diff --git a/docs/spec/BTB-001-tool-json-formatter/BTB-001-architecture.md b/docs/spec/BTB-001-tool-json-formatter/BTB-001-architecture.md
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+---
+specId: BTB-001
+title: tool-json-formatter — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-001-architecture.md
+
+## 1) Architecture design (OOP / module-level)
+
+### 1.1 Components and responsibilities
+
+- `src/tools/json-formatter/JsonFormatterTool.tsx`
+  - Tool page orchestration: buttons (Prettify/Minify/Validate), options (indent, sort keys), output + error/status.
+
+- `src/tools/json-formatter/JsonCodeEditor.tsx`
+  - CodeMirror 6 wrapper
+  - Provides:
+    - JSON syntax highlighting (`@codemirror/lang-json`)
+    - line numbers / basic setup
+    - lint diagnostics (inline range underline) based on JSON.parse
+
+- `src/lib/json.ts`
+  - `sortJsonKeysDeep` for recursive key sorting.
+
+### 1.2 Data model / types
+
+- Editor value: string
+- Validation status: { ok: boolean, message?: string, line?: number, column?: number }
+
+### 1.3 Key flows
+
+- Prettify/Minify:
+  1) read editor value
+  2) `JSON.parse`
+  3) optional `sortJsonKeysDeep`
+  4) `JSON.stringify` with indent (prettify) or none (minify)
+  5) set output
+
+- Validate:
+  1) run JSON.parse
+  2) if error has position, compute line/column
+  3) set CodeMirror diagnostic at that position
+
+### 1.4 Dependencies / constraints
+
+- CodeMirror 6 packages:
+  - `@codemirror/view`, `@codemirror/state`, `@codemirror/language`, `@codemirror/lang-json`, `@codemirror/lint`
+- Constraint: no server.
+
+### 1.5 Compatibility notes
+
+- Keep route `/tools/json-formatter` stable.
+- Existing output semantics preserved.
diff --git a/docs/spec/BTB-001-tool-json-formatter/BTB-001-requirements.md b/docs/spec/BTB-001-tool-json-formatter/BTB-001-requirements.md
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+---
+specId: BTB-001
+title: tool-json-formatter — JSON prettify/minify/sort/validate with CodeMirror editor
+owner: Vincent
+status: implemented
+---
+
+# BTB-001-requirements.md
+
+## 0) Context
+
+- Problem:
+  - Users need to format/validate JSON quickly, with helpful inline error location.
+- Users/persona:
+  - Beginners + developers pasting JSON from APIs/logs.
+- Non-goals:
+  - No backend.
+  - No guarantee of accepting non-JSON variants (JSON5, comments) in v1.
+- Constraints:
+  - Runs 100% in-browser.
+  - Must handle large inputs reasonably without freezing.
+
+---
+
+## 1) Requirements
+
+### 1.1 Functional (expected)
+
+- [ ] BTB-001-REQ-001 (Functional / Expected): Provide an editor input for JSON with **line numbers**.
+- [ ] BTB-001-REQ-002 (Functional / Expected): Provide **Prettify** (indent) operation.
+- [ ] BTB-001-REQ-003 (Functional / Expected): Provide **Minify** operation.
+- [ ] BTB-001-REQ-004 (Functional / Expected): Provide **Sort keys (recursive)** option.
+- [ ] BTB-001-REQ-005 (Functional / Expected): Provide **Validate** operation.
+- [ ] BTB-001-REQ-006 (Functional / Expected): On invalid JSON, show an error message including **line/column**.
+- [ ] BTB-001-REQ-007 (Functional / Expected): On invalid JSON, show **inline error highlighting** in the editor.
+- [ ] BTB-001-REQ-008 (Functional / Expected): Editor should provide JSON syntax highlighting.
+- [ ] BTB-001-REQ-009 (Functional / Expected): Output panel supports copy and does not lose last successful output unnecessarily.
+
+### 1.2 Functional (forbidden)
+
+- [ ] BTB-001-REQ-010 (Functional / Forbidden): Must not send JSON content to any server.
+- [ ] BTB-001-REQ-011 (Functional / Forbidden): Must not embed unbounded JSON input into URL.
+
+### 1.3 Non-functional
+
+- [ ] BTB-001-REQ-012 (Non-functional): Must be usable on mobile widths (~420px).
+- [ ] BTB-001-REQ-013 (Non-functional): All repo quality gates must pass (test/lint/build/e2e).
+
+---
+
+## 2) Acceptance criteria
+
+- [ ] BTB-001-AC-001 (maps to BTB-001-REQ-001): Editor shows line numbers and accepts multi-line input.
+- [ ] BTB-001-AC-002 (maps to BTB-001-REQ-002): Prettify formats compact JSON into indented output.
+- [ ] BTB-001-AC-003 (maps to BTB-001-REQ-005/006/007): Validate on invalid JSON shows error message with line/col and an inline error marker.
+- [ ] BTB-001-AC-004 (maps to BTB-001-REQ-004): When sort keys is enabled, output JSON has recursively sorted object keys.
+
+---
+
+## 3) Test plan
+
+- Unit:
+  - `sortJsonKeysDeep` behavior.
+- E2E:
+  - `e2e/json-formatter.spec.ts` covers prettify + validate success/failure + inline marker.
+
+---
+
+## 4) Rollout / rollback
+
+- Rollout: Static deploy.
+- Rollback: revert commits affecting editor integration.
+- Risks:
+  - CodeMirror chunk size increase.
+
+---
+
+## 5) Open questions
+
+- Q1: Should we support JSON5 (comments/trailing commas) later?
diff --git a/docs/spec/BTB-002-ui-global-search/BTB-002-architecture.md b/docs/spec/BTB-002-ui-global-search/BTB-002-architecture.md
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+++ b/docs/spec/BTB-002-ui-global-search/BTB-002-architecture.md
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+---
+specId: BTB-002
+title: ui-global-search — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-002-architecture.md
+
+## 1) Architecture design (OOP / module-level)
+
+### 1.1 Components and responsibilities
+
+- `src/App.tsx` (Header + pages)
+  - Holds search query state.
+  - Syncs with short URL param `q`.
+  - When query changes off Home, navigates to Home.
+
+- Home page
+  - Filters `TOOLS` by query.
