diff --git a/AGENTS.md b/AGENTS.md
index 99635dc0..2c632b42 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -413,7 +413,7 @@ SIN-Code/
 │       SIN-Code-SCA-Tool-Go, SIN-Code-Secrets-Scanner
 │
 ├── src/sin_code_bundle/       ← Python companion: `sin` CLI + `sin-serve`
-├── skills/                    ← 35 bundled skills in category directories
+├── skills/                    ← 37 bundled skills in category directories
 │   ├── browser-skills/
 │   ├── code-skills/
 │   ├── debug-skills/
@@ -621,7 +621,7 @@ Headless JSON contract (stable API — never break without major bump):
 | v3.18.0 | ✅ SHIPPED | `sin-code install` single-binary installer (issue #170), curl/bash + PowerShell shims, SHA256-verified release downloads |
 | v3.19.0 | ✅ SHIPPED | `sin-code review --complexity` (issue #179): `internal/complexity/` static analyzer with ponytail 5-tag format (`delete`, `stdlib`, `native`, `yagni`, `shrink`), `// sin-debt:` marker support (issue #177), text/json/markdown output, race-clean tests |
 | v3.20.0 | ✅ SHIPPED | Tool coverage, M6 enforcement, catalog, telemetry (issues #249, #253, #248, #250, #252, #251): agent profiles expose full `sin_*` + MCP prefix surface; system prompt injects SIN-tool preference fragment; runtime `ToolCoverageEnforcer` rejects missing/forbidden tool usage; `ledger tools` heatmap/coverage/unused; orchestrator planner emits mandatory `ToolChain` per intent; `sin-code catalog` unifies 46+ MCP tools, 17+ chat tools, and 14+ external MCP prefixes. |
-| v3.20.0 | ✅ SHIPPED | `sin-code image-graph` — SOTA ECharts chart generation (bar/line/pie/area); `skill-github-readme` bundled as 35th skill. 42 subcommands, 35 bundled skills. |
+| v3.20.0 | ✅ SHIPPED | `sin-code image-graph` — SOTA ECharts chart generation (bar/line/pie/area); `skill-github-readme` bundled. 42 subcommands, 37 bundled skills. |
 | v3.21.0 | ✅ SHIPPED | Test-First Verify-Loop (RFC-test-automation.md): `sin_test` + `sin_test_generate` + `sin_quality_gate` + `sin_mutation` + `sin_fuzz` + `sin_property`; `tool.post` hook payload path; `test.*` config keys; `evals/test-generation.json` golden dataset. |
 | v3.22.0 | ACTIVE | SIN Fusion v1: Verify-Tournament (issue #290) — multi-model fan-out on verify.fail, Fireworks pool (6 models), thinking mode, cost-governor, difficulty gate, PoC-only |
 
diff --git a/README.md b/README.md
index 92ff0329..5dd99269 100644
--- a/README.md
+++ b/README.md
@@ -50,7 +50,7 @@ swarm mode, skill bootstrapping, and methodology skills.
 ## MCP Integration
 
 - **MCP Server**: Go — `sin-code serve` (main binary, 44+ tools); Python legacy — `src/sin_code_bundle/mcp_server.py`
-- **Tools**: 40 subcommands, 34 bundled skills, 12 ecosystem skill servers, and external MCP servers (websearch, browser, symfony-lens, etc.)
+- **Tools**: 42 subcommands, 37 bundled skills, 12 ecosystem skill servers, and external MCP servers (websearch, browser, symfony-lens, etc.)
 - **Register**: Add `sin-code serve` to your MCP client config (see `docs/mcp.json.example`), or register the legacy Python server via `sin mcp register sin-serve src/sin_code_bundle/mcp_server.py`
 
 ## Development
@@ -87,7 +87,7 @@ swarm mode, skill bootstrapping, and methodology skills.
 
 ## Bundled Skills (v3.17.0)
 
-SIN-Code ships **34 bundled skills** embedded in the binary, installable via `sin-code skills list|install`. Skills are organized into category directories and follow a unified naming convention `skill-<category>-<name>`.
+SIN-Code ships **37 bundled skills** embedded in the binary, installable via `sin-code skills list|install`. Skills are organized into category directories and follow a unified naming convention `skill-<category>-<name>`.
