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fix: call onerror for silently swallowed transport errors - #1576

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qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom
qing-ant:fix/onerror-transport-errors
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fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom
qing-ant:fix/onerror-transport-errors

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@qing-ant

@qing-antqing-ant commented Feb 23, 2026

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Summary

Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.

Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.

Changes

packages/server/src/server/streamableHttp.ts

Added this.onerror?.(new Error(...)) calls at 16 locations:

  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)

packages/server/test/server/streamableHttp.test.ts

Added 11 test cases verifying onerror is called for each error condition:

  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method

Pattern Used

Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):

this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');

Testing

  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds

KKonstantinovand others added 30 commits December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others added 19 commits February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
qing-ant requested a review from a team as a code ownerFebruary 23, 2026 17:56
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Latest commit: 7e10f2c

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.

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npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1576

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npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1576

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commit: 7e10f2c

@qing-ant
qing-antforce-pushed the fix/onerror-transport-errors branch from 9d0b31f to 68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed the fix/onerror-transport-errors branch from 68401d6 to 7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant changed the base branch from main to v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant requested a review from a team as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit to qing-ant/typescript-sdk that referenced this pull request Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant mentioned this pull request Feb 24, 2026
Merged
3 tasks
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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage

17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
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(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
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;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix: call onerror for silently swallowed transport errors - #1576
Closed
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
Closed
fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
Conversation
@qing-ant
@qing-antqing-ant
commented
Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
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68401d6 to
7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
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Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

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fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
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fix: call onerror for silently swallowed transport errors - #1576
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fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
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@qing-ant
@qing-antqing-ant
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Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
qing-ant
requested a review
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as a code ownerFebruary 23, 2026 17:56
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⚠️ No Changeset found
Latest commit: 7e10f2c
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@1576

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1576

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1576

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1576

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1576

commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
68401d6 to
7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
 Merged

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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
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found = true;
var frag = document.createDocumentFragment();
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parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
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fix: call onerror for silently swallowed transport errors - #1576
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qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
Closed
fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
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@qing-ant
@qing-antqing-ant
commented
Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 23, 2026 17:56
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Feb 23, 2026•

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Latest commit: 7e10f2c
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.
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1576

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1576

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1576

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1576

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1576

commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
68401d6 to
7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
 Merged

3 tasks
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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix: call onerror for silently swallowed transport errors - #1576
Closed
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
Closed
fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
Conversation
@qing-ant
@qing-antqing-ant
commented
Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
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commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
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fix/onerror-transport-errors
branch
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7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
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qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
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function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
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fix: call onerror for silently swallowed transport errors - #1576
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fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
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qing-ant:fix/onerror-transport-errors
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@qing-ant
@qing-antqing-ant
commented
Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
qing-ant
requested a review
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as a code ownerFebruary 23, 2026 17:56
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commit: 7e10f2c
@qing-ant
qing-antforce-pushed
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fix/onerror-transport-errors
branch
from
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68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
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fix/onerror-transport-errors
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qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
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to qing-ant/typescript-sdk
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Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
 Merged

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Some transport errors are silently swallowed due to missing onerror callback usage


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@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

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fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
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fix: call onerror for silently swallowed transport errors - #1576
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qing-ant wants to merge 71 commits into
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qing-ant:fix/onerror-transport-errors
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fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
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qing-ant:fix/onerror-transport-errors
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Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
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Latest commit: 7e10f2c
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.
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@modelcontextprotocol/client
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1576

@modelcontextprotocol/server
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1576

@modelcontextprotocol/express
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1576

@modelcontextprotocol/hono
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1576

@modelcontextprotocol/node
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1576

commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
68401d6 to
7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
 Merged

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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring

