diff --git a/AGENTS.md b/AGENTS.md
index 06ac3fc..fb6d9bd 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -1,8 +1,8 @@
 # PROJECT KNOWLEDGE BASE
 
-**Generated:** 2026-07-01T00:00:00Z
+**Generated:** 2025-01-20T00:00:00Z
 **Branch:** main
-**Refresh:** reconciled against `plans/*` (scheduled-tasks pipeline); verified scheduled event routing, config loader, handler symbols, manual `/zai update-agents` command, action.yml inputs, and line counts. Gaps flagged: no scheduled test coverage, no `docs/`, README not updated.
+**Refresh:** reconciled against actual file tree and `plans/*`; verified scheduled event routing, config loader, handler symbols, manual `/zai update-agents` command, action.yml inputs, and test coverage. Fixed stale workflow filenames (replaced nonexistent `code-review.yml` with actual `zai-code-bot.yml`, `zai-agents-init-example.yml`). Confirmed: scheduled test coverage exists (`tests/handlers/scheduled.test.js`, `tests/scheduled-config.test.js`, `tests/repository-context.test.js`, `tests/agents-validation.test.js`); `docs/scheduled-tasks.md` present; README updated with scheduled-tasks section and `/zai update-agents` command.
 
 ## OVERVIEW
 JavaScript GitHub Action with three event flows: (1) PR auto-review, (2) collaborator-gated `/zai` PR comment commands, and (3) cron-triggered scheduled tasks (`.zai-scheduled.yml`) that regenerate AGENTS.md files and open PRs. Runtime executes bundled `dist/index.js`; maintained logic lives in `src/index.js` plus modular services in `src/lib/*`.
@@ -10,7 +10,7 @@ JavaScript GitHub Action with three event flows: (1) PR auto-review, (2) collabo
 ## STRUCTURE
 ```text
 zai-code-bot/
-├── src/index.js                      # Runtime orchestration and event dispatch (~1095 lines)
+├── src/index.js                      # Runtime orchestration and event dispatch
 ├── src/lib/                          # Commands/auth/context/comments/api/services
 ├── src/lib/events.js                 # Event-type detection incl. `schedule` (cron) routing
 ├── src/lib/commands.js               # `/zai` parser + allowlist (incl. `update-agents`)
@@ -18,19 +18,29 @@ zai-code-bot/
 ├── src/lib/changed-files.js          # Paginated changed-files fetch (3000 file limit)
 ├── src/lib/pr-context.js             # Shared PR context fetch (files, content at ref, refs)
 ├── src/lib/code-scope.js             # Token-budget calculation for prompt sizing
+├── src/lib/context.js                # Changed-file fetch + truncation/range helpers
 ├── src/lib/config/scheduled-config.js # Scheduled-task config loader (.zai-scheduled.yml)
 ├── src/lib/repository-context.js     # Real repo context collection (tree + AGENTS.md discovery + key files)
 ├── src/lib/agents-validation.js      # Hallucination guard: validates generated AGENTS.md vs real repo
 ├── src/lib/handlers/                 # Command + scheduled handlers (ask/review/explain/describe/impact/help/scheduled)
-├── tests/                            # Unit and integration coverage
+├── tests/                            # Unit and integration coverage (Vitest v3)
 ├── dist/index.js                     # Generated ncc bundle executed by GitHub
 ├── dist/licenses.txt                 # Generated third-party licenses
 ├── action.yml                        # Action inputs (incl. ZAI_SCHEDULED_*, ZAI_AGENTS_GIST_URL)
 ├── .zai-scheduled.yml                # Scheduled-task config for THIS repo (AGENTS.md upkeep)
 ├── .zai-scheduled.yml.template       # Consumer template for scheduled tasks
-├── .github/workflows/ci.yml          # Test/build/dist-drift/audit gates
-├── .github/workflows/zai-agents-update.yml  # Self-hosted scheduled AGENTS.md upkeep workflow
-└── .github/workflows/code-review.yml # Consumer usage example
+├── .github/workflows/ci.yml                     # Test/build/dist-drift/audit gates
+├── .github/workflows/zai-agents-update.yml      # Self-hosted scheduled AGENTS.md upkeep
+├── .github/workflows/zai-code-bot.yml           # Bot execution on this repo's own PRs
+├── .github/workflows/zai-agents-init-example.yml # Example workflow for AGENTS.md init
+├── docs/scheduled-tasks.md           # Scheduled-tasks configuration reference
+├── plans/                            # Planning docs (scheduled-tasks integration)
+├── ARCHITECTURE.md                   # Layered architecture and invariants catalog
+├── CONTRIBUTING.md                   # Contribution guide and review checklists
+├── RUNBOOK.md                        # Operational runbook and rollback procedures
+├── SECURITY.md                       # Security policies and authorization rules
+├── README.md                         # User-facing inputs, commands, quickstart
+└── vitest.config.js                  # Vitest configuration
 ```
 
