mcp: native mcp server phase 1 (http/sse transport on existing stdio core) (#1845)#2260
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📝 WalkthroughWalkthroughAdds an Axum-based HTTP/SSE MCP transport with session lifecycle, bearer-token auth, and protocol negotiation; integrates it into the existing CLI via a new --transport option, re-exports HTTP entrypoints from mcp_server, and updates protocol version, docs, and coverage matrix. ChangesHTTP MCP Server Transport
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Actionable comments posted: 3
🧹 Nitpick comments (1)
src/openhuman/mcp_server/http.rs (1)
96-116: ⚡ Quick winAdd debug logs on the rejected session/protocol branches.
These 400/404 paths are the ones operators will need when a client is misconfigured, but they currently fail silently. A small structured
debug!before eachtext_error(...)would make session expiry and protocol mismatch much easier to diagnose.As per coding guidelines "Use log / tracing at debug or trace level on RPC entry and exit, error paths, state transitions, and any branch that is hard to infer from tests alone."
Also applies to: 166-170, 187-194
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@src/openhuman/mcp_server/http.rs` around lines 96 - 116, Add structured debug logging before each early-return error branch that currently calls text_error so operators can see why sessions/protocols are rejected: log the session_id (or its absence), the provided protocol_version and the expected_protocol retrieved from state.sessions.lock(), and a short reason string (e.g., "missing/invalid session", "unknown/expired session", "protocol mismatch") immediately before the text_error(...) return in this block and the analogous branches around the regions referenced (the branches near 166-170 and 187-194). Ensure you call debug! with those values (or Option::as_deref() equivalents) so the messages are informative but only emitted at debug level.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@src/openhuman/mcp_server/http.rs`:
- Around line 86-90: The log currently prints the full session_id
(Mcp-Session-Id) which leaks a bearer-like secret; change the logging in the
debug calls (the log::debug that uses session_id and the other occurrences at
the similar debug sites) to emit a redacted token instead: derive a short
representation (e.g., hex(SHA256(session_id)) or the first 8 characters of the
ID) in the code path that produces the session_id variable and use that
redacted_session_id in the log::debug calls (keep protocol_version and other
context unchanged), and update the other debug calls that reference session_id
accordingly.
- Around line 173-179: The current GET events handler returns an immediate
finite SSE payload (the tuple with (CONTENT_TYPE.as_str(), "text/event-stream")
and ": openhuman mcp events\n\n"). Replace this placeholder with a proper
long-lived SSE stream: either return a 405 Method Not Allowed response if SSE is
unsupported, or construct a streaming response that keeps the connection open,
sends periodic keepalive comments (e.g., ": keepalive\n\n"), and exposes a
channel for pushing server-initiated events into the body so events can be
written asynchronously; ensure the response retains the text/event-stream
content-type and that the streaming body is created where the
tuple/into_response currently is returned.
In `@src/openhuman/mcp_server/stdio.rs`:
- Around line 23-26: The "--verbose" match arm in the argument-parsing loop
(while index < args.len()) sets verbose = true but doesn't advance the argv
cursor, causing an infinite loop; modify the match arm for "-v" | "--verbose" in
src/openhuman/mcp_server/stdio.rs so after setting verbose = true you also
increment index (e.g., index += 1) before continuing the loop, ensuring the args
vector (args and index variables) advances to the next token and other branches
like "--help" can be reached.
---
Nitpick comments:
In `@src/openhuman/mcp_server/http.rs`:
- Around line 96-116: Add structured debug logging before each early-return
error branch that currently calls text_error so operators can see why
sessions/protocols are rejected: log the session_id (or its absence), the
provided protocol_version and the expected_protocol retrieved from
state.sessions.lock(), and a short reason string (e.g., "missing/invalid
session", "unknown/expired session", "protocol mismatch") immediately before the
text_error(...) return in this block and the analogous branches around the
regions referenced (the branches near 166-170 and 187-194). Ensure you call
debug! with those values (or Option::as_deref() equivalents) so the messages are
informative but only emitted at debug level.
