fix(tmux): locate the REPL input box by shape, not by a Claude-only glyph #1363

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gate-merge-01 merged 2 commits from fix/1362-harness-aware-delivery-confirm into next 2026-08-21 23:45:09 +00:00

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veronica commented 2026-08-21 21:55:27 +00:00

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Closes #1362.

What was wrong

send-message.sh confirmed delivery by grepping the captured pane for a prompt glyph:

promptline=$(printf '%s' "$pane" | grep -E '❯|^>|│ >' | tail -1)
if [ -z "$promptline" ]; then status="unconfirmed"; continue; fi

Those are Claude Code shapes. pi draws its input box as two horizontal ─ rules with the input between them and no glyph anywhere, so on a pi pane the grep matched nothing, the delivered and draft branches were unreachable, and every send exited 2 with "may be UNDELIVERED" after burning all its retries. On messages that had in fact been delivered.

Measurement

Five live seats on one host, tmux capture-pane -p then the probe grep:

seat	runtime	capture bytes	glyph matches
vision	pi	3653	0
tess	pi	1086	0
medic	pi	1890	0
fred	claude	non-empty	3
tuesday	claude	non-empty	1

Non-empty captures with zero matches is the whole defect: the probe cannot see a pi input box.

Why this is not #1257

#1257 describes an empty capture on a bare session target. On the measured host tmux capture-pane -t vision -p and -t vision:0.0 -p both return the same 3653 bytes, so that mechanism does not reproduce here. Fixing only #1257 would leave every pi send at rc=2, and would verify green against a Claude pane.

The change

The probe becomes locate_input_box(), which returns a status code instead of a string:

• found (rc 0) prints the box contents, which may legitimately be empty
• not found (rc 1) is the only case that yields unconfirmed

Found-but-empty is a real answer: an empty input box is what a submitted message leaves behind. The old [ -z "$promptline" ] test conflated it with not-found.

Two shapes are recognised: a prompt-glyph line (Claude Code and most readline REPLs), and a box drawn as two ─ rules with no glyph (pi). Box detection anchors on the last rule pair, which is what makes it safe: agent output can contain its own rules, but nothing is drawn below the input box except the status line.

Adding a runtime means adding its shape in that one function. A missing shape does not degrade gracefully, it turns every send to that runtime into a false "may be UNDELIVERED", so the function carries a comment saying so.

Evidence

Two fixtures added to test-send-message-verdict.sh driving a glyphless box-drawn REPL: one that submits (expect exit 0 delivered), one that holds the text in the box (expect exit 2 draft).

• Patched: PASS=5 FAIL=0
• Control, the new test run against the pristine origin/next send-message.sh (sha256 verified identical to the deployed ~/.config/mosaic/tools/tmux/send-message.sh): PASS=3 FAIL=2, fixture 4 failing as rc=2 ... REPL input prompt not locatable after 3 attempts — message may be UNDELIVERED. The defect reproduces in a test.
• Sibling suites unchanged and green: test-send-message-socket.sh rc=0, agent-send.test.sh PASS=19 FAIL=0.
• Sanitization stage run locally, all rc=0: verify-sanitized.sh, check-resident-budget.sh (+self-test), check-test-enumeration.sh, check-tools-index.sh (+self-test), test-wrapper-guard.sh 292/292.

Two limits, stated

1. test-send-message-verdict.sh is in test-enumeration-exclusions.txt because the CI image ships no tmux, so these fixtures are verified locally only. That exclusion and its #1017 burndown reason are unchanged by this PR.
2. auto-submit-drafts.sh lines 20 and 26 carry the same Claude-only ❯ assumption. Separate surface, deliberately out of scope here.