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})();
})();
fix: call onerror for silently swallowed transport errors by qing-ant · Pull Request #1576 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix: call onerror for silently swallowed transport errors - #1576
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qing-ant wants to merge 71 commits into
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qing-ant:fix/onerror-transport-errors
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fix: call onerror for silently swallowed transport errors#1576
qing-ant wants to merge 71 commits into
modelcontextprotocol:v1.xfrom 
qing-ant:fix/onerror-transport-errors
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Feb 23, 2026

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Summary
Fixes#1395 - Transport errors are silently swallowed due to missing onerror callback invocation.
Several handleRequest error paths in WebStandardStreamableHTTPServerTransport were returning error responses via createJsonErrorResponse() without calling the onerror callback, making transport errors invisible to consumers who set transport.onerror.
Changes
packages/server/src/server/streamableHttp.ts
Added this.onerror?.(new Error(...)) calls at 16 locations:
  • handleGetRequest: Missing Accept header (406), concurrent SSE stream conflict (409)
  • replayEvents: Event store not configured (400), invalid event ID format (400), stream conflict (409)
  • handlePostRequest: Invalid Accept header (406), unsupported Content-Type (415), JSON parse error (400), invalid JSON-RPC message (400), re-initialization attempt (400), multiple init requests (400)
  • validateSession: Server not initialized (400), missing session ID (400), session ID mismatch (404)
  • validateProtocolVersion: Unsupported protocol version (400)
  • handleUnsupportedRequest: Method not allowed (405)
  • writeSSEEvent: SSE write failure (was silently returning false)
packages/server/test/server/streamableHttp.test.ts
Added 11 test cases verifying onerror is called for each error condition:
  • Invalid JSON
  • Invalid JSON-RPC message
  • Missing Accept header on POST
  • Unsupported Content-Type
  • Server not initialized
  • Invalid session ID
  • Re-initialization attempt
  • Missing Accept header on GET
  • Concurrent SSE streams
  • Unsupported protocol version
  • Unsupported HTTP method
Pattern Used
Follows the existing pattern already present in the codebase (e.g., validateRequestHeaders):
this.onerror?.(newError('Error message here'));returnthis.createJsonErrorResponse(status,code,'Error message here');
Testing
  • pnpm typecheck:all passes
  • pnpm --filter @modelcontextprotocol/server test — all tests pass (existing + 11 new)
  • pnpm build:all succeeds
KKonstantinovand others
added 30 commits
December 19, 2025 14:19
@KKonstantinov
[v2] Мonorepo,sdk-client,sdk-server,sdk-corepackage split (m…
71ae3ac
…odelcontextprotocol#1279)
@felixweinberger
fix: v2 follow-up improvements (modelcontextprotocol#1318)
8a1b457
@KKonstantinov
Changesets: add @changesets/changelog-github (modelcontextprotocol#1323)
f1f2550
@KKonstantinov
v2: changeset config fix (modelcontextprotocol#1324)
d4bd9fe
@KKonstantinov
changeset action update (modelcontextprotocol#1325)
f82c997
@starfish719
test: use toStrictEqual instead of toEqual in in-memory tests (modelc…
6b4d99f
…ontextprotocol#1330)
@DevJanderson@pcarleton
fix: prevent ReDoS vulnerability in UriTemplate regex patterns (model…
0a75810
…contextprotocol#1363)
Co-authored-by: Paul Carleton <paulc@anthropic.com>
@grimmerk@KKonstantinov
fix(client): replace body.cancel() with text() to prevent hanging (mo…
09a658b
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mattzcarey
fix(server): application/json header for notifictions (modelcontextpr…
8b6e455
…otocol#1373)
@mattzcarey
fix(server): add missing changeset for body.cancel() fix (modelcontex…
3466a9e
…tprotocol#1372)
@pcarleton
feat: add client conformance testing (modelcontextprotocol#1360)
1014d9f
@pcarleton
feat: add workflow to publish v1.x releases on tag push (modelcontext…
