Context and Problem Statement

src/runtime/next/event_emitter.py defines a concrete class RuntimeEventEmitter whose eight emit_* callbacks are permanently no-op (pass / del payload, event_emitter.py:65-88) and whose seed_from_snapshot is an explicit no-op (:60-61). It is the residue of the retired sync EventEmitter (issue #5): the journal/outbox producer died with the sync transport, and what remained is the seam — a call surface the next bridge already threads so a future producer can register here without reshaping the bridge.

The dead-code census (report 25 §1a) flagged this class as DORMANT with a stale justification and leaned toward retiring it — replacing the construction with _internal_runtime.events.NullEmitter, retyping the signatures against the Protocol of the same name, and deleting the file (88 LOC, plus the bridge threading). The design red-team (report 24 §4) challenged that lean as wrong-headed and recommended REWIRE-or-explicit-defer instead.

This decision matters because the disposition is a prerequisite for the Mission B dead-port-disposition work: WP01 of that mission acts on this seam, and it must know whether it is deleting a dead port or consolidating a reserved one. Getting it wrong in either direction is costly — a naive deletion throws away a designed last mile and silently changes rollback behavior; leaving it untouched preserves a name collision, a stale docstring, and a latent correctness bug.

The following facts were verified against src/ at HEAD e721763759 (3.2.7rc1) and against the installed spec_kitty_events 9.1.6 package:

• The hosted contract already exists and is waiting for a producer. Installed spec_kitty_events 9.1.6 carries all six mission_next runtime moments — MissionRunStarted, NextStepIssued, NextStepAutoCompleted, DecisionInputRequested, DecisionInputAnswered, MissionRunCompleted — in zeitgeist_attrs.VOLATILE_EVENT_TYPES (verified: 6/6 present), with codec and per-type redaction entries. The seam is the designed last mile of that contract, not speculative 4.0.0 vocabulary.
• The seam is explicitly reserved in-tree. Two conformance tests name runtime.next.event_emitter as the reserved E3 producer seam and say its payloads "belong back in this file" when a real emitter is wired (tests/status/test_producer_conformance.py, tests/contract/test_identity_contract_matrix.py).
• The retention docstring is stale. event_emitter.py:1-10 claims E3 will "register a real handler (the zeitgeist moment fan-out) at this seam." The zeitgeist moment fan-out already landed at a different seam — src/specify_cli/status/adapters.py:364-365 (ensure_zeitgeist_moment_handlers(), gated by SPEC_KITTY_SYNC_MINIMAL_IMPORT). The docstring points E3 at a seam E3 already bypassed.
• There is a name collision. A second, live class named RuntimeEventEmitter — a Protocol — exists at src/runtime/next/_internal_runtime/events.py:67-88, alongside a concrete NullEmitter (:95-123) and real structural adapters (DecisionGitLog, _BufferingRuntimeEmitter). Two classes with one name in the same subtree is the duplication smell the census (report 25 §1f) named.
• The concrete class carries surface the Protocol/NullEmitter lack. The bridge binds the concrete class: it constructs it via RuntimeEventEmitter.for_feature(...) at runtime_bridge.py:1552 and :2739, and calls sync_emitter.seed_from_snapshot(...) at :1614 and :2745. Neither for_feature nor seed_from_snapshot exists on the _internal_runtime Protocol or on NullEmitter. A "just swap in NullEmitter" retirement is therefore not a drop-in.
• A latent correctness bug lives on this chain. Under the strict retrospective gate, engine_emitter is replaced by a _BufferingRuntimeEmitter (runtime_bridge.py:2149-2150) so a rolled-back terminal advance cannot fire an unretractable MissionRunCompleted. On gate-pass the buffer is flushed with buffer.flush(ctx.sync_emitter) (:2187) — into the plain no-op sync_emitter, not ctx.emitter_for_engine, the DecisionGitLog-wrapped emitter the non-gated path uses (:2124-2126, wrapped at :1560). The buffer is installed for every advance under strict policy (:2129), not only terminal ones, and DecisionGitLog persists only DecisionInputRequested / DecisionInputAnswered (src/specify_cli/events/decision_log.py:147-160; every other emit is pass-through). In the engine decision_required and terminal are mutually exclusive branches (_internal_runtime/engine.py:448,476), so a terminal advance buffers only MissionRunCompleted, which the git log ignores anyway. Consequence: under strict policy, every decision_required advance through the legacy runtime_next_step path buffers its DecisionInputRequested and flushes it into the no-op — decisions.events.jsonl is never appended — whereas on the non-gated path the same event reaches the coordination-branch decision git log (via emitter_for_engine). Today this is masked because sync_emitter is no-op and DecisionGitLog is the only real channel — but any disposition that touches this chain will either silently freeze or silently fix it, so it must be adjudicated explicitly.
• A second bypass sits on the composition dispatch path. runtime_bridge.py:1976 passes the plain ctx.sync_emitter (not emitter_for_engine) into _advance_run_state_after_composition, whose _emit_decision_required calls sync_emitter.emit_decision_input_requested(payload) (runtime_bridge_engine.py:226). Decision events on that path never reach DecisionGitLog regardless of retrospective policy. Same defect class; named here so the Mission B implementer does not fix it silently under cover of the retype.

