Pi extension that renders Mermaid diagrams as ASCII in the TUI. It uses Mermaid's parser for syntax validation and beautiful-mermaid to render the ASCII art.
Pi → https://pi.dev/
- Renders Mermaid blocks as ASCII diagrams inside Pi's TUI
- Width-aware rendering: auto-selects tighter padding presets and clips output for narrow terminals
- Collapsible output with source shown only on expand (ctrl+o)
- Token efficiently adds parser warnings/errors to LLM context
- Handles large blocks with safety limits and caching
pi install npm:pi-mermaidOr, clone into your Pi extensions directory and enable it:
git clone https://github.com/Gurpartap/pi-mermaid ~/.pi/agent/extensions/pi-mermaidAfter installing, enter /reload or restart Pi.
Use Mermaid fenced blocks in chat:
```mermaid
graph TD
Start --> End
```
Or render the last assistant message:
/pi-mermaid
More examples: https://agents.craft.do/mermaid
Mermaid (ASCII)
┌───────┐ ┌────────┐ ┌──────────┐
│ │ │ │ │ │
│ Start ├────►│ Choice ├─Yes►│ Do thing │
│ │ │ │ │ │
└───────┘ └────┬───┘ └──────────┘
│
│
│
No
│
│ ┌──────────┐
│ │ │
└────────►│ Skip │
│ │
└──────────┘
```mermaid
flowchart LR
A[Start] --> B{Choice}
B -->|Yes| C[Do thing]
B -->|No| D[Skip]
```
Mermaid (ASCII)
┌──────┐ ┌─────┐ ┌─────┐
│ User │ │ Web │ │ API │
└───┬──┘ └──┬──┘ └──┬──┘
│ │ │
│ Submit form │ │
│─────────────────▶ │
│ │ │
│ │ POST /submit │
│ │─────────────────▶
│ │ │
│ │ 201 Created │
│ ◀╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌│
│ │ │
│ Show success │ │
◀╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌│ │
│ │ │
┌───┴──┐ ┌──┴──┐ ┌──┴──┐
│ User │ │ Web │ │ API │
└──────┘ └─────┘ └─────┘
```mermaid
sequenceDiagram
participant U as User
participant W as Web
participant API as API
U->>W: Submit form
W->>API: POST /submit
API-->>W: 201 Created
W-->>U: Show success
```
Mermaid (ASCII)
┌────────┐ ┌─────┐ ┌──────────┐
│ Client │ │ API │ │ Database │
└────┬───┘ └──┬──┘ └─────┬────┘
│ │ │
│ transfer │ │
│─────────────▶ │
│ │ │
│ │ txn (debit/credit/log) │
│ │───────────────────────────▶
│ │ │
┌alt [ok]─────────────────────────────────────────┐
│ │ │ │ │
│ │ │ commit │ │
│ │ │───────────────────────────▶ │
│ │ │ │ │
│ │ 200 │ │ │
│ ◀╌╌╌╌╌╌╌╌╌╌╌╌╌│ │ │
│ │ │ │ │
├[fail]╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ │ │ │ │
│ │ │ rollback │ │
│ │ │───────────────────────────▶ │
│ │ │ │ │
│ │ 400 │ │ │
│ ◀╌╌╌╌╌╌╌╌╌╌╌╌╌│ │ │
│ │ │ │ │
└─────────────────────────────────────────────────┘
│ │ │
┌────┴───┐ ┌──┴──┐ ┌─────┴────┐
│ Client │ │ API │ │ Database │
└────────┘ └─────┘ └──────────┘
```mermaid
sequenceDiagram
participant Client
participant API
participant Database
Client->>API: transfer
API->>Database: txn (debit/credit/log)
alt ok
API->>Database: commit
API-->>Client: 200
else fail
API->>Database: rollback
API-->>Client: 400
end
```
Mermaid (ASCII)
┌─────┐ ┌───────┐ ┌──────────┐
│ App │ │ Cache │ │ Database │
└──┬──┘ └───┬───┘ └─────┬────┘
│ │ │
│ Get data │ │
│───────────────────▶ │
│ │ │
│ Cache miss │ │
◀╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌│ │
│ │ │
┌opt [Cache miss]────────────────────────┐
│ │ │ │ │
│ │ Query │ │ │
│ │────────────────────────────────▶ │
│ │ │ │ │
│ │ Results│ │ │
│ ◀╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌│ │
│ │ │ │ │
│ │ Store in cache │ │ │
│ │───────────────────▶ │ │
│ │ │ │ │
└────────────────────────────────────────┘
│ │ │
┌──┴──┐ ┌───┴───┐ ┌─────┴────┐
│ App │ │ Cache │ │ Database │
└─────┘ └───────┘ └──────────┘
```mermaid
sequenceDiagram
participant A as App
participant C as Cache
participant DB as Database
A->>C: Get data
C-->>A: Cache miss
opt Cache miss
A->>DB: Query
DB-->>A: Results
A->>C: Store in cache
end
```
Mermaid (ASCII)
┌───────────────┐
│ Animal │
├───────────────┤
│ +name: String │
├───────────────┤
│ +eat: void │
└───────────────┘
△
└──────────────────────┐
│ │
┌────────────────┐ ┌─────────────────┐
│ Dog │ │ Cat │
├────────────────┤ ├─────────────────┤
│ +breed: String │ │ +isIndoor: bool │
├────────────────┤ ├─────────────────┤
│ +bark: void │ │ +meow: void │
└────────────────┘ └─────────────────┘
```mermaid
classDiagram
class Animal {
+String name
+eat() void
}
class Dog {
+String breed
+bark() void
}
class Cat {
+bool isIndoor
+meow() void
}
Animal <|-- Dog
Animal <|-- Cat
```
This extension depends on and is made possible by these projects:
Thank you to the maintainers and contributors of these projects.
MIT © 2026 Gurpartap Singh (https://x.com/Gurpartap)