diff --git a/scripts/lib/bot-comment-retry.sh b/scripts/lib/bot-comment-retry.sh
index d2f12e86c..add112d0b 100644
--- a/scripts/lib/bot-comment-retry.sh
+++ b/scripts/lib/bot-comment-retry.sh
@@ -202,10 +202,35 @@ bcr_retry_decisions() {
 
 # bcr_fetch_pr_comments <repo> <pr_number>
 #   Echo every PR issue-comment node (paginated GraphQL) as one JSON array with
-#   the fields bcr_retry_decisions reads. Returns 1 (echoing nothing) on any API or
-#   parse failure — a partial list could hide a disposition, so callers fail closed.
+#   the fields bcr_retry_decisions reads. Returns 1 (echoing nothing on stdout, one
+#   `[warn]` line naming the failure on stderr) on any API or parse failure — a
+#   partial list could hide a disposition, so callers fail closed.
+#   Pages are merged from a temp file, never passed to jq as arguments: a PR's
+#   accumulated comment JSON outgrows the exec argument limit (#2072, PR #1953).
 bcr_fetch_pr_comments() {
-  local repo="$1" pr="$2"
+  local pages_file rc
+  pages_file=$(mktemp "${TMPDIR:-/tmp}/bcr-comments.XXXXXX") || {
+    echo "  [warn] bot-comment retry: could not create a temp file for PR $2 comments" >&2
+    return 1
+  }
+  # A subshell with its own EXIT trap removes the temp file (it holds fetched
+  # comment bodies) even on interruption, without touching the caller's traps;
+  # `|| rc=$?` keeps errexit from skipping the status capture.
+  rc=0
+  (
+    trap 'rm -f "$pages_file"' EXIT
+    _bcr_fetch_pr_comments_into "$1" "$2" "$pages_file"
+  ) || rc=$?
+  rm -f "$pages_file"
+  return "$rc"
+}
+
+# _bcr_fetch_pr_comments_into <repo> <pr_number> <pages_file>
+#   bcr_fetch_pr_comments' body: appends each page's nodes array to <pages_file>
+#   (one per line) and echoes their concatenation once every page has been read.
+_bcr_fetch_pr_comments_into() {
+  local repo="$1" pr="$2" pages_file="$3"
+  local warn="  [warn] bot-comment retry: PR ${pr} comments in ${repo}:"
   # shellcheck disable=SC2016  # $owner/$repo/$pr/$cursor are GraphQL variables
   local query='query($owner:String!,$repo:String!,$pr:Int!,$cursor:String){
     repository(owner:$owner,name:$repo){
@@ -217,27 +242,41 @@ bcr_fetch_pr_comments() {
       }
     }
   }'
-  local all='[]' cursor="" has_next="true" page nodes
+  local cursor="" prev_cursor="" has_next="true" page
   local cursor_args=()
   while [ "$has_next" = "true" ]; do
     page=$(gh api graphql -f query="$query" -F owner="${repo%%/*}" -F repo="${repo##*/}" \
-      -F pr="$pr" "${cursor_args[@]}" 2>/dev/null) || return 1
+      -F pr="$pr" "${cursor_args[@]}" 2>/dev/null) || {
+      echo "${warn} API request failed" >&2; return 1; }
     # A partial response (GraphQL errors alongside data) or an unreadable page
     # cursor is a partial snapshot — it could hide a disposition. Fail closed.
-    printf '%s' "$page" | jq -e '(.errors // []) | length == 0' >/dev/null 2>&1 || return 1
-    nodes=$(printf '%s' "$page" | jq -ce '.data.repository.pullRequest.comments.nodes | arrays' 2>/dev/null) \
-      || return 1
-    all=$(jq -cn --argjson a "$all" --argjson b "$nodes" '$a + $b') || return 1
+    printf '%s' "$page" | jq -e 'type == "object"' >/dev/null 2>&1 || {
+      echo "${warn} unparseable API response" >&2; return 1; }
+    printf '%s' "$page" | jq -e '(.errors // []) | length == 0' >/dev/null 2>&1 || {
+      echo "${warn} response carried GraphQL errors" >&2; return 1; }
+    printf '%s' "$page" | jq -ce '.data.repository.pullRequest.comments.nodes | arrays' \
+      >> "$pages_file" 2>/dev/null || {
+      echo "${warn} unparseable comment page (no nodes array)" >&2; return 1; }
     has_next=$(printf '%s' "$page" | jq -r '.data.repository.pullRequest.comments.pageInfo.hasNextPage
-      | if type == "boolean" then tostring else "invalid" end' 2>/dev/null) || return 1
-    case "$has_next" in true|false) ;; *) return 1 ;; esac
-    cursor=$(printf '%s' "$page" | jq -r '.data.repository.pullRequest.comments.pageInfo.endCursor // ""')
+      | if type == "boolean" then tostring else "invalid" end' 2>/dev/null) || has_next="invalid"
+    cursor=$(printf '%s' "$page" | jq -r '.data.repository.pullRequest.comments.pageInfo.endCursor // ""' 2>/dev/null) \
+      || cursor=""
+    case "$has_next" in true|false) ;; *)
+      echo "${warn} invalid pagination info (hasNextPage)" >&2; return 1 ;;
+    esac
     if [ "$has_next" = "true" ] && [ -z "$cursor" ]; then
-      return 1
+      echo "${warn} invalid pagination info (no endCursor)" >&2; return 1
+    fi
+    # A cursor that did not advance would re-fetch the same page forever.
+    if [ "$has_next" = "true" ] && [ "$cursor" = "$prev_cursor" ]; then
+      echo "${warn} invalid pagination info (endCursor did not advance)" >&2; return 1
     fi
+    prev_cursor="$cursor"
     cursor_args=(-f "cursor=${cursor}")
   done
-  printf '%s\n' "$all"
+  # Concatenate the pages from the file — never via jq arguments (#2072).
+  jq -cs 'add // []' "$pages_file" 2>/dev/null || {
+    echo "${warn} could not merge comment pages" >&2; return 1; }
 }
 
