mobxjs/mobx-state-tree

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Full-featured reactive state management without the boilerplate

Stars: 7.1k
Forks: 638
Open beginner issues: 0
Indexed issues: 97
Avg merge: 3d 18h
Merged PRs (30d): 3

Dominant language: TypeScript
License: MIT
Last GitHub push: Sep 2, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: hacktoberfest

Beginner friendly Everything

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97 open issues indexed

React 19.2 dev mode breaks MST: "creation of the observable instance must be done on the initializing phase" Open

bug needs reproduction/info

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2279 · 5 comments · Opened Dec 5, 2025
Error when React 19 component has MST node as prop with observer defined later Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2277 · 13 comments · Opened Oct 24, 2025
MSTMap does not have `observe` method, but IMSTMap does Open

bug Typescript

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2275 · 12 comments · Opened Jul 23, 2025
Duplicates in Identifier Cache Open

needs reproduction/info

Difficulty 4/5 3-5 days Newbie friendliness 25/100

mobxjs/mobx-state-tree#2255 · 3 comments · Opened Mar 27, 2025
SnapshotIn Type unexpectedly changed behavior in MST version 7 (when upgrading from 6) Open

Typescript

Difficulty 4/5 3-5 days Newbie friendliness 38/100

mobxjs/mobx-state-tree#2254 · 4 comments · Opened Mar 25, 2025
`types.compose` does not override base properties for snapshot requirements. Open

docs or examples help/PR welcome level: easy

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2253 · 4 comments · Opened Mar 17, 2025
Remove ts-essentials dependency Open

dependencies help/PR welcome level: intermediate

mobxjs/mobx-state-tree#2246 · 1 comment · 1 assignee · Opened Feb 17, 2025
Replacing large array very slow (possibly due to reconciliation) Open

bug help/PR welcome level: intermediate

mobxjs/mobx-state-tree#2237 · 4 comments · 1 assignee · Opened Dec 30, 2024
Use Changesets Open

enhancement hacktoberfest help/PR welcome level: easy

Difficulty 3/5 1-2 days Newbie friendliness 38/100

mobxjs/mobx-state-tree#2232 · Opened Dec 13, 2024
Move off TSLint Open

help/PR welcome level: easy

mobxjs/mobx-state-tree#2227 · 1 comment · 1 assignee · Opened Nov 27, 2024
got 「unknown」 type when using Instance<typeof SomeModel> Open

docs or examples Typescript

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2217 · 7 comments · 1 reaction · Opened Oct 22, 2024
TypeScript does not recognize overriding mandatory property with optional one in sub-model Open

Typescript

mobxjs/mobx-state-tree#2216 · 6 comments · 1 assignee · Opened Oct 11, 2024
Unexpected patches for Dates with applySnapshot Open

enhancement help/PR welcome level: intermediate

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2215 · 3 comments · Opened Sep 16, 2024
onBecomeUnobserved is never called Open

can't fix

Difficulty 3/5 1-2 days Newbie friendliness 38/100

mobxjs/mobx-state-tree#2211 · 10 comments · Opened Aug 23, 2024
Model Creation/Instantiation Allows Duplicate names (except for properties) Open

enhancement hacktoberfest help/PR welcome level: easy

Difficulty 3/5 1-2 days Newbie friendliness 48/100

mobxjs/mobx-state-tree#2208 · 2 comments · Opened Aug 16, 2024
Invalidate Parent (Not just Immediate object) on Types.SafeReference Open

enhancement hacktoberfest help/PR welcome level: easy

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2205 · 5 comments · Opened Aug 12, 2024
Mobx/Mobx-state-tree doesnt work in module federation of Webpack. Open

needs reproduction/info

Difficulty 4/5 3-5 days Newbie friendliness 25/100

mobxjs/mobx-state-tree#2185 · 8 comments · Opened Jun 15, 2024
Missing docs for `types.lazy` Open

docs or examples

Difficulty 2/5 1-3 hours Newbie friendliness 52/100

mobxjs/mobx-state-tree#2156 · 4 comments · Opened Feb 26, 2024
Better documentation on action/view definitions and their impact on IDE introspection, navigation and refactoring Open

docs or examples

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#2155 · 3 comments · Opened Feb 26, 2024
Unexpected error "Сannot finalize the creation of a node that is already dead" while applying snapshot Open

bug docs or examples

Difficulty 3/5 1-2 days Newbie friendliness 45/100

mobxjs/mobx-state-tree#2136 · 18 comments · Opened Jan 30, 2024
Add safeMap utility (or something like it) Open

brainstorming/wild idea docs or examples enhancement hacktoberfest level: easy

Difficulty 5/5 Over a week Newbie friendliness 25/100

mobxjs/mobx-state-tree#2109 · 4 reactions · Opened Oct 24, 2023
When observe() a MST node's primitive property, TypeScript get the wrong type of oldValue & newValue Open

bug help/PR welcome

Difficulty 3/5 1-2 days Newbie friendliness 45/100

mobxjs/mobx-state-tree#2105 · 1 comment · Opened Oct 16, 2023
Use getTime() to check for Date equality Open

breaking change level: intermediate

Difficulty 2/5 1-3 hours Newbie friendliness 48/100

mobxjs/mobx-state-tree#2080 · 8 comments · Opened Sep 11, 2023
Document how MST lazily creates objects Open

docs or examples

mobxjs/mobx-state-tree#2058 · 1 comment · 2 reactions · 1 assignee · Opened Aug 7, 2023
RootStore type becomes "any" the moment we call a RootStore model action using yield on a child model action Open

help/PR welcome Typescript

Difficulty 4/5 3-5 days Newbie friendliness 32/100

mobxjs/mobx-state-tree#2040 · 3 comments · 1 reaction · Opened Jul 5, 2023
Aborting action with AbortController does not work immediately, causes trouble with React.StrictMode Open

bug help/PR welcome level: intermediate

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1987 · 3 comments · Opened Dec 4, 2022
refinement doesn't run type checks in production 😱 Open

brainstorming/wild idea breaking change help/PR welcome level: intermediate not a bug

