Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909

Open
Open
Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
Assignees
chargome
Labels
BrowserBugNext.jsTraces

Description

@chargome
chargome
opened on Sep 2, 2026

What

With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.

Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.

Evidence

Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:

navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.

Likely mechanism

In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.

The popstate listener is then supposed to rename that same span:

if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}

Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.

Impact

navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.

Status

The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.

Activity

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    , 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
     blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

    Skip to content
    Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
    Open
    Open
    Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
    Assignees
    chargome
    Labels
    BrowserBugNext.jsTraces
    Description
    @chargome
    chargome
    opened on Sep 2, 2026
    What
    With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
    Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
    Evidence
    Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
    navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

    The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
    Likely mechanism
    In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
    The popstate listener is then supposed to rename that same span:
    if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
    Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
    Impact
    navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
    Status
    The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
    Activity
    Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
    Metadata
    Metadata
    Assignees
    Labels
    BrowserBugNext.jsTraces
    Projects
    No projects
      Milestone
      No milestone
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      None yet
      Development
      No branches or pull requests
      Issue actions
      
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

      Skip to content
      Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
      Open
      Open
      Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
      Assignees
      chargome
      Labels
      BrowserBugNext.jsTraces
      Description
      @chargome
      chargome
      opened on Sep 2, 2026
      What
      With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
      Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
      Evidence
      Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
      navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

      The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
      Likely mechanism
      In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
      The popstate listener is then supposed to rename that same span:
      if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
      Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
      Impact
      navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
      Status
      The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
      Activity
      Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
      Metadata
      Metadata
      Assignees
      Labels
      BrowserBugNext.jsTraces
      Projects
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        Milestone
        No milestone
        Relationships
        None yet
        Development
        No branches or pull requests
        Issue actions
        
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

        Skip to content
        Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
        Open
        Open
        Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
        Assignees
        chargome
        Labels
        BrowserBugNext.jsTraces
        Description
        @chargome
        chargome
        opened on Sep 2, 2026
        What
        With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
        Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
        Evidence
        Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
        navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

        The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
        Likely mechanism
        In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
        The popstate listener is then supposed to rename that same span:
        if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
        Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
        Impact
        navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
        Status
        The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
        Activity
        Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
        Metadata
        Metadata
        Assignees
        Labels
        BrowserBugNext.jsTraces
        Projects
        No projects
          Milestone
          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

          Skip to content
          Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
          Open
          Open
          Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
          Assignees
          chargome
          Labels
          BrowserBugNext.jsTraces
          Description
          @chargome
          chargome
          opened on Sep 2, 2026
          What
          With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
          Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
          Evidence
          Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
          navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

          The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
          Likely mechanism
          In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
          The popstate listener is then supposed to rename that same span:
          if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
          Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
          Impact
          navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
          Status
          The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
          Activity
          Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
          Metadata
          Metadata
          Assignees
          Labels
          BrowserBugNext.jsTraces
          Projects
          No projects
            Milestone
            No milestone
            Relationships
            None yet
            Development
            No branches or pull requests
            Issue actions
            
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

            Skip to content
            Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
            Open
            Open
            Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
            Assignees
            chargome
            Labels
            BrowserBugNext.jsTraces
            Description
            @chargome
            chargome
            opened on Sep 2, 2026
            What
            With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
            Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
            Evidence
            Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
            navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

            The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
            Likely mechanism
            In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
            The popstate listener is then supposed to rename that same span:
            if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
            Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
            Impact
            navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
            Status
            The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
            Activity
            Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
            Metadata
            Metadata
            Assignees
            Labels
            BrowserBugNext.jsTraces
            Projects
            No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
              Open
              Open
              Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
              Assignees
              chargome
              Labels
              BrowserBugNext.jsTraces
              Description
              @chargome
              chargome
              opened on Sep 2, 2026
              What
              With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
              Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
              Evidence
              Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
              navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

              The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
              Likely mechanism
              In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
              The popstate listener is then supposed to rename that same span:
              if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
              Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
              Impact
              navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
              Status
              The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
              Activity
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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                Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming #23909
                Open
                Open
                Next.js app router: router.back()/router.forward() navigations are tagged browser.popstate under span streaming#23909
                Assignees
                chargome
                Labels
                BrowserBugNext.jsTraces
                Description
                @chargome
                chargome
                opened on Sep 2, 2026
                What
                With span streaming enabled, a router.back() or router.forward() navigation in the Next.js app router produces a navigation span with navigation.type: 'browser.popstate' instead of router.back / router.forward.
                Under traceLifecycle: 'static' the same navigations are tagged router.back / router.forward.
                Evidence
                Observed in the nextjs-app-dir E2E app (Next 14.2.35, production build) while porting it to span streaming in #23905. The streamed event dump for a full run contains no router.back, router.forward or router.traverse value at all — only browser.popstate (6), router.push (7) and router.replace (2). The corresponding navigation spans:
                navigation /navigation/:param/router-back navigation.type=browser.popstate
navigation /navigation/:param/router-push navigation.type=browser.popstate (router.forward() case)

                The transaction-based versions of these two tests pass on develop today, so this is specific to streaming.
                Likely mechanism
                In packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts, router-patch mode (which is what Next 14 uses, since it has no onRouterTransitionStart hook) starts a navigation span tagged router.back/router.forward with the placeholder name INCOMPLETE_APP_ROUTER_INSTRUMENTATION_TRANSACTION_NAME, because back()/forward() carry no href.
                The popstate listener is then supposed to rename that same span:
                if(currentRouterPatchingNavigationSpanRef.current?.isRecording()){currentRouterPatchingNavigationSpanRef.current.updateName(spanName);// ... does not touch navigation.type}else{// creates a NEW span tagged 'browser.popstate'}
                Under streaming the ref appears to no longer be recording when popstate fires, so the else branch creates a second span tagged browser.popstate, and the original placeholder-named span is filtered out by the ignoreSpans entry that matches the placeholder name. The net effect is that the back/forward distinction is lost.
                Impact
                navigation.type no longer distinguishes back/forward from a plain popstate under streaming, for app router apps in router-patch mode.
                Status
                The two affected E2E tests (Creates a navigation span for \router.back()`and... `router.forward()``) are skipped in #23905 with a pointer to this issue, rather than having their expectations relaxed.
                Activity
                Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
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