 # bcr_retry_marker <comment_id> <version> <attempt> <now_iso>
diff --git a/tests/dev-lead/unit/test_bot_comment_retry.bats b/tests/dev-lead/unit/test_bot_comment_retry.bats
index dbffafc35..d20a8b86a 100644
--- a/tests/dev-lead/unit/test_bot_comment_retry.bats
+++ b/tests/dev-lead/unit/test_bot_comment_retry.bats
@@ -9,6 +9,8 @@
 #   • the sweep wiring in dev-lead-retry.sh (exactly one dispatch, dedup marker,
 #     payload carries the comment node id — never its body).
 
+bats_require_minimum_version 1.5.0
+
 SCRIPT_DIR="$(cd "$(dirname "$BATS_TEST_FILENAME")/../../.." && pwd)"
 LIB="$SCRIPT_DIR/scripts/lib/bot-comment-retry.sh"
 RETRY_SCRIPT="$SCRIPT_DIR/scripts/dev-lead-retry.sh"
@@ -304,21 +306,109 @@ $(_ours '<!-- dev-lead-bot-comment-retry id=IC_cr version=2026-10-01T23:05:43Z a
 
 @test "bcr_fetch_pr_comments: a GraphQL response carrying errors fails closed" {
   gh() { printf '%s' '{"errors":[{"message":"rate limited"}],"data":{"repository":{"pullRequest":{"comments":{"pageInfo":{"hasNextPage":false,"endCursor":null},"nodes":[]}}}}}'; }
-  run bcr_fetch_pr_comments "petry-projects/.github-private" 2009
-  [ "$status" -ne 0 ]
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
   [ -z "$output" ]
+  [[ "$stderr" == *"GraphQL errors"* ]]
 }
 
 @test "bcr_fetch_pr_comments: hasNextPage true without a cursor fails closed" {
   gh() { printf '%s' '{"data":{"repository":{"pullRequest":{"comments":{"pageInfo":{"hasNextPage":true,"endCursor":null},"nodes":[]}}}}}'; }
-  run bcr_fetch_pr_comments "petry-projects/.github-private" 2009
-  [ "$status" -ne 0 ]
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *"pagination"* ]]
 }
 
