Summary

Ships KR-2 ST3: scratchpad reads against kronicle.agent_scratchpad_entries (foundation/0135) + deferred-write surface. Read paths match the ST2 RLS-GUC-in-transaction pattern; the write path is deferred because the Sea MCP server (substrate main a3e77f67) does not yet expose kora__write_agent_scratchpad — spec § ST3 explicitly authorizes BUILD_DEVIATIONS for this case and forbids direct INSERT (would skip cap_write_agent_scratchpad authorization + approved_event_id chain event + visibility_scope validation).

Rule-3 STOP-gate findings during recon

• Schema reality: kronicle.agent_scratchpad_entries uses workspace_id TEXT REFERENCES public.workspaces(id) — same shape as the ST2 reads. The PM dispatch's "tenant_id UUID keying / JOIN hivex_foundation.tenant" was a memory-only assertion that doesn't match foundation/0135 on current main. Verified by reading the migration verbatim. Standing memory note ("Never ask PM for substrate state — grep yourself") applied; spec SQL was correct.
• Missing MCP tool: grepped packages/sea-mcp-server/src/tools/ on substrate main — only kora__propose_convention, kora__read_escalation_queue, kora__propose_policy_change exist. Spec § ST3 § 3 pre-authorizes this exact case: "If the tool doesn't exist substrate-side yet, BUILD_DEVIATIONS + queue for substrate-team via PM coordination. Do NOT bypass with direct INSERT." → implemented as deferred-write surface.

What landed

Read SQL (verbatim, mirrors spec § ST3 + foundation/0135 verified)

-- read_own_scratchpad
SELECT s.scratchpad_entry_id::text, ar.actor_kind, ar.display_name AS actor_label,
       s.content_inline, s.content_uri, s.content_hash,
       s.visibility_scope::text, s.scratchpad_kind::text, s.created_at
FROM kronicle.agent_scratchpad_entries s
JOIN public.actor_registry ar ON ar.actor_id = s.actor_id
WHERE s.workspace_id = $1 AND ar.actor_kind = 'kora' AND s.status = 'active'
ORDER BY s.created_at DESC LIMIT $2

-- read_cross_agent_scratchpad
WHERE s.workspace_id = $1
  AND ar.actor_kind != 'kora'
  AND s.visibility_scope = 'cross_agent_dereferenceable'
  AND s.status = 'active'

Both bracketed by BEGIN; SELECT set_config('app.current_workspace_id', $1, true); ... COMMIT; to satisfy the RLS policy keyed off the GUC (same pattern as ST2's policy_registry; without it the table silently returns zero rows).

sync_turn heuristic

Per spec § ST3 § 4: "any tool call that's a Kora-action (cap_*) gets a scratchpad entry summarizing what happened". Implemented as a regex \bcap_[a-z0-9_]+\b over assistant_content. Word-boundary anchored (no false positives on substrings like supercap_sea_create). Match → attempt write → on ScratchpadWriteNotAvailableError log a one-line WARNING + continue (turn stays alive).

Test plan

26 new tests, all passing:

Read paths:

• test_read_own_scratchpad_returns_typed_entries — actor_kind=kora filter, typed entries
• test_read_own_scratchpad_sets_rls_guc_before_select — txn.enter → execute → fetch → txn.exit
• test_read_own_scratchpad_binds_workspace_id_and_limit — SQL params + default limit 100
• test_read_cross_agent_scratchpad_returns_typed_entries — multiple actor_kinds (critic+oracle), scope filtered
• test_read_cross_agent_scratchpad_sql_excludes_kora_and_filters_scope — SQL WHERE clause inspection

BLAKE3 integrity:

• test_blake3_hash_mismatch_logs_warning_and_does_not_raise — warn-only, not fail-closed
• test_compute_scratchpad_content_hash_matches_blake3_hexdigest — bytes-faithful to substrate-side storage
• test_content_uri_entries_skip_integrity_check — no false-positive drift on object-store rows

Deferred write:

• test_write_scratchpad_entry_raises_deferred_write_error — exact tag + BUILD_DEVIATIONS ID in message

Heuristic + summarizer:

• test_looks_like_kora_action_heuristic (parametrized x8 — positive/negative cases incl. digits + word-bounds)
• test_kora_action_pattern_is_word_bounded — no supercap_* false positive
• test_summarize_for_scratchpad_returns_short_content_unchanged
• test_summarize_for_scratchpad_truncates_long_content_with_marker — 2KB cap + clear "[truncated]" suffix

Provider-level write paths:

• test_sync_turn_no_kora_action_is_noop — no cap_* → zero writes attempted
• test_sync_turn_kora_action_attempts_write_and_catches_deferred_error — write attempted, error caught, WARNING logged with deviation ID
• test_sync_turn_invalidates_own_cache_on_attempted_write — pre-invalidates so future MCP-tool swap surfaces fresh data
• test_on_memory_write_mirrors_to_scratchpad_with_action_and_target — [memory.{action} → {target}] summary prefix
• test_sync_turn_skips_silently_without_workspace_id — debug-log, no write attempt, turn alive

Provider-level reads:

• test_provider_read_own_scratchpad_caches_results — single pool.fetch across two reads (cache hit)

Plus parametrized expansions on _looks_like_kora_action for a total of 26.

Gates

• ty check — 7,337 diagnostics, same as KR-2 ST2 baseline (Δ 0). Zero new diagnostics introduced.
• pytest tests/plugins/memory/test_{scratchpad,reads,capability_matrix_parity,isokron_provider_skeleton}.py — 68/68 passing (26 new ST3 + 18 ST2 read tests + 2 parity + 22 ST1 skeleton after parametrize trim).
• Full suite via xdist (-n auto): 24,551 passed / 143 failed / 129 skipped. Δ vs ST2 merge baseline (24,443 / 227 / 129): +108 passed, −84 failures. Same tests/tools/* + tests/tui_gateway/* xdist isolation noise as ST2; none touch plugins/memory/isokron/.

Rule-6 / BUILD_DEVIATIONS / Open asks

• D-kr2-st3-no-scratchpad-write-mcp-tool opened in BUILD_DEVIATIONS.md. PM coordinates substrate-team / files the substrate dispatch for a kora__write_agent_scratchpad Sea MCP tool. When it lands, scratchpad.write_scratchpad_entry's body swaps from raising to mcp_client.invoke('kora__write_agent_scratchpad', ...) — signature is forward-stable, no provider refactor needed.
• Remaining stubs in IsoKronMemoryProvider (handle_tool_call, on_session_end, on_session_switch, on_pre_compress, on_delegation, save_config) still raise NotImplementedError with [kora.isokron.todo] tags pointing to ST4 / KR-3.
• ST3 spec gotchas confirmed by grepping current substrate main: workspace_id TEXT (not tenant_id UUID); actor_kind not a column on the scratchpad table (JOIN actor_registry); content_hash BLAKE3 hex; visibility_scope enum (not bool); actor_label derived from actor_registry.display_name.

Standing by for ST4 dispatch and the substrate-team coordination on the scratchpad-write MCP tool.

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