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1962 · 7 comments · Opened Sep 19, 2022
Add support for keepAlive Open

enhancement help/PR welcome level: intermediate

Difficulty 5/5 Over a week Newbie friendliness 30/100

mobxjs/mobx-state-tree#1949 · 3 comments · 1 reaction · Opened Aug 23, 2022
Middlewares can not detect modification directly made in the parent action Open

docs or examples level: intermediate on hold

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1948 · 3 comments · Opened Aug 23, 2022
Symbol as model key Open

enhancement help/PR welcome level: intermediate

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1939 · 4 comments · 2 reactions · Opened Jul 27, 2022
Additional `undefined` case inside `union` type Open

question

Difficulty 4/5 3-5 days Newbie friendliness 25/100

mobxjs/mobx-state-tree#1929 · 1 comment · 1 reaction · Opened Jul 14, 2022
Using new Array(n) constructor in snapshot doesn't work Open

on hold

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1912 · 2 comments · Opened May 18, 2022
snapshotProcessor modifies the type it wraps Open

bug help/PR welcome level: intermediate

Difficulty 4/5 3-5 days Newbie friendliness 42/100

mobxjs/mobx-state-tree#1897 · 1 comment · 2 reactions · Opened Apr 9, 2022
Are Sets supported (using typescript)? Open

hacktoberfest help/PR welcome level: easy

Difficulty 5/5 Over a week Newbie friendliness 25/100

mobxjs/mobx-state-tree#1886 · 7 comments · Opened Mar 17, 2022
Reference's `onInvalidated()` called after `map.put(snapshot)` when snapshot doesn't have an id Open

bug help/PR welcome level: intermediate

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1874 · 3 comments · 1 reaction · Opened Feb 14, 2022
Make `preSnapshot` and `postSnapshot` actions in middleware ? Open

help/PR welcome level: intermediate

Difficulty 5/5 Over a week Newbie friendliness 30/100

mobxjs/mobx-state-tree#1861 · 3 comments · Opened Jan 22, 2022
getParent not useable in child view with TypeScript when adding actions to parent Open

help/PR welcome Typescript

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1851 · 1 comment · 2 reactions · Opened Jan 5, 2022
Accessing a field of a model that inherits from another leads to a missing type error Open

help/PR welcome Typescript

Difficulty 4/5 3-5 days Newbie friendliness 25/100

mobxjs/mobx-state-tree#1833 · 2 comments · 2 reactions · Opened Nov 17, 2021
resolveIdentifier type signature doesn't allow for snapshotProcessor types Open

help/PR welcome Typescript

Difficulty 3/5 1-2 days Newbie friendliness 38/100

mobxjs/mobx-state-tree#1778 · 1 comment · 3 reactions · Opened Aug 30, 2021
Cast doesn't seem to work in combination with types.references Open

bug help/PR welcome

Difficulty 4/5 3-5 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1760 · Opened Aug 13, 2021
Instance node can't be used to instantiate a reference Open

help/PR welcome

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1745 · 1 comment · 2 reactions · Opened Jul 20, 2021
types.reference is not working on instance creation Open

bug help/PR welcome level: intermediate

Difficulty 3/5 1-2 days Newbie friendliness 42/100

mobxjs/mobx-state-tree#1738 · 6 comments · Opened Jul 8, 2021
Memory consumption explodes with large number of nodes. 40MB of data becomes ~16GB in MST Open

brainstorming/wild idea breaking change

Difficulty 5/5 Over a week Newbie friendliness 35/100

mobxjs/mobx-state-tree#1683 · 24 comments · 11 reactions · Opened Apr 7, 2021
My model returns fields as null, if I created model fields with types.maybeNull and use model in types.union Open

has PR

Difficulty 4/5 3-5 days Newbie friendliness 25/100

mobxjs/mobx-state-tree#1648 · 3 comments · Opened Jan 19, 2021
Get Error: [mobx-state-tree] Cannot modify 'AnonymousModel@..., the object is protected and can only be modified by using an action. Open

docs or examples

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

mobxjs/mobx-state-tree#1647 · 8 comments · Opened Jan 17, 2021
`cast` TS error when `types.array` sub-type has reference Open

Typescript

Difficulty 3/5 1-2 days Newbie friendliness 45/100

mobxjs/mobx-state-tree#1640 · 2 comments · Opened Jan 16, 2021
`types.Date` expects a number in postProcessSnapshot Open

bug help/PR welcome level: intermediate

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1631 · 2 comments · Opened Jan 7, 2021
Rare unstable performance problem (caching turns off) Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 18/100

mobxjs/mobx-state-tree#1596 · 1 comment · Opened Oct 22, 2020
getRoot in afterAttach returns undefined in Jest tests Open

has PR

Difficulty 3/5 1-2 days Newbie friendliness 42/100

mobxjs/mobx-state-tree#1551 · 11 comments · Opened Jul 14, 2020
Destroying a model with a preprocessor that returns a new object triggers onSnapshot Open

bug help/PR welcome

Difficulty 3/5 1-2 days Newbie friendliness 35/100

mobxjs/mobx-state-tree#1547 · 2 comments · Opened Jul 9, 2020

mobxjs/mobx-state-tree

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