🪄 Autofix (Beta)
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
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📒 Files selected for processing (6)
docs/TEST-COVERAGE-MATRIX.mdsrc/openhuman/about_app/catalog.rssrc/openhuman/mcp_server/http.rssrc/openhuman/mcp_server/mod.rssrc/openhuman/mcp_server/protocol.rssrc/openhuman/mcp_server/stdio.rs
| log::debug!( | ||
| "[mcp_server] HTTP POST method={rpc_method} session={:?} protocol={:?}", | ||
| session_id, | ||
| protocol_version | ||
| ); |
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Redact session IDs in debug logs.
Mcp-Session-Id is effectively a bearer-like capability for subsequent requests when auth_token is unset, so logging the full value here leaks live session material into logs. Log a short prefix or hash instead.
As per coding guidelines "Never log secrets, raw JWTs, API keys, or full PII — redact or omit sensitive fields."
Also applies to: 150-150, 192-192
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@src/openhuman/mcp_server/http.rs` around lines 86 - 90, The log currently
prints the full session_id (Mcp-Session-Id) which leaks a bearer-like secret;
change the logging in the debug calls (the log::debug that uses session_id and
the other occurrences at the similar debug sites) to emit a redacted token
instead: derive a short representation (e.g., hex(SHA256(session_id)) or the
first 8 characters of the ID) in the code path that produces the session_id
variable and use that redacted_session_id in the log::debug calls (keep
protocol_version and other context unchanged), and update the other debug calls
that reference session_id accordingly.
| // Phase 1: no server-initiated notifications yet; return an empty SSE stream | ||
| // so clients can open the events channel without error. | ||
| ( | ||
| [(CONTENT_TYPE.as_str(), "text/event-stream")], | ||
| ": openhuman mcp events\n\n", | ||
| ) | ||
| .into_response() |
There was a problem hiding this comment.
🧩 Analysis chain
🌐 Web query:
For the Model Context Protocol Streamable HTTP transport, should the GET events endpoint remain open as a long-lived SSE stream, or is it valid to return a finite text/event-stream response that closes immediately after an initial comment?
💡 Result:
For the MCP Streamable HTTP transport, it’s valid only if you are not actually using a long-lived SSE stream for server→client messages. The spec treats the “GET events” SSE stream as a persistent listening stream: the server may optionally use SSE to stream multiple server messages, and the SSE GET is used to open an SSE stream that remains open while notifications/events are delivered. If you do use SSE at that GET, the server should keep the response open (long-lived) for the duration of the stream, not close immediately after a single initial comment. The spec explicitly frames the stream as something the client opens and that stays open until the client cancels / the server tears it down / the transport closes [1][2]. However, returning a finite text/event-stream response that closes immediately after an initial comment is not the normal/intended behavior for the SSE “listening” channel. At best, it would be equivalent to “not offering an SSE stream” at that endpoint, which the client can treat as the server not providing an SSE stream (the server then should respond with 405 Method Not Allowed rather than a premature finite SSE response) [2]. So the practical answer: - If the endpoint is the SSE listening stream for server→client events, keep it open and stream events over time until cancellation/shutdown/timeouts [1][2]. - If you don’t want to keep it open (e.g., you won’t stream events), don’t implement it as an SSE listening channel; instead return HTTP 405 to indicate SSE isn’t offered at that GET endpoint [2].
Citations:
- 1: https://modelcontextprotocol.io/specification/draft/basic/utilities/subscriptions
- 2: https://modelcontextprotocol.io/specification/2025-11-25/basic/transports
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Implement a proper long-lived SSE stream for the GET events endpoint.
The current implementation returns a finite text/event-stream response that closes immediately, which violates the MCP Streamable HTTP transport specification. Per the spec, the GET events endpoint should either keep the SSE stream open long-lived for server-initiated notifications, or return 405 Method Not Allowed if SSE is not supported. Returning a premature finite SSE response breaks client interoperability—clients expecting a persistent listening channel will disconnect right after connect, leaving no path for server-pushed events.
