Labour and Plaid Cymru have formed a co-operation deal in the Senedd.
Talks have been taking place during the summer, after Labour won 30 seats in the Senedd elections while Plaid took 13 seats.
Now, both parties have unveiled a three-year agreement to work together, with plans to deliver ''radical change and reform''.
But the deal stops short of Labour and Plaid forming a coalition Welsh government.
The agreement is a joint policy programme covering 46 areas, ranging from free school meals for all primary pupils; a commitment to tackle the second homes crisis, to long-term reform of the Senedd itself.
First Minister Mark Drakeford said: ''The Welsh Government has an ambitious Programme for Government, which it will deliver over this Senedd term. But we do not have a monopoly on good ideas and we will work with progressive parties where we have shared and common interests to benefit people in Wales.''
''This Co-operation Agreement brings the Welsh Government and Plaid Cymru together to respond to some of the most pressing issues facing Wales today, such as climate change and the energy and cost-of-living crisis.''
''We can achieve more for people in Wales by working together and the Co-operation Agreement is both a response to the external challenges we face and a chance to build on the opportunities in our future. It will also help us secure a stable Senedd over the next three years, capable of delivering radical change and reform.''
''These commitments build on our shared values of social solidarity, a sustainable planet and a vibrant democracy.''
The ruling bodies of the two parties agreed to the co-operation deal when they met to discuss at the weekend.
But it still needs to be ratified by Plaid Cymru members, when they meet virtually for their annual conference next Saturday
Plaid leader Adam Price said the agreement was founded on ''common ground on a range of issues that will make a long-lasting difference to people's lives.''
He added: ''Almost a quarter of a century ago, people in Wales voted for self-government for Wales, with a promise of a new type of politics.''
''They placed their trust in a new democracy with an instruction to work differently – inclusively and co-operatively.''
''The challenges we face require real ambition to deliver radical ideas. The fallout from leaving the European Union, the legacy of the pandemic, and the UK Government's determination to erode the Senedd's powers all increase the need for transformational change.''
''Taken together, the bold policy pledges will unite Wales and benefit every generation, from all primary school pupils receiving free school meals to a national care service, free at the point of need.''
Reacting to the agreement, the Welsh Conservatives said it failed to ''deliver on the priorities of the people of Wales''.
Darren Millar MS, shadow minister for the constitution, said: ''It does nothing to address the crisis in our NHS; nothing to improve our ailing Welsh infrastructure; and nothing to fire up our sluggish economy.''
''Prioritising more politicians and constitutional reform over action to secure treatment for the one in five on an NHS waiting list or improving take home pay for the low paid is appalling.''
''Yet again, Plaid has betrayed its voters with another deal that cements a failing Labour administration into power for years to come.''
The Welsh Liberal Democrats said they would work constructively with the Welsh Government - but were ''ready to hold Labour and Plaid Cymru to account'', particularly over how the parties would reach their net zero carbon goal by 2035.
Leader Jane Dodds MS added: ''On the surface, there are a number of issues which have been covered in the announcement that were part of our manifesto, including work to tackle Wales' high child poverty levels through the expansion of free school meals and greater childcare provision.''
''I am also concerned the agreement does include measures to tackle long NHS and ambulance waiting times. It is absolutely vital that all parties and stakeholders work together to tackle the crisis in healthcare provision in Wales as we continue to recover from COVID-19.''