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fix(herdr): fetch captures as ansi to avoid 0.8.0's scroll-based history harvest #2373

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fix(herdr): fetch captures as ansi to avoid 0.8.0's scroll-based history harvest #2373

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12 changes: 10 additions & 2 deletions bin/backends/herdr.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -2587,14 +2587,22 @@ fm_backend_herdr_send_key() { # <target> <key>
# the composer-state guard/fallback reads around submit and injection). Workaround:
# always request a generous fetch far above any realistic viewport height, then
# trim to the caller's requested bound ourselves with `tail`.
#
# Fetches --format ansi and strips locally instead of asking for text: on herdr
# 0.8.0 a text-format `pane read --source recent` against an idle alt-screen
# agent triggers the wheel-event history harvest (src/server/alt_screen_read.rs)
# — the pane VISIBLY scrolls up for seconds and snaps back on every poll
# (herdrdev/herdr#2669, closed as dup of #2387). The ansi path skips the
# harvest entirely and returns herdr's retained rows instantly, which matches
# the pre-0.8.0 text behavior this capture was written against.
fm_backend_herdr_capture() { # <target> <lines>
fm_backend_herdr_target_ready "$1" || return 1
local lines=${2:-200} fetch out
case "$lines" in ''|*[!0-9]*) lines=200 ;; esac
fetch=$lines
case "$fetch" in ''|*[!0-9]*) fetch=200 ;; *) [ "$fetch" -ge 200 ] || fetch=200 ;; esac
out=$(fm_backend_herdr_cli "$FM_BACKEND_HERDR_SESSION" pane read "$FM_BACKEND_HERDR_PANE" --source recent --lines "$fetch" 2>/dev/null) || return 1
printf '%s' "$out" | tail -n "$lines"
out=$(fm_backend_herdr_cli "$FM_BACKEND_HERDR_SESSION" pane read "$FM_BACKEND_HERDR_PANE" --source recent --lines "$fetch" --format ansi 2>/dev/null) || return 1
printf '%s' "$out" | tail -n "$lines" | fm_composer_strip_ansi
Comment on lines +2604 to +2605

@chatgpt-codex-connector chatgpt-codex-connector Bot Aug 14, 2026

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P2 Badge Record live verification for ANSI capture

Captain, for Herdr 0.8.0 idle alternate-screen panes, the fix depends on vendor-specific behavior that the updated fake test cannot exercise: it only confirms that --format ansi appears in argv and returns an already-plain fixture. The maintained verification matrix still records the old text command at docs/verification/runtime-backends.md:231-238, so there is no live evidence that this path both avoids the history harvest and produces escape-free plain captures after local stripping. Update the real-Herdr guard/evidence with the new command and observed output so future Herdr upgrades cannot silently restore scrolling or leak control sequences.

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}

fm_backend_herdr_capture_ansi() { # <target> <lines>
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9 changes: 6 additions & 3 deletions tests/fm-backend-herdr.test.sh
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Expand Up @@ -2856,9 +2856,12 @@ test_capture_calls_pane_read() {
out=$( PATH="$fb:$PATH" FM_HERDR_LOG="$log" FM_HERDR_RESPONSES="$resp" \
bash -c '. "$0/bin/backends/herdr.sh"; fm_backend_herdr_capture default:w1:p2 250' "$ROOT" )
[ "$out" = $'line one\nline two\nline three' ] || fail "capture did not pass through pane read output, got '$out'"
assert_contains "$(cat "$log")" "HERDR_SESSION=default"$'\x1f''pane'$'\x1f''read'$'\x1f''w1:p2'$'\x1f''--source'$'\x1f''recent'$'\x1f''--lines'$'\x1f''250' \
"capture did not call pane read with the right pane id and line bound"
pass "fm_backend_herdr_capture: calls 'pane read <pane> --source recent --lines N' with the session set"
# --format ansi is load-bearing, not cosmetic: on herdr 0.8.0 a text-format
# recent read of an idle alt-screen agent triggers the wheel-event history
# harvest and the pane visibly scrolls for seconds (herdrdev/herdr#2669).
assert_contains "$(cat "$log")" "HERDR_SESSION=default"$'\x1f''pane'$'\x1f''read'$'\x1f''w1:p2'$'\x1f''--source'$'\x1f''recent'$'\x1f''--lines'$'\x1f''250'$'\x1f''--format'$'\x1f''ansi' \
"capture did not call pane read with the right pane id, line bound, and the harvest-skipping ansi format"
pass "fm_backend_herdr_capture: calls 'pane read <pane> --source recent --lines N --format ansi' with the session set"
}

test_capture_works_around_small_lines_bug() {
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