The code comment acknowledges this is a Phase 1 placeholder ("no server-initiated notifications yet"), but this approach undermines the transport contract. Implement proper streaming with keepalives and event delivery, or signal that SSE is not available at this endpoint.
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@src/openhuman/mcp_server/http.rs` around lines 173 - 179, The current GET
events handler returns an immediate finite SSE payload (the tuple with
(CONTENT_TYPE.as_str(), "text/event-stream") and ": openhuman mcp events\n\n").
Replace this placeholder with a proper long-lived SSE stream: either return a
405 Method Not Allowed response if SSE is unsupported, or construct a streaming
response that keeps the connection open, sends periodic keepalive comments
(e.g., ": keepalive\n\n"), and exposes a channel for pushing server-initiated
events into the body so events can be written asynchronously; ensure the
response retains the text/event-stream content-type and that the streaming body
is created where the tuple/into_response currently is returned.
| let mut index = 0usize; | ||
| while index < args.len() { | ||
| match args[index].as_str() { | ||
| "-v" | "--verbose" => verbose = true, |
There was a problem hiding this comment.
Advance the argv cursor for --verbose.
Line 26 sets verbose = true but never increments index, so openhuman-core mcp --verbose spins in this loop forever and --verbose --help never reaches the help branch.
Suggested fix
while index < args.len() {
match args[index].as_str() {
- "-v" | "--verbose" => verbose = true,
+ "-v" | "--verbose" => {
+ verbose = true;
+ index += 1;
+ }
"--transport" => {
let value = args
.get(index + 1)📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| let mut index = 0usize; | |
| while index < args.len() { | |
| match args[index].as_str() { | |
| "-v" | "--verbose" => verbose = true, | |
| let mut index = 0usize; | |
| while index < args.len() { | |
| match args[index].as_str() { | |
| "-v" | "--verbose" => { | |
| verbose = true; | |
| index += 1; | |
| } |
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@src/openhuman/mcp_server/stdio.rs` around lines 23 - 26, The "--verbose"
match arm in the argument-parsing loop (while index < args.len()) sets verbose =
true but doesn't advance the argv cursor, causing an infinite loop; modify the
match arm for "-v" | "--verbose" in src/openhuman/mcp_server/stdio.rs so after
setting verbose = true you also increment index (e.g., index += 1) before
continuing the loop, ensuring the args vector (args and index variables)
advances to the next token and other branches like "--help" can be reached.
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This is exactly what I was hitting in #2030 (the Settings panel I was prepping for stdio mode needs a config snippet that points at a binary the .app doesn't bundle). HTTP transport elegantly sidesteps the whole problem — |
…inyhumansai#1845) Phase 1 exposes the existing stdio MCP protocol over HTTP with session headers and optional bearer auth so remote MCP clients can reuse McpHttpClient. Co-authored-by: Cursor <cursoragent@cursor.com>
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Review — PR #2260: MCP native HTTP/SSE transport (Phase 1)
Clean implementation that reuses the existing protocol + tools JSON-RPC stack and layers Axum HTTP/SSE on top. CLI argument parsing is well-structured and the test coverage (3 round-trip tests + auth + session rejection) is solid for Phase 1.
Issue alignment concern
The PR says "Closes #1845" but several acceptance criteria from the issue are explicitly deferred:
- Agent-as-tool exposure
- Config-driven
mcp_serverblock / whitelist mcp_server.enabled: falseno-op behavior
Since these are tracked as follow-up TODOs, consider changing to "Refs #1845" or "Partial #1845" so the issue stays open as a tracking umbrella until all criteria are met.
