Fix live-stream SSE endpoint 500 by passing an explicit broadcast handler

Message

stream-events-handler called http-response/sse-broadcast while omitting the broadcast handler positional, relying on it defaulting to identity. That default only exists in the . opts form (sigil-http 0.16.7+). Releases 0.16.1-0.16.6 typed the handler as a required positional; omitting it (and jumping straight to the on-connect: keyword) crashed the SSE connect with "car: expected pair" - a 500 on GET /feed, most visible when the server runs interpreted and loads one of those releases.

Pass identity explicitly. It is correct for every release: the hub carries pre-formatted SSE strings so identity is the right handler, and the . opts form accepts a leading procedure too. Bumps to 0.16.1 and adds a regression test for the live-routes -> handler call contract.

Changed

 CHANGELOG.md                 | 13 +++++++++++++
 package.sgl                  |  2 +-
 src/sigil/web/live.sgl       |  9 +++++++++
 test/test-live-sse-repro.sgl | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+), 1 deletion(-)

Diff

CHANGELOG.mdmodified

@@ -5,6 +5,19 @@ All notable changes to **sigil-web** are documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),

and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [0.16.1] - 2026-07-10

+10

### Fixed

+11

+12

- Live-stream SSE endpoints (`live-routes`) no longer return `500 Internal

+13

Server Error` with `car: expected pair` when a client connects.

+14

`stream-events-handler` now passes the broadcast handler (`identity`)

+15

explicitly to `http-response/sse-broadcast` instead of relying on its default.

+16

The stream hub carries pre-formatted SSE strings, so `identity` is the correct

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handler; passing it explicitly keeps `GET` on a live-stream endpoint working

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across every `sigil-http` release, including ones that type the broadcast

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handler as a required positional argument.

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## [0.16.0] - 2026-07-10

### Added

package.sglmodified

@@ -9,7 +9,7 @@

(package

name: "sigil-web"

−12

version: "0.16.0"

+12

version: "0.16.1"

sigil: "^0.17"

description: "Web application framework for Sigil"

url: "https://codeberg.org/sigil/sigil-web"

src/sigil/web/live.sglmodified

@@ -131,10 +131,19 @@

131

(when (channel-try-send (live-stream-rec-heartbeat-latch stream) 'started)

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(start-sse-heartbeat! (live-stream-rec-hub stream))))

133

+134

;; The stream hub already carries pre-formatted SSE strings (live-push!

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;; broadcasts `ui-*` update strings verbatim), so the broadcast handler is

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;; `identity`. We pass it EXPLICITLY rather than relying on the default:

+137

;; some `sigil-http` releases (0.16.1 through 0.16.6) typed the handler as a

+138

;; *required* positional, and omitting it there triggers a keyword-dispatch

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;; crash ("car: expected pair") instead of using the identity default.

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;; Passing it explicitly is correct for every release: the `. opts` form

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;; (0.16.7+) also accepts a leading procedure as the handler.

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(define (stream-events-handler stream)

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(lambda (request)

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(ensure-heartbeat! stream)

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(http-response/sse-broadcast (live-stream-rec-hub stream)

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identity

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on-connect: (live-stream-rec-on-connect stream))))

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;;; Return a handler that serves the SSE endpoint for a stream or a

test/test-live-sse-repro.sgladded

@@ -0,0 +1,53 @@

;; Regression test for the live-stream SSE endpoint 500 ("car: expected pair").

;;

;; `stream-events-handler` called `http-response/sse-broadcast` while OMITTING

;; the broadcast handler positional, relying on it defaulting to the identity

;; function. That default only exists in the `. opts` form of

;; `http-response/sse-broadcast` (sigil-http 0.16.7+). In releases 0.16.1–0.16.6

;; the signature was a `keys:` form with `handler` as a *required* positional;

;; omitting it (and jumping to the `on-connect:` keyword) crashed the SSE connect

;; with `type-error: car: expected pair` — a 500 on GET /feed. The fix passes the

+10

;; identity handler EXPLICITLY, which is valid for every release.

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;;

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;; NOTE: fully invoking the handler starts the lazy heartbeat via `(go ...)`,

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;; which needs a live scheduler and never terminates, so we can't drive it from

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;; a plain `sigil test`. Instead we pin the two things the fix actually depends

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;; on: (1) the exact `http-response/sse-broadcast` call SHAPE the handler now

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;; uses builds a well-formed streaming SSE response, and (2) `live-routes` wires

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;; a handler for both a stream and a collection. End-to-end proof (GET /feed ->

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;; 200 text/event-stream on a real server) is recorded in the task note.

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+20

(import (sigil test)

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(sigil core)

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(sigil channels)

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(sigil web live)

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(sigil web routes)

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(sigil http request)

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(sigil http response))

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(test-group "live-stream SSE endpoint (regression: /feed 500)"

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;; This is the call shape stream-events-handler now emits. Under the keys-form

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;; sigil-http releases this exact shape is what avoids the "car: expected pair"

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;; crash (the handler positional is supplied); under the `. opts` form it is the

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;; identity handler, matching the previous default behaviour.

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(test "sse-broadcast with an explicit identity handler + on-connect: builds an SSE response"

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(let* ((hub (make-broadcast))

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(resp (http-response/sse-broadcast hub identity on-connect: #f)))

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(assert-true (http-response? resp))

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(assert-equal 200 (http-response-status resp))

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;; streaming responses carry a procedure body (write-chunk close) ...

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(assert-true (procedure? (http-response-body resp)))

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;; ... and advertise the SSE content type.

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(assert-equal "text/event-stream"

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(dict-ref (http-response-headers resp) content-type:))))

+43

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(test "live-routes wires a handler for a plain stream"

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(let* ((feed (live-stream path: "/feed"))

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(app (live-routes feed)))

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(assert-true (procedure? app))))

+48

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(test "live-routes wires a handler for a collection"

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(let* ((coll (live-collection render: (lambda (item) `(li ,(dict-ref item text:)))

+51

container: "#list" path: "/events"))

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(app (live-routes coll)))

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(assert-true (procedure? app)))))