@vincentkoc @steipete — this addresses the highly-requested #9157 (12 thumbs-up). Adds an opt-in contextInjection: "first-message-only" config that skips re-injecting workspace files on every message, cutting token costs by ~93%. Default is "always" so zero breaking changes. Supersedes the closed #28072. Happy to squash commits.

Greptile Summary

This PR adds a contextInjection config option to agents.defaults that lets users opt into skipping workspace context file re-injection (AGENTS.md, SOUL.md, USER.md, etc.) on every turn after the first, yielding a reported ~93% token reduction for long conversations. The implementation is minimal and backwards-compatible — "always" remains the default. The type definition and Zod schema are clean and consistent with the rest of the codebase.

Two things worth addressing before merging:

• Duplicate fs.stat call (attempt.ts lines 1430–1435): The new stat check is repeated almost identically ~300 lines later as hadSessionFile. Moving the bootstrap-context resolution to after hadSessionFile is computed and reusing that variable would eliminate one unnecessary I/O operation and keep the "first message?" logic in a single place.

• Undocumented post-compaction behaviour (attempt.ts lines 1436–1446, types.agent-defaults.ts line 146): When compaction runs and clears the conversation history, the session file still exists, so workspace files will never be re-injected for that session even after compaction. The existing compaction.postCompactionSections only re-injects named AGENTS.md sections, not the full bootstrap context. The JSDoc on contextInjection should call this tradeoff out explicitly so operators know to configure postCompactionSections when they enable this option.

Confidence Score: 4/5

• Safe to merge with minor documentation and code-quality improvements recommended
• The core logic is sound, default behaviour is unchanged, and the type/schema additions are consistent with the codebase. The two identified issues (duplicate stat call, undocumented post-compaction behaviour) are style/documentation concerns rather than correctness bugs for the common case.
• attempt.ts — duplicate fs.stat call and undocumented compaction interaction

This is a comment left during a code review.
Path: src/agents/pi-embedded-runner/run/attempt.ts
Line: 1430-1435

Comment:
**Duplicate `fs.stat` call**

The `fs.stat(params.sessionFile)` call introduced here is duplicated approximately 300 lines later (line 1731–1734) where `hadSessionFile` is computed with the exact same logic:

```typescript
const hadSessionFile = await fs
  .stat(params.sessionFile)
  .then(() => true)
  .catch(() => false);
```

Additionally, `repairSessionFileIfNeeded` runs between the two stat calls (line 1727), which could theoretically produce inconsistent results if the repair alters the file's existence.

Consider moving the bootstrap context resolution to after `hadSessionFile` is computed, and reusing it:

```typescript
const skipContextInjection =
  contextInjection === "first-message-only" && hadSessionFile;
```

This eliminates one unnecessary filesystem I/O operation and keeps the "did a session file already exist?" logic in one place.

How can I resolve this? If you propose a fix, please make it concise.

---

This is a comment left during a code review.
Path: src/agents/pi-embedded-runner/run/attempt.ts
Line: 1436-1446

Comment:
**No re-injection after compaction**

When context compaction occurs, the session file still exists on disk, so `skipContextInjection` will remain `true` for every subsequent `runEmbeddedAttempt` call — including the first one after a compaction event. Because compaction replaces or summarises the message history (including the initial bootstrap system prompt content), workspace files like `SOUL.md` and `USER.md` that were only injected on the very first message of the session may no longer be present in the model's effective context after compaction.

The existing `compaction.postCompactionSections` mechanism re-injects named sections from `AGENTS.md`, but it does not cover the full bootstrap context that `resolveBootstrapContextForRun` would have provided.

Consider documenting this tradeoff explicitly in the `contextInjection` JSDoc, e.g.:

```typescript
/**
 * ...
 * Note: with "first-message-only", workspace context is NOT re-injected after
 * context compaction. Use compaction.postCompactionSections to explicitly
 * preserve critical sections from AGENTS.md across compaction boundaries.
 */
contextInjection?: "always" | "first-message-only";
```

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: e0e0733}

closing this one out.

this idea is obsolete now: main already has a landed contextInjection implementation in the agent runtime/config surfaces, so keeping an older parallel PR open just creates review noise.

if there is still a missing edge case here, it should come back as a narrowly scoped follow-up against current main, not as the older pre-landing version.