Decision Drivers

• Do not discard a reserved, contract-backed seam. The hosted vocabulary is provisioned and the seam is explicitly reserved by tests; retiring it means re-adding ~29 sync_emitter threading sites plus two construction sites when E3 lands.
• Do not overreach into feature work. Wiring a live zeitgeist producer is E3 work with hosted-egress and redaction implications; a disposition ADR (and a dead-port-disposition mission) must not smuggle that in.
• Resolve the honest defects the census surfaced — the name collision, the stale docstring, and the flush-target bug — rather than freezing them under a "leave it alone" decision.
• Preserve behavior for every current caller. The only live behavior on this chain is DecisionGitLog wrapping the no-op; a consolidation must keep decision events durably committed, and must not add commit semantics to plain-door callers.
• Give Mission B a fail-closed boundary so WP01 knows exactly what is safe to change and what is ADR-blocked.

Considered Options

1. Rewire-ready consolidation (chosen) — keep the seam; merge the duplicate concrete class into the _internal_runtime Protocol/NullEmitter world (promote for_feature + seed_from_snapshot onto the seam surface, delete event_emitter.py, retype the bridge against the single Protocol); fix the flush target; correct the docstring. Do not wire a live producer — defer that to E3.
2. Retire now — delete the seam, collapse construction onto NullEmitter, drop for_feature/seed_from_snapshot, remove the threading.
3. Status quo — keep both classes, the stale docstring, and the latent bug as-is.
4. Rewire fully now — wire a live zeitgeist-moment producer at the seam immediately. Out of scope (this is E3 feature work); listed only to name it.

Decision Outcome

Chosen option: "Rewire-ready consolidation" (Option 1), because it is the only option that (a) honors the reserved, contract-backed seam, (b) removes the name collision and stale docstring the census flagged, (c) forces the latent flush-target bug to be adjudicated rather than silently frozen, and (d) keeps live-producer feature work (E3) cleanly deferred. It is a rename-and-merge plus a bug fix, not a port deletion and not feature work.

Concretely, the ADR adjudicates the five questions Mission B WP01 must answer:

(a) Rewire target + registry mechanism. The canonical interface is the _internal_runtime/events.py RuntimeEventEmitter Protocol; the seam's null-object is NullEmitter. The construction sites (runtime_bridge.py:1552,2739) become the registry seam: a factory that returns NullEmitter by default (and under SPEC_KITTY_SYNC_MINIMAL_IMPORT) and, when E3 registers one, a real Protocol-conforming producer — mirroring the env-gated import-tail registration pattern proven at status/adapters.py:364-365 (ensure_zeitgeist_moment_handlers()). The bridge depends on the Protocol and a factory, never on a concrete class import.

(b) The Protocol's missing surface. for_feature (mission-identity resolution, the one thing a future adapter needs — runtime_bridge.py:1552,2739) and seed_from_snapshot (:1614,2745) must be added to the seam before/as the concrete class is deleted. Preferred shape: a NullEmitter classmethod (or a module-level factory) and seed_from_snapshot as a no-op/​pass-through on NullEmitter, so the bridge's two construction sites and two seed sites keep compiling against the consolidated seam. Name the promoted constructor for_mission, not for_feature: the Terminology Canon forbids minting new feature* aliases for the Mission domain object, and the consolidated seam is a new public surface. Keep for_feature only as a transitional alias with a removal note, if the two construction sites cannot be renamed in the same change.

