diff --git a/src/Contracts/CheckRunQueryInterface.php b/src/Contracts/CheckRunQueryInterface.php
new file mode 100644
index 0000000..320225e
--- /dev/null
+++ b/src/Contracts/CheckRunQueryInterface.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\CheckRun;
+use ConduitUI\Pr\DataTransferObjects\CheckSummary;
+use Illuminate\Support\Collection;
+
+/**
+ * Contract for querying check runs
+ */
+interface CheckRunQueryInterface
+{
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function get(): Collection;
+
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function wherePassing(): Collection;
+
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function whereFailing(): Collection;
+
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function wherePending(): Collection;
+
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function whereNeutral(): Collection;
+
+    /**
+     * @return Collection<int, CheckRun>
+     */
+    public function whereSkipped(): Collection;
+
+    public function latest(): ?CheckRun;
+
+    public function byName(string $name): ?CheckRun;
+
+    public function summary(): CheckSummary;
+}
diff --git a/src/Contracts/CommentManagerInterface.php b/src/Contracts/CommentManagerInterface.php
new file mode 100644
index 0000000..51b0a57
--- /dev/null
+++ b/src/Contracts/CommentManagerInterface.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\Comment;
+use Illuminate\Support\Collection;
+
+/**
+ * Contract for managing comments
+ */
+interface CommentManagerInterface
+{
+    /**
+     * @return Collection<int, Comment>
+     */
+    public function get(): Collection;
+
+    public function create(string $body): Comment;
+
+    public function update(int $commentId, string $body): Comment;
+
+    public function delete(int $commentId): bool;
+}
diff --git a/src/Contracts/FileQueryInterface.php b/src/Contracts/FileQueryInterface.php
new file mode 100644
index 0000000..c5dc302
--- /dev/null
+++ b/src/Contracts/FileQueryInterface.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\File;
+use ConduitUI\Pr\DataTransferObjects\FileStats;
+use Illuminate\Support\Collection;
+
+/**
+ * Contract for querying changed files
+ */
+interface FileQueryInterface
+{
+    /**
+     * @return Collection<int, File>
+     */
+    public function get(): Collection;
+
+    /**
+     * @return Collection<int, File>
+     */
+    public function whereAdded(): Collection;
+
+    /**
+     * @return Collection<int, File>
+     */
+    public function whereModified(): Collection;
+
+    /**
+     * @return Collection<int, File>
+     */
+    public function whereRemoved(): Collection;
+
+    /**
+     * @return Collection<int, File>
+     */
+    public function whereRenamed(): Collection;
+
+    /**
+     * @param  string  $pattern  Glob pattern for file paths
+     * @return Collection<int, File>
+     */
+    public function wherePath(string $pattern): Collection;
+
+    /**
+     * @return Collection<int, File>
+     */
+    public function whereExtension(string $extension): Collection;
+
+    public function stats(): FileStats;
+}
diff --git a/src/Contracts/MergeManagerInterface.php b/src/Contracts/MergeManagerInterface.php
new file mode 100644
index 0000000..44accfe
--- /dev/null
+++ b/src/Contracts/MergeManagerInterface.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\PullRequest;
+
+/**
+ * Contract for merge operations
+ */
+interface MergeManagerInterface
+{
+    public function merge(?string $commitTitle = null, ?string $commitMessage = null): PullRequest;
+
+    public function squash(?string $commitTitle = null, ?string $commitMessage = null): PullRequest;
+
+    public function rebase(): PullRequest;
+
+    public function canMerge(): bool;
+
+    public function deleteBranch(): bool;
+}
diff --git a/src/Contracts/PullRequestBuilderInterface.php b/src/Contracts/PullRequestBuilderInterface.php
new file mode 100644
index 0000000..24a7d21
--- /dev/null
+++ b/src/Contracts/PullRequestBuilderInterface.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\PullRequest;
+
+/**
+ * Contract for creating pull requests
+ */
+interface PullRequestBuilderInterface
+{
+    public function title(string $title): self;
+
+    public function body(string $body): self;
+
+    public function head(string $branch): self;
+
+    public function base(string $branch): self;
+
+    public function draft(bool $draft = true): self;