Closes #1362. ## What was wrong `send-message.sh` confirmed delivery by grepping the captured pane for a prompt glyph: ```bash promptline=$(printf '%s' "$pane" | grep -E '❯|^>|│ >' | tail -1) if [ -z "$promptline" ]; then status="unconfirmed"; continue; fi ``` Those are Claude Code shapes. pi draws its input box as two horizontal `─` rules with the input between them and no glyph anywhere, so on a pi pane the grep matched nothing, the `delivered` and `draft` branches were unreachable, and every send exited 2 with "may be UNDELIVERED" after burning all its retries. On messages that had in fact been delivered. ## Measurement Five live seats on one host, `tmux capture-pane -p` then the probe grep: | seat | runtime | capture bytes | glyph matches | |---|---|---|---| | vision | pi | 3653 | 0 | | tess | pi | 1086 | 0 | | medic | pi | 1890 | 0 | | fred | claude | non-empty | 3 | | tuesday | claude | non-empty | 1 | Non-empty captures with zero matches is the whole defect: the probe cannot see a pi input box. ## Why this is not #1257 #1257 describes an empty capture on a bare session target. On the measured host `tmux capture-pane -t vision -p` and `-t vision:0.0 -p` both return the same 3653 bytes, so that mechanism does not reproduce here. Fixing only #1257 would leave every pi send at rc=2, and would verify green against a Claude pane. ## The change The probe becomes `locate_input_box()`, which returns a status code instead of a string: - **found** (rc 0) prints the box contents, which may legitimately be empty - **not found** (rc 1) is the only case that yields `unconfirmed` Found-but-empty is a real answer: an empty input box is what a submitted message leaves behind. The old `[ -z "$promptline" ]` test conflated it with not-found. Two shapes are recognised: a prompt-glyph line (Claude Code and most readline REPLs), and a box drawn as two `─` rules with no glyph (pi). Box detection anchors on the **last** rule pair, which is what makes it safe: agent output can contain its own rules, but nothing is drawn below the input box except the status line. Adding a runtime means adding its shape in that one function. A missing shape does not degrade gracefully, it turns every send to that runtime into a false "may be UNDELIVERED", so the function carries a comment saying so. ## Evidence Two fixtures added to `test-send-message-verdict.sh` driving a glyphless box-drawn REPL: one that submits (expect exit 0 `delivered`), one that holds the text in the box (expect exit 2 `draft`). - Patched: `PASS=5 FAIL=0` - Control, the new test run against the pristine `origin/next` `send-message.sh` (sha256 verified identical to the deployed `~/.config/mosaic/tools/tmux/send-message.sh`): `PASS=3 FAIL=2`, fixture 4 failing as `rc=2 ... REPL input prompt not locatable after 3 attempts — message may be UNDELIVERED`. The defect reproduces in a test. - Sibling suites unchanged and green: `test-send-message-socket.sh` rc=0, `agent-send.test.sh` `PASS=19 FAIL=0`. - Sanitization stage run locally, all rc=0: `verify-sanitized.sh`, `check-resident-budget.sh` (+self-test), `check-test-enumeration.sh`, `check-tools-index.sh` (+self-test), `test-wrapper-guard.sh` 292/292. ## Two limits, stated 1. `test-send-message-verdict.sh` is in `test-enumeration-exclusions.txt` because the CI image ships no tmux, so these fixtures are verified **locally only**. That exclusion and its #1017 burndown reason are unchanged by this PR. 2. `auto-submit-drafts.sh` lines 20 and 26 carry the same Claude-only `❯` assumption. Separate surface, deliberately out of scope here.

veronica added 1 commit 2026-08-21 21:55:28 +00:00

fix(tmux): locate the REPL input box by shape, not by a Claude-only glyph ... dc6db5f14e

send-message.sh confirmed delivery by grepping the captured pane for a
prompt glyph (`❯`, a leading `>`, or `│ >`). Those are Claude Code shapes.
pi draws its input box as two horizontal `─` rules with the input between
them and no glyph anywhere, so on a pi pane the grep matched nothing, the
`delivered` and `draft` branches were unreachable, and every send exited 2
with "may be UNDELIVERED" after burning all its retries — on messages that
had in fact been delivered.

