Troubleshooting

PNG returns 500 with "No CJK font loaded from KV"

Cause: font:arial-unicode-cn-gb2312 is missing or zero-byte in the SHORT_LINKS KV namespace. Without it, loadFonts throws (src/render.ts L92).

Fix: re-upload the CJK font (see Configuration page). SVG endpoints will still work — only PNG is affected.

Short link returns 404 short_link_not_found

The 30-day TTL expired or the KV record was deleted. resolveShortLink (src/index.ts L2372) calls env.SHORT_LINKS.get("short:" + token) — if null, returns 404.

For permanent references, use the long ?d= URL form. buildShortUrl (L2306) falls back to long URL when the encoded payload is <= 3600 chars.

SVG rendered but no CJK characters appear

SVG output uses regular <text> elements. Browsers may fall back to a default font if the device doesn't have CJK support. The PNG path uses pathifyCjkText (src/render.ts L139) which converts CJK glyphs to SVG paths — PNG is reliable across viewers.

expr-eval parse error on math expression

Parser.parse(expr) throws Parse error on.... The expression is truncated to 400 chars (MAX_EXPR_LENGTH) before parsing. Supported: +, -, *, /, ^ (power), sin/cos/tan/asin/acos/atan, log/ln/exp/sqrt/abs, min/max, PI/e constants, if/then/else, parentheses.

Force analysis diagram looks crowded

sanitizeForceAnalysisPayload (src/index.ts L848) auto-simplifies dense layouts. If you have 5+ forces on a single body, components/axes/angle labels/resultant may be hidden with a warning field. Pass show_components: true, show_axes: true, show_resultant: true, show_angle_labels: true explicitly to override.

Circuit template produces wrong layout

10 templates, each with different parameters. The default series template expects no extra params. parallel, switch_lamp, source_resistor, etc. each take specific resistor_label/source_label/switch_label args. See src/index.ts L529-545 for the schema.

Tool call returns unknown_tool:{name}

The name didn't resolve via lookupCompat (legacy) or resolveCanonicalToLegacy (canonical). Check spelling. Use one of the 24 names from the tools/list response or from the Tools Reference page.

PNG output is huge (multi-MB)

Default canvas is 1200x720. For subplot grids, outerWidth scales with row*col. If you have a 3x3 grid with large series, expect 5-10 MB PNGs. Pass a smaller series (points) or use SVG (render.format = "svg") which compresses better.

Deploy fails with "binding SHORT_LINKS not found"

The KV namespace ID in wrangler.toml (L12) doesn't match your account. Either update the id field or run wrangler kv:namespace create SHORT_LINKS and replace.

Force analysis drift detected

npm run check:force-drift computes a hash of the local-generated SVG and compares to the deployed worker. If they differ, the rendered output has changed — usually because sanitizeForceAnalysisPayload auto-simplification rules changed, or a renderForceAnalysisSvg in src/extras.ts was modified. Read both diffs before re-deploying.

Deploy preflight flags an issue

npm run check:deploy-preflight runs several sanity checks (type-check, font presence in KV, KV namespace accessibility). If it fails, read the script's stderr — it tells you which check failed.