Prevents setting headers multiple times#552

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Merged
w3nl merged 3 commits into from
Feb 18, 2026
Merged

Prevents setting headers multiple times #552

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2d52fa3
Prevents setting headers multiple times
pieterwigboldus-visma Feb 18, 2026
3cf3812
Prevents further processing after headers are sent
pieterwigboldus-visma Feb 18, 2026
e0ac0ac
Prevents further processing after headers sent
pieterwigboldus-visma Feb 18, 2026
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4 changes: 3 additions & 1 deletion src/handlers/not-found.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
response.status(404)
if (!response.headersSent) {
response.status(404)
}
return {
status: 404,
timestamp: new Date(),
Expand Down
4 changes: 3 additions & 1 deletion src/handlers/request-validation.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
response.status(400)
if (!response.headersSent) {
response.status(400)
}
return {
errors: context.validation.errors,
status: 400,
Expand Down
20 changes: 14 additions & 6 deletions src/handlers/response-validation.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
// Prevent sending response if headers are already sent (e.g., after redirect)
if (response.headersSent) {
return undefined
}
Comment on lines +3 to +5

CopilotAIFeb 18, 2026

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This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.

Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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@copilot open a new pull request to apply changes based on this feedback


const responseDoesntNeedValidation = response.statusCode >= 400
if (responseDoesntNeedValidation) {
return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
response: context.response
})
}
return response.status(502).json({
errors: valid.errors,
status: 502,
timestamp: new Date(),
message: 'Bad response'
})
if (!response.headersSent) {
return response.status(502).json({
errors: valid.errors,
status: 502,
timestamp: new Date(),
message: 'Bad response'
})
}
return undefined
}
Comment on lines +30 to 39

CopilotAIFeb 18, 2026

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In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).

Copilot uses AI. Check for mistakes.

if (!context.response) {
Expand Down
4 changes: 3 additions & 1 deletion src/handlers/unauthorized.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
response.status(401)
if (!response.headersSent) {
response.status(401)
}
return {
status: 401,
timestamp: new Date(),
Expand Down
Loading
, '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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Prevents setting headers multiple times#552

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 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

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This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

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In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

, '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
Prevents setting headers multiple times#552

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

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The reason will be displayed to describe this comment to others. Learn more.

This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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ContributorAuthor
Choose a reason for hiding this comment

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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

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

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Prevents setting headers multiple times#552

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 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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ContributorAuthor
Choose a reason for hiding this comment

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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

Copy link

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The reason will be displayed to describe this comment to others. Learn more.

In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

, '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
Prevents setting headers multiple times#552

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
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 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

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+5

CopilotAIFeb 18, 2026

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This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

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In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

, '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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Prevents setting headers multiple times#552

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 Merged

w3nl
merged 3 commits into

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Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

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This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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ContributorAuthor
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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

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In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

, '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
Prevents setting headers multiple times#552

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 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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3 commits


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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

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The reason will be displayed to describe this comment to others. Learn more.

This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

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ContributorAuthor
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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading

, '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
Prevents setting headers multiple times#552

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

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 Merged

w3nl
merged 3 commits into

from

Feb 18, 2026
 Merged


Prevents setting headers multiple times
#552
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2d52fa3

Prevents setting headers multiple times


pieterwigboldus-visma Feb 18, 2026
3cf3812

Prevents further processing after headers are sent


pieterwigboldus-visma Feb 18, 2026
e0ac0ac

Prevents further processing after headers sent


pieterwigboldus-visma Feb 18, 2026

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4 changes: 3 additions & 1 deletion
src/handlers/not-found.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const notFound = (_context, request, response) => {
 response.status(404)
 if (!response.headersSent) {
 response.status(404)
 }
 return {
 status: 404,
 timestamp: new Date(),
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/request-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const requestValidation = (context, request, response) => {
 response.status(400)
 if (!response.headersSent) {
 response.status(400)
 }
 return {
 errors: context.validation.errors,
 status: 400,
Expand Down

20 changes: 14 additions & 6 deletions
src/handlers/response-validation.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,4 +1,9 @@
export default (logger, validateResponse) => (context, request, response) => {
 // Prevent sending response if headers are already sent (e.g., after redirect)
 if (response.headersSent) {
 return undefined
 }

Comment on lines

+3
 to 
+5

CopilotAIFeb 18, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This early return when headers are already sent is inconsistent with the pattern used in other handlers (unauthorized.js, request-validation.js, not-found.js), where the handler still returns a response object even if headers were already sent - they just skip setting the status code. Returning undefined here might prevent downstream code from understanding what should have been returned. Consider removing this early return and instead checking headersSent before each response.json/response.send/response.end call, which would allow the handler to still process and validate the response while avoiding sending headers twice.
Copilot uses AI. Check for mistakes.

@w3nlw3nlFeb 18, 2026

Copy link


Copy Markdown

ContributorAuthor
Choose a reason for hiding this comment

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@copilot open a new pull request to apply changes based on this feedback

 const responseDoesntNeedValidation = response.statusCode >= 400
 if (responseDoesntNeedValidation) {
 return response.json(context.response)
Expand All@@ -22,12 +27,15 @@ export default (logger, validateResponse) => (context, request, response) => {
 response: context.response
 })
 }
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 if (!response.headersSent) {
 return response.status(502).json({
 errors: valid.errors,
 status: 502,
 timestamp: new Date(),
 message: 'Bad response'
 })
 }
 return undefined
 }

Comment on lines

+30
 to 
39

CopilotAIFeb 18, 2026

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

In the validation-error path, falling back to response.end() when headersSent is true has the same risk of terminating an in-progress streamed/manual response. Prefer returning without writing, or only ending when the response hasn't already been ended (writableEnded/finished).
Copilot uses AI. Check for mistakes.


 if (!context.response) {
Expand Down

4 changes: 3 additions & 1 deletion
src/handlers/unauthorized.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
export const unauthorized = async (context, request, response) => {
 response.status(401)
 if (!response.headersSent) {
 response.status(401)
 }
 return {
 status: 401,
 timestamp: new Date(),
Expand Down
Loading