fix(agent/openclaw): read --json from stdout, not stderr

Multica's openclaw runtime adapter has been reading agent output from
stderr since the early openclaw integration days. Current openclaw
(2026.5.5, c37871e) writes its --json blob exclusively to stdout:

    $ openclaw agent --local --json --agent main --message 'say hi' >stdout 2>stderr
    STDOUT bytes: 27401
    STDERR bytes:     0

Result: every successful turn was followed by a daemon-generated system
comment 'openclaw returned no parseable output', visible to users,
looked like the agent broke when it didn't. Reproduced live on WOR-2,
turn at 2026-05-05 16:35 UTC; daemon log confirmed the full result JSON
arrived on the [openclaw:stdout] debug channel and was discarded while
the empty stderr pipe hit the no-events fallback.

Changes
- server/pkg/agent/openclaw.go: swap pipes, StdoutPipe() for the JSON
  stream, cmd.Stderr = newLogWriter(...) for log overflow. Cleanup
  goroutine now closes stdout on cancel. Comments and the read-error
  errMsg updated to reflect the new pipe.
- server/pkg/agent/openclaw_test.go: TestOpenclawProcessOutputReadError
  asserts on 'read stdout' (was 'read stderr'), string-only fix,
  no behavior change. New TestOpenclawProcessOutputStdoutFixture feeds
  a recorded openclaw 2026.5.5 --json blob through processOutput and
  asserts result + messages parse cleanly.
- server/pkg/agent/testdata/openclaw-2026.5.5-stdout.json: 27401-byte
  fixture captured fresh from the openclaw CLI for the regression test.

Side effects (net positive)
- Log lines openclaw writes to stderr (security warnings, tool errors)
  now show up under [openclaw:stderr] instead of being silently consumed
  by the JSON parser.
- Daemon's success_pattern heuristic (empty-output -> 'blocked')
  becomes meaningful again because result.Output actually populates.

Closes WOR-10.

server/pkg/agent/openclaw.go

@@ -60,13 +60,16 @@ func (b *openclawBackend) Execute(ctx context.Context, prompt string, opts ExecO
 	}
 	cmd.Env = buildEnv(b.cfg.Env)
 
-	// openclaw writes its --json output to stderr, not stdout.
-	stderr, err := cmd.StderrPipe()
+	// openclaw writes its --json output to stdout. Stderr carries log
+	// overflow (security warnings, tool errors, etc.) — capture it via a
+	// log writer so it surfaces in daemon logs without being fed into the
+	// JSON parser.
+	stdout, err := cmd.StdoutPipe()
 	if err != nil {
 		cancel()
-		return nil, fmt.Errorf("openclaw stderr pipe: %w", err)
+		return nil, fmt.Errorf("openclaw stdout pipe: %w", err)
 	}
-	cmd.Stdout = newLogWriter(b.cfg.Logger, "[openclaw:stdout] ")
+	cmd.Stderr = newLogWriter(b.cfg.Logger, "[openclaw:stderr] ")
 
 	if err := cmd.Start(); err != nil {
 		cancel()
@@ -78,10 +81,10 @@ func (b *openclawBackend) Execute(ctx context.Context, prompt string, opts ExecO
 	msgCh := make(chan Message, 256)
 	resCh := make(chan Result, 1)
 
-	// Close stderr when the context is cancelled so the scanner unblocks.
+	// Close stdout when the context is cancelled so the scanner unblocks.
 	go func() {
 		<-runCtx.Done()
-		_ = stderr.Close()
+		_ = stdout.Close()
 	}()
 
 	go func() {
@@ -90,7 +93,7 @@ func (b *openclawBackend) Execute(ctx context.Context, prompt string, opts ExecO
 		defer close(resCh)
 
 		startTime := time.Now()
-		scanResult := b.processOutput(stderr, msgCh)
+		scanResult := b.processOutput(stdout, msgCh)
 
 		// Wait for process exit.
 		exitErr := cmd.Wait()
@@ -202,9 +205,10 @@ type openclawEventResult struct {
 	model string
 }
 
-// processOutput reads the JSON output from openclaw --json stderr and returns
-// the parsed result. OpenClaw writes its JSON output to stderr, which may also
-// contain non-JSON log lines. The stream may contain:
+// processOutput reads the JSON output from openclaw --json stdout and returns
+// the parsed result. OpenClaw writes its JSON output to stdout; stderr carries
+// log overflow and is captured separately by the caller. The stream may
+// contain:
 //
 //   - NDJSON streaming events (type: "text", "tool_use", "tool_result", "error",
 //     "step_start", "step_finish") — emitted in real time as the agent works
@@ -309,12 +313,12 @@ func (b *openclawBackend) processOutput(r io.Reader, ch chan<- Message) openclaw
 		}
 
