Issue #7: mid-stream robustness fix discovered via 2026-05-22 crash. Long
mimir TUI conversation (turn 93, 1077 events consumed) crashed on event
1078 with JSONDecodeError("Expecting value: line 1 column 1 (char 0)")
from json.loads('') on an empty-data SSE frame. _iter_events
unconditionally called json.loads on every dispatched event; when
httpx_sse surfaces a frame with id: present but data: empty/missing
(a known library-vs-spec divergence), parsing fails and propagates.
Two-rule fix in _iter_events:
- Empty sse.data (exact `== ''`): SKIP silently per SSE spec (keepalive
semantics). Don't yield, don't advance last_sse_id, don't set
terminal_seen. ORDERING: skip fires BEFORE _parse_sse_id, so a
keepalive with a malformed id is still a keepalive (intentional).
- Non-empty sse.data that fails json.loads: raise new MalformedSseData
(sibling to MalformedSseId, mirrors raw[:200] truncation pattern).
Wire-level protocol error; presenters route to [malformed_sse_data]
+ exit 22 in cli, transcript label + state→idle in tui (INV-008).
Volva paraphrase round: 4 ambiguities, all amended:
1. INV-001 prose tightened — exact `sse.data == ''` rule made
prominent; "keepalive" framing demoted to intent-not-rule;
whitespace-only data explicitly listed as malformed (not skipped);
specific state names (last_sse_id, terminal_seen) instead of vague
"any counter".
2. STEPS pseudocode spells out the ordering — empty-skip happens
BEFORE _parse_sse_id; empty-data with bad id is silently swallowed.
3. empty_data_skipped test description fixed (had off-by-one count +
wrong wording around last_sse_id intermediate state).
4. (paired with #1 above).
Volva code-review post-implementation: 3 findings, all addressed:
F1 (test-gap): empty_data_skipped proves yielded events but not
internal last_sse_id non-advancement. New
empty_data_skip_preserves_last_seen_sse_id test probes via
SseConnectionDropped.last_seen_sse_id after a drop following the
skipped frame — if the skip had transiently advanced last_sse_id,
the exception payload would carry the wrong value.
F2 (precision, contract amend): MalformedSseData ERROR_ROUTING said
"log truncated raw" but stream_turn doesn't log — sse_client is a
library, presenters own observability. Amended to "propagate to
caller (no logging at sse_client layer); presenters log exc.raw."
F3 (test-gap): cli malformed_sse_data test asserted label but not
`raw='X'` shape and not truncation. Tightened existing test +
added malformed_sse_data_truncation with 5000-char payload —
verifies MalformedSseData.raw truncation carries through the
presenter's repr() rendering.
**Calibration milestone**: issue #7 is the first issue with ZERO drift
findings from Volva code-review. TDD caught all runtime behavior
cleanly. The 3 findings were assertion-precision and
architectural-correctness-of-wording, not behavioral. Hypothesis:
tighter contract spec + smaller code surface shifts Volva's role
from "catch behavioral drift" to "tighten observability + wording".
Cumulative calibration table: #1 (4 findings, 3 drift + 1 test-gap),
#2 (3, 1+1+1 precision), #3 (5, 3+1+1), #4 (8, 5+2+1), #7 (3, 0 drift
+ 2 test-gap + 1 precision).
Contracts touched (all drift-check clean):
- docs/contracts/issues/7.contract.md (new): the coordinating record.
- docs/contracts/issues/1.contract.md: _iter_events STEP 3.0
empty-skip + ordering note; STEP 3.c JSONDecodeError → MalformedSseData;
new MalformedSseData ERROR_ROUTING (propagate-to-caller wording per
F2); 4 new TESTS entries including F1's last-seen probe.
- docs/contracts/issues/3.contract.md: _run_turn ERROR_ROUTING +
malformed_sse_data tests (incl. F3 truncation).
- docs/contracts/issues/4.contract.md: INV-008 mentions MalformedSseData;
_stream_turn_worker ERROR_ROUTING + new TEST.
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