When AI edit a file it strips all generics in TS

[ouwargui]

Description

Every time AI edits a file, if there's any generic tags it strips without me asking. And if I ask to add it back it can't, it keeps trying to edit but nothing happens. It happens with all models, I think it is related to the edit tool.

This started after I removed oh-my-opencode, I tried doing a clean re-install, but it didn't work.

Here's a few examples:

diff

- <DashboardSectionWithSheet<ProductShowcaseRecord & { _id: string }>
+ <DashboardSectionWithSheet

- export const getStaticProps: GetStaticProps<ExplorePageProps> = async () => {
+ export const getStaticProps: GetStaticProps = async () => {

- return result as ObjectTypeParser<SqlFeaturedBusiness, Date, string>;
+ return result as ObjectTypeParser;

asking it to re-insert my generics

Plugins

only built-ins

OpenCode version

1.4.3

Steps to reproduce

1. Ask it to make changes to a TS file with generics
2. Watch it strip all your generic without you asking for it

Screenshot and/or share link

https://opncd.ai/share/2db8Z5yU

Operating System

macOS 26.3.1

Terminal

Ghostty

[rekram1-node]

huh will look

[ouwargui]

@rekram1-node thx, let me know if there's anything i can do to help - i understand this is a weird bug and it might be on my side since i searched the issues and didn't find anything similar

[soulsam480]

omg, just hit this, it literally stripped everything 😭 . i used go/kimi and go/glm-5.1 😭

[ouwargui]

@rekram1-node so after fighting with the AI for a bit, it stopped using the "edit" tool and now every time it needs to edit a file it creates a python script for doing so, it's kinda weird but it's working so far, the python script doesn't strip any generics from my files

[ouwargui]

@rekram1-node opus just compacted my chat and something he wrote on instructions stood out:

• The Edit tool in this environment strips TypeScript generic angle brackets (treats them as HTML). All file modifications involving generics must use Python or bash (not the Edit tool) to avoid corruption

dunno if that helps

[gschambers]

Confirming this and adding some supporting evidence on root cause.

It's not the model and not Prettier — it's the XML serialisation layer.

We hit this on a TypeScript codebase and investigated thoroughly. Here's what we found:

When the agent writes a newString containing TypeScript generics via the Edit tool, the <T> angle brackets are being interpreted as XML tags by the tool call serialiser and stripped before the content ever reaches the file system. The model outputs the correct content; the corruption happens in transit.

Evidence:

• OpenCode's session DB showed the agent writing type AnyArray<T> = Array<T> at one timestamp, and the subsequent oldString read-back showing type AnyArray<T> = Array on disk — the <T> on the right side was gone
• We ran the same source through Prettier 3.0.0 and 3.8.x with the project's actual .prettierrc.json — the generic survived byte-for-byte intact both times. Prettier is not involved.
• The loop behaviour (agent keeps trying to re-insert the generic but nothing sticks) is explained by the same mechanism: every write attempt strips <T> again

The workaround in this thread is correct: using bash/Python to write file content sidesteps the XML serialisation path. Claude's own compacted context in this thread correctly identified this: "The Edit tool treats < as HTML".

The fix needs to be in how the Edit/Write tool parameters are serialised — < and > in newString/content values need to be escaped as </> before XML wrapping, or the tool parameters need a different transport (e.g. base64 for content containing angle brackets).

Happy to share more detail if useful.