> For the complete documentation index, see [llms.txt](https://ai-os-and-trend-finder.gitbook.io/ai-os-and-trend-finder-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ai-os-and-trend-finder.gitbook.io/ai-os-and-trend-finder-docs/.spec_system/archive/sessions/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md).

# Implementation Notes

**Session ID**: `phase27-session05-velocity-dynamics-upgrade` **Started**: 2026-06-12 23:42 **Last Updated**: 2026-06-13 00:14

***

## Session Progress

| Metric              | Value     |
| ------------------- | --------- |
| Tasks Completed     | 20 / 20   |
| Estimated Remaining | 0 minutes |
| Blockers            | 0         |

***

## Task Log

### 2026-06-12 - Session Start

**Environment verified**:

* [x] Prerequisites confirmed
* [x] Tools available
* [x] Directory structure ready

***

### Task T001 - Verify analyzer state, Session 04 completion, and Session 05 PRD scope

**Started**: 2026-06-12 23:42 **Completed**: 2026-06-12 23:43 **Duration**: 1 minute

**Notes**:

* Analyzer resolved current session as `phase27-session05-velocity-dynamics-upgrade` and confirmed the session directory contains `spec.md` and `tasks.md`.
* `state.json` and analyzer output list `phase27-session04-daily-time-series-persistence-and-sparklines` as completed.
* Phase 27 Session 05 PRD scope matches this implementation: acceleration, velocity significance, burst support, bounded schema fields, score breakdown display, and focused tests.
* The Phase 27 Session 04 stub still says `Status: Not Started`; tracked project state marks it completed, so implementation proceeds from `state.json` and analyzer facts.

**Files Changed**:

* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Created and recorded setup verification.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T001 complete and updated progress.

### Task T002 - Inspect scoring, historical context, trend-series, collector, schema, score-breakdown, and Engine Replay baselines

**Started**: 2026-06-12 23:43 **Completed**: 2026-06-12 23:44 **Duration**: 1 minute

**Notes**:

* `scripts/lib/ai-runtime/scoring.ts` currently computes momentum from recency, engagement, volume, single-run velocity, historical score momentum, demand, and source-local lift; it does not carry acceleration, significance, burst, or sparkline context.
* `scripts/lib/ai-runtime/historical-context.ts` already loads dated snapshots in deterministic order and assembles bounded sparklines, but it does not expose per-snapshot evidence-count history or delta history.
* `scripts/lib/ai-runtime/trend-series.ts` already provides 14-day zero-filled sparkline helpers suitable for burst input.
* `scripts/extensions/trend-finder/collector.ts` currently attaches topic sparklines after scoring, so scoring must receive historical sparkline context before score calculation for burst support.
* `src/extensions/trend-finder/schema.ts`, `view-model.ts`, `score-breakdown.tsx`, `trend-card.tsx`, `engine-trace.ts`, and `engine-replay-model.ts` all use additive bounded patterns that can be extended without replacing existing payload contracts.
* Relevant tests exist for scoring, historical context, schema parsing, view models, sparkline components, and Engine Replay; no score-breakdown component test exists yet.
* ADR `docs/adr/0001-extension-platform-foundation.md` confirms static extension boundaries and no dynamic code loading.

**Files Changed**:

* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Recorded source orientation findings.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T002 complete and updated progress.

### Task T003 - Create pure velocity dynamics helper with acceleration, significance, burst, caps, and explicit unavailable states

**Started**: 2026-06-12 23:44 **Completed**: 2026-06-12 23:46 **Duration**: 2 minutes

**Notes**:

* Added pure `deriveVelocityDynamics` helpers for evidence-count delta series, acceleration, significance, burst, and capped burst momentum support.
* Acceleration returns unavailable for missing history or fewer than two consecutive deltas.
* Significance returns unavailable below three historical snapshots and when historical delta variance is zero.
* Burst uses the final two daily buckets from a bounded 14-day series and returns capped support points.
* Normalization clamps browser-bound counts, de-duplicates timestamps, and preserves deterministic ordering.