 ## WHERE TO LOOK
@@ -45,6 +55,7 @@ zai-code-bot/
 | Large PR batching and synthesis | `src/lib/auto-review.js` | Batch creation, context limit handling, synthesis prompt |
 | Paginated changed-files fetch | `src/lib/changed-files.js` | Handles GitHub's 3000 file API limit |
 | Shared PR context fetch | `src/lib/pr-context.js` | `fetchPrFiles`, `fetchFileAtRef`, `resolvePrRefs`; user-safe fallbacks, size limits |
+| Token budget calculation | `src/lib/code-scope.js` | Window extraction, enclosing block detection for prompt sizing |
 | Scheduled-task config loading | `src/lib/config/scheduled-config.js` | `loadScheduledConfig`, `getTasksToRun`, `validateAndNormalizeConfig`, `validateAgentsConfig`, `getGistUrl`; scoping fields (`context_paths`/`target_paths`/`exclude_paths`/budgets) |
 | Scheduled-task execution | `src/lib/handlers/scheduled.js` | `handleScheduledEvent`, `handleUpdateAgentsTask` (grounded flow: context→prompt→validate→PR), `SCHEDULED_HANDLERS`; see child `src/lib/handlers/AGENTS.md` |
 | Repository context for AGENTS.md gen | `src/lib/repository-context.js` | `collectRepositoryContext` (git tree + existing AGENTS.md discovery + key files, budgeted), `renderRepositoryContext` |
@@ -52,7 +63,11 @@ zai-code-bot/
 | Manual `/zai update-agents` | `src/index.js` (`dispatchCommand`) | Reuses `handleUpdateAgentsTask` for ad-hoc AGENTS.md updates |
 | Command-specific behavior | `src/lib/handlers/AGENTS.md` | Local guide for each handler module |
 | Test strategy and fixtures | `tests/AGENTS.md` | Test map and suite conventions |
-| Action runtime contract | `action.yml` | Node runtime + dist entrypoint |
+| Scheduled-tasks reference | `docs/scheduled-tasks.md` | Configuration reference, cron syntax, troubleshooting |
+| Architecture and invariants | `ARCHITECTURE.md` | Layered architecture, dependency direction, life-of-request flows |
+| Operational procedures | `RUNBOOK.md` | Rollback and incident response |
+| Security policies | `SECURITY.md` | Authorization rules and permission model |
+| Action runtime contract | `action.yml` | Node 20 runtime + dist entrypoint |
 | Build and drift policy | `package.json`, `.github/workflows/ci.yml` | `ncc` build and `dist/` drift gate |
 
 ## CODE MAP
@@ -111,7 +126,7 @@ zai-code-bot/
 - Asking an LLM to "scan the repo" without providing real repo context (causes hallucinated AGENTS.md — PR #15 bug).
 - Committing AGENTS.md output that references files/languages not present in the repo.
 - Editing `dist/` manually or shipping source changes without rebuilt artifacts.
-- Treating `.github/workflows/code-review.yml` example as runtime logic.
+- Confusing consumer-facing workflow examples (README snippet) with this repo's own `.github/workflows/` runtime logic.
 
