PR_26175_DELTA_004: expand runtime event test coverage

docs_build/dev/ProjectInstructions/backlog/BACKLOG_MASTER.md

@@ -247,7 +247,8 @@ Current OWNER clarification:
   - Completed by PR_26175_DELTA_003_API_Client_Standardization.
 - [x] Delta - Runtime performance audit
   - Completion reference: PR_26175_DELTA_001_Runtime_Performance_Optimization.
-- [ ] Delta - Engine test coverage improvements
+- [x] Delta - Engine test coverage improvements
+  - Completed by PR_26175_DELTA_004_Runtime_Test_Expansion.
 - [ ] Delta - Event system audit
 - [ ] Delta - Controls runtime framework audit
 - [ ] Delta - Object runtime framework audit

docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-branch-validation.md

@@ -0,0 +1,15 @@
+# PR_26175_DELTA_004 Branch Validation
+
+| Gate | Status | Evidence |
+| --- | --- | --- |
+| Current branch before work | PASS | `main` after PR_003 merge |
+| Worktree before work | PASS | Clean |
+| Local/origin sync before work | PASS | `0 0` |
+| Team ownership | PASS | Team Delta owns Runtime, Event systems, and Runtime test coverage. |
+| Work branch | PASS | `PR_26175_DELTA_004_Runtime_Test_Expansion` |
+| Previous Delta PR closed | PASS | PR_003 was merged and `main` was verified before PR_004 started. |
+| Scope boundary | PASS | Runtime event system test expansion and backlog/report updates only. |
+
+## Instruction Reads
+
+PASS - All files under `docs_build/dev/ProjectInstructions/` were read before the Delta sequence, and updated instructions were reread after pulling latest `main`.

docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-manual-validation-notes.md

@@ -0,0 +1,15 @@
+# PR_26175_DELTA_004 Manual Validation Notes
+
+## Manual Review
+
+- Confirmed runtime implementation files were not modified.
+- Confirmed expanded assertions cover invalid runtime event records and output immutability.
+- Confirmed no Theme V2, UI, API client, browser-owned data, or status bar files changed.
+
+## Manual Validation
+
+PASS - Code review found no unrelated runtime behavior change.
+
+## Follow-Up
+
+- Remaining Delta runtime work continues in the next sequential PR for technical debt cleanup.

docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-requirement-checklist.md

@@ -0,0 +1,18 @@
+# PR_26175_DELTA_004 Requirement Checklist
+
+| Requirement | Status | Notes |
+| --- | --- | --- |
+| Team Delta ownership only | PASS | Runtime event test coverage is Delta-owned. |
+| One PR purpose | PASS | Runtime event coverage expansion only. |
+| Preserve backward compatibility | PASS | No runtime code changed. |
+| Update backlog | PASS | `Delta - Engine test coverage improvements` marked complete. |
+| Update tool state if applicable | PASS | Not applicable; no tool tile/status changed. |
+| Produce governance reports | PASS | Summary, branch validation, checklist, validation lane, manual notes, Codex diff, changed-file list, and ZIP. |
+| Runtime validation | PASS | Focused runtime tests and final systems test passed. |
+| No unrelated files | PASS | Changes are limited to runtime test coverage, backlog, and reports. |
+| No branch deletion | PASS | Source branch retained. |
+
+## Compatibility Notes
+
+- Existing runtime event publishing fixtures continue to pass.
+- Trigger and action runtime tests continue to pass against the expanded event test contract.

docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-validation.md

@@ -0,0 +1,31 @@
+# PR_26175_DELTA_004 Validation Lane
+
+## Commands
+
+```powershell
+node --check tests/engine/RuntimeEventSystem.test.mjs
+node tests/engine/RuntimeEventSystem.test.mjs
+node tests/engine/RuntimeTriggerProcessing.test.mjs
+node tests/engine/RuntimeActionSystem.test.mjs
+node tests/final/FinalSystems.test.mjs
+git diff --check
+```
+
+## Results
+
+| Command | Status |
+| --- | --- |
+| `node --check tests/engine/RuntimeEventSystem.test.mjs` | PASS |
+| `node tests/engine/RuntimeEventSystem.test.mjs` | PASS |
+| `node tests/engine/RuntimeTriggerProcessing.test.mjs` | PASS |
+| `node tests/engine/RuntimeActionSystem.test.mjs` | PASS |
+| `node tests/final/FinalSystems.test.mjs` | PASS |
+| `git diff --check` | PASS |
+
+## Browser Validation
+
+SKIP - No browser UI files changed.
+
+## Playwright Validation
+
+SKIP - Runtime test expansion is covered by focused Node tests.

docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion.md

@@ -0,0 +1,40 @@
+# PR_26175_DELTA_004_Runtime_Test_Expansion
+
+## Summary
+
+Team Delta expanded runtime event system coverage without changing runtime behavior.
+
+`tests/engine/RuntimeEventSystem.test.mjs` now covers invalid existing runtime event records and verifies published results are isolated from later source-object mutation. This strengthens the event publishing contract around validation and immutable result handling.
+
+## Scope
+
+- Team: Delta
+- Backlog item: `Delta - Engine test coverage improvements`
+- Test file changed: `tests/engine/RuntimeEventSystem.test.mjs`
+- Backlog updated: `docs_build/dev/ProjectInstructions/backlog/BACKLOG_MASTER.md`
+
+## Runtime Impact
+
+PASS - No runtime code changed.
+
+- Runtime event publishing behavior is unchanged.
+- Test coverage now confirms invalid runtime events report `EVENT_ID_REQUIRED`, `EVENT_TYPE_REQUIRED`, and `RUNTIME_EVENT_INVALID`.
+- Test coverage now confirms returned event arrays and event records reject mutation and are isolated from source-object mutations after publish.
+
+## Backlog Update
+
+PASS - `Delta - Engine test coverage improvements` is marked complete with this PR as the completion reference.
+
+## Tool State Update
+
+SKIP - No Build Path tool status or tool tile state changed.
+
+## Validation Summary
+
+PASS - Focused runtime event, trigger, action, and final systems validation completed.
+
+See `PR_26175_DELTA_004_Runtime_Test_Expansion-validation.md` for command details.
+
+## Branch Disposition
+
+Source branch should be retained after merge unless OWNER later approves branch deletion.

docs_build/dev/reports/codex_changed_files.txt

@@ -1,13 +1,9 @@
 docs_build/dev/ProjectInstructions/backlog/BACKLOG_MASTER.md
-docs_build/dev/reports/PR_26175_DELTA_003_API_Client_Standardization-branch-validation.md
-docs_build/dev/reports/PR_26175_DELTA_003_API_Client_Standardization-manual-validation-notes.md
-docs_build/dev/reports/PR_26175_DELTA_003_API_Client_Standardization-requirement-checklist.md
-docs_build/dev/reports/PR_26175_DELTA_003_API_Client_Standardization-validation.md
-docs_build/dev/reports/PR_26175_DELTA_003_API_Client_Standardization.md
+docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-branch-validation.md
+docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-manual-validation-notes.md
+docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-requirement-checklist.md
+docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion-validation.md
+docs_build/dev/reports/PR_26175_DELTA_004_Runtime_Test_Expansion.md
 docs_build/dev/reports/codex_changed_files.txt
 docs_build/dev/reports/codex_review.diff
-src/api/admin-setup-api-client.js
-src/api/db-viewer-api-client.js
-src/api/server-api-client.js
-src/api/session-api-client.js
-tests/dev-runtime/ServerApiClientStandardization.test.mjs
+tests/engine/RuntimeEventSystem.test.mjs