+  - Renders result count.
+
+### 1.2 Data model / types
+
+- Query: string (bounded for URL)
+
+### 1.3 Key flows
+
+- User types in header search:
+  - update state
+  - if not on Home, navigate to Home
+  - filter tool list
+
+- Enter key:
+  - if exactly one match → navigate `/tools/<id>`
+
+### 1.4 Dependencies / constraints
+
+- No dependencies.
+- Constraint: keep URL param short.
+
+### 1.5 Compatibility notes
+
+- Routes unchanged.
diff --git a/docs/spec/BTB-002-ui-global-search/BTB-002-requirements.md b/docs/spec/BTB-002-ui-global-search/BTB-002-requirements.md
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+++ b/docs/spec/BTB-002-ui-global-search/BTB-002-requirements.md
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+---
+specId: BTB-002
+title: ui-global-search — Header search across all tools
+owner: Vincent
+status: implemented
+---
+
+# BTB-002-requirements.md
+
+## 0) Context
+
+- Problem:
+  - As tool count grows, users need fast discovery without scrolling.
+- Users/persona:
+  - Users who remember partial tool names (e.g., “json”, “diff”).
+- Non-goals:
+  - No backend search.
+  - No fuzzy ranking beyond simple contains match in v1.
+- Constraints:
+  - Must work from any page.
+  - Search query should be bounded if stored in URL.
+
+---
+
+## 1) Requirements
+
+### 1.1 Functional (expected)
+
+- [ ] BTB-002-REQ-001 (Functional / Expected): Provide a search input in the header (desktop) and accessible on mobile.
+- [ ] BTB-002-REQ-002 (Functional / Expected): Search is global across all tools (name + description + id).
+- [ ] BTB-002-REQ-003 (Functional / Expected): Typing from any page navigates to Home and filters tool cards.
+- [ ] BTB-002-REQ-004 (Functional / Expected): Escape clears query.
+- [ ] BTB-002-REQ-005 (Functional / Expected): Enter with exactly one result navigates directly to that tool.
+- [ ] BTB-002-REQ-006 (Functional / Expected): Show result count when filtering.
+- [ ] BTB-002-REQ-007 (Functional / Expected): Support shareable short URL param `q` (bounded length).
+
+### 1.2 Functional (forbidden)
+
+- [ ] BTB-002-REQ-008 (Functional / Forbidden): Must not store unbounded queries in URL.
+- [ ] BTB-002-REQ-009 (Functional / Forbidden): Must not require backend.
+
+### 1.3 Non-functional
+
+- [ ] BTB-002-REQ-010 (Non-functional): Does not significantly degrade performance on Home.
+
+---
+
+## 2) Acceptance criteria
+
+- [ ] BTB-002-AC-001 (maps to BTB-002-REQ-003): From `/music`, typing in search returns to Home and filters results.
+- [ ] BTB-002-AC-002 (maps to BTB-002-REQ-005): With one match, Enter navigates to tool page.
+- [ ] BTB-002-AC-003 (maps to BTB-002-REQ-007): Loading `/#/?q=json` filters the Home tool list.
+
+---
+
+## 3) Test plan
+
+- E2E: `e2e/search.spec.ts` covers navigation, Enter, Esc, URL param.
+
+---
+
+## 4) Rollout / rollback
+
+- Rollout: static.
+- Rollback: revert UI/search commit.
+
+---
+
+## 5) Open questions
+
+- Q1: Add fuzzy matching / ranking?
diff --git a/docs/spec/BTB-003-ui-theme-system/BTB-003-architecture.md b/docs/spec/BTB-003-ui-theme-system/BTB-003-architecture.md
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+++ b/docs/spec/BTB-003-ui-theme-system/BTB-003-architecture.md
@@ -0,0 +1,28 @@
+---
+specId: BTB-003
+title: ui-theme-system — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-003-architecture.md
+
+## 1) Architecture design (module-level)
+
+### 1.1 Components and responsibilities
+
+- `src/lib/theme.ts`
+  - Reads/writes `btb:theme`.
+  - Computes effective theme (`system` → light/dark).
+  - Applies `.dark` class on `<html>` and sets `color-scheme`.
+  - Sync: listens to media query changes when pref is `system`.
+
+- `src/styles/design-system.css` + `src/styles/theme.css`
+  - CSS variables for colors.
+  - `.dark { ... }` overrides.
+
+- `src/tools/settings/SettingsPage.tsx`
+  - Radio toggle for theme preference.
+
+- `src/App.tsx`
+  - Calls `initThemeSync()` on mount.
diff --git a/docs/spec/BTB-003-ui-theme-system/BTB-003-requirements.md b/docs/spec/BTB-003-ui-theme-system/BTB-003-requirements.md
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+++ b/docs/spec/BTB-003-ui-theme-system/BTB-003-requirements.md
@@ -0,0 +1,46 @@
+---
+specId: BTB-003
+title: ui-theme-system — Light/Dark/System theme with Settings toggle
+owner: Vincent
+status: implemented
+---
+
+# BTB-003-requirements.md
+
+## 0) Context
+
+- Problem: Users need light/dark modes, ideally following system, with manual override.
+- Non-goals: No theming per-tool; no design overhaul.
+- Constraints: In-browser only; no backend.
+
+## 1) Requirements
+
+### 1.1 Functional (expected)
+
+- [ ] BTB-003-REQ-001: Provide theme preference values: `system | light | dark`.
+- [ ] BTB-003-REQ-002: Persist preference locally (localStorage key `btb:theme`).
+- [ ] BTB-003-REQ-003: Apply effective theme without full page reload.
+- [ ] BTB-003-REQ-004: `system` follows `prefers-color-scheme` changes.
+
+### 1.2 Functional (forbidden)
+
+- [ ] BTB-003-REQ-005: Must not store theme preference on a server.
+
+### 1.3 Non-functional
+
+- [ ] BTB-003-REQ-006: Theme must keep text/background contrast readable.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-003-AC-001: Settings offers System/Light/Dark and switching updates UI immediately.
+- [ ] BTB-003-AC-002: With System selected, OS theme change updates the app.
+
+## 3) Test plan
+
+- Integration/manual: verify theme switch + system follow.
+- Optional e2e: could be added later.