**Files Changed**:

* `scripts/lib/ai-runtime/velocity-dynamics.ts` - Created pure velocity dynamics math and default state helpers.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T003 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: helper outputs stable bounded shapes with explicit unavailable states for every missing or invalid input path (`scripts/lib/ai-runtime/velocity-dynamics.ts`).

### Task T004 - Extend historical topic context with bounded evidence-count and delta history from dated snapshots with deterministic ordering

**Started**: 2026-06-12 23:46 **Completed**: 2026-06-12 23:48 **Duration**: 2 minutes

**Notes**:

* Added bounded `evidenceCountHistory` and consecutive `evidenceDeltaHistory` arrays to historical topic contexts.
* Evidence-count points are derived per dated snapshot from topic evidence counts, normalized, de-duplicated by timestamp, and sorted deterministically.
* Updated typed historical-context fixtures to include the new fields.
* Focused validation passed: `bun run test -- scripts/lib/ai-runtime/__tests__/historical-context.test.ts`.

**Files Changed**:

* `scripts/lib/ai-runtime/historical-context.ts` - Added evidence-count and delta history assembly.
* `scripts/lib/ai-runtime/__tests__/scoring.test.ts` - Updated typed historical context fixture defaults.
* `scripts/lib/ai-runtime/__tests__/topic-identity.test.ts` - Updated typed historical context fixture.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T004 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: historical topic contexts now expose deterministic evidence-count history required by scoring without leaking private snapshot paths (`scripts/lib/ai-runtime/historical-context.ts`).

### Task T005 - Extend scoring input and topic output types for velocity dynamics and historical sparkline context with types matching declared contract

**Started**: 2026-06-12 23:48 **Completed**: 2026-06-12 23:53 **Duration**: 5 minutes

**Notes**:

* Added `historicalSparklines` to scoring input and `velocityDynamics` to topic output.
* Refactored score calculation to return both score factors and velocity dynamics.
* Built scoring-side sparkline points by merging historical sparkline points with current evidence day buckets.
* Added capped burst support to momentum without changing the six factor weight keys.
* Focused validation passed: `bun run test -- scripts/lib/ai-runtime/__tests__/scoring.test.ts`.

**Files Changed**:

* `scripts/lib/ai-runtime/scoring.ts` - Added velocity dynamics input/output types, derivation, sparkline lookup, and capped burst support.
* `src/extensions/trend-finder/schema.ts` - Added the additive browser schema contract consumed by scoring output.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T005 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: scoring output now matches a bounded additive schema field and keeps existing score factor keys stable (`scripts/lib/ai-runtime/scoring.ts`, `src/extensions/trend-finder/schema.ts`).
* Duplicate action prevention: burst support is computed from raw per-call inputs and applied once to the newly calculated momentum value, avoiding cumulative mutation across repeated scoring calls (`scripts/lib/ai-runtime/scoring.ts`).

### Task T006 - Add bounded velocity dynamics schemas and additive defaults with schema-validated input and explicit error mapping

**Started**: 2026-06-12 23:50 **Completed**: 2026-06-12 23:53 **Duration**: 3 minutes

**Notes**:

* Added additive schemas and defaults for acceleration, significance, and burst.
* Bounded deltas, scores, support points, sample counts, z-scores, and 14-day burst day counts.
* `TrendTopicSchema` now defaults missing `velocityDynamics` to explicit unavailable states for legacy payload compatibility.
* Focused validation passed: `bun run test -- src/lib/__tests__/trend-finder-schema.test.ts`.

**Files Changed**:

* `src/extensions/trend-finder/schema.ts` - Added velocity dynamics constants, defaults, schemas, and topic field.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T006 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Trust boundary enforcement: browser payload parsing now validates and bounds every velocity dynamics field before UI consumption (`src/extensions/trend-finder/schema.ts`).
* Failure path completeness: malformed dynamics objects catch to explicit unavailable defaults instead of failing the whole legacy payload parse (`src/extensions/trend-finder/schema.ts`).

