\n%s", got)
+	}
+	if !strings.Contains(got, `[profiles.default]`) {
+		t.Errorf("unrelated tables should be preserved, got:\n%s", got)
+	}
+	if !strings.Contains(got, `model = "o3"`) {
+		t.Errorf("top-level keys should be preserved, got:\n%s", got)
+	}
+}
+
+func TestSanitizeCopiedCodexConfigNoop(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.toml")
+	original := "model = \"o3\"\n"
+	if err := os.WriteFile(configPath, []byte(original), 0o644); err != nil {
+		t.Fatalf("write fixture: %v", err)
+	}
+	infoBefore, err := os.Stat(configPath)
+	if err != nil {
+		t.Fatalf("stat before: %v", err)
+	}
+
+	if err := sanitizeCopiedCodexConfig(configPath); err != nil {
+		t.Fatalf("sanitizeCopiedCodexConfig failed: %v", err)
+	}
+
+	infoAfter, err := os.Stat(configPath)
+	if err != nil {
+		t.Fatalf("stat after: %v", err)
+	}
+	if !infoAfter.ModTime().Equal(infoBefore.ModTime()) {
+		t.Errorf("file should not be rewritten when there is nothing to strip")
+	}
+	data, _ := os.ReadFile(configPath)
+	if string(data) != original {
+		t.Errorf("content drifted: got %q, want %q", data, original)
+	}
+}
+
+func TestSanitizeCopiedCodexConfigMissingFile(t *testing.T) {
+	t.Parallel()
+
+	missing := filepath.Join(t.TempDir(), "does-not-exist.toml")
+	if err := sanitizeCopiedCodexConfig(missing); err != nil {
+		t.Errorf("missing file should be a no-op, got error: %v", err)
+	}
+}

server/internal/daemon/execenv/execenv_test.go

@@ -1125,6 +1125,57 @@ func TestPrepareCodexHomeSeedsFromShared(t *testing.T) {
 	}
 }
 
+// Regression test for #1753 — Codex Desktop writes plugin-backed
+// `[[skills.config]]` entries without a `path` field, and the CLI's TOML
+// parser rejects them with `missing field path`. prepareCodexHome must drop
+// every `[[skills.config]]` entry while copying the user's config.toml so
+// the per-task home stays parseable.
+func TestPrepareCodexHomeStripsSkillsConfigEntries(t *testing.T) {
+	// Cannot use t.Parallel() with t.Setenv.
+
+	sharedHome := t.TempDir()
+	sharedConfig := `model = "o3"
+
+[[skills.config]]
+path = "/Users/x/SKILL.md"
+enabled = false
+
+[[skills.config]]
+name = "superpowers:brainstorming"
+enabled = false
+
+[profiles.default]
+model = "o3"
+`
+	if err := os.WriteFile(filepath.Join(sharedHome, "config.toml"), []byte(sharedConfig), 0o644); err != nil {
+		t.Fatalf("write shared config.toml: %v", err)
+	}
+	t.Setenv("CODEX_HOME", sharedHome)
+
+	codexHome := filepath.Join(t.TempDir(), "codex-home")
+	if err := prepareCodexHome(codexHome, testLogger()); err != nil {
+		t.Fatalf("prepareCodexHome failed: %v", err)
+	}
+
+	data, err := os.ReadFile(filepath.Join(codexHome, "config.toml"))
+	if err != nil {
+		t.Fatalf("read per-task config.toml: %v", err)
+	}
+	tomlStr := string(data)
+	if strings.Contains(tomlStr, "[[skills.config]]") {
+		t.Errorf("per-task config.toml should not inherit [[skills.config]] entries, got:\n%s", tomlStr)
+	}
+	if strings.Contains(tomlStr, "superpowers:brainstorming") {
+		t.Errorf("per-task config.toml should not retain plugin skill names, got:\n%s", tomlStr)
+	}
+	if !strings.Contains(tomlStr, `model = "o3"`) {
+		t.Errorf("top-level keys should be preserved, got:\n%s", tomlStr)
+	}
+	if !strings.Contains(tomlStr, "[profiles.default]") {
+		t.Errorf("unrelated tables should be preserved, got:\n%s", tomlStr)
+	}
+}
+
 func TestPrepareCodexHomeSkipsMissingFiles(t *testing.T) {
 	// Cannot use t.Parallel() with t.Setenv.