refactor: convert SessionSummary to frozen dataclass (#1067)

[microsasa]

Closes #1067

Summary

Converts SessionSummary from a Pydantic BaseModel to a @dataclasses.dataclass(frozen=True, slots=True) to align with the coding guideline: "Internal intermediate state uses frozen dataclasses with slots=True".

SessionSummary is internal intermediate state — populated by build_session_summary from already-validated SessionEvent objects, never parsed directly from JSON. Making it a frozen dataclass prevents accidental field mutation on cached instances.

Changes

File	Change
src/copilot_usage/models.py	Replace BaseModel with frozen dataclass; move @model_validator to __post_init__; use dataclasses.field for mutable defaults; remove unused Self and model_validator imports
src/copilot_usage/parser.py	Replace summary.model_copy(update={...}) with dataclasses.replace(summary, ...)
tests/copilot_usage/test_models.py	Update invariant tests to expect ValueError (not ValidationError); add TestSessionSummaryFrozen class with FrozenInstanceError, __post_init__ validation, and dataclasses.replace tests
tests/copilot_usage/test_parser.py	Replace model_dump() comparison with direct dataclass equality
src/copilot_usage/docs/architecture.md	Update models.py description to reflect the change

Testing

• Added TestSessionSummaryFrozen with 3 tests:
  • Field assignment raises FrozenInstanceError
  • __post_init__ raises ValueError when active_model_calls > model_calls
  • dataclasses.replace produces a new instance with updated fields
• Updated existing invariant tests to match new ValueError exception type

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[Copilot]

Pull request overview

Refactors copilot_usage’s internal session aggregation type by converting SessionSummary from a Pydantic BaseModel to a frozen, slotted stdlib dataclass, aligning internal-state modeling with the project’s “Pydantic at the boundary” direction while keeping invariant validation.

Changes:

• Converted SessionSummary to @dataclasses.dataclass(frozen=True, slots=True) and moved invariants to __post_init__.
• Updated parser/cache update logic to use dataclasses.replace(...) instead of Pydantic model_copy(update=...).
• Adjusted tests and docs to reflect dataclass semantics (equality, exception types, frozen behavior).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/copilot_usage/models.py	Converts SessionSummary to a frozen dataclass and enforces invariants in __post_init__; updates mutable defaults to dataclasses.field(default_factory=...).
src/copilot_usage/parser.py	Updates cached-summary name refresh to use dataclasses.replace(...) for immutable SessionSummary.
tests/copilot_usage/test_models.py	Updates invariant tests to ValueError and adds coverage for frozen/dataclass replace behavior.
tests/copilot_usage/test_parser.py	Replaces model_dump()-based comparisons with direct dataclass equality for cached summaries.
src/copilot_usage/docs/architecture.md	Updates architecture docs to reflect SessionSummary as a frozen dataclass rather than a Pydantic model.

[Copilot]

shutdown_cycles uses dataclasses.field(default_factory=lambda: []). Prefer default_factory=list (or default_factory=list[tuple[...]] not possible) to avoid an unnecessary lambda and keep the field factory picklable/readable; also the extra parentheses around the field(...) call can be dropped for clarity.

Suggested change

	shutdown_cycles: list[tuple[datetime | None, SessionShutdownData]] = (
	dataclasses.field(default_factory=lambda: [])
	shutdown_cycles: list[tuple[datetime | None, SessionShutdownData]] = dataclasses.field(
	default_factory=list

[github-actions]

Commit pushed: 38ea4c8

Generated by CI Fixer

[microsasa]

CI Fix

Root cause: model_metrics field on SessionSummary used default_factory=dict in the dataclasses.field() call. Per coding guidelines, dataclass fields must use default_factory=lambda: {} (not bare dict) to avoid a known pyright strict-mode false-positive.

Fix: Changed default_factory=dict → default_factory=lambda: {} in src/copilot_usage/models.py.

Note: Could not run make check locally — the agent environment firewall blocks pypi.org and astral.sh, preventing tool installation. Fix is based on static analysis of the code against pyright strict-mode requirements documented in the coding guidelines.

Warning

⚠️ Firewall blocked 2 domains

The following domains were blocked by the firewall during workflow execution:

• astral.sh
• pypi.org

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "astral.sh"
    - "pypi.org"

See Network Configuration for more information.

Generated by CI Fixer · ● 12.9M · ◷

[microsasa]

❌ Pipeline orchestrator: CI still failing after ci-fixer attempt. Marking as stuck for human review.

[microsasa]

CI fix already attempted once — stopping to prevent loops. Manual intervention needed.

Generated by CI Fixer · ● 438.3K · ◷