 ## UNIQUE STYLES
 - Event-first architecture: `src/index.js` orchestrates; `src/lib/*` isolates concerns.
@@ -130,8 +145,7 @@ After source changes: run `npm run build` and commit `dist/index.js` + `dist/lic
 ## NOTES
 - CI (`.github/workflows/ci.yml`) enforces tests, build, dist drift, and security audit across Node 20 + 22.
 - No linting/formatting configs (ESLint, Prettier) — rely on code review and CI gates.
-- 7 command handlers + scheduled pipeline: ask (521), review (218), explain (355), describe (129), impact (336), help (95), scheduled (~1180 — largest handler, drives scheduled tasks via `.zai-scheduled.yml`). `update-agents` (manual `/zai` command) reuses `handleUpdateAgentsTask` from the scheduled module.
-- AGENTS.md upgrade flow (the `update-agents` task) is grounded + validated: `handleUpdateAgentsTask` calls `collectRepositoryContext` (`src/lib/repository-context.js`) to gather the real file tree, auto-discover existing AGENTS.md files, and fetch key file contents; `buildAgentsUpgradePrompt` embeds that context and tells the model it has NO live repo access; `validateGeneratedAgentFiles` (`src/lib/agents-validation.js`) rejects hallucinated/non-AGENTS/out-of-scope output before any PR. Scoping knobs live in `.zai-scheduled.yml` task config: `context_paths`, `target_paths`, `exclude_paths`, `max_context_chars`, `max_file_chars`, `max_files_to_fetch`, `allow_create_new`, `update_existing_only`.
-- Scheduled pipeline gaps (per `plans/*`): `docs/scheduled-tasks.md` not created; README has no scheduled section. (Scheduled unit/integration tests now exist: `tests/handlers/scheduled.test.js`, `tests/scheduled-config.test.js`, `tests/repository-context.test.js`, `tests/agents-validation.test.js`.)
-- Test framework: Vitest v3 (not Jest). Command: `npm test` → `vitest run --coverage`.
-- Large files: src/lib/handlers/scheduled.js (1081 lines), src/index.js (1095 lines), src/lib/handlers/ask.js (521 lines), src/lib/pr-context.js (433 lines).
+- 7 command handlers + scheduled pipeline: `ask`, `review`, `explain`, `describe`, `impact`, `help`, plus `scheduled` (largest handler, drives cron tasks via `.zai-scheduled.yml`).
+- Scheduled test coverage: `tests/handlers/scheduled.test.js`, `tests/scheduled-config.test.js`, `tests/repository-context.test.js`, `tests/agents-validation.test.js` (unit-level); end-to-end schedule integration test is still a gap.
+- Scheduled-tasks configuration reference: `docs/scheduled-tasks.md`.
+- Architecture and invariants catalog: `ARCHITECTURE.md`.
diff --git a/src/lib/handlers/AGENTS.md b/src/lib/handlers/AGENTS.md
index 1b0464a..da2dbf9 100644
--- a/src/lib/handlers/AGENTS.md
+++ b/src/lib/handlers/AGENTS.md
@@ -4,17 +4,17 @@
 Command handlers implement `/zai` behavior only after parsing + authorization; each module owns prompt construction, API call wiring, and response formatting. The `scheduled` handler is distinct: it executes scheduled tasks defined in `.zai-scheduled.yml` (and the manual `/zai update-agents` command) rather than responding to a standard review command.
 
