"I don't know if I ever thanked him," said special agent George Crouch, who interrogated Hamdan in 2002.
Agents have said that Hamdan identified key terrorist leaders, mapped out bin Laden's escape routes and led them to al-Qaida safehouses after he was captured at a roadblock in southern Afghanistan in November 2001.
Hamdan's lawyers say he has been interrogated by more than 40 U.S. agents, and argue all his statements were tainted by coercive tactics including sleep deprivation and solitary confinement.
The target of the first U.S. war crimes trial since World War II, Hamdan faces a maximum life sentence if convicted of conspiracy and supporting terrorism.
Friday's court session adjourned early because Hamdan, who was treated for a fever at the prison hospital Thursday, still was not feeling well, said Navy Lt. Cmdr. Brian Mizer, his Pentagon-appointed attorney. The trial is scheduled to resume Monday.
The defense team lost a bid earlier this week to have Hamdan's statements thrown out because he was not advised of a right against providing incriminating information. But in questioning government witnesses, his lawyers have suggested to the jury of American military officers that he had no way of knowing that he was the target of a criminal investigation.
"Did anyone ever say, 'You've got to understand, somebody can use this against you?"' said Harry Schneider, one of Hamdan's lawyers, as he cross-examined Crouch. The agent said he did not remember.
Military prosecutors argue Hamdan cooperated reluctantly, and by the time he shared important information, it was of little tactical value.
The agents who testified said Hamdan was polite and generally provided reliable information, but was not necessarily forthcoming.
Crouch said Hamdan, like many detainees, was often evasive.
"You want to tell the interrogator what you think they already know, and hold out on what you think they don't know," he said.
While the Pentagon chose Hamdan as one of the first detainees to face charges, some of his peers who did not cooperate with their captors have been sent home from Guantanamo.
Michael St. Ours, a Naval Criminal Investigative Service agent, said a man identified by Hamdan as bin Laden's top bodyguard, Abdellah Tabarak, refused to meet with him for interrogations.
Tabarak was released to his native Morocco in 2004.
Hamdan's lawyers have raised doubts about the tactics used to obtain Hamdan's statements, arguing in court that newly discovered classified records show he was kept up for questioning late at night ahead of an interrogation by one of the FBI agents who testified Friday.
Responding to McMillan, the agent, Daniel William, testified that he was not aware of any effort to disrupt Hamdan's sleep before his interrogation in August 2002.
"There was no 'good cop, bad cop.' It was not anything we do," William told the court.
The judge, Navy Capt. Keith Allred, has suppressed some of Hamdan's statements, ruling they were obtained under "coercive" conditions.
This week, the defense received hundreds of pages of classified records on Hamdan's confinement that his lawyers are reviewing for other potential examples of harsh treatment.
Michael Berrigan, the deputy chief defense counsel, said the military provided the documents after a court-imposed deadline and the defense is now scrambling to review them.
The chief prosecutor for the tribunals, Army Col. Lawrence Morris, said he regrets that the documents were released late and his office is working with the government to deliver records more efficiently.
Crouch said he gained Hamdan's confidence in June 2002 through favors such as arranging for him to speak with his wife for the first time since being taken into U.S. custody.
"He cried quite a bit," he said. "He was very grateful for the opportunity to speak with his wife."