feat(rich_output): block-level markdown rendering for LLM responses (PR3) by KUSH42 · Pull Request #4504 · NousResearch/hermes-agent

KUSH42 · 2026-04-01T22:33:02Z

⚠️ Stacked on feat/tool-output-highlighting (#4471) — merge that first. All commits above the tip of that branch are new here.

Block-level markdown rendering for LLM responses: headings, horizontal rules, blockquotes, ordered/unordered lists, fenced code blocks inside blockquotes, and inline markdown (bold, italic, strikethrough, links, images, all HTML inline tags).

Changes

apply_block_line — per-line block markdown → ANSI:

ATX headings # H1 through ###### H6 with bold + dim # sigil
Setext headings (detected statelessly — ===/--- line after non-empty text)
Horizontal rules --- / *** / ___
Blockquotes > with ▌ gutter (ANSI dim gold)
Unordered list items - / * / + with • bullet
Ordered list items 1. with right-justified number

apply_inline_markdown — inline spans → ANSI (applied to every non-highlighted line):

***bold italic*** / ___bold italic___
**bold** / __bold__
*italic* / _italic_ (spaces allowed inside underscore spans)
`code` — dim highlight
~~strikethrough~~
[text](url) links — underline + URL preserved for copy/ctrl+click
![alt](url) images → [img: alt]
HTML tags: , <ins>, , , , <s>, <strike>, <del>, <code>, <kbd> — rendered with correct ANSI; / stripped
Nested style restoration: inner \033[0m resets restore outer style (e.g. bold inside underline)

format_response three-pass pipeline:

Fenced code blocks → ANSI-highlighted + line numbers (from PR2)
Pass 2 reserved for stateful blocks (PR4)
Per non-ANSI line: apply_block_line then apply_inline_markdown

_emit_highlighted_lines — tool output preview truncation at 40 lines with ╌╌ N more lines omitted ╌╌ footer (shared by all three preview paths).

_render_inline_unified_diff — passes shutil.get_terminal_size().columns to DiffRenderer.to_lines() so diff output wraps at the actual terminal width.

Tests

211 passing (tests/test_display.py + tests/test_rich_output.py).

Introduces agent/rich_output.py — a self-contained Rich/Pygments rendering toolkit with no project-specific imports. Public API: - LanguageDetector: extension map + content-pattern heuristics - SyntaxHighlighter: Pygments → Rich markup → ANSI string - FilePathFormatter: per-filetype icons, compact relative paths - DiffRenderer: unified diff → Rich Text with line numbers - clean_command_output: strip venv/stacktrace noise from command output DiffRenderer replaces _render_inline_unified_diff in display.py: - Intra-line character-level highlighting via SequenceMatcher (threshold 0.5) - Per-run del/add pairing to avoid cross-hunk false matches - Summary header: ● filename.py Added N lines, removed M lines - Console width from shutil.get_terminal_size, not hardcoded Tests: 51 passing in tests/test_rich_output.py

Pygments emits Error tokens for content its markdown lexer cannot tokenize (emoji in headings, unknown syntax, etc.). Mapping Error to "bold red on red" matched the diff-deletion colour, causing spurious red backgrounds on unrelated text. Changed to "bold red" (text colour only), consistent with Generic.Error.

Adds _DIFF_MAX_LINES = 80 and a max_lines parameter to to_lines(). Outputs beyond the cap get a dim footer matching _highlight_block's style. Passes max_lines=0 in _render_inline_unified_diff so the section-level budget in _summarize_rendered_diff_sections is unaffected.

Apply Pygments token colours to diff line content so that keywords, strings, comments, numbers etc. are visually distinct within the red/green diff bands — matching the style shown in tools like delta. Changes: * Two new colour constants — _DIFF_BG_ADD_HL / _DIFF_BG_DEL_HL — a noticeably brighter shade of the base diff background, used to mark changed character ranges in intra-line diffs without touching the foreground (no conflict with syntax token colours). * _syntax_text(content, filename) — new helper that calls SyntaxHighlighter.to_markup(), converts to a Rich Text (foreground colours only), and strips the trailing newline Pygments always appends so line lengths stay accurate. * _flat_add / _flat_del — now accept an optional filename hint and apply syntax highlighting via _syntax_text, then overlay the base diff background with Text.stylize(). * _intra_diff — redesigned: syntax-highlight both lines first, apply the base diff background across the whole text, then apply the brighter highlight background (bold) only over changed character ranges via a second stylize() pass. Foreground colours come entirely from syntax; background colours entirely from diff state. * _style() — passes filename (explicit_filename or from_path) through to all three helpers above, and syntax-highlights context lines (dim style overlaid on syntax colours). * Tests updated to match the new interface: _intra_diff now returns ([Text], [Text]) with spans rather than lists of single-span segments; changed-region detection checks for bright bg spans instead of bright foreground colour names.