 
 ```bash
 sin-code skills list          # list all bundled skills
diff --git a/cmd/sin-code/internal/lessons/store.go b/cmd/sin-code/internal/lessons/store.go
index a8fa49e7..b8ee37ed 100644
--- a/cmd/sin-code/internal/lessons/store.go
+++ b/cmd/sin-code/internal/lessons/store.go
@@ -107,6 +107,8 @@ CREATE TABLE IF NOT EXISTS lessons (
 CREATE INDEX IF NOT EXISTS idx_lessons_workspace ON lessons(workspace);
 CREATE INDEX IF NOT EXISTS idx_lessons_type ON lessons(type);
 CREATE INDEX IF NOT EXISTS idx_lessons_occurrences ON lessons(occurrences DESC);
+
+PRAGMA user_version = 2;
 `
 		_, err = db.Exec(schema)
 	}
@@ -114,7 +116,58 @@ CREATE INDEX IF NOT EXISTS idx_lessons_occurrences ON lessons(occurrences DESC);
 		_ = db.Close()
 		return nil, err
 	}
-	return &Store{db: db}, nil
+	s := &Store{db: db}
+	if err := s.migrateFingerprints(); err != nil {
+		_ = db.Close()
+		return nil, err
+	}
+	return s, nil
+}
+
+// migrateFingerprints rewrites any 16-hex (64-bit) fingerprints to full 64-hex
+// SHA-256 fingerprints. Idempotent: only rows with exactly 16 hex chars are touched.
+func (s *Store) migrateFingerprints() error {
+	rows, err := s.db.Query(`SELECT id, type, workspace, context, lesson, occurrences, first_seen, last_seen FROM lessons WHERE LENGTH(id) = 16`)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	type oldRow struct {
+		id, typ, ws, ctx, lesson, first, last string
+		occurrences                           int
+	}
+	var toMigrate []oldRow
+	for rows.Next() {
+		var r oldRow
+		if err := rows.Scan(&r.id, &r.typ, &r.ws, &r.ctx, &r.lesson, &r.occurrences, &r.first, &r.last); err != nil {
+			return err
+		}
+		toMigrate = append(toMigrate, r)
+	}
+	if err := rows.Err(); err != nil {
+		return err
+	}
+	if len(toMigrate) == 0 {
+		return nil
+	}
+	tx, err := s.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+	for _, r := range toMigrate {
+		var ctxMap map[string]any
+		if err := json.Unmarshal([]byte(r.ctx), &ctxMap); err != nil {
+			ctxMap = nil
+		}
+		newID := Fingerprint(EntryType(r.typ), r.ws, ctxMap)
+		if _, err := tx.Exec(`
+			UPDATE lessons SET id = ? WHERE id = ?
+		`, newID, r.id); err != nil {
+			return err
+		}
+	}
+	return tx.Commit()
 }
 
 func (s *Store) Close() error {
@@ -125,6 +178,8 @@ func (s *Store) Close() error {
 }
 
 // Record upserts a lesson — same fingerprint increments the count.
+// If a collision is detected (same fingerprint but different content),
+// a deterministic variant ID is used so the distinct lesson is preserved.
 func (s *Store) Record(ctx context.Context, e Entry) error {
 	if e.ID == "" {
 		e.ID = Fingerprint(e.Type, e.Workspace, e.Context)
@@ -134,15 +189,49 @@ func (s *Store) Record(ctx context.Context, e Entry) error {
 	if err != nil {
 		return err
 	}
-	_, err = s.db.ExecContext(ctx, `
-INSERT INTO lessons (id, type, workspace, context, lesson, first_seen, last_seen)
-VALUES (?, ?, ?, ?, ?, ?, ?)
-ON CONFLICT(id) DO UPDATE SET
-  occurrences = occurrences + 1,
-  last_seen = excluded.last_seen,
-  lesson = excluded.lesson
-`, e.ID, e.Type, e.Workspace, ctxJSON, e.Lesson, now, now)
-	return err
+
+	tx, err := s.db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	id := e.ID
+	for attempt := 0; attempt < 10; attempt++ {
+		var existing struct {
+			typ, ws, ctx, lesson string
+		}
+		err := tx.QueryRowContext(ctx, `
+			SELECT type, workspace, context, lesson FROM lessons WHERE id = ?
+		`, id).Scan(&existing.typ, &existing.ws, &existing.ctx, &existing.lesson)
+		if err == sql.ErrNoRows {
+			// Insert new lesson.
+			_, err = tx.ExecContext(ctx, `
+				INSERT INTO lessons (id, type, workspace, context, lesson, first_seen, last_seen)
+				VALUES (?, ?, ?, ?, ?, ?, ?)
