anomalyco/sst · error

failed to decode cloudflare unenv config: %w %s

Error message

failed to decode cloudflare unenv config: %w
%s

What it means

After the `unenv.mjs` Node script runs successfully, SST parses its stdout as JSON into the `unenv` struct. This error means the process exited 0 but its output was not valid JSON of the expected shape, so the polyfill config cannot be used for bundling.

Source

Thrown at pkg/runtime/worker/worker.go:266

	}
	w.lock.RUnlock()

	cmd := process.CommandContext(
		ctx,
		"node",
		filepath.Join(path.ResolvePlatformDir(cfgPath), "src/runtime/worker/unenv.mjs"),
		string(payload),
	)
	cmd.Dir = path.ResolvePlatformDir(cfgPath)
	cmd.Env = []string{}
	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf("failed to load cloudflare unenv config: %w\n%s", err, output)
	}

	var result unenv
	if err := json.Unmarshal(output, &result); err != nil {
		return nil, fmt.Errorf("failed to decode cloudflare unenv config: %w\n%s", err, output)
	}

	w.lock.Lock()
	w.unenv[key] = &result
	w.lock.Unlock()

	return &result, nil
}

func (w *Runtime) Match(runtime string) bool {
	return runtime == "worker"
}

func (w *Runtime) getFile(input *runtime.BuildInput) (string, bool) {
	dir := filepath.Dir(input.Handler)
	base := strings.Split(filepath.Base(input.Handler), ".")[0]
	for _, ext := range node.NODE_EXTENSIONS {
		file := filepath.Join(path.ResolveRootDir(input.CfgPath), dir, base+ext)

View on GitHub (pinned to a0bd20f762)

Solutions

1. Run `bun run setup` / reinstall so `.sst/platform` matches your SST CLI version, then retry
2. Remove `.sst/` directory and rebuild to clear stale platform artifacts
3. Patch or silence any extra console output in unenv.mjs so stdout contains only JSON
4. Pin a single SST version across CI and local machines

// sanity-check that unenv.mjs emits pure JSON before deploying
const { execSync } = require("child_process");
const out = execSync("node .sst/platform/src/runtime/worker/unenv.mjs '{}'").toString();
JSON.parse(out); // throws if extra non-JSON output pollutes stdout

try {
  await run("sst", ["deploy"]);
} catch (e) {
  if (/failed to decode cloudflare unenv config/.test(String(e))) {
    console.error("unenv.mjs output was not JSON. Reinstall .sst/platform to match your SST CLI version.");
  } else throw e;
}

When it happens

Trigger: `json.Unmarshal(output, &result)` fails in `getUnenv` — e.g. unenv.mjs printed a warning/extra text before the JSON, an older platform script emitted a different schema, or the process was truncated.

Common situations: Out-of-sync `.sst/platform` (old unenv.mjs with new CLI or vice versa); npm update banners or noisy console.log injected into stdout; manually patched platform scripts; mixed SST version artifacts after an upgrade.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• failed to load cloudflare unenv config: %w %s
• Invalid worker definition for the "${name}" Worker
• failed to parse properties: %w
• not implemented
• failed to parse API response: %v

AI-assisted analysis of anomalyco/sst@a0bd20f762 (2026-08-30). Data as JSON: /api/errors/6deb6969d2210349. Report an issue: GitHub.