 ## WHERE TO LOOK
-| Command | File | Lines | Notes |
-|---------|------|-------|-------|
-| `/zai ask` | `src/lib/handlers/ask.js` | 521 | Uses continuity state and broad PR context |
-| `/zai review <path>` | `src/lib/handlers/review.js` | 218 | Targeted diff review, file-in-PR validation |
-| `/zai explain <path>#Lx-Ly` | `src/lib/handlers/explain.js` | 355 | Range parsing + snippet extraction |
-| `/zai describe` | `src/lib/handlers/describe.js` | 129 | File/directory description |
-| `/zai impact` | `src/lib/handlers/impact.js` | 336 | Change impact analysis |
-| `/zai help` | `src/lib/handlers/help.js` | 95 | Static help output with auth gate |
-| `/zai update-agents` | `src/index.js` (`dispatchCommand`) | — | Manual AGENTS.md regen; reuses `handleUpdateAgentsTask` |
-| scheduled tasks | `src/lib/handlers/scheduled.js` | ~1180 | Largest module; cron-driven `.zai-scheduled.yml` tasks; grounded + validated AGENTS.md upgrades |
-| Handler registry | `src/lib/handlers/index.js` | 42 | Dispatcher map consumed by runtime (note: `scheduled` is exported but not in the `/zai` HANDLERS map) |
+| Command | File | Notes |
+|---------|------|-------|
+| `/zai ask` | `src/lib/handlers/ask.js` | Uses continuity state and broad PR context |
+| `/zai review <path>` | `src/lib/handlers/review.js` | Targeted diff review, file-in-PR validation |
+| `/zai explain <path>#Lx-Ly` | `src/lib/handlers/explain.js` | Range parsing + snippet extraction |
+| `/zai describe` | `src/lib/handlers/describe.js` | File/directory description |
+| `/zai impact` | `src/lib/handlers/impact.js` | Change impact analysis |
+| `/zai help` | `src/lib/handlers/help.js` | Static help output with auth gate |
+| `/zai update-agents` | `src/index.js` (`dispatchCommand`) | Manual AGENTS.md regen; reuses `handleUpdateAgentsTask` |
+| scheduled tasks | `src/lib/handlers/scheduled.js` | Largest module; cron-driven `.zai-scheduled.yml` tasks; grounded + validated AGENTS.md upgrades |
+| Handler registry | `src/lib/handlers/index.js` | Dispatcher map consumed by runtime (note: `scheduled` is exported but not in the `/zai` HANDLERS map) |
 
 ## SCHEDULED MODULE (`scheduled.js`) KEY SYMBOLS
 - `handleScheduledEvent` (entry) → `executeScheduledTask` (per-task) → `buildExecutionContext` → `getScheduledHandler` (registry lookup).
@@ -32,7 +32,7 @@ Command handlers implement `/zai` behavior only after parsing + authorization; e
 - Return user-safe failures; log internal details through shared logging helpers.
 
 ## TESTING
-- Local handler unit coverage exists in this folder (`review.test.js`, `explain.test.js`, `scheduled.test.js`).
+- Local handler unit coverage exists in `tests/handlers/`: `ask.test.js`, `explain.test.js`, `impact.test.js`, `review.test.js`, `scheduled.test.js`.
 - Scheduled pipeline coverage: `tests/handlers/scheduled.test.js` (registry, PR creation, parse, grounded `handleUpdateAgentsTask` flow incl. hallucination rejection), `tests/scheduled-config.test.js` (config + `validateAgentsConfig` scoping fields), `tests/repository-context.test.js` (tree/AGENTS.md discovery/budgets/globs), `tests/agents-validation.test.js` (path/hallucination/target-path guards incl. PR #15 regression).
 - End-to-end command pipeline behavior is validated in `tests/integration/command-pipeline.test.js`.
 - When changing parsing or output contracts, update both unit and integration assertions.
diff --git a/tests/AGENTS.md b/tests/AGENTS.md
index 5762080..4fb56f8 100644
--- a/tests/AGENTS.md
+++ b/tests/AGENTS.md
@@ -7,10 +7,10 @@ Repository test coverage mixes module-focused tests in `tests/*.test.js` and sce
 ```text
 tests/
 ├── *.test.js        # Module-level tests for lib/runtime units
-├── handlers/        # Handler-focused test helpers/cases
+├── handlers/        # Handler-focused test cases (ask, explain, impact, review, scheduled)
 ├── helpers/         # Shared mocks and fixtures utilities
-├── lib/             # Shared test helpers (e.g. events.js) + code-scope tests
-├── fixtures/        # Static test payloads
+├── lib/             # Shared test helpers + code-scope tests
+├── fixtures/        # Static test payloads (issue-comment-event.json, pr-event.json)
 └── integration/     # End-to-end command/review pipeline checks
 ```
 