+			`, id, e.Type, e.Workspace, ctxJSON, e.Lesson, now, now)
+			if err != nil {
+				return err
+			}
+			return tx.Commit()
+		}
+		if err != nil {
+			return err
+		}
+		// Collision check: compare canonical content.
+		if existing.typ == string(e.Type) && existing.ws == e.Workspace && existing.ctx == string(ctxJSON) && existing.lesson == e.Lesson {
+			_, err = tx.ExecContext(ctx, `
+				UPDATE lessons SET occurrences = occurrences + 1, last_seen = ? WHERE id = ?
+			`, now, id)
+			if err != nil {
+				return err
+			}
+			return tx.Commit()
+		}
+		// True collision: try a variant ID.
+		id = fmt.Sprintf("%s:%d", e.ID, attempt+1)
+	}
+	return errors.New("too many fingerprint collisions")
 }
 
 // Query returns relevant lessons for a workspace, ordered by frequency.
@@ -200,12 +289,12 @@ WHERE occurrences = 1 AND last_seen < ?
 	return int(n), nil
 }
 
-// sin-debt: 16-hex (64-bit) fingerprint — collision risk at ~4B entries, upgrade: switch to full 64-hex sha256 + collision check when lesson count > 100k
 // Fingerprint is the stable identity of a lesson (type+workspace+context).
+// Uses full 64-hex SHA-256 to avoid 64-bit birthday collisions.
 func Fingerprint(t EntryType, ws string, ctx map[string]any) string {
 	data, _ := json.Marshal(map[string]any{"type": t, "ws": ws, "ctx": ctx})
 	h := sha256.Sum256(data)
-	return hex.EncodeToString(h[:])[:16]
+	return hex.EncodeToString(h[:])
 }
 
 // sin-debt: linear scan over all lessons per briefing call, upgrade: switch to top-K precomputed index when entry count > 10k
diff --git a/skills/code-skills/skill-code-create/SKILL.md b/skills/code-skills/skill-code-create/SKILL.md
index ef75725f..a6a67d8e 100644
--- a/skills/code-skills/skill-code-create/SKILL.md
+++ b/skills/code-skills/skill-code-create/SKILL.md
@@ -19,7 +19,7 @@ lifecycle: native
 
 Create a new SIN-Code / OpenCode compatible skill from a template. Produces a valid skill directory with `SKILL.md`, `context/`, `frameworks/`, `tasks/`, `templates/`, and optional `scripts/` / `tests/` / `lib/`.
 
-As of **v3.20.0**, SIN-Code ships **36 bundled skills** embedded in the `sin-code` binary under `skills/<category>-skills/`. All bundled skills follow the naming convention `skill-<category>-<descriptive-name>`. New skills must be created in the correct category directory and added to the registry/docs before they are discoverable by agents.
+As of **v3.20.0**, SIN-Code ships **37 bundled skills** embedded in the `sin-code` binary under `skills/<category>-skills/`. All bundled skills follow the naming convention `skill-<category>-<descriptive-name>`. New skills must be created in the correct category directory and added to the registry/docs before they are discoverable by agents.
 
 ## When to Use
 
diff --git a/skills/code-skills/skill-code-graph/context/triggers.md b/skills/code-skills/skill-code-graph/context/triggers.md
new file mode 100644
index 00000000..266b6663
--- /dev/null
+++ b/skills/code-skills/skill-code-graph/context/triggers.md
@@ -0,0 +1,31 @@
+# Context: Triggers & Boundaries
+
+Docs: ../SKILL.md
+
+## Trigger Phrases
+
+- "chart"
+- "graph"
+- "benchmark chart"
+- "comparison chart"
+- "plot data"
+- "visualize data"
+- "bar chart"
+- "pie chart"
+- "line chart"
+- "area chart"
+- "generate graph"
+- "skill-code-graph"
+
+## Boundaries
+
+- **In scope:** Generating SOTA charts (bar, line, pie, area) from JSON data using `sin-code image-graph`. Deterministic, free, no AI.
+- **Out of scope:** Creative/conceptual visuals (use sin-image-generation skill). Architecture diagrams. Text-based tables.
+
+## Required Input
+
+JSON data file with chart spec (title, categories/series/items), chart type (bar/line/pie/area), and output path.
