Migrating from GAMA 2025-06 to 2026-06

This page lists all breaking changes and deprecations between GAMA 2025-06 and 2026-06, with guidance on how to update your models.

For a complete list of all changes, see the Changelog.

Before You Start

1. Back up your models before applying any changes.
2. Use the auto-upgrade tool included in GAMA 2026-06 — it will automatically fix most syntax changes (diffuse, transition, with: pairs, arrow braces, do parentheses, display/experiment names, etc.). It ships in the gaml.grammar plugin and can be run from the command line on a directory of models: java gaml.grammar.transition.GamlFileProcessor <root> [--dry-run] (with --dry-run, changes are only previewed, no file is written).
3. Read the full Changelog — Major changes from 1.9.3 to 2026-0 covers everything listed here plus additional improvements.

GAML Language Changes

diffuse statement

The diffuse statement no longer accepts the var: facet.

Before (2025-06)	After (2026-06)
diffuse var: my_variable amount: 0.1	diffuse my_variable amount: 0.1

See Diffusion.

transition statement

The transition statement no longer accepts to: or from:.

Before	After
transition to: my_action	transition my_action
transition from: my_action	transition my_action

with: pairs syntax

The with: facet no longer uses square brackets [] and double colons ::. Use parentheses () and single colons :.

Before	After
create foo with: [size::2, color::red]	create foo with: (size: 2, color: red)

Note: the with: modifier in the global section follows the same rule. Nested [...] list expressions inside the argument list are untouched: with: [values::[1, 2]] becomes with: (values: [1, 2]).

do and invoke statements

Parameter-less action calls now require an explicit (empty) argument list.

Before	After
do my_action;	do my_action();

The returns facet of do is removed. Call the action as an expression and assign directly.

Before	After
do some_action returns: result;	result <- some_action();

Arrow (->) expressions — braces removed

The outer curly braces around the body of -> expressions are no longer valid.

Before	After
int my_var -> { cycle * 2 };	int my_var -> cycle * 2;

Display and experiment names — explicit title:

The name right after display or experiment must now be a valid identifier (no spaces or special characters); the human-readable label goes in the title: facet.

Before	After
display "3 Simulations" { ... }	display _3_Simulations title: "3 Simulations" { ... }
experiment "Hello World!" { ... }	experiment Hello_World title: "Hello World!" { ... }

action declaration

Actions no longer use the deprecated declaration syntax. Actions are always declared at the top of the species block in GAML 2026-06.

let and set statements

Let-variables now behave differently at the scope level. They are fully local and do not propagate to other agents.

The let ... type: ... and set forms are replaced by plain typed declarations and assignments:

Before	After
let x type: int value: 5;	int x <- 5;
set x value: 5; (or set x <- 5;)	x <- 5;

list of: type syntax

Before	After
list of: int	list<int>
list of: my_species	list<my_species>

arg statements in action bodies

Arguments are no longer declared with arg statements inside the action body; declare them in the action signature.

Before	After
int my_action { arg x type: int default: 1; ... }	int my_action (int x <- 1) { ... }

value → update

The value facet on variable declarations is now update.

Before	After
int my_var value: 10	int my_var update: 10

save and restore

The save_simulation() action has been removed. The Save statement now uses format: instead of type:, and attributes: instead of with:.

Before	After
save_simulation()	save format: "json"
save to: "file.sim" type: "json"	save to: "file.sim" format: "json"
save to: "file.sim" with: [a, b]	save to: "file.sim" attributes: [a, b]

See Save and restore Simulations for examples with save / restore.

Statement & Display Changes

Display facets

See Defining Displays Generalities.

Deprecated	Replacement
refresh_every	use refresh: every(n)
focus	use camera default target: the_agent; in layer definitions (not available in Java2D)
synchronized	now a property of output, not per-view
scale	always displayed, facet removed
draw_env	use axes
ambient_light, diffuse_light, draw_diffuse_light	use light statement
camera_pos, camera_location, etc.	use camera statement
rotate	removed
draw_as_dem, dem	use elevation
lines	use border

image → picture

The image layer has been renamed to picture.

Before	After
layer image	layer picture
image file: "bg.png"	picture "bg.png"

do → action call without colon

Before	After
do action: my_action;	do my_action();

Skill Changes

Old name (deprecated)	New name	Notes
skill_advanced_driving / advanced_driving	driving	Using Driving Skill
skill_road	road_skill	Using Driving Skill
skill_road_node	intersection	Using Driving Skill
communicating	fipa	Using FIPA ACL

Moving skill: destination removed

The destination variable has been removed from the moving skill. Use destination: facet on goto or wander actions.

See Built-in Skills#moving.

