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Design only (no library code). Revision 3 answers two review rounds from Codex and agy (round one: 4 P0, 26 P1; round two: 13 P1; round three: 5 P1, no P0); see the "Review resolutions" section. Introspection v1 for spawned 0.9 (priority tier 2): docs/design/introspection.md.

• info() (process_info) out of band, readable while a handler is wedged; get_state/get_status in band between turns (OTP sys), state redacted unless Inspect.
• Tier 0 (always on, nothing added to send/dispatch/turn) vs the introspection feature (message type, ages, mailbox length; a few relaxed stores per turn, no clock read), with a cost table per field.
• Supervision trees (which_children/count_children/tree, types shared with design: dynamic supervisor (rank 12a) #245), system snapshots, structured crash/supervisor/stall tracing events, a multi-session event sink.
• Stall watchdog (rank 8) on an OS thread: long poll, long turn, group starvation, long mailbox; report by default, fenced Killed opt-in.
• Remote console (G23): local Unix socket on by default, read-only by default, no TCP, no eval; spawned-ctl; versioned NDJSON protocol shared with spawned-top.
• Flight recorder (rank 9) deferred to 0.10; turn abort at an await deferred (open question).
• TLA+: verification/tla/Introspection.tla (fenced kill, status between turns and at death), revision 4: 47,968 states (4 messages: 80,482), 20 negative controls each failing on its named invariant (run on fede).
• Test plan, client mapping (ethrex d958dcba4 and 535647e45, ethlambda chain actor), ROADMAP and semantics entries.

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