ci: add CodSpeed benchmark suite

[farnabaz]

What

Adds CodSpeed performance tracking with 41 Vitest benches (benchmarks/*.bench.ts) covering parse, auto-close and streaming, HTML/ANSI/markdown rendering, and plugins including shiki/rangi highlighting, run in CPU simulation on main and every PR. Supersedes #388 and #389, combining #389's setup (OIDC, action v5) with #388's benchmark design, and removes packages/comark/test/benchmark.test.ts, which benchmarked parseMarkdown against itself under a "markdown-it" label.

Why

Performance is a core Comark claim, and parser changes can quietly cause regressions. Both earlier PRs had issues: #388's lockfile downgraded the root workspace to vite 7, and #389's streaming bench mostly measured a cache hit, its benches had no warmup (noisy numbers), and it had no adversarial or component-heavy inputs. @codspeed/vitest-plugin@6 supports vite 8, so no packageExtensions workaround is needed.

Walkthrough

Setup

• benchmarks/vitest.config.ts: separate config with the CodSpeed plugin (a no-op locally), so benches and the root bundle-size test never pick up each other's files. Run them with pnpm bench (pnpm bench parse for one file).
• .github/workflows/codspeed.yml: CodSpeedHQ/action@v5, simulation mode, OIDC (no secret), cancels runs replaced by a newer commit. No build step, since the postinstall stubs point package dist/ at the sources.
• tinybench (peer) and @comark/html added as root dev deps; benches import packages by name. Benches are included in pnpm typecheck.

Benchmark design

• Every parser is created once and warmed at module load, Shiki's highlighter included, so samples measure steady-state work.
• Streaming benches each get their own parser and reset the incremental cache inside the bench body, so they measure actual parsing. A heading-free chat answer covers the path that reuses parsed nodes; the medium document has headings, which force a full reparse each time. Final streamed output was checked against a fresh parse.
• adversarialMarkdown (long delimiter runs, deep bracket/component nesting) is there to catch any parse time that grows faster than linear.

Docs

• New Benchmarks section in CONTRIBUTING.md, matching updates to AGENTS.md, CodSpeed badge in the README.

Local checks: pnpm lint, pnpm typecheck, pnpm bench, comark tests (1760 passing).

Summary by CodeRabbit

• New Features
  • Added benchmark coverage for Markdown parsing, rendering, plugins, and streaming across a range of document types and sizes.
  • Benchmarks run automatically for pull requests and pushes to the main branch, and can also be started manually.
• Documentation
  • Added guidance for running benchmarks locally, adding benchmark cases, and using separate cross-library comparisons.
  • Added a CodSpeed badge to the project README.

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Project	Deployment	Actions	Updated
comark	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-binding	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-json-render	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-nextjs	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-nuxt	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-svelte	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-sveltekit	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-twoslash	Ready	Preview	Oct 15, 2026 3:30pm UTC
comark-vue	Ready	Preview	Oct 15, 2026 3:30pm UTC

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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• .github/workflows/codspeed.yml

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• .github/workflows/codspeed.yml

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📝 Walkthrough

The pull request adds a CodSpeed-powered Vitest benchmark suite for parsing, plugins, rendering, and streaming. It adds shared Markdown fixtures, a CI workflow, benchmark commands and dependencies, and supporting documentation. It removes the previous logging-only benchmark test.

Changes: Benchmark suite

Layer / File(s)	Summary
Benchmark fixtures and runner benchmarks/fixtures.ts, benchmarks/vitest.config.ts, package.json, pnpm-workspace.yaml, tsconfig.json, test/bundle.test.ts	Adds shared Markdown fixtures and stream chunk generation. Configures Vitest for benchmark files, adds the pnpm bench script and development dependencies, includes benchmark files in TypeScript configuration, and updates the bundle-size snapshot.
Parsing and plugin benchmarks benchmarks/parse.bench.ts, benchmarks/plugins.bench.ts, packages/comark/test/benchmark.test.ts	Adds parser comparisons across document sizes and options, and plugin and syntax-highlighting comparisons. Removes the previous logging-only benchmark test.
Rendering benchmarks benchmarks/render.bench.ts	Adds HTML, ANSI, and Markdown render benchmarks, including selected parse-and-render cases.
Streaming benchmarks benchmarks/streaming.bench.ts	Adds auto-close and chunked streaming benchmarks. The replay helper resets incremental state before parsing each chunk sequence.
CI and benchmark guidance .github/workflows/codspeed.yml, AGENTS.md, CONTRIBUTING.md, packages/comark/README.md	Adds a CodSpeed workflow that runs pnpm bench in simulation mode. Documents benchmark commands and configuration, and adds a CodSpeed badge.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Other

Sequence Diagram(s)

sequenceDiagram
  participant CodSpeedWorkflow
  participant Pnpm
  participant Vitest
  participant BenchmarkSuites
  CodSpeedWorkflow->>Pnpm: Run pnpm bench in simulation mode
  Pnpm->>Vitest: Start benchmark mode with Vitest configuration
  Vitest->>BenchmarkSuites: Load benchmark files

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Merge Risk: ⚪ Minimal · up to 40ef5

This PR adds CodSpeed benchmarks and a CI workflow without changing library behavior. No actionable merge-blocking risk remains.

Pre-merge checks: 5

Passed checks: 5 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding a CodSpeed benchmark suite and its CI integration.
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 7 files. (1 skipped: 1 …
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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commit: 40ef5e6

[codspeed]

Congrats! CodSpeed is installed 🎉

🆕 41 new benchmarks were detected.

You will start to see performance impacts in the reports once the benchmarks are run from your default branch.

Detected benchmarks

• medium document without auto-close: 7.9 ms
• medium document without default plugins: 6.7 ms
• large document: 100.8 ms
• medium document: 8.7 ms
• small document: 2.8 ms
• all of the above combined: 12.7 ms
• baseline (default plugins only): 9.7 ms
• emoji: 9.7 ms
• footnotes: 10 ms
• punctuation: 10.5 ms
• security: 10.8 ms
• summary: 9.7 ms
• toc: 10.1 ms
• large document: 36.9 ms
• medium document: 2.9 ms
• large document: 64.5 ms
• medium document: 3 ms
• small document: 1.2 ms
• large document: 40.5 ms
• medium document: 3.7 ms
• ...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @.github/workflows/codspeed.yml:
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📥 Commits

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📒 Files selected for processing: 14

• .github/workflows/codspeed.yml
• AGENTS.md
• CONTRIBUTING.md
• benchmarks/fixtures.ts
• benchmarks/parse.bench.ts
• benchmarks/plugins.bench.ts
• benchmarks/render.bench.ts
• benchmarks/streaming.bench.ts
• benchmarks/vitest.config.ts
• package.json
• packages/comark/README.md
• packages/comark/test/benchmark.test.ts
• pnpm-workspace.yaml
• tsconfig.json

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