Unable to read wrangler config, variables defined in it will

Error message

Unable to read wrangler config, variables defined in it will not be available to astro:env at build time.

What it means

The Cloudflare adapter reads your wrangler config (wrangler.toml / wrangler.jsonc) to copy its `vars` entries into process.env so astro:env variables resolve at build time. The whole read runs in a try/catch; any throw — missing file, unreadable, invalid TOML/JSONC, unexpected shape — logs this warning and continues, with the original error only visible via logger.debug.

Source

Thrown at packages/integrations/cloudflare/src/utils/wrangler-config.ts:68

			config.configPath,
			undefined,
			config.vars,
			env,
			true,
			config.secrets,
		);

		for (const [key, binding] of Object.entries(vars)) {
			// `vars` can hold non-string JSON values (numbers, booleans, objects).
			// `process.env` only stores strings.
			const value = binding.value;
			if (value === undefined || value === null) {
				continue;
			}
			process.env[key] = typeof value === 'string' ? value : JSON.stringify(value);
		}
	} catch (e) {
		logger.warn(
			`Unable to read wrangler config, variables defined in it will not be available to astro:env at build time.`,
		);
		logger.debug(String(e));
	}
}

View on GitHub (pinned to 52e6c34790)

Solutions

Create or repair the wrangler config at the project root and fix the syntax error
Confirm it parses with Wrangler itself: `npx wrangler deploy --dry-run --outdir /tmp/cf-dry` (or `npx wrangler types`) exits cleanly
Re-run with debug logging (e.g. ASTRO_LOG_LEVEL=debug) to see the swallowed exception
Mirror build-critical vars in properly scoped .env files so builds do not depend solely on wrangler config

Example fix

# before: wrangler.toml invalid (unclosed table)
name = "site"
[vars
PUBLIC_API_URL = "https://api.example.com"

# after: valid config
name = "site"
compatibility_date = "2025-01-01"

[vars]
PUBLIC_API_URL = "https://api.example.com"

Defensive patterns

Strategy: validation

Validate before calling

# Validate the wrangler config before building
npx wrangler types || npx wrangler deploy --dry-run --outdir /tmp/cf-dry-run

Prevention

Keep wrangler.toml / wrangler.jsonc valid at the repo root and lint it in CI with a Wrangler dry-run
Run builds with debug logging (ASTRO_LOG_LEVEL=debug) when vars seem missing — the parse error is only visible there
Mirror build-critical astro:env variables in scoped .env files instead of relying solely on wrangler config

When it happens

Trigger: The wrangler config is absent (never created, renamed, or not checked out in CI), syntactically invalid after editing bindings, or lives where the adapter does not look. Afterwards, every astro:env variable defined only in wrangler `vars` is undefined during the build.

Common situations: Renaming wrangler.toml to wrangler.jsonc mid-migration and leaving broken syntax; CI jobs that skip copying the config; developers who run builds without Wrangler installed and never validate the file.

Related errors

AI-assisted analysis of withastro/astro@52e6c34790 (2026-08-18). Data as JSON: /api/errors/948be2a324754452. Report an issue: GitHub.