+
+    public function maintainerCanModify(bool $allowed = true): self;
+
+    public function create(): PullRequest;
+}
diff --git a/src/Contracts/PullRequestManagerInterface.php b/src/Contracts/PullRequestManagerInterface.php
new file mode 100644
index 0000000..33c41e8
--- /dev/null
+++ b/src/Contracts/PullRequestManagerInterface.php
@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\PullRequest;
+
+/**
+ * Contract for managing pull requests
+ */
+interface PullRequestManagerInterface
+{
+    public function find(int $number): PullRequest;
+
+    public function get(int $number): PullRequest;
+
+    public function query(): PullRequestQueryInterface;
+
+    public function create(): PullRequestBuilderInterface;
+}
diff --git a/src/Contracts/ReviewQueryInterface.php b/src/Contracts/ReviewQueryInterface.php
new file mode 100644
index 0000000..73e1c95
--- /dev/null
+++ b/src/Contracts/ReviewQueryInterface.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use ConduitUI\Pr\DataTransferObjects\Review;
+use Illuminate\Support\Collection;
+
+/**
+ * Contract for querying reviews
+ */
+interface ReviewQueryInterface
+{
+    /**
+     * @return Collection<int, Review>
+     */
+    public function get(): Collection;
+
+    /**
+     * @return Collection<int, Review>
+     */
+    public function whereApproved(): Collection;
+
+    /**
+     * @return Collection<int, Review>
+     */
+    public function whereChangesRequested(): Collection;
+
+    /**
+     * @return Collection<int, Review>
+     */
+    public function wherePending(): Collection;
+
+    /**
+     * @return Collection<int, Review>
+     */
+    public function byUser(string $username): Collection;
+
+    public function latest(): ?Review;
+}
diff --git a/src/DataTransferObjects/CheckSummary.php b/src/DataTransferObjects/CheckSummary.php
new file mode 100644
index 0000000..dac1cd4
--- /dev/null
+++ b/src/DataTransferObjects/CheckSummary.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\DataTransferObjects;
+
+class CheckSummary
+{
+    public function __construct(
+        public readonly int $total,
+        public readonly int $passing,
+        public readonly int $failing,
+        public readonly int $pending,
+        public readonly int $neutral,
+        public readonly int $skipped,
+    ) {}
+
+    /**
+     * @param  array{total: int, passing: int, failing: int, pending: int, neutral: int, skipped: int}  $data
+     */
+    public static function fromArray(array $data): self
+    {
+        return new self(
+            total: $data['total'],
+            passing: $data['passing'],
+            failing: $data['failing'],
+            pending: $data['pending'],
+            neutral: $data['neutral'],
+            skipped: $data['skipped'],
+        );
+    }
+
+    public function allPassing(): bool
+    {
+        return $this->total > 0 && $this->failing === 0 && $this->pending === 0;
+    }
+
+    public function hasFailures(): bool
+    {
+        return $this->failing > 0;
+    }
+
+    public function hasPending(): bool
+    {
+        return $this->pending > 0;
+    }
+
+    /**
+     * @return array<string, int>
+     */
+    public function toArray(): array
+    {
+        return [
+            'total' => $this->total,
+            'passing' => $this->passing,
+            'failing' => $this->failing,
+            'pending' => $this->pending,
+            'neutral' => $this->neutral,
+            'skipped' => $this->skipped,
+        ];
+    }
+}
diff --git a/src/DataTransferObjects/FileStats.php b/src/DataTransferObjects/FileStats.php
new file mode 100644
index 0000000..b512779
--- /dev/null
+++ b/src/DataTransferObjects/FileStats.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\DataTransferObjects;
+
+class FileStats
+{
+    public function __construct(
+        public readonly int $total,
+        public readonly int $added,
+        public readonly int $modified,
+        public readonly int $removed,
+        public readonly int $renamed,
+        public readonly int $totalAdditions,
+        public readonly int $totalDeletions,
+        public readonly int $totalChanges,
+    ) {}
+
+    /**
+     * @param  array{total: int, added: int, modified: int, removed: int, renamed: int, total_additions: int, total_deletions: int, total_changes: int}  $data
+     */
+    public static function fromArray(array $data): self