Driving skill variable renames

Old	New
max_speed	speed_max
actual_speed	current_speed
acceleration	speed_acceleration

GAMA Operators

Old operator	New operator
with_optimizer_type (graph, string)	with_shortestpath_algorithm (graph, string)
as_json_string	to_json
is_clockwise, change_clockwise (geometry)	removed (all geometries now clockwise)
user_input	user_input_dialog

Grid Operator Changes

• buffer(shape, map) → buffer(shape, distance, number_of_segments)
• enlarged_by(shape, map) → enlarged_by(shape, distance, number_of_segments, end_cap)
• + for shapes and maps → + with added parameters (shape, distance, number_of_segments, end_cap)

Charts & Layout

Chart layer font facets

Font size and style facets have been merged.

Old	New
tick_font_size, tick_font_style	tick_font: "12px Bold"
label_font_size, label_font_style	label_font: "12px Bold"
legend_font_size, legend_font_style	legend_font: "12px Bold"
title_font_size, title_font_style	title_font: "12px Bold"

Layout

The layout facet on Permanent is now a standalone layout statement.

Variable Facet Changes

Old facet	New facet
value: 10 on variable	update: 10
size, fill_with on container	matrix_with(size, fill_with) or list_with(size, fill_with)
category, parameter on variable	use parameter statement and category facet on experiment

Lights / Camera

Light statement

Old facet	New facet
position	location
spot_angle	angle
color	intensity
draw_light	show
update	dynamic

See Manipulate lights.

Camera

All camera facets (camera_pos, camera_location, camera_target, etc.) are now handled by the camera statement.

Save/Restore

Save facet changes

Old	New
type: "json"	format: "json"
with: [a, b]	attributes: [a, b]

Restore changes

Restore now uses the restore statement instead of a model loading action.

See Save and restore Simulations.

Checklists

Quick checklist (most common changes)

• diffuse var: X → diffuse X
• transition to: X → transition X
• with: [a::1] → with: (a: 1)
• do X; → do X(); (parameter-less calls need parentheses)
• -> { expr } → -> expr (arrow braces removed)
• display "My Title" → display My_Title title: "My Title" (same for experiment)
• save_simulation() → save format: "json"
• type: → format: on save/restore
• with: (save) → attributes:
• image layer → picture layer
• skill_advanced_driving → driving
• skill_road → road_skill
• skill_road_node → intersection
• communicating → fipa
• value: → update: on variable declarations
• do action: X → do X()
• do X returns: v → v <- X()

Complete change checklist

• diffuse: remove var: facet
• transition: remove to: / from: keywords
• with: pairs: replace [] with () and :: with :
• image → picture: rename all image layers
• do/invoke: remove action: keyword, remove returns: facet, add () to parameter-less calls
• arrow expressions: remove braces around -> bodies
• display/experiment names: use identifiers, move labels to title:
• let/set: replace with typed declarations and plain assignments
• list of: T: replace with list<T>
• arg statements: move action arguments into the signature
• save/restore: use format: and attributes:, remove save_simulation()
• value → update: replace value: facet with update:
• save type: replace type: with format: on save statement
• save with: replace with: with attributes: on save statement
• skills: rename skill declarations
  • advanced_driving → driving
  • skill_road → road_skill
  • skill_road_node → intersection
  • communicating → fipa
• moving skill: remove destination variable references
• driving skill: rename variables (max_speed → speed_max, etc.)
• fipa skill: replace send with start_conversation
• database skill: replace timeStamp with gama.machine_time
• grid context: replace neighbours with neighbors
• operators: update deprecated operator names
  • with_optimizer_type → with_shortestpath_algorithm
  • as_json_string → to_json
  • user_input → user_input_dialog
  • remove is_clockwise, change_clockwise
• display facets: update deprecated facets
  • refresh_every → refresh: every(n)
  • focus → camera in layer
  • camera_* → camera statement
  • light_* → light statement
  • draw_as_dem → elevation
  • lines → border
  • empty → wireframe
  • bitmap → perspective on draw
  • rounded → squircle on draw
  • chart font facets → merged into tick_font, label_font, etc.
  • Permanent layout/toolbar tabs → layout statement
  • Solve variable renames → steps_size
  • image layer file/matrix → direct or field/mesh
• variable facets: replace value: with update:
• let variables: review scope behavior
• Matrix variable: use matrix_with() / list_with() instead of size / fill_with facets

Notes

• Models created in GAMA 2026-06 are not compatible with GAMA 2025-06.
• The auto-upgrade tool can fix most syntax changes but may not handle semantic changes (e.g., skill renames, operator name changes).
• For the full list of changes from GAMA 1.9.3 → 2026-06 and beyond, see the Changelog.