+
+## 4) Rollout / rollback
+
+- Rollout: static.
+- Rollback: revert theme commits.
diff --git a/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-architecture.md b/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-architecture.md
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+++ b/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-architecture.md
@@ -0,0 +1,20 @@
+---
+specId: BTB-004
+title: ui-settings-storage-reset — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-004-architecture.md
+
+## 1) Architecture design
+
+- `src/lib/localStorageAdmin.ts`
+  - Central mapping: toolId → key prefixes/keys.
+  - Implements `clearTool(toolId)` and `clearAll()`.
+
+- `src/tools/settings/SettingsPage.tsx`
+  - Renders clear-all and per-tool clear UI with confirm.
+
+- `src/components/ToolPage.tsx`
+  - Conditionally shows "Reset this tool" button for tools with storage mapping.
diff --git a/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-requirements.md b/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-requirements.md
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--- /dev/null
+++ b/docs/spec/BTB-004-ui-settings-storage-reset/BTB-004-requirements.md
@@ -0,0 +1,36 @@
+---
+specId: BTB-004
+title: ui-settings-storage-reset — Clear per-tool and all-app saved data
+owner: Vincent
+status: implemented
+---
+
+# BTB-004-requirements.md
+
+## 0) Context
+
+- Problem: Tool inputs/options are stored locally; user needs a safe way to clear them.
+- Constraints: Must not delete unrelated site/app keys.
+
+## 1) Requirements
+
+### 1.1 Functional (expected)
+
+- [ ] BTB-004-REQ-001: Provide Settings page for clearing data.
+- [ ] BTB-004-REQ-002: Provide "Clear all saved data" for this app only.
+- [ ] BTB-004-REQ-003: Provide per-tool clear buttons.
+- [ ] BTB-004-REQ-004: Provide per-tool "Reset this tool" on tool pages (where applicable).
+- [ ] BTB-004-REQ-005: Confirm before destructive clear.
+
+### 1.2 Functional (forbidden)
+
+- [ ] BTB-004-REQ-006: Must not wipe unrelated localStorage keys.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-004-AC-001: Settings clear-all removes only mapped keys.
+- [ ] BTB-004-AC-002: Per-tool clear removes only that tool’s keys.
+
+## 3) Test plan
+
+- E2E: confirm dialogs + key removal checks.
diff --git a/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-architecture.md b/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-architecture.md
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+++ b/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-architecture.md
@@ -0,0 +1,17 @@
+---
+specId: BTB-005
+title: ui-mobile-hamburger-nav — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-005-architecture.md
+
+## 1) Architecture design
+
+- `src/App.tsx` Header
+  - `menuOpen` state
+  - event listeners for Esc and pointerdown outside
+
+- `src/App.css`
+  - media query <=640px to toggle visibility of desktop nav vs hamburger.
diff --git a/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-requirements.md b/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-requirements.md
new file mode 100644
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--- /dev/null
+++ b/docs/spec/BTB-005-ui-mobile-hamburger-nav/BTB-005-requirements.md
@@ -0,0 +1,29 @@
+---
+specId: BTB-005
+title: ui-mobile-hamburger-nav — Mobile dropdown navigation
+owner: Vincent
+status: implemented
+---
+
+# BTB-005-requirements.md
+
+## 0) Context
+
+- Problem: Top nav has many links; mobile needs a compact navigation.
+- Constraints: Must be accessible and work with touch.
+
+## 1) Requirements
+
+- [ ] BTB-005-REQ-001: At <=640px, hide horizontal nav links.
+- [ ] BTB-005-REQ-002: Show hamburger button.
+- [ ] BTB-005-REQ-003: Clicking hamburger opens a top dropdown listing all nav destinations.
+- [ ] BTB-005-REQ-004: Menu closes on outside click, Esc, or selecting an item.
+- [ ] BTB-005-REQ-005: Provide basic aria attributes (`aria-label`, `aria-expanded`).
+
+## 2) Acceptance criteria
+
+- [ ] BTB-005-AC-001: Mobile e2e opens hamburger, navigates, and menu closes.
+
+## 3) Test plan
+
+- E2E: `e2e/mobile.spec.ts` hamburger test.
diff --git a/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-architecture.md b/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-architecture.md
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--- /dev/null
+++ b/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-architecture.md
@@ -0,0 +1,17 @@
+---
+specId: BTB-006
+title: ui-category-landing-pages — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-006-architecture.md
+
+## 1) Architecture design
+
+- `src/App.tsx`
+  - Adds routes for category pages.
+  - Uses simple hardcoded toolId lists per category.
+
+- `src/components/ToolCard.tsx`
+  - Shared rendering of cards.
diff --git a/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-requirements.md b/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-requirements.md
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index 0000000..0313e01
--- /dev/null
+++ b/docs/spec/BTB-006-ui-category-landing-pages/BTB-006-requirements.md
@@ -0,0 +1,26 @@
+---
+specId: BTB-006
+title: ui-category-landing-pages — Category pages for tool discovery
+owner: Vincent
+status: implemented
+---
+
+# BTB-006-requirements.md
+
+## 0) Context
+
+- Problem: Users need easier discovery than scrolling the full Home list.
+
+## 1) Requirements
+
+- [ ] BTB-006-REQ-001: Provide category pages: Data Formats, Text, Encoding, Dev, Music.
+- [ ] BTB-006-REQ-002: Each page lists selected tools via ToolCard.
+- [ ] BTB-006-REQ-003: Home remains "All Tools".
+
+## 2) Acceptance criteria
+
+- [ ] BTB-006-AC-001: Category routes load and show expected cards.
+
+## 3) Test plan
+
+- E2E: smoke tests for category pages.
diff --git a/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-architecture.md b/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-architecture.md
new file mode 100644
index 0000000..76da072
--- /dev/null
+++ b/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-architecture.md
@@ -0,0 +1,14 @@
+---
+specId: BTB-007
+title: perf-route-code-splitting — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-007-architecture.md
+
+## 1) Architecture design
+
+- `src/App.tsx`
+  - Uses `React.lazy(() => import(...))` for each tool.
