* fix: include http_request_id in request-wise priming event IDs
* refactor: use Option::into_iter and usize::from for priming
* fix: retain event cache for completed request-wise channels
* fix: track completed_at for cache eviction and resume
* fix: log resume failures at warn level
* test: add completed_cache_ttl eviction test
* fix: return empty stream on failed resume
* test: add resume after completion test
* fix(http): reduce latency on subsequent StreamableHttp calls
* refactor: rely on stream drain for connection reuse
* refactor: clean up comments and naming
* fix: restore pool_max_idle_per_host(0) for Linux
* feat(streamable-http): add json_response option for stateless server mode
Adds `json_response: bool` field to `StreamableHttpServerConfig`.
When true and `stateful_mode` is false, the server returns
`Content-Type: application/json` directly instead of `text/event-stream`,
eliminating SSE framing overhead for simple request-response patterns.
This completes server-side JSON response support (client-side was added
in #540) and contributes to the stateless server goals of SEP-1442 (#526).
Backwards-compatible: `json_response: false` (default) preserves all
existing SSE behaviour unchanged, and `stateful_mode: true` is unaffected.
Benchmark evidence (50 VUs, 5min, 2 CPUs):
- RPS: 770 → 1139 (+48%)
- get_user_cart latency: 41ms → 0.76ms (-98%)
- checkout latency: 41ms → 0.55ms (-99%)
- Zero regressions, zero errors
* fix(tower): add cancellation awareness and logging to JSON response path
* fix(test): add missing Default to StreamableHttpServerConfig in concurrent streams test
Made-with: Cursor
* fix(streamable-http): return 409 Conflict when standalone SSE stream already active
LocalSessionWorker::resume() unconditionally replaced self.common.tx on
every GET request, orphaning the receiver the first SSE stream was
reading from. All subsequent server-to-client notifications were sent to
the new sender while the original client was still listening on the old,
now-dead receiver. notify_tool_list_changed().await returned Ok(())
silently.
This is triggered by VS Code's MCP extension which reconnects SSE every
~5 minutes with the same session ID.
Fix: Check tx.is_closed() before replacing the common channel sender.
If an active stream exists, return SessionError::Conflict which is
propagated as HTTP 409 Conflict. This matches the TypeScript SDK
behavior (streamableHttp.ts:423).
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* fix(streamable-http): handle resume with completed request-wise channel
When a client sends GET with Last-Event-ID from a completed POST SSE
response, the request-wise channel no longer exists in tx_router.
Previously this returned ChannelClosed -> 500, causing clients like
Cursor to enter an infinite re-initialization loop.
Now falls back to the common channel when the request-wise channel is
completed, per MCP spec: "Resumption applies regardless of how the
original stream was initiated (POST or GET)."
* fix: allow SSE channel replacement instead of 409 Conflict
Per MCP spec §Streamable HTTP, "The client MAY remain connected to
multiple SSE streams simultaneously." Returning 409 Conflict when a
second GET arrives causes Cursor to enter an infinite re-initialization
loop (~3s cycle).
Instead of rejecting, replace the old common channel sender. Dropping
the old sender closes the old receiver, cleanly terminating the
previous SSE stream so the client can reconnect on the new stream.
This fixes both code paths:
- GET with Last-Event-ID from a completed POST SSE response
- GET without Last-Event-ID (standalone stream reconnection)
* fix: skip cache replay when replacing active SSE stream
When a client opens a new GET SSE stream while a previous one is
still active, the old sender is dropped (terminating the old stream)
and a new channel is created. Previously, sync() replayed all cached
events to the new stream, but the client already received those events
on the old stream. This caused an infinite notification loop:
1. Client receives notifications (e.g. ResourceListChanged)
2. Old SSE stream dies (sender replaced)
3. Client reconnects after sse_retry (3s)
4. sync() replays cached notifications the client already handled
5. Client processes them again → goto 2
Fix: check tx.is_closed() BEFORE replacing the sender. If the old
stream was still alive, skip replay entirely — the client already has
those events. Only replay when the old stream was genuinely dead
(network failure, timeout) so the client catches up on missed events.
