A guide to Streamdown, a React library for displaying Markdown while AI responses are still arriving. Markdown is plain text with formatting such as headings, links, and code blocks.

Use it when building AI chat screens, displaying output from useChat or streamText, or replacing react-markdown with a streaming-friendly renderer.

It helps chat interfaces render incomplete or changing AI output correctly while it streams, including migration from react-markdown.

streamdown — Skill for Codex by BjornMelin/dev-skills

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add BjornMelin/dev-skills --skill streamdown

Clone the repo

git clone --depth 1 https://github.com/BjornMelin/dev-skills

Made for: Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/bjornmelin/dev-skills/streamdown/github.svg)](https://agentmods.dev/skills/bjornmelin/dev-skills/streamdown)

Your own site

<a href="https://agentmods.dev/skills/bjornmelin/dev-skills/streamdown"><img src="https://agentmods.dev/badge/skills/bjornmelin/dev-skills/streamdown/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/bjornmelin/dev-skills/streamdown"><img src="https://agentmods.dev/badge/skills/bjornmelin/dev-skills/streamdown.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 186 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,268 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00186	$0.02268
Opus 5.5	$0.00074	$0.00907
Sonnet 5.5	$0.00037	$0.00454
Haiku 4.5	$0.00019	$0.00227

Measured 2mo ago against content hash 981ce0b56825, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

streamdown scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/ai_stack_scan.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/streamdown/SKILL.md · 335 lines

The source is not reproduced here

No licence file

Read it on GitHub

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 335 lines · 186 tokens per session scan A 981ce0b56825

Subscribe to this mod's changes

streamdown is a skill published in the GitHub repository BjornMelin/dev-skills (8 stars, last pushed 10d ago), with no licence file. It adds 186 tokens to every session and 2,268 once invoked, about $0.0007 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Data and AI Frontend React agent-skills agentic agentskills ai-agents ai-sdk codex

streamdown next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
streamdownBjornMelin/dev-skills	Skill	8	10d ago	none	A	186	Codex
pinecone-quickstartpinecone-io/pinecone-cursor-plugin	Skill	3	1mo ago	MIT	A	79	Cursor
pinecone-n8npinecone-io/pinecone-cursor-plugin	Skill	3	1mo ago	MIT	A	67	Cursor
pinecone-full-text-searchpinecone-io/pinecone-cursor-plugin	Skill	3	1mo ago	MIT	A	162	Cursor
ai-enterprise-ai-usecase-priority-assessmentskillsaiagent/aiskills	Skill	5	5mo ago	none	A	79	Codex
pinecone-clipinecone-io/pinecone-cursor-plugin	Skill	3	1mo ago	MIT	A	74	Claude Code, Cursor
pinecone-helppinecone-io/pinecone-cursor-plugin	Skill	3	1mo ago	MIT	A	52	Cursor