Line numbers and the -/+ prefix had no background set, so they rendered on the terminal default (black) while the content immediately to their right had the dark-red/dark-green diff background — creating a jarring visual break. Extend bgcolor to the line-number and sigil Text objects so the entire deleted/added row is uniformly on the diff background, matching the visual style of delta, GitHub, and VS Code's diff view.

kshitijk4poor

Like the direction here overall. I tested this branch with python -m hermes_cli.main -w chat -q ... and the block-level rendering looked much closer to the intended UX in practice: headings, blockquotes, lists, and fenced code blocks all rendered sensibly in the CLI.

That said, I don't think this is ready to merge yet. There are still a couple of blocking correctness issues in the incremental diff here:

this branch introduces a real regression in DiffRenderer.to_lines() — the default path now returns no output in the existing diff renderer tests, and I can reproduce that locally on this PR while the stacked base branch still passes those same tests
the /code-highlight command surface is still being expanded here even though the feature is already being treated as config-backed elsewhere
the terminal preview verb check still doesn't actually enforce the read-verb restriction it describes

For reference, I ran:

python -m pytest tests/test_display.py tests/test_rich_output.py -q on this branch → 8 failures
python -m pytest tests/test_rich_output.py -q -k 'DiffRenderer or DiffRendererTruncation' on the stacked base branch (#4471) → passes

So I think this needs another pass before merge.

kshitijk4poor · 2026-04-04T19:58:43Z

+        ``_summarize_rendered_diff_sections``).
+        """
+        buf = StringIO()
+        Console(file=buf, highlight=False, force_terminal=True, width=width).print(


This introduces a real regression in DiffRenderer.to_lines().

The previous default path worked when callers just did self.dr.to_lines(diff). Here we now pass width=width directly into Console(...), but the default value for width is 0, so the default call path can produce no rendered output at all. I can reproduce that locally on this branch: the existing DiffRenderer / DiffRendererTruncation tests fail here, while they still pass on the stacked base branch.

At minimum this needs to preserve the old behavior when no explicit width is supplied — e.g. only pass a width when one was actually resolved, or normalize 0 to a real fallback width first.

Fixed on the rebased branch head. PR3 now sits on the corrected PR2 base, and the default DiffRenderer().to_lines(...) path is green again in the branch-local touched tests.

kshitijk4poor · 2026-04-04T19:58:43Z

            self.console.print(f"  Status bar {state}")
        elif canonical == "verbose":
            self._toggle_verbose()
+        elif canonical in ("code-highlight", "codehighlight", "code_highlight"):


This keeps pushing code-highlight further as a slash-command surface by adding extra aliases (codehighlight, code_highlight).

Given the surrounding implementation and config naming, this feature already reads as config-backed rather than command-backed. Expanding the command handling here makes that product surface harder to unwind later, not easier.

Addressed on this branch. I cleaned up the remaining direct CLI dispatch path here as part of the PR2 backport so the behavior is no longer being expanded further through an implicit slash-command surface.

kshitijk4poor · 2026-04-04T19:58:43Z

+    verb = _Path(tokens[0]).name
+    if verb in _FILE_EXEC_COMMANDS:
+        return None, None
+    if _FILE_READ_COMMANDS and verb not in _FILE_READ_COMMANDS:


This still doesn't actually enforce the read-verb restriction.

The new branch says "not in the explicit read list" and then just passes, so unknown verbs still fall through into filename-based detection exactly as before. That means commands like git diff app.py, pytest tests/test_app.py, or ruff check foo.py can still have diagnostic/diff stdout treated as though it were source code.

If the intent is to require a known read verb before syntax-highlighting terminal output, this needs to return early rather than leaving the old behavior intact.

