Well, I didn't make any progress over the holidays (too many relatives, too many feasts), but now that things are back to abnormal, I'm resuming my interrupted game.
It's turn 104 now, and the previous turn witnessed the biggest battle I've seen so far. As I mentioned last time, I've sent cloaked scouts into most of the enemy-controlled border systems. One of them spotted a fleet of 97 Tessellate ships (mostly CR) apparently headed for the Resshrak system, which I had recently captured. With two turns' warning, I gathered four fleets from neighboring stars, stripped most of the planets in the system, and fortified the most valuable planet (it has several captured Tessellate shrines) with 3 medium weapons platforms, four captured small missile sats, and 8 medium PPB sats.
On the third turn, the enemy fleet did indeed attack the expected target. On the replay, the enemy fleet packed into the northeast corner of the tactical map; my sats were to their west, and my fleets (40 LC, CR, & BC, 1 BB) were deployed around the planet. Despite my defensive efforts, my ships were still outnumbered about 2 to 1.
Unfortunately for the Tessellate, they had learned nothing from previous encounters; their fleet consisted almost entirely of napalm-armed planet killers. They were tough and heavily armored, to be sure, but they had no way of hurting my ships other than ramming. Worse, they inexplicably passed up nearly all their (rare) ramming opportunities. Even then they might have scorched the planet with sheer numbers, but for some reason the main body headed south, passing east of the planet, apparently just to ram my lone repair space station.
With the station gone, the six survivors finally turned to my world, but they were vaporized instantly. The combat ships were gone by turn eight; the don't-get-hurt ships lasted until turn 20. For the loss of 97 ships, the Tessellate destroyed one space station and inflicted negligible damage on one supply ship.
I'm at a loss to explain the poor performance of the Tessellate in the game so far. I can only speculate that the expensive tech option has hit them harder than the other AIs. Perhaps they'll rally later.
On the western front, I've located the Pyrochette home world; in a few turns I should have enough troops assembled to take it. To the northwest the Aquilaeians are fielding fleets of 20 to 30 battlecruisers each, but I'm capturing 1-2 per turn via Intel and slowly capturing more worlds. The Tessellate to the northeast are weakened after their disaster in Resshrack.
To the east, in Zanthris, two Narn worlds are still holding out, guarded by 60 and 71 sats, respectively. Assuming Talisman sats, PPBs, and a few weapons platforms, it would probably cost me several ships each to take them out by direct attack. Instead, I'm going to try launching large numbers of my own sats over these worlds and see if they can do the job.
The victory condition in this game is a 300% lead over the second place empire. With the Acks and Tessies still pretty much intact, it looks like the game will go on for some time.