(c) The buffer flush-target bug. It is real and must be fixed, not frozen. buffer.flush(...) (runtime_bridge.py:2187) must target the durable decision sink the non-gated path uses — ctx.emitter_for_engine (the DecisionGitLog wrap, :2124-2126) — not the plain no-op ctx.sync_emitter. The fix is a coupled correctness change and must land with a red-first test whose fixture is a strict-policy decision_required advance (the only kind that buffers a git-loggable event): it must prove the buffered DecisionInputRequested is appended to decisions.events.jsonl after the flush. A terminal-advance fixture cannot go red because the git log ignores MissionRunCompleted; keep the terminal/rollback scenario as a separate assertion that a gate refusal discards the buffer and writes nothing. (There is no double-emit risk: on the gated path the engine wrote only into the buffer, so the flush is the first and only DecisionGitLog write. Rollback is preserved: the gate at :2178-2181 runs before the flush and the buffer is one-shot, runtime_bridge_retrospective.py:138-149.) The composition-path bypass (:1976 → runtime_bridge_engine.py:226) is the same defect class and is in scope for WP01 with its own red-first test; fixing one and freezing the other is prohibited.

(d) The name collision. Resolve it by removing the duplicate: delete the concrete event_emitter.py::RuntimeEventEmitter and keep the single canonical RuntimeEventEmitter Protocol in _internal_runtime/events.py. (If a transitional step must keep both classes momentarily, the concrete one is renamed NullRuntimeEventEmitter — but the target state has one name.)

(e) Mission B scoping. See Consequences.

Consequences

Positive

• The reserved E3 seam and its constructor (shipped as for_mission, per (b)) and seed_from_snapshot capability survive; a future producer registers an adapter without re-threading the bridge.
• One class named RuntimeEventEmitter remains; the duplication smell is gone.
• The stale docstring is corrected to point at status/adapters.py (the real zeitgeist seam), so the next agent is not misdirected.
• A latent correctness bug (strict-gated decision events skipping the git log) is fixed with a regression test instead of being silently frozen.
• Net LOC still drops (~88 LOC of concrete class + collapsed threading), so the census's simplification goal is largely met — just via merge, not deletion. Amended 2026-09-06 after merge (PR #3921): this estimate was wrong. The factory, registry, for_mission, and seam docstring the decision itself requires add +120 lines to _internal_runtime/events.py; the mission's net under src/runtime/next/ is +161/−105 = +56. The structural goals (one seam class, no collision, no dead duplicate) are met; the LOC reduction is not, and E3 should not expect one from wiring (#3929).

Negative

• More work than a straight git rm: the merge touches runtime_bridge.py, runtime_bridge_engine.py, _internal_runtime/events.py, the two conformance tests' comments, and the one live importer of the concrete class (tests/specify_cli/events/test_decision_log_coord.py:17), and adds red-first tests for the two flush-target fixes.
• The flush-target fix is a behavior change (decision events now durably commit on the strict-gated path). It is a correctness change, but it must be called out and tested, not slipped in.
• The seam remains no-op end-to-end until E3; this ADR does not deliver a live producer, so the "waiting for a producer" state persists (by design).

Neutral

• The zeitgeist moment fan-out at status/adapters.py:364 is unaffected — it is a separate, already-live seam; this decision only stops the emitter docstring from claiming to be it.

Mission B (dead-port-disposition) scope boundary

ADR-BLOCKED — Mission B must NOT:

• Delete event_emitter.py as a pure port deletion / "collapse onto NullEmitter and drop the seam."
• Remove the constructor (for_mission) / seed_from_snapshot capability.
• Change the buffer flush semantics without fixing the flush target (freezing the bug is prohibited).
• Wire a live zeitgeist producer (that is E3, out of scope).

SAFE under this ADR — Mission B WP01 may:

• Perform the rename-and-merge consolidation (behavior-preserving apart from the flush fix): promote the constructor (as for_mission) and seed_from_snapshot onto the seam, delete the duplicate concrete class, retype the bridge against the Protocol + factory.
• Fix the flush target at :2187 to ctx.emitter_for_engine, and the composition dispatch emitter at :1976 likewise, each with a red-first regression test whose fixture is a strict-policy decision_required advance.
• Correct the event_emitter.py docstring (or its successor's) and update the two conformance tests' comments to point at the consolidated seam.

