fix(daemon): raise proxy daemon file-descriptor limit at startup

CHANGELOG.md

@@ -22,6 +22,7 @@ Adds HTTP request-body inspection to Keep policies. File- and pack-based `networ
 
 ### Fixed
 
+- Fix all Claude sessions inside moat freezing at once on macOS during a package install — previously, the shared credential-injecting proxy daemon inherited the host's default `RLIMIT_NOFILE` soft limit (typically 256 on macOS), so a burst of concurrent connections through the single proxy (`bun install` opens up to 64 parallel connections) could exhaust its file descriptors and stall every run's `claude.ai` traffic until the burst cleared, then recover. The daemon now raises its file-descriptor soft limit toward 65536 (capped at the hard limit) at startup, before the proxy accepts connections. ([#439](https://github.com/majorcontext/moat/pull/439))
 - Fix the injected agent context misrepresenting network access — previously, the "Moat Environment" instructions file (CLAUDE.md/AGENTS.md) listed grant/rule hosts under "Allowed hosts" regardless of policy, so under the default `permissive` policy (where all outbound traffic is allowed) it read as an egress allowlist restricting the agent to those few hosts. The Network Policy section is now policy-aware: `permissive` states that all outbound access is allowed (surfacing only explicit per-path rules, which still apply), and `strict` is described as the allowlist it actually is. The context also now reflects **Docker/DIND availability**, the resolved **workspace mode** (bind vs. ephemeral `volume`), and **installed tool dependencies** — all previously omitted, which could lead an agent to assume capabilities were absent. ([#431](https://github.com/majorcontext/moat/pull/431))
 - Fix `moat logs -f` silently doing nothing — previously, follow mode printed a debug-log line ("not yet implemented", only visible with `--verbose`) and exited 0 as if it had streamed, so `-f` looked like it worked. moat now prints a visible notice that follow mode isn't supported yet and shows the current logs. ([#413](https://github.com/majorcontext/moat/pull/413))
 - Fix non-deterministic Dockerfile generation causing spurious image rebuilds — previously, dependency `ENV` lines were emitted in random map order, so the generated Dockerfile changed between runs and missed Docker's layer cache. `ENV` keys are now sorted. ([#413](https://github.com/majorcontext/moat/pull/413))

cmd/moat/cli/daemon.go

@@ -44,6 +44,19 @@ func runDaemon(_ *cobra.Command, _ []string) error {
 		daemonDir = filepath.Join(config.GlobalConfigDir(), "proxy")
 	}
 
+	// Raise the file-descriptor limit before the proxy starts accepting. The
+	// daemon is the single shared egress proxy for every run, so a burst of
+	// concurrent connections from one container (e.g. `bun install` opens up to
+	// 64 parallel connections) must not exhaust its FDs and stall every other
+	// run's traffic. Best-effort: a failure is non-fatal.
+	if oldSoft, newSoft, ferr := daemon.RaiseFileLimit(); ferr != nil {
+		log.Warn("could not read daemon file-descriptor limit", "error", ferr)
+	} else if newSoft > oldSoft {
+		log.Info("raised daemon file-descriptor limit", "from", oldSoft, "to", newSoft)
+	} else {
+		log.Debug("daemon file-descriptor limit unchanged", "soft", oldSoft)
+	}
+
 	// Expose build version to daemon package so the health endpoint can
 	// report it. This allows detecting version skew between daemon and CLI.
 	daemon.BuildCommit = commit