### Task T007 - Add velocity dynamics view-model labels, tones, descriptions, and accessibility text with exhaustive state handling

**Started**: 2026-06-12 23:53 **Completed**: 2026-06-12 23:55 **Duration**: 2 minutes

**Notes**:

* Added velocity dynamics row and summary view models for acceleration, significance, and burst.
* Added compact labels, detail labels, tones, descriptions, and ARIA labels.
* Added exhaustive state and direction handling through existing `assertNever` patterns.
* Wired dynamics projection into `getTopicDerivedSignalsViewModel`.
* Focused validation passed: `bun run test -- src/extensions/trend-finder/__tests__/view-model.test.ts`.

**Files Changed**:

* `src/extensions/trend-finder/view-model.ts` - Added velocity dynamics view-model projection.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T007 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Accessibility and platform compliance: dynamics rows now expose explicit ARIA labels and unavailable copy for UI rendering (`src/extensions/trend-finder/view-model.ts`).
* Contract alignment: state and direction switches are exhaustive against schema enums (`src/extensions/trend-finder/view-model.ts`).

### Task T008 - Add available and unavailable velocity dynamics fixture states for browser and UI coverage

**Started**: 2026-06-12 23:55 **Completed**: 2026-06-12 23:56 **Duration**: 1 minute

**Notes**:

* Added a reusable available velocity dynamics fixture covering acceleration, significance, and burst.
* Added unavailable dynamics defaults to the fixture topic factory and explicitly set an unavailable example on the cooling topic.
* Focused validation passed: `bun run test -- src/extensions/trend-finder/__tests__/view-model.test.ts`.

**Files Changed**:

* `src/extensions/trend-finder/fixtures.ts` - Added available and unavailable velocity dynamics fixture states.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T008 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: fixture topics now exercise both available and unavailable schema-compatible dynamics states (`src/extensions/trend-finder/fixtures.ts`).

### Task T009 - Derive acceleration from consecutive evidence-count deltas in scoring with explicit low-sample and missing-history states

**Started**: 2026-06-12 23:48 **Completed**: 2026-06-12 23:57 **Duration**: 9 minutes

**Notes**:

* Scoring now derives acceleration from the current evidence count and historical evidence-count deltas for the matched canonical topic.
* Missing history and low-sample paths return explicit unavailable states instead of invented values.
* Current evidence-count input uses linked topic evidence count, while legacy velocity score behavior remains separate.
* Focused scoring validation passed earlier in this block: `bun run test -- scripts/lib/ai-runtime/__tests__/scoring.test.ts`.

**Files Changed**:

* `scripts/lib/ai-runtime/scoring.ts` - Wired acceleration derivation through `deriveTopicVelocityDynamics`.
* `scripts/lib/ai-runtime/velocity-dynamics.ts` - Provides acceleration state derivation.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T009 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Failure path completeness: acceleration has explicit missing-history and low-sample unavailable states (`scripts/lib/ai-runtime/velocity-dynamics.ts`).

### Task T010 - Derive significance against historical delta variance in scoring with minimum-sample and zero-variance guards

**Started**: 2026-06-12 23:48 **Completed**: 2026-06-12 23:57 **Duration**: 9 minutes

**Notes**:

* Scoring now attaches significance derived from current evidence-count delta against historical delta mean and variance.
* Significance requires at least three historical snapshots and at least two historical deltas.
* Zero historical variance returns an explicit unavailable state with baseline context.
* Direction labels are derived from current delta relative to the historical baseline.

**Files Changed**:

* `scripts/lib/ai-runtime/scoring.ts` - Wired significance output into topic dynamics.
* `scripts/lib/ai-runtime/velocity-dynamics.ts` - Provides significance score, z-score, direction, and unavailable guards.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T010 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Failure path completeness: significance has explicit low-sample and zero-variance unavailable states (`scripts/lib/ai-runtime/velocity-dynamics.ts`).

