No more than one provider_installation block may be…

Error message

No more than one provider_installation block may be specified

What it means

Thrown when the CLI configuration contains more than one provider_installation block. Terraform permits at most one provider_installation block to keep provider installation methods unambiguous. Multiple installation methods should be nested as separate method blocks within a single provider_installation block.

Solutions

Consolidate into a single provider_installation block with multiple nested method blocks (filesystem_mirror, direct, etc.)
Remove duplicate provider_installation blocks
Review all config files in the merge chain

Example fix

// before
provider_installation {
  filesystem_mirror { path = "/local/mirror" }
}
provider_installation {
  direct {}
}

// after
provider_installation {
  filesystem_mirror { path = "/local/mirror" }
  direct {}
}

Defensive patterns

Strategy: validation

Validate before calling

// Count provider_installation blocks in config before deployment
func countProviderInstallations(path string) (int, error) {
    src, err := os.ReadFile(path)
    if err != nil {
        return 0, err
    }
    return strings.Count(string(src), "provider_installation"), nil
}

Prevention

Use a single provider_installation block with multiple nested method blocks (filesystem_mirror, direct, etc.)
Avoid defining provider_installation in multiple merged config files
Review full config after merging files for duplicate top-level blocks
Consolidate provider installation methods rather than duplicating the block

When it happens

Trigger: len(c.ProviderInstallation) > 1 after parsing. Occurs when multiple provider_installation blocks are defined in one file or appear across merged config files.

Common situations: Adding a new provider_installation block without removing the old one; merging config files that each define provider_installation; copy-paste from documentation alongside existing config.

Related errors

AI-assisted analysis of hashicorp/terraform@d32a084675 (2026-08-11). Data as JSON: /api/errors/f4a17611c9256fcc. Report an issue: GitHub.

Appendix: source

Thrown at internal/command/cliconfig/cliconfig.go:323

		_, err := svchost.ForComparison(givenHost)
		if err != nil {
			diags = diags.Append(
				fmt.Errorf("The credentials %q block has an invalid hostname: %s", givenHost, err),
			)
		}
	}

	// Should have zero or one "credentials_helper" blocks
	if len(c.CredentialsHelpers) > 1 {
		diags = diags.Append(
			fmt.Errorf("No more than one credentials_helper block may be specified"),
		)
	}

	// Should have zero or one "provider_installation" blocks
	if len(c.ProviderInstallation) > 1 {
		diags = diags.Append(
			fmt.Errorf("No more than one provider_installation block may be specified"),
		)
	}

	if c.PluginCacheDir != "" {
		_, err := os.Stat(c.PluginCacheDir)
		if err != nil {
			diags = diags.Append(
				fmt.Errorf("The specified plugin cache dir %s cannot be opened: %s", c.PluginCacheDir, err),
			)
		}
	}

	return diags
}

// Merge merges two configurations and returns a third entirely
// new configuration with the two merged.
func (c *Config) Merge(c2 *Config) *Config {

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