Workers, Durable Objects - Workers traces now automatically include JavaScript RPC session spans

<p>Workers traces can now follow JavaScript RPC calls across Worker boundaries and into Durable Objects. Previously, a trace stopped at the caller's RPC boundary. The dashboard now shows the caller-side session and method calls alongside the callee invocation, nested calls, and callbacks into another Worker.</p> <p>A session span covers the lifetime of a caller-side session and groups calls that reuse it. Individual call spans show each method invocation. Execution colors distinguish the Workers or Durable Object entrypoints involved, while arrows mark outgoing and incoming calls. Together, these details show where time was spent, which calls reused a session, and how returned stubs and callbacks fit into the request.</p> <img src="https://developers.cloudflare.com/cdn-cgi/image/onerror=redirect,width=2878,height=1576,format=webp/_astro/jsrpc-session-spans.DQuwQrpm.png" alt="A Workers trace of a Worker-to-Worker RPC session, showing the session span, the caller's getCounter and increment call spans, and the callee's invocation and matching call spans" loading="lazy" decoding="async" width="2878" height="1576"> <p>Enable tracing with one setting in your <a href="https://developers.cloudflare.com/workers/wrangler/configuration/#observability">Wrangler configuration file</a>:</p> <div data-nb-tabs data-nb-sync-key="wranglerConfig" class><div class="relative flex border-b border-border" role="tablist" data-nb-tabs-list><span class="bg-primary pointer-events-none absolute -bottom-px h-0.5 rounded-t-sm transition-[left,width] duration-200 ease-out" data-nb-tabs-indicator aria-hidden="true"></span></div><div class="mt-3"><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.jsonc" class><figure class="nb-code-figure" data-nb-lang="jsonc"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="jsonc" data-nb-lang="jsonc"><code><span class="line"><span class="nb-shiki-140thh">{</span></span> <span class="line"><span class="nb-shiki-dzsirb"> "$schema"</span><span class="nb-shiki-140thh">: </span><span class="nb-shiki-mdbnqw">"./node_modules/wrangler/config-schema.json"</span><span class="nb-shiki-140thh">,</span></span> <span class="line"><span class="nb-shiki-dzsirb"> "observability"</span><span class="nb-shiki-140thh">: {</span></span> <span class="line"><span class="nb-shiki-dzsirb"> "traces"</span><span class="nb-shiki-140thh">: {</span></span> <span class="line"><span class="nb-shiki-dzsirb"> "enabled"</span><span class="nb-shiki-140thh">: </span><span class="nb-shiki-dzsirb">true</span></span> <span class="line"><span class="nb-shiki-140thh"> }</span></span> <span class="line"><span class="nb-shiki-140thh"> }</span></span> <span class="line"><span class="nb-shiki-140thh">}</span></span></code></pre></figure></div><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.toml" class><figure class="nb-code-figure" data-nb-lang="toml"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="toml" data-nb-lang="toml"><code><span class="line"><span class="nb-shiki-140thh">[</span><span class="nb-shiki-1t8gfj">observability</span><span class="nb-shiki-140thh">.</span><span class="nb-shiki-1t8gfj">traces</span><span class="nb-shiki-140thh">]</span></span> <span class="line"><span class="nb-shiki-140thh">enabled = </span><span class="nb-shiki-dzsirb">true</span></span></code></pre></figure></div></div></div><script type="module" src="https://developers.cloudflare.com/home/runner/work/cloudflare-docs/cloudflare-docs/src/components/ui/tabs/Tabs.astro?astro&type=script&index=0&lang.ts"></script> <p>Cloudflare records these spans automatically. You do not need to change your application code or add an observability SDK.</p> <p>For supported spans and attributes, refer to <a href="https://developers.cloudflare.com/workers/observability/traces/spans-and-attributes/">Spans and attributes</a>.</p>