+    {
+        return new self(
+            total: $data['total'],
+            added: $data['added'],
+            modified: $data['modified'],
+            removed: $data['removed'],
+            renamed: $data['renamed'],
+            totalAdditions: $data['total_additions'],
+            totalDeletions: $data['total_deletions'],
+            totalChanges: $data['total_changes'],
+        );
+    }
+
+    /**
+     * @return array<string, int>
+     */
+    public function toArray(): array
+    {
+        return [
+            'total' => $this->total,
+            'added' => $this->added,
+            'modified' => $this->modified,
+            'removed' => $this->removed,
+            'renamed' => $this->renamed,
+            'total_additions' => $this->totalAdditions,
+            'total_deletions' => $this->totalDeletions,
+            'total_changes' => $this->totalChanges,
+        ];
+    }
+}
diff --git a/tests/Unit/ContractsTest.php b/tests/Unit/ContractsTest.php
new file mode 100644
index 0000000..93beca0
--- /dev/null
+++ b/tests/Unit/ContractsTest.php
@@ -0,0 +1,176 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUI\Pr\Contracts\CheckRunQueryInterface;
+use ConduitUI\Pr\Contracts\CommentManagerInterface;
+use ConduitUI\Pr\Contracts\FileQueryInterface;
+use ConduitUI\Pr\Contracts\MergeManagerInterface;
+use ConduitUI\Pr\Contracts\PullRequestBuilderInterface;
+use ConduitUI\Pr\Contracts\PullRequestManagerInterface;
+use ConduitUI\Pr\Contracts\PullRequestQueryInterface;
+use ConduitUI\Pr\Contracts\ReviewBuilderInterface;
+use ConduitUI\Pr\Contracts\ReviewQueryInterface;
+
+describe('PullRequestManagerInterface', function () {
+    it('defines all required manager methods', function () {
+        $reflection = new ReflectionClass(PullRequestManagerInterface::class);
+
+        expect($reflection->hasMethod('find'))->toBeTrue()
+            ->and($reflection->hasMethod('get'))->toBeTrue()
+            ->and($reflection->hasMethod('query'))->toBeTrue()
+            ->and($reflection->hasMethod('create'))->toBeTrue();
+    });
+
+    it('returns PullRequestQueryInterface from query method', function () {
+        $reflection = new ReflectionClass(PullRequestManagerInterface::class);
+        $method = $reflection->getMethod('query');
+
+        expect($method->getReturnType()?->getName())->toBe(PullRequestQueryInterface::class);
+    });
+
+    it('returns PullRequestBuilderInterface from create method', function () {
+        $reflection = new ReflectionClass(PullRequestManagerInterface::class);
+        $method = $reflection->getMethod('create');
+
+        expect($method->getReturnType()?->getName())->toBe(PullRequestBuilderInterface::class);
+    });
+});
+
+describe('PullRequestBuilderInterface', function () {
+    it('defines all required builder methods', function () {
+        $reflection = new ReflectionClass(PullRequestBuilderInterface::class);
+
+        expect($reflection->hasMethod('title'))->toBeTrue()
+            ->and($reflection->hasMethod('body'))->toBeTrue()
+            ->and($reflection->hasMethod('head'))->toBeTrue()
+            ->and($reflection->hasMethod('base'))->toBeTrue()
+            ->and($reflection->hasMethod('draft'))->toBeTrue()
+            ->and($reflection->hasMethod('maintainerCanModify'))->toBeTrue()
+            ->and($reflection->hasMethod('create'))->toBeTrue();
+    });
+
+    it('has chainable methods returning self', function () {
+        $reflection = new ReflectionClass(PullRequestBuilderInterface::class);
+
+        $title = $reflection->getMethod('title');
+        expect($title->getReturnType()?->getName())->toBe('self');
+
+        $body = $reflection->getMethod('body');
+        expect($body->getReturnType()?->getName())->toBe('self');
+
+        $head = $reflection->getMethod('head');
+        expect($head->getReturnType()?->getName())->toBe('self');
+    });
+});
+
+describe('ReviewBuilderInterface', function () {
+    it('defines all required review builder methods', function () {
+        $reflection = new ReflectionClass(ReviewBuilderInterface::class);
+
+        expect($reflection->hasMethod('approve'))->toBeTrue()
+            ->and($reflection->hasMethod('requestChanges'))->toBeTrue()
+            ->and($reflection->hasMethod('comment'))->toBeTrue()
+            ->and($reflection->hasMethod('addInlineComment'))->toBeTrue()
