Iran's decision, announced on Tuesday, to accept a protocol allowing tougher nuclear inspections and also to suspend its attempts to enrich uranium, has had a mixed reception among Iranian hardliners.
Some ultra-conservatives have denounced the move, seeing it as an ignominious capitulation to Western pressure.
As the three European foreign ministers were negotiating the agreement with Iranian leaders on Tuesday, a group of hardliners staged a noisy demonstration denouncing the additional protocol as "a source of shame for Iran".
The deal had the blessing of Iranian conservatives
That viewpoint is reflected in the most hardline of the Tehran newspapers, Jumhouri Islami, which described signing the protocol as "an everlasting disgrace" which would "bring the curse of future generations on the country".
It portrayed the Europeans as agents of the United States, and said that if Iranian leaders did not stand up to the West, it would keep going until the Islamic Republic was destroyed.
But the right-wing was clearly divided.
One of the other conservative papers drew a clear distinction between Europe and the United States, and said that by playing on their contradictions, Iran had been able to foil American strategies in the region.
A moderate conservative daily, Entekhab, saw the announcement as a great victory for Iran over the Americans and others "who wanted to plunge the region into further crisis".
Predictably, the development was welcomed by papers reflecting reformist views - not without a good deal of crowing over the discomfiture of hardliners, who had bitterly denounced the protocol for months before.
The hardline denunciation raises the question of whether those who reached the agreement with the European ministers were speaking for the regime as a whole, and whether it will stick.
The main negotiator on the Iranian side, Hassan Rowhani, is secretary of the Supreme National Security Council, a body which represents all the main Iranian power centres.
He is a pragmatic conservative who was appointed by the Supreme Leader, Ayatollah Ali Khamenei.
So the decision had the support of all the regime's key strands, leaving its opponents on the margins.
Not all hard-liners are happy with Iran's Supreme Leader
For many conservatives, the fact that the decision could not have happened without the say-so of the Leader puts it beyond criticism.
Iran was under pressure to accept the Additional Protocol [to the Nuclear Non-Proliferation Treaty] for months before it was formally urged to do so in the International Atomic Energy Agency's tough resolution of 12 September.
It was bitterly denounced by many prominent hardliners from the outset, while many reformists argued all along that it should be accepted before the stepping-up of pressure made it hard to do so without losing face.
The decision was seen by many as something imperative but unpalatable, on the same level as the late Ayatollah Khomeini's agreement to end the war with Iraq in 1988, which he compared to "drinking a poisoned chalice".
In the end, because the regime as a whole was perceived to be under threat over the nuclear issue, the leadership was obliged to rise above its own contradictions and take a strategic national decision.
Iran was at a clear crossroads: if it had taken the other course, defying the IAEA, that would have led to a period of international isolation and possible sanctions, with special negative impact on Tehran's relations with Europe. That was a course which all but the most extreme hardliners ultimately shied away from.
To that extent, the decision represented a victory for the reformists, who had generally advocated compliance all along.
But the key decisions were taken by conservatives, and the main reform symbol, President Mohammad Khatami, played little more than a ceremonial role in the talks.
Some Iranian analysts did not rule out the possibility that disgruntled hardliners might try to stage some spectacular action to discredit the course the regime has decided to take.
"I'm sure they'll do something to sabotage or undermine the achievement," said one. "There are some people out there who are saying, we can't even trust the Leader now."