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Version: v2

Configuration Hierarchy

Backstage's native config system merges multiple --config files in the order they are supplied. The merge is deep (object keys are combined) and last-wins on scalar values: if two files set the same leaf key, the later file's value survives. DevPortal's entrypoint assembles that --config chain at boot from base distribution files, preset-generated files, and your overrides. Knowing the chain tells you exactly where to put a setting and why it takes effect — or why it doesn't.

Quick answer — where do I put my override?

  • Operator customizations (branding, catalog locations, integration credentials): app-config.local.yaml (layer 5).
  • Auth provider and SCM integration (set once per environment): selected via VEECODE_PRESETS, which generates the preset layer (layer 4). See Presets.
  • Plugin-specific backend config (Kubernetes cluster URLs, SonarQube base URL, etc.): also goes in app-config.local.yaml, or is injected via pluginConfig in dynamic-plugins.yaml (layer 6). See Composing a Portal for the relationship between plugin loading and backend config.

The precedence chain​

Entries are listed lowest to highest priority. A file loaded later wins on any overlapping key.

OrderFileWhen loaded
1app-config.yamlBase distribution defaults (shipped in the image)
2app-config.production.yamlContainer / production overrides (shipped in the image)
3app-config.distro.yamlVeeCode distro defaults (~10 lines, escape hatch; shipped in the image)
4app-config.preset-<name>.yamlOne per selected preset, in VEECODE_PRESETS order
5app-config.local.yamlYour operator overrides (volume-mounted app-config.local.yaml only)
6dynamic-plugins-root/app-config.dynamic-plugins.yamlGenerated at boot from each enabled plugin's pluginConfig:
7app-config.saas.yamlDecoded from VEECODE_APP_CONFIG (base64); wins over all earlier layers

Files 1–3 are always present inside the image. File 4 is emitted once per preset that declares an appConfig: block, in VEECODE_PRESETS order. Files 5–7 are conditional — each is skipped if absent.

The source of truth is the EXTRA_ARGS construction in entrypoint.sh.

This is not the V1 seven-layer profile chain

V2 has no app-config.<profile>.yaml layer. The profile slot (old layer 3) is replaced by one file per selected preset (layer 4 above), assembled in VEECODE_PRESETS order. See Presets.

Where app-config.local.yaml sits​

app-config.local.yaml is your primary customization target. It loads at position 5 — after every preset-generated config, so it wins over preset fragments. You do not need to replicate anything from earlier files; supply only the keys you want to override or add, and Backstage deep-merges the rest.

docker run \
  -v $(pwd)/app-config.local.yaml:/app/app-config.local.yaml:ro \
  veecode/devportal:2.1.3

Example: override a single preset value​

Suppose the github preset enables the GitHub catalog provider at a 30-minute refresh frequency and you want 5 minutes. In your app-config.local.yaml:

catalog:
  providers:
    github:
      default:
        schedule:
          frequency: { minutes: 5 }

Because app-config.local.yaml loads after all preset files, your frequency wins. You do not repeat the rest of the provider block — the deep-merge keeps it.

VEECODE_APP_CONFIG — config without a file mount

In deployments where you cannot mount a file (ArgoCD managing plain manifests, a CI-injected environment, or the VeeCode SaaS), encode your operator config as base64 and pass it as VEECODE_APP_CONFIG. The entrypoint decodes it into /app/app-config.saas.yaml (position 7), which wins over everything — preset configs, plugin configs, and any mounted local.yaml. Use it for deployment-specific values (database URLs, ingress hosts, secret references) that must not be hardcoded.

Variable substitution​

Any value in any config file may contain ${VAR} or ${VAR:-default}. Backstage resolves these from the process environment at startup, after all --config files are merged.

  • ${VAR} — replaced with the env value; if the variable is unset it resolves to an empty string (Backstage does not error).
  • ${VAR:-default} — replaced with the env value if set; falls back to default otherwise.

If a preset declares a variable as required: true, the entrypoint validates it before Backstage starts. A missing required var exits with code 78, so substitution never runs on an incomplete environment. See Presets for the full validation flow.

Substitution applies equally to all files in the chain. The chain position only controls which file's containing key wins, not the substitution outcome.

app.title is baked at build time

app.title is compiled into the frontend bundle at image build time and cannot be overridden at runtime through app-config.local.yaml or any later layer. Runtime config overrides apply to backend-read keys and frontend config delivered at boot, but the window title is fixed in the built bundle.

Inspecting and debugging the chain​

To see the assembled --config flags and their order:

docker logs <container> 2>&1 | grep -E "EXTRA_ARGS|preset"

If a setting is not taking effect, check, in order:

  1. Which layer is setting the conflicting value.
  2. Whether a higher-priority layer (a later file in the chain) is overriding it.
  3. Whether the key path is correct (e.g. app.branding.theme.light.palette.*).
  4. Whether a ${VAR} substitution resolved to something other than you expect.

Backstage does not expose a stock "merged config" endpoint. Verify a setting either by reading the boot logs (many keys emit a Found N config(s) or Configured for ... line) or by testing the behavior the key controls.

  • Presets — the preset model and how preset configs (layer 4) are generated.
  • Dynamic Plugins — how app-config.dynamic-plugins.yaml (layer 6) is built.
  • Composing a Portal — how app-config backend sections relate to plugin loading and entity annotations.
  • For branding-specific keys, see Simple Branding.
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