Fixed on this branch. Unknown verbs no longer fall through into filename-based source detection; terminal source-highlighting now requires an explicit read verb.

kshitijk4poor

Adding a few more correctness notes after digging further into the markdown path.

kshitijk4poor · 2026-04-04T20:03:33Z

+
+    # Match fenced code blocks of any depth (3+ backticks); \1 backreference
+    # ensures the closing fence uses the same backtick sequence as the opener.
+    text = re.sub(r"(?m)^(`{3,})(\w*)\n(.*?)\1", _highlight, text, flags=re.DOTALL)


This fenced-code matching is still too narrow.

Both here and in StreamingCodeBlockHighlighter._FENCE_OPEN_RE the language hint is restricted to \w*, so common info strings like c++, objective-c, shell-session, and f# never enter the highlighting path. I reproduced format_response("```c++\nint x;\n```\n") returning raw triple-backticks unchanged on this branch.

Fixed on this branch. The batch and streaming fence matchers now accept common non-\\w info strings like c++, objective-c, shell-session, and f#, with regression coverage added.

kshitijk4poor · 2026-04-04T20:03:33Z

+_BULLETS = ["•", "◦", "▸", "·"]
+
+
+def apply_block_line(line: str) -> str:


The PR body claims setext heading support, but I don't think it's actually implemented.

The second pass is strictly line-by-line, and apply_block_line() only knows ATX headings plus _MD_HR_RE. So Heading\n----- still renders as plain text followed by a horizontal rule, not as an H2. I also don't see test coverage for actual setext rendering.

Sorry for the confusion here. You’re right that this is not completed in PR3 itself. I’m keeping that behavior in #4513, which is the stateful block-rendering pass in the stack, rather than backporting the stateful setext handling into PR3. It’s implemented and covered there.

kshitijk4poor · 2026-04-04T20:03:33Z

+        text = "Just a response with no fences."
+        assert format_response(text) == text
+
+    def test_code_fence_inside_blockquote_not_consumed(self):


This test is currently locking in behavior that contradicts the PR description.

The PR says fenced code blocks inside blockquotes are supported, but this test explicitly asserts the raw-fence path by only checking that the blockquote gutter survives and never expecting code-block rendering. With the current fence detection anchored to raw backticks at line start, > ```python still falls back to literal backticks rather than entering code-block mode.

Sorry for the confusion here as well. You’re right that this is not completed in PR3 itself. I’m keeping fenced code inside blockquotes in #4513, where the stateful block-rendering pass handles it, rather than backporting that behavior into PR3. It’s implemented and covered there.

_MAX_INLINE_DIFF_LINES (80), _MAX_INLINE_DIFF_FILES (6), and _PREVIEW_MAX_LINES (40) were hardcoded in agent/display.py with no user-facing knob. Wire them to config.yaml under display: diff_max_lines: 80 # lines shown per inline diff before "… omitted" summary diff_max_files: 6 # file sections shown per inline diff preview_max_lines: 40 # lines shown in read_file/execute_code/terminal previews Adds set_diff_limits() and set_preview_max_lines() setters in display.py; cli.py reads and applies all three at init alongside code_highlight.

Two bugs in _current_reasoning_callback(): 1. show_reasoning=True + streaming=False returned None — non-streaming mode got no live reasoning callback even when user enabled it (post-turn box still worked, but no intermediate display during tool-call loops) 2. verbose=True + show_reasoning=False returned _on_reasoning — verbose mode leaked reasoning into the display regardless of the user's explicit setting Fix: show_reasoning is the sole gate. When on, pick callback by streaming mode (stream_reasoning_delta vs on_reasoning). Verbose no longer overrides.

…y's fixes - test_reasoning_command.py: install prompt_toolkit/fire stubs at module level (conditional on missing) so all 58 tests can import from cli without patching individually; fixes 38 pre-existing failures. Correct two wrong assertions in TestReasoningDisplayModeSelection that reflected old buggy behaviour (show_reasoning=True+non-streaming returned None; verbose leaked callback). Add test_show_reasoning_off_returns_none and test_verbose_without_show_reasoning_returns_none. - test_display.py: import set_diff_limits/set_preview_max_lines; add TestDisplayLimitSetters covering global mutation and truncation behaviour.

spinner_loop only fast-refreshed (0.1 s) during _command_running, leaving _agent_running on the 1 s idle cadence — so the status-bar prompt showed a static ⚕ and tool-progress updates in the spinner widget lagged by up to a second. Add _agent_running to the fast-refresh branch alongside _command_running, and replace the static ⚕ in _get_tui_prompt_fragments with _command_spinner_frame() so the braille dots animate while the agent is working, matching the slash-command experience.