2bb7f47
…protocol#1367)
@pcarleton
Add server conformance testing (modelcontextprotocol#1375)
0073ab2
@felixweinberger
docs: add guidance on discussing features before opening PRs (modelco…
227c125
…ntextprotocol#1311)
@domdomegg
chore: update licensing to Apache 2.0 for new contributions (modelcon…
5ce4b5e
…textprotocol#1377)
@KKonstantinov
[v2] Decouple server from express and hono - http framework-agn…
f495077
…ostic MCP server (modelcontextprotocol#1326)
@KKonstantinov
readme fix (modelcontextprotocol#1391)
17a2c39
@KKonstantinov
flaky test fix (modelcontextprotocol#1392)
8bf13e4
@olaservo@claude@pcarleton
Use correct schema for client sampling validation when tools are pres…
2edbe8c
…ent (modelcontextprotocol#1347)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>
@KKonstantinov@mattzcarey
[v2] move to Headers object (modelcontextprotocol#1327)
40f6ba7
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@mattzcarey
Revert "fix(server): application/json header for notifictions" (model…
f66a55b
…contextprotocol#1388)
@mattzcarey
fix: prevent Hono from overriding global Response object (modelcontex…
9296459
…tprotocol#1410)
@KKonstantinov@mattzcarey
v2ESlint fixes (modelcontextprotocol#1403)
9fc7e28
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com>
@jonathanhefner@KKonstantinov
Add API documentation with GitHub Pages deployment (modelcontextproto…
25f288b
…col#1109)
Co-authored-by: Konstantin Konstantinov <konstantin@mach5technology.com>
@dependabot
chore(deps): bump hono from 4.11.3 to 4.11.4 in the npm_and_yarn grou…
55a28ed
…p across 1 directory (modelcontextprotocol#1413)
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@KKonstantinov
eslint fixes in tests (modelcontextprotocol#1418)
bf6f16c
@KKonstantinov
v2: pnpm audit fixes (modelcontextprotocol#1394)
3eb18ec
@felixweinberger
fix: resolve pnpm audit vulnerabilities by removing @pnpm/workspace.*…
11e3266
… deps (modelcontextprotocol#1422)
@KKonstantinov@felixweinberger
v2- clean deprecated methods and exports (modelcontextprotocol#1419)
dcf708d
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@su-ram@felixweinberger
fix(server): handle undefined arguments for tools with all optional p…
b2326af
…arams (modelcontextprotocol#1404)
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
jonathanhefnerand others
added 19 commits
February 10, 2026 23:45
@jonathanhefner@claude
docs: add missing code fences to JSDoc@exampleblocks (modelcontex…
64fb21d
…tprotocol#1485)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
@jonathanhefner@claude
docs: add{@link}and@seetags to JSDoc comments (modelcontextpr…
efed431
…otocol#1490)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
docs: fix grammar, typos, and style in JSDoc comments (modelcontextpr…
7778c74
…otocol#1491)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@LucaButBoring@KKonstantinov
feat: add streaming methods for elicitation and sampling (modelcontex…
91f6a27
…tprotocol#1210)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@jonathanhefner@claude@felixweinberger
Add code reference links and backticks to JSDoc comments (modelcontex…
42b3359
…tprotocol#1484)
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>
@jonathanhefner@claude
Addsync-snippetsscript for type-checked examples (modelcontextpro…
553d6d4
…tocol#1487)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
ci: add TypeDoc validation to check:all with treatWarningsAsErrors (
55857a8
modelcontextprotocol#1522)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add JSDoc@exampletags with companion.examples.tsfiles (modelc…
c9ac842
…ontextprotocol#1524)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Overhaul docs/server.md to be a more complete, self-contained serve…
20d5e4e
…r guide (modelcontextprotocol#1525)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Add new sections and inline code snippets todocs/client.md(modelc…
288eaf8
…ontextprotocol#1526)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@felixweinberger@hassan123789
feat: expose discoverOAuthServerInfo() and add provider caching for a…
dc896e1