### Task T011 - Derive burst from 14-day series and apply capped momentum support with idempotency protection for repeated scoring calls

**Started**: 2026-06-12 23:48 **Completed**: 2026-06-12 23:57 **Duration**: 9 minutes

**Notes**:

* Scoring now derives burst from a bounded 14-day series using the final two day buckets as the last-48-hour window.
* Burst support is capped at four momentum points and leaves the six factor weight keys unchanged.
* Historical sparkline points are merged with current evidence day buckets for scoring input.
* Repeated scoring calls are idempotent because support is computed from raw inputs and applied to a fresh breakdown.

**Files Changed**:

* `scripts/lib/ai-runtime/scoring.ts` - Merged scoring sparkline context and applied capped burst support to momentum.
* `scripts/lib/ai-runtime/velocity-dynamics.ts` - Provides burst scoring and capped support helper.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T011 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Duplicate action prevention: burst support is applied from immutable per-call inputs, not by mutating a persisted score (`scripts/lib/ai-runtime/scoring.ts`).
* Contract alignment: burst exposes score, support points, recent share, and unavailable reasons within schema bounds (`scripts/lib/ai-runtime/velocity-dynamics.ts`, `src/extensions/trend-finder/schema.ts`).

### Task T012 - Pass historical sparkline context into scoring and log aggregate dynamics counters without private paths

**Started**: 2026-06-12 23:57 **Completed**: 2026-06-12 23:58 **Duration**: 1 minute

**Notes**:

* Collector now passes `historicalContext.context.topicSparklines` into `scoreTrendTopics`.
* `scoring.completed` logs aggregate availability counters and burst support point totals.
* Per-topic trace data includes dynamics states and burst support points only; no snapshot paths or private archive locations are logged.
* Focused validation passed: `bun run test -- scripts/extensions/trend-finder/__tests__/collector.test.ts`.

**Files Changed**:

* `scripts/extensions/trend-finder/collector.ts` - Passed historical sparkline context into scoring and added sanitized velocity dynamics trace counters.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T012 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Error information boundaries: trace additions expose only aggregate counters and bounded per-topic states, not private snapshot paths (`scripts/extensions/trend-finder/collector.ts`).

### Task T013 - Preserve sanitized Engine Replay scoring labels and counters for velocity dynamics and capped burst support

**Started**: 2026-06-12 23:58 **Completed**: 2026-06-13 00:01 **Duration**: 3 minutes

**Notes**:

* Added sanitized velocity dynamics states and capped burst support points to Engine Trace topic summaries.
* Legacy traces without dynamics parse with `unknown` states and zero burst support.
* Script-side trace mapping sanitizes nested dynamics values to enum states and clamps support points to 0-4.
* Focused validation passed: `bun run test -- scripts/extensions/trend-finder/__tests__/engine-trace.test.ts`.

**Files Changed**:

* `src/extensions/trend-finder/engine-trace.ts` - Added trace schema fields and defaults for velocity dynamics summaries.
* `scripts/extensions/trend-finder/engine-trace.ts` - Mapped sanitized velocity dynamics states and support counters.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T013 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Error information boundaries: Engine Trace stores bounded state labels and counters only, with no raw historical series or private paths (`src/extensions/trend-finder/engine-trace.ts`, `scripts/extensions/trend-finder/engine-trace.ts`).

### Task T014 - Render acceleration, significance, and burst rows in score breakdown with explicit unavailable, empty, and error states

**Started**: 2026-06-13 00:01 **Completed**: 2026-06-13 00:03 **Duration**: 2 minutes

**Notes**:

* `ScoreBreakdown` now accepts optional `velocityDynamics` and renders acceleration, significance, and burst rows when provided.
* Rows use view-model labels, tones, detail copy, stable minimum height, and ARIA labels.
* Unavailable and schema-caught malformed states render through the view-model as explicit unavailable rows.
* Typecheck initially found Engine Trace fixture topic summaries missing the new sanitized dynamics summary; fixture summaries were updated and typecheck then passed.
* Validation passed: `bun run typecheck`.