+  - Wraps tool rendering in `Suspense` fallback.
diff --git a/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-requirements.md b/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-requirements.md
new file mode 100644
index 0000000..4f4d6a6
--- /dev/null
+++ b/docs/spec/BTB-007-perf-route-code-splitting/BTB-007-requirements.md
@@ -0,0 +1,26 @@
+---
+specId: BTB-007
+title: perf-route-code-splitting — Lazy-load tool routes
+owner: Vincent
+status: implemented
+---
+
+# BTB-007-requirements.md
+
+## 0) Context
+
+- Problem: Loading every tool upfront increases initial bundle size.
+
+## 1) Requirements
+
+- [ ] BTB-007-REQ-001: Tool components should be lazy-loaded per route.
+- [ ] BTB-007-REQ-002: Tool page shell should render with a loading fallback.
+- [ ] BTB-007-REQ-003: Production build emits multiple JS chunks.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-007-AC-001: `dist/assets` contains >1 JS chunk.
+
+## 3) Test plan
+
+- Build inspection.
diff --git a/docs/spec/BTB-008-tool-data-converter/BTB-008-architecture.md b/docs/spec/BTB-008-tool-data-converter/BTB-008-architecture.md
new file mode 100644
index 0000000..1d81fe7
--- /dev/null
+++ b/docs/spec/BTB-008-tool-data-converter/BTB-008-architecture.md
@@ -0,0 +1,21 @@
+---
+specId: BTB-008
+title: tool-data-converter — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-008-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/data-converter/DataConverterTool.tsx`
+  - UI: input/output + format selectors + options.
+
+- `src/lib/dataConverter.ts`
+  - Pure conversion functions.
+
+- Dependencies:
+  - `yaml`
+  - `papaparse`
+  - `@iarna/toml`
diff --git a/docs/spec/BTB-008-tool-data-converter/BTB-008-requirements.md b/docs/spec/BTB-008-tool-data-converter/BTB-008-requirements.md
new file mode 100644
index 0000000..68a4502
--- /dev/null
+++ b/docs/spec/BTB-008-tool-data-converter/BTB-008-requirements.md
@@ -0,0 +1,31 @@
+---
+specId: BTB-008
+title: tool-data-converter — Convert JSON↔YAML/CSV/TOML
+owner: Vincent
+status: implemented
+---
+
+# BTB-008-requirements.md
+
+## 0) Context
+
+- Problem: Users need quick conversions between common data formats.
+- Constraints: In-browser only; conversion is not lossless for all formats.
+
+## 1) Requirements
+
+- [ ] BTB-008-REQ-001: Support JSON↔YAML.
+- [ ] BTB-008-REQ-002: Support JSON↔CSV.
+- [ ] BTB-008-REQ-003: Support JSON↔TOML.
+- [ ] BTB-008-REQ-004: Provide minimal options (indent, delimiter).
+- [ ] BTB-008-REQ-005: Show clear errors on invalid input.
+- [ ] BTB-008-REQ-006: JSON→CSV rejects nested structures in v1 (clear message).
+
+## 2) Acceptance criteria
+
+- [ ] BTB-008-AC-001: Tool loads at `/tools/data-converter` and converts at least one example per format.
+
+## 3) Test plan
+
+- Unit: conversion helpers.
+- E2E: smoke route load.
diff --git a/docs/spec/BTB-009-tool-json-diff/BTB-009-architecture.md b/docs/spec/BTB-009-tool-json-diff/BTB-009-architecture.md
new file mode 100644
index 0000000..6b76469
--- /dev/null
+++ b/docs/spec/BTB-009-tool-json-diff/BTB-009-architecture.md
@@ -0,0 +1,18 @@
+---
+specId: BTB-009
+title: tool-json-diff — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-009-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/json-diff/JsonDiffTool.tsx`
+  - UI and calling diff.
+
+- `src/lib/jsonDiff.ts`
+  - Computes path-based diffs.
+
+- Uses JSON.parse and optional key-sort.
diff --git a/docs/spec/BTB-009-tool-json-diff/BTB-009-requirements.md b/docs/spec/BTB-009-tool-json-diff/BTB-009-requirements.md
new file mode 100644
index 0000000..eb0ca8c
--- /dev/null
+++ b/docs/spec/BTB-009-tool-json-diff/BTB-009-requirements.md
@@ -0,0 +1,28 @@
+---
+specId: BTB-009
+title: tool-json-diff — Compare two JSON inputs and show changed paths
+owner: Vincent
+status: implemented
+---
+
+# BTB-009-requirements.md
+
+## 0) Context
+
+- Problem: Users need quick JSON comparison.
+
+## 1) Requirements
+
+- [ ] BTB-009-REQ-001: Two JSON inputs (left/right).
+- [ ] BTB-009-REQ-002: Show added/removed/changed paths.
+- [ ] BTB-009-REQ-003: Option to sort keys before diff.
+- [ ] BTB-009-REQ-004: Clear errors on invalid JSON.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-009-AC-001: Diff shows changed path for simple change.
+
+## 3) Test plan
+
+- Unit: diff logic.
+- E2E: smoke assertions.
diff --git a/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-architecture.md b/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-architecture.md
new file mode 100644
index 0000000..cd212e2
--- /dev/null
+++ b/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-architecture.md
@@ -0,0 +1,16 @@
+---
+specId: BTB-010
+title: tool-jsonpath-query — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-010-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/jsonpath/JsonPathTool.tsx` — UI.
+- `src/lib/jsonpath.ts` — wrapper around JSONPath evaluation.
+- Dependency: `jsonpath-plus`.
+
+Constraints: do not put JSON input in URL.
diff --git a/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-requirements.md b/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-requirements.md
new file mode 100644
index 0000000..6bb3c5b
--- /dev/null
+++ b/docs/spec/BTB-010-tool-jsonpath-query/BTB-010-requirements.md
@@ -0,0 +1,29 @@
+---
+specId: BTB-010
+title: tool-jsonpath-query — Query JSON with JSONPath expressions
+owner: Vincent
+status: implemented
+---
+
+# BTB-010-requirements.md
+
+## 0) Context
+
+- Problem: Extract values from JSON quickly using JSONPath.
+
+## 1) Requirements
+
+- [ ] BTB-010-REQ-001: JSON input textarea.
+- [ ] BTB-010-REQ-002: Expression input.
+- [ ] BTB-010-REQ-003: Output list of matches.