 @test "bcr_fetch_pr_comments: a non-boolean hasNextPage fails closed" {
   gh() { printf '%s' '{"data":{"repository":{"pullRequest":{"comments":{"pageInfo":{"endCursor":null},"nodes":[]}}}}}'; }
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *"pagination"* ]]
+}
+
+# #2072: a failed API call and an unparseable page each fail closed with their
+# own reason, so a fetch failure is distinguishable from a parse failure.
+@test "bcr_fetch_pr_comments: a failed API call fails closed with a fetch reason" {
+  gh() { return 1; }
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *"API request failed"* ]]
+}
+
+@test "bcr_fetch_pr_comments: an unparseable page fails closed with a parse reason" {
+  gh() { printf '%s' '<html>502 Bad Gateway</html>'; }
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *"unparseable"* ]]
+  [[ "$stderr" != *"API request failed"* ]]
+}
+
+# A page that reports more pages but repeats the cursor it was fetched with
+# would loop on the same page forever; it fails closed instead.
+@test "bcr_fetch_pr_comments: a repeated non-empty endCursor fails closed" {
+  gh() { printf '%s' '{"data":{"repository":{"pullRequest":{"comments":{"pageInfo":{"hasNextPage":true,"endCursor":"same"},"nodes":[]}}}}}'; }
+  run --separate-stderr bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$output" ]
+  [[ "$stderr" == *"did not advance"* ]]
+}
+
+# The temp file holds fetched comment bodies; it is removed on success and failure.
+@test "bcr_fetch_pr_comments: leaves no temp file behind" {
+  export TMPDIR="$BATS_TEST_TMPDIR/tmp"
+  mkdir -p "$TMPDIR"
+  gh() { printf '%s' '{"data":{"repository":{"pullRequest":{"comments":{"pageInfo":{"hasNextPage":false,"endCursor":null},"nodes":[]}}}}}'; }
   run bcr_fetch_pr_comments "petry-projects/.github-private" 2009
-  [ "$status" -ne 0 ]
+  [ "$status" -eq 0 ]
+  gh() { return 1; }
+  run bcr_fetch_pr_comments "petry-projects/.github-private" 2009
+  [ "$status" -eq 1 ]
+  [ -z "$(ls -A "$TMPDIR")" ]
+}
+
+# #2072: PR #1953's comment history grew past the per-argument size limit and the
+# scan died with "jq: Argument list too long" because pages were merged through
+# `jq --argjson`. Thousands of comments and several MB of body text — far beyond
+# ARG_MAX — must be read in full.
+@test "bcr_fetch_pr_comments: reads thousands of comments and MBs of text (well over ARG_MAX)" {
+  local pages_dir="$BATS_TEST_TMPDIR/pages" pages=30 per_page=100 i
+  mkdir -p "$pages_dir"
+  for ((i = 1; i <= pages; i++)); do
+    jq -nc --argjson p "$i" --argjson n "$per_page" --argjson last "$pages" '
+      ("x" * 2048) as $pad
+      | {data: {repository: {pullRequest: {comments: {
+          pageInfo: {hasNextPage: ($p < $last),
+                     endCursor: (if $p < $last then "c\($p + 1)" else null end)},
+          nodes: [range($n) as $k
+            | {id: "IC_\($p)_\($k)", author: {login: "coderabbitai", __typename: "Bot"},
+               authorAssociation: "NONE", body: "comment \($p)/\($k) \($pad)",
+               createdAt: "2026-10-01T23:05:43Z", lastEditedAt: null,
+               isMinimized: false, minimizedReason: null}]}}}}}' > "$pages_dir/c$i.json"
+  done
+  export PAGES_DIR="$pages_dir"
+  gh() {
+    local a cursor="c1"
+    for a in "$@"; do
+      case "$a" in cursor=*) cursor="${a#cursor=}" ;; esac
+    done
+    cat "$PAGES_DIR/$cursor.json"
+  }
+  local out_file="$BATS_TEST_TMPDIR/out.json" err_file="$BATS_TEST_TMPDIR/err.txt"
+  bcr_fetch_pr_comments "petry-projects/.github-private" 1953 > "$out_file" 2> "$err_file"
+  [ ! -s "$err_file" ]
+  # Well over ARG_MAX, so it could never have been passed as one argument.
+  [ "$(wc -c < "$out_file")" -gt "$(getconf ARG_MAX)" ]
+  [ "$(jq 'length' "$out_file")" -eq $((pages * per_page)) ]
+  [ "$(jq -r 'first.id' "$out_file")" = "IC_1_0" ]
+  [ "$(jq -r 'last.id' "$out_file")" = "IC_${pages}_$((per_page - 1))" ]
+  # The full set still drives the pure decision without hitting the size limit.
+  run bcr_retry_decisions "$(cat "$out_file")" "$TRUSTED" "$INFO" "$NOW_EPOCH" "$AUTOMATION"
+  [ "$status" -eq 0 ]
+  [ "$(jq 'length' <<< "$output")" -eq $((pages * per_page)) ]
 }
 
 # ── dev-lead-retry.sh sweep wiring ───────────────────────────────────────────