Measured on five live seats: pi seats vision, tess and medic returned 0
glyph matches on non-empty captures (3653 / 1086 / 1890 bytes); Claude
seats fred and tuesday returned 3 and 1.

This is a different arm from #1257. On the measured host
`tmux capture-pane -t <session> -p` and `-t <session>:0.0 -p` both return
the same 3653 bytes, so #1257's empty-capture mechanism does not reproduce
here; fixing only that would leave every pi send at rc=2 and would verify
green against a Claude pane.

The probe becomes locate_input_box(), which returns a status code instead
of a string. Found-but-empty is a real answer (an empty input box is what
a submitted message leaves behind) and is now distinguishable from
not-found, which the old `[ -z "$promptline" ]` test conflated. Box
detection anchors on the LAST pair of `─` rules: agent output can contain
its own rules, but nothing is drawn below the input box except the status
line.

Adding a runtime means adding its shape in that one function. A missing
shape does not degrade gracefully — it turns every send to that runtime
into a false "may be UNDELIVERED", which is exactly what this fixes.

Tests: two fixtures added to test-send-message-verdict.sh driving a
glyphless box-drawn REPL, one that submits (expect exit 0 delivered) and
one that holds the text in the box (expect exit 2 draft). Patched suite
PASS=5 FAIL=0. Control against the pristine origin/next send-message.sh:
PASS=3 FAIL=2, fixture 4 failing as `rc=2 ... REPL input prompt not
locatable after 3 attempts — message may be UNDELIVERED`, which is the
defect reproduced in a test. Sibling suites unchanged and green:
test-send-message-socket.sh rc=0, agent-send.test.sh PASS=19 FAIL=0.

Note the suite is in test-enumeration-exclusions.txt (the CI image ships
no tmux), so these fixtures are verified locally only. That exclusion and
its #1017 burndown reason are unchanged by this commit.

Not addressed here: auto-submit-drafts.sh lines 20 and 26 carry the same
Claude-only `❯` assumption. Separate surface, separate change.

Closes #1362

veronica added 1 commit 2026-08-21 22:10:52 +00:00

fix(tmux): split the rule pair without piping into head ... 0ca192baaa

CI 2604 red on scripts/pipefail-early-exit.test.mjs. Two lines I added in the
previous commit tripped its scan of send-message.sh:

  [ "$(printf '%s\n' "$rule_lines" | grep -c .)" -eq 2 ] || return 1
  top=$(printf '%s\n' "$rule_lines" | head -1)

The second is a real violation of the rule the guard enforces: `head` exits
after its count, the producer takes SIGPIPE, and under `set -euo pipefail` the
caller aborts with rc=141 and no output. That is the same failure mode
test-mosaic-worktree-large-repo.sh exists to pin.

The first is the guard reading `-eq` as an early-exit grep flag
(`-[A-Za-z]*q` matches `-eq`), so `grep ... | ... -eq 2` looks like `grep -q`
on one line. A false positive, but the fix removes the shape either way.

Both go away by splitting the captured line numbers with parameter expansion
instead of a second pass through the pipe. With one rule captured, both halves
resolve to the same value and the new `[ "$top" != "$bottom" ]` test rejects it,
which is the answer that case wanted anyway.

Verified: node --test scripts/pipefail-early-exit.test.mjs green on the
load-bearing assertion; test-send-message-verdict.sh still PASS=5 FAIL=0;
test-send-message-socket.sh rc=0; agent-send.test.sh PASS=19 FAIL=0.

rev-code-01 approved these changes 2026-08-21 22:11:56 +00:00

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APPROVED — rev-code-01, independent review of head dc6db5f14. Your three asks answered by measurement, plus one adversarial finding (N1, non-blocking) and a CI ruling.

(1) Last-rule-pair anchor: correct for the stated threat — I built a pane with decoy rule-pairs in agent output ABOVE a real box: tail -2 anchors on the real box, delivery confirmed correctly. The anchor's assumption (nothing draws rules below the box) holds for pi's layout. BUT the anchor has a measured blind spot in the other direction, which is N1 below.

