Blog
How Context Mode is built, what changed, and what we measured. Also as an Atom feed.
Worker exceeded memory limit: 18 days on Cloudflare Workers
Your coding agent showed "API Error" because a Cloudflare Worker isolate ran out of memory. The causes (a 64-character slice that kept 25 MB alive, an unbounded queue, garbage made faster than GC frees it), the move to Rust and Wasm, our mistakes, and a checklist.
One night with Cloudflare's on-demand Workers profiling
Logs could not explain why our busiest Durable Object queued for seconds. Cloudflare's on-demand profiling could. What the profiles showed, what we fixed in one night, the pitfalls, our mistakes, and our wish list.
Wrong skills, noisy memory, false resumes: the fixes behind them
Your agent loaded the wrong skill, got facts it did not need, or replayed yesterday's session after a "hi". We moved those choices to Cloudflare's Clef decision models, measured each move, and shipped three of four.
The right skill on the right turn, or none at all
Skills only help if the right one loads on the right turn and stays out when you are chatting. How Context Mode now makes that choice, what improved (4 of 10 to 10 of 10 on a small sample, p95 from 4,728 ms to 612 ms), and what we have not measured yet.
Agent memory that knows when a fact changed
Your agent forgets what you said yesterday, or remembers the old answer. Context Mode memory closes facts that changed, keeps them in the right worktree, and sends back fewer, more relevant facts: 41 tokens instead of 262 in an offline eval.
All-day agent sessions without compaction: how Recall works
A long agent session either compacts and forgets your morning, or resends the whole history on every request. Recall keeps every word in an exact archive: in a pre-registered A/B it never compacted and answered 9 of 10 early-detail questions against 4 of 10.
Your agent pays for the same test log on every call
A test log your agent read once is paid for again on every later call. Context Mode folds it on first sight, keeps every byte in your archive, and in paired runs cut a 30-step Opus 5.5 session from $7.20 to $2.49.
Why 39% fewer tokens cost us 149.6% more, and what we changed
Cutting tokens can raise your agent bill when it breaks the prompt cache. Here is how Context Mode trims tool schemas, holds the cached prefix still, and counts price tiers and Codex cost, with the numbers.
Rules your coding agent cannot rename its way around
Guarding a coding agent by tool name misses argv shells, hidden substitutions and new agents' tools. Protect now reads a shell by the shape of its input, and an API key can no longer loosen your rules: 126 of 126 production checks pass.
How we prove Context Mode does not break your coding agent
Anything between your agent and the model must not break a turn or turn off a feature you pay for. Here is how we test Context Mode with both real clients, every account state, and every new model.
What happens when your plan runs out: your agent keeps working
A quota should never break your agent in the middle of a task. When Context Mode pauses, your agent runs as plain Claude Code or Codex, with a heads-up first and a one-click way back.
Durable Objects in production: 14 lessons from Slipstream
Measured lessons from rebuilding our request path on Cloudflare Workers and Durable Objects: placement, location hints, wake time and script size, the six-call limit, an RPC trap that cost us 2.5 hours, and partial indexes.
Slipstream: a shorter path from your agent to the model
The memory stores moved to their own Worker, a request makes at most two store calls before the model call, and memory and skills are picked by newer models. What we measured, and what went wrong during the rollout.