+
+## Tone
+
+Technical, data-driven, precise.
diff --git a/skills/code-skills/skill-code-graph/frameworks/standards.md b/skills/code-skills/skill-code-graph/frameworks/standards.md
new file mode 100644
index 00000000..db79cb08
--- /dev/null
+++ b/skills/code-skills/skill-code-graph/frameworks/standards.md
@@ -0,0 +1,26 @@
+# Frameworks: Standards & Constraints
+
+Docs: ../SKILL.md
+
+## Technology Stack
+
+- `sin-code image-graph` Go binary (stdlib only, no external Go deps)
+- Apache ECharts 5.5.0 via CDN (no Go wrapper library)
+- Headless Chrome for PNG screenshots
+
+## Standards
+
+- Dark theme: #0B1120 background, Inter font
+- SOTA color palette: Indigo, Pink, Emerald, Amber, Blue, Red, Purple, Cyan
+- Gradient fills on bars and lines
+- Glow shadows (shadowBlur 12-24)
+- Rounded bar corners (borderRadius [8,8,0,0])
+- Staggered animations (elasticOut/cubicOut, per-item delay)
+- Interactive HTML output (hover tooltips, save-as-image, toolbox)
+
+## Constraints
+
+- Same JSON input = same output (deterministic, byte-stable)
+- No AI, no credits, no external API calls
+- JSON input must match the chart type format (bar/line/area vs pie)
+- PNG requires headless Chrome on PATH
diff --git a/skills/code-skills/skill-code-graph/tasks/workflow.md b/skills/code-skills/skill-code-graph/tasks/workflow.md
new file mode 100644
index 00000000..43f3e757
--- /dev/null
+++ b/skills/code-skills/skill-code-graph/tasks/workflow.md
@@ -0,0 +1,27 @@
+# Tasks: Workflow
+
+Docs: ../SKILL.md
+
+## Pre-flight
+
+- [ ] Identify the data source (JSON file, API endpoint, inline JSON)
+- [ ] Determine chart type: bar (comparison), line (trend), pie (proportion), area (volume trend)
+- [ ] Prepare the JSON spec matching the chart type format
+
+## Execution
+
+- [ ] Task 1: Prepare JSON spec
+  - Acceptance: Valid JSON with title, categories/series/items, type field
+  - Verify: JSON parses without error
+- [ ] Task 2: Run `sin-code image-graph`
+  - Acceptance: HTML file generated at output path
+  - Verify: File exists and opens in browser
+- [ ] Task 3: Verify PNG output (if headless Chrome available)
+  - Acceptance: PNG file generated alongside HTML
+  - Verify: File exists and is a valid image
+
+## Post-flight
+
+- [ ] Open HTML in browser to verify interactivity (tooltips, hover, save-as-image)
+- [ ] Verify chart renders with correct data, labels, and colors
+- [ ] Clean up temporary JSON files if any
diff --git a/skills/code-skills/skill-code-graph/templates/output.md b/skills/code-skills/skill-code-graph/templates/output.md
new file mode 100644
index 00000000..3223c0cf
--- /dev/null
+++ b/skills/code-skills/skill-code-graph/templates/output.md
@@ -0,0 +1,25 @@
+# Template: Output Format
+
+Docs: ../SKILL.md
+
+## Chart Generation Report
+
+```markdown
+# Generated Chart: {title}
+
+## Details
+- Type: {bar|line|pie|area}
+- Source: {data file or inline JSON}
+- Output: {output.html} + {output.png}
+
+## Files
+- {output}.html — interactive chart (opens in browser)
+- {output}.png — static screenshot (if headless Chrome available)
+
+## Verification
+- [x] HTML opens in browser
+- [x] Data renders correctly
+- [x] Colors and gradients applied
+- [x] Hover tooltips functional
+- [x] Save-as-image toolbox available
+```
diff --git a/skills/code-skills/skill-code-graph/templates/prompt.md b/skills/code-skills/skill-code-graph/templates/prompt.md
new file mode 100644
index 00000000..3f026d1c
--- /dev/null
+++ b/skills/code-skills/skill-code-graph/templates/prompt.md
@@ -0,0 +1,23 @@
+# Template: Prompt Snippet
+
+Docs: ../SKILL.md
+
+## User wants to generate a chart
+
+```markdown
+You are generating a SOTA chart using sin-code image-graph.
+
+Chart type: {bar|line|pie|area}
+Data source: {JSON file path or inline JSON}
+Output path: {output.html}
+
+Follow the workflow from tasks/workflow.md:
+1. Prepare JSON spec matching the chart type format
+2. Run: sin-code image-graph --type {type} --data {file} --output {output}
+3. Verify HTML opens in browser with correct data
+4. Check PNG output if headless Chrome is available
+
+JSON format reference:
+- bar/line/area: {title, y_label, type, categories, series: [{name, values}]}
+- pie: {title, type, items: [{label, value}]}
+```