**Files Changed**:

* `src/extensions/trend-finder/components/score-breakdown.tsx` - Rendered velocity dynamics rows.
* `src/extensions/trend-finder/fixtures.ts` - Added trace-safe dynamics summaries to Engine Trace fixture topics.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T014 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Accessibility and platform compliance: dynamics rows carry ARIA labels and compact stable sizing (`src/extensions/trend-finder/components/score-breakdown.tsx`).
* Contract alignment: component consumes view-model rows instead of raw math internals (`src/extensions/trend-finder/components/score-breakdown.tsx`).

### Task T015 - Pass topic velocity dynamics into trend card score breakdown with platform-appropriate accessibility labels, focus management, and input support

**Started**: 2026-06-13 00:03 **Completed**: 2026-06-13 00:04 **Duration**: 1 minute

**Notes**:

* Trend cards now pass `topic.velocityDynamics` into `ScoreBreakdown`.
* Rendering remains read-only, so no new keyboard or pointer interaction paths are introduced.
* Accessibility labels are provided by the score-breakdown dynamics rows.
* Validation passed: `bun run typecheck`.

**Files Changed**:

* `src/extensions/trend-finder/components/trend-card.tsx` - Passed topic velocity dynamics into score breakdown.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T015 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Accessibility and platform compliance: read-only dynamics rows are surfaced with ARIA labels and do not add unmanaged focus or input behavior (`src/extensions/trend-finder/components/trend-card.tsx`, `src/extensions/trend-finder/components/score-breakdown.tsx`).

### Task T016 - Update Engine Replay scoring proof view model to describe capped burst support and unavailable dynamics context

**Started**: 2026-06-13 00:04 **Completed**: 2026-06-13 00:06 **Duration**: 2 minutes

**Notes**:

* Engine Replay scoring factors now include acceleration, significance, and burst rows.
* Full topic payloads use the velocity dynamics view-model projection; trace-only payloads use sanitized state labels and capped burst support points.
* Scoring stage and empty text now mention velocity dynamics and capped burst support.
* Focused validation passed: `bun run test -- src/lib/__tests__/trend-finder-engine-replay.test.tsx`.
* Type validation passed: `bun run typecheck`.

**Files Changed**:

* `src/extensions/trend-finder/engine-replay-model.ts` - Added dynamics scoring factors and updated scoring-stage copy.
* `src/extensions/trend-finder/engine-trace.ts` - Updated scoring empty text for dynamics proof.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T016 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: Engine Replay handles full topic dynamics and sanitized trace-only dynamics without requiring raw historical data (`src/extensions/trend-finder/engine-replay-model.ts`).

### Task T017 - Write hand-computed helper tests for acceleration, significance, burst, caps, and unavailable states

**Started**: 2026-06-13 00:06 **Completed**: 2026-06-13 00:07 **Duration**: 1 minute

**Notes**:

* Added hand-computed tests for acceleration, significance mean/variance/z-score, burst share, support caps, sorting, de-duplication, low-sample states, zero variance, missing series, and no volume.
* Focused validation passed: `bun run test -- scripts/lib/ai-runtime/__tests__/velocity-dynamics.test.ts`.

**Files Changed**:

* `scripts/lib/ai-runtime/__tests__/velocity-dynamics.test.ts` - Added pure helper regression tests.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T017 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Contract alignment: helper tests lock the expected unavailable and capped-support contracts (`scripts/lib/ai-runtime/__tests__/velocity-dynamics.test.ts`).

### Task T018 - Extend historical-context and scoring regression tests for low-sample, new-topic, missing-history, and capped burst behavior

**Started**: 2026-06-13 00:07 **Completed**: 2026-06-13 00:08 **Duration**: 1 minute

**Notes**:

* Historical-context tests now assert evidence-count history and consecutive delta assembly.
* Scoring tests now cover missing-history/new-topic unavailable states, low-sample acceleration and significance, capped burst support, and idempotent repeated scoring calls.
* Focused validation passed: `bun run test -- scripts/lib/ai-runtime/__tests__/historical-context.test.ts scripts/lib/ai-runtime/__tests__/scoring.test.ts`.

