Summary

When sharp is not installed (common on Linux global installs or slim Docker images) every resizeToJpeg / resizeToPng call inside the optimization loops throws MODULE_NOT_FOUND. The loop silently swallows all 25 (JPEG) or 20 (PNG) errors via an empty catch {}, so the final throw surfaces only a generic "Failed to optimize image" with no diagnostic information. Users have no way to tell whether the failure is a missing native dependency, an unsupported format, or a memory limit.

Root cause

optimizeImageToJpeg in src/web/media.ts (lines ~454-477) and optimizeImageToPng in src/media/image-ops.ts (lines ~429-454) both had:

} catch {
  // Continue trying other size/quality combinations
}
// ... after loop exhausted:
throw new Error("Failed to optimize image");

The catch block discarded the error entirely and the terminal throw provided no context.

Fix

Capture the last loop error in lastResizeErr. After the loop, include its message in the thrown error and attach it as cause:

let lastResizeErr: unknown;
// ... in loop:
} catch (err) {
  lastResizeErr = err;
}
// ... after loop:
const cause = lastResizeErr instanceof Error ? lastResizeErr : undefined;
const detail = lastResizeErr instanceof Error ? lastResizeErr.message : typeof lastResizeErr === "string" ? lastResizeErr : "";
throw new Error(
  detail ? `Failed to optimize image: ${detail}` : "Failed to optimize image",
  cause ? { cause } : undefined,
);

This is minimal -- no behavior change for successful paths, and the smallest fallback return is still reached before the throw when any combination succeeds.

Test plan

• Three new regression tests in src/web/media.test.ts (image optimization error surfacing describe block): mock resizeToJpeg to always reject with a specific Error, verify the caught error message includes the underlying cause, verify .cause is set, verify non-Error thrown values fall back to the generic message.
• All 27 tests in src/web/media.test.ts pass (vitest run src/web/media.test.ts)

Closes openclaw#73148

Generated by Claude Code