+- [ ] BTB-010-REQ-004: Clear errors for invalid JSON/expression.
+- [ ] BTB-010-REQ-005: Optional short URL param for expr only.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-010-AC-001: Query `$.a.b` returns `42` for input `{ "a": {"b":42}}`.
+
+## 3) Test plan
+
+- Unit: jsonpath wrapper.
+- E2E: tool smoke + run query.
diff --git a/docs/spec/BTB-011-tool-metronome/BTB-011-architecture.md b/docs/spec/BTB-011-tool-metronome/BTB-011-architecture.md
new file mode 100644
index 0000000..f26a221
--- /dev/null
+++ b/docs/spec/BTB-011-tool-metronome/BTB-011-architecture.md
@@ -0,0 +1,17 @@
+---
+specId: BTB-011
+title: tool-metronome — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-011-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/metronome/MetronomeTool.tsx`
+  - Uses Web Audio API scheduling.
+  - Handles lifecycle (visibility/page show).
+  - Parses/clamps URL params.
+
+- No backend.
diff --git a/docs/spec/BTB-011-tool-metronome/BTB-011-requirements.md b/docs/spec/BTB-011-tool-metronome/BTB-011-requirements.md
new file mode 100644
index 0000000..ce8ef04
--- /dev/null
+++ b/docs/spec/BTB-011-tool-metronome/BTB-011-requirements.md
@@ -0,0 +1,32 @@
+---
+specId: BTB-011
+title: tool-metronome — WebAudio metronome with countdown and URL params
+owner: Vincent
+status: implemented
+---
+
+# BTB-011-requirements.md
+
+## 0) Context
+
+- Problem: Provide a simple metronome in-browser.
+- Constraints: Background playback across iOS is not guaranteed.
+
+## 1) Requirements
+
+- [ ] BTB-011-REQ-001: BPM control (bounded).
+- [ ] BTB-011-REQ-002: Start/Stop.
+- [ ] BTB-011-REQ-003: Beat count + accent option.
+- [ ] BTB-011-REQ-004: Volume control.
+- [ ] BTB-011-REQ-005: Countdown before start (0/3/5/10).
+- [ ] BTB-011-REQ-006: iOS lifecycle handling: on return from background attempt resume; prompt "Tap to resume audio" if needed.
+- [ ] BTB-011-REQ-007: Short URL params for bpm/beats/accent/vol/countdown with clamping.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-011-AC-001: `/tools/metronome?bpm=140` pre-fills BPM.
+- [ ] BTB-011-AC-002: Visibility change triggers resume hint UI.
+
+## 3) Test plan
+
+- E2E: smoke tests for URL params + resume hint.
diff --git a/docs/spec/BTB-012-tool-tuner/BTB-012-architecture.md b/docs/spec/BTB-012-tool-tuner/BTB-012-architecture.md
new file mode 100644
index 0000000..7633829
--- /dev/null
+++ b/docs/spec/BTB-012-tool-tuner/BTB-012-architecture.md
@@ -0,0 +1,20 @@
+---
+specId: BTB-012
+title: tool-tuner — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-012-architecture.md
+
+## 1) Architecture design
+
+- `src/lib/pitch.ts`
+  - YIN pitch detection + smoothing helpers.
+
+- `src/tools/tuner/TunerTool.tsx`
+  - WebAudio capture via getUserMedia + AudioContext + Analyser.
+  - Uses pitch detector to compute frequency.
+  - Maps frequency → note + cents.
+
+- Tool settings persisted via localStorage (e.g. A4).
diff --git a/docs/spec/BTB-012-tool-tuner/BTB-012-requirements.md b/docs/spec/BTB-012-tool-tuner/BTB-012-requirements.md
new file mode 100644
index 0000000..cb2d78a
--- /dev/null
+++ b/docs/spec/BTB-012-tool-tuner/BTB-012-requirements.md
@@ -0,0 +1,31 @@
+---
+specId: BTB-012
+title: tool-tuner — Guitar-style tuner using microphone pitch detection
+owner: Vincent
+status: implemented
+---
+
+# BTB-012-requirements.md
+
+## 0) Context
+
+- Problem: Tune instruments by detecting pitch from microphone.
+- Constraints: Requires mic permission; works best for monophonic signals.
+
+## 1) Requirements
+
+- [ ] BTB-012-REQ-001: Start/Stop microphone capture.
+- [ ] BTB-012-REQ-002: Display note name + octave.
+- [ ] BTB-012-REQ-003: Display frequency in Hz.
+- [ ] BTB-012-REQ-004: Display cents deviation indicator (-50..+50).
+- [ ] BTB-012-REQ-005: A4 calibration control (e.g., 430–450, default 440).
+- [ ] BTB-012-REQ-006: Handle error states (permission denied, insecure context).
+
+## 2) Acceptance criteria
+
+- [ ] BTB-012-AC-001: Tool loads at `/tools/tuner` and shows controls.
+
+## 3) Test plan
+
+- Unit: `src/lib/pitch.ts` tests on generated sine waves.
+- E2E: smoke loads tuner page.
diff --git a/docs/spec/BTB-013-tool-music-box-designer/BTB-013-architecture.md b/docs/spec/BTB-013-tool-music-box-designer/BTB-013-architecture.md
new file mode 100644
index 0000000..e5c646b
--- /dev/null
+++ b/docs/spec/BTB-013-tool-music-box-designer/BTB-013-architecture.md
@@ -0,0 +1,18 @@
+---
+specId: BTB-013
+title: tool-music-box-designer — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-013-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/music-box-designer/MusicBoxDesignerTool.tsx`
+  - UI grid and playback.
+
+- `src/lib/musicBox.ts`
+  - Pattern data model + serialize/deserialize.
+
+- Uses WebAudio for sound generation.
diff --git a/docs/spec/BTB-013-tool-music-box-designer/BTB-013-requirements.md b/docs/spec/BTB-013-tool-music-box-designer/BTB-013-requirements.md
new file mode 100644
index 0000000..19b76b6
--- /dev/null
+++ b/docs/spec/BTB-013-tool-music-box-designer/BTB-013-requirements.md
@@ -0,0 +1,29 @@
+---
+specId: BTB-013
+title: tool-music-box-designer — Step-grid sequencer with export/import
+owner: Vincent
+status: implemented
+---
+
+# BTB-013-requirements.md
+
+## 0) Context
+
+- Problem: Simple grid-based pattern editor with playback.