**Files Changed**:

* `scripts/lib/ai-runtime/__tests__/historical-context.test.ts` - Added evidence-count and delta-history assembly coverage.
* `scripts/lib/ai-runtime/__tests__/scoring.test.ts` - Added velocity dynamics scoring regression coverage.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T018 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Duplicate action prevention: scoring tests verify repeated calls do not compound burst support (`scripts/lib/ai-runtime/__tests__/scoring.test.ts`).
* Failure path completeness: regression tests assert unavailable states for missing history and low samples (`scripts/lib/ai-runtime/__tests__/scoring.test.ts`).

### Task T019 - Add schema, view-model, component, and Engine Replay tests for dynamics defaults, labels, rows, and legacy payloads

**Started**: 2026-06-13 00:08 **Completed**: 2026-06-13 00:11 **Duration**: 3 minutes

**Notes**:

* Schema tests now cover legacy dynamics defaults, valid bounded dynamics, and malformed dynamics fallback.
* View-model tests now cover available and unavailable dynamics rows.
* Added `score-breakdown.test.tsx` for available and unavailable dynamics row rendering.
* Engine Replay tests now assert dynamics rows are part of the scoring proof.
* Focused validation passed: `bun run test -- src/lib/__tests__/trend-finder-schema.test.ts src/extensions/trend-finder/__tests__/view-model.test.ts src/extensions/trend-finder/components/__tests__/score-breakdown.test.tsx src/lib/__tests__/trend-finder-engine-replay.test.tsx`.

**Files Changed**:

* `src/lib/__tests__/trend-finder-schema.test.ts` - Added dynamics schema defaults and bounds tests.
* `src/extensions/trend-finder/__tests__/view-model.test.ts` - Added velocity dynamics view-model tests.
* `src/extensions/trend-finder/components/__tests__/score-breakdown.test.tsx` - Added score-breakdown row rendering tests.
* `src/lib/__tests__/trend-finder-engine-replay.test.tsx` - Added Engine Replay dynamics row assertions.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T019 complete and updated progress.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Logged implementation details.

**BQC Fixes**:

* Accessibility and platform compliance: component tests assert dynamics rows are reachable through ARIA labels (`src/extensions/trend-finder/components/__tests__/score-breakdown.test.tsx`).
* Trust boundary enforcement: schema tests assert malformed dynamics fall back to bounded defaults (`src/lib/__tests__/trend-finder-schema.test.ts`).

### Task T020 - Run focused validation, ASCII checks, and record implementation results

**Started**: 2026-06-13 00:11 **Completed**: 2026-06-13 00:14 **Duration**: 3 minutes

**Notes**:

* Formatted touched implementation, test, and session files with Prettier.
* Focused validation passed: `bun run test -- scripts/lib/ai-runtime/__tests__/velocity-dynamics.test.ts scripts/lib/ai-runtime/__tests__/historical-context.test.ts scripts/lib/ai-runtime/__tests__/scoring.test.ts scripts/lib/ai-runtime/__tests__/topic-identity.test.ts scripts/extensions/trend-finder/__tests__/collector.test.ts scripts/extensions/trend-finder/__tests__/engine-trace.test.ts src/lib/__tests__/trend-finder-schema.test.ts src/extensions/trend-finder/__tests__/view-model.test.ts src/extensions/trend-finder/components/__tests__/score-breakdown.test.tsx src/lib/__tests__/trend-finder-engine-replay.test.tsx`.
* Type validation passed: `bun run typecheck`.
* Script type validation passed: `bun run typecheck:scripts`.
* ASCII scan passed with no non-ASCII matches across touched files.
* CRLF scan passed with no carriage returns across touched files.

**Files Changed**:

* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/tasks.md` - Marked T020 complete, completed checklist, and updated next step.
* `.spec_system/specs/phase27-session05-velocity-dynamics-upgrade/implementation-notes.md` - Recorded final validation results.

**BQC Fixes**:

* Contract alignment: final focused tests and type checks passed across runtime, schema, collector, UI, and Engine Replay surfaces.


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The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.