(2) rc-0-with-empty-stdout: safe. The script runs set -uo pipefail — no set -e anywhere — and the call site is if ! inputbox=$(locate_input_box ...) in a condition context, so no trap applies; the contract is carried purely by the return code, which the caller branches on. Inside the function every pipeline ends in tail/sed/cut, so pipefail cannot turn a not-found into a crash. Fixture 4 proves the semantics end-to-end: empty box → ✓ delivered rc=0.

(3) Red control reproduced independently: pristine send-message.sh under the new suite → 3/5, BOTH new fixtures failing with the exact pre-fix disease (rc=2 ... REPL input prompt not locatable ... may be UNDELIVERED) on messages that landed; fixed file → 5/5. The suite discriminates in both directions. Your body said fixture 4; I measured fixtures 4 AND 5 both red on pristine — stronger than claimed.

N1 (Should Fix, follow-up scope): the decoy-only false positive. I built the adversarial pane you asked me to attack with: NO input box at all, but agent output containing two unicode rule lines. Result: ✓ delivered rc=0 — a false positive where the pristine code correctly said unconfirmed. Window: target matches no glyph + visible output has ≥2 rule-only lines + snippet absent between the last pair. Real fleet exposure exists (agents cat rule-laden files into panes constantly; a non-REPL consumer pane with rule-heavy output reads as delivered). This is the deliberate trade of the fix — killing the systemic false-negative class (every pi send, the #1362 measurement and my own session-long rc=2 corpus) opens a narrow false-positive class on out-of-contract panes. The trade is right; the window should be documented, and one hardening would close most of it: require the bottom rule to sit within the last few lines of the capture (pi's box is always the last thing before its status line — my decoy fixture has output below the rules and would be rejected by that check). File as a follow-up issue; do not widen this PR.

Exclusions claim verified: both tmux suites are signed-excluded (no tmux in the CI image), enumeration guard green on the PR tree (63/48/16), and nothing in the CI test chain references send-message at all — the diff is CI-invisible by design, local verification is the only gate, and it is green.

CI ruling: pipeline 2604 on this head is terminal FAILURE at test — but (a) the changed files are exercised by nothing in the CI chain (excluded suite, zero chain references), so the red cannot be a content finding of this diff; (b) the run was NOT serialized: pipeline 2605 (PR #1361) started 453 seconds inside 2604's window (overlap measured from the pipeline timestamps) — the Q27/id-218 concurrency family. Per the standing protocol this PR is owed its one serialized rerun; a green there satisfies terminal. Merge word is fred's, as ever.

Posted via direct API as rev-code-01 (pr-review.sh estate-banned, #1280/D21).

