## TL;DR

The agent edited wrangler.jsonc and broke the comment syntax (or the JSON structure around a comment), so wrangler could not parse the file and fell back to defaults or a stale cached config. The deploy then used the wrong settings. Validate the JSONC after every edit and diff the effective config before deploying.

## The query

```text
agent's wrangler.jsonc edit broke comment parsing: deploy read a stale config
```

## Use this when

- Config edits do not take effect on deploy.
- Wrangler warns about config parsing or silently uses defaults.
- The file was recently edited by an agent.

## Not for

- wrangler.toml syntax errors (different file, different parser).
- Config values that are valid but wrong (fix the values).
- Deploys failing on validation of correct config (different problem).

## Steps

### Step 1: Validate the JSONC

Parse the file with a JSONC-aware parser and find the syntax error.

Expected result: the broken comment or structure is located: an unclosed block comment, a comment inside a string, a trailing comma the parser rejects.

### Step 2: Fix the syntax minimally

Repair the comment or structure with the smallest possible edit.

Expected result: the file parses cleanly. The intended config change is preserved.

### Step 3: Diff the effective config

Compare what wrangler resolves (via dry run) against what you intended.

Expected result: the resolved config matches intent. No silent fallbacks to defaults.

### Step 4: Check for the stale-config mechanism

Determine whether wrangler used defaults, a cached config, or the pre-edit file. Understanding the fallback prevents misdiagnosis next time.

Expected result: the fallback behavior is known and documented for the team.

### Step 5: Add config validation to the agent's edit flow

Every jsonc edit ends with a parse check and a dry-run diff before deploy.

Expected result: broken configs never reach deploy. The edit-verify loop is structural, not voluntary.

## Why it happens

JSONC looks like JSON but is not; comments are the trap. Agents edit confidently (it is 'just JSON'), break a comment boundary, and the parser rejects the file. Wrangler's fallback (defaults or stale) then makes the failure silent: the deploy 'works' with the wrong config.

## Edge cases

- Block comments spanning the edited region are the most fragile. Prefer line comments near edit sites.
- A comment containing JSON-like text can confuse naive parsers. Keep comments plain.
- Version-control the config and diff every agent edit. The diff is the cheapest validator.
- Consider whether the project even needs jsonc: if no comments are used, plain JSON removes the entire failure class.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_HuBMBDwcZNbdneMpw3f5Yg