 		// Not JSON — treat as log line.
-		b.cfg.Logger.Debug("[openclaw:stderr] " + line)
+		b.cfg.Logger.Debug("[openclaw:stdout] " + line)
 		rawLines = append(rawLines, line)
 	}
 
 	if err := scanner.Err(); err != nil {
-		return openclawEventResult{status: "failed", errMsg: fmt.Sprintf("read stderr: %v", err)}
+		return openclawEventResult{status: "failed", errMsg: fmt.Sprintf("read stdout: %v", err)}
 	}
 
 	// If we got no events at all, fall back to raw output.

server/pkg/agent/openclaw_test.go

@@ -3,6 +3,7 @@ package agent
 import (
 	"encoding/json"
 	"log/slog"
+	"os"
 	"strings"
 	"testing"
 	"time"
@@ -234,8 +235,8 @@ func TestOpenclawProcessOutputReadError(t *testing.T) {
 	if res.status != "failed" {
 		t.Errorf("status: got %q, want %q", res.status, "failed")
 	}
-	if !strings.Contains(res.errMsg, "read stderr") {
-		t.Errorf("errMsg: got %q, want it to contain 'read stderr'", res.errMsg)
+	if !strings.Contains(res.errMsg, "read stdout") {
+		t.Errorf("errMsg: got %q, want it to contain 'read stdout'", res.errMsg)
 	}
 
 	close(ch)
@@ -1163,3 +1164,67 @@ func countOccurrences(args []string, s string) int {
 	}
 	return n
 }
+
+// TestOpenclawProcessOutputStdoutFixture is the regression test for WOR-10.
+// It feeds a recorded `openclaw agent --local --json` blob (captured from
+// openclaw 2026.5.5 at the time of the fix) into processOutput exactly as
+// the swapped pipe would deliver it, and asserts the result + messages parse.
+//
+// Before the fix, the daemon read this same byte stream from stderr (where
+// nothing was written), produced "openclaw returned no parseable output",
+// and surfaced a system-typed comment to users. After the fix, processOutput
+// reads from stdout and this fixture parses cleanly.
+func TestOpenclawProcessOutputStdoutFixture(t *testing.T) {
+	t.Parallel()
+
+	data, err := os.ReadFile("testdata/openclaw-2026.5.5-stdout.json")
+	if err != nil {
+		t.Fatalf("read fixture: %v", err)
+	}
+	if len(data) < 1000 {
+		t.Fatalf("fixture too small (%d bytes); did the file get truncated?", len(data))
+	}
+
+	b := &openclawBackend{cfg: Config{Logger: slog.Default()}}
+	ch := make(chan Message, 256)
+
+	res := b.processOutput(strings.NewReader(string(data)), ch)
+
+	if res.status != "completed" {
+		t.Errorf("status: got %q, want %q", res.status, "completed")
+	}
+	if res.errMsg != "" {
+		t.Errorf("errMsg: got %q, want empty", res.errMsg)
+	}
+	if res.output != "hi" {
+		t.Errorf("output: got %q, want %q", res.output, "hi")
+	}
+	if res.sessionID == "" {
+		t.Errorf("sessionID: got empty, want non-empty")
+	}
+	if res.model != "anthropic/claude-opus-4.7" {
+		t.Errorf("model: got %q, want %q", res.model, "anthropic/claude-opus-4.7")
+	}
+	if res.usage.InputTokens != 34620 {
+		t.Errorf("usage.InputTokens: got %d, want %d", res.usage.InputTokens, 34620)
+	}
+	if res.usage.OutputTokens != 6 {
+		t.Errorf("usage.OutputTokens: got %d, want %d", res.usage.OutputTokens, 6)
+	}
+	if res.usage.CacheWriteTokens != 46482 {
+		t.Errorf("usage.CacheWriteTokens: got %d, want %d", res.usage.CacheWriteTokens, 46482)
+	}
+
+	close(ch)
+
+	// At least one MessageText event should have been emitted carrying "hi".
+	var gotText bool
+	for msg := range ch {
+		if msg.Type == MessageText && strings.Contains(msg.Content, "hi") {
+			gotText = true
+		}
+	}
+	if !gotText {
+		t.Errorf("expected a MessageText event containing %q", "hi")
+	}
+}