fix(examples): use 404 status for invalid session IDs - #1560

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fix(examples): use 404 status for invalid session IDs#1560
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Summary

  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency

Files changed

  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers

Closes#389

Test plan

  • Verify all session-related 400 responses changed to 404
  • Non-session 400 responses (e.g., missing parameters) left unchanged

🤖 Generated with Claude Code

@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent requested a review from a team as a code ownerFebruary 20, 2026 16:43
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Latest commit: cbe631d

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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@modelcontextprotocol/server

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express

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@modelcontextprotocol/hono

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Just checking in — all checks are passing. Let me know if there's anything I should adjust!

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Thanks for the contribution! Closing in favor of #1770.

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Streamable HTTP examples use incorrect status code for invalid session IDs

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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" + '

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fix(examples): use 404 status for invalid session IDs - #1560
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fix(examples): use 404 status for invalid session IDs#1560
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@corvid-agent
@corvid-agentcorvid-agent
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Feb 20, 2026

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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


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, '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
fix(examples): use 404 status for invalid session IDs - #1560
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fix(examples): use 404 status for invalid session IDs#1560
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@corvid-agent
@corvid-agentcorvid-agent
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Feb 20, 2026

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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


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, '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
fix(examples): use 404 status for invalid session IDs - #1560
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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
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 Merged

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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


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@corvid-agent@felixweinberger

, '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
fix(examples): use 404 status for invalid session IDs - #1560
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fix(examples): use 404 status for invalid session IDs#1560
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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
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Mar 26, 2026
 Merged

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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


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@corvid-agent@felixweinberger

, '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('^' + ".*" + '

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fix(examples): use 404 status for invalid session IDs - #1560
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corvid-agent:fix/invalid-session-status-code
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fix(examples): use 404 status for invalid session IDs#1560
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corvid-agent:fix/invalid-session-status-code
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@corvid-agent
@corvid-agentcorvid-agent
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Feb 20, 2026

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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
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Feb 27, 2026

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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
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Mar 26, 2026
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@felixweinberger
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Mar 26, 2026

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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


2 participants

@corvid-agent@felixweinberger

, '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
fix(examples): use 404 status for invalid session IDs - #1560
Closed
corvid-agent wants to merge 1 commit into
modelcontextprotocol:mainfrom 
corvid-agent:fix/invalid-session-status-code
Closed
fix(examples): use 404 status for invalid session IDs#1560
corvid-agent wants to merge 1 commit into
modelcontextprotocol:mainfrom 
corvid-agent:fix/invalid-session-status-code
Conversation
@corvid-agent
@corvid-agentcorvid-agent
commented
Feb 20, 2026

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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
@changeset-bot
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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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Feb 20, 2026

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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
@corvid-agent
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Feb 27, 2026

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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
mentioned this pull request
Mar 26, 2026
 Merged

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@felixweinberger
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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


2 participants

@corvid-agent@felixweinberger

, '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
fix(examples): use 404 status for invalid session IDs - #1560
Closed
corvid-agent wants to merge 1 commit into
modelcontextprotocol:mainfrom 
corvid-agent:fix/invalid-session-status-code
Closed
fix(examples): use 404 status for invalid session IDs#1560
corvid-agent wants to merge 1 commit into
modelcontextprotocol:mainfrom 
corvid-agent:fix/invalid-session-status-code
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@corvid-agent
@corvid-agentcorvid-agent
commented
Feb 20, 2026

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Summary
  • Changes HTTP status code from 400 to 404 for invalid/missing session ID responses across all streamable HTTP examples
  • Per the MCP spec: "When a client receives HTTP 404 in response to a request containing an Mcp-Session-Id, it MUST start a new session"
  • Updated error messages from "Bad Request" to "Not Found" for consistency
Files changed
  • jsonResponseStreamableHttp.ts — POST handler
  • simpleStreamableHttp.ts — POST, GET, DELETE handlers
  • standaloneSseWithGetStreamableHttp.ts — POST, GET handlers
  • simpleTaskInteractive.ts — POST, GET, DELETE handlers
  • elicitationFormExample.ts — POST, GET, DELETE handlers
  • elicitationUrlExample.ts — POST, GET, DELETE handlers
Closes#389
Test plan
  •  Verify all session-related 400 responses changed to 404
  •  Non-session 400 responses (e.g., missing parameters) left unchanged
🤖 Generated with Claude Code
@corvid-agent@claude
fix(examples): use 404 status for invalid session IDs
cbe631d
Per the MCP spec, servers should respond with 404 when presented with
an invalid session ID, so clients know to start a new session. The
examples incorrectly used 400 for this case.
Closesmodelcontextprotocol#389
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@corvid-agent
corvid-agent
requested a review
from a team
as a code ownerFebruary 20, 2026 16:43
@changeset-bot
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Feb 20, 2026

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⚠️ No Changeset found
Latest commit: cbe631d
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1560

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1560

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1560

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1560

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1560

commit: cbe631d
@corvid-agent
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Just checking in — all checks are passing. Let me know if there's anything I should adjust!
@felixweinbergerfelixweinberger
mentioned this pull request
Mar 26, 2026
 Merged

9 tasks
@felixweinberger
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commented
Mar 26, 2026

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Thanks for the contribution! Closing in favor of #1770.
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Streamable HTTP examples use incorrect status code for invalid session IDs


2 participants

@corvid-agent@felixweinberger