+            ->and($reflection->hasMethod('addSuggestion'))->toBeTrue()
+            ->and($reflection->hasMethod('submit'))->toBeTrue();
+    });
+
+    it('has chainable methods returning self', function () {
+        $reflection = new ReflectionClass(ReviewBuilderInterface::class);
+
+        $approve = $reflection->getMethod('approve');
+        expect($approve->getReturnType()?->getName())->toBe('self');
+
+        $comment = $reflection->getMethod('comment');
+        expect($comment->getReturnType()?->getName())->toBe('self');
+    });
+});
+
+describe('ReviewQueryInterface', function () {
+    it('defines all required review query methods', function () {
+        $reflection = new ReflectionClass(ReviewQueryInterface::class);
+
+        expect($reflection->hasMethod('get'))->toBeTrue()
+            ->and($reflection->hasMethod('whereApproved'))->toBeTrue()
+            ->and($reflection->hasMethod('whereChangesRequested'))->toBeTrue()
+            ->and($reflection->hasMethod('wherePending'))->toBeTrue()
+            ->and($reflection->hasMethod('byUser'))->toBeTrue()
+            ->and($reflection->hasMethod('latest'))->toBeTrue();
+    });
+});
+
+describe('CheckRunQueryInterface', function () {
+    it('defines all required check run query methods', function () {
+        $reflection = new ReflectionClass(CheckRunQueryInterface::class);
+
+        expect($reflection->hasMethod('get'))->toBeTrue()
+            ->and($reflection->hasMethod('wherePassing'))->toBeTrue()
+            ->and($reflection->hasMethod('whereFailing'))->toBeTrue()
+            ->and($reflection->hasMethod('wherePending'))->toBeTrue()
+            ->and($reflection->hasMethod('whereNeutral'))->toBeTrue()
+            ->and($reflection->hasMethod('whereSkipped'))->toBeTrue()
+            ->and($reflection->hasMethod('latest'))->toBeTrue()
+            ->and($reflection->hasMethod('byName'))->toBeTrue()
+            ->and($reflection->hasMethod('summary'))->toBeTrue();
+    });
+});
+
+describe('MergeManagerInterface', function () {
+    it('defines all required merge manager methods', function () {
+        $reflection = new ReflectionClass(MergeManagerInterface::class);
+
+        expect($reflection->hasMethod('merge'))->toBeTrue()
+            ->and($reflection->hasMethod('squash'))->toBeTrue()
+            ->and($reflection->hasMethod('rebase'))->toBeTrue()
+            ->and($reflection->hasMethod('canMerge'))->toBeTrue()
+            ->and($reflection->hasMethod('deleteBranch'))->toBeTrue();
+    });
+});
+
+describe('FileQueryInterface', function () {
+    it('defines all required file query methods', function () {
+        $reflection = new ReflectionClass(FileQueryInterface::class);
+
+        expect($reflection->hasMethod('get'))->toBeTrue()
+            ->and($reflection->hasMethod('whereAdded'))->toBeTrue()
+            ->and($reflection->hasMethod('whereModified'))->toBeTrue()
+            ->and($reflection->hasMethod('whereRemoved'))->toBeTrue()
+            ->and($reflection->hasMethod('whereRenamed'))->toBeTrue()
+            ->and($reflection->hasMethod('wherePath'))->toBeTrue()
+            ->and($reflection->hasMethod('whereExtension'))->toBeTrue()
+            ->and($reflection->hasMethod('stats'))->toBeTrue();
+    });
+});
+
+describe('CommentManagerInterface', function () {
+    it('defines all required comment manager methods', function () {
+        $reflection = new ReflectionClass(CommentManagerInterface::class);
+
+        expect($reflection->hasMethod('get'))->toBeTrue()
+            ->and($reflection->hasMethod('create'))->toBeTrue()
+            ->and($reflection->hasMethod('update'))->toBeTrue()
+            ->and($reflection->hasMethod('delete'))->toBeTrue();
+    });
+});
+
+describe('Contract Type Safety', function () {
+    it('ensures ReviewQueryInterface methods return Collection', function () {
+        $reflection = new ReflectionClass(ReviewQueryInterface::class);
+
+        $get = $reflection->getMethod('get');
+        expect($get->getReturnType()?->getName())->toBe('Illuminate\Support\Collection');
+
+        $whereApproved = $reflection->getMethod('whereApproved');
+        expect($whereApproved->getReturnType()?->getName())->toBe('Illuminate\Support\Collection');
+    });
+
+    it('ensures nullable return types are properly defined', function () {
+        $reflection = new ReflectionClass(PullRequestQueryInterface::class);
