Allan Dulles, Heinrich Himmler and the Failed Assassination of AdolfHitler

Christ, there's tonnes of evidence for this one...

And it appears that he was REPEATEDLY warned by Washington that his codes were compromised and the Germans were probably reading every single thing he sent (which they were), and he kept on doing it anyway.

Incompetence theory....?

Even the Finns were reading it - and although they never formally joined the Axis, Finland was most assuredly a German ally and would have been sharing military intelligence with Berlin.

The Soviets and Finland agreed an armistice during 1944 (at Yalta, it was agreed that the Finnish-Soviet conflict was a separate, yet simultaneous war, not part of World War II, because that made things way more messy and complicated), but this was an armistice, not a peace treaty or a surrender - Finland was still at war with the USSR at the same time Germany was, and on the same side, right the way through 1940-1945; in fact, the Finns had actually been at war with the Soviet Union 18 months longer and earlier than the German Reich had, during a period in which the Soviets and the Nazis were formally allies...

As of 2015, apparently there is no extant record known to exist of the Bern OSS decrypts extant in the Finnish archives - but they certainly were taken down and recorded, so either they are lost, have yet to be found, or were destroyed subsequently...

From ‘The secret front: the story of Nazi political espionage’ by Wilhelm Höttl, p268

In the autumn of 1944 the Headquarters of the Secret Service in Berlin received its first intimation that an American office existed in Switzerland, the duties of which appeared to be more than those of a normal Intelligence Center. The head of it was a lawyer name Allen Welsh Dulles, who had become prominent at the end of first war as a member of the American diplomatic service in the Versailles peace treaty negotiations, and particularly in the Austro-Yugoslav disputes. The fact that he had been installed in the American Legation in Berne, gave some indication of his real activities. And from his wireless messages to Washington that were picked up and for the most part deciphered and passed to the Germans by the Hungarian monitor service, the German Secret Service was able to obtain accurate knowledge of his views on the great problems of world politics. Unlike the American Minister in Berne, who forwarded to Washington as established facts the wildest and stupidest rumors, which emanated from Germany, Dulles showed himself to be only a man of high intelligence, but also an implacable enemy of Bolshevism, whose opposition was based on knowledge, reasoned argument and clear-sighted vision. This unequivocal attitude seemed to their group, which had for years sought contact with an authoritative American organization, to offer the very chance they had been seeking so long. They set about trying to get in touch with Dulles. Through the intermediary of an Austrian industrial magnate and the German Deputy Air Attache in Berne they quickly succeeded in doing so. 

Höttl was head of SD foreign intelligence  for Southeastern Europe.

By the time the COI became the OSS in 1942, high officials had recognized the value of having a well-stocked base in neutral Switzerland, nearly surrounded by the Axis powers, prepared to defend itself if attacked, but otherwise steering a delicately balanced course. Switzerland had so many economic links with both Germany and Italy that there was bound to be leakage of information through corporate channels. Prominent exiles from Nazi Germany in the country still had lines of information into Berlin. The  Swiss government, the International Red Cross, and the Bank of International Settlements might each yield some Nazi secrets if the right people plied their officials. Dulles had just the right qualifications. He almost left for Switzerland too late the journey was strewn with obstacles, and Dulles barely made it across the French border before Germany shut off this route in response to the Allied invasion of French North Africa. Dulles was given the cover of being special assistant to the American minister in Bern, Leland Harrison. Dulles had regular contact with Embassy officials, including Harrison; he even used some State Department codes when his own facilities for communication with Washington were overloaded.

p107:

To prove his bona fides, Schellenberg also gave Hewitt another message for Washington: the Gestapo was “onto” Allen Dulles’ espionage work in Bern. They were feeding him false information from informants, and they had broken his codes. Both items turned out to be essentially false—apparently designed to disrupt Dulles’ effective operations. Dulles made little secret of what he was doing, but he was good at separating valuable informants from Nazi plants, and his codes were never broken. He recognized Schellenberg’s ploy.

Schellenberg was head of SD foreign intelligence. During the war he tried to come in contact with allied personalities who could promote a peace initiative between the Reich and the Western Powers. It seems the information he gave Dulles was supposed to prove he was not a provocateur but the outcome was the exact opposite.