StreamableHttpClientTransport fails to list tools #468

Closed
Closed
StreamableHttpClientTransport fails to list tools#468
Labels
T-bugBug fixes and error corrections

Description

@min-mwei
min-mwei
opened on Oct 3, 2025

Describe the bug
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.

The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.

To Reproduce
Steps to reproduce the behavior:

  1. Currently I tested using an internal MCP server

Expected behavior
RMCP based client can connect and list tools.

Additional context
I add a patch to show what the fix could be: #467

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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
      StreamableHttpClientTransport fails to list tools #468
      Closed
      Closed
      StreamableHttpClientTransport fails to list tools#468
      Labels
      T-bugBug fixes and error corrections
      Description
      @min-mwei
      min-mwei
      opened on Oct 3, 2025
      Describe the bug
      
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
      The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
      To Reproduce
      
Steps to reproduce the behavior:
      1. Currently I tested using an internal MCP server
      Expected behavior
      
RMCP based client can connect and list tools.
      Additional context
      
I add a patch to show what the fix could be: #467
      Metadata
      Metadata
      Assignees
      No one assigned
        Labels
        T-bugBug fixes and error corrections
        Type
        No type
        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("// 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
          StreamableHttpClientTransport fails to list tools #468
          Closed
          Closed
          StreamableHttpClientTransport fails to list tools#468
          Labels
          T-bugBug fixes and error corrections
          Description
          @min-mwei
          min-mwei
          opened on Oct 3, 2025
          Describe the bug
          
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
          The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
          To Reproduce
          
Steps to reproduce the behavior:
          1. Currently I tested using an internal MCP server
          Expected behavior
          
RMCP based client can connect and list tools.
          Additional context
          
I add a patch to show what the fix could be: #467
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            T-bugBug fixes and error corrections
            Type
            No type
            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("// 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
              StreamableHttpClientTransport fails to list tools #468
              Closed
              Closed
              StreamableHttpClientTransport fails to list tools#468
              Labels
              T-bugBug fixes and error corrections
              Description
              @min-mwei
              min-mwei
              opened on Oct 3, 2025
              Describe the bug
              
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
              The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
              To Reproduce
              
Steps to reproduce the behavior:
              1. Currently I tested using an internal MCP server
              Expected behavior
              
RMCP based client can connect and list tools.
              Additional context
              
I add a patch to show what the fix could be: #467
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                T-bugBug fixes and error corrections
                Type
                No type
                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
                  StreamableHttpClientTransport fails to list tools #468
                  Closed
                  Closed
                  StreamableHttpClientTransport fails to list tools#468
                  Labels
                  T-bugBug fixes and error corrections
                  Description
                  @min-mwei
                  min-mwei
                  opened on Oct 3, 2025
                  Describe the bug
                  
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
                  The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
                  To Reproduce
                  
Steps to reproduce the behavior:
                  1. Currently I tested using an internal MCP server
                  Expected behavior
                  
RMCP based client can connect and list tools.
                  Additional context
                  
I add a patch to show what the fix could be: #467
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    T-bugBug fixes and error corrections
                    Type
                    No type
                    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
                      StreamableHttpClientTransport fails to list tools #468
                      Closed
                      Closed
                      StreamableHttpClientTransport fails to list tools#468
                      Labels
                      T-bugBug fixes and error corrections
                      Description
                      @min-mwei
                      min-mwei
                      opened on Oct 3, 2025
                      Describe the bug
                      
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
                      The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
                      To Reproduce
                      
Steps to reproduce the behavior:
                      1. Currently I tested using an internal MCP server
                      Expected behavior
                      
RMCP based client can connect and list tools.
                      Additional context
                      
I add a patch to show what the fix could be: #467
                      Metadata
                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        T-bugBug fixes and error corrections
                        Type
                        No type
                        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
                          StreamableHttpClientTransport fails to list tools #468
                          Closed
                          Closed
                          StreamableHttpClientTransport fails to list tools#468
                          Labels
                          T-bugBug fixes and error corrections
                          Description
                          @min-mwei
                          min-mwei
                          opened on Oct 3, 2025
                          Describe the bug
                          
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
                          The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
                          To Reproduce
                          
Steps to reproduce the behavior:
                          1. Currently I tested using an internal MCP server
                          Expected behavior
                          
RMCP based client can connect and list tools.
                          Additional context
                          
I add a patch to show what the fix could be: #467
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            T-bugBug fixes and error corrections
                            Type
                            No type
                            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("// 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); }
})();
})();

                              Skip to content
                              StreamableHttpClientTransport fails to list tools #468
                              Closed
                              Closed
                              StreamableHttpClientTransport fails to list tools#468
                              Labels
                              T-bugBug fixes and error corrections
                              Description
                              @min-mwei
                              min-mwei
                              opened on Oct 3, 2025
                              Describe the bug
                              
I have a case using RMCP based client connects successfully to the MCP server but it fails to list tools.
                              The streamable HTTP transport can deliver server-sent notifications (e.g., logging or connection-established events) before the JSON‑RPC initialize response. The previous implementation read only the first SSE frame and treated it as the response, which could stall initialization and cause later requests (like tools/list) to time out. This change makes the handshake resilient by waiting for the actual response.
                              To Reproduce
                              
Steps to reproduce the behavior:
                              1. Currently I tested using an internal MCP server
                              Expected behavior
                              
RMCP based client can connect and list tools.
                              Additional context
                              
I add a patch to show what the fix could be: #467
                              Metadata
                              Metadata
                              Assignees
                              No one assigned
                                Labels
                                T-bugBug fixes and error corrections
                                Type
                                No type
                                Projects
                                No projects
                                  Milestone
                                  No milestone
                                  Relationships
                                  None yet
                                  Development
                                  No branches or pull requests
                                  Issue actions