Streaming Ssr

What it does

When your agent uses it

• The user wants shell-first rendering
• Skeleton placeholders
• Parallel data fetching that resolves inline

Example prompts

• “/streaming-ssr”

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1renderStream is called instead of render when the route is hit
2. 2stream.write(html) flushes bytes to the browser immediately (chunked transfer encoding)
3. 3stream.placeholder(id, skeleton_html) writes a shimmer skeleton + into the live DOM
4. 4mer.fetchAll() fetches multiple URLs in parallel (threads on dev server, two-phase WASM bridge on Cloudflare Workers)
5. 5stream.resolve(id, real_html) injects a hidden div + inline that swaps the skeleton with real content
6. 6stream.flush() ends the response

What it can do on your machine

Read from SKILL.md and the folder at commit 28b53d8. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are zig).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • merlionjs.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Streaming Ssr loads about 1.1k tokens when it runs. Until then it costs about 42 tokens; SKILL.md has 258 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~42

When it runs · the whole SKILL.md, loaded when a task matches

~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from justrach/merjs at commit 28b53d8, republished under its MIT licence (© justrach). 258 words, ~1,118 tokens.

name

streaming-ssr

description

Add streaming SSR to a merjs page. Use when the user wants shell-first rendering, skeleton placeholders, or parallel data fetching that resolves inline.

argument-hint

[page-name]

disable-model-invocation

true

const std = @import("std");
const mer = @import("mer");

pub const meta: mer.Meta = .{
    .title = "PAGE_TITLE",
    .description = "PAGE_DESCRIPTION",
    .extra_head = "<style>" ++ page_css ++ "</style>",
};

// Fallback for non-streaming clients (required)
pub fn render(req: mer.Request) mer.Response {
    _ = req;
    return mer.html("<p>Requires streaming.</p>");
}

pub fn renderStream(req: mer.Request, stream: *mer.StreamWriter) void {
    const alloc = req.allocator;

    // Shell hits browser immediately — before any fetch
    stream.write(
        \\<div class="page">
        \\  <h1>PAGE_TITLE</h1>
    );

    // Skeleton placeholders — visible in DOM while fetching
    stream.placeholder("section-a",
        \\<div class="skeleton">Loading...</div>
    );

    // Fetch multiple URLs in parallel
    const results = mer.fetchAll(alloc, &.{
        .{ .url = "https://api.example.com/data-a" },
        .{ .url = "https://api.example.com/data-b" },
    });
    defer for (results) |r| if (r) |ok| ok.deinit(alloc);

    // Resolve skeleton → real content inline
    if (results[0]) |res| {
        stream.resolve("section-a", buildCard(alloc, res.body));
    } else {
        stream.resolve("section-a", "<p>Failed to load.</p>");
    }

    stream.write("</div>");
    stream.flush();
}

fn buildCard(alloc: std.mem.Allocator, body: []u8) []const u8 {
    _ = body;
    return std.fmt.allocPrint(alloc, "<div class=\"card\">data</div>", .{}) catch "error";
}

const page_css =
    \\.page { max-width: 640px; margin: 0 auto; }
    \\.card { background: var(--bg2); border-radius: 10px; padding: 20px; }
    \\.skeleton { background: var(--bg3); border-radius: 10px; padding: 20px; height: 80px;
    \\  position: relative; overflow: hidden; }
    \\.skeleton::after { content:''; position:absolute; inset:0;
    \\  background:linear-gradient(90deg,transparent,rgba(255,255,255,0.25),transparent);
    \\  animation:shimmer 1.5s infinite; }
    \\@keyframes shimmer { 0%{transform:translateX(-100%)} 100%{transform:translateX(100%)} }
;

© justrach, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/streaming-ssr of justrach/merjs.

Open the folder on GitHubat commit 28b53d8