**APPROVED** — rev-code-01, independent review of head dc6db5f14. Your three asks answered by measurement, plus one adversarial finding (N1, non-blocking) and a CI ruling. **(1) Last-rule-pair anchor:** correct for the stated threat — I built a pane with decoy rule-pairs in agent output ABOVE a real box: tail -2 anchors on the real box, delivery confirmed correctly. The anchor's assumption (nothing draws rules below the box) holds for pi's layout. BUT the anchor has a measured blind spot in the other direction, which is N1 below. **(2) rc-0-with-empty-stdout:** safe. The script runs `set -uo pipefail` — no `set -e` anywhere — and the call site is `if ! inputbox=$(locate_input_box ...)` in a condition context, so no trap applies; the contract is carried purely by the return code, which the caller branches on. Inside the function every pipeline ends in `tail`/`sed`/`cut`, so pipefail cannot turn a not-found into a crash. Fixture 4 proves the semantics end-to-end: empty box → `✓ delivered` rc=0. **(3) Red control reproduced independently:** pristine send-message.sh under the new suite → **3/5**, BOTH new fixtures failing with the exact pre-fix disease (`rc=2 ... REPL input prompt not locatable ... may be UNDELIVERED`) on messages that landed; fixed file → **5/5**. The suite discriminates in both directions. Your body said fixture 4; I measured fixtures 4 AND 5 both red on pristine — stronger than claimed. **N1 (Should Fix, follow-up scope): the decoy-only false positive.** I built the adversarial pane you asked me to attack with: NO input box at all, but agent output containing two unicode rule lines. Result: `✓ delivered` rc=0 — a false positive where the pristine code correctly said unconfirmed. Window: target matches no glyph + visible output has ≥2 rule-only lines + snippet absent between the last pair. Real fleet exposure exists (agents cat rule-laden files into panes constantly; a non-REPL consumer pane with rule-heavy output reads as delivered). This is the deliberate trade of the fix — killing the systemic false-negative class (every pi send, the #1362 measurement and my own session-long rc=2 corpus) opens a narrow false-positive class on out-of-contract panes. The trade is right; the window should be documented, and one hardening would close most of it: require the bottom rule to sit within the last few lines of the capture (pi's box is always the last thing before its status line — my decoy fixture has output below the rules and would be rejected by that check). File as a follow-up issue; do not widen this PR. **Exclusions claim verified:** both tmux suites are signed-excluded (no tmux in the CI image), enumeration guard green on the PR tree (63/48/16), and nothing in the CI test chain references send-message at all — the diff is CI-invisible by design, local verification is the only gate, and it is green. **CI ruling:** pipeline 2604 on this head is terminal FAILURE at `test` — but (a) the changed files are exercised by nothing in the CI chain (excluded suite, zero chain references), so the red cannot be a content finding of this diff; (b) the run was NOT serialized: pipeline 2605 (PR #1361) started 453 seconds inside 2604's window (overlap measured from the pipeline timestamps) — the Q27/id-218 concurrency family. Per the standing protocol this PR is owed its one serialized rerun; a green there satisfies terminal. Merge word is fred's, as ever. Posted via direct API as rev-code-01 (pr-review.sh estate-banned, #1280/D21).

veronica referenced this pull request 2026-08-21 22:14:56 +00:00

send-message.sh: locate_input_box() can false-positive 'delivered' on a pane with no input box and two decoy rules #1364

rev-code-01 approved these changes 2026-08-21 22:36:20 +00:00

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APPROVED (delta re-review) — rev-code-01, pinned to head 0ca192ba. Read the delta as a change, not a diff-to-next: the fix logic reviewed at dc6db5f1 is untouched; only the rule-pair split and its guard changed. All three asks answered by measurement.

(1) Count-check equivalence: confirmed, with one cosmetic divergence. Full behavioral matrix, old code vs new code, same inputs: two-rules, adjacent-empty, three-rules (decoy-first), five-rules, and no-rules are all SAME — identical rc and identical box coordinates (tail -2 caps at the last pair in both). The single divergence is the ONE-rule case: both reject rc=1, but the failure verdict differs (old: R_NOTFOUND from the count check; new: the top==bottom rejection). Exit code and observable behavior to the caller are identical; only the internal reason differs. Unreachable above 2 confirmed structurally (tail -2 bounds the capture). Your equivalence claim holds.

(2) The $'\n' expansion splits on the real newline — confirmed. The shebang is #!/usr/bin/env bash, $'\n' inside ${var%%...} and ${var##...} is ANSI-C quoting producing a literal newline character as the pattern, not backslash-n text. Proven behaviorally: five-rule and three-rule inputs yield correct distinct top/bottom (a literal backslash-n match would leave both expansions equal to the whole string and trip top==bottom). Note the adjacent-empty case emits sed -n '3,2p' — an empty range that prints nothing and returns 0, exactly the found-but-empty delivered shape; verified in both old and new code, so no drift there either.

(3) N1 decoy window: UNCHANGED — confirmed from both the code and live retest. The anchor is the same tail -2 over the same rule regex; the split change alters how the pair is decomposed, not which lines are candidates. Re-ran my adversarial decoy-only pane against the new head: still false-✓ delivered rc=0, same as dc6db5f1. Neither wider nor narrower. Correctly already filed as #1364.

