Tarek Kharsa https://tarekkharsa.github.io/ 2026-10-09T00:00:00Z Tarek Kharsa https://tarekkharsa.github.io/ Lessons from great codebases https://tarekkharsa.github.io/posts/guess-the-codebase.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Eight engineering lessons per open-source codebase, each verified in the source and linked to it. OpenCode #1: Admit the prompt first, run it later https://tarekkharsa.github.io/posts/gtc3-01-admit-then-run.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z A durable inbox between “you pressed Enter” and “the model sees it.” OpenCode #2: Never rewrite the system prompt https://tarekkharsa.github.io/posts/gtc3-02-never-rewrite-the-system-prompt.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Freeze the baseline, append what changed, and keep the provider cache warm. OpenCode #3: Record real HTTP once, replay it forever https://tarekkharsa.github.io/posts/gtc3-03-record-once-replay-forever.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Cassettes instead of mocks, and a CI that refuses to record. OpenCode #4: Bound what the model sees https://tarekkharsa.github.io/posts/gtc3-04-bound-what-the-model-sees.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z One size limit per tool result: keep the head and the tail, save the rest to a file. OpenCode #5: One API, even in-process https://tarekkharsa.github.io/posts/gtc3-05-one-api-even-in-process.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z The embedded SDK sends real requests to the real router, without a network. OpenCode #6: Rebuild on the main branch https://tarekkharsa.github.io/posts/gtc3-06-rebuild-on-the-main-branch.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z A new major version grown next to the old one, with a dated log of every contract change. OpenCode #7: Configured is not allowed https://tarekkharsa.github.io/posts/gtc3-07-configured-is-not-allowed.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Policy is its own layer, and the last matching rule wins. OpenCode #8: Compact before you overflow https://tarekkharsa.github.io/posts/gtc3-08-compact-before-you-overflow.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Summarize old turns before the request stops fitting, keep recent ones word for word. OpenCode: 20 power-user tips https://tarekkharsa.github.io/posts/gtc3-reveal-power-user-tips.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z 20 power-user tips for OpenCode as it ships today, plus a recap of the eight engineering lessons from its upcoming v2. Pi #1: Ship a small core, and make your own features replaceable https://tarekkharsa.github.io/posts/gtc2-01-small-replaceable-core.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Its MCP support is a plugin, and a third-party plugin can replace it. That's the point. Pi #2: Entry points are cost contracts https://tarekkharsa.github.io/posts/gtc2-02-entry-points-are-cost-contracts.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Importing one 6 KB function loaded 106 files. Now a commit check counts them. Pi #3: A fake model and an empty environment https://tarekkharsa.github.io/posts/gtc2-03-fake-model-empty-environment.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Agent tests with no real models, no real keys, and nothing from your machine. Pi #4: Never mutate history https://tarekkharsa.github.io/posts/gtc2-04-never-mutate-history.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Sessions as an append-only tree: branches, summaries and even edits are new entries. Pi #5: Treat the lockfile as code https://tarekkharsa.github.io/posts/gtc2-05-lockfile-is-code.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Three packages may run install scripts. Every other dependency change has to ask. Pi #6: Design a tool a model can't misuse https://tarekkharsa.github.io/posts/gtc2-06-tool-a-model-cant-misuse.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Exact match first, fuzzy match second, loud errors, and one queue per file. Pi #7: Decide who owns the scrollback https://tarekkharsa.github.io/posts/gtc2-07-who-owns-the-scrollback.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Two terminal renderers, one interface, and a test that counts full redraws. Pi #8: Measure whether your docs help https://tarekkharsa.github.io/posts/gtc2-08-measure-your-docs.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Run the agent with and without the docs, and keep what moves the number. Pi: 20 power-user tips https://tarekkharsa.github.io/posts/gtc2-reveal-power-user-tips.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z 20 power-user tips for Pi, the minimal, extensible coding agent harness, plus a recap of the eight engineering lessons from its source. T3 Code #1: Decide, commit, then act https://tarekkharsa.github.io/posts/gtc-01-decide-commit-then-act.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z The three-step server pattern that keeps AI agents from leaving your app in a weird state. T3 Code #2: Performance budgets belong in unit tests https://tarekkharsa.github.io/posts/gtc-02-performance-budgets-as-tests.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Seven performance patterns from one repo's commit log, and why their budgets fail the build. T3 Code #3: Mock the boundary, not the logic https://tarekkharsa.github.io/posts/gtc-03-mock-the-boundary.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z “A test that needs a timeout to pass is wrong.” Testing rules from a repo that bans sleeps. T3 Code #4: A PR process for the AI era https://tarekkharsa.github.io/posts/gtc-04-pr-process-for-the-ai-era.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z When anyone can generate a 2,000-line PR in ten minutes, review time is what you protect. T3 Code #5: Turn taste into lint rules https://tarekkharsa.github.io/posts/gtc-05-taste-as-lint-rules.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Review comments don't scale. A repo with 14 custom lint rules shows what does. T3 Code #6: A dev setup built for ten agents on one laptop https://tarekkharsa.github.io/posts/gtc-06-dev-setup-for-parallel-agents.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z Ports, databases, processes and URLs: everything shared becomes a collision once agents run in parallel. T3 Code #7: Lying spinners, stale labels, one-way doors https://tarekkharsa.github.io/posts/gtc-07-honest-ui.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z UX rules from a repo whose users stare at it all day and notice every lie the UI tells. T3 Code #8: Write docs for your most frequent contributor https://tarekkharsa.github.io/posts/gtc-08-write-docs-for-agents.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z In this repo, the most frequent contributor is an AI agent running inside the app itself. T3 Code: 30 power-user tips https://tarekkharsa.github.io/posts/gtc-reveal-t3-code-power-user-tips.html 2026-10-09T00:00:00Z 2026-10-09T00:00:00Z 30 power-user tips for T3 Code, the open-source GUI for coding agents, plus a recap of the eight engineering lessons from its source. Turning my Linux PC into a T3 Code server https://tarekkharsa.github.io/posts/t3-code-tailscale-home-server.html 2026-09-28T00:00:00Z 2026-10-09T00:00:00Z Run T3 Code on a Linux PC and reach it privately from your laptop and phone with Tailscale. A short, step-by-step guide.