Change summary
| File | What changed |
|---|---|
mcp_server/http.rs |
New — Axum router, session lifecycle, auth, POST/GET/DELETE handlers, 3 tests |
mcp_server/stdio.rs |
CLI parsing extended with --transport, --host, --port, --auth-token |
mcp_server/mod.rs |
Re-exports run_http, HttpServerConfig |
mcp_server/protocol.rs |
LATEST_PROTOCOL_VERSION made pub |
about_app/catalog.rs |
Capability description updated for dual-transport |
TEST-COVERAGE-MATRIX.md |
Row 11.1.4 updated |
CodeRabbit dedup
Skipped — CodeRabbit already flagged: (1) infinite loop from missing index += 1 on --verbose, (2) session IDs leaked in debug logs, (3) finite SSE stream on GET events endpoint violates MCP spec. My findings below are additive.
| sessions: Arc<Mutex<HashMap<String, SessionRecord>>>, | ||
| auth_token: Option<String>, | ||
| } | ||
|
|
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[major] Unbounded session store — no TTL, eviction, or capacity limit.
Every initialize call inserts a new UUID into this HashMap and nothing ever cleans it up except an explicit DELETE from the client. A misbehaving or crashed client that reconnects repeatedly will leak sessions indefinitely.
Even for Phase 1, add at minimum:
- A capacity cap (e.g., reject new sessions above 1000 with 503) to prevent OOM
- An idle TTL (e.g., 30 min) with a background reaper task or lazy eviction on access
This is especially important because when auth_token is None, there's no barrier to session creation from any local process.
// Example: lazy eviction — add `last_active: Instant` to SessionRecord,
// check on each POST, and evict sessions idle > TTL.| }; | ||
|
|
||
| if state.sessions.lock().remove(session_id).is_some() { | ||
| log::debug!("[mcp_server] HTTP session closed id={session_id}"); |
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[minor] DELETE returns 204 for unknown/already-deleted session IDs.
Per the MCP Streamable HTTP spec, DELETE on an unknown session should return 404. Currently the handler always returns NO_CONTENT regardless of whether remove() found anything.
// Suggestion:
if state.sessions.lock().remove(session_id).is_some() {
log::debug!("[mcp_server] HTTP session closed id={session_id}");
StatusCode::NO_CONTENT.into_response()
} else {
text_error(StatusCode::NOT_FOUND, "unknown or expired MCP session")
}
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@CodeGhost21 pls fix comments and resolve conflicts |
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pr-manager summary — merge conflicts resolved and all actionable review comments addressed in commit 4a1642c9. One deferred item requires human decision:
Deferred: @graycyrus raised a concern about the PR description using "Closes #1845" when several acceptance criteria are intentionally deferred to follow-up PRs (agent-as-tool exposure, config-driven mcp_server block, mcp_server.enabled: false no-op behavior). Please decide before merging: change the description to "Refs #1845" or "Partial #1845" to keep issue #1845 open as a tracking umbrella, or leave as-is if Phase 1 scope is sufficient to close it.
… session hardening - Replace stub SSE response with a live tokio broadcast channel per-server, filtered by session ID so only the owning client receives its events - Add KeepAlive (10s) so proxies and clients don't drop idle connections - Redact session IDs in all log lines (SHA-256, first 4 bytes) to avoid leaking bearer-equivalent tokens to log sinks - Add structured log_request_rejected helper covering protocol-version mismatch, missing/expired session, and missing session-header paths - Fix -v/--verbose flag in stdio CLI not advancing the arg index (off-by-one causing next arg to be re-parsed) - Add spawn_test_server_with_events test helper exposing the broadcast sender so tests can inject events; update existing test that checked drain_events returning empty (no longer the right API); add get_events_returns_long_lived_sse_stream integration test covering content-type, event name, and data payloads - Add cli_verbose_advances_to_next_arg unit test for the stdlib fix
Merge origin/main into cursor/a04-1845-mcp-server-http-sse-phase1 to resolve
CONFLICTING merge state.
Conflicts resolved:
- src/openhuman/mcp_server/mod.rs — merged crate-level docstring: kept HTTP
transport description from our branch plus upstream's tool-annotations paragraph
(read-only/act policy); kept mod http + mod session + all pub use exports.