…uth server URL (modelcontextprotocol#1527)
Co-authored-by: hassan123789 <49031989+hassan123789@users.noreply.github.com>
@jonathanhefner@claude
Dissolvecapabilities.mdintoserver.mdandclient.md(modelcon…
284a413
…textprotocol#1532)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
fix: resolve TypeDoc warnings from directory-pointing relative links (m…
2b620d7
…odelcontextprotocol#1546)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build a weather server" quickstart guide (modelcontextprotoco…
6cd75c6
…l#1549)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Import "Build an LLM-powered chatbot" quickstart guide (modelcontextp…
d6dc0ab
…rotocol#1550)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@localden
Update SECURITY.md to use GitHub Security Advisories (modelcontextpro…
3c31f96
…tocol#1555)
@jonathanhefner@claude
Add JSDoc descriptions and @example blocks to Client public metho…
1c4c77a
…ds (modelcontextprotocol#1556)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Replace Claude for Desktop with VS Code + Copilot in server quickstart (
ad6b177
modelcontextprotocol#1557)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jonathanhefner@claude
Rewritedocs/client.mdas a code-heavy, prose-light how-to guide (m…
c4ee360
…odelcontextprotocol#1551)
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@qing-ant
qing-ant
requested a review
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as a code ownerFebruary 23, 2026 17:56
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Latest commit: 7e10f2c
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commit: 7e10f2c
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
9d0b31f to
68401d6CompareFebruary 23, 2026 18:20
@qing-ant
fix: call onerror for silently swallowed transport errors
7e10f2c
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
All tests verified to fail without the fix and pass with it.
@qing-ant
qing-antforce-pushed
the
fix/onerror-transport-errors
branch
from
68401d6 to
7e10f2cCompareFebruary 23, 2026 19:25
@qing-ant
qing-ant
changed the base branch from
main
to
v1.xFebruary 24, 2026 20:07
@qing-ant
qing-ant
requested a review
from a team
as a code ownerFebruary 24, 2026 20:07
qing-ant added a commit
to qing-ant/typescript-sdk
that referenced
this pull request
Feb 24, 2026
@qing-ant
fix: call onerror for silently swallowed transport errors
d9dbb1b
Fixesmodelcontextprotocol#1395 - Several handleRequest error paths in
WebStandardStreamableHTTPServerTransport were returning error responses
via createJsonErrorResponse() without calling the onerror callback,
making transport errors invisible to consumers.
Added this.onerror?.() calls at 16 locations:
- handleGetRequest: Missing Accept header (406), concurrent SSE stream (409)
- replayEvents: Event store not configured (400), invalid event ID (400),
stream conflict (409)
- handlePostRequest: Invalid Accept header (406), unsupported Content-Type
(415), JSON parse error (400), invalid JSON-RPC (400), re-initialization
(400), multiple init requests (400)
- validateSession: Server not initialized (400), missing session ID (400),
session ID mismatch (404)
- validateProtocolVersion: Unsupported protocol version (400)
- handleUnsupportedRequest: Method not allowed (405)
- writeSSEEvent: SSE write failure
Added 12 test cases verifying onerror is called for each error condition.
Rebased from PR modelcontextprotocol#1576 (main) onto v1.x branch with path adjustments:
- Source: src/server/webStandardStreamableHttp.ts (v1.x) vs
packages/server/src/server/streamableHttp.ts (main)
- Tests: Added to existing test/server/streamableHttp.test.ts
@qing-antqing-ant
mentioned this pull request
Feb 24, 2026
 Merged

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Successfully merging this pull request may close these issues.

Some transport errors are silently swallowed due to missing onerror callback usage


17 participants

@qing-ant@KKonstantinov@felixweinberger@starfish719@DevJanderson@grimmerk@mattzcarey@pcarleton@domdomegg@olaservo@jonathanhefner@su-ram@christso@PederHP@localden@corvid-agent@LucaButBoring