+- Constraints: In-browser only.
+
+## 1) Requirements
+
+- [ ] BTB-013-REQ-001: Step grid (time × pitch) with toggle notes.
+- [ ] BTB-013-REQ-002: Playback using WebAudio.
+- [ ] BTB-013-REQ-003: Export/import pattern as JSON (local).
+- [ ] BTB-013-REQ-004: Mobile-friendly UI.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-013-AC-001: Tool renders grid and can toggle steps.
+
+## 3) Test plan
+
+- Unit: pattern serialization helpers.
+- E2E: smoke grid visible.
diff --git a/docs/spec/BTB-014-tool-base64/BTB-014-architecture.md b/docs/spec/BTB-014-tool-base64/BTB-014-architecture.md
new file mode 100644
index 0000000..52fe085
--- /dev/null
+++ b/docs/spec/BTB-014-tool-base64/BTB-014-architecture.md
@@ -0,0 +1,16 @@
+---
+specId: BTB-014
+title: tool-base64 — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-014-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/base64/Base64Tool.tsx`
+  - UI for encode/decode.
+
+- `src/lib/base64.ts`
+  - Pure encode/decode helpers.
diff --git a/docs/spec/BTB-014-tool-base64/BTB-014-requirements.md b/docs/spec/BTB-014-tool-base64/BTB-014-requirements.md
new file mode 100644
index 0000000..0efbc0f
--- /dev/null
+++ b/docs/spec/BTB-014-tool-base64/BTB-014-requirements.md
@@ -0,0 +1,34 @@
+---
+specId: BTB-014
+title: tool-base64 — Encode/decode Base64
+owner: Vincent
+status: implemented
+---
+
+# BTB-014-requirements.md
+
+## 0) Context
+
+- Problem: Quick Base64 encode/decode in-browser.
+- Constraints: No backend.
+
+## 1) Requirements
+
+### 1.1 Functional (expected)
+
+- [ ] BTB-014-REQ-001: Encode input text to Base64.
+- [ ] BTB-014-REQ-002: Decode Base64 to text.
+- [ ] BTB-014-REQ-003: Show clear error for invalid Base64.
+
+### 1.2 Functional (forbidden)
+
+- [ ] BTB-014-REQ-004: Must not send user input to server.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-014-AC-001: Invalid Base64 shows an error and does not crash.
+
+## 3) Test plan
+
+- Unit: `src/lib/__tests__/base64.test.ts`.
+- E2E: smoke route load.
diff --git a/docs/spec/BTB-015-tool-url-encoder/BTB-015-architecture.md b/docs/spec/BTB-015-tool-url-encoder/BTB-015-architecture.md
new file mode 100644
index 0000000..c25532e
--- /dev/null
+++ b/docs/spec/BTB-015-tool-url-encoder/BTB-015-architecture.md
@@ -0,0 +1,17 @@
+---
+specId: BTB-015
+title: tool-url-encoder — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-015-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/url-encoder/UrlEncoderTool.tsx`
+  - UI + localStorage.
+  - Reads short URL params via `src/lib/urlParams.ts`.
+
+- `src/lib/urlParams.ts`
+  - `getShortSearchParam`, `getEnumSearchParam`.
diff --git a/docs/spec/BTB-015-tool-url-encoder/BTB-015-requirements.md b/docs/spec/BTB-015-tool-url-encoder/BTB-015-requirements.md
new file mode 100644
index 0000000..f22fdbb
--- /dev/null
+++ b/docs/spec/BTB-015-tool-url-encoder/BTB-015-requirements.md
@@ -0,0 +1,27 @@
+---
+specId: BTB-015
+title: tool-url-encoder — Encode/decode URL strings
+owner: Vincent
+status: implemented
+---
+
+# BTB-015-requirements.md
+
+## 0) Context
+
+- Problem: Encode/decode URL components and full URLs.
+
+## 1) Requirements
+
+- [ ] BTB-015-REQ-001: Encode/decode using component mode (encodeURIComponent/decodeURIComponent).
+- [ ] BTB-015-REQ-002: Encode/decode using full URL mode (encodeURI/decodeURI).
+- [ ] BTB-015-REQ-003: URL params support short input `text` and options `op`/`scope` (bounded).
+- [ ] BTB-015-REQ-004: Show clear error on invalid decode.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-015-AC-001: `/#/tools/url-encoder?text=hello%20world&op=encode&scope=component` pre-fills and outputs encoded value.
+
+## 3) Test plan
+
+- E2E: smoke + URL param test.
diff --git a/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-architecture.md b/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-architecture.md
new file mode 100644
index 0000000..7b757b9
--- /dev/null
+++ b/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-architecture.md
@@ -0,0 +1,14 @@
+---
+specId: BTB-016
+title: tool-timestamp-converter — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-016-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/timestamp-converter/TimestampConverterTool.tsx`
+  - Two conversion paths.
+  - URL param parsing via `urlParams`.
diff --git a/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-requirements.md b/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-requirements.md
new file mode 100644
index 0000000..e8e7e6c
--- /dev/null
+++ b/docs/spec/BTB-016-tool-timestamp-converter/BTB-016-requirements.md
@@ -0,0 +1,27 @@
+---
+specId: BTB-016
+title: tool-timestamp-converter — Convert UNIX timestamps and dates
+owner: Vincent
+status: implemented
+---
+
+# BTB-016-requirements.md
+
+## 0) Context
+
+- Problem: Convert between timestamp seconds/ms and human-readable date.
+
+## 1) Requirements
+
+- [ ] BTB-016-REQ-001: Convert timestamp → UTC/local date strings.
+- [ ] BTB-016-REQ-002: Convert date → timestamp.
+- [ ] BTB-016-REQ-003: URL params support short `ts` plus `unit` (s/ms).
+- [ ] BTB-016-REQ-004: Clear error messages for invalid input.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-016-AC-001: `/#/tools/timestamp-converter?ts=1700000000&unit=s` pre-fills input.