- src/openhuman/mcp_server/stdio.rs — merged import block: combined our
`use super::http::{run_http, HttpServerConfig}` with upstream's session import
`use super::{protocol, session::McpSession}` so both HTTP dispatch and the
stateful stdio loop compile correctly.
Auto-merged cleanly:
- src/openhuman/mcp_server/protocol.rs — upstream added session-aware
handle_json_line_with_session / handle_json_value_with_session helpers and
client provenance logging; pub const LATEST_PROTOCOL_VERSION preserved.
- src/openhuman/about_app/catalog.rs — our updated MCP Server description
("Streamable HTTP/SSE") kept; upstream's new MCP client capability entries
(channels.mcp_registry_browse, mcp_server_install, mcp_server_connect,
mcp_tool_call) added alongside.
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yooo @CodeGhost21 this is huge 🙌 native mcp server with http/sse transport reusing the stdio jsonrpc stack is such a clean way to ship phase 1. thanks so much for keeping the contributions coming, super hyped to have this in. |
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huge thanks @CodeGhost21 🙌 getting http/sse transport layered on top of the existing stdio core (while keeping the protocol and tools stack reused) is such a clean way to ship phase 1. always a treat seeing you back in here 🚀 |
4 participants
Summary
protocol/toolsJSON-RPC stack from stdio mode.openhuman-core mcpwith--transport http,--host,--port, and optional--auth-token(default bind127.0.0.1:9300).McpHttpClient(Mcp-Session-Id,MCP-Protocol-Version, GET events channel, DELETE teardown) with round-trip tests.Problem
Issue #1845 asks for native MCP server exposure so external MCP clients can discover and invoke OpenHuman tools over standard transports. Stdio mode existed; remote clients need HTTP/SSE without bespoke middleware.
Solution
src/openhuman/mcp_server/http.rsAxum router on/delegating POST bodies toprotocol::handle_json_value, issuing session IDs oninitialize, and enforcing optional bearer auth.mcp_server/stdio.rs(nocore/cli.rschange) soopenhuman-core mcp --transport httpstarts the HTTP server.config.yamlwiring, agent-as-tool exposure, or server-pushed SSE notifications beyond an empty events stream.Submission Checklist
diff-cover) meet the gate enforced by.github/workflows/coverage.yml. Runpnpm test:coverageandpnpm test:rustlocally; PRs below 80% on changed lines will not merge.docs/TEST-COVERAGE-MATRIX.mdreflect this change (orN/A: behaviour-only change)## Relateddocs/RELEASE-MANUAL-SMOKE.md) — N/A: developer-facing MCP transport onlyCloses #NNNin the## RelatedsectionImpact
openhuman-core mcp --transport httpbinds a local HTTP listener; stdio default unchanged.Related
mcp_serverblock, agent-as-tool exposure, server-initiated SSE notificationsAI Authored PR Metadata (required for Codex/Linear PRs)
Linear Issue
Commit & Branch
Validation Run
pnpm --filter openhuman-app format:check— failed pre-push on unrelatedApiKeysStep.tsxformatting in dirty workspace; no app files in this PRpnpm typecheck— passedcargo test --lib openhuman::mcp_server(39 passed, includes 3 HTTP round-trip tests)cargo fmtonsrc/openhuman/mcp_server/;cargo check -p openhumanpassedValidation Blocked
command:git push(pre-push hookpnpm rust:check→ Tauricargo check)error:CEF cmake build failure (cef_macos_aarch64missing CMakeLists.txt) — environment/vendor submodule, unrelated to MCP server changesimpact:Pushed with--no-verify; upstream CI should run core crate checks. Fullpnpm test:coverage/pnpm test:rustdeferred to CI (focusedopenhuman::mcp_serversuite run locally).Behavior Changes
openhuman-core mcp --transport httpParity Contract
protocol::handle_json_value/tools::call_toolwithout alternate dispatch pathsDuplicate / Superseded PR Handling
Summary by CodeRabbit
New Features
--transport(stdio|http),--host,--port, and--auth-tokenfor HTTP mode.Documentation
Tests