* fix: use shadow channels to prevent SSE reconnect loops
When POST SSE responses include a `retry` field, the browser's
EventSource automatically reconnects via GET after the stream ends.
This creates multiple competing EventSource connections that each
replace the common channel sender, killing the other stream's receiver.
Both reconnect every sse_retry seconds, creating an infinite loop.
Instead of always replacing the common channel, check if the primary
is still active. If so, create a "shadow" stream — an idle SSE
connection kept alive by keep-alive pings that doesn't receive
notifications or interfere with the primary channel.
Also removes cache replay (sync) on common channel resume, as
replaying server-initiated list_changed notifications causes clients
to re-process old signals.
Signed-off-by: Myko Ash <myko@mcpmux.com>
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* test: comprehensive shadow channel tests (15 cases)
Rewrite test suite for SSE channel replacement fix:
- Shadow creation: standalone GET returns 200, multiple GETs coexist
- Dead primary: replacement, notification delivery, repeated cycles
- Notification routing: primary receives, shadow does not
- Resume paths: completed request-wise, common alive/dead
- Real scenarios: Cursor leapfrog, VS Code reconnect
- Edge cases: invalid session, missing header, shadow cleanup
Fix Accept header bug (was missing text/event-stream for
notifications/initialized POST, causing 406 rejection).
* fix: use correct HTTP status codes for session errors per MCP spec
MCP spec (2025-11-25) section "Session Management" requires:
- Missing session ID header → 400 Bad Request (not 401)
- Unknown/terminated session → 404 Not Found (not 401)
Using 401 Unauthorized caused MCP clients (e.g. VS Code) to
trigger full OAuth re-authentication on server restart, instead
of simply re-initializing the session.
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* fix: address review feedback — remove dead Conflict variant, restore sync on resume, rename test
- Remove unused SessionError::Conflict and dead string-matching in tower.rs
(leftover from abandoned 409 approach)
- Restore sync() replay when replacing a dead primary common channel so
server-initiated requests and cached notifications are not lost on reconnect
- Rename test from test_sse_channel_replacement_bug to test_sse_concurrent_streams
per reviewer suggestion (describe what tests verify, not what triggered them)
- Add test for cache replay on dead primary replacement
- Use generic "MCP clients" in comments instead of specific client names
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* fix: use minimal buffer for shadow streams and cap at 32
- Shadow streams only receive SSE keep-alive pings, so use capacity 1
instead of full channel_capacity
- Cap shadow_txs at 32 to prevent unbounded growth from misbehaving
clients, dropping the oldest shadow when the limit is reached
- Add test verifying primary works after exceeding shadow limit
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* fix: remove redundant single-component `use reqwest` import
Fixes clippy::single_component_path_imports lint error in
test_sse_concurrent_streams.rs.
---------
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
Signed-off-by: Myko Ash <myko@mcpmux.com>
Co-authored-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>
* feat: allow failable service creation in streamable HTTP tower service
In our setup we need to lookup some info that may fail before we serve
the request.
* Fix examples build
* feat: provide more context information
1. provide context for notification
2. allow extract more info from tool call
3. inject http request part for streamable http server
* docs: add document for getting peer from context
* refactor: a transport trait and streamable http client
* test: test with js streamable http server
* refactor: separate sse stream connection
* fix(test): streamable http client test with js
* fix(test): wait longer time for js server startup
* feat(transport): support streamable http server
* refactor(transport): add common module for shared transport utilities
* perf(tracing): add more log for streamable http session
* fix(test): fix port conflict in test with js
* fix(transport): fix id generating and session management
1. cancel when deleting
2. use `wrapping` and `saturating` correctly
* chore(naming): rename sse server to streamable http server