@@ -18,17 +18,19 @@ tests/
 | Task | Location | Notes |
 |------|----------|-------|
 | Parser/auth/comment unit behavior | `tests/commands.test.js`, `tests/auth.test.js`, `tests/comments.test.js` | Fast regression checks |
-| Runtime orchestration checks | `tests/action.test.js`, `tests/handlers.test.js` | Entry flow and dispatch behavior |
+| Runtime orchestration checks | `tests/action.test.js`, `tests/handlers.test.js`, `tests/index.test.js` | Entry flow and dispatch behavior |
 | API and logging resilience | `tests/api.test.js`, `tests/logging.test.js` | Retry/error categorization |
 | Context, PR fetch, and batching | `tests/context.test.js`, `tests/pr-context.test.js`, `tests/changed-files.test.js`, `tests/auto-review.test.js` | Diff scoping, file-at-ref fetch, paginated/batched review |
 | Continuity and events | `tests/continuity.test.js`, `tests/events.test.js` | Hidden-marker state, event-type detection |
+| Code scope and window extraction | `tests/lib/code-scope.test.js` | Token budget, enclosing block, window extraction |
+| Describe handler | `tests/describe.test.js` | PR description generation |
 | Scheduled pipeline | `tests/handlers/scheduled.test.js`, `tests/scheduled-config.test.js`, `tests/repository-context.test.js`, `tests/agents-validation.test.js` | Config load + `validateAgentsConfig` scoping; `parseFileUpdatesFromResponse`; grounded `handleUpdateAgentsTask` flow incl. hallucination rejection; repo-context collection (tree/budgets/globs); validation guards incl. PR #15 regression |
-| Scheduled pipeline (integration) | (pending) | End-to-end schedule event → context → Z.ai mock → validated PR is still a gap worth adding; unit coverage of the grounded flow exists via the `handleUpdateAgentsTask` seam (`__callZaiForTest`). |
+| Scheduled pipeline (integration) | (pending) | End-to-end schedule event → context → Z.ai mock → validated PR is still a gap; unit coverage of the grounded flow exists via the `handleUpdateAgentsTask` seam (`__callZaiForTest`). |
 | Full command pipeline | `tests/integration/command-pipeline.test.js` | Parse -> auth -> handler -> output contract |
 | PR auto-review behavior | `tests/integration/pr-auto-review.test.js` | Marker upsert and PR event lifecycle |
 
 ## CONVENTIONS
-- Test framework: Vitest v3 (uses vitest globals: describe/test/expect).
+- Test framework: Vitest v3 (uses vitest globals: describe/test/expect); configured via `vitest.config.js`.
 - Keep tests deterministic with explicit mock payloads and marker assertions.
 - Prefer scenario names that encode trigger + expected visible outcome.
 - When changing comment markers or command UX, update integration snapshots/assertions immediately.
@@ -42,4 +44,3 @@ tests/
 - Test command: `npm test` → `vitest run --coverage`.
 - Coverage uploaded to Codecov.
 - Integration tests are the safety net for command threading and marker idempotency.
-- Large test files: tests/index.test.js (1057 lines), tests/integration/command-pipeline.test.js (664 lines), tests/pr-context.test.js.
diff --git a/tests/integration/AGENTS.md b/tests/integration/AGENTS.md
index 0ca77d2..3f8f542 100644
--- a/tests/integration/AGENTS.md
+++ b/tests/integration/AGENTS.md
@@ -8,7 +8,7 @@ Integration tests verify end-to-end GitHub event pipelines and visible bot behav
 |----------|------|-------|
 | Issue comment command pipeline | `tests/integration/command-pipeline.test.js` | Event classification, command parse, auth, dispatch, response shape |
 | Pull request auto-review pipeline | `tests/integration/pr-auto-review.test.js` | PR event handling, marker create/update, no-change short-circuits |
-| Integration fixture data | `tests/integration/fixtures/` | Shared payloads for realistic event simulation |
+| Integration fixture data | `tests/integration/fixtures/events.js` | Shared event payloads for realistic event simulation |
 
 ## CONVENTIONS
 - Test the public behavior chain from event input to final comment/reaction outcome.