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Known issues and limitations

What does not work yet, what was never meant to, and what works differently on purpose. Three different things, kept apart — a deliberate trade-off listed as a bug makes a considered decision look like neglect.

Applies to the prepared rich 0.0.4 / rs-rich 0.0.4 source snapshot, reviewed 2026-09-10 against Python rich 15.0.0. Each entry links to its issue so you can check the status without waiting for this page to be updated.

Bugs

Things that should work and do not.

Narrow --json output is display output, not machine-readable JSON

Scope. Default builds match upstream: narrow output may wrap or crop inside an escape, and --width crops overlong JSON lines. The optional, off-by-default json-escape-safe Cargo feature avoids partial escapes when cropping and keeps escapes together when folding at widths that can fit them. See DIVERGENCES §22. Neither mode promises machine-readable output; use the original JSON with jq when every value must survive.

Limitations

Things that are not implemented, and are not claimed to be.

Windows legacy console is not supported

rich assumes a VT-capable terminal. On Windows it enables virtual terminal processing; on a console that cannot do VT (very old cmd.exe), output will contain raw escape sequences.

Upstream falls back to the Win32 console API for these. That port has not been done — #12. Workaround: use Windows Terminal, or --no-color.

No Jupyter integration, and no Python-object inspection

jupyter.py and inspect/repr have no equivalent: they render live Python objects, which has no meaning in a Rust port. pretty and traceback are reimplemented Rust-natively instead — see Divergences.

SVG export is not self-contained offline

--export-svg references its font from a CDN. The HTML from --export-html is self-contained. If you need an offline SVG, embed the font yourself after export.

GIF interruption and export limitations

The 0.0.4 development build supports --gif-mode blocks; see the capability matrix. ASCII remains the default and the redirected/colorless fallback. Normal playback restores the cursor; Ctrl-C can leave it hidden, as before. GIF export and Sixel playback are unsupported.

CSV output still retains source rows

Undecorated CSV output streams styled rows, reducing output-buffer overhead. The 0.0.4 development build removes duplicate parsed-cell storage and trims row capacity, reducing the measured 100k-row peak RSS by about 46%. Source rows remain in memory for measurement, so memory still scales with input. Decorated, aligned, paged and exported CSV output still buffers. The 0.0.4 work in #74 reduces retained memory; it does not provide bounded-memory processing.

Long-line rendering still allocates memory

The 0.0.4 development build removes repeated UTF-8 prefix scans during Text wrapping. On the recorded Linux benchmark, the 5 MiB Markdown paragraph now finishes in 531 ms; it previously timed out after 10 seconds. Source and rendered lines still occupy memory. See measured results for input-path distinctions, output verification and reproducible samples.

Headerless text encodings must be selected explicitly

The development build supports --encoding utf-16, utf-16le, utf-16be and utf-8. Default files retain UTF-8 replacement decoding; stdin and URLs remain strict UTF-8. A recognized UTF-16 BOM gets an actionable hint. Headerless UTF-16 is not guessed: select its byte order explicitly or convert to UTF-8. See encoding troubleshooting.

Syntax parsing remains costly for varied source

The off-by-default 0.0.4 syntax-cache Cargo feature helps repeated boilerplate whose parser state stays unchanged. Default builds use uncached Syntect. Measured real-source files showed essentially unchanged runtime; loading and parsing new syntax still costs more than plain text. See the workload-specific results. Historical 0.0.2 Windows/Python comparisons are retained separately in the benchmark page; they are not current 0.0.4 measurements. The implemented scope of #45 is repeated-line parsing reuse, not a blanket syntax speedup.

Deliberate divergences

Things that work differently on purpose. The full list, each with its reasoning, is in Divergences; these are the ones you are most likely to notice.

Highlighted code does not match Python byte-for-byte

Upstream uses Pygments; this port uses syntect, which ships different grammars and themes. Colours therefore differ. Everything around the code — width, padding, wrapping, the background block — is parity-tested.

Replacing syntect would mean shipping a Pygments-equivalent lexer set, which is out of scope. This is divergence #18.

Raw ESC in input reaches the terminal

An escape character in a rendered file is passed through, exactly as upstream passes it through. It is listed here because it surprises people, not because it is a defect: matching upstream is the project's whole purpose.

If you render untrusted input and want it neutralised, that needs an opt-in sanitiser — #64. BEL, backspace, vertical tab and form feed are stripped, as upstream strips them.

Upstream tags OSC 8 hyperlinks with a random id derived from Python's RNG. Reproducing the byte sequence would mean reproducing the RNG, so ours omits it. Terminals do not depend on it. Divergence #20.

Fixed recently

Kept here so anyone on an older build still finds the symptom. Full detail in the changelog.

Symptom Fixed in
Diff exports lost graphical content when stdout was redirected 0.0.3
Notebook layout flags were ignored; title markup printed literally 0.0.3
Windows default pager failed to launch more.com 0.0.3
Redirected GIFs emitted cursor controls or looped forever 0.0.3
JSON rejected deep/non-finite input or rounded large integers 0.0.3
Early-closing CSV consumers produced an error 0.0.3
--csv printed a made-up one-column table and exited 0 on unreadable input 0.0.2 (round 9)
Markdown link destinations vanished from piped output 0.0.2 (round 9)
--syntax deleted every blank line in the file 0.0.2 (round 8)
Long lines in Markdown code blocks were cropped and their tail lost 0.0.2 (round 8)
Emoji and Indic text broke table and panel borders 0.0.2 (rounds 8–9)
Deeply nested Markdown crashed the process 0.0.2 (round 6)

Reporting something not listed here

Please open an issue with the exact command, the input if you can share it, and what you expected. If it is a parity difference from Python rich, Reporting a parity bug explains what makes those reports useful.

SVG export can squeeze CJK glyphs

SVG textLength uses character counts for some runs; wide CJK glyphs may overlap in the exported image. The same case reproduces in pinned Python Rich 15.0.0. Decoded text and plain terminal output retain the original characters. This is an export-layout limitation, separate from encoding support.