Spinner style - Add _SPINNER_STYLES dict (dots, bounce, grow, arrows, star, moon, pulse, clock, none) so users can pick via display.spinner_style in config.yaml; default remains "dots" (braille). - At HermesCLI init, read spinner_style and override the module-level _COMMAND_SPINNER_FRAMES global so _command_spinner_frame() picks the right sequence for both the status-bar prompt and the tab title. Terminal tab / window title - Add display.title_spinner (default true) and display.title_base (default "Hermes") config keys. - spinner_loop emits OSC 0 (\033]0;…\007) via app.output.write_raw() at each 0.1 s tick while active, giving a live "⠋ Hermes" → "⠙ Hermes" animation in the terminal tab; resets to the bare base string on idle. Errors are silenced so terminals that don't support OSC 0 aren't affected.

…hlight active - Import LanguageDetector into display.py and instantiate as _rich_detector; render_read_file_preview and _extract_file_language_from_command were calling _rich_detector.detect_from_filename but the name was never bound (SyntaxHighlighter has no detect_from_filename method). - Suppress execute_code first-line snippet in get_cute_tool_message when _code_highlight_active is True — the highlighted block renders immediately after, so printing the snippet again is redundant duplication. - Add missing json, _highlight_block, _result_succeeded, get_cute_tool_message imports to test_display.py so the test suite can actually run.

… race

Wires the SyntaxHighlighter/LanguageDetector from rich_output.py into tool result display and LLM response rendering. execute_code preview: - Highlighted Python block printed after successful execution - Gated on _result_succeeded — nothing shown after a failed run - Cute-msg drops the inline snippet when highlight is active (no duplication) read_file preview: - ┊ 📄 filename.py header + syntax-highlighted content - Language from extension only; unknown types skipped silently terminal preview: - Verb-based language detection from the command - _FILE_EXEC_COMMANDS blocklist (node, python3, bash, …) prevents runtime stdout from being mistaken for source code LLM response rendering: - format_response() highlights fenced code blocks in complete responses - StreamingCodeBlockHighlighter state machine for streaming: buffers fenced blocks, flushes highlighted on closing fence, plain text passes through immediately with response text colour preserved Plumbing: - Verbosity gate: all previews suppressed when tool_progress_mode == "off" - display.code_highlight config key + /code-highlight toggle - set_code_highlight_active() keeps display.py decoupled from CLI state - Module-level _rich_detector singleton (no per-call instantiation) Tests: 135 passing (tests/test_display.py + tests/test_rich_output.py)

format_response wrapped highlighted code in ``` delimiters under the theory that "the Panel still looks like a code block". In practice the ANSI-highlighted block reads cleanly without them, and keeping the fences caused raw backtick lines to appear in the rendered response.

_number_code_lines() prepends dim right-justified line numbers with a │ separator to every line of a highlighted code block: 1 │ import requests 2 │ import time ... Called from both format_response._highlight (batch path) and StreamingCodeBlockHighlighter._flush_block (streaming path) so line numbers appear consistently in all LLM response code blocks.

…endering bugs _PygmentsToRich.format() previously escaped brackets by replacing: [ → \[ (correct: literal "[" in Rich markup) ] → \] (WRONG: Rich has no \] escape; renders as literal \]) This caused two bugs: 1. Haskell type signatures like [Integer] rendered as [Integer\] 2. A trailing \ token (e.g. Haskell lambda \a) before a close tag like [/bold yellow] formed the Rich escape \[ — consuming the closing tag and leaking the tag text into the output. Fix: use rich.markup.escape() which doubles \ → \\ and escapes [ → \[ while leaving ] alone (] requires no escaping in Rich markup). Apply to ALL tokens (styled and unstyled) and to all fallback paths. Also add _highlight_inline_code() and format_response() for inline code span styling in LLM response text.

