Model & Image Config in Sesi

model() and image() take an optional config block between the model name and the prompt. Config keys are unquoted identifiers.

model_call := 'model' '(' string ')' config_block? '{' prompt '}'
image_call := 'image' '(' string ')' config_block? '{' prompt '}'
config_block := '{' key ':' value (',' key ':' value)* '}'

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Basic Call (No Config)

let response = model("gemini-3.5-flash") {"Say hello"}
print response

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model() Config Keys

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thinkingLevel

Controls how much reasoning effort the model applies before responding:

// Fastest — minimal reasoning
let r1 = model("gemini-3.5-flash") {thinkingLevel: "minimal"} {"Summarize in one sentence:" text}

// Balanced
let r2 = model("gemini-3.5-flash") {thinkingLevel: "low"} {"Analyze this code:" code}

// Deep reasoning
let r3 = model("gemini-3.5-flash") {thinkingLevel: "medium"} {"Solve this step by step:" problem}

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max_tokens

Cap the response length:

let brief = model("gemini-3.1-flash-lite") {max_tokens: 100} {"Explain quantum computing."}

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images — Vision Input

Pass a local image path to give the model visual input:

// Single image
let description = model("gemini-3-flash-preview") {images: "photo.png"} {"Describe what you see."}

// Multiple images
let comparison = model("gemini-3.5-flash") {images: ["before.png", "after.png"]} {"What changed between these two images?"}

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stream

Stream tokens as they arrive instead of waiting for the full response.

To stdout

let response = model("gemini-3.1-flash-lite") {stream: true} {"Write a short poem."}

// tokens print to terminal in real-time
print "Final:" response

To a callback function

fn handleChunk(chunk) {
  print "Chunk:" chunk
}

let response = model("gemini-3.1-flash-lite") {stream: handleChunk} {"Explain closures."}
print "Final:" response

The return value is always the fully accumulated response string, regardless of whether streaming is on.

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search — Web Search Grounding

search takes no value. Adding it to the config block tells the model to ground its response in live web search results:

let response = model("gemini-3.1-flash-lite") {search} {"What is the weather in Tokyo right now?"}
print response

Combine with other keys normally:

let response = model("gemini-3.1-flash-lite") {search, max_tokens: 200} {"Latest news in Media this week."}

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cache

Sesi caches model responses by default. Set cache: false to force a fresh call:

let fresh = model("gemini-3-flash-preview") {cache: false} {"What time is it?"}

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Combining Config Keys

Multiple keys are comma-separated on one line:

let result = model("gemini-3.5-flash") {thinkingLevel: "medium", max_tokens: 500} {"Analyze this document:" doc}

let scan = model("gemini-3.5-flash") {images: "receipt.png", thinkingLevel: "minimal"} {"Extract all line items as JSON."}

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image() Config Keys

let logo = image("gemini-3.1-flash-image") {ratio: "1:1", size: "512"} {"A minimal logo for a programming language"}
write_image("logo.png", logo)

let banner = image("gemini-2.5-flash-image") {ratio: "16:9", size: "1K"} {"A dark futuristic cityscape at night"}
write_image("banner.png", banner)

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Quick Reference

// No config
let r = model("gemini-3.5-flash") {"Hello"}

// thinkingLevel
let r = model("gemini-3.5-flash") {thinkingLevel: "low"} {"Summarize:" text}

// max_tokens
let r = model("gemini-3.5-flash") {max_tokens: 200} {"Explain this."}

// Vision input
let r = model("gemini-3.5-flash") {images: "scan.png"} {"Transcribe all text."}

// Streaming to stdout
let r = model("gemini-3.1-flash-lite") {stream: true} {"Write a poem."}

// Streaming with callback
fn onChunk(chunk) { print chunk }
let r = model("gemini-3.1-flash-lite") {stream: onChunk} {"Tell a story."}

// No cache
let r = model("gemini-3.1-flash-lite") {cache: false} {"What's trending?"}

// Combined
let r = model("gemini-3.5-flash") {thinkingLevel: "medium", max_tokens: 500, images: "doc.png"} {"Analyze this."}

// image()
let img = image("gemini-2.5-flash-image") {ratio: "16:9", size: "1K"} {"A sunset over the ocean"}
write_image("output.png", img)

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