fix(evi): frame mcp post responses as sse when the client accepts it - #546
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📝 WalkthroughWalkthroughThe MCP channel now returns SSE-framed ChangesMCP response negotiation
Estimated code review effort: 2 (Simple) | ~10 minutes Possibly related PRs
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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🧪 Generate unit tests (beta)
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Actionable comments posted: 2
🤖 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 `@apps/evi/agent/channels/mcp.ts`:
- Around line 71-73: Update the comment above the streamable HTTP response
handling to remove the specific `Linear` client reference and implementation
history. Keep only the durable protocol constraint: return one SSE message when
the request accepts `text/event-stream`.
- Line 74: Update the SSE selection condition in the MCP request handler to
parse the Accept header’s media ranges rather than using
includes('text/event-stream'). Match media types case-insensitively, allow
media-type parameters, and select SSE only when text/event-stream has effective
q greater than zero, including rejecting q=0. Add tests covering q=0, positive q
values, parameters, and case variants.
🪄 Autofix
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
ℹ️ Review info
⚙️ Run configuration
Configuration used: Organization UI
Review profile: ASSERTIVE
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Run ID: 1108dfa6-8d07-4394-95b8-2425f2f95995
📒 Files selected for processing (1)
apps/evi/agent/channels/mcp.ts
| // Streamable HTTP lets the server answer POSTs as JSON or as an SSE | ||
| // frame; clients built against SSE-framing servers (Linear's among | ||
| // them) expect the frame when their Accept says so. |
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📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win
Keep the comment focused on the durable protocol constraint.
The reference to Linear records implementation motivation and a specific client. Replace it with a vendor-neutral statement such as // Return one SSE message when the request accepts text/event-stream.
As per coding guidelines, comments should state only durable constraints and should not narrate implementation history.
🤖 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 `@apps/evi/agent/channels/mcp.ts` around lines 71 - 73, Update the comment
above the streamable HTTP response handling to remove the specific `Linear`
client reference and implementation history. Keep only the durable protocol
constraint: return one SSE message when the request accepts `text/event-stream`.
Source: Coding guidelines
| // Streamable HTTP lets the server answer POSTs as JSON or as an SSE | ||
| // frame; clients built against SSE-framing servers (Linear's among | ||
| // them) expect the frame when their Accept says so. | ||
| if (req.headers.get('accept')?.includes('text/event-stream')) { |
There was a problem hiding this comment.
🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🧩 Analysis chain
🏁 Script executed:
#!/usr/bin/env bash
set -euo pipefail
# Expect: negotiation code or tests cover q-values and case-insensitive media types.
rg -n -C 5 'Accept|text/event-stream|q=0|Text/Event-Stream' apps/eviRepository: HugoRCD/evlog
Length of output: 2006
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf 'Target file outline and relevant section:\n'
ast-grep outline apps/evi/agent/channels/mcp.ts || true
sed -n '1,120p' apps/evi/agent/channels/mcp.ts
printf '\nPackage lock/typescript availability:\n'
(git ls-files | rg '(^|/)package\.json$|(^|/)pnpm-lock.yaml$|(^|/)package-lock\.json$|(^|/)yarn\.lock$' | sed -n '1,80p')
(node -e 'console.log("node", process.version)' 2>/dev/null || true)Repository: HugoRCD/evlog
Length of output: 4900
🌐 Web query:
RFC 9110 Accept header q=0 media type unacceptable case-insensitive media type type subtype
💡 Result:
In RFC 9110, the Accept header allows a user agent to specify media types that are acceptable for the response [1]. When a media type in the Accept header is assigned a quality value (q-value) of 0 (e.g., media-type;q=0), it indicates that the media type is "not acceptable" to the client [2]. Regarding media type casing, the type and subtype components of a media type are case-insensitive [3][4]. While they are traditionally written in lowercase, RFC 9110 and related standards treat them as case-insensitive identifiers [3][4]. Parameter names within media types are also case-insensitive, though the case-sensitivity of parameter values depends on the specific semantics of the parameter name [3][5].
Citations:
- 1: https://runebook.dev/en/docs/http/rfc9110/section-12.5.1
- 2: https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
- 3: https://www.rfc-editor.org/rfc/rfc9110.html
- 4: https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types
- 5: https://www.rfc-editor.org/info/rfc9110/
🏁 Script executed:
#!/bin/bash
set -euo pipefail
node - <<'JS'
const examples = [
'text/event-stream;q=0, application/json;q=0.9',
'application/json;q=0.5, text/event-stream;q=0.1',
'TEXT/Event-Stream, application/json;q=0.5',
'TEXT/Event-STREAM; charset=utf-8, application/json',
'text/event-stream, application/json;q=0'
]
for (const accept of examples) {
const include = accept.includes('text/event-stream')
console.log(JSON.stringify({ accept, includes_lowercase_text_event_stream: include }))
}
JS
printf '\nExisting test directories and mcp-related files:\n'
git ls-files | rg '(^|/)(test|specs|vitest|jest|node_modules|dist|build)' | sed -n '1,200p'
rg -n "mcp|Accept|event-stream|q=" apps/evi/agent apps packages -g '!node_modules' | sed -n '1,220p'Repository: HugoRCD/evlog
Length of output: 24464
Parse Accept media ranges before selecting SSE.
Use strict Accept negotiation instead of includes('text/event-stream') so SSE is returned only when text/event-stream has effective quality greater than zero. This rejects Accept: text/event-stream;q=0 correctly and matches case-insensitive media types such as TEXT/Event-Stream.
Add tests for q=0, positive q values, media-type parameters, and case variants.
🤖 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 `@apps/evi/agent/channels/mcp.ts` at line 74, Update the SSE selection
condition in the MCP request handler to parse the Accept header’s media ranges
rather than using includes('text/event-stream'). Match media types
case-insensitively, allow media-type parameters, and select SSE only when
text/event-stream has effective q greater than zero, including rejecting q=0.
Add tests covering q=0, positive q values, parameters, and case variants.
1 participant
Raycast connects but the session setup fails against plain-JSON POST responses; Linear's MCP (which Raycast handles) frames POST responses as a single SSE message event. The channel now mirrors that: when the request's Accept includes text/event-stream, the JSON-RPC response is returned as an SSE frame with content-type text/event-stream; plain JSON otherwise. GET stays a spec-compliant 405. No changeset: confined to apps/evi. Verified: tsc, 63 unit tests, eve build; curl with both Accept variants validates on the preview.
Summary by CodeRabbit
text/event-streamnow receive responses in Server-Sent Events format.