hashicorp/terraform · error

Failed to negotiate acceptable chunk size. Expected size > 0

Error message

Failed to negotiate acceptable chunk size. Expected size > 0 and <= %d bytes, provider wants %d bytes

What it means

Returned by Pluggable.Configure when negotiating the chunk size for state transfers with a custom state-store provider. After ConfigureStateStore returns, Terraform validates the provider's reported ChunkSize: it must be > 0 and <= chunks.MaxStateStoreChunkSize. A zero or oversized value means the provider is non-compliant or buggy.

Source

Thrown at internal/backend/pluggable/pluggable.go:129

	var diags tfdiags.Diagnostics
	req := providers.ConfigureStateStoreRequest{
		TypeName: p.typeName,
		Config:   config,
		Capabilities: providers.StateStoreClientCapabilities{
			// The core binary will always request the default chunk size from the provider to start
			ChunkSize: chunks.DefaultStateStoreChunkSize,
		},
	}
	resp := p.provider.ConfigureStateStore(req)
	diags = diags.Append(resp.Diagnostics)
	if diags.HasErrors() {
		return diags
	}

	// Validate the returned value from chunk size negotiation
	chunkSize := resp.Capabilities.ChunkSize
	if chunkSize == 0 || chunkSize > chunks.MaxStateStoreChunkSize {
		diags = diags.Append(fmt.Errorf("Failed to negotiate acceptable chunk size. "+
			"Expected size > 0 and <= %d bytes, provider wants %d bytes",
			chunks.MaxStateStoreChunkSize, chunkSize,
		))
		return diags
	}

	// Negotiated chunk size is valid, so set it in the provider server
	// that will use the value for future RPCs to read/write state.
	cs := p.provider.(providers.StateStoreChunkSizeSetter)
	cs.SetStateStoreChunkSize(p.typeName, int(chunkSize))
	log.Printf("[TRACE] Pluggable.Configure: negotiated a chunk size of %v when configuring state store %s",
		chunkSize,
		p.typeName,
	)

	return resp.Diagnostics
}

View on GitHub (pinned to c9def3e214)

Solutions

1. Update/upgrade the state-store provider to a version that correctly returns a chunk size within the allowed range.
2. Report the bug to the provider author — the provider's ConfigureStateStore must populate ChunkSize in its Capabilities response.
3. Fall back to a built-in backend (s3/azurerm/gcs/etc.) until the provider is fixed.

// Validate provider chunk size contract before relying on it.
if resp.Capabilities.ChunkSize == 0 || resp.Capabilities.ChunkSize > chunks.MaxStateStoreChunkSize {
    return errors.New("provider returned invalid chunk size")
}

When it happens

Trigger: Configuring a pluggable state store (a provider implementing the StateStore interface) whose ConfigureStateStore response returns ChunkSize == 0 (unset/default) or a value exceeding the negotiated maximum. Happens at terraform init/Configure time for that backend.

Common situations: Using a custom/alpha state-store provider that doesn't set ChunkSize; a provider bug returning an uninitialized value; version mismatch where the provider targets an older contract with different size semantics.

Related errors

• encountered a malformed backend state file with a 'state_sto
• attempted to encode a malformed backend state file; provider
• state store is not valid: %w
• state store is not valid: provider version data is missing d
• Attempted to initialize pluggable state with a nil provider

AI-assisted analysis of hashicorp/terraform@c9def3e214 (2026-08-07). Data as JSON: /api/errors/92cb03a65270a42b. Report an issue: GitHub.