Live probe

Use when the question is "what does TWS actually send/accept", not "does our code handle X". Docs, C# samples and field names have each been wrong (stale FundamentalReportType values, VOL units, what_if_type semantics); the paper gateway is the authority.

State the question as one falsifiable sentence before writing code: $ARGUMENTS.

0. Cheaper checks first

A probe costs a gateway session and often a market-hours wait. Try these first:

• Grep the captured-wire fixtures in src/**/*tests.rs for the field; real TWS values appear there as assertions.
• Read the C# reference (EDecoder.cs for inbound fields, EClient.cs / EClientUtils for what's sent, Order.cs / Contract.cs for types). See wire enum typing.

Probe when those disagree, are silent, or the question is about what TWS accepts (rejection codes, defaults for absent fields, units). Neither source answers those.

1. Preflight

$S below is your scratchpad directory.

TZ=America/New_York date '+%a %H:%M ET'
lsof -nP -iTCP -sTCP:LISTEN | grep -E ':(4002|7497) '   # expect java; ssh = tunnel, remote may be down

• Reset windows: the gateway accepts TCP but ignores the handshake. Daily 00:15–01:45 ET (Sun–Fri), weekend Fri 23:00 – Sat 03:00 ET; other regions in troubleshooting. Wait; don't debug.
• Market session decides what you can observe: RTH 09:30–16:00 ET for fills, live ticks, PnL. What-if, contract details, option chains and order acceptance work off-hours; overnight books are live, so "off-hours" is not "no quote". If the question needs RTH and it isn't, add a - [ ] line to plans/live-checks.md and stop.
• Paper only. Port 4002 (Gateway) or 7497 (TWS). In the probe, assert managed_accounts() ids start with D before sending anything that mutates state.
• Client id: pick one outside 200–399 (the integration tests' ibapi_test::ClientId pool) that no other session uses. A 326 "client id already in use" means a clash.
• Log client.server_version() — every finding is tagged with it.

2. Probe shape

Pick the lightest that answers the question:

Probe rules:

• Bound every read with a deadline; on async, check Instant::now() >= deadline at the loop top (timeout_at polls the inner future first and keeps returning queued items).
• Write output to a file and flush after each line, or eprintln! + RUST_LOG=debug; timeout cmd > file loses block-buffered stdout on kill.
• Orders: prefer what-if (.analyze()). Otherwise non-marketable limit, then cancel. Paper fills arrive in chunks; re-read filled from the cancel reply before flattening, and flatten anything that filled.
• Probe each variant/value separately; record which code each draws (e.g. 321 vs 430).
• A capture covers only the instruments and session it ran against. 512 futures fills carried only BOT / SLD; SSHORT / SLONG need equity short sales. Match both to the question before calling a vocabulary complete, and list what wasn't covered under Not probed.

3. Hang triage

In this order — each has been misdiagnosed as a gateway problem:

1. Zero output, even pre-connect prints → sample $(pgrep -f <bin>) 1. _dyld_start = macOS holding a freshly built binary (~50s). Give fresh binaries ≥60s before timeout.
2. Output stops at connect, TCP accepts → re-check the reset window; check the listener is java, not an ssh forwarder.
3. Outside the window, still silent → post-reset wedge. Ask the user to restart the gateway; don't assume.
4. Immediate EOF after handshake → 326 client id clash; pick another id.
5. UnexpectedEof / WouldBlock across many connections → gateway connection limit; serialize (--test-threads=1).

4. Record

Write the finding as you get it, in the entry format (date, session, server version, what was not probed).

• Durable wire fact (a field's presence, units, accepted values, error code) → docs/wire-facts/<domain>.md. Ships in the PR the fact informs; a probe no PR acts on yet gets its own small docs PR. Rewrite an entry a new probe supersedes (keep the old result as one line).
• Changes how a caller uses an API → also the item's rustdoc, with a live: <date> note.
• Check waiting on market hours → plans/live-checks.md under ## #N <title>: - [ ] while pending, ticked - [x] with the line above when run; then move the result to docs/wire-facts/. Not a GitHub issue (plans and issues).
• Confirms or contradicts a rule node → append to its precedents:.
• Don't commit probe code; cite the probe in the PR body.

5. Clean up

Delete temp #[ignore] / diagnostic tests from the tree before the PR (investigation artifacts, not suite). Cancel open orders and flatten positions the probe created. Scratchpad crates can stay, but never cite their paths in the repo: they are session-scoped.