+
+## 3) Test plan
+
+- E2E: URL param smoke.
diff --git a/docs/spec/BTB-017-tool-color-converter/BTB-017-architecture.md b/docs/spec/BTB-017-tool-color-converter/BTB-017-architecture.md
new file mode 100644
index 0000000..607d8af
--- /dev/null
+++ b/docs/spec/BTB-017-tool-color-converter/BTB-017-architecture.md
@@ -0,0 +1,14 @@
+---
+specId: BTB-017
+title: tool-color-converter — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-017-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/color-converter/ColorConverterTool.tsx`
+- `src/lib/color.ts` (pure conversions)
+- URL params via `urlParams`.
diff --git a/docs/spec/BTB-017-tool-color-converter/BTB-017-requirements.md b/docs/spec/BTB-017-tool-color-converter/BTB-017-requirements.md
new file mode 100644
index 0000000..27c6d69
--- /dev/null
+++ b/docs/spec/BTB-017-tool-color-converter/BTB-017-requirements.md
@@ -0,0 +1,20 @@
+---
+specId: BTB-017
+title: tool-color-converter — Convert between HEX/RGB/HSL and preview color
+owner: Vincent
+status: implemented
+---
+
+# BTB-017-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-017-REQ-001: Accept color input and show conversions.
+- [ ] BTB-017-REQ-002: Show color preview swatch.
+- [ ] BTB-017-REQ-003: Support short URL param `color` (and optional `format`).
+- [ ] BTB-017-REQ-004: Show error for invalid color.
+
+## 2) Test plan
+
+- Unit: `src/lib/__tests__/color.test.ts`.
+- E2E: URL param test.
diff --git a/docs/spec/BTB-018-tool-regex-tester/BTB-018-architecture.md b/docs/spec/BTB-018-tool-regex-tester/BTB-018-architecture.md
new file mode 100644
index 0000000..d10ac20
--- /dev/null
+++ b/docs/spec/BTB-018-tool-regex-tester/BTB-018-architecture.md
@@ -0,0 +1,13 @@
+---
+specId: BTB-018
+title: tool-regex-tester — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-018-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/regex-tester/RegexTesterTool.tsx`
+  - Uses JS RegExp.
diff --git a/docs/spec/BTB-018-tool-regex-tester/BTB-018-requirements.md b/docs/spec/BTB-018-tool-regex-tester/BTB-018-requirements.md
new file mode 100644
index 0000000..522a2d7
--- /dev/null
+++ b/docs/spec/BTB-018-tool-regex-tester/BTB-018-requirements.md
@@ -0,0 +1,19 @@
+---
+specId: BTB-018
+title: tool-regex-tester — Test regex patterns against text
+owner: Vincent
+status: implemented
+---
+
+# BTB-018-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-018-REQ-001: Input regex pattern and flags.
+- [ ] BTB-018-REQ-002: Input test text.
+- [ ] BTB-018-REQ-003: Show matches or errors.
+- [ ] BTB-018-REQ-004: No backend.
+
+## 3) Test plan
+
+- E2E: smoke route load.
diff --git a/docs/spec/BTB-019-tool-markdown-preview/BTB-019-architecture.md b/docs/spec/BTB-019-tool-markdown-preview/BTB-019-architecture.md
new file mode 100644
index 0000000..66bcb7b
--- /dev/null
+++ b/docs/spec/BTB-019-tool-markdown-preview/BTB-019-architecture.md
@@ -0,0 +1,13 @@
+---
+specId: BTB-019
+title: tool-markdown-preview — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-019-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/markdown-preview/MarkdownPreviewTool.tsx`
+  - Uses a markdown renderer (in-browser).
diff --git a/docs/spec/BTB-019-tool-markdown-preview/BTB-019-requirements.md b/docs/spec/BTB-019-tool-markdown-preview/BTB-019-requirements.md
new file mode 100644
index 0000000..c8feeb8
--- /dev/null
+++ b/docs/spec/BTB-019-tool-markdown-preview/BTB-019-requirements.md
@@ -0,0 +1,18 @@
+---
+specId: BTB-019
+title: tool-markdown-preview — Preview markdown as HTML
+owner: Vincent
+status: implemented
+---
+
+# BTB-019-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-019-REQ-001: Input markdown text.
+- [ ] BTB-019-REQ-002: Render preview output.
+- [ ] BTB-019-REQ-003: No backend.
+
+## 3) Test plan
+
+- E2E: smoke route load.
diff --git a/docs/spec/BTB-020-tool-hash-generator/BTB-020-architecture.md b/docs/spec/BTB-020-tool-hash-generator/BTB-020-architecture.md
new file mode 100644
index 0000000..2e86016
--- /dev/null
+++ b/docs/spec/BTB-020-tool-hash-generator/BTB-020-architecture.md
@@ -0,0 +1,14 @@
+---
+specId: BTB-020
+title: tool-hash-generator — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-020-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/hash-generator/HashGeneratorTool.tsx`
+  - Uses Web Crypto.
+  - Reads `alg` URL param (bounded enum).
diff --git a/docs/spec/BTB-020-tool-hash-generator/BTB-020-requirements.md b/docs/spec/BTB-020-tool-hash-generator/BTB-020-requirements.md
new file mode 100644
index 0000000..9356aa2
--- /dev/null
+++ b/docs/spec/BTB-020-tool-hash-generator/BTB-020-requirements.md
@@ -0,0 +1,18 @@
+---
+specId: BTB-020
+title: tool-hash-generator — Hash text with selectable algorithm
+owner: Vincent
+status: implemented
+---
+
+# BTB-020-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-020-REQ-001: Hash input text with SHA-* algorithms.
+- [ ] BTB-020-REQ-002: URL param can set `alg` (enum); must not set input via URL.
+- [ ] BTB-020-REQ-003: No backend.
+
+## 3) Test plan
+
+- E2E: URL param sets active algorithm.
diff --git a/docs/spec/BTB-021-tool-uuid-generator/BTB-021-architecture.md b/docs/spec/BTB-021-tool-uuid-generator/BTB-021-architecture.md
new file mode 100644
index 0000000..32fc85e
--- /dev/null
+++ b/docs/spec/BTB-021-tool-uuid-generator/BTB-021-architecture.md
@@ -0,0 +1,14 @@
+---
+specId: BTB-021
+title: tool-uuid-generator — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-021-architecture.md
+
+## 1) Architecture design
+
+- `src/tools/uuid-generator/UuidGeneratorTool.tsx`
+  - Generates values (uuid/ulid).