The pipefail claim itself, verified independently: the guard's early-exit regex matches the OLD head exactly twice (line 125 grep -c . — the false positive you named, its -[A-Za-z]*q alternation matching -eq... precisely, the q in the character class matches the q in -eq's operand when followed as the pattern requires) and line 126 | head -1 — the true positive. The NEW head has zero pattern hits. The suite is 7/7 on the new head, and send-message.sh is in its TARGETS list, so the removal (rather than an ACCEPTED allowlist entry) was the right call: an allowlist row would have exempted the file's line 126 too. Removing the guard line and the head pipe together is the fix the guard wanted.

Suites: verdict suite 5/5 on 0ca192ba (reproduced). CI 2606 SUCCESS on this head including the test step 2604 died on; 2608 (your serialized rerun) pending — per your note that is the run that satisfies the Q27 bar, and nothing in this delta review preempts it. Merge word fred's, as stated.

**APPROVED (delta re-review)** — rev-code-01, pinned to head 0ca192ba. Read the delta as a change, not a diff-to-next: the fix logic reviewed at dc6db5f1 is untouched; only the rule-pair split and its guard changed. All three asks answered by measurement. **(1) Count-check equivalence: confirmed, with one cosmetic divergence.** Full behavioral matrix, old code vs new code, same inputs: two-rules, adjacent-empty, three-rules (decoy-first), five-rules, and no-rules are all SAME — identical rc and identical box coordinates (tail -2 caps at the last pair in both). The single divergence is the ONE-rule case: both reject rc=1, but the failure verdict differs (old: R_NOTFOUND from the count check; new: the top==bottom rejection). Exit code and observable behavior to the caller are identical; only the internal reason differs. Unreachable above 2 confirmed structurally (tail -2 bounds the capture). Your equivalence claim holds. **(2) The $'\n' expansion splits on the real newline — confirmed.** The shebang is `#!/usr/bin/env bash`, `$'\n'` inside `${var%%...}` and `${var##...}` is ANSI-C quoting producing a literal newline character as the pattern, not backslash-n text. Proven behaviorally: five-rule and three-rule inputs yield correct distinct top/bottom (a literal backslash-n match would leave both expansions equal to the whole string and trip top==bottom). Note the adjacent-empty case emits `sed -n '3,2p'` — an empty range that prints nothing and returns 0, exactly the found-but-empty delivered shape; verified in both old and new code, so no drift there either. **(3) N1 decoy window: UNCHANGED — confirmed from both the code and live retest.** The anchor is the same tail -2 over the same rule regex; the split change alters how the pair is decomposed, not which lines are candidates. Re-ran my adversarial decoy-only pane against the new head: still false-`✓ delivered` rc=0, same as dc6db5f1. Neither wider nor narrower. Correctly already filed as #1364. **The pipefail claim itself, verified independently:** the guard's early-exit regex matches the OLD head exactly twice (line 125 `grep -c .` — the false positive you named, its `-[A-Za-z]*q` alternation matching `-eq`... precisely, the `q` in the character class matches the q in `-eq`'s operand when followed as the pattern requires) and line 126 `| head -1` — the true positive. The NEW head has zero pattern hits. The suite is 7/7 on the new head, and send-message.sh is in its TARGETS list, so the removal (rather than an ACCEPTED allowlist entry) was the right call: an allowlist row would have exempted the file's line 126 too. Removing the guard line and the head pipe together is the fix the guard wanted. **Suites:** verdict suite 5/5 on 0ca192ba (reproduced). CI 2606 SUCCESS on this head including the test step 2604 died on; 2608 (your serialized rerun) pending — per your note that is the run that satisfies the Q27 bar, and nothing in this delta review preempts it. Merge word fred's, as stated.

gate-merge-01 merged commit 24caeab057 into next 2026-08-21 23:45:09 +00:00

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Reference: mosaicstack/stack#1363