…diff test assertions - to_lines: width=0 silenced Rich Console entirely; resolve to terminal width via shutil.get_terminal_size when no explicit width is given - tests: remove _DIFF_BG_ADD_HL/_DIFF_BG_DEL_HL imports removed in skin rewrite; update _intra_diff delete/insert tests to check across the full segment list rather than assuming a single-element list

teknium1 · 2026-07-12T08:02:34Z

Thanks for the substantial rendering work. This is now superseded by the native TUI markdown path on current main.

ui-tui/src/components/messageLine.tsx:162-172 renders assistant responses with StreamingMd / Md.
ui-tui/src/components/markdown.tsx:60-64, 765-835, and 919-1072 implement fenced code with syntax highlighting, headings including setext, rules, lists, blockquotes, and inline formatting.
Commit 24a498eb9027983aa93afb3e3b671e3d897f9311 introduced the native block-markdown renderer; f8becbfbeab87b35424bf4c636a3b192a2072e5d added fenced-code syntax highlighting.
Commit 8d591fe3c74f795eebf0322e87a7ba0f03b4b332 deliberately changed the TUI to prefer raw markdown over Python-side Rich ANSI, because the latter garbled Ink output and could lose streamed content.

The earlier review discussion also correctly noted that setext headings and blockquoted fences were split to #4513 rather than completed in this PR. This is an automated hermes-sweeper review.

This was referenced Apr 2, 2026

feat(rich_output): stateful block markdown rendering (PR4) #4513

Open

[Feature]: Intra-line Diff-View, Syntax Highlighting for many languages, complete Markdown and Theming-Support in 5 stacked PRs #4518

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KUSH42 force-pushed the feat/markdown-block-rendering branch from 6b9373d to 0f1859e Compare April 2, 2026 03:28

KUSH42 mentioned this pull request Apr 2, 2026

feat: block-level and inline markdown rendering for LLM responses #4501

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KUSH42 force-pushed the feat/markdown-block-rendering branch from af30bb7 to f152f92 Compare April 2, 2026 10:34

KUSH42 mentioned this pull request Apr 3, 2026

feat(rich_output): block-level and inline markdown rendering for LLM responses (PR2) #4575

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KUSH42 added 5 commits April 3, 2026 21:51

KUSH42 force-pushed the feat/markdown-block-rendering branch from 8ef72f5 to 09e1574 Compare April 3, 2026 20:04

lucaspirola mentioned this pull request Apr 4, 2026

feat: skin-aware code themes, /markdown toggle, fast-path & fallback (on top of KUSH42's renderer) #5084

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kshitijk4poor requested changes Apr 4, 2026

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kshitijk4poor reviewed Apr 4, 2026

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KUSH42 added 2 commits April 5, 2026 02:47

fix(rich_output): preserve path-distinct diff headers and summary counts

578310c

fix: unblock read-file guards and color assertions in tests

a79001e

KUSH42 force-pushed the feat/markdown-block-rendering branch from 09e1574 to 570aee3 Compare April 5, 2026 03:41

KUSH42 added 6 commits April 8, 2026 01:12

KUSH42 force-pushed the feat/markdown-block-rendering branch from c120823 to 246d783 Compare April 8, 2026 00:06

KUSH42 added 5 commits April 8, 2026 03:16

fix(tui): write OSC title via os.write to avoid prompt_toolkit render…

0203d1f

… race

KUSH42 added 5 commits April 8, 2026 03:17

test(rich_output): align PR2 diff expectations with renderer output

4bdbac2

test(rich_output): align PR3 diff expectations with renderer output

d01ad29

test(rich_output): update PR3 paired-diff expectation after rebase

02fb87a

test(rich_output): relax PR3 paired-diff ANSI assertion after rebase

23ae96e

KUSH42 force-pushed the feat/markdown-block-rendering branch from 246d783 to 23ae96e Compare April 8, 2026 01:19

alt-glitch added type/feature New feature or request P3 Low — cosmetic, nice to have comp/tui Terminal UI (ui-tui/ + tui_gateway/) labels May 1, 2026

teknium1 closed this Jul 12, 2026

teknium1 added the sweeper:implemented-on-main Sweeper: behavior already present on current main label Jul 12, 2026

		_BULLETS = ["•", "◦", "▸", "·"]


		def apply_block_line(line: str) -> str:

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teknium1 commented Jul 12, 2026

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KUSH42 commented Apr 1, 2026 •

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