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      Peren documentation

      Compatibility dates and flags

      How Peren stores compatibility_date and which compatibility_flags pass or fail at process start.

      compatibility_date is a required service field. Peren stores it and checks that it is a valid YYYY-MM-DD calendar date. Peren does not implement Cloudflare’s compatibility-date flag calendar. Changing the date does not flip Cloudflare feature gates inside the isolate.

      compatibility_flags is an optional list of strings on the same service. Config parse accepts any string list after the date format check. Flag meaning is resolved when the node builds providers, before listeners open.

      What the date does

      Step Behavior
      Config validation Rejects a date that is not YYYY-MM-DD.
      Process start Parses the same date again into an internal compatibility record.
      Runtime effect Node compatibility mode is always disabled. The date is retained; it does not enable Cloudflare-dated APIs.

      Flags that pass resolution

      These flags are accepted. They do not change Node compatibility mode:

      • no_nodejs_compat
      • no_nodejs_compat_v2

      Duplicates of any flag fail resolution.

      Flags that fail resolution

      These names are recognized and refused as not implemented:

      • nodejs_compat
      • nodejs_compat_v2
      • nodejs_als
      • durable_object_fetch_requires_full_url
      • streams_enable_constructors

      Any other flag name fails as unknown.

      When resolution fails, provider construction fails and the process does not open listeners. Remove or replace the flag, then start again.

      Migration versus runtime

      peren migrate uses a separate Wrangler flag table. It can accept some of the names above with partial-support notices, or refuse unknown flags during import. A fragment that migrates cleanly can still fail at process start if the runtime resolver refuses the flag. Prefer empty compatibility_flags unless you need no_nodejs_compat or no_nodejs_compat_v2.

      See Migration overview and Migrate from Cloudflare Workers.

      Example

      [[services]]
name = "api"
worker_bundle_path = "worker.js"
compatibility_date = "2026-01-01"
compatibility_flags = ["no_nodejs_compat"]