Use HTTP/1.1 default connection semantics

docs/agent-guide/implemented/feature/2026-10-18-http-default-connection.md

@@ -0,0 +1,42 @@
+# Default connection semantics for ordinary HTTP
+
+## Problem
+
+Ordinary requests explicitly send Connection close. A controlled iPhone comparison reproduced truncated responses with this legal header and complete responses with explicit keep-alive, including reversed request order. This isolates a trigger, not a proven server, VPN or TLS root cause. The user requests omitting the header and a minimal PR.
+
+## Decision
+
+Remove only the unconditional Connection close entry from ordinary Http_eio request headers, relying on HTTP1.1 defaults. Keep per-attempt TCP/TLS setup and owner retirement after response completion. Do not introduce pooling or change DNS, TLS, proxy, buffers, deadlines, retries, dependencies or WebSocket Upgrade.
+
+Header serialization and socket lifetime are transport-owned: Core events cannot execute either, and injecting a completion would not reproduce them. Extend existing public Runner/independent TLS-peer tests to inspect actual ordinary GET/PUT headers while retaining full-body, truncated-body and resource-retirement checks. Assert WebSocket Upgrade headers remain present and sequential requests through one Runner still retire separate connections. No test bypasses public interfaces or adds a duplicate lower-level suite.
+
+This clean branch is based on current origin/main. It excludes all earlier diagnostic switches, Swift/C instrumentation, temporary fixtures and other fixes. Device build1.5877.47 contained the same ordinary header change in the prior diagnostic checkout; normal ready and actual WebSocket were observed. It is not the exact clean PR binary, full cross-ABI validation is not established, and manual initial graph-download acceptance remains pending. Do not publish private logs, graph contents, identifiers or credentials.
+
+## Alternatives considered
+
+### Explicit keep-alive or a connection pool
+
+The user requests omission only. Pooling would change ownership beyond scope.
+
+## Acceptance criteria
+
+- Existing real-wire GET/PUT tests demonstrate the prior header-presence RED and pass after omission.
+- Complete framing, truncation rejection, Upgrade headers and attempt-owned cleanup retain coverage.
+- Final diff contains only the header deletion, necessary tests and this repository-required decision; independent review and exact-head CI are recorded.
+- Publish a non-draft PR without merging or claiming an identified external root cause.
+
+## Risks
+
+- This mitigation does not identify the component responsible for the observed premature close.
+- Each attempt still closes its connection; no cross-request reuse is introduced.
+- Close-delimited bodies still need read EOF or the existing timeout.
+
+## Questions
+
+None. The user explicitly authorizes submission of this minimal PR.
+
+## Consequences
+
+The production change is one deleted header entry. The final clean-source build and sync suite pass with the original locked host providers: 313 reported cases, including all 139 transport cases. Before deletion, 16 ordinary GET/download checks, five PUT checks and the same-Runner sequence failed on the actual captured Connection header; existing WebSocket Upgrade checks passed. Independent read-only review against main 21dbe01 found no evidence-backed issue. Exact-head CI is required after publication; manual real-graph initialization remains pending.
+
+This document validates. Full decision-document validation reports only the three unchanged historical documents already missing required sections; unrelated documents are outside this PR.

logseq_sync/lib/effect_runner/eio/http_eio.ml

@@ -173,7 +173,6 @@ let with_attempt ~sw ~authenticator ~network ~clock ~response_budget request ~co
                      let headers =
                        Httpun.Headers.of_list
                          (("host", host_header)
-                          :: ("connection", "close")
                           :: request_headers)
                      in
                      let target = Uri.path_and_query request.uri in

logseq_sync/test/transport_contract.ml

@@ -567,6 +567,33 @@ let check_retired report =
     rows
 ;;
 
+let captured_request_headers row =
+  let encoded = Yojson.Basic.Util.(row |> member "request" |> to_string) in
+  let request =
+    String.init (String.length encoded / 2) (fun n ->
+      Char.chr (int_of_string ("0x" ^ String.sub encoded (2 * n) 2)))
+  in
+  let rec headers = function
+    | [] | "" :: _ -> []
+    | line :: rest -> line :: headers rest
+  in
+  String.split_on_char '\n' request
+  |> List.tl
+  |> List.map (fun line -> String.lowercase_ascii (String.trim line))
+  |> headers
+;;
+
+let check_default_connection report =
+  Yojson.Basic.Util.to_list report
+  |> List.iter (fun row ->
+    Alcotest.(check bool)
+      "ordinary request omits Connection"
+      false
+      (List.exists
+         (String.starts_with ~prefix:"connection:")
+         (captured_request_headers row)))
+;;
+
 let http_test
       ~download
       ~success
@@ -623,7 +650,8 @@ let http_test
                  (read_file (Filename.concat staging name))));
          Runner.shutdown t)
   in
-  check_retired report
+  check_retired report;
+  check_default_connection report
 ;;
 
 let frame ?(fin = true) opcode payload =
@@ -708,6 +736,13 @@ let ws_test ?(extra = "") ?(segment = 16384) ~messages ~terminal wire () =
          Runner.shutdown t)
   in
   check_retired report;
+  Yojson.Basic.Util.to_list report
+  |> List.iter (fun row ->
+    let headers = captured_request_headers row in
+    Alcotest.(check bool) "WebSocket keeps Connection Upgrade" true
+      (List.mem "connection: upgrade" headers);
+    Alcotest.(check bool) "WebSocket keeps Upgrade websocket" true
+      (List.mem "upgrade: websocket" headers));
   if not terminal
   then (
     let frames =
@@ -1917,6 +1952,7 @@ let asset_upload ~status ~refresh () =
       Runner.shutdown runner)
   in
   check_retired report;
+  check_default_connection report;
   Yojson.Basic.Util.to_list report
   |> List.iter (fun row ->
     let encoded = Yojson.Basic.Util.(row |> member "request" |> to_string) in
@@ -4214,3 +4250,33 @@ let scenarios =
            {|{"graphs":[{"graph-id":"11111111-1111-4111-8111-111111111111","graph-name":null,"graph-ready-for-use?":true,"future":true}]}|})
     ]
 ;;
+
+let test_default_connection_sequence () =
+  let wire =
+    response ~headers:"Content-Length: 3\r\nConnection: keep-alive\r\n" "abc"
+  in
+  let report =
+    with_peer [ case wire; case wire ] (fun ~environment ~sw ~support ~origin ->
+      let posted = ref [] and invalidations = ref 0 in
+      let t = runner ~environment ~sw ~support ~posted ~invalidations () in
+      Fun.protect ~finally:(fun () -> Runner.shutdown t) (fun () ->
+        List.iter (fun download ->
+          posted := [];
+          Runner.submit t (operation ~download origin);
+          wait (Eio.Stdenv.clock environment) (fun () ->
+            Option.is_some (completed !posted));
+          Alcotest.(check bool) "response completes without waiting for peer EOF" true
+            (Result.is_ok (Option.get (completed !posted))))
+          [ false; true ]))
+  in
+  Alcotest.(check int) "same Runner opens two separate connections" 2
+    (List.length (Yojson.Basic.Util.to_list report));
+  check_retired report;
+  check_default_connection report
+;;
+
+let scenarios =
+  scenarios
+  @ [ Alcotest.test_case "HTTP default connection retires between requests"
+        `Quick test_default_connection_sequence ]
+;;