+        $method = $reflection->getMethod('first');
+        $returnType = $method->getReturnType();
+
+        expect($returnType)->not->toBeNull()
+            ->and($returnType->allowsNull())->toBeTrue();
+    });
+});
diff --git a/tests/Unit/DataTransferObjects/CheckSummaryTest.php b/tests/Unit/DataTransferObjects/CheckSummaryTest.php
new file mode 100644
index 0000000..ad9dd99
--- /dev/null
+++ b/tests/Unit/DataTransferObjects/CheckSummaryTest.php
@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUI\Pr\DataTransferObjects\CheckSummary;
+
+it('can create CheckSummary from array', function () {
+    $data = [
+        'total' => 10,
+        'passing' => 8,
+        'failing' => 1,
+        'pending' => 1,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($data);
+
+    expect($summary->total)->toBe(10)
+        ->and($summary->passing)->toBe(8)
+        ->and($summary->failing)->toBe(1)
+        ->and($summary->pending)->toBe(1)
+        ->and($summary->neutral)->toBe(0)
+        ->and($summary->skipped)->toBe(0);
+});
+
+it('can check if all checks are passing', function () {
+    $passingData = [
+        'total' => 5,
+        'passing' => 5,
+        'failing' => 0,
+        'pending' => 0,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($passingData);
+    expect($summary->allPassing())->toBeTrue();
+
+    $failingData = [
+        'total' => 5,
+        'passing' => 4,
+        'failing' => 1,
+        'pending' => 0,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($failingData);
+    expect($summary->allPassing())->toBeFalse();
+});
+
+it('can check if has failures', function () {
+    $data = [
+        'total' => 5,
+        'passing' => 4,
+        'failing' => 1,
+        'pending' => 0,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($data);
+    expect($summary->hasFailures())->toBeTrue();
+});
+
+it('can check if has pending', function () {
+    $data = [
+        'total' => 5,
+        'passing' => 4,
+        'failing' => 0,
+        'pending' => 1,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($data);
+    expect($summary->hasPending())->toBeTrue();
+});
+
+it('can serialize to array', function () {
+    $data = [
+        'total' => 10,
+        'passing' => 8,
+        'failing' => 1,
+        'pending' => 1,
+        'neutral' => 0,
+        'skipped' => 0,
+    ];
+
+    $summary = CheckSummary::fromArray($data);
+    $array = $summary->toArray();
+
+    expect($array)->toBe($data);
+});
diff --git a/tests/Unit/DataTransferObjects/FileStatsTest.php b/tests/Unit/DataTransferObjects/FileStatsTest.php
new file mode 100644
index 0000000..0be858a
--- /dev/null
+++ b/tests/Unit/DataTransferObjects/FileStatsTest.php
@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUI\Pr\DataTransferObjects\FileStats;
+
+it('can create FileStats from array', function () {
+    $data = [
+        'total' => 10,
+        'added' => 3,
+        'modified' => 5,
+        'removed' => 2,
+        'renamed' => 0,
+        'total_additions' => 150,
+        'total_deletions' => 75,
+        'total_changes' => 225,
+    ];
+
+    $stats = FileStats::fromArray($data);
+
+    expect($stats->total)->toBe(10)
+        ->and($stats->added)->toBe(3)
+        ->and($stats->modified)->toBe(5)
+        ->and($stats->removed)->toBe(2)
+        ->and($stats->renamed)->toBe(0)
+        ->and($stats->totalAdditions)->toBe(150)
+        ->and($stats->totalDeletions)->toBe(75)
+        ->and($stats->totalChanges)->toBe(225);
+});
+
+it('can serialize to array', function () {
+    $data = [
+        'total' => 10,
+        'added' => 3,
+        'modified' => 5,
+        'removed' => 2,
+        'renamed' => 0,
+        'total_additions' => 150,
+        'total_deletions' => 75,
+        'total_changes' => 225,
+    ];
+
+    $stats = FileStats::fromArray($data);
+    $array = $stats->toArray();
+
+    expect($array)->toBe($data);
+});
+
+it('handles zero values correctly', function () {
+    $data = [
+        'total' => 0,
+        'added' => 0,
+        'modified' => 0,
+        'removed' => 0,
+        'renamed' => 0,
+        'total_additions' => 0,
+        'total_deletions' => 0,
+        'total_changes' => 0,
+    ];
+
+    $stats = FileStats::fromArray($data);
+
+    expect($stats->total)->toBe(0)
+        ->and($stats->added)->toBe(0)
+        ->and($stats->totalChanges)->toBe(0);
+});