Confirmation

This decision is validated when Mission B WP01 lands a change in which: (1) exactly one class named RuntimeEventEmitter exists under src/runtime/next/; (2) the bridge constructs the seam via a factory returning NullEmitter by default with the constructor/seed_from_snapshot capability intact; (3) new regression tests prove that a strict-policy decision_required advance appends its buffered DecisionInputRequested to the decision git log after the flush, that the same holds on the composition dispatch path, and that a refused terminal gate discards the buffer without a git write; and (4) the existing bridge-parity and producer-conformance tests stay green. Confidence: high on the facts (all verified at e721763759 against installed spec_kitty_events 9.1.6); medium on the exact consolidation mechanics, which are Mission B's to finalize within this boundary.

Pros and Cons of the Options

Option 1 — Rewire-ready consolidation (chosen)

Keep the seam, merge the duplicate class into the Protocol/NullEmitter, fix the flush target, correct the docstring; defer the live producer.

Pros:

• Preserves a reserved, contract-backed seam and its identity-resolution surface.
• Eliminates the name collision and the stale docstring.
• Fixes the latent flush-target bug under test.
• Still achieves most of the census's LOC reduction. (Amended 2026-09-06: it does not — see Consequences.)

Cons:

• More involved than a deletion; touches several bridge files and adds a test.
• Introduces a (correct, tested) behavior change on the strict-gated path.

Option 2 — Retire now

Delete event_emitter.py, collapse onto NullEmitter, drop the threading.

Pros:

• Maximal immediate simplification; smallest diff to count.

Cons:

• Not a drop-in: for_feature/seed_from_snapshot are absent from the Protocol and NullEmitter, so the bridge would need surgery anyway.
• Throws away a reserved seam the hosted spec_kitty_events 9.1.6 contract is waiting on; E3 must re-thread ~29 sites + 2 construction sites later.
• Silently freezes the flush-target bug (or, if it re-points construction, silently changes it) without adjudication or a test.
• Contradicts two in-tree conformance tests that reserve the seam.

Option 3 — Status quo

Leave both classes, the stale docstring, and the bug in place.

Pros:

• Zero immediate risk; no diff.

Cons:

• Preserves the two-classes-one-name collision the census flagged.
• Keeps a docstring that actively misdirects the next agent about the E3 seam.
• Leaves a real correctness bug (strict-gated decision events skipping the git log) latent and undocumented.

Option 4 — Rewire fully now (out of scope)

Wire a live zeitgeist-moment producer at the seam immediately.

Pros:

• Delivers the end-to-end runtime-moment fan-out.

Cons:

• Feature work (E3) with hosted-egress, redaction, and ordering concerns — not a disposition, and outside a dead-port-disposition mission. Named only to exclude it.

More Information

• Evidence: report 24 (work/post-convergence/24-coreloop-design-redteam-alphonso.md, §4 port dispositions) and report 25 (25-dead-code-census-randy.md, §1a/§1f/§4). Both are local, untracked (work/ is gitignored); every load-bearing fact above was re-verified in-tree and cites its code anchor, so the decision does not rest on them.
• Related decision: 2026-04-25-1-shared-package-boundary.md (the _internal_runtime internalization that produced the second seam).
• Code anchors (HEAD e721763759): src/runtime/next/event_emitter.py; src/runtime/next/_internal_runtime/events.py:67-123; src/runtime/next/runtime_bridge.py:195,1215,1472,1552,1560,1614,2124-2126,2149-2150,2187,2739,2745,2754; src/runtime/next/runtime_bridge_retrospective.py:69-149; src/specify_cli/status/adapters.py:364-365; installed spec_kitty_events/zeitgeist_attrs.py (VOLATILE_EVENT_TYPES); tests/status/test_producer_conformance.py, tests/contract/test_identity_contract_matrix.py.
• Consumed by: the planned Mission B dead-port-disposition (WP01; not yet minted). Sibling governance PR: #3888.
• Accepted by the operator on 2026-09-06 (PR #3898): Option 1, rewire-ready consolidation. Codemap retirement in the same PR confirmed. Consequences amended post-merge (PR #3921): the net-LOC claim was withdrawn. Amended the same day after a pre-merge adversarial squad (architect / debugger / reviewer lenses): bug restated onto decision_required advances, confirmation test made satisfiable, composition path brought in scope, promoted constructor renamed for_mission.