Property, plant and equipment - Disclosure of reconciliation of property, plant and equipment (Details) - EUR (€) € in Thousands	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	€ 2,090
Property, plant and equipment including right-of-use assets at end of period	1,522	€ 2,159
ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	1,563
Property, plant and equipment including right-of-use assets at end of period	1,007	1,547
BUILDINGS
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	1,706
Property, plant and equipment including right-of-use assets at end of period	1,086	1,801
EQUIPMENT
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	59
Property, plant and equipment including right-of-use assets at end of period	54	75
FURNITURE AND COMPUTER EQUIPMENT
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	325
Property, plant and equipment including right-of-use assets at end of period	382	283
GROSS VALUES \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	4,274	4,029
Acquisition	168	106
Disposal		(54)
Effect of the change in foreign currency exchange rates	16	(61)
Property, plant and equipment including right-of-use assets at end of period	4,457	4,020
GROSS VALUES \| ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	2,865	2,526
Acquisition	0	52
Disposal		(20)
Effect of the change in foreign currency exchange rates	12	(49)
Property, plant and equipment including right-of-use assets at end of period	2,877	2,508
GROSS VALUES \| BUILDINGS \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	3,204	2,818
Acquisition	5	80
Disposal		0
Effect of the change in foreign currency exchange rates	12	(49)
Property, plant and equipment including right-of-use assets at end of period	3,221	2,849
GROSS VALUES \| EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	463	513
Acquisition	11	0
Disposal		(16)
Effect of the change in foreign currency exchange rates	0	0
Property, plant and equipment including right-of-use assets at end of period	474	497
GROSS VALUES \| FURNITURE AND COMPUTER EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	607	698
Acquisition	152	26
Disposal		(39)
Effect of the change in foreign currency exchange rates	4	(11)
Property, plant and equipment including right-of-use assets at end of period	763	673
DEPRECIATION \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(2,184)	(1,363)
Disposal		54
Effect of the change in foreign currency exchange rates	(11)	21
Increase	(741)	(573)
Property, plant and equipment including right-of-use assets at end of period	(2,935)	(1,860)
DEPRECIATION \| ROU
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(1,302)	(575)
Disposal		20
Effect of the change in foreign currency exchange rates	(9)	16
Increase	(559)	(422)
Property, plant and equipment including right-of-use assets at end of period	(1,870)	(961)
DEPRECIATION \| BUILDINGS \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(1,498)	(613)
Disposal		0
Effect of the change in foreign currency exchange rates	(9)	16
Increase	(627)	(452)
Property, plant and equipment including right-of-use assets at end of period	(2,135)	(1,048)
DEPRECIATION \| EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(404)	(419)
Disposal		16
Effect of the change in foreign currency exchange rates	0	0
Increase	(17)	(19)
Property, plant and equipment including right-of-use assets at end of period	(420)	(422)
DEPRECIATION \| FURNITURE AND COMPUTER EQUIPMENT \| Property, plant and equipment
Reconciliation of changes in property, plant and equipment [abstract]
Property, plant and equipment including right-of-use assets at beginning of period	(281)	(332)
Disposal		39
Effect of the change in foreign currency exchange rates	(2)	5
Increase	(97)	(102)
Property, plant and equipment including right-of-use assets at end of period	€ (380)	€ (390)

The amount of additions to property, plant and equipment including right-of-use assets other than those acquired through business combinations. [Refer: Total for all business combinations [member]; Property, plant and equipment including right-of-use assets]

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- References

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- Definition

The decrease in property, plant and equipment including right-of-use assets resulting from disposals. [Refer: Property, plant and equipment including right-of-use assets]

+ References

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- Definition

The increase (decrease) in property, plant and equipment including right-of-use assets resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Property, plant and equipment including right-of-use assets]

+ References

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- Definition

The amount of property, plant and equipment including right-of-use assets whose underlying assets would be presented as property, plant and equipment if they were owned. [Refer: Property, plant and equipment; Right-of-use assets]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2025-01-01
-Paragraph 47
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-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2025-en-r&anchor=para_47_a&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
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-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_a&doctype=Standard
-URIDate 2025-03-27

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- References

No definition available.

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