internal/daemon/filelimit.go

@@ -0,0 +1,69 @@
+//go:build unix
+
+package daemon
+
+import "golang.org/x/sys/unix"
+
+// desiredNofile is the soft RLIMIT_NOFILE the proxy daemon targets at startup.
+//
+// The daemon is the single shared egress proxy for every active run, so a burst
+// of concurrent connections from one container must not exhaust its file
+// descriptors and stall every other run's traffic. A package install is the
+// common trigger: `bun install` opens up to 64 parallel connections (Bun's
+// default since v1.1.33), each consuming FDs on both the client and upstream
+// sides, and several runs can install at once. The frequent 1024 soft default
+// (and macOS's 256) is easily exhausted by that; 65536 gives ample headroom.
+const desiredNofile = 65536
+
+// RaiseFileLimit raises this process's RLIMIT_NOFILE soft limit toward
+// desiredNofile, capped at the hard limit. It returns the previous soft limit
+// and the soft limit in effect afterward (always >= oldSoft). It is a no-op
+// (equal values) when the soft limit is already at or above the target.
+//
+// A limit that cannot be raised is not an error — the process keeps its
+// existing, already-in-effect limit and err stays nil. err is non-nil only when
+// the current limit cannot be read. Some systems, notably macOS, reject a soft
+// limit above kern.maxfilesperproc even when the hard limit is nominally
+// higher; when the full target is rejected, the fallback binary-searches the
+// highest value the system will accept between the old soft limit and the
+// target.
+func RaiseFileLimit() (oldSoft, newSoft uint64, err error) {
+	var lim unix.Rlimit
+	if err = unix.Getrlimit(unix.RLIMIT_NOFILE, &lim); err != nil {
+		return 0, 0, err
+	}
+	oldSoft = lim.Cur
+
+	target := uint64(desiredNofile)
+	if lim.Max < target { // the hard limit caps the soft limit
+		target = lim.Max
+	}
+	if oldSoft >= target {
+		return oldSoft, oldSoft, nil // already sufficient
+	}
+
+	// Fast path: the full target is usually accepted.
+	lim.Cur = target
+	if unix.Setrlimit(unix.RLIMIT_NOFILE, &lim) == nil {
+		return oldSoft, target, nil
+	}
+
+	// Fallback: the target was rejected (e.g. macOS caps the soft limit at
+	// kern.maxfilesperproc, below the hard limit). Binary-search the highest
+	// value in (oldSoft, target) the system accepts. lo is always known-good
+	// (oldSoft is currently in effect), hi is always known-bad (a rejected
+	// value). Each successful Setrlimit leaves the process at that value, so
+	// once the search narrows, the process's soft limit equals best.
+	best := oldSoft
+	lo, hi := oldSoft, target
+	for hi-lo > 1 {
+		mid := lo + (hi-lo)/2
+		lim.Cur = mid
+		if unix.Setrlimit(unix.RLIMIT_NOFILE, &lim) == nil {
+			best, lo = mid, mid
+		} else {
+			hi = mid
+		}
+	}
+	return oldSoft, best, nil
+}

internal/daemon/filelimit_other.go

@@ -0,0 +1,10 @@
+//go:build !unix
+
+package daemon
+
+// RaiseFileLimit is a no-op on platforms without POSIX rlimits. The proxy
+// daemon runs on the host (macOS or Linux, both unix), so this stub exists only
+// to keep the package building on other GOOS values.
+func RaiseFileLimit() (oldSoft, newSoft uint64, err error) {
+	return 0, 0, nil
+}

internal/daemon/filelimit_test.go

@@ -0,0 +1,64 @@
+//go:build unix
+
+package daemon
+
+import (
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+func currentNofile(t *testing.T) (soft, hard uint64) {
+	t.Helper()
+	var lim unix.Rlimit
+	if err := unix.Getrlimit(unix.RLIMIT_NOFILE, &lim); err != nil {
+		t.Fatalf("Getrlimit: %v", err)
+	}
+	return lim.Cur, lim.Max
+}
+
+func TestRaiseFileLimit(t *testing.T) {
+	beforeSoft, hard := currentNofile(t)
+
+	oldSoft, newSoft, err := RaiseFileLimit()
+	if err != nil {
+		t.Fatalf("RaiseFileLimit: %v", err)
+	}
+	if oldSoft != beforeSoft {
+		t.Errorf("reported oldSoft %d, want the current soft limit %d", oldSoft, beforeSoft)
+	}
+	if newSoft < oldSoft {
+		t.Errorf("newSoft %d must never be below oldSoft %d (the limit is only ever raised)", newSoft, oldSoft)
+	}
+	if newSoft > hard {
+		t.Errorf("newSoft %d must not exceed the hard limit %d", newSoft, hard)
+	}
+	// The process's actual soft limit must reflect the reported new value.
+	gotSoft, _ := currentNofile(t)
+	if gotSoft != newSoft {
+		t.Errorf("process soft limit is %d, want the reported newSoft %d", gotSoft, newSoft)
+	}
+}
+
+// TestRaiseFileLimitNonLowering asserts a second call never reduces the limit —
+// it either reaches the target once and no-ops, or (on systems that cap the
+// soft limit below the hard limit, e.g. macOS) stays put. A limit that cannot
+// be raised further is reported as success, not an error.
+func TestRaiseFileLimitNonLowering(t *testing.T) {
+	_, firstNew, err := RaiseFileLimit()
+	if err != nil {
+		t.Fatalf("first RaiseFileLimit: %v", err)
+	}
+
+	_, secondNew, err := RaiseFileLimit()
+	if err != nil {
+		t.Fatalf("second RaiseFileLimit: %v", err)
+	}
+	if secondNew < firstNew {
+		t.Errorf("second call lowered the soft limit: %d -> %d", firstNew, secondNew)
+	}
+	afterSoft, _ := currentNofile(t)
+	if afterSoft < firstNew {
+		t.Errorf("process soft limit dropped after a second call: %d -> %d", firstNew, afterSoft)
+	}
+}