+  - Reads URL params; clamps count.
diff --git a/docs/spec/BTB-021-tool-uuid-generator/BTB-021-requirements.md b/docs/spec/BTB-021-tool-uuid-generator/BTB-021-requirements.md
new file mode 100644
index 0000000..ab16449
--- /dev/null
+++ b/docs/spec/BTB-021-tool-uuid-generator/BTB-021-requirements.md
@@ -0,0 +1,18 @@
+---
+specId: BTB-021
+title: tool-uuid-generator — Generate UUID/ULID with URL params
+owner: Vincent
+status: implemented
+---
+
+# BTB-021-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-021-REQ-001: Generate UUIDs.
+- [ ] BTB-021-REQ-002: Generate ULIDs.
+- [ ] BTB-021-REQ-003: URL params set `type` and `count` (capped).
+
+## 3) Test plan
+
+- E2E: URL params generation tests.
diff --git a/docs/spec/BTB-022-ui-data-formats-landing/BTB-022-architecture.md b/docs/spec/BTB-022-ui-data-formats-landing/BTB-022-architecture.md
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@@ -0,0 +1,12 @@
+---
+specId: BTB-022
+title: ui-data-formats-landing — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-022-architecture.md
+
+## 1) Architecture design
+
+- `src/App.tsx` provides route and filters tool cards shown.
diff --git a/docs/spec/BTB-022-ui-data-formats-landing/BTB-022-requirements.md b/docs/spec/BTB-022-ui-data-formats-landing/BTB-022-requirements.md
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+---
+specId: BTB-022
+title: ui-data-formats-landing — Data Formats landing page
+owner: Vincent
+status: implemented
+---
+
+# BTB-022-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-022-REQ-001: Provide `/data-formats` page listing data-format related tools.
+
+## 3) Test plan
+
+- E2E: smoke loads `/#/data-formats`.
diff --git a/docs/spec/BTB-023-ui-music-landing/BTB-023-architecture.md b/docs/spec/BTB-023-ui-music-landing/BTB-023-architecture.md
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+++ b/docs/spec/BTB-023-ui-music-landing/BTB-023-architecture.md
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+---
+specId: BTB-023
+title: ui-music-landing — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-023-architecture.md
+
+## 1) Architecture design
+
+- `src/App.tsx` provides route and filters tool cards shown.
diff --git a/docs/spec/BTB-023-ui-music-landing/BTB-023-requirements.md b/docs/spec/BTB-023-ui-music-landing/BTB-023-requirements.md
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+++ b/docs/spec/BTB-023-ui-music-landing/BTB-023-requirements.md
@@ -0,0 +1,16 @@
+---
+specId: BTB-023
+title: ui-music-landing — Music landing page
+owner: Vincent
+status: implemented
+---
+
+# BTB-023-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-023-REQ-001: Provide `/music` page listing music-related tools.
+
+## 3) Test plan
+
+- E2E: smoke loads `/#/music`.
diff --git a/docs/spec/BTB-024-ui-mobile-support/BTB-024-architecture.md b/docs/spec/BTB-024-ui-mobile-support/BTB-024-architecture.md
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+++ b/docs/spec/BTB-024-ui-mobile-support/BTB-024-architecture.md
@@ -0,0 +1,13 @@
+---
+specId: BTB-024
+title: ui-mobile-support — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-024-architecture.md
+
+## 1) Architecture design
+
+- CSS media queries in shared styles.
+- Playwright mobile viewport coverage.
diff --git a/docs/spec/BTB-024-ui-mobile-support/BTB-024-requirements.md b/docs/spec/BTB-024-ui-mobile-support/BTB-024-requirements.md
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+++ b/docs/spec/BTB-024-ui-mobile-support/BTB-024-requirements.md
@@ -0,0 +1,17 @@
+---
+specId: BTB-024
+title: ui-mobile-support — Mobile layout baseline
+owner: Vincent
+status: implemented
+---
+
+# BTB-024-requirements.md
+
+## 1) Requirements
+
+- [ ] BTB-024-REQ-001: Pages usable at ~420px width.
+- [ ] BTB-024-REQ-002: Tool layouts stack/fit on mobile.
+
+## 3) Test plan
+
+- E2E: mobile viewport tests.
diff --git a/docs/spec/BTB-025-ui-url-input-policy/BTB-025-architecture.md b/docs/spec/BTB-025-ui-url-input-policy/BTB-025-architecture.md
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--- /dev/null
+++ b/docs/spec/BTB-025-ui-url-input-policy/BTB-025-architecture.md
@@ -0,0 +1,13 @@
+---
+specId: BTB-025
+title: ui-url-input-policy — Architecture
+owner: Vincent
+status: implemented
+---
+
+# BTB-025-architecture.md
+
+## 1) Architecture design
+
+- `src/lib/urlParams.ts` implements bounded param parsing.
+- Individual tools opt into URL param support.
diff --git a/docs/spec/BTB-025-ui-url-input-policy/BTB-025-requirements.md b/docs/spec/BTB-025-ui-url-input-policy/BTB-025-requirements.md
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index 0000000..29d3c61
--- /dev/null
+++ b/docs/spec/BTB-025-ui-url-input-policy/BTB-025-requirements.md
@@ -0,0 +1,26 @@
+---
+specId: BTB-025
+title: ui-url-input-policy — Only short bounded inputs/options in URL
+owner: Vincent
+status: implemented
+---
+
+# BTB-025-requirements.md
+
+## 0) Context
+
+- Problem: Large inputs in URL are unreliable and can leak sensitive data.
+
+## 1) Requirements
+
+- [ ] BTB-025-REQ-001: Only allow short bounded URL params.
+- [ ] BTB-025-REQ-002: Enforce hard length limit for any text param (default 500 chars).
+- [ ] BTB-025-REQ-003: Prefer URL for options; store large inputs locally.
+
+## 2) Acceptance criteria
+
+- [ ] BTB-025-AC-001: Long `text` params are ignored.
+
+## 3) Test plan
+
+- E2E: URL param tests cover behavior.