Append custom task instructions in Pi executor

[glittercowboy]

Summary

• Bumps protocol-go to v0.23.0.
• Carries Task.customInstructions through the session actor.
• Passes non-empty task instructions to Pi with --append-system-prompt.
• Adds focused executor and actor coverage.

Dependency order

1. Add task custom instructions to protocol protocol-go#29 merged and tagged v0.23.0.
2. Merge this daemon PR.
3. Merge the cloud app PR after relay also consumes v0.23.0.

Verification

• go test ./...
• go build -o gsd-cloud .

Summary by CodeRabbit

• New Features

  • Added support for custom instructions, enabling users to append additional guidance to configure how tasks are executed.

• Tests

  • Added tests to verify custom instructions are correctly integrated and propagated through the system.

• Chores

  • Upgraded protocol dependency to v0.23.0.
  • Added spikes directory to .gitignore.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: fa316786-dd10-489a-a70e-2b2c910ae09a

📥 Commits

Reviewing files that changed from the base of the PR and between 7078d8f and aad9a7b.

⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

📒 Files selected for processing (6)

• .gitignore
• go.mod
• internal/pi/executor.go
• internal/pi/executor_test.go
• internal/session/actor.go
• internal/session/actor_test.go

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📝 Walkthrough

Walkthrough

Custom instructions support is added to the PI execution pipeline. A new CustomInstructions field is introduced to the executor options and task context, threading through the protocol layer to the pi subprocess via the --append-system-prompt argument. Dependencies are bumped and comprehensive tests validate the propagation chain.

Changes

Cohort / File(s)	Summary
Git Configuration .gitignore	Adds ignore pattern for spikes/ directory to prevent tracking of spike experiment files.
Dependencies go.mod	Upgrades github.com/gsd-build/protocol-go from v0.22.0 to v0.23.0.
PI Executor Layer internal/pi/executor.go, internal/pi/executor_test.go	Adds CustomInstructions field to executor Options struct. When non-empty (after trimming), the field is passed to the pi subprocess via --append-system-prompt flag. Startup logging includes custom instructions length. Test validates argument propagation through fake pi binary.
Task Execution Layer internal/session/actor.go, internal/session/actor_test.go	Introduces CustomInstructions field in taskContext, populated from protocol.Task.CustomInstructions in executeTask, and forwarded to pi executor via CustomInstructions option in runPiExecutor. Test verifies the flag value is correctly written to captured args file.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• Persist Pi sessions by GSD session ID #52: Modifies PI executor invocation in internal/session/actor.go to pass additional executor options (ResumeSession), following the same pattern as this PR's CustomInstructions addition.
• Remove task prompt injection #32: Changes how task-level prompt/instruction handling occurs in internal/session/actor.go, removing SystemPrompt while this PR introduces CustomInstructions field propagation.
• feat: support cloud scheduled task execution #37: Modifies the executeTask flow in internal/session/actor.go to add task origin logging, touching the same control path.

Poem

🐰 A whispered instruction, so custom and bright,
Through layers of code, it takes flight!
From protocol down to the pi subprocess call,
These instructions now echo through all! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Append custom task instructions in Pi executor' accurately and specifically describes the main change: adding support for custom task instructions